JPH0118414B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive compound as a main component. Conventionally, as electrophotographic photoreceptors, those mainly composed of inorganic photoconductors such as selenium, zinc oxide, and cadmium sulfide have been widely used. However, these are not necessarily satisfactory in terms of properties such as thermal stability, durability, or moisture resistance, and furthermore, they are toxic and pose problems in production and handling. On the other hand, electrophotographic photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component are relatively easy to manufacture, inexpensive, and easy to handle, and generally compared to selenium photoreceptors. It has many advantages such as excellent thermal stability.
In recent years, it has attracted a lot of attention. Poly-N-vinylcarbazole is the best known such organic photoconductive compound, and 2,
Electrophotographic photoreceptors having a photosensitive layer containing a charge transfer complex formed from 4,7-trinitro-9-fluorenone as a main component have already been put into practical use. On the other hand, electrophotographic photoreceptors are known that have a functionally separated photosensitive layer of a laminated type or a dispersion type in which the carrier generation function and the carrier transport function of the photoconductor are shared by separate substances. An electrophotographic photoreceptor has been put into practical use having a photosensitive layer that combines a carrier generation layer made of a thin regular selenium layer and a carrier transport layer made of poly-N-vinylcarbazole. However, since poly-N-vinylcarbazole lacks flexibility, its coating is hard and brittle and prone to cracking and peeling, so electrophotographic photoreceptors using it have poor durability. If a plasticizer is added to improve this drawback, the residual potential will increase when subjected to the electrophotographic process, and as it is repeatedly used, the residual potential will accumulate and gradually cause fog in the copied image. It has the following drawback. Furthermore, since low molecular weight organic photoconductive compounds generally do not have film-forming ability, they are used in combination with any binder. Therefore, it is preferable that the physical properties or electrophotographic properties of the film can be controlled to some extent by selecting the type and composition ratio of the binder used, but it is preferable that the film has high compatibility with the binder. The types of organic photoconductive compounds that can be used are limited, and the reality is that there are not many that can actually be used in the composition of the photosensitive layer of an electrophotographic photoreceptor. For example, 2,5-bis(p-diethylaminophenyl)-1,3,4-exadiazole described in U.S. Pat. No. 3,189,447 is usually preferred as a material for the photosensitive layer of an electrophotographic photoreceptor. Since it has low compatibility with the binder used, for example, if it is mixed with a binder such as polyester or polycarbonate in the ratio required to obtain favorable electrophotographic properties to form a photosensitive layer, Oxadiazole crystals begin to precipitate at temperatures of 50° C. or higher, resulting in a disadvantage that electrophotographic properties such as charge retention, sensitivity, and residual potential deteriorate. On the other hand, the diarylalkane derivatives described in U.S. Pat. is repeated. When used in the construction of a photosensitive layer of a repeat transfer type electrophotographic photoreceptor, it has the disadvantage that the sensitivity of the photosensitive layer gradually decreases. In addition, the hydrazone compound represented by the following structural formula [) described in U.S. Patent No. 4150987 is When used as a carrier transport material constituting an electrophotographic photoreceptor, the initial sensitivity and residual potential characteristics are relatively good, but as the photoreceptor is used repeatedly, the sensitivity gradually decreases and residual potential accumulates. Therefore, it has the disadvantage of poor durability. As described above, the reality is that an organic photoconductive compound having practically preferable characteristics for producing an electrophotographic photoreceptor has not yet been found. An object of the present invention is to provide an electrophotographic photoreceptor containing a novel organic photoconductive compound that has excellent compatibility with a binder and excellent carrier transport ability. Another object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity and low residual potential. Still another object of the present invention is to charge, expose, develop, and
To provide an electrophotographic photoreceptor of excellent durability that exhibits stable characteristics over a long period of time with little fatigue deterioration due to repeated use when used as a repeat transfer type electrophotographic photoreceptor in which a transfer process is repeated. be. As a result of intensive research to achieve the above object, the present inventors have discovered that the object can be achieved by using a specific hydrazone derivative as a constituent material of the photosensitive layer of an electrophotographic photoreceptor, and have developed the present invention. It is completed. The above object can be achieved by using a hydrazone derivative represented by the following general formula [] or [] as a constituent component of the photosensitive layer. General formula [] General formula [] R ₁ , R ₅ and R ₇ represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
Here, a preferable alkyl group is an alkyl group having 1 to 4 carbon atoms, and a preferable aryl group is a phenyl group. R ₂ and R ₆ represent a hydrogen atom or a substituted or unsubstituted alkyl group. Preferred alkyl groups are those having 1 to 4 carbon atoms. R ₈ is a hydrogen atom or a halogen atom. R ₃ and R ₉ represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Preferred alkyl groups have 1 to 8 carbon atoms.
Examples of the alkyl group, preferred aryl group are:
These are phenyl group and naphthyl group. R ₄ and R ₁₀ represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group. Preferred aryl groups are phenyl, naphthyl, and anthryl, and preferred heterocyclic groups are furyl, thienyl, indolyl, benzofuryl, benzothienyl, and carbazolyl. Preferred substituents for these alkyl groups, aryl groups, and heterocyclic groups include alkyl groups, aryl groups, alkoxy groups, hydroxyl groups, halogen atoms,
