JP2688485B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member excellent in charging stability even after repeated use for a long period of time. [Prior Art] Inorganic substances such as selenium, cadmium sulfide, and zinc oxide have been known as photoconductive materials for electrophotographic photoreceptors. However, these inorganic substances are required as electrophotographic photoreceptors. The characteristics such as photosensitivity, thermal stability, and durability, and manufacturing conditions are not always satisfactory. For example, selenium tends to crystallize due to heat, dirt, etc., and its characteristics are likely to deteriorate. In addition, there are drawbacks such as manufacturing cost, impact resistance, toxicity, and other precautions required in handling. Photoconductors using cadmium sulfide are inferior in moisture resistance and durability,
There are also problems such as toxicity. Zinc oxide also has the drawback of being inferior in moisture resistance and durability. In contrast to electrophotographic photoreceptors using these inorganic photoconductive materials, photoreceptors using organic photoconductive materials are actively used due to their light weight, ease of film formation, manufacturing costs, or wide variation as organic compounds. Research and development are being conducted. For example, in the early stage, polyvinylcarbazole and 2,4,7-trinitro-9-described in Japanese Patent Publication No. 10496/1975 were used.
A photoreceptor containing fluorenone, a photoreceptor obtained by sensitizing polyvinyl carbazole described in JP-B-48-25658 with a pyrylium salt dye, and a photoreceptor containing a eutectic complex as a main component have been proposed. However, these photoreceptors have
It is not enough in terms of durability. Therefore, in recent years, a function-separated type photoconductor in which a charge generation layer and a charge transport layer are separated has been proposed, and a photoconductor in which chlordian blue described in JP-B-55-42380 and a hydrazone compound are combined, and a bisazo compound is used as a charge generation substance. JP-A-53-133445, JP-A-54-21728, JP-A-54-22834
JP-A No. 58-198043, as a charge transport material,
JP-A-58-199352 and the like are known. However, even these function-separated type photoreceptors are not particularly satisfactory in terms of durability, and securing the charging stability has become a problem that cannot be ignored in view of the increasing demand for durability in recent years. That is, when the charging property is lowered, the image density of the copy is lowered in the copying machine, and in the case of the laser printer using the reversal development, the image quality is lowered by causing background stains. In order to solve these problems, it has been proposed to provide an intermediate layer between the conductive substrate and the photosensitive layer. However, in order to stabilize the chargeability of the intermediate layer, when a high resistance material having a high barrier property is used, the chargeability is improved,
There is a drawback that the photosensitivity decreases and the residual potential increases. Further, when a material having a relatively low resistance that does not increase the residual potential is used, the charging stability becomes insufficient. [Objective] In view of such circumstances, an object of the present invention is to provide a photoreceptor having excellent charging stability, in which the charging property does not decrease even after repeated use. [Structure] The present inventor has carried out research to solve the above-mentioned problems, but it is preferable that the photosensitive layer contain a specific group of compounds as a charge transport material and hydroquinone or a derivative thereof in combination. The present invention has been found to be effective, and the present invention has been completed. That is, the present invention provides a charge generation layer on a conductive support,
In an electrophotographic photoreceptor having a photosensitive layer in which charge transport layers are sequentially laminated, the charge transport substance is a compound represented by the following general formula (I), and the photosensitive layer contains hydroquinone or a derivative thereof. Characteristic electrophotographic photoreceptor. In the formula, R ⁴ is a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or (R ⁵ and R ⁶ represent an alkyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group, and R ⁵ and R ⁶
May form a ring), R ² and R ³ are hydrogen atoms, alkyl groups or substituted or unsubstituted phenyl groups, and X is (R ¹ is the same as R ⁴ above), an anthracene ring, or a substituted or unsubstituted N-alkylcarbazole ring, n is 0 or 1, m is 0, 1,
Indicates 2 or 3. Examples of hydroquinone or a derivative thereof used in the present invention include hydroquinone, methylhydroquinone, and 2.
3-dimethylhydroquinone, 2.5-dimethylhydroquinone, trimethylhydroquinone, 2.5-di-amylhydroquinone, t-butylhydroquinone, 2.5-di-
HQ derivatives such as t-butylhydroquinone, 2.5-di-amylhydroquinone, chlorohydroquinone, 2.5-di-t-octylhydroquinone, 2-t-butyl-5-methylhydroquinone, 1,4-diolnaphthalene, 9.10-diolanthracene Is mentioned. Further, examples of the charge transport substance of the formula (I) used in the present invention include: Are not limited to these. Examples of the charge generating substance include the organic compounds shown below. Perylene-based pigments such as perylene anhydride and perylene imide. Indigo pigment. Quinacridone pigment. Polycyclic quinones such as anthraquinones, pyrenequinones, anthanthros and flavantrons. Bisbenzimidazole pigment. Square methine pigment. Induslon pigment. Phthalocyanine-based pigments such as metal phthalocyanines such as copper phthalocyanine and metal-free phthalocyanines. Azo pigments such as monoazo pigments, disazo pigments and triazo pigments. Examples of monoazo pigments include monoazo pigments having anthraquinone, N-phenylcarbazole, and the like as a central skeleton, and examples of disazo pigments include benzidine-based pigments such as diane blue and chlordian blue, and N-ethylcarbazole, stilbene, diphenyl, and the like. Stillebenzene, naphthalene, fluorenone, fluorene, anthraquinone, 2,5-diphenine-1,3,4-
There are disazo pigments having oxadiazole, dibenzothiophene, dibenzodiophene dioxide, acridone, phenanthrenequinone and the like as a central skeleton, and trisazo pigments such as triphenylamine and N.
There are trisazo pigments having phenylcarbazole as a central skeleton. Examples include azurenium salt compounds. The photosensitive layer of the electrophotographic photoreceptor of the present invention comprises a charge generating layer containing a binder for a charge generating substance on a substrate, and a charge transporting substance thereon.
It forms a charge transport layer containing a binder. Further, an intermediate layer may be provided between the photosensitive layer and the substrate to improve the adhesiveness or the charge blocking property. Further, in order to improve mechanical durability such as abrasion resistance, a protective layer may be provided on the photosensitive layer. As the binder used in forming the charge generation layer and the charge transport layer, polycarbonate, polyester, methacrylic resin, acrylic resin, polyethylene, vinyl chloride, vinyl acetate, polystyrene, phenol resin, epoxy resin,
Polyurethane, vinylidene chloride, alkyd resin, silicone resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, etc. are used. These binders can be used alone or as a mixture of two or more kinds. When a photoconductor is formed by using the above-mentioned layer-constituting substances, the film thickness and the ratio of the substances have preferable ranges. In the case of negative charging type (substrate-charge generation layer-charge transport layer),
In the charge generation layer, the ratio of the charge generation substance to the binder is preferably 20 to 500% by weight and the film thickness is preferably 0.1 to 10 μm. In the charge transport layer, the ratio of the charge transport material to the binder is 20 to 20.
It is preferable that the amount is 0% by weight and the film thickness is 5 to 50 μm. The amount of hydroquinone added to the photosensitive layer is preferably 0.01 to 5.0 wt% with respect to the charge transport material when it is added to the charge transport layer in the function-separated type. When it is added to the charge generation layer, it is preferably 0.1 to 20.0 wt% with respect to the charge generation substance. In the case of the dispersion type, it is desirable that the content is 0.01 to 5.0 wt% with respect to the charge transport material. The intermediate layer, which is provided as necessary, generally contains a resin as a main component, but these resins have high solvent resistance against general organic solvents considering that the photosensitive layer is coated thereon with a solvent. Is desirable. Examples of such resins include polyvinyl alcohol, casein, water-soluble resins such as sodium polyacrylate, copolymer nylon, alcohol-soluble resins such as methoxymethylated nylon, polyurethane,
Examples thereof include curable resins that form a three-dimensional network structure such as melamine resin, alkyd resin, phenol resin, and epoxy resin. Further, a fine powder pigment of a metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide or indium oxide may be added to the intermediate layer in order to prevent moire and reduce the residual potential. Further, the charge generation layer of the present invention, the solvent or dispersion medium used in forming the charge transport layer, N, N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexane, benzene, toluene, xylene, chloroform, 1,2-dichloroethane , Dichloromethane, monochlorobenzene, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl acetate,
Butyl acetate, dimethyl sulfoxide, etc. can be mentioned. Substrates used in the electrophotographic photoreceptor of the present invention include metal drums such as aluminum, brass, stainless steel and Ni, and sheet substrates. Alternatively, a metal such as Al or Ni is vapor-deposited on a material such as polyethylene terephthalate, polypropylene, nylon or paper, or a conductive substance such as titanium oxide, tin oxide or carbon black is applied together with an appropriate binder. Examples thereof include electrically conductive treated plastic, sheet-shaped or cylindrical substrates such as paper. The electrophotographic photosensitive member having the above-described structure does not deteriorate the characteristics of the photosensitive member such as charging stability even when used for a long period of time, and the image does not deteriorate. Examples of the present invention will be shown below. Examples 1 to 3 1 part by weight of an alcohol-soluble polyamide (Amilan CM-8000; manufactured by Toray) was dissolved in a mixed solvent of 8 parts by weight of methanol and 5 parts by weight of n-butanol. To this, 3 parts by weight of titanium oxide powder (Taipaque A-100; made by Ishihara Sangyo Co., Ltd.) was added and dispersed by a ball mill for 12 hours to prepare an intermediate layer coating solution. This was applied to an aluminum drum having a long diameter of Φ40 mm and a length of 255 mm by a dip coating method and dried to form an intermediate layer having a thickness of 2 μm. Next, polyvinyl butyral resin [S-REC BL-S
(Sekisui Chemical Co., Ltd.)] 2 parts by weight of 1.2 dichloroethane 125
It was dissolved in 1 part by weight, and 1 part by weight of x-type metal-free phthalocyanine prepared in the same direction as described in JP-B-49-4338 was added thereto, and dispersed by an ultrasonic disperser. The charge generation layer coating liquid thus obtained was applied onto the intermediate layer by a dip coating method and dried to form a charge generation layer having a thickness of 0.5 μm. Further, 8 parts by weight of a charge transport material represented by the following structural formula (II): 10 parts by weight of a polycarbonate resin (Panlite K-1300; Teijin Chemicals Ltd.) Silicone oil (KF: 50; manufactured by Shin-Etsu Chemical Co., Ltd.) 0.002 parts by weight and 0.04 parts by weight of the hydroquinone derivative shown below were dissolved in 85 parts by weight of methylene chloride, and Example 1 Methylhydroquinone Example 2 2.5-di-tert-butyl Hydroquinone Example 3 1.4-diol naphthalene A charge transport layer coating solution was prepared. This was applied onto the charge generation layer by a dip coating method and dried to form a charge transport layer having a thickness of 20 μm. Comparative Examples 1 to 3 Photoreceptors were produced in the same manner as in Examples 1 to 3 except that the additives added to the charge transport layers of Examples 1 to 3 were changed to the following. Comparative Example 1 2.6-Di-tert-butyl-4-methylphenol Comparative Example 2 4.4-Thiobis (3-methyl-6-tert-butylphenol) Comparative Example 3 Additive-free Example 4 Charge generation of Example 1 A photoconductor was prepared in exactly the same manner as in Example 1 except that methylhydroquinone was added to the layer in an amount of 3 wt% with respect to the charge generating substance, and methylhydroquinone was removed from the charge transport layer. The photoconductor obtained above was laser-printed (PC-LASE
R-6000; manufactured by Ricoh Co., Ltd.) and the photoreceptor was evaluated. The evaluation was carried out by measuring the image and the photoreceptor surface potential after 20,000 copies at the initial stage. The surface potential was measured by removing the developing device and attaching a surface potential meter at the developing position. As described above, the ones to which the hydroquinone derivative was added exhibited stable charging characteristics, and the other ones showed a drastic decrease in the surface potential of the unexposed area. Since this laser printer uses the reversal development method, when the surface potential is lowered, the unexposed portion is stained as shown in the comparative example. Reference Example 1 Similar to Example 2, an intermediate layer was formed on an aluminum drum, and the charge transport layer coating solution of Example 2 was applied onto the intermediate layer and dried to form a charge transport layer having a thickness of 20 μm. did. Next, 4 parts by weight of polycarbonate resin (Panlite L-1250; manufactured by Teijin Chemicals) was added to 200 parts by weight of 1.2-dichloroethane.
It was dissolved in 200 parts by weight of 1.2-trichloroethane, and 1 part by weight of the x-type metal-free phthalocyanine shown in Example 1 was added thereto and dispersed by an ultrasonic disperser. Furthermore, 3 parts by weight of the charge transport material (II) shown in Example 1 was added to the above dispersion liquid and dissolved to prepare a charge generation layer coating liquid. This was spray-coated on the charge-transporting layer and dried to form a charge-generating layer having a thickness of 3 μm to prepare an electrophotographic photoreceptor. Comparative Example 4 A photoconductor was prepared in the same manner as in Example 5 except that 2.5-di-tert-butylhydroquinone was removed from the charge transport layer of Reference Example 1. Reference Example 2 In the same manner as in Example 1, an intermediate layer was formed on an aluminum drum. Polycarbonate resin (Panlite L-
1300; Teijin Kasei) 20 parts by weight of 1.2-dichloroethane 250
It was dissolved in 5 parts by weight, and 5 parts by weight of the x-type metal-free phthalocyanine shown in Example 1 was added thereto and dispersed by an ultrasonic disperser. Further, the above-mentioned dispersion liquid is represented by the following structural formula (III). 15 parts by weight of a charge transport material and 0.1 part by weight of 2.5-di-amyl hydridoquinone were added and dissolved to prepare a photosensitive layer coating solution. This liquid was applied onto the above-mentioned intermediate layer by a dip coating method and dried to form a photosensitive layer having a film thickness of 16 μm to prepare a photoreceptor. Comparative Example 5 A photoconductor was prepared in the same manner as in Reference Example 2 except that 2.5-di-amylhydroquinone was removed from Reference Example 2. The photoreceptors obtained in Reference Examples 1 and 2 and Comparative Examples 4 and 5 were evaluated using a modified laser printer (PC-LASER-6000). The contents of the remodeling are that the polarity of the charger and various biases is reversed, and the charger, quenching lamp, and
The laser writing system was activated. Further, the developing machine was removed and a surface electrometer was attached there. Initial and photoreceptor 10,000 with the above modified laser printer
The photoconductor surface potential after rotation was measured. [Effect] As described above, the photoconductor of the present invention has good charging stability, and does not cause image defects such as reduction in image density and background stain even when it is repeatedly used.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kenji Seki               1-3-6 Nakamagome, Ota-ku, Tokyo               Ricoh Company (72) Inventor Shoichi Ota               1-3-6 Nakamagome, Ota-ku, Tokyo               Ricoh Company                (56) References JP-A-63-18366 (JP, A)

Claims (1)

(57) [Claims] In an electrophotographic photoreceptor having a photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support, the charge transport substance is a compound represented by the following general formula (I), and the above photosensitive layer An electrophotographic photoconductor characterized by containing hydroquinone or a derivative thereof. In the formula, R ⁴ is a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or (R ⁵ and R ⁶ represent an alkyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group, and R ⁵ and R ⁶
May form a ring), R ² and R ³ are a hydrogen atom, an alkyl group or a substituted or unsubstituted phenyl group, and X is (R ¹ has the same meaning as R ⁴ above), an anthracene ring, or a substituted or unsubstituted N-alkylcarbazole ring, n is 0 or 1, m is 0, 1,
Indicates 2 or 3.