JPH073591B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive compound as a main component.

2. Description of the Related Art Generally, in electrophotography, the surface of a photosensitive layer of a photoconductor is charged and exposed to form an electrostatic latent image, which is developed with a developer to be visualized. Direct method of fixing on top to obtain a copy image, or powder image transfer method of transferring a visible image on a photoreceptor onto a transfer paper such as paper and fixing the transferred image to obtain a copy image or on a photoreceptor Transfer the electrostatic latent image onto the transfer paper and develop the electrostatic latent image on the transfer paper.
A latent image transfer method for fixing is known.

Conventionally, it has been known to use an inorganic photoconductive material such as selenium, cadmium sulfide, or zinc oxide as a photoconductive material for forming a photosensitive layer of a photoconductor used in this type of electrophotography. . These photoconductive materials have many advantages, such as being able to be charged to an appropriate potential in the dark, having a small dissipation of electric charges in the dark, or being capable of rapidly dissipating electric charges by irradiation with light. On the other hand, it has the following various drawbacks. For example, with selenium-based photoreceptors,
The manufacturing cost is high, and it is vulnerable to heat and mechanical shocks, so it requires careful handling. In addition, with cadmium sulfide-based photoreceptors and zinc oxide photoreceptors, stable sensitivity cannot be obtained in humid environments, and the dye added as a sensitizer causes charge deterioration due to corona charging and photobleaching due to exposure. It has the drawback that stable characteristics cannot be provided over a long period of time.

On the other hand, various organic photoconductive polymers such as polyvinylcarbazole have been proposed, but these polymers are superior to the above-mentioned inorganic photoconductive materials in terms of film-forming property and light weight. However, it is still inferior to inorganic photoconductive materials in terms of sufficient sensitivity, durability and stability due to environmental changes.

Problems to be Solved by the Invention In recent years, various researches and developments have been carried out in order to solve the drawbacks and problems of these photoreceptors, but a charge generation layer and a charge transport layer are formed on a conductive support. There has been proposed a function-separated type photoconductor in which the layers are laminated, and a single-layer type photoconductor in which a photoconductive layer having a charge generation function and a charge transport function is laminated on a support.

The former function-separated type photoconductor has a wide selection range of each substance, and is a high-performance photoconductor by combining the best substances in electrophotographic properties such as charging property, sensitivity, residual potential, repetitive property and printing durability. Can be provided.

In the case of such a function-separated type photoreceptor, it is necessary to select a material in which the charge carriers generated in the charge generation layer are transported to the surface without being trapped during the presence of an electric field. Is. In this regard, for example, a photoconductor using a hydrazone compound, a pyrazoline compound, or the like as a charge transport substance is known.

However, even with such a photoconductor, it is not easy to obtain a photoconductor that satisfies the general electrostatic characteristics, and it is difficult to obtain a photoconductor having good photosensitivity. The reality is that few have

Further, even in a photoreceptor having a photosensitive layer containing a charge-generating substance and a charge-transporting substance, few have a charge-transporting substance having an excellent charge-transporting ability and practically satisfy all the requirements such as sensitivity and repeatability.

The present invention has been made in view of the above facts, and an object thereof is electrophotographic light containing a charge-transporting substance that is excellent in overall electrostatic properties, particularly high in photosensitivity, and excellent in charge-transporting ability. It is to provide a feeling.

Another object of the present invention is to provide an electrophotographic photosensitive member which has less residual potential and fatigue deterioration due to repeated use, has good stability to light, and has excellent durability.

Means for Solving the Problems The present invention achieves the above object by using a specific organic compound as a charge transport material of an electrophotographic photoreceptor.

That is, the electrophotographic photosensitive member according to the present invention, on the conductive substrate,
An electrophotographic photoreceptor containing at least one of the compounds represented by the following general formula [I] or [II] as a charge transport material.

[In the formula, R ₁ , R ₃ , R ₄ and R ₅ represent an aryl group which may have a substituent. At least one of R ₁ , R ₃ , R ₄ and R ₅ is an aryl group having a substituted amino group.

R ₂ represents hydrogen or an alkyl group. ] [In the formula, R ₆ and R ₇ represent an aryl group which may have a substituent, R ₈ represents a hydrogen atom or an alkyl group, and R ₉ represents an aryl group having a substituted amino group. The above-mentioned general formula [I] of the present invention is represented by the formula R ₁ , R ₃ , R ₄ and R ₅
At least one of them is an aryl group having a substituted amino group, and in the general formula [II], R ₉ is an aryl group having a substituted amino group.

Therefore, in the present invention, at least one of the above-mentioned compounds [1] or [II] is used in the charge-transporting layer in the function-separated type laminated photoreceptor and in the dispersion-type photoreceptor. By using it as a charge transport material in a photoconductive layer, an electrophotographic photoreceptor having excellent electrophotographic properties such as charge retention ability, sensitivity and residual potential, and excellent charge transport ability is produced.

Specific preferred examples of the organic compound of the present invention include, but are not limited to, those having the following structural formulas.

The general method for synthesizing the organic compound of the present invention is described in detail in JP-B-43-22909 and JP-B-42-27192, and the compound can be easily synthesized based on the method.

The above organic compounds may be used alone or in combination of two or more.

The organic compound of the present invention mainly functions as a charge transport material, and is used together with a photoconductive substance (charge generating substance) such as copper phthalocyanine in a usual electrophotographic copying machine.

A structural example of an electrophotographic photosensitive member using the organic compound of the present invention is schematically shown in FIGS. 1 to 5.

FIG. 1 shows a photoreceptor in which a photoconductive layer (4) in which a photoconductive material (3) and a charge transport material (2) are mixed with a binder is formed on a substrate (1). The organic compound of the present invention is used.

FIG. 2 shows a function-separated type photoreceptor having a charge generation layer (6) and a charge transport layer (5) as a photosensitive layer. The charge transport layer (5) is formed on the surface of the charge generation layer (6). There is. The compound of the present invention is incorporated in the charge transport layer (5).

Similar to FIG. 2, FIG. 3 shows a function-separated type photoreceptor having a charge generation layer (6) and a charge transport layer (5). On the contrary to FIG. A charge generation layer (6) is formed.

FIG. 4 shows the surface of the photoreceptor of FIG. 2 further provided with a surface protective layer (7). The photosensitive layer (4) is divided into a charge generation layer (6) and a charge transport layer (5). It may be a separated function type.

FIG. 5 shows an intermediate layer (8) provided between the substrate (1) and the photosensitive layer (4). The intermediate layer (8) has improved adhesion, improved coatability, and substrate protection. , Can be provided to improve the charge injection property from the substrate to the photoconductive layer. As the intermediate layer, polyimide resin, polyester resin, polyvinyl butyral resin, casein or the like may be used. In the photoreceptor of this aspect, the photosensitive layer may have a function-separated type.

The electrophotographic photoreceptor of the present invention comprises an organic compound represented by the general formula [I] or [II] dissolved or dispersed in a suitable solvent together with a binder and, if necessary, a photoconductive material and an electron. A coating solution obtained by adding an inhalable compound, a sensitizing dye, or other pigment is coated on a conductive substrate and dried, and usually 5 to
It can be produced by forming a photosensitive layer having a film thickness of 30 μm, preferably 6 to 20 μm.

Specifically, in the function-separated type photoreceptor having the same structure as that shown in FIG. 2 which is formed by laminating the charge generation layer and the charge transport layer on the conductive support, the photoconductive material is formed on the conductive support. Is vacuum-deposited, or is dispersed in a suitable solvent or, if necessary, a solution in which a binder resin is dissolved, is applied and dried to form a charge generation layer. It can be obtained by applying a solution prepared by dissolving the organic compound of the invention and a binder in a suitable solvent and drying the solution to form a charge transport layer. At this time, the thickness of the charge generation layer is 4 μm or less, preferably 2 μm or less, and the thickness of the charge transport layer is 3 to 30 μm.
m, preferably 5 to 20 μm. The ratio of the organic compound in the charge transport layer is 1 part by weight of the binder resin.
The amount is preferably 0.02 to 2 parts by weight, preferably 0.03 to 1.3 parts by weight. Also, other charge transport materials may be combined. In the case of the polymer charge transport material which itself can be used as a binder, other binder may not be used.
The photosensitive member may have a structure in which a charge transport layer is formed on a conductive support, and a charge generating layer is further laminated thereon, similarly to the photosensitive member of FIG. 3 described above. Four
As shown in FIGS. 5 and 5, an adhesive layer / intermediate layer (8) and a surface protective layer (7) may be provided if necessary.

The charge transport layer used in the present invention is preferably formed by applying a solution prepared by dissolving an organic compound represented by the general formula [I] or [II] and a binder in a suitable solvent and drying the solution. .

A dispersion type photoconductor having a photosensitive layer laminated on a conductive support and having the same structure as the photoconductor of FIG. 1 described above is prepared by dissolving fine particles of a photoconductive material in an organic compound of the present invention and a resin. It is obtained by dispersing in a solution, coating this on a conductive support, and drying to form a photosensitive layer. At this time, the thickness of the photosensitive layer is 3 to 30 μm, preferably 5 to 20 μm. If the amount of the photoconductive material used is too small, the sensitivity is poor, and if it is too large, the charging property is deteriorated or the strength of the photosensitive layer is weakened. 0.01 to 2 parts by weight, preferably 0.05 to 1 part by weight, is preferable, and the ratio of the compound of the present invention is 0.01 to 2 parts by weight with respect to 1 part by weight of the resin.
2 parts by weight, preferably 0.02 to 1.2 parts by weight are suitable.
Further, a polymer photoconductor such as polyvinyl carbazole which itself can be used as a binder may be used in combination. It may also be combined with other charge transport materials such as hydrazone compounds.

Examples of materials used for the photoconductive material of the photoreceptor of the present invention include bisazo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, cyanine dyes, styryl dyes, pyrylium dyes. , Azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indathlon pigments, squarylium pigments, phthalocyanine pigments, and other organic substances, selenium, selenium, Inorganic substances such as tellurium, selenium / arsenic, cadmium sulfide, and amorphous silicon can be given. In addition, any material can be used as long as it absorbs light and generates charge carriers with extremely high efficiency.

As the binder in the present invention, a thermoplastic resin, a thermosetting resin, a photocurable resin, or a photoconductive resin, which is known per se, which is electrically insulating, can be used.

Suitable binder resins include, for example, saturated polyester resins, polyamide resins, acrylic resins, ethylene-vinyl acetate copolymers, ion-crosslinked olefin copolymers (ionomers), styrene-butadiene block copolymers, polyarylates, polycarbonates, Thermoplastic binder such as vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide, styrene resin; epoxy resin, urethane resin, silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin, thermosetting acrylic resin Thermosetting binders such as; photocurable resins; photoconductive resins such as poly-N-vinylcarbazole, polyvinylpyrene, and polyvinylanthracene. These can be used alone or in combination.

These electrically insulating resins are individually measured 1 × 10 ¹² Ω · cm
It is desirable to have the above volume resistance. More preferred are polyester resin, polycarbonate resin, and acrylic resin.

The photoreceptor of the present invention, together with a binder, a plasticizer such as halogenated paraffin, polychlorinated biphenyls, dimethylnaphthalene, dibutyl phthalate, o-terphenyl, chloranil, tetracyanoethylene, 2,4,7-trinitro-
9-fluorenone, 5,6-dicyanobenzoquinone, tetracyanoquinodimethane, tetrachlorophthalic anhydride, 3,
An electron-withdrawing sensitizer such as 5-dinitrobenzoic acid, a sensitizer such as methyl violet, rhodamine B, a cyanine dye, a pyrylium salt, and a thiapyrylium salt may be used.

Hereinafter, the present invention will be specifically described with reference to examples.

Example General formula 1 part by weight of a bisazo pigment represented by the formula, 1 part by weight of a polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) and 50 parts by weight of tetrahydrofuran were placed in a ball mill pot and dispersed for 24 hours to obtain a photosensitive coating. This was applied onto an aluminum substrate and dried to form a charge generation layer having a thickness of 1 μm.

On the charge generation layer, 10 parts by weight of the above-mentioned organic compound (1) of the present invention, a polycarbonate resin (Panlite K
-1300, manufactured by Teijin Chemicals Ltd.) 10 parts by weight of tetrahydrofuran
The coating liquid dissolved in 80 parts by weight is applied and dried to a thickness of 20μ.
The charge-transporting layer of 1 was formed to prepare a laminated type photoreceptor.

The photoconductor A thus obtained was subjected to corona charging at -6.0 KV using a commercially available electrophotographic copying machine (EP450Z manufactured by Minolta Camera Co.) to obtain an initial surface potential V _O (V) and an initial surface potential of 1 /. Exposure required to reach 2 E _1/2 (lux · sec), 5
Attenuation rate DDR of initial surface potential when left in the dark for 2 seconds
₁ (%) and residual potential V _R (V) were measured.

Examples 2 to 3 Two types of laminated photoreceptors were produced in the same manner as in Examples except that the compounds (2) and (3) of the present invention were used instead of the organic compound (1) used in Example 1. .

For the photoreceptor thus obtained, V _O , E _1/2 and DDR ₁ were measured in the same manner as in Example 1.

Example 4 The following general formula 2 parts by weight of the bisazo pigment represented by the formula, 1 part by weight of a polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) and 100 parts by weight of methyl ethyl ketone were placed in a ball mill pot and dispersed for 24 hours to obtain a photosensitive coating solution. This was applied onto an aluminum substrate and dried to form a charge generation layer having a thickness of 1 μm.

Onto this charge generation layer, 10 parts by weight of the above-mentioned organic compound (5) of the present invention and 10 parts by weight of polyarylate resin (U-100, manufactured by Unitika Ltd.) are dissolved in 100 parts by weight of chlorobenzene to apply a coating solution. Then, it was dried to form a charge transport layer having a thickness of 20 μm to prepare a laminated type photoreceptor.

For the photoreceptor thus obtained, V _O , E _1/2 and DDR ₁ were measured in the same manner as in Example 1.

Examples 5-6 Two kinds of laminated photoreceptors were prepared in the same manner as in Example 4 except that the compounds (7) and (9) of the invention were used instead of the organic compound (5) used in Example 4. It was made.

For the photoreceptor thus obtained, V _O , E _1/2 and DDR ₁ were measured in the same manner as in Example 1.

Example 7 50 parts by weight of copper phthalocyanine and 0.2 parts by weight of tetranitrocopper phthalocyanine were dissolved in 500 parts by weight of 98% concentrated sulfuric acid with sufficient stirring, and this was poured into 5000 parts by weight of water to obtain photoconductivity of copper phthalocyanine and tetranitrocopper phthalocyanine. After depositing the material composition, it was filtered, washed with water, and dried at 120 ° C. under reduced pressure.

10 parts by weight of the photoconductive composition thus obtained was used as a thermosetting acrylic resin (Acridic A405, manufactured by Dainippon Ink and Chemicals).
22.5 parts by weight, melamine resin (Super Beckamine J820,
(Dainippon Ink and Co., Ltd.) 7.5 parts by weight and 10 parts by weight of the organic compound (10) of the present invention are placed in a ball mill pot together with 100 parts by weight of a mixed solvent of methyl ethyl ketone and xylene in the same amount, and dispersed for 48 hours for photoconductivity. Adjust the coating liquid,
Apply this coating solution on an aluminum substrate and dry it to a thickness of approximately
A photosensitive layer was formed by forming a photosensitive layer of 15 μm.

Corona charging of the photoconductor thus obtained is + 6KV
Except that carried out in the same method as in Example 1, V _O,
E _1/2 and DDR ₁ were measured.

Examples 8 to 9 Instead of the organic compound (10) used in Example 7, the compound (1
A photoconductor using (2) and (13) was prepared.

For the photoreceptor thus obtained, V _O , E _1/2 and DDR ₁ were measured in the same manner as in Example 7.

Table 1 shows the measurement results of V _O , E _1/2 and DDR ₁ of the photoconductors obtained in Examples 1 to 9.

As is apparent from Table 1, the photoconductor using the organic compound of the present invention has a sufficient initial potential in the electrophotographic process, has excellent photosensitivity, has a small dark decay rate, and has a good charging ability.

Further, repeated positive charging actual tests using a copying machine were carried out for Examples 7 to 9. When 10,000 copies were made, both the initial and final images were excellent in gradation, and clear images were obtained without sensitivity change. .

EFFECTS OF THE INVENTION As is clear from the results of the above examples, the photoconductor of the present invention is a photoconductor having high sensitivity, a small residual potential, and a small sensitivity change even in repeated copying.

[Brief description of drawings]

1 to 5 are schematic views of a photosensitive member according to the present invention, and FIGS. 1, 4, and 5 show a dispersion type photosensitive member obtained by laminating a photosensitive layer on a conductive support. The structure is shown in FIGS. 2 and 3 which shows the structure of a function-separated type photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support. (1) ... Conductive support, (2) ... Charge transport material (3) ... Photoconductive material, (4) ... Photosensitive layer (5) ... Charge transport layer, (6) ... Photoconductive layer (7) ... Surface protective layer, (8) ... Intermediate layer

Claims (1)

[Claims] 1. An electrophotographic photosensitive member according to the present invention, wherein an electrophotographic photosensitive member comprises, on a conductive substrate, at least one compound represented by the following general formula [I] or [II] as a charge transporting material. Photoconductor. [In the formula, R ₁ , R ₃ , R ₄ and R ₅ represent an aryl group which may have a substituent. At least one of R ₁ , R ₃ , R ₄ and R ₅ is an aryl group having a substituted amino group. R ₂ represents hydrogen or an alkyl group. ] [In the formula, R ₆ and R ₇ represent an aryl group which may have a substituent, R ₈ represents a hydrogen atom or an alkyl group, and R ₉ represents an aryl group having a substituted amino group. ]