JP2013029689A - Developer for electrostatic latent image development and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide developer for electrostatic latent image development that prevents image defects to be caused by coarse surface of a latent image carrier during consecutive image formation and image defects to be caused by toner having fallen in a developer when an image is formed by an image forming device including the latent image carrier with a photosensitive layer formed of amorphous silicon and a cleaning part with an elastic blade, and to provide an image forming method using the developer for electrostatic latent image development.SOLUTION: The developer for electrostatic latent image development contains positively charged toner and organic carboxylic acid metal salt. The organic carboxylic acid metal salt is zinc salt, calcium salt, or magnesium salt, and has specific volume average particle diameter and irregularity.

Description

  The present invention relates to an electrostatic latent image developing used in an image forming apparatus including a latent image carrying portion in which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate and a cleaning portion having an elastic blade. The present invention relates to a developer and an image forming method using the above-described image forming apparatus.

  In general, in electrophotography, a latent image carrier made of a photoconductive photoreceptor or dielectric is charged by corona charging or the like, and then exposed to a static image formed on the charged latent image carrier by a laser, LED, or the like. The electrostatic latent image is visualized by using a developer such as toner, or the electrostatic latent image is visualized by reversal development to form a high-quality image.

  Conventionally, as a latent image carrier used in such an image forming method, a latent image carrier having a photosensitive layer made of an organic photoconductor (OPC) is generally used. However, in recent years, the use of a latent image carrier having a photosensitive layer made of amorphous silicon has been studied in response to demands for improving the durability of image forming apparatuses. Although the latent image carrier is worn by being rubbed against a printing material or an elastic blade described later, amorphous silicon is extremely excellent in wear resistance. Therefore, from the viewpoint of wear of the latent image carrier, an image forming apparatus is High durability can be realized. Specifically, the reduction rate of the film thickness due to the abrasion of amorphous silicon is 1/100 or less of the organic photoconductor.

  For this reason, in an image forming apparatus having a positively chargeable latent image carrier having a photosensitive layer made of amorphous silicon, the latent image carrier (photoreceptor) has a long life, and the image formation cost per image is reduced. can do. Because of this advantage, the use of a latent image carrier having a photosensitive layer made of amorphous silicon is widespread.

  Further, after the toner image is transferred to the surface of the printing material such as paper, the toner remaining on the surface of the latent image carrying portion having the photosensitive layer made of amorphous silicon is removed by the cleaning portion. As such a cleaning unit, one having a simple structure with few movable parts and having an elastic blade is widely used since the image forming apparatus can be miniaturized.

  As described above, the latent image carrying unit having the photosensitive layer made of amorphous silicon and the cleaning unit having the elastic blade are often used in combination from the respective advantages.

  However, the latent image carrier having a photosensitive layer made of amorphous silicon has a drawback that the surface of the latent image carrier tends to become rough when images are continuously output. When the surface of the latent image carrier is roughened, an elastic blade is likely to roll up in an image forming apparatus including a latent image carrier having a photosensitive layer made of amorphous silicon and a cleaning unit having an elastic blade. There's a problem. Also, when the surface of the latent image carrier becomes rough, toner components such as a release agent contained in the toner are likely to adhere to the surface of the latent image carrier, and image defects such as dash marks may occur in the formed image. There is a problem that filming is likely to occur on the surface of the latent image carrier.

  As a method for solving the above problems in an image forming apparatus comprising a combination of a latent image carrier having a photosensitive layer made of amorphous silicon and a cleaning unit having an elastic blade, a lubricant having a particle size of 1 μm or less is lubricated with a brush or the like. There has been proposed a method of applying to the surface of the latent image carrier by the agent supply means (Patent Document 1).

JP 2005-275166 A

  However, in the method described in Patent Document 1, it is necessary to add a lubricant supply unit such as a brush to the image forming apparatus, which hinders downsizing of the image forming apparatus and increases the manufacturing cost of the image forming apparatus. There's a problem.

  As a method of supplying the lubricant to the surface of the latent image carrying unit without using the lubricant supply means, it is conceivable to add a lubricant to the developer containing toner. However, since the fatty acid metal salt that is preferably used as the lubricant particles is negatively charged, if the fatty acid metal salt is contained in a developer containing a positively charged toner, the charge amount of the toner may decrease. is there. Further, the fatty acid metal salt particles having a small particle diameter are likely to adhere strongly to the toner surface, and the fatty acid metal salt moves together with the toner. In such a case, a sufficient amount of the fatty acid metal salt is not supplied to the surface of the latent image carrying unit, and it is difficult to suppress roughening of the surface of the latent image carrying unit (an increase in the friction coefficient).

  In this regard, if the particle diameter of the fatty acid metal salt is increased, the adhesion of the fatty acid metal salt to the toner can be suppressed. However, in this case, when the toner is supplied from the developing unit to the surface of the latent image carrier, the fatty acid metal salt easily falls to the lower part of the magnetic roll in the developing unit due to its own weight, and the toner easily falls together with the fatty acid metal salt. Become. The toner dropped on the lower part of the magnetic roll stays in the lower part of the developing roll, and when the toner staying on the lower part of the developing roll is accumulated to some extent, the dropped toner may move to the latent image carrier. For this reason, when a fatty acid metal salt having a large particle size is added to a developer containing toner, an image defect due to the falling toner may occur.

  The present invention has been made in view of such circumstances, and in the case where an image is formed by an image forming apparatus including a combination of a latent image carrying unit having a photosensitive layer made of amorphous silicon and a cleaning unit having an elastic blade. Positive charging that can suppress image defects in various formed images due to roughening of the surface of the latent image carrier during continuous image formation and image defects in formed images due to toner dropped in the developing device It is an object to provide a developer for developing an electrostatic latent image containing a conductive toner and an image forming method using the developer for developing an electrostatic latent image.

  The inventors of the present invention provide a developer for developing an electrostatic latent image including a positively charged toner and an organic carboxylic acid metal salt, wherein the organic carboxylic acid metal salt is a zinc salt, a calcium salt, or a magnesium salt. In addition, by using a developer for developing an electrostatic latent image having a specific volume average particle diameter and a degree of unevenness, a latent image carrying unit including a photosensitive layer made of amorphous silicon, and a cleaning unit including an elastic blade are provided. The present inventors have found that the above problems in an image forming apparatus provided in combination can be solved, and have completed the present invention. Specifically, the present invention provides the following.

(1) A developer for developing an electrostatic latent image used in an image forming apparatus including a latent image carrying portion in which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate and a cleaning portion having an elastic blade. Because
The developer includes a positively charged toner and an organic carboxylic acid metal salt,
The organic carboxylic acid metal salt is a zinc salt, a calcium salt, or a magnesium salt,
The organic carboxylic acid metal salt has a volume average particle diameter of 2 to 10 μm,
The organic carboxylic acid metal salt calculated by the following formula from the circumference and area of the particles of the organic carboxylic acid metal salt obtained from the image of the organic carboxylic acid metal salt photographed at a magnification of 1000 times with a scanning electron microscope A developer for developing an electrostatic latent image, wherein the degree of unevenness of the particles is 1.10 to 1.30.
(Unevenness calculation formula)
Unevenness = (perimeter length) ² / (area × 4π)

  (2) The developer for developing an electrostatic latent image according to (1), wherein the organic carboxylic acid metal salt is a metal salt of an organic carboxylic acid having 6 to 20 carbon atoms.

  (3) The developer for electrostatic latent image development according to (2), wherein the organic carboxylic acid metal salt is a metal salt of stearic acid.

  (4) The electrostatic latent image according to (1) or (2), wherein the content of the organic carboxylic acid metal salt is 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the positively chargeable toner. Developer for development.

(5) In an image forming apparatus comprising: a latent image carrying portion in which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate; and a cleaning portion having an elastic blade.
A positively chargeable toner and an organic carboxylic acid metal salt,
The organic carboxylic acid metal salt is a zinc salt, a calcium salt, or a magnesium salt,
The organic carboxylic acid metal salt has a volume average particle diameter of 2 to 10 μm,
The organic carboxylic acid metal salt calculated by the following formula from the circumference and area of the particles of the organic carboxylic acid metal salt obtained from the image of the organic carboxylic acid metal salt photographed at a magnification of 1000 times with a scanning electron microscope An image forming method of forming an image using a developer for developing an electrostatic latent image, wherein the degree of unevenness of the particles is 1.10 to 1.30.
(Unevenness calculation formula)
Unevenness = (perimeter length) ² / (area × 4π)

  According to the present invention, image defects in various formed images due to roughening of the surface of the latent image carrier during continuous image formation, and image defects in a formed image due to toner dropped in the developing device are obtained. An electrostatic latent image developing developer containing a positively chargeable toner and an image forming method using the above-described electrostatic latent image developing developer can be provided.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. . In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

[First Embodiment]
The first embodiment of the present invention relates to a developer for developing an electrostatic latent image (hereinafter also referred to as a developer). The developer for developing an electrostatic latent image according to the first embodiment includes a latent image carrying unit in which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate, and a cleaning unit having an elastic blade. Used in a forming apparatus, and includes a positively chargeable toner (hereinafter also referred to as toner) and a specific type of organic carboxylic acid metal salt having a specific range of irregularities and particle diameters. In addition, the electrostatic latent image developing developer of the present invention can be made into a three-component developer by blending a carrier, if desired.

  Hereinafter, the developer according to the first embodiment will be described in order of a positively chargeable toner, an organic carboxylic acid metal salt, a developer preparation method, and a carrier used when a three-component developer is used.

[Positively chargeable toner]
The positively chargeable toner contained in the developer for developing an electrostatic latent image of the present invention is not particularly limited, and is appropriately selected from various positively charged toners conventionally used for developing an electrostatic latent image. be able to. Examples of suitable toners to be contained in the developer for developing an electrostatic latent image include toners containing a binder resin, a colorant, and, if desired, a charge control agent and a release agent. Further, the toner may be provided with an external additive such as silica on the surface thereof. Hereinafter, the binder resin, the colorant, the charge control agent, the release agent, the external additive, and the toner preparation method will be described in order.

(Binder resin)
The binder resin contained in the positively chargeable toner is not particularly limited as long as it is a resin conventionally used as a binder resin when a toner is manufactured. Specific examples of the binder resin include styrene resin, acrylic resin, styrene acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether. And thermoplastic resins such as styrene resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, styrene acrylic resins and polyester resins are preferable from the viewpoints of dispersibility with respect to the colorant in the toner, chargeability of the toner, and fixing properties with respect to the paper. Hereinafter, the styrene acrylic resin and the polyester resin will be described.

  The styrene acrylic resin is a copolymer of a styrene monomer and an acrylic monomer. Specific examples of the styrene monomer include styrene, α-methylstyrene, vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-ethylstyrene, and the like. Specific examples of the acrylic monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, meta Examples include (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.

  As the polyester resin, those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used. The components used when synthesizing the polyester resin include the following alcohol components and carboxylic acid components.

  Specific examples of the divalent or trivalent or higher alcohol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1 Diols such as 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A, Bisphenols such as hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, Entaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4- Examples include trivalent or higher alcohols such as butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

  Specific examples of the divalent or trivalent or higher carboxylic acid component include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic 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-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid Divalent carboxylic acids such as acids, isododecyl succinic acid, isododecenyl succinic acid and the like or alkyl or alkenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid Acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphtha Tricarboxylic 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, emporic trimer acid, and other trivalent or higher carboxylic acids. These divalent or trivalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  When the binder resin is a polyester resin, the softening point of the polyester resin is preferably 80 to 150 ° C, and more preferably 90 to 140 ° C.

  As the binder resin, it is preferable to use a thermoplastic resin because it has good fixability. However, not only the thermoplastic resin alone but also a crosslinking agent or a thermosetting resin should be added to the thermoplastic resin. Can do. By introducing a partially crosslinked structure into the binder resin, it is possible to improve the storage stability, form retention, durability and the like of the toner without deteriorating the fixability.

  As the thermosetting resin that can be used together with the thermoplastic resin, for example, an epoxy resin or a cyanate resin is preferable. Specific examples of suitable thermosetting resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, cycloaliphatic type epoxy resins, cyanate resins and the like. It is done. These thermosetting resins can be used in combination of two or more.

  The glass transition point (Tg) of the binder resin is preferably 50 to 65 ° C, and more preferably 50 to 60 ° C. If the glass transition point of the binder resin is too low, the toners may be fused inside the developing unit of the image forming apparatus, or the storage stability may be reduced. May be partly fused. On the other hand, when the glass transition point is too high, the strength of the binder resin is reduced, and the toner tends to adhere to the latent image carrying portion. When the glass transition point is too high, the low-temperature fixability of the toner tends to decrease.

  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). More specifically, it can be determined by measuring an endothermic curve using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as a measuring device. An endothermic curve obtained by placing 10 mg of a measurement sample in an aluminum pan, using an empty aluminum pan as a reference, and measuring at a measurement temperature range of 25 to 200 ° C. and a temperature increase rate of 10 ° C./min. The glass transition point can be obtained more.

(Coloring agent)
As the colorant contained in the toner, a known pigment or dye can be used in accordance with the color of the toner particles. Specific examples of suitable colorants to be added to the toner include black pigments such as carbon black, acetylene black, lamp black, and aniline black; yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow , Yellow pigments such as Navels Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; Red Yellow Yellow Lead, Molybdenum Orange, Permanent Orange Orange pigments such as GTR, Pyrazolone Orange, Vulcan Orange, Indanthrene Brilliant Orange GK; Bengala, Cadmium Red, Lead Tan, Mercury Cadmium, Permanent Red 4R, Lithium Red pigments such as Lured, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B; Purple such as Manganese Purple, Fast Violet B, Methyl Violet Lake Pigment: Blue pigment such as bitumen, cobalt blue, alkali blue lake, Victoria blue partially chlorinated, First Sky Blue, Indanthrene Blue BC; Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Final Yellow Green G, etc. Green pigments; white pigments such as zinc white, titanium oxide, antimony white, zinc sulfide; barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white, etc. It includes the quality pigments. These colorants may be used in combination of two or more for the purpose of adjusting the toner to a desired hue.

  The amount of the colorant used is not particularly limited as long as the object of the present invention is not impaired. Specifically, 1-10 mass parts is preferable with respect to 100 mass parts of binder resin, and 3-7 mass parts is more preferable.

(Release agent)
The toner may contain a release agent for the purpose of improving fixability and offset resistance. The type of release agent added to the toner is not particularly limited as long as the object of the present invention is not impaired. The mold release agent is preferably a wax, and examples of the wax include polyethylene wax, polypropylene wax, fluororesin-based wax, Fischer-Tropsch wax, paraffin wax, ester wax, montan wax, rice wax and the like. These waxes can be used in combination of two or more. By adding such a release agent to the toner, it is possible to more efficiently suppress the occurrence of offset and image smearing (dirt around the image when the image is rubbed).

  The amount of the release agent used is not particularly limited as long as the object of the present invention is not impaired. A specific amount of the release agent used is preferably 1 to 5 parts by mass when the total amount of toner is 100 parts by mass. If the amount of release agent used is too small, the desired effect may not be obtained with respect to suppression of occurrence of offset and image smearing. If the amount of release agent used is excessive, fusion between toners may occur. Depending on the case, the storage stability may decrease.

(Charge control agent)
The charge control agent is used for the purpose of obtaining a toner having excellent durability and stability by improving a charge level and a charge rising characteristic that is an index as to whether or not charging is possible in a short time to a predetermined charge level. Since the toner contained in the developer according to the first embodiment is a positively chargeable toner, a positively chargeable charge control agent is used as the charge control agent.

  The type of the positively chargeable charge control agent is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from positively chargeable and static charge control agents conventionally used in toners. Specific examples of the positively chargeable charge control agent 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, 1,3,5-thiadiazine, 1, 2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, Azine compounds such as phthalazine, quinazoline, quinoxaline; azine fast red FC, azine fast red 12BK, azine violet BO, azine Direct dyes composed of azine compounds such as Laun 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Dep Black EW, and Azin Dee Black 3RL; Nigrosine Compounds such as Nigrosine, Nigrosine Salts, Nigrosine Derivatives; Nigrosine Acid dyes comprising nigrosine compounds such as BK, nigrosine NB, nigrosine Z; metal salts of naphthenic acid or higher organic carboxylic acids; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride Is mentioned. Among these positively chargeable charge control agents, a nigrosine compound is particularly preferable in that a quicker charge rising property can be obtained. These positively chargeable charge control agents can be used in combination of two or more.

  Quaternary ammonium salts, carboxylates, or resins 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. The molecular weight of these resins is not particularly limited as long as the object of the present invention is not impaired, and may be an oligomer or a polymer.

  Among resins that can be used as a positively chargeable charge control agent, a styrene-acrylic copolymer having a quaternary ammonium salt as a functional group from the viewpoint that the charge amount can be easily adjusted to a value within a desired range. A resin is more preferable. Specific examples of preferable acrylic comonomers to be copolymerized with styrene units in a styrene-acrylic copolymer resin having a quaternary ammonium salt as a functional group include methyl acrylate, ethyl acrylate, n-propyl acrylate, and acrylic acid. (Meth) such as iso-propyl, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate Examples include alkyl acrylates.

  As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate, dialkyl (meth) acrylamide, or dialkylaminoalkyl (meth) acrylamide through a quaternization step is used. Specific examples of the dialkylaminoalkyl (meth) acrylate include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like. Specific examples of dialkyl (meth) acrylamide include dimethylmethacrylamide, and specific examples of dialkylaminoalkyl (meth) acrylamide include dimethylaminopropylmethacrylamide. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

  The amount of the charge control agent used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of charge control agent used is preferably 1.5 to 15 parts by weight, more preferably 2.0 to 8.0 parts by weight, and more preferably 3.0 to 100 parts by weight of the total amount of toner. -7.0 mass parts is particularly preferred. When the amount of the charge control agent used is too small, it is difficult to stably charge the toner, so that the image density of the formed image becomes lower than a preferable value, or the image density of the formed image is difficult to maintain for a long time. Further, in such a case, the charge control agent is difficult to disperse uniformly, and fogging in the formed image and contamination of the latent image carrier are likely to occur. When the amount of the charge control agent used is excessive, charging failure under high temperature and high humidity due to deterioration of environmental resistance, image failure in the formed image, contamination of the latent image carrier, and the like are likely to occur.

(External additive)
For the positively chargeable toner, an external additive may be attached to the surface for the purpose of improving the fluidity, storage stability, cleaning properties, etc. of the toner.

  The type of external additive is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from external additives conventionally used for toners. Specific examples of suitable external additives include silica and metal oxides such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These external additives can be used in combination of two or more.

  The particle diameter of the external additive is not particularly limited as long as the object of the present invention is not impaired, and typically 0.01 to 1.0 μm is preferable.

  The volume specific resistance value of the external additive can be adjusted by forming a coating layer made of tin oxide and antimony oxide on the surface of the external additive and changing the thickness of the coating layer and the ratio of tin oxide to antimony oxide. .

  The amount of the external additive used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the external additive used is preferably 0.1 to 10 parts by mass, and more preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the toner particles before being processed with the external additive. When the external additive is used in such an amount, it is easy to obtain a toner excellent in fluidity, storage stability, and cleaning properties.

(Preparation method of positively chargeable toner)
The method for preparing the positively chargeable toner is not particularly limited as long as components such as a colorant, a charge control agent, and a release agent can be satisfactorily dispersed in the binder resin. You can choose. As a suitable production method, for example, a binder resin and components such as a colorant, a charge control agent, and a release agent are mixed with a mixer, and then melt-kneaded, and the obtained kneaded product is pulverized and classified. Can be manufactured. The melt-kneading apparatus used for producing the positively chargeable toner is not particularly limited, and can be appropriately selected from apparatuses used for melt-kneading the thermoplastic resin. Specific examples of the melt-kneading apparatus include a uniaxial or biaxial extruder. The average particle size of the pulverized and classified toner is not particularly limited as long as the object of the present invention is not impaired, but generally 5 to 10 μm is preferable.

  The surface of the toner thus obtained may be treated with an external additive as necessary. The particles to be externally added are referred to as “toner mother particles”. The method for treating the toner with the external additive is not particularly limited, and can be appropriately selected from conventionally known methods for treating the external additive. Specifically, the processing conditions are adjusted so that the particles of the external additive are not embedded in the toner base particles, and the toner base particles are processed with the external additive by a mixer such as a Henschel mixer or a Nauter mixer. .

[Organic carboxylic acid metal salt]
The developer for developing an electrostatic latent image according to the first embodiment contains a metal salt of an organic carboxylic acid selected from the group consisting of zinc, calcium, and magnesium as the organic carboxylic acid metal salt. The structure of the organic carboxylic acid constituting the organic carboxylic acid metal salt is not particularly limited as long as the object of the present invention is not impaired, and may be an aliphatic carboxylic acid or an aromatic carboxylic acid.

  When the organic carboxylic acid is an aliphatic carboxylic acid, it may be a linear organic carboxylic acid, a branched organic carboxylic acid, or an alicyclic carboxylic acid. The aliphatic carboxylic acid may be a saturated organic carboxylic acid or an unsaturated organic carboxylic acid. When the organic carboxylic acid is an aliphatic carboxylic acid, a linear saturated aliphatic carboxylic acid is more preferable because it is easily available and has excellent storage stability.

  The aromatic carboxylic acid is an organic carboxylic acid having an aromatic group in the molecule, and may be an organic carboxylic acid such as benzoic acid or naphthoic acid in which the carboxyl group is directly linked to the aromatic group. Organic carboxylic acids in which a carboxyl group is not directly bonded to an aromatic group such as an acid may be used. The aromatic group contained in the aromatic carboxylic acid is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a phenoxy group, and the like, as long as the object of the present invention is not impaired. It may have one or more substituents selected from the group consisting of a hydroxyl group, a nitro group, a halogen atom, and a cyano group.

  The number of carbon atoms of the organic carboxylic acid constituting the organic carboxylic acid metal salt is not particularly limited as long as the object of the present invention is not impaired. The number of carbon atoms of the organic carboxylic acid is typically preferably 6-20. When the number of carbon atoms of the organic carboxylic acid is too small, the molecular weight of the organic carboxylic acid metal salt is decreased, and the number of molecules of the organic acid carboxylic acid metal salt contained in the unit weight is increased. For this reason, the charge amount of the toner may decrease, or the organic acid metal salt may easily adhere to the positively chargeable toner. When the number of carbon atoms of the organic carboxylic acid is excessive, it may be difficult to suppress an increase in the coefficient of friction on the surface of the latent image carrier, and a dash mark tends to be generated. Among the organic carboxylic acids constituting the organic carboxylic acid metal salt, stearic acid, which is a straight-chain saturated organic carboxylic acid having 18 carbon atoms, is preferable because it easily suppresses roughening of the latent image carrier surface. preferable.

  Moreover, the organic carboxylic acid metal salt contained in the developer has a volume average particle diameter of 2 to 10 μm and a degree of unevenness of 1.10 to 1.30. In the developer according to the first embodiment, since an organic carboxylic acid metal salt having an average particle size and a size close to that of the toner is used, the organic carboxylic acid metal salt hardly adheres to the toner surface. Therefore, most of the organic carboxylic acid metal salt in the developer is released from the toner, and together with the toner, a suitable amount of the organic carboxylic acid metal salt can be supplied to the latent image carrier surface. It is easy to suppress roughening.

  When the particle size of the organic carboxylic acid metal salt is excessive, when the toner and the organic carboxylic acid metal salt move from the developing device to the surface of the latent image carrier, the organic carboxylic acid metal salt easily falls due to its own weight. At this time, as the organic carboxylic acid metal salt falls, the toner easily falls into the developing device, and an image defect due to the dropped toner may occur in the formed image. In addition, when the particle size of the organic carboxylic acid metal salt is excessive, the organic carboxylic acid metal salt is softer than the toner. Therefore, the organic carboxylic acid metal salt is stretched by the thickness of the cleaning portion, so that the film is filled. Ming is likely to occur.

  When the particle size of the organic carboxylic acid metal salt is too small, particles of the organic carboxylic acid metal salt having a relatively small diameter are likely to adhere to the positively charged toner, and supply of the organic carboxylic acid metal salt to the surface of the latent image carrier Therefore, it is difficult to suppress the roughening of the surface of the latent image carrier. In this case, the toner on which fine particles of the organic carboxylic acid metal salt adhere to the surface easily adheres to the roughened latent image carrier surface, and image defects such as dash marks are likely to occur in the formed image.

  If the unevenness of the organic carboxylic acid metal salt is too large, the organic carboxylic acid metal salt adheres to the surface of the latent image carrier due to the interaction between the unevenness of the surface of the organic carboxylic acid metal salt and the minute unevenness of the surface of the latent image carrier. It becomes easy to do. In such a case, the toner particles are liable to stay on the surface of the latent image carrier so as to be caught by the organic carboxylic acid metal salt adhering to the surface of the latent image carrier, and image defects such as dashes are likely to occur in the formed image.

  When the degree of unevenness of the organic carboxylic acid metal salt is too small, the organic carboxylic acid metal salt particles tend to slip through the elastic blade of the cleaning unit. In such a case, the toner particles existing adjacent to the organic carboxylic acid metal salt on the surface of the latent image carrying part are likely to pass through the elastic blade together with the organic carboxylic acid metal salt, and an image defect due to toner slipping easily occurs in the formed image. .

  The method for adjusting the volume average particle diameter of the organic carboxylic acid metal salt is not particularly limited. Specifically, when the organic carboxylic acid metal salt is pulverized and classified by a known apparatus, the volume average particle diameter of the organic carboxylic acid metal salt is adjusted by appropriately changing the conditions of the pulverization step and the classification step. can do. For the preparation of the organic carboxylic acid metal salt whose volume average particle diameter is adjusted, for example, an airflow type pulverization apparatus can be used as the pulverization apparatus, and for example, an airflow type classification apparatus can be used as the classification apparatus.

  In addition, the method for preparing the degree of unevenness of the organic carboxylic acid metal salt is not particularly limited. For example, the degree of unevenness of the organic carboxylic acid metal salt is prepared by a method of heat treating particles of the organic carboxylic acid metal salt at a temperature near the melting point. can do. The unevenness degree of the organic carboxylic acid metal salt can be measured by the following method.

<Roughness measurement method>
A sample of an organic carboxylic acid metal salt is observed with a scanning electron microscope in a field of magnification of 1000 times, element mapping is performed by an X-ray spectrometer, and an image of a field of view in which particles of a predetermined metal salt are detected is acquired. . The obtained image was subjected to image processing with image analysis software (WinRoof (manufactured by Mitani Corporation)), and the peripheral length (μm) and area (μm ² ) of the organic carboxylic acid metal salt particles were calculated. The degree of unevenness of the organic carboxylic acid metal salt is calculated from the equation. The degree of unevenness is measured for 100 particles of the organic carboxylic acid metal salt, and the average value of the obtained unevenness is defined as the degree of unevenness of the organic carboxylic acid metal salt.
(Unevenness calculation formula)
Unevenness = (perimeter length) ² / (area × 4π)

  Among the organic carboxylic acid metal salts, zinc salts or calcium salts are preferable, and zinc salts are more preferable because the effect of suppressing image defects due to suppression of roughening on the surface of the latent image carrying portion is high.

  Specific examples of organic carboxylic acid metal salts that can be incorporated into the developer include zinc salts, calcium salts, or magnesium salts of fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and arachidic acid, and benzoic acid. Acid, salicylic acid, p-hydroxybenzoic acid, 2-chlorobenzoic acid, 4-chlorobenzoic acid, 4-nitrobenzoic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 2-ethylbenzoic acid Acid, 3-ethylbenzoic acid, 4-ethylbenzoic acid, 2-n-propylbenzoic acid, 3-n-propylbenzoic acid, 4-n-propylbenzoic acid, phenylacetic acid, 3-phenylpropionic acid, α-naphthoic acid Examples thereof include zinc salts, calcium salts, and magnesium salts of acids and aromatic carboxylic acids such as β-naphthoic acid.

  The content of the organic carboxylic acid metal salt of the developer is not particularly limited as long as the object of the present invention is not impaired, but is preferably 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the positively chargeable toner. 0.05-0.2 mass part is more preferable. By blending such an amount of the organic carboxylic acid metal salt into the developer, it becomes easy to suppress roughening of the surface of the latent image carrier.

[Method for preparing developer for developing electrostatic latent image]
The method for preparing the developer for developing an electrostatic latent image according to the first embodiment is not particularly limited as long as the positively chargeable toner and the organic carboxylic acid metal salt can be mixed uniformly. Examples of the method of mixing the positively chargeable toner and the organic carboxylic acid metal salt include a method using a mixing device such as a Henschel mixer.

  From the viewpoint of suppressing the adhesion of fine powder of organic carboxylic acid metal salt to the surface of the positively chargeable toner, a method of mixing the toner having the external additive attached to the surface and the organic carboxylic acid metal salt is a developer. It is preferable as a preparation method. In addition, since the external addition treatment and the organic carboxylic acid metal salt and the toner can be mixed at the same time, and the preparation of the developer can be simplified, the external additive can be adhered to the surface of the toner base particles. In addition, a method of adding an organic carboxylic acid metal salt together with an external additive to a mixing apparatus is also preferable as a method for preparing a developer.

[Carrier]
The developer for developing an electrostatic charge image of the first embodiment can be used as a three-component developer by mixing a desired carrier in addition to the positively chargeable toner and the organic carboxylic acid metal salt. Such a three-component developer can be handled in the same manner as a two-component developer comprising a toner and a carrier widely used for developing an electrostatic latent image. When preparing a three-component developer, it is preferable to use a magnetic carrier.

  Suitable carriers when the developer is a three-component developer include those in which a carrier core material is coated with a resin. Specific examples of carrier core materials include particles of iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, cobalt, etc., and particles of alloys of these materials with manganese, zinc, aluminum, etc. , Particles such as iron-nickel alloy, iron-cobalt alloy, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate , Ceramic particles such as lead zirconate and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt, resin carriers in which the above magnetic particles are dispersed in a resin, etc. Is mentioned.

  Specific examples of the resin covering the carrier core material include (meth) acrylic polymers, styrene polymers, styrene- (meth) acrylic copolymers, olefin polymers (polyethylene, chlorinated polyethylene, polypropylene, etc. ), Polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyfluoride) Vinylidene chloride, etc.), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, amino resin and the like. These resins can be used in combination of two or more.

  The particle diameter of the carrier is not particularly limited as long as the object of the present invention is not impaired, but is preferably 20 to 120 μm, more preferably 25 to 80 μm, as measured by an electron microscope.

The apparent density of the carrier is not particularly limited as long as the object of the present invention is not impaired. The apparent density varies depending on the carrier composition and surface structure, but is typically 2.0 to 2.5 g / cm ³ .

  When the developer is used as a three-component developer, the total content of the toner and the organic carboxylic acid metal salt is preferably 1 to 20% by mass, and 3 to 15% by mass with respect to the mass of the three-component developer. Is preferred. By setting the toner content in the three-component developer within such a range, an appropriate image density in the formed image is maintained, and toner contamination is suppressed and toner adhesion to the transfer paper and the like is suppressed. it can.

  When the developer contains a carrier, an organic carboxylic acid metal salt may be mixed in the mixture of the positively chargeable toner and the carrier, or in the developer in which the positively chargeable toner and the organic carboxylic acid metal salt are mixed, Further, a carrier may be mixed.

  According to the developer for developing an electrostatic latent image according to the first embodiment prepared by the materials and methods described above, a latent image carrying unit including a photosensitive layer made of amorphous silicon, and a cleaning unit including an elastic blade; When an image is formed by an image forming apparatus comprising a combination of the above, image defects in various formed images due to roughening of the surface of the latent image carrier during continuous image formation, and falling into the developing device Image defects in the formed image with toner can be suppressed.

[Second Embodiment]
The second embodiment of the present invention is an image forming apparatus provided with a latent image carrying portion in which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate and a cleaning portion having an elastic blade. The present invention relates to an image forming method for forming an image using a developer for developing an electrostatic latent image according to the embodiment. The image forming method according to the second embodiment of the present invention will be described below.

  The image forming apparatus used in the image forming method according to the second embodiment is particularly provided as long as it includes a latent image carrying part in which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate and a cleaning part having an elastic blade. It is not limited. In such an image forming apparatus, since a higher resolution image is obtained than when the photosensitive layer made of amorphous silicon is thick, the distance from the surface on the photosensitive layer side of the conductive substrate to the outermost surface of the latent image carrying portion. An image forming apparatus provided with a latent image carrier having a thickness of 30 μm or less is more preferable.

  As an image forming apparatus used in the image forming method according to the second embodiment, a tandem color image forming apparatus using a plurality of color developers as described later is preferable. Here, an image forming method using a tandem color image forming apparatus will be described.

  Note that a tandem color image forming apparatus described below is configured to form a toner image on the surfaces of a plurality of latent image carrying portions with positively chargeable toners contained in different color developers. A plurality of latent image carrying portions arranged in parallel to each other, and arranged to face each latent image carrying portion, carry toner carried on the surface, and carry the conveyed toner to the surface of each latent image carrying portion. And a plurality of developing units each having a developing roller to be supplied to the developer, and the developer for supplying the electrostatic latent image developing of the present invention is supplied to the latent image carrying unit.

  FIG. 1 is a schematic diagram illustrating a configuration of a suitable image forming apparatus used in the image forming method according to the second embodiment. Here, the color printer 1 will be described as an example of the image forming apparatus.

  As shown in FIG. 1, the color printer 1 has a box-shaped device body 1a. In the apparatus main body 1a, a toner image based on image data and the like is transferred to the paper P while feeding the paper P fed from the paper feeding unit 2 and the paper P fed from the paper feeding unit 2. An image forming unit 3 and a fixing unit 4 for performing a fixing process for fixing the unfixed toner image transferred onto the paper P by the image forming unit 3 to the paper P are provided. Further, on the upper surface of the apparatus main body 1a, a paper discharge unit 5 for discharging the paper P subjected to the fixing process by the fixing unit 4 is provided.

  The paper feed unit 2 includes a paper feed cassette 121, a pickup roller 122, paper feed rollers 123, 124, 125, and a registration roller pair 126. The paper feed cassette 121 is provided so as to be detachable from the apparatus main body 1a and stores the paper P. The pickup roller 122 is provided at the upper left position of the paper feed cassette 121 shown in FIG. 1 and takes out the paper P stored in the paper feed cassette 121 one by one. The paper feed rollers 123, 124, and 125 send out the paper P picked up by the pickup roller 122 to the paper transport path. The registration roller 126 temporarily waits for the paper P sent to the paper transport path by the paper feed rollers 123, 124, 125, and then supplies the paper P to the image forming unit 3 at a predetermined timing.

  The paper feeding unit 2 further includes a manual feed tray (not shown) and a pickup roller 127 that are attached to the left side surface of the device main body 1a shown in FIG. The pickup roller 127 takes out the paper P placed on the manual feed tray. The paper P taken out by the pickup roller 127 is sent out to the paper transport path by the paper feed rollers 123 and 125, and is supplied to the image forming unit 3 by the registration roller 126 at a predetermined timing.

  The image forming unit 3 includes an image forming unit 7, an intermediate transfer belt 31 on which a toner image based on image data transmitted from a computer or the like to the surface (contact surface) of the image forming unit 7 is primarily transferred, A secondary transfer roller 32 is provided for secondary transfer of the toner image on the intermediate transfer belt 31 onto the paper P fed from the paper feed cassette 121.

  The image forming unit 7 includes a black unit 7K, a yellow unit 7Y, and a cyan unit 7C that are sequentially arranged from the upstream side (right side in FIG. 1) to the downstream side in the moving direction of the intermediate transfer belt 31. And a magenta unit 7M. In each of the units 7K, 7Y, 7C, and 7M, a drum-type latent image carrier 37, which is an image carrier, is disposed at the center position so as to be rotatable in the arrow (clockwise) direction. Around each latent image carrier 37, a charging unit 39, an exposure unit 38, a developing unit 71, a cleaning unit 8, a static eliminator, and the like are sequentially arranged from the upstream side in the rotation direction of the latent image carrier 37. ing.

  The charging unit 39 uniformly charges the peripheral surface of the latent image carrying unit 37 rotated in the direction of the arrow. The charging unit 39 is not particularly limited as long as the peripheral surface of the latent image carrying unit 37 can be uniformly charged, and may be a non-contact type or a contact type. Specific examples of the charging unit include a corona charging device, a charging roller, and a charging brush.

  The surface potential (charging potential) of the latent image carrier 37 is not particularly limited as long as the object of the present invention is not impaired. Considering the balance between the developability and the charging ability of the latent image carrier 37, the surface potential is preferably +200 to + 500V, more preferably + 200V to + 300V. When the surface potential is too low, the developing electric field is insufficient and it is difficult to ensure the image density of the formed image. When the surface potential is too high, problems such as insufficient charging ability, dielectric breakdown of the latent image carrier 37, and increase in the amount of ozone generated are likely to occur depending on the film thickness of the photosensitive layer.

  In the latent image carrier 37, a photosensitive layer made of amorphous silicon is formed on a drum-shaped conductive substrate. The photosensitive layer made of amorphous silicon can be formed by, for example, a vapor phase growth method such as a glow discharge decomposition method, a sputtering method, an ECR method, or an evaporation method. When forming a photosensitive layer made of amorphous silicon, the photosensitive layer can contain H or a halogen element. Further, in order to adjust the characteristics of the photosensitive layer, an element such as C, N, or O may be included, or a group 13 element or a group 15 element in the periodic table (long period type) may be included in the photosensitive layer. Good.

The material constituting the photosensitive layer made of amorphous silicon is not particularly limited as long as it is amorphous silicon. Suitable amorphous silicon materials include amorphous Si, amorphous SiC, amorphous SiO, amorphous SiON and the like. Among these amorphous silicon materials, amorphous SiC is more preferable because of its high resistance and excellent charging characteristics, wear resistance, and environmental resistance. When amorphous SiC is used as the amorphous silicon material, amorphous Si _(1-X) C _X (X is 0.3 or more and less than 1) is preferable, and amorphous Si _(1-X) C _X (X is 0.5 or more). 0.95 or less) is more preferable. Amorphous SiC having such a composition exhibits an extremely high resistance value of 10 ¹² to 10 ¹³ Ωcm, so that the latent image charge flow of the latent image carrier 37 can be suppressed, and the latent image carrier having excellent electrostatic latent image maintenance capability. 37 is obtained. Further, by using amorphous SiC having such a composition, the latent image carrying portion 37 having excellent moisture resistance can be obtained.

  The photosensitive layer may be formed on a carrier blocking layer formed on the conductive substrate. A surface protective layer may be provided on the surface of the photosensitive layer. As the latent image carrier 37, a laminate in which an electroconductive substrate, a carrier blocking layer, a photosensitive layer, and a surface protective layer are laminated in this order is particularly preferably used.

  When the surface protective layer is provided, it is possible to suppress the formation of an oxide film that easily adsorbs discharge products, water molecules, and the like on the surface of the photosensitive layer made of amorphous silicon during discharge by the charging unit 39. Further, by providing the surface protective layer, it is possible to improve the withstand voltage of the latent image carrier 37 and the wear resistance during repeated use. Examples of the material for the surface protective layer include inorganic insulating materials such as amorphous SiC, amorphous SiO, amorphous SiN, amorphous SiON, and amorphous SiCON.

  Although the film thickness of a surface protective layer is not specifically limited in the range which does not inhibit the objective of this invention, 20000 kg or less is preferable and 5000-15000 kg is more preferable. By setting the film thickness of the surface protective layer in such a range, the latent image carrying part 37 in which the pressure resistance performance hardly deteriorates can be produced with excellent efficiency.

  When a carrier blocking layer is provided, during development, carrier injection into the photosensitive layer made of amorphous silicon is blocked to increase electrostatic contrast between the exposed and non-exposed areas, thereby improving image density and reducing background fog. Can be planned. Materials for the carrier blocking layer include amorphous insulating materials such as amorphous SiC, amorphous SiO, amorphous SiN, amorphous SiON, and amorphous SiCON, polyethylene terephthalate, parylene (registered trademark), polytetrafluoroethylene, polyimide, and polyfluorinated ethylene propylene. , Organic insulating materials such as polyurethane, epoxy resin, polyester, polycarbonate, and cellulose acetate resin.

  The thickness of the carrier blocking layer is not particularly limited as long as the object of the present invention is not impaired, but is preferably 0.01 to 5 μm, and more preferably 0.1 to 3 μm. When the carrier blocking layer is too thin, it is difficult to obtain a desired carrier blocking effect. When the carrier blocking layer is too thick, it takes a long time to form a film, and the productivity of the latent image carrier 37 may be reduced. There is.

  The distance from the surface on the photosensitive layer side of the conductive substrate of the latent image carrying part 37 to the outermost surface of the latent image carrying part 37 is not particularly limited, but the manufacturing cost of the latent image carrying part 37 can be reduced, and the image with excellent resolution. Is preferably 30 μm or less. The outermost surface of the latent image carrier is the surface of the surface protective layer when the surface protective layer is formed, and the surface of the photosensitive layer when the surface protective layer is not formed. Further, the distance from the surface of the conductive substrate on the photosensitive layer side to the outermost surface of the latent image carrier 37 is the total thickness of the carrier blocking layer, the photosensitive layer, and the surface protective layer.

  The lower limit of the distance from the surface of the latent image carrier 37 on the photosensitive layer side of the conductive substrate to the surface of the latent image carrier 37 on the photosensitive layer side is not particularly limited as long as the object of the present invention is not impaired, but is 10 μm. The above is preferable. If the distance is too short, the latent image carrier 37 may have insufficient charging performance, or interference fringes may occur in the half pattern due to irregular reflection of laser light used for exposure.

  The exposure unit 38 is a so-called laser scanning unit, and laser light based on image data input from a personal computer (PC), which is a host device, on the peripheral surface of the latent image carrier 37 uniformly charged by the charging unit 39. To form an electrostatic latent image based on the image data on the latent image carrier 37. The developing unit 71 supplies the developer according to the first embodiment including the positively chargeable toner and the organic carboxylic acid metal salt to the peripheral surface of the latent image holding unit 37 on which the electrostatic latent image is formed. A toner image based on the image data is formed while suppressing an increase in the friction coefficient on the surface of the image carrier 37. The configuration of the developing unit 71 is appropriately changed depending on the type of developer and the developing method. The toner image formed on the peripheral surface of the latent image carrier 37 by the developing unit 71 is primarily transferred to the intermediate transfer belt 31.

  After the primary transfer of the toner image to the intermediate transfer belt 31 is completed, the toner remaining on the peripheral surface of the latent image carrier 37 is cleaned by the cleaning unit 8. The cleaning unit 8 includes an elastic blade 81, and removes toner remaining on the peripheral surface of the latent image holding unit 37 by the elastic blade 81. The elastic blade is made of urethane rubber or ethylene-propylene rubber. When the developer according to the first embodiment is used, an increase in the coefficient of friction on the surface of the latent image carrier 37 is suppressed, so that the occurrence of image defects such as winding up of the elastic blade and “blank” can be suppressed. .

  The static eliminator neutralizes the peripheral surface of the latent image carrier 37 after the primary transfer is completed. The peripheral surface of the latent image carrier 37 cleaned by the cleaning unit 8 and the static eliminator goes to the charging unit 39 for a new charging process, and a new charging process is performed.

  The intermediate transfer belt 31 is an endless belt-like rotating body, and includes a driving roller 33, a driven roller 34, a backup roller 35, and a front surface (contact surface) side in contact with the peripheral surface of each latent image carrier 37. And a plurality of rollers such as the primary transfer roller 36. The intermediate transfer belt 31 is configured to rotate endlessly by a plurality of rollers in a state in which the intermediate transfer belt 31 is pressed against the latent image carrier 37 by a primary transfer roller 36 disposed to face each latent image carrier 37. . The driving roller 33 is rotationally driven by a driving source such as a stepping motor (not shown), and gives a driving force to the intermediate transfer belt 31 for endless rotation. The driven roller 34, the backup roller 35, and the primary transfer roller 36 are rotatably provided, and are driven to rotate with the endless rotation of the intermediate transfer belt 31 by the driving roller 33. These rollers 34, 35, and 36 are driven to rotate via the intermediate transfer belt 31 in accordance with the main rotation of the drive roller 33 and support the intermediate transfer belt 31.

  The primary transfer roller 36 applies a negative primary transfer bias to the intermediate transfer belt 31. By doing so, the toner image formed on each latent image carrying portion 37 is moved between each latent image carrying portion 37 and the primary transfer roller 36 by driving the drive roller 33 (counterclockwise). The images are sequentially transferred (primary transfer) in an overcoated state to the intermediate transfer belt 31 that circulates in the direction.

  The secondary transfer roller 32 applies a negative secondary transfer bias to the paper P. By doing so, the toner image primarily transferred onto the intermediate transfer belt 31 is secondarily transferred onto the paper P between the secondary transfer roller 32 and the backup roller 35, thereby transferring the color onto the paper P. An image (unfixed toner image) is transferred.

  The fixing unit 4 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 3. The fixing unit 4 is disposed opposite to the heating roller 41 heated by the energized heating element and the heating roller 41. Is provided with a pressure roller 42 that is pressed against the peripheral surface of the heating roller 41.

  The transfer image transferred to the paper P by the secondary transfer roller 32 in the image forming unit 3 is fixed by heating and pressurization when the paper P passes between the heating roller 41 and the pressure roller 42. It is fixed on the paper P by the processing. The paper P subjected to the fixing process is discharged to the paper discharge unit 5. Further, in the color printer 1 of the present embodiment, a plurality of conveyance roller pairs 6 are disposed at appropriate positions between the fixing unit 4 and the paper discharge unit 5.

  The paper discharge unit 5 is formed by recessing the top of the device main body 1a of the color printer 1, and a paper discharge tray 51 for receiving the discharged paper P is formed at the bottom of the concave portion. .

  The color printer 1 forms an image on the paper P by the image forming operation as described above. In the case of performing development using the electrostatic latent image developing developer according to the first embodiment by the tandem image forming apparatus having the above configuration, the image forming apparatus is mounted on the elastic blade 81 and the conductive substrate. Even if it has a latent image carrier portion 37 on which a photosensitive layer made of at least amorphous silicon is formed, an increase in the friction coefficient of the surface of the latent image carrier portion during continuous image formation can be suppressed, and the toner can be improved. The toner can be charged, and the occurrence of image defects such as toner scattering and fogging can be suppressed by suppressing the generation of reversely charged toner.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

[Preparation Example 1]
(Preparation of organic carboxylic acid metal salt particles)
The organic carboxylic acid metal salt particles were classified after heat treatment to prepare organic carboxylic acid metal salt particles AK having different irregularities and volume average particle diameters. Examples of organic carboxylic acid metal salt particles to be subjected to heat treatment include zinc stearate (SZ-TF (manufactured by Sakai Chemical Co., Ltd.)), calcium stearate (calcium stearate FI (manufactured by NOF Corporation)), and magnesium stearate (magnesium). Stearate (manufactured by NOF Corporation)), zinc benzoate (manufactured by Mitsuwa Chemicals Co., Ltd.), zinc oleate (manufactured by Mitsuwa Chemicals Co., Ltd.), and zinc laurate (manufactured by Mitsuwa Chemicals Co., Ltd.) Was used.

  Specifically, the organic carboxylic acid metal salt was spheroidized by heat treatment with meteoleinbo (MR-10A (manufactured by Nippon Pneumatic Industrial Co., Ltd.)) at the temperatures shown in Table 1, and the spheroidized organic carboxylic acid was formed. The metal salt was classified by elbow jet (EJ-LABO type (manufactured by Nippon Steel Industries Co., Ltd.)) to prepare organic carboxylic acid metal salt particles AK shown in Table 1. About obtained organic carboxylate metal salt AK, the volume average particle diameter was measured with the particle size distribution analyzer (Multisizer III (made by Beckman Coulter)), and the unevenness | corrugation degree was measured according to the following method. Table 1 shows the volume average particle diameter and the degree of unevenness of the organic carboxylic acid metal salt particles A to K.

<Roughness measurement method>
Samples of organic carboxylic acid metal salts A to K are observed with a scanning electron microscope at a magnification of 1000 times, and element mapping is performed by an X-ray spectrometer to obtain an image in which particles of a predetermined metal salt are detected. did. The obtained image was subjected to image processing with image analysis software (WinRoof (manufactured by Mitani Corporation)), and the peripheral length (μm) and area (μm ² ) of the organic carboxylic acid metal salt particles were calculated. The unevenness degree of the organic carboxylic acid metal salt was calculated by the formula. The degree of unevenness is measured for 100 particles of the organic carboxylic acid metal salt, and the average value of the obtained unevenness is defined as the degree of unevenness of the organic carboxylic acid metal salt.
(Unevenness calculation formula)
Unevenness = (perimeter length) ² / (area × 4π)

[Preparation Example 2]
(Preparation of toner base particles)
Binder resin (polyester resin, Tufton NE-7200 (manufactured by Kao Corporation)) 100 parts by mass, mold release agent (carnauba wax, C1 (manufactured by Kato Yoko Co., Ltd.)), 5.5 parts by mass, colorant (carbon black, 4 parts by mass of MA100 (Mitsubishi Chemical Co., Ltd.) and 5.0 parts of a positive charge control agent (quaternary ammonium salt monomer copolymer, FCA201PS (manufactured by Fujikura Kasei Co., Ltd., product number: FCA201PS)) (FM20B (Nippon Coke Co., Ltd.)) was mixed at 2400 rpm, and the resulting mixture was mixed with a twin-screw extruder (PCM-30 (Ikegai Co., Ltd.)) at a material input rate of 5 kg / h, shaft rotation. The mixture was melt-kneaded at several 160 rpm and a set temperature range of 100 to 130 ° C. After cooling the melt-kneaded product, a rotoplex mill (8/16 type (Co., Ltd. The coarsely pulverized product was finely pulverized with a jet mill (ultrasonic jet mill type I (manufactured by Nippon Pneumatic Industry Co., Ltd.)), and the resulting finely pulverized product was elbow jet (EJ). A toner base particle was obtained by classification with a LABO type (manufactured by Nippon Steel Industries Co., Ltd.) The volume average particle diameter of the toner base particle measured by a particle size distribution measuring device (Multisizer III (manufactured by Beckman Coulter)) was It was 6.8 μm.

[Example 1]
1 part by mass of hydrophobic silica fine particles (RA-200H (manufactured by Nippon Aerosil Co., Ltd.)) and 0.5 parts by mass of titanium oxide fine particles (ST-100 (manufactured by Titanium Industry Co., Ltd.)) with respect to 100 parts by mass of toner base particles. And 0.1 part by mass of organic carboxylic acid metal salt are added and mixed for 4 minutes with a Henschel mixer (FM-20B (manufactured by Nippon Coke Co., Ltd.)) to obtain a mixture of toner and organic carboxylic acid metal salt. Obtained.

Toner obtained for carrier (coating agent: fluororesin, volume resistivity: 10 ⁷ Ωcm, saturation magnetization: 70 emu / g, average particle size 35 μm, Cu—Zn ferrite carrier (Powder Tech Co., Ltd.)) A mixture of the organic carboxylic acid metal salt was blended so that the content in the developer was 12% by mass, and mixed for 30 minutes by a ball mill (manufactured by Kyocera Mita Co., Ltd.) to prepare a three-component developer.

  Using the resulting three-component developer, a mixture of toner and organic carboxylic acid metal salt A, according to the following method, the presence or absence of image defects in the formed image due to toner dropping in the developing unit, a dash mark, The presence or absence of image defects in the formed image due to filming and toner passing through the cleaning portion was evaluated. These evaluation results are shown in Table 2.

(Evaluation of image defects due to toner removal)
Black color of a multifunctional machine (TASKalfa500ci (manufactured by Kyocera Mita Corporation)), which is an image forming apparatus comprising a latent image carrier having a photosensitive layer made of amorphous silicon formed on a conductive substrate and a cleaning unit having an elastic blade. A three-component developer was installed in the developing section, and a toner cartridge for black toner was filled with a mixture of toner and organic carboxylic acid metal salt A. The voltage (ΔV) between the developing sleeve and the magnet roll is set to 250 V, the alternating voltage (Vpp) applied to the magnet roll is set to 2.0 kV, and 10,000 sheets are continuously printed at a printing rate of 5%. Printing was performed. During continuous printing of 10,000 sheets, the presence or absence of an image defect due to toner dropping in the developing device was confirmed by visually observing the printed image. With respect to 10,000 printed images, the case where the number of occurrences of image defects was 0 to 20 was judged as ◯, 21 to 100 were judged as Δ, and 101 or more were judged as x.

(Evaluation of image defects due to dash marks, filming, and slipping through)
In the evaluation of defective images due to toner loss, after continuous printing of 10,000 sheets at a printing rate of 5%, a half image with a printing rate of 25% was printed on the entire surface of the A3 paper, and the obtained image was visually observed. Thus, image defects due to dash marks, filming, and toner passing through the cleaning portion were evaluated. The case where a dash mark occurred was determined as “good”, and the case where no dash mark occurred was determined as “x”. For filming, the case where it occurred was determined as ◯, and the case where it did not occurred was determined as x. As for the image defect due to slipping through the toner cleaning portion, it was determined as “good”, and when it did not occur, it was determined as “poor”. These evaluation results are shown in Table 2.

[Examples 2-7 and Comparative Examples 1-4]
A three-component developer was prepared in the same manner as in Example 1 except that the organic carboxylic acid metal salt A was changed to the organic carboxylic acid metal salt shown in Table 2. Using the mixture of the three-component developer obtained in each of Examples and Comparative Examples and a toner and a metal salt of an organic carboxylic acid, according to the above method, image defects in the formed image due to toner dropping in the developing device The presence / absence of occurrence, dash marks, filming, and presence / absence of image defects in the formed image due to slipping through the toner cleaning portion were evaluated. These evaluation results are shown in Table 2.

  According to Examples 1-7, the organic carboxylic acid metal salt contains zinc salt, calcium salt, or magnesium salt of organic carboxylic acid, the volume average particle diameter is 2 to 10 μm, and the unevenness degree is 1.10. According to the developer of 1.30, image defects such as dash marks, filming, and image defects caused by toner passing through the cleaning unit due to the roughening of the surface of the latent image carrying unit, It can be seen that image defects due to the dropped toner can be suppressed.

  According to Comparative Example 1, it can be seen that when the particle size of the organic carboxylic acid metal salt contained in the developer is too small, a dash mark is likely to occur in the formed image. The organic carboxylic acid metal salt particles having a relatively small diameter are likely to adhere to the positively charged toner. For this reason, when the developer of Comparative Example 1 is used, since the supply of the organic carboxylic acid metal salt to the surface of the latent image carrying portion is insufficient, it becomes difficult to suppress the roughening of the surface of the latent image carrying portion. The toner on which the fine particles of the metal salt adhere to the surface easily adheres to the surface of the roughened latent image carrier. For this reason, it is considered that a dash mark is likely to occur in the formed image.

  According to Comparative Example 2, when the particle size of the organic carboxylic acid metal salt contained in the developer is excessive, image defects due to the toner dropped in the developing device and filming on the surface of the latent image carrier occur. I understand that it is easy. When the particle size of the organic carboxylic acid metal salt is excessive, when the toner and the organic carboxylic acid metal salt move from the developing device to the surface of the latent image carrier, the organic carboxylic acid metal salt easily falls due to its own weight. At this time, it is considered that as the organic carboxylic acid metal salt falls, the toner easily falls into the developing device, and an image defect due to the dropped toner tends to occur in the formed image. In addition, when the particle size of the organic carboxylic acid metal salt is excessive, the organic carboxylic acid metal salt is a softer particle than the toner. Filming tends to occur on the surface of the image carrier.

  According to Comparative Example 3, it is found that when the degree of unevenness of the organic carboxylic acid metal salt contained in the developer is excessively small, an image defect due to the toner that has passed through the cleaning portion is likely to occur in the formed image. The organic carboxylic acid metal salt particles having a small unevenness are likely to slip through the elastic blade of the cleaning portion. In such a case, toner particles existing adjacent to the organic carboxylic acid metal salt on the surface of the latent image carrying part are likely to slip through the cleaning blade together with the organic carboxylic acid metal salt, and image defects due to toner slippage are likely to occur in the formed image. It is considered to be.

  According to Comparative Example 4, it can be seen that a dash mark is likely to occur when the degree of unevenness of the organic carboxylic acid metal salt contained in the developer is excessive. Organic carboxylic acid metal salt particles with large irregularities adhere to the surface of the latent image carrier due to the interaction between the irregularities on the surface of the organic carboxylic acid metal salt and the minute irregularities on the surface of the latent image carrier. It becomes easy to do. In such a case, the toner particles are likely to stay on the surface of the latent image carrying part by being caught by the organic carboxylic acid metal salt adhering to the surface of the latent image carrying part, and image defects such as dash marks are likely to occur in the formed image. It is done.

DESCRIPTION OF SYMBOLS 1 Color printer 1a Apparatus main body 2 Paper feed part 3 Image formation part 37 Latent image holding part 38 Exposure part 39 Charging part 4 Fixing part 6 Conveyance roller 5 Paper discharge part 7 Image formation unit 71 Development part 8 Cleaning part 81 Elastic blade P Paper

Claims (5)

An electrostatic latent image developing developer used in an image forming apparatus, comprising: a latent image carrying portion on which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate; and a cleaning portion having an elastic blade. ,
The developer includes a positively charged toner and an organic carboxylic acid metal salt,
The organic carboxylic acid metal salt is a zinc salt, a calcium salt, or a magnesium salt,
The organic carboxylic acid metal salt has a volume average particle diameter of 2 to 10 μm,
The organic carboxylic acid metal salt calculated by the following formula from the circumference and area of the particles of the organic carboxylic acid metal salt obtained from the image of the organic carboxylic acid metal salt photographed at a magnification of 1000 times with a scanning electron microscope A developer for developing an electrostatic latent image, wherein the degree of unevenness of the particles is 1.10 to 1.30.
(Unevenness calculation formula)
Unevenness = (perimeter length) ² / (area × 4π)   The developer for developing an electrostatic latent image according to claim 1, wherein the organic carboxylic acid metal salt is a metal salt of an organic carboxylic acid having 6 to 20 carbon atoms.   The developer for developing an electrostatic latent image according to claim 2, wherein the organic carboxylic acid metal salt is a metal salt of stearic acid.   The developer for electrostatic latent image development according to claim 1 or 2, wherein the content of the organic carboxylic acid metal salt is 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the positively chargeable toner. In an image forming apparatus, comprising: a latent image carrying unit in which a photosensitive layer made of at least amorphous silicon is formed on a conductive substrate; and a cleaning unit having an elastic blade.
A positively chargeable toner and an organic carboxylic acid metal salt,
The organic carboxylic acid metal salt is a zinc salt, a calcium salt, or a magnesium salt,
The organic carboxylic acid metal salt has a volume average particle diameter of 2 to 10 μm,
The metal organic carboxylate calculated by the following equation from the circumference and cross-sectional area of the particles of the organic metal carboxylate obtained from the image of the metal organic carboxylate photographed at a magnification of 1000 times with a scanning electron microscope An image forming method for forming an image using a developer for developing an electrostatic latent image, wherein the unevenness of the salt particles is 1.10 to 1.30.
(Unevenness calculation formula)
Unevenness = (perimeter length) ² / (area × 4π)

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