JPS628158A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a laminate type electrophotographic sensitive body high in sensitiv ity and extremely low in residual potential even after a durability test by forming a layer containing a specified quinone type pigment as an electrostatic charge generat ing layer and a layer containing a hydrazone type compound as a charge transfer layer. CONSTITUTION:The charge generating layer contains the polycyclic quinone type pigment represented by structural formula (I) and the charge transfer layer contains the hydrazone type compound represented by general formula (II). The charge generat ing layer can be formed by coating a substrate with said pigment, and when needed, the charge transfer material together with a proper binder. The charge transfer layer is electrically connected with the charge generating layer, and has a function of receiv ing charge carriers injected from the charge generating layer in the presence of an electric field and transferring them to the surface. The hydrazone type compound to be used as the charge transfer material is typified by formulae (1)-(3), and when the charge transfer material is added to the charge generating layer, it is proper to add it in an amount of 1-100pts.wt. per 100pts.wt. of the charge generating material from the view points of high sensitivity, low residual potential, and stability against repeated uses. In the formula II, R is bivalent org residual 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. Low-molecular organic photoconductors and phthalocyanine pigments such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkanes.

Organic pigments and dyes such as azo pigments, silane pigments, polycyclic bovine pigments, perylene pigments, indigo dyes, thioindigo dyes, and methine squarate 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. 0672, No. 4268596, No. 427874
No. 7, No. 4293628, etc., an electrophotographic photoreceptor using a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer functionally separated into a charge generation layer and a charge transport layer. 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 selection.

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 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 bovine non-based pigment in the charge generation layer and a specific hydrazone compound in the charge transport layer in a multilayer electrophotographic photoreceptor having two layers.

The present invention provides an electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer is a layer containing a polycyclic bovine non-based pigment of structural formula (I). The charge transport layer consists of a hydrazone compound represented by the general formula (n) (wherein R3 and a substituted or unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or a nitrogen atom and a Indicates the atomic group necessary to complete the membered ring or 6-membered ring, R6 and R-substituted or unsubstituted alkyl group,
Together with a substituted or unsubstituted 7-aryl group or a nitrogen atom, R9 and R7 represent a hydrogen atom, a halogen atom, a nitro group, or a substituted or unsubstituted 7-aryl group or a nitrogen atom. from a layer containing an alkyl group, an alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted 7-mino group, and R represents a divalent organic residue) It is composed of an electrophotographic photoreceptor characterized by:

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 in order to efficiently inject the generated charge carriers into the charge transport layer. and a thin film layer, e.g. 10IL.
Hereinafter, it is desirable to use a thin film layer with a thickness of preferably 0.01 to IIL. This means that most of the incident light is absorbed by the charge generation layer and many charge carriers are generated. recombination and capture of charge carriers (
This is due to the need to inject into the charge transport layer without being deactivated by traps.

The charge generating material included 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 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 polybodies 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, POIJ' acrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. can. The resin contained in the charge generation layer is
A content of 80% by weight or less, preferably 40% by 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 charge transport layer or subbing layer described below.Specific organic solvents include methanol, ethanol, Alcohols such as isopropanol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, amides such as N,N-dimethylformamide, N,N-dimethylacetamide,
Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as S-methyl vinegar and ethyl acetate, and aliphatics such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene. Halogenated hydrocarbons or benzene, toluene, xylene.

Aromatics such as ligroin, monochlorobenzene, dichlorobenzene, etc. can be used.

Coating methods include dip coating, spray coating, spinner coating, bead coating,
Drying coating methods such as Mayer bar coating method, blade coating method, roller coating method, curtain coating method, etc. should be done after drying to the touch at room temperature.
A method of heating and drying is preferable.
It can be carried out at a temperature of 0° C. for a period of time ranging from 5 minutes to 2 hours, either stationary or under blowing air.

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 laminated with a Δ substance (hereinafter simply referred to as a charge transport material) that transports charge carriers in the charge transport layer. ) 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 matches or overlaps that of the charge generation layer, the charge carriers generated in both trap each other, and the charge transport material used in the present invention has the general formula (II). This is a hydrazone compound represented by the following formula.

In the formula, R8 and R2 represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted 7-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 ~ are substituted or an unsubstituted alkyl group,
Indicates the atomic group necessary to complete a 5-membered ring or 6-membered ring together with a substituted or unsubstituted 7-aryl group or a nitrogen atom, ~ and R & are hydrogen atoms, halogen atoms, nitro groups,
Represents a substituted or unsubstituted alkyl group, alkoxy group, substituted or unsubstituted 7-aryloxy group, substituted or unsubstituted acyl group, or 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.

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 becomes even more remarkable. When a charge transporting material is added to the charge generation layer, the hydrazone compound should be added in an amount not more than 10 times (-weight ratio) as much as the charge generation material, preferably 0.0
A ratio of 1 to 1 times (weight ratio) is appropriate from the viewpoints of high sensitivity, low residual potential, and 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 the binder include, for example, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber. Examples thereof include insulating resins such as, etc., and pacifying photoconductive polymers such as poly-H-vinylcarbazole, polyvinylanthracene, and 1-rivinylpyrene. Since the charge transport layer has a separation field that allows charge carriers to be transported, the film thickness cannot be increased more than necessary. Generally, the thickness is 5 to 30 p, but the preferred range is 8 to 20 IL. 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. Substrates that support the conductive layer include those that themselves have conductivity, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, and nickel.

Indium, gold, platinum, etc. can be used, and in addition, plastics (e.g. Polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoroethylene, etc.), conductive particles (e.g. carbon black, silver particles, etc.) are coated on plastic with a suitable binder, conductive particles are A substrate impregnated with plastic or paper, 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 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 liquefaction or the like. The thickness of the undercoat layer is 0.1 to 40
g, preferably 0.1 to 3 g.

When using a photoreceptor having a conductive layer, a charge generation layer, and a charge transport layer in this order, and the charge transport material in the charge transport layer is 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 in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic charge between the exposed area and the unexposed area. Contrast 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, 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, causing a decrease in surface potential and creating a gap between the exposed area and the unexposed area. 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 deteriorates due to ultraviolet rays, ozone, etc. - dirt from oil etc., scratches from metal chips, etc., damage to the photoreceptor from photoreceptor contact members such as developing members, transfer members, cleaning members, etc. 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 protective layer used in the present invention is preferably 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 in the range of 0.05 to 20 mm, preferably 0.2 to 5 mm.

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,
222 ml of water) was applied by dip coating and dried to form a subbing layer with a coating weight of 1 and 0 g/rtr.

Next, 1 part by weight of the charge generating material having the structural formula CI), 1 part by weight of butyral resin (manufactured by Eslet BM-2, a Water 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 generation 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,
+9! The mixture was stirred and dissolved using a stirrer. This solution was applied onto the charge generation layer by dip coating and dried to form a charge transport layer.

The film thickness was approximately 12.5 μl.

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 v9).

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

These results were as follows.

Vo: -580V, v5-: -570V, E
1/2:3, Olux, sec Examples 2 to 5 Examples 2 to 5 except that hydrazone compound examples (2) to (5) were used in place of hydrazone compound example (1) used in Example 1, respectively. 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.

11J Temporary fixing 3Vo -V V -V E 1/2
lux 5ec2 (2) 575 58
0 2.93 (3) 570 513
5 3.34 (4) 590 580
3.95 (g) eo0590 3.8 Comparative Examples 1 to 6 The following comparative charge transport substances (1) to (8) were used in place of the hydrazone compound used in Example 1, and the other methods were exactly the same. Photoreceptors of Comparative Examples 1 to 6 were prepared, and their charging characteristics were measured.

C Engineering Hr Charging characteristics 1 (1) 5110 585 4.
32 (2) 580 580 4.
83 (3) 585 555 5.
04 (4) 810 11100
Ei, 25 (5) 585 555
5.76 (6) 815 805
4.4 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, images were produced 20,000 times using a copying machine (manufactured by Canon Inc., NP-1502) on the photoreceptors of Examples 1 to 5.

As a result, good quality images were obtained even after repeating 20,000 times with each photoreceptor, and the electrophotographic photoreceptor of the present invention
It can be seen that the durability is also extremely excellent.

[Effects 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 also uses a specific hydrazone-based compound to This made it possible to provide a laminated electrophotographic photoreceptor with extremely high sensitivity compared to conventional ones.

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).