JPH0542662B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor. Specifically, the present invention relates to a highly sensitive electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive substance.

Conventionally, the photosensitive layer of electrophotographic photoreceptors contains selenium,
Inorganic photoconductive materials such as cadmium sulfide and zinc oxide were widely used. However, selenium and cadmium sulfide need to be recovered as poisonous substances, selenium crystallizes when exposed to heat and has poor heat resistance, and cadmium sulfide and zinc oxide have poor moisture resistance.
Furthermore, zinc oxide has drawbacks such as lack of printing durability, and efforts are being made to develop new photoreceptors. Recently, research has progressed on the use of organic photoconductive substances in the photosensitive layer of electrophotographic photoreceptors, and some of them have been put into practical use. Compared to inorganic photoconductive materials, organic photoconductive materials have advantages such as being lighter, easier to form a film, easier to manufacture photoreceptors, and depending on the type, transparent photoreceptors can be manufactured. has advantages.

Despite having such many advantages, organic photoconductive materials have not been widely used as electrophotographic photoreceptors because they are inferior to inorganic materials in terms of sensitivity and durability.

Recently, so-called functionally separated photoreceptors, in which the functions of charge carrier generation and transfer are shared by separate compounds, have become the mainstream of development because they are effective in increasing sensitivity. Photoreceptors are also being put into practical use.

As the charge carrier transfer medium, a polymeric photoconductive compound such as polyvinylcarbazole may be used, or a low molecular weight photoconductive compound may be dispersed and dissolved in a binder polymer.

On the other hand, for organic low-molecular photoconductive compounds, polymers with excellent film properties, flexibility, and adhesive properties can be selected as binders, making it easy to obtain photoreceptors with excellent mechanical properties. However, it has been difficult to find compounds suitable for making highly sensitive photoreceptors.

Therefore, the present inventors conducted intensive research on organic low-molecular photoconductive compounds that provide electrophotographic photoreceptors with high sensitivity and high durability, and found that a specific hydrazone compound is suitable. Reached.

That is, the gist of the present invention is the general formula [] (In the formula, Ar ₁ represents phenyl which may have a substituent, Ar ₂ may have a substituent,
Represents a naphthyl group, acenaphthenyl group or carbazolyl group, R represents a hydrogen atom, a lower alkyl group, an allyl group, an aryl group or an aralkyl group which may have a substituent, and Z represents a hydrogen atom, a lower alkyl group, a lower It represents an alkoxy group or an arylalkoxy group, and n represents an integer of 0 or 1. ) A photoreceptor for electrophotography is characterized by having a photosensitive layer containing a hydrazone compound represented by:

The present invention will be described in detail below. The electrophotographic photoreceptor of the present invention contains a hydrazone compound represented by the general formula [] in the photosensitive layer.

In the general formula [], Ar ₁ represents a phenyl group, and Ar ₂ represents a naphthyl group, an acenaphthenyl group or a carbazolyl group.

Both Ar ₁ and Ar ₂ described above may have a substituent. Examples of such substituents include lower alkyl groups such as methyl, ethyl, propyl, butyl, and hexyl; lower alkoxy groups such as methoxy, ethoxy, and butoxy; and aryloxy such as phenoxy and trioxy. Groups; arylalkoxy groups such as benzyloxy group and phenethyloxy group; aryl groups such as phenyl group and naphthyl group; styryl group; dialkylamino groups such as dimethylamino group and diethylamino group. R is a hydrogen atom; a lower alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group; an allyl group; an aryl group such as a phenyl group, a naphthyl group, an anthryl group; a benzyl group, a phenethyl group, a cinnamyl group, etc. Examples include aralkyl groups. Note that the above aryl group and aralkyl group may have a substituent. Examples of such substituents include lower alkyl groups such as methyl, ethyl, propyl, and butyl; lower alkoxy groups such as methoxy, butoxy, and hexyloxy; and arylalkoxy groups such as benzyloxy and phenethyloxy. can be mentioned. Z is a hydrogen atom; a lower alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group; a methoxy group, a butoxy group,
Examples include lower alkoxy groups such as hexyl groups; arylalkoxy groups such as benzyloxy groups and phenethyloxy groups. n represents an integer of 0 or 1.

In the general formula [], R is preferably a phenyl group or a naphthyl group.

The hydrazone compound represented by the general formula [] can be easily produced by a known method.

For example, the following general formula [] (In the formula, Ar ₁ , Ar ₂ and n have the same meanings as in the general formula []). An aromatic hydrocarbon such as benzene, toluene, chlorobenzene, nitrobenzene; methanol, ethanol, butanol, etc. alcohol; tetrahydrofuran, 1,2-dimethoxyethane, 1,4
-Ethers such as dioxane; methyl cellosolve,
Cellosolve such as ethyl cellosolve; N,N-dimethylformamide, dimethyl sulfoxide, N-
In a solvent inert to the reaction such as methylpyrrolidone, the following general formula [] (wherein, R and Z have the same meanings as above) or their hydrochlorides or sulfates at 10 to 200°C, preferably at 20°C.
Obtained by reaction at a temperature of ~100°C.

In some cases, p-
Toluenesulfonic acid, benzenesulfonic acid, hydrochloric acid, sulfuric acid, potassium acetate, sodium acetate, etc. may be added.

In addition, the aldehyde represented by the above general formula [] and the following general formula [] (wherein Z has the same meaning as above) in an organic solvent inert to the reaction in the same manner as above, optionally p-toluenesulfonic acid, benzenesulfonic acid, hydrochloric acid, By reacting in the presence of a reaction accelerator such as sulfuric acid, potassium acetate, or sodium acetate, the following general formula [] (In the formula, Ar ₁ , Ar ₂ , n, and Z are the above general formula []
A hydrazone represented by the following formula [] R-W ... [] (wherein R has the same meaning as in the general formula []), and W represents a halogen atom such as a chlorine atom, a bromine atom, an iodine atom, etc.) or a dialkyl sulfate such as dimethyl sulfate or diethyl sulfate. Nitrobenzene, tetrahydrofuran, dioxane, N,N
- Sodium hydroxide, potassium hydroxide, in an organic solvent inert to the reaction such as dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, etc.
At a temperature of 10 to 200°C in the presence of a deoxidizing agent such as sodium carbonate, potassium carbonate, triethylamine, pyridine, or trimethylbenzylammonium hydroxide,
By the reaction, a hydrazone represented by the above general formula [] can be produced.

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing one or more hydrazone compounds represented by the above general formula [].

The hydrazone compound represented by the general formula [] shows extremely excellent performance as an organic optical semiconductor. In particular, when used as a charge transfer medium, it provides a photoreceptor with particularly high sensitivity and excellent durability.

Various forms of the photosensitive layer of an electrophotographic photoreceptor are known, and the photosensitive layer of the electrophotographic photoreceptor of the present invention may take any of these forms. For example, a photosensitive layer containing a hydrazone compound in a binder and optionally a sensitizer dye or an electron-withdrawing compound, and a binder containing photoconductive particles that generate charge carriers with extremely high efficiency when absorbing light and a hydrazone compound. A photosensitive layer added to
Examples include a photosensitive layer in which a charge transfer layer consisting of a hydrazone compound and a binder is laminated with a charge generation layer consisting of photoconductive particles that generate charge carriers with extremely high efficiency upon absorption of light, or a charge generation layer consisting of photoconductive particles and a binder.

In these photosensitive layers, a known hydrazone compound having excellent performance as an organic optical semiconductor may be mixed together with the hydrazone compound represented by the general formula [].

In the present invention, when the hydrazone compound represented by the above general formula [] is used as the charge transfer layer of a photosensitive layer consisting of two layers, a charge generation layer and a charge transfer layer, it has particularly high sensitivity, low residual potential, and can be used repeatedly. In this case, it is possible to obtain a photoreceptor with excellent durability and less fluctuation in surface potential, lowering of sensitivity, and accumulation of residual potential.

The electrophotographic photoreceptor of the present invention is produced by dissolving a hydrazone compound represented by the above general formula [] in a suitable solvent together with a binder according to a conventional method, and absorbing light as necessary to generate charge carriers with extremely high efficiency. A coating solution obtained by adding photoconductive particles, a sensitizing dye, an electron-withdrawing compound, a plasticizer, a pigment, and other additives is coated onto a conductive support, dried, and the coating solution is usually several microns or more. It can be manufactured by forming a photosensitive layer with a thickness of several tens of microns. In the case of a photosensitive layer consisting of two layers, a charge generation layer and a charge transfer layer, the above coating liquid is applied on the charge generation layer, or the charge generation layer is applied on the charge transfer layer obtained by coating the above coating liquid. It can be manufactured by forming.

Solvents for preparing the coating solution include ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as methyl ethyl ketone and cyclohexanone;
Aromatic hydrocarbons such as toluene and xylene; N, N
-dimethylformamide, acetonitrile, N-
Aprotic polar solvents such as methylpyrrolidone and dimethyl sulfoxide; ethyl acetate, methyl formate,
Examples include esters such as methyl cellosolve acetate; solvents that dissolve hydrazone compounds such as chlorinated hydrocarbons such as dichloroethane and chloroform. Of course, it is necessary to select one that dissolves the binder from among these. In addition, binders include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic esters, methacrylic esters, butadiene, polyvinyl acetal, polycarbonate,
Polyester, polysulfone, polyphenylene oxide, polyurethane, cellulose ester,
Examples include various polymers that are compatible with hydrazone, such as cellulose ether, phenoxy resin, silicone resin, and epoxy resin. The amount of binder used is usually 0.5 to 30 times, preferably 0.7 to 10 times the weight of hydrazone.

As the photoconductive particles, dyes, and electron-withdrawing compounds to be added to the photosensitive layer, well-known ones can be used. Photoconductive particles that generate charge carriers with extremely high efficiency upon absorption of light include inorganic photoconductive particles such as selenium, selenium-tellurium alloy, selenium-arsenic alloy, cadmium sulfide, and amorphous silicon; copper phthalocyanine, and perinone-based particles. Examples include organic photoconductive particles such as pigments, thioindigo, quinacridone, perylene pigments, anthraquinone pigments, azo pigments, bisazo pigments, and cyanine pigments. Examples of dyes include triphenylmethane dyes such as methyl violet, brilliant green, and crystal violet, thiazine dyes such as methylene blue, quinone dyes such as quinizarin, cyanine dyes, pyrylium salts, thiapyrylium salts, and benzopyrylium salts. It will be done. Examples of electron-withdrawing compounds that form a charge transfer complex with a hydrazone compound include chloranil, 2,3-dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1-chloro-5-nitro Quinones such as anthraquinone, 2-chloroanthraquinone, phenanthrenequinone, aldehydes such as 4-nitrobenzaldehyde, 9-benzoylanthracene, indanedione, 3,5-dinitrobenzophenone, 2,4,7-tri Ketones such as nitrofluorenone, 2,4,5,-tetranitrofluorenone, 3,3',5,5'-tetranitrobenzophenone, acid anhydrides such as phthalic anhydride, 4-chloronaphthalic anhydride, Cyano compounds such as tetracyanoethylene, terephthalmalononitrile, 9-anthrylmethylidenemalononitrile, 4-nitrobenzalmalononitrile, 4-(p-nitrobenzoyloxy)benzalmalononitrile; 3-benzalphthalide, 3-( α-cyano-p-nitrobenzal) phthalide, 3-(α-cyano-p-nitrobenzal)-4,5,6,7-
Examples include electron-withdrawing compounds such as phthalides such as tetrachlorophthalide.

Furthermore, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a well-known plasticizer in order to improve film formability, flexibility, and mechanical strength. For this purpose, examples of the plasticizer added to the coating solution include phthalic esters, phosphoric esters, epoxy compounds, chlorinated paraffins, chlorinated fatty acid esters, aromatic compounds such as methylnaphthalene, and the like. When a hydrazone compound is used as a charge transfer medium in a charge transfer layer, the coating liquid may have the above composition, but photoconductive particles, dyes, electron-withdrawing compounds, etc. may be excluded or added in small amounts. In this case, the charge generation layer is a coating solution obtained by dissolving or dispersing the photoconductive particles and, if necessary, a binder, a polymer, an organic photoconductive substance, a dye, an electron-withdrawing compound, etc. in a solvent, and then drying the coating solution. Examples include a thin layer made of the photoconductive particles, or a layer made of the photoconductive particles formed into a thin film by means such as vapor deposition.

It goes without saying that the photoreceptor formed in this manner may also have an adhesive layer, an intermediate layer, a transparent insulating layer, etc., if necessary. As the conductive support on which the photosensitive layer is formed, any of those used in well-known electrophotographic photoreceptors can be used. Specific examples include metal drums and sheets made of aluminum, stainless steel, copper, etc., and laminates and vapor deposits of these metal foils. Further examples include plastic films, plastic drums, paper, paper tubes, etc., which are coated with a conductive substance such as metal powder, carbon black, copper iodide, or polymer electrolyte together with a suitable binder to conductivity treatment. Also included are plastic sheets and drums that contain conductive substances such as metal powder, carbon black, and carbon fibers and are rendered conductive.

The electrophotographic photoreceptor of the present invention has been described in detail above. The photoreceptor of the present invention has extremely high sensitivity, has a low residual potential that causes fogging, and is particularly resistant to optical fatigue, so it can withstand repeated use. It is characterized by excellent durability with little accumulation of residual potential and small fluctuations in surface potential and sensitivity.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, "parts" in the examples indicate "parts by weight."

Production example 1 3-(5'-acenaphthenyl)-3-phenyl-2
-3 g of propenal and 3 g of N,N-diphenylhydrazine hydrochloride were dissolved in 40 ml of methanol, and the mixture was stirred at room temperature for 3 hours to react. The precipitated crystals were purified by silica gel column chromatography to give pale yellow crystals of 3-(5'-acenaphthenyl)-3.
-Phenyl-2-propenal N,N-diphenylhydrazone 3.8g was obtained.

Melting point 154.7-156.7℃ Elemental analysis value C H N Calculated value (%) 87.97 5.82 6.22 Measured value (%) 88.13 5.88 6.21 Example 1 Naphthalic acid bisazo pigment having the above structure
1.4 parts and polyvinyl butyral (Sekisui Chemical Co., Ltd.)
2.8 g of ESLETSUKU B) (manufactured by ESLEC B) was dispersed into fine particles using a sand grinder in 100 g of tetrahydrofuran.

This dispersion was applied with a wire bar onto the aluminum vapor deposited layer deposited on a polyester film with a film thickness of 75 μm so that the weight after drying was 0.3 g/m ² , and then dried to form a charge generation layer. I let it happen.

On top of this, the following structural formula 80 parts of 3-(5'-acenaphthenyl)-3-phenyl-2-propenal N,N-diphenylhydrazone and methacrylic resin (Mitsubishi Rayon Co., Ltd.)
100 parts of Dianal BR-80) manufactured by Toluene.
Apply a coating solution dissolved in 570 parts, dry, and measure the film thickness.
A charge transport layer of 15 μm was formed.

The sensitivity, that is, the half-decreased exposure (E1/2) of the electrophotographic photoreceptor having the two-layer photosensitive layer thus obtained was measured and found to be 5.5 lux·sec.

The half-decreased exposure amount is calculated by first charging the photoreceptor in a dark place with -5.5KV corona discharge, then exposing it to white light, and measuring the amount of exposure required for the surface potential to attenuate to 1/2 of the initial surface potential. I asked for it.

Example 2 The following structural formula obtained in the same manner as Production Example 1 instead of the hydrazone compound used in Example 1 3-(4'-methoxy-1'-naphthyl) represented by
-3-(p-methoxyphenyl)-2-propenal N,N-diphenylhydrazone (melting point 181-182
A photoreceptor was produced in the same manner as in Example 1, except that the temperature was 100°C. The sensitivity of this photoreceptor was 5.7 lux·sec.

Example 3 Production Example 1 was used instead of the hydrazone used in Example 1.
The following structural formula was obtained in the same manner as 3-(5'-acenaphthenyl)-3- represented by
A photoreceptor was prepared in the same manner as in Example 1 except that (p-tolyl)-2-propenal N,N-diphenylhydrazone (melting point 154-155°C) was used, and the sensitivity was measured to be 5.8 lux·sec. It was hot.

Example 4 Production Example 1 was used instead of the hydrazone used in Example 1.
The following structural formula was obtained in the same manner as 3-(N-ethyl-3-carbazolyl)-3-(p-methoxyphenyl)-2-propenal N,N-diphenylhydrazone (amorphous) represented by
A photoreceptor was prepared in the same manner as in Example 1, except that the sensitivity was measured, and the sensitivity was 3.9 lux·sec.

Example 5 The following structural formula was used instead of the pigment used in Example 1. A photoreceptor was produced in the same manner as in Example 1, except that the naphthalic acid bisazo pigment represented by was used. This photoreceptor had a power of 1.5 lux·sec.

Claims (1)

[Claims] 1. General formula (In the formula, Ar ₁ represents a phenyl group that may have a substituent, Ar ₂ represents a naphthyl group, acenaphthenyl group, or carbazolyl group that may have a substituent, R is a hydrogen atom, represents a lower alkyl group, an allyl group, an aryl group or an aralkyl group which may have a substituent, Z represents a hydrogen atom, a lower alkyl group, a lower alkoxy group or an arylalkoxy group, and n is an integer of 0 or 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a hydrazone compound represented by: