JP2006184438A - Method for forming full-color image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a full-color image by whichfailure such as character void and toner scattering can be suppressed even when a nonmagnetic toner and a magnetic toner are used. <P>SOLUTION: When the charge amount of a nonmagnetic toner on a photoreceptor is larger by ≥10 μC/g than the charge amount of a magnetic toner, the nonmagnetic toner is discharged or the magnetic toner is charged prior to transferring a toner image onto a recording material to decrease the difference in charges amounts of the both toners to less than 10 μC/g. Preferably, before the above treatment, the charge amount of the magnetic toner on the photoreceptor is 1 to 15 μC/g, and the charge amount of the nonmagnetic toner on the photoreceptor is 16 to 40 μC/g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a full-color image forming method that can be used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine using an electrophotographic system.

  As a full-color image forming method, toner on a photosensitive member (for example, a photosensitive drum) is temporarily transferred (primary transfer) to an intermediate transfer member, and then toners of four colors are collectively transferred onto a recording material such as paper (2 Next transfer) is used. In this method, if the transferability of each toner is different at the time of secondary transfer, there may be a large amount of transfer residue, resulting in missing characters or toner scattering due to overtransfer. Therefore, the four color toners must have the same transferability.

  In the black toner used for forming a full-color image, magnetic powder that is safer than carbon black, which has safety problems, is used as the pigment, and only black toner is used as magnetic toner as described in Patent Document 1 below. There is a case. However, when this method is applied to the above-described full-color image forming method, the amount of charge is reduced because magnetic powder is added to the black toner, and the pigment contained in the toner differs depending on the color. The amount may vary greatly. The charge amount of the toner affects the transferability of the toner. If the transferability of each toner varies greatly due to the difference in the charge amount, problems such as missing characters and scattered toner occur.

Patent Documents 2 to 4 describe methods for charging or discharging toner. However, the methods of Patent Documents 2 to 3 below improve the cleaning performance of the toner on the drum or transfer belt. The method disclosed in Patent Document 4 described below is intended to improve the toner holding charge amount of the intermediate transfer member. Therefore, the methods described in Patent Documents 2 to 4 cannot solve the problem that the transferability of each toner differs due to the difference in charge amount.
JP-A-5-249742 JP 2002-258708 A JP 2001-337546 A JP-A-8-63003

  An object of the present invention is to provide a full-color image forming method capable of suppressing the occurrence of defects such as missing characters and scattered toner even when non-magnetic toner and magnetic toner are used.

  As a result of intensive studies to solve the above problems, the present inventors have found that character voids and toner are lost when the charge amount of the non-magnetic toner on the photoreceptor is 10 μC / g or more larger than the charge amount of the magnetic toner. The inventors have found that problems such as scattering occur and have completed the present invention. That is, the full color image forming method of the present invention is as follows.

  (1) After transferring each color toner image formed on the surface of the photoreceptor using a non-magnetic toner and a magnetic toner onto the intermediate transfer member, the toner images of each color on the intermediate transfer member are collectively placed on the recording material. And transferring the toner image to the recording material when the charge amount of the non-magnetic toner on the photosensitive member is 10 μC / g or more larger than the charge amount of the magnetic toner. An image forming method, wherein the toner is subjected to a charge elimination process so that a difference in charge amount between the two toners is less than 10 μC / g.

  (2) After transferring each color toner image formed on the surface of the photosensitive member using the non-magnetic toner and the magnetic toner onto the intermediate transfer member, the toner images of each color on the intermediate transfer member are collectively put on the recording material. And transferring the toner image before transferring the toner image onto the recording material when the charge amount of the non-magnetic toner on the photosensitive member is 10 μC / g or more larger than the charge amount of the magnetic toner. An image forming method, wherein the toner is charged to make a difference in charge amount between the two toners less than 10 μC / g.

  (3) Before the treatment, the charge amount of the magnetic toner on the photoconductor is 1 to 15 μC / g, and the charge amount of the nonmagnetic toner on the photoconductor is 16 to 40 μC / g. The image forming method according to (1) or (2).

  (4) The image forming method according to any one of (1) to (3), wherein the processing is performed on a photoreceptor.

  (5) The image forming method according to any one of (1) to (4), wherein the nonmagnetic toner is a polymerized toner, and the magnetic toner is a pulverized toner.

  According to the above (1) and (2), before the toner image is transferred onto the recording material, the non-magnetic toner is neutralized or the magnetic toner is charged, so that the difference in charge between the magnetic toner and the non-magnetic toner is different. Is less than 10 μC / g. That is, the difference in transferability of each toner is reduced by reducing the difference in charge amount of each toner. As a result, it is possible to provide a full-color image forming method that can suppress the occurrence of problems such as missing characters and scattered toner even when non-magnetic toner and magnetic toner are used.

  According to the above (3), the charge amount of the magnetic toner on the photoconductor is 1 to 15 μC / g before the charge removal process of the nonmagnetic toner or the magnetic toner is charged. Since the charge amount is 16 to 40 μC / g, it is possible to prevent the occurrence of toner scattering and the occurrence of thin layer unevenness and image density reduction, thereby forming a better image.

  According to the above (4), when the charge removal process is performed on the photosensitive member, cleaning of the photosensitive member and the intermediate transfer member can be facilitated, and defective cleaning of the photosensitive member and the intermediate transfer member can be reduced. In addition, when the charging process is performed on the photosensitive member, by making the charge amount appropriate, there is an effect that transferability can be improved and scattering of uncharged toner in the transfer part and the fixing part can be prevented.

  According to (5) above, by using a polymerized toner as the nonmagnetic toner, the sphericity can be increased, the particle size can be reduced, and the image quality can be improved. By using the pulverized toner as the magnetic toner, it is possible to produce a frequently used black at a low cost and to reduce the cost.

<Full color image forming method>
Hereinafter, an embodiment of the present invention will be described in detail. In the full color image forming method of the present invention, a non-magnetic toner and a magnetic toner are used. The magnetic toner here is a toner containing a magnetic material as a component, and is used as a black toner because the magnetic material has a dark color. When magnetic toner is used, since no carrier is used, a mechanism for stirring the carrier and toner becomes unnecessary, and the cost of the developing unit can be reduced.

  On the other hand, the non-magnetic toner is a toner that does not contain a magnetic material, and includes a two-component toner and a one-component toner. In the present invention, both a two-component toner and a one-component toner can be used as the non-magnetic toner. Further, since the non-magnetic toner does not contain a magnetic material, it is used as a color toner, that is, a magenta toner, a cyan toner, or a yellow toner.

  When the magnetic toner and the non-magnetic toner are used in this way, the charge amount of the non-magnetic toner is larger than the charge amount of the magnetic toner on the photoreceptor. Further, when the difference between the charge amount of the non-magnetic toner and the charge amount of the magnetic toner is 10 μC / g or more, problems such as missing characters and scattered toner are likely to occur. Therefore, some processing is performed before the toner image is transferred onto the recording material, so that the difference between the charge amount of the non-magnetic toner and the charge amount of the magnetic toner is less than 10 μC / g.

  As a process for reducing the difference in charge amount between the two toners to less than 10 μC / g, first, a charge removal process is performed on the non-magnetic toner. Examples of the static elimination treatment include a method of applying a corona discharge having a polarity opposite to that of the nonmagnetic toner, and a method of applying a bias having a polarity opposite to that of the nonmagnetic toner.

  As another process for reducing the difference in charge amount between the two toners to less than 10 μC / g, a magnetic toner is charged. Examples of the charging method include a method of applying corona discharge having the same polarity as that of the magnetic toner, and a method of applying a bias having the same polarity as that of the magnetic toner.

  As specific examples of the charge removal process and the charge process, a corona discharger using a charger wire is provided around the photoreceptor so that charge removal or charging can be performed before the primary transfer, and the corona discharger is used. The neutralization of the non-magnetic toner on the photoreceptor or the charging of the magnetic toner can be mentioned.

  The neutralization process and the charging process may be performed before the toner image is transferred onto the recording material, but are preferably performed on the photoreceptor before the primary transfer. When the charge amount of the toner is high, the adhesion force between the photosensitive member and the intermediate transfer member and the toner increases, and cleaning failure of the photosensitive member and the like may occur. In particular, when polymerized toner is used, cleaning defects are more likely to occur due to high sphericity. Therefore, if the non-magnetic toner is neutralized on the photoconductor, the charge amount of the toner can be reduced and the cleaning failure of the photoconductor and the like can be reduced. Further, if the magnetic toner is charged on the photosensitive member, it is possible to obtain an effect that transfer failure and toner scattering due to uncharged toner can be prevented. Note that the charge removal process and the charging process may be performed at a place other than on the photosensitive member, for example, on the intermediate transfer member.

  In the full-color image forming method of the present invention, the charge amount of the magnetic toner on the photoconductor is 1 to 15 μC / g and the charge amount of the nonmagnetic toner on the photoconductor is 16 to before the charge removal and charging process. 40 μC / g is preferred.

  The magnetic toner is restrained mainly on the developing sleeve by a magnetic force and an electric force. When the charge amount of the magnetic toner on the photoconductor is less than 1 μC / g, the amount of uncharged toner becomes excessive and toner scattering occurs. On the other hand, when the charge amount of the magnetic toner on the photoconductor is larger than 15 μC / g, the charge amount of the developing portion also becomes high, causing thin layer unevenness and image density reduction. Therefore, the charge amount of the magnetic toner on the photoreceptor is preferably 1 to 15 μC / g before the charge removal and charging process.

  The nonmagnetic toner is mainly restrained on the developing sleeve by an electric force. When the charge amount of the non-magnetic toner on the photoreceptor is less than 16 μC / g, toner scattering occurs. On the other hand, when the charge amount of the non-magnetic toner on the photoconductor is larger than 40 μC / g, the charge amount of the developing portion also becomes high, causing thin layer unevenness and image density reduction. Accordingly, the charge amount of the non-magnetic toner on the photoreceptor is preferably 16 to 40 μC / g before the charge removal and charging treatment.

The charge amount of the toner on the photosensitive member is a solid patch (2.Pg) in which the toner amount is 0.2 to 0.4 mg / cm ² for each color such as black, cyan, magenta, and yellow in the mono color mode. 5 cm × 2.5 cm) and the toner charge amount of the solid patch on the photoconductor is measured.

<Manufacture of toner>
The magnetic toner and non-magnetic toner used in the present invention are produced using a release agent and a charge control agent together with a binder resin. The magnetic toner is manufactured using magnetic powder, and the non-magnetic toner is manufactured using a colorant.

(Binder resin)
The type of the binder resin is not particularly limited. For example, polystyrene resin, polyacrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide And thermoplastic resins such as styrene resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins.

  The polystyrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. As copolymerizable monomers, p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate, propion Vinyl esters such as vinyl acrylate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, acrylic (Meth) acrylic acid esters such as phenyl acid, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; Vinyl ethers such as nyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidene, etc. N-vinyl compounds of One of these copolymerization monomers can be copolymerized alone with the styrene monomer, or two or more of these copolymerization monomers can be copolymerized with the styrene monomer. The polystyrene resin preferably has two weight average molecular weight peaks (low molecular weight peak and high molecular weight peak). Specifically, the low molecular weight peak is preferably in the range of 3000 to 20000, and the other high molecular weight peak is preferably in the range of 300000 to 1500,000. Furthermore, it is preferable that Mw / Mn is 10 or more for the weight average molecular weight (Mw) and the number average molecular weight (Mn). If the weight average molecular weight peak is within such a range, the toner can be easily fixed, and offset resistance can be improved.

  Examples of the polyester-based resin include resins obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. Examples of the alcohol component include divalent or trivalent or higher alcohol components, and specific examples include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4- Butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol Diols such as bisphenol A, hydrogenated bisphenol A, bisphenols such as polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6- Xanthetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, Examples include trivalent or higher alcohols such as 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5, -trihydroxymethylbenzene.

  Examples of the carboxylic acid component include divalent or trivalent carboxylic acids, acid anhydrides or lower alkyl esters thereof, and include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid. Acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n- Divalent carboxylic acids such as alkyl succinic acid or alkenyl succinic acid such as octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid and isododecenyl succinic acid; 1,2,4-benzenetricarboxylic acid (Trimellitic acid), 1,2,5-benzene Carboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl- 2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid, etc. And trivalent or higher carboxylic acids.

  The binder resin is preferably a thermoplastic resin from the viewpoint of good fixability, but the cross-linked portion amount (gel amount) measured using a Soxhlet extractor is 10% by weight or less, more preferably 0.1 to 10%. A thermosetting resin may be used as long as the value is within the range of% by weight. By introducing a partially crosslinked structure in this way, it is possible to further improve the storage stability, form retention, and durability of the toner without deteriorating the fixability. Therefore, it is not necessary to use 100% by weight of the thermoplastic resin as the binder resin for the toner, and a crosslinking agent may be added or a part of the thermosetting resin may be used. As the thermosetting resin, for example, an epoxy resin or a cyanate resin can be used. More specifically, one or more of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyalkylene ether type epoxy resin, cycloaliphatic type epoxy resin, cyanate resin, etc. Combinations are listed.

  When the binder resin is used in the production of a magnetic toner, in order to improve the dispersibility of the magnetic powder, at least one functional group selected from a hydroxyloxy (hydroxy acid) group, a carboxyl group, an amino group, and a glycidoxy (epoxy) group It is preferable to use a binder resin having in the molecule. In addition, it can be confirmed using an FT-IR apparatus whether it has these functional groups, and also can be quantified using a titration method.

  In the binder resin, the glass transition point (Tg) is preferably set to a value in the range of 55 to 70 ° C. When the glass transition point of the binder resin is less than 55 ° C., the obtained toners are fused with each other, and the storage stability tends to be lowered. On the other hand, when the glass transition point of the binder resin exceeds 70 ° C., the fixability of the toner tends to be poor. In addition, the glass transition point of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC).

(Release agent)
Examples of mold release agents include plant waxes such as carnauba wax, sugar wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, and wool wax; Fischer-Tropsch wax and polyethylene wax having ester in the side chain And synthetic hydrocarbon waxes such as polypropylene wax. The release agent preferably has an endothermic main peak in a range of 70 to 100 ° C. in an endothermic curve obtained by a differential scanning calorimeter. This is because when the endothermic main peak is less than 70 ° C., toner blocking and hot offset may occur, and when the endothermic main peak exceeds 100 ° C., low temperature fixability may not be obtained. The amount of the wax added is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. If the addition amount of the wax is less than 0.1 parts by weight, it is difficult to obtain a sufficient effect of the wax. On the other hand, if the addition amount is more than 20 parts by weight, the anti-blocking property is lowered and the toner may be detached. is there.

(Charge control agent)
Examples of the charge control agent include positively chargeable charge control agents, and specific examples include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine. 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, , 3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1, Azine compounds such as 3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline; Azin Fast Red FC, Azin Fast Red 12 Direct dyes composed of azine compounds such as K, azine violet BO, azine brown 3G, azine light brown GR, Azinda-Kugrain BH / C, azine dip black EW and azine black 3RL; nigrosine, nigrosine salt, nigrosine derivative Nigrosine compounds such as: nigrosine BK, nigrosine NB, nigrosine compounds such as nigrosine Z; acid dyes; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; benzylmethylhexyldecylammonium, decyltrimethylammonium chloride, etc. Quaternary ammonium salts can be exemplified, and these can be used alone or in combination of two or more.

  Further, a quaternary ammonium salt, a carboxylate, or a resin or an oligomer having a carboxyl group as a functional group can also be used as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, a carboxylic acid Styrene resin with salt, acrylic resin with carboxylate, styrene-acrylic resin with carboxylate, polyester resin with carboxylate, polystyrene resin with carboxyl group, acrylic with carboxyl group 1 type, or 2 or more types, such as resin, the styrene-acrylic resin which has a carboxyl group, and the polyester-type resin which has a carboxyl group, are mentioned.

  As the charge control agent exhibiting negative chargeability, for example, organometallic complexes and chelate compounds are effective. Examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-di-tert-butylsalicylate chromium. In particular, acetylacetone metal complexes, salicylic acid metal complexes or salts are preferable, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferable.

  The addition amount of the charge control agent is 1 to 15.0 parts by weight, preferably 1.5 to 8.0 parts by weight with respect to 100 parts by weight of the binder resin. If the amount of the charge control agent added is less than the above range, it may be difficult to stably charge the toner, and the electrostatic latent image was developed using the toner to form an image. In some cases, a decrease in image density may occur. On the other hand, when the amount of the charge control agent is larger than the above range, there may be disadvantages such as environmental resistance, particularly charging failure or image failure under high temperature and high humidity, and contamination of the photoreceptor.

(Magnetic powder)
Magnetic powders include, for example, ferrite, magnetite and other iron, cobalt, nickel and other metals that exhibit ferromagnetism, alloys of these metal elements, compounds containing these metal elements, and those that do not contain ferromagnetic elements but are subjected to appropriate heat treatment. Examples thereof include alloys that exhibit ferromagnetism and chromium dioxide. As these magnetic powders, fine powders having an average particle diameter of 0.1 to 1 μm, preferably 0.1 to 0.5 μm, may be used. Moreover, you may use the magnetic powder surface-treated with surface treatment agents, such as a titanium coupling agent and a silane coupling agent. The addition amount of the magnetic powder is 30 to 60 parts by weight, preferably 40 to 60 parts by weight with respect to 100 parts by weight of the binder resin. If the magnetic powder is added in a larger amount than the above range, the durability of the image density is lowered and the fixability tends to be extremely lowered. If the amount is less than the above range, fogging in image density durability tends to occur. In the black toner, carbon black may be further added together with the magnetic powder.

(Coloring agent)
The colorant is not particularly limited, and examples thereof include magenta, cyan and yellow colorants. These colorants are added in an amount of 2 to 20 parts by weight, preferably 4 to 15 parts by weight, based on 100 parts by weight of the binder binder resin.

  As the magenta colorant, for example, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Pigment red 57, C.I. Pigment Red 49, C.I. I. Solvent Red 49, C.I. I. Solvent Red 19, C.I. I. Solvent Red 52, C.I. I. Basic Red 10, C.I. I. Disperse Red 15 etc. are mentioned.

  As the cyan colorant, for example, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15-1, C.I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 86, C.I. I. Direct Blue 25 etc. are mentioned.

  Examples of yellow colorants include nitro pigments such as naphthol yellow S, azo pigments such as Hansa Yellow 5G, Hansa Yellow 3G, Hansa Yellow G, Benzidine Yellow G, and Vulcan Fast Yellow 5G, or yellow iron oxide and ocher. And inorganic pigments. In addition, C.C. I. Pigment yellow 12, C.I. I. Pigment yellow 180, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 16, C.I. I. Solvent Yellow 19, C.I. I. Solvent yellow 21 etc. are mentioned.

(Other ingredients)
As other components, silica powder may be added to the toner. Examples of the silica powder include Aerosil R972, R974, Silica D-17, T-805, R-812, RA200, HRX-C manufactured by Nippon Aerosil Co., Ltd. Taranox 500 manufactured by Tarco Co., Ltd., Cab-o- manufactured by Cabot Corporation. Examples include SilM-5, MS-7, MS-75, HS-5, EH-5, S-17, TS-72, and the like. When these silica powders are used, the content is preferably 3% by weight or less based on the total weight of the toner.

  Further, as other components, a metal oxide may be added to the toner. Examples of the metal oxide include titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, magnesium titanate, and calcium titanate. By adding such a metal oxide, transfer defects and fixing defects can be suppressed.

(Production method)
A predetermined amount of a binder resin, a release agent, a charge control agent, and a colorant (in the case of magnetic toner, magnetic powder instead of the colorant) are added, and the mixture is stirred and mixed by a mixing device such as a Henschel mixer. Next, the mixture is melt-kneaded with a twin screw extruder or the like, cooled, and then pulverized with a pulverizer such as a hammer mill or a jet mill. Next, toner particles having a predetermined particle diameter are obtained using a classifier such as an air classifier. Next, a predetermined amount of an external additive (for example, silica powder, metal oxide, etc.) is added to the obtained toner particles, and agitated and mixed with a mixing device such as a Henschel mixer to produce a toner.

  In the present invention, the non-magnetic toner may be processed by a method such as a dissolution suspension method or a suspension polymerization method to obtain a toner. In the dissolution suspension method, for example, toner is obtained by the following method. First, with respect to 100 parts by weight of the toner, 150 parts by weight of ethyl acetate is dispersed with a ball mill for 48 hours to obtain Liquid A. On the other hand, 60 parts by weight of calcium carbonate (average particle size 80 nm) and 40 parts by weight of water were dispersed with a ball mill for 48 hours, and then 7 parts by weight of calcium carbonate dispersion and carboxymethyl cellulose (trade name “Serogen BS-H”: Daiichi Kogyo Seiyaku Co., Ltd.) 100 parts by weight of a 2% aqueous solution (made by Kogyo Co., Ltd.) is stirred (this liquid is referred to as B liquid). Next, 100 parts by weight of B liquid was stirred with an emulsifier (trade name “Auto Homo Mixer”: manufactured by Tokushu Kika Kogyo Co., Ltd.), and 50 parts by weight of A liquid was slowly added to suspend the mixed liquid. . Thereafter, the solvent is removed under reduced pressure, and then 100 parts by weight of 6N hydrochloric acid is added to remove calcium carbonate, followed by washing with water, drying and classification.

  A polymerized toner obtained by a known suspension polymerization method may be used as a nonmagnetic toner. For example, a composition containing a polymerizable monomer, a colorant, a polymerization initiator, a charge control agent, etc. is added to an aqueous phase with stirring, and granulated. After the polymerization reaction, the particles are filtered and dried. A polymerized toner can be obtained. Examples of the polymerizable monomer include a monovinyl aromatic monomer, an acrylic monomer, a vinyl ester monomer, a vinyl ether monomer, a diolefin monomer, and a monoolefin monomer. Can be mentioned. As the colorant, the same colorant as described above can be used. Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichloroylbenzoyl peroxide, methyl ethyl ketone peroxide, and the like. As the charge control agent, the same charge control agent as described above can be used.

<Image forming apparatus>
An image forming apparatus that can suitably use the image forming method of the present invention will be described with reference to FIG. In the full-color image forming apparatus 10 shown in FIG. 1, developing sleeves 31, 32, 33, 34 corresponding to the toners T 1, T 2, T 3, T 4 are arranged on the photosensitive drum 61 in the housing 11. A full-color toner image is formed on one photosensitive drum, and the toner image is transferred onto an intermediate transfer drum 45 (intermediate transfer member), and then the toner image on the intermediate transfer drum 45 is placed on a sheet (recording material). This is a full-color image forming apparatus that performs batch transfer. Further, around the photosensitive drum 61, not only the developing sleeves 31, 32, 33, and 34 but also a charging unit 1, an exposure unit 2, a cleaning unit 5, and a charge eliminating unit 6 are provided.

  A known material can be used as the photosensitive drum 61. For example, a photosensitive member such as an amorphous silicon photosensitive member, an organic photosensitive member, a Se photosensitive member, a ZnO photosensitive member, or a CdS photosensitive member is used. it can.

  The charging unit 1 is configured to be able to apply a predetermined bias voltage to the surface of the photosensitive drum 61. The exposure unit 2 irradiates the charged surface of the photosensitive drum 61 with image information from an external terminal as laser light to form a latent image. In the exposure means 2, LED light may be used instead of laser light. The cleaning unit 5 removes the toner that has not been transferred by the intermediate transfer drum 45 from the photosensitive drum 61.

  The neutralization unit 6 is provided for performing a neutralization process on the non-magnetic toner on the photosensitive drum 61, and for example, a corona discharger using a charger wire can be used. Specifically, corona discharge having a polarity opposite to that of the non-magnetic toner is applied so that the difference in charge amount between the magnetic toner and the non-magnetic toner is less than 10 μC / g. When charging the magnetic toner to reduce the difference in charge amount to less than 10 μC / g, a magnetic toner charging unit is installed at the same position as the neutralizing unit 6 in FIG. 1 instead of the neutralizing unit 6. That's fine.

  The full-color image forming apparatus 10 is provided with four developing means 38. In the toner container of these developing means 38, toner T1 (black toner) as magnetic toner and toner T2 (yellow toner) as non-magnetic toner are provided. ), Toner T3 (magenta toner) and toner T4 (cyan toner) are stored.

  The toners T1, T2, T3, and T4 are used to form a toner image on the surface of the photosensitive drum 61. Specifically, first, the toner T1 is conveyed to the developing sleeve 31 via a conveyance path (not shown), the toner T2 is conveyed to the developing sleeve 32, the toner T3 is conveyed to the developing sleeve 33, and the toner T4 is conveyed to the developing sleeve 34. .

  Next, an image forming process of the full-color image forming apparatus 10 will be outlined. First, the surface of the photosensitive drum 61 is uniformly charged by the charging unit 1. Next, an electrostatic latent image is formed on the surface of the photosensitive drum 61 by the exposure unit 2. In the developing unit 38, the toners T1 to T4 are sequentially supplied to the developing sleeves 31 to 34. In this supply, the toner may be stirred by the developing unit 38 and the toners T2 to T4 may be supplied to the developing sleeves 32 to 34. The supplied toners T1 to T4 form a toner layer on the developing sleeves 31 to 34. A predetermined amount of frictional charge is applied to the toners T1 to T4 in the toner layer, and the charged toners T1 to T4 adhere to the electrostatic latent image on the photosensitive drum 61, and the toner is adhered to the surface of the photosensitive drum 61. An image is formed. When the charge removal process is not performed after the toner image is formed on the surface of the photosensitive drum 61, the difference between the charge amount of the toners T2 to T4 and the charge amount of the toner T1 becomes 10 μC / g or more. Therefore, when the toner images of the toners T2 to T4 are formed on the surface of the photosensitive drum 61, the toner is discharged by using the discharging unit 6. Since the difference between the charge amount of the toners T2 to T4 and the charge amount of the toner T1 is less than 10 μC / g by this charge removal, the full-color image forming apparatus 10 does not suffer from problems such as missing characters and toner scattering. When a magnetic toner charging unit is used in place of the charge eliminating unit 6, the toner T1 is charged using the magnetic toner charging unit when the toner image of the toner T1 is formed on the surface of the photosensitive drum 61. Thus, the difference between the charge amount of the toners T2 to T4 and the charge amount of the toner T1 is set to be less than 10 μC / g.

  The toner image formed on the surface of the photosensitive drum 61 is transferred onto the intermediate transfer drum 45. In the intermediate transfer drum 45, color transfer is performed by repeating the transfer of the toner image on the photosensitive drum 61 for each of the toners T1 to T4.

  On the other hand, a sheet (not shown) conveyed from a sheet feeding cassette 13 provided in the lower part of the full-color image forming apparatus 10 is conveyed to registration rollers 50 and 51, and after aligning the leading edge and timing, a secondary transfer roller. 44. Then, the full color image transferred onto the intermediate transfer drum 45 is transferred to a sheet conveyed between the intermediate transfer drum 45 and the transfer roller 44. After the transfer, the sheet is conveyed to a fixing unit 7 having a pair of rollers 73 and 74 having a built-in heat source such as a heater. The toner is melted and fixed on the sheet conveyed to the fixing unit 7 by heat and pressure. Thereafter, the paper is conveyed to the paper discharge unit 78. The toner remaining on the intermediate transfer drum 45 without being transferred to the paper is removed by the cleaning means 46.

  The full-color image forming method of the present invention can also be suitably used for the image forming apparatus shown in FIG. In FIG. 2, four image forming units 101, 102, 103, and 104 are provided, and four photosensitive drums 61, 62, 63, and 64 are arranged on an intermediate transfer belt (intermediate transfer member). 1 illustrates a transfer tandem type full-color image forming apparatus. The full-color image forming apparatus 10 includes an intermediate transfer belt 47 that runs while being stretched around rollers 41, 42, and 43. The toner image is transferred onto the intermediate transfer belt 47 in order of toner image transfer (in order from the upstream side). Body drums 61, 62, 63, 64 are arranged. Further, around the photosensitive drum 61, the magnetic toner charging means 9 is used to charge the toner T1 formed on the surface of the photosensitive drum 61, thereby charging the toners T2 to T4 and the charging amount of the toner T1. Is less than 10 μC / g. When the charge removal of the toners T2 to T4 is performed so that the difference between the charge amount of the toners T2 to T4 and the charge amount of the toner T1 is less than 10 μC / g, the charge removal is performed around the photosensitive drums 62, 63, and 64. Means may be provided. In the full-color image forming apparatus 10, the toner images visualized on the photosensitive drums 61, 62, 63, 64 are sequentially transferred from the upstream photosensitive drum 61 to the surface of the intermediate transfer belt 47. . Then, the full color image transferred onto the intermediate transfer belt 47 is transferred to a sheet (not shown) conveyed from the paper feed cassette 13 between the roller 41 and the transfer roller 44. The toner that has not been transferred onto the intermediate transfer belt 47 is removed by the cleaning means 46. Other portions are denoted by the same reference numerals as those in FIG.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to a following example.

[Example]
In accordance with the following formulation, the materials are mixed and stirred with a mixing stirrer (Henschel mixer), then melt-kneaded with a twin screw extruder, pulverized with a jet mill, and air-classified with a classifier to produce a toner material having an average particle size of 8 μm. Got. Next, 0.6 parts by weight of silica fine particles (RA200, manufactured by Aerosil Co.) and 0.5 parts by weight of titanium oxide (EC100, manufactured by Titanium Industry Co., Ltd.) are added to 100 parts by weight of the toner raw material, and the mixing and stirring are performed. The final toner was obtained by performing a spraying process in the machine.

<Toner prescription>
(Magenta toner)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Colorant: Toner Magenta E02 (manufactured by Clariant Japan) 5.0 parts by weight Charge control agent: N-21 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei) 5.0 parts by weight (cyan toner)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Colorant: Toner Cyan BG (manufactured by Clariant Japan) 5.0 parts by weight Charge control agent: N-21 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei) 5.0 parts by weight (yellow toner)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Colorant: Toner Yellow HG (manufactured by Clariant Japan) 5.0 parts by weight Charge control agent: N-21 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei) 5.0 parts by weight (black toner)
Binder resin: SE-0040 (manufactured by Sekisui Chemical Co., Ltd.) 100 parts by weight Magnetic powder: MTS-106 (manufactured by Toda Kogyo Co., Ltd.) 45.0 parts by weight Charge control agent: N-21 (manufactured by Orient Chemical Co., Ltd.) 2.0 weights Part release agent: Carnauba wax (manufactured by Toa Kasei) 5.0 parts by weight

[Example 1 and Comparative Examples 1-2]
Using each of the toners, an image output test, a toner charge amount measurement, and a cleaning failure test were performed.

(Image output test)
The black developer of the image forming apparatus KM-C850 (manufactured by Kyocera Mita) is converted to a magnetic one-component developing system, and the color developer is converted to a non-magnetic one-component developing system, and each toner manufactured by the above method is used as an image forming apparatus. I set it. Further, a non-magnetic toner was appropriately neutralized by providing a corona discharger with a charger wire around the photosensitive drum. The results of the image output test are shown in the item “Image defects” in Tables 1-3. The conditions for the static elimination treatment were applied by applying a corona discharge with a DC polarity opposite to that of the non-magnetic toner, with the distance between the charger wire of the corona discharger and the photosensitive drum being 8 mm. In the item of “treatment voltage” in Tables 1 to 3, the applied voltage is shown for those that have been subjected to the charge removal process, and “none” for those that have not been removed.

  Next, a full-color image was output on a sheet, and it was confirmed whether or not voids and dust were generated in the character portion of each of the four colors (magenta, yellow, cyan, and black). The results are shown in the item “Image defects” in Tables 1 to 3 below. In the image forming apparatus, an amorphous silicon photosensitive drum is used as the photoreceptor, and the primary transfer setting is DC-300 V with constant voltage control, and the secondary transfer setting is DC-15 μA with constant current control. It was.

(Measurement of toner charge)
Using the same image forming apparatus as in the above image output test, a solid patch (2.Pg) in which the toner amount is 0.2 to 0.4 mg / cm ² for each color of cyan, magenta, yellow, and black in the mono color mode. 5cm and 2.5cm), the front cover of the machine body is opened during the output of each solid patch, and the toner charge amount (μC / g) of the solid patch on the photosensitive drum is determined by a q / m meter (MODEL 210HS Trek) Manufactured). The results are shown in Tables 1 to 3 below. In the table, the measurement result before the charge removal process is shown in the item “Charge amount of the photoreceptor”, and the measurement result after the charge removal process is shown in the item “Charge amount after the process”.

(Cleaning failure test)
In the mono color mode, for each color of cyan, magenta, yellow, and black, 50 sheets of solid 2 cm wide and 10 cm long were output in the paper passing direction to test whether or not a cleaning failure occurred. In this test, when vertical streak-like images were generated in the non-image area due to the output, it was determined that there was a cleaning defect. The results are shown in Tables 1 to 3 below.

  As shown in Table 1, in Example 1, image defects and cleaning failures did not occur, and good results were obtained. This is presumably because the charge removal difference between the non-magnetic toner and the magnetic toner was made less than 10 μC / g by performing the charge removal process on the non-magnetic toner.

  On the other hand, as shown in Table 2, in Comparative Example 1, since the neutralization process was not performed on the nonmagnetic toner, the difference in charge amount between the nonmagnetic toner and the magnetic toner is larger than 10 μC / g. As a result, image defects such as missing characters have occurred, and cleaning defects have also occurred. As shown in Table 3, in Comparative Example 2, the neutralization treatment was performed on the non-magnetic toner, but in the cyan toner in which the difference in the charge amount between the non-magnetic toner and the magnetic toner is larger than 10 μC / g, A malfunction of the image occurred.

[Example 2 and Comparative Examples 3 to 4]
Using each of the above toners, an image output test and a toner charge amount measurement were performed. However, in Example 2 and Comparative Examples 3 to 4, instead of the charge removal process in Example 1 or the like, the magnetic toner was charged.

(Image output test)
Instead of the charge removal process in the image output test, the magnetic toner was appropriately charged. Specifically, the distance between the charger wire of the corona discharger and the photosensitive drum was set to 8 mm, and application was performed by applying a corona discharge having the same polarity as the magnetic toner with a direct current. The results are shown in Tables 4-6. In addition, in the item of “treatment voltage” in Tables 4 to 6, the applied voltage is indicated for the case where the charging process is performed, and “none” is indicated for the case where the charging process is not performed. The image forming apparatus used was the same as that used in Example 1, but the primary transfer setting was DC-500 V with constant voltage control, and the secondary transfer setting was DC-30 μA with constant current control. Other test methods are the same as those in the image output test.

(Measurement of toner charge)
The measurement was performed in the same manner as the measurement of the toner charge amount, except that the magnetic toner was charged instead of the charge removal process. The results are shown in Tables 4-6. The measurement result before the charging process is shown in the item “Charge amount of the photoreceptor”, and the measurement result after the charging process is shown in the item “Charge amount after the process”.

  As shown in Table 4, in Example 2, no image defect occurred, and the result was good. This is presumably because the difference in the charge amount between the non-magnetic toner and the magnetic toner was reduced to less than 10 μC / g by charging the magnetic toner.

  On the other hand, as shown in Table 5, in Comparative Example 3, since the magnetic toner was not charged, the difference in charge amount between the non-magnetic toner and the magnetic toner is larger than 10 μC / g. As a result, image defects such as the occurrence of dust in the character portion occurred. As shown in Table 6, in Comparative Example 4, the magnetic toner was charged. However, in the black toner in which the difference in the charge amount between the non-magnetic toner and the magnetic toner is larger than 10 μC / g, An image defect occurred.

[Example 3]
For magenta toner, yellow toner, and cyan toner, polymerized toners were produced by suspension polymerization, and the same tests as in Example 1 were performed using them. The prescription of the polymerized toner is as follows. As the black toner, the same toner as in Example 1 was used.

<Formulation of polymerized toner>
(Polymerized magenta toner)
80 parts by weight of styrene, 20 parts by weight of 2-ethylhexyl methacrylate, 5 parts by weight of colorant (Toner Magenta E02, manufactured by Clariant Japan), 3 parts by weight of low molecular weight polypropylene, 2 parts by weight of charge control agent (P-53), divinylbenzene (Crosslinking agent) After 1 part by weight of the mixed solution was sufficiently dispersed by a ball mill, 2 parts by weight of a polymerization initiator 2,2-azobis (2,4-dimethylvaleronitrile) was added, and this was added to ion-exchanged water 400. In addition to 5 parts by weight, 5 parts by weight of tribasic calcium phosphate and 0.1 part by weight of sodium dodecylbenzenesulfonate were added as suspension stabilizers, and 20 times at a rotation speed of 7000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). After stirring for 10 minutes and carrying out a polymerization reaction at 70 ° C. and 100 rpm for 10 hours in a nitrogen atmosphere, acid washing is performed to obtain tricalcium phosphate. It was obtained removed by the volume average particle size 8μm toner mother particle dispersion. This dispersion was filtered, washed and dried to obtain a toner raw powder. Next, 0.6 part by weight of silica fine particles (RA200, manufactured by Aerosil Co.) and 0.5 part by weight of titanium oxide (EC100, manufactured by Titanium Industry Co., Ltd.) are added to 100 parts by weight of the toner raw material. The final toner was obtained by a dusting process.
(Polymerized yellow toner)
It was produced in the same manner as the above polymerized magenta toner except that 5 parts by weight of Toner Yellow HG (manufactured by Clariant Japan) was used as a colorant.
(Polymerized cyan toner)
It was produced in the same manner as the above polymerized magenta toner except that 5 parts by weight of Toner Cyan BG (manufactured by Clariant Japan) was used as the colorant.

According to Table 7, even in Example 3 in which polymerized toner was used as the nonmagnetic toner and pulverized toner was used as the magnetic toner, the charge removal of the nonmagnetic toner and the magnetic toner was performed by subjecting the nonmagnetic toner to charge removal. It can be seen that by making the difference less than 10 μC / g, image defects and poor cleaning did not occur, and good results were obtained.

It is a schematic sectional drawing which shows an example of the full-color image formation apparatus which can use the full-color image formation method of this invention suitably. It is a schematic sectional drawing which shows the other example of the full-color image formation apparatus which can use the full-color image formation method of this invention suitably.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging means 2 Exposure means 5 Cleaning means 6 Static elimination means 7 Fixing means 9 Magnetic toner charging means 10 Full color image forming apparatus 45 Intermediate transfer drum (intermediate transfer body)
47 Intermediate transfer belt (intermediate transfer member)
61-64 photoconductor drum (photoconductor)
T1 black toner (magnetic toner)
T2 Yellow toner (non-magnetic toner)
T3 Magenta toner (non-magnetic toner)
T4 cyan toner (non-magnetic toner)

Claims (5)

After the toner images of each color formed on the surface of the photoreceptor using non-magnetic toner and magnetic toner are transferred onto the intermediate transfer member, the toner images of each color on the intermediate transfer member are collectively transferred onto the recording material. A full color image forming method comprising:
When the charge amount of the non-magnetic toner on the photosensitive member is 10 μC / g or more larger than the charge amount of the magnetic toner, the non-magnetic toner is neutralized before transferring the toner image onto the recording material. An image forming method, wherein the difference in charge amount is less than 10 μC / g. After the toner images of each color formed on the surface of the photoreceptor using non-magnetic toner and magnetic toner are transferred onto the intermediate transfer member, the toner images of each color on the intermediate transfer member are collectively transferred onto the recording material. A full color image forming method comprising:
When the charge amount of the non-magnetic toner on the photosensitive member is 10 μC / g or more larger than the charge amount of the magnetic toner, the magnetic toner is charged before transferring the toner image onto the recording material. An image forming method, wherein the difference in amount is less than 10 μC / g.   The charge amount of the magnetic toner on the photoconductor is 1 to 15 μC / g and the charge amount of the nonmagnetic toner on the photoconductor is 16 to 40 μC / g before the processing. Item 3. The image forming method according to Item 1 or 2.   The image forming method according to claim 1, wherein the processing is performed on a photoreceptor. The image forming method according to claim 1, wherein the nonmagnetic toner is a polymerized toner, and the magnetic toner is a pulverized toner.

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