JPS622261A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a laminate type electrophotographic sensitive body having very high sensitivity by using a specified polycyclic quinone pigment as a charge generating material in a charge generating layer and a specified hydrazone compound in a charge transferring layer. CONSTITUTION:A charge generating layer is made of a layer contg. a polycyclic quinone pigment represented by formula I and a charge transferring layer is made of a layer contg. a hydrazone compound represented by formula II. The charge generating layer can be formed by mixing the pigment represented by formula I with a proper binder, adding a charge transferring material as necessary and coating the mixture on a substrate. The charge generating layer may be obtd. by forming a vacuum-deposited film with a vacuum depositing device. The charge transferring layer is electrically connected to the charge generating layer, receives charge carriers implanted from the charge generating layer in the presence of an electric field and can transfer the charge carriers to the surface. Since there is a limit in the capacity of the charge transferring layer to transfer charge carriers, the thickness of the layer can not be made larger than the necessary thickness. The preferred thickness is 8-20mum.

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 weight 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 that the sensitive wavelength range can be freely controlled by selecting the .

A multilayer photoreceptor obtained by MIMing a charge transport layer and a charge generation layer mainly composed of a charge generation material has advantages over other single layer photoreceptors 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 provide an i-layer type electrophotographic photoreceptor having 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 rust layer type 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 R4 and R 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 ring, R3 and R4 are substituted or unsubstituted alkyl groups, substituted or unsubstituted aryl groups, and are necessary to complete the 5-membered ring or 6-membered ring together with the nitrogen atom. Indicates atomic groups, R9 and R.

represents 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 amine group, R represents a substituted or unsubstituted arylene group.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 10 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 charges are generated. This is due to the need to generate 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 generation layer can be formed by coating the above pigment and, if necessary, a charge transporting material together with a suitable binder (or without a binder) on the substrate, or by forming a vapor deposited film by vacuum deposition. 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.)
, polycarbonate, polyester, phenoxy horizontal axis,
polyvinyl acetate, acrylic resin, polyacrylamide,
polyamide, polyvinylpyridine, cellulose resin,
Examples include insulating resins such as urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is 80
Weight % or less, preferably 40 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 ring or subbing layer.Specific organic solvents include methanol, ethanol, Alcohols such as Impropatol, 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 7 Ethers such as trimethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, benzene, toluene, xylene, ligroin, Aromatic compounds such as monochlorobenzene 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 is capable of receiving and receiving 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 trap each other, resulting in a decrease in sensitivity.

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

In the formula, R1 and R 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 an 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, R- and R4 are hydrogen atoms, halogen atoms, nitro groups 1M Represents a substituted or unsubstituted alkyl group, alkoxy group, substituted or unsubstituted 7-aryloxy group, substituted or unsubstituted acyl group, or substituted or unsubstituted 7-mino group, and R represents a substituted or unsubstituted arylene group. show.

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.

Furthermore, in the present invention, the above-mentioned hydrazone compound used in the charge transport layer can be added to the charge generation layer, and the sensitizing effect thereof 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 0.0
1 to 1 times (weight ratio) is appropriate from the viewpoint of high sensitivity, low residual potential, &1 repeat 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 resin, polyarylate, polyester, polycarbonate, polystyrene,
Acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral,
Polyvinyl formal, polysulfone, polyacrylamide.

Insulating resins such as polyamide and chlorinated rubber, or poly-N-vinylcarbazole, polyvinylanthracene,
Mention may be made of organic photoconductive polymers such as 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 JL, but the preferred range is 8 to 20 JL.
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. As the substrate for supporting the conductive layer, it is possible to use materials that are themselves conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, platinum, etc. Plastics (e.g. polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin ,
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 6B, -)
-flon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the subbing layer is 0.1 to 4.
0 JL, preferably 0.1 to 3 JL is suitable.

8 in the order of conductive layer, charge generation layer, and charge transport layer! When using a layered photoreceptor, if the charge transport material in the charge transport layer is made of an electron transport material, it is necessary to charge the surface of the charge transport layer positively, and when exposed to light after charging, the charge transport material is generated in the charge generation layer in the exposed area. The electrons are injected into the charge transport layer, then reach the surface, neutralize the positive charges, cause attenuation of one surface type, and create an 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, 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. , which then reaches the surface and neutralizes the negative charge, resulting in an attenuation of the surface potential and 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 protective layer may be further provided on the charge generation layer for the purpose of preventing scratching.An electrostatic latent image is formed on this protective layer! 1, it is desirable that the surface resistivity is 100 or more. The protective layer used in the present invention is made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene. It can be formed by applying a solution prepared by dissolving a resin such as -butadiene copolymer, styrene-acrylic acid copolymer, or styrene-acrylonitrile copolymer 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.
．． The range is 0.05 to 20 JL, preferably 0.2 to 5 JL.

The present invention will be explained below according to examples.

Example 1 A 7 ammonia aqueous solution of casein (2 g of casein 11, 28% ammonia Ig, 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 glrm. was formed.

Next, 1 part by weight of the charge generating material of structural formula (I), butyral resin (Eslec BM-2, Sekisui Chemical ■1) lffi
part 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 13 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 Vs). /2
1ux, 5ea).
These results were as follows.

V, knee 59sv, V: -385V.

E 1/2:4, 1 lux, sea Examples 2 to 5 Hydrazone compound examples (2) to (5) were used in place of hydrazone compound example (1) used in Example 1. A photoreceptor was prepared in exactly the same manner as in Example 1, and the characteristics of this photoreceptor were measured.

These results are shown below.

"l, j14JIJ m V6-V Vj -V
E 1/21u! 5ec2 (2) El
oo 595 4.33 (3) 59
0 580 3.94 (4) 585
575 4.05 (5) 595 58
5 4.9 Comparative Examples 1 to 6 Comparative Examples 1 to 6 were conducted in exactly the same manner except that the following comparative charge transport substances (1) and (6) were used in place of the hydrazone compound used in Example 1. A photoreceptor was prepared and its charging characteristics were measured.

CyuH5 ■Charging characteristics 1 (1) 1300 575 8.
22 (2) 590 585 8.
03 (3) 595 570 8.
84 (4) 815 580 7.
45 (5) 585 555 7.
16 (6) 580 555 8.
As is clear from the results of Example 8 and Comparative Example, 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., NP-
1502), 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 it can be seen that the electrophotographic photoreceptor of the present invention has extremely excellent durability.

[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. This makes it possible to provide a layer-type electrophotographic photoreceptor that has an extremely high sensitivity compared to conventional photoreceptors.

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).