JP4100915B2 - Developer and image forming method - Google Patents

Description

【００３７】
表面摩擦係数は、ポリエチレンテレフタレートフィルム基準なので、多少の測定条件のバラツキには影響されない。また、感光ドラムの直径にも影響されず、一定の値を示す。
【００３８】
本発明においては、次のような測定条件の範囲が許容される。
・ウレタンゴム：硬度；６２〜７２°、厚み；１〜５ｍｍ、製造元；バンドー化学（株）、北辰ゴム（株）、東海ゴム（株）など
・ポリエチレンテレフタレートフィルム：製造元；東レ（株）（商品名：ルミラー）、帝人（株）（商品名：ＴＲ８５５０）、デュポン（商品名：マイラー）など、厚み；１０〜５０μｍ
・ドラム直径：２０〜２００ｍｍ（なお、ドラムの径を変化させてもポリエチレンテレフタレート基準の表面摩擦係数は変化しない。）
【００３９】
なお、本発明における表面特性の評価は全て室温（約２１〜２５℃）で行われるものとする。
【００４０】
また、本発明における静電潜像担持体表面の特性で、耐久性の観点から一定以上の硬度を有することが良く、具体的にはユニバーサル硬さＨＵが２００Ｎ／ｍｍ²以上であることが好ましい。
【００４１】
本発明におけるユニバーサル硬さは、以下のような表面皮膜物性試験によって得ることができる。かかる表面皮膜物性試験とは、薄膜、硬化皮膜及び有機皮膜等の硬度の解析を行うための試験であり、測定においては、図４に示す試験機（フィッシャー・インストルメンツ製、フィッシャースコープＨ１００Ｖ）にて、四角錐のダイヤモンド圧子で対面角度が１３６°に規定されているダイヤモンド圧子３３を使用し、サンプル（電子写真静電潜像担持体）３１に対して、測定荷重を段階的にかけてサンプル皮膜に押し込んでいったときの、荷重をかけた状態での押込み深さｈを電気的に検出して読み取るものである。図４中３４は移動式テーブル、３２はサンプル置き台である。
【００４２】
硬さＨは、試験荷重をその試験荷重で生じた圧痕の表面積で除した値で表示される。また、ユニバーサル硬さＨＵは、設定最大押込み深さｈｘ（本発明においては、ｈｘ＝１μｍ）での硬さで表される。硬さＨおよびユニバーサル硬さＨＵにおいては、各々数値が高いほど膜硬度が高いことを意味する。測定は資料表面が割れない程度で行うものとする。
【００４３】
この様な表面特性を有する電子写真静電潜像担持体は、例えば、通常の構成の電子写真静電潜像担持体の表面層について、ユニバーサル硬さを上記範囲にするために、バインダー樹脂として特定の樹脂を用い、また、表面摩擦係数または表面の純水との接触角を上記範囲とするために特定量のフッ素系樹脂粉体を表面層に均一に分散させ、必要に応じて表面を研磨することによって得られるものである。
【００４４】
ユニバーサル硬さの調整手段は、バインダー樹脂とそのバインダー樹脂に分散、溶解されている電荷発生材料もしくは電荷輸送材料、あるいは金属およびその酸化物、窒化物、塩、合金およびカーボン等の導電材料の種類やこれらの比率を変えること等が挙げられる。すなわち、バインダー樹脂に分散する材料にもよるが、上記のような材料の場合、通常分散する材料が少ない方が、ユニバーサル硬度は大きくなる。また、別の手段としては、バインダー樹脂の分子量、重合官能基数等を変えることも挙げられる。すなわち、バインダー樹脂の分子量を高くすれば、ユニバーサル硬さは大きくなり、また、重合官能基数を増やすことにより樹脂の架橋度を上げると、ユニバーサル硬さは大きくなる。更には、フッ素系樹脂粉体等の分散状態によっても変化し得る。
【００４５】
これらの要件は、当然表面摩擦係数にも影響を与えるが、ユニバーサル硬さと表面係数の間には一定の関係は見出されていない。
【００４６】
本発明の画像形成方法に好適な現像剤担持体について説明する。現像剤担持体は、一般的に一成分の接触現像方法に用いられるものであれば特に限定するものではないが、好ましくは、弾性層を有するローラが用いられる。
【００４７】
弾性ローラ表面の弾性層硬度としては、現像性と耐久性の両立の観点から２０〜６５度（ＡＳＫＥＲ Ｃ）程度が好ましく、３０〜６０度が更に好ましい。弾性ローラの材質としては公知の材質、構造のものが使用可能である。特にシリコーンゴム、ウレタンゴム、ＮＢＲの如きソリッドのゴム弾性体、あるいはこれらの発泡弾性体が好ましく使用される。また、表面に中心部と異なるコート層を有する公知の多層構造ローラも使用できる。また、帯電性付与や搬送性付与の目的で公知の表面処理を施しても良い。またこの際に、弾性層表面の帯電系列が現像剤に対して帯電付与する対極に位置するような系列を取ることが摩擦帯電付与性、及び現像ローラ上の現像剤の入れ替わりという観点から好ましい。
【００４８】
現像剤担持体の表面形状としては、その表面粗度を制御することが高画質及び高耐久性を両立するために好ましい。現像剤担持体の表面粗度として、たとえばＲａ（μｍ）「ＪＩＳ Ｂ ０６０１」を０．２〜３．０となるように設定すると、高画質及び高耐久性を両立できる。該現像剤担持体の表面粗度Ｒａが３．０を超えると、該現像剤担持体上の現像剤層の薄層化が困難となるばかりか、現像剤の帯電性が改善されないので画質の向上は望めない。３．０以下にすることで現像剤担持体表面の現像剤の搬送能力を抑制し、該現像剤担持体上の現像剤層を薄層化すると共に、該現像剤担持体と現像剤の接触回数が多くなるため、該現像剤の帯電性も改善されるので相乗的に画質が向上する。一方、表面粗度Ｒａが０．２よりも小さくなると、現像剤コート量の制御が難しくなる。また、現像部分での摺擦をより効率的に行うために、該現像剤担持体の表面粗度Ｒａが上記範囲にあることが好ましい。
【００４９】
また、表面粗度Ｒｚに関しては、現像剤のコートを均一化するために８．０μｍ以下にすることが好ましい。現像剤担持体の最表層に成型時の異物等によって表面粗度Ｒｚが８．０μｍより大きくなるケースが発生することがあるが、このような場合は、現像剤規制部材表面や潜像担持体表面の表面性を変化させる恐れがあり、現像剤担持体上の現像剤の帯電やコート量を不均一にすることが生じ、その結果、現像後の画像にスジが発生するため好ましくない。従って、現像剤担持体表面の状態は上記の範囲が好ましいものである。
【００５０】
また、該静電潜像担持体と現像剤担持体の回転方向は順方向であることが好ましい。一成分接触現像で該回転方向を逆方向に設定すると、該現像部分での摩擦帯電性はさらに向上するものの、接触部分の機械的ストレスが非常に大きくなり、装置寿命が短くなり問題である。
【００５１】
そこで該静電潜像担持体と現像剤担持体の回転方向を順方向とすることで上記のごときストレスを低減でき、装置寿命を改善することが可能である。
【００５２】
そこでより負荷の少ない、効率的な帯電付与を実現するために該現像剤担持体に対する該静電潜像担持体の相対速度と帯電性付与能、及び現像剤劣化の関係を調べた結果を図３に示した。ここでの現像剤の帯電量は一定枚数の耐久を行った後の５０％印字率時静電潜像を顕像化したものの転写前現像剤の帯電量であり、現像剤劣化は、電子顕微鏡での同現像剤の表面観察より得られる画像をランク見本を用いて数値化したものである。
【００５３】
相対速度が１２０％未満では規制部材での摩擦帯電に頼る部分が多く、本来の狙いが達成できていないことがわかる。かかる部分での摩擦帯電で現像剤に十分な帯電能を与えるには、現像剤担持体と規制部材の当接部分での強い摺擦が必要であり、かかる摺擦を達成する手段としては一般的に規制部材の当接圧を高める方法が取られる。しかし、このような方法により当接圧を高めると、現像剤への帯電付与性は高まるものの、現像剤に対する負荷が強く、現像剤表面の外添剤付着状態に変化を与え、現像剤自体の形状変化を招きやすく、その結果、規制部材表面への現像剤融着を生じ易くなって、規制部材表面へ現像剤の融着塊が発生し、現像剤担持体上の現像剤の帯電やコート量を不均一にすることが生じ、その結果、現像後の画像にスジが発生するため好ましくない。
【００５４】
しかし、本発明の静電潜像担持体を用い、且つ、該相対速度が１２０％を上回る場合は、現像剤への帯電付与を規制部材と現像部の２点に役割を分割することが可能となるため、上記のごとき規制部材より当接圧を低めることができ、かかる問題を解決することが可能となるものである。
【００５５】
一方、該相対速度が２５０％を超える場合、帯電付与能力は低下する。この詳細な原理は定かではないが、２００％近傍から帯電能力が劣ってきていることから、周速差が高速になると摩擦帯電の均一性が損なわれるためではないかと思われる。また、さらに現像剤の劣化も促進され、摩擦帯電の均一性が損なわれることとの相乗効果により悪化しているものと考えられる。
【００５６】
従って、現像剤担持体表面の状態は上記の範囲が好ましいものである。
【００５７】
本発明のように現像剤担持体が、特定の表面性を有する静電潜像担持体に対して、相対速度が１２０〜２５０％の範囲になるように周速比をもって構成されていることにより、現像剤担持体と静電潜像担持体との接触部分において現像剤粒子同士の摩擦により良好な帯電性が付与され、また、現像剤劣化による現像性悪化を生じにくくなる。さらに、現像剤として本願の現像剤を組合せることで、現像部での摺擦時により有効で安定した帯電付与が達成でき、本願の効果が得られるものである。
【００５８】
なお、静電潜像担持体と現像剤担持体の相対速度は、静電潜像担持体と現像剤担持体それぞれを駆動する歯車の歯数を調整することで操作することができる。
【００５９】
現像剤担持体上の現像剤は、現像剤担持体表面に圧接するよう配置されている規制部材（現像ブレード）により規制され、現像剤担持体上の現像剤層を形成する。
【００６０】
現像ブレードを現像剤担持体表面へ圧接し現像剤担持体上の層厚を規制する圧力は、現像剤のコート層厚を一定に規制し、且つ、上述の第一の摩擦帯電を適切に行うように、当接圧や形状を調節することが好ましい。
【００６１】
現像ブレードを現像剤担持体表面へ圧接し現像剤担持体上の層厚を規制する圧力は、９．８Ｎ／ｍ（１０ｇ／ｃｍ）から５８．８Ｎ／ｍ（６０ｇ／ｃｍ）が好ましく、より好ましくは１９．６Ｎ／ｍ（２０ｇ／ｍ）から３９．２Ｎ／ｍ（３０ｇ／ｍ）である。このような範囲に現像ブレードがある場合は、現像ブレードへの現像剤の融着を防ぎつつ、現像剤担持体上の現像剤に対して適当な第１の帯電を付与できる。
【００６２】
現像剤コート量の規制部材の材質としては、特に限定するものではなく公知の金属製板状部材、あるいは金属ブレード表面に有機層を有するものが使用できる。特に有機層としては、現像剤に対し所望の帯電を付与する摩擦帯電系列の材質を選択することが好ましく、シリコーンゴム、ウレタンゴム、ＮＢＲの如きゴム弾性体、ポリエチレンテレフタレートの如き合成樹脂弾性体、ステンレス、鋼、リン青銅の如き金属弾性体が使用でき、また、それらの複合体が使用できる。
【００６３】
更に、弾性の規制部材中に有機物や無機物を添加してもよく、溶融混合させても良いし、分散させても良い。例えば、金属酸化物、金属粉、セラミックス、炭素同素体、ウィスカー、無機繊維、染料、顔料、界面活性剤などを添加することにより、現像剤の帯電性をコントロールできる。特に、弾性体がゴムや樹脂等の成型体の場合には、シリカ、アルミナ、チタニア、酸化錫、酸化ジルコニア、酸化亜鉛等の金属酸化物微粉末、カーボンブラック、一般に現像剤に用いられる荷電制御剤等を含有させることも好ましい。
【００６４】
また、導電性の規制部材と現像剤担持体の組合せで使用する場合は、規制部材と現像剤担持体の間に直流電場及び／または交流電場を印加することも好ましい。このような電場を印加することによって、均一薄層塗布や、均一帯電性が向上し、充分な画像濃度の達成及び良質の画像を得ることができる。
【００６５】
さらに本発明は、転写後の静電潜像担持体表面をブレードクリーニングする機構を有するものであるが、ブレードクリーニングのクリーニング部材としては、公知のブレードが使用できる。
【００６６】
また、ブレードクリーニング後の帯電方法としては、公知の接触あるいは非接触の帯電方式が使用可能であるが、帯電時にオゾンの発生を抑制する効果のある接触帯電方式がより好ましい。本発明の画像形成方法と現像剤の組合せにおいては、転写後の静電潜像担持体表面に残留する転写残の多くが疎水性シリカ微粒子と、該疎水性シリカ粒子の逆極性の第二外添剤であるため、上述のブレードクリーニング部材と接触帯電との組合せの相性のいいものを選択する必要がある。これらの組合せが正常に機能しない場合は、帯電部材上に外添剤を主体とした粒子が付着し、帯電ローラ表面の抵抗値を局部的に上昇させることにより、静電潜像担持体表面の帯電を阻害し、その結果、帯電不良による画像欠陥を生じるため好ましくない。
【００６７】
次に本発明の第二のポイントである現像剤について述べる。
【００６８】
該現像剤は少なくとも結着樹脂、着色剤と離型剤からなる着色粒子と、該着色粒子表面に、少なくとも２種以上の金属酸化物微粒子を有する非磁性の一成分現像剤であり、該金属酸化物微粒子の少なくとも一種が疎水性シリカ微粒子であり、さらに他の外添剤のうち少なくとも１種が該疎水性シリカに対し逆極性に帯電する粒子であることを特徴とするものである。
【００６９】
本発明の現像剤用樹脂に用いられる結着樹脂は、現像剤を製造する際に用いられるものであれば特に限定されるものではない。本発明の現像剤用樹脂に用いられる結着樹脂としては、公知の重合体、又は、共重合体、あるいはこれらの混合物が挙げられる。更に具体的には、スチレン−（メタ）アクリル酸共重合体あるいはポリエステル系樹脂が好ましい。
【００７０】
本発明の現像剤を得るためには、本発明で好ましい範囲の現像剤粒子径や形状を達成可能なものであればその製造方法は特に限定するものではないが、本発明の効果がより顕著に発現するための形状を達成するためには、現像剤の構成成分を溶融混練後に粉砕しさらに球形化処理を施した後に所望の粒子径に分級操作する方法、または、懸濁重合の如き重合方法によって、現像剤を構成する材料を直接モノマー単位から球形化して重合を行い、重合後の粒子を単離する現像剤の製造方法、または、懸濁重合や乳化重合法によってモノマーの重合により現像剤粒子径よりも小さい着色粒子を合成した後にこれらの凝集操作を行って所望の粒度になるように制御する凝集法の如き方法が使用可能である。
【００７１】
現像剤を構成する原材料は、粉砕法であれば上記の如き結着樹脂成分、また、重合法あるいは凝集法であれば結着樹脂を構成するモノマーと、公知の現像剤に使用可能な重合開始剤や架橋剤、分子量調整剤等からなる結着樹脂成分と、公知の着色剤、荷電制御剤、帯電補助剤、離型剤等が使用できる。
【００７２】
一般的に現像剤の機械的ストレスは構成する原材料の性質と加工後の現像剤中でのこれら構成材料の相互作用状態が影響を与えるものである。従って本発明の如き現像剤においては、これらの機械的ストレスに耐えうる物理的特性、たとえば、粘性力や弾性力特性において強靱なことが現像剤の部材融着を防止し、帯電特性を高める上で好ましく、また、このような粘弾特性を達成するためには、化学的観点から分子量やゲル分、充填剤の分散状態等が適切にコントロールされていることが好ましい。
【００７３】
また、本発明の現像剤及び画像形成方法を用いてモノカラー、あるいはフルカラーの画像形成を行う場合は、着色剤を変化させることでイエロー、マゼンタ、シアン、ブラックの現像剤を使用することができる。
【００７４】
着色剤として、従来から広く知られている無機、有機の染料、顔料が使用可能である。具体的には次の様なものが挙げられる。
【００７５】
イエロー用着色顔料の具体例としては、縮合アゾ化合物，イソインドリノン化合物，アンスラキノン化合物，アゾ金属錯体，メチン化合物，アリルアミド化合物に代表される化合物が用いられる。さらに具体的には、Ｃ．Ｉ．ピグメントイエロー１，２，３，４，５，６，７，１０，１１，１２，１３，１４，１５，１６，１７，２３，６５，７３，８３、９３、９４、９５、９７、１０９、１１０、１１１、１２０、１２７、１２８、１２９、１４７、１６８、１７４、１７６、１８０、１８１、１９１、Ｃ．Ｉ．バットイエロー１，３，２０等が挙げられる。また、黄鉛、カドミウムイエロー、ミネラルファストイエロー、ネーブルイエロー、ナフトールイエローＳ、ハンザイエローＧ、パーマネントイエローＮＣＧ、タートラジンレーキなども使用することができる。
【００７６】
マゼンタ用着色顔料の具体例としては、Ｃ．Ｉ．ピグメントレッド１，２，３，４，５，６，７，８，９，１０，１１，１２，１３，１４，１５，１６，１７，１８，１９，２１，２２，２３，３０，３１，３２，３７，３８，３９，４０，４１，４８，４９，５０，５１，５２，５３，５４，５５，５７，５８，６０，６３，６４，６８，８１，８３，８７，８８，８９，９０，１１２，１１４，１２２，１２３，１６３，２０２，２０６，２０７，２０９、Ｃ．Ｉ．ピグメントバイオレット１９、Ｃ．Ｉ．バットレッド１，２，１０，１３，１５，２３，２９，３５等が挙げられる。
【００７７】
さらに染料としては、Ｃ．Ｉ．ソルベントレッド１，３，８，２３，２４，２５，２７，３０，４９，８１，８２，８３，８４，１００，１０９，１２１、Ｃ．Ｉ．ディスパースレッド９、Ｃ．Ｉ．ディスパースバイオレット１等の油溶染料、Ｃ．Ｉ．ベーシックレッド１，２，９，１２，１３，１４，１５，１７，１８，２２，２３，２４，２７，２９，３２，３４，３５，３６，３７，３８，３９，４０等の塩基性染料、Ｃ．Ｉ．アシッドレッド１、Ｃ．Ｉ．ダイレクトレッド１，４、Ｃ．Ｉ．モーダントレッド３０等が挙げられる。
【００７８】
シアン用着色顔料の具体例としては、Ｃ．Ｉ．ピグメントブルー２，３，１５，１６，１７、Ｃ．Ｉ．ベーシックブルー３、５、Ｃ．Ｉ．バットブルー６、Ｃ．Ｉ．ダイレクトブルー１，２、Ｃ．Ｉ．アシッドブルー９，１５，４５、Ｃ．Ｉ．モーダントブルー７、又は銅フタロシアニン顔料等がある。
【００７９】
黒用着色顔料の具体例としては、カーボンブラック、アリニンブラック、アセチレンブラック、オイルブラック等がある。また、色用の着色剤を混合し、黒色着色剤として使用することも可能である。
【００８０】
また、上記着色剤の他に、チタンホワイト、Ｃ．Ｉ．ダイレクトグリーン６、Ｃ．Ｉ．ベーシックグリーン４，６、ピグメントグリーンＢ、マラカイトグリーンレーキ、ファイナルイエローグリーンＧ、クロムグリーン、モリブデンオレンジ、パーマネントオレンジＧＴＲ、ピラゾロンオレンジ、ベンジジンオレンジＧ、Ｃ．Ｉ．ベーシックバイオレット１，３，７，１０，１４，１５，２１，２５，２６，２７，２８、Ｃ．Ｉ．ソルベントバイオレット８，１３，１４，２１，２７、マンガン紫、ファストバイオレットＢ、メチルバイオレットレーキ等を使用して、上記色以外の色現像剤用着色剤として使用することも可能である。
【００８１】
これらは、単独、あるいは組合せて使用することができ、通常、結着樹脂１００質量部に対して、０．１〜６０質量部好ましくは０．５〜２０質量部使用される。
【００８２】
さらに、本発明の現像剤には、定着時の離型性向上のためにワックス成分を含有することが好ましい。ワックス成分としては、具体的に以下の化合物が挙げられる。
【００８３】
例えばシリコーン樹脂、ポリエステル、ポリウレタン、ポリアミド、エポキシ樹脂、ポリビニルブチラール、ロジン、変性ロジン、テルペン樹脂、フェノール樹脂、低分子量ポリエチレン又は低分子量ポリプロピレンの如き脂肪族又は脂環族炭化水素樹脂、芳香族系石油樹脂、塩素化パラフィン、パラフィンワックスなどである。
【００８４】
これらのワックスから、種々の方法によりワックスを分子量により分別したワックスも本発明に好ましく用いられる。また、分別後に酸化やブロック共重合、グラフト変性を行っても良い。
【００８５】
中でも好ましく用いられるワックスは、低分子量ポリプロピレン及びこの副生成物、低分子量ポリエステルおよびエステル系ワックス、脂肪族の誘導体である。
【００８６】
これらのうち、更に好ましいエステルワックスの代表的化合物の例をエステルワックスの一般構造式▲１▼〜▲６▼として以下に示す。
【００８７】
【化１】

（式中、ａ及びｂは０〜４の整数を示し、ａ＋ｂは４であり、Ｒ₁及びＲ₂は炭素数が１〜４０の有機基を示し、且つＲ₁とＲ₂との炭素数差が１０以上である基を示し、ｎ及びｍは０〜１５の整数を示し、ｎとｍが同時に０になることはない。）
【００８８】
【化２】

（式中、ａ及びｂは０〜４の整数を示し、ａ＋ｂは４であり、Ｒ₁は炭素数が１〜４０の有機基を示し、ｎ及びｍは０〜１５の整数を示し、ｎとｍが同時に０になることはない。）
【００８９】
【化３】

（式中、ａ及びｂは０〜３の整数を示し、ａ＋ｂは３以下であり、Ｒ₁及びＲ₂は炭素数が１〜４０の有機基を示し、且つＲ₁とＲ₂との炭素数差が１０以上である基を示し、Ｒ₃は炭素数が１以上の有機基を示し、ｎ及びｍは０〜１５の整数を示し、ｎとｍが同時に０になることはない。）
【００９０】
【化４】
エステルワックスの一般構造式▲４▼
Ｒ₁ＣＯＯＲ₂
（式中、Ｒ₁及びＲ₂は炭素数が１〜４０の炭化水素基を示し、且つＲ₁及びＲ₂は、お互いに同じでも異なる炭素数でもよい。）
【００９１】
【化５】
エステルワックスの一般構造式▲５▼
Ｒ₁ＣＯＯ（ＣＨ₂）_nＯＯＣＲ₂
（式中、Ｒ₁及びＲ₂は炭素数が１〜４０の炭化水素基を示し、ｎは２〜２０の整数であり、且つＲ₁及びＲ₂は、お互いに同じでも異なる炭素数でもよい。）
【００９２】
【化６】
エステルワックスの一般構造式▲６▼
Ｒ₁ＯＯＣ（ＣＨ₂）_nＣＯＯＲ₂
（式中、Ｒ₁及びＲ₂は炭素数が１〜４０の炭化水素基を示し、ｎは２〜２０の整数であり、且つＲ₁及びＲ₂は、お互いに同じでも異なる炭素数でもよい。）
【００９３】
これらのワックスは定着時の離型性向上を達成するために、現像剤１００質量部中に一般的に２〜３０質量部、より好ましくは５〜２０質量部が使用される。ワックス成分が２質量部未満の場合、ワックスとしての離型効果がほとんど発揮できず、また、ワックス成分が３０質量部を超えると、現像剤の離型性は満足されるものの現像剤の現像性が悪化し、現像スリーブや潜像担持体表面に現像剤が融着するといった弊害を生じやすくなるため好ましくない。
【００９４】
本発明に係るワックス成分は、示差走査熱量計により測定されるＤＳＣ曲線において、昇温時に５０〜１２０℃の領域に最大吸熱ピークを示し、該最大吸熱ピークを含む吸熱ピークの始点のオンセット温度が４０℃以上であることが好ましく、特に該最大吸熱ピークのピーク温度と該オンセット温度の温度差が７〜５０℃の範囲であることが好ましい。
【００９５】
上記温度領域に吸熱ピークおよび最大吸熱ピークを有することにより、低温定着に大きく貢献しつつ、離型性をも効果的に発現し、本発明の定着方法とのマッチングが良好なものとなる。該吸熱ピークが５０℃未満に存在すると現像剤の耐高温オフセット性が著しく損なわれ、１２０℃を超えると現像剤の低温定着性が著しく損なわれる。また、該最大吸熱ピークが昇温測定時に５０℃未満、降温測定時に４０℃未満であると、ワックス成分の自己凝集力が弱くなり、結果として耐高温オフセット性が悪化する。一方、該最大吸熱ピークが１２０℃を超えると、定着温度が高くなり低温オフセットが発生しやすくなり好ましくない。
【００９６】
昇温時のＤＳＣ曲線において、上記温度領域で溶融するワックス成分を用いることにより、他の添加剤の分散性を良好なものとすることができると共に、ワックス成分自身を前述の如き分散状態に容易にコントロールすることができる。
【００９７】
これにより現像剤の良好な定着性はもとより、該ワックス成分による離型効果が効果的に発現され、十分な定着領域が確保されると共に、従来から知られるワックス成分による現像性、耐ブロッキング性や画像形成装置への悪影響が排除されるのでこれらの特性が格段に向上する。特に粒子形状が球形化するに従い、現像剤の比表面積は減少していくので、ワックス成分の分散状態をコントロールすることは、非常に効果的なものとなる。
【００９８】
本発明は、現像部分での帯電付与性が特徴であるが、このような特徴を発現するためには、荷電制御剤を適宜使用することが好ましい。荷電制御剤としては本発明の効果が得られるものなら特に限定するものではなく、公知の荷電制御剤が使用できる。
【００９９】
現像剤を負荷電性に制御するものの例として下記物質がある。例えば、有機金属化合物、キレート化合物が有効であり、具体的には、モノアゾ金属化合物、アセチルアセトン金属化合物、芳香族ハイドロキシカルボン酸、芳香族ダイカルボン酸系の金属化合物がある。他には、芳香族ハイドロキシカルボン酸、芳香族モノ及びポリカルボン酸及びその金属塩、無水物、エステル類、ビスフェノール等のフェノール誘導体類などがある。また、尿素誘導体、含金属サリチル酸系化合物、含金属ナフトエ酸系化合物、ホウ素化合物、４級アンモニウム塩、カリックスアレーン、ケイ素化合物、スチレン−アクリル酸共重合体、スチレン−メタクリル酸共重合体、スチレン−アクリル−スルホン酸共重合体、ノンメタルカルボン酸系化合物等が挙げられる。
【０１００】
現像剤を正荷電性に制御するものの具体例として下記物質がある。例えば、ニグロシン及び脂肪酸金属塩等による変性物、グアニジン化合物、イミダゾール化合物、トリブチルベンジルアンモニウム−１−ヒドロキシ−４−ナフトスルホン酸塩、テトラブチルアンモニウムテトラフルオロボレートなどの４級アンモニウム塩、及びこれらの類似体であるホスホニウム塩等のオニウム塩及びこれらのレーキ顔料、トリフェニルメタン染料及びこれらのレーキ顔料（レーキ化剤としては、りんタングステン酸、りんモリブデン酸、りんタングステンモリブデン酸、タンニン酸、ラウリン酸、没食子酸、フェリシアン化物、フェロシアン化物など）、高級脂肪酸の金属塩；ジブチルスズオキサイド、ジオクチルスズオキサイド、ジシクロヘキシルスズオキサイドなどのジオルガノスズオキサイド；ジブチルスズボレート、ジオクチルスズボレート、ジシクロヘキシルスズボレートなどのジオルガノスズボレート類；これらを単独で或は２種類以上組合せて用いることができる。これらの中でも、ニグロシン系、４級アンモニウム塩の如き荷電制御剤が特に好ましく用いられる。
【０１０１】
本発明の特徴の一つである金属酸化物微粒子について説明する。本発明は着色粒子表面に、少なくとも２種以上の金属酸化物微粒子を有する非磁性の一成分現像剤であり、該金属酸化物微粒子の少なくとも一種が該着色粒子と同極に帯電する疎水性シリカ微粒子であり、さらに他の外添剤のうち少なくとも１種が該着色粒子に対して逆極性に帯電する粒子であることを特徴とするものである。
【０１０２】
ここで、第一の外添剤である疎水性シリカ粒子としては、たとえば、ＢＥＴ法で測定した窒素吸着による比表面積が２０ｍ²／ｇ以上が好ましく、更に３０〜４００ｍ²／ｇの範囲内のものがより良好な結果を与える。
【０１０３】
該シリカ微粉末は、必要に応じ、疎水化及び帯電性コントロールの目的で、シリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シランカップリング剤、官能基を有するシランカップリング剤、その他の有機ケイ素化合物の如き処理剤で処理することが好ましい。所望の効果を得る目的でこれらの処理剤は単体でも、混合して使用しても良い。また、上記の如き表面処理を行った後に後処理として、加熱処理などの補助的表面処理や、粉砕処理等の物理的処理を行うことが好ましい。
【０１０４】
本発明のトナーに用いられる該疎水性シリカ微粒子の量は、帯電性及び現像安定性の観点から、着色粒子１００質量部に対し０．０１〜５．０質量部が好ましく、より好ましくは０．１〜４．０質量部、さらに好ましくは０．５〜３．０質量部である。該疎水性シリカ微粒子の量が０．０１質量部を下回る場合は、現像部での静電潜像担持体表面への現像剤の融着や、流動性阻害による転写性悪化や、帯電部での撹拌不良によるカブリ悪化等のため好ましくない。
【０１０５】
一方、該疎水性シリカ微粒子の量が５．０質量部を超える場合、静電潜像担持体表面や現像剤担持体表面へのトナー汚染が生じやすくなり、画像の連続印字において、静電潜像担持体表面への融着や現像剤担持体の下層汚染を生じることにより、潜像担持体への融着などの現像弊害を生じるため好ましくない。
【０１０６】
さらに、本発明は、該疎水性シリカ微粒子に対し逆極性に帯電する粒子を含有することが好ましい。かかる粒子が逆極性に帯電する粒子であるか否かの判断は、原材料ならば、溶融混練粉砕法を用いて帯電粒子を適当な樹脂中にモデル的に混練し、粉砕、分級を行ったものを公知の傾斜帯電測定器あるいは、鉄粉キャリア等の二成分現像方法に使用するキャリアと混合後、公知の二成分帯電量測定装置の如き測定器によって測定することで原材料同士の帯電量が測定可能である。
【０１０７】
更に、別途、着色粒子自体の帯電量測定を同様の方法で行い着色粒子の帯電量を得ることが可能である。
【０１０８】
ここで疎水性シリカ粒子と第２の外添剤粒子、さらに組合せる着色粒子自体の帯電量測定結果の値を並べたときに、着色粒子の帯電量を挟んで前後にこれらの外添剤がくるような下記の関係
（疎水性シリカ粒子）＞（着色粒子の帯電量）＞（第２の外添剤粒子の帯電量）
あるいは
（第２の外添剤粒子の帯電量）＞（着色粒子の帯電量）＞（疎水性シリカ粒子）
なる関係を満たすものが、本願の言及する「一種が該着色粒子と同極に帯電する疎水性シリカ微粒子であり、さらに第２の外添剤が該着色粒子に対して逆極性に帯電する粒子」であると定義するものである。
【０１０９】
また、上記関係の中に第３の外添剤を含むものについても上記関係に当てはまるものであるならば、本願の定義が適用できる。
【０１１０】
また、該着色粒子に対し逆極性に帯電する粒子が現像剤中に含まれる場合、現像前後の静電潜像担持体表面に残留する粒子の成分から「逆極性に帯電する粒子」の存在を確認することができる。「逆極性に帯電する粒子」は一般的に転写バイアスで転写材上に転写されにくいものである。これは、現像剤の帯電特性と一般的な疎水性シリカが同極性の帯電状態にあるのに対して、「逆極性に帯電する粒子」は転写時の挙動が現像剤や疎水性シリカと異なり、静電潜像担持体上に残留しやすい傾向がある。そこで、現像剤中の外添剤量と転写後の静電潜像担持体上に残留する外添剤量を比較することで、第２の外添剤が「該着色粒子に対し逆極性に帯電する粒子」であるかどうか判断することができる。
【０１１１】
この場合の判断をするために、定量化を行う必要があるが、定量化して判断するために、第１の外添剤と第２の外添剤の元素や粒子径の差を利用する方法として、たとえば、横河電気社製のパーティクルアナライザーＰＴ１０００の如き微少元素分析計を用いる方法や、電子顕微鏡と２次電子元素分析装置（ＥＤＡＸ）を併用する方法、また、第１の外添剤と第２の外添剤の結晶構造の違いや屈折率の違いを利用する方法として、レーザ回折型の粒度分布計を使用し、その屈折率の違いから２種の外添剤量を定量化する方法がある。
【０１１２】
原材料として、疎水性シリカ微粒子と、疎水性シリカ微粒子に対し逆極性に帯電する粒子を外添処理した現像剤を本願記載の画像形成方法にて画像出力を行ったところ、現像前後の静電潜像担持体表面に残留する粒子の成分から「該着色粒子に対し逆極性に帯電する粒子」の存在を確認することができ、現像剤中に含まれる２種以上の外添剤粒子の極性関係を検証することが可能であることがわかった。
【０１１３】
さらに、転写後の該静電潜像担持体表面に該金属酸化物微粒子のうち少なくとも一つが現像剤組成の１．３〜１０倍の比率で残留するような状態がカブリと画像品質を両立する上で好ましい。転写後の該静電潜像担持体表面に該金属酸化物微粒子のうち少なくとも一つが現像剤組成の１．３倍未満のような系では、摺擦での帯電付与効果が弱くなり、本発明の効果を得られない。また、１０倍超では、クリーニングや帯電といった転写後のプロセスに対して負荷が大きくなり、例えば、クリーニング不良や帯電不良を併発し、現像スジの要因となるため好ましくない。
【０１１４】
本発明の現像剤においては、帯電安定性、現像性、流動性、耐久性向上の目的で、第１の外添剤として疎水化シリカ微粉末が使用できる。
【０１１５】
疎水化処理を行うシリカ微粉末母体としては、特に限定するものではなく公知のシリカが使用できるが、疎水化処理後のシリカ微粉末の特性として、ＢＥＴ法で測定した窒素吸着による比表面積が２０ｍ²／ｇ以上（特に３０〜４００ｍ²／ｇの範囲内）のものが現像性、流動性の点で好ましい。
【０１１６】
また、疎水化剤の具体例としては、シリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シランカップリング剤、官能基を有するシランカップリング剤、その他の有機ケイ素化合物が挙げられる。これらの処理剤は単独でもあるいは混合して使用しても良い。
【０１１７】
これらのシリカ微粉末を疎水化する方法は、公知の製造方法により行うことが可能である。なお、疎水化シリカ微粉末の疎水化の程度（疎水化度）としては、メタノール／水混合溶媒系で濡れ性が９０％以上であることが本願の目的から好ましい。
【０１１８】
また、疎水化シリカ微粉末の使用量としては、現像剤粒子１００質量部に対してシリカ微粉体０．０１〜８質量部、好ましくは０．１〜５質量部使用するのが良い。
【０１１９】
シリコーンオイル処理された無機微粉体があり、具体的な例としては、シリコーンオイル処理により疎水化したシリカ微粉末、シリコーンオイル処理により疎水化した酸化チタン、シリコーンオイル処理により疎水化したアルミナなどが挙げられる。
【０１２０】
本発明で好適に使用できる第２の外添剤としては以下のような公知の無機粉体中で本願の範囲を満たすものであれば特に限定するものではない。第２の外添剤として具体的には、マグネシウム、亜鉛、アルミニウム、セリウム、コバルト、鉄、ジルコニウム、クロム、マンガン、ストロンチウム、錫、アンチモンの如き金属の酸化物；チタン酸カルシウム、チタン酸マグネシウム、チタン酸ストロンチウムの如き複合金属酸化物；炭酸カルシウム、炭酸マグネシウム、炭酸アルミニウムの如き金属塩；カオリンの如き粘土鉱物；アパタイトの如きリン酸化合物；炭化ケイ素、窒化ケイ素の如きケイ素化合物；カーボンブラックやグラファイトの如き炭素粉末などのもので、「該着色粒子に対し逆極性に帯電する粒子」であれば使用できる。
【０１２１】
これらのなかでも、マグネシウムあるいはチタンを含有する微粉体が好ましく、具体的にはハイドロタルサイト類やチタニア類、特にルチル型酸化チタンが好ましく、適宜、表面処理することで「該着色粒子に対し逆極性に帯電する粒子」とすることもより好ましい。
【０１２２】
本発明の現像剤においては、現像部分での帯電安定性、現像剤の耐久性の観点から、現像剤形状を制御することが好ましい。
【０１２３】
本発明の現像剤における形状の範囲としては、フロー式粒子像測定装置で計測される現像剤の個数基準の円相当径−円形度スキャッタグラムにおいて、該現像剤の平均円形度が０．９５０〜０．９９０であり、且つ、円形度標準偏差が０．０４０未満であることがより好ましい結果を得られる。
【０１２４】
現像剤の平均円形度が０．９５０未満の現像剤とは、形状が球形から離れて不定形に近づいた現像剤を意味する。このような不定形の現像剤は、現像ニップ内での帯電付与能が低下する。これは不定形のために現像ニップ部で現像剤の転がりが悪く、所期の摺擦がなされないことによるものであると考えられる。
【０１２５】
現像剤の平均円形度が０．９９０を上回る現像剤とは、形状がより真球状に近い現像剤を意味する。このような真球状に近い現像剤は、帯電性や転写性に優れるものの、一般にブレードクリーニングのごときクリーニング手段によるクリーニング不良が発生しやすくなり、現像後に潜像担持体上に残留した残現像剤をブレードクリーニング機構で除去しにくくなるため、その結果、クリーニング不良による画像欠陥や、帯電・露光妨害による画像欠陥を生じるといった現像上不都合な現象を生じやすくなるため好ましくない。
【０１２６】
現像剤の円形度標準偏差が０．０４０以上の現像剤とは、形状にバラツキが多い現像剤を意味する。このような現像剤は、ブレードクリーニングに関しては良いが、帯電均一性に関して問題があり、このような現像剤を用いた場合は帯電が不均一なことにより、例えば、画像カブリを生じるため問題がある。
【０１２７】
本発明における現像剤の円相当径、円形度及びそれらの頻度分布とは、現像剤粒子の形状を定量的に表現する簡便な方法として用いたものであり、本発明ではフロー式粒子像測定装置ＦＰＩＡ−１０００型（東亜医用電子社製）を用いて測定を行ない、下式を用いて算出した。
【０１２８】
【数２】

【０１２９】
ここで、「粒子投影面積」とは二値化された現像剤粒子像の面積であり、「粒子投影像の周囲長」とは該現像剤粒子像のエッジ点を結んで得られる輪郭線の長さと定義する。
【０１３０】
本発明における円形度は現像剤粒子の凹凸の度合いを示す指標であり、現像剤粒子が完全な球形の場合に１．００を示し、表面形状が複雑になる程、円形度は小さな値となる。
【０１３１】
本発明において、現像剤の個数基準の粒径頻度分布の平均値を意味する円相当個数平均粒子径Ｄ１と粒径標準偏差ＳＤｄは、粒度分布の分割点ｉでの粒径（中心値）をｄｉ、頻度をｆ_iとすると次式から算出される。
【０１３２】
【数３】

【０１３３】
また、円形度頻度分布の平均値を意味する平均円形度と円形度標準偏差ＳＤｃは、粒度分布の分訊点ｉでの円形度（中心値）をｃｉ，頻度をｆｃｉとすると、次式から算出される。
【０１３４】
【数４】

【０１３５】
また、本発明での粒度分布は、コールターマルチサイザーで測定するところの該現像剤の粒度分布において、５μｍ以下の粒径を有する現像剤粒子が１６〜５０個数％含有され、８〜１２．７μｍの粒径を有する現像剤粒子が１〜３０個数％含有され、１６μｍ以上の粒径を有する現像剤粒子が１．５体積％以下含有される一成分現像剤であることが好ましい。
【０１３６】
現像剤中の５μｍ以下の粒径を有する現像剤粒子が１６個数％未満では、本発明の効果である現像剤のカブリ、及びドット抜けが悪化するため好ましくない。また、現像剤中の５μｍ以下の粒径を有する現像剤粒子が５０個数％超含有される場合は、現像剤の規制部材への融着に由来するところの現像スジが発生するために好ましくない。さらに、このような現像剤を達成するためには、８〜１２．７μｍの粒径を有する現像剤粒子が１〜３０個数％含有される系が上記のごとき現像剤をさらに安定化するために良好であり、また、さらに、１６μｍ以上の粒径を有する現像剤粒子の量は１．５体積％以下含有されることで、現像スジの発生をさらに抑制することが可能となる。
【０１３７】
現像剤の平均粒径及び粒度分布はコールターカウンターＴＡ−ＩＩ型あるいはコールターマルチサイザー（コールター社製）等種々の方法で測定可能であるが、本発明においてはコールターカウンターＴＡ−ＩＩ型（コールター社製）を用い、個数分布、体積分布を出力するインターフェイス（日科機製）及びＰＣ９８０１パーソナルコンピューター（ＮＥＣ製）を接続し、電解液は１級塩化ナトリウムを用いて１％ＮａＣｌ水溶液を調整する。たとえば、ＩＳＯＴＯＮ Ｒ−ＩＩ（コールターサイエンティフィックジャパン社製）が使用できる。測定法としては、前記電解水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤、好ましくはアルキルベンゼンスルフォン酸塩を０．１〜５ｍｌ加え、更に測定試料を２〜２０ｍｇ加える。試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行ない前記コールターカウンターＴＡ−ＩＩ型によりアパーチャーとして１００μｍアパーチャーを用いて、２μｍ以上のトナーの体積、個数を測定して体積分布と個数分布とを算出した。
【０１３８】
【実施例】
静電潜像担持体の製造例（１）
以下の方法により、本実施例に用いる、アルミニウムシリンダー／導電層／下引層／電荷発生層／電荷輸送層／表面保護層からなる負帯電極性のＯＰＣ静電潜像担持体を作製した。
【０１３９】
（ｉ）導電層の作製
外径３０ｍｍ、長さ３５７．５ｍｍのアルミニウムシリンダーに、
導電性酸化チタン ・・・・・１０質量部
（酸化スズコート、数平均粒径０．４μｍ）
フェノール樹脂前駆体（レゾール型） ・・・・・１０質量部
メタノール ・・・・・１０質量部
ブタノール ・・・・・１０質量部
をサンドミル分散して得られる分散液を浸漬塗布し、１４０℃で硬化することで、体積抵抗５×１０⁹Ω・ｃｍ、厚さ２０μｍの導電層を設けた。
【０１４０】

を混合溶解した後に、前記導電層上に浸漬塗布し、１μｍの下引層を設けた。
【０１４１】
（ｉｉｉ）電荷発生層の作製
次に、ＣｕＫαのＸ線回折における回折角２θ±０．２°が、９．０°、１４．２°、２３．９°および２７．１°に強いピークを有するＴｉＯＰｃ（オキシチタニウムフタロシアニン）４質量部とポリビニルブチラール（商品名：エスレックＢＭ２、積水化学製）２質量部およびシクロヘキサノン６０質量部をφ１ｍｍガラスビーズを用いたサンドミル装置で４時間分散した後、エチルアセテート１００質量部を加えて電荷発生層用分散液を調整した。これを上記で得られた下引層上に浸漬塗布し、０．３μｍの電荷発生層を設けた。
【０１４２】
（ｉｖ）電荷輸送層の作製
トリフェニルアミン ・・・・・１０質量部
ポリアリレート樹脂（重量平均分子量１５００００） ・・・・・１０質量部
モノクロロベンゼン ・・・・・５０質量部
ジクロロメタン ・・・・・１５質量部
を撹拌混合した後、前記電荷発生層上に浸漬塗布し、２０μｍの電荷輸送層を設けた。
【０１４３】
（ｖ）表面保護層の作製
次に、下記アクリル系モノマー ・・・・・３０質量部
【０１４４】
【化７】

分散前の数平均粒径が４０ｎｍの酸化スズ超微粒子 ・・・・・５０質量部
光重合開始剤として２−メチルチオキサンソン ・・・・・１８質量部
エタノール ・・・・１５０質量部
をサンドミルにて６６時間分散した。この調合液を、先の電荷輸送層上に浸漬塗布して、高圧水銀灯にて２００Ｗ／ｃｍ²の光強度で、６０秒間の光硬化を行い、その後１２０℃、２時間熱風乾燥して表面保護層を得た。得られた表面保護層の膜厚は３μｍであった。この静電潜像担持体を静電潜像担持体Ａとして、以下の電子写真画像形成装置の製造に用いた。
【０１４５】
この様にして作製した表面保護層について、静電潜像担持体を回転させ、そこに富士フィルム製＃Ｃ−２０００ラッピングテープを接触させながら圧をかけることで、０．２μｍの研磨を行った。表面保護層研磨後の静電潜像担持体を静電潜像担持体Ａ’とする。
【０１４６】
（ｖｉ）表面特性の測定
このようにして得られた静電潜像担持体Ａ’について、表面の皮膜物性試験を行った。また、表面摩擦係数および純水との接触角の測定を前述の方法で行った。
【０１４７】
結果は、表面摩擦係数が０．８０であり、ユニバーサル硬さＨＵが３００Ｎ／ｍｍ²であった。
【０１４８】
静電潜像担持体の製造例（２）
静電潜像担持体の製造例（１）で「（ｖ）表面保護層の作製」工程を省略し、且つ、０．１μｍの研磨を行う他は静電潜像担持体の製造例（１）と同様の方法で、静電潜像担持体Ｂ’を得た。
【０１４９】
このようにして得られた静電潜像担持体Ｂ’について、各測定を行ったところ、表面摩擦係数が０．７、ユニバーサル硬さＨＵが２９０Ｎ／ｍｍ²であった。
【０１５０】
静電潜像担持体の製造例（３）
静電潜像担持体の製造例（２）で０．５μｍの研磨を行うことに変えた他は静電潜像担持体の製造例（２）と同様にして、静電潜像担持体Ｃ’を得た。
【０１５１】
このようにして得られた静電潜像担持体Ｃ’について、各測定を行ったところ、表面摩擦係数が１．１、ユニバーサル硬さＨＵが２９０Ｎ／ｍｍ²であった。
【０１５２】
静電潜像担持体の製造例（４）
（１）静電潜像担持体Ｂの製造および表面特性の測定
外径３０ｍｍ、長さ３５７．５ｍｍのアルミニウムシリンダー上に、導電層、下引層、電荷発生層および電荷輸送層を順次作製するまでは製造例（１）と同様に行った。次いで、前記電荷輸送層上への表面保護層の作製は下記の要領にて行った。すなわち、
下記アクリル系モノマー ・・・・・１０質量部
【０１５３】
【化８】

をサンドミルにて６６時間分散した。この調合液を、先の電荷輸送層上に浸漬塗布して、高圧水銀灯にて１５０Ｗ／ｃｍ²の光強度で、８０秒間の光硬化を行い、その後１２０℃、１時間熱風乾燥して表面保護層を得た。得られた表面保護層の膜厚は４μｍであった。この静電潜像担持体を静電潜像担持体Ｄとして、以下の電子写真画像形成装置の製造に用いた。
【０１５４】
この様にして作製した表面保護層について、静電潜像担持体を回転させ、そこに富士フィルム製＃Ｃ−２０００ラッピングテープを接触させながら圧をかけることで、０．３μｍの研磨を行った。表面保護層研磨後の静電潜像担持体を静電潜像担持体Ｄ’とする。
【０１５５】
このようにして得られた静電潜像担持体Ｄ’について、各測定を行ったところ、表面摩擦係数が０．４、ユニバーサル硬さＨＵが２８０Ｎ／ｍｍ²であった。
【０１５６】
静電潜像担持体の製造例（５）
静電潜像担持体の製造例（２）で使用したポリアリレートの粘度平均分子量を５０００に変えた他は静電潜像担持体の製造例（２）と同様にして静電潜像担持体を静電潜像担持体Ｅを得た。この静電潜像担持体Ｅを研磨し、研磨後の静電潜像担持体Ｅ’について、各測定を行ったところ、表面摩擦係数が１．４、ユニバーサル硬さＨＵが３１０Ｎ／ｍｍ²であった。
【０１５７】
静電潜像担持体の製造例で製造した静電潜像担持体の内容と表面特性を表１にまとめる。
【０１５８】
【表１】

【０１５９】
外添剤
本実施例で使用した外添剤を以下にまとめる。さらに、これらの外添剤について、その帯電特性を測定する目的で、スチレン−アクリル酸ブチル−マレイン酸ブチルハーフエステル共重合体（ピーク分子量：約２００００）１００質量部に対して、以下の外添剤を２０質量部混合し溶融混練し、冷却後粉砕、分級して一定の粒度に調整したものについて、鉄粉キャリア（ＥＦＶ）と混合し、図６に示した二成分帯電量測定装置にて帯電量を測定した。これらの結果を以下にまとめる。
【０１６０】
【表２】

【０１６１】
現像剤の製造例（１）
高速撹拌装置ＴＫ−ホモミキサーを具備した２リットル用四つ口フラスコ中に、イオン交換水７１０質量部と０．１ｍｏｌ／Ｌ−Ｎａ₃ＰＯ₄水溶液４５０質量部を添加し、回転数を７０００ｒｐｍに調整し、６０℃に加温せしめた。ここに１．０ｍｏｌ／Ｌ−ＣａＣｌ₂水溶液６８質量部を徐々に添加し、微小な難水溶性分散剤Ｃａ₃（ＰＯ₄）₂を含む水系分散媒体を調製した。
【０１６２】
一方、
・スチレン単量体 ８０質量部
・２−エチルヘキシルアクリレート単量体 ２０質量部
・ポリエステル １０質量部
（酸価２０ｍｇＫＯＨ／ｇ、ピーク分子量７５００）
・カーボンブラック（一次粒子径４４ｎｍ） １０質量部
・エステルワックスＮｏ．４ １０質量部
（Ｒ₁、Ｒ₂：Ｃ₁₈Ｈ₃₇）
・モノアゾクロム錯体 １質量部
上記材料をボールミルを用い充分に分散させた後、ボールミルより内容物を単離した。この内容物に対して、重合開始剤である２，２’−アゾビス（２，４−ジメチルブチロニトリル）３質量部を添加した重合性単量体組成物を、前記水系分散媒体中に投入し回転数７０００ｒｐｍを維持しつつ造粒した。その後、パドル撹拌翼で撹拌しつつ６０℃で４時間反応させた後、８０℃で５時間重合させ、更に８５℃で減圧し蒸留し、反応を終了させた。
【０１６３】
反応終了後、懸濁液を冷却し、塩酸を加えて難水溶性分散剤Ｃａ₃（ＰＯ₄）₂を溶解し、濾過、水洗、乾燥した後に風力分級によって所望の粒度に分級し、着色剤粒子（１）を得た。得られた着色剤粒子（１）を鉄粉キャリアと混合し、二成分帯電量測定装置にて帯電量を測定したところ−４５ｍＣ／ｋｇであった。
【０１６４】
続いて、該着色粒子１００質量部対して、外添剤（１）を１．５質量部と外添剤（３）を０．２質量部とをヘンシェルミキサーで高速撹拌し、該着色粒子の表面を処理することで本発明の現像剤（１）を調製した。
【０１６５】
現像剤（１）において、着色剤粒子、外添剤（１）、外添剤（３）のそれぞれの帯電量は
着色剤粒子（１）＝−４５ｍＣ／ｋｇ
外添剤（１）＝−８０ｍＣ／ｋｇ
外添剤（３）＝＋１０ｍＣ／ｋｇ
であり、外添剤（１）及び着色剤粒子（１）に対し、外添剤（３）は逆極性に帯電しているものである。
【０１６６】
このように、着色粒子と同極で帯電量の高い疎水性シリカと、逆極に帯電する外添剤の２種類を組合せて外添を行い、現像剤を作製した場合、本願の示すところの「該着色粒子表面に、少なくとも２種以上の金属酸化物微粒子を有する非磁性の一成分現像剤であり、該金属酸化物微粒子の少なくとも一種が該着色粒子と同極に帯電する疎水性シリカ微粒子であり、さらに他の外添剤のうち少なくとも１種が該着色粒子に対して逆極性に帯電する粒子」になる。
【０１６７】
現像剤の製造例（２）〜（４）
表３に示す処方のみ変更する他は現像剤の製造例（１）同様の方法で、現像剤（２）〜（４）を製造した。
【０１６８】
現像剤の製造例（５）
着色剤粒子の製造方法を以下に示す溶融粉砕法により行った。具体的な製造方法としては、
まず下記材料をヘンシェルミキサー（ＦＭ−７５型、三井三池化工機（株）製）で混合した。
・スチレン−アクリル酸ブチル−マレイン酸ブチルハーフエステル共重合体
（ピーク分子量：約４００００、ガラス転移点Ｔｇ：６３℃） １００質量部
・カーボンブラック（一次粒子径４０ｎｍ） １０質量部
・ジカルボン酸アルミ錯体 ２質量部
・ポリエチレン ５質量部
（分子量分布＝１．０８、ＤＳＣ吸熱ピーク：１０７℃）
【０１６９】
続いて、スクリュー押し出し混練機のスクリュー最後尾側のニーディング部におけるバレル部設定温度をＴ０（℃）＝１１０℃、溶融混練機排出口温度Ｔ１＝１５０℃になるように二軸混練機（ＰＣＭ−３０型、池貝鉄工（株）製）で混練した。得られた混練物を冷却し、ハンマーミルにて１ｍｍ以下に粗粉砕し、トナー粗砕物を得た。次に、該粗砕物を衝突式気流粉砕機で微粉砕した後、機械的衝撃力を利用する表面改質装置を用いて球形化処理を行い、球形の粉砕原料を得た。次に、得られた粉砕原料を、多分割分級装置エルボジェット分級装置（日鉄鉱業製）に導入し、所望の粒度分布になるよう分級操作して着色粒子（５）を得た。得られた着色剤粒子（５）を鉄粉キャリアと混合し、二成分帯電量測定装置にて帯電量を測定したところ−４０ｍＣ／ｋｇであった。
【０１７０】
続いて、該着色粒子１００質量部対して、外添剤（２）を１．３質量部と外添剤（８）を０．２質量部と、さらに外添剤（７）を０．２質量部をヘンシェルミキサーで高速撹拌し、該着色粒子の表面を処理することで本発明の現像剤（５）を調製した。
【０１７１】
現像剤の製造例（６）〜（８）
表３に示す処方のみ変更する他は現像剤の製造例（５）同様の方法で、現像剤（６）〜（８）を製造した。
【０１７２】
現像剤の製造例（９）
現像剤の製造例（５）において、機械的衝撃力を利用する表面改質装置を用いて球形化処理を行う工程を省き、且つ、分級条件を操作した他は現像剤の製造例（５）と同様の方法で、現像剤（９）を製造した。
【０１７３】
現像剤の比較製造例（１）
現像剤の製造例（５）において、表３に示す処方に変更し、且つ、分級条件を操作して着色粒子を得た。この着色粒子を鉄粉キャリアと混合し、二成分帯電量測定装置にて帯電量を測定したところ−４５ｍＣ／ｋｇであった。この着色粒子に対して、外添剤（１）を１．５質量部と外添剤（７）を０．３質量部、用いて表面処理することで比較現像剤（１）を調製した。
【０１７４】
現像剤の比較製造例（２）
現像剤の製造例（９）において、表３に示す処方に変更し、且つ、分級条件を操作して着色粒子を得た。この着色粒子を鉄粉キャリアと混合し、二成分帯電量測定装置にて帯電量を測定したところ−４０ｍＣ／ｋｇであった。この着色粒子に対して、外添剤（２）を１．５質量部と外添剤（９）を０．３質量部と外添剤（７）を０．１質量部、用いて表面処理することで比較現像剤（２）を調製した。
【０１７５】
現像剤の比較製造例（３）
現像剤の比較製造例（２）で作製した着色粒子に対して、外添剤（２）を１．７質量部、用いて表面処理することで比較現像剤（３）を調製した。
【０１７６】
以上合成した現像剤を表３にまとめる。
【０１７７】
【表３】

