JPS628155A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a laminate type electrophotographic sensitive body high in sensitivity and extremely low in residual potential even after a durability test by forming a layer containing a specified quinone type pigment as an electrostatic charge generating layer and a layer containing a hydrazone type compound as a charge transfer layer. CONSTITUTION:The charge generating layer contains the polycyclic quinone type pigment represented by structural formula (I) and the charge transfer layer contains the hydrazone type compound represented by general formula (II). The charge generating layer can be formed by coating a substrate with said pigment, together with a proper binder, and when needed, a charge transfer material. The charge transfer layer is electrically connected with the charge generating layer, and has a function of receiving charge carriers injected from the charge generating layer in the presence of an electric field and transferring them to the surface. The hydrazone type compound to be used as the charge transfer material is typified by formulae (a)-(3), and when the charge transfer material is added to the charge generating layer, it is proper to add it in an amount of 1-100pts.wt. per 100pts.wt. of the charge generating material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an organic photoconductor, and particularly to an electrophotographic photoreceptor having a charge generation layer and a charge transport layer.

[Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known. On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. Low-molecular organic photoconductors and phthalocyanine pigments such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkanes.

Organic pigments and dyes such as azo pigments, cyanine pigments, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes, and squaric acid methine dyes are known. In particular, photoconductive organic pigments and dyes are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has expanded, making it possible to use a large number of photoconductive compounds. Conductive organic pigments and dyes have been proposed. For example, US Pat. No. 4,123,270, US Pat. No. 4,247,614, US Pat.
No. 51614, No. 4256821, No. 42606
As disclosed in No. 72, No. 4268596, No. 4278747, and No. 4293628, disazo exhibiting photoconductivity is used as a charge generating substance in a photosensitive layer functionally separated into a charge generation layer and a charge transport layer. Electrophotographic photoreceptors using pigments are known. Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, making it possible to provide photoreceptors with extremely high productivity and low cost. It has the advantage of being able to freely control the sensitive wavelength range.

A multilayer photoreceptor, which is obtained by laminating a charge transport layer and a charge generation layer mainly composed of a charge generation material, has higher sensitivity and increased residual potential after durability tests than other single layer photoreceptors. Although it was advantageous, it was still not at a sufficient level.

[Problems to be Solved by the Invention] An object of the present invention is to improve the above-mentioned drawbacks and to provide a laminated electrophotographic photoreceptor with high sensitivity and extremely low residual potential even after a durability test.

[Means for Solving the Problems 1 Effect] The present invention achieves the above-mentioned object by forming a charge generation layer containing a charge generation material as a main component and a charge transport layer containing a charge transport material as a main component on a conductive support. The present invention aims to achieve this by using a specific polycyclic quinone pigment in the charge generation layer and a specific hydrazone compound in the charge transport layer in a laminated electrophotographic photoreceptor having two layers. is a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer comprising a layer containing a polycyclic non-based pigment of structural formula (I), The charge transport layer is a hydrazone compound represented by the general formula (n) (where RI and R2 are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or an alkoxy group).

It represents a substituted or unsubstituted 7-aryloxy group or a substituted amino group, provided that at least one of R2 and R2 is a substituted amino group or an alkoxy group, and R3 and R4 each represent a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkyl group. ≧ represents an unsubstituted aryl group, provided that at least one of R3 and R1 is a substituted or unsubstituted aryl group, and RJ and R may complete a nitrogen-containing heterocycle <, -1R
t, R, and R5 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted amino group, and n represents 0 or 1. The present invention will now be described in detail.

In the laminated electrophotographic photoreceptor of the present invention, the charge generation layer contains as much charge generation material as possible in order to obtain sufficient absorbance, and in order to efficiently inject the generated charge carriers into the charge transport layer. In addition, it is desirable to use a thin film layer, for example, a thin film layer having a thickness of 10p or less, preferably 0.01 to IIL. This means that most of the incident light is absorbed by the charge generation layer and many charge carriers are absorbed. This is due to the fact that the generated charge carriers need to be injected into the charge transport layer without being deactivated by recombination or trapping.

The charge generating material used in the present invention is a polycyclic bovine non-based pigment represented by the structural formula.

The charge generation layer can be formed by coating the above-mentioned pigment and, if necessary, a charge transport material together with a suitable binder (or without a binder) on a substrate, or by forming a vapor deposited film using a vacuum vapor deposition device. can be obtained by Binders that can be used to form the charge generating layer by coating can be selected from a wide variety of insulating resins, and can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthra7ane, and polyvinylpyrene. . Preferably polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.)
Insulating resins such as polycarbonate, polyester, carbonaceous resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, polyvinylpyrrolidone, etc. can be mentioned. The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. Solvents that dissolve these resins vary depending on the type of resin, and are preferably selected from those that do not dissolve the charge transport layer or subbing layer described below.Specific organic solvents include methanol, ethanol, and isopropanol. Alcohols such as tools, ketones such as acetone, methyl ethyl ketone, cyclohexanone, amides such as N,N-dimethylformamide, N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, etc. ethers, esters such as methyl acetate and ethyl acetate, chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichlorethylene, aliphatic halogenated hydrocarbons, benzene, toluene, xylene, ligroin, monochlorobenzene, Aromatics such as dichlorobenzene can be used.

Coating methods include dip coating, spray coating, spinner coating, bead coating,
This can be carried out using a coating method such as a Mayer bar coating method, a blade coating method, a roller coating method, or a curtain coating method.

Drying is preferably carried out by drying to the touch at room temperature, followed by heat drying. Heat drying can be carried out at a temperature of 30 to 200''C for a time in the range of 5 minutes to 2 hours, either still or under blowing air.

The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving and taking charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. have. At this time, this charge transport layer may be laminated on the charge generation layer, or may be layered 1ti1 below it. Preferably, the material (hereinafter referred to as "substance") is substantially insensitive to the wavelength range of electromagnetic waves to which the above-mentioned charge generation layer is sensitive.

The term "electromagnetic waves" as used herein includes a broad definition of "light rays" that includes gamma rays, X-rays, ultraviolet rays, visible light, near infrared rays, infrared rays, far infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both layers trap each other, resulting in a decrease in sensitivity.

The charge transport material used in the present invention has the general formula (TI)
It is a hydrazone compound represented by

In the formula, R1 and R2 represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted amino group.
However, at least one of Ro and R is a substituted amino group or an alkoxy group, R3 and R4 are substituted or unsubstituted alkyl groups, or substituted or unsubstituted 7-aryl groups, provided that R1 and R4 are At least one of them is a substituted or unsubstituted aryl group, and R
1 and R may complete the nitrogen-containing heterocycle, eaves, R6,
Rfu and R? represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted amide group, and n
indicates O or 1.

This hydrazone compound satisfies the above-mentioned conditions as a charge transport material, and has excellent properties particularly in terms of sensitivity and durability.

Typical hydrazone compounds used in the present invention are illustrated below.

Further, in the present invention, the above-mentioned hydrazone compound used in the charge transport layer can be added to the charge generation layer.
The sensitizing effect becomes even more remarkable. When adding a charge transporting material to the charge generation layer, the hydrazone compound should be added in an amount not more than 10 times (weight ratio) as much as the charge generation material, preferably 0,0
A ratio of 1-1 times (weight ratio) is suitable from the viewpoints of high sensitivity, low residual potential, and repeated stability. To form a charge transport layer containing a hydrazone compound, a film can be formed by selecting an appropriate binder. Resins that can be used as binders include acrylic resins, polyarylates, polyesters, polycarbonates, polyethylene styrene, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfones, polyacrylamides, polyamides, and chlorinated rubbers. and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

Since the charge transport layer has a limit to its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, the thickness is 5 to 30 IL, but the preferred range is 8 to 20 IL.
It is. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

A photosensitive layer having such an aM structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. Examples of the substrate having a conductive layer include those whose substrate itself is conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, and nickel.

Indium, gold, platinum, etc. can be used, and plastics (e.g., polyethylene, polypropylene, , polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluorinated ethylene, etc.), conductive particles (e.g. carbon black, silver particles, etc.) are coated on plastic with a suitable binder, and conductive particles are coated on plastic or paper. A substrate impregnated with a conductive polymer, a plastic having a conductive polymer, etc. can be used.

A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. The undercoat layer is casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 610° copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, It can be deposited using aluminum oxide or the like.゛The thickness of the undercoat layer is 0.1 to 40
River, preferably 0.1 to 3 liters is suitable.

When using a photoconductor having a conductive layer, a charge generation layer, and a charge transport layer in this order, and the charge transport material is made of an electron transporting material, the surface of the charge transport layer must be positively charged, and after charging, When exposed to light, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface and neutralize the positive charge, resulting in attenuation of the surface potential and creating electrostatic contrast with the unexposed area. . A visible image is obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be directly fixed, or the toner image can be transferred to paper, plastic film, etc. and then developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or methods, and are not limited to specific ones or methods.

On the other hand, if the charge transport material is a hole transport material, it is necessary to charge the surface of the charge transport layer.

After charging, when exposed to light, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the negative charge, causing a decrease in surface potential and creating a gap between the exposed area and the unexposed area. Electrostatic contrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transport material is used.

The electrophotographic photoreceptor used in the present invention is subject to deterioration due to ultraviolet rays, ozone, etc., dirt due to oil, etc., scratches due to metal chips, etc., damage to the photoreceptor due to photoreceptor contact members such as developing members, transfer members, cleaning members, etc. A protective layer may be further provided on the charge generation layer for the purpose of preventing scratching.
In order to form an electrostatic latent image on the i-layer, the surface resistivity must be 1.
The protective layer used in the present invention is preferably made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene.
It can be formed by dissolving a resin such as butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer or the like in a suitable organic solvent and coating the photosensitive layer on the photosensitive layer and drying it. Additionally, additives such as ultraviolet absorbers can be added to the resin liquid. At this time, the thickness of the protective layer is generally in the range of 0.05 to 20 IL, preferably 0.2 to 5 IL.

Hereinafter, the present invention will be explained according to examples.

Example 1 An ammonia aqueous solution of casein (2 g of casein 11, 1 g of 28% ammonia, 222 ml of water) was coated on an aluminum cylinder by dip coating, and dried to a coating weight of 1.0 g/m. formed a layer.

Next, 1 part by weight of the charge generating material of structural formula (I), 1 part by weight of butyral resin (Eslec BM-2, manufactured by Sekisui Chemical Co., Ltd.) and 30 parts by weight of isopropyl alcohol were dispersed for 4 hours using a ball mill disperser.

This dispersion was applied onto the previously formed subbing layer by a dip coating method and dried to form a charge generation layer. The film thickness was 0.31L.

Next, 1 part by weight of the aforementioned hydrazone compound example (1), 1 part by weight of polysulfone (P1700, manufactured by Union Carbide), and 6 parts by weight of monochlorobenzene were mixed and dissolved by stirring with a stirrer.

This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer.

This film thickness was 12.51L.

A corona discharge of 15 KV was applied to the photoreceptor thus prepared. The surface potential (initial potential Vo) at this time was measured. Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay v5).

Sensitivity was evaluated by measuring the exposure amount (E 1/21ux, aec) required to attenuate the potential V5 after dark decay to 1/2.

These results were as follows.

V, knee 590V, V: -580V, E 1/2:
5', 2 Iux, sec Examples 2 to 5 Example 1 except that hydrazone compound examples (2) to (5) were used in place of hydrazone compound example (1) used in Example 1. Create a photoreceptor in exactly the same way as
The characteristics of this photoreceptor were measured.

These results are shown below.

Trap presentation 1V -V V -V E '/2 lu
x 5ec2 (2) 590 580
5.03 (3) 5115 585 5
．． 54 (4) 590 580 5.3
5 (5) 800 590 5.8 Comparative Examples 1 to 6 The following comparative charge transport substances (1) to (fl) were used in place of the hydrazone compound used in Example 1, and other comparisons were made in exactly the same manner. Photoreceptors of Examples 1 to 6 were prepared and their charging characteristics were measured.

C yo HL size
B6 (6) 590
580 7.5 As is clear from the results of Examples and Comparative Examples.

The laminated photoreceptor of the soft invention was found to have extremely high sensitivity compared to the photoreceptors of Comparative Examples 1 to 6. Furthermore, image formation of the photoreceptors of Examples 1 to 5 was repeated 20,000 times using a copying machine (manufactured by Yanon Co., Ltd., NP-1502).

As a result, good quality images were obtained even after 20,000 cycles of each photoreceptor.
It can be seen that the motsu is also extremely durable.

[Effects of the Invention] As is clear from the above, the present invention uses a specific polycyclic bovine non-based pigment as a charge-generating material in the charge-generating layer, and a specific hydrazone-based compound in the charge-transporting layer. By using this, it has become possible to provide an M-type electrophotographic photoreceptor with extremely high C sensitivity compared to conventional ones.

Claims (2)

[Claims] (1) In a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer consists of a layer containing a polycyclic quinone pigment of structural formula (I), and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) Hydrazone compounds whose charge transport layer is represented by the general formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) (In the formula, R_1 and R_2 are hydrogen atoms , halogen atom,
Represents a substituted or unsubstituted alkyl group, alkoxy group, substituted or unsubstituted aryloxy group, or substituted amino group, provided that at least one of R_1 and R_2 is a substituted amino group or alkoxy group, and R_3 and R_
4 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, provided that at least one of R_3 and R_4 is a substituted or unsubstituted aryl group, and R_3 and R_4 represent a nitrogen-containing heterocycle. It may be completed, R_5, R_6, R_7 and R_8 hydrogen atoms,
a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted amino group, and n represents 0 or 1. Photographic photoreceptor. (2) The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains a hydrazone compound represented by formula (II).