JPS61196250A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a laminate type electrophotographic sensitive body high in sensitivity and extremely low in residual potential after durability test by laminating an electrostatic charge generating layer contg. a specified polycyclic quinone type pigment and a charge transfer layer contg. a specified hydrazone deriv. CONSTITUTION:The charge generating layer contains the polycyclic quinone type pigment represented by formula (I) and the charge transfer layer contains the hydrazone deriv. represented by formula (II) in which each of R1, R2 is H, or optionally substd. aryl or heterocyclic, and each of R3, R4 is optionally substd. alkyl, aralkyl, aryl, or hererocyclic, and R6 is a divalent org. residue. It is preferred for the charge generating layer to contain the charge generating material as much as possible in order to obtain sufficient light absorbance, and to have film thickness as thin as 0.01-1mum in order to injet generated charge carriers efficiently to the charge transfer layer.

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 transport layer and a charge generation layer.

[Conventional technology]

Hitherto, good electrophotographic photoreceptors have been known that utilize inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components.

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, privinylanthracene, carbazole,
Low molecular organic photoconductors such as anthracene, pyrazolines, oxadiazoles, hydrazones, polyarylalkanes, phthalocyanine pigments, azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindib dyes Alternatively, organic pigments and dyes such as methine squaric acid dyes are known. In particular, organic pigments and dyes with photoconductivity are easier to synthesize than inorganic materials, and moreover, they are photoconductive in an appropriate wavelength range. Due to the expansion of the selection of compounds that exhibit
Many photoconductive organic pigments and dyes have been proposed.

For example, US Pat. No. 4,123,270 and US Pat. No. 42,476
No. 14, No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747, No. 429
3628, an electrophotographic photoreceptor using a disazo pigment exhibiting photoconductivity as a charge generation material in a photosensitive layer functionally separated into a charge generation layer and a charge transport layer is known.

Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, so it is possible to provide photoreceptors with extremely high productivity and at low cost. It has the advantage of being able to freely control the sensitive wavelength range.

A multilayer photoreceptor 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 desensitizers in terms of sensitivity and increased residual potential after durability tests. However, it was still not at a sufficient level.

[Problem that the invention seeks to solve]

An object of the present invention is to improve the above-mentioned drawbacks and provide a laminated electrophotographic photoreceptor with high sensitivity and extremely low residual potential even after a durability test. A laminated electrophotographic photoreceptor comprising two layers, a charge generation layer containing a generation material as a main component and a charge transport layer containing a charge transport material as a main component, in which a specific polycyclic quinone pigment is used in the charge generation layer, and This is attempted to be achieved by using a specific hydrazone compound in the charge transport layer.

[Means for solving problems]

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 1wL charge generation layer is composed of a layer containing a polycyclic quinone pigment represented by the formula (1). ), the charge transport layer has the general formula (n) (wherein R1 and R2 represent a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; R3 and R4 are Represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group. R5 represents a divalent organic residue 1) An electrophotographic photoreceptor characterized by comprising a layer containing a hydrazone compound.

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. Therefore, it is desirable to use a thin film layer, for example, a thin film layer having a thickness t of 10 microns or less, preferably 0.01 micron to 1 micron. This means that most of the incident light is absorbed by the charge generation layer, generating many charge carriers, and that the generated charge carriers are transported by recombination or trapping without being deactivated. This is due to the need to inject into the layer.

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

The charge generation layer can be formed by coating the above-mentioned pigment and, if necessary, a charge transporting material together with a suitable binder (or without a binder) on the substrate, and then forming a vapor-deposited film using a vacuum vapor deposition apparatus. You can get it by doing

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 ta polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol and heptalic acid, etc.), polycargenate, polyester, phenoxy resin, vinyl acetate, acrylic resin, polyacrylamide resin,
Polyamide, polyvinyl resin, cellulose resin,
Examples include insulating resins such as urethane resin, polyurethane resin, casein, polyvinyl alcohol, and privinylpyrrolidone. The resin contained in the charge generation layer is 80
1j11 or less, preferably 40 gw leeward is suitable.

The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the above-mentioned charge generation layer and undercoat layer.

Specific organic solvents include methanol, ethanol,
Alcohols such as inglo and p4nol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone,
Amides such as N,N-dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, Aliphatic halogenated hydrocarbons such as methylene chloride, dichloroethylene, carbon tetrachloride, trichlorethylene, etc., or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used.

Coating can be carried out using coating methods such as dip coating method 1, soufflé coating method, spinner coating method, bead coating method, Mayer-Par coating method, blade coating method, roller coach ink method, curtain coating method, etc. . For drying, it is preferable to dry to the touch at room temperature and then heat dry.

Heat drying can be carried out at 30° C. to 200° C. for a period of 5 minutes to 2 hours while still being blown with air.

The charge transport layer is electrically connected to the charge generation layer described above, and has the function 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. However, since the charge transport layer is laminated on the charge generation layer, there is less deterioration of the surface of the photoreceptor during repeated durability tests, and further, by selecting the binder in the charge transport layer, This is desirable in that a good photoreceptor surface can be formed.

The material that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport material) is preferably practically 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 a hydrazone compound represented by general formula (II).

(In the formula, R1 and R2 represent a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group. R3 and R4 represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group) group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group. R5 represents a divalent organic residue.) This hydrazone compound satisfies the above conditions as a charge transport substance. It has excellent properties, especially in terms of sensitivity and durability.

Typical compounds*1 of the hydrazicine compounds represented by the general formula (It) used in the present invention are illustrated in Table 1.

c4 N In addition, in the present invention, the above-mentioned hydrazone compound used in the charge transport layer can be added to the t-charge generation layer,
The sensitizing effect becomes even more remarkable.

When adding a charge transport material to the charge generation layer, the hydrazone compound should be 10 times or less (weight ratio), preferably 0.01 to 1 times (weight ratio) of the charge generation material to achieve high sensitivity, low residual potential, and repeatability. This is appropriate from the viewpoint of return stability.

To form a charge transport layer containing a hydrazone compound, a film can be formed by selecting an appropriate binder. Examples of resins that can be used as binders include acrylic resin, polyacrylate, polyester, and polycarbonate.
nate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer,
Examples include insulating resins such as polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and chlorinated rubber, and organic photoconductive polymers such as stream-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 range is 5 microns to 30 microns, but the preferred range is 8 microns to 20 microns. When forming the charge transport layer by coating, use an appropriate coating method as described above. Can be done.

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, that is, a conductive support. As the substrate having the conductive layer, materials that are themselves conductive can be used, such as aluminum, aluminum alloy, copper, zinc, stainless steel, pananoum, molybdenum, chromium, titanium, nickel, indium, gold, and platinum. In addition, there are glass materials (flj, Riki-men Plac,
A substrate made of plastic coated with silver particles, etc.) together with a suitable binder, a substrate made of glass or paper impregnated with conductive particles, a glass stick containing 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 subbing layer is casein,
- Lipinyl alcohol, nitrocellulose, ethylene -
It can be formed from acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 610° copolymerized nylon, alkoxymethylated nylon, etc. x polyurethane, gelatin, aluminum oxide, etc.).

The thickness of the undercoat layer is suitably 0.1 micron to 40 micron, preferably 0.1 micron to 3 micron.

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 an electron transport material, it is necessary to positively charge the surface of the charge transport layer. 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 the surface potential to attenuate and creating static between the unexposed area and the exposed area. Electrocontrast occurs. A visible image can be 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., 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 known methods, and are not limited to specific ones.

On the other hand, when the charge transport material consists of hole transport properties, the surface of the charge transport layer must be negatively charged, and when exposed to light after charging, holes are generated in the charge generation layer in the exposed area and holes are injected into the charge transport layer. After that, the negative charges on the surface are completely neutralized, the surface potential is attenuated, and an electrostatic contrast is generated between the surface 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 subject to deterioration due to ultraviolet rays, ozone, etc., dirt due to oil, etc., scratches due to cutting powder of metal, etc., and 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 or the charge transport layer for the purpose of preventing scratching. To form an electrostatic latent image on this protective layer,
It is desirable that the surface resistivity be 10 Ω or more.

The protective layer used in the present invention is made of polyvinyl butyral, polyester, polycarnate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer, etc. The photosensitive layer can be formed by dissolving a resin in a suitable organic solvent and applying the solution onto the photosensitive layer and drying it.

Additives such as ultraviolet absorbers can be added to the resin liquid. At this time, the thickness of the protective layer is generally KO, 05~
201 microns, particularly preferably in the range 0.2" to 5 microns!

Hereinafter, the present invention will be explained according to t-Example.

Example 1 Aqueous ammonia solution of casein (casein 11.2.9,281 ammonia water 1.9
, water 2221114) by a coating method, and dried to a twisting amount of 1. Next, 1 part by weight of a charge generating material represented by formula (I), 1 part by weight of butyral resin (S-LEC BM-2: manufactured by Sekisui Chemical Co., Ltd.) and isopropylene were added. Alcohol 30 heavy seeds part 1&-
The mixture was dispersed for 4 hours using a Lumil disperser. This dispersion was first formed and coated on the subbing layer by dip coating, and dried to form a charge generation layer.The film thickness at this time was 0.3 .mu.m. Next, 1 part by weight of P-diethylaminobenzaldehyde-N-7enyl-α-naphthylhydrazone, which is the compound (1) in Table 1, and polysulfone resin (P1700
: Union Carbide Co., Ltd.) 1 part by weight and 6 parts by weight of monochlorobenzene were mixed together and stirred and dissolved using a stirrer. This liquid was coated on the charge generation layer by dip coating and dried to form a charge transport layer. The film thickness at this time is 12μ
Met.

The thus prepared photoreceptor was subjected to corona emission mt of 15 kV.The surface potential at this time was measured (initial potential Vo)
. Furthermore, the surface potential of this photoreceptor was measured after it was left in the dark for t-5 seconds (dark decay v5).

The sensitivity is the exposure 1 (E1/21ux-see) t-$ required to attenuate the potential v5 after dark decay to 1/2.
Evaluation was made by determining 1.

These results were confirmed in the following steps.

Vo: -570 Delt V5: -550yj #Ruto El 72: 4.51ux1mea Refreshing N2-10 In place of the chemical compound (1) used in Example 1, the compounds shown in Table 1 were used, respectively. A photoreceptor was prepared in exactly the same manner as in Example 1, and the characteristics of this photoreceptor were measured.The results are shown in Table 2.

Table 2 Example Compound 4 Vo(-V) V5(-V)
E... 8 8 570 555 5.2 9 9 585 570 4.8 10 10 575 560 5.0 Comparison rows 1 to 6 Except for using the charge transport substance shown in Table 3 instead of the 9 hydrazone compound used in Example 1, A photoreceptor was produced in exactly the same manner. The charging characteristics are shown in Table 4.

Zhong Rui-yong - Acupuncture = 1 sun 4
ψ table 4 1 1 575 550 7.6 2 2 570 540 7.2 3 3 580 555 8.0 4 4 585 560 8.3 5 5 580 550 7.4 6 6 575 545 7.7 Implementation and ratio e As is clear from the results of the examples, it can be seen that the laminated photoreceptor of the present invention has extremely high sensitivity compared to the photoreceptors A1 to A6 of the comparative examples. Furthermore, one image was output t-20,000 times using the photoconductor copying machine (NP-150z: CA//Co., Ltd.*>1) of Examples 1 to 3. As a result, each photoconductor was repeated 20,000 times. A good quality image was obtained even after the photoreceptor was used.As a result, it is clear 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, thereby achieving extremely high sensitivity compared to conventional ones. It is possible to provide highly laminated electrophotographic photoreceptors.

Claims (2)

[Claims] (1) In a laminated photographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer is expressed by the formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) It consists of a layer containing a polycyclic quinone pigment, and the charge transport layer has the general formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R_1 and R_2 are hydrogen atoms, substituted or unsubstituted. represents an aryl group or a substituted or unsubstituted heterocyclic group. R_3 and R_4 are a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group,
Indicates a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group. R_5 represents a divalent organic residue. ) An electrophotographic photoreceptor comprising a layer containing a hydrazone compound represented by: (2) The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains a hydrazone compound represented by formula (II).