JPS61294448A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To increase the sensitivity by forming a charge generating layer contg. a specified polycyclic quinone pigment and a charge transferring layer contg. a specified hydrazone compound. CONSTITUTION:When a charge generating layer and a charge transferring layer are formed on an electrically conductive support to obtain a laminate type electrophotographic sensitive body, the charge generating layer is made of a layer contg. a polycyclic quinone pigment represented by formula I and the charge transferring layer is made of a layer contg. a hydrazone compound represented by formula II. The charge generating layer contains the charge generating material to the utmost limit and has a small thickness of <=10mum, preferably 0.01-1mum. The charge transferring layer is electrically connected to the charge generating layer and has functions to receive charge carriers implanted from the charge generating layer in the presence of an electric field and to transfer the charge carriers to the surface. Thus, a sensitive body having very high sensitivity can be obtd.

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 such as polymers, carbazole, anthra7ane, pyrazolines, oxadiazoles, hydrazones, polyaryl alkanes, phthalocyanine pigments, azo pigments, cyanine pigments, polycyclic quinone pigments, perylene pigments Organic pigments and dyes such as indigo dyes, thioindigo dyes, and methine squaric acid 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. Nos. 4,123,270 and 42,476.
No. 14, No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747, No. 429
As disclosed in Japanese Patent Application No. 3628, etc., electrophotographic photoreceptors are known that use a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer that is functionally separated into a charge generation layer and a charge transport layer. Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, making it possible to provide extremely high productivity and inexpensive photoreceptors. It has the advantage of being able to freely control the 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. In a laminated electrophotographic photoreceptor having two layers, this is achieved by using a specific polycyclic non-based pigment in the charge generation layer and a specific hydrazone-based compound in the charge transport layer. The invention provides an A-layer 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 comprises a layer containing a polycyclic quinone pigment of structural formula (I), The charge transport layer is a hydrazone compound represented by the general formula (II) (wherein R and R are a substituted or unsubstituted alkyl group, a substituted or unsubstituted 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 ring, and together with R3, R, and l, a substituted or unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or a nitrogen atom, necessary to complete the 5- or 6-membered ring. R6 and R6 represent a hydrogen atom, a halogen atom, 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 acyl group. The electrophotographic photoreceptor is composed of a layer containing an unsubstituted 7-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 efficiently injects generated charge carriers into the charge transport layer. For example, a thin film layer, e.g. 1OI
It is desirable to use a thin film layer having a thickness of L or less, preferably 0.01 to 1. This means that most of the incident light is absorbed by the charge generation layer and many charge carriers are generated. Furthermore, the generated charge carriers are recombined and captured (
This is due to the need to inject into the charge transport layer without being deactivated by traps.

The charge generating material used in the present invention is a polycyclic quinone 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 the substrate, or by forming a vapor deposited layer using a vacuum vapor deposition device. It can be obtained by article. 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 (condensation polymer of bisphenol A and heptalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane Examples include insulating resins such as resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is 8
A content of 0% by weight or less, preferably 40% by weight or less is suitable. 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 in-propyl alcohol. Alcohols such as tools, ketones such as acetone, methyl ethyl ketone, cyclohexanone, amides such as N,N-dimethylformamide p, N, *-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethylene glycol monomethyl Ethers such as ether, esters such as methyl acetate, ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, or benzene, toluene, xylene, ligroin, monochlor Aromatics such as benzene and 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 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. At this time, this charge transport layer may be laminated on or under the charge generation layer.

The substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport substance) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. "Electromagnetic waves" includes the broad definition of "light rays" including gamma 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 substance used in the present invention is a hydrazone compound represented by the general formula (ff).

In the formula, R2 and R2 represent a substituted or unsubstituted alkyl group, an N-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 R1 and R, represents an atomic group necessary to complete a 5-membered ring or 6jl ring together with a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a nitrogen atom, R6 and R6 are hydrogen atoms, halogen atoms,
Nitro group, substituted or unsubstituted alkyl group, alkoxy group, substituted or unsubstituted 7-aryloxy group, substituted or unsubstituted acyl group, or substituted or unsubstituted 7-aryloxy group
It represents a mino group, and R represents a divalent organic residue.

This hydrazone compound satisfies the above-mentioned conditions as a charge transport material, especially sensitivity.

It has excellent properties in terms of 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 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.

Resins that can be used as binders include, for example, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, etc. Insulating resin or poly-N-vinylcarbazole,
Organic photoconductive polymers such as polyvinylanthracene and polyvinylpyrene may be mentioned.

Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary; it is generally 5 to 30 mm thick, but is preferred. , range is 8~20JL
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 a laminated 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, nickel, indium, gold, platinum, etc. can be used, and in addition, aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. can be coated by vacuum evaporation method. Plastics (e.g. polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resins, polyfluorinated ethylene, etc.) with formed particles, conductive particles (e.g. carbon black, silver particles, etc.) are deposited on the plastic with a suitable binder. A substrate coated with a conductive material, a substrate made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used.

A subbing layer having barrier and adhesive functions can also be provided between the ML guiding layer and the photosensitive layer. The subbing layer is casein,
Polyvinyl alcohol, nitrocellulose, ethylene-
It can be formed from acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, +ylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the subbing layer is 0.1 to 4
0p, preferably 0.1 to 3 pots is suitable.

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, causing a decrease in surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast 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, the surface of the charge transport layer must be negatively charged, 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 that, it reaches the surface and neutralizes the negative charges, resulting in an attenuation of the surface potential and an electrostatic contrast between it and 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 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 this protective layer, the surface resistivity must be 100.
It is desirable that the retention layer used in the present invention is made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene. - Applying a solution prepared by dissolving a resin such as acrylonitrile copolymer in a suitable organic solvent onto the photosensitive layer,
Can be formed by drying. 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 JL, preferably 0.2 to 20 JL.
It is in the range of 5 castings.

The present invention will be explained below according to examples.

Example 1 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia, 222 ml of water) was coated on an aluminum cylinder by dip coating, and dried to form a subbing layer with a coating weight of 1.0 g/m. Formed.

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 Tsukiki Kagaku ■), 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 generating layer. The film thickness is 0.3. Met.

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,
The leaves were melted using a blower.

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

The film thickness was 12#L.

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

Sensitivity was evaluated by measuring the exposure amount (E 1/21ux, 5 ec) required to attenuate the potential V after dark decay to 1/2.

These results were as follows.

■. : -585V, vJ, : -575V.

E 1/2:4, Ojug, see Examples 2 to 5 Human razone compound examples (2) to (5) were used in place of the hydrazone compound example (1) used in Example 1, respectively. , a photoreceptor was prepared in exactly the same manner as in Example 1,
The characteristics of this photoreceptor were measured.

These results are shown below.

Support 1m Va-vV-vE'/21u! 5ec
2 (2) 590 580 4.23
(3) 590 575 4.84
(4) 805 595 5.15 (
5) 800 590 4.8 Comparative Examples 1 to 6 Comparative Example 1 was carried out 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. Photoreceptors No. 6 to 6 were prepared and their charging characteristics were measured.

C,)l.

! Charging characteristics 1 (1) 585 575 8.
02 (2) 585 5130 5
．． 93 (3) 590 5E15
B, 84 (4) 805 585
7.85 (5) 800 580
8.46 (6) 815 800
7.0 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,
Copying the photoreceptors of Examples 1 to 5 41! (manufactured by Canon Inc., NP-1502) and image generation was repeated 20,000 times.

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 non-containing pigment as a charge generating material in the charge generating layer and a specific hydrazone compound in the charge transporting layer. The aim is to provide a laminated electrophotographic photoreceptor with extremely high 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 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).