JP4523393B2 - Electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to an electrophotographic photoreceptor excellent in sensitivity characteristics and stability.

  In an image forming apparatus such as an electrostatic copying machine, a facsimile, or a laser beam printer, an electrophotographic photosensitive member having sensitivity in a wavelength region of a light source used in the apparatus is used. In recent years, semiconductor lasers and light-emitting diodes having a wavelength region of about 600 to 830 nm (orange, red, and near-infrared region) are widely used as light sources. There is a strong demand for the development of products with excellent sensitivity.

Phthalocyanine (TiOPc) pigments have attracted attention as highly sensitive charge generating agents in the near-infrared region. Among them, α-type, Y-type titanyl phthalocyanine (Y-TiOPc), TiOPc and hydroxymetal phthalocyanine, etc. A laminated electrophotographic photosensitive member using a mixed crystal as a charge generating agent has already been put into practical use.
On the other hand, the single-layer type electrophotographic photosensitive member has an advantage that the structure is simpler than the laminated type electrophotographic photosensitive member, is easy to manufacture, and can be used for both positive and negative charging types. When TiOPc is used as a charge generator, there is a problem that a highly sensitive electrophotographic photosensitive member cannot be obtained. This is because the affinity between TiOPc and the binder resin (for example, polycarbonate, polyarylate, polyester, polystyrene, polymethacrylic acid ester, etc.) that forms the single-layer type photosensitive layer is low, or the binder resin and the charge transport. From the viewpoint of solubility in the agent, the dispersion medium of the coating solution for the photosensitive layer is limited to non-alcohol solvents (eg, tetrahydrofuran, dioxane, dioxolane, toluene, methylene chloride, etc.) that are poor solvents for TiOPc. It is thought that it is caused.

Therefore, various studies have been made to improve the dispersibility of TiOPc in the photosensitive layer. Patent Documents 1 to 11 disclose an electrophotographic photoreceptor containing TiOPc in the photosensitive layer together with an azo pigment. Proposed.
The applicant has also proposed an electrophotographic photoreceptor in which a specific insoluble azo pigment having no OH group in the molecule is contained in the same photosensitive layer together with the phthalocyanine pigment (Patent Document 12).
JP 2000-47406 A JP 2000-47407 A JP 2000-147810 A JP 2001-123087 A JP 2000-239553 A JP-A-7-175241 JP-A-9-34148 JP 2000-147809 A Japanese Patent Laid-Open No. 2000-24201 JP 2002-55470 A JP-A-7-199493 JP 2004-117558 A

However, in the inventions described in Patent Documents 1 to 11, the stability of the coating solution for forming the photosensitive layer is still poor, and even in the pot life (usable time) of the coating solution, Sensitivity cannot be improved sufficiently.
On the other hand, according to the invention described in Patent Document 12, the insoluble azo pigment does not have an OH group in the molecule and has a low cohesiveness per se, and the NOx gas is contained in the molecule. Therefore, it is possible to obtain an electrophotographic photosensitive member with high sensitivity and excellent charging stability and NOx resistance.

  However, in recent years, in order to meet the demand for extending the life of an electrophotographic photoreceptor, it has been required to exhibit more stable charging characteristics even after repeated exposure and development processes.

  An object of the present invention is an electrophotographic photosensitive member that is highly sensitive, excellent in charging stability and NOx resistance, and that can stably exhibit excellent charging characteristics even after repeated exposure and development processes. Is to provide.

In order to achieve the above object, the present invention provides:
(1) A photosensitive layer containing a charge generator and a pigment is provided on a conductive substrate, and the pigment is a condensed azo pigment represented by the following general formula (1) or the following general formula (2). isoindolinone pigments electric conductivity is washed with water below 10 [mu] S / cm, the electric conductivity of the aqueous extract of the pigment after the washing, wherein the following der Turkey 25 .mu.s / cm represented An electrophotographic photoreceptor ,

（一般式（１）中、Ｒ^１およびＲ^２は、独立して、水素原子、アルキル基または塩素原子を示す。Ｒ^３、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１およびＲ^１２は、独立して、水素原子、アルキル基、塩素原子、パーフルオロアルキル基、置換基を有することのあるフェノキシ基を示す。一般式（２）中、Ｒ^１３は、アルキル基を有することのあるフェニレン基またはアルキル基を有することのあるビフェニレン基を示す。）
（２） 前記電荷発生剤がフタロシアニン系顔料であることを特徴とする、前記（１）に記載の電子写真感光体、
（３） 前記フタロシアニン系顔料がチタニルフタロシアニンであることを特徴とする、前記（２）に記載の電子写真感光体、
（４） 前記チタニルフタロシアニンが、Ｘ線回折スペクトルにおいて、ブラッグ角（２θ±０．２°）が７．６°と２８．６°に主たる回折ピークを有するもの、または、ブラッグ角（２θ±０．２°）が２７．２°に主たる回折ピークを有するものであることを特徴とする、前記（３）に記載の電子写真感光体、
（５） 前記電荷発生剤、および、顔料が、電荷輸送剤とともに、同一の感光層に含有されていることを特徴とする、前記（１）〜（４）のいずれかに記載の電子写真感光体、
を提供するものである。

(In General Formula (1), R ¹ and R ² independently represent a hydrogen atom, an alkyl group, or a chlorine atom. R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , ^{R 10, R 11} and ^{R 12} are independently a hydrogen atom, an alkyl group, a chlorine atom, a perfluoroalkyl group, in indicating a phenoxy group which may have a substituent group. formula ^{(2), R 13} Represents a phenylene group which may have an alkyl group or a biphenylene group which may have an alkyl group.
(2) The electrophotographic photosensitive member according to (1) , wherein the charge generating agent is a phthalocyanine pigment,
(3) The electrophotographic photosensitive member according to (2) , wherein the phthalocyanine pigment is titanyl phthalocyanine,
(4) In the X-ray diffraction spectrum, the titanyl phthalocyanine has a main diffraction peak at Bragg angles (2θ ± 0.2 °) of 7.6 ° and 28.6 °, or a Bragg angle (2θ ± 0). .2 °) having a main diffraction peak at 27.2 °, the electrophotographic photosensitive member according to (3) above,
(5) The electrophotographic photosensitive material according to any one of (1) to (4) , wherein the charge generating agent and the pigment are contained in the same photosensitive layer together with a charge transporting agent. body,
Is to provide.

