JPH0715582B2 - Photoconductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photoreceptor containing a low molecular weight organic compound as a charge transport material.

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 copy image, or powder image transfer method of transferring visible image on photoreceptor to transfer paper such as paper and fixing the transferred image to obtain copy image or on 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 a dark place, less dissipation of charges in a dark place, and being capable of rapidly dissipating charges by light irradiation. It has various drawbacks. For example, selenium-based photoconductors are expensive to manufacture, and are sensitive to heat and mechanical shocks, and thus require 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 light-guiding polymers such as polyvinylcarbazole have been proposed, but these polymers are superior to the above-mentioned inorganic photoconductive materials in film forming property, lightness, and the like. However, it is still inferior to the inorganic photoconductive material in terms of sufficient sensitivity, durability and stability due to environmental changes.

Further, the low molecular weight organic light-transmitting compound is preferable in that the physical properties of the coating film or the electrophotographic properties can be controlled by selecting the type of binder to be used, the composition ratio and the like. Since it is used in combination with a binder, high compatibility with the binder is required.

The photoconductor in which these high-molecular weight and low-molecular weight organic photoconductive compounds are dispersed in the binder resin has drawbacks such as a large residual potential and a low sensitivity due to many carrier traps. Therefore, it has been proposed to blend an organic photoconductive compound with a charge transport material to solve the above-mentioned drawbacks.

Many organic compounds are known as charge transport materials. For example, US Pat. No. 3,189,447 discloses 2,5-bis (p
-Diethylaminophenyl) -1,3,4-oxadiazole is described. U.S. Patent No. 3820989 describes diarylalkane derivatives. In addition,
54-59143 describes hydrazone compounds.

The present invention is a charge-transporting material having a structure different from that of the above-mentioned charge-transporting material, containing an organic charge-transporting material having excellent compatibility with a binder and excellent charge-transporting ability, and having high sensitivity and excellent charging ability. It is an object of the present invention to provide a photoconductor in which fatigue deterioration is small even after repeated use and electrophotographic characteristics are stable.

Means for Solving the Problems The present invention achieves the above object by containing a specific styryl compound as a charge transport material.

The present invention is characterized by having a photosensitive layer containing at least one styryl compound selected from compounds represented by the following general formulas [I] and [II] as a charge transport material: [Wherein R ₁ and R ₅ represent hydrogen, an alkyl group, an alkoxy group or an aralkyl group; R ₂ and R ₆ are alkyl groups,
Represents an aryl group or a heterocyclic group, each group may have a substituent; R ₃ and R ₇ represent an aryl group, a condensed polycyclic group or a heterocyclic group, each group is R ₄ represents hydrogen, an alkyl group, an aryl group or a heterocyclic group, each group may have a substituent; R ₈ represents hydrogen, an alkyl group or Represents an aryl, and each group may have a substituent; R ₃ and R ₄ , R ₇ and R ₈ may together form a ring; n is 1 or 2 Represent ].

Specific examples of the styryl compound represented by the general formulas [I] and [II] according to the present invention include, but are not limited to, those having the following structures.

The styryl compounds represented by the general formulas [I] and [II] according to the present invention can be easily produced by known methods. For example, the following general formula [III] or [IV]: [In the formula, R ₁ and R ₂ are as defined in the formula [I], as defined and R ₅ and R ₆ are as in formula [II], X is ^{_{-P + (R 9) 3 A}} - triphenyl represented by A phosphonium group or a trialkylphosphonium group, or a dialkyl phosphite group represented by -PO (OR ₁₀ ) ₂ . R ₉ represents an alkyl group or an aryl group, A represents a halogen ion, and R ₁₀ represents an alkyl group. ] And a phosphorus compound represented by the following general formula [V] or [VI]: [Wherein R ₃ and R ₄ have the same meanings as [I], and R ₇ and R ₈ have the same meanings as those of the formula [II]].

The phosphorus compound represented by the general formulas [III] and [IV] can be easily prepared by heating the corresponding halomethyl compound and triarylphosphine, or trialkylphosphine or trialkylphosphite directly or in a solvent such as toluene or xylene. Can be manufactured.

Examples of the reaction solvent in the above method include hydrocarbon,
Good alcohols and ethers, methanol, ethanol, isopropanol, butanol, 2-methoxyethanol, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, dioxane, tetrahydrofuran, toluene, xylene, dimethyl sulfoxide, N , N
-Dimethylformamide, N-methylpyrrolidone, 1,3
-Dimethyl-2-imidazolidinone and the like. Among these solvents, polar solvents such as N, N-dimethylformamide and dimethylsulfoxide are preferable.

Examples of condensing agents include caustic soda, caustic potash, sodium sodium hydrogen amide, sodium methylate, potassium-
An alcoholate such as t-butoxide is used.

The reaction temperature can be selected within a wide range from about 0 ° C to about 100 ° C, but is preferably 10 ° C to 80 ° C.

First Construction Example of Photoreceptor Using Styryl Compound of the Present Invention
It is schematically shown in FIGS.

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 styryl 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 styryl 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. 1 further provided with a surface protective layer (7). The photosensitive layer (4) is separated into a charge generation layer (6) and a charge transport layer (5). It may be a function separation 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 photosensitive 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 photoreceptor of the present invention comprises a styryl compound represented by the general formula [I] or [II] dissolved or dispersed in a suitable solvent together with a binder resin, and if necessary, a photoconductive material and an electron attractive compound, Alternatively, a sensitizing dye and a coating solution obtained by adding other pigments are coated on a conductive substrate and dried,
It can be usually produced by forming a photosensitive layer with a film thickness of 5 to 30 μm, preferably 6 to 20 μm.

Specifically, the function-separated type photoreceptor having the same structure as that shown in FIG. 2 in which a charge generation layer and a charge transport layer are laminated on a conductive substrate is used, and a photoconductive material is vacuumed on the conductive substrate. A charge generation layer is formed by vapor deposition or by dispersing in a suitable solvent or a solution in which a binder resin is dissolved, if necessary, and drying to form a charge generation layer, on which a styryl compound and a binder resin are formed. It is obtained by applying a solution dissolved in an appropriate solvent and drying it to form a charge transport layer. At this time, the thickness of the charge generation layer is 4 μm or less, preferably 2 μm.
The thickness of the charge transport layer is 3 to 30 μm, preferably 5 to 20 μm. The proportion of the styryl compound in the charge transport layer is 0.02 to 2 parts by weight, preferably 0.03 to 1.3 parts by weight, based on 1 part by weight of the binder resin. 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 transporting layer is formed on a conductive substrate and a charge generating layer is laminated on the charge transporting layer, similarly to the photosensitive member shown in FIG.

A dispersion type photoconductor having a photosensitive layer laminated on a conductive substrate and having the same structure as the photoconductor of FIG. 1 described above is obtained by dispersing fine particles of a photoconductive material in a solution in which a styryl compound and a resin are dissolved. Then, this is coated on a conductive substrate and dried 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 chargeability becomes poor, or the strength of the photosensitive layer becomes weak.Therefore, the amount of the photoconductive material in the photosensitive layer is 0.01 to 2 parts by weight, preferably 0.05 to 1 part by weight per 1 part by weight, and the ratio of the styryl compound is 0.01 to 1 part by weight of the resin.
˜2 parts by weight, preferably 0.02 to 1.2 parts by weight. It may also be used in combination with a polymeric photoconductive material such as polyvinyl carbazole which itself can be used as a binder. 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-based pigments, quinacridone-based pigments, indigo-based pigments, perylene-based pigments, polycyclic quinone-based pigments, bis-urine imidazole-based pigments, indathlon-based pigments, squarylium-based pigments,
Organic substances such as phthalocyanine pigments, selenium and tellurium,
Inorganic substances such as selenium / arsenic, cadmium sulfide, and amorphous silicon can be used. Other than these, any material can be used as long as it absorbs light and generates charge carriers with extremely high efficiency.

As the binder that can be used in the present invention, all known electrically insulating thermoplastic resins, thermosetting resins, photocurable resins, and photoconductive resins can be used.

Examples of suitable binder resins include, but are not limited to, saturated polyester resins, polyamide resins, acrylic resins, ethylene-vinyl acetate copolymers, ionic or crosslinked olefin copolymers (ionomers), styrene-
Thermoplastic binder such as butadiene block copolymer, polyarylate resin, polycarbonate resin, vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide, styrene resin; epoxy resin, urethane resin, silicone resin, phenol resin, melamine Thermosetting binders such as resins, xylene resins, alkyd resins, and thermosetting acrylic resins; 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 biphenyl, dimethylnaphthalene, dibutyphthalate, o-terphenyl, chloranil, tetracyanoethylene, 2,4,7-trinitro-9.
-Fluorenone, 5,6-dicyanobenzoquinone, tetracyanoquinodimethane, tetrachlorophthalic anhydride, 3,5
An electron-withdrawing sensitizer such as dinitrobenzoic acid, a sensitizer such as methyl violet, rhodamine B, cyanine dye, pyrylium salt and thiapyrylium salt may be used.

The photoreceptor thus formed may optionally have an adhesive layer, an intermediate layer (8) and a surface protective layer (7) as shown in FIGS. 4 and 5 described above.

EFFECTS OF THE INVENTION The photoconductor of the present invention contains the above-mentioned styryl compound as a charge transport material, and thus has a significantly excellent charge transport ability, a stable initial surface potential, and a dark decay rate. It is small enough to be used for a photoconductor and has good charging ability. Further, since the photoconductor of the present invention is excellent in charge transporting ability, it has few carrier traps and high sensitivity and little fatigue deterioration even after repeated use.

Example 1 Chloro diamble represented by the following formula [A] -1 part by weight,
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 solution. This was applied onto an aluminum substrate and dried to form a charge generation layer having a thickness of 1 μm.

The styryl compound (2) 10 described above is formed on the charge generation layer.
Parts by weight, polycarbonate resin (Panlite K-1300;
Teijin Kasei Co., Ltd.) 10 parts by weight of tetrahydrofuran 100
15μm thickness after applying the coating solution dissolved in parts by weight and drying
A photoconductor A was prepared by forming the charge transport layer of

The photoreceptor A thus obtained was corona-charged at -6.0 KV using a commercially available electrophotographic copying machine (EP450Z manufactured by Minolta Co., Ltd.) to obtain an initial potential V ₀ (V) and an initial potential of 1/2. The required exposure amount E _1/2 (lux · sec) and the attenuation rate DDR ₅ (%) of the initial potential when left in the dark for 5 seconds were measured.

Example 2 A styryl compound (4), (5), (7) or (8) was used in the same manner as in Example 1 except that the styryl compound (2) used in Example 1 was replaced with the styryl compound (4). Photosensitive members B, C, D and E to be used respectively were prepared.

With respect to the photoconductors B, C, D and E thus obtained, V ₀ , E _1/2 and DDR ₅ were measured by the same method as in Example 1.

Example 3 2 parts by weight of a bisazo pigment represented by the following formula [B], 1 part by weight of a polyester resin (Vylon 200; manufactured by Toyobo Co., Ltd.),
100 parts by weight of methyl ethyl ketone was 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.

The styryl compound (9) 10 described above is formed on the charge generation layer.
Parts by weight, polyarylate resin (U-100; manufactured by Unitika Ltd.)
A coating liquid prepared by dissolving 10 parts by weight of tetrahydrofuran in 100 parts by weight was applied and dried to form a charge transporting layer having a thickness of 15 μm to prepare a photoconductor F.

With respect to the photoconductor F thus obtained, V ₀ , E _1/2 and DDR ₅ were measured in the same manner as in Example 1.

Example 4 A photoreceptor having the same structure as in Example 3 except that the styryl compounds (11), (12) and (13) are used instead of the styryl compound (9) used in Example 3, respectively. G, H and I were produced.

With respect to the photoconductors G, H, and I thus obtained, V ₀ , E _1/2 , and DDR ₅ were measured by the same method as in Example 1.

Example 5 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 5,000 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; Dainippon Ink and Chemicals, Inc.)
22.5 parts by weight, melamine resin (Super Beckamine J8)
20; Dainippon Ink and Co., Ltd.) 7.5 parts by weight, 10 parts by weight of the styryl compound (14) described above were placed in a ball mill pot together with 100 parts by weight of a mixed solvent prepared by mixing methyl ethyl ketone and xylene in the same amount, and dispersed for 48 hours. A photoconductive coating liquid was prepared, and the coating liquid was applied onto an aluminum substrate and dried to form a photosensitive layer having a thickness of about 15 μm, thereby preparing a photoconductor J.

With respect to the photoconductor J thus obtained, V ₀ , E _1/2 and DDR ₅ were measured by the same method as in Example 1, except that corona charging was performed at +6 KV.

Example 6 A photoconductor K having the same structure as in Example 5 except that the styryl compound (18) was used in place of the styryl compound (14) used in Example 5 was prepared.

V ₀ , E _1/2 and DDR ₅ of the thus obtained photoreceptor K were measured in the same manner as in Example 5.

Comparative Example 1 A photoconductor L having the same structure as in Example 5 except that the styryl compound (14) used in Example 5 was used instead of the styryl compound (14) was prepared.

With respect to the photoconductor L thus obtained, V ₀ , E _1/2 and DDR ₅ were measured by the same method as in Example 5.

Table 1 shows the measurement results of V ₀ , E _1/2 and DDR ₅ of the photoconductors A to K obtained in Examples 1 to 6 and the photoconductor L obtained in Comparative Example 1.

It can be seen that the photoconductors A to K containing the styryl compound of the present invention all have an initial surface potential of 600 V or more, good sensitivity, small dark decay rate and excellent electrophotographic characteristics. The photoconductor L containing no styryl compound of the present invention is
The sensitivity is poor and the dark decay rate is high. Further, a repeated positive charging actual test using a copying machine was conducted on the photoconductors J and K of Examples 5 to 6, and it was found that even after copying 10,000 sheets, both the initial and final images were excellent in gradation and no clear change in sensitivity was observed. Was obtained.

[Brief description of drawings]

1 to 5 are schematic views of a photoreceptor according to the present invention, and FIGS. 1, 4, and 5 are dispersion type photoreceptors in which a photosensitive layer is laminated on a conductive support. 2 and 3 show 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. DESCRIPTION OF SYMBOLS 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 ... … Middle class

Claims (1)

[Claims] 1. A photoreceptor having a photosensitive layer containing as a charge transport material at least one styryl compound selected from compounds represented by the following general formulas [I] and [II]: [Wherein R ₁ and R ₅ represent hydrogen, an alkyl group, an alkoxy group or an aralkyl group; R ₂ and R ₆ are alkyl groups,
Represents an aryl group or a heterocyclic group, each group may have a substituent; R ₃ and R ₇ represent an aryl group, a condensed polycyclic group or a heterocyclic group, each group is R ₄ represents hydrogen, an alkyl group, an aryl group or a heterocyclic group, each group may have a substituent; R ₈ represents hydrogen, an alkyl group or Represents an aryl, and each group may have a substituent; R ₃ and R ₄ , R ₇ and R ₈ may together form a ring; n is 1 or 2 Represent ].