JPS61189554A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity and to reduce residual potential after durability test by using a polycyclic quinone type pigment for an electrostatic charge generating layer and a specified hydrazone deriv. for a charge transfer layer. CONSTITUTION:The charge generating layer formed together with the charge transfer layer on the conductive substrate of a laminate type electrophotographic sensitive body contains the polycyclic quinone type pigment presented by formula (1) and the charge transfer layer contains the charge transfer material of a hydrazone deriv. represented by formula (2) in which R1, R2 are each H, optionally substd. aryl or optionally substd. heterocyclic, and R3, R4 are each optionally substd. alkyl, such aralkyl, such aryl, or such heterocyclic, and R5 is a divalent org. residue. It is preferred that the charge generating layer contains the charge generating material as much as possible in order to obtain sufficient light absorbance, and is formed into a thin layer, for example, <=10mum thick in order to inject generated charge carriers efficiently to the charge transfer layer. Since the charge transfer layer is limited to the upper thickness limit for transferring the charge carriers, it is impossible to make the layer too thick, and it is formed generally in a thickness of 5-30mum, general, and preferably, 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 transport layer and a charge generation layer.

[Conventional technology]

Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known so far.

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, polyvinylanthracene, 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, thioindigo 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 the range in which compounds that exhibit photoconductivity in an appropriate wavelength range can be selected has been expanded.
Many photoconductive organic pigments and dyes have been proposed.

For example, US Pat. No. 4,123,270, US Pat. No. 42,476
No. 14, No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747, No. 429
As disclosed in Japanese Patent No. 3628, 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, 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 photosensitive wavelength moths.

When a charge transport layer and a charge generation layer mainly composed of a charge generation material are laminated, the laminated photoreceptor obtained by K has a higher sensitivity than other single-layer photoreceptors, such as increased sensitivity and residual potential after durability tests. Although it is advantageous, it is still not at a sufficient level.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION 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.

The present invention aims to achieve the above object in a laminated electrophotographic photoreceptor having two layers, 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 generation layer and a specific hydrazone compound in the charge transport layer.

[Means for solving problems]

The present invention provides a multilayer 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 composed of a layer containing a polycyclic quinone pigment represented by formula (1). C, the charge transport layer is general 2Q[) R, -C=xllJ-N-R5-N-N-C-R,Q[
) (wherein, 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 an aralkyl group, a substituted or unsubstituted 7-aryl group, or a substituted or unsubstituted heterocyclic group; R5 represents a divalent organic residue). This is an electrophotographic photoreceptor.

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 form a thin film layer, for example, a thin film layer having a thickness 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 (1).

υ The charge generation layer can be formed by coating the above-mentioned pigments and, if necessary, a charge transporting material together with a suitable binder (or without a binder) on the substrate, and can also be formed by applying a vapor-deposited film using a vacuum vapor deposition apparatus. can be obtained by forming .

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.), polycargenate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, acrylamide resin,
polyamide, privinylpyridine, cellulose resin,
Examples include insulating resins such as urethane resin, epoxy resin, casein, 4-rivinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is 80
A weight below -, preferably below 40% by weight is suitable.

The solvent that dissolves these resins varies depending on the type of resin, and it is preferable to select a solvent that does not dissolve the underlying charge generation layer or undercoat layer.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, N,
Amides such as 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, and methylene chloride. , aliphatic halogenated hydrocarbons such as dichloroethylene, carbon tetrachloride, and trichlorethylene, or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene.

Coating methods include dip coating method, spray coach ink method, spinner coating method, bead coating method,
This can be carried out using a coating method such as a Mayer bar coating method, a blade coating method, a roller coach ink 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 can be carried out at 30° C. to 200° C. for a period of 5 minutes to 2 hours, either stationary or with air blowing.

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 furthermore, the selection of the binder in the charge transport layer is more effective. This is desirable in that a good photoreceptor surface can be formed.

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. The term "electromagnetic waves" used herein includes the broad definition of "light rays" including r-rays, X-rays, far-infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps with that of the charge generation layer, charge carriers generated in both 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 ω).

(In the formula, R4 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 of the general hydrazone compound represented by 2ω) used in the present invention are illustrated in Table IK.

(J(J) 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, and the sensitizing effect thereof 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 suitable 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. Resins that can be used as binders include, for example, acrylic resins, polyacrylates, polyesters, 4-liquorates, polystyrenes, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formals, polysulfones, polyacrylamides, polyamides. , insulating resin such as chlorinated rubber, or poly-N-vinylcarbazole, ? Organic photoconductive polymers such as ribinyanthracene and 4-rivinylpyrene 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. Typically it is 5 microns to 30 microns, with a preferred range of 8 microns to 20 microns. 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, that is, a conductive support. As the substrate having a conductive layer, the substrate itself is conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, dichloride, indium, gold, platinum, etc. In addition, plastics (e.g., force pump rack, silver particles, etc.) having a layer formed by vacuum evaporation of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. A substrate coated on a plastic together with a binder, 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 a barrier function and an adhesive function can be provided between the conductive layer and the photosensitive layer.
Holivinyl alcohol, nitrocellulose, ethylene-
It can be formed from acrylic acid copolymer, previnyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), 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 made of 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. 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, 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 a hole transport material, it is necessary to negatively charge the surface of the charge transport layer, 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 charges, resulting in attenuation of the surface potential and an electrostatic contrast between the surface potential 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 is 10 Ω or more.

The protective layer used in the present invention is 4-rivinyl petyral, polyester, polycarbonate, etc. A solution prepared by dissolving resins such as ester, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butanoene copolymer, styrene-acrylic acid coterimer, and styrene-acrylonitrile copolymer in a suitable organic solvent is used to form a photosensitive layer. Can be formed by coating and drying.

It can also be achieved by adding additives such as ultraviolet absorbers to the resin liquid. At this time, the thickness of the protective layer is generally 0.05~
20 microns, particularly preferably in the range 0.2 to 5 microns.

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

Example 1 Casein ammonia 7H on aluminum cylinder
Liquid I (casein 11.2?, 28% ammonia water IP,
Water 2224) was applied using a coating method, dried, and the coating amount was 1. A Of/- undercoat layer was formed.

1 part by weight of the charge generating material represented by the following formula (1), 1 part by weight of butyral resin (S-LEC BM-2, manufactured by Sekisui Chemical Co., Ltd.) and 30 parts by weight of isopropyl alcohol were dispersed for 4 hours using a sol mill disperser. This dispersion was first formed and coated on top of the nine sublayers by dip coating, and dried to form a charge generation layer.

The film thickness at this time was 0.3μ. Next, P-diethylaminobenzaldehyde, which is the compound amount (1) in Table 1,
1 part by weight of N-phenyl-α-naphthyl human 2-syn, ? 1 part by weight of risulfone resin (P 1700, manufactured by Union Carbide Co., Ltd.) and 76 parts by weight of 74-benzene were mixed and dissolved by stirring with a stirrer. This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer. The film thickness at this time was 12μ.

A corona discharge of 15 kV was applied to the photoreceptor thus prepared. 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 a dark place for 5 seconds (dark decay Vs).

Sensitivity was evaluated by measuring the exposure amount ('By, 1ux-s@e) required to attenuate the potential V after dark decay to W.

These results were as follows:
595 is Ruto V, : -580 is Ruto Ey, : 5.41uxeaee Example 2
~10 A photoconductor was prepared in exactly the same manner as in Example 1, using each of the compounds shown in Table 1 in place of the compound amount (1) used in Example 1. We measured the characteristics of These results are shown in Table 2.

Table 2 Example Compound, /, V, (-V) V@
(-V) E141ux・5ee22600 58
5 5.7 33610 600 6.4 44615 600 6.2 55590 575 5.5 66595 580 5゜6 77600 585 5.4 88585 570 5.9 99605 590 5.5 1010585 560 6.1 Comparative Examples 1 to 6 Implementation A photoreceptor was prepared in exactly the same manner, except that the charge transport material shown in Table 3 was used in place of the hydrazone compound used in Example 1. The charging characteristics are shown in Table 4.
E141ux・sec Transport substance plate 1 1 605 580
7.82 2 600 580
7.43 3 610 5
85 7.94 4 620
600 8.35 5 61
0 585 8.06 6
600 580 7.8 As is clear from the results of the Examples and Comparative Examples, the laminated photoconductor of the present invention has extremely high sensitivity compared to the Comparative Examples of Photoconductor 1 to Black 6. I understand. Furthermore, the photoreceptors of Examples 1 to 3 were used in a copying machine (NP-150Z: manufactured by Canon Inc.).
Image generation was repeated 20,000 times. As a result, good quality images were obtained for all photoreceptors even after repeating 20,000 times. As a result, it can be seen 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-based pigment as a charge-generating material in the charge-generating layer and a specific hydrazone-based compound in the charge transport layer, thereby achieving extremely high sensitivity compared to conventional methods. This made it possible to provide a high-quality laminated electrophotographic photoreceptor.

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).