  In the present invention, the electrical conductivity (S / cm) of the pigment aqueous extract is the electrical resistance measured according to the method described in JIS K 5101-18: 2004 (pigment test method—Part 18: electrical resistivity). The reciprocal of the rate (Ω · cm) is shown. The smaller the electrical conductivity value of the water extract, the greater the electrical resistivity. Therefore, the amount of ionic eluate eluted in the water extract, i.e. the amount of ionic eluate present in the pigment, is reduced. Indicates less.

The pigment used in the present invention are that it does not have an OH group in the molecule, the electrical conductivity of the aqueous extract of the pigment is extremely small, therefore, extremely content of inorganic ionic impurities in the pigment It is characterized by little. For this reason, the above pigments are not only compared with the azo pigments described in Patent Documents 1 to 11, but also compared with the insoluble azo pigments described in Patent Document 12 in the photosensitive layer of the electrophotographic photoreceptor. It is excellent in terms of dispersibility, and is excellent in the effect of improving the dispersibility in a photosensitive layer of a charge generating agent, particularly a phthalocyanine pigment such as titanyl phthalocyanine. Moreover, according to the said pigment , the favorable dispersion state of a charge generating agent can be maintained. Furthermore, since the pigment does not have a naphthol moiety in the molecule, the NOx resistance of the electrophotographic photosensitive member is not lowered.

Therefore, the pigment is suitable for use in producing an electrophotographic photoreceptor excellent in sensitivity, charging characteristics after repeated exposure, NOx resistance and the like.
Therefore, according to the electrophotographic photoreceptor of the present invention, since the above-mentioned pigment is contained in the photosensitive layer, it has high sensitivity, excellent charging stability and NOx resistance, and repeats exposure and development processing. Even after this, it is possible to stably exhibit excellent charging characteristics.

The pigment used in the present invention is a pigment having no OH group in the molecule, washed with water having an electric conductivity of 10 μS / cm or less, preferably 1 μS / cm or less. It is characterized in that the electrical conductivity of the water extract is adjusted to be 25 μS / cm or less.
The pigment, the electrical conductivity of the aqueous extract of the pigment is 25 .mu.s / cm or less and very small, therefore, the content of inorganic ionic impurities in the pigment is extremely small, in the pigment molecule Combined with the fact that it does not have an OH group, aggregation of the pigment itself in the photosensitive layer can be suppressed. In addition, the dispersibility of the charge generating agent in the photosensitive layer can also be improved, and in particular, with respect to the coating solution for forming the photosensitive layer, it is possible to prevent the dispersibility of the charge generating agent from decreasing in the pot life. .

The electrical conductivity of the pigment extract is preferably 20 μS / cm or less, more preferably 15 μS / cm or less, and even more preferably 10 μS / cm, particularly within the above range.
The pigment may be subjected to a so-called acid paste treatment in which a pigment having no OH group in the molecule is dissolved with an acid, precipitated with water, and washed with water. When the acid paste treatment is performed on the pigment, water having an electric conductivity of 10 μS / cm or less, preferably 1 μS / cm or less is used not only when the pigment is washed with water but also when the pigment is deposited. preferable.

Examples of the pigment include a condensed azo pigment represented by the general formula (1) or an isoindolinone pigment represented by the general formula (2).
In the condensed azo pigment represented by the general formula (1), R ¹ and R ² independently represent a hydrogen atom, an alkyl group, or a chlorine atom.
Examples of the alkyl group include, but are not limited to, alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, and t-butyl.

In the condensed azo pigment represented by the general formula (1), R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are independent. A hydrogen atom, an alkyl group, a chlorine atom, a perfluoroalkyl group, and a phenoxy group which may have a substituent.
Examples of the alkyl group and the alkyl group of the perfluoroalkyl group include, but are not limited to, the same alkyl group having 1 to 4 carbon atoms as described above.

Examples of the substituent of the phenoxy group that may have a substituent include an alkyl group, an alkoxy group, a chlorine atom, and a perfluoroalkyl group.
Examples of the alkyl group as a substituent of the phenoxy group and the alkyl group of the perfluoroalkyl group include, but are not limited to, the same alkyl group having 1 to 4 carbon atoms as described above.

  Specific examples of the condensed azo pigment represented by the general formula (1) are not limited thereto, but examples thereof include C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 95, C.I. I. Pigment yellow 128, C.I. I. Pigment red 144, C.I. I. Pigment red 220, C.I. I. Pigment red 221, C.I. I. Pigment red 242 and the like.

上記一般式（２）で示されるイソインドリノン系顔料において、Ｒ^１３は、アルキル基を有することのあるフェニレン基またはアルキル基を有することのあるビフェニレン基を示す。

In the isoindolinone pigment represented by the general formula (2), R ¹³ represents a phenylene group that may have an alkyl group or a biphenylene group that may have an alkyl group.

Examples of the alkyl group that may be substituted with the phenylene group or the biphenylene group include, but are not limited to, the same alkyl group having 1 to 4 carbon atoms as described above.
Specific examples of the isoindolinone pigment represented by the general formula (2) are not limited thereto, but examples thereof include C.I. I. Pigment yellow 110, C.I. I. And CI Pigment Yellow 109.

上記顔料は、本発明の電子写真感光体の感光層にあって、電荷発生剤の分散性を向上させるためのものである。この顔料は、感光層に含有されている電荷発生剤の吸収波長領域において、電荷発生剤の電荷発生作用に悪影響を及ぼさないものであることが好ましい。それゆえ、顔料の吸光度は、電荷発生剤の吸収波長領域において、当該電荷発生剤の吸光度を１としたときに、０．３３以下であることが好ましく、より好ましくは、０．１以下、さらに好ましくは、０．０１以下である。

The pigment is used in the photosensitive layer of the electrophotographic photosensitive member of the present invention to improve the dispersibility of the charge generating agent. This pigment is preferably one that does not adversely affect the charge generating action of the charge generating agent in the absorption wavelength region of the charge generating agent contained in the photosensitive layer. Therefore, the absorbance of the pigment is preferably 0.33 or less, more preferably 0.1 or less, more preferably 0.1 or less, in the absorption wavelength region of the charge generator, where the absorbance of the charge generator is 1. Preferably, it is 0.01 or less.

Specifically, for example, as a charge generating agent, in the case of using a phthalocyanine pigment such as titanyl phthalocyanine, a pigment that does not adversely affect the charge generating action of the electric charge generating material, among the pigments exemplified above, C. I. It is preferable to use a pigment classified as pigment yellow, and in particular, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 110 and C.I. I. More preferably, CI Pigment Yellow 128 is used.

The electrophotographic photosensitive member of the present invention includes a photosensitive layer on a conductive substrate, and the photosensitive layer contains a charge generating agent and the pigment .
The pigment contained in the photosensitive layer is not particularly limited except that it is the pigment described above. The pigments exemplified above can be used alone or in admixture of two or more.

  In the electrophotographic photoreceptor of the present invention, examples of the conductive substrate include various materials in which the substrate itself has conductivity or the surface of the substrate has conductivity. Specifically, for example, simple metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass; Examples thereof include laminated plastic materials; glass coated with aluminum iodide, tin oxide, indium oxide, and the like; and a resin substrate in which conductive fine particles such as carbon black are dispersed. As the shape of the conductive substrate, various shapes such as a sheet shape and a drum shape can be adopted depending on the structure of the image forming apparatus using the electrophotographic photosensitive member of the present invention.

In the electrophotographic photosensitive member of the present invention, the layer structure of the photosensitive layer may be a single-layer type photosensitive layer containing the charge generating agent, the pigment and the charge transporting agent in the same photosensitive layer, or the charge layer A layered photosensitive layer in which a layer containing a generator and the pigment (charge generation layer) and a layer containing a charge transport agent (charge transport layer) are separated may be used. Is a layer.

  In the electrophotographic photoreceptor of the present invention, examples of the charge generator include phthalocyanine pigments such as titanyl phthalocyanine (TiOPc), metal-free phthalocyanine, hydroxygallium phthalocyanine, chlorogallium phthalocyanine; disazo pigments, disazo condensation pigments, monoazo pigments, Perylene pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azurenium pigments, cyanine pigments, pyrylium salts, ansanthrone pigments, triphenylmethane pigments Selenium pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments, and the like. The charge generation agent may be appropriately selected according to the wavelength of the exposure light source of the image forming apparatus, and the charge generation agents exemplified above may be used alone or in combination of two or more. Good.

Incidentally, with the possible inclusion of the pigment in the photosensitive layer, effects of the present invention of improving the dispersibility in the photosensitive layer of the charge-generating agent, in particular, when the electric charge generating material is a phthalocyanine pigment, Especially, when a charge generating agent is titanyl phthalocyanine, it is exhibited notably.
A digital optical image forming apparatus such as a laser beam printer generally uses a semiconductor laser (LD) or a light emitting diode (LED) as an exposure light source, and its wavelength is around 680 to 830 nm (near infrared region). Mainstream. Therefore, when the electrophotographic photosensitive member of the present invention is used in an image forming apparatus of a digital optical system, it is preferable that the charge generator is titanyl phthalocyanine, metal-free phthalocyanine, hydroxy, which has excellent sensitivity in the near infrared region. And phthalocyanine pigments such as gallium phthalocyanine and chlorogallium phthalocyanine.

  The crystal form of the phthalocyanine pigment is not particularly limited. For example, titanyl phthalocyanine is α-type (diffracted mainly at Bragg angles (2θ ± 0.2 °) of 7.6 ° and 28.6 ° in the X-ray diffraction spectrum). It is preferable that it has a peak) or a Y-type (having a main diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.2 °). The metal-free phthalocyanine is preferably X-type or τ-type, the hydroxygallium phthalocyanine is preferably V-type, and the chlorogallium phthalocyanine is preferably II-type.

Although titanyl phthalocyanine is not limited to this, for example, in differential scanning calorimetry, it does not have an endothermic peak other than the peak accompanying vaporization of adsorbed water when the temperature is raised from 50 ° C. to 400 ° C. It is preferable.
Moreover, although titanyl phthalocyanine is not limited to this, For example, it is preferable that it is Y-type titanyl phthalocyanine manufactured according to the manufacture example 1 of patent 3463032.

When the electrophotographic photoreceptor of the present invention is used in an analog optical image forming apparatus that uses a white light source such as a halogen lamp as an exposure light source, the perylene having a sensitivity in the visible region is preferably used as the charge generator. And pigments and bisazo pigments.
In the electrophotographic photoreceptor of the present invention, examples of the charge transport agent include an electron transport agent and / or a hole transport agent.

  Examples of the electron transfer agent include benzoquinone compounds, naphthoquinone compounds, anthraquinone compounds, diphenoquinone compounds, dinaphthoquinone compounds, naphthalene tetracarboxylic acid diimide compounds, fluorenone compounds, malononitrile compounds, thiopyran compounds, tri Examples thereof include nitrothioxanthone compounds, dinitroanthracene compounds, dinitroacridine compounds, nitroantharaquinone compounds, and dinitroanthraquinone compounds.

  As the hole transport agent, for example, a compound obtained by substituting one, two or three diarylamino groups which may have a substituent on an aromatic hydrocarbon which may have a substituent (specifically, For example, N, N, N ′, N′-tetraphenylbenzidine compound, N, N, N ′, N′-tetraphenylphenylenediamine compound, N, N, N ′, N′-tetraphenylnaphthylenediamine Compounds, N, N, N ′, N′-tetraphenylphenanthrylenediamine compounds, for example, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, etc.); 2,5-di (4- Oxadiazole compounds such as methylaminophenyl) -1,3,4-oxadiazole; carbazole compounds such as polyvinylcarbazole; 1-phenyl- -Pyrazoline compounds such as (p-dimethylaminophenyl) pyrazoline; organic polysilane compounds, hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds Compounds, triazole compounds, and the like.

  In the above-mentioned “compound formed by substituting one, two or three diarylamino groups which may have a substituent on an aromatic hydrocarbon which may have a substituent”, an aromatic which may have a substituent Examples of the aromatic hydrocarbon of hydrocarbon include benzene, naphthalene, phenanthrene, anthracene, biphenyl, o-, m-, p-terphenyl, binaphthalene, stilbene, styryl stilbene, and the like.

  In addition, examples of the substituent of the aromatic hydrocarbon which may have a substituent include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, and an arylalkenyl group. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, sec-pentyl, 2-methylpentyl, tert- C1-C6 alkyl groups, such as pentyl, n-hexyl, and isohexyl, are mentioned. Examples of the cycloalkyl group include cycloalkyl groups having 3 to 8 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of the alkenyl group include alkenyl groups having 1 to 6 carbon atoms such as vinyl, 1-propenyl, allyl, isopropenyl, 2-butenyl, 1,3-butadienyl, 1-pentenyl, 2-hexenyl and the like. . Examples of the aryl group include phenyl, o, m or p-tolyl, 2,3-, 2,4-, 2,5-, 3,4- or 3,5-xylyl, o, m or p-cumenyl. , Aryl groups having 6 to 18 carbon atoms, such as mesityl, naphthyl and biphenyl. Examples of the aralkyl group include benzyl, 1-phenylethyl, phenethyl, 1-phenylpropyl, benzhydryl, o, m or p-methylbenzyl, 2,3-, 2,4-, 2,5-, 3,4 -Or an aralkyl group having 7 to 18 carbon atoms such as 3,5-dimethylbenzyl. Examples of the arylalkenyl group include arylalkenyl groups having 8 to 12 carbon atoms such as styryl and cinnamyl.

In the above-mentioned “compound formed by substituting one, two or three diarylamino groups which may have a substituent on an aromatic hydrocarbon which may have a substituent”, a diarylamino which may have a substituent Examples of the diarylamino group include diphenylamino, dinaphthylamino, dibenzylamino, and distyrylamino.
Examples of the substituent of the diarylamino group that may have a substituent include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, and an arylalkenyl group. Examples of these groups include the same groups as those exemplified above.

In the electrophotographic photosensitive member of the present invention, the photosensitive layer is prepared by dispersing the charge generating agent, the pigment, and the charge transporting agent together with a binder resin in a dispersion medium, and the thus obtained coating solution for forming a photosensitive layer is obtained as described above. It can be formed by coating on a conductive substrate.
The binder resin is not particularly limited. For example, a polycarbonate having a bisphenol such as a bisphenol A type, a bisphenol F type, a bisphenol AD type, a bisphenol Z type, a bisphenol A type, a bisphenol C type, or a bisphenol ZC type in a repeating unit. Resin; bisphenol A type, bisphenol F type, bisphenol AD type, bisphenol Z type, bisphenol A type, bisphenol C type, bisphenol ZC type and the like, benzenedicarboxylic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid , Aromatic dicarboxylic acids such as anthracene dicarboxylic acid and phenanthrene dicarboxylic acid; polyester resins, polyarylate resins, polystyrene trees , And poly (meth) acrylic acid esters.

  Among these, the polycarbonate resin and the polyarylate resin can make the strength and abrasion resistance of the photosensitive layer even better, and are particularly suitable when the photosensitive layer is a single layer type. . Moreover, since it has excellent compatibility with the charge transport agent and does not have a site that interferes with the charge transport ability of the charge transport agent in its molecule, it is also suitable for obtaining a highly sensitive electrophotographic photoreceptor. is there.

In addition, as a suitable example of binder resin which forms the photosensitive layer of a single layer type photoreceptor, for example, polycarbonate, polyarylate, polyester, polystyrene, polymethacrylic acid ester and the like can be mentioned. These binder resins are exemplified above. Among these charge generating agents, in particular, the affinity with phthalocyanine pigments such as TiOPc tends to be low. However, in the present invention, in the coating liquid for forming a photosensitive layer, together with the charge generating material, since the pigment of the present invention is blended, even when using the above binder resin, the coating solution In the pot life, the dispersed state of the charge generating agent can be maintained in a good state.

When the electrophotographic photosensitive member of the present invention is a single layer type photosensitive member having a single layer type photosensitive layer, the photosensitive layer needs, for example, a charge generating agent, the above-described pigment , a charge transporting agent, and a binder resin. Accordingly, it can be produced by dispersing or dissolving it in a dispersion medium described later together with other components described later, applying the coating solution for forming a photosensitive layer thus obtained on the conductive substrate, and drying it. . The photosensitive layer may be formed directly on the conductive substrate or may be formed via an undercoat layer (barrier layer). Further, a protective layer may be formed on the surface of the photoreceptor.

  Examples of the dispersion medium for preparing a coating solution for forming a photosensitive layer include alcohols such as methanol, ethanol, isopropanol, and butanol; aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane; benzene, toluene, Aromatic hydrocarbons such as xylene; Halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, chlorobenzene; Ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; Acetone, methyl ethyl ketone , Ketones such as cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide, , 3-dioxolane, and 1,4-dioxane. These dispersion media may be used alone or in combination of two or more.

In addition, as a suitable example of the dispersion medium in the coating solution for forming a single-layer type photosensitive layer, for example, non-alcohol solvents such as tetrahydrofuran, dioxane, dioxolane, toluene, methylene chloride, and the like, these dispersion media are Among the charge generators exemplified above, it is a poor solvent for phthalocyanine pigments such as TiOPc. However, in the present invention, since the pigment according to the present invention is blended with the charge generating agent in the coating liquid for forming the photosensitive layer, the coating liquid is used even when the above non-alcohol solvent is used. In the pot life, the dispersion state of the charge generating agent can be maintained in a good state.

  Other components include, for example, dispersants, sensitizers; antioxidants, radical scavengers, singlet quenchers, UV absorbers and other deterioration inhibitors; softeners, plasticizers, surface modifiers, extenders , Thickeners, dispersion stabilizers, waxes, acceptors, donors; surfactants for improving the dispersibility of charge transport agents and charge generators, smoothness of the photosensitive layer surface, leveling agents, and the like. Examples of the dispersant include a dispersant for improving the dispersibility of the charge generator in the binder resin. Examples of such a dispersant include disazo yellow, dianisidine orange, pyrazolone orange, Examples include azo pigments such as pyrazolone red. Examples of the sensitizer include terphenyl, halonaphthoquinones, acenaphthylene, and the like.

The photosensitive layer forming coating solution is obtained by, for example, dispersing and mixing a charge generator, a charge transport agent, a binder resin, and the like together with a dispersion medium using a roll mill, a ball mill, an attritor, a paint shaker, an ultrasonic disperser, and the like. Can be prepared.
The thickness of the single-layer type photosensitive layer is not particularly limited, but is preferably 5 to 100 μm, and more preferably 10 to 50 μm.

In the single-layer type photosensitive layer, the content ratio of the charge generator is not particularly limited, but is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 30 parts by weight with respect to 100 parts by weight of the binder resin. Part.
Although the content rate of a pigment is not specifically limited, For example, Preferably it is 5-300 weight part with respect to 100 weight part of charge generating agents, More preferably, it is 20-200 weight part.

  In the case of using a hole transport agent as the charge transport agent, the content ratio of the hole transport agent is not particularly limited, but is preferably 10 to 200 parts by weight, more preferably 20 parts by weight with respect to 100 parts by weight of the binder resin. ~ 100 parts by weight. On the other hand, when an electron transport agent is used as the charge transport agent, the content ratio of the electron transport agent is not particularly limited, but is preferably 5 to 100 parts by weight, more preferably 10 parts by weight with respect to 100 parts by weight of the binder resin. ~ 80 parts by weight. In the case where a hole transport agent and an electron transport agent are used in combination as the charge transport agent, the total amount of the hole transport agent and the electron transport agent is not particularly limited, but is preferably based on 100 parts by weight of the binder resin. 20 to 300 parts by weight, more preferably 30 to 200 parts by weight.

In the case where the electrophotographic photosensitive member of the present invention is a so-called laminated photosensitive member having a laminated photosensitive layer, the photosensitive layer is formed, for example, by first forming a charge generating layer on a conductive substrate. It can be manufactured by forming a charge transport layer on the surface of the charge generation layer.
The charge generation layer can be obtained by, for example, dispersing or dissolving the charge generator, the pigment and the binder resin in the dispersion medium together with the charge transport agent and the other components as necessary. It can be produced by applying a layer forming coating solution on a conductive substrate and drying it. The charge transport layer is prepared by, for example, dispersing or dissolving the charge transport agent and the binder resin in the dispersion medium together with the other components as necessary, and the thus obtained charge transport layer forming coating solution is used as described above. It can be produced by coating on a charge generation layer and drying.

  The stacking order of the charge generation layer and the charge transport layer may be the reverse order of the above case, but in general, the charge generation layer is thin and the strength is not sufficient. The stacking order is preferable. Of the charge generation layer and the charge transport layer, the layer formed on the conductive substrate side may be formed directly on the conductive substrate or may be formed via an undercoat layer. Further, a protective layer may be formed on the surface of the charge generation layer and the charge transport layer formed on the outer surface side of the photoreceptor.

Examples of the dispersion medium in the charge generation layer forming coating solution and the charge transport layer forming coating solution include the same ones as described above.
The charge generation layer forming coating liquid and the charge transport layer forming coating liquid are, for example, a predetermined component such as a charge generating agent, a charge transporting agent, a binder resin, a dispersion medium, a roll mill, a ball mill, an attritor, a paint shaker, It can be prepared by dispersing and mixing using an ultrasonic disperser or the like.

The thickness of the multilayer photosensitive layer is not particularly limited, but the charge generation layer is preferably 0.01 to 5 μm, more preferably 0.1 to 3 μm, and the charge transport layer is preferably 2 to 2 μm. It is 100 micrometers, More preferably, it is 5-50 micrometers.
In the charge generation layer of the multilayer photosensitive layer, the content ratio of the charge generation agent is not particularly limited, but is preferably 5 to 1000 parts by weight, more preferably 30 to 500 parts with respect to 100 parts by weight of the binder resin. Parts by weight.

Although the content rate of a pigment is not specifically limited, For example, Preferably it is 5-300 weight part with respect to 100 weight part of charge generating agents, More preferably, it is 20-200 weight part.
In the charge transport layer of the multilayer photosensitive layer, the content ratio of the charge transport agent (hole transport agent or electron transport agent) is not particularly limited, but is preferably 10 to 500 with respect to 100 parts by weight of the binder resin. Part by weight, more preferably 25 to 200 parts by weight.

  The electrophotographic photoreceptor of the present invention performs image formation by wet development using an image forming apparatus such as an electrostatic copying machine, a facsimile machine, or a laser beam printer, in particular, using a wet developer using a paraffinic solvent. The image forming apparatus is suitable.

EXAMPLES Next, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited by the following Example.
<Manufacture of pigments >
Production Example 1
C. shown in the above formula. I. Pigment Yellow 128 (condensed azo pigment, chromoftal yellow 8GN, manufactured by Ciba Specialty Chemicals Co., Ltd.) and 30 parts by weight of sulfuric acid (98% by weight) were mixed and stirred for 1 hour. After the pigment was completely dissolved, the pigment solution was dropped into 6000 parts by weight of ion-exchanged water (electric conductivity 1 μS / cm) to obtain a precipitate (acid paste treatment). Next, the obtained precipitate was filtered off, and ion-exchanged water (electric conductivity 1 μS / cm) was used to repeatedly perform water washing and filtration (pure water washing treatment) to obtain a pigment paste. The water washing and filtration (pure water washing treatment) were repeated until the pH of the filtrate reached 6.8 or higher.

When the electrical conductivity of the water extract of the precipitate was measured according to the method described in JIS K 5101-18: 2004 (pigment test method—Part 18: electrical resistivity) (hereinafter the same), 10 μS / cm.
Next, the pigment paste thus obtained was dried at 90 ° C. and pulverized to obtain a pigment having an average particle size (50% particle size) of 90 nm.

Production Example 2
As a pigment, C.I. I. Instead of CI Pigment Yellow 128, C.I. I. Acid paste treatment and pure water washing treatment as in Production Example 1 except that 30 parts by weight of Pigment Yellow 93 (condensed azo pigment, chromoftal yellow 3G, manufactured by Ciba Specialty Chemicals Co., Ltd.) was used To obtain a pigment .

About the deposit after the said pure water washing process, when the electrical conductivity of the water extract was measured, it was 5 microsiemens / cm.
Production Example 3
As a pigment, C.I. I. Instead of CI Pigment Yellow 128, C.I. I. Acid paste treatment and pure water washing treatment as in Production Example 1 except that 30 parts by weight of Pigment Yellow 95 (condensed azo pigment, chromoftal yellow GR, manufactured by Ciba Specialty Chemicals Co., Ltd.) was used. To obtain a pigment .

About the deposit after the said pure water washing process, when the electrical conductivity of the water extract was measured, it was 7 microsiemens / cm.
Production Example 4
As a pigment, C.I. I. Instead of CI Pigment Yellow 128, C.I. I. Acid paste treatment and pure water washing treatment as in Production Example 1 except that 30 parts by weight of Pigment Yellow 94 (condensed azo pigment, chromophthal yellow 6G, manufactured by Ciba Specialty Chemicals Co., Ltd.) was used. To obtain a pigment .

About the deposit after the said pure water washing process, when the electrical conductivity of the water extract was measured, it was 10 microsiemens / cm.
Production Example 5
As a pigment, C.I. I. Instead of CI Pigment Yellow 128, C.I. I. Acid paste treatment and pure water washing treatment as in Production Example 1 except that 30 parts by weight of Pigment Yellow 110 (isoindolinone pigment, Irgazine Yellow 3RT, manufactured by Ciba Specialty Chemicals Co., Ltd.) was used. To obtain a pigment .

About the deposit after the said pure water washing process, when the electrical conductivity of the water extract was measured, it was 5 microsiemens / cm.
Production Example 6
C. shown in the above formula. I. For 30 parts by weight of Pigment Yellow 128 (condensed azo pigment, “chromoftal yellow 8GN” described above), water washing with ion-exchanged water (electric conductivity 1 μS / cm) and filtration were repeatedly performed (pure Water washing treatment) to obtain a pigment paste. The water washing and filtration (pure water washing treatment) were repeated until the pH of the filtrate reached 6.8 or higher.

After the pure water cleaning treatment, the electrical conductivity of the pigment water extract was measured and found to be 10 μS / cm.
Next, the pigment paste thus obtained was dried at 90 ° C. and pulverized to obtain a pigment having an average particle size (50% particle size) of 90 nm.
Comparative production example 1
After the acid paste treatment, water washing and filtration treatment were performed using tap water (electric conductivity of about 290 μS / cm) instead of ion-exchanged water (electric conductivity of 1 μS / cm) (tap water washing treatment). Except for this, a pigment was obtained in the same manner as in Production Example 1.

About the deposit after the said tap water washing process, when the electrical conductivity of the water extract was measured, it was 120 microsiemens / cm.
<Manufacture of electrophotographic photoreceptor>
Example 1
4 parts by weight of Y type titanyl phthalocyanine of the following formula (CGM-1) as a charge generating material, 3 parts by weight of pigment obtained in Production Example 1 as a pigment, the following formula as a hole transporting agent (HTM-1 ) And 40 parts by weight of an N-phenylnaphthalimide compound represented by the following formula (ETM-1) as an electron transporting agent, and the following formula (ETM-2). 30 parts by weight of a diphenoquinone compound, 100 parts by weight of a polycarbonate resin (Resin-1) as a binder resin, and dimethyl silicone oil (product number “KF-96-50CS” manufactured by Shin-Etsu Chemical Co., Ltd.) as a leveling agent is 0. 1 part by weight and 750 parts by weight of tetrahydrofuran as a solvent were mixed, and mixed and dispersed for 50 hours with an ultrasonic disperser. To prepare a coating solution for single-layer type photosensitive layer.

  The Y-type titanyl phthalocyanine was produced according to Production Example 1 described in Japanese Patent No. 3463032, and in the X-ray diffraction spectrum, the Bragg angle (2θ ± 0.2 °) was mainly 27.2 °. In the differential scanning calorimetry, the sample had a peak, and had no endothermic peak other than the peak accompanying vaporization of adsorbed water when the temperature was raised from 50 ° C. to 400 ° C. The polycarbonate resin (Resin-1) contains a repeating unit represented by the following formula (RU-1) and a repeating unit represented by the following formula (RU-2) in a molar ratio of 15:85. The viscosity average molecular weight (conversion value using bisphenol A type polycarbonate resin as a standard substance; viscosity method) was 50500.

上記塗布液を、１０日間、常温にて静置した後、導電性基体としてのアルミニウム素管（直径３０ｍｍ、長さ２５４ｍｍ）の表面に塗布して、１３０℃で３０分間熱風乾燥することにより、膜厚２２μｍの単層型感光層を備える電子写真感光体（感光体ドラム）を製造した。

The coating solution is allowed to stand at room temperature for 10 days, and then applied to the surface of an aluminum base tube (diameter 30 mm, length 254 mm) as a conductive substrate, followed by hot-air drying at 130 ° C. for 30 minutes, An electrophotographic photosensitive member (photosensitive drum) having a single-layer type photosensitive layer having a thickness of 22 μm was manufactured.

Comparative Example 1
As a pigment, in place of a pigment obtained in Production Example 1, except for using 3 parts by weight of pigment obtained in Comparative Preparation Example 1, in the same manner as in Example 1, for single-layer type photosensitive layer A coating solution was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Comparative Example 2
As a pigment, in place of a pigment obtained in Production Example 1, C. represented by the above formula I. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 300 parts by weight of Pigment Yellow 128 (not subjected to acid paste treatment) was used. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Example 2
As a pigment, in place of a pigment obtained in Production Example 1, except for using 3 parts by weight of pigment obtained in Production Example 2, in the same manner as in Example 1, the coating for the monolayer type photosensitive layer A liquid was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Comparative Example 3
As a pigment, in place of a pigment obtained in Production Example 1, C. represented by the above formula I. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 300 parts by weight of Pigment Yellow 93 (not subjected to acid paste treatment) was used. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Example 3
As a pigment, in place of a pigment obtained in Production Example 1, except for using 3 parts by weight of pigment obtained in Production Example 3, in the same manner as in Example 1, the coating for the monolayer type photosensitive layer A liquid was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Comparative Example 4
As a pigment, in place of a pigment obtained in Production Example 1, C. represented by the above formula I. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 300 parts by weight of Pigment Yellow 95 (not subjected to acid paste treatment) was used. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Example 4
As a pigment, in place of a pigment obtained in Production Example 1, except for using 3 parts by weight of pigment obtained in Production Example 4, in the same manner as in Example 1, the coating for the monolayer type photosensitive layer A liquid was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Comparative Example 5
As a pigment, in place of a pigment obtained in Production Example 1, C. represented by the above formula I. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 300 parts by weight of Pigment Yellow 94 (not subjected to acid paste treatment) was used. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Example 5
As a pigment, in place of a pigment obtained in Production Example 1, except for using 3 parts by weight of pigment obtained in Production Example 5, in the same manner as in Example 1, the coating for the monolayer type photosensitive layer A liquid was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Comparative Example 6
As a pigment, in place of a pigment obtained in Production Example 1, C. represented by the above formula I. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 300 parts by weight of Pigment Yellow 110 (not subjected to acid paste treatment) was used. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Example 6
As a pigment, in place of a pigment obtained in Production Example 1, except for using 3 parts by weight of pigment obtained in Production Example 6, in the same manner as in Example 1, the coating for the monolayer type photosensitive layer A liquid was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

Comparative Example 7
A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that no pigment was blended. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.
Comparative Example 8
As a pigment, in place of a pigment obtained in Production Example 1, except for using the compound represented by the following formula (c-1), in the same manner as in Example 1, the coating solution for single-layer type photosensitive layer Was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

  The pigment represented by the following formula (c-1) has an OH group and a naphthol moiety in the molecule.

比較例９
顔料として、製造例１で得られた顔料に代えて、下記式（ｃ−２）で示される化合物を使用したこと以外は、実施例１と同様にして、単層型感光層用の塗布液を調製した。次いで、上記塗布液を、１０日間、常温にて静置し、さらに、実施例１と同様にして、膜厚２２μｍの単層型感光層を備える電子写真感光体を製造した。

Comparative Example 9
As a pigment, in place of a pigment obtained in Production Example 1, except for using the compound represented by the following formula (c-2), in the same manner as in Example 1, the coating solution for single-layer type photosensitive layer Was prepared. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

  The pigment represented by the following formula (c-2) has an OH group and a naphthol moiety in the molecule.

（式（ｃ−２）中、Ｒ^ｃ２は、下記式で示される基を示す。）

(In formula (c-2), R ^c2 represents a group represented by the following formula.)

比較例１０
顔料として、製造例１で得られた顔料に代えて、下記式で示されるＣ．Ｉ．ピグメントイエロー１５１（大日本インキ化学工業（株）製）を使用したこと以外は、実施例１と同様にして、単層型感光層用の塗布液を調製した。次いで、上記塗布液を、１０日間、常温にて静置し、さらに、実施例１と同様にして、膜厚２２μｍの単層型感光層を備える電子写真感光体を製造した。

Comparative Example 10
As a pigment, in place of a pigment obtained in Production Example 1, represented by the following formula C. I. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that CI Pigment Yellow 151 (manufactured by Dainippon Ink & Chemicals, Inc.) was used. Next, the coating solution was allowed to stand at room temperature for 10 days, and an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 22 μm was produced in the same manner as in Example 1.

  C. shown in the following formula. I. Pigment Yellow 151 has an OH group in the molecule.

＜電子写真感光体の性能評価＞
（Ｉ）帯電電位および明電位の測定
ＧＥＮＴＥＣ社製のドラム感度試験機を用いて、上記実施例１〜６および比較例１〜１０で得られた電子写真感光体の初期感度特性を評価した。

<Performance evaluation of electrophotographic photoreceptor>
(I) Measurement of Charging Potential and Bright Potential Initial sensitivity characteristics of the electrophotographic photoreceptors obtained in Examples 1 to 6 and Comparative Examples 1 to 10 were evaluated using a drum sensitivity tester manufactured by GENTEC.

The measurement was performed according to the following procedure. First, after setting the surface potential to be +900 V and charging the surface of the electrophotographic photosensitive member, the actual surface potential (charging potential V ₀ , unit: V) was measured.
Then, on the surface of the electrophotographic photosensitive member, a halogen lamp monochromatic light from white light of a wavelength 780nm extracted using a band-pass filter (exposure light source) (half-width 20 nm, light intensity 1.0μJ · ^{cm -2)} 40 The surface potential (bright potential V _R , unit: V) was measured when 0.5 seconds had elapsed from the start of exposure after irradiation by millisecond exposure. The smaller the value of the bright potential VR, the higher the sensitivity of the electrophotographic photosensitive member.

The results of the initial sensitivity characteristics are shown in the “initial” column of Table 1.
As a measure durability test charge potential V ₀ which and bright potential V _R variation after (II) endurance test, the process of charging and exposure is shown in the (I), it was carried out continuously 2400 cycles. Then, by measuring the charge potential V ₀ which and bright potential V _R after the durability test was calculated variation between the obtained initial charge potential V ₀ which and bright potential V _R in the above (I).

The results of the sensitivity characteristics after the durability test are shown in the “After durability test” column of Table 1.
(III) Calculation of Absorbance Ratio The absorbance of each of the pigments used in Examples 1 to 6 and Comparative Examples 1 to 10 and Y-type titanyl phthalocyanine used as a charge generator was measured by the following method.

First, Z-type polycarbonate (Teijin Kasei Co., Ltd. Table name "Panlite TS2050") and 100 parts by weight, the pigment 1 part by weight of dimethyl silicone oil (manufactured by Shin-Etsu Chemical Co. of Co. No. "KF-96- 50CS ") 0.1 part by weight and 450 parts by weight of tetrahydrofuran were blended, and mixed and dispersed for 50 hours with an ultrasonic disperser to prepare a coating solution. Next, the obtained coating solution was applied to the surface of an aluminum base tube (diameter 30 mm, length 254 mm), and dried with hot air at 130 ° C. for 30 minutes to form a film having a thickness of 1 μm. Further, the film was peeled off from the aluminum base tube to obtain a measurement sample, and the absorbance of the measurement sample at wavelengths of 600 nm and 780 nm was measured in the film thickness direction of the measurement sample with a spectrocolorimeter.

A measurement sample was prepared in the same manner as above except that 1 part by weight of Y-type titanyl phthalocyanine was used in place of the specific pigment , and the absorbance at wavelengths of 600 nm and 780 nm was measured with a spectrocolorimeter. Measurements were made in the film thickness direction of the sample.
Based on the measured values thus obtained, the ratio of the absorbance of the pigment when the absorbance of the Y-type titanyl phthalocyanine was 1 was obtained at the same measurement wavelength.

Table 1 below shows the absorbance ratio of the larger value when comparing the absorbance ratio at a wavelength of 600 nm and the absorbance ratio at a wavelength of 780 nm.
The absorbance ratio is preferably 0.33 or less, more preferably 0.1 or less, and still more preferably 0.01 or less.
The results of the absorbance ratio are shown in the “absorbance ratio” column of Table 1.

(IV) Evaluation of NOx resistance The electrophotographic photosensitive members obtained in Examples 1 to 6 and Comparative Examples 1 to 10 were respectively manufactured by electrostatic copying machines (manufactured by Kyocera Mita Corporation, product name “Creage 7325”). The surface of the electrophotographic photosensitive member was charged by setting a grid voltage so that the surface potential was + 800V. Next, the electrophotographic photoreceptor was exposed to a 24 ppm NOx gas atmosphere for 50 hours, charged under the same conditions as the grid voltage set before the exposure, and the surface potential was measured.

Thus, the NOx resistance of the electrophotographic photosensitive member was evaluated by calculating the amount of change ΔV (V) in the surface potential before and after exposure to NOx gas.
When the surface potential before exposure is 800 V and the surface potential after exposure is 690 V, the change amount ΔV of the surface potential is −110 V.
The change amount ΔV of the surface potential before and after exposure to NOx gas is preferably −150 V or more (the decrease in surface potential is 150 V or less).

The evaluation results of the NOx resistance are shown in the “NOx resistance” column of Table 1.
The results are shown in Table 1.

表１中、顔料の「処理」欄の「酸＋純水」は、酸で溶解した後に、電気伝導度１μＳ／ｃｍのイオン交換水を用いて、顔料を析出させ、かつ、洗浄したことを示す。また、「酸＋水」は、酸で溶解した後に、電気伝導度約２９０μＳ／ｃｍの水道水を用いて、顔料を析出させ、かつ、洗浄したことを示す。顔料の「伝導度」欄の数値は、洗浄処理後の顔料について測定された、水抽出液の電気伝導度（μＳ／ｃｍ）である。

In Table 1, "acid + pure water" in the "processing" column of the pigment, after dissolving in acid with deionized water electric conductivity of 1 [mu] S / cm, pigment to precipitate, and that the washed Show. “Acid + water” indicates that the pigment was precipitated and washed with tap water having an electric conductivity of about 290 μS / cm after being dissolved with acid. Figures "conductivity" column of the pigment, was measured for the pigment after the cleaning process, an electric conductivity of a water extract (μS / cm).

In Table 1, the units in the “initial” and “after endurance test” columns are [V].
As is clear from Table 1, as a pigment , a pigment having no OH group in the molecule was dissolved with an acid, precipitated with water having an electric conductivity of 10 μS / cm or less, and washed ( When Examples 1 to 5) or a pigment having no OH group in the molecule was washed with water having an electric conductivity of 10 μS / cm or less (Example 6), the electric conduction was carried out for washing and precipitation treatment. The charged potential after the durability test was more stable than when water having a degree of more than 10 μS / cm was used.

In addition, the NOx resistance was significantly different from that when a pigment having an OH group in the molecule was used.
The present invention is not limited to the above description, and various design changes can be made within the scope of the matters described in the claims.

Claims (5)

A photosensitive layer containing a charge generator and a pigment is provided on a conductive substrate, and the pigment is a condensed azo pigment represented by the following general formula (1) or an isoform represented by the following general formula (2). indolinone pigments electric conductivity is washed with water below 10 [mu] S / cm, the electric conductivity of the aqueous extract of the pigment after the cleaning is characterized the following der Turkey 25 .mu.s / cm, Electrophotographic photoreceptor.

(In the general formula (1), R ¹ and R ² independently represent a hydrogen atom, an alkyl group or a chlorine atom. R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² independently represent a hydrogen atom, an alkyl group, a chlorine atom, a perfluoroalkyl group, or a phenoxy group which may have a substituent, in the general formula (2), R ¹³ Represents a phenylene group which may have an alkyl group or a biphenylene group which may have an alkyl group. The electrophotographic photosensitive member according to claim 1 , wherein the charge generating agent is a phthalocyanine pigment. The electrophotographic photosensitive member according to claim 2 , wherein the phthalocyanine pigment is titanyl phthalocyanine. In the X-ray diffraction spectrum, the titanyl phthalocyanine has main diffraction peaks at Bragg angles (2θ ± 0.2 °) of 7.6 ° and 28.6 °, or Bragg angle (2θ ± 0.2 °). The electrophotographic photosensitive member according to claim 3 , which has a main diffraction peak at 27.2 °. The charge generating agent and pigment, together with a charge-transporting material, characterized in that it is contained in the same photosensitive layer, the electrophotographic photosensitive member according to any one of claims 1-4.