JP2004139105A - Electrophotographic photoreceptor and electrophotographic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly durable electrophotographic photoreceptor which solves a color drift and density unevenness, an electrophotographic method, and an electrophotographic system. <P>SOLUTION: The electrophotographic system has an electrostatic charging means for subjecting an electrophotographic photoreceptor having a photosensitive layer on a conductive support to electrostatic charge, an image exposing means for subjecting the photoreceptor to image exposure, a developing means for subjecting the photoreceptor to reversal development, and a transferring means. The modulus of a change in electrostatic capacity after the electrophotographic photoreceptor is subjected to recursive fatigue to the reverse polarity from the electrostatic charge polarity thereof is ≤30%. In addition, the electrophotographic photoreceptor has an intermediate layer and the surface roughness Rz of the intermediate layer is ≥0.6 μm. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to an electrophotographic photosensitive member, and is suitably used for a copying machine, a laser printer, a laser facsimile, and the like.

As the electrophotographic method, the Carlson process and various deformation processes thereof are known, and are widely used in copiers and printers. Among the photoreceptors used in such an electrophotographic method, those using an organic photosensitive material have begun to be used in recent years because of their advantages such as low cost, mass productivity, and no pollution.
Organic electrophotographic photoreceptors include a photoconductive resin represented by polyvinyl carbazole (PVK), a charge transfer complex type represented by PVK-TNF (2,4,7-trinitrofluorenone), and a phthalocyanine-binder. And a function-separated type photoreceptor using a combination of a pigment dispersion type, a charge generation material, and a charge transport material are known, and a function-separated type photoreceptor is particularly attracting attention.
The mechanism of the formation of an electrostatic latent image in this function-separated type photoreceptor is as follows: when light is irradiated after charging the photoreceptor, light passes through a transparent charge transport layer and is absorbed by the charge generating substance in the charge generation layer, The charge-generating substance that has absorbed the light generates charge carriers, which are injected into the charge transport layer, move in the charge transport layer according to the electric field generated by the charge, and remove the charge on the photoreceptor surface. The latent image is formed by neutralization. In a function-separated type photoreceptor, it is known and useful to use a charge transport material having absorption mainly in the ultraviolet region and a charge generation material having absorption mainly in the visible region.
Many charge transporting substances have been developed as low molecular weight compounds. However, since low molecular weight compounds alone do not have film-forming properties, they are usually used by being dispersed and mixed in an inert polymer. However, the charge transport layer composed of a low-molecular charge transport material and an inert polymer is generally soft, and has a drawback that the Carlson process easily causes film abrasion due to repeated use.

  In recent years, there has been remarkable progress in the electrophotographic process using the above-described photoconductor, and various improvements have been made to the conventional Carlson process. For example, improvement of a cleaning method for keeping no copy history (Patent Document 1), improvement of a charging method for reducing the amount of ozone generated (Patent Documents 2 to 8), and improvement of a transfer method for improving image quality ( Patent Documents 9 and 10) and the like.

However, in an electrophotographic method using reversal development, carriers are trapped at the intermediate layer-charge generation layer interface, the charge generation layer-charge transport layer interface, the photosensitive layer-protection layer interface, etc. because of the opposite polarity to the charge during transfer. Easy to be. In particular, if carriers having the opposite polarity to the charge are accumulated, it cannot be easily erased. In the reversal developing system, the transfer is performed with the polarity opposite to the charging, so that the carrier receiving the transfer charge of the photoconductor is trapped, the charging potential is different between the first rotation and the second rotation and thereafter, and the charging is performed from the plural rotations and thereafter. Has the disadvantage of being stable. In particular, the color photoconductor has a problem in that the color shift occurs when a plurality of copies are made due to a slight change in the charging potential. This phenomenon is related to the number of copies and the standing time after forming the image process, and becomes remarkable when the standing time after repeated use is short.
That is, the time until the charging potential stabilizes differs depending on the accumulated amount of the trapped carriers and the release time from the traps. As a solution, the process of the first rotation in which the change in the charging potential is large is not used for image formation, and a countermeasure on the process side used for image formation from the second rotation onward when the charging potential is stable can be considered. In digital copiers and the like with a high copy speed, there is a major obstacle to speeding up, and there is an effect of leaving time after forming an image process. Therefore, only measures on the process side are not sufficient.
Further, a photoconductor in which a semiconductor material having a band gap of 2.2 eV or more and a binder resin are contained in an undercoat layer and a charge generation material has a phthalocyanine compound has been proposed (Patent Document 11), but the effect is not sufficient. Absent.

JP-A-58-102273 JP-A-56-104351 JP-A-57-178267 JP-A-58-40566 JP-A-58-139156 JP-A-58-150975 JP-A-63-149669 JP-A-5-45916 JP-A-7-152217 JP-A-10-186703

  The present invention relates to an electrophotographic apparatus having a charging unit, an image exposing unit, a developing unit for performing reversal development and a transferring unit, and a charging unit for a stacked type electrophotographic photosensitive member in which a charge transport layer and a charge generating layer are overlapped. In an electrophotographic method having a process, an image exposure process, a development process for performing reversal development, and a transfer process, the charging means performs reverse polarity charging, so that the charging potential differs between the first rotation and the second and subsequent rotations. In some cases, an abnormal image such as uneven density occurs. Therefore, it is possible to solve the problem that the charging potential is different between the first rotation and the second rotation and thereafter, to solve abnormal images such as color shift and density unevenness, and to provide a highly durable electrophotographic photosensitive member, an electrophotographic method, and an electrophotographic apparatus. The purpose is to do.

The present inventors have examined these points and found that the main development is caused by the reverse charging characteristic when the electrophotographic photosensitive member is used.
In other words, by receiving the charge of the opposite polarity in the transfer, the carrier is injected into the photoconductor at the portion of the photoconductor that receives the transfer charge. The injected charges are trapped at various interfaces such as an intermediate layer, a charge generation layer, a charge generation layer, a charge transport layer, and a charge transport layer, which are present in the photosensitive layer. Under the influence, the carrier is not canceled at the time of charging for the next image formation and is accumulated in the photosensitive layer, so that carriers are trapped. In this case, there is a drawback that the charging potential is different between the first rotation and the second rotation and thereafter, and the charging is stabilized after the plurality of rotations. As a result, the charged potential and the exposed portion potential are lowered, and an abnormal image such as density unevenness or color misregistration occurs when a plurality of copies or a color process for forming an image by multiple rotations are taken. This phenomenon is related to the number of copies and the discharge time after the formation of the image process. The frequency of repeated use is high. That is, the time until the charging potential stabilizes differs depending on the accumulated amount of the trapped carriers and the release time from the traps.

Further, when the transfer member is in contact with the transfer member (transfer belt, transfer roller, intermediate transfer belt, or the like), the carrier is particularly remarkably injected, resulting in an abnormal image such as uneven density or color shift.
As a result of intensive studies on the reverse charging characteristics of the photoreceptor, if the change in capacitance after applying reverse charging is 30% or less, injection of carriers can be suppressed when receiving reverse polarity during transfer. The charging potential after the first rotation can be stabilized, and it has been found that abnormal images such as density unevenness and color misregistration do not occur, leading to the present invention.

  Therefore, according to the present invention, there is provided (1) a charging step of charging at least a solvent-containing electrophotographic photosensitive member having a charge generating layer and a charge transporting layer on a conductive support, and performing image exposure by image exposure. In an electrophotographic method having an exposure step, a development step of performing reversal development, and a transfer step, the rate of change of the electrostatic charge after the electrophotographic photosensitive member is repeatedly subjected to fatigue of the opposite polarity to the charging polarity is 30% or less. (2) "The electrophotographic method according to the above (1), wherein the transfer means used in the transfer step is in contact with the electrophotographic photosensitive member". (3) An electrophotographic method according to (2), wherein the transfer means used in the transfer step is a transfer belt having a belt-like form.

  Further, according to the present invention, (4) “a charging means for charging an electrophotographic photosensitive member containing at least a charge generating layer and a charge transport layer on a conductive support, and performing image exposure, In an electrophotographic apparatus having an image exposing means, a developing means for performing reversal development, and a transferring means, a rate of change in capacitance of the electrophotographic photosensitive member after repeated fatigue of a polarity opposite to the charging polarity is 30% or less. (5) “The electrophotographic apparatus according to the above (4), wherein the transfer means is in contact with the electrophotographic photosensitive member”, (6) "The electrophotographic apparatus according to the above mode (5), wherein the transfer means is a transfer belt having a belt-like form" is provided.

  Further, according to the present invention, (7) “a charging step for charging an electrophotographic photosensitive member having a photosensitive layer on a conductive support, an image exposing image step for performing image exposure, and a developing step for performing reversal development And an electrophotographic photoreceptor for use in an electrophotographic method having a transfer step, wherein the photosensitive layer contains a solvent and has a capacitance change rate of 30% or less after repeated fatigue of a polarity opposite to a charging polarity. And an electrophotographic photoreceptor characterized in that the electrophotographic photoreceptor has an intermediate layer ", (8)" an electrophotograph comprising at least a charge generation layer and a charge transport layer provided on a conductive support, and containing a solvent. An electrophotographic photoreceptor for use in an electrophotographic apparatus having a charging unit for performing charging, an image exposing unit for performing image exposure, a developing unit for performing reversal development, and a transfer unit, wherein the photosensitive layer contains a solvent. And the charging polarity Capacitance change rate after having received the repeated fatigue polarity is 30% electrophotographic photosensitive member is an electrophotographic photosensitive member characterized by having an intermediate layer "is provided.

  Furthermore, according to the present invention, (9) “the electrophotographic photosensitive member according to the above (7) or (8), wherein the electrophotographic photosensitive member has an intermediate layer”; 10) “The electrophotographic photoreceptor according to the above item (9), wherein the electrophotographic photoreceptor has a surface protective layer”, and (11) “The surface protective layer contains at least conductive fine particles. (10) The electrophotographic photosensitive member according to (10), wherein the surface protective layer used in the electrophotographic photosensitive member contains at least fluorine atom-containing resin fine particles. (12) “The electrophotographic photoconductor according to the above (9), wherein the electrophotographic photoconductor contains a phthalocyanine pigment”; (13) "Phthalo contained in the electrophotographic photoreceptor The above item (12), wherein the anine is titanyl phthalocyanine having an X-ray diffraction peak at a Bragg angle 2θ of at least 27.2 ± 0.2 ° with respect to at least the characteristic X-ray (wavelength 1.514 °) of CuKα. The described electrophotographic photoreceptor is provided.

As means for constituting the present invention, the trap sites existing at the interface of the electrophotographic photosensitive member may be reduced as much as possible, the energy level of the trap may be reduced, and / or the mobility of the trap may be increased. For example, in the case of a photoreceptor having an intermediate layer and a charge generation layer, this can be achieved by appropriately selecting the pigment, binder resin, and solvent for the intermediate layer and the charge generation layer, and further adjusting the ratio.
Further, in the photoreceptor having the interface between the charge generation layer and the charge transport layer, the ratio is further adjusted by appropriately selecting the pigment and the binder resin and the solvent of the charge generation layer and the charge transport material and the binder resin of the charge transport layer. It is achieved by doing.
Further, in the photoreceptor having the photosensitive layer-protective layer, the charge transport material and the binder resin of the charge transport layer, the pigment and the binder resin of the protective layer are appropriately selected, and the ratio is further adjusted to adjust the ratio. .

  It is also achieved by adjusting the roughness at the interface of each layer and the drying conditions after coating. Further, it is possible to reduce the number of trap sites, to reduce the energy level of the trap, and / or to increase the mobility of the trap by controlling the amount of the solvent contained. The amount of the solvent contained is 10 to 10000 ppm, preferably 100 to 1000 ppm. If it is 10 ppm or less, the residual stress in the film is high, and the film tends to peel off. If it is 10,000 ppm or more, the effect is not sufficient. When the contained solvent is a non-halogen solvent, the amount of film displacement of the photosensitive layer may be reduced.

The reverse-charging fatigue characteristic according to the present invention is a method adopted as one of the convenient methods showing the carrier injection property by the reverse charging, and its evaluation method will be described with reference to FIG. FIG. 1 is a schematic diagram of a measuring device for evaluating the reverse charging fatigue characteristic. In FIG. 1, charging charger (1) (DC1), erasing LED (2) (LED1), image exposure means (3) (EX1), reverse charging charger (4) (DC2), quenching LED (5) ) (LED2) is installed around the photoreceptor. First, the photoreceptor is charged to 800 V by DC1, exposed by EX1, and attenuated. The amount of charge Q required for charging is determined, and the relationship between the photoconductor surface potentials is substituted into the following equation to determine the electrostatic capacity (initial) C0 of the photoconductor.
C = Q / V (Q represents the amount of charge, and V represents the surface potential of the photoconductor)
Thereafter, reverse charging fatigue is applied. The reverse charging fatigue characteristic is such that the photoconductor is rotated, DC1, LD1, DC2, and LD2 are turned on, and the photoconductor is repeatedly charged and exposed. Thereafter, DC1, LD1, DC2, and LD2 are turned off. Then, the photoreceptor is immediately charged to 800 V with DC1, exposed with EX1, and attenuated. Similarly to the above, the charge amount Q required for charging is obtained, and the electrostatic potential (after fatigue) C1 of the photoconductor is obtained by substituting the relationship of the photoconductor surface potential into the above equation. The amount of change between the capacitance C0 (initial) and the capacitance C1 (after fatigue) is defined as the capacitance change rate.

Hereinafter, the present invention will be described in detail.
FIG. 2 is a schematic diagram for explaining an example of the electrophotographic process and the electrophotographic apparatus of the present invention, and the following modified examples also belong to the category of the present invention. In FIG. 2, a photosensitive member (6) is provided with a photosensitive layer of the present invention on a conductive support, and in this order, a charging member (8), an eraser (9), an image exposure unit (10), and a developing unit. A unit (11), a transfer belt (15), a separation claw (16), a cleaning unit (18) (which is composed of a fur brush (19a) and a cleaning blade (19b)), and a charge removing lamp (7). It is arranged around. If necessary, a pre-transfer charger (12) and a pre-cleaning charger (17) are provided. These units include a corotron, a scorotron, a solid state charger (solid state charger), a roller, and a belt. A known means is used.

Light sources such as an image exposure unit (10) and a neutralizing lamp (7) include a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and an electroluminescence (EL). ) Can be used. To irradiate only light in a desired wavelength range, various filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used.
Such a light source or the like irradiates the photosensitive member with light by providing a transfer step, a charge removal step, a cleaning step, or a pre-exposure step using light irradiation in addition to the step shown in FIG.

Now, the toner developed on the photoconductor (6) by the developing unit (11) is transferred to the transfer paper (14), but not all is transferred, and remains on the photoconductor (6). Toner also forms. Such toner is removed from the photoreceptor by the fur brush (19a) and the blade (19b). Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.
A known method is applied to the developing unit, and a known method is also used for the charge removing unit.

  The image forming means as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, or may be incorporated in the apparatus in the form of a process cartridge. The process cartridge is one device (part) including a photoconductor, and further including a charging unit, an exposing unit, a developing unit, a transferring unit, a cleaning unit, and a discharging unit. Although there are many shapes and the like of the process cartridge, a general example is shown in FIG. A photoreceptor (23) having a contact charging member (20), an image exposing unit (21), a cleaning brush (22), a developing roller (24), and a transfer roller (25) disposed therearound is provided on a conductive support. It has the photosensitive layer of the invention.

Next, the electrophotographic photosensitive member of the present invention will be described with reference to the drawings.
FIG. 4 is a cross-sectional view showing a configuration example of a photoreceptor used in the present invention, in which a photosensitive layer on a conductive support (26) is laminated with a charge generation layer (27) and a charge transport layer (28). It is composed of

  FIG. 5 is a cross-sectional view showing another configuration example, in which an intermediate layer (29) is provided between the photosensitive layer (30) and the conductive support (26). In this case, the photosensitive layer (30) may be a single-layer photosensitive layer or a laminated photosensitive layer.

  FIG. 6 is a cross-sectional view showing still another configuration example, in which a photosensitive layer (30) and a protective layer (31) are formed on a conductive support (26). In this case, the photosensitive layer (30) may be a single-layer photosensitive layer or a laminated photosensitive layer.

Next, the configuration of the electrophotographic photosensitive member will be described.
Examples of the conductive support (26) include those exhibiting conductivity of not more than 10 ¹⁰ Ω, such as metals such as aluminum, nickel, chromium, nichrome, copper, silver, gold, and platinum, tin oxide, and indium oxide. A film or cylindrical plastic or paper coated with an oxide by vapor deposition or sputtering, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc. I. , I .. I. For example, pipes that have been surface-treated by cutting, superfinishing, polishing, or the like after being formed into a tube by a method such as extrusion or drawing can be used.

The photosensitive layer (30) in the present invention may be a single layer type or a laminated type. Here, for convenience of explanation, the laminated type will be described first.
First, the charge generation layer (27) will be described. The charge generation layer (27) is a layer containing a charge generation substance as a main component, and uses a binder resin as needed. As the charge generation substance, an inorganic material and an organic material can be used.
Examples of the inorganic material include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compound, and amorphous silicon. As amorphous silicon, a material in which a dangling bond is terminated with a hydrogen atom or a halogen atom, or a material in which a boron atom, a phosphorus atom, or the like is doped, is suitably used.

  On the other hand, as the organic material, a known material can be used. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulhenium salt pigments, methine squaric acid pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having a fluorenone skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, azo pigments having a distyryl carbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinone imine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, i Jigoido based pigments, and bisbenzimidazole pigments. These charge generating substances can be used alone or as a mixture of two or more kinds.

  As the binder resin used as needed, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinyl carbazole, polyacrylamide, etc. Used. These binder resins can be used alone or as a mixture of two or more. Further, a charge transporting material described below may be added as needed.

As a method for forming the charge generation layer (27), a vacuum thin film preparation method and a casting method from a solution dispersion system are mainly mentioned.
For the former method, a vacuum evaporation method, a glow discharge decomposition method, an ion plating method, a sputtering method, a reactive sputtering method, a CVD method, or the like is used. As the charge generation layer (27), the above-mentioned inorganic material, organic A good base material can be formed.
Further, in order to provide a charge generation layer by a casting method described later, if the inorganic or organic charge generation material described above is necessary, a ball mill and an atomizer using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone together with a binder resin, if necessary. It can be formed by dispersing with a lighter, a sand mill, or the like, diluting the dispersion liquid appropriately, and applying. The coating can be performed by a dip coating method, a spray coating method, a bead coating method, or the like.
The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, and preferably 0.05 to 2 μm.

Next, the charge transport layer (28) will be described.
The charge transporting layer (28) can be formed by dissolving or dispersing the charge transporting substance and the binder resin in a suitable solvent, and applying and drying this. If necessary, a plasticizer and a leveling agent can be added.
The charge transport materials include a hole transport material and an electron transport material.
Examples of the electron transporting substance include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-Tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4one, 1,3,7-trinitro An electron accepting substance such as dibenzothiophene-5,5-dioxide is exemplified. These electron transport materials can be used alone or as a mixture of two or more.
Examples of the hole transport material include the electron donating materials shown below and are preferably used. For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline Phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives and the like. These hole transporting substances can be used alone or as a mixture of two or more.

  As the binder resin used for the charge transport layer (28), polycarbonate (bisphenol A type, bisphenol Z type, bisphenol C type, etc.), polyester, methacrylic resin, acrylic resin, polyethylene, vinyl chloride, vinyl acetate, polystyrene, phenol resin , Epoxy resin, polyurethane, polyvinylidene chloride, alkyd resin, silicon resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyacrylate, polyacrylamide, phenoxy resin, and the like. Among them, a polycarbonate resin having a bisphenol A and particularly a bisphenol C and a bisphenol Z structure in a repeating unit is effectively used. These binders can be used alone or as a mixture of two or more.

Further, a polymer charge transport material having both functions of a binder resin and a charge transport material can be used as the binder resin. Examples of the polymer charge transporting material used in this case include the following.
(A) Polymer having a carbazole ring in the main chain and / or side chain For example, poly-N-vinylcarbazole, JP-A-50-82056, JP-A-54-9632, JP-A-54-11737 And JP-A-4-183719.
(B) Polymer having a hydrazone structure in the main chain and / or side chain For example, compounds described in JP-A-57-78402 and JP-A-3-50555 are exemplified.
(C) Polysilylene polymer For example, compounds described in JP-A-63-285552, JP-A-5-19497, JP-A-5-70595 and the like are exemplified.
(D) Polymer having a tertiary amine structure in the main chain and / or side chain For example, N, N-bis (4-methylphenyl) -4-aminopolystyrene, JP-A-1-13061, JP-A-1-13061 -19049, JP-A-1-1728, JP-A-1-105260, JP-A-2-167335, JP-A-5-66598, and compounds described in JP-A-5-40350. Is exemplified.
(E) Other Polymers Examples thereof include formaldehyde polycondensates of nitropyrene and compounds described in JP-A-51-73888, JP-A-56-150749, and the like.
The polymer charge transporting material used in the present invention includes not only the above-mentioned polymers, but also copolymers of known monomers, block polymers, graft polymers, star polymers, and, for example, JP-A-3-109406. It is also possible to use a crosslinked polymer having an electron donating group as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 6-131, and the like.

The thickness of the charge transport layer (28) is suitably about 5 to 100 μm. In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer (28).
As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount of the plasticizer is suitably about 0 to 30% by weight based on the binder resin.
As the leveling agent, a polymer or oligomer having a perfluoroalkyl group in a side chain is used, and its amount is suitably about 0 to 1% by weight based on the binder resin.

Next, a case where the photosensitive layer (30) has a single-layer structure will be described.
When a single-layer photosensitive layer is provided by a casting method, a function-separated type of a charge-generating substance and a charge-transporting substance is often used. That is, the above-described materials can be used as the charge generating substance and the charge transporting substance.
The single-layer photosensitive layer can be formed by dissolving or dispersing a charge generating substance, a charge transporting substance, and a binder resin in an appropriate solvent, and applying and drying the resultant. If necessary, a plasticizer and a leveling agent can be added.
As the binder resin, the binder resin described for the charge transport layer (28) may be used as it is, or the binder resin described for the charge generation layer (27) may be mixed and used.

The single-layer photosensitive layer is obtained by dispersing a charge generating substance, a charge transporting substance, and a binder resin using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone by a ball mill, an attritor, a sand mill, etc., and appropriately diluting the dispersion. It can be formed by applying by applying. The coating can be performed by a dip coating method, a spray coating method, a bead coating method, or the like.
A photoreceptor in which a charge transporting substance is added to a eutectic complex formed from a pyrylium-based dye or bisphenol A-based polycarbonate can be formed by a similar coating method from a suitable solvent. The thickness of the single-layer photoreceptor is suitably about 5 to 100 μm.

  The electrophotographic photoreceptor used in the present invention includes an intermediate layer (29) between a conductive support (26) and a photosensitive layer (30) (in the case of a laminated type, a charge generation layer (27)). Can be provided. The intermediate layer (29) is provided for the purpose of improving adhesiveness, preventing moiré, improving the coating property of the upper layer, reducing residual potential, and the like. The intermediate layer (29) generally contains a resin as a main component. However, considering that a photosensitive layer is applied thereon using a solvent, these resins are resins having high resistance to dissolution in general organic solvents. Desirably. As such a resin, polyvinyl alcohol, casein, water-soluble resin such as sodium polyacrylate, copolymerized nylon, alcohol-soluble resin such as methoxymethylated nylon, polyurethane, melamine resin, alkyd-melamine resin, epoxy resin, etc. Curable resins that form a three-dimensional network structure are exemplified. Further, fine powders such as metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide and indium oxide, or metal sulfides and metal nitrides may be added. These intermediate layers can be formed using an appropriate solvent and a coating method as in the case of the above-described photosensitive layer.

Further, as the intermediate layer of the present invention, a metal oxide layer formed by, for example, a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like is also useful.
In addition, the intermediate layer of the present invention is provided with Al ₂ O ₃ by anodic oxidation, an organic substance such as polyparaxylylene (parylene), SiO, SnO ₂ , TiO ₂ , ITO, CeO _{2 and the} like. An inorganic material provided by a vacuum thin film manufacturing method can also be used favorably. The thickness of the intermediate layer is suitably from 0 to 5 μm.

The protective layer (31) is a layer provided for the purpose of protecting the photoconductor surface. The protective layer (31) can be formed by dissolving or dispersing the polymer charge transport substance in a suitable solvent, for example, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, cyclohexanone, etc., and applying and drying.
For the protective layer, the above-described polymer charge transporting material can be used, and in addition, an electrically inactive binder resin can be used. Materials used for this include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallyl sulfone, polybutylene, polybutylene terephthalate, Polycarbonate, polyether sulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, epoxy resin, etc. Among these, a cured product of a curable material and a curing agent is exemplified. Among them, the polycarbonate resin as shown above is effectively used in the repeating unit.

  In addition, an organic or inorganic filler material according to the purpose can be added to the protective layer for the purpose of improving abrasion resistance / surface resistance / surface energy. Examples of the organic filler material include fluororesin powder such as polytetrafluoroethylene, silicone resin powder, a-carbon powder, and the like.Examples of the inorganic filler material include copper, tin, aluminum, and metal powder such as indium. Inorganic materials such as metal oxides such as tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide and tin-doped indium oxide, and potassium titanate are exemplified. These filler materials are used alone or in combination of two or more. These filler materials can be dispersed in the protective layer coating liquid by using an appropriate disperser. The average particle size of the filler is preferably 0.5 μm or less, more preferably 0.2 μm or less from the viewpoint of the transmittance of the protective layer.

In the present invention, a plasticizer or a leveling agent may be added to the protective layer (31). As the plasticizer and the leveling agent, the materials specified for the charge transport layer can be used as they are.
An ordinary coating method is adopted as a method for forming the protective layer. Incidentally, the film thickness is suitably about 0.5 to 10 μm.
The silicone oil added to the electrophotographic photoreceptor of the present invention is added at least to the protective layer. As a result, the surface energy of the outermost layer is reduced, and the wear resistance is improved. Further, as described above, it is also possible and effective to add the protective layer to the protective layer and a layer closer to the support.

In the present invention, an antioxidant can be added for the purpose of improving the environmental resistance, especially for the purpose of preventing a decrease in sensitivity. The antioxidant may be added to any layer containing an organic substance, but good results can be obtained by adding it to a layer containing a charge transport material.
The antioxidants that can be used in the present invention include the following.

Monophenolic compound 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate and the like.

Bisphenol compounds 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-t-butylphenol), 4,4'- Thiobis- (3-methyl-6-t-butylphenol), 4,4′-butylidenebis- (3-methyl-6-t-butylphenol) and the like.

High molecular phenolic compound 1,1,3-tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5 -Di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3' -Bis (4'-hydroxy-3'-t-butylphenyl) butyric acid] glycol ester, tocophenols and the like.

Paraphenylenediamines N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylenediamine, N , N'-di-isopropyl-p-phenylenediamine, N, N'-dimethyl-N, N'-di-t-butyl-p-phenylenediamine and the like.

Hydroquinones 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2 -Octadecenyl) -5-methylhydroquinone and the like.

Organic sulfur compounds Dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate and the like.

Organic phosphorus compounds Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like.

These compounds are known as antioxidants for rubber, plastics, oils and the like, and can be easily obtained as commercial products.
The addition amount of the antioxidant in the present invention is 0.1 to 100 parts by weight, preferably 2 to 30 parts by weight based on 100 parts by weight of the charge transporting substance.

  As is clear from the above detailed and specific description, according to the invention of the present application, there is provided a photoconductor in which abnormal images such as color shift and density unevenness due to reverse charging polarity are eliminated.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. All parts used in the examples are parts by weight.

Example 1
On an aluminum cylindrical support having a diameter of 30 mm, a coating solution for a charge generation layer having the following composition,
The coating liquid for the charge transport layer is sequentially applied and dried to form a charge generation layer of about 0.3 μm and a charge transport layer of about 20 μm, and then annealed at 120 ° C. for 20 minutes to obtain the electrophotographic photoreceptor of the present invention. Produced.
(Coating solution for charge generation layer)
2.5 parts of charge generating material with the following structure

X-type H2-Pc 2.5 parts Polyvinyl butyral (UCC: XYHL) 2 parts Cyclohexanone 200 parts Tetrahydrofuran 200 parts (Coating solution for charge transport layer)
Polyarylate resin (Unitika U-Polymer U-100) 10 parts Charge transporting material with the following structure 7 parts

90 parts of methylene chloride <drying conditions>
Charge generation layer drying temperature 110 ° C 20min
Charge transport layer drying temperature 100 ° C 20min

Example 2
On an aluminum cylindrical support having a diameter of 30 mm, the surface roughness of the intermediate layer after coating is Rz = 0.
. A coating liquid for an intermediate layer, a coating liquid for a charge generation layer, and a coating liquid for a charge transport layer each having the following composition are sequentially applied and dried so as to have a thickness of 6 μm. An electrophotographic photoreceptor of the present invention was prepared by forming a charge generation layer of 3 μm and a charge transport layer of about 20 μm.
(Coating liquid for intermediate layer)
375 parts of alkyd resin solution (Dainippon Ink & Chemicals: Beckolite M-6401-50)
210 parts of melamine resin solution (Dainippon Ink and Chemicals: Super Beckamine G821-60)
Titanium dioxide (Ishihara Sangyo: Taipe CR-EL) 1250 parts 2-butanone 7800 parts (Coating solution for charge generation layer)
5 parts of charge generating material with the following structure

Polyvinyl butyral (UCC: XYHL) 2 parts Cyclohexanone 200 parts Tetrahydrofuran 200 parts (Coating solution for charge transport layer)
Polyarylate resin (Unitika U-Polymer U-100) 10 parts Charge transporting material with the following structure 7 parts

90 parts of methylene chloride <drying conditions>
Middle layer drying temperature 130 ℃ 20min
Charge generation layer drying temperature 110 ° C 20min
Charge transport layer drying temperature 100 ° C 20min

Example 3
A coating liquid for a charge generation layer, a coating liquid for a charge transport layer, and a coating liquid for a protective layer having the following composition are sequentially coated and dried on an aluminum cylindrical support having a diameter of 30 mm to form a charge of about 0.3 μm. A generation layer, a charge transport layer of about 20 μm is formed by dip coating, and further a layer of about 3 μm
m was formed by spray coating to prepare an electrophotographic photoreceptor of the present invention.
(Coating solution for charge generation layer)
5 parts of charge generating material with the following structure

Polyvinyl butyral (UCC: XYHL) 2 parts Cyclohexanone 200 parts Tetrahydrofuran 200 parts (Coating solution for charge transport layer)
Polyarylate resin (Unitika U-Polymer U-100) 10 parts Charge transporting material with the following structure 7 parts

90 parts of methylene chloride (coating solution for protective layer)
Bisphenol C-type polycarbonate 10 parts Charge transport material of the following structure 5 parts

500 parts of methylene chloride <drying conditions>
Charge generation layer drying temperature 110 ° C 20min
Charge transport layer drying temperature 120 ° C 20min
Protective layer drying temperature 120 ° C 20min

Example 4
A photoconductor of the present invention was produced in the same manner as in Example 3 except that the coating liquid for the protective layer was changed as follows.
(Coating liquid for protective layer)
Bisphenol C type polycarbonate 10 parts Tin oxide 5 parts Methylene chloride 500 parts

Example 5
A photoconductor of the present invention was produced in the same manner as in Example 3 except that the coating liquid for the protective layer was changed as follows.
(Coating liquid for protective layer)
Bisphenol Z-type polycarbonate 10 parts Polyfluoroethylene fine particles 6 parts Charge transport material of the following structure 5 parts

    500 parts of methylene chloride

Example 6
A photoconductor was prepared in the same manner as in Example 1, except that the coating solution for the charge generation layer in Example 1 was changed to a coating solution for the charge generation layer having the following composition.
(Coating solution for charge generation layer)
X-type Pc pigment powder 3 parts Polyvinyl butyral 2 parts Tetrahydrofuran 50 parts 4-methyl-2-pentanone 90 parts

Example 7
A photoconductor was prepared in the same manner as in Example 1, except that the coating solution for the charge generation layer in Example 1 was changed to a coating solution for the charge generation layer having the following composition.
(Coating solution for charge generation layer)
TiOPc pigment powder (X-ray diffraction peak figure 7) 3 parts Polyvinyl butyral 2 parts Tetrahydrofuran 50 parts 4-methyl-2-pentanone 90 parts

Example 8
A photoreceptor of Example 8 was prepared in the same manner as in Example 1, except that methylene chloride in the coating solution for the charge transport layer of Example 1 was replaced with tetrahydrofuran.

Example 9
A photoreceptor of Example 9 was produced in the same manner as in Example 1 except that dioxane was used instead of methylene chloride in the coating solution for the charge transport layer of Example 1.

Comparative Example 1
A photoconductor of Comparative Example 1 was prepared in the same manner as in Example 1, except that the coating solution for the charge transport layer was changed to the following and annealing was not performed.
(Coating solution for charge transport layer)
Polyarylate resin 10 parts Charge transport material of the following structure 15 parts

    90 parts of methylene chloride

Comparative Example 2
The dispersion time was adjusted, and the intermediate layer coating liquid and drying conditions were changed as follows so that the intermediate layer surface roughness after coating was Rz = 3.0 μm. The photoreceptor of Example 2 was produced.
(Coating liquid for intermediate layer)
375 parts of alkyd resin solution (Dainippon Ink & Chemicals: Beckolite M-6401-50)
210 parts of melamine resin solution (Dainippon Ink and Chemicals: Super Beckamine G821-60)
Titanium dioxide (Ishihara Sangyo: Taipe CR-EL) 2500 parts 2-butanone 7800 parts <Drying conditions>
Middle layer drying temperature 130 ℃ 20min
Charge generation layer drying temperature 130 ° C 20min
Charge transport layer drying temperature 100 ° C 10min

Comparative Example 3
A photoconductor of Comparative Example 3 was produced in the same manner as in Example 3, except that the coating liquid for the protective layer and the drying conditions were changed as follows.
(Coating liquid for protective layer)
Bisphenol Z-type polycarbonate 10 parts Charge transport material of the following structure 15 parts

90 parts of methylene chloride <drying conditions>
Charge generation layer drying temperature 110 ° C 20min
Charge transport layer drying temperature 100 ° C 20min
Protective layer drying temperature 120 ° C 20min

The photoconductors of Examples 1 to 9 and Comparative Examples 1 to 3 produced as described above were repeatedly fatigued using the reverse charging fatigue characteristic device shown in FIG. 1, and then the capacitance was measured. The rate of change was evaluated.
The photosensitive members of Examples 1 to 9 and Comparative Examples 1 to 3 were mounted on the electrophotographic apparatus shown in FIG. In this state, the remaining time (1 min, 10 min, 30 min) after continuous copying of 100 sheets was changed, and the charging potential (VD) and the exposed portion potential (VL) were measured to evaluate the potential stability.
Further, after the photoconductors of Examples 1 to 9 and Comparative Examples 1 to 3 were mounted on the process cartridge for electrophotography shown in FIG. The image density difference between the first sheet and the 1000th sheet was evaluated. Further, printing was performed on 100,000 sheets, and the abrasion loss of the charge transport layer in Examples 1, 8, and 9 was measured. The results are shown in Table 1.

It is a schematic diagram of a measuring device for evaluating reverse charging fatigue characteristics in the present invention. FIG. 1 is a schematic diagram for explaining an example of an electrophotographic process and an electrophotographic apparatus of the present invention. FIG. 2 is a diagram illustrating an example of an electrophotographic process cartridge of the present invention. FIG. 2 is a cross-sectional view illustrating a configuration example of a photoconductor used in the present invention. FIG. 9 is a cross-sectional view illustrating another example of the configuration of the photoconductor used in the present invention. FIG. 9 is a cross-sectional view illustrating still another example of the configuration of the photoconductor used in the present invention. 3 is an X-ray diffraction peak of a pigment powder used in the coating solution for a charge generation layer of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Charger 2 Erase light source 3 Image exposure means 4 Reverse charge charger 5 Quenching light source 6 Photoreceptor 7 Static elimination lamp 8 Contact charging member 9 Eraser 10 Image exposure part 11 Developing unit 12 Pre-transfer charger 13 Registration roller 14 Transfer paper 15 Transfer belt Reference Signs List 16 separation claw 17 pre-cleaner charger 18 cleaning unit 19a fur brush 19b cleaning blade 20 contact charging member 21 image exposure means 22 cleaning brush 23 photoconductor 24 developing roller 25 transfer roller 26 conductive support 27 charge generating layer 28 charge transport layer 29 Intermediate layer 30 Photosensitive layer 31 Protective layer

Claims (9)

In an electrophotographic apparatus having a charging means for charging, an image exposure image means for performing image exposure, a developing means for performing reversal development, and a transfer means, an electrophotographic photosensitive member having a photosensitive layer on a conductive support is provided. An electrophotographic photosensitive member having a photosensitive layer containing a solvent in the layer is used, and a rate of change in capacitance after repeated fatigue of a polarity opposite to the charging polarity of the electrophotographic photosensitive member is 30% or less; An electrophotographic apparatus, wherein the electrophotographic photoreceptor has an intermediate layer, and the intermediate layer has a surface roughness Rz of 0.6 μm or more. 2. An electrophotographic apparatus according to claim 1, wherein said transfer means is in contact with said electrophotographic photosensitive member. 3. An electrophotographic apparatus according to claim 2, wherein said transfer means is a transfer belt having a belt-like form. An electrophotographic device having an electrophotographic photoreceptor having a photosensitive layer on a conductive support, a charging unit for charging, an image exposure image unit for image exposure, a developing unit for reversal development, and an electrophotographic apparatus having a transfer unit In a photographic photoreceptor, an electrophotographic photoreceptor having a photosensitive layer containing a solvent in a photosensitive layer is used, and a capacitance change rate after repeated fatigue of a polarity opposite to the charging polarity of the electrophotographic photoreceptor is reduced. 30% or less, and the electrophotographic photosensitive member has an intermediate layer, and the intermediate layer has a surface roughness Rz of 0.6 μm or more. The electrophotographic photosensitive member according to claim 4, wherein the electrophotographic photosensitive member has a surface protective layer. The electrophotographic photosensitive member according to claim 5, wherein the surface protective layer of the electrophotographic photosensitive member contains at least conductive fine particles. The electrophotographic photoreceptor according to claim 6, wherein the surface protective layer of the electrophotographic photoreceptor contains at least fluorine atom-containing resin fine particles. The electrophotographic photoconductor according to claim 4, wherein the electrophotographic photoconductor contains a phthalocyanine pigment. The phthalocyanine contained in the electrophotographic photoreceptor is a titanyl phthalocyanine having a Bragg angle 2θ diffraction peak at 27.2 ± 0.2 ° with respect to at least the characteristic X-ray (wavelength 1.514 °) of CuKα. The electrophotographic photosensitive member according to claim 8, wherein

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