JP2019060928A - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

To provide an electrophotographic photoreceptor that prevents an increase in residual potential.SOLUTION: An electrophotographic photoreceptor comprises: a conductive substrate; an undercoat layer that is provided on the conductive substrate, the undercoat layer containing an electron transport material and silica particles, where the content of the silica particles is 30 mass% or more; and a photosensitive layer that is provided on the undercoat layer.SELECTED DRAWING: None

Description

  The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an image forming apparatus.

  Conventionally, as an electrophotographic image forming apparatus, processes such as charging, electrostatic latent image formation, development, transfer and cleaning are sequentially performed using an electrophotographic photosensitive member (hereinafter sometimes referred to as "photosensitive member"). The devices to perform are widely known.

  As an electrophotographic photosensitive member, a functionally separated photosensitive member in which a charge generation layer generating charges and a charge transport layer transporting charges are laminated on a conductive substrate such as aluminum, or a charge is generated. Single-layer type photoreceptors in which the same layer performs the function and the function of transporting charges are known.

For example, Patent Document 1 shows an electrophotographic photosensitive member having a support, an undercoat layer, and a photosensitive layer in this order, the undercoat layer comprising a crosslinking agent and a compound represented by a specific formula. An electrophotographic photosensitive member containing a polymer of a composition containing the same is disclosed.
Patent Document 2 discloses an electrophotographic photosensitive member having a support, an undercoat layer formed on the support, and a photosensitive layer formed on the undercoat layer, the undercoat layer having a specific formula And a resin having a repeating structural unit represented by a specific formula, and a hydroxy group, a thiol group, an amino group, a carboxyl group and a methoxy group. There is disclosed an electrophotographic photosensitive member containing a polymer of a composition containing an electron transporting material having at least one substituent selected from the group.

Further, Patent Document 3 discloses an electrophotographic photosensitive member in which an undercoat layer, a carrier generation layer, and a carrier transport layer are sequentially laminated on a conductive support or a substrate made of an insulating support and a conductive film. There is disclosed an electrophotographic photoreceptor using SiO ₂ as the undercoat layer in the body.
Patent Document 4 discloses a support, an undercoat layer formed on the support, a charge generation layer formed directly on the undercoat layer, and a hole transport layer formed on the charge generation layer. An electrophotographic photosensitive member, wherein the undercoat layer contains an electron transporting material having a polar group selected from the group consisting of a hydroxy group, a thiol group, an amino group, a carboxy group, and a methoxy group, and a crosslinking agent Polymer and a silica particle, and the content of the electron transport material in the composition is 30% by mass or more and 70% by mass or less based on the total mass of the composition, and the content of the silica particle There is disclosed an electrophotographic photosensitive member whose amount is 1% by mass or more and 30% by mass or less with respect to the total mass of the electron transporting material.
According to Patent Document 5, in an electrophotographic photosensitive member having a photosensitive layer via an intermediate layer on a conductive support, the intermediate layer is coated with silica on alkoxymethylated nylon and copolymerized nylon and then coated with alumina. An electrophotographic photosensitive member, which comprises 30 to 75% by weight of two-layer-coated titanium oxide particles dispersed with respect to the total weight of the intermediate layer, and a weight ratio of alumina to silica of 3: 7 to 8: 2. It is disclosed.

JP, 2016-085458, A JP, 2014-029480, A JP 06-043681 A JP, 2016-138931, A Unexamined-Japanese-Patent No. 09-152731 gazette

  In the electrophotographic photosensitive member, an undercoat layer may be provided between the conductive substrate and the photosensitive layer using, for example, an organic material such as a resin in order to improve the image quality. The residual potential of the electrophotographic photosensitive member provided with the undercoating layer may increase due to the accumulation of charges in the undercoating layer during repeated use.

  Therefore, an object of the present invention is to provide an electrophotographic photosensitive member having an undercoating layer, which suppresses an increase in residual potential as compared with the case where the amount of silica particles contained in the undercoating layer is less than 30% by mass. It is to provide.

  The above-mentioned subject is solved by the following means.

The invention according to claim 1 is
A conductive substrate,
An undercoating layer provided on the conductive substrate, which contains an electron transporting material and silica particles, and the content of the silica particles is 30% by mass or more;
A photosensitive layer provided on the undercoat layer;
An electrophotographic photosensitive member having

The invention according to claim 2 is
The electrophotographic photosensitive member according to claim 1, wherein the content of the electron transport material is 15% by mass or more with respect to the entire undercoat layer.
The invention according to claim 3 is
The electrophotographic photosensitive member according to claim 2, wherein the content of the electron transport material is 30% by mass or more with respect to the entire undercoat layer.

The invention according to claim 4 is
The electrophotographic photosensitive member according to any one of claims 1 to 3, wherein a volume average particle diameter of the silica particles is 20 nm or more and 200 nm or less.
The invention according to claim 5 is
The electrophotographic photosensitive member according to claim 4, wherein the volume average particle diameter of the silica particles is 20 nm or more and 60 nm or less.
The invention according to claim 6 is
The electrophotographic photosensitive member according to any one of claims 1 to 5, wherein a condensation ratio of the silica particles is 80% or more.
The invention according to claim 7 is
The electrophotographic photosensitive member according to claim 6, wherein a condensation ratio of the silica particles is 90% or more.
The invention according to claim 8 is
The electrophotographic photosensitive member according to claim 6 or 7, wherein the silica particle is a silica particle having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group on the surface of the silica particle.

The invention according to claim 9 is
The electrophotographic photosensitive member according to any one of claims 1 to 8, wherein a layer in contact with the undercoat layer among the photosensitive layers is a layer containing a gallium phthalocyanine pigment.
The invention according to claim 10 is
The electrophotographic photosensitive member according to claim 9, wherein the gallium phthalocyanine pigment is at least one selected from a hydroxygallium phthalocyanine pigment and a chlorogallium phthalocyanine pigment.

The invention according to claim 11 is
The electrophotographic photosensitive member according to any one of claims 1 to 10, further comprising an intermediate layer between the conductive substrate and the undercoat layer.

The invention according to claim 12 is
An electrophotographic photosensitive member according to any one of claims 1 to 11.
Process cartridge to be attached to and removed from the image forming apparatus.
The invention according to claim 13 is
An electrophotographic photosensitive member according to any one of claims 1 to 11.
Charging means for charging the surface of the electrophotographic photosensitive member;
Electrostatic latent image forming means for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member charged;
Developing means for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
A transfer unit that transfers the toner image to the surface of a recording medium;
An image forming apparatus comprising:

According to the invention as set forth in claim 1, in the electrophotographic photosensitive member having the undercoat layer, the electrophotography in which the increase in residual potential is suppressed as compared with the case where the silica particles contained in the undercoat layer is less than 30% by mass. A photoreceptor is provided.
According to the invention as set forth in claims 2 and 3, an electrophotographic photosensitive member in which an increase in residual potential is suppressed as compared with the case where the content of the electron transport material is less than 15% by mass with respect to the entire undercoat layer. Provided.

According to the inventions of claims 4 and 5, an electrophotographic photosensitive member is provided which suppresses the increase in residual potential as compared with the case where the volume average particle diameter of the silica particles exceeds 200 nm.
According to the inventions of claims 6 and 7, an electrophotographic photosensitive member is provided in which an increase in residual potential is suppressed as compared to the case where the condensation ratio of silica particles is less than 80%.
According to the invention of claim 8, the silica particles have a trimethylsilyl group, a decylsilyl group or a phenylsilyl group on the surface of the silica particles, as compared to the case where the silica particles contained in the undercoat layer is less than 30% by mass. Provided is an electrophotographic photosensitive member which is a silica particle and in which an increase in residual potential is suppressed.

According to the invention as claimed in claims 9 and 10, the photosensitive layer in contact with the undercoating layer contains a gallium phthalocyanine pigment and the residual potential is increased, as compared with the case where the silica particles contained in the undercoating layer is less than 30% by mass. There is provided an electrophotographic photosensitive member in which
According to the invention of claim 11, compared with the case where the amount of silica particles contained in the undercoat layer is less than 30% by mass, an intermediate layer is provided between the conductive substrate and the undercoat layer, and the residual potential is obtained. An electrophotographic photosensitive member is provided in which the increase of

  According to the invention as set forth in claims 12 and 13, in the electrophotographic photosensitive member having the undercoat layer, the increase in residual potential is suppressed as compared with the case where the amount of silica particles contained in the undercoat layer is less than 30% by mass. A process cartridge or an image forming apparatus provided with an electrophotographic photosensitive member is provided.

FIG. 1 is a schematic partial cross-sectional view showing an example of the configuration of an electrophotographic photosensitive member according to the present embodiment. FIG. 6 is a schematic partial cross-sectional view showing another configuration example of the electrophotographic photosensitive member according to the present embodiment. FIG. 6 is a schematic partial cross-sectional view showing another configuration example of the electrophotographic photosensitive member according to the present embodiment. FIG. 1 is a schematic configuration view showing an example of an image forming apparatus according to the present embodiment. FIG. 6 is a schematic configuration view showing another example of the image forming apparatus according to the present embodiment.

  The electrophotographic photosensitive member according to the present embodiment is a conductive substrate and an undercoat layer provided on the conductive substrate, and contains an electron transport material and silica particles, and the content of the silica particles is 30% by mass It has the undercoating layer which is the above, and the photosensitive layer provided on the undercoating layer.