These include substituted amino groups, cyano groups, and nitro groups. Further, it is particularly preferable that R ₂ , R ₅ , R ₆ , R ₇ and R ₈ are hydrogen atoms. n and m represent 0 or 1. That is, in the present invention, the general formula []
Alternatively, by using at least one of the hydrazone derivatives represented by [ ] as a photoconductive substance for an electrophotographic photoreceptor, or by utilizing only the excellent carrier transport ability of the hydrazone derivative of the present invention, this can be used to reduce the generation of carriers. By using it as a carrier transport material in a so-called functionally separated electrophotographic photoreceptor in which transport and transport are performed using separate substances, the film has excellent physical properties and electrophotographic properties such as charge retention, sensitivity, and residual potential, and can be used repeatedly. It is possible to create an electrophotographic photoreceptor that exhibits stable characteristics with little fatigue deterioration even when subjected to Specific examples of the hydrazone derivatives represented by the above general formulas [] and [] that are effective in the present invention include:
For example, those having the following structural formula can be mentioned,
The hydrazone derivative of the present invention is not limited thereby. Exemplary compound The above hydrazone derivatives can be easily synthesized by known methods. For example, according to the following reaction formula, hydrazine derivatives represented by general formulas [] and [] and aromatic carbonyl compounds represented by general formulas [] and [] are mixed in a solvent such as alcohol in the presence of an acid catalyst. It can be easily synthesized by dehydration condensation. Here, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ ,
R ₉ , R ₁₀ and n, m represent the same as shown in the above general formulas [] and []. Next, a typical method for synthesizing the hydrazone derivative of the present invention will be specifically explained. Synthesis Example (Synthesis of Exemplified Compound []-4) The hydrazone derivative represented by Exemplified Compound []-4 can be synthesized according to the following reaction formula. That is, iminodibenzyl (A) in an acetic acid solvent,
21.0 g (0.1 mole) of hydrazine (C) obtained by nitrosation (B) with sodium nitrite and then reduction with zinc dust
and N,N-diethylaminobenzaldehyde 17.7
g (0.1 mole) in 300 ml of ethanol,
10 ml of acetic acid was added and the mixture was heated under reflux for 4 hours. After cooling, the precipitated crystals were collected by filtration and recrystallized twice from a mixed solvent of toluene and isopropyl alcohol.
25.5 g of pale yellow crystals were obtained. Yield 69.1% Elemental analysis Experimental value C 81.27% H 7.35 N 11.42 Since the hydrazone derivative of the present invention has almost no photosensitivity to visible light, it is necessary to perform sensitization treatment when exposing it to visible light. be. Various methods have been proposed for sensitizing organic photoconductive compounds. The first method is to add an organic dye and thereby perform spectral sensitization (dye sensitization). The second method is to form a charge transfer complex to perform sensitization. Since the hydrazone derivative of the present invention is an electron-donating substance, it is preferably used in combination with an electron-accepting substance in this case. The third method utilizes only the carrier transport ability of the hydrazone derivative of the present invention and combines it with other organic dyes, pigments, or carrier-generating substances having carrier-generating ability such as inorganic photoconductors to form functionally separated photoreceptors. This is a method to do so. The hydrazone derivative of the present invention exhibits good effects by any of the above-mentioned sensitization methods, and any suitable method may be selected depending on the purpose. Next, typical examples of organic dyes for spectral sensitization used in the present invention are listed. (A-1) Triphenylmethane dyes such as methyl violet, climactic violet, and malachite green (A-2) Xanthene dyes such as erythrosin and rose bengal (A-3) Thiazine dyes such as methylene blue and methylene green Pigments (A-4) Oxazine dyes such as Capri Blue and Meldora Blue (A-5) Cyanine dyes such as thiocyanine and oxacyanine (A-6) Styryl dyes such as p-dimethylaminostyrylquinoline (A- 7) Pyrylium salt, thiopyrylium salt,
Pyrylium salt dyes such as benzopyrylium salts and benzothiopyrylium salts (A-8) 3,3'-dicarbazolylmethane dyes These can also be used as carrier generating substances. Further, in addition to the above-mentioned dyes, the following may be used as carrier generating substances. (B-1) Azo dyes such as monoazo dyes, disazo dyes, and trisazo dyes (B-2) Perylene dyes such as perylenic anhydride and perylenic acid imide (B-3) Indigoid dyes such as indigo, thioindigo, etc. (B-4) Polycyclic quinones such as anthraquinone, pyrenequinone, and flavanthrones (B-5) Quinacridone dyes (B-6) Bisbenzimidazole dyes (B-7) Indanthrone dyes (B -8) Squarelium dyes (B-9) Phthalocyanine dyes such as metal phthalocyanine and non-metal phthalocyanine (B-10) Selenium and selenium alloys (B-11) Inorganic photoconductors such as CdS and CdSe amorphous silicon ( B-12) Eutectic complex formed from pyrylium salt, thiopyrylium salt, and polycarbonate Examples of electron-accepting substances that can form a charge transfer complex with the hydrazone derivative of the present invention include 2,4,7-
Lewis acids such as trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, and tetracyanoquinodimethane are mentioned. Further, chemical sensitizers can also be effectively used in the photoreceptor of the present invention. The hydrazone derivatives of the present invention, as such,
Since it does not have the ability to form a film, a photosensitive layer is formed by combining it with various binders. Although any binder can be used here, it is preferable to use a film-forming polymer that is hydrophobic, has a high dielectric constant, and is electrically insulating. Examples of such high molecular weight polymers include, but are not limited to, the following. (C-1) Polycarbonate (C-2) Polyester (C-3) Methacrylic resin (C-4) Acrylic resin (C-5) Polystyrene (C-6) Polyvinyl chloride (C-7) Polyvinylidene chloride (C -8) Polyvinyl acetate (C-9) Styrene-butadiene copolymer (C-10) Vinylidene chloride-acrylonitrile copolymer (C-11) Vinyl chloride-vinyl acetate copolymer (C-12) Vinyl chloride-acetic acid Vinyl-maleic anhydride copolymer (C-13) Silicone resin (C-14) Silicone-alkyd resin (C-15) Phenol-formaldehyde resin (C-16) Styrene-alkyd resin (C-17) Poly-N -Vinylcarbazole These binders can be used alone, in combination of two or more, or as a copolymer obtained by arbitrarily combining the monomers that are the constituent units of these binders. As shown in FIGS. 1 and 2, the photoreceptor of the present invention comprises a carrier generating layer 2 containing a carrier generating substance as a main component on a conductive support 1 and a hydrazone derivative of the present invention as a carrier transporting substance. A photosensitive layer 4 made of a laminate with a carrier transport layer 3 is provided. As shown in FIGS. 3 and 4, this photosensitive layer 4 may be provided on the conductive support 1 with an intermediate layer 5 interposed therebetween. When the photosensitive layer 4 has a two-layer structure in this manner, a photoreceptor having the most excellent electrophotographic properties can be obtained. In addition, in the present invention, the fifth
As shown in FIG. 6 and FIG. 6, a photosensitive layer 4 consisting of a layer 6 containing the carrier transport material as a main component and a carrier generating substance 7 in the form of fine particles dispersed therein is deposited either directly on the conductive support 1 or as an intermediate layer. It may also be provided via layer 5. In addition, preferable results may be obtained by adding a sensitizing agent or a Lewis acid to the hydrazone derivative of the present invention and providing a single-layer photosensitive layer 4 as shown in FIGS. 5 and 6 instead of using a functionally separated photoreceptor. is obtained. Here, when the photosensitive layer 4 has a two-layer structure, which of the carrier generation layer 2 and the carrier transport layer 3 is used as the upper layer is determined depending on whether the charging polarity is positive or negative. That is, when used with negative charge, it is advantageous to use the carrier transport layer 3 as the upper layer, because the hydrazone derivative in the carrier transport layer is a substance that has a high transport ability for holes. . The carrier generation layer 2 constituting the two-layered photosensitive layer 4 may be formed directly on the conductive support 1 or the carrier transport layer 3, or provided with an intermediate layer such as an adhesive layer or a barrier layer as necessary. In addition, it can be formed by the following method. (D-1) Vacuum deposition method. (D-2) A method of dissolving a carrier generating substance in a suitable solvent and applying it. (D-3) A method of forming a carrier-generating substance into fine particles in a dispersion medium using a ball mill, homomixer, etc., and applying a dispersion obtained by mixing and dispersing a binder as necessary. The thickness of the carrier generation layer 2 thus formed is preferably 0.01 to 5 microns, and more preferably 0.05 to 3 microns. Further, the thickness of the carrier transport layer 3 can be changed as necessary, but it is usually preferably 5 to 30 microns. The composition ratio in this carrier transport layer 3 is such that the binder is added to 1 part by weight of the carrier transport material whose main component is the hydrazone derivative mentioned above.
The amount of the binder is preferably 0.8 to 10 parts by weight, but when forming the photosensitive layer 4 in which a fine powder carrier-generating substance is dispersed, the amount of the binder is 5 parts by weight or less per 1 part by weight of the carrier-generating substance. It is preferable to use it in The conductive support 1 used in the construction of the electrophotographic photoreceptor of the present invention may be a metal plate, a conductive polymer, a conductive compound such as indium oxide, or a metal thin film such as aluminum, palladium, gold, etc. Paper, plastic film, etc. that have been made conductive by coating, vapor depositing, or laminating a layer are used. For the intermediate layer 5 such as an adhesive layer or barrier layer, in addition to the polymer used as the binder, organic polymer substances such as casein, polyvinyl alcohol, ethyl cellulose, and carboxymethyl cellulose, or aluminum oxide are used. . The electrophotographic photoreceptor of the present invention has the above-described structure, and as is clear from the examples described later, has excellent charging characteristics, sensitivity characteristics, and image forming characteristics, and is particularly suitable for repeated transfer electrophotography. It exhibits excellent durability with little fatigue deterioration even when subjected to Examples of the present invention will be specifically described below.
This does not limit the embodiments of the present invention. Example 1 Vinyl chloride-vinyl acetate-maleic anhydride copolymer ``Eslec'' was deposited on a conductive support consisting of a polyester film laminated with aluminum foil.
A 0.05 micron thick intermediate layer made of MF-10 (manufactured by Sekisui Chemical Co., Ltd.) was provided. Next, 4,10-dibromoanthrone “Monolite Red 2Y” (ICI
CI No. 59300) was vapor-deposited to form a carrier generation layer with a thickness of 0.5 microns. Furthermore, 4.6 parts by weight of exemplified compound [] and polycarbonate resin are added thereon.
A carrier transport layer is formed by coating a solution obtained by dissolving 10 parts by weight of 1,2-dichloroethane in 90 parts by weight of 1,2-dichloroethane so that the film thickness after drying becomes 12 microns. Created. The sensitivity of this electrophotographic photoreceptor was measured using an electrostatic copying paper tester "Model SP-428" (manufactured by Kawaguchi Electric Seisakusho). That is, the surface of the photosensitive layer of the photoreceptor is charged with a -
The surface potential V _A when charged at 6KV for 5 seconds, and then the amount of exposure required to attenuate the surface potential V _A by half by irradiating light from a tungsten lamp so that the illumination intensity on the photoreceptor surface is 35 lux. (Half-reduced exposure dose) E1/2 (lux・sec) and surface potential after irradiation with an exposure dose of 30lux・sec (residual potential)
V _R was calculated for each. Similar measurements were also repeated 100 times.
The results are shown in Table 1.

[Table] Comparative Example 1 A comparative photoreceptor was prepared in the same manner as in Example 1, except that a hydrazone derivative represented by the following structural formula was used as a carrier transport substance, and the same measurements were performed. The results are shown in Table 2.

[Table] As is clear from the above results, the electrophotographic photoreceptor of the present invention is significantly superior to the comparative photoreceptor in terms of sensitivity, residual potential characteristics, and repetition stability. Example 2 A bisazo pigment represented by the following structural formula, 1, was prepared by vapor-depositing aluminum on a polyester film.
Parts by weight were dispersed and mixed in 80 parts by weight of 1,2-dichloroethane, and the mixture was coated to a dry film thickness of 0.3 microns to form a carrier generation layer. Next, 6 parts by weight of exemplified compound []-25 and polymethyl methacrylate resin "Acrypet"
(manufactured by Mitsubishi Rayon) in 100 parts by weight of 1,2-dichloroethane, and the film thickness after drying was 13
An electrophotographic photoreceptor of the present invention was prepared by applying the coating to a micron thickness. When this electrophotographic photoreceptor was measured in the same manner as in Example 1, the results shown in Table 3 were obtained.

[Table] Comparative Example 2 A comparative photoreceptor was prepared in the same manner as in Example 2, except that a hydrazone derivative represented by the following structural formula was used as a carrier transport substance. This photoreceptor was measured in the same manner as in Example 1, and the results shown in Table 4 were obtained.

[Table] As is clear from the above results, the electrophotographic photoreceptor of the present invention is extremely superior in sensitivity, residual potential characteristics, and repeated stability compared to the comparative photoreceptor. Examples 3 to 10 Exemplary compounds []- as carrier transport substances
6, []-11, []-13, []-26, []-9
，
Electrophotographic photoreceptors of the present invention were prepared in the same manner as in Example 2, except that []-13, []-17, and []-21 were used, respectively. When the initial characteristics of these electrophotographic photoreceptors were measured in the same manner as in Example 1, the results shown in Table 5 were obtained. It can be seen that both have extremely good sensitivity and residual potential characteristics.

【table】

[Table] Example 11 A 0.5 micron thick intermediate layer made of polyester "Vylon 200" (manufactured by Toyobo Co., Ltd.) was provided on a polyester film laminated with aluminum foil. Next, 2 parts by weight of a bisazo compound represented by the following structural formula as a carrier generating substance and polycarbonate were added. A carrier generation layer was formed by applying a solution prepared by dispersing 2 parts by weight of "Panlite L-1250" (manufactured by Teijin Kasei) in 140 parts by weight of 1,2-dichloroethane so that the film thickness after drying was 1 micron. Formed. Exemplary compound []-
46 parts by weight and polycarbonate “Panlite L-
1250'' (manufactured by Teijin Chemicals) in 100 parts by weight of 1,2-dichloroethane was applied to form a carrier transport layer such that the film thickness after drying was 16 microns. An electrophotographic photoreceptor was created. This electrophotographic photoreceptor is used in an electrophotographic copying machine U-
When I attached it to Bix2000R (manufactured by Konishiroku Photo Industry) and copied the image, I obtained a copied image that was faithful to the original, had high contrast, and had excellent gradation. Even after repeating this process 20,000 times, the same copy image as the initial one was obtained without any change. Example 12 A carrier generating layer was formed in the same manner as in Example 11 except that a bisazo compound represented by the following structural formula was used as the carrier generating substance. On this carrier generation layer, the exemplified compound []
-12, 6 parts by weight and 10 parts by weight of polycarbonate "Iupilon S-1000" (manufactured by Mitsubishi Gas Chemical),
A carrier transport layer was formed by coating a solution dissolved in 100 parts by weight of 2-dichloroethane so that the film thickness after drying was 15 microns, thereby producing an electrophotographic photoreceptor of the present invention. This electrophotographic photoreceptor was measured in the same manner as in Example 1. In addition, the electrophotographic copying machine U-
The sample was attached to Bix2000R (manufactured by Konishi Roku Photo Co., Ltd.), and charging, exposure, and cleaning were repeated 10,000 times, and the same measurements were performed again. The results shown in Table 6 were obtained. Comparative Example 3 Except for using the following hydrazone derivative as the carrier transport material A comparative photoreceptor was prepared in the same manner as in Example 12. When this comparative photoreceptor was measured in the same manner as in Example 12, the results shown in Table 6 were obtained.

[Table] As is clear from the above results, the electrophotographic photoreceptor of the present invention is significantly superior in sensitivity characteristics and durability than the comparative photoreceptor.

[Brief explanation of drawings]

1 to 6 are sectional views showing examples of the mechanical structure of the electrophotographic photoreceptor of the present invention, respectively. 1... Conductive support, 2... Carrier generation layer, 3...
Carrier transport layer, 4... Photosensitive layer, 5... Intermediate layer, 6...
A layer containing a carrier transport substance, 7... a carrier generation substance.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a layer containing a hydrazone derivative represented by the following general formula [] or [] on a conductive support. General formula [] General formula [] However, in the formula, R ₁ : hydrogen atom, alkyl group, aryl group, R ₂ : hydrogen atom, alkyl group, R ₃ : hydrogen atom, alkyl group, aryl group, R ₄ : aryl group, heterocyclic group, R ₅ : hydrogen Atom, alkyl group, aryl group, R ₆ : hydrogen atom, alkyl group, R ₇ : hydrogen atom, alkyl group, aryl group, R ₈ : hydrogen atom, halogen atom, R ₉ : hydrogen atom, alkyl group, aryl group, R ₁₀ :aryl group, heterocyclic group, n and m represent 0 or 1.