JP2017049425A - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that suppresses a variation in surface potential after exposure due to environmental difference.SOLUTION: There is provided an electrophotographic photoreceptor comprising: a conductive substrate; and a single-layer photosensitive layer provided on the conductive substrate, the photosensitive layer containing a binder resin, at least one charge generating material selected from a hydroxygallium phthalocyanine pigment and a chlorogallium phthalocyanine pigment, a hole transport material, and an electron transport material, where a position at which the transmissivity of the photosensitive layer with respect to light at an exposure wavelength of 780 nm becomes 50% is located at a position within 25% of the thickness of the photosensitive layer from its surface.SELECTED DRAWING: None

Description

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

  In a conventional electrophotographic image forming apparatus, a toner image formed on the surface of an electrophotographic photosensitive member is transferred to a recording medium through processes of charging, electrostatic latent image formation, development, and transfer.

  For example, Patent Document 1 discloses a “single-layer electrophotographic photoreceptor containing a charge generation material, an electron transfer material having a specific structure, and a hole transfer material in a single photosensitive layer”. Has been.

  Patent Document 2 states that “in an electrophotographic photosensitive member having a photosensitive layer containing a charge generating substance and a charge transporting substance in the same layer on a conductive support, the photosensitive layer is formed with a film thickness of 5 μm. The electrophotographic photosensitive member is characterized in that the transmittance of the photosensitive layer to light having a wavelength of 780 nm is 20% or less.

JP 2003-98702 A JP 2009-162916 A

  An object of the present invention is a conductive substrate and a single-layer type photosensitive layer provided on the conductive substrate, wherein the binder resin, at least one selected from hydroxygallium phthalocyanine pigment and chlorogallium phthalocyanine pigment In an electrophotographic photosensitive member having a photosensitive layer containing a charge generating material, a hole transporting material, and an electron transporting material, the position where the transmittance of the photosensitive layer with respect to light having an exposure wavelength of 780 nm is 50% is It is to provide an electrophotographic photosensitive member in which fluctuations in surface potential after exposure due to environmental differences are suppressed as compared with the case where the film thickness exceeds 25% from the surface side.

  The above problem is solved by the following means.

The invention according to claim 1
A conductive substrate;
A monolayer type photosensitive layer provided on the conductive substrate, comprising a binder resin, at least one charge generation material selected from hydroxygallium phthalocyanine pigment and chlorogallium phthalocyanine pigment, and a hole transport material A photosensitive layer having a position at which the transmittance of the photosensitive layer with respect to light having an exposure wavelength of 780 nm is within a range of 25% from the surface side of the film thickness of the photosensitive layer, And an electrophotographic photoreceptor.

The invention according to claim 2
The electron transport material is at least one selected from the group consisting of an electron transport material represented by the following general formula (ET1) and an electron transport material represented by the following general formula (ET2),
The hole transport material is at least one selected from the group consisting of a hole transport material represented by the following general formula (HT1) and a hole transport material represented by the following general formula (HT2). The electrophotographic photosensitive member described.

(In General Formula (ET1), R ¹¹¹ and R ¹¹² each independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group, or an aralkyl group. R ¹¹³ represents an alkyl group, —L ¹¹⁴ —O -R ^115, an aryl group, or .n1 an aralkyl group, and n2 are each independently the ^{.L 114} represents an integer of 0 to 3, an alkylene ^{group, R 115} represents an alkyl group. )

(In General Formula (ET2), R ²¹¹ , R ²¹² , R ²¹³ , and R ²¹⁴ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a phenyl group.)

(In the general formula (HT1), Ar ^T1 , Ar ^T2 , and Ar ^T3 each independently represent an aryl group, or —C ₆ H ₄ —C (R ^T4 ) ═C (R ^T5 ) (R ^T6 ). R ^T4 , R ^T5 , and R ^T6 each independently represent a hydrogen atom, an alkyl group, or an aryl group, and R ^T5 and R ^T6 may combine to form a hydrocarbon ring.)

(In General Formula (HT2), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or a carbon number. 1 represents an alkoxy group having 1 to 20 carbon atoms, or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to each other to form a hydrocarbon ring structure, where n and m are each Independently represents 0, 1 or 2.)

The invention according to claim 3
The electrophotographic photosensitive member according to claim 1 or 2,
A process cartridge that can be attached to and detached from an image forming apparatus.

The invention according to claim 4
The electrophotographic photosensitive member according to claim 1 or 2,
Charging means for charging the surface of the electrophotographic photosensitive member;
An electrostatic latent image forming means for exposing the charged surface of the electrophotographic photosensitive member to form an electrostatic latent image;
Developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring the toner image to the surface of the recording medium;
An image forming apparatus comprising:

  According to the first or second aspect of the invention, there is provided a conductive substrate and a single-layer type photosensitive layer provided on the conductive substrate, comprising a binder resin, a hydroxygallium phthalocyanine pigment, and a chlorogallium phthalocyanine pigment. In an electrophotographic photoreceptor having a photosensitive layer containing at least one selected charge generating material, hole transport material, and electron transport material, the transmittance of the photosensitive layer to light having an exposure wavelength of 780 nm is 50%. Compared with the case where the position is more than 25% from the surface side of the film thickness of the photosensitive layer, there is provided an electrophotographic photoreceptor in which fluctuations in the surface potential after exposure due to environmental differences are suppressed.

  According to the invention of claim 3 or 4, a conductive substrate, a single-layer type photosensitive layer provided on the conductive substrate, comprising a binder resin, a hydroxygallium phthalocyanine pigment, and a chlorogallium phthalocyanine pigment. In an electrophotographic photoreceptor having a photosensitive layer containing at least one selected charge generating material, hole transport material, and electron transport material, the transmittance of the photosensitive layer to light having an exposure wavelength of 780 nm is 50%. Compared to the case where the position is provided with an electrophotographic photosensitive member at a position exceeding 25% from the surface side of the film thickness of the photosensitive layer, an electrophotographic photosensitive member in which fluctuations in surface potential after exposure due to environmental differences are suppressed is provided. A process cartridge or an image forming apparatus is provided.

1 is a schematic partial cross-sectional view showing an electrophotographic photosensitive member according to the present embodiment. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the image forming apparatus which concerns on other this embodiment.

  Hereinafter, an embodiment which is an example of the present invention will be described in detail.

[Electrophotographic photoreceptor]
An electrophotographic photoreceptor according to the exemplary embodiment (hereinafter also referred to as “photoreceptor”) includes a conductive substrate, and a positively charged organic photoreceptor (hereinafter, referred to as a single layer type photosensitive layer on the conductive substrate). , Sometimes referred to as a “single layer type photoreceptor”.
The single-layer type photosensitive layer (hereinafter sometimes simply referred to as “photosensitive layer”) includes a binder resin and at least one charge generating material selected from hydroxygallium phthalocyanine pigment and chlorogallium phthalocyanine pigment. The position where the transmittance with respect to light having an exposure wavelength of 780 nm is 50% is within 25% from the surface side of the film thickness of the photosensitive layer, including the hole transport material and the electron transport material.
Here, the single-layer type photosensitive layer is a photosensitive layer having hole transportability and electron transportability as well as charge generation ability.
The “position where the transmittance with respect to light having an exposure wavelength of 780 nm is 50%” indicates an average position where charges are generated in the photosensitive layer. Specifically, when the transmittance with respect to the film thickness (depth) of the entire photosensitive layer from the outermost surface side of the photosensitive layer to the conductive substrate is 100%, the position where the transmittance is 50% is defined. This is expressed as a ratio of the depth from the outermost surface side of the photosensitive layer. Hereinafter, the average position where this charge is generated will be referred to as “charge generation center of gravity”.
“Position within 25% of the thickness of the photosensitive layer from the surface side” means within 25% of the thickness (depth) of the thickness of the photosensitive layer from the outermost surface side of the photosensitive layer toward the conductive substrate. The corresponding area is shown.

Here, conventionally, as the electrophotographic photoreceptor, a single-layer photoreceptor is desirable from the viewpoint of manufacturing cost and the like.
A single-layer type photoreceptor has a structure containing a charge generation material, a hole transport material, and an electron transport material in the single layer type photosensitive layer, and the charge generation capability and the charge transport capability are within the same layer. Therefore, it is difficult to obtain stable sensitivity characteristics. In particular, when an environmental difference (for example, a difference in temperature and humidity environment) occurs, the surface potential after exposure is likely to vary.
This variation in surface potential after exposure is due to the interaction between the charge generating material and the charge transporting material (hole transporting material and electron transporting material) in the photosensitive layer, which reduces the dispersibility of the charge generating material and generates charge. This is considered to be because the material tends to aggregate and the charge generation center of gravity tends to be located far from the surface side of the film thickness of the photosensitive layer. This phenomenon is also inferred from the fact that sufficient transfer efficiency is difficult to obtain even when an electron transport material (for example, a diphenoquinone compound) having a relatively high electron mobility is included in the photosensitive layer.
Therefore, in the photoreceptor according to the exemplary embodiment, the photosensitive layer contains the binder resin, the hole transport material, the electron transport material, and the specific pigment as the charge generation material in the photosensitive layer. The position at which the transmittance for light having an exposure wavelength of 780 nm is 50% is set to a position within 25% from the surface side of the film thickness of the photosensitive layer. That is, the “charge generation center of gravity” is controlled so as to be actively present on the surface side of the film thickness of the photosensitive layer, thereby shortening the electron transport distance.
As a result, when the photosensitive member is exposed, electrons are actively generated on the surface side of the photosensitive layer, and the efficiency of movement of the generated electrons is increased.
Therefore, according to the photoconductor according to the present embodiment, fluctuations in the surface potential after exposure due to environmental differences are suppressed.

Hereinafter, the electrophotographic photoreceptor according to the exemplary embodiment will be described in detail with reference to the drawings.
FIG. 1 schematically shows a cross section of a part of an electrophotographic photosensitive member 10 according to this embodiment.
An electrophotographic photoreceptor 10 shown in FIG. 1 includes, for example, a conductive substrate 3, and an undercoat layer 1 and a single-layer type photosensitive layer 2 are provided on the conductive substrate 3 in this order.
The undercoat layer 1 is a layer provided as necessary. That is, the single-layer type photosensitive layer 2 may be provided directly on the conductive substrate 3 or may be provided via the undercoat layer 1.
Moreover, you may provide another layer as needed. Specifically, for example, a protective layer may be provided on the single-layer type photosensitive layer 2 as necessary.

  Hereinafter, each layer of the electrophotographic photoreceptor according to the exemplary embodiment will be described in detail. Note that the reference numerals are omitted.

(Conductive substrate)
Examples of the conductive substrate include metal plates (eg, aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.), metal drums, metal belts, etc. Is mentioned. In addition, as the conductive substrate, for example, paper, resin film, belt, etc. coated, vapor-deposited or laminated with a conductive compound (for example, conductive polymer, indium oxide, etc.), metal (for example, aluminum, palladium, gold, etc.) or an alloy, etc. Also mentioned. Here, “conductive” means that the volume resistivity is less than 10 ¹³ Ωcm.

  When the electrophotographic photosensitive member is used in a laser printer, the surface of the conductive substrate has a center line average roughness Ra of 0.04 μm or more and 0.5 μm for the purpose of suppressing interference fringes generated when laser light is irradiated. The surface is preferably roughened below. When non-interfering light is used as a light source, roughening for preventing interference fringes is not particularly required, but it is suitable for extending the life because it suppresses generation of defects due to irregularities on the surface of the conductive substrate.

  Examples of roughening methods include wet honing by suspending an abrasive in water and spraying the conductive substrate, centerless grinding in which the conductive substrate is pressed against a rotating grindstone, and grinding is performed continuously. And anodizing treatment.

  As a roughening method, without roughening the surface of the conductive substrate, conductive or semiconductive powder is dispersed in the resin to form a layer on the surface of the conductive substrate. The method of roughening by the particle | grains disperse | distributed in a layer is also mentioned.

  In the roughening treatment by anodic oxidation, a metal (for example, aluminum) conductive substrate is used as an anode, and an oxide film is formed on the surface of the conductive substrate by anodizing in an electrolyte solution. 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 contaminated, and has a large resistance fluctuation due to the environment. Therefore, the pores of the oxide film are blocked by the volume expansion due to the hydration reaction in pressurized water vapor or boiling water (a metal salt such as nickel may be added) against the porous anodic oxide film, and more stable hydration oxidation It is preferable to perform a sealing treatment for changing to a product.

  The thickness of the anodized film is preferably, for example, 0.3 μm or more and 15 μm or less. When this film thickness is within the above range, the barrier property against implantation 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 acidic treatment liquid or boehmite treatment.
The treatment with the acidic treatment liquid is performed as follows, for example. First, an acidic treatment liquid containing phosphoric acid, chromic acid and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid and hydrofluoric acid in the acidic treatment liquid is, for example, in the range of 10% by mass to 11% by mass of phosphoric acid, in the range of 3% by mass to 5% by mass of chromic acid, The concentration of these acids is preferably in the range of 13.5% by mass or more and 18% by mass or less. The treatment temperature is preferably 42 ° C. or higher and 48 ° C. or lower, for example. The film thickness is preferably from 0.3 μm to 15 μm.

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

(Undercoat layer)
The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

Examples of the 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 resistance value, for example, 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 by the BET method is preferably 10 m ² / g or more, for example.
The volume average particle diameter of the inorganic particles is, for example, preferably from 50 nm to 2000 nm (preferably from 60 nm to 1000 nm).

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

  The inorganic particles may be subjected to a surface treatment. Two or more inorganic particles having different surface treatments or particles having different particle diameters may be mixed and used.

  Examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, and a surfactant. In particular, a silane coupling agent is preferable, and an amino group-containing silane coupling agent is more preferable.

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

  Two or more silane coupling agents may be used in combination. For example, a silane coupling agent having an amino group and another silane coupling agent may be used in combination. Other silane coupling agents include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycol. Sidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- ( Aminoethyl) -3-aminopropylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and the like, but are not limited thereto. It is not a thing.

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

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

  Here, the undercoat layer may contain an electron-accepting compound (acceptor compound) together with the inorganic particles from the viewpoint of enhancing the long-term stability of the electric characteristics and the carrier blocking property.

Examples of the electron accepting compound include quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, and the like. 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (4-naphthyl) -1,3,4- Oxadiazole compounds such as oxadiazole and 2,5-bis (4-diethylaminophenyl) -1,3,4 oxadiazole; xanthone compounds; thiophene compounds; 3,3 ′, 5,5 ′ tetra- electron transporting substances such as diphenoquinone compounds such as t-butyldiphenoquinone;
In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure. As the compound having an anthraquinone structure, for example, a hydroxyanthraquinone compound, an aminoanthraquinone compound, an aminohydroxyanthraquinone compound, and the like are preferable, and specifically, for example, anthraquinone, alizarin, quinizarin, anthralfin, and purpurin are preferable.

  The electron-accepting compound may be dispersed and included in the undercoat layer together with the inorganic particles, or may be included in a state of being attached to the surface of the inorganic particles.

  Examples of the method for attaching the electron accepting compound to the surface of the inorganic particles include a dry method and a wet method.

  In the dry method, for example, while stirring inorganic particles with a mixer having a large shearing force or the like, an electron-accepting compound dissolved directly or in an organic solvent is dropped and sprayed with dry air or nitrogen gas. It is a method of adhering to the surface of inorganic particles. When the electron-accepting compound is dropped or sprayed, it is preferably performed at a temperature not higher than the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be performed at 100 ° C. or higher. The baking is not particularly limited as long as it is a temperature and time for obtaining electrophotographic characteristics.

  In the wet method, for example, an electron-accepting compound is added while dispersing inorganic particles in a solvent by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, etc., and after stirring or dispersing, the solvent is removed to remove electrons. This is a method of attaching a receptive compound to the surface of inorganic particles. The solvent removal method is distilled off by filtration or distillation, for example. After removing the solvent, baking may be performed at 100 ° C. or higher. The baking is not particularly limited as long as it is a temperature and time for obtaining electrophotographic characteristics. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples thereof include a method of removing while stirring and heating in a solvent, and a method of removing by azeotropic distillation with a solvent. Can be mentioned.

  The attachment of the electron-accepting compound may be performed before or after the surface treatment with the surface treatment agent is performed on the inorganic particles, or may be performed simultaneously with the attachment of the electron-accepting compound and the surface treatment with the surface treatment agent.

  The content of the electron-accepting compound is, for example, from 0.01% by mass to 20% by mass with respect to the inorganic particles, and preferably from 0.01% by mass to 10% by mass.

Examples of the binder resin used for the undercoat layer include acetal resins (eg, polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, and unsaturated polyesters. 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, Known polymer compounds such as urethane resin, alkyd resin, epoxy resin; zirconium chelate compound; titanium chelate compound; aluminum chelate compound; titanium alkoxide compound ; Organic titanium compounds; known materials silane coupling agent, and the like.
Examples of the binder resin used for the undercoat layer include a charge transport resin having a charge transport group, a conductive resin (for example, polyaniline) and the like.

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

The undercoat layer may contain various additives for improving electrical characteristics, improving environmental stability, and improving image quality.
Additives include known materials such as electron transport pigments such as polycyclic condensation systems and azo systems, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. It is done. The silane coupling agent is used for the surface treatment of the inorganic particles as described above, but may be further added to the undercoat layer as an additive.

  Examples of the silane coupling agent as the additive include 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- (Aminoethyl) -3-aminopropylmethylmethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane and the like can be mentioned.

  Examples of the zirconium chelate compound include zirconium butoxide, zirconium zirconium acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octoate, Zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, isostearate zirconium butoxide and the like.

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

  Examples of the aluminum chelate compound include aluminum isopropylate, monobutoxy aluminum diisopropylate, aluminum butyrate, diethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate) 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 / (4n) (n is the refractive index of the upper layer) of the exposure laser wavelength λ used to suppress the moire image (1/2). ) It is preferable that the adjustment is made up to λ.
Resin particles or the like may be added to the undercoat layer for adjusting the surface roughness. Examples of the resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. Further, the surface of the undercoat layer may be polished for adjusting the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, and grinding.

  There is no particular limitation on the formation of the undercoat layer, and a well-known formation method is used. For example, a coating film for forming an undercoat layer in which the above components are added to a solvent is formed, and the coating film is dried. And heating as necessary.

Solvents for preparing the coating solution for forming the undercoat layer include known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents. Examples include solvents and ester solvents.
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, Examples include ordinary organic solvents such as n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

  Examples of the dispersion method of 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 vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

  Examples of the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include, for example, a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method. The usual methods, such as these, are mentioned.

  The thickness of the undercoat layer is, for example, preferably set in the range of 15 μm or more, more preferably 20 μm or more and 50 μm or less.

(Middle layer)
Although illustration is omitted, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer.
An intermediate | middle layer is a layer containing resin, for example. Examples of the resin used for the intermediate layer include an acetal resin (for example, polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, Polymer compounds such as polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, melamine resin, and the like can be given.
The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used for the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.
The compounds used for these intermediate layers may be used alone or as a mixture or polycondensate of a plurality of compounds.

  Among these, the intermediate layer is preferably a layer containing an organometallic compound containing a zirconium atom or a silicon atom.

The formation of the intermediate layer is not particularly limited, and a well-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 necessary. It is performed by heating according to.
As the coating method for forming the intermediate layer, usual methods such as a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, and a curtain coating method are used.

  For example, the thickness of the intermediate layer is preferably set in a range of 0.1 μm to 3 μm. An intermediate layer may be used as the undercoat layer.

(Single layer type photosensitive layer)
In the present embodiment, the single-layer type photosensitive layer has a position where the transmittance of the photosensitive layer with respect to light having an exposure wavelength of 780 nm is 50% (charge generation center of gravity) is a position within 25% from the surface side of the film thickness of the photosensitive layer. Preferably within 20%, more preferably within 18%. For example, when the film thickness of the photosensitive layer is 22 μm, the charge generation center of gravity is located within 25% of the surface side of the film thickness of the photosensitive layer when the depth from the outermost surface side of the photosensitive layer toward the conductive substrate. An area within 5.5 μm (22 μm × 0.25).
By setting the charge generation center of gravity to a position within 25% from the surface side of the film thickness of the photosensitive layer, the charge generation center of gravity exists at a position close to the surface side of the film thickness of the photosensitive layer. Shorter. As a result, when the photosensitive member is exposed, electrons are actively generated on the surface side of the photosensitive layer, and the efficiency of movement of the generated electrons is increased. As a result, even when an environmental difference occurs, fluctuations in the surface potential of the photoreceptor after exposure are suppressed.

The charge generation center of gravity is measured by the following method.
First, a sample of the photosensitive layer obtained by scraping the photosensitive layer from the photoconductor to be measured is attached to a glass plate. After measuring the film thickness with SURFCOM 1400G manufactured by Tokyo Seimitsu Co., Ltd., the absorbance with respect to light having a wavelength of 780 nm is measured. The absorbance is measured using an ultraviolet-visible spectrophotometer UV2600 manufactured by Shimadzu Corporation. Next, the sample is scraped from the surface until the film thickness becomes three-quarters of the total thickness of the sample by the method of polishing the surface of the film, and the absorbance of the sample after scraping is measured by the same method as described above. . Thereafter, similarly, the operation of scraping the sample from the surface and measuring the absorbance is repeated until the film thickness becomes ½ or ¼ of the total thickness of the sample.
Then, the extinction coefficient α is obtained from the absorbance measured at each thickness according to the following formula (1), and the average value α _AVE of the extinction coefficient α is calculated. Using the calculated average value α _AVE of the extinction coefficient α according to the following formula (2), the position where the transmittance T is 50% (depth from the outermost surface of the photosensitive layer (film thickness (optical path length) L )), And the value obtained by dividing the depth from the outermost surface of the photosensitive layer by the film thickness of the entire photosensitive layer is calculated as the charge generation center of gravity.
Formula (1): Absorbance A _λ = α × L × C
(Sample concentration C (constant), extinction coefficient α, and film thickness (optical path length) L)
Formula (2): Absorbance A _λ = α × L × C = −log ₁₀ T
(Transmissivity T)

  A method for controlling the charge generation center of gravity to a position within 25% from the surface side of the film thickness of the photosensitive layer will be described later.

  The film thickness of the single-layer type photosensitive layer is preferably 15 μm or more and 40 μm or less, more preferably 18 μm or more and 30 μm or less, and even more preferably 20 μm or more, from the viewpoint of suppressing fluctuations in the surface potential of the photoreceptor after exposure due to environmental differences. The range is set to 25 μm or less.

-Binder resin-
The binder resin is not particularly limited. For example, 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 Resins, poly-N-vinylcarbazole, polysilane and the like can be mentioned. These binder resins may be used alone or in combination of two or more.
Among these binder resins, in particular, from the viewpoint of film formability of the photosensitive layer, for example, a polycarbonate resin having a viscosity average molecular weight of 30,000 to 80,000 is preferable.
The content of the binder resin with respect to the total solid content of the photosensitive layer is from 35% by mass to 60% by mass, and preferably from 20% by mass to 35% by mass.

-Charge generation material-
As the charge generation material, at least one selected from hydroxygallium phthalocyanine pigment and chlorogallium phthalocyanine pigment is applied.
As the charge generation material, these pigments may be used alone or in combination as required. The charge generating material is preferably a hydroxygallium phthalocyanine pigment from the viewpoint of suppressing fluctuations in the surface potential of the photoreceptor after exposure due to environmental differences.

  In particular, as a hydroxygallium phthalocyanine pigment, for example, in a spectral absorption spectrum in a wavelength region of 600 nm to 900 nm, a hydroxygallium phthalocyanine pigment having a maximum peak wavelength in a range of 810 nm to 839 nm can provide more excellent dispersibility. It is preferable from the viewpoint. When used as a material for an electrophotographic photosensitive member, excellent dispersibility, sufficient sensitivity, chargeability, and dark decay characteristics are easily obtained.

The hydroxygallium phthalocyanine pigment having the maximum peak wavelength in the range of 810 nm or more and 839 nm or less preferably has an average particle diameter in a specific range and a BET specific surface area in a specific range. Specifically, the average particle size is preferably 0.20 μm or less, and more preferably 0.01 μm or more and 0.15 μm or less. On the other hand, the BET specific surface area is preferably 45 m ² / g or more, more preferably 50 m ² / g or more, and particularly preferably 55 m ² / g or more and 120 m ² / g or less. The average particle size is a volume average particle size (d50 average particle size) measured by a laser diffraction / scattering particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.). Moreover, it is the value measured by the nitrogen substitution method using the BET-type specific surface area measuring device (Shimadzu Corporation make: Flow soap II2300).
Here, when the average particle diameter is larger than 0.20 μm, or when the specific surface area value is less than 45 m ² / g, the pigment particles may be coarsened or aggregates of the pigment particles may be formed. . In some cases, defects such as dispersibility, sensitivity, chargeability, and dark attenuation characteristics are likely to occur, which may cause image quality defects.

  The maximum particle size (maximum primary particle size) of the hydroxygallium phthalocyanine pigment is preferably 1.2 μm or less, more preferably 1.0 μm or less, and more preferably 0.3 μm or less. When the maximum particle size exceeds the above range, black spots tend to occur.

The hydroxygallium phthalocyanine pigment has an average particle size of 0.2 μm or less and a maximum particle size of 1.2 μm or less from the viewpoint of suppressing density unevenness due to exposure of the photoreceptor to a fluorescent lamp or the like, and The specific surface area value is preferably 45 m ² / g or more.

  The hydroxygallium phthalocyanine pigment has a Bragg angle (2θ ± 0.2 °) of at least 7.3 °, 16.0 °, 24.9 °, 28.0 ° in an X-ray diffraction spectrum using CuKα characteristic X-rays. It is preferable that it is V type which has a diffraction peak.

On the other hand, there is no particular limitation on the chlorogallium phthalocyanine pigment, but Bragg angles (2θ ± 0.2 °) of 7.4 °, 16.6 °, and 25. It is preferable to have diffraction peaks at 5 ° and 28.3 °.
The maximum peak wavelength, average particle diameter, maximum particle diameter, and specific surface area value of a suitable spectral absorption spectrum of the chlorogallium phthalocyanine pigment are the same as those of the hydroxygallium phthalocyanine pigment.

  The content of the charge generating material with respect to the total solid content of the photosensitive layer is preferably 1% by mass or more and 5% by mass or less, and preferably 1.2% by mass or more and 4.5% by mass or less.

-Hole transport material-
Although there is no restriction | limiting in particular as a hole transport material, For example, oxadiazole derivatives, such as 2, 5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole; Pyrazoline derivatives such as phenyl-pyrazoline, 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline; triphenylamine, N, N′-bis (3 Aromatic tertiary amino compounds such as 4-dimethylphenyl) biphenyl-4-amine, tri (p-methylphenyl) aminyl-4-amine, dibenzylaniline; N, N′-bis (3-methylphenyl)- Aromatic tertiary diamino compounds such as N, N'-diphenylbenzidine, 3- (4'-dimethylaminophenyl) -5,6-di- (4'-methoxyphene) 1) 1,2,4-triazine derivatives such as 1,2,4-triazine; hydrazone derivatives such as 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone; quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline Benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) benzofuran; α-stilbene derivatives such as p- (2,2-diphenylvinyl) -N, N-diphenylaniline; enamine derivatives; N -Carbazole derivatives such as ethyl carbazole; poly-N-vinyl carbazole and derivatives thereof; polymers having groups composed of the above-described compounds in the main chain or side chain; These hole transport materials may be used alone or in combination of two or more.

  Among these, from the viewpoint of charge mobility, an aromatic tertiary amino compound is preferable, and among them, a triarylamine-based hole transport material represented by the following general formula (HT1) and a general formula (HT2) Preferred is a butadiene-based hole transport material. Further, as the triarylamine-based hole transport material, a benzidine-based hole transport material represented by the following general formula (HT1a) may be used.

The triarylamine-based hole transport material (HT1) will be described.
The triarylamine-based hole transport material (HT1) is a hole transport material represented by the following general formula (HT1).

In the general formula (HT1), Ar ^T1 , Ar ^T2 , and Ar ^T3 each independently represent an aryl group or —C ₆ H ₄ —C (R ^T4 ) ═C (R ^T5 ) (R ^T6 ). R ^T4 , R ^T5 , and R ^T6 each independently represent a hydrogen atom, an alkyl group, or an aryl group. R ^T5 and R ^T6 may combine to form a hydrocarbon ring.

In the general formula (HT1), examples of the aryl group represented by Ar ^T1 , Ar ^T2 , and Ar ^T3 include an aryl group having 6 to 15 carbon atoms (preferably 6 to 9 and more preferably 6 to 8). It is done.
Specific examples of the aryl group include a phenyl group, a naphthyl group, and a fluorene group.
Among these, as the aryl group, a phenyl group is preferable.

In the general formula (HT1), the alkyl group represented by R ^T4 , R ^T5 , and R ^T6 is the same as the alkyl group represented by R ^C21 , R ^C22 , and R ^C23 in the general formula (HT1a) described later. The preferred range is also the same.

In the general formula (HT1), the aryl group represented by R ^T4 , R ^T5 , and R ^T6 is the same as the aryl group represented by Ar ^T1 , Ar ^T2 , and Ar ^T3 in the general formula (HT1). The preferable range is also the same.

Note that in the general formula (HT1), each of the substituents represented by Ar ^T1 , Ar ^T2 , and Ar ^T3 , and R ^T4 , R ^T5 , and R ^T6 further includes a group having a substituent. Examples of the substituent include a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and an aryl group having 6 to 10 carbon atoms. Examples of the substituent for each substituent include a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

  The triarylamine-based hole transport material (HT1) may be used alone or in combination of two or more.

Here, from the viewpoint of charge mobility, among the triarylamine-based hole transport materials represented by the general formula (HT1), in particular, “—C ₆ H ₄ —C (R ^T4 ) = C (R ^T5 ) ( ^Triarylamine hole transport materials having R ^T6 ) ”are preferred. Especially, the triarylamine type hole transport material shown by the specific example (HT1-4) of the triarylamine type hole transport material (HT1) mentioned later is preferable.

The benzidine hole transport material (HT1a) will be described.
The benzidine-based hole transport material (HT1a) is a hole transport material represented by the following general formula (HT1a).

In the general formula (HT1a), R ^C21 , R ^C22 , and R ^C23 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or Represents an aryl group having 6 to 10 carbon atoms.

In the general formula (HT1a), examples of the halogen atom represented by R ^C21 , R ^C22 , and R ^C23 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, as a halogen atom, a fluorine atom and a chlorine atom are preferable and a chlorine atom is more preferable.

In the general formula (HT1a), the alkyl group represented by R ^C21 , R ^C22 , and R ^C23 is a straight chain having 1 to 10 carbon atoms (preferably 1 to 6 and more preferably 1 to 4). A branched alkyl group is exemplified.
Specific examples of the linear alkyl group include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n- Nonyl group, n-decyl group, etc. are mentioned.
Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. , Isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert- A decyl group etc. are mentioned.
Among these, the alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, or an isopropyl group.

In the general formula (HT1a), the alkoxy group represented by R ^C21 , R ^C22 , and R ^C23 is a straight chain having 1 to 10 carbon atoms (preferably 1 to 6 and more preferably 1 to 4). A branched alkoxy group is mentioned.
Specific examples of the linear alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, and an n-octyloxy group. Group, n-nonyloxy group, n-decyloxy group and the like.
Specific examples of the branched alkoxy group include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec -Hexyloxy group, tert-hexyloxy group, isoheptyloxy group, sec-heptyloxy group, tert-heptyloxy group, isooctyloxy group, sec-octyloxy group, tert-octyloxy group, isononyloxy group, A sec-nonyloxy group, a tert-nonyloxy group, an isodecyloxy group, a sec-decyloxy group, a tert-decyloxy group and the like can be mentioned.
Among these, as an alkoxy group, a methoxy group is preferable.

In the general formula (HT1a), examples of the aryl group represented by R ^C21 , R ^C22 , and R ^C23 include aryl groups having 6 to 10 carbon atoms (preferably 6 to 9 or less, more preferably 6 or more and 8 or less). It is done.
Specific examples of the aryl group include a phenyl group and a naphthyl group.
Among these, as the aryl group, a phenyl group is preferable.

Note that in the general formula (HT1a), each of the substituents represented by R ^C21 , R ^C22 , and R ^C23 further includes a group having a substituent. Examples of the substituent include the atoms and groups exemplified above (for example, a halogen atom, an alkyl group, an alkoxy group, an aryl group, etc.).

  The benzidine-based hole transport material (HT1a) may be used alone or in combination of two or more.

  Specific examples (HT1-1) to (HT1-7) of the triarylamine-based hole transport material (HT1) and the benzidine-based hole transport material (HT1a) are shown below, but are not limited thereto. Absent.

The butadiene-based hole transport material (HT2) will be described.
The butadiene-based hole transport material (HT2) is a hole transport material represented by the following general formula (HT2).

In General Formula (HT2), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 carbon atom. It represents an alkoxy group having 20 or less or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure.
n and m each independently represents 0, 1 or 2.

In the general formula (HT2), examples of the halogen atom represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, as a halogen atom, a fluorine atom and a chlorine atom are preferable and a chlorine atom is more preferable.

In the general formula (HT2), the alkyl group represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 has 1 to 20 carbon atoms (preferably 1 to 6 or less, more preferably 1 4 or less), a linear or branched alkyl group.
Specific examples of the linear alkyl group include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n- Nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n- Nonadecyl group, n-icosyl group, etc. are mentioned.
Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. , Isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert- Decyl group, isoundecyl group, sec-undecyl group, tert-undecyl group, neoundecyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, neododecyl group, isotridecyl group, sec-tridecyl group, tert-tridecyl group, neotridecyl group Group, isotetradecyl group, sec-tetradecyl group, tert-tetradecyl group, neotetradecyl group, 1-isobutyl-4-ethyloctyl group, isopentadecyl group, sec-pentadecyl group, tert-pentadecyl group, neopenta Decyl group, isohexadecyl group, sec-hexadecyl group, tert-hexadecyl group, neohexadecyl group, 1-methylpentadecyl group, isoheptadecyl group, sec-heptadecyl group, tert-heptadecyl group, neoheptadecyl group, isooctadecyl group, sec-octadecyl group, tert-octadecyl group, neooctadecyl group, isonononadecyl group, sec-nonadecyl group, tert-nonadecyl group, neononadecyl group, 1-methyloctyl group, isoicosyl group, sec-icosyl group, te t- eicosyl group, Neoikoshiru group and the like.
Among these, the alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, or an isopropyl group.

In the general formula (HT2), the alkoxy group represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 has 1 to 20 carbon atoms (preferably 1 to 6 or less, more preferably 1 Or a linear or branched alkoxy group of 4 or less).
Specific examples of the linear alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, and an n-octyloxy group. Group, n-nonyloxy group, n-decyloxy group, n-undecyloxy group, n-dodecyloxy group, n-tridecyloxy group, n-tetradecyloxy group, n-pentadecyloxy group, n-hexadecyl group An oxy group, n-heptadecyloxy group, n-octadecyloxy group, n-nonadecyloxy group, n-icosyloxy group, etc. are mentioned.
Specific examples of the branched alkoxy group include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec -Hexyloxy group, tert-hexyloxy group, isoheptyloxy group, sec-heptyloxy group, tert-heptyloxy group, isooctyloxy group, sec-octyloxy group, tert-octyloxy group, isononyloxy group, sec-nonyloxy group, tert-nonyloxy group, isodecyloxy group, sec-decyloxy group, tert-decyloxy group, isoundecyloxy group, sec-undecyloxy group, tert-undecyloxy group, neoundecyloxy group , Isodo Siloxy group, sec-dodecyloxy group, tert-dodecyloxy group, neododecyloxy group, isotridecyloxy group, sec-tridecyloxy group, tert-tridecyloxy group, neotridecyloxy group, isotetradecyloxy group Group, sec-tetradecyloxy group, tert-tetradecyloxy group, neotetradecyloxy group, 1-isobutyl-4-ethyloctyloxy group, isopentadecyloxy group, sec-pentadecyloxy group, tert-pentadecyl group Oxy group, neopentadecyloxy group, isohexadecyloxy group, sec-hexadecyloxy group, tert-hexadecyloxy group, neohexadecyloxy group, 1-methylpentadecyloxy group, isoheptadecyloxy group, sec -Heptadecyloxy Group, tert-heptadecyloxy group, neoheptadecyloxy group, isooctadecyloxy group, sec-octadecyloxy group, tert-octadecyloxy group, neooctadecyloxy group, isononadecyloxy group, sec-nonadecyloxy group, tert- Examples include nonadecyloxy group, neononadecyloxy group, 1-methyloctyloxy group, isoicosyloxy group, sec-icosyloxy group, tert-icosyloxy group, neoicosyloxy group and the like.
Among these, as an alkoxy group, a methoxy group is preferable.

In the general formula (HT2), the aryl group represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 has 6 to 30 carbon atoms (preferably 6 to 20 or less, more preferably 6 And aryl groups of 16 or less).
Specific examples of the aryl group include a phenyl group, a naphthyl group, a phenanthryl group, and a biphenylyl group.
Among these, the aryl group is preferably a phenyl group or a naphthyl group.

Note that in the general formula (HT2), each of the substituents represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 further includes a group having a substituent. Examples of the substituent include the atoms and groups exemplified above (for example, a halogen atom, an alkyl group, an alkoxy group, an aryl group, etc.).

In the general formula (HT2), two adjacent substituents of R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 (for example, R ^C11 and R ^C12 , R ^C13 and R ^C14 , R R ^In the hydrocarbon ring structure in which ^C15 and R ^C16 are connected, the groups connecting the substituents are a single bond, 2,2′-methylene group, 2,2′-ethylene group, 2,2′- A vinylene group etc. are mentioned, Among these, a single bond and a 2,2'-methylene group are preferable.
Here, specific examples of the hydrocarbon ring structure include a cycloalkane structure, a cycloalkene structure, a cycloalkanepolyene structure, and the like.

  In general formula (HT2), n and m are preferably 1.

In the general formula (HT2), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are a hydrogen atom and a carbon number from the viewpoint of forming a photosensitive layer (hole transport layer) having a high hole transport capability. Represents an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms, and m and n preferably represent 1 or 2, and R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , And R ^C16 represents a hydrogen atom, and m and n preferably represent 1.
That is, the butadiene-based hole transport material (HT2) is more preferably a hole transport material (exemplary compound (HT2-3)) represented by the following structural formula (HT2a).

  Specific examples (HT2-1) to (HT2-24) of the butadiene-based hole transport material (HT2) are shown below, but are not limited thereto.

In addition, the abbreviations in the above exemplary compounds have the following meanings. Moreover, the number attached | subjected before a substituent has shown the substitution position with respect to a benzene ring.
· CH ₃ : methyl group · OCH ₃ : methoxy group

  A butadiene type hole transport material (HT2) may be used individually by 1 type, and may use 2 or more types together.

  The content of the hole transport material is, for example, 10% by mass to 98% by mass with respect to the binder resin, desirably 60% by mass to 95% by mass, and more desirably 70% by mass to 90% by mass. It is.

-Electron transport material-
Although there is no restriction | limiting in particular as an electron transport material, For example, quinone type compounds, such as chloranil and bromoanil; Tetracyanoquinodimethane type compound; 2,4,7-trinitro fluorenone, 9- dicyanomethylene-9-fluorenone- Fluorenone compounds such as octyl 4-carboxylate, 2,4,5,7-tetranitro-9-fluorenone; 2- (4-biphenyl) -5- (4-tert-butylphenyl) -1,3,4-oxa Oxadiazoles such as diazole, 2,5-bis (4-naphthyl) -1,3,4-oxadiazole, 2,5-bis (4-diethylaminophenyl) 1,3,4-oxadiazole Compound; xanthone compound; thiophene compound; dinaphthoquinone compound such as 3,3′-di-tert-pentyl-dinaphthoquinone; 3,3′-di-t diphenoquinone compounds such as rt-butyl-5,5′-dimethyldiphenoquinone, 3,3 ′, 5,5′-tetra-tert-butyl-4,4′-diphenoquinone; And polymers having a main chain or a side chain. These electron transport materials may be used alone or in combination of two or more.

  Among these, an electron transport material represented by the following general formula (ET1) and an electron transport material represented by the following general formula (ET2) are preferable.

  The electron transport material represented by the general formula (ET1) will be described.

In General Formula (ET1), R ¹¹¹ and R ¹¹² each independently represent a halogen atom, an alkyl group, an alkoxy group, an aryl group, or an aralkyl group. R ¹¹³ represents an alkyl group, —L ¹¹⁴ —O—R ¹¹⁵ , an aryl group, or an aralkyl group. n1 and n2 each independently represent an integer of 0 or more and 3 or less. L ¹¹⁴ represents an alkylene group, and R ¹¹⁵ represents an alkyl group.

In the general formula (ET1), examples of the halogen atom represented by R ¹¹¹ and R ¹¹² include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In the general formula (ET1), examples of the alkyl group represented by R ¹¹¹ and R ¹¹² include linear or branched alkyl groups having 1 to 4 (preferably 1 to 3) carbon atoms. . Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group.

In the general formula (ET1), examples of the alkoxy group represented by R ¹¹¹ and R ¹¹² include an alkoxy group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms), and specifically, a methoxy group. Ethoxy group, propoxy group, butoxy group, and the like.

In the general formula (ET1), examples of the aryl group represented by R ¹¹¹ and R ¹¹² include a phenyl group and a tolyl group.
In the general formula (ET1), examples of the aralkyl group represented by R ¹¹¹ and R ¹¹² include a benzyl group, a phenethyl group, and a phenylpropyl group.
Among these, a phenyl group is desirable.

In general formula (ET1), examples of the alkyl group represented by R ¹¹³ include a linear alkyl group having 1 to 15 carbon atoms (preferably 5 to 10 carbon atoms), and 3 to 15 carbon atoms ( A branched alkyl group having 5 to 10 carbon atoms is preferable.
Examples of the linear alkyl group having 1 to 15 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n Examples include -octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group and the like.
Examples of the branched alkyl group having 3 to 15 carbon atoms include isopropyl group,
Isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, Isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, isoundecyl group, sec-undecyl group, tert-undecyl group Group, isododecyl group, sec-dodecyl group, tert-dodecyl group, isotridecyl group, sec-tridecyl group, tert-tridecyl group, isotetradecyl group, sec-tetradecyl group, tert-tetradecyl group, isopentadecyl group, sec Pentadecyl group, tert- pentadecyl group and the like.

In the general formula (ET1), as a group represented by —L ¹¹⁴ —O—R ¹¹⁵ represented by R ¹¹³ , L ¹¹⁴ represents an alkylene group, and R ¹¹⁵ represents an alkyl group.
^Examples of the alkylene group represented by L ¹¹⁴ include linear or branched alkylene groups having 1 to 12 carbon atoms, and include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, and an isobutylene. Group, sec-butylene group, tert-butylene group, n-pentylene group, isopentylene group, neopentylene group, tert-pentylene group and the like.
Examples of the alkyl group represented by R ¹¹⁵ include the same groups as the alkyl groups represented by R ¹¹¹ and R ¹¹² .

In the general formula (ET1), examples of the aryl group represented by R ¹¹³ include a phenyl group, a methylphenyl group, and a dimethylphenyl group.
In general formula (ET1), when R ¹¹³ is an aryl group, the aryl group is preferably further substituted with an alkyl group from the viewpoint of solubility. Examples of the alkyl group substituted by the aryl group include the same groups as the alkyl groups represented by R ¹¹¹ and R ¹¹² . Furthermore, specific examples of the aryl group further substituted with an alkyl group include an ethylphenyl group in addition to the above methylphenyl group and dimethylphenyl group.

In the general formula (ET1), examples of the aralkyl group represented by R ¹¹³ include a group represented by -R ¹¹⁶ -Ar. However, ^R116 shows an alkylene group and Ar shows an aryl group.
^Examples of the alkylene group represented by R ¹¹⁶ include linear or branched alkylene groups having 1 to 12 carbon atoms, and include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, and an isobutylene. Group, sec-butylene group, tert-butylene group, n-pentylene group, isopentylene group, neopentylene group, tert-pentylene group and the like.
Examples of the aryl group represented by Ar include a phenyl group, a methylphenyl group, an ethylphenyl group, and a dimethylphenyl group.

In the general formula (ET1), specific examples of the aralkyl group represented by R ¹¹³ include benzyl group, methylbenzyl group, dimethylbenzyl group, phenylethyl group, methylphenylethyl group, ethylphenylethyl group, phenylpropyl group, phenylbutyl. Groups and the like.

As an electron transport material represented by the general formula (ET1), from the viewpoint of increasing sensitivity, an electron transport material exhibiting an aralkyl group represented by R ¹¹³ or a branched alkyl group having 5 to 10 carbon atoms is particularly preferable. Preferably, an electron transport material in which R ¹¹¹ and R ¹¹² each independently represents a halogen atom or an alkyl group, and R ¹¹³ represents an aralkyl group or a branched alkyl group having 5 to 10 carbon atoms is preferable. From the same viewpoint, —CO (═O) —R ¹¹³ is more preferably substituted at the 2-position or 4-position, and particularly preferably substituted at the 4-position.

  As the electron transport material represented by the general formula (ET1), one type may be used alone, or two or more types may be used in combination.

  Hereinafter, although the exemplary compound of the electron transport material represented by general formula (ET1) is shown, it is not necessarily limited to this. In addition, the following exemplary compound numbers are described as an exemplary compound (ET1-number) below. Specifically, for example, “Exemplary Compound (ET1-2)” is represented below.

In addition, the abbreviations in the above exemplary compounds have the following meanings.
“Number-” represents a substituent substituted at the position of the number of the fluorene ring. For example, “1-Cl” substitutes Cl (chlorine atom) at the 1-position of the fluorene ring, and 4-CO (═O) —R ¹¹³ substitutes —CO (═O) at the 4-position of the fluorene ring. -R ¹¹³ is represented respectively.
“1-3-” means that the substituent is substituted at all positions 1 to 3; “5-8-” means that the substituent is located at all positions 5 to 8; It represents that it has substituted.
“Ph” represents a phenyl group.

  The electron transport material represented by the general formula (ET2) will be described.

In General Formula (ET2), R ²¹¹ , R ²¹² , R ²¹³ , and R ²¹⁴ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a phenyl group.

In the general formula (ET2), examples of the alkyl group represented by R ^{211 to} R ²¹⁴ include a linear or branched alkyl group having 1 to 6 carbon atoms, specifically, for example, methyl Group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, hexyl group and the like.
The alkyl group represented by R ^{211 to} R ²¹⁴ may be a substituted alkyl group. Examples of the substituent of the substituted alkyl group include a cycloalkyl group and a fluorine-substituted alkyl group.

In the general formula (ET2), examples of the alkoxy group represented by R ^{211 to} R ²¹⁴ include an alkoxy group having 1 to 6 carbon atoms, specifically, a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Etc.

In the general formula (ET2), examples of the halogen atom represented by R ^{211 to} R ²¹⁴ include a chlorine atom, an iodine atom, a bromine atom, and a fluorine atom.

In general formula (ET2), the phenyl group represented by R ^{211 to} R ²¹⁴ may be a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group (for example, an alkyl group having 1 to 6 carbon atoms), an alkoxy group (for example, an alkoxy group having 1 to 6 carbon atoms), a biphenyl group, and the like.

  As the electron transport material represented by the general formula (ET2), one type may be used alone, or two or more types may be used in combination.

  Hereinafter, although the exemplary compound of the electron transport material shown by general formula (ET2) is shown, it is not necessarily limited to this. In addition, the number attached | subjected to the following exemplary compounds is described below with an exemplary compound (ET2-number). Specifically, for example, “Exemplary Compound (ET2-2)” is represented below.

  The content of the electron transport material is, for example, 4% by mass to 70% by mass with respect to the binder resin, desirably 8% by mass to 50% by mass, and more desirably 10% by mass to 30% by mass. is there.

-Mass ratio of hole transport material and electron transport material-
The ratio of the hole transport material to the electron transport material is preferably 50/50 or more and 90/10 or less, more preferably 60/40 or more and 80/20 or less in terms of mass ratio (hole transport material / electron transport material). is there.

-Other additives-
The single-layer type photosensitive layer may contain other known additives such as an antioxidant, a light stabilizer, and a heat stabilizer. Further, when the single-layer type photosensitive layer is a surface layer, it may contain fluororesin particles, silicone oil and the like.

(Formation of single-layer type photosensitive layer)
The single-layer type photosensitive layer includes a photosensitive layer component (charge generation material, hole transport material, electron transport material, binder resin, etc.), a solvent, and an additive such as a dispersion aid as necessary. It is formed using a photosensitive layer forming coating solution obtained by mixing the solutions. The photosensitive layer forming coating solution may be a solution obtained by mixing the above photosensitive layer components in a solvent at once, or a solution obtained by mixing at least one of the above photosensitive layer components in a solvent. These may be mixed.

  The photosensitive layer in this embodiment has a charge generation center of gravity at a position within 25% from the surface side of the film thickness of the photosensitive layer. In order to control the charge generation center of gravity to the position within the above range from the surface side of the film thickness of the photosensitive layer, an operation for increasing the dispersibility of the charge generation material is performed when preparing the coating solution for forming the photosensitive layer. Good. As an operation for improving the dispersibility of the charge generation material, for example, when preparing a coating solution for forming a photosensitive layer, a solution in which the charge generation material is dispersed in a solvent (hereinafter also referred to as “charge generation material dispersion solution”). ) Separately prepared and added to the coating solution for forming the photosensitive layer (preliminary mixing method of charge generation material). In order to disperse the charge generating material in the solvent, a dispersing means may be used.

Dispersing means include ball mills, vibrating ball mills, attritors, sand mills, horizontal sand mills, media dispersers, agitators, ultrasonic dispersers, roll mills, high-pressure homogenizers (impact method, penetration method, etc.), ultrasonic homogenizers, nanomizer dispersions Medialess disperser such as a machine. Among these, from the viewpoint of improving the dispersibility of the charge generating material, an ultrasonic homogenizer, a nanomizer disperser, and an ultrasonic disperser are preferable.
In order to further improve the dispersibility of the charge generation material, it is preferable to use a dispersion aid (for example, an amine compound) when preparing the charge generation material dispersion solution. Furthermore, after adding the charge generation material dispersion solution to the photosensitive layer forming coating solution, other photosensitive layer components (hole transporting material, electron transporting material, binder resin, etc.) contained in the photosensitive layer forming coating solution In addition, it is preferable to disperse the charge generation material. Examples of the dispersing means used at this time include the above-described dispersing means. From the viewpoint of further improving the dispersibility of the charge generating material, a nanomizer dispersing machine is preferable.
By the above operation, the dispersibility of the charge generating material in the photosensitive layer forming coating solution is enhanced. Therefore, it is considered that the photosensitive layer formed using this photosensitive layer forming coating solution is in a state where the charge generation material is dispersed in a nearly uniform state, and the charge generation center of gravity is likely to be present at a position close to the surface side. . This facilitates efficient generation of electrons on the surface side of the photosensitive layer, and increases the efficiency of movement of the generated electrons. As a result, even when an environmental difference occurs, fluctuations in the surface potential of the photoreceptor after exposure are suppressed.

Solvents include aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and ethylene chloride, tetrahydrofuran and ethyl ether. And usual organic solvents such as cyclic ethers and linear ethers. These solvents are used alone or in combination of two or more.

  Examples of the method for applying the photosensitive layer forming coating solution obtained by the above operation onto a conductive substrate or an undercoat layer include a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, and a blade. Examples thereof include a coating method, a knife coating method, and a curtain coating method.

(Protective layer)
The protective layer is provided on the photosensitive layer as necessary. 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, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of these layers include the layers shown in 1) or 2) below.

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

The reactive group of the reactive group-containing charge transport material includes a chain polymerizable group, an epoxy group, —OH, —OR [wherein R represents an alkyl group], —NH ₂ , —SH, —COOH, —SiR. ^Q1 _3-Qn (OR ^Q2 ) _Qn [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, and other well-known reactive groups.

  The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization. For example, it is a functional group having a group containing at least a carbon double bond. Specific examples include groups containing at least one selected from vinyl groups, vinyl ether groups, vinyl thioether groups, styryl groups (vinyl phenyl groups), acryloyl groups, methacryloyl groups, and derivatives thereof. Among these, the chain polymerizable group is a group containing at least one selected from a vinyl group, a styryl group (vinylphenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof because of its excellent reactivity. Preferably there is.

  The charge transporting skeleton of the reactive group-containing charge transporting material is not particularly limited as long as it is a known structure in an electrophotographic photoreceptor, and examples thereof include triarylamine compounds, benzidine compounds, hydrazone compounds, and the like. And a structure conjugated from a nitrogen-containing hole transporting compound and conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferable.

  The reactive group-containing charge transport material having a reactive group and a charge transport skeleton, a non-reactive charge transport material, and a reactive group-containing non-charge transport material may be selected from well-known materials.

  In addition, the protective layer may contain known additives.

  The formation of the protective layer is not particularly limited, and a well-known forming method is used. It is performed by performing a curing process such as heating as necessary.

Solvents for preparing the coating solution for forming the protective layer include 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 protective layer forming coating solution may be a solventless coating solution.

  As a method for coating the coating solution for forming the protective layer on the photosensitive layer, a normal method such as a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, a curtain coating method, etc. Is mentioned.

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

[Image forming apparatus (and process cartridge)]
The image forming apparatus according to this embodiment includes an electrophotographic photosensitive member, a charging unit that charges the surface of the electrophotographic photosensitive member, and an electrostatic that exposes the surface of the charged electrophotographic photosensitive member to form an electrostatic latent image. A latent image forming unit, a developing unit that develops an electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image, and a transfer that transfers the toner image to the surface of the recording medium Means. 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 an apparatus having fixing means for fixing a toner image transferred to the surface of a recording medium; direct transfer for directly transferring the toner image formed on the surface of the electrophotographic photosensitive member to the recording medium Type apparatus; intermediate transfer in which the toner image formed on the surface of the electrophotographic photosensitive member is primarily transferred onto the surface of the intermediate transfer member, and the toner image transferred onto the surface of the intermediate transfer member is secondarily transferred onto the surface of the recording medium. Type of apparatus; apparatus with cleaning means for cleaning the surface of the electrophotographic photosensitive member after the toner image is transferred and before charging; after the toner image is transferred, the surface of the electrophotographic photosensitive member is irradiated with a charge eliminating light before charging. A known image forming apparatus such as an apparatus provided with an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative temperature is applied.

  In the case of an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred to the surface, and a primary transfer that primarily transfers the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the intermediate transfer body. A configuration including a transfer unit and a secondary transfer unit that secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto 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).

  Note that 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) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to this embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include 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, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto. In addition, the main part shown to a figure is demonstrated and the description is abbreviate | omitted about others.

FIG. 2 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment.
As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment 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. Transfer device) and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where the electrophotographic photosensitive member 7 can be exposed from the opening of the process cartridge 300, and the transfer device 40 is interposed between the electrophotographic photosensitive member via the intermediate transfer member 50. 7, and a part of the intermediate transfer member 50 is disposed in contact with the electrophotographic photosensitive member 7. Although not shown, it also has a secondary transfer device that transfers the toner image transferred to the intermediate transfer member 50 to a recording medium (for example, paper). The intermediate transfer member 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer unit.

  A process cartridge 300 in FIG. 2 includes an electrophotographic photosensitive member 7, a charging device 8 (an example of a charging unit), a developing device 11 (an example of a developing unit), and a cleaning device 13 (an example of a cleaning unit) in a housing. I support it. The cleaning device 13 includes a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is disposed so as to contact 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. 2, as an image forming apparatus, a fibrous member 132 (roll shape) for supplying the lubricant 14 to the surface of the electrophotographic photosensitive member 7 and a fibrous member 133 (flat brush shape) for assisting in cleaning are shown. Examples are provided, but these are arranged as necessary.

  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 charger 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. Further, a non-contact type roller charger, a known charger such as a scorotron charger using a corona discharge or a corotron charger may be used.

-Exposure device-
Examples of the exposure device 9 include optical system devices that expose the surface of the electrophotographic photoreceptor 7 with light such as semiconductor laser light, LED light, and liquid crystal shutter light in a predetermined image-like manner. The wavelength of the light source is set within the spectral sensitivity region of the electrophotographic photosensitive member. As the wavelength of the semiconductor laser, near infrared having an oscillation wavelength near 780 nm is the mainstream. However, the present invention is not limited to this wavelength, and an oscillation wavelength laser in the 600 nm range or a laser having an oscillation wavelength of 400 nm to 450 nm as a blue laser may be used. In addition, a surface-emitting type laser light source that can output a multi-beam is also effective for color image formation.

-Developer-
Examples of the developing device 11 include a general developing device that performs development by bringing a developer into contact or non-contact with the developer. The developing device 11 is not particularly limited as long as it has the functions described above, and is selected according to the purpose. For example, a known developing device having a function of attaching a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, a roller, or the like can be used. Among these, those using a developing roller holding the developer on the surface are preferable.

  The developer used in the developing device 11 may be a one-component developer including a toner alone or a two-component developer including a toner and a carrier. Further, the developer may be magnetic or non-magnetic. A well-known thing is applied for these developers.

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

-Transfer device-
As the transfer device 40, for example, a contact transfer charger using a belt, a roller, a film, a rubber blade, etc., or a known transfer charger such as a scorotron transfer charger using a corona discharge or a corotron transfer charger. Can be mentioned.

-Intermediate transfer member-
As the intermediate transfer member 50, a belt-like member (intermediate transfer belt) containing polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber or the like having semiconductivity is used. Further, as the form of the intermediate transfer member, a drum-like one may be used in addition to the belt-like.

FIG. 3 is a schematic configuration diagram illustrating another example of the image forming apparatus according to the present embodiment.
An image forming apparatus 120 shown in FIG. 3 is a tandem multicolor image forming apparatus equipped with four process cartridges 300. 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 it is a tandem system.

  Hereinafter, although an embodiment explains this embodiment in detail, this embodiment is not limited to these examples at all. In the following description, “part” and “%” are all based on mass unless otherwise specified.

<Example 1>
-Production of electrophotographic photoreceptor (1)-
First, the Bragg angle (2θ ± 0.2 °) of an 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 °. V-type hydroxygallium phthalocyanine pigment (CG1) having a diffraction peak at the position, and the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using Cukα characteristic X-ray is at least 7.4 °, 16.6 2 parts in total (CG2: CG1 = 3: 2 (mass ratio)) of chlorogallium phthalocyanine pigment (CG2) having diffraction peaks at the positions of °, 25.5 ° and 28.3 °, and amine as a dispersion aid A solution comprising 0.2 part of the compound and 13 parts of tetrahydrofuran as a solvent was prepared, stirred for 20 hours using a magnetic stirrer, and then using an ultrasonic homogenizer. Then, stirring was carried out for 4 hours until the charge generating material was dispersed in a nearly uniform state. Thereby, a dispersion solution (1) was obtained.
Separately, 4 parts of an electron transport material (ET1A), 12 parts of a hole transport material material (HT1A) and 22 parts of a hole transport material material (HT2A), and a bisphenol Z polycarbonate resin (viscosity average molecular weight: 4) as a binder resin .50,000) 60 parts, 77 parts of tetrahydrofuran as a solvent and 10 parts of toluene were prepared, and stirred using a universal ball mill until the binder resin was dissolved. This obtained the dispersion solution (2).
Next, the dispersion solution (1) and the dispersion solution (2) were mixed, and similarly, using a universal ball mill, stirring was performed until these solutions were mixed in a nearly uniform state. This obtained the coating liquid.
Finally, this coating solution was dispersed six times using a nanomizer dispersing machine until the charge generating material was dispersed in a nearly uniform state, thereby preparing a coating solution for forming a photosensitive layer.

  Next, the photosensitive layer forming coating solution is dip-coated on an aluminum substrate (aluminum cutting tube) having an outer diameter of 30 mm, a length of 245 mm, and a thickness of 0.75 mm by dip coating, and 135 ° C. for 24 minutes. Was dried and cured to form a photosensitive layer having a thickness of 22 μm to produce a single layer type electrophotographic photosensitive member (1).

<Examples 2-8, Comparative Example 1>
According to Tables 1 and 2, in the composition of the coating solution for forming the photosensitive layer, the type and amount of the charge generation material, the presence or absence of a dispersion aid, the type and amount of the electron transport material, the type and amount of the hole transport material, and the binding An electrophotographic photosensitive member was produced in the same manner as the electrophotographic photosensitive member (1) of Example 1 except that the amount of the resin was changed. However, in Example 8, the electron transport material (ET2A) was used as the electron transport material instead of the electron transport material (ET1A).

<Comparative example 2>
Bragg angles (2θ ± 0.2 °) of X-ray diffraction spectrum using Cukα characteristic X-ray as a charge generating material are at least 7.3 °, 16.0 °, 24.9 °, 28.0 °. A V-type hydroxygallium phthalocyanine pigment (CG1) having a diffraction peak and a Bragg angle (2θ ± 0.2 °) of an X-ray diffraction spectrum using Cukα characteristic X-ray is at least 7.4 °, 16.6 °, A total of 2 parts of chlorogallium phthalocyanine pigment (CG2) having diffraction peaks at 25.5 ° and 28.3 ° (CG2: CG1 = 3: 2 (mass ratio)), an electron transport material (ET1A) 4 Part, hole transport material (HT1A) 12 parts and hole transport material (HT2A) 22 parts, bisphenol Z polycarbonate resin (viscosity average molecular weight: 45,000) 60 parts as a binder resin, A mixed solution consisting of 90 parts of tetrahydrofuran and 10 parts of toluene as an agent was dispersed in a sand mill for 4 hours using glass beads having a diameter of 1 mmφ to obtain a coating solution for forming a photosensitive layer.
Thereafter, an electrophotographic photosensitive member was produced in the same manner as the electrophotographic photosensitive member (1) of Example 1.

[Evaluation]
(Charge generation center of gravity of photosensitive layer)
For the photosensitive layer of the electrophotographic photoreceptor obtained in each example, the charge generation center of gravity was measured by the method described above. Specifically, first, a position where the transmittance with respect to light having an exposure wavelength of 780 nm is 50% from the outermost surface side of the photosensitive layer toward the aluminum substrate (conductive substrate) (depth from the outermost surface side of the photosensitive layer). This depth was calculated by dividing the depth by the film thickness (22 μm) of the entire photosensitive layer. The results are shown in Tables 1 and 2.

(Electrical characteristics of photoconductor due to environmental differences)
The electrophotographic photosensitive member obtained in each example was mounted on an image forming apparatus (manufactured by Brother, HL-2240D), and the image forming apparatus was modified for potential measurement. Specifically, a surface potential measurement probe (Trek, Model 555P-1) is installed so as to face the electrophotographic photosensitive member instead of the developing device, and connected to a surface potential meter (Trek, Trek 334). The potential was measured.
First, in an environment of low temperature and low humidity (10 ° C., 15% RH), exposure is performed to output an image (solid image) having an image density of 100% by an exposure device, and the surface potential (solid density latent image) of the photoconductor. Was measured as a surface potential VL1 after exposure in a low-temperature and low-humidity environment.
Next, in a high-temperature and high-humidity (28 ° C., 85% RH) environment, the surface potential VL2 after the exposure in the high-temperature and high-humidity environment is set by the same method as the surface potential VL1 after the exposure in the low-temperature and low-humidity environment. It was measured.
Then, a difference | ΔVL | (| ΔVL | = | VL1−VL2 |) between the surface potential VL1 after exposure in a low-temperature and low-humidity environment and the surface potential VL2 after exposure in a high-temperature and high-humidity environment is obtained. The electrical characteristics of the photoreceptor were evaluated according to the following criteria. The results are shown in Tables 1 and 2.

-Evaluation criteria-
G1 + (◎): | ΔVL | ≦ 10V
G1 (◎): 10V <| ΔVL | ≦ 20V
G2 (◯): 20V <| ΔVL | ≦ 30V
G3 (Δ): 30V <| ΔVL | ≦ 40V
G4 (×): 40 V <| ΔVL |

From the above results, it can be seen that the charge generation center of gravity is present on the surface side of the film thickness of the photosensitive layer as compared with the comparative example. It can also be seen that the difference between the surface potential VL1 after exposure in a low temperature and low humidity environment and the surface potential VL2 after exposure in a high temperature and high humidity environment is small. This is considered due to the fact that the center of charge generation exists on the surface side of the film thickness of the photosensitive layer.
From the above, it has been found that the use of the electrophotographic photosensitive member of this example suppresses fluctuations in the surface potential after exposure due to environmental differences.

The details of the abbreviations in the table are shown below.
-Charge generation material-
CG1: Charge generating material represented by the following structural formula (hydroxygallium phthalocyanine pigment)

CG2: a charge generating material represented by the following structural formula (chlorogallium phthalocyanine pigment)

TiPc: charge generation material (α-type titanyl phthalocyanine pigment)
InPc: charge generation material (indium phthalocyanine pigment)

-Electron transport material-
ET1A: an electron transport material represented by the following structural formula (Exemplary Compound ET1-2)

ET2A: an electron transport material represented by the following structural formula (3,3′-di-tert-butyl-5,5′-dimethyldiphenoquinone (Exemplary Compound ET2-3))

-Hole transport material-
HT1A: hole transport material represented by the following structural formula (exemplary compound HT1-4)

HT2A: hole transport material represented by the following structural formula (exemplary compound HT2-3)

DESCRIPTION OF SYMBOLS 1 Undercoat layer, 2 Photosensitive layer, 3 Conductive substrate, 7 Electrophotographic photoreceptor, 8 Charging device, 9 Exposure device, 10 Electrophotographic photoreceptor, 11 Developing device, 13 Cleaning device, 14 Lubricant, 40 Transfer device, 50 Intermediate transfer body, 100 Image forming apparatus, 120 Image forming apparatus, 131 Cleaning blade, 132 Fibrous member, 133 Fibrous member, 300 Process cartridge

Claims (4)

A conductive substrate;
A monolayer type photosensitive layer provided on the conductive substrate, comprising a binder resin, at least one charge generation material selected from hydroxygallium phthalocyanine pigment and chlorogallium phthalocyanine pigment, and a hole transport material A photosensitive layer having a position at which the transmittance of the photosensitive layer with respect to light having an exposure wavelength of 780 nm is within a range of 25% from the surface side of the film thickness of the photosensitive layer, And an electrophotographic photoreceptor. The electron transport material is at least one selected from the group consisting of an electron transport material represented by the following general formula (ET1) and an electron transport material represented by the following general formula (ET2),
The hole transport material is at least one selected from the group consisting of a hole transport material represented by the following general formula (HT1) and a hole transport material represented by the following general formula (HT2). The electrophotographic photosensitive member described.


(In General Formula (ET1), R ¹¹¹ and R ¹¹² each independently represents a halogen atom, an alkyl group, an alkoxy group, an aryl group, or an aralkyl group. R ¹¹³ represents an alkyl group, —L ¹¹⁴ —O -R ^115, an aryl group, or .n1 an aralkyl group, and n2 are each independently the ^{.L 114} represents an integer of 0 to 3, an alkylene ^{group, R 115} represents an alkyl group. )


(In General Formula (ET2), R ²¹¹ , R ²¹² , R ²¹³ , and R ²¹⁴ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a phenyl group.)


(In the general formula (HT1), Ar ^T1 , Ar ^T2 , and Ar ^T3 each independently represent an aryl group, or —C ₆ H ₄ —C (R ^T4 ) ═C (R ^T5 ) (R ^T6 ). R ^T4 , R ^T5 , and R ^T6 each independently represent a hydrogen atom, an alkyl group, or an aryl group, and R ^T5 and R ^T6 may combine to form a hydrocarbon ring.)


(In General Formula (HT2), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or a carbon number. 1 represents an alkoxy group having 1 to 20 carbon atoms, or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to each other to form a hydrocarbon ring structure, where n and m are each Independently represents 0, 1 or 2.) The electrophotographic photosensitive member according to claim 1 or 2,
A process cartridge that can be attached to and detached from an image forming apparatus. The electrophotographic photosensitive member according to claim 1 or 2,
Charging means for charging the surface of the electrophotographic photosensitive member;
An electrostatic latent image forming means for exposing the charged surface of the electrophotographic photosensitive member to form an electrostatic latent image;
Developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring the toner image to the surface of the recording medium;
An image forming apparatus comprising: