JPH0659479A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide an electrophotographic sensitive body having high sensitivity and excellent in repetitive characteristics and light resistance. CONSTITUTION:A photosensitive layer contg. a diphenoquinonophene compd. represented by formula I as an electron transferring material and a compd. represented by formula II as a positive hole transferring material is formed on an electric conductive substrate. In the formulae, each of R1-R4 is H, alkyl, optionally substd. aryl, benzyl or alkoxy, each of R5-R10 is alkyl or alkoxy, each of (l), (m), (p) and (q) is an integer of 0-5 and each of (n) and (o) is an integer of 0-4.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used in an image forming apparatus using an electrophotographic method such as an electrostatic copying machine and a laser beam printer.

2. Description of the Related Art The electrophotographic method such as the Carlson process is a step of uniformly charging the surface of an electrophotographic photosensitive member by corona discharge, and exposing the charged surface of the electrophotographic photosensitive member to an electrostatic latent image on the surface. An exposure step of forming an image, a developing step of bringing a developer into contact with the formed electrostatic latent image, and developing the electrostatic latent image into a toner image by toner contained in the developer, and a toner image Transfer step of transferring the toner to paper, a fixing step of fixing the transferred toner image, and a transfer step,
And a cleaning step for removing the toner remaining on the photoconductor. Examples of the electrophotographic photosensitive member used in the electrophotographic method include an inorganic photosensitive member using a photosensitive layer containing an inorganic material such as selenium and an organic photosensitive member using a photosensitive layer containing an organic material. Organic photoreceptors are cheaper and more pollution-free than inorganic photoreceptors, and because of their diverse molecular structures, they have many advantages such as a high degree of freedom in functional design and high productivity. In recent years, extensive research has been advanced. In such an organic photoreceptor, generally, a function-separated type photosensitive layer containing a charge generating material that generates charges by light irradiation and a charge transporting material that transports the generated charges is often used. In order to satisfy various conditions desired for such an organic photoreceptor, it is necessary to appropriately select materials to be combined such as a charge generating material and a charge transporting material. As the charge-transporting material, various kinds of substances have been conventionally studied, and many substances such as polyvinylcarbazole, oