JP6551004B2 - Electrophotographic photosensitive member, electrophotographic photosensitive member cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a highly sensitive electrophotographic photosensitive member for positive charging, an electrophotographic photosensitive member cartridge using the electrophotographic photosensitive member, and an image forming apparatus.

Electrophotographic technology is widely used in the fields of copiers and various printers because of its immediacy and high quality images. An electrophotographic photosensitive member (hereinafter, also simply referred to as "photosensitive member"), which is the core of the electrophotographic technology, is an organic photoconductive substance having advantages such as non-pollution, easy film formation, and easy production. Is used. The sensitivity of an electrophotographic photosensitive member using an organic photoconductive material differs depending on the wavelength of exposure light and the type of charge generating material.

As a charge generation material having sensitivity to light having a long wavelength of 600 to 800 nm, phthalocyanine compounds are mainly used. In particular, metal-containing phthalocyanines such as hydroxygallium phthalocyanine, chlorogallium phthalocyanine, and oxytitanium phthalocyanine, or no metal Research on phthalocyanine and the like has been conducted energetically.
With the recent increase in speed and full color of electrophotographic processes in copying machines, laser printers, plain paper fax machines and the like, high sensitivity and high speed response have become essential as the characteristics of electrophotographic photosensitive members. In order to achieve high sensitivity, a charge generation material having a high charge generation capability is essential. Among them, it is known that oxytitanium phthalocyanine that exhibits high sensitivity to LD exposure currently exhibits a crystal polymorphism. As a known crystal type, many crystal types such as α type, β type, C type, D type, Y type, M type, M-α type, and I type have been reported.

  Among them, oxytitanium phthalocyanine (commonly known as Y-type or D-type oxytitanium phthalocyanine) pigment exhibiting a maximum diffraction peak at Bragg angle (2θ ± 0.2 °) of 27.2 ° in powder X-ray diffraction spectrum by CuKα characteristic X-ray It is known that the photoconductor is particularly sensitive (Patent Document 1). However, D-type oxytitanium phthalocyanine is difficult to maintain a crystal state in a dispersion state in a solution, and particularly in a dispersion containing no binder resin or a polar group having a large adsorption ability to a pigment such as a hydroxyl group. In a dispersion using a binder resin that does not have a solvent, the crystal is likely to transfer to the stable β type (A type) over time due to the influence of the solvent, and there is a problem that 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, although the electrophotographic photosensitive member according to the technology described in Patent Document 2 does not have a defect as a photosensitive member manufactured in a short amount in a short period, the sensitivity when the coating liquid is manufactured in a large amount and manufactured in a long period Was out of the product specification. That is, an object of the present invention is to provide an electrophotographic photosensitive member with high productivity and high sensitivity 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 is difficult to prolong the pot life of the coating liquid for producing a photosensitive layer of a single-layer type positively charged electrophotographic photosensitive member having high sensitivity by using polyvinyl alcohol and polyvinyl butyral resin.

  As a result of intensive studies, the present inventor has found that the photosensitive layer contains a polyvinyl acetal resin, and the number average molecular weight of the polyvinyl acetal resin and the amount of acetyl groups are within a specific range, whereby the coating solution is heated in an environment. It was found that the rate of change in half-exposure amount of the electrophotographic photosensitive member produced using the coating solution was small before and after placing under the coating solution, and the productivity of the extremely high-sensitive electrophotographic photosensitive member could be improved. It came to The gist of the present invention resides in the following <1> to <11>.

An electrophotographic photosensitive member having a photosensitive layer on a <1> conductive support, wherein the photosensitive layer contains a polyvinyl acetal resin, the number average molecular weight of the polyvinyl acetal resin is 50,000 or less, and an acetyl group 3 to 10 mol% of an electrophotographic photosensitive member.
<2> The electrophotographic photosensitive member according to <1>, wherein the photosensitive layer contains a binder resin and the polyvinyl acetal resin is contained in an amount of 0.1 to 50 parts by mass with respect to 100 parts by mass of the binder resin.

<3> The electrophotographic photoreceptor according to <1> or <2>, wherein the photosensitive layer contains a binder resin, a charge generation material, a hole transport material, and an electron transport material in the same layer.
<4> The electrophotograph according to <3>, wherein the charge generation material is oxytitanium phthalocyanine showing a strong diffraction peak at a Bragg angle (2θ ± 0.2) of 27.2 ° in X-ray diffraction by CuKα rays. Photoconductor.
<5> The electrophotographic photosensitive member according to <3> or <4>, wherein the electron transport material is a compound represented by the following formula (1).

[In formula (1), R ^{1 to} R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a substituent, or carbon which may have a substituent 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. ]
<6> The electrophotographic photosensitive member according to <5>, wherein in the formula (1), X is any organic residue represented by the following formulas (2) to (5).

(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 each independently represent a hydrogen atom, a halogen atom, or 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.)
<7> The electrophotographic photosensitive member according to any one of <3> to <6>, wherein the binder resin is a polycarbonate resin or a polyarylate resin.
<8> The energy level E_homo of 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), <3> The electrophotographic photosensitive member according to any one of to <7>.

Formula (A)
E_homo> -4.67 (eV)
The electrophotographic photosensitive member according to any one of <9><1> to <8>, and a charging device for charging the electrophotographic photosensitive member, and the charged electrophotographic photosensitive member is exposed to electrostatic charge. An electrophotographic photosensitive member comprising at least one selected from the group consisting of an exposure device for forming a latent image and a developing device for developing an electrostatic latent image formed on the electrophotographic photosensitive member cartridge.

The electrophotographic photosensitive member according to any one of <10><1> to <8>, a charging device for charging the electrophotographic photosensitive member, and exposure of the charged electrophotographic photosensitive member for exposure. An image forming apparatus comprising: an exposure device that forms an electrostatic latent image; and a developing device that develops an electrostatic latent image formed on the electrophotographic photosensitive member.
<11> The image forming apparatus according to <10>, wherein the image forming apparatus has no static elimination light.

  According to the present invention, an electrophotographic photosensitive member with high productivity and high sensitivity can be provided. In particular, high sensitivity can be maintained even in the case of using D-type oxytitanium phthalocyanine which easily changes in crystals with time or in the case of a single-layer type photosensitive layer in which a large number of materials are mixed.

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, the embodiment of the present invention will be described in detail, but the description of the constituent requirements described below is a representative example of the embodiment of the present invention, and the embodiment is appropriately modified without departing from the scope of the present invention. can do.
<Electrophotographic photosensitive member>
The electrophotographic photosensitive member has a photosensitive layer on a conductive support. An undercoat layer may be provided between the conductive support and the photosensitive layer. The photosensitive layer contains a polyvinyl acetal resin, the number average molecular weight of the polyvinyl acetal resin is 50,000 or less, and an acetyl group is contained in an amount of 3 to 6 mol%. As an electrophotographic photoreceptor, a multilayer photoreceptor having a multilayer photosensitive layer including a charge generation layer (a layer containing a charge generation material) and a charge transport layer (a layer containing a charge transport material), or a charge generation material and a charge transport. Examples thereof include a single-layer type photoreceptor including materials and the like in the same photosensitive layer. In the case of a single layer type, it is preferable that the photosensitive layer contains a binder resin, a charge generation material, a hole transport material, and an electron transport material in the same layer. For negative charging, a multilayer photoreceptor is preferable, and for positive charging, a single-layer photoreceptor is preferable. The film thickness of the photosensitive layer is preferably 45 μm or less from the viewpoint of film formability of the photosensitive layer, and more preferably 40 μm or less from the viewpoint of high resolution. From the viewpoint of long life, 15 μm or more is preferable, and from the viewpoint of image stability, 20 μm or more is more preferable.

[Conductive Support]
The conductive support is not particularly limited. For example, a conductive material such as aluminum, aluminum alloy, stainless steel, copper, nickel or the like, or metal, carbon, tin oxide or the like conductive powder is 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. Furthermore, a conductive material having a suitable resistance value may be coated on a conductive support made of a metal material for control of conductivity, surface property and the like and defect coating.

  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 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 of metal oxide or the like, an organic pigment or the like are dispersed, 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 a crystal form of titanium oxide particles, any of rutile, anatase, brookite and amorphous can be used. A plurality of crystalline states may be included.

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, those obtained by dispersing and coating a phthalocyanine pigment, an azo pigment or a perylene pigment in a binder resin are preferably used. In this case, adhesion and electrical properties are excellent. As the binder resin, polyvinyl acetal resins are preferably used, and from the viewpoint of electrical properties, polyvinyl butyral resin is particularly preferable.

The addition ratio of the dispersant such as particles and pigment to the binder resin can be arbitrarily selected, but it is preferable to use in the range of 10% by mass to 500% by mass in view of the stability of the dispersion and the coatability.
The film thickness of the undercoat layer can be selected arbitrarily, 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.

[Polyvinyl acetal resin]
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, acetal, or the like. 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 group, cyclohexyl group and cyclopentyl group, and halogenated alkyl groups such as chloromethyl group and fluoromethyl group. 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, and C1-C4 is still 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.

  A polyvinyl acetal resin contains 3-10 mol% of acetyl groups. The content of the acetyl group is preferably 8 mol% or less from the viewpoint of film formability and electrical characteristics of the photosensitive layer, and is preferably 3.5 mol% or more from the viewpoint of dispersibility of phthalocyanine and storage stability of the coating solution. By containing an appropriate amount of acetyl group, it is considered that the acetyl group interacts with the charge generation material to suppress aggregation of the charge generation materials. For example, the acetyl group content can be measured by dissolving in deuterated dimethyl sulfoxide and analyzing the composition by 1H-NMR measurement.

  The polyvinyl acetal resin preferably contains a hydroxyl group in consideration of dispersibility of 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. For example, the hydroxyl group content can be measured by dissolving in deuterated dimethyl sulfoxide and analyzing the composition by 1H-NMR measurement.

  The number average molecular weight of the polyvinyl acetal resin is 50,000 or less, preferably 30,000 or less from the viewpoint of compatibility with the binder resin. 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. For example, the number average molecular weight can be measured by dissolving in tetrahydrofuran and measuring by gel permeation chromatography [GPC method].

The blend ratio of the polyvinyl acetal resin and the binder resin used for the photosensitive layer is 0.1 parts by mass or more from the viewpoint of the crystal stability and dispersibility of the charge generation material with respect to 100 parts by mass of the binder resin. The content is preferably 0.5 parts by mass or more, and more preferably 1.0 part by mass or more. On the other hand, from the viewpoint of compatibility between the binder resin and the polyvinyl acetal resin, the polyvinyl acetal resin is preferably contained in an amount of 30 parts by mass or less with respect to 100 parts by mass of the binder resin. Is more preferable, and it is still more preferable to contain 10 mass parts or less.

[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 resins or polyarylate resins are preferable from the viewpoint of light attenuation characteristics as a photosensitive member 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 properties 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 above structures, 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 illustrative purposes, and any known binder resin may be mixed and used as long as it does not depart from the spirit of the present invention.

  The binder resin has a viscosity average molecular weight of usually 20,000 or more, preferably 30,000 or more, more preferably 40,000 or more, still more preferably 50,000 or more, 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.

[Charge generation materials]
Examples of charge generation materials include selenium and its alloys, cadmium sulfide, and other inorganic photoconductive materials; phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, benzimidazole pigments Various photoconductive materials such as organic pigments; In particular, organic pigments are preferable, and phthalocyanine pigments and azo pigments are particularly preferable. Note that one type of charge generation substance may be used, or two or more types may be used in combination in an optional combination and an optional ratio.

  Among these, from the viewpoint of electrical characteristics, it is preferable to use 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-rays. 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, Having a main diffraction peak at 9.6 °, 24.1 °, 27.2 °, or 9.5 °, 9.7 °, 24.1 °, 27.2 ° from the viewpoint of the characteristics of the photosensitive body 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 °, It is more preferable to have 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 and exhibit various crystal types and particle shapes depending on the manufacturing method, and also have characteristics as an electrophotographic photosensitive member such as charge generation ability, chargeability, dark decay and the like. It is known to be dependent on
As a solvent which 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. Halogenated solvents, substituted aromatic solvents such as nitrobenzene, 1,2-methylenedioxybenzene, acetophenone and the like can be mentioned, among which cyclic ethers, chlorotoluenes, halogenated hydrocarbon solvents, aromatic hydrocarbon solvents are 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 crystals obtained after the crystal conversion are to be subjected to a drying step, and the drying method can be dried by a known method such as blast drying, heat drying, vacuum drying, lyophilization and 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. The amount is preferably 1 part by mass or more, and usually 20 parts by mass or less, preferably 10 parts by mass or less, more preferably 5 parts by mass or less from the viewpoint of dispersibility. 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]
From the viewpoint of achieving low residual potential when D-type titanyl phthalocyanine is used as the charge generation material as the hole transport material, structure optimization using B3LYP / 6-31G (d, p) of the 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 preferable. A charge transport film containing a charge transport material having a large value of αcal exhibits high charge mobility, and by using the charge transport film, an electrophotographic photosensitive member excellent in chargeability, sensitivity and the like can be obtained. On the other hand, since the solubility of the charge transport material is reduced if α cal is too large, it is usually α cal <200 (Å ³ ), and preferably α cal <150 (Å ³ ).

  Examples of the structure of the hole transport material include carbazole derivatives, indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, heterocyclic compounds such as thiadiazole derivatives, benzofuran derivatives, 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 compounds 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 thermal stability of the photosensitive layer, it is preferable to blend the hole transport material in a proportion 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 each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a substituent, or a carbon number which may have a substituent And 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 linear alkyl groups such as methyl, ethyl and hexyl, iso-propyl, tert-butyl and tert-amyl And a branched alkyl group such as a group, and a cyclic alkyl group such as a cyclohexyl group and a cyclopentyl group. Among them, an alkyl group having 1 to 15 carbon atoms is preferable from the viewpoint of versatility of the raw material, and an alkyl group having 1 to 10 carbon atoms is more preferable from the handleability at the time of production. Further preferred. In addition, linear alkyl groups and branched alkyl groups are preferable from the viewpoint of the electron transport ability, among which methyl group, tert-butyl group and tert-amyl group are more preferable, and from the viewpoint of solubility in the organic solvent used for the coating solution, More preferred are tert-butyl and tert-amyl groups.

Examples of the alkenyl group having 1 to 20 carbon atoms which may have a substituent include linear alkenyl groups such as ethenyl group, branched alkenyl groups such as 2-methyl-1-propenyl group, cyclohexenyl group and the like 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 are bonded to each other, It is more preferable to have 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 from the viewpoint of the light attenuation characteristics of the photoreceptor, X is any of organics represented by the following formulas (2) to (5) 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 each independently represent a hydrogen atom, a halogen atom, or 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.)
Examples of the alkyl group having 1 to 6 carbon atoms as R ^{5 to} R ¹⁴ include linear alkyl groups such as methyl group, ethyl group and hexyl group, branched groups such as iso-propyl group, tert-butyl group and 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 preferable in terms of electron transportability. 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 above formulas (2) to (5), X is preferably the formula (2) or the formula (3) from the viewpoint of image quality stability when an image is repeatedly formed, and it is the formula (3) 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 it 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 to 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 the compatibility between the electron transport material and the binder resin, 80 parts by mass or less is preferable, more preferably 60 parts by mass or less, and still more preferably 50 parts by mass 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, it is preferable to blend the charge transport material in a proportion 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.

[Other additives]
Each layer constituting the photosensitive layer or each layer is an antioxidant such as hindered amine or hindered phenol, or tar 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. In addition, particles and fillers made of fluorocarbon resin, silicone resin, polyethylene resin, etc. for the purpose of reducing the friction resistance and abrasion of the photoreceptor surface and enhancing the transfer efficiency of 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 aggregation suppression. 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 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 size [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 the substance constituting the particles.
d = 6 // s [ρ: density (true specific gravity) s: specific surface area according to 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 preferably 100 nm or less from the viewpoint of coatability at the time of forming the photosensitive layer, and from the viewpoint of 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.

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

  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 dispersible viewpoint. 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. It is preferable to contain tetrahydrofuran from the viewpoint of dispersibility and storage stability. 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, and is 30 parts by mass or more and 70 parts by mass or more from the viewpoint of dispersibility. 90 mass parts or less are preferable from a viewpoint of applicability | paintability.

The amount of the solvent or dispersion medium used is not particularly limited, but in consideration of the purpose of each layer and the properties of the selected solvent and dispersion medium, the physical properties such as the solid content concentration and viscosity of the coating liquid fall within the desired range. It is preferable to adjust.
The coating solution is preferably dried by heating at room temperature, usually in a temperature range of 30 ° C. or more and 200 ° C. or less, for 1 minute to 2 hours, at rest or under air flow. 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 photosensitive member 1 is not particularly limited as long as it is the electrophotographic photosensitive member of the present invention described above, but in FIG. 1, as an example thereof, a drum in which the photosensitive layer described above is formed on the surface of a cylindrical conductive support. Shows a photoreceptor of the shape of a circle. A charging device 2, an exposure device 3, a developing device 4, a transfer device 5 and a cleaning device 6 are disposed along the outer peripheral surface of the electrophotographic photosensitive member 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 charge removal step is a step for discharging the electrophotographic photosensitive member by exposing the electrophotographic photosensitive member, and a fluorescent lamp, an LED or the like is used as the charge eliminating 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.

In addition, the image forming apparatus may be configured to be further modified, for example, it can be configured to perform steps such as a pre-exposure step and an auxiliary charging step, be configured to perform offset printing, and further, a plurality of types. 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 shown to explain the present invention in detail, and the present invention is not limited to the examples shown below unless it deviates from the gist thereof. can do. In addition, the description of “parts” in the following examples and comparative examples indicates “parts by mass” unless otherwise specified.

<Method of measuring viscosity average molecular weight of binder resin>
First, a method for measuring the viscosity average molecular weight of the binder resin will be described. A binder 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 a Ubbelohde capillary viscometer having a flow time of t0 of the solvent (dichloromethane) of 136.16 seconds. The viscosity average molecular weight Mv is calculated according to the following equation.

a = 0.438 × ηsp + 1 ηsp = (t / t0) −1
b = 100 x sp sp / C C = 6.00
η = b / a
Mv = 3207 ×× 1.205

<Creating an electrophotographic photosensitive member>
Example 1
Oxytitanium phthalocyanine (hereinafter referred to as CGM-1) shown in FIG. 2 having strong diffraction peaks at Bragg angles (2θ ± 0.2) of 9.6 °, 24.1 °, and 27.2 ° in X-ray diffraction by CuKα rays. 10 parts by mass was added to 150 parts by mass of 1,2-dimethoxyethane and pulverized and dispersed in a sand grind mill to prepare a pigment dispersion. In this way, 160 parts by mass of the pigment dispersion obtained was dissolved in 100 parts by mass of a 5% by mass solution of polyvinyl butyral (manufactured by Denki Kagaku Kogyo K.K., trade name: # 6000C) and an appropriate amount of 1,2- In addition to dimethoxyethane, finally a dispersion for subbing with a solid content concentration of 4.0% by mass 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 pull layer was formed.
Next, the oxytitanium phthalocyanine (CGM-1) was dispersed by a sand grind mill together with toluene to obtain a dispersion having a solid content concentration of 3.5% by mass. Next, silica particles [Nippon Aerosil Co., Ltd. trade name: AEROSIL R972 primary particle diameter = 16 nm specific surface area = 110 m 2 / g] were dispersed together with tetrahydrofuran to obtain a dispersion having a solid content concentration of 4.0 mass%. Next, polyvinyl acetal A having the following physical properties was dissolved in tetrahydrofuran to obtain a solution having a solid content concentration of 10% by mass.

  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 part 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 this solution. The silica particle dispersion and the polyvinyl acetal solution are mixed uniformly with a homogenizer to prepare a single-layer type photosensitive layer coating solution having a solid concentration of 24% [tetrahydrofuran / toluene = 8/2 (mass ratio)]. did. The coating solution for a single layer type photosensitive layer prepared in this manner is coated on the above undercoat layer so that the film thickness after drying becomes 30 μm, and a single layer type electrophotographic photosensitive member A ]. The composition ratio of each material is shown in Table 1.

  The single-layer type photosensitive layer coating solution thus obtained is placed in a closed container so that the solvent in the coating solution does not evaporate, and stored for 96 hours under the conditions of a temperature of 55 ° C. and a relative humidity of 10%. The warping treatment of the coating solution was performed. A single layer type electrophotographic photosensitive member A having a photosensitive layer with a film thickness of 30 μm is obtained by using the obtained coating solution after warping and performing the same operation as that for preparing the photoreceptor before warping. ].

Polyvinyl acetal A
Number average molecular weight: 11,200
Acetyl group: 4.8 mol%
Acetalization degree: 72.3 mol%
Hydroxyl group: 22.9 mol%

[Examples 2 and 3]
By performing the same operation as in Example 1 except that a compound represented by the following structural formula (AD-1) was additionally used as the material used in Example 1, the composition ratio shown in Table-1 was simply used. A layer type photosensitive layer coating solution was prepared to obtain a single layer type photoreceptor having a film thickness of 30 μm.

Example 4
By performing the same operation as in Example 1 except that the silica particles were not used among the materials used in Example 1, a coating solution for a single layer type photosensitive layer was prepared at the composition ratio described in Table 1. A single layer type photoreceptor D having a thickness of 30 μm was obtained.
[Example 5]
The same operation as in Example 1 except that the silica particles used in Example 1 were changed to different silica particles [trade name: AEROSIL RY200, primary particle diameter = 16 nm, specific surface area = 100 m ² / g, manufactured by Nippon Aerosil Co., Ltd.]. Was performed to adjust the single-layer photosensitive layer coating solution at the composition ratio shown in Table 1, and a single-layer photoreceptor E having a thickness of 30 μm was obtained.

[Example 6]
Different silica particles used in Example 1 [Nippon Aerosil Co., Ltd., trade name:
AEROSIL RX300 The procedure of Example 1 is repeated except that the primary particle diameter is 7 nm and the specific surface area is 210 m ² / g]. Thus, a single layer type photoreceptor F having a film thickness of 30 μm was obtained.

[Example 7]
The composition described in Table 1 was obtained by performing the same operation as in Example 3 except that the hole transport material used in Example 3 was changed to the hole transport material represented by the structural formula (HTM-2) below. The coating solution for a single-layer type photosensitive layer was adjusted according to the ratio to obtain a single-layer type photoconductor G having a thickness of 30 μm.

[Example 8]
The composition described in Table 1 was obtained by performing the same operation as in Example 3 except that the hole transport material used in Example 3 was changed to the hole transport material represented by the structural formula (HTM-3) below. The coating solution for the single-layer type photosensitive layer was adjusted according to the ratio to obtain a single-layer type photosensitive member H having a thickness of 30 μm.

[Example 9]
The composition described in Table 1 was obtained by performing the same operation as in Example 3 except that the hole transport material used in Example 3 was changed to the hole transport material represented by the structural formula (HTM-4) below. The coating solution for the single-layer type photosensitive layer was adjusted according to the ratio to obtain a single-layer type photosensitive member I having a film thickness of 30 μm.

[Example 10]
The composition described in Table 1 was obtained by performing the same operation as in Example 3 except that the hole transport material used in Example 3 was changed to the hole transport material represented by the structural formula (HTM-5) below. The single-layer photosensitive layer coating solution was prepared by adjusting the ratio of the single-layer photosensitive layer coating solution.

[Example 11]
The binder resin used in Example 8 was changed to a polycarbonate resin represented by the following structural formula (P-2) [viscosity average molecular weight: Mv = 40, 200 o / p = 84.3 / 15.7 (molar ratio)]. Except for the change, the same operation as in Example 8 was performed to adjust the single-layer photosensitive layer coating solution at the composition ratio shown in Table 1, and a single-layer photoreceptor K having a thickness of 30 μm was obtained. It was.

[Example 12]
The binder resin used in Example 8 is changed to a polycarbonate resin represented by the following structural formula (P-3) [viscosity average molecular weight: Mv = 40,700 q / r = 49/51 (mol ratio)] By carrying out the same operation as in Example 8, a coating solution for a single layer type photosensitive layer was prepared at the composition ratio shown in Table 1, to obtain a single layer type photosensitive member L having a film thickness of 30 μm.

[Example 13]
The same operation as in Example 11 except that the electron-transporting material used in Example 11 is changed to use the electron-transporting material in admixture with the formula (ETM-1) and the following structural formula (ETM-2). Was performed to adjust the single-layer photosensitive layer coating solution at the composition ratio shown in Table 1, and a single-layer photosensitive member M having a thickness of 30 μm was obtained.

Example 14
By applying the same operations as in Example 11 except that the polyvinyl acetal resin used in Example 11 was changed to polyvinyl acetal B having the following physical properties, coating for a single-layer type photosensitive layer was performed at the composition ratio shown in Table-1. The solution was adjusted to obtain a single layer type photoreceptor N having a thickness of 30 μm.
Polyvinyl acetal B
Number average molecular weight: 10,800
Acetyl group: 5.6 mol%
Acetalization degree: 69.8 mol%
Hydroxyl group: 24.6 mol%

[Example 15]
Except that the polyvinyl acetal used in Example 11 was changed to polyvinyl acetal C having the following physical properties, the same operation as in Example 11 was performed to adjust the coating solution for the photosensitive layer at the composition ratio shown in Table-1. A single layer type photoreceptor O having a thickness of 30 μm was obtained.

Polyvinyl acetal C
Number average molecular weight: 12,400
Acetyl group: 4.2 mol%
Degree of acetalization: 73.7 mol%
Hydroxyl group: 22.1 mol%

Comparative Example 1
Except that the polyvinyl acetal used in Example 1 was changed to polyvinyl acetal RA having the following physical properties, the same operation as in Example 1 was performed to obtain a positively charged single-layer type photosensitive layer with the composition ratio shown in Table-1. The coating solution was adjusted to obtain a positively charged single layer type photoreceptor RA having a film thickness of 30 μm.

Polyvinyl acetal RA
Number average molecular weight: 20, 400
Acetyl group: 0.6 mol%
Acetalization degree: 74.3 mol%
Hydroxyl group: 25.1 mol%

Comparative Example 2
By performing the same operation as in Example 1 except that the polyvinyl acetal used in Example 1 is changed to polyvinyl acetal RB having the following physical properties, for a positively charged single layer type photosensitive layer at the composition ratio described in Table 1. The coating solution was adjusted to obtain a positively charged single layer type photoreceptor RB having a thickness of 30 μm.

Polyvinyl acetal RB
Number average molecular weight: 120, 300
Acetyl group: 0.7 mol%
Degree of acetalization: 65.1 mol%
Hydroxyl group: 34.2 mol%

Comparative Example 3
By using the same operation as in Example 1 except that the compound represented by the structural formula (AD-1) was additionally used without using the silica particles used in Comparative Example 1, the compounds described in Table-1 were used. The coating solution for a positive charge single-layer type photosensitive layer was adjusted by the composition ratio to obtain a positive charge single-layer type photosensitive member RC having a film thickness of 30 μm.

Comparative Example 4
By performing the same operation as in Example 1 except that the silica particles used in Comparative Example 1 are not used, a coating solution for a positively charged single layer type photosensitive layer is prepared at a composition ratio described in Table 1, A positively charged single layer type photoreceptor RD having a thickness of 30 μm was obtained.

Comparative Example 5
By carrying out the same operation as in Example 1 except that the compound having the structural formula (AD-1) is additionally used in the material used in Example 1, positively charged single compounds having the composition ratios described in Table 1 are used. A layer-type photosensitive layer coating solution was prepared to obtain a positively charged single-layer type photoreceptor RE having a film thickness of 30 μm.

<Electrical characteristics test>
Using the electrophotographic characterization apparatus manufactured according to the Electrophotographic Society measurement standard (the Electrophotographic Society ed., “The basics and applications of electrophotographic technology”, Corona Corporation 1996, pages 404 to 405) The drum was rotated at a constant rotational speed of 100 rpm, and an electrical property evaluation test was conducted by a cycle of charging, exposure, measurement of potential, and discharging.

At this time, the initial surface potential of the photosensitive member is charged to +700 V under conditions of a temperature of 25 ° C. and a humidity of 50%, and the light of a halogen lamp is exposed to monochromatic light of 780 nm by an interference filter. The irradiation energy (half exposure energy) at which + was 350 V was measured as half exposure amount E1 / 2 (unit: μJ / cm ² ). Then, a photoreceptor prepared using the coating solution immediately after the preparation of each example and a photoreceptor prepared using the coating solution subjected to warping treatment [temperature 55 ° C., relative humidity 10% 96 hours storage] The durability of the coating liquid to aging is evaluated by calculating the following formula (X) using the respective half-exposure amounts E1 / 2 obtained by measuring. It was shown to.

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

Claims (10)

An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer is a polyvinyl acetal resin , a binder resin (excluding the polyvinyl acetal resin), a charge generating material, a hole
An electrophotographic photoreceptor comprising a transport material and an electron transport material in the same layer , wherein the polyvinyl acetal resin has a number average molecular weight of 50,000 or less, and contains 3 to 10 mol% of acetyl groups. Before SL containing 0.1 to 50 parts by mass relative to polyvinyl acetal resin 100 parts by weight of the binder resin, electrophotographic photosensitive member according to claim 1. The charge generation material has a Bragg angle (2θ ± 0.2) in X-ray diffraction using CuKα rays.
There is oxytitanium phthalocyanine showing a 27.2 strong diffraction peaks, according to claim 1
Or the electrophotographic photosensitive member according to 2. The electron transport material is any one of claims 1 to 3 , which is a compound represented by the following formula (1) .
2. The electrophotographic photosensitive member according to item 1 .

[In formula (1), R ^{1 to} R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a substituent, or carbon which may have a substituent 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 electrophotographic photoreceptor according to claim 4 , wherein, in the formula (1), X is any organic residue represented by the following formulas (2) to (5).

(In formula (2), R ^{5 to} R ⁷ each independently represent 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 binder resin is a polycarbonate resin or polyarylate resin, according to claim 1 to 5,
The electrophotographic photosensitive member according to any one of the above. The hole density of the transport material functional calculations B3LYP / 6-31G (d, p) by the energy levels E_homo HOMO of the resulting structure optimization calculation satisfies the following formula (A), of claims 1 to 6, The coating liquid for forming a positively chargeable monolayer type electrophotographic photosensitive member photosensitive layer according to any one of the above.
Formula (A)
E_homo> -4.67 (eV) An electrophotographic photosensitive member according to any one of claims 1 to 6 , a charging device for charging the electrophotographic photosensitive member, and an electrostatic latent image formed by exposing the charged electrophotographic photosensitive member. An electrophotographic photosensitive member cartridge comprising at least one selected from the group consisting of an exposure device and a developing device for developing an electrostatic latent image formed on the electrophotographic photosensitive member. An electrophotographic photosensitive member according to any one of claims 1 to 6 , a charging device for charging the electrophotographic photosensitive member, and an electrostatic latent image formed by exposing the charged electrophotographic photosensitive member. An image forming apparatus comprising: an exposure apparatus that performs the above-described process; and a developing apparatus that develops the electrostatic latent image formed on the electrophotographic photosensitive member. The image forming apparatus according to claim 9 , wherein the image forming apparatus has no static elimination light.

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