JP2017021211A - Coating liquid for forming single layer type positive charge electrophotographic photoreceptor photosensitive layer, electrophotographic photoreceptor, electrophotographic photoreceptor cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve a pot life of a coating liquid for producing a photosensitive layer of a single layer type positive charge electrophotographic photoreceptor having high sensitivity from the viewpoint of cost reduction and environmental consideration.SOLUTION: There is provided a coating liquid for forming a single layer type positive charge electrophotographic photoreceptor photosensitive layer which contains a binder resin, a charge generating material, a hole transport material, an electron transport material and a solvent, where the photosensitive layer contains oxytitanium phthalocyanine showing a strong diffraction peak at 27.2° of the Bragg angle (2θ±0.2) in X-ray diffraction by CuKα rays as the charge generating material, and a change rate of a half exposure amount E1/2 as a photoreceptor when the coating liquid has been stored for 96 hours on conditions of a temperature of 55°C and a relative humidity of 10% is 75% or less.SELECTED DRAWING: None

Description

Electrophotographic technology is widely used in the fields of copiers and various printers because of its immediacy and high quality images. An electrophotographic photosensitive material (hereinafter also simply referred to as “photosensitive material”) that is the core of electrophotographic technology is an organic photoconductive material that has the advantages of being pollution-free, easy to form, and easy to manufacture. A photoconductor using is used.
In organic electrophotographic photoreceptors, so-called function-separated type photoreceptors that share the functions of charge generation and movement with separate compounds have a large room for material selection, and the characteristics of the photoreceptor can be easily controlled. Since then, it has become the mainstream of development. From the viewpoint of the layer structure, a single layer type electrophotographic photosensitive member (hereinafter referred to as a single layer type photosensitive member) having a charge generation material and a charge transport material in the same layer, and the charge generation material and the charge transport material are separated. There is known a laminated electrophotographic photoreceptor (hereinafter referred to as a laminated photoreceptor) that is separated and laminated in these layers (charge generation layer and charge transport layer).

  Of these, the laminated type photoreceptors are of this type because most of the current photoreceptors are of this type because the functions are easily optimized for each layer and the characteristics can be easily controlled from the viewpoint of the photoreceptor design. Such a multilayer photoreceptor is often used in a negative charging system, and when the photoreceptor is charged by negative corona discharge, the generated ozone may adversely affect the environment and photoreceptor characteristics. On the other hand, in the case of a single-layer type positively charged photoreceptor, the aforementioned ozone generation can be reduced. In addition to the effect on the generation of ozone, there are advantages that the coating process is reduced and interference fringes with respect to the semiconductor laser light are hardly generated.

  As such a single-layer type positively charged photoconductor, a titanyl phthalocyanine (also known as oxytitanium phthalocyanine) pigment, particularly a powder X-ray diffraction spectrum by CuKα characteristic X-ray, has a Bragg angle (2θ ± 0.2 °) of 27.3 °. It is known that a photoreceptor using a titanyl phthalocyanine (commonly called Y-type or D-type titanyl phthalocyanine) pigment exhibiting the maximum diffraction peak has high sensitivity (Patent Document 1). However, D-type titanyl phthalocyanine is difficult to maintain a crystalline state in a dispersion state in a solution, and in particular, a polar group having a high adsorbing ability to a pigment such as a hydroxyl group in a dispersion solution not containing a binder resin. In the dispersion using the binder resin that does not have, there is a problem that the crystal is likely to transfer to the stable β type (A type) over time due to the influence of the solvent, and the sensitivity of the coating solution decreases over time. It was.

  In response to this problem, a titanyl phthalocyanine produced using a specific reaction solvent is dispersed in an organic solvent having a low dielectric constant to prepare a coating solution that is prominent over a long period of time. It is known to show the effect of crystallization (Patent Document 2).

JP 2001-33996 A JP 2011-7873 A

However, the coating solution for producing a photosensitive layer of a single-layer type positively charged electrophotographic photosensitive member according to the technique described in Patent Document 2 has no problem as a photosensitive member that is produced in a small amount in the short term, but produces a large amount of coating solution. However, there is a problem that the sensitivity of the photoconductor manufactured for a long time deviates from the product standard. The storage period of the coating solution is about 120 days when converted to normal temperature and normal pressure, and still has a short life, and only an appropriate amount depending on a short-term production plan can be produced. That is, an object of the present invention is to further improve the pot life of a coating solution for producing a photosensitive layer of a highly sensitive single-layer type positively charged electrophotographic photosensitive member from the viewpoint of cost reduction and environmental consideration.

  Further, in the background art of Patent Document 2, “a resin such as polyvinyl alcohol or polyvinyl butyral resin often used in a coating solution for a charge generation layer of a laminated photoreceptor in which a charge generation layer and a charge transport layer are laminated” is used. If used, the pigment particles can be coated and protected from the crystal transition caused by the solvent, but the resin having a large number of polar groups has little influence on the electrical characteristics at a very thin film thickness of 1 μm or less. “A practical film thickness of 10 μm or more cannot be used because the electrical characteristics are significantly degraded.” As described above, it has been difficult to extend the pot life of the coating solution for producing a photosensitive layer of a single-layer positively charged electrophotographic photosensitive member having high sensitivity by using polyvinyl alcohol or polyvinyl butyral resin.

  As a result of intensive studies, the present inventor has found that a coating solution for forming a positively chargeable single-layer type electrophotographic photosensitive member containing a binder resin, a charge generating material, a hole transporting material, an electron transporting material, and a solvent. In the above, by containing the oxytitanium phthalocyanine having a specific crystal structure and before and after placing the coating solution in a heating environment, the half-exposure change rate of the electrophotographic photosensitive member prepared by using the coating solution is set within a specific range. The inventors have found that the productivity of an electrophotographic photosensitive member for positive charging with extremely high sensitivity can be improved, and the present invention has been completed as follows. The gist of the present invention resides in the following <1> to <12>.

<1> In a positively charging single-layer type electrophotographic photosensitive member-forming coating solution containing a binder resin, a charge generation material, a hole transport material, an electron transport material, and a solvent, CuKα rays are used as the charge generation material. Containing oxytitanium phthalocyanine showing a strong diffraction peak at a Bragg angle (2θ ± 0.2) of 27.2 ° in the X-ray diffraction by X-ray diffraction, and storing the coating solution for 96 hours under conditions of a temperature of 55 ° C. and a relative humidity of 10% A coating solution for forming a positively chargeable single-layer type electrophotographic photosensitive member, wherein the change rate of the half-exposure amount E1 / 2 of the photosensitive member is 75% or less.

<2> The positively charging single-layer type electrophotographic photosensitive member for forming a photosensitive layer according to <1>, wherein the solvent is an organic solvent, and at least one of the organic solvents is tetrahydrofuran. Coating liquid.

<3> The positively charging single-layer type electrophotographic photosensitive member formation layer according to <1> or <2>, wherein the electron transport material is a compound represented by the following formula (1): Coating liquid.

[In Formula (1), R ^{1 to} R ⁴ are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 20 carbon atoms, or an optionally substituted carbon atom. It represents an alkenyl group of formula 1 to 20, and R ¹ and R ² or R ³ and R ⁴ may be bonded to each other to form a cyclic structure. X represents an organic residue having a molecular weight of 120 or more and 250 or less. ]

<4> In the formula (1), X is any one of organic residues represented by the following formulas (2) to (5), wherein any one of <1> to <3> A coating solution for forming a positively charged single-layer type electrophotographic photosensitive member as described in 1.

(In Formula (2), R ^{5 to} R ⁷ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)

(In the formula ^(3), R 8 ^{to R 11} are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms.)

(In the formula ^{(4), R 12} represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom.)

(In Formula (5), R ¹³ and R ¹⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)

<5> The positively charging single-layer electrophotographic photosensitive member according to any one of <1> to <4>, wherein the binder resin is a polycarbonate resin or a polyarylate resin. Coating liquid for forming.

<6> The coating solution for forming a positively chargeable single-layer electrophotographic photosensitive member photosensitive layer according to any one of <1> to <5>, which contains a filler.

<7> The coating solution for forming a positively chargeable single-layer electrophotographic photosensitive member according to any one of <1> to <6>, comprising a polyvinyl acetal resin.

<8> The HOMO energy level E_homo obtained as a result of the structural optimization calculation by density functional calculation B3LYP / 6-31G (d, p) of the hole transport material satisfies the following formula (A): The coating solution for forming a positively chargeable single-layer electrophotographic photosensitive member according to any one of <1> to <7>.
Formula (A)
E_homo> −4.67 (eV)

<9> A photosensitive layer is formed using the positively charging single-layer type electrophotographic photosensitive member photosensitive layer forming coating solution according to any one of <9> and <1> to <8>. Photoconductor.

<10> The electrophotographic photosensitive member according to <9>, a charging device that charges the electrophotographic photosensitive member, an exposure device that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image, and An electrophotographic photosensitive member cartridge comprising at least one selected from the group consisting of developing devices for developing an electrostatic latent image formed on the electrophotographic photosensitive member.

<11> <9> The electrophotographic photosensitive member, a charging device that charges the electrophotographic photosensitive member, and an exposure device that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image, An image forming apparatus comprising: a developing device that develops an electrostatic latent image formed on the electrophotographic photosensitive member.

<12> The image forming apparatus according to <11>, wherein the image forming apparatus does not have static elimination light.

  In the powder X-ray diffraction spectrum by CuKα characteristic X-ray, the present invention is a high-sensitivity single-layer positive positive electrode containing oxytitanium phthalocyanine having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.2 °. The pot life of the coating solution for producing the photosensitive layer of the charged electrophotographic photosensitive member can be further extended, and the productivity of the photosensitive member can be improved.

1 is a schematic diagram illustrating a main configuration of an embodiment of an image forming apparatus of the present invention. It is a figure which shows the diffraction spectrum by CuK (alpha) characteristic X-ray of D-type oxytitanium phthalocyanine used in the Example.

  Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is a representative example of the embodiments of the present invention, and is appropriately modified and implemented without departing from the spirit of the present invention. can do.

<Coating solution for forming photosensitive layer>
The coating solution of the present invention is a coating solution used for a positively charging single layer type electrophotographic photosensitive member. The coating liquid contains a binder resin, a charge generation material, a hole transport material, an electron transport material, and a solvent. In addition, the coating solution contains oxytitanium phthalocyanine (D type) having a strong diffraction peak at a Bragg angle (2θ ± 0.2) of 27.2 ° in X-ray diffraction using CuKα rays as the charge generation material. . When the coating solution is stored for 96 hours under conditions of a temperature of 55 ° C. and a relative humidity of 10%, the change rate of the half-exposure dose E1 / 2 as a photoreceptor is 75% or less. From the viewpoint of the production efficiency of the photoreceptor, it is preferably 50% or less, more preferably 25% or less, and still more preferably 10% or less. In order to satisfy the rate of change, for example, the coating liquid contains a coating liquid containing D-type oxytitanium phthalocyanine together with a filler and polyvinyl acetal resin, in which D-type oxytitanium phthalocyanine is dispersed in polyvinyl acetal resin, and other materials A technique such as mixing with a coating solution is used. By applying the coating solution onto a conductive support to form a photosensitive layer, a positively charged electrophotographic photoreceptor can be obtained. The coating solution may be applied on the undercoat layer on the conductive support or may be applied on the charge transport layer.

[Binder resin]
As the binder resin, vinyl polymers such as polymethyl methacrylate, polystyrene, polyvinyl chloride, and copolymers thereof, thermoplastic resins such as polycarbonate, polyarylate, polyester, polyester polycarbonate, polysulfone, phenoxy, epoxy, silicone resin, etc. And various thermosetting resins. Among these resins, polycarbonate resin or polyarylate resin is preferable from the viewpoint of light attenuation characteristics as a photoreceptor and mechanical strength. As a specific structure, it is preferable to use a resin having a unit structure represented by the following formula (P) from the viewpoint of electrical characteristics and dispersibility.

(In formula (P), X represents a single bond or a linking group, and Y ^{1 to} Y ⁸ each independently represent a hydrogen atom or an alkyl group.)
In formula (P), X is preferably a single bond or a group represented by the following structure. “Single bond” refers to a state in which there is no “X” atom and the two benzene rings on the left and right in formula (P) are simply bonded by a single bond.

In the structure, Ra and Rb each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group, and Ra and Rb are bonded to each other to form a cyclic alkyl structure having 5 to 12 carbon atoms. May be. Examples of the alkyl group include a straight chain alkyl group such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-hexyl group, and an n-octyl group, an isopropyl group, an ethylhexyl group, and a tertiary butyl group. Examples thereof include cyclic alkyl groups such as branched alkyl groups and cyclohexyl groups. Among these, a methyl group or an ethyl group is preferable from the viewpoint of electrical characteristics. Examples of the aryl group include a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, a tolyl group, and an anisyl group. As the alkyl group for Y ^{1 to} Y ⁸ , those exemplified as Ra and Rb can be applied.

  Specific examples of the repeating structural unit suitable for the binder resin are shown below. These specific examples are shown for illustration, and any known binder resin may be mixed and used as long as it does not contradict the gist of the present invention.

The viscosity average molecular weight of the binder resin is usually 20,000 or more, preferably 30,000 or more, more preferably 40,000 or more, further preferably 50,000 or more, and photosensitive layer formation from the viewpoint of mechanical strength. From the viewpoint of preparing a coating solution for the above, it is usually 150,000 or less, preferably 120,000 or less, more preferably 100,000 or less.
From the viewpoint of maintaining the crystal form of D-type oxytitanium phthalocyanine and maintaining a low residual potential, it is preferable to use the binder resin and the polyvinyl acetal resin in combination. Examples of the polyvinyl acetal resin include a polyvinyl butyral resin, a polyvinyl formal resin, and a partially acetalized polyvinyl butyral resin in which a part of the butyral is modified with formal or acetal. It is preferable that the structural unit represented is included.

R represents a hydrogen atom, an alkyl group, or an aryl group which may have a substituent. Examples of the aryl group include a phenyl group and a naphthyl group, and examples of the alkyl group include a linear alkyl group such as a methyl group, an ethyl group, and a propyl group, and a branched group such as an isopropyl group, a tert-butyl group, and an isobutyl group. Examples thereof include cyclic alkyl groups such as alkyl groups, cyclohexyl groups and cyclopentyl groups, and halogenated alkyl groups such as chloromethyl groups and methyl fluoride groups. In consideration of mechanical properties and solubility in a coating solution for forming a photosensitive layer, an alkyl group is preferable. As an alkyl group, C1-C10 is preferable, C1-C8 is more preferable, C1-C4
Is more preferable. Among these, from the viewpoint of synthesis, a linear alkyl group is preferable, and a methyl group or an ethyl group is more preferable. Examples of the substituent of the aryl group that may have a substituent include an alkyl group, an alkoxy group, and an amino group.

The polyvinyl acetal resin preferably contains a hydroxyl group in consideration of the dispersibility of the phthalocyanine. The hydroxyl group content is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less.
From the viewpoint of compatibility with the binder resin, the number average molecular weight of the polyvinyl acetal resin is preferably 150,000 or less, more preferably 100,000 or less, still more preferably 50,000 or less, and particularly preferably 30,000 or less. . From the viewpoint of crystal stability and dispersibility, it is preferably 3,000 or more, more preferably 5,000 or more, and still more preferably 7,000 or more.

  The blending ratio of the polyvinyl acetal resin and the total charge generation material is preferably 10 parts by mass or more of the polyvinyl acetal resin with respect to 100 parts by mass of the total charge generation material from the viewpoint of crystal stability and dispersibility. It is more preferable to contain 30 parts by mass or more. On the other hand, from the viewpoint of electrical characteristics, the polyvinyl acetal resin is preferably contained in an amount of 400 parts by mass or less, more preferably 300 parts by mass or less, and still more preferably 250 parts by mass with respect to 100 parts by mass of the total charge generating material. Or less.

[Charge generation materials]
As the charge generation material, oxytitanium phthalocyanine having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.2 ° in a powder X-ray diffraction spectrum by CuKα characteristic X-ray is used. The composition may contain various titanyl phthalocyanine derivatives such as titanyl phthalocyanine having a substituent. The oxytitanium phthalocyanine preferably has a clear diffraction peak at a Bragg angle (2θ ± 0.2 °) of 9.0 ° to 9.7 ° in a powder X-ray diffraction spectrum by CuKα characteristic X-ray. From the aspect of photographic photoreceptor characteristics, it has main diffraction peaks at 9.6 °, 24.1 °, 27.2 °, or 9.5 °, 9.7 °, 24.1 °, 27.2 °. From the viewpoint of stability at the time of dispersion, it is preferable that there is no peak in the vicinity of 26.2 °. Among the oxytitanium phthalocyanines mentioned above, 7.3 °, 9.6 °, 11.6 °, 14.2 °, 18.0 °, 24.1 ° and 27.2 °, or 7.3 °, More preferably, it has main diffraction peaks at 9.5 °, 9.7 °, 11.6 °, 14.2 °, 18.0 °, 24.2 ° and 27.2 °.

These crystalline forms are mainly produced by crystal conversion from amorphous or low crystalline oxytitanium phthalocyanine. These crystal types are metastable crystal types, exhibit various crystal types and particle shapes depending on the manufacturing method, and have characteristics as an electrophotographic photosensitive member such as charge generation ability, charging property, and dark decay. It is known to depend on
As a solvent that can be used for crystal conversion, any of a solvent compatible with water and a solvent incompatible with water can be used. Preferable examples of the solvent compatible with water include cyclic ethers such as tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane. In addition, preferable examples of solvents incompatible with water include aromatic hydrocarbon solvents such as toluene, naphthalene, and methylnaphthalene, chlorotoluene, o-dichlorotoluene, dichlorofluorobenzene, 1,2-dichloroethane, and the like. Examples include halogenated solvents, substituted aromatic solvents such as nitrobenzene, 1,2-methylenedioxybenzene, and acetophenone. Among them, cyclic ethers, chlorotoluene, halogenated hydrocarbon solvents, and aromatic hydrocarbon solvents were obtained. This is preferable because the electrophotographic characteristics of the crystal are good, and tetrahydrofuran, o-dichlorobenzene, 1,2-dichlorotoluene, dichlorofluorobenzene, toluene, and naphthalene are more preferable in terms of stability during dispersion of the obtained crystal. . The crystal obtained after the crystal conversion is subjected to a drying step, and the drying method can be dried by a known method such as blow drying, heat drying, vacuum drying, freeze drying or the like.

  From the viewpoint of charge generation efficiency, the compounding ratio (mass) of the binder resin and the oxytitanium phthalocyanine is usually 0.1 parts by mass or more of the oxytitanium phthalocyanine with respect to 100 parts by mass of the binder resin in the photosensitive layer. It is preferably 1 part by mass or more, and from the viewpoint of dispersibility, it is usually 20 parts by mass or less, preferably 10 parts by mass or less, more preferably 5 parts by mass or less. The particle diameter of the oxytitanium phthalocyanine is usually 1 μm or less, and preferably 0.5 μm or less from the viewpoint of dispersibility.

[Hole transport material]
As a hole transport material, from the viewpoint of achieving a low residual potential when D-type titanyl phthalocyanine is used as a charge generation material, a structure optimization using B3LYP / 6-31G (d, p) as a hole transport material The calculated energy level E_homo of HOMO is preferably E_homo> −4.67 (eV), and more preferably E_homo> −4.63 (eV). This is because the higher the HOMO energy level, the lower the potential after exposure and the better the electrophotographic photosensitive member can be obtained. On the other hand, if E_homo is too high, problems such as a decrease in gas resistance and the occurrence of ghosts occur. Therefore, E_homo <−4.20 (eV) is usually satisfied, and E_homo <−4.30 (eV) is preferable. The calculated value αcal of the polarizability α by the HF / 6-31G (d, p) calculation in the stable structure obtained after the structure optimization calculation using B3LYP / 6-31G (d, p) is αcal> 80 (Å ³ ) is preferred. This is because a charge transport film containing a charge transport material having a large αcal value exhibits high charge mobility, and by using the charge transport film, an electrophotographic photoreceptor excellent in chargeability and sensitivity can be obtained. On the other hand, if αcal is too large, the solubility of the charge transport material is lowered. Therefore, it is usually preferable that αcal <200 (通常³ ) and αcal <150 ( ^{３ 3} ).

  Examples of the structure of the hole transport material include carbazole derivatives, indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, thiadiazole derivatives, benzofuran derivatives and other heterocyclic compounds, aniline derivatives, hydrazone derivatives, aromatic amine derivatives, arylamine derivatives. , Stilbene derivatives, butadiene derivatives, enamine derivatives and those obtained by bonding a plurality of these compounds, or electron donating substances such as polymers having groups composed of these compounds in the main chain or side chain. Among these, carbazole derivatives, aromatic amine derivatives, arylamine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives and those in which a plurality of these compounds are bonded are preferable. Examples of general formulas having a structure suitable as a hole transport material are shown below.

Among the hole transport materials, compounds having a structure of HTM34, 35, 36, 37, 39, 40, 41, 42, 43, 44 are preferable from the viewpoint of residual potential.
The mixing ratio of the binder resin constituting the photosensitive layer and the hole transport material is arbitrary, but the hole transport material is usually blended at a ratio of 20 parts by mass or more with respect to 100 parts by mass of the binder resin. Among these, from the viewpoint of reducing the residual potential, it is preferable to blend the hole transport material at a ratio of 30 parts by mass or more with respect to 100 parts by mass of the binder resin, and from the viewpoint of stability and charge mobility when repeatedly used. Therefore, it is more preferable to mix the hole transport material in a proportion of 40 parts by mass or more. On the other hand, from the viewpoint of the thermal stability of the photosensitive layer, the hole transport material is preferably blended at a ratio of 200 parts by mass or less with respect to 100 parts by mass of the binder resin. From the viewpoint of compatibility, the hole transport material is more preferably blended at a ratio of 150 parts by mass or less.

[Electron transport materials]
The photosensitive layer preferably contains a compound represented by the following formula (1) as an electron transport material.

(In formula (1), R ^{1 to} R ⁴ are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 20 carbon atoms, or an optionally substituted carbon number. R ¹ and R ² or R ³ and R ⁴ may be bonded to each other to form a cyclic structure, and X represents an organic residue having a molecular weight of 120 or more and 250 or less. )
R ^{1 to} R ⁴ each independently represents a hydrogen atom, an optionally substituted alkyl group having 1 to 20 carbon atoms, or an alkenyl group having 1 to 20 carbon atoms. Examples of the alkyl group having 1 to 20 carbon atoms which may have a substituent include a linear alkyl group such as a methyl group, an ethyl group and a hexyl group, an iso-propyl group, a tert-butyl group, and a tert-amyl group. And a branched alkyl group such as a group, and a cyclic alkyl group such as a cyclohexyl group and a cyclopentyl group. Among these, an alkyl group having 1 to 15 carbon atoms is preferable from the viewpoint of versatility of raw materials, and an alkyl group having 1 to 10 carbon atoms is more preferable, and an alkyl group having 1 to 5 carbon atoms is more preferable from the viewpoint of handling during production. Further preferred. In addition, a straight chain alkyl group and a branched alkyl group are preferable from the viewpoint of electron transport capability, and among them, a methyl group, a tert-butyl group, and a tert-amyl group are more preferable, and from the viewpoint of solubility in an organic solvent used for a coating solution, A tert-butyl group and a tert-amyl group are more preferable.

Examples of the alkenyl group having 1 to 20 carbon atoms that may have a substituent include a straight-chain alkenyl group such as an ethenyl group, a branched alkenyl group such as a 2-methyl-1-propenyl group, and a cyclohexenyl group. And cyclic alkenyl groups. Among these, a linear alkenyl group having 1 to 10 carbon atoms is preferable from the viewpoint of light attenuation characteristics of the photoreceptor.
In the substituents R ^{1 to} R ⁴ , R ¹ and R ² or R ³ and R ⁴ may be bonded to each other to form a cyclic structure. From the viewpoint of electron mobility, when R ¹ and R ² are both alkenyl groups, they are preferably bonded to each other to form an aromatic ring, and R ¹ and R ² are both ethenyl groups and bonded to each other, More preferably, it has a benzene ring structure.

  In the formula (1), X represents an organic residue having a molecular weight of 120 or more and 250 or less, and X is any one of the organic compounds represented by the following formulas (2) to (5) from the viewpoint of light attenuation characteristics of the photoreceptor. It is preferably a residue.

(In Formula (2), R ^{5 to} R ⁷ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)

In formula (3), R ^{8 to} R ¹¹ are each independently a hydrogen atom, a halogen atom, or a carbon number of 1 to 6.
Represents an alkyl group. )

(In the formula ^{(4), R 12} represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom.)

(In Formula (5), R ¹³ and R ¹⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)
Examples of the alkyl group having 1 to 6 carbon atoms in R ^{5 to} R ¹⁴ include branched alkyl groups such as a methyl group, an ethyl group, and a hexyl group, an iso-propyl group, a tert-butyl group, and a tert-amyl group. Examples thereof include cyclic alkyl groups such as an alkyl group and a cyclohexyl group. From the viewpoint of electron transport capability, a methyl group, a tert-butyl group, and a tert-amyl group are more preferable. Examples of the halogen atom include fluorine, chlorine, bromine and iodine, and chlorine is preferred from the viewpoint of electron transport capability. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group and a naphthyl group. From the viewpoint of film properties of the photosensitive layer, a phenyl group and a naphthyl group are preferable, and a phenyl group is more preferable. Among the formulas (2) to (5), X is preferably the formula (2) or the formula (3) from the viewpoint of image quality stability upon repeated image formation, and is the formula (2). Is more preferable.

Moreover, the compound represented by Formula (1) may be used independently, the compound represented by Formula (1) from which a structure differs may be used together, and can also be used together with another electron transport material. .
Examples of the structure of an electron transport material suitable for the present invention are shown below. The following structures are illustrated to make the present invention more concrete, and are not limited to the following structures unless departing from the concept of the present invention.

  The ratio of the binder resin and the electron transport material in the photosensitive layer is usually 5 parts by mass or more of the electron transport material with respect to 100 parts by mass of the binder resin. 10 parts by mass or more is preferable from the viewpoint of residual potential reduction, and 20 parts by mass or more is more preferable from the viewpoint of stability and charge mobility when repeatedly used. On the other hand, from the viewpoint of thermal stability of the photosensitive layer, the charge transport material is usually used at 100 parts by mass or less. From the viewpoint of compatibility between the electron transport material and the binder resin, the amount is preferably 80 parts by weight or less, more preferably 60 parts by weight or less, and still more preferably 50 parts by weight or less.

The blending ratio of the binder resin constituting the photosensitive layer and the charge transport material (electron transport material and / or hole transport material) is arbitrary, but usually the charge transport material is added to 100 parts by weight of the binder resin. It mix | blends in the ratio of 20 mass parts or more. Among these, from the viewpoint of reducing the residual potential, it is preferable to blend the charge transport material at a ratio of 30 parts by mass or more with respect to 100 parts by mass of the binder resin, and further, from the viewpoint of stability and charge mobility when repeatedly used. Therefore, it is more preferable to mix the charge transport material in a proportion of 40 parts by mass or more. On the other hand, from the viewpoint of the thermal stability of the photosensitive layer, the charge transport material is preferably blended at a ratio of 200 parts by mass or less with respect to 100 parts by mass of the binder resin, and further the phase of the charge transport material and the binder resin. From the viewpoint of solubility, the charge transport material is more preferably blended at a ratio of 150 parts by mass or less, more preferably 125 parts by mass or less, and particularly preferably 100 parts by mass or less. In addition, when using several charge transport material, it is made for the sum total of those charge transport materials to be in the said range.

[Conductive support]
There is no particular limitation on the conductive support, but for example, metal materials such as aluminum, aluminum alloy, stainless steel, copper, and nickel, and conductive powder such as metal, carbon, and tin oxide are added to impart conductivity. A resin material, a resin, glass, paper, or the like on which a conductive material such as aluminum, nickel, or ITO (indium tin oxide) is deposited or applied on the surface is mainly used. These may be used alone or in combination of two or more in any combination and ratio. As a form of the conductive support, a drum form, a sheet form, a belt form or the like is used. Further, a conductive material having an appropriate resistance value may be used on a conductive support made of a metal material in order to control conductivity and surface properties and to cover defects.

Moreover, when using metal materials, such as an aluminum alloy, as an electroconductive support body, you may use, after giving an anodic oxide film. When an anodized film is applied, it is desirable to perform a sealing treatment by a known method. The surface of the support may be smooth, or may be roughened by using a special cutting method or by performing a roughening treatment. Further, it may be roughened by mixing particles having an appropriate particle diameter with the material constituting the support. In order to reduce the cost, it is possible to use the drawing tube as it is without performing the cutting process.

[Underlayer]
An undercoat layer may be provided between the conductive support and the photosensitive layer in order to improve adhesion and blocking properties. As the undercoat layer, a resin alone, or a resin in which particles such as metal oxides or organic pigments are dispersed in the resin, or the like is used. Examples of metal oxide particles used for the undercoat layer include metal oxide particles containing one metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, iron oxide, calcium titanate, titanium Examples thereof include metal oxide particles containing a plurality of metal elements such as strontium acid and barium titanate. In this way, only one type of particle may be used, or a plurality of types of particles may be mixed and used. Among these metal oxide particles, titanium oxide and aluminum oxide are preferable, and titanium oxide is particularly preferable. The surface of the titanium oxide particles may be treated with an inorganic substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic substance such as stearic acid, polyol, or silicone. As the crystal form of the titanium oxide particles, any of rutile, anatase, brookite, and amorphous can be used. A thing of a several crystalline state may be contained.

In addition, various particle diameters of the metal oxide particles can be used. Among these, from the viewpoint of characteristics and liquid stability, the average primary particle diameter is preferably 1 nm to 100 nm, particularly preferably 10 nm to 50 nm. It is as follows.
The undercoat layer is preferably formed in a form in which metal oxide particles are dispersed in a binder resin. The binder resin used for the undercoat layer is a form in which phenoxy, epoxy, polyvinylpyrrolidone, polyvinyl alcohol, casein, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, etc. are cured alone or with a curing agent. Among them, alcohol-soluble copolymerized polyamides, modified polyamides and the like are preferable because they exhibit good dispersibility and coating properties.

  In addition, a layer corresponding to the charge generation layer constituting the multilayer photoreceptor can be used as an undercoat layer of the single-layer photoreceptor. In this case, a phthalocyanine pigment, an azo pigment or a perylene pigment dispersed in a binder resin is preferably used. In this case, adhesiveness and electrical characteristics are excellent. As the binder resin, polyvinyl acetal resins are preferably used, and polyvinyl butyral resin is particularly preferable from the viewpoint of electrical characteristics.

The addition ratio of the dispersing agent such as particles and pigment to the binder resin can be arbitrarily selected, but it is preferably used in the range of 10% by mass or more and 500% by mass or less in terms of the stability of the dispersion and the coating property.
The thickness of the undercoat layer can be arbitrarily selected, but is preferably 0.1 μm to 25 μm from the viewpoint of photoreceptor characteristics and coatability. Moreover, you may add a well-known antioxidant etc. to an undercoat layer. It is possible to provide several layers having different configurations as the undercoat layer.

[Other additives]
Each layer constituting the photosensitive layer or the like is provided with an antioxidant, a hindered amine, a hindered phenol or the like for the purpose of improving film forming property, flexibility, coating property, stain resistance, gas resistance, light resistance, etc. Additives such as plasticizers such as phenyl and benzyl naphthyl ether, ultraviolet absorbers, electron-withdrawing compounds such as cyano compounds, leveling agents such as silicone oil, and visible light shading agents such as azo compounds may be added. Also, particles and fillers made of fluororesin, silicone resin, polyethylene resin, etc. for the purpose of reducing the frictional resistance and wear on the surface of the photoreceptor and increasing the transfer efficiency of the toner from the photoreceptor to the transfer belt and paper. Can be contained.

Among these, by containing the filler, the dispersion of the charge generating material can be kept good. Examples of the filler include metal oxide particles such as silica, alumina, titanium oxide, barium titanate, zinc oxide, lead oxide, and indium oxide. Among these, the electrical properties when used as a photosensitive layer of an electrophotographic photosensitive member are mentioned. Silica or alumina is preferable from the viewpoint of characteristics, and silica is preferable from the viewpoint of dispersibility. The average primary particle diameter of the filler is usually 0.001 μm or more, preferably 0.003 μm or more, and more preferably 0.005 μm or more from the viewpoint of suppressing aggregation. Further, it is usually 1 μm or less, preferably 0.5 μm or less, more preferably 0.1 μm or less from the viewpoint of coating solution stability.

The content of the filler is usually 0.5 parts by mass or more with respect to 100 parts by mass of the binder resin, and is preferably 1.0 part by mass or more from the viewpoint of dispersion stability. On the other hand, from the viewpoint of electrical characteristics, it is usually 15 parts by mass or less, and preferably 10 parts by mass or less.
As the silica, the surface thereof may be treated with an inorganic substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic substance such as stearic acid, polyol, or silicon. When the surface treatment is performed, it is preferable to perform the treatment with a silane treatment agent or a silane coupling agent, and among them, the treatment with the silane treatment agent is preferable. Examples of silane treatment agents and silane coupling agents [silane treatment agents] include dimethylsilyl [dimethyldichlorosilane], trimethylsilyl [hexamethyldisilazane], dimethylpolysiloxane [reactive dimethylsilicone oil], dimethylsiloxane, alkylylsilyl, Examples include methacryl silyl, alkyl silyl, vinyl silane, styryl silane, epoxy silane, acrylic silane, isocyanurate silane, mercapto silane, sulfide silane, isocyanate silane and the like.

The average primary particle diameter [d] of silica is calculated according to the following formula (I) using the specific surface area measured by the BET method and the density (true specific gravity) of substances constituting the particles.
d = 6 / ρs [ρ: density (true specific gravity) s: specific surface area by BET method] (I)
For example, in the case of silica particles having a specific surface area measured by the BET method of 110 m ² / g, calculation is performed using the true specific gravity of silicon dioxide, which is a component of silica = 2.2 g / cm ³ , and the average primary particle diameter is It becomes 24.8 nm. The average primary particle diameter of the particles calculated by the above formula is usually 200 nm or less, but from the viewpoint of applicability at the time of forming the photosensitive layer, it is preferably 100 nm or less, from the viewpoint of the light attenuation characteristics of the electrophotographic photosensitive member. More preferably, it is 50 nm or less, More preferably, it is 40 nm or less. The thickness is usually 1 nm or more, but preferably 3 nm or more from the viewpoint of suppressing aggregation, and more preferably 5 nm or more from the viewpoint of light attenuation characteristics of the electrophotographic photosensitive member.

[solvent]
Although there is no restriction | limiting in particular in the solvent or dispersion medium used for preparation of a coating liquid, An organic solvent is preferable from a dispersibility or a soluble viewpoint of the material to be used. Specific examples include alcohols such as methanol, ethanol, propanol and 2-methoxyethanol, ethers such as tetrahydrofuran, 1,4-dioxane and dimethoxyethane, esters such as methyl formate and ethyl acetate, acetone, methyl ethyl ketone and cyclohexanone. , Ketones such as 4-methoxy-4-methyl-2-pentanone, aromatic hydrocarbons such as benzene, toluene, xylene, dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, 1, Chlorinated hydrocarbons such as 1,1-trichloroethane, tetrachloroethane, 1,2-dichloropropane, trichloroethylene, n-butylamine, isopropanolamine, diethylamine, triethanolamine, ethylenediamine, triethylene Nitrogen-containing compounds such as amine, acetonitrile, N- methylpyrrolidone, N, N- dimethylformamide, aprotic polar solvents such as dimethyl sulfoxide and the like. Moreover, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and kinds. From the viewpoint of dispersibility and storage stability, it is preferable to contain tetrahydrofuran. In that case, the content of tetrahydrofuran is usually 10 parts by mass or more with respect to 100 parts by mass of the whole solvent, preferably 30 parts by mass or more, and more preferably 70 parts by mass or more from the viewpoint of dispersibility. 90 mass parts or less are preferable from a viewpoint of applicability | paintability.

<Method for forming each layer>
Each layer constituting the photosensitive member is formed by immersing, coating, spraying, nozzle coating, bar coating, roll coating, blade coating, or the like on a conductive support, by applying a coating solution obtained by dissolving or dispersing a substance to be contained in a solvent. In this method, the coating and drying steps are sequentially repeated for each layer.

The amount of the solvent or dispersion medium used is not particularly limited, but considering the purpose of each layer and the properties of the selected solvent / dispersion medium, it is appropriate so that the physical properties such as solid content concentration and viscosity of the coating liquid are within a desired range. It is preferable to adjust.
The coating solution is preferably dried by touching at room temperature, followed by heating or drying in a temperature range of usually 30 ° C. or more and 200 ° C. or less for 1 minute to 2 hours, while still or blowing. Further, the heating temperature may be constant, or heating may be performed while changing the temperature during drying.

<Image forming apparatus, cartridge>
Next, an embodiment of an image forming apparatus using the electrophotographic photosensitive member of the present invention (an image forming apparatus of the present invention) will be described with reference to FIG. However, the embodiment is not limited to the following description, and can be arbitrarily modified without departing from the gist of the present invention.

  The electrophotographic photoreceptor 1 is not particularly limited as long as it is the above-described electrophotographic photoreceptor of the present invention, but in FIG. 1, as an example, a drum in which the above-described photosensitive layer is formed on the surface of a cylindrical conductive support. The photoconductor is shown. A charging device 2, an exposure device 3, a developing device 4, a transfer device 5, and a cleaning device 6 are arranged along the outer peripheral surface of the electrophotographic photoreceptor 1. Since the generation of ozone can be reduced, the charging device 2 is preferably a positively charging device.

  In addition to the above-described configuration, the image forming apparatus may be configured to perform, for example, a static elimination process. The neutralization step is a step of neutralizing the electrophotographic photosensitive member by exposing the electrophotographic photosensitive member, and a fluorescent lamp, an LED, or the like is used as the neutralizing device. In addition, the light used in the static elimination process is often light having an exposure energy that is at least three times that of the exposure light. From the viewpoint of miniaturization and energy saving, it is preferable not to have a static elimination step.

The image forming apparatus may be further modified. For example, the image forming apparatus may be configured to perform a pre-exposure process, an auxiliary charging process, or the like, or may be configured to perform offset printing. A full-color tandem system configuration using toner may be used.
The electrophotographic photosensitive member 1 is combined with one or more of the charging device 2, the exposure device 3, the developing device 4, the transfer device 5, the cleaning device 6, and the fixing device 7 to form an integrated cartridge ( The electrophotographic photosensitive member cartridge may be configured to be detachable from the main body of an electrophotographic apparatus such as a copying machine or a laser beam printer.

  Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. However, the following examples are given in order to explain the present invention in detail, and the present invention is not limited to the examples shown below without departing from the gist thereof, and can be arbitrarily modified and implemented. can do. In addition, the description of “parts” in the following examples and comparative examples indicates “parts by mass” unless otherwise specified.

<Measurement method of viscosity average molecular weight of resin>
First, a method for measuring the viscosity average molecular weight of the resin will be described. The resin to be measured is dissolved in dichloromethane to prepare a solution having a concentration C of 6.00 g / L. The flow time t of the sample solution is measured in a constant temperature water bath set at 20.0 ° C. using an Ubbelohde capillary viscometer with a flow time t0 of the solvent (dichloromethane) of 136.16 seconds. The viscosity average molecular weight Mv is calculated according to the following formula.
a = 0.438 × ηsp + 1 ηsp = (t / t0) −1
b = 100 × ηsp / C C = 6.00
η = b / a
Mv = 3207 × η1.205

<Creation of electrophotographic photoreceptor>
[Example 1]
In X-ray diffraction by CuKα rays, oxytitanium phthalocyanine (hereinafter referred to as “Bragg angles (2θ ± 0.2) as shown in FIG. 2) having strong diffraction peaks at 9.6 °, 24.1 °, and 27.2 °” 10 parts by weight (referred to as CGM-1) was added to 150 parts by weight of 1,2-dimethoxyethane, and pulverized and dispersed in a sand grind mill to prepare a pigment dispersion. 160 parts by weight of the pigment dispersion thus obtained was mixed with 100 parts by weight of a 5% 1,2-dimethoxyethane solution of polyvinyl butyral (trade name # 6000C, manufactured by Denki Kagaku Kogyo Co., Ltd.) and an appropriate amount of 1,2- In addition to dimethoxyethane, a final dispersion of a solid content concentration of 4.0% by weight was prepared.

A cylinder made of an aluminum alloy having an outer diameter of 30 mm, a length of 244 mm, and a wall thickness of 0.75 mm is dip-applied to the subbing dispersion so that the film thickness after drying is 0.4 μm. A pulling layer was formed.
Next, the said oxytitanium phthalocyanine (CGM-1) was disperse | distributed with toluene by the sand grind mill, and the dispersion liquid with a solid content concentration of 3.5 mass% was obtained. Next, silica particles [
Nippon Aerosil Co., Ltd. product name: AEROSIL R972, primary particle size = 16 nm, specific surface area = 110 m ² / g] was dispersed together with tetrahydrofuran to obtain a dispersion having a solid concentration of 4.0% by mass. Next, polyvinyl acetal resin [Sekisui Chemical Co., Ltd., trade name: ESREC KS-10 (Mn: 20,400, hydroxyl group: 25.3 mol%, acetalization degree: 74.1 mol%, acetyl group: 0.6 mol% or less) ] Was dissolved in tetrahydrofuran to obtain a 10% by mass solid solution.

On the other hand, a hole transport material represented by the following structural formula (HTM-1), an electron transport material represented by the following structural formula (ETM-1), a polycarbonate resin represented by the following structural formula (P-1) [viscosity average Molecular weight: Mv = 39,600] is dissolved in a mixed solvent of tetrahydrofuran and toluene, 0.05 parts by mass is added as a leveling agent to 100 parts by mass of the binder resin, and the oxytitanium phthalocyanine dispersion is added to the solution. The silica particle dispersion and the polyvinyl acetal resin solution are mixed so as to be uniform by a homogenizer, and applied to a positively charged single layer type photosensitive layer having a solid content concentration of 24% [tetrahydrofuran / toluene = 8/2 (mass ratio)]. The liquid was adjusted. The positively charged single-layer type photosensitive layer coating solution thus prepared is applied onto the above-described undercoat layer so that the film thickness after drying becomes 30 μm. [Before change]
Got. The composition ratio of each material is shown in Table-1.

  The obtained coating solution for positively charged single-layer type photosensitive layer is put in a sealed container so that the solvent in the coating solution does not volatilize, and stored for 96 hours under conditions of a temperature of 55 ° C. and a relative humidity of 10%. The transformation process of the coating solution for single layer type photosensitive layers was performed. Then, by using the obtained coating solution after the transformation, the same operation as that for producing the photoreceptor before the transformation is carried out, whereby a positively charged single layer type electrophotographic photoreceptor A having a photosensitive layer having a thickness of 30 μm [ After transformation] was obtained.

[Examples 2 and 3]
Using the same material as in Example 1, a positively charged single layer type photosensitive layer coating solution was prepared at a composition ratio shown in Table 1, and a positively charged single layer type photoreceptor having a film thickness of 30 μm was obtained.

[Example 4]
Polyvinyl acetal resin used in Example 1 is different from the polyvinyl acetal resin [trade name: Mowital B 14S (Mn: about 11,400 hydroxyl group: about 23.6 mol%) degree of acetalization: 71.4 mol% acetyl group : 5.0 mol%)], except that the coating solution for positively charged single layer type photosensitive layer was adjusted with the composition ratio shown in Table 1 by performing the same operation as in Example 1, and the film thickness A positively charged single layer type photoreceptor D having a thickness of 30 μm was obtained.

[Examples 5 and 6]
By performing the same operations as in Example 4 except that an aromatic compound represented by the structural formula (AD-1) was additionally used as the material used in Example 4, the composition ratios shown in Table-1 were obtained. Then, a positively charged single layer type photosensitive layer coating solution was prepared to obtain a positively charged single layer type photoreceptor having a film thickness of 30 μm.

[Example 7]
A positively charged single layer type photosensitive layer coating solution was prepared at the composition ratio shown in Table 1 by performing the same operation as in Example 4 except that silica particles were not used as the material used in Example 4. Thus, a positively charged single layer type photoreceptor G having a thickness of 30 μm was obtained.
[Example 8]
Different silica particles used in Example 4 [Nippon Aerosil Co., Ltd., trade name:
AEROSIL RY200 Primary particle diameter = 16 nm Specific surface area = 100 m ² / g] By performing the same operation as in Example 4, the composition ratio shown in Table-1 was used for a positively charged single layer type photosensitive layer. The coating solution was adjusted to obtain a positively charged single layer type photoreceptor H having a film thickness of 30 μm.

[Example 9]
Different silica particles used in Example 4 [Nippon Aerosil Co., Ltd., trade name:
AEROSIL RX300 Primary particle diameter = 7 nm Specific surface area = 210 m ² / g] The same operation as in Example 4 was performed except that the coating ratio for the positively charged single layer type photosensitive layer was applied at the composition ratio shown in Table 1. The solution was adjusted to obtain a positively charged single layer type photoreceptor I having a film thickness of 30 μm.

[Example 10]
By performing the same operation as in Example 6 except that the hole transport material used in Example 6 was changed to the hole transport material represented by the structural formula (HTM-2) below, the operations described in Table 1 were performed. A positively charged single layer type photosensitive layer coating solution was prepared with a composition ratio to obtain a positively charged single layer type photosensitive member J having a thickness of 30 μm.

[Example 11]
By performing the same operations as in Example 6 except that the hole transport material used in Example 6 was changed to the hole transport material represented by the structural formula (HTM-3) below, the operations described in Table 1 were performed. The coating solution for positively charged single layer type photosensitive layer was adjusted with the composition ratio to obtain a positively charged single layer type photosensitive member K having a film thickness of 30 μm.

[Example 12]
The composition described in Table 1 was obtained by performing the same operation as in Example 6 except that the hole transport material used in Example 6 was changed to the hole transport material represented by the structural formula (HTM-4) below. The coating solution for positively charged single layer type photosensitive layer was adjusted according to the ratio to obtain a positively charged single layer type photoreceptor L having a thickness of 30 μm.

[Example 13]
The composition described in Table 1 was obtained by performing the same operation as in Example 6 except that the hole transport material used in Example 6 was changed to the hole transport material represented by the structural formula (HTM-5) below. The coating solution for the positively charged single layer type photosensitive layer was adjusted according to the ratio to obtain a positively charged single layer type photoreceptor M having a thickness of 30 μm.

[Example 14]
The binder resin used in Example 11 was changed to the polycarbonate resin [viscosity average molecular weight: Mv = 40, 200 o / p = 84.3 / 15.7 (mol ratio)] represented by the following structural formula (P-2). Except for the change, the same operation as in Example 11 was performed to adjust the positively charged single layer type photosensitive layer coating solution with the composition ratio shown in Table 1, and the positively charged single layer type photosensitive film having a film thickness of 30 μm. Body N was obtained.

[Example 15]
Except for changing the binder resin used in Example 11 to a polycarbonate resin [viscosity average molecular weight: Mv = 40,700 q / r = 49/51 (mol ratio)] represented by the following structural formula (P-3) By performing the same operation as in Example 11, a positively charged single layer type photosensitive layer coating solution was prepared with the composition ratio shown in Table 1, and a positively charged single layer type photosensitive member O having a film thickness of 30 μm was obtained. It was.

[Example 16]
The same operation as in Example 14 except that the electron transport material used in Example 14 was changed to a mixture of the electron transport material represented by the above formula (ETM-1) and the following structural formula (ETM-2). Thus, a positively charged single layer type photosensitive layer coating solution was prepared at a composition ratio shown in Table 1 to obtain a positively charged single layer type photosensitive member P having a film thickness of 30 μm.

[Comparative Example 1]
By performing the same operation as in Example 1 except that the polyvinyl acetal resin used in Example 1 is not used, a positively charged single layer type photosensitive layer coating solution is prepared with the composition ratio shown in Table 1 to obtain a film. A positively charged single layer type photoreceptor RA having a thickness of 30 μm was obtained.

[Comparative Example 2]
A positively charged single layer type photosensitive layer coating solution was prepared at the composition ratio shown in Table 1 by performing the same operation as in Example 1 except that the polyvinyl acetal resin and silica particles used in Example 1 were not used. Thus, a positively charged single layer type photoreceptor RB having a film thickness of 30 μm was obtained.

[Comparative Example 3]
By using the same operation as in Example 1 except that the aromatic compound represented by the structural formula (AD-1) was additionally used without using the polyvinyl acetal resin and silica particles used in Example 1, A positively charged single layer type photosensitive layer coating solution was prepared with the composition ratio shown in Table 1 to obtain a positively charged single layer type photoreceptor RC having a film thickness of 30 μm.

[Comparative Example 4]
By performing the same operation as in Example 1 except that the aromatic compound represented by the structural formula (AD-1) was additionally used without using the polyvinyl acetal resin used in Example 1, Table 1 A positively charged single layer type photosensitive layer coating solution was prepared with the composition ratio described above to obtain a positively charged single layer type photoreceptor RD having a thickness of 30 μm.

<Electrical characteristics test>
Using the electrophotographic characteristic evaluation apparatus manufactured in accordance with the electrophotographic society measurement standard (Electrophotographic Society, edited by “Basic and Application of Electrophotographic Technology”, Corona 1996, pages 404 to 405) The drum was rotated at a constant rotational speed of 100 pm, and an electrical property evaluation test was performed by a cycle of charging, exposure, potential measurement, and static elimination. At that time, charging was performed so that the initial surface potential of the photoconductor was +700 V under conditions of a temperature of 25 ° C. and a humidity of 50%, and the halogen lamp light was exposed to a monochromatic light of 780 nm with an interference filter, and the surface potential was exposed. The irradiation energy (half-exposure energy) when V is +350 V was measured as the half-exposure dose E1 / 2 (unit: μJ / cm ² ). The photosensitive member prepared using the coating solution immediately after the preparation of each example and the coating solution after undergoing a transformation process [temperature 55 ° C., relative humidity 10%, storage for 96 hours]. Using the values of the respective half-exposure amounts E1 / 2 obtained by measuring the values, the following formula (B) was used to evaluate the durability against changes with time of the coating solution. It was shown to.

Half-exposure change rate (%)
= ([E1 / 2 (after time change)] / [E1 / 2 (before time change)]-1) * 100
... Formula (B)

Claims (12)

  In a coating solution for forming a positively chargeable single-layer type electrophotographic photosensitive member containing a binder resin, a charge generating material, a hole transporting material, an electron transporting material, and a solvent, X-rays using CuKα rays as the charge generating material Oxytitanium phthalocyanine having a diffraction peak with a Bragg angle (2θ ± 0.2) of 27.2 ° in diffraction is contained, and the coating solution is stored for 96 hours under conditions of a temperature of 55 ° C. and a relative humidity of 10%. A coating solution for forming a positively charged single-layer type electrophotographic photosensitive member photosensitive layer, wherein the change rate of the half-exposure amount E1 / 2 of the photosensitive member is 75% or less.   2. The coating solution for forming a positively chargeable single-layer electrophotographic photosensitive member according to claim 1, wherein the solvent is an organic solvent, and at least one of the organic solvents is tetrahydrofuran. The coating solution for forming a positively chargeable single-layer electrophotographic photosensitive member according to claim 1, wherein the electron transport material is a compound represented by the following formula (1).

[In Formula (1), R ^{1 to} R ⁴ are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 20 carbon atoms, or an optionally substituted carbon atom. It represents an alkenyl group of formula 1 to 20, and R ¹ and R ² or R ³ and R ⁴ may be bonded to each other to form a cyclic structure. X represents an organic residue having a molecular weight of 120 or more and 250 or less. ] The positive electrode according to any one of claims 1 to 3, wherein in the formula (1), X is any organic residue represented by the following formulas (2) to (5). Coating solution for forming a single layer type electrophotographic photosensitive member photosensitive layer for charging.

(In Formula (2), R ^{5 to} R ⁷ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)

(In the formula ^{(3), R} 8 ~R ¹¹ are each independently a hydrogen atom, a halogen atom, having 1 to 6 carbon atoms
Represents an alkyl group. )

(In the formula ^{(4), R 12} represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom.)

(In Formula (5), R ¹³ and R ¹⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)   The coating solution for forming a positively chargeable single-layer type electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the binder resin is a polycarbonate resin or a polyarylate resin.   The coating solution for forming a positively chargeable single-layer type electrophotographic photosensitive member according to claim 1, comprising a filler.   The coating solution for forming a positively chargeable monolayer type electrophotographic photosensitive member according to claim 1, comprising a polyvinyl acetal resin. The energy level E_homo of HOMO obtained as a result of structural optimization calculation by density functional calculation B3LYP / 6-31G (d, p) of the hole transport material satisfies the following formula (A): Item 8. The coating solution for forming a positively chargeable single-layer type electrophotographic photosensitive member photosensitive layer according to any one of Items 1 to 7.
Formula (A)
E_homo> -4.67 (eV)   An electrophotographic photosensitive member, wherein a photosensitive layer is formed using the coating solution for forming a positively chargeable single-layer type electrophotographic photosensitive member according to claim 1.   The electrophotographic photosensitive member according to claim 9, a charging device for charging the electrophotographic photosensitive member, an exposure device for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image, and the electron An electrophotographic photosensitive member cartridge comprising at least one selected from the group consisting of developing devices for developing an electrostatic latent image formed on a photographic photosensitive member.   The electrophotographic photosensitive member according to claim 9, a charging device that charges the electrophotographic photosensitive member, an exposure device that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image, and An image forming apparatus comprising a developing device for developing an electrostatic latent image formed on an electrophotographic photosensitive member.   The image forming apparatus according to claim 11, wherein the image forming apparatus has no static elimination light.

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