In recent years, it has been required to suppress an increase in residual potential of the undercoat layer by increasing the sensitivity of the photosensitive layer and increasing the speed of the image forming apparatus provided with the electrophotographic photosensitive member.
For example, in the electrophotographic photosensitive member, an undercoat layer may be provided between the conductive substrate and the photosensitive layer using, for example, an organic material such as a resin, in order to improve the image quality. The residual potential of the electrophotographic photosensitive member provided with the undercoating layer may increase due to the accumulation of charges in the undercoating layer during repeated use. And, as the residual potential rises, the obtained image quality may be degraded. This is considered to be due to the low electron transport ability of the undercoat layer. For example, when the film thickness of the undercoat layer increases, this phenomenon tends to be noticeable.

  On the other hand, in the electrophotographic photosensitive member according to the present embodiment, the increase in residual potential is suppressed by the above configuration. The reason for this is not clear, but is presumed as follows.

  When using an electron transport material to improve the electron transport ability of the undercoat layer, it is better to increase the content of the electron transport material with respect to the entire undercoat layer. However, since there are few electron transport materials having high electron transport ability, the electron transport material has high crystallinity and polarity when trying to enhance the electron transport ability of the electron transport material. As a result, if it is attempted to increase the content of the entire undercoat layer using an electron transport material having high crystallinity and polarity, deposition of the electron transport material may make film formation of the undercoat layer difficult. .

Therefore, in the electrophotographic photosensitive member according to the present embodiment, the electron transport material and the silica particles are used in combination in the undercoat layer. It is thought that crystallization of the electron transport material is suppressed by using an electron transport material and silica particles in combination in the undercoat layer and containing 30% by mass or more of the silica particles. Therefore, it is considered that the film forming property is also secured and the electron transporting ability of the undercoat layer is improved by suppressing the crystallization even if the electron transporting material is used.
Furthermore, since the silica particles are electrically inactive, even if the content of the silica particles is increased, it is difficult to inhibit the electron transport ability. Moreover, an electron transport material adheres easily to the surface of a silica particle by using together a silica particle and an electron transport material. Therefore, it is thought that the distance of electron transport materials adhering to the surface of a silica particle becomes near by containing a silica particle 30 mass% or more. Since electrons move along the electron transport material, the close distance between the electron transport materials is advantageous for the electron transport ability. As a result of shortening the distance between the electron transporting materials, it is considered that the electron transporting ability of the undercoat layer is improved.

  From the above reasons, in the electrophotographic photosensitive member according to the present embodiment, the electron transportability of the undercoat layer is improved by the above configuration, and therefore, it is presumed that the increase in residual potential is suppressed.

Hereinafter, the electrophotographic photosensitive member according to the present embodiment will be described with reference to the drawings.
FIG. 1 is a schematic partial cross-sectional view showing an example of the layer configuration of an electrophotographic photosensitive member 7A according to the present embodiment. The electrophotographic photoreceptor 7A shown in FIG. 1 has a structure in which an intermediate layer 10, an undercoat layer 1, a charge generation layer 2, a charge transport layer 3, and a protective layer 6 are laminated in this order on a conductive substrate 4. Have. The charge generation layer 2 and the charge transport layer 3 constitute a photosensitive layer 5.
FIG. 2 is a schematic partial cross-sectional view showing an example of the layer configuration of the electrophotographic photosensitive member 7B according to the present embodiment. An electrophotographic photosensitive member 7B shown in FIG. 2 has a structure in which an intermediate layer 10, an undercoat layer 1, a charge transport layer 3, a charge generation layer 2, and a protective layer 6 are laminated in this order on a conductive substrate 4. Have. The charge generation layer 2 and the charge transport layer 3 constitute a photosensitive layer 5.
FIG. 3 is a schematic partial cross-sectional view showing an example of the layer configuration of the electrophotographic photoreceptor 7C according to the present embodiment. The electrophotographic photoreceptor 7C shown in FIG. 3 has a structure in which an intermediate layer 10, an undercoat layer 1, a photosensitive layer 5, and a protective layer 6 are laminated in this order on the conductive substrate 4. The photosensitive layer 5 constitutes a single-layered photosensitive layer 5 in which the functions of the charge generation layer 2 and the charge transport layer 3 are integrated.

  The electrophotographic photoreceptors 7A to 7C may have a layer configuration in which the intermediate layer 10 is not provided. The electrophotographic photoreceptors 7A to 7C may have a layer configuration in which the protective layer 6 is not provided.

  Further, in the electrophotographic photosensitive member according to the present embodiment, since the electron transporting ability of the undercoat layer is high, among the photosensitive layers, the layer in contact with the undercoat layer contains a charge generating material (preferably gallium phthalocyanine pigment). It is good to be a layer. As the photoreceptor of such an embodiment, for example, like the electrophotographic photoreceptor 7A shown in FIG. 1, it is preferable to be the charge generation layer 2 in contact with the undercoat layer 1. Further, as in the case of the electrophotographic photosensitive member 7C shown in FIG. 3, the photosensitive layer 5 is preferably a single layer type.

  Hereinafter, each layer of the electrophotographic photosensitive member according to the present embodiment will be described in detail. In addition, the code | symbol is abbreviate | omitted and demonstrated.

(Conductive substrate)
As the conductive substrate, for example, a metal plate containing metal (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum etc.) or alloy (stainless steel etc.), metal drum, metal belt etc. Can be mentioned. In addition, as the conductive substrate, for example, paper coated with a conductive compound (eg, conductive polymer, indium oxide etc.), metal (eg, aluminum, palladium, gold etc.) or alloy, vapor deposition or lamination, resin film, belt etc. Can also be mentioned. Here, “conductive” means that the volume resistivity is less than 10 ¹³ Ωcm.

  When the electrophotographic photosensitive member is used for a laser printer, the surface of the conductive substrate has a center line average roughness Ra of not less than 0.04 μm and not more than 0.5 μm for the purpose of suppressing interference fringes generated when irradiating a laser beam. It is preferable to be roughened below. In the case where non-interference light is used as a light source, roughening for preventing interference fringes is not particularly required, but it is more suitable for prolonging the life to suppress generation of defects due to unevenness on the surface of the conductive substrate.

  As a method of surface roughening, for example, wet honing performed by suspending an abrasive in water and spraying it onto a conductive substrate, centerless grinding in which a conductive substrate is pressed against a rotating grindstone and grinding is continuously performed , Anodizing treatment, and the like.

  As a method of roughening, conductive or semiconductive powder is dispersed in a resin without roughening the surface of the conductive substrate to form a layer on the surface of the conductive substrate, and A method of roughening with particles dispersed in a layer may also be mentioned.

  In the surface roughening treatment by anodizing, an oxide film is formed on the surface of a conductive substrate by anodizing in a electrolytic solution using a metal (for example, aluminum) conductive substrate as an anode. Examples of the electrolyte solution include a sulfuric acid solution and an oxalic acid solution. However, the porous anodic oxide film formed by anodic oxidation is chemically active as it is, easily polluted, and has a large resistance fluctuation due to the environment. Therefore, for the porous anodic oxide film, the fine pores of the oxide film are blocked by volume expansion due to hydration reaction with pressurized steam or boiling water (a metal salt such as nickel may be added), and more stable hydrated oxidation It is preferable to carry out the sealing process which changes into a thing.

  The thickness of the anodic oxide film is preferably, for example, 0.3 μm or more and 15 μm or less. When the film thickness is in the above range, the barrier property against injection tends to be exhibited, and the increase in residual potential due to repeated use tends to be suppressed.

The conductive substrate may be treated with an acid treatment liquid or boehmite treatment.
The treatment with the acid treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid and hydrofluoric acid is prepared. The blending ratio of phosphoric acid, chromic acid and hydrofluoric acid in the acid treatment solution is, for example, 10% by mass to 11% by mass of phosphoric acid, 3% by mass to 5% by mass of chromic acid, and hydrofluoric acid The total concentration of these acids is preferably in the range of 13.5 mass% to 18 mass% in the range of 0.5 mass% to 2 mass%. The processing temperature is preferably, for example, 42 ° C. or more and 48 ° C. or less. The film thickness of the film is preferably 0.3 μm or more and 15 μm or less.

  The boehmite treatment is performed, for example, by immersing in pure water of 90 ° C. to 100 ° C. for 5 minutes to 60 minutes, or by bringing the substrate into contact with heated steam of 90 ° C. to 120 ° C. for 5 minutes to 60 minutes. The film thickness of the film is preferably 0.1 μm to 5 μm. This is further anodized using an electrolyte solution with low film solubility such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, citrate and the like. Good.

(Intermediate layer)
In the electrophotographic photosensitive member according to the present embodiment, an intermediate layer may be further provided between the conductive substrate and an undercoat layer described later. That is, the electrophotographic photosensitive member according to the present embodiment may have a conductive substrate, an intermediate layer provided between the conductive substrate and the undercoat layer, an undercoat layer, and a photosensitive layer. . The configuration in which the intermediate layer is provided is preferable in terms of suppressing an increase in residual potential.

The intermediate layer is, for example, a layer containing a binder resin, and at least one conductive substance selected from metal oxide particles and carbon black.
In the present specification, conductivity means that the volume resistivity at 20 ° C. is 10 ¹⁴ Ωcm or less.

  Examples of metal oxide particles include zinc oxide, lead white, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, tin-doped indium oxide, antimony And particles of tin oxide doped with tantalum. Among these, titanium oxide particles and zinc oxide particles are preferable. In particular, titanium oxide particles are hardly absorbed to visible light and near infrared light, and are white, and thus are preferable from the viewpoint of preventing interference fringes and high sensitivity. Further, two or more types of metal oxide particles may be selected from the above metal oxide particles and used in combination. Examples of crystal forms of titanium oxide include rutile type, anatase type, brookite type, and amorphous type, and any crystal form may be used. Further, titanium oxide particles of needle crystals or granular crystals may also be used. More preferably, they are particles of rutile type titanium oxide crystals.

  The metal oxide particles may be subjected to surface treatment. The metal oxide particles may be used as a mixture of two or more particles having different surface treatments or particles having different particle sizes.

  As a surface treating agent, a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, surfactant etc. are mentioned, for example. In particular, a silane coupling agent is preferable, and a silane coupling agent having an amino group is more preferable.

  As a silane coupling agent having an amino group, for example, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-amino Examples include, but are not limited to, propylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, and the like.

  You may use a silane coupling agent in mixture of 2 or more types. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Other silane coupling agents include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glylic Cidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- ( Aminoethyl) -3-aminopropylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, etc., but is limited thereto It is not a thing.

  The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

  The processing amount of the surface treatment agent is preferably, for example, 0.5% by mass or more and 10% by mass or less with respect to the metal oxide particles.

  0.03 micrometer or more and 1.0 micrometer or less are preferable, and, as for the number average primary particle diameter of metal oxide particle | grains, 0.1 micrometer or more and 0.5 micrometer or less are more preferable. It is preferable that content of a metal oxide particle is 50 to 75 mass% with respect to the total mass of an intermediate | middle layer, and it is more preferable that it is 60 to 75 mass%.

  Carbon black is not particularly limited. As carbon black, for example, Mitsubishi Chemical's # 2300 (pH 8.0, volatile content 2.0%), # 980 (pH 7.5, volatile content 1.5%), # 850 (pH 8.0) Volatile content 1.5%), # 52 (pH 8.0, volatile content 0.8%), # 45 (pH 8.0, volatile content 1.1%), # 30 (pH 8.0, volatile content 0. 6%), # 95 (pH 8.0, volatile matter 0.7%). Alternatively, oxidized carbon black in which an oxygen-containing functional group (such as a carboxyl group, a quinone group, a lactone group, or a hydroxyl group) is formed on the surface of carbon black by oxidation treatment can also be used. Oxidized carbon black is an air oxidation method in which carbon black is brought into contact with air in a high temperature atmosphere and reacted, a method in which carbon black is reacted with nitrogen oxides and ozone at normal temperature (25 ° C.), low temperature after air oxidation at high temperature It can be obtained by a method such as ozone oxidation below.

  As the binder resin contained in the intermediate layer, any known resin can be used as long as it can form a good film and can obtain the desired characteristics. For example, an acetal such as polyvinyl butyral can be used. Resin, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin And polymer resin compounds such as silicone-alkyd resin, phenol resin, phenol-formaldehyde resin, melamine resin and urethane resin. These polymer resin compounds may be used alone or in combination of two or more. Among these, at least one of an acetal resin and a polyvinyl alcohol resin is preferable as the binder resin, an acetal resin is more preferable, and polyvinyl butyral is more preferable.

The binder resin contained in the intermediate layer may be cured with blocked isocyanate.
As a blocked isocyanate to be cured with a binder resin, an isocyanate to which a known blocking agent such as phenol, alcohol, dimethyl malonate, ethyl acetoacetate, dimethylpyrazole, MEK (methyl ethyl ketone) oxime, or ε-caprolactam is added is used. . Further, the isocyanate to which the blocking agent is added is not particularly limited. Examples thereof include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and dimers, trimers and the like of these.

  Among these, hexamethylene diisocyanate to which MEK oxime is added as a blocking agent is preferable because the boiling point of the blocking agent is low and it is difficult to remain in the cured film. Specific examples of the blocked isocyanate include, for example, Sumidur BL3175 (manufactured by Sumitomo Bavaria Urethane Co., Ltd.) and the like.

  Preferred embodiments of the intermediate layer include, for example, an intermediate layer including at least one binder resin of an acetal resin and a polyvinyl alcohol resin, and conductive particles of at least one of carbon black and metal oxide particles. The binder resin is at least one of an acetal resin and a polyvinyl alcohol resin, and may be a cured product (that is, a urethane resin) cured with a blocked isocyanate.

The volume resistivity of the intermediate layer is preferably 10 ⁹ Ω · cm or less, and preferably 10 ⁷ Ω · cm or less. The lower limit of the volume resistivity of the intermediate layer is preferably 10 ² Ω · cm or more.

  The formation of the intermediate layer is not particularly limited, and a known formation method is used. For example, a coating film of an intermediate layer forming coating solution in which the above components are added to a solvent is formed, and the coating film is dried and heated as necessary.

The solvent for preparing the coating solution for forming the intermediate layer is selected from known organic solvents such as alcohols, aromatics, halogenated hydrocarbons, ketones, ketone alcohols, ethers, esters and the like. . As the solvent, for example, methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, Common organic solvents such as dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like can be used.
Moreover, you may use the solvent used for these dispersion | distribution individually or in mixture of 2 or more types.

  Examples of the dispersion method for preparing the coating solution for forming an intermediate layer include known methods such as a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill and a paint shaker.

  As a coating method of the coating liquid for forming an intermediate layer, even if a usual method such as blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method or curtain coating method is used. Good.

  The thickness of the intermediate layer is preferably 1 μm or more, preferably 1 μm to 50 μm, more preferably 3 μm to 30 μm, and still more preferably 3 μm to 20 μm. When the intermediate layer is provided, if the film thickness of the intermediate layer is 1 μm or more and 50 μm or less, the rise of the residual potential is suppressed, and it is possible to prevent the leak due to the unevenness of the substrate or the penetration of foreign matter.

(Sublayer)
The undercoat layer contains an electron transport material and silica particles, and the content of the silica particles is 30% by mass or more with respect to the entire undercoat layer. By containing the electron transporting material and the silica particles of 30% by mass or more in the undercoat layer, the increase in residual potential is suppressed.
In the electrophotographic photosensitive member according to the present embodiment, when the undercoat layer contains an electron transporting material and 30% by mass or more of silica particles, when the photosensitive member receives an impact such as falling, It also has the advantage that the occurrence of peeling between the conductive substrate and the undercoat layer (intermediate layer and undercoat layer if there is an intermediate layer) is suppressed. The reason for this is that, for example, silica particles are more flexible than metal oxides (eg, titanium oxide, zinc oxide, etc.), so the occurrence of peeling is suppressed even when the content of silica particles is 30% by mass or more. It is conceivable that In addition, the adhesive strength is considered to be improved by increasing the amount of the binder resin as compared with the case where the metal oxide is contained in a large amount (for example, 60% by mass or more).

-Electron transport material-
Specific examples of the electron transport material include quinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone derivatives, fluorenone derivatives, dinitroanthracene derivatives, dinitroacridine derivatives, nitroanthraaraquinone derivatives, Examples thereof include dinitroanthraquinone derivatives, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride and the like. These electron transport materials may be used alone or in combination of two or more.
As an electron transport material, the electron transport material shown by following Structural formula (ET-A)-(ET-I) as a specific structure is mentioned, for example.

  Among these, the electron transporting material represented by the general formula (I) including the structural formula (ET-F) is preferable.

In the general formula (1), R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, or Indicates an aralkyl group. R ¹⁸ represents an alkyl group.

In the general formula ^(1), the halogen atom represented by R 11 ^{to R 17,} for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the alkyl group represented by R ^{11 to} R ¹⁷ in the general formula (1) include linear or branched alkyl groups having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms), Specifically, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and the like can be mentioned.

Examples of the alkoxy group represented by R ^{11 to} R ¹⁷ in the general formula (1) include an alkoxy group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms), and specific examples thereof include a methoxy group, Examples include ethoxy, propoxy and butoxy.

In the general formula ^(1), the aryl group represented by R 11 ^{to R 17,} for example, a phenyl group, a tolyl group and the like. Among ^them, the aryl group represented by R 11 ^{to R 17,} a phenyl group is preferable.

Examples of the aralkyl group represented by R ^{11 to} R ¹⁷ in the general formula (1) include a benzyl group, a phenethyl group and a phenylpropyl group.

Examples of the alkyl group represented by R ¹⁸ in the general formula (1) include a linear or branched alkyl group, and a linear alkyl group having 5 to 10 carbon atoms is preferable. Specifically, for example, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group and n-decyl group can be mentioned.

  Hereinafter, although the illustrated compound of the electron transport material of General formula (1) is shown, it is not necessarily limited to this. In addition, the following exemplary compound number is described as an exemplary compound (1-number) below. Specifically, for example, Exemplified Compound 2 is hereinafter described as “exemplified compound (1-2)”. In addition, the exemplary compound (1-2) represents the same compound as the structural formula (ET-F) described above.

  The content of the electron transport material is, for example, preferably 15% by mass or more, and preferably 30% by mass or more, based on the entire undercoat layer (solid content of the undercoat layer). The upper limit of the content of the electron transporting material is not particularly limited, but is preferably 50% by mass or less, and more preferably 45% by mass or less, based on the entire undercoating layer (solid content of the undercoating layer).

-Silica particles-
Examples of silica particles include dry silica particles and wet silica particles.
Examples of the dry silica particles include combustion method silica (fumed silica) obtained by burning a silane compound, and deflagration method silica obtained by explosively burning metal silicon powder.
Wet silica particles include wet silica particles obtained by neutralization reaction of sodium silicate and mineral acid (precipitation method silica synthesized and aggregated under alkaline conditions, gel method silica particles synthesized and aggregated under acidic conditions), and acidic silica Examples thereof include colloidal silica particles (silica sol particles) obtained by alkalization and polymerization, and sol-gel method silica particles obtained by hydrolysis of organic silane compounds (for example, alkoxysilanes).
Among these, from the viewpoint of suppressing an increase in residual potential, it is desirable to use a combustion method silica particle having a low void structure and a small number of silanol groups.

  The volume average particle size of the silica particles may be, for example, 20 nm or more and 200 nm or less. The volume average particle size of the silica particles may be 30 nm or more, or 40 nm or more. The volume average particle diameter of the silica particles may be 150 nm or less, 120 nm or less, 80 nm or less, or 60 nm or less. The volume average particle diameter of the silica particles is preferably 20 nm or more and 60 nm or less in terms of suppressing the increase in residual potential.

  This volume average particle size separates the silica particles from the layer, and 100 primary particles of the silica particles are observed with a scanning electron microscope (SEM) at a magnification of 40,000, and the image analysis of the primary particles The longest diameter and the shortest diameter are measured, and the sphere equivalent diameter is measured from this intermediate value. The 50% diameter (D50v) in the cumulative frequency of the obtained sphere equivalent diameter is determined, and this is measured as the volume average particle diameter of the silica particles.

The silica particles may be surface-treated with a hydrophobizing agent. As a result, silanol groups on the surface of the silica particles are reduced, and an increase in residual potential is easily suppressed.
The hydrophobizing agent includes well-known silane compounds such as chlorosilane, alkoxysilane, silazane and the like.
Among these, as a hydrophobization treatment agent, a silane compound having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group is preferable from the viewpoint of easily suppressing the generation of the residual potential. That is, on the surface of the silica particle, it is preferable to have a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group.
Examples of the silane compound having a trimethylsilyl group include trimethylchlorosilane, trimethylmethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane and the like.
Examples of the silane compound having a decylsilyl group include decyltrichlorosilane, decyldimethylchlorosilane, decyltrimethoxysilane and the like.
Examples of silane compounds having a phenyl group include triphenylmethoxysilane and triphenylchlorosilane.

The condensation ratio (the ratio of Si—O—Si in the bond of SiO ₄ − in the silica particles) of the hydrophobicized silica particles (hereinafter sometimes referred to as “hydrophobized silica particles”) may be, for example, The content is preferably 80% or more, 90% or more, 91% or more, or 95% or more based on silanol groups on the surface of the silica particles. When the condensation ratio of the silica particles is in the above range, silanol groups of the silica particles are reduced, and an increase in residual potential is easily suppressed.

The condensation ratio of the hydrophobizing agent indicates the ratio of silicon condensed to the total bondable site of silicon in the condensation portion detected by NMR, and is measured as follows.
First, the silica particles are separated from the layer. The separated silica particles were subjected to Si CP / MAS NMR analysis with AVANCE III 400 manufactured by Bruker to determine the peak area according to the number of substitution of SiO, and each of them was disubstituted (Si (OH) ₂ (O-Si) ₂ -), 3-substituted (Si (OH) (O- Si) 3 -), 4 -substituted _{(Si (O-Si) 4} - the value of) the Q2, Q3, Q4, condensation rate formula of hydrophobizing agent Calculated by: (Q2 × 2 + Q3 × 3 + Q4 × 4) / 4 × (Q2 + Q3 + Q4).

The volume resistivity of the silica particles is, for example, 10 ¹¹ Ω · cm or more, desirably 10 ¹² Ω · cm or more, and more desirably 10 ¹³ Ω · cm or more.
When the volume resistivity of the silica particles is in the above range, an increase in residual potential is likely to be suppressed.

The volume resistivity of the silica particles is measured as follows. The measurement environment is a temperature of 20 ° C. and a humidity of 50% RH.
First, the silica particles are separated from the layer. Then, the separated silica particles to be measured are placed on the surface of a circular jig having a 20 cm ² electrode plate to a thickness of about 1 mm or more and 3 mm or less to form a silica particle layer. The same 20 cm ² electrode plate is placed on top of this and the silica particle layer is sandwiched. In order to eliminate voids between the silica particles, a load of 4 kg is applied onto the electrode plate mounted on the silica particle layer, and then the thickness (cm) of the silica particle layer is measured. The upper and lower electrodes of the silica particle layer are connected to an electrometer and a high voltage power source generator. A high voltage is applied to both electrodes so that the electric field has a predetermined value, and the volume resistivity (Ω · cm) of the silica particles is calculated by reading the current value (A) flowing at this time. The formula for calculating the volume resistivity (Ω · cm) of the silica particles is as shown in the following formula.
In the formula, ρ is the volume resistivity (Ω · cm) of the silica particles, E is the applied voltage (V), I is the current value (A), I0 is the current value (A) at 0 V applied voltage, and L is the silica The thickness (cm) of the particle layer is respectively represented. In this evaluation, the volume resistivity at an applied voltage of 1000 V was used.
Formula: == E × 20 / (I−I0) / L

  The content of the silica particles is 30% by mass or more based on the entire undercoat layer (solid content of the undercoat layer). More than 30 mass% may be sufficient and 35 mass% or more may be sufficient. In addition, the content of the silica particles is preferably 60% by mass or less, preferably 50% by mass or less, and 45% by mass or less based on the entire undercoat layer (solid content of the undercoat layer). Good to have.

  As the silica particles, an electron transport material may be previously attached to the surface of the silica particles, and the surface may be coated with the electron transport material. Even if silica particles in which an electron transport material is previously attached to the surface are used, the rise in residual potential is suppressed. The amount of the electron transport material attached to the surface of the silica particles is not particularly limited.

  As a method of attaching an electron transport material to the surface of a silica particle, any method of a dry method and a wet method may be used. There is no particular limitation on the method of depositing the electron transport material in advance by the dry method and the wet method.

In the case where the electron transport material is attached to the surface of the silica particles by a dry method, for example, the following method may be mentioned.
A method of attaching the electron transport material to the surface of the silica particles by dropping the electron transport material dissolved directly or in an organic solvent while stirring the silica particles with a mixer with large shear force or the like and spraying it with dry air or nitrogen gas. It is. By this method, the variation of the electron transport material attached to the surface of the silica particle is suppressed.
When dripping or spraying an electron transport material, it is good to carry out at the temperature below the boiling point of the organic solvent. After dropping or spraying the electron transporting material, baking may be further performed at 100 ° C. or higher. Baking is not particularly limited as long as the temperature and time at which electrophotographic characteristics can be obtained.

  In the wet method, for example, while dispersing silica particles in a solvent by stirring, ultrasonic waves, sand mills, attritors, ball mills, etc., an electron transport material is added, stirred or dispersed, and then the solvent is removed to carry out electron transport. It is a method of adhering material to the surface of silica particles. The solvent removal method is distilled off, for example, by filtration or distillation. After solvent removal, baking may be further performed at 100 ° C. or higher. Baking is not particularly limited as long as the temperature and time at which electrophotographic characteristics can be obtained.

  In the undercoat layer, other inorganic particles may be used in addition to the above-mentioned electron transport material and silica particles.

Examples of the other inorganic particles (hereinafter, may be simply referred to as inorganic particles) include inorganic particles having a powder resistance (volume resistivity) of 10 ² Ωcm or more and 10 ¹¹ Ωcm or less.
Among these, as the inorganic particles having the above-mentioned resistance value, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles are preferable, and zinc oxide particles are particularly preferable.

The specific surface area of the inorganic particles according to the BET method is, for example, 10 m ² / g or more.
The volume average particle diameter of the inorganic particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

  The content of the inorganic particles is, for example, preferably 10% by mass to 80% by mass, and more preferably 40% by mass to 80% by mass, with respect to the binder resin.

  The inorganic particles may be subjected to surface treatment. The inorganic particles may be used as a mixture of two or more kinds of particles different in surface treatment or different in particle diameter.

  As a surface treating agent, a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, surfactant etc. are mentioned, for example. In particular, a silane coupling agent is preferable, and a silane coupling agent having an amino group is more preferable.

  As a silane coupling agent having an amino group, for example, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-amino Examples include, but are not limited to, propylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, and the like.

  You may use a silane coupling agent in mixture of 2 or more types. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Other silane coupling agents include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glylic Cidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- ( Aminoethyl) -3-aminopropylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, etc., but is limited thereto It is not a thing.

  The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

  The processing amount of the surface treatment agent is preferably, for example, 0.5% by mass or more and 10% by mass or less with respect to the inorganic particles.

Examples of the binder resin used for the undercoat layer include acetal resin (for example, polyvinyl butyral etc.), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, unsaturated polyester Resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, Well-known materials, such as a urethane resin, are mentioned.
Examples of the binder resin used for the undercoat layer also include a charge transporting resin having a charge transporting group, a conductive resin (for example, polyaniline and the like), and the like.

Among these, as the binder resin used in the undercoat layer, resins insoluble in the coating solvent of the upper layer are preferable, and in particular, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester Thermosetting resin such as resin, alkyd resin, epoxy resin; and at least one resin selected from the group consisting of polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin and polyvinyl acetal resin Resins obtained by reaction with curing agents are preferred.
When two or more of these binder resins are used in combination, the mixing ratio thereof is set as necessary.

The binder resin used in the undercoat layer may be cured with a blocked isocyanate.
As a blocked isocyanate to be cured with a binder resin, an isocyanate to which a known blocking agent such as phenol, alcohol, dimethyl malonate, ethyl acetoacetate, dimethylpyrazole, MEK (methyl ethyl ketone) oxime, or ε-caprolactam is added is used. . Further, the isocyanate to which the blocking agent is added is not particularly limited. Examples thereof include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and dimers, trimers and the like of these.

  Among these, hexamethylene diisocyanate to which MEK oxime is added as a blocking agent is preferable because the boiling point of the blocking agent is low and it is difficult to remain in the cured film. Specific examples of the blocked isocyanate include, for example, Sumidur BL3175 (manufactured by Sumitomo Bavaria Urethane Co., Ltd.) and the like.

  For example, as the binder resin cured with the blocked isocyanate, a cured product (that is, a urethane resin) obtained by curing at least one resin of an acetal resin and a polyvinyl alcohol resin with the blocked isocyanate may be used.

The undercoat layer may contain various additives to improve the electrical properties, the environmental stability, and the image quality.
Examples of the additive include known materials such as zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. The silane coupling agent is used for surface treatment of the inorganic particles as described above, but may be further added to the undercoat layer as an additive.

  As a silane coupling agent as an additive, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3- Glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- Examples include (aminoethyl) -3-aminopropylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane and the like.

  As a zirconium chelate compound, for example, zirconium butoxide, ethyl zirconium acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, Examples thereof include zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, isostearate zirconium butoxide and the like.

  Examples of titanium chelate compounds include tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt And titanium lactate, titanium lactate ethyl ester, titanium triethanolaminate, polyhydroxy titanium stearate and the like.

  Examples of the aluminum chelate compound include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, aluminum tris (ethylacetoacetate) and the like.

  These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

The undercoat layer preferably has a Vickers hardness of 35 or more.
The surface roughness (ten-point average roughness) of the undercoat layer is from 1 / (4 n) (n is the refractive index of the upper layer) to 1/2 of the exposure laser wavelength λ used for moire image suppression It is good to be adjusted.
Resin particles and the like may be added to the undercoat layer to adjust the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. In addition, the surface of the undercoat layer may be polished to adjust the surface roughness. The polishing method may, for example, be buffing, sand blasting, wet honing or grinding.

  The formation of the undercoat layer is not particularly limited, and a known formation method is used. For example, a coating film of the undercoat layer forming solution obtained by adding the above components to a solvent is formed, and the coating film is dried. And by heating if necessary.

As a solvent for preparing the coating liquid for undercoat layer formation, known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents Solvents, ester solvents and the like can be mentioned.
Specific examples of these solvents include methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, Common organic solvents such as n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like can be mentioned.

  Examples of the method of dispersing the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill and a paint shaker.

  As a method of applying the coating liquid for undercoat layer formation on a conductive substrate, for example, blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, curtain coating method Etc. can be mentioned.

  The thickness of the undercoat layer is preferably 0.1 μm or more, preferably 1.0 μm to 50 μm (preferably) in terms of suppressing the rise of the residual potential and preventing the leak due to the unevenness of the substrate or the penetration of foreign matter. Is preferably 1.5 to 25 μm, more preferably 2 to 10 μm).

(Charge generation layer)
The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. The charge generation layer may be a vapor deposition layer of a charge generation material. The deposition layer of the charge generation material is suitable when using an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

  Examples of the charge generating material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; trigonal selenium and the like. Among these,

  Among these, in order to cope with laser exposure in the near infrared region, it is preferable to use a metal phthalocyanine pigment or a metal free phthalocyanine pigment as the charge generation material. Specifically, for example, hydroxygallium phthalocyanine disclosed in JP-A-5-263007, JP-A-5-279591 and the like; chlorogallium phthalocyanine disclosed in JP-A-5-98181 and the like; JP-A-5 Dichlorotin phthalocyanine disclosed in -140472, JP-A-5-140473 and the like; and titanyl phthalocyanine disclosed in JP-A-4-189873 and the like are more preferable. Among these, gallium phthalocyanine pigments are preferable, and at least one selected from hydroxygallium phthalocyanine and chlorogallium phthalocyanine is preferable.

  On the other hand, in order to cope with laser exposure in the near ultraviolet region, as charge generating materials, condensed aromatic pigments such as dibromoanthanthrone; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; The bisazo pigment etc. which were disclosed by 2004-78147 and Unexamined-Japanese-Patent No. 2005-181992 are preferable.

  Even when using an incoherent light source such as an LED or organic EL image array having a central wavelength of light emission from 450 nm to 780 nm, the above charge generation material may be used, but from the viewpoint of resolution, the photosensitive layer is 20 μm or less When used as a thin film, the electric field strength in the photosensitive layer becomes high, and charge reduction due to charge injection from the substrate tends to cause image defects called so-called black spots. This becomes remarkable when using a charge generating material which is a p-type semiconductor such as trigonal selenium, phthalocyanine pigment or the like and tends to cause dark current.

On the other hand, when an n-type semiconductor such as a fused aromatic pigment, a perylene pigment, or an azo pigment is used as a charge generation material, it is difficult to generate a dark current, and an image defect called black point can be suppressed even in a thin film. . Examples of the n-type charge generation material include compounds (CG-1) to (CG-27) described in paragraphs [0288] to [0291] of JP 2012-155282 A, and examples thereof It is not limited.
In addition, determination of n-type is determined by the polarity of the photocurrent which flows using the time of flight method normally used, and makes what is easy to flow an electron as a carrier rather than a hole be n-type.

The binder resin used for the charge generation layer is selected from a wide range of insulating resins, and the binder resin is selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinyl anthracene, polyvinyl pyrene, polysilane and the like. You may choose.
As the binder resin, for example, polyvinyl butyral resin, polyarylate resin (polycondensate of bisphenol and aromatic divalent carboxylic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, Polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, etc. may be mentioned. Here, "insulating" means that the volume resistivity is 10 ¹³ Ωcm or more.
These binder resins may be used alone or in combination of two or more.

  The compounding ratio of the charge generating material to the binder resin is preferably in the range of 10: 1 to 1:10 by mass ratio.

  The charge generation layer may further contain known additives.

  The formation of the charge generation layer is not particularly limited, and a known formation method is used. For example, a coating film of the charge generation layer forming coating solution obtained by adding the above components to a solvent is formed, and the coating film is dried. And by heating if necessary. Note that the charge generation layer may be formed by vapor deposition of a charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a fused aromatic pigment or perylene pigment is used as the charge generation material.

  As a solvent for preparing a coating solution for forming a charge generation layer, methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, acetic acid n And -butyl, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like. These solvents are used singly or in combination of two or more.

As a method of dispersing particles (for example, charge generation material) in the coating liquid for charge generation layer formation, for example, media dispersion machines such as ball mill, vibration ball mill, attritor, sand mill, horizontal sand mill, stirring, ultrasonic dispersion machine Medialess dispersing machines such as roll mills and high pressure homogenizers are used. Examples of the high-pressure homogenizer include a collision method in which the dispersion is dispersed by causing liquid-liquid collision or liquid-wall collision in a high pressure state to disperse it, and a penetration method in which a fine flow path is dispersed by being dispersed in a high pressure state.
At the time of this dispersion, it is effective to set the average particle diameter of the charge generation material in the coating solution for forming a charge generation layer to 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.15 μm or less. .

  As a method of applying the coating liquid for charge generation layer formation on the undercoat layer (or on the intermediate layer), for example, blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating And ordinary methods such as curtain coating method.

  The film thickness of the charge generation layer is, for example, preferably in the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

(Charge transport layer)
The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may be a layer containing a polymeric charge transport material.

  As charge transport materials, quinone compounds such as p-benzoquinone, chloranil, bromanyl, anthraquinone and the like; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds Cyanovinyl compounds; electron transporting compounds such as ethylene compounds. Examples of the charge transporting material also include hole transporting compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl substituted ethylene compounds, stilbene compounds, anthracene compounds, hydrazone compounds and the like. Although these charge transport materials are used individually by 1 type or in 2 or more types, it is not limited to these.

  From the viewpoint of charge mobility, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferable as the charge transport material.

In structural formula (a-1), Ar ^T1 , Ar ^T2 and Ar ^T3 each independently represent a substituted or unsubstituted aryl group, -C ₆ H ₄ -C (R ^T4 ) = C (R ^T5 ) (R ^{T 5} ) ^T6), or _{-C 6 H 4 -CH = CH-} CH = C (R T7) shows the ^{(R T8).} R ^T4 , R ^T5 , R ^T6 , R ^T7 and R ^T8 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
As a substituent of each said group, a halogen atom, a C1-C5 alkyl group, and a C1-C5 alkoxy group are mentioned. Moreover, as a substituent of said each group, the substituted amino group substituted by the C1-C3 alkyl group is also mentioned.

In Structural Formula (a-2), ^RT91 and ^RT92 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. R ^T101 , R ^T102 , R ^T111 and R ^T112 are each independently ^substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkyl group having 1 to 2 carbon atoms A substituted amino group, a substituted or unsubstituted aryl group, -C ( ^RT12 ) = C ( ^RT13 ) ( ^RT14 ), or -CH = CH-CH = C ( ^RT15 ) ( ^RT16 ); R ^T12 , R ^T13 , R ^T14 , R ^T15 and R ^T16 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, Tn1 and Tn2 each independently represent an integer of 0 or more and 2 or less.
As a substituent of each said group, a halogen atom, a C1-C5 alkyl group, and a C1-C5 alkoxy group are mentioned. Moreover, as a substituent of said each group, the substituted amino group substituted by the C1-C3 alkyl group is also mentioned.

Here, among the triarylamine derivative represented by the structural formula (a-1) and the benzidine derivative represented by the structural formula (a-2), in particular, “—C ₆ H ₄ —CH = CH—CH = Triarylamine derivatives having C (R ^T7 ) (R ^T8 ), and benzidine derivatives having “—CH = CH—CH = C (R ^T15 ) (R ^T16 )” are preferred in view of charge mobility.

  As the polymer charge transport material, known materials having charge transportability such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester type polymer charge transport materials disclosed in JP-A-8-176293 and JP-A-8-208820 are particularly preferable. The polymer charge transport material may be used alone or in combination with a binder resin.

The binder resin used for the charge transport layer is polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, Vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N -Vinylcarbazole, polysilane and the like can be mentioned. Among these, polycarbonate resin or polyarylate resin is suitable as the binder resin. These binder resins may be used alone or in combination of two or more.
The compounding ratio of the charge transport material to the binder resin is preferably 10: 1 to 1: 5 in mass ratio.

  The charge transport layer may further contain known additives.

  The formation of the charge transport layer is not particularly limited, and a known formation method is used. For example, a coating film of a charge transport layer forming solution obtained by adding the above components to a solvent is formed, and the coating film is dried. Perform by heating if necessary.

  As a solvent for preparing a coating liquid for charge transport layer formation, aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene; ketones such as acetone and 2-butanone; methylene chloride, chloroform, ethylene chloride and the like Commonly used organic solvents such as halogenated aliphatic hydrocarbons; cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents are used alone or in combination of two or more.

  As a coating method at the time of coating the coating liquid for charge transport layer formation on the charge generation layer, blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, curtain A usual method such as a coating method may be mentioned.

  The thickness of the charge transport layer is, for example, preferably in the range of 5 μm to 50 μm, and more preferably in the range of 10 μm to 30 μm.

(Protective layer)
A protective layer is provided on the photosensitive layer as needed. The protective layer is provided, for example, for the purpose of preventing chemical change of the photosensitive layer during charging or further improving the mechanical strength of the photosensitive layer.
Therefore, as the protective layer, a layer formed of a cured film (crosslinked film) may be applied. Examples of these layers include the layers shown in the following 1) or 2).

1) A layer composed of a cured film of a composition containing a reactive group-containing charge transporting material having a reactive group and a charge transporting skeleton in the same molecule (that is, a polymer or a crosslink of the reactive group-containing charge transporting material Layer containing the body)
2) A layer composed of a cured film of a composition including a non-reactive charge transport material and a reactive group-containing non-charge transport material having no charge transport skeleton and having a reactive group (that is, A layer comprising a non-reactive charge transport material and a polymer or cross-linked product of the reactive group-containing non-charge transport material

As a reactive group of the reactive group-containing charge transporting material, a chain polymerizable group, an epoxy group, -OH, -OR (wherein R represents an alkyl group), -NH ₂ , -SH, -COOH, -SiR ^{Q 1} _3- ^Q _n (OR ^{Q 2} ) ^Q _n [wherein, R ^Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, and R ^Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. Qn represents an integer of 1 to 3] and the like.

  The chain polymerizable group is not particularly limited as long as it is a radically polymerizable functional group, and is, for example, a functional group having a group containing at least a carbon double bond. Specifically, a group containing at least one selected from vinyl group, vinyl ether group, vinyl thioether group, styryl group (phenyl vinyl group), vinyl phenyl group, acryloyl group, methacryloyl group, and derivatives thereof, etc. It can be mentioned. Among them, at least one selected from a vinyl group, a styryl group (phenyl vinyl group), a vinyl phenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof as the chain polymerizable group because of its excellent reactivity. It is preferable that it is the group containing.

  The charge transporting skeleton of the reactive group-containing charge transporting material is not particularly limited as long as it has a known structure in an electrophotographic photosensitive member, and, for example, triarylamine compounds, benzidine compounds, hydrazone compounds, etc. And a structure derived from the nitrogen-containing hole-transporting compound of the above, which is conjugated to a nitrogen atom. Among these, a triarylamine skeleton is preferable.

  The reactive group-containing charge transporting material having the reactive group and the charge transporting skeleton, the nonreactive charge transporting material, and the reactive group-containing non-charge transporting material may be selected from known materials.

  The protective layer may further contain known additives.

  The formation of the protective layer is not particularly limited, and a known formation method is used. For example, a coating film of a coating solution for forming a protective layer obtained by adding the above components to a solvent is formed, and the coating film is dried. It is carried out by curing treatment such as heating if necessary.

As a solvent for preparing a coating solution for forming a protective layer, aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; tetrahydrofuran And ether solvents such as dioxane; cellosolv solvents such as ethylene glycol monomethyl ether; alcohol solvents such as isopropyl alcohol and butanol. These solvents are used alone or in combination of two or more.
The coating solution for forming a protective layer may be a non-solvent coating solution.

  As a method of applying a coating solution for forming a protective layer on a photosensitive layer (for example, charge transport layer), dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating The usual methods such as the law can be mentioned.

  The film thickness of the protective layer is, for example, preferably in the range of 1 μm to 20 μm, more preferably 2 μm to 10 μm.

(Single-layer type photosensitive layer)
The single-layer type photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material, a charge transport material, and, if necessary, a binder resin and other known additives. Note that these materials are the same as the materials described in the charge generation layer and the charge transport layer.
The content of the charge generation material in the single-layer type photosensitive layer is preferably 0.1% by mass to 10% by mass, and preferably 0.8% by mass to 5% by mass, with respect to the total solid content. . Further, the content of the charge transport material in the single-layer type photosensitive layer is preferably 5% by mass to 50% by mass with respect to the total solid content.
The method of forming the single-layer type photosensitive layer is the same as the method of forming the charge generation layer or the charge transport layer.
The film thickness of the single layer type photosensitive layer is, for example, 5 μm to 50 μm, and preferably 10 μm to 40 μm.

[Image forming apparatus (and process cartridge)]
The image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging unit that charges the surface of the electrophotographic photosensitive member, and an electrostatic latent image forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member. Developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner, thereby forming a toner image, and transfer means for transferring the toner image to the surface of the recording medium, Equipped with Then, the electrophotographic photosensitive member according to the present embodiment is applied as the electrophotographic photosensitive member.

  The image forming apparatus according to the present embodiment includes a fixing unit that fixes a toner image transferred to the surface of a recording medium; a direct transfer that directly transfers a toner image formed on the surface of an electrophotographic photosensitive member to a recording medium Type of device; primary transfer of the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the intermediate transfer member, and secondary transfer of the toner image transferred onto the surface of the intermediate transfer member to the surface of the recording medium A device of the method; a device comprising a cleaning means for cleaning the surface of the electrophotographic photosensitive member before charging after transfer of the toner image; irradiating the surface of the electrophotographic photosensitive member with charge removing light before charging after transfer of the toner image A known image forming apparatus such as an apparatus including a discharging unit for discharging electricity; an apparatus including an electrophotographic photosensitive member heating member for raising the temperature of the electrophotographic photosensitive member and reducing the relative temperature is applied.

  In the case of an intermediate transfer type apparatus, for example, an intermediate transfer member to which a toner image is transferred on the surface, and a primary transfer unit primary-transfers the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the intermediate transfer member. A configuration including the transfer unit and a secondary transfer unit for secondarily transferring the toner image transferred to the surface of the intermediate transfer member to the surface of the recording medium is applied.

  The image forming apparatus according to the present embodiment may be either a dry developing type image forming apparatus or a wet developing type (developing type using a liquid developer) image forming apparatus.

  In the image forming apparatus according to the present embodiment, for example, the portion including the electrophotographic photosensitive member may have a cartridge structure (process cartridge) which is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge provided with the electrophotographic photosensitive member according to the present embodiment is suitably used. The process cartridge may include, in addition to the electrophotographic photosensitive member, at least one selected from the group consisting of a charging unit, an electrostatic latent image forming unit, a developing unit, and a transfer unit.

  Hereinafter, although an example of the image forming apparatus according to the present embodiment is shown, the present invention is not limited to this. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

FIG. 4 is a schematic configuration view showing an example of the image forming apparatus according to the present embodiment.
The image forming apparatus 100 according to the present embodiment, as shown in FIG. 4, includes a process cartridge 300 including an electrophotographic photosensitive member 7, an exposure device 9 (an example of an electrostatic latent image forming unit), and a transfer device 40 (primary). A transfer device) and an intermediate transfer member 50 are provided. In the image forming apparatus 100, the exposure device 9 is disposed from the opening of the process cartridge 300 at a position where exposure to the electrophotographic photosensitive member 7 is possible, and the transfer device 40 is the electrophotographic photosensitive member via the intermediate transfer member 50. The intermediate transfer member 50 is disposed so as to be in contact with the electrophotographic photosensitive member 7. Although not shown, it also has a secondary transfer device for transferring the toner image transferred to the intermediate transfer member 50 to a recording medium (for example, a sheet). The intermediate transfer member 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to an example of the transfer unit.

  In the process cartridge 300 shown in FIG. 4, the electrophotographic photosensitive member 7, the charging device 8 (an example of the charging means), the developing device 11 (an example of the developing means), and the cleaning device 13 (an example of the cleaning means) In favor of The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is disposed in contact with the surface of the electrophotographic photosensitive member 7. The cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

  In FIG. 4, as an image forming apparatus, a fibrous member 132 (roll-shaped) for supplying the lubricant 14 to the surface of the electrophotographic photosensitive member 7 and a fibrous member 133 for assisting cleaning (flat brush-shaped) An example is shown, but these are arranged as needed.

  Hereinafter, each configuration of the image forming apparatus according to the present embodiment will be described.

-Charging device-
As the charging device 8, for example, a contact type charging device using a conductive or semiconductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube or the like is used. In addition, non-contact type roller chargers, scorotron chargers utilizing corona discharge, corotron chargers, etc., per se known chargers and the like are also used.

-Exposure apparatus-
Examples of the exposure device 9 include an optical system device that exposes the surface of the electrophotographic photosensitive member 7 with light such as semiconductor laser light, LED light, liquid crystal shutter light, etc. in a defined image. The wavelength of the light source is in the spectral sensitivity region of the electrophotographic photosensitive member. As the wavelength of the semiconductor laser, near infrared light having an oscillation wavelength around 780 nm is the mainstream. However, the wavelength is not limited to this, and a laser having an oscillation wavelength of 400 nm or more and 450 nm or less may be used as an oscillation wavelength laser of about 600 nm or a blue laser. In addition, a surface emitting laser light source of a type capable of outputting multiple beams is also effective for color image formation.

-Development device-
Examples of the developing device 11 include, for example, a general developing device which develops with a developer in contact or non-contact. The developing device 11 is not particularly limited as long as it has the above-described function, and is selected according to the purpose. For example, a known developing device or the like having a function of causing the one-component developer or the two-component developer to adhere to the electrophotographic photosensitive member 7 using a brush, a roller or the like can be mentioned. Among them, one using a developing roller holding a developer on the surface is preferable.

  The developer used in the developing device 11 may be a single component developer of toner alone, or may be a two component developer including toner and carrier. The developer may be magnetic or nonmagnetic. As these developers, known ones are applied.

-Cleaning device-
As the cleaning device 13, a cleaning blade type device provided with a cleaning blade 131 is used.
In addition to the cleaning blade method, a fur brush cleaning method or a development simultaneous cleaning method may be employed.

-Transfer device-
The transfer device 40 may be, for example, a contact type transfer charger using a belt, a roller, a film, a rubber blade or the like, a scorotron transfer charger using corona discharge, a corotron transfer charger, etc. It can be mentioned.

-Intermediate transfer body-
As the intermediate transfer member 50, a belt-like member (intermediate transfer belt) containing semiconductive conductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber and the like is used. The intermediate transfer member may be in the form of a drum other than the belt.

FIG. 5 is a schematic configuration view showing another example of the image forming apparatus according to the present embodiment.
An image forming apparatus 120 shown in FIG. 5 is a tandem multicolor image forming apparatus in which four process cartridges 300 are mounted. In the image forming apparatus 120, four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photosensitive member is used for one color. The image forming apparatus 120 has the same configuration as that of the image forming apparatus 100 except that the image forming apparatus 120 is a tandem system.

  Hereinafter, the present invention will be more specifically described based on examples and comparative examples, but the present invention is not limited to the following examples. In addition, unless there is particular notice, "part" shows that it is "mass part" and "%" is "mass%."

<Preparation of silica particles>
-Silica particle A-
To 100 parts by mass of silica particles "trade name: OX 50 (manufactured by Aerosil)", 30 parts by mass of 1,1,1,3,3,3-hexamethyldisilazane (manufactured by Tokyo Chemical Industry Co., Ltd.), and 50 parts by mass of toluene Was added, and the mixture was refluxed for 24 hours, and then the solid was collected by filtration and dried at 150 ° C. for 30 minutes to obtain hydrophobized silica particles. This was named silica particle A.

-Silica particle B-
The same operation as silica particle A is carried out except that 30 parts by mass of 1,1,1,3,3,3-hexamethyldisilazane (manufactured by Tokyo Chemical Industry Co., Ltd.) is changed to 10 parts by mass to make it hydrophobic Silica particles are obtained. This was named silica particle B.

-Silica particle C-
Same as silica particle A, except that 30 parts by mass of 1,1,1,3,3,3-hexamethyldisilazane (manufactured by Tokyo Chemical Industry Co., Ltd.) was changed to 10 parts by mass and the treatment temperature was changed to 40 ° C. Were carried out to obtain hydrophobized silica particles. This was named silica particle C.

-Silica particle D-
Silica particles that have been hydrophobized by the same operation as silica particle A, except that the silica particles "trade name: OX50 (manufactured by Aerosil)" are changed to "trade name: R812 (manufactured by Aerosil)" I got This was designated as silica particle D.

-Silica particle E-
Perform the same operation as silica particle A, except that the silica particle "trade name: OX50 (manufactured by Aerosil)" is changed to "trade name: X24-9163 (manufactured by Shin-Etsu Chemical Co., Ltd.)" The obtained silica particles were obtained. This was named silica particle E.

-Silica particle F-
Silica particles A, except that 1,1,1,3,3,3-hexamethyldisilazane was changed to decylsilane (decyltrimethoxysilane "trade name: KBM-3103 (manufactured by Shin-Etsu Chemical Co., Ltd.)") The same operations as in were carried out to obtain hydrophobized silica particles. This was named silica particle F.

-Silica particle G-
Silica particles except that 1,1,1,3,3,3-hexamethyldisilazane was changed to phenylsilane (phenyltriethoxysilane "trade name: KBE-103 (manufactured by Shin-Etsu Chemical Co., Ltd.)") The same operation as in A was carried out to obtain hydrophobized silica particles. This was designated as silica particle G.

-Coating of silica particle surface with electron transport material-
As an electron transporting material, 200 parts by mass of toluene is added to 30 parts by mass of the electron transporting material represented by the above-mentioned structural formula (ET-G), 30 parts by mass of silica particles A is further added, and stirring is performed at 100 ° C. for one hour did. Thereafter, the solvent was distilled off under reduced pressure to obtain silica particles coated (coated) with an electron transport material.
Similarly, according to Table 1, the type and amount of silica particles, and the type and amount of electron transport material were changed to obtain each silica particle whose surface was coated with the electron transport material.
In the surface coating column of the electron transport material in the table, "present" represents a silica particle coated in advance with the electron transport material, and "none" represents a silica particle not coated in advance with the electron transport material.

Example 1
(Formation of middle layer)
Carbon black VXC 72 (Cabot Corporation, pH 8.5, volatile content 1.5 mass%) 10 parts by mass, blocked isocyanate Semidur BL 3175 (Sumitomo Bayer Urethane Co., Ltd.) 47 parts by mass, butyral resin (Eslek BM-1, Sekisui Eighty-one parts by mass of Chemical Industries, Ltd. were mixed with 90 parts by mass of methyl ethyl ketone to obtain a mixed solution. 38 parts by mass of this mixed solution and 30 parts by mass of methyl ethyl ketone were mixed, and dispersed for 90 minutes in a sand mill using glass beads of 1 mmφ to obtain a dispersion.
To the obtained dispersion, 0.05 parts by mass of dioctyltin dilaurate as a catalyst was added to obtain a coating solution for an intermediate layer. This coating solution was dip-coated on an aluminum substrate and dried and cured at 170 ° C. for 45 minutes to obtain an intermediate layer with a thickness of 12 μm. The volume resistivity of this film was 3 × 10 ³ Ωcm.

(Formation of undercoat layer)
30 parts by mass of silica particles A coated with 30 parts by mass of the electron transport material represented by the structural formula (ET-G) described above on the surface, 15 parts by mass of blocked isocyanate semidur BL 3175 (manufactured by Sumitomo Bavaria Urethane Co., Ltd.) A mixed solution was obtained by mixing 25 parts by mass of butyral resin (S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) with 300 parts by mass of methyl ethyl ketone. The mixed solution was dispersed by a sand mill for 90 minutes using 1 mmφ glass beads to obtain a dispersion.
To the obtained dispersion, 0.07 parts by mass of dioctyltin dilaurate as a catalyst and 5 parts by mass of silicone resin particles (Tospearl 145, manufactured by Momentive Performance Materials) are added to obtain a coating liquid for forming an undercoat layer. The The coating solution was applied onto the intermediate layer by dip coating, and was dried and cured at 160 ° C. for 60 minutes to obtain a 6 μm thick undercoat layer.

(Formation of charge generation layer)
The Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using Cukα characteristic X-ray as a charge generation material is at least 7.3 °, 16.0 °, 24.9 °, 28.0 ° A mixture comprising 15 parts by mass of hydroxygallium phthalocyanine having a diffraction peak in the above, 10 parts by mass of vinyl chloride / vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar Co., Ltd.) and 200 parts by mass of n-butyl acetate as a binder resin The mixture was dispersed by stirring with a sand mill for 4 hours using glass beads having a diameter of 1 mmφ. To the obtained dispersion, 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added and stirred to obtain a coating liquid for forming a charge generation layer. The coating solution for forming a charge generation layer was dip-coated on the undercoat layer and dried at 140 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.2 μm.

(Formation of charge transport layer)
40 parts by mass of N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1 '] biphenyl-4,4'-diamine, 4- (2,2-diphenylphenyl) -4 8 parts by mass of 4′-dimethyltriphenylamine and 52 parts by mass of bisphenol Z polycarbonate resin (viscosity average molecular weight: 50,000) are added to 800 parts by mass of chlorobenzene and dissolved to obtain a coating liquid for forming a charge transport layer The coating solution was applied onto the charge generation layer and dried at 140 ° C. for 40 minutes to form a charge transport layer having a thickness of 22 μm.
Through the above steps, an electrophotographic photosensitive member of Example 1 was obtained.

[Examples 2-7, 9-11, 13-19, Comparative Examples 1-4]
Example 1 and Example 1 except that the type and amount of electron transport material used in the undercoat layer, the type and amount of silica particles, the presence or absence of the intermediate layer, and the thickness of the intermediate layer and the undercoat layer are changed according to Table 1 In the same manner, the electrophotographic photosensitive members of the respective examples were produced.

[Example 8]
An electrophotographic photosensitive member of Example 8 was produced in the same manner as Example 1, except that silica particles not coated with an electron transport material in advance were used and the following undercoat layer was provided.

(Formation of undercoat layer)
30 parts by mass of the electron transporting material represented by the structural formula (ET-F), 30 parts by mass of the silica particles A, 15 parts by mass of blocked isocyanate SMIDUR BL 3175 (manufactured by Sumitomo Bavaria Urethane Co., Ltd.) 1, 25 parts by mass of Sekisui Chemical Co., Ltd.) was mixed with 300 parts by mass of methyl ethyl ketone to obtain a mixed solution. The mixed solution was dispersed by a sand mill for 90 minutes using 1 mmφ glass beads to obtain a dispersion.
To the obtained dispersion, 0.07 parts by mass of dioctyltin dilaurate as a catalyst and 5 parts by mass of silicone resin particles (Tospearl 145, manufactured by Momentive Performance Materials) are added to obtain a coating liquid for forming an undercoat layer. The This coating solution was applied onto an aluminum substrate by a dip coating method, and dried and cured at 160 ° C. for 60 minutes to obtain a 6 μm thick undercoat layer.

[Example 12]
An electrophotographic photosensitive member of Example 12 was produced in the same manner as Example 1 except that the following undercoat layer was provided without providing the intermediate layer.

(Formation of undercoat layer)
30 parts by mass of silica particles A coated on the surface with 45 parts by mass of the electron transporting material represented by the above-mentioned structural formula (ET-G), 15 parts by mass of blocked isocyanate semidur BL3175 (manufactured by Sumitomo Bavaria Urethane Co., Ltd.) A mixed solution was obtained by mixing 25 parts by mass of butyral resin (S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) with 300 parts by mass of methyl ethyl ketone. The mixed solution was dispersed by a sand mill for 90 minutes using 1 mmφ glass beads to obtain a dispersion.
To the obtained dispersion, 0.07 parts by mass of dioctyltin dilaurate as a catalyst and 5 parts by mass of silicone resin particles (Tospearl 145, manufactured by Momentive Performance Materials) are added to obtain a coating liquid for forming an undercoat layer. The This coating solution was applied onto an aluminum substrate by a dip coating method, and was dried and cured at 160 ° C. for 60 minutes to obtain a 13 μm thick undercoat layer.

[Evaluation]
-Electrical characteristics evaluation-
Attach a photometer to the photosensitive layer, install an electrometer at the position of the development unit of Docu Print C1100 made by Fuji Xerox Co., and further modify the potential adjustment sequence, charge and expose at 10 ° C temperature and 10% humidity. The test was repeated 20000 times. The difference ΔV between the initial post exposure potential and the post exposure potential at the end of the test was evaluated.
-Evaluation criteria-
A: 10 V or less, no problem at all.
B: No problem in practical use at more than 10V and less than 20V.
C: 20 V or more and less than 30 V, but no problem if a potential adjustment sequence is inserted.
D: 30 V or more and less than 40 V, and there is a problem with color image quality.
E: Problematic level above 40V.

-Image quality evaluation-
A half-tone image of 50% image density is printed on A4 paper at 28 ° C. and 90% humidity using Docu Print C1100 manufactured by Fuji Xerox Co., Ltd. using Docu Print C1100 manufactured by Fuji Xerox Co., Ltd. The occurrence of image quality defects (black spots etc.) when printing on the entire surface at 0% density was evaluated according to the following criteria.
-Evaluation criteria-
A: There is no image quality defect.
B: When viewing with a magnifying glass, 10 or less image quality defects can be seen, but there is no problem in practical use.
C: Eleven or more image quality defects are visible when viewed with a magnifying glass, but this level can not be confirmed with the naked eye and there is no problem in practical use.
D: Even if the naked eye sees five or less image quality defects, it is a level which has a problem as color image quality.
E: 6 or more image quality defects visible to the naked eye, which is a practically problematic level.

  From the above results, it can be seen that in the present example, the increase in residual potential in the photosensitive layer is suppressed as compared to the comparative example.

  In Table 1, "-" indicates that the corresponding material is not used.

The details of the abbreviations and the like in Table 1 are as follows.
"ET-A": a compound represented by the above-mentioned structural formula (ET-A) "ET-B": a compound represented by the above-mentioned structural formula (ET-B) "ET-F": the above-mentioned Compounds represented by the structural formula (ET-F) of the formula (exemplified compound (1-2) of the electron transporting material represented by the formula (1))
-"ET-G": compound represented by the above-mentioned structural formula (ET-G) "ET-I": compound represented by the above-mentioned structural formula (ET-I)

  1 subbing layer, 2 charge generation layer, 3 charge transport layer, 4 conductive substrate, 7A, 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 10 interlayer, 11 developing device, 13 cleaning device, 14 lubrication Agent, 40 transfer device, 50 intermediate transfer member, 100 image forming device, 120 image forming device, 131 cleaning blade, 132 fibrous member (roll shape), 133 fibrous member (flat brush shape), 300 process cartridge

Claims (13)

A conductive substrate,
An undercoating layer provided on the conductive substrate, which contains an electron transporting material and silica particles, and the content of the silica particles is 30% by mass or more;
A photosensitive layer provided on the undercoat layer;
An electrophotographic photosensitive member having   The electrophotographic photosensitive member according to claim 1, wherein the content of the electron transport material is 15% by mass or more with respect to the entire undercoat layer.   The electrophotographic photosensitive member according to claim 2, wherein the content of the electron transport material is 30% by mass or more with respect to the entire undercoat layer.   The electrophotographic photosensitive member according to any one of claims 1 to 3, wherein a volume average particle diameter of the silica particles is 20 nm or more and 200 nm or less.   The electrophotographic photosensitive member according to claim 4, wherein the volume average particle diameter of the silica particles is 20 nm or more and 60 nm or less.   The electrophotographic photosensitive member according to any one of claims 1 to 5, wherein a condensation ratio of the silica particles is 80% or more.   The electrophotographic photosensitive member according to claim 6, wherein a condensation ratio of the silica particles is 90% or more.   The electrophotographic photosensitive member according to claim 6 or 7, wherein the silica particle is a silica particle having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group on the surface of the silica particle.   The electrophotographic photosensitive member according to any one of claims 1 to 8, wherein a layer in contact with the undercoat layer among the photosensitive layers is a layer containing a gallium phthalocyanine pigment.   The electrophotographic photosensitive member according to claim 9, wherein the gallium phthalocyanine pigment is at least one selected from a hydroxygallium phthalocyanine pigment and a chlorogallium phthalocyanine pigment.   The electrophotographic photosensitive member according to any one of claims 1 to 10, further comprising an intermediate layer between the conductive substrate and the undercoat layer. An electrophotographic photosensitive member according to any one of claims 1 to 11.
Process cartridge to be attached to and removed from the image forming apparatus. An electrophotographic photosensitive member according to any one of claims 1 to 11.
Charging means for charging the surface of the electrophotographic photosensitive member;
Electrostatic latent image forming means for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member charged;
Developing means for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
A transfer unit that transfers the toner image to the surface of a recording medium;
An image forming apparatus comprising: