JPS627057A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhances sensitivity and to improve durability by incorporating a specified polycyclic quinone type pigment in an electrostatic charge generating layer and a specified hydrazone type compound in a charge transfer layer. CONSTITUTION:The charge generating layer containing the polycyclic quinone type pigment represented by formula I and the charge transfer layer containing the hydrazone type compound represented by formula II (each of R1, R2, R3, R4 is optionally substituted alkyl or such aryl, and each may combine with a N atom to form a 5- or 6-membered ring; and each of R5-R6 is H, halogen, nitro, optionally substituted alkyl, alkoxy, such aryloxy, such acyl, or such amino; and R is a divalent organic group) are laminated on a conductive substrate. Such a structure permits the obtained photosensitive body to be enhanced in photosensitivity and further, the addition of said hydrazone type compound of formula II to the charge generating layer permits the sensitizing effect to be made more remarkable.

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. For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene, low-molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkane, and phthalocyanine pigments. .

Organic pigments and dyes such as azo pigments, cyanine pigments, polycyclic bovine 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;
Same No. 4247614, Same No. 4251613, Same No. 4
No. 251614, No. 4256821, No. 4260
No. 672, fJJ4268596, fJJ42787
As disclosed in No. 47 and No. 4293628, an electrophotographic photoreceptor using a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer functionally separated into a charge generation layer and a charge transport layer is disclosed. 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 photosensitive wavelength range.

A multilayer photoconductor obtained by laminating a charge transport layer and a charge generation layer mainly composed of a charge generation material has advantages over other single-layer photoconductors in terms of sensitivity and increased residual potential after durability tests. However, 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 and effects for solving the problems] The present invention achieves the above 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. This is achieved 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.

The present invention provides an aN type electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, wherein the charge generation layer is a layer containing a polycyclic bovine non-based pigment of structural formula (I). , the charge transport layer is a hydrazone compound represented by the general formula (II) (wherein R and R2 are a substituted or unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or a 5-membered ring or a 6-membered ring together with a nitrogen atom) Indicates the atomic group necessary to complete the membered ring, and R3 and R4 are substituted or unsubstituted alkyl groups, substituted or unsubstituted aryl groups, or atoms necessary to complete the 5-membered ring or 6-membered ring together with the nitrogen atom. R5 and R (represent a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted acyl group) 7
□represents a mino group, and R represents a divalent organic residue).

The present invention will be explained in detail below.

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, the thin film layer 1 should be a thin film layer having a thickness of, for example, 10 μl or less, preferably 0.01 to 1 μl (desirably, this means that most of the incident light is absorbed by the charge generation layer, This is due to the need to generate charge carriers and to inject the generated charge carriers into the charge transport layer without being deactivated by recombination or trapping.

The charge generating material used in the present invention is a polycyclic quinone pigment represented by the structural formula.

The charge generating layer can be obtained by coating the above-mentioned pigment and, if necessary, a charge transporting material together with a suitable binder (or without a binder) on a substrate. The binder that can be used when forming 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, polyvinylanthracene, and polyvinylpyrene. Preferably polyvinyl butyral, polyarylate (li!f of bisphenol A and phthalic acid)
fi coalescence, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein,
Examples include insulating resins such as polyvinyl alcohol and polyvinylpyrrolidone. 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 underlying charge transport layer or subbing layer.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, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene, or benzene, toluene, and xylene.

Aromatics such as ligroin, monochlorobenzene, dichlorobenzene, etc. 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 and then heating. Drying by heating is performed at a temperature of 30 to 200°C for 5 minutes to
It can be carried out stationary or under draft for a period of time in the range of 2 hours.

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. In this case, this charge transport layer may be laminated on the charge generation layer, or may be formed as a layer under it, and is a substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as a charge transport material). ) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive.

The term "electromagnetic waves" as used herein includes the broad definition of "light rays" including γ-rays, X-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 is general
It is a hydrazone compound represented by

In the formula, R1 and R represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or an atomic group necessary to complete a 5-membered ring or a 6-membered ring together with a nitrogen atom, and R5 and R4 are Indicates an atomic group necessary to complete a 5-membered ring or 6-membered ring together with a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a nitrogen atom, and RJ, R, and H are hydrogen atoms and halogen atoms. , a nitro group, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted 7-aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted 7-mino group, R is a divalent organic Residues are shown.

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.

N N In addition, 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 a charge transporting material is added to the charge generation layer, the hydrazone compound is 10 times or less (weight ratio) of the charge generation material, preferably 0.01
~1 times (weight ratio) is suitable from the viewpoint of high sensitivity, low residual potential, and repetition stability. To form a charge transport layer containing a hydrazone compound, a film can be formed by selecting an appropriate binder. One example of resin that can be used as a binder is acrylic resin.

polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer,
Examples include insulating resins such as acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and chlorinated rubber, and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. be able to. The charge transport layer is a charge
□There is a limit to how much carrier can be transported, so the film cannot be made thicker than necessary. Generally 5-30
#L, but the preferred range is 8 to 20 L. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is a conductive layer provided on a substrate having a conductive layer.
21! Examples of the substrate having i include those whose substrate itself is electrically conductive, such as aluminum, aluminum alloy, copper,
Zinc, stainless steel, vanadium, molybdenum, chromium,
Titanium, nickel, indium, gold, platinum, etc. can be used, and in addition, aluminum, aluminum alloy,
Plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyethylene fluoride, etc.) that are coated with indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. by vacuum deposition, conductive A substrate in which particles (for example, carbon black, silver particles, etc.) are coated on a plastic together with a suitable binder, a substrate in which plastic or paper is impregnated with conductive particles, 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 formed from aluminum oxide or the like. The thickness of the undercoat layer is suitably 0.1 to 40μ, preferably 0.1 to 3μ.

When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material in the charge transport layer is composed of an electron transport material, the surface of the charge transport layer must be positively charged; When exposed to light after being charged, 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 an electrostatic contrast between it and the unexposed area. occurs.

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, and then visually imaged 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, when the charge transport material is a hole transport material, it is necessary to charge the surface of the charge transport layer negatively, and when exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. , after which it reaches the surface and neutralizes the negative charges, resulting in attenuation of one surface type, creating an electrostatic contrast with the unexposed area. 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 according to the present invention is susceptible to deterioration due to ultraviolet rays, ozone, etc., dirt from oil, etc., scratches from metal chips, etc., and damage to the photoreceptor due to photoreceptor contact members such as developing members, transfer members, and cleaning members. A retention 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 this retention layer, a surface resistivity of 1 is required.
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-butadiene copolymer, styrene-acrylic acid copolymer, styrene. It can be formed by applying a solution prepared by dissolving a resin such as acrylonitrile covolure in a suitable organic solvent onto the photosensitive layer and drying it. Moreover, additives such as ultraviolet absorbers can be added to the resin liquid. At this time, the thickness of the protective layer is generally 0.05 to 20 mm, preferably 0.05 to 20 mm.
It ranges from 2 to 5 IL.

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

Example 1 Aqueous solution of casein in ammonia (2 g of casein 11, 1 g of 28% ammonia,
Apply 222 ml of water by dip coating method, dry and apply 111. A subbing layer of og/m was formed.

Next, 1 part by weight of a charge generating material of structural formula (I).

Butyral resin (S-LEC BM-2, manufactured by Block Chemical Industry Co., Ltd.)
1 part by weight and 30 parts 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 generating layer. The film thickness was 0.31L.

Next, 1 part by weight of the above-mentioned hydrazone compound example (1), 1 part by weight of polysulfone (P1700, manufactured by Union Carbide), and 6 parts by weight of monochlorobenzene were mixed,
Wl and f# were dissolved in an agitator and dryer.

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

This film thickness was 12JL.

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 V,).

Sensitivity was evaluated by measuring the amount of exposure (E 1/2 tux, 5 ec) required to attenuate the potential η after dark decay to 1/2.

These results were as follows.

V, knee 590V, Vj knee 580V.

E 1/2:4, 6 lux, sec Example 2~
5 A photoreceptor was prepared in exactly the same manner as in Example 1, except that hydrazone compound examples (2) to (5) were used in place of hydrazone compound example (1) used in Example 1, The characteristics of this photoreceptor were measured.

These results are shown below.

'JUAUj blood blisters' Va -V V -V E
1/2 lux 5ea2 (2) 585
575 4.93 (3) 580 5
70 5.14 (4) 5s5585
8.05 (5) 590 580 5
．． 4 Comparative Examples 1 to 6 The photoreceptors of Comparative Examples 1 to 6 were prepared in exactly the same manner except that the following comparative charge transport substances (1) to (6) were used in place of the hydrazone compound used in Example 1. were prepared and their charging characteristics were measured.

Charging characteristics 1 (1) 800 570 7.
22 (2) 595 570 L
93 (3) 605 585 7.
44 (4) 815 590 8.
15, (5) 580 555 7
．． 76 (6) 590 51110
7.5 As is clear from the results of Examples and Comparative Examples,
It can be seen that the laminated photoreceptor of the present invention has extremely high sensitivity compared to the photoreceptors of Comparative Examples 1 to 6. Furthermore, the photoconductors of Examples 1 to 5 were used in a copying machine (manufactured by Canon Co., Ltd.,
Image generation was repeated 20,000 times using NP-1502).

As a result, good quality images were obtained even after repeating 20,000 times with each photoreceptor, and the electrophotographic photoreceptor of the present invention
It can be seen that the durability is also extremely excellent.

[Effects of the Invention] As is clear from the above, the present invention uses a specific polycyclic quinone pigment as a charge generation material in the charge generation layer and a specific hydrazone compound in the charge transport layer, thereby improving the conventional method. 8 which is extremely sensitive compared to other things! This made it possible to provide a layered electrophotographic photoreceptor.

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 substituted or R_3 and R_4 represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or an atomic group necessary to complete a 5- or 6-membered ring together with a nitrogen atom. Indicates the atomic group necessary to complete a 5-membered ring or 6-membered ring together with a substituted aryl group or nitrogen atom, R_5 and R_6 are hydrogen atoms, halogen atoms, nitro groups, substituted or unsubstituted alkyl groups,
an alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted amino group, and R represents a divalent organic residue). Electrophotographic photoreceptor. (2) The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains a hydrazone compound represented by formula (II).