JP2000122337A - Positive charge type toner for developing electrostatic latent image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a positive charge type toner for developing an electrostatic latent image capable of attaining a remarkably prolonged service life of a developer. SOLUTION: Two or more additives are mixed and added to toner particles used for a two-component developer after it is mixed with a carrier and containing at least a colorant and a binder resin to obtain the objective positive charge type toner. The additives are at least negative charge type inorganic particles A of 80-800 nm number average diameter including <=20% by number of particles of >=1,000 nm diameter, and positive charge type inorganic particles B of 5-50 nm number average diameter. The release rates (d) of the inorganic particles A and B under the application of a certain level of ultrasonic energy to the toner are 20-50 wt.% each of the weight of the added particles. The weight ratio of the inorganic particles A to B contained in the toner is 2.5:7.5 to 8.5:1.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positively chargeable toner for developing an electrostatic latent image used in electrophotography, electrostatic printing and the like.

[0002]

2. Description of the Related Art At present, as a dry developing method in various electrostatic copying methods that are put into practical use, a two-component developing method using a carrier such as toner and iron powder is the most widely used method. It is known that toner particles and toner constituents, particularly external additives, adhere to the carrier surface, thereby reducing the charge-imparting ability of the carrier and deteriorating the developer. Such a phenomenon becomes more remarkable in a toner for a digital copying machine or a toner for a full-color copying machine which has a large amount of an external additive in order to enhance the fluidity of the toner. In general, the developer of digital and full-color copiers has a faster carrier deterioration rate than the developer of analog copiers, and therefore causes poor charging with fewer copies than the developer for analog copiers, causing fogging and toner scattering in the machine. And so on.

[0003] Various approaches have been devised to address such problems. For example, a charge control agent such as a metal-containing dye is added to the toner to sufficiently charge the deteriorated carrier, or the toner externally added component is strongly fixed to the toner surface by mechanical energy to the carrier. Transfer of external additives (JP-A-9-146293), or by coating the carrier surface with a low-energy material such as a fluororesin or silicone resin so that the toner constituents are less likely to adhere to the carrier surface. In order to suppress carrier deterioration, it has been devised. However, it is difficult to completely eliminate the adhesion of the toner component, particularly the fluidizing agent, to the carrier by any of the methods, and at present, the life of the developer has not been significantly increased.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a positively chargeable toner for developing an electrostatic latent image capable of achieving a drastically long life of a developer. Aim.

[0005]

According to the present invention, a toner is used as a two-component developer by being mixed with a carrier, and at least two or more external additives are mixed with toner particles containing at least a colorant and a binder resin. A positively chargeable toner for developing an electrostatic latent image, wherein the number of external additives is at least 80 to 800 nm, and 1000 nm.
It comprises negatively chargeable inorganic particles A in which the number ratio of the above particles is 20% or less and positively chargeable inorganic particles B having a number average diameter of 5 to 50 nm, and imparts a certain amount of ultrasonic energy to the toner. Is 20% by weight or more and 50% by weight or less of the added weight, and the content ratio of inorganic particles A and B (inorganic particles A: inorganic particles B) is 2. 5: 7.5 to 8.5: 1.5, which relates to a positively chargeable toner for developing an electrostatic latent image.

The inventors of the present invention have earnestly studied the life of the developer from the viewpoints of physical properties such as the chargeability and particle size of the external additive particles and the state of attachment of the external additive particles to the toner particles. By defining at least two types of inorganic particles used for the external additive in terms of particle size and chargeability, and setting the adhesion strength (separation rate) between these external additives and toner particles in a specific range, It has been found that the durability of a developer using a toner is dramatically improved, and the present invention has been completed.

In the present invention, a relatively large negatively chargeable inorganic particle A is replaced with a positively chargeable relatively small particle size inorganic particle B.
When used together, the inorganic particles A are easily peeled off from the toner particles, and the inorganic particles B are hardly peeled off from the toner particles. The negative chargeability does not decrease the polarity of the carrier while balancing the amount of transfer of these particles to the carrier. Is positively transferred to the carrier. For this reason, since the carrier polarity is maintained (assisted), a decrease in the charge capability of the carrier due to the transfer of the small-diameter inorganic particles B to the carrier, which has conventionally been a problem, is prevented, whereby the toner can be used. It is considered that a longer life of the developer used can be achieved.

The positively chargeable toner of the present invention is obtained by mixing (externally adding) at least inorganic particles A and B to toner particles containing at least a colorant and a binder resin.

In the positively chargeable toner of the present invention, the externally added inorganic particles A have a number average diameter of 80 to 800 nm, preferably 150 to 750 nm, more preferably 280 to 7 nm.
20 nm and the number of particles of 1000 nm or more is 2
0% or less, preferably 10% or less. Particle size 80n
If it is smaller than m, the number of the negatively chargeable particles covering the toner is too large to obtain proper positive chargeability of the toner. On the other hand, if it is larger than 800 nm, the particles hardly adhere to the toner, and even in the developer. As a result, the particles are suspended between the toner and the carrier, and the effect of the particles to supplement the negative chargeability of the carrier is impaired. On the other hand, if the number of particles having a size of 1000 nm or more exceeds 20%, the photosensitive member is easily damaged, which causes noise such as image defects.

The material of the inorganic particles A is not particularly limited, and any known inorganic particles conventionally used as a fluidizing agent can be used. For example, silica particles, alumina particles , Inorganic oxide particles such as titania particles, aluminum stearate particles,
Inorganic stearic acid compound fine particles such as zinc stearate particles, and inorganic titanate compound particles such as strontium titanate particles and zinc titanate particles can be used.

Further, the inorganic particles A have a negative charging property with respect to the toner particles in order to exhibit the above-described effect of improving the developer durability of the present invention. That is, the chargeability of the inorganic particles is determined by the relative relationship between the toner particles and the carrier in the triboelectric series, and the inorganic particles A become more negative than the toner particles by mixing and stirring with the toner particles and the carrier in the developer. Be charged. In other words, the charge amount of the inorganic particles A is located on the minus side of the charge amount of the toner particles in the triboelectric series. Of course, the inorganic particles A are preferably made of a material whose charge amount is located on the minus side in the triboelectric series than the charge amount of any of the toner particles and the carrier particles, but on the plus side of the charge amount of the carrier particles. The present invention can be achieved by a material that is located on the minus side to some extent from the charge amount of the toner particles even if it is made of a material that is located. Further, even if the material does not have the above-mentioned relationship, it can be controlled to the above-mentioned relationship by performing a surface treatment. Further, the material having negative charge may be further controlled to be negative charge. As means for controlling the inorganic particles A to be negatively chargeable, a known surface treatment agent having no amino group or nitrile group, for example, a method of performing a surface treatment with a silane coupling agent, silicone oil, or the like may be used. it can. Specifically, silane coupling agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltrimethoxysilane Ethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyl Trimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysila Etc. is available and as the silicone oil, such as dimethyl polysiloxane, methyl hydrogen polysiloxane, methyl phenyl polysiloxane can be used. If it is desired to further enhance the negative chargeability, a fluorine-based silane coupling agent, silicone oil, or the like can be used.

Further, the inorganic particles A are separated from the toner by a constant ultrasonic energy applied to the toner.
(%) Is 20% or more, preferably 30%, based on the added weight.
It is controlled to ~ 70%. When the detachment rate d of the inorganic particles A is less than 20%, the transfer amount of the inorganic particles A to the carrier is small, and it is difficult to obtain the auxiliary effect of the chargeability of the carrier. If the detachment rate exceeds 70%, the chargeability of the developer tends to be lost, and there is a strong tendency that the charge level continues to increase with repeated use.

The detachment ratio indicates the ease of detachment of the inorganic particles from the toner particles. The higher the detachment ratio, the easier the inorganic particles detach from the toner particles. In the present specification, "constant application of ultrasonic energy" means that ultrasonic vibration is performed for 1 minute at a frequency of 15 kHz and an output of 40 W using an ultrasonic homogenizer (US1200T; manufactured by Nippon Seiki Seisakusho). Specifically, the detachment rate d is determined by using a surfactant (polyoxyethylene octyl phenyl ether having a degree of polymerization of 10) of 0.2 wt% aqueous solution of 40 cc.
After 2 g of the toner is wet and immersed therein, an ultrasonic vibrator of 36φ is immersed in the dispersion using an ultrasonic homogenizer (US1200T; manufactured by Nippon Seiki Seisaku-sho, Ltd.), and the frequency is 15 kHz and the output is 40 W for 1 minute The ultrasonic vibration is used to promote the separation of the inorganic particles from the surface of the toner particles, and then the dispersion is separated into a supernatant and a precipitate (toner) by decantation (rest), and the precipitate (toner) is washed. This is a value calculated by subjecting the dried toner to X-ray fluorescence analysis after drying, and simultaneously quantifying the inorganic particles A and B remaining on the surface of the toner particles.

The inorganic particles A are replaced with inorganic particles B described later.
(For example, inorganic particles A and B
Are both silica or the like), since the inorganic particles A and B cannot be simultaneously determined by the above means,
Except for using the toner obtained by adding the inorganic particles A alone, the detachment rate calculated in the same manner as the above-described measuring means is defined as the detachment rate of the inorganic particles A.

The detachment rate d can be controlled by mechanical energy at the time of externally adding the inorganic particles to the toner, as described later. Specifically, a Q mixer or a Henschel mixer (both are Mitsui Kinzoku It can be controlled by the blade rotation speed of a mixer such as Mining Co., Ltd.) and the mixing processing time.

The externally added inorganic particles B in the positively chargeable toner of the present invention have a number average diameter of 5 to 50 nm, preferably 10 to 35 nm. When the particle diameter is smaller than 5 nm, the particles are easily buried in the toner due to mechanical stress in the developing device, and characteristic changes such as a decrease in fluidity are likely to occur. When the particle diameter is larger than 50 nm, the coverage of the toner decreases. In addition, appropriate fluidity cannot be obtained.

The material of the inorganic particles B is not particularly limited, and the same materials as the above-mentioned materials of the inorganic particles A can be used. Among them, silica fine particles, alumina fine particles, titania fine particles, etc. The inorganic oxide fine particles are preferably used. In addition, the inorganic particles B are desirably subjected to a hydrophobic treatment with a known hydrophobizing agent from the viewpoint of environmental resistance.

Further, the inorganic particles B have a positive charging property with respect to the carrier in order to exhibit the above-mentioned effect of improving the developer durability of the present invention. That is, as described above, the chargeability of the inorganic particles is determined by the relative relationship between the toner particles and the carrier in the triboelectric series, and the inorganic particles B are mixed in the developer and mixed with the toner particles and the carrier to stir the carrier. It is more positively charged. In other words, the charge amount of the inorganic particles B is on the positive side of the charge amount of the carrier particles in the triboelectric series. The inorganic particles B preferably have the same charge amount as the toner particles. However, the inorganic particles B are made of a material whose charge amount is located on the triboelectric series in the plus direction with respect to the charge amounts of both the toner particles and the carrier particles. Alternatively, the charge amount may be made of a material located on the minus side of the charge amount of the toner particles and a material located on the plus side of the charge amount of the carrier particles. Further, even if the material does not have the above-mentioned relationship, it can be controlled to the above-mentioned relationship by performing a surface treatment. As a means for controlling the inorganic particles B to be positively chargeable, a chargeable base material of externally added particles such as alumina particles, strontium titanate particles, aluminum stearate particles, and zinc stearate particles is selected to have a positive chargeability. There is a method of adding a treatment agent having a positive charge to the surface of the base material and coating the same, but the latter method that can be controlled to a positive charge regardless of the type of inorganic material. Are suitable.

As a treating agent used to impart a positive charge to the inorganic particles B, a known surface treating agent having an amino group, a nitrile group, or an isocyanate group can be used. For example, synthetic resins such as urethane-modified resin and acrylonitrile resin, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl)
Aminopropylmethyldimethoxysilane, aminosilane, γ-aminopropyltriethoxysilane, N- (2
-Aminoethyl) 3-aminopropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ
Silane coupling agents such as aminopropyltrimethoxysilane, and silicone oils such as amino-modified silicone oil.

In addition, the inorganic particles B are separated from the toner by a constant ultrasonic energy application to the toner.
(%) Is 50% or less, preferably 10%,
It is controlled to ４０40%. The detachment rate d here has the same meaning as described above, and is a value calculated by the same means. When the detachment rate d of the inorganic particles B exceeds 50%, the transfer amount of the inorganic particles B to the carrier increases, and the charge capability of the carrier decreases. If the detachment rate is less than 10%, the inorganic particles B are almost completely embedded in the toner base particles, and problems such as a decrease in the fluidity of the toner are likely to occur.

When the inorganic particles B are made of the same material as the inorganic particles A, the inorganic particles A
Since B and B cannot be simultaneously determined, the detachment rate calculated in the same manner as the above-described measuring means except that the toner obtained by adding the inorganic particles B alone is used as the detachment rate of the inorganic particles B.

The detachment rate d can also be controlled by mechanical energy at the time of externally adding the inorganic particles to the toner, as described later. Specifically, a Q mixer and a Henschel mixer (both are Mitsui It can be controlled by the blade rotation speed of a mixer such as a metal mining company or the like and the mixing processing time.

The content ratio of the inorganic particles A and B (the inorganic particles A: the inorganic particles B) in the positively chargeable toner of the present invention is 2.5: 7.5 to 8.5: 1.5 by weight. Preferably 2.5: 7.5 to 8: 2, more preferably 3: 7.
7: 3. If the amount is out of this range, the balance of the amount of each inorganic particle transferred to the carrier is lost, so that the effect of improving the durability of the developer cannot be obtained, and the fluidity of the toner and the chargeability cannot be balanced.

The content of the inorganic particles A and the inorganic particles B is as follows:
If the content ratio is within the above range, it can be appropriately adjusted according to the flow characteristics and the like required in the process, but the total content thereof is 0.5 to 5% by weight, preferably 1%, based on the toner particles. It is desirable that the content be contained to be about 3% by weight. When the total content is less than 0.5% by weight, desired fluidity cannot be obtained, and when the total content exceeds 5% by weight, side effects such as photoconductor noise in a blade cleaning process and an increase in photoconductor polishing amount are concerned. Not suitable.

Further, in the positively chargeable toner of the present invention,
It is preferable that the inorganic particles A and B have a specific value of a blow-off charge amount for a carrier used later. The blow-off charge amount for iron powder is -3 for inorganic particles A.
00 to -50 (μc / g), inorganic particles B are +100 to +
It is preferably 2000 (μc / g). By setting the blow-off charge amount to a specific value in this manner, the above-described effect of improving the developer durability of the present invention appears more remarkably. Blow-off charge of inorganic particles A is -50 μc
If the ratio is higher than / g, the ability to assist the negative property of the carrier is low even when the carrier is transferred. On the other hand, -300
If it is lower than μc / g, the carrier becomes extremely negative when transferred to the carrier, making it impossible to obtain a proper chargeability of the developer, or because the negative chargeability of the inorganic particles A is too strong. A phenomenon occurs in which the toner is not easily transferred to the carrier due to too strong adhesion to the carrier, and in any case, it is difficult to control the chargeability of the developer, which is not preferable. When the blow-off charge amount of the inorganic particles B is higher than +2000, the positive chargeability of the toner becomes extremely strong, which is not preferable.
If it is lower than this, the positive chargeability of the toner becomes extremely weak, which is not preferable. The blow-off charge is a value measured using an iron powder as a carrier and a blow-off charge measuring device (TB-200: manufactured by Toshiba Chemical Corporation) based on a blow-off method.

Further, in the positively chargeable toner of the present invention, the blow-off charge amount Q
It is preferable that the product of (μc / g) and the separation rate d of the inorganic particles A be within a specific range. The relationship between the blow-off charge amount Q (μc / g) of the inorganic particles A with respect to the iron powder and the release rate d of the inorganic particles A is −50 ≦ Q · d ≦ −10, preferably −50 ≦ Q · d ≦ −20. It is desirable to satisfy. The action of improving the negative chargeability of the carrier by the transfer of the inorganic particles A to the carrier is based on the principle that the electrostatic charge (blow-off charge amount Q) of the inorganic particles A and the easiness of peeling from the toner (detachment rate d) are reduced. This is considered to be a major factor, and by defining the product of these, the effect of improving the developer durability of the present invention is optimally exhibited. That is, Q · d in the above equation is an index of the ease of charge transfer to the carrier as a substance of the inorganic particles A. When this value is smaller than −50, the effect of maintaining the carrier charging ability is not obtained. If the value is larger than -10, the negative charge level of the carrier tends to increase in accordance with the durability, the charge amount of the developer increases, and the development amount decreases. The blow-off charge amount Q is -90 (μc /
g) and Q when the detachment rate d is 30 (wt%)
D is -27.

In the positively chargeable toner of the present invention, in addition to the above-described inorganic particles A and B, organic fine particles having lubricity may be added to assist cleaning properties. For example, fine particles such as polyolefin wax, fine particles such as metal soap, and Teflon fine particles can be added.

The toner particles to which the above-mentioned inorganic particles are externally added contain at least a binder resin and a colorant, and optionally contain a magnetic fine powder, a release agent, a charge control agent, and the like as needed. ing.

As the binder resin used in the present invention, any known synthetic resins and natural resins can be used. Specifically, synthesis of styrene resin, acrylic resin, olefin resin, diene resin, polyester resin, polyamide resin, epoxy resin, silicone resin, phenol resin, petroleum resin, urethane resin, etc. Resins and natural resins.

As the coloring agent, known pigments and dyes are used. For example, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow,
Methylene blue chloride, copper phthalocyanine, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment Red 48: 1, C.I. I.
Pigment Red 122, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 184, C.I.
I. Pigment Yellow 97, C.I. I. Pigment
Yellow 12, C.I. I. Pigment Yellow 17,
C. I. Solvent Yellow 162, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 1
5: 3 and the like. It is desirable that the colorant is contained in an amount of 1.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

When used as a magnetic toner, a part or all of the colorant may be replaced with a magnetic substance. Examples of such a magnetic material include magnetite, ferrite, iron powder, nickel and the like. The magnetic material is desirably contained in an amount of 100 to 200 parts by weight based on 100 parts by weight of the binder resin. When a plurality of magnetic substances are used, the total amount is used within the above range.

The toner particles of the present invention may contain additives such as a charge controlling agent and a release agent in the binder resin according to the purpose. For example, examples of the charge control agent include a fluorine-containing surfactant, a metal-containing dye such as a salicylic acid metal complex and an azo-based metal compound, a polymer acid such as a copolymer containing maleic acid as a monomer component, and a quaternary. Ammonium salts, azine dyes such as nigrosine, carbon black and the like can be added. In particular, carbon black is effective for adjusting the resistance. As the release agent, paraffins and olefins having 8 or more carbon atoms are preferable, and for example, paraffin wax, paraffin latex, microcrystalline wax, low molecular weight polypropylene, low molecular weight polyethylene and the like can be used. The charge control agent and the release agent are each 0 to 5 parts by weight based on 100 parts by weight of the binder resin.
Parts by weight, preferably 0 to 5 parts by weight,
When two or more are used, they are used so that the total amount is within the above range.

The toner particles of the present invention can be produced by any known method, but a method of kneading and pulverizing is particularly preferable. That is, a binder resin and a colorant,
A method is preferred in which other additives are melt-kneaded using a kneader, cooled, pulverized and classified. It is preferable that the toner particles thus obtained have a volume average particle diameter of 4 to 12 μm. If it is smaller than this, it tends to cause a decrease in fluidity and fog,
On the other hand, if it is larger than this, the resolution is reduced, and a high-quality image cannot be obtained.

The positively chargeable toner of the present invention is obtained by externally adding inorganic particles A and B to the toner particles thus obtained, and using a known mixer, for example, Q
It can be obtained by mixing with a mixer, Henschel mixer or the like.

In the present invention, the inorganic particles A and B have the above-mentioned detachment ratio d in the toner, and the detachment ratio may be adjusted by any means. For example, the detachment rate can be controlled by mechanical energy at the time of externally adding inorganic particles to toner particles. For example, a predetermined amount of the inorganic particles B is added to the toner particles, and the Q mixer (manufactured by Mitsui Mining Co., Ltd.) is used.
After mixing for a minute, a predetermined amount of inorganic particles A is further added,
By further mixing at the same rotation speed for 1 to 20 minutes, the toner of the present invention can be obtained.

The toner thus obtained is mixed with a predetermined carrier and used as a two-component developer, whereby a drastically long life of the developer can be achieved. As the carrier used together with the toner of the present invention, known carriers can be used, for example, a carrier composed of magnetic particles such as iron powder and ferrite, and a coat type in which the surface of the magnetic particles is coated with a coating material such as a resin. Either a carrier or a binder-type carrier obtained by dispersing magnetic fine powder in a binder resin can be used. Such a carrier has a volume average particle size of 15 to 100 μm,
Preferably, the thickness is 20 to 80 μm.

The positively chargeable toner of the present invention is preferably used together with a carrier having a negatively chargeable resin on the surface. Examples of such resins include polyester resins, polyolefin resins such as polyethylene, tetrafluoroethylene, vinylidene fluoride, homopolymerization of fluorine-containing vinyl monomers or copolymers with other vinyl monomers. Fluorinated resins and the like can be mentioned. Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “parts” means “parts by weight” unless otherwise specified.

[0038]

EXAMPLES <Types of Inorganic Particles A> As the inorganic particles A, the following inorganic particles A1 to A4 were used. (A1) Strontium titanate particles having a number average particle size of 300 nm were subjected to a surface treatment with a fluorine-based silicone oil to obtain negatively chargeable inorganic particles A1. The blow-off charge Q of the particles was [-96] μc / g. 1000n
The number ratio of particles having a particle size of m or more was 5%. (A2) Titanium oxide particles having a number average particle size of 350 nm were subjected to a surface treatment with fluorine-based silane to obtain negatively chargeable inorganic particles A2. The blow-off charge amount Q of these particles is [-114] μc
/ G. The number ratio of particles having a size of 1000 nm or more was 6%.

(A3) Silica particles having a number average particle diameter of 700 nm were subjected to a surface treatment with methyl hydrogen polysiloxane to obtain negatively chargeable inorganic particles A3. The blow-off charge Q of these particles was [-221] μc / g. Also, 1
The number ratio of particles having a size of 000 nm or more was 7%. (A4) Strontium titanate particles having a number average particle size of 300 nm were subjected to a surface treatment with N- (2-aminoethyl) 3-aminopropyltrimethoxysilane to obtain positively chargeable inorganic particles A4. The blow-off charge amount Q of these particles is [+9
3] μc / g. The number ratio of particles having a size of 1000 nm or more was 4%.

<Type of Inorganic Particle B> As the inorganic particles B, the following inorganic particles B1 to B3 were used. (B1) γ- (2
-Aminoethyl) aminopropylmethyldimethoxysilane was subjected to a surface treatment to obtain positively chargeable inorganic particles B1. The blow-off charge Q of the particles was [+1247] μc / g. (B2) Anatase type titania particles having a number average particle size of 30 nm are subjected to a surface treatment with γ- (2-aminoethyl) aminopropylmethyldimethoxysilane to form positively chargeable inorganic particles B2.
I got The blow-off charge amount Q of these particles is [+352]
μc / g. (B3) Silica particles having a number average particle size of 15 nm were subjected to a surface treatment with methyl hydrogen polysiloxane to obtain negatively chargeable inorganic particles B3. The blow-off charge amount Q of the particles was [−408] μc / g.

<Production of Toner Particles> 100.0 parts of thermoplastic styrene-acrylic resin (styrene-butyl acrylate-butyl methacrylate-methacrylic acid copolymer, monomer polymerization ratio = 7: 1.4: 1.4) : 0.2, acid value 6.5 KOHmg / g)-Additive for preventing offset Polypropylene wax (softening point: about 145 ° C) 4.0 parts (Viscol 660P; manufactured by Sanyo Chemical Industries) Polyethylene wax (softening point: about 140) ° C) 0.5 part (High Wax 800P; manufactured by Mitsui Chemicals, Inc.) ・ Carbon black (Mogal L; manufactured by Cabot Corporation) 10.0 parts ・ Nigrosine dye 5.0 parts (Nigrosine Base EX; manufactured by Orient Chemical Co., Ltd.)

The above materials were mixed with a Henschel mixer (capacity 7
5L) at 3000 rpm for 3 minutes. The mixture was continuously extruded and kneaded by a screw extrusion kneader (TEM50; manufactured by Toshiba Machine Co., Ltd.) under the conditions of a temperature of 120 ° C., a supply amount of 30 kg / hr, and a screw rotation speed of 150 rpm, followed by rolling with a press roller having a nip width of 1 mm. It was forcibly cooled on a belt cooler. This kneaded material was pulverized with a feather mill (2 mm mesh). The crushed material is mechanically crushed (Kryptron KTM-O type; manufactured by Kawasaki Heavy Industries, Ltd.)
And coarsely cut with a jet mill (IDS-2 type; manufactured by Nippon Pneumatic) equipped with a natural air flow classifier, and further, a rotary rotor classifier (50ATP classifier; manufactured by Hosokawa Micron) Cut the fine powder with
Toner particles having a volume average particle diameter of 7.2 μm were obtained.

Example 1 One part (first addition) of the inorganic particles B1 was added to 100 parts of the toner particles, and the mixture was mixed by a Q mixer (manufactured by Mitsui Mining Co., Ltd.) at a blade rotation speed of 5000 rpm for 2 minutes. Next, 1 part of the inorganic particles A1 was added (second addition), and 2 parts were further added.
And then passed through a 150 mesh sieve to obtain a toner.

Examples 2 to 9 and Comparative Examples 1 to 5 In each of Examples and Comparative Examples, the inorganic particles A1
, The inorganic particles A shown in Table 1 were used only in the indicated amounts, the inorganic particles B shown in Table 1 were used in the indicated amounts instead of the inorganic particles B1, and the mixing order and mixing of the inorganic particles A and B were performed. A toner was obtained in the same manner as in Example 1, except that the time was changed as shown in Table 2.

<Measurement of Detachment Rate d> In each toner obtained above, the detachment rate d of the inorganic particles from the toner particles was measured for each inorganic particle as follows. After 2 g of the toner is wetted and immersed in 40 cc of a 0.2% by weight aqueous solution of a surfactant (polyoxyethylene octyl phenyl ether having a degree of polymerization of 10), an ultrasonic homogenizer (U
S1200T; manufactured by Nippon Seiki Seisaku-sho, Ltd.), and immersed a 36φ ultrasonic vibrator in the dispersion liquid at a frequency of 15 kHz.
z, by ultrasonic vibration for 1 minute at an output of 40 W,
The inorganic particles were separated from the toner particle surfaces. Thereafter, the dispersion was separated into a supernatant and a precipitate (toner) by decantation (static), and the supernatant containing the separated inorganic particles was removed. The precipitate (toner) was gently washed with pure water and dried. The dried toner is subjected to X-ray fluorescence analysis to simultaneously determine each of the inorganic particles A and B remaining on the surface of the toner particles, and the ratio of the weight of the separated inorganic particles to the weight of the inorganic particles added to the toner particles (weight ratio) ) Was calculated as the withdrawal rate d.

When the inorganic particles A and B are of the same material (for example, Example 3 in which the inorganic particles A and B are both silica), the inorganic particles A and B cannot be simultaneously determined. Was used as the release rate of the inorganic particles A in the toner manufactured in the same manner as in the example or the comparative example, except that the inorganic particles B were added alone. Alternatively, the detachment rate of the toner produced in the same manner as in the comparative example was defined as the detachment rate of the inorganic particles B.

<Manufacture of Developer> Each toner was mixed with Carrier 1 described below so that the toner concentration was 6% by weight, to prepare a developer (starter).

<Manufacture of carrier 1> 100 parts of polyester resin (NE-1110; manufactured by Kao Corporation) 500 parts of inorganic magnetic powder (MFP-2; manufactured by TDK Corporation) 2 parts of carbon black (MA # 8; Mitsubishi Chemical The above-mentioned materials are sufficiently mixed and pulverized by a Henschel mixer, and then the cylinder part 180 ° C. and the cylinder head part 17
Melt kneading was performed using an extrusion kneader set at 0 ° C. The kneaded product was cooled, coarsely pulverized, finely pulverized with a jet mill, and further classified using an air classifier to obtain a magnetic carrier 1 having a volume average particle size of 55 μm.

<Evaluation Method of Carrier Deterioration> (Carrier Chargeability after Durability Test) The obtained developer was set in an analog copying machine (EP8015; manufactured by Minolta Co., Ltd.), and a 15% image portion of the original was used. 1 million printing endurance test, printing endurance 0 (starter), 500,000 and 10
The developer at the point of time of 100,000 sheets was sampled. The toner is separated from these developers by an electric field, and the carrier separated from the developer (starter) and the reference positively chargeable toner (EP8015 black toner: manufactured by Minolta Co., Ltd.) at the time when the number of printed sheets is 0, the charge amount Q0, The charge amount Q50 of the carrier separated from the developer and the reference positively chargeable toner at the time of 500,000 prints, and the charge amount Q50 of the carrier separated from the developer and the reference positively chargeable toner at the time of 1 million prints. The charge amount Q100 was measured by the charge amount measuring device shown in FIG. 1 according to the following to evaluate the chargeability of the carrier. First, 1 g of the developer weighed by a precision balance is applied to the conductive sleeve (41).
The magnet roll (42) provided in the conductive sleeve (41) was set at a rotation speed of 100 rpm. Then, a bias voltage of 3 KV is applied from the bias power supply (43) with the same polarity as the charged potential of the toner, and the conductive sleeve (41) is rotated for 30 seconds to stop the conductive sleeve (41). The potential Vm at the cylindrical electrode (44) is read, and the conductive sleeve (4) is read.
From 1), the weight of the toner adhering to the cylindrical electrode (44) is measured with a precision balance, and the average charge amount (μC /
g) was determined.

The evaluation criteria are as follows. “△” has no practical problem, and “×” has practical problem. <Chargeability after 500,000 sheets have been printed> A: Change in charge amount (Q50-Q0) is ± 10 compared to Q0.
%: Change in charge amount (Q50-Q0) ± 20 compared to Q0
Δ: change in charge amount (Q50−Q0) ± 30 compared to Q0
%: Charge change (Q50-Q0) ± 30 compared to Q0
%that's all. <Chargeability after 1,000,000 sheets have been printed> A: Change in charge amount (Q100-Q0) is ± 1 compared to Q0
0 or less; Δ: change in charge amount (Q100−Q0) ± 2 compared to Q0
0% or less; Δ: charge amount change (Q100-Q0) ± 3 compared to Q0
0% or less; ×: change in charge amount (Q100-Q0) ± 3 compared to Q0
0% or more.

The results of these evaluations are shown together with the respective production conditions in Tables 1 and 2 below.

[Table 1]

[0052]

[Table 2]

<Measurement Method> The measurement values in the present specification are values obtained by employing the following measurement methods. (Number average particle diameter and number ratio of inorganic particles) The inorganic particles are observed with a TEM, and a photograph of 100,000 times is taken. The number average particle size distribution of the particles was calculated from the obtained photograph. (Blow-off Charge Amount of Inorganic Particle with Iron Powder) The blow-off charge amount was measured using a blow-off charge amount measuring device (TB-200: manufactured by Toshiba Chemical Corporation) based on the blow-off method. 25 g of a reference iron powder carrier (Z150 / 250: manufactured by Powder Tech) and 50 mg of a sample are placed in a 25 cc plastic bottle, mixed for 1 minute by a turbula mixer, and then 0.1 g of the carrier mixed sample is 400 mesh stainless screen. And a nitrogen gas as a carrier gas at a pressure of 1.0 kgf / cm 2 and a pressure of 6 kg.
It was calculated from the value indicated by the above device when the gas was allowed to flow for 0 seconds.

(Glass transition point) The glass transition point was determined by using a differential scanning calorimeter (DSC-200: manufactured by Seiko Denshi Co., Ltd.) with a reference of alumina and a 10 mg sample at a heating rate of 10 ° C./min. The temperature was measured between ℃ 120 ° C., and the shoulder value of the main endothermic peak was defined as the glass transition point. (Softening point of resin) The softening point of the resin was measured using a flow tester (CF
Using a T-500 (manufactured by Shimadzu Corporation), a 1 cm ² sample was melted and flown out under the conditions of pores of a die (diameter 1 mm, length 1 mm), pressurization 30 kg / cm ² , and heating rate 3 ° C./min. 1 / h of the height from the outflow start point to the outflow end point
The temperature corresponding to 2 was taken as the softening point. (Toner Particle Size) The particle size of the toner was measured using Coulter Multisizer 2 (manufactured by Coulter Inc.).

[0055]

According to the toner of the present invention, the life of the developer can be significantly increased.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration diagram of a charge amount measuring device.

[Explanation of symbols]

41: conductive sleeve, 42: magnet roll, 4
3: Bias power supply, 44: cylindrical electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Haki 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Ken Arai Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-1-3 Osaka International Building Minolta Co., Ltd. F-term (reference) 2H005 AA08 BA06 CA26 CA28 CB04 CB07 CB08 CB13 DA02 DA03 EA01 EA05 EA07 EA10 FA02

Claims (3)

[Claims] 1. An electrostatic latent image formed by mixing with a carrier to be used as a two-component developer and mixing and adding at least two or more external additives to toner particles containing at least a colorant and a binder resin. A positively chargeable toner for development, wherein the external additive has at least a number average diameter of 80 to 800 n.
m and the number ratio of particles of 1000 nm or more is 2
0% or less of negatively-chargeable inorganic particles A, and positively-chargeable inorganic particles B having a number average diameter of 5 to 50 nm,
The detachment rate d of the inorganic particles A and B by applying a constant ultrasonic energy to the toner is 20% by weight or more and 50% by weight or less of the added weight, respectively, and the content ratio of the inorganic particles A and B (inorganic particles A: inorganic Particles B) having a weight ratio of 2.5:
7.5 to 8.5: 1.5. A positively chargeable toner for developing an electrostatic latent image, wherein the ratio is 1.5 to 1.5. 2. The blow-off charge Q of the inorganic particles A with respect to iron powder is -300 to -50 (μc / g), and the blow-off charge of the inorganic particles B with respect to iron powder is +100 to +2.
2. The positively chargeable toner for developing an electrostatic latent image according to claim 1, wherein the toner has a molecular weight of 000 (μc / g). 3. The blow-off charge amount Q (μc / g) of the inorganic particles A with respect to the iron powder and the detachment rate d of the inorganic particles A by applying a constant ultrasonic energy to the toner are -50 ≦ Q · d ≦ −10. The positively chargeable toner for developing an electrostatic latent image according to claim 1, wherein the relationship is satisfied.