JPS61292157A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity of a photosensitive body by forming an electrostatic charge generating layer and a charge transfer layer each containing a substance having a specified chemical structure on a conductive substrate. CONSTITUTION:A laminate type electrophotographic sensitive body high in sensitivity can be obtained by forming on the conductive substrate the charge generating layer containing the polycyclic quinone type pigment represented by formula (I), and the charge transfer layer containing the hydrazone derivative represented by formula (II) in which each of R1, R2, R3, R4 is optionally substituted alkyl or such aryl or an atomic group necessary to complete a 5- or 6-membered ring together with the adjacent N atom; each of R3, R4 is optionally substituted alkyl or such aryl; each of R5, R6 is H, halogen, nitro, optionally substituted alkyl or alkoxy, such aryloxy, such acyl, or such amino; and R is a divalent organic group.

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. For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene; low-molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkane; and phthalocyanine pigments. Organic pigments and dyes such as , azo pigments, cyanine pigments, polycyclic pigments, perylene pigments, indigo dyes, thioindigo dyes, and methine squaric acid dyes are known. □In particular, organic pigments and dyes with photoconductivity are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in the appropriate wavelength range has been expanded, so there are many possibilities. Photoconductive organic pigments and dyes have been proposed. For example, U.S. Patent Nos. 4,123,270 and 424
No. 7614, No. 4251613, No. 425161
No. 4, No. 4256821, No. 4260672,
Same No. 4268596, Same No. 4278747, Same No. 4
As disclosed in Japanese Patent No. 293,628, 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 extremely highly productive and inexpensive photoreceptor.
Moreover, it has the advantage that the sensitive wavelength range can be freely controlled by selecting the organic pigment.

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 operation for solving problems] The present invention aims to achieve the above-mentioned 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 R3 and R2 are a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a 5- or 6-membered ring together with a nitrogen atom). Indicates the atomic group necessary to complete the ring, and R3 and R+ indicate the atomic group necessary to complete the 5-membered ring or 6-membered ring together with a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a nitrogen atom. , Machi and R1 are hydrogen atoms, halogen atoms, nitro groups, substituted or unsubstituted alkyl groups, alkoxy groups,
a substituted or unsubstituted 7-aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted amino group, R represents a divalent organic residue). 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. , a thin film layer, e.g. lO#L
Hereinafter, it is desirable that the thin film layer preferably has a thickness of 0.01 to tg.

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 injected into the charge transport layer without being deactivated by recombination or trapping. This is due to the need to do so.

The charge generating material used in the present invention is a polycyclic ironone 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 a substrate, or by forming a vapor deposited film using a vacuum vapor deposition device. can be obtained by The binder that can be used in 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 resin,
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.

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 transport layer or undercoat layer.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, N, N
-dimethylformamide, N.

Amides such as N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate,
Aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, etc., or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, 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 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.

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" as used herein includes the broad definition of "light rays" including γ-rays, X-rays, far-infrared rays, and the like.

When the photosensitive liquid wall of the charge transport layer coincides with or overlaps 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 has the general formula (II)
It is a hydrazone compound represented by

In the formula, R1 and R2 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 R□ 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, R1 and R7 are a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, alkoxy group,
It represents 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.

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.

Further, 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 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 provide high sensitivity, low residual potential,
This is appropriate from the viewpoint of repeated 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. Generally it is 5-30JL, but the 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. A layer of plastic (e.g. polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoroethylene, etc.) with a formed layer, conductive particles (e.g. carbon black, silver particles, etc.) on top of 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 conductive layer and the photosensitive layer.

The subbing layer consists of 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, aluminum oxide, etc.

The thickness of the undercoat layer is 0.1 to 40 mm, preferably 0.1 to 40 mm.
3IL is appropriate.

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, resulting in attenuation of the surface potential and an electrostatic contrast between it and the unexposed area. 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, 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. In order to form an electrostatic latent image on this protective layer, the surface resistivity must be 100.
The above is desirable. The protective 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,
It can be formed by applying a solution prepared by dissolving a resin such as 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 0.05 to 20μ, preferably 0.2 to 5μ.
It is within the range of L.

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

Example 1 An ammonia aqueous solution of casein (2 g of casein 11, 1 g of 28% ammonia, 222 ml of water) was coated on an aluminum cylinder by dip coating and dried to a coating weight of 1. A subbing layer of Og/m was formed.

Next, 1 part by weight of a charge generating material of structural formula (I).

Butyral resin (Eslec BM-2, manufactured by Miki Kagaku ■)
1 part by weight 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 generation layer. The film thickness was 0.3 mm.

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 12.51L.

A corona discharge of 15 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 %).

Sensitivity was evaluated by measuring the exposure amount (E 1/21ux, 5ee) required to attenuate the potential Vt after dark decay to 172.

These results were as follows.

V□knee 595V, V: -585V, E 1/2:
4, 5 lux, sec Examples 2 to 5 Completely the same as 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 in a similar manner, and the characteristics of this photoreceptor were measured.

These results are shown below.

'1LjiLJs 彽q Vo -V V -V
E 1/2 lux 5ee2 (2)
800 590 4.73 (3)
590 580 4.94 (4) 6
15 805 5.85 (5) 13
05 595 5.0 Comparative Examples 1 to 6 Comparative Examples 1 to 6 were 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. A photoreceptor was prepared and its charging characteristics were measured.

C, H5- Charging characteristics 1 (1) 595 570 7.
42 (2) 590 570 B
, 113 (3) 800 575
7.14 (4) e15 585
8.05 (5) 5130 580
7.76 (6) 585 585
7.5 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,
The photoconductors of Examples 1 to 5 were transferred to 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 the test 20,000 times with each photoreceptor, indicating that the 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 made it possible to provide a laminated electrophotographic photoreceptor with extremely high sensitivity compared to conventional products.

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).