JPS627056A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance 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 optionally substituted arylene) 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, a number of organic photoconductors have been developed9. Low-molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, polyaryl alkanes, phthalocyanine pigments, azo pigments, cyanine pigments, polycyclic quinone pigments, perylene pigments, indigo dyes, Organic pigments and dyes such as 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 pigments and dyes have been proposed. For example, U.S. Pat. Nos. 4,123,270 and 4,247.
No. 614, No. 4251613, No. 4251614
No. 4256821, No. 4260672, No. 4268596, No. 4278747, No. 42
As disclosed in Japanese Patent No. 93628, etc., electrophotographic photoreceptors are known that use a photoconductive disazo pigment as a charge generation substance in a photosensitive layer that is functionally separated into a charge generation layer and a charge transport layer. An electrophotographic photoreceptor using such an organic photoconductor can be produced by coating by appropriately selecting a binder, so it is possible to provide an inexpensive photoreceptor with extremely high skewness, and the selection of organic pigments is This has the advantage that the sensitive wavelength range can be freely controlled.

The laminated photoconductor 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 photoconductors. 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 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 a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, in which the charge generation layer is comprised of 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 R1 and R1 are a substituted or unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or a 5- or 6-membered ring together with a nitrogen atom). Indicates the atomic group necessary to complete the 5-membered ring or 6-membered ring together with R5 and R toga substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group, or nitrogen atom. and R and R/ are a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, an alkoxy group,
A layer containing a substituted or unsubstituted 7-aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted 7-mino group, and R represents a substituted or unsubstituted arylene group. The present invention will be described 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. , ¥iJ film layer, for example 10
It is desirable to use a thin film layer with a thickness of 0.01 to 1 μl or less, preferably 0.01 to 1 μl. 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 a substrate, or by forming a vapor deposited film using a vacuum vapor deposition apparatus. can be obtained by 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 phthalic acid, etc.),
Examples include insulating resins such as polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, 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 in-propyl alcohol. Alcohols such as tools, ketones such as acetone, methyl ethyl ketone, cyclohexanone, N, N-dimethylform 7mide,
Amides such as N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, chloroform, methylene chloride, dichloroethylene,
Aliphatic halogenated hydrocarbons such as carbon tetrachloride and trichloroethylene, or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene and 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.

For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying is performed at a temperature of 30 to 200°C for 5 minutes or more.
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, and may be 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 capture each other.

As a result, this causes a decrease in sensitivity.

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

In the formula, R9 and RY represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or an atomic group necessary to complete a 5-membered ring or a 6-membered ring together with a nitrogen atom, and R3 and R4 are substituted or represents an atomic group necessary to complete a 5- or 6-membered ring together with an unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or a nitrogen atom, and R and R are hydrogen atoms, halogen atoms, and nitro groups. , substituted or unsubstituted alkyl group, alkoxy group,
It represents a substituted or unsubstituted 7-aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted 7-mino group, and R represents a substituted or unsubstituted arylene group.

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.

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 of −M becomes 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 in terms of high sensitivity, low residual potential, and yJ 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. Examples include insulating resins and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, the thickness is 5 to 30 μl, but the preferred range is 8 to 20 μl. 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 used by vacuum evaporation method. plastics (e.g. polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resins,
Polyfluorinated ethylene, etc.), conductive particles (e.g. carbon black, silver particles, etc.) coated on plastic with a suitable binder, substrates made of plastic or paper impregnated with conductive particles, and plastics with conductive polymers. 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 0.1 to 40J.
L, preferably 0.1 to 3 L, is suitable.

aJ! in the order of conductive layer, charge generation layer, and charge transport layer. 'I.

When using a photoconductor, when the charge transport material in the charge transport layer is composed of an electron transport material, it is necessary to positively charge the surface of the charge transport layer, and when exposed to light after charging, the charge transport material generated in the charge generation layer in the exposed area is Electrons are injected into the charge transport layer and then reach the surface to neutralize the positive charge, resulting in a decay of the surface potential and an electrostatic contrast with the unexposed areas.

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.

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, resulting in attenuation of one surface type, and the gap between the exposed area and the unexposed area is injected into the charge transport layer. 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 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, it is desirable that the surface resistivity is 100 or more. The protective layer used in the invention is made of a suitable resin such as polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer, etc. Organic solvent,
The photosensitive layer can be formed by coating a solution dissolved thereon on 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 in the range of 0.05 to 20 IL, preferably 0.2 to 5 IL.

The present invention will be explained below according to examples.

Example 1 An ammonia aqueous solution of casein (casein 11, 2 g, 28% ammonia Ig, water 222'ml) was coated on an aluminum cylinder by dip coating, dried, and coated with 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 Tsukiki 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 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,
The mixture was stirred and dissolved using 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 12IL.

A corona discharge of 15 KV was applied to the photoreceptor thus prepared. The surface potential (initial potential V) 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 vd).

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

These results were as follows.

Vo: -575V, Vr: -565V, E 1/
2:4, 51u! , sec Examples 2 to 5 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. A photoreceptor was prepared and the characteristics of this photoreceptor were measured.

These results are shown below.

! JlkJI W v-v"'-v"1/2""
5ec2 (2) 580 570 4
．． 73 (3) 570 580 4.
04 (4) 575 585 4.25
(5) 585 575 5.5 Comparative Examples 1 to 6 Comparative examples were carried out in exactly the same manner except that the following comparative charge transport substances (1) to (8) were used in place of the hydrazone compound used in Example 1. Photoreceptors Nos. 1 to 6 were prepared and their charging characteristics were measured.

CyuHs Charging characteristics 1 (18005707,2 2(2) 595 570 8.93
(3) f! 05 585 7.44
(4) 815 590 8.15
(5) 580 555 7.76
(6) 590 580 7.5 As is clear from the results of Examples and Comparative Examples, the laminated photoreceptor of the present invention has extremely high sensitivity than the photoreceptors of Comparative Examples 1 to 6. It turns out that Furthermore, Examples 1 to 5
The photoreceptor was transferred to a copying machine (NP-150 manufactured by Canon Corporation)
Image generation was repeated 20,000 times using 2).

As a result, good quality images were obtained even after repeating the test 20,000 times with each photoreceptor, indicating that the photoreceptor of the present invention has extremely excellent durability.

〔Effect 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, so that the present invention is significantly superior to conventional ones. This makes it possible to provide a laminated electrophotographic photoreceptor with high sensitivity.

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,
It represents 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 substituted or unsubstituted arylene group. ) An electrophotographic photoreceptor comprising a layer containing: (2) The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains a hydrazone compound represented by formula (II).