【０１７８】
現像装置例（１）
次に、本実施例で使用する現像装置について、具体的に説明する。
【０１７９】
図１は、本実施例で使用した一成分接触現像方式の電子写真プロセスを利用した６００ｄｐｉレーザービームプリンタ（キヤノン製：ＬＢＰ−８６０）改造機の概略図である。本実施例では以下の（ａ）〜（ｈ）の部分を改造した装置を使用した。
（ａ）プロセススピードを１２９ｍｍ／ｓに変更した。
（ｂ）装置の帯電方式をゴムローラ当接による直接帯電とし、印加電圧を直流成分とした。
（ｃ）現像剤担持体をカーボンブラックを分散したシリコーンゴムからなる中抵抗ゴムローラ（１６φ、硬度ＡＳＫＥＲ Ｃ４５度、抵抗１０⁵Ω・ｃｍ、Ｒａ＝２．１μｍ、Ｒｚ＝３．５μｍ）に変更し、静電潜像担持体にニップ幅３．０ｍｍで圧接するよう配置した。
（ｄ）該現像剤担持体の回転周速は、静電潜像担持体との接触部分において順方向であり、該静電潜像担持体に対する該現像剤担持体の相対速度が１５５％の速度になるよう調整した。
（ｅ）静電潜像担持体を静電潜像担持体Ａ’とした。
（ｆ）現像剤担持体に現像剤を塗布する手段として、現像器内に塗布ローラを設け、該現像剤担持体に当接させた。
（ｇ）厚さ０．５ｍｍのリン青銅表面に、溶剤希釈したウレタンをディッピング加工したブレードを、現像剤担持体との接触圧が線圧約２９．６Ｎ／ｍ（約３０ｇ／ｃｍ）となるように取付けた。
（ｈ）現像時の印加電圧をＤＣ成分のみとした。
（ｊ）静電潜像担持体上のクリーニングブレードの当接圧が線圧約３９．２Ｎ／ｍ（約４０ｇ／ｃｍ）となるように取付けた。
【０１８０】
これらのプロセスカートリッジの改造に適合するよう電子写真装置に以下のように改造及びプロセス条件設定を行った。
【０１８１】
改造された装置はローラ帯電器（直流のみを印加）を用い像担持体を一様に帯電する。帯電に次いで、レーザ光で画像部分を露光することにより静電潜像を形成し、現像剤により可視画像とした後に、電圧を＋７００Ｖ印加したローラにより現像剤像を転写材に転写するプロセスを持つ。概略を図１に示した。
【０１８２】
（ｋ）静電潜像担持体を、静電潜像担持体の製造例（１）の静電潜像担持体に交換した。
【０１８３】
（ｍ）静電潜像担持体帯電電位を、暗部電位が−７００Ｖ、明部電位を−１００Ｖとなるよう帯電電圧を調整した。
【０１８４】
現像装置例（２）〜（５）
現像装置例（１）において、（ｅ）静電潜像担持体を静電潜像担持体Ｂ’〜Ｅ’とした点以外は、同様にして現像装置例（２）〜（５）を準備した。
【０１８５】
現像装置例（６）
現像装置例（１）において、（ｄ）現像剤担持体の回転周速を該静電潜像担持体に対する該現像剤担持体の相対速度が１１０％の速度になるよう調整する点以外は、同様にして現像装置例（６）を準備した。
【０１８６】
現像装置例（７）
現像装置例（１）において、（ｄ）現像剤担持体の回転周速を該静電潜像担持体に対する該現像剤担持体の相対速度が２６０％の速度になるよう調整する点以外は、同様にして現像装置例（７）を準備した。
【０１８７】
現像装置例（８）
本例では、現像装置例（１）で使用した６００ｄｐｉレーザービームプリンタ（キヤノン製：ＬＢＰ−８６０）改造機に変えて、中間転写体を有する非磁性一成分のフルカラー画像形成装置である６００ｄｐｉカラーレーザービームプリンタ改造機を使用した。
【０１８８】
本例の基本的な構成を図２に示す。
【０１８９】
本画像形成方法は、静電潜像担持体１上に顕像化された画像を着脱可能なクリーニング装置１０を有する中間転写体５上に各色の現像剤を順次重ねて転写していくことによって、中間転写体５上に４色の画像を形成した後、記録材Ｐ上に一括転写し、定着することによって定着画像を得るものである。
【０１９０】
図２に示す装置システムにおいて、現像器４−１、４−２、４−３、４−４に、それぞれブラック、イエロー、マゼンタ、及びシアン現像剤が導入される。
【０１９１】
現像装置例（１）から以下の点を変更した。
（ａ）プロセススピードを９４ｍｍ／ｓに変更した。
（ｊ）静電潜像担持体１上のクリーニングブレード８の当接圧を線圧約３９．２Ｎ／ｍ（約４０ｇ／ｃｍ）となるようにし、クリーニングブレード１０を着脱式とした。
【０１９２】
実施例（１）〜（８）、参考例（１）及び、比較実施例（１）〜（３）
画像形成装置として現像装置例（１）を、現像剤として現像剤（１）〜（９）、比較現像例（１）〜（３）のそれぞれを用いて、２３℃、１５％の環境下でＡ４サイズの用紙に横線パターン画像を連続して８０００枚耐久した。
【０１９３】
実施例（１）〜（８）、参考例（１）及び、比較実施例（１）〜（３）のプリントアウト評価結果を表４にまとめる（評価の詳細は後述）。
【０１９４】
さらに、実施例（２）について、現像剤中の外添剤量と転写後の静電潜像担持体上に残留する外添剤量をＳＥＭ及び、ＥＤＡＸで定量した。実施例（２）で使用した外添剤（１）、及び外添剤（４）はその組成比も粒子径も異なることから、両者を容易に判別することができる。その結果、現像剤中の外添剤に含まれる外添剤（１）と外添剤（４）の比に対して、転写後の静電潜像担持体上に残留する成分中の外添剤（１）と外添剤（４）の比は、明らかにその比率が異なり、転写後の静電潜像担持体上には選択的に外添剤（４）が多く残留していた。このことから、このような現像系で、実施例（２）のよう現像剤の組合せを出力した場合は、転写後の静電潜像担持体上に、着色粒子に対し逆極性に帯電する粒子が含まれていることが検証できるものとなる。
【０１９５】
ここで、実施例（１）〜（８）、参考例（１）が良好な性能を発揮したが、これは、着色粒子と同極に帯電する疎水性シリカ微粒子と、着色粒子と逆極性に帯電する外添剤の組合せが適切であり、現像装置例（１）において現像剤に適切な帯電付与を行ったために、本発明の効果であるところの現像剤の融着や現像性が向上したものである。また、現像剤が適切な粒度分布及び粒子形状を有することで、さらに本発明の効果が顕著に現れることが明らかになった。これは、現像剤の粒度分布及び粒子形状が本発明の如き範囲にあるとき、現像部位での摩擦帯電がより有効に行われていることを意味している。
【０１９６】
また、かかる現像剤は、低温低湿といった過酷な環境下の耐久試験にもかかわらず、耐久中に規制部材表面や静電潜像担持体表面に現像剤が融着せず、耐久中の濃度変化が少なく、また、耐久後半でも、初期と変わらない安定した性能が発揮できている。このような効果が発現する機構については明らかではないが、現像を繰り返し行っていく上で、着色粒子と同極に帯電する疎水性シリカ微粒子と着色粒子と逆極性に帯電する外添剤を組合せた現像剤が摩擦部位で摺擦されるときに、現像剤中の微少領域に静電気的凝集力が働き、遊離状態の外添剤を減少させることで、各部材表面への外添剤の付着を低減させ、各部材表面が常に初期に近い状態を維持していることが理由であると考えられる。
【０１９７】
実施例（１０）〜（１１）、及び比較実施例（４）〜（７）
画像形成装置として表５に示す現像装置例（２）〜（７）のそれぞれを用い、現像剤として現像剤（１）を用いて２３℃、３０％の環境下でＡ４サイズの用紙に横線パターン画像を連続して８０００枚の耐久試験を実施した。
【０１９８】
実施例（１０）〜（１１）、及び比較実施例（４）〜（７）のプリントアウト評価結果を表５にまとめる評価の詳細は後述）。
【０１９９】
ここで、静電潜像担持体の製造例（２）〜（３）が良好な性能を発揮したが、これは、静電潜像担持体表面の表面摩擦係数が適当であり、本発明の効果である現像部分での摩擦帯電が有効に行われているためである。さらに、８０００枚という耐久にも現像性に変化がないことから、かかる静電潜像担持体の静電潜像担持体表面の硬さが充分にあり、摩耗性に対して有効であって静電潜像担持体の初期特性を耐久後半も維持できたためであると考えられる。
【０２００】
また、比較実施例（４）において、ドット抜けや耐久での画像濃度変化が不十分な結果になったが、これは、静電潜像担持体の表面摩擦係数が好ましい範囲に満たないため、現像部分での摩擦帯電が不十分であることが原因であると考えられる。また、比較実施例（５）において、画像スジや帯電部材汚染が不十分な結果になったが、これは、静電潜像担持体の表面摩擦係数が高いことで、静電潜像担持体表面に現像剤中の外添剤成分が付着し、さらに静電潜像担持体の表面摩擦係数が高いことで、ブレードクリーニング部材でのクリーニングが困難になり、転写残成分中の外添剤が通過してしまうために接触帯電部材を汚染したものと考えられる。そこで、このような表面摩擦係数を有する静電潜像担持体は好ましい範囲を上回るものである。
【０２０１】
さらに、比較実施例（６）において、画像カブリが悪化したが、これは、該静電潜像担持体に対する該現像剤担持体の相対速度が低く、現像部分での帯電付与が不十分であるためであると考えられる。また、比較実施例（７）では、耐久によって画像スジが悪化したが、これは、現像剤担持体と静電潜像担持体の周速差が大きいために、現像剤表面の外添剤に対する機械的ストレスが大きくなり、現像剤の表面で外添剤の存在状態が変化し帯電性特性が変化したため出あると考えられる。
【０２０２】
実施例（１２）
現像装置例（８）のフルカラー画像形成装置を用い、現像器４−１、４−２、４−３、４−４に現像剤（１）、現像剤（２）、現像剤（３）、現像剤（４）を導入した。この画像形成装置を用いて、２３℃、４０％環境下で印字率５％のフルカラー画像を連続で８０００枚の耐久試験を実施した。その結果、画像カブリ、ドット抜け、画像濃度が安定したカラー画像が得られた。また、現像スジや帯電部材汚染においても優れた結果が得られた。
【０２０３】
実施例（１３）
実施例（１２）同様に、現像剤（５）、現像剤（６）、現像剤（７）、現像剤（８）を用いて耐久試験を実施した。その結果、画像カブリ、ドット抜け、画像濃度が安定したカラー画像が得られた。また、実施例（１２）に比較して若干現像スジや帯電部材汚染が悪化するという結果が得られた。この理由として、実施例（１３）で使用した現像剤は、現像剤粒子の表面形状の球形度が比較的低いことで、現像部位での摩擦帯電での摺擦で均一性が若干悪化していることが考えられる。
【０２０４】
【表４】

【０２０５】
【表５】

【０２０６】
実施例１〜１３、並びに、比較例１〜７中に記載の評価項目の説明とその評価基準について述べる。
【０２０７】
［プリントアウト画像評価］
＜１＞画像カブリ
「リフレクトメータ」（東京電色社製）により測定したプリントアウト画像の白地部分の白色度と転写紙の白色度の差から、カブリ濃度（％）を算出し、画像カブリを評価した
Ａ：非常に良好（１．０％未満）
Ｂ：良好 （１．０％以上、２．０％未満）
Ｃ：実用可 （２．０％以上、３．０％未満）
Ｄ：実用難あり（３．０％以上、４．０％未満）
Ｅ：実用不可 （４％以上）
【０２０８】
＜２＞ドット抜け
図５に示すチェッカー模様をプリントアウトし、そのドット再現性を評価した。
Ａ：非常に良好（欠損１個以下／１００個）
Ｂ：良好 （欠損２〜４個／１００個）
Ｃ：実用可 （欠損５〜８個／１００個）
Ｄ：実用難あり（欠損９〜１１個／１００個）
Ｅ：実用不可 （欠損１２個以上／１００個）
【０２０９】
＜３＞画像濃度
通常の複写機用普通紙（７５ｇ／ｍ²）に所定の枚数のプリントアウトを終了した時の画像濃度維持により評価した。尚、画像濃度は「マクベス反射濃度計」（マクベス社製）を用いて、原稿濃度が０．００の白地部分のプリントアウト画像に対する相対濃度を測定した。
Ａ：１．４０以上
Ｂ：１．３５以上、１．４０未満
Ｃ：１．２５以上、１．３５未満
Ｄ：１．００以上、１．２５未満
Ｅ：１．００未満
【０２１０】
＜４＞現像スジ
３０００枚時点で２５％ハーフトーン画像を出力し、画像上の現像スジ（連続する画像上の濃スジ）の発生の程度を目視で評価した。
Ａ：非常に良好（未発生）
Ｂ：良好 （ほとんど発生せず）
Ｃ：実用可 （弱いスジが数本発生するが、実用上問題にならないレベル）
Ｄ：実用難あり（弱いスジが多数発生し、実用上問題となるレベル）
Ｅ：実用不可 （著しいスジが発生し、実用外のレベル）
【０２１１】
＜５＞帯電部材汚染
各耐久枚数での接触帯電部材上の部材汚染について、ハーフトーン画像上に発生する現象を下記基準で評価した。
Ａ：非常に良好（未発生）
Ｂ：良好 （わずかに部材汚染の現象が見られるが、画像への影響はない）
Ｃ：実用可 （部材汚染の現象が見られるが、画像への影響が少なく、実用上問題ないレベル）
Ｄ：実用難あり（明らかな部材汚染が見られるが、使い方によっては問題となるレベル）
Ｅ：実用不可 （明らかな部材汚染が見られ、実用上問題となるレベル）
【０２１２】
【発明の効果】
以上説明したように、本発明によれば、一成分接触現像方式において、少なくとも２種以上の金属酸化物微粒子を粒子表面に有する現像剤を薄層で保持する現像剤担持体と、一定の表面摩擦係数の有機物層を有する静電潜像担持体とが、現像部で周速差を持って接触することで、現像剤に対して適切な摩擦帯電付与することが可能となり、カブリ、ドット抜け、濃度不足を防止しつつ、画像スジの発生しない画像形成方法を提供することが可能となる。また、一成分接触現像系において、現像剤の帯電特性を改善しつつ、帯電弊害による画像欠陥を防止した画像形成方法を提供することができる。
【０２１３】
さらに、現像剤の粒度分布と形状を制御することで、耐久性に優れ、初期特性と同等の安定した現像剤、及び、画像形成方法が得られる。
【図面の簡単な説明】
【図１】本発明の画像形成装置の一例の概略構成図である。
【図２】本実施例で使用したフルカラー一成分画像形成装置の概略構成図である。
【図３】静電潜像担持体に対する現像剤担持体の相対速度と帯電性付与能、及び現像剤劣化の関係の概略を示す図である。
【図４】表面被膜物性試験の測定装置を概略的に示す図である。
【図５】本発明のドット抜けを評価するために用いた画像の例である。
【図６】現像剤の二成分帯電量測定装置の概略図である。
【図７】摩擦係数測定器ヘイドン１４型の概略図である。
【図８】摩擦係数測定の際に用いたウレタンゴムブレードの形状を示す図である。
【図９】図７におけるウレタンゴムブレードとサンプルの接触部分を拡大した図である。
【符号の説明】
７ 像加熱装置（定着装置）
Ｐ 転写材（記録材）
１ 静電潜像担持体（感光体ドラム）
２ 帯電装置（帯電ローラ）
３ レーザ光
４ 現像器
５ 中間転写体ドラム
６ 転写ローラ
８ クリーナ（感光体ドラム用クリーナ）
１０ クリーナ（中間転写体ドラム用クリーナ）
Ｔ１ 一次転写部
Ｔ２ 二次転写部
４１ 吸引機
４２ 測定容器
４３ 導電性スクリーン（５００メッシュ）
４４ フタ
４５ 真空計
４６ 風量調節弁
４７ 吸引口
４８ コンデンサー
４９ 電位計
２２ 上部ホルダー
２３ 下部ホルダー
２４ 固定ビス[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developer used in a recording method using an electrophotographic method, an electrostatic recording method, a magnetic recording method, or the like, or a developer used in a full-color image forming method, and an image forming method. More specifically, the present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a fax machine, which forms a developer image on a latent electrostatic image bearing member in advance and then transfers the image onto a transfer material to form an image. The present invention relates to a developer used for electrostatic printing and an image forming method.
[0002]
[Prior art]
Conventionally, electrophotography generally utilizes a photoconductive material, forms an electrostatic latent image on a latent image carrier (photoconductor) by various means, and then develops the latent image using a developer, If necessary, an image is transferred to a recording material using direct or indirect means, and then fixed by heating, pressure, etc. to obtain a copy.
[0003]
Conventionally, the two-component development method and the one-component development method are widely used as the development method. However, as a printer for business or personal use by electrophotography, in recent years, due to the demand for miniaturization and high performance, Component development methods are increasing.
[0004]
A general one-component development method is to visualize an electrostatic latent image by bringing a developer carrying body coated with a developer into a thin layer on the surface of the developer carrying body and an electrostatic latent image carrying body. A recorded image is obtained by sequentially transferring and fixing the visible image on a recording material. Here, the developer takes an arbitrary charged state. However, the charging to the developer is performed by forming a thin layer of the developer on the surface of the developer carrying member by the regulating member and developing the surface of the regulating member at the same time. This is done by rubbing the agent. Further, the electrostatic latent image is visualized in terms of potential by using an electric field in the developing portion by utilizing the charging polarity of the developer. Therefore, by applying appropriate electrification to the developer, it is possible to prevent image defects such as image fogging on the white background portion, insufficient development density, and lack of lines, and achieve high-quality image formation.
[0005]
Therefore, accurate charging of the developer at the site where the electrostatic latent image is visualized is very important for improving the image quality of the printed image.
[0006]
For example, in Japanese Patent Application Laid-Open No. 10-133469, the developing roller is formed of an elastic body that is negatively charged on the charging series with respect to the amorphous silicon drum, and the peripheral speed ratio is in the range of 1.5 to 2.5 times. An image forming method is set. According to such an image forming method, a clear image free from fogging, missing dots, and insufficient density can be obtained. However, the surface of the latent electrostatic image bearing member is not an organic material, and the external additive composition / particle size in the developer is not mentioned, which is a problem in a one-component contact development system. The effect on the image streak is not recognized.
[0007]
In addition, an image forming method for defining a charging series at a developer charging portion is disclosed in order to provide more accurate charging by such a friction charging method. For example, US Pat. No. 5,379,097 discloses a developer that defines a charge series of a developer base, a developer carrier surface, and an external additive. It is possible to impart an appropriate charge to the developer by performing frictional charging in such a charge series relationship, but during this development method, an electrostatic latent image in contact development is included. The frictional charging between the carrier and the developer is not mentioned and is not clear. Further, when such an image forming method is verified, it is necessary to increase the pressing pressure at the regulating member portion, and the developer is likely to be fused to the regulating member surface. As a result, lines (development streaks) are generated in the image, and it is necessary to perform equivalent tribocharging while further reducing the load on the development system.
[0008]
On the other hand, the charge imparting method in the two-component development method is based on friction with the carrier surface, but in the one-component development system, as an alternative to this carrier, a microparticle having a particle size distribution smaller than the developer particle size. An image forming method in which friction charging is performed using a carrier is disclosed. In such an image forming method, particles having different charging series are mixed in a developer. Examples thereof include JP-A-61-20053, JP-A-61-250658, JP-A-63-143172, and the like. A developer in which fluidizing agent particles having the same polarity as the developer and fluidizing agent particles having a polarity opposite to that of the developer is mixed is disclosed. Such a combination of fluidizing agent particles in the developer is effective in optimizing the charging of the developer at the time of frictional charging. However, the fluidizing agent having a polarity opposite to that of the developer is transferred to the recording material. When the toner is used as a transfer residue on the surface of the electrostatic latent image carrier and used in a contact charging system such as roller charging, a fluidizing agent having a polarity opposite to that of the developer is potentialally adsorbed on the surface of the contact charging member. If this reverse polarity fluidizing agent is excessive or unevenly accumulated on the charging roller, it will change the surface resistance of the charging member. Since there is a possibility of an image defect resulting from a defect, it is necessary to keep it within a suitable range. Therefore, when a system in which particles of different charge series are mixed in a developer is used in the contact charging system, a developing system that takes into consideration not only the charging of the developer but also the behavior of these opposite polarity particles is required.
[0009]
In JP-A-4-346372, the charge amount q1 of the developer and the charge amount q2 on the surface of the regulating member are of the same polarity, and | q2 | <| q1 |, and the charge amount q3 on the surface of the developing roller is −4. A developing device having a relationship of 0.0 ≦ q1 / q3 ≦ −1.2 is disclosed. In such a developing method, it is possible to stably provide an effective charge to the developer by disposing a member of an effective charging series for charging the developer, so that a clear image or solid image can be obtained. A uniform density image can be obtained. However, the place for charging the developer with such a developing device is only the regulating member portion, and there is no description regarding frictional charging with the electrostatic latent image carrier. Therefore, when the developer is fused to the surface of the regulating member as described above during durability, a change occurs in the charge amount q2 on the surface of the regulating member during durability and the charge amount q3 on the surface of the developing roller during durability. Therefore, with such a developing method, stable performance in the second half of durability cannot be maintained, and a clear image and a uniform density image in the second half of durability cannot be obtained.
[0010]
[Problems to be solved by the invention]
The above prior art cannot provide an image forming method in which image streaking does not occur while preventing fogging, missing dots, and insufficient density. In addition, it is difficult to provide an image forming method that improves the charging characteristics of a developer and prevents image defects due to charging effects in a one-component contact development system. Furthermore, it is difficult to maintain stable performance during durability.
[0011]
Therefore, it is necessary to achieve a developing method that balances the appropriate charging and development streaks and prevents charging problems.
[0012]
[Means and Actions for Solving the Problems]
As a result of intensive studies, the present inventor has found that in a one-component contact development method, a developer carrier that holds a developer having at least two or more kinds of metal oxide fine particles on the particle surface in a thin layer, and a certain surface The electrostatic latent image carrier having an organic material layer having a friction coefficient is contacted with a peripheral speed difference at the developing portion to perform tribocharging, and can impart an appropriate charge to the developer. As a result, the inventors have found that the above problems can be solved, and have reached the present invention.
[0013]
As a result of further investigations, the present inventors have found that the effects as described above are more remarkable in a developer having a specific particle size distribution. Further, the inventors have found that the durability is improved when the shape of the developer is close to a circle, and that the effects of the present invention become more remarkable, leading to the present invention.
[0014]
  That is, according to the present invention, a developer carrying member is placed in pressure contact with an electrostatic latent image carrying member, and the developer on the electrostatic latent image carrying member is formed on the developer carrying member with a thin layer. In the image forming method for developing an electrostatic latent image, the rotation direction of the electrostatic latent image carrier and the developer carrier is a forward direction, and the relative speed of the developer carrier to the electrostatic latent image carrier Is a developer used in an image forming method in which charging is imparted to the developer by rubbing within a range of 120 to 250%,
  The latent electrostatic image bearing member is an electrostatic latent image bearing member formed of an organic material, and its surface friction coefficient(Friction force of electrostatic latent image carrier sample / Friction force of polyethylene terephthalate)Has an organic layer of 0.5 to 1.2,
  The developer is a non-magnetic one-component developer having at least a binder resin, colored particles composed of a colorant and a release agent, and at least two or more kinds of metal oxide fine particles on the surface of the colored particles. At least one of the oxide fine particles is a hydrophobic silica fine particle that is charged to the same polarity as the colored particles, and at least one of the other external additives is a particle that is charged with a polarity opposite to that of the colored particles.The
  In the particle size distribution of the developer, 16 to 50 number% of developer particles having a particle size of 5 μm or less are contained, 1 to 30 number% of developer particles having a particle diameter of 8 to 12.7 μm are contained, and 16 μm. The developer particles having the above particle diameter are contained by 1.5% by volume or less,
  In the developer-based circle equivalent diameter-circularity scattergram measured by the flow type particle image measuring apparatus, the average circularity of the developer is 0.950 to 0.990 and the circularity standard deviation is 0. Less than 040The present invention relates to a developer.
[0015]
  Further, according to the present invention, a developer carrying member is disposed in pressure contact with an electrostatic latent image carrying member, and a developer layered on the developer carrying member is used to form an electrostatic on the electrostatic latent image carrying member. In the image forming method for visualizing the latent image, the rotation direction of the electrostatic latent image carrier and the developer carrier is a forward direction, and the relative speed of the developer carrier to the electrostatic latent image carrier is An image forming method in which charging is imparted to the developer by rubbing within a range of 120 to 250%,
  The latent electrostatic image bearing member is an electrostatic latent image bearing member formed of an organic material, and its surface friction coefficient(Friction force of electrostatic latent image carrier sample / Friction force of polyethylene terephthalate)Has an organic layer of 0.5 to 1.2,
  The developer is a non-magnetic one-component developer having at least a binder resin, colored particles composed of a colorant and a release agent, and at least two or more kinds of metal oxide fine particles on the surface of the colored particles. At least one of the oxide fine particles is a hydrophobic silica fine particle that is charged to the same polarity as the colored particles, and at least one of the other external additives is a particle that is charged with a polarity opposite to that of the colored particles.The
  In the particle size distribution of the developer, 16 to 50 number% of developer particles having a particle size of 5 μm or less are contained, 1 to 30 number% of developer particles having a particle diameter of 8 to 12.7 μm are contained, and 16 μm. The developer particles having the above particle diameter are contained by 1.5% by volume or less,
  In the developer-based circle equivalent diameter-circularity scattergram measured by the flow type particle image measuring apparatus, the average circularity of the developer is 0.950 to 0.990 and the circularity standard deviation is 0. Less than 040The present invention relates to an image forming method.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more specifically.
[0017]
An image forming apparatus that is one of the features of the present invention will be described in detail below with reference to the accompanying drawings.
[0018]
FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to the present invention.
[0019]
The electrophotographic image forming apparatus of this example is a non-magnetic one-component contact development type laser beam printer having a cleaning mechanism. In the figure, reference numeral 100 denotes an electrostatic latent image carrier, and 117 denotes a contact charging member. Here, a roller-type charging member is shown. 121 is a laser beam light source, and 123 is laser light from this light source. Reference numeral 140 denotes a developer container, in which a developer 142, a developer supply member 141, and developer regulating members 143 and 104 are developer carriers. Here, the electrostatic latent image carrier 100 and the developer carrier having elasticity on the surface of the roller 104 are pressed against each other, and are rotated in the forward direction with a peripheral speed difference within a preferable range in the present invention. The developer to which frictional electrification is applied due to the pressure contact and peripheral speed difference between the electrostatic latent image carrier 100 and the developer carrier 104 visualizes the electrostatic latent image, and the transfer bias is applied to the recording material 127 by the transfer means 114. 134 is transferred 129 and fixed by 128 fixing means to form a permanent image. The transfer residual developer 124 remaining on the surface of the electrostatic latent image carrier after the transfer is scraped off by a cleaning means using a blade 120a and separated into a 120 cleaning container. The electrostatic latent image carrier having been cleaned is charged again by the contact charging member 117. Image formation is performed by repeating these series of operations continuously.
[0020]
The configuration of the electrophotographic electrostatic latent image carrier used in the present invention is not particularly limited as long as it has the surface characteristics of the present invention and functions as an electrophotographic electrostatic latent image carrier. In general, an electrostatic latent image bearing member having a photosensitive layer provided on a conductive support is used, but a protective layer is provided on the photosensitive layer and between the conductive support and the photosensitive layer. An undercoat layer or a conductive layer may be provided on the substrate. Therefore, the outermost surface layer of the electrostatic latent image carrier is a photosensitive layer or a protective layer, and these layers are a binder resin and a charge generation material, a charge transport material or a conductive material contained in an appropriate amount in the binder resin. Etc.
[0021]
In the present invention, it is important to satisfy the surface characteristics of the present invention, and the means for achieving it are not particularly limited. For example, as a method of controlling the surface friction coefficient, in addition to selecting the type and amount of the material to be used, a method of providing a protective layer having specific surface characteristics on the outermost surface, or after producing an electrostatic latent image carrier It is also possible to polish the surface of the electrostatic latent image carrier.
[0022]
As a kind of material used for controlling the surface friction coefficient of the electrostatic latent image carrier, it is possible to use a combination of known resin materials and lubricants. For example, fluororesin and fluorine-based co-polymers can be used. A polymer etc. can be used.
[0023]
Further, as a method of surface polishing as means for achieving surface property control, for example, when the electrostatic latent image carrier is a drum type, it is rotated, and Fujifilm # C-2000 wrapping tape, Sumitomo Examples thereof include a method of applying pressure while contacting 3M polishing film # 2000 (aluminum oxide).
[0024]
The photosensitive layer of the electrophotographic electrostatic latent image carrier used in the present invention has a single layer or a laminated structure. In the case of a single layer structure, the photosensitive layer contains both a charge generating material that generates carriers and a charge transport material that transports carriers. In the case of a laminated structure, a charge generation layer containing a charge generation material that generates carriers and a charge transport layer containing a charge transport material that transports carriers are stacked to form a photosensitive layer. The surface layer may be formed by either a charge generation layer or a charge transport layer.
[0025]
The single-layer photosensitive layer preferably has a thickness of 5 to 100 μm, particularly preferably 10 to 60 μm. Moreover, it is preferable to contain 20-80 mass% of charge generation materials and charge transport materials with respect to the total mass of a layer, and it is preferable that it is 30-70 mass% especially. The single-layer photosensitive layer contains a binder resin in addition to the charge generation material and the charge transport material, and may contain an ultraviolet absorber, an antioxidant, other additives and the like as necessary.
[0026]
In the laminated photosensitive layer, the thickness of the charge generation layer is preferably 0.001 to 6 μm, and particularly preferably 0.01 to 2 μm. The content of the charge generating material is preferably 10 to 100% by mass, particularly 40 to 100% by mass, based on the total mass of the layer. The charge generation layer may be composed of only a charge generation material. In other cases, the charge generation layer may contain the binder resin or the like. The thickness of the charge transport layer is preferably 5 to 100 μm, and particularly preferably 10 to 60 μm. The content of the charge transport material is preferably 20 to 80% by mass, and particularly preferably 30 to 70% by mass. The charge transport layer contains a binder resin in addition to the charge transport material, and may contain other optional components similar to those described above.
[0027]
Examples of charge generating materials used in the present invention include phthalocyanine pigments, polycyclic quinone pigments, azo pigments, perylene pigments, indigo pigments, quinacridone pigments, azulenium salt dyes, squarylium dyes, cyanine dyes, pyrylium dyes, thiopyrylium dyes, xanthene dyes. Quinoneimine dye, triphenylmethane dye, styryl dye, selenium, selenium-tellurium, amorphous silicon, and hardened cadmium.
[0028]
Examples of charge transport materials used in the present invention include pyrene compounds, carbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds, and stilbene compounds. Is mentioned.
[0029]
As binder resin used for the photosensitive layer, polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, polyamideimide, polysulfone, polyallyl ether, polyacetal, phenol resin, acrylic resin, silicone resin, Examples thereof include epoxy resins, urea resins, allyl resins, alkyd resins, and butyral resins. Furthermore, reactive epoxy, (meth) acrylic monomers and oligomers can also be used after being mixed and cured.
[0030]
The electroconductive support used for the electrophotographic electrostatic latent image carrier used in the present invention is made of metal or alloy such as iron, copper, nickel, aluminum, titanium, tin, antimony, indium, lead, zinc, gold and silver. Alternatively, oxides, carbons, conductive resins, or the like thereof can be used. There are cylindrical, belt-like and sheet-like shapes. Moreover, although the said electroconductive material may be shape-processed, you may apply | coat as a coating material or may vapor-deposit. In addition, the electroconductive support body used for this example is a cylindrical thing about 30 mm in diameter as above-mentioned.
[0031]
Further, as described above, an undercoat layer may be provided between the conductive support and the photosensitive layer. The undercoat layer is mainly composed of a binder resin, but may contain the conductive material or an acceptor compound. The binder resin that forms the undercoat layer is polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, polyamideimide, polysulfone, polyallyl ether, polyacetal, phenol resin, acrylic resin, silicone Examples thereof include resins, epoxy resins, urea resins, allyl resins, alkyd resins, and butyral resins.
[0032]
Further, as described above, a conductive layer may be provided between the conductive support and the photosensitive layer. When the photoreceptor has both the undercoat layer and the conductive layer, the conductive support, the conductive layer, the undercoat layer, and the photosensitive layer are usually laminated in this order. The conductive layer generally has a configuration in which the conductive material is dispersed in a binder resin similar to that used in the undercoat layer.
[0033]
As a method for producing an electrophotographic electrostatic latent image carrier used in the present invention, a method of laminating an undercoat layer, a photosensitive layer, a protective layer, etc. on a conductive support by vapor deposition or coating is usually used. It is done. For coating, a bar coater, knife coater, roll coater, attritor, spray, dip coating, electrostatic coating, powder coating and the like are used. In addition, in order to form the undercoat layer, the photosensitive layer, the protective layer, and the like by a coating method, a solution in which each component is dissolved and dispersed in an organic solvent, a dispersion, or the like is applied by the above method. After that, the solvent may be removed by drying or the like. Alternatively, when a reaction-curable binder resin is used, a solution, a dispersion, or the like in which the constituent components of each layer are dissolved and dispersed in the resin raw material component and an appropriate organic solvent that is added as necessary is used as described above. After the coating, for example, the resin raw material may be reacted and cured by heat or light, and the solvent may be removed by drying or the like as necessary.
[0034]
The method for measuring the surface friction coefficient of the electrostatic latent image carrier in the present invention is as follows. As shown in FIG. 7, the measuring instrument is a modified version of Haydon surface property tester type 14 for measuring drum-shaped samples. In FIG. 7, reference numeral 12 denotes a sample, but by selecting the sample stage 11, it is possible to measure either a drum-shaped sample or a plate-shaped sample. In measuring the surface friction coefficient, a urethane rubber blade 13 is used. The rubber hardness of the urethane rubber blade 13 (Vancolan, manufactured by Bando Chemical Co., Ltd.) is 65 ± 3 °, and the dimensions are 5 mm wide, 10 mm long and 2 mm thick as shown in FIG. FIG. 9 is an enlarged view showing a contact portion between the urethane rubber blade 13 and the sample 12. The blade 13 has a free length (so that the contact angle with the sample 12 is 30 ° using a fixing screw 24 between the upper holder 22 and the lower holder 23 connected to the holder support arm 21 at the tip of the support column 14. The length of the portion of the blade 13 not restrained by the holders 22 and 23 is fixed to 8 mm.
[0035]
At the time of measurement, 0.098N (load 10 g) is applied to the blade 13 through the support column 14 by the weight 16 placed on the tray 15, and the sample drum (electrophotographic electrostatic latent image carrier) is fixed to the sample drum. The base 11 is moved in the bus direction in the forward direction with the blade 13 by the motor 20. The load at this time is read as a friction force by the mechanism of the support point 17, the balancer 18, and the load converter 19 in FIG. In addition, a polyethylene terephthalate (Mylar (trade name), manufactured by DuPont) film having a thickness of 25 μm is used as a reference sample, wound around a cylinder having the same diameter as the sample, and the frictional force is measured under the same conditions as the sample. The surface friction coefficient of the sample is calculated by the following formula (I).
[0036]
[Expression 1]

[0037]
Since the surface friction coefficient is based on a polyethylene terephthalate film, it is not affected by variations in some measurement conditions. Further, it is not affected by the diameter of the photosensitive drum and shows a constant value.
[0038]
In the present invention, the following measurement condition ranges are allowed.
-Urethane rubber: hardness: 62-72 °, thickness: 1-5 mm, manufacturer: Bando Chemical Co., Ltd., Hokushin Rubber Co., Ltd., Tokai Rubber Co., Ltd., etc.
-Polyethylene terephthalate film: Manufacturer: Toray Industries, Inc. (trade name: Lumirror), Teijin Ltd. (trade name: TR8550), DuPont (trade name: Mylar), etc. Thickness: 10-50 μm
-Drum diameter: 20 to 200 mm (Note that the surface friction coefficient based on polyethylene terephthalate does not change even if the drum diameter is changed.)
[0039]
In addition, all the evaluation of the surface characteristic in this invention shall be performed at room temperature (about 21-25 degreeC).
[0040]
In addition, the electrostatic latent image carrier surface characteristics of the present invention preferably have a certain hardness or more from the viewpoint of durability. Specifically, the universal hardness HU is 200 N / mm.²The above is preferable.
[0041]
The universal hardness in the present invention can be obtained by the following surface film physical property test. The surface film physical property test is a test for analyzing the hardness of a thin film, a cured film, an organic film, and the like. In the measurement, a tester (Fischer Instruments, Fisherscope H100V) shown in FIG. 4 is used. Then, using a diamond indenter 33 whose face angle is defined as 136 ° with a diamond pyramid indenter, a sample (electrophotographic electrostatic latent image carrier) 31 is subjected to a measurement load stepwise to form a sample film. The indentation depth h in a state where a load is applied when pushing in is electrically detected and read. In FIG. 4, 34 is a mobile table, and 32 is a sample table.
[0042]
The hardness H is represented by a value obtained by dividing the test load by the surface area of the indentation generated by the test load. The universal hardness HU is represented by the hardness at the set maximum indentation depth hx (in the present invention, hx = 1 μm). In the hardness H and the universal hardness HU, the higher the numerical value, the higher the film hardness. Measurement shall be performed to the extent that the surface of the material is not broken.
[0043]
An electrophotographic electrostatic latent image bearing member having such surface characteristics is, for example, a binder resin in order to bring the universal hardness to the above range for the surface layer of an electrophotographic electrostatic latent image bearing member having a normal configuration. A specific resin is used, and a specific amount of fluororesin powder is uniformly dispersed in the surface layer so that the surface friction coefficient or the contact angle with pure water on the surface is within the above range. It is obtained by polishing.
[0044]
The universal hardness adjustment means includes a binder resin and a charge generation material or a charge transport material dispersed or dissolved in the binder resin, or a kind of conductive material such as a metal and its oxide, nitride, salt, alloy and carbon. And changing the ratio of these. That is, although it depends on the material dispersed in the binder resin, in the case of the above-described materials, the universal hardness increases as the amount of materials that are normally dispersed is smaller. Another means is to change the molecular weight of the binder resin, the number of polymerization functional groups, and the like. That is, if the molecular weight of the binder resin is increased, the universal hardness increases, and if the degree of cross-linking of the resin is increased by increasing the number of polymerization functional groups, the universal hardness increases. Furthermore, it may change depending on the dispersion state of the fluorine resin powder or the like.
[0045]
These requirements naturally affect the surface friction coefficient, but no constant relationship has been found between universal hardness and surface coefficient.
[0046]
A developer carrier suitable for the image forming method of the present invention will be described. The developer carrying member is not particularly limited as long as it is generally used in a one-component contact development method, but a roller having an elastic layer is preferably used.
[0047]
The elastic layer hardness of the elastic roller surface is preferably about 20 to 65 degrees (ASKER C), more preferably 30 to 60 degrees, from the viewpoint of both developability and durability. Known materials and structures can be used for the elastic roller. In particular, solid rubber elastic bodies such as silicone rubber, urethane rubber and NBR, or foamed elastic bodies thereof are preferably used. Moreover, a well-known multilayer structure roller having a coating layer different from the central part on the surface can also be used. In addition, a known surface treatment may be performed for the purpose of imparting chargeability or imparting transportability. At this time, it is preferable to take a series in which the charging series on the surface of the elastic layer is positioned at a counter electrode for applying a charge to the developer from the viewpoints of tribocharging and replacement of the developer on the developing roller.
[0048]
As the surface shape of the developer carrier, it is preferable to control the surface roughness in order to achieve both high image quality and high durability. When the surface roughness of the developer carrying member is set to Ra (μm) “JIS B 0601” to be 0.2 to 3.0, for example, both high image quality and high durability can be achieved. If the surface roughness Ra of the developer carrier exceeds 3.0, it is difficult not only to thin the developer layer on the developer carrier but also the chargeability of the developer is not improved. I cannot expect improvement. The developer carrying capacity on the surface of the developer carrying body is suppressed by setting it to 3.0 or less, the developer layer on the developer carrying body is thinned, and the contact between the developer carrying body and the developer is reduced. Since the number of times increases, the chargeability of the developer is also improved, so that the image quality is synergistically improved. On the other hand, when the surface roughness Ra is smaller than 0.2, it becomes difficult to control the developer coating amount. Further, in order to more efficiently perform the rubbing at the developing portion, it is preferable that the surface roughness Ra of the developer carrier is in the above range.
[0049]
The surface roughness Rz is preferably 8.0 μm or less in order to make the developer coat uniform. In some cases, the surface roughness Rz may be greater than 8.0 μm on the outermost layer of the developer carrier due to foreign matters during molding. In such a case, the surface of the developer regulating member or the latent image carrier There is a risk of changing the surface properties of the surface, and the charge on the developer on the developer carrying member and the coating amount may become non-uniform. As a result, streaks occur in the developed image, which is not preferable. Therefore, the above range is preferable for the state of the surface of the developer carrying member.
[0050]
The rotation direction of the electrostatic latent image carrier and the developer carrier is preferably a forward direction. If the rotation direction is set in the reverse direction in the one-component contact development, although the triboelectric chargeability at the development portion is further improved, the mechanical stress at the contact portion becomes very large and the life of the apparatus is shortened.
[0051]
Therefore, by making the rotation direction of the electrostatic latent image carrier and the developer carrier forward, the stress as described above can be reduced, and the life of the apparatus can be improved.
[0052]
Therefore, in order to realize more efficient charging with less load, the relationship between the relative speed of the electrostatic latent image carrier with respect to the developer carrier, chargeability imparting ability, and developer deterioration is shown in FIG. It was shown in 3. The charge amount of the developer here is the charge amount of the developer before transfer of the electrostatic latent image at 50% printing rate after the endurance of a certain number of sheets, and the developer deterioration is caused by an electron microscope. The image obtained by observing the surface of the developer in Fig. 2 is digitized using a rank sample.
[0053]
It can be seen that when the relative speed is less than 120%, there are many parts that rely on frictional charging by the regulating member, and the original aim cannot be achieved. In order to provide the developer with sufficient charging ability by frictional charging at such a portion, strong rubbing at the contact portion between the developer carrying member and the regulating member is required, and means for achieving such rubbing is generally used. In particular, a method of increasing the contact pressure of the regulating member is taken. However, when the contact pressure is increased by such a method, the charge imparting property to the developer is increased, but the load on the developer is strong, the external additive adhesion state on the developer surface is changed, and the developer itself is changed. The shape is likely to change, and as a result, the developer is likely to be fused to the surface of the regulating member, and a developer agglomeration occurs on the surface of the regulating member, and the developer is charged or coated on the developer carrying member. This is not preferable because the amount becomes non-uniform, and as a result, streaks occur in the developed image.
[0054]
However, when the electrostatic latent image carrier of the present invention is used and the relative speed exceeds 120%, it is possible to divide the role of charging the developer into two points: a regulating member and a developing unit. Therefore, the contact pressure can be made lower than that of the restriction member as described above, and this problem can be solved.
[0055]
On the other hand, when the relative speed exceeds 250%, the charge imparting ability decreases. Although this detailed principle is not clear, it seems that the charging ability is inferior from around 200%, so that the uniformity of frictional charging is impaired when the peripheral speed difference becomes high. Further, it is considered that the deterioration of the developer is further promoted, and the deterioration is caused by a synergistic effect with the fact that the uniformity of the triboelectric charge is impaired.
[0056]
Therefore, the above range is preferable for the state of the surface of the developer carrying member.
[0057]
According to the present invention, the developer carrier is configured with a peripheral speed ratio so that the relative speed is in the range of 120 to 250% with respect to the electrostatic latent image carrier having a specific surface property. In the contact portion between the developer carrier and the electrostatic latent image carrier, good chargeability is imparted by the friction between the developer particles, and developability deterioration due to developer deterioration is less likely to occur. Furthermore, by combining the developer of the present application as the developer, more effective and stable charging can be achieved at the time of rubbing in the developing portion, and the effects of the present application can be obtained.
[0058]
The relative speed between the electrostatic latent image carrier and the developer carrier can be controlled by adjusting the number of teeth of the gear that drives the electrostatic latent image carrier and the developer carrier.
[0059]
The developer on the developer carrier is regulated by a regulating member (developing blade) arranged so as to be in pressure contact with the surface of the developer carrier to form a developer layer on the developer carrier.
[0060]
The pressure that presses the developing blade against the surface of the developer carrying member to regulate the layer thickness on the developer carrying member regulates the coating layer thickness of the developer to be constant and appropriately performs the first frictional charging described above. Thus, it is preferable to adjust the contact pressure and shape.
[0061]
The pressure that presses the developing blade against the surface of the developer carrier and regulates the layer thickness on the developer carrier is preferably 9.8 N / m (10 g / cm) to 58.8 N / m (60 g / cm). It is preferably 19.6 N / m (20 g / m) to 39.2 N / m (30 g / m). When the developing blade is in such a range, an appropriate first charge can be imparted to the developer on the developer carrying member while preventing the developer from fusing to the developing blade.
[0062]
The material for the developer coating amount regulating member is not particularly limited, and a known metal plate-like member or a material having an organic layer on the surface of the metal blade can be used. In particular, as the organic layer, it is preferable to select a material of a triboelectric charge series that imparts a desired charge to the developer, a rubber elastic body such as silicone rubber, urethane rubber, NBR, a synthetic resin elastic body such as polyethylene terephthalate, Metal elastic bodies such as stainless steel, steel and phosphor bronze can be used, and composites thereof can be used.
[0063]
Furthermore, an organic substance or an inorganic substance may be added to the elastic regulating member, and it may be melt-mixed or dispersed. For example, the chargeability of the developer can be controlled by adding a metal oxide, metal powder, ceramics, carbon allotrope, whisker, inorganic fiber, dye, pigment, surfactant or the like. In particular, when the elastic body is a molded body such as rubber or resin, fine particles of metal oxide such as silica, alumina, titania, tin oxide, zirconia and zinc oxide, carbon black, and charge control generally used for developers It is also preferable to contain an agent or the like.
[0064]
In the case of using a combination of a conductive regulating member and a developer carrier, it is also preferable to apply a DC electric field and / or an AC electric field between the regulating member and the developer carrier. By applying such an electric field, uniform thin layer coating and uniform chargeability are improved, and sufficient image density can be achieved and a good quality image can be obtained.
[0065]
Furthermore, the present invention has a mechanism for blade cleaning the surface of the electrostatic latent image carrier after transfer, but a known blade can be used as a cleaning member for blade cleaning.
[0066]
As a charging method after blade cleaning, a known contact or non-contact charging method can be used, but a contact charging method that has an effect of suppressing the generation of ozone during charging is more preferable. In the combination of the image forming method of the present invention and the developer, most of the transfer residue remaining on the surface of the latent electrostatic image bearing member after transfer is composed of hydrophobic silica fine particles and a second outer layer having a polarity opposite to that of the hydrophobic silica particles. Since it is an additive, it is necessary to select a material that is compatible with the combination of the above-described blade cleaning member and contact charging. When these combinations do not function properly, particles mainly composed of external additives adhere to the charging member, and the resistance value of the surface of the charging roller is locally increased, so that the surface of the electrostatic latent image carrier surface is increased. This is not preferable because charging is hindered and as a result, image defects due to poor charging occur.
[0067]
Next, the developer which is the second point of the present invention will be described.
[0068]
The developer is a non-magnetic one-component developer having at least a binder resin, colored particles composed of a colorant and a release agent, and at least two or more kinds of metal oxide fine particles on the surface of the colored particles. At least one of the oxide fine particles is a hydrophobic silica fine particle, and at least one of the other external additives is a particle that is charged with a polarity opposite to that of the hydrophobic silica.
[0069]
The binder resin used for the developer resin of the present invention is not particularly limited as long as it is used when the developer is produced. Examples of the binder resin used in the developer resin of the present invention include known polymers, copolymers, and mixtures thereof. More specifically, a styrene- (meth) acrylic acid copolymer or a polyester resin is preferable.
[0070]
In order to obtain the developer of the present invention, the production method is not particularly limited as long as the developer particle diameter and shape within the preferable range of the present invention can be achieved, but the effect of the present invention is more remarkable. In order to achieve a shape that can be expressed in the above, a constituent component of the developer is pulverized after melt-kneading and further spheronized, and then classified to a desired particle size, or polymerization such as suspension polymerization Depending on the method, the material constituting the developer is directly spheronized from the monomer unit and polymerized, and then the developer is produced by polymerizing the developer by suspension polymerization or emulsion polymerization. It is possible to use a method such as an agglomeration method in which colored particles smaller than the particle size of the agent are synthesized and then these agglomeration operations are performed to control the particles to have a desired particle size.
[0071]
The raw materials constituting the developer are the binder resin components as described above in the case of the pulverization method, the monomers constituting the binder resin in the case of the polymerization method or the aggregation method, and the polymerization initiation that can be used for known developers. A binder resin component composed of an agent, a crosslinking agent, a molecular weight adjusting agent, and the like, a known colorant, a charge control agent, a charge auxiliary agent, a release agent, and the like can be used.
[0072]
In general, the mechanical stress of the developer is influenced by the properties of the constituent raw materials and the interaction state of these constituent materials in the developer after processing. Therefore, in a developer such as the present invention, the physical characteristics that can withstand these mechanical stresses, for example, the toughness in the viscous force and elastic force characteristics prevent the developer from fusing members and improve the charging characteristics. In order to achieve such viscoelastic properties, it is preferable that the molecular weight, gel content, dispersed state of the filler, and the like are appropriately controlled from a chemical viewpoint.
[0073]
In addition, when performing monocolor or full color image formation using the developer and image forming method of the present invention, yellow, magenta, cyan, and black developers can be used by changing the colorant. .
[0074]
As the colorant, conventionally known inorganic and organic dyes and pigments can be used. Specific examples include the following.
[0075]
Specific examples of the color pigment for yellow include compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds. More specifically, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 168, 174, 176, 180, 181, 191, C.I. I. Vat yellow 1, 3, 20 etc. are mentioned. Further, yellow lead, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, Hansa yellow G, permanent yellow NCG, tartrazine lake and the like can also be used.
[0076]
Specific examples of the color pigment for magenta include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are mentioned.
[0077]
Further, as the dye, C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Oil-soluble dyes such as disperse violet 1, C.I. I. Basic dyes such as Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40 , C.I. I. Acid Red 1, C.I. I. Direct Red 1, 4, C.I. I. Modern tread 30 etc. are mentioned.
[0078]
Specific examples of the color pigment for cyan include C.I. I. Pigment blue 2, 3, 15, 16, 17, C.I. I. Basic Blue 3, 5, C.I. I. Bat Blue 6, C.I. I. Direct Blue 1, 2, C.I. I. Acid Blue 9, 15, 45, C.I. I. For example, Modern Blue 7 or copper phthalocyanine pigment.
[0079]
Specific examples of black coloring pigments include carbon black, arinin black, acetylene black, and oil black. Moreover, it is also possible to mix a colorant for color and use it as a black colorant.
[0080]
In addition to the colorant, titanium white, C.I. I. Direct Green 6, C.I. I. Basic Green 4,6, Pigment Green B, Malachite Green Lake, Final Yellow Green G, Chrome Green, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, C.I. I. Basic violet 1,3,7,10,14,15,21,25,26,27,28, C.I. I. Solvent violet 8, 13, 14, 21, 27, manganese purple, fast violet B, methyl violet lake, etc. can also be used as a color developer for a color developer other than the above colors.
[0081]
These can be used alone or in combination. Usually, 0.1 to 60 parts by mass, and preferably 0.5 to 20 parts by mass are used with respect to 100 parts by mass of the binder resin.
[0082]
Further, the developer of the present invention preferably contains a wax component in order to improve releasability at the time of fixing. Specific examples of the wax component include the following compounds.
[0083]
For example, silicone resin, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin such as low molecular weight polyethylene or low molecular weight polypropylene, aromatic petroleum Resins, chlorinated paraffin, paraffin wax and the like.
[0084]
Of these waxes, waxes obtained by fractionating waxes by molecular weight by various methods are also preferably used in the present invention. In addition, oxidation, block copolymerization, and graft modification may be performed after fractionation.
[0085]
Among these, low molecular weight polypropylene and its by-products, low molecular weight polyesters and ester waxes, and aliphatic derivatives are preferably used.
[0086]
Among these, examples of more preferable representative compounds of the ester wax are shown below as general structural formulas (1) to (6) of the ester wax.
[0087]
[Chemical 1]

(In the formula, a and b represent an integer of 0 to 4, a + b is 4, and R₁And R₂Represents an organic group having 1 to 40 carbon atoms, and R₁And R₂And n and m are integers of 0 to 15, and n and m are not 0 at the same time. )
[0088]
[Chemical formula 2]

(In the formula, a and b represent an integer of 0 to 4, a + b is 4, and R₁Represents an organic group having 1 to 40 carbon atoms, n and m represent integers of 0 to 15, and n and m are not 0 at the same time. )
[0089]
[Chemical Formula 3]

(Wherein, a and b represent an integer of 0 to 3, a + b is 3 or less, R₁And R₂Represents an organic group having 1 to 40 carbon atoms, and R₁And R₂And a group having a carbon number difference of 10 or more, and R_ThreeRepresents an organic group having 1 or more carbon atoms, n and m represent an integer of 0 to 15, and n and m are not 0 at the same time. )
[0090]
[Formula 4]
General structural formula of ester wax (4)
R₁COOR₂
(Wherein R₁And R₂Represents a hydrocarbon group having 1 to 40 carbon atoms, and R₁And R₂May be the same or different carbon numbers. )
[0091]
[Chemical formula 5]
General structural formula of ester wax (5)
R₁COO (CH₂)_nOOCR₂
(Wherein R₁And R₂Represents a hydrocarbon group having 1 to 40 carbon atoms, n is an integer of 2 to 20 and R₁And R₂May be the same or different carbon numbers. )
[0092]
[Chemical 6]
General structural formula of ester wax (6)
R₁OOC (CH₂)_nCOOR₂
(Wherein R₁And R₂Represents a hydrocarbon group having 1 to 40 carbon atoms, n is an integer of 2 to 20 and R₁And R₂May be the same or different carbon numbers. )
[0093]
These waxes are generally used in an amount of 2 to 30 parts by mass, more preferably 5 to 20 parts by mass in 100 parts by mass of the developer in order to achieve improvement in releasability at the time of fixing. When the wax component is less than 2 parts by mass, the release effect as a wax can hardly be exhibited. When the wax component exceeds 30 parts by mass, the developer releasability is satisfied, but the developer developability. This is not preferable because the deterioration of the toner tends to cause a problem that the developer is fused to the surface of the developing sleeve or the latent image carrier.
[0094]
The wax component according to the present invention has a maximum endothermic peak in the region of 50 to 120 ° C. at the time of temperature rise in the DSC curve measured by a differential scanning calorimeter, and the onset temperature of the start point of the endothermic peak including the maximum endothermic peak Is preferably 40 ° C. or higher, and in particular, the temperature difference between the peak temperature of the maximum endothermic peak and the onset temperature is preferably in the range of 7 to 50 ° C.
[0095]
By having an endothermic peak and a maximum endothermic peak in the above temperature range, while making a great contribution to low-temperature fixing, the releasability is also effectively exhibited, and matching with the fixing method of the present invention is good. When the endothermic peak is below 50 ° C., the high temperature offset resistance of the developer is remarkably impaired, and when it exceeds 120 ° C., the low temperature fixing property of the developer is remarkably impaired. Further, when the maximum endothermic peak is less than 50 ° C. at the time of temperature rise measurement and less than 40 ° C. at the time of temperature fall measurement, the self-cohesion force of the wax component becomes weak, and as a result, the high temperature offset resistance deteriorates. On the other hand, if the maximum endothermic peak exceeds 120 ° C., the fixing temperature becomes high and low temperature offset tends to occur, which is not preferable.
[0096]
By using a wax component that melts in the above temperature range in the DSC curve at the time of temperature rise, the dispersibility of other additives can be improved, and the wax component itself can be easily dispersed as described above. Can be controlled.
[0097]
As a result, not only good fixability of the developer but also a release effect by the wax component is effectively expressed, a sufficient fixing area is secured, and developability and blocking resistance by a conventionally known wax component Since the adverse effect on the image forming apparatus is eliminated, these characteristics are remarkably improved. In particular, as the particle shape becomes spherical, the specific surface area of the developer decreases, so it becomes very effective to control the dispersion state of the wax component.
[0098]
The present invention is characterized by charge imparting properties at the development portion. In order to exhibit such characteristics, it is preferable to appropriately use a charge control agent. The charge control agent is not particularly limited as long as the effects of the present invention can be obtained, and known charge control agents can be used.
[0099]
Examples of those that control the developer to be negatively charged include the following substances. For example, an organic metal compound and a chelate compound are effective, and specifically, there are a monoazo metal compound, an acetylacetone metal compound, an aromatic hydroxycarboxylic acid, and an aromatic dicarboxylic acid metal compound. Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and metal salts thereof, anhydrides, esters, and phenol derivatives such as bisphenol. Further, urea derivatives, metal-containing salicylic acid compounds, metal-containing naphthoic acid compounds, boron compounds, quaternary ammonium salts, calixarene, silicon compounds, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene- An acrylic-sulfonic acid copolymer, a nonmetal carboxylic acid compound, etc. are mentioned.
[0100]
As specific examples of controlling the developer to be positively charged, there are the following substances. For example, modified products with nigrosine and fatty acid metal salts, quaternary ammonium salts such as guanidine compounds, imidazole compounds, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and the like Onium salts such as phosphonium salts and their lake pigments, triphenylmethane dyes and their lake pigments (as rake agents, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, Gallic acid, ferricyanide, ferrocyanide, etc.), metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; DOO, dioctyl tin borate, diorgano tin borate such as dicyclohexyl tin borate; can be used in combination of these alone, or two or more kinds. Among these, a charge control agent such as a nigrosine-type quaternary ammonium salt is particularly preferably used.
[0101]
The metal oxide fine particles that are one of the features of the present invention will be described. The present invention is a non-magnetic one-component developer having at least two or more types of metal oxide fine particles on the surface of the colored particles, and at least one of the metal oxide fine particles is hydrophobically charged to the same polarity as the colored particles It is a fine particle, and at least one of the other external additives is a particle that is charged with a polarity opposite to that of the colored particle.
[0102]
Here, as the hydrophobic silica particles as the first external additive, for example, the specific surface area by nitrogen adsorption measured by the BET method is 20 m.²/ G or more, more preferably 30 to 400 m²Those in the range of / g give better results.
[0103]
The silica fine powder, if necessary, for the purpose of hydrophobization and charge control, silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, It is preferable to treat with other treating agents such as organosilicon compounds. These treatment agents may be used alone or in combination for the purpose of obtaining a desired effect. In addition, after the surface treatment as described above, it is preferable to perform an auxiliary surface treatment such as a heat treatment or a physical treatment such as a pulverization treatment as a post-treatment.
[0104]
The amount of the hydrophobic silica fine particles used in the toner of the present invention is preferably from 0.01 to 5.0 parts by weight, more preferably from 0.005 parts by weight, based on 100 parts by weight of the colored particles, from the viewpoints of chargeability and development stability. 1 to 4.0 parts by mass, more preferably 0.5 to 3.0 parts by mass. When the amount of the hydrophobic silica fine particles is less than 0.01 parts by mass, the developer is fused to the surface of the latent electrostatic image bearing member in the developing part, the transferability is deteriorated due to fluidity inhibition, or the charged part is This is not preferable because of fog deterioration due to poor stirring.
[0105]
On the other hand, when the amount of the hydrophobic silica fine particles exceeds 5.0 parts by mass, toner contamination on the surface of the electrostatic latent image carrier or the developer carrier tends to occur, and electrostatic latent images are continuously printed. Since fusing to the surface of the image carrier or contamination of the lower layer of the developer carrier causes development problems such as fusing to the latent image carrier, it is not preferable.
[0106]
Furthermore, it is preferable that this invention contains the particle | grains charged in reverse polarity with respect to this hydrophobic silica fine particle. The determination as to whether or not the particles are charged with a reverse polarity is made by using a melt kneading pulverization method to knead charged particles in an appropriate resin in a model manner and then pulverize and classify them. Is measured with a measuring device such as a known two-component charge amount measuring device after mixing with a known gradient charge measuring device or a carrier used in a two-component development method such as an iron powder carrier to measure the charge amount between raw materials. Is possible.
[0107]
Furthermore, separately, the charge amount of the colored particles can be measured by the same method to obtain the charge amount of the colored particles.
[0108]
Here, when the values of the charge amount measurement results of the hydrophobic silica particles and the second external additive particles and the colored particles themselves to be combined are arranged, these external additives are placed before and after the charged amount of the colored particles. The following relationship
(Hydrophobic silica particles)> (charge amount of colored particles)> (charge amount of second external additive particles)
Or
(Charge amount of second external additive particles)> (Charge amount of colored particles)> (Hydrophobic silica particles)
What satisfies the above relationship is “particles that are hydrophobic silica fine particles that are charged to the same polarity as the colored particles, and that the second external additive is charged to the opposite polarity to the colored particles. ".
[0109]
In addition, the definition of the present application can be applied to those including the third external additive in the above relationship as long as the above relationship is applicable.
[0110]
In addition, when the developer contains particles that are charged with the opposite polarity to the colored particles, the presence of “particles charged with the opposite polarity” from the components of the particles remaining on the surface of the electrostatic latent image carrier before and after development. Can be confirmed. “Particles charged in reverse polarity” are generally difficult to be transferred onto a transfer material by a transfer bias. This is because the charging characteristics of developers and general hydrophobic silica are in the same polarity charged state, whereas “particles with opposite polarity” are different in behavior during transfer from developers and hydrophobic silica. , It tends to remain on the electrostatic latent image carrier. Therefore, by comparing the amount of the external additive in the developer and the amount of the external additive remaining on the electrostatic latent image bearing member after the transfer, the second external additive can be expressed as “reverse polarity with respect to the colored particles. It can be determined whether the particle is a “charged particle”.
[0111]
In order to make a determination in this case, it is necessary to perform quantification, but in order to make a quantification and determination, a method of using a difference in element or particle size between the first external additive and the second external additive. For example, a method using a microelement analyzer such as a particle analyzer PT1000 manufactured by Yokogawa Electric Co., Ltd., a method using an electron microscope and a secondary electron element analyzer (EDAX), and a first external additive As a method of utilizing the difference in crystal structure and refractive index of the second external additive, a laser diffraction type particle size distribution meter is used, and the amounts of the two external additives are quantified based on the difference in refractive index. There is a way.
[0112]
As a raw material, a hydrophobic silica fine particle and a developer obtained by externally adding particles charged with a reverse polarity to the hydrophobic silica fine particle were subjected to image output by the image forming method described in this application. The presence of “particles charged to the opposite polarity to the colored particles” can be confirmed from the components of the particles remaining on the surface of the image carrier, and the polarity relationship between two or more kinds of external additive particles contained in the developer It was found that it is possible to verify.
[0113]
Furthermore, a state in which at least one of the metal oxide fine particles remains on the surface of the latent electrostatic image bearing member after transfer at a ratio of 1.3 to 10 times the developer composition is compatible with fog and image quality. Preferred above. In a system in which at least one of the metal oxide fine particles is less than 1.3 times the developer composition on the surface of the latent electrostatic image bearing member after transfer, the effect of imparting charge by rubbing becomes weak, and the present invention The effect of cannot be obtained. On the other hand, if it is more than 10 times, the load is increased with respect to processes after transfer such as cleaning and charging, and for example, cleaning defects and charging defects occur at the same time, which causes development streaks.
[0114]
In the developer of the present invention, hydrophobized silica fine powder can be used as the first external additive for the purpose of improving charging stability, developability, fluidity and durability.
[0115]
The silica fine powder matrix to be hydrophobized is not particularly limited and known silica can be used. However, as a characteristic of the silica fine powder after the hydrophobizing treatment, the specific surface area by nitrogen adsorption measured by the BET method is 20 m.²/ G or more (especially 30 to 400 m²/ G) is preferable in terms of developability and fluidity.
[0116]
Specific examples of the hydrophobizing agent include silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having a functional group, and other organosilicon compounds. These treatment agents may be used alone or in combination.
[0117]
The method of hydrophobizing these silica fine powders can be performed by a known production method. The degree of hydrophobicity (hydrophobization degree) of the hydrophobized silica fine powder is preferably 90% or more in a methanol / water mixed solvent system for the purpose of the present application.
[0118]
The amount of the hydrophobized silica fine powder used is 0.01 to 8 parts by mass, preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the developer particles.
[0119]
There are inorganic fine powders treated with silicone oil. Specific examples include silica fine powder hydrophobized by silicone oil treatment, titanium oxide hydrophobized by silicone oil treatment, and alumina hydrophobized by silicone oil treatment. It is done.
[0120]
The second external additive that can be suitably used in the present invention is not particularly limited as long as it satisfies the scope of the present application in the following known inorganic powders. Specific examples of the second external additive include magnesium, zinc, aluminum, cerium, cobalt, iron, zirconium, chromium, manganese, strontium, tin, and oxides of metals such as antimony; calcium titanate, magnesium titanate, Composite metal oxides such as strontium titanate; metal salts such as calcium carbonate, magnesium carbonate and aluminum carbonate; clay minerals such as kaolin; phosphate compounds such as apatite; silicon compounds such as silicon carbide and silicon nitride; carbon black and graphite The carbon powder can be used as long as it is “particles charged with a reverse polarity to the colored particles”.
[0121]
Among these, fine powders containing magnesium or titanium are preferable. Specifically, hydrotalcites and titanias, particularly rutile type titanium oxide is preferable. It is more preferable to use “polarly charged particles”.
[0122]
In the developer of the present invention, it is preferable to control the shape of the developer from the viewpoint of charging stability at the development portion and durability of the developer.
[0123]
As the range of the shape of the developer of the present invention, the average circularity of the developer is 0.950 to 0.95 in the equivalent circle diameter-circularity scattergram based on the number of developers measured by a flow type particle image measuring device. A more preferable result is 0.990 and the circularity standard deviation is less than 0.040.
[0124]
A developer having an average circularity of less than 0.950 means a developer whose shape has moved away from a spherical shape and has approached an indeterminate shape. Such an irregular-shaped developer reduces the charge imparting ability in the development nip. This is considered to be because the rolling of the developer is poor at the development nip due to the irregular shape, and the desired rubbing is not performed.
[0125]
The developer whose average circularity of the developer exceeds 0.990 means a developer whose shape is more nearly spherical. Such a nearly spherical developer is excellent in chargeability and transferability, but generally tends to cause poor cleaning by a cleaning means such as blade cleaning, and the residual developer remaining on the latent image carrier after development is removed. Since it becomes difficult to remove with a blade cleaning mechanism, an image defect due to poor cleaning and an image defect due to charging / exposure interference are likely to occur, which is not preferable.
[0126]
The developer having a standard deviation of the circularity of 0.040 or more means a developer having a large variation in shape. Such a developer is good for blade cleaning, but has a problem with respect to charging uniformity. When such a developer is used, there is a problem because, for example, image fogging occurs due to non-uniform charging. .
[0127]
The equivalent-circle diameter, circularity, and frequency distribution of the developer in the present invention are used as a simple method for quantitatively expressing the shape of the developer particles. In the present invention, the flow-type particle image measuring device is used. Measurement was performed using an FPIA-1000 type (manufactured by Toa Medical Electronics Co., Ltd.), and the calculation was performed using the following equation.
[0128]
[Expression 2]

[0129]
Here, the “particle projected area” is the area of the binarized developer particle image, and the “peripheral length of the particle projected image” is the contour line obtained by connecting the edge points of the developer particle image. Define length.
[0130]
The circularity in the present invention is an index indicating the degree of unevenness of the developer particles, and indicates 1.00 when the developer particles are perfectly spherical. The more complicated the surface shape, the smaller the circularity. .
[0131]
In the present invention, the circle-equivalent number average particle diameter D1 and the particle diameter standard deviation SDd, which mean the average value of the particle number frequency distribution based on the number of developers, are the particle diameter (center value) at the dividing point i of the particle size distribution. di, frequency f_iThen, it is calculated from the following formula.
[0132]
[Equation 3]

[0133]
In addition, the average circularity and the circularity standard deviation SDc, which mean the average value of the circularity frequency distribution, can be expressed by the following equation, where the circularity (center value) at the distribution point i of the particle size distribution is ci and the frequency is fci. Calculated.
[0134]
[Expression 4]

[0135]
In the present invention, the particle size distribution is 16 to 50% by number of developer particles having a particle size of 5 μm or less, as measured with a Coulter Multisizer, and 8 to 12.7 μm. It is preferable that the developer particles have a particle size of 1 to 30% by number and developer particles having a particle size of 16 μm or more are contained in an amount of 1.5% by volume or less.
[0136]
If the developer particles having a particle size of 5 μm or less in the developer are less than 16% by number, the developer fogging and dot omission, which are the effects of the present invention, are not preferable. Further, when the developer particle having a particle diameter of 5 μm or less in the developer is more than 50% by number, it is not preferable because a development streak resulting from the fusion of the developer to the regulating member is generated. . Furthermore, in order to achieve such a developer, a system containing 1 to 30% by number of developer particles having a particle diameter of 8 to 12.7 μm further stabilizes the developer as described above. Further, the amount of developer particles having a particle diameter of 16 μm or more is contained in an amount of 1.5% by volume or less, so that development streaks can be further suppressed.
[0137]
The average particle size and particle size distribution of the developer can be measured by various methods such as Coulter Counter TA-II or Coulter Multisizer (Coulter). In the present invention, Coulter Counter TA-II (Coulter) ) Is connected to an interface (manufactured by Nikka) and a PC9801 personal computer (manufactured by NEC) that outputs a number distribution and volume distribution, and a 1% NaCl aqueous solution is prepared using first-grade sodium chloride as the electrolyte. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and number of toners of 2 μm or more were measured using the Coulter counter TA-II with a 100 μm aperture as an aperture. Volume distribution and number distribution were calculated.
[0138]
【Example】
Production example of electrostatic latent image carrier (1)
The negatively charged polar OPC electrostatic latent image carrier comprising aluminum cylinder / conductive layer / undercoat layer / charge generation layer / charge transport layer / surface protective layer used in this example was prepared by the following method.
[0139]
(I) Production of conductive layer
To an aluminum cylinder with an outer diameter of 30 mm and a length of 357.5 mm,
Conductive titanium oxide: 10 parts by mass
(Tin oxide coating, number average particle size 0.4 μm)
Phenolic resin precursor (Resol type) ・ ・ ・ ・ ・ 10 parts by mass
Methanol: 10 parts by mass
Butanol: 10 parts by mass
The dispersion obtained by sand mill dispersion is applied by dip coating and cured at 140 ° C., so that the volume resistance is 5 × 10.⁹A conductive layer of Ω · cm and a thickness of 20 μm was provided.
[0140]

After mixing and dissolving, an undercoat layer of 1 μm was provided by dip coating on the conductive layer.
[0141]
(Iii) Preparation of charge generation layer
Next, TiOPc (oxytitanium phthalocyanine) 4 having diffraction peaks 2θ ± 0.2 ° in X-ray diffraction of CuKα having strong peaks at 9.0 °, 14.2 °, 23.9 ° and 27.1 °. Disperse 4 parts by mass of polyvinyl butyral (trade name: ESREC BM2, manufactured by Sekisui Chemical Co., Ltd.) and 60 parts by mass of cyclohexanone with a sand mill apparatus using φ1 mm glass beads, and add 100 parts by mass of ethyl acetate to generate charge. A layer dispersion was prepared. This was dip-coated on the subbing layer obtained above to provide a 0.3 μm charge generation layer.
[0142]
(Iv) Preparation of charge transport layer
Triphenylamine: 10 parts by mass
Polyarylate resin (weight average molecular weight 150000) ・ ・ ・ ・ ・ 10 parts by mass
Monochlorobenzene 50 parts by mass
Dichloromethane: 15 parts by mass
Were mixed by dip coating on the charge generation layer to provide a 20 μm charge transport layer.
[0143]
(V) Preparation of surface protective layer
Next, the following acrylic monomer: 30 parts by mass
[0144]
[Chemical 7]

Tin oxide ultrafine particles with a number average particle size of 40 nm before dispersion: 50 parts by mass
2-methylthioxanthone as a photopolymerization initiator: 18 parts by mass
Ethanol 150 parts by mass
Was dispersed for 66 hours in a sand mill. This preparation solution is dip-coated on the previous charge transport layer and 200 W / cm with a high-pressure mercury lamp.²The surface protective layer was obtained by performing photocuring for 60 seconds at 120 ° C. and then drying with hot air at 120 ° C. for 2 hours. The film thickness of the obtained surface protective layer was 3 μm. This electrostatic latent image carrier was used as an electrostatic latent image carrier A in the production of the following electrophotographic image forming apparatus.
[0145]
The surface protective layer thus produced was polished to 0.2 μm by rotating the electrostatic latent image carrier and applying pressure while contacting the # C-2000 wrapping tape made by Fuji Film. . The electrostatic latent image carrier after polishing the surface protective layer is referred to as an electrostatic latent image carrier A ′.
[0146]
(Vi) Measurement of surface characteristics
A surface film physical property test was performed on the electrostatic latent image carrier A 'thus obtained. Further, the surface friction coefficient and the contact angle with pure water were measured by the methods described above.
[0147]
As a result, the surface friction coefficient is 0.80 and the universal hardness HU is 300 N / mm.²Met.
[0148]
Example of production of electrostatic latent image carrier (2)
Production example (1) of the electrostatic latent image carrier except that the step (v) Preparation of the surface protective layer is omitted in the production example (1) of the electrostatic latent image carrier and polishing is performed to 0.1 μm. ) To obtain an electrostatic latent image carrier B ′.
[0149]
The electrostatic latent image carrier B 'thus obtained was measured and found to have a surface friction coefficient of 0.7 and a universal hardness HU of 290 N / mm.²Met.
[0150]
Example of production of electrostatic latent image carrier (3)
The electrostatic latent image carrier C is the same as the electrostatic latent image carrier production example (2) except that the polishing is performed to 0.5 μm in the electrostatic latent image carrier production example (2). 'I got.
[0151]
The electrostatic latent image carrier C ′ thus obtained was measured and found to have a surface friction coefficient of 1.1 and a universal hardness HU of 290 N / mm.²Met.
[0152]
Example of production of electrostatic latent image carrier (4)
(1) Production of electrostatic latent image carrier B and measurement of surface characteristics
The same process as in Production Example (1) was performed until a conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were sequentially formed on an aluminum cylinder having an outer diameter of 30 mm and a length of 357.5 mm. Next, the surface protective layer on the charge transport layer was produced in the following manner. That is,
The following acrylic monomer: 10 parts by mass
[0153]
[Chemical 8]

Was dispersed for 66 hours in a sand mill. This preparation solution is dip-coated on the charge transport layer and 150 W / cm using a high-pressure mercury lamp.²The surface protective layer was obtained by performing photocuring for 80 seconds at a light intensity of 1, and then drying with hot air at 120 ° C. for 1 hour. The film thickness of the obtained surface protective layer was 4 μm. This electrostatic latent image carrier was used as an electrostatic latent image carrier D in the production of the following electrophotographic image forming apparatus.
[0154]
The surface protective layer thus produced was polished to 0.3 μm by rotating the electrostatic latent image carrier and applying pressure while contacting a Fujifilm # C-2000 wrapping tape. . The electrostatic latent image carrier after polishing the surface protective layer is referred to as an electrostatic latent image carrier D ′.
[0155]
When the electrostatic latent image carrier D ′ thus obtained was measured, the surface friction coefficient was 0.4 and the universal hardness HU was 280 N / mm.²Met.
[0156]
  Production example of electrostatic latent image carrier (5)
  Poly used in production example (2) of electrostatic latent image carrierArilateAn electrostatic latent image carrier E was obtained in the same manner as in Production Example (2) of an electrostatic latent image carrier, except that the viscosity average molecular weight was changed to 5000. The electrostatic latent image carrier E was polished, and each measurement was performed on the polished electrostatic latent image carrier E ′. As a result, the surface friction coefficient was 1.4 and the universal hardness HU was 310 N / mm.²Met.
[0157]
Table 1 summarizes the contents and surface characteristics of the electrostatic latent image carrier produced in the production example of the electrostatic latent image carrier.
[0158]
[Table 1]

[0159]
External additive
The external additives used in this example are summarized below. Further, for the purpose of measuring the charging characteristics of these external additives, the following external additives are added to 100 parts by mass of a styrene-butyl acrylate-maleic acid butyl half ester copolymer (peak molecular weight: about 20000). About 20 parts by mass of the agent, melted and kneaded, cooled, pulverized, classified and adjusted to a certain particle size, mixed with an iron powder carrier (EFV), and then mixed with the two-component charge measuring device shown in FIG. The amount of charge was measured. These results are summarized below.
[0160]
[Table 2]

[0161]
Developer production example (1)
In a 4-liter flask for 2 liters equipped with a high-speed stirring device TK-homomixer, 710 parts by mass of ion-exchanged water and 0.1 mol / L-Na_ThreePO_Four450 mass parts of aqueous solution was added, the rotation speed was adjusted to 7000 rpm, and it heated at 60 degreeC. Here 1.0 mol / L-CaCl₂Gradually add 68 parts by mass of an aqueous solution, and add a minute water-insoluble dispersant Ca_Three(PO_Four)₂An aqueous dispersion medium containing was prepared.
[0162]
on the other hand,
・ 80 parts by mass of styrene monomer
・ 20 parts by mass of 2-ethylhexyl acrylate monomer
・ Polyester 10 parts by mass
(Acid value 20 mg KOH / g, peak molecular weight 7500)
Carbon black (primary particle size 44nm) 10 parts by mass
・ Ester wax No. 4 10 parts by mass
(R₁, R₂: C₁₈H₃₇)
・ Monoazochrome complex 1 part by mass
After the above materials were sufficiently dispersed using a ball mill, the contents were isolated from the ball mill. A polymerizable monomer composition in which 3 parts by mass of 2,2′-azobis (2,4-dimethylbutyronitrile), which is a polymerization initiator, was added to the content was charged into the aqueous dispersion medium. The granulation was carried out while maintaining the rotational speed of 7000 rpm. Thereafter, the mixture was reacted at 60 ° C. for 4 hours while stirring with a paddle stirring blade, then polymerized at 80 ° C. for 5 hours, and further distilled under reduced pressure at 85 ° C. to complete the reaction.
[0163]
After completion of the reaction, the suspension is cooled, and hydrochloric acid is added to form a poorly water-soluble dispersant Ca._Three(PO_Four)₂After being dissolved, filtered, washed with water and dried, it was classified to a desired particle size by air classification to obtain colorant particles (1). The obtained colorant particles (1) were mixed with an iron powder carrier, and the charge amount was measured by a two-component charge amount measuring device, which was -45 mC / kg.
[0164]
Subsequently, with respect to 100 parts by mass of the colored particles, 1.5 parts by mass of the external additive (1) and 0.2 parts by mass of the external additive (3) were stirred at high speed with a Henschel mixer, The developer (1) of the present invention was prepared by treating the surface.
[0165]
In the developer (1), the charge amounts of the colorant particles, the external additive (1), and the external additive (3) are as follows:
Colorant particles (1) = − 45 mC / kg
External additive (1) = − 80 mC / kg
External additive (3) = + 10 mC / kg
In contrast to the external additive (1) and the colorant particles (1), the external additive (3) is charged with a reverse polarity.
[0166]
In this way, when a developer is prepared by combining two kinds of hydrophobic silica having the same polarity as the colored particles and a high charge amount, and an external additive charged to the opposite polarity, “Non-magnetic one-component developer having at least two or more kinds of metal oxide fine particles on the surface of the colored particles, and at least one of the metal oxide fine particles is charged with the same polarity as the colored particles. In addition, at least one of the other external additives is a particle that is charged with a polarity opposite to that of the colored particle.
[0167]
Developer production examples (2) to (4)
Developers (2) to (4) were produced in the same manner as in Developer Production Example (1) except that only the formulation shown in Table 3 was changed.
[0168]
Developer production example (5)
The colorant particles were produced by the melt pulverization method shown below. As a specific manufacturing method,
First, the following materials were mixed using a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.).
・ Styrene-butyl acrylate-maleic acid butyl half ester copolymer
(Peak molecular weight: about 40000, glass transition point Tg: 63 ° C.) 100 parts by mass
・ Carbon black (primary particle size 40nm) 10 parts by mass
・ 2 parts by weight of dicarboxylic acid aluminum complex
・ Polyethylene 5 parts by mass
(Molecular weight distribution = 1.08, DSC endothermic peak: 107 ° C.)
[0169]
Subsequently, a twin-screw kneader (PCM) is used so that the barrel set temperature at the kneading section on the rearmost side of the screw extrusion kneader becomes T0 (° C.) = 110 ° C. and the melt kneader outlet temperature T1 = 150 ° C. -30 type, manufactured by Ikekai Tekko Co., Ltd.). The obtained kneaded product was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized toner. Next, the coarsely crushed material was finely pulverized with a collision-type airflow pulverizer, and then subjected to spheronization treatment using a surface modification device utilizing mechanical impact force to obtain a spherical pulverized raw material. Next, the obtained pulverized raw material was introduced into a multi-division classifier elbow jet classifier (manufactured by Nippon Steel Mining) and classified so as to obtain a desired particle size distribution, whereby colored particles (5) were obtained. The obtained colorant particles (5) were mixed with an iron powder carrier, and the charge amount was measured with a two-component charge amount measuring device. As a result, it was -40 mC / kg.
[0170]
Subsequently, 1.3 parts by mass of the external additive (2), 0.2 parts by mass of the external additive (8), and 0.2 parts of the external additive (7) with respect to 100 parts by mass of the colored particles. A developer (5) of the present invention was prepared by stirring a mass part at a high speed with a Henschel mixer and treating the surface of the colored particles.
[0171]
Developer production examples (6) to (8)
Developers (6) to (8) were produced in the same manner as in Developer Production Example (5) except that only the formulation shown in Table 3 was changed.
[0172]
Developer production example (9)
Developer production example (5) except that in the developer production example (5), the step of performing the spheronization treatment using a surface modification device utilizing mechanical impact force is omitted and the classification conditions are operated. A developer (9) was produced in the same manner as described above.
[0173]
Comparative developer example (1)
In the developer production example (5), the prescription shown in Table 3 was changed, and the classification conditions were operated to obtain colored particles. The colored particles were mixed with an iron powder carrier, and the charge amount was measured by a two-component charge amount measuring device, which was -45 mC / kg. A comparative developer (1) was prepared by subjecting the colored particles to surface treatment using 1.5 parts by mass of the external additive (1) and 0.3 parts by mass of the external additive (7).
[0174]
Comparative production example of developer (2)
In the developer production example (9), the prescription shown in Table 3 was changed, and the classification conditions were operated to obtain colored particles. The colored particles were mixed with an iron powder carrier, and the charge amount was measured with a two-component charge amount measuring device. As a result, it was -40 mC / kg. Surface treatment using 1.5 parts by mass of external additive (2), 0.3 part by mass of external additive (9) and 0.1 part by mass of external additive (7) with respect to the colored particles Thus, a comparative developer (2) was prepared.
[0175]
Comparative production example of developer (3)
Comparative developer (3) was prepared by subjecting the colored particles prepared in Comparative Production Example (2) of the developer to surface treatment using 1.7 parts by mass of external additive (2).
[0176]
The developers synthesized above are summarized in Table 3.
[0177]
[Table 3]

[0178]
Development device example (1)
Next, the developing device used in this embodiment will be specifically described.
[0179]
FIG. 1 is a schematic diagram of a modified 600 dpi laser beam printer (Canon: LBP-860) using the one-component contact developing type electrophotographic process used in this example. In this example, an apparatus in which the following parts (a) to (h) were modified was used.
(A) The process speed was changed to 129 mm / s.
(B) The charging method of the apparatus was direct charging by contact with a rubber roller, and the applied voltage was a direct current component.
(C) Medium resistance rubber roller (16φ, hardness ASKER C45 degree, resistance 10) made of silicone rubber in which carbon black is dispersed as a developer carrier.^Five(Ω · cm, Ra = 2.1 μm, Rz = 3.5 μm), and arranged so as to be in pressure contact with the electrostatic latent image carrier with a nip width of 3.0 mm.
(D) The rotational peripheral speed of the developer carrier is a forward direction at the contact portion with the electrostatic latent image carrier, and the relative speed of the developer carrier to the electrostatic latent image carrier is 155%. The speed was adjusted.
(E) The electrostatic latent image carrier is referred to as an electrostatic latent image carrier A ′.
(F) As a means for applying the developer to the developer carrying member, a coating roller was provided in the developing device and brought into contact with the developer carrying member.
(G) A blade obtained by dipping a solvent-diluted urethane on a phosphor bronze surface having a thickness of 0.5 mm so that the contact pressure with the developer carrier is about 29.6 N / m (about 30 g / cm). Installed on.
(H) Only the DC component was applied during development.
(J) The cleaning blade on the electrostatic latent image carrier was attached so that the contact pressure was about 39.2 N / m (about 40 g / cm).
[0180]
The electrophotographic apparatus was remodeled and process conditions were set as follows in order to conform to the remodeling of these process cartridges.
[0181]
The modified device uses a roller charger (applying only direct current) to uniformly charge the image carrier. After charging, an image portion is exposed with a laser beam to form an electrostatic latent image, and after making a visible image with a developer, the developer image is transferred to a transfer material by a roller to which a voltage of +700 V is applied. . The outline is shown in FIG.
[0182]
(K) The electrostatic latent image carrier was replaced with the electrostatic latent image carrier of Production Example (1) of an electrostatic latent image carrier.
[0183]
(M) The electrostatic latent image carrier charging potential was adjusted such that the dark portion potential was −700 V and the light portion potential was −100 V.
[0184]
Developing device examples (2) to (5)
In the developing device example (1), the developing device examples (2) to (5) are similarly prepared except that (e) the electrostatic latent image carrier is changed to the electrostatic latent image carriers B ′ to E ′. did.
[0185]
Development device example (6)
In the developing device example (1), except that (d) the rotational peripheral speed of the developer carrier is adjusted so that the relative speed of the developer carrier to the electrostatic latent image carrier is 110%. Similarly, a developing device example (6) was prepared.
[0186]
Development device example (7)
In the developing apparatus example (1), except that (d) the rotational peripheral speed of the developer carrier is adjusted so that the relative speed of the developer carrier to the electrostatic latent image carrier is 260%. Similarly, a developing device example (7) was prepared.
[0187]
Development device example (8)
In this example, in place of the 600 dpi laser beam printer (Canon: LBP-860) modified in the developing device example (1), a 600 dpi color laser which is a non-magnetic one-component full color image forming apparatus having an intermediate transfer member. A beam printer modification machine was used.
[0188]
The basic configuration of this example is shown in FIG.
[0189]
In this image forming method, the developer of each color is sequentially transferred onto the intermediate transfer body 5 having the cleaning device 10 that can attach and detach the image visualized on the electrostatic latent image carrier 1. Then, after four-color images are formed on the intermediate transfer member 5, the images are transferred onto the recording material P and fixed, whereby a fixed image is obtained.
[0190]
In the apparatus system shown in FIG. 2, black, yellow, magenta, and cyan developers are introduced into the developing devices 4-1, 4-2, 4-3, and 4-4, respectively.
[0191]
The following points were changed from the developing device example (1).
(A) The process speed was changed to 94 mm / s.
(J) The contact pressure of the cleaning blade 8 on the electrostatic latent image carrier 1 is set to a linear pressure of about 39.2 N / m (about 40 g / cm), and the cleaning blade 10 is detachable.
[0192]
  Examples (1) to (8), Reference Example (1), and Comparative Examples (1) to (3)
  Using the developing device example (1) as an image forming apparatus, the developers (1) to (9) and the comparative developing examples (1) to (3) as developers, respectively, in an environment of 23 ° C. and 15%. 8000 continuous horizontal line pattern images were lasted on A4 size paper.
[0193]
  Examples (1) to (8),Reference example (1)And the printout evaluation result of comparative example (1)-(3) is put together in Table 4 (details of evaluation are mentioned below).
[0194]
  Furthermore, for Example (2), the amount of external additive in the developer and the amount of external additive remaining on the electrostatic latent image carrier after transfer were quantified by SEM and EDAX. Since the external additive (1) and the external additive (4) used in Example (2) have different composition ratios and particle sizes, both can be easily distinguished. As a result, the external additive (1) and the external additive contained in the external additive in the developer (4) Ratio of the external additive (1) and external additive (1) in the component remaining on the electrostatic latent image carrier after transfer.4) Ratio is clearly different, and the external additive (optional) is selectively applied on the electrostatic latent image carrier after transfer.4) Remained. Therefore, when the developer combination as in Example (2) is output in such a development system, particles that are charged with opposite polarity to the colored particles on the electrostatic latent image carrier after transfer. Can be verified to be included.
[0195]
  Here, Examples (1) to (8)Reference example (1)However, the combination of the hydrophobic silica fine particles charged to the same polarity as the colored particles and the external additive charged to the opposite polarity to the colored particles is suitable. Thus, the developer is appropriately charged, so that the developer fusion and developability, which are the effects of the present invention, are improved. Further, it has been clarified that the effects of the present invention are remarkably exhibited when the developer has an appropriate particle size distribution and particle shape. This means that when the particle size distribution and particle shape of the developer are in the ranges as in the present invention, tribocharging at the development site is more effectively performed.
[0196]
In addition, the developer does not adhere to the regulating member surface or the electrostatic latent image carrier surface during durability, despite the durability test under severe environment such as low temperature and low humidity. There are few, and the stable performance which is not different from the initial stage can be demonstrated even in the second half of the endurance. Although the mechanism by which such an effect is manifested is not clear, a combination of hydrophobic silica fine particles that are charged to the same polarity as the colored particles and external additives that are charged to the opposite polarity to the colored particles is used for repeated development. When the developed developer is rubbed at the friction site, electrostatic cohesive force acts on a minute area in the developer, reducing the amount of free external additive, so that the external additive adheres to the surface of each member. It is thought that this is because the surface of each member always maintains a state close to the initial state.
[0197]
Examples (10) to (11) and Comparative Examples (4) to (7)
Using each of the developing device examples (2) to (7) shown in Table 5 as an image forming apparatus and using the developer (1) as a developer, a horizontal line pattern on A4 size paper in an environment of 23 ° C. and 30% A durability test of 8000 images was continuously performed.
[0198]
Details of the evaluation that summarizes the printout evaluation results of Examples (10) to (11) and Comparative Examples (4) to (7) in Table 5 are described later.
[0199]
Here, the production examples (2) to (3) of the electrostatic latent image carrier exhibited good performance. This is because the surface friction coefficient of the surface of the electrostatic latent image carrier is appropriate. This is because the effect of frictional charging at the developing portion is effectively performed. Further, since there is no change in developability even with the durability of 8,000 sheets, the surface of the electrostatic latent image carrier has sufficient hardness, and is effective against wear and static. This is considered to be because the initial characteristics of the electrostatic latent image carrier were maintained even in the latter half of the durability.
[0200]
In Comparative Example (4), dot omission and image density change due to durability were insufficient, but this is because the surface friction coefficient of the electrostatic latent image carrier is less than the preferred range. This is considered to be caused by insufficient triboelectric charging at the development portion. Further, in the comparative example (5), image streaks and charging member contamination were insufficient. This is because the electrostatic latent image carrier has a high surface friction coefficient. Since the external additive component in the developer adheres to the surface and the surface friction coefficient of the electrostatic latent image carrier is high, cleaning with the blade cleaning member becomes difficult, and the external additive in the transfer residual component becomes difficult. It is thought that the contact charging member was contaminated because it passed. Therefore, the electrostatic latent image carrier having such a surface friction coefficient exceeds the preferable range.
[0201]
Further, in Comparative Example (6), the image fog was deteriorated, but this was because the relative speed of the developer carrying member to the electrostatic latent image carrying member was low, and the charge application at the developing portion was insufficient. This is probably because of this. In Comparative Example (7), the image streak deteriorated due to endurance. This is because the difference in peripheral speed between the developer carrying member and the electrostatic latent image carrying member is large. This is considered to be due to the increase in mechanical stress, the presence of the external additive on the surface of the developer, and the change in charging characteristics.
[0202]
Example (12)
Using the full-color image forming apparatus of the developing apparatus example (8), the developing devices 4-1, 4-2, 4-3, 4-4 have developer (1), developer (2), developer (3), Developer (4) was introduced. Using this image forming apparatus, a durability test was continuously performed on 8000 sheets of full-color images with a printing rate of 5% in an environment of 23 ° C. and 40%. As a result, a color image with stable image fog, missing dots, and stable image density was obtained. Excellent results were also obtained in terms of development streaks and charging member contamination.
[0203]
Example (13)
In the same manner as in Example (12), a durability test was carried out using developer (5), developer (6), developer (7), and developer (8). As a result, a color image with stable image fog, missing dots, and stable image density was obtained. Further, as compared with Example (12), the result that the development streak and the charging member contamination were slightly deteriorated was obtained. This is because the developer used in Example (13) has a relatively low sphericity of the surface shape of the developer particles, and the uniformity is slightly deteriorated due to rubbing due to frictional charging at the development site. It is possible that
[0204]
[Table 4]

[0205]
[Table 5]

[0206]
Description of the evaluation items described in Examples 1 to 13 and Comparative Examples 1 to 7 and evaluation criteria thereof will be described.
[0207]
[Printout image evaluation]
<1> Image fog
The fog density (%) was calculated from the difference between the whiteness of the white portion of the printout image measured by “Reflectometer” (manufactured by Tokyo Denshoku) and the whiteness of the transfer paper, and the image fogging was evaluated.
A: Very good (less than 1.0%)
B: Good (1.0% or more and less than 2.0%)
C: Practical use possible (2.0% or more, less than 3.0%)
D: Practical difficulty (3.0% or more and less than 4.0%)
E: Impractical (4% or more)
[0208]
<2> missing dots
The checker pattern shown in FIG. 5 was printed out, and the dot reproducibility was evaluated.
A: Very good (less than 1 defect / 100 defects)
B: Good (2-4 defects / 100 defects)
C: Practical use possible (5-8 defects / 100 defects)
D: Practical difficulties (9 to 11 defects / 100 defects)
E: Not practical (Defect 12 or more / 100)
[0209]
<3> Image density
Ordinary paper for ordinary copying machines (75 g / m²) Was evaluated by maintaining the image density when a predetermined number of printouts were completed. The image density was measured by using a “Macbeth reflection densitometer” (manufactured by Macbeth Co., Ltd.) to measure a relative density with respect to a printout image of a white background portion having a document density of 0.00.
A: 1.40 or more
B: 1.35 or more and less than 1.40
C: 1.25 or more and less than 1.35
D: 1.00 or more and less than 1.25
E: Less than 1.00
[0210]
<4> Development stripe
At the time of 3000 sheets, a 25% halftone image was output, and the degree of development streaks on the image (dark streaks on continuous images) was visually evaluated.
A: Very good (not generated)
B: Good (almost never occurs)
C: Practical use possible (Several weak streaks occur, but does not cause practical problems)
D: Practical difficulty (a level where a lot of weak streaks occur and becomes a practical problem)
E: Not practical (significant streaks occur and is not practical)
[0211]
<5> Charging member contamination
Regarding member contamination on the contact charging member at each durable number, the phenomenon occurring on the halftone image was evaluated according to the following criteria.
A: Very good (not generated)
B: Good (Slight component contamination is observed, but there is no effect on the image)
C: Practical use possible (Partial contamination is observed, but there is little effect on the image and there is no practical problem)
D: Practical difficulty (obviously obvious component contamination is seen, but depending on the usage level)
E: Not practical (level of obvious material contamination and problematic in practical use)
[0212]
【The invention's effect】
As described above, according to the present invention, in the one-component contact development method, a developer carrier that holds a developer having at least two kinds of metal oxide fine particles on the particle surface in a thin layer, and a constant surface When the electrostatic latent image carrier having the organic material layer having a coefficient of friction comes into contact with the peripheral portion of the developing portion with a difference in peripheral speed, it becomes possible to impart an appropriate frictional charge to the developer, thereby causing fogging and missing dots. Thus, it is possible to provide an image forming method in which image streaking does not occur while preventing insufficient density. In addition, in a one-component contact development system, it is possible to provide an image forming method in which the charging characteristics of a developer are improved and image defects due to charging effects are prevented.
[0213]
Furthermore, by controlling the particle size distribution and shape of the developer, it is possible to obtain a stable developer and an image forming method that are excellent in durability and equivalent to the initial characteristics.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus of the present invention.
FIG. 2 is a schematic configuration diagram of a full-color one-component image forming apparatus used in the present embodiment.
FIG. 3 is a diagram showing an outline of a relationship between a relative speed of a developer carrying member with respect to an electrostatic latent image carrying member, chargeability imparting ability, and developer deterioration.
FIG. 4 is a diagram schematically showing a measuring apparatus for a surface coating physical property test.
FIG. 5 is an example of an image used to evaluate missing dots according to the present invention.
FIG. 6 is a schematic view of a two-component charge amount measuring apparatus for developer.
FIG. 7 is a schematic view of a friction coefficient measuring instrument Haydon 14 type.
FIG. 8 is a diagram showing the shape of a urethane rubber blade used in measuring the friction coefficient.
9 is an enlarged view of a contact portion between a urethane rubber blade and a sample in FIG.
[Explanation of symbols]
7 Image heating device (fixing device)
P Transfer material (recording material)
1 Electrostatic latent image carrier (photosensitive drum)
2 Charging device (charging roller)
3 Laser light
4 Developer
5 Intermediate transfer drum
6 Transfer roller
8 Cleaner (photosensitive drum cleaner)
10 Cleaner (Cleaner for intermediate transfer drum)
T1 Primary transfer part
T2 Secondary transfer section
41 Suction machine
42 Measuring container
43 Conductive screen (500 mesh)
44 Lid
45 Vacuum gauge
46 Air volume control valve
47 Suction port
48 condenser
49 Electrometer
22 Upper holder
23 Lower holder
24 Fixed screws

Claims (18)

The developer carrier is placed in pressure contact with the electrostatic latent image carrier, and the electrostatic latent image on the electrostatic latent image carrier is visualized with the developer thinned on the developer carrier. In the image forming method, the rotation direction of the electrostatic latent image carrier and the developer carrier is a forward direction, and the relative speed of the developer carrier to the electrostatic latent image carrier is 120 to 250%. A developer used in an image forming method for charging the developer by rubbing in a range,
The surface of the electrostatic latent image bearing member is an electrostatic latent image bearing member formed of an organic substance, and the surface friction coefficient (the frictional force of the electrostatic latent image bearing member sample / the frictional force of polyethylene terephthalate) is 0.5. Having an organic layer of ~ 1.2,
The developer is a non-magnetic one-component developer having at least a binder resin, colored particles composed of a colorant and a release agent, and at least two or more kinds of metal oxide fine particles on the surface of the colored particles. At least one of the oxide fine particles is a hydrophobic silica fine particle that is charged to the same polarity as the colored particles, and at least one of the other external additives is a particle that is charged with a polarity opposite to that of the colored particles. The
In the particle size distribution of the developer, 16 to 50% by number of developer particles having a particle size of 5 μm or less are contained, 1 to 30% by number of developer particles having a particle size of 8 to 12.7 μm are contained, and 16 μm. The developer particles having the above particle diameter are contained by 1.5% by volume or less,
In the developer-based circle equivalent diameter-circularity scattergram measured by the flow type particle image measuring apparatus, the average circularity of the developer is 0.950 to 0.990, and the circularity standard deviation is 0. A developer characterized by being less than 040 . According to claim 1, characterized in that at least one of the metal oxide fine particles to the electrostatic latent image bearing member surface after transfer remaining at a ratio of 1.3 to 10 times the developer compositions Developer. An image forming method having a mechanism in which after transferring the visible image onto a recording material, the transfer residual developer on the surface of the electrostatic latent image carrier is subjected to blade cleaning, and further charged in contact with the electrostatic latent image carrier. developer according to claim 1 or 2 characterized in that it is a one-component developer used in. The developer carrying member of the developer unit for thinning, the developer according to any one of claims 1 to 3, characterized in that it consists of a metal blade having an elasticity. Developer according to any one of claims 1 to 4, characterized in that the material of the photosensitive layer surface is one selected polycarbonate, from polyarylate. The universal hardness HU of the surface of the photosensitive layer is 200 N / mm ² or more (provided that the curve indicating the relationship between the hardness H and the indentation depth h has no inflection point). Item 6. The developer according to any one of Items 1 to 5 . Colorant yellow, cyan, magenta, developer according to any one of claims 1 to 6, wherein the full-color forming either a black or a coloring agent for monochrome. The developer according to any one of claims 1 to 7 , wherein the developer is a full-color developer used in a method of sequentially transferring an electrostatic latent image after development to form a full-color image on a recording material. The developer according to any one of claims 1 to 8 , wherein the developer is a full-color developer used in a method of forming a full-color image on an intermediate transfer member. The developer carrier is placed in pressure contact with the electrostatic latent image carrier, and the electrostatic latent image on the electrostatic latent image carrier is visualized with the developer thinned on the developer carrier. The rotation direction of the electrostatic latent image carrier and the developer carrier is a forward direction, and the relative speed of the developer carrier to the electrostatic latent image carrier is 120 to 250%. An image forming method for charging the developer by rubbing in a range,
The surface of the electrostatic latent image bearing member is an electrostatic latent image bearing member formed of an organic substance, and the surface friction coefficient (the frictional force of the electrostatic latent image bearing member sample / the frictional force of polyethylene terephthalate) is 0.5. Having an organic layer of ~ 1.2,
The developer is a non-magnetic one-component developer having at least a binder resin, colored particles composed of a colorant and a release agent, and at least two or more kinds of metal oxide fine particles on the surface of the colored particles. At least one of the oxide fine particles is a hydrophobic silica fine particle that is charged to the same polarity as the colored particles, and at least one of the other external additives is a particle that is charged with a polarity opposite to that of the colored particles. The
In the particle size distribution of the developer, 16 to 50% by number of developer particles having a particle size of 5 μm or less are contained, 1 to 30% by number of developer particles having a particle size of 8 to 12.7 μm are contained, and 16 μm. The developer particles having the above particle diameter are contained by 1.5% by volume or less,
In the developer-based circle equivalent diameter-circularity scattergram measured by the flow type particle image measuring apparatus, the average circularity of the developer is 0.950 to 0.990 and the circularity standard deviation is 0. An image forming method, wherein the image forming method is less than 040 . According to claim 10, characterized in that at least one of the metal oxide fine particles to the electrostatic latent image bearing member surface after transfer remaining at a ratio of 1.3 to 10 times the developer compositions Image forming method. It has a mechanism in which after transferring the visible image onto a recording material, the transfer residual developer on the surface of the latent electrostatic image bearing member is subjected to blade cleaning, and further charged in contact with the latent electrostatic image bearing member. The image forming method according to claim 10 or 11 . The developer carrying member of the developer means for thinning the image forming method according to any one of claims 10 to 12, characterized in that it consists of a metal blade having an elasticity. The image forming method according to any one of claims 10 to 13 the material of the photosensitive layer surface is characterized in that selected polycarbonate, from polyarylate. The universal hardness HU of the surface of the photosensitive layer is 200 N / mm ² or more (however, the curve showing the relationship between the hardness H and the indentation depth h has no inflection point). Item 15. The image forming method according to any one of Items 10 to 14 . 16. The image forming method according to claim 10 , wherein the colorant is a full-color or monocolor colorant that forms any one of yellow, cyan, magenta, and black. The electrostatic latent image is sequentially transferred after development, an image forming method according to any one of claims 10 to 16, characterized in that to form a full color image on the recording material. An intermediate transfer member, the image forming method according to any one of claims 10 to 17, characterized in that to form a full color image on the intermediate transfer body.

Images