JP4678160B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer, and more particularly to an image forming apparatus including a contact charging device.

  Conventionally, a configuration in which a peripheral speed is provided between a charging device and a photoreceptor has been studied for the purpose of improving charging uniformity or efficiently removing deposits on a charger (for example, patents). References 1 and 2). However, because the frictional force of the photoconductor is actually large, problems such as an increase in rotational torque, uneven wear of the photoconductor, and toner sticking to the charging roll are serious and difficult to realize with a solid roll. there were.

  In order to avoid such a problem, the contact charging device is configured in a fur brush shape or sponge shape with a small frictional force (for example, refer to Patent Document 3), or in a non-contact state so as not to generate a frictional force (for example, , See Patent Document 4).

However, in a brush or sponge-like member, even when a voltage obtained by superimposing a DC voltage on an AC voltage is applied, the charging uniformity is lowered. Therefore, there is a problem that it cannot be applied to a color image forming apparatus that requires high image quality. In addition, toner or the like is clogged in the sponge cell, and there is a problem in maintaining the initial image quality. On the other hand, even in the case of non-contact arrangement, in order to obtain charging stability, variations in the resistance value and surface property of the member must be suppressed to the utmost, and the usable surface resistance is large due to the electrical conductivity of the space. There are limitations, and fluctuations of a minute gap tend to appear as a potential unevenness in a picture, resulting in poor environmental stability.
JP-A-5-303256 Japanese Patent Laid-Open No. 11-174784 JP-A-5-303256 Japanese Patent Laid-Open No. 7-301973

  In view of the above, an object of the present invention is to solve the above conventional problems. That is, an object of the present invention is to provide an image forming apparatus that can suppress an increase in frictional force generated by contact between a charging device and a photoconductor, and can reduce wear of the photoconductor.

The above object is achieved by the present invention described below.
In other words, the first image forming apparatus of the present invention is an image forming apparatus comprising at least a photoconductor and a charging device that charges the surface of the photoconductor by bringing a charging member into contact therewith, and the surface of the photoconductor The layer contains 0.1 to 40% by mass of fluororesin particles, the Vickers hardness of the surface of the photoconductor is 20 to 30 at a load of 10 g, and the contact portion of the charging member that contacts the surface of the photoconductor The charging member is fixed, and a conductive elastic layer having a volume resistance of 2 × 10 ^{2 to} 5 × 10 ⁹ Ωcm in which a conductive agent is dispersed in a rubber material, and a surface of the conductive elastic layer A formed resistance adjusting layer having a volume resistance of 3 × 10 ^{3 to} 5 × 10 ¹⁰ Ωcm in which a conductive agent is dispersed in a resin, and a protective layer formed on the surface of the resistance adjusting layer, or the protective layer And a surface layer formed on the surface of the protective layer, the protective layer or the front layer The surface layer contains 1 to 30% by mass of fluorine-based resin particles having a volume average particle diameter of 0.05 to 1 μm.

The second image forming apparatus of the present invention is an image forming apparatus comprising at least a photoconductor and a charging device for charging the surface of the photoconductor by bringing a charging member into contact therewith, the surface of the photoconductor The layer contains 0.1 to 40% by mass of fluororesin particles, the Vickers hardness of the surface of the photoconductor is 20 to 30 at a load of 10 g, and the charging member in contact with the surface of the photoconductor is the photosensitive member. A conductive elastic body that is rotationally driven in the same direction as or in the opposite direction of the body rotation, and the charging member has a volume resistance value of 2 × 10 ^{2 to} 5 × 10 ⁹ Ωcm in which a conductive agent is dispersed in a rubber material. A resistance adjusting layer having a volume resistance of 3 × 10 ^{3 to} 5 × 10 ¹⁰ Ωcm in which a conductive agent is dispersed in a resin, and a resistance adjusting layer formed on the surface of the conductive elastic layer; Protective layer formed on the surface, or formed on the protective layer and the protective layer surface And the protective layer or the surface layer contains 1 to 30% by mass of fluorine-based resin particles having a volume average particle size of 0.05 to 1 μm.

The first and second image forming apparatuses of the present invention preferably include any one or more of the following first to sixth aspects.
(1) the first aspect, further, Ru aspect der having at least two charging devices.
(2 ) In the second aspect, at least one of the fluororesin particles contained in the surface layer of the charging member and at least 1 of the fluororesin particles contained in the surface layer of the photoreceptor. This is an embodiment in which the seeds are the same kind.
( 3 ) In the third aspect, the friction coefficient of the surface layer of the photosensitive member is smaller than the friction coefficient of the surface layer of the charging member.
( 4 ) A fourth aspect is an aspect in which the cleanerless image forming apparatus does not require a cleaning blade for removing deposits remaining on the photosensitive member.
( 5 ) The fifth aspect is an aspect in which the voltage applied to the charging device is a voltage obtained by superimposing an AC voltage on a DC voltage.
( 6 ) The sixth aspect is the second image forming apparatus, wherein the rotational speed (surface speed) of the photoconductor and the rotational speed (surface speed) of the charging member are substantially constant. is there.

  According to the present invention, it is possible to provide an image forming apparatus that can suppress an increase in frictional force generated by contact between the charging device and the photoconductor, and can reduce wear of the photoconductor.

[First image forming apparatus]
The first image forming apparatus of the present invention comprises at least a photoreceptor having a surface layer containing fluorine-based resin particles, and a charging device for charging the photoreceptor surface by bringing a charging member into contact with the photoreceptor surface. It has. By doping fluororesin particles such as PTFE into the surface layer of the photoconductor, the friction coefficient of the surface can be made extremely small, and the peripheral speed difference from the photoconductor is free even with contact charging using a rubber roll. It becomes possible to set to. As a result, even if the photosensitive member is rotated at a peripheral speed, there is an effect that the wear rate of the photosensitive member is reduced as compared with the conventional photosensitive member.

  In addition, although the contact portion of the charging member that contacts the surface of the photoconductor is fixed, the surface layer of the photoconductor contains fluororesin particles. Can be reduced. Here, “the contact portion of the charging member is fixed” means that the contact portion of the charging member with the surface of the photosensitive member is always fixed at a fixed position with respect to the rotating photosensitive member. Say.

  A first image forming apparatus of the present invention is illustrated in FIG. A first image forming apparatus shown in FIG. 1 includes a photoconductor 10, and a charging roll 12 as a charging device (charging member) for charging the surface of the photoconductor 10 around the photoconductor 10, an exposure device 14, and a developing device. 16 and a cleaning device 18, and a transfer roll 20 is further provided.

  The photosensitive member 10 is rotationally driven at a predetermined surface speed (for example, about 100 mm / sec) along the arrow direction. A charging roll 12 is in contact with the surface of the photoreceptor 10. The charging roll 12 is fixed so as not to rotate even when the photosensitive member 10 moves. Then, the surface of the photoreceptor 10 is charged to a predetermined potential of about −700V. Thereafter, an image exposure is performed by the exposure device 14 on the surface of the photoconductor 10 so that the exposed portion is neutralized, and an electrostatic latent image corresponding to the image information is formed. The electrostatic latent image formed on the surface of the photoconductor 10 is developed in a state where the potential of the image portion is at a level of −150 V or less and a developing bias of about −600 V is applied by the developing device 16. A negative toner image is formed on the surface. The developed toner image is transferred onto a transfer material 22 that is conveyed while being sandwiched between nip portions of the rotating transfer roll 20 and the photoreceptor 10. At this time, a voltage of about 1000 V to 4000 V is applied to the transfer roll 20. The transfer material 22 onto which the toner image has been transferred is conveyed to a fixing device (not shown), and the toner image is fixed on the transfer material 22 by heat and / or pressure.

  The toner that has not been transferred onto the transfer material 22 remains on the photosensitive drum 10 after transfer as a deposit. The residual toner is removed from the surface of the photosensitive drum 10 by the cleaning device 18 that contacts the surface of the photosensitive drum 10. Thereafter, the surface of the clean photosensitive drum 10 reaches the charging device 12 as it rotates, and the above series of operations is repeated.

  Here, in the present invention, a cleanerless image forming apparatus that does not require a cleaning blade may be provided. Further, by providing at least two charging devices before and after the cleaning device of the image forming apparatus of the present invention, the charging potential can be stabilized.

  Hereinafter, the photoreceptor and the charging device provided in the image forming apparatus of the present invention will be described in detail.

(Photoconductor)
In the photoreceptor used in the image forming apparatus of the present invention, an organic photosensitive layer is formed on a conductive support. The organic photosensitive layer includes at least a charge generation layer formed by binding a charge generation material with a suitable resin as a binder (binder resin), and a charge transport layer in which the charge transport material is dispersed or dissolved in the binder resin. The undercoat layer, the protective layer, and the like are formed as necessary. Further, the surface layer of the photoreceptor contains 0.1 to 40% by mass of fluorine-based resin particles based on the mass of the surface layer.

  Here, the “surface layer” means a layer formed on the outermost surface of the photoreceptor. For example, when the charge transport layer is provided on the outermost surface of the photoreceptor, the charge transport layer becomes the surface layer, Further, when a protective layer is provided, the protective layer becomes a surface layer. Each surface layer contains fluorine resin particles. Hereinafter, the conductive support and each layer will be described.

-Conductive support:
Any conductive support may be used as long as it is conventionally used.
For example, metals such as aluminum, nickel, chromium, stainless steel; plastic films provided with thin films such as aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, ITO; And paper coated with or impregnated with an agent, plastic film, and the like. Furthermore, if necessary, the surface of the conductive support can be subjected to various treatments within a range that does not affect the image quality. For example, surface anodization treatment, chemical treatment or coloring treatment, or irregular reflection treatment such as graining or liquid honing can be performed.

An undercoat layer may be formed on the surface of the conductive support as desired. The undercoat layer is acetal resin such as polyvinyl butyral, polyvinyl alcohol resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate In addition to polymer resin compounds such as maleic anhydride resin, silicone resin, phenol-formaldehyde resin, and melamine resin, there are organometallic compounds containing zirconium, titanium, aluminum, manganese, silicon atoms, and the like. These compounds can be used alone or as a mixture or polycondensate of a plurality of compounds.
The thickness of the undercoat layer is preferably 0.1 to 50 μm, and more preferably 0.2 to 30 μm.

-Charge generation layer:
The charge generation layer is formed on the conductive support (when the undercoat layer is formed, on the undercoat layer).
As the charge generation material contained in the charge generation layer, phthalocyanine pigments such as metal-free phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine can be used. Chlorogallium phthalocyanine crystal having strong diffraction peaks at least at 7.4 °, 16.6 °, 25.5 ° and 28.3 ° of (2θ ± 0.2 °), Bragg angle (2θ ± 0.2 °) metal-free phthalocyanine crystal having strong diffraction peaks at 7.7 °, 9.3 °, 16.9 °, 17.5 °, 22.4 ° and 28.8 °, CuKα characteristic X Bragg angle to the line (2θ ± 0.2 °) at least 7.5 °, 9.9 °, 12.5 A hydroxygallium phthalocyanine crystal having strong diffraction peaks at 16.3 °, 18.6 °, 25.1 ° and 28.3 °, a Bragg angle (2θ ± 0.2 °) with respect to CuKα characteristic X-ray of at least 9. Titanyl phthalocyanine crystals having strong diffraction peaks at 6 °, 24.1 ° and 27.2 ° can be used.

In addition, as the charge generation material, a quinone pigment, a perylene pigment, an indigo pigment, a bisbenzimidazole pigment, an anthrone pigment, a quinacridone pigment, and the like can be used.
The above charge generation materials can be used alone or in admixture of two or more.

Examples of the binder resin in the charge generation layer include the following. That is, polycarbonate resin such as bisphenol A type or bisphenol Z type, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer Examples thereof include a coalescing resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, phenol-formaldehyde resin, poly-N-vinylcarbazole and the like. These binder resins can be used alone or in combination of two or more.
The compounding ratio (mass ratio) of the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10.

  As a solvent used for dispersion of the charge generating material, a solvent capable of dissolving the binder resin can be appropriately selected. As a method for dispersing the charge generating material in the resin, methods such as a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a high pressure homogenizer can be used.

  Examples of the coating method include dip coating, push-up coating, spray coating, roll coater coating, and gravure coater coating. The thickness of the charge generation layer is generally set in the range of 0.01 to 5 μm, preferably 0.05 to 2.0 μm.

-Charge transport layer:
The charge transport layer is formed on the charge generation layer. When the charge transport layer is the surface layer of the photoreceptor, the charge transport layer contains fluorine-based resin particles. The content of the fluororesin particles in the charge transport layer is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, based on the total mass of the charge transport layer. If the content is less than 1% by mass, the modification effect due to the dispersion of the fluororesin particles may not be sufficient. If the content exceeds 40% by mass, the light transmission property decreases, and the residual potential increases due to repeated use. May come.

  Fluorine resin particles include polytetrafluoroethylene, polychlorotrifluoroethylene, polyhexafluoroethylenepropylene, polyvinylidene fluoride, polyvinyl fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetra Examples include fluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-ethylene copolymers, and tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymers.

Primary particle size of the fluororesin particles is a volume average particle diameter is 0.05 to 1 [mu] m, it is good preferable to 0.1 to 0.5 [mu] m. When the volume average particle size is less than 0.05 μm, aggregation at the time of dispersion may easily proceed, and when it exceeds 1 μm, image quality defects may easily occur.

  The charge transport layer may contain inorganic particles. The content of the inorganic particles in the charge transport layer is suitably from 0.1 to 30% by weight, particularly preferably from 1 to 20% by weight, based on the total amount of the charge transport layer. If the content is less than 1% by mass, the modification effect due to the dispersion of inorganic particles is not sufficient. On the other hand, if the content exceeds 30% by mass, the residual potential increases due to repeated use.

  Examples of inorganic particles include alumina, silica, titanium oxide, zinc oxide, cerium oxide, zinc sulfide, magnesium oxide, copper sulfate, sodium carbonate, magnesium sulfate, potassium chloride, calcium chloride, sodium chloride, nickel sulfate, antimony, and dioxide. Manganese, chromium oxide, tin oxide, zirconium oxide, barium sulfate, aluminum sulfate, silicon carbide, titanium carbide, boron carbide, tungsten carbide, zirconium carbide and the like can be mentioned, and silica is preferably used. These may be used alone or in combination of two or more as required.

  The silica particles are preferably produced by chemical flame CVD, and as a specific example, produced by gas phase reaction of chlorosilane gas in a high-temperature flame of oxygen-hydrogen mixed gas or hydrocarbon-oxygen mixed gas. Is preferred.

  The inorganic particles are preferably those that have been hydrophobized with a hydrophobizing agent. As the hydrophobizing agent, for example, a siloxane compound, a silane coupling agent, a titanium coupling agent, a polymer fatty acid or a metal salt thereof is used.

Examples of the siloxane compound include dihydroxypolysiloxane and octamethylcyclotetrasiloxane.
Examples of the silane coupling agent include γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N -Vinylbenzylaminoethyl) γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane , Dodecyltrimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, and the like.

  The primary particle size of the inorganic particles is preferably 0.005 to 2.0 μm, and more preferably 0.01 to 1.0 μm, as the number average particle size. If it is less than 0.005 μm, sufficient mechanical strength on the surface of the photoreceptor cannot be obtained, and aggregation during dispersion may easily proceed. If it exceeds 2 μm, the surface roughness of the photoreceptor increases, the cleaning blade is worn and damaged, the cleaning characteristics are deteriorated, and image blurring tends to occur.

  Examples of the charge transport material include oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole; 1,3,5-triphenyl-pyrazolin, 1- [ Pyrazoline derivatives such as pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline; triphenylamine, tri (p-methylphenyl) aminyl-4-amine, dibenzylaniline Aromatic tertiary amino compounds such as N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine etc .; 3- (4′-dimethylaminophenyl) 1,2,4-triazine derivatives such as -5,6-di- (4'-methoxyphenyl) -1,2,4-triazine; Hydrazone derivatives such as zaldehyde-1,1-diphenylhydrazone; quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline; benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) benzofuran; p Α-stilbene derivatives such as — (2,2-diphenylvinyl) -N, N-diphenylaniline; enamine derivatives; carbazole derivatives such as N-ethylcarbazole; hole transport such as poly-N-vinylcarbazole and its derivatives; Mention may be made of substances.

  In addition, quinone compounds such as chloranil and broanthraquinone; tetraanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; xanthone An electron transport material such as a compound; a thiophene compound; and the like, and a polymer having a group composed of the above-described compound in the main chain or side chain can also be exemplified. These charge transport materials can be used alone or in combination of two or more.

  Examples of the binder resin include an acrylic resin, polyarylate, polyester resin, bisphenol A type or bisphenol Z type polycarbonate resin; polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, and the like. Insulating resins such as polysulfone, polyacrylamide, polyamide, and chlorine rubber; organic photoconductive polymers such as polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene;

  The charge transport layer is a solution in which the charge transport material and the binder resin are dissolved in an appropriate solvent (when the charge transport layer is a surface layer, together with the aforementioned fluorine-based resin particles and, if necessary, inorganic particles). It can form by apply | coating and drying.

  Examples of the solvent used for forming the charge transport layer include aromatic hydrocarbon solvents such as toluene and chlorobenzene; aliphatic alcohol solvents such as methanol, ethanol and n-butanol; acetone, cyclohexanone and 2-butanone. Ketone solvents such as; halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform and ethylene chloride; cyclic or linear ether solvents such as tetrahydrofuran, dioxane, ethylene glycol and diethyl ether; or a mixed solvent thereof Can be used.

  The blending ratio (mass ratio) of the charge transport material and the binder resin is preferably 10: 1 to 1: 5. As a method for dispersing the fluorine resin particles and further inorganic particles in the charge transport layer, it is possible to use a method such as a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a high-pressure homogenizer, an ultrasonic disperser, a colloid mill. it can.

  Examples of dispersion of the coating liquid for forming the charge transport layer include dispersion of fluorine resin particles when inorganic particles or the charge transport layer is a surface layer in a solution of a binder resin or charge transport material dissolved in the above solvent. The method of doing is mentioned. It is also effective to add a small amount of a dispersion aid in order to improve the dispersion stability of the dispersion and to prevent aggregation during the formation of the coating film.

  Examples of the dispersion aid include fluorine-based surfactants, fluorine-based polymers, silicone-based polymers, and silicone oils. From the viewpoint of high sensitivity and reduction in residual potential during repeated use, 0.1 to 1.0. A mass% fluorine-based graft polymer is preferably used.

  Examples of the coating method include dip coating, push-up coating, spray coating, roll coater coating, and gravure coater coating. The thickness of the charge transport layer is generally 5 to 60 μm, and preferably 10 to 50 μm. The above range is preferably selected from the viewpoint of surface abrasion resistance and charge retention performance. Further, the surface roughness Rz in the case where the charge transport layer is a surface layer is measured by, for example, a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., JIS-94 standard), and is in the range of 0.01 to 1.0 μm (preferably, 0.1 to 0.8 μm) is preferably selected from the viewpoints of maintaining the transfer performance, the cleaning performance, and both.

・ Protective layer:
The protective layer is an arbitrary layer formed on the charge transport layer, and if the fluorine-containing resin particles are contained in an amount of 0.1 to 40% by mass of the surface layer mass, other compositions are conventionally known. Can be applied. The film thickness is preferably 1 to 50 μm, and the surface roughness Rz is preferably 0.01 to 1.0 μm.

The surface hardness of the photoreceptor is represented by Vickers hardness. More Vickers hardness of the surface of the photoreceptor having a layer structure as is Ri range near 20 to 30 in a time 10g load, abrasion resistance due to the high hardness cleaner, and its value in terms of wear reduction give cleaner Is selected.

  Additives such as antioxidants, light stabilizers, and heat stabilizers in the photosensitive layer for the purpose of preventing deterioration of the photoreceptor due to ozone, oxidizing gas, or light or heat generated when the electrophotographic apparatus is operated. Can be added.

  For example, examples of the antioxidant include hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds.

  Examples of light stabilizers include derivatives such as benzophenone, benzoazole, dithiocarbamate, and tetramethylpipen. For the purpose of improving the smoothness of the surface, a leveling agent such as silicone oil can be added to the surface layer.

(Charging device)
The charging device includes a charging member that performs charging by contacting a photoreceptor (charged body). The form of the charging member is not particularly limited as long as it can stably come into contact with the member to be charged and can uniformly charge the surface of the member to be charged by applying a voltage. For example, various shapes such as a roll shape, a plate shape, a block shape, a spherical shape, and a brush shape can be used, but in consideration of image quality and maintainability, a roll shape is preferable.

  The configuration when the charging member is used as a charging roll is, for example, as described below. That is, a conductive elastic layer is formed on a solid columnar or hollow cylindrical conductive support, and a surface layer is further formed on the conductive elastic layer. Moreover, you may provide a resistance adjustment layer between a conductive elastic layer and a surface layer as needed. Moreover, it is good also as a single layer structure where an elastic body layer serves as a surface layer.

  The conductive support functions as an electrode and a support member of the charging member. For example, a metal or alloy such as aluminum, copper alloy, or stainless steel; iron plated with chromium, nickel, etc .; conductive resin It is composed of a conductive material such as;

  The conductive elastic layer forms a nip with the charged body so that the charging member is pressed against the surface of the charged body with an appropriate nip pressure and can uniformly charge the charged body surface. It is provided to obtain a predetermined resistance value.

The conductive elastic layer is formed by dispersing a conductive agent in rubber material. Rubber materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, ethylene-propylene. -Diene copolymer rubber, acrylonitrile-butadiene copolymer rubber, natural rubber, etc., and blended rubbers thereof. Of these, isoprene rubber, silicone rubber, and ethylene propylene rubber are preferably used. These rubber materials may be foamed or non-foamed.

  As the conductive agent, an electronic conductive agent or an ionic conductive agent is used. Examples of electronic conductive agents include carbon blacks such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, and stainless steel; tin oxide, indium oxide, titanium oxide Examples thereof include fine powders such as various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution; Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; perchlorates and chlorates of alkaline earth metals Can be mentioned.

  These conductive agents may be used alone or in combination of two or more. Moreover, the addition amount is not particularly limited, but in the case of the electronic conductive agent, it is preferably in the range of 1 to 50 parts by mass, and in the range of 5 to 35 parts by mass with respect to 100 parts by mass of the rubber material. More preferably. On the other hand, in the case of the ionic conductive agent, the range is preferably 0.01 to 5 parts by mass, and more preferably 0.1 to 4 parts by mass with respect to 100 parts by mass of the rubber material.

Thus, it adjusts the volume resistivity of the conductive elastic layer in the range of ^{2 × 10 2 ~5 × 10 9} Ωcm. This volume resistance value is closely related to the volume resistance value of the resistance adjustment layer described later. The conductive elastic layer preferably has an Asker C hardness of 70 ° or less.

Resistance adjusting layer for adjusting the resistance of a static-member further protective layer is provided, et al is in view of preventing contamination of the member to be charged surface to form a surface layer on the surface of the holding Mamoruso. However, the surface layer can also serve as a protective layer. Moreover, you may provide an electrode layer between a conductive elastic layer and a resistance adjustment layer as needed. The electrode layer is provided in order to disperse the concentration of current due to non-uniform dispersion of conductive particles in the conductive elastic layer, and is composed only of a conductive inorganic substance.

  The resistance adjustment layer is provided to adjust the charging member to a predetermined resistance value, and is composed of a thin film in which the conductive particles are dispersed in a resin. The resin used is not particularly limited, but a resin belonging to a somewhat soft category such as polyurethane, polyamide, polyester, acrylic resin, and the like is preferable. Further, as the conductive agent, those used for the conductive elastic layer are preferably used.

  Although there is no restriction | limiting in particular in the addition amount of the said electrically conductive agent, For example, in the case of an electronic electrically conductive agent, it is preferable that it is the range of 1-50 mass parts with respect to 100 mass parts of resin used, and the range of 5-35 mass parts is used. It is more preferable that

Thus the volume resistivity of the resistance adjusting layer Ru is adjusted to a range of ^{3 × 10 3 ~5 × 10 10} Ωcm. The thickness of the resistance adjustment layer is preferably in the range of 1 to 500 μm, and more preferably in the range of 5 to 400 μm. When the film thickness is less than 1 μm, not only the function as a resistance adjusting layer cannot be sufficiently exhibited, but also leakage tends to occur and the surface of the member to be charged may be damaged. On the other hand, if the film thickness is greater than 500 μm, the resistance value and hardness of the charging member may increase more than necessary.

A protective layer can be further provided on the surface of the resistance adjustment layer . This protective layer functions as a layer for preventing the charging member from sticking to the surface of the member to be charged. Furthermore, the charging member is prevented from being contaminated by the toner remaining on the surface of the body to be charged and its external additives, and the paper powder adheres to and adheres to the surface of the body to be charged. It is provided to prevent the occurrence of

  The material constituting the protective layer is not particularly limited, and a resin, rubber, or the like that has little contamination with respect to an object to be charged and is relatively flexible can be used. Further, the surface of the resistance adjustment layer 1c may be formed as a protective layer by forming a layer having physical properties and composition different from those of the resistance adjustment layer 1c by performing chemical treatment such as UV irradiation, heat treatment, and a coupling agent.

  The surface layer is formed on the surface of the conductive elastic layer, the resistance adjustment layer, or the protective layer (particularly around the charging member). And it is preferable that the fluorine resin particle contains in the surface layer.

Examples of the fluorine resin particles include the same ones as the fluorine resin particles contained in the surface layer of the photoreceptor. The content of the fluorine resin particles, in consideration of the total resistance and the like, Ru 1-30% by mass of the total amount of the surface layer. Further, at least one of the fluororesin particles contained in the surface layer and at least one of the fluororesin particles contained in the surface layer of the photoreceptor may be the same type (same material). Preferably, all of the respective fluororesin particles are the same type. By using the same type, an effect of reducing friction can be obtained.

  Binder resins used for the surface layer include polyester, polyamide, polyurethane, melamine resin, acrylic resin such as PMMA or PMBA, polyvinyl butyral, polyvinyl acetal, polyarylate, polycarbonate, phenoxy resin, polyurea, polyvinyl acetate, etc. Can be mentioned.

  The charging method of the charging device may be either a method of charging a photoconductor by applying a voltage in which a direct current is superimposed on an oscillating voltage such as an alternating current, or a method of charging a photoconductor by applying only a DC voltage. The former method of applying the superimposed voltage is preferable. The former method is relatively excellent in charging uniformity, and dirt such as toner hardly adheres. Moreover, even if dirt adheres, it has an excellent charging ability, and therefore has an advantage that charging failure due to dirt is less likely to occur compared to the latter method. However, since the former method has a drawback that damage to the photoreceptor is increased, the latter method may be preferable from the viewpoint of image quality and maintainability.

  In the image forming apparatus of the present invention, it is preferable that the coefficient of friction of the surface layer of the photosensitive member is smaller than the coefficient of friction of the surface layer of the charging member. By reducing the size, filming and the like can be prevented. In order to reduce the coefficient of friction of the surface layer of the photoreceptor, there are methods such as using a charge transport material having a relatively large molecular weight, reducing the amount of fluorine particles to be added, and increasing the amount. Specifically, the molecular weight of the charge transport material is preferably 30,000 or more, the particle size is 3 μm or less, and the amount of fluorine is preferably in the range of 0.5% to 10% by mass.

[Second image forming apparatus]
An image forming apparatus including at least a photosensitive member and a charging device that contacts and charges the surface of the photosensitive member. The charging member of the charging device that contacts the surface of the photosensitive member has the same rotation direction as the photosensitive member. It is the same as that of the first image forming apparatus except that it is rotationally driven in the direction or the reverse direction. That is, the same members and conditions as those of the first image forming apparatus can be applied. In order to rotate the charging member together with the photosensitive member, it is preferable that the charging member has a roll shape.

By rotating and driving in the same direction as or in the opposite direction to the rotation direction of the photosensitive member, the contact portion of the charging member with the photosensitive member becomes the entire circumference of the charging member. The lifetime can be extended.
In addition, the peripheral speed can be increased when the transfer residual toner adhering to the surface of the charging device in the cleanerless image forming apparatus is discharged to the photosensitive member side in the cleaning cycle, so that there is an advantage that the discharge efficiency is improved. When giving a peripheral speed, it is preferable to set it as 0.75-1.8 from a viewpoint of image quality.

  From the viewpoint of further reducing the friction, it is preferable that the rotation speed (surface speed) of the photosensitive member and the rotation speed (surface speed) of the charging member are substantially constant, and preferably constant. . Here, “substantially constant speed” means that the speed difference between them is 1% or less regardless of the rotational speed of the photoconductor.

  When the printing durability is evaluated in the second image forming apparatus as shown in FIG. 1 (however, the charging roll rotates counterclockwise on the drawing), the following results are obtained. It was. That is, the photoconductor containing polytetrafluoroethylene as fluororesin fine particles in the surface layer is rotated in the direction of the arrow (rotation speed: 104 mm / sec), the charging roll is brought into contact with the photoconductor, and the counterclockwise direction on the drawing ( (Rotation speed: 104 mm / sec) and is driven to rotate so as to be substantially equal to the photosensitive member. When a printing durability test was performed with such an apparatus, the effect of reducing the amount of photoconductor wear compared with the conventional photoconductor ("Conventional: 100 nm / kcycle" → "Invention: 40 nm / kcycle") was found to be effective. It was.

  The content of polytetrafluoroethylene particles in the surface layer of the photoreceptor was 8% by mass and the thickness was 26 μm. Further, 10% by mass of polytetrafluoroethylene particles were also contained in the surface layer (binder resin: polyamide, thickness: 9 μm) of the charging roll.

  Furthermore, if the printing durability test is continued, conventionally, scratches and filming occur on the photoconductor, resulting in a decrease in charging uniformity, and in particular, a white streak-like image quality defect occurs in a halftone. On the other hand, in the photoconductor of the present invention (second image forming apparatus), it is only slightly generated, and the image quality is not affected at all. From this result, it became clear that the life of the CRU (customer repair unit) is extended by the present invention, and image quality defects are less likely to occur.

  Next, when the coefficient of dynamic friction was measured with a HEIDON friction tester, it was 1.15 for the conventional photoconductor and 0.95 for the present invention. Thus, the effect of reducing the frictional force by the photoconductor of the present invention was quantitatively confirmed.

  Next, when the charging roll is driven with a peripheral speed difference with respect to the rotational speed of the photosensitive member, a frictional noise is generated unless the biting amount is set to about 0.05 mm, or due to frictional vibration of the charging roll. In contrast to the occurrence of uneven potential, it was confirmed that the present invention (second image forming apparatus) stably charges even when the thickness is set to 0.1 mm or more.

  From the above, it has also been found that setting latitudes such as the amount of biting and the hardness of the charging roll are widened by combining a photoreceptor formed on the surface containing fluororesin particles and a contact-type charging device that is driven to rotate.

1 is a configuration diagram illustrating an example of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Photoconductor 12 ... Charging roll 14 ... Exposure apparatus 16 ... Developing apparatus 18 ... Cleaning apparatus 20 ... Transfer roll 22 ... Transfer material

Claims (8)

An image forming apparatus comprising at least a photoconductor and a charging device that charges the surface of the photoconductor by bringing a charging member into contact therewith,
The surface layer of the photoreceptor contains 0.1 to 40% by mass of fluorine resin particles,
The surface of the photoreceptor has a Vickers hardness of 20 to 30 at a load of 10 g,
A contact portion of the charging member that contacts the surface of the photoreceptor is fixed;
The charging member is formed on a conductive elastic layer having a volume resistance value of 2 × 10 ^{2 to} 5 × 10 ⁹ Ωcm in which a conductive agent is dispersed in a rubber material, and on the surface of the conductive elastic layer. A resistance adjusting layer having a volume resistance of 3 × 10 ^{3 to} 5 × 10 ¹⁰ Ωcm, in which a conductive agent is dispersed in a resin, and a protective layer formed on the surface of the resistance adjusting layer, or the protective layer and the protective layer An image forming apparatus comprising: a surface layer formed on a surface, wherein the protective layer or the surface layer contains 1 to 30% by mass of fluorine-based resin particles having a volume average particle diameter of 0.05 to 1 μm. An image forming apparatus comprising at least a photoconductor and a charging device that charges the surface of the photoconductor by bringing a charging member into contact therewith,
The surface layer of the photoreceptor contains 0.1 to 40% by mass of fluorine resin particles,
The surface of the photoreceptor has a Vickers hardness of 20 to 30 at a load of 10 g,
The charging member in contact with the surface of the photoconductor is driven to rotate in the same direction as or in the reverse direction of the photoconductor;
The charging member is formed on a conductive elastic layer having a volume resistance value of 2 × 10 ^{2 to} 5 × 10 ⁹ Ωcm in which a conductive agent is dispersed in a rubber material, and on the surface of the conductive elastic layer. A resistance adjusting layer having a volume resistance of 3 × 10 ^{3 to} 5 × 10 ¹⁰ Ωcm, in which a conductive agent is dispersed in a resin, and a protective layer formed on the surface of the resistance adjusting layer, or the protective layer and the protective layer An image forming apparatus comprising: a surface layer formed on a surface, wherein the protective layer or the surface layer contains 1 to 30% by mass of fluorine-based resin particles having a volume average particle diameter of 0.05 to 1 μm.   The image forming apparatus according to claim 1, further comprising at least two charging devices.   At least one of the fluororesin particles contained in the surface layer of the charging member and at least one of the fluororesin particles contained in the surface layer of the photoreceptor are the same type. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein a friction coefficient of a surface layer of the photosensitive member is smaller than a friction coefficient of a surface layer of the charging member.   6. The image forming apparatus according to claim 1, wherein the image forming apparatus is a cleanerless image forming apparatus that does not require a cleaning blade for removing deposits remaining on the photosensitive member.   The image forming apparatus according to claim 1, wherein the voltage applied to the charging device is a voltage obtained by superimposing an AC voltage on a DC voltage. 8. The rotation speed (surface speed) of the photoconductor and the rotation speed (surface speed) of the charging member are substantially constant. Image forming apparatus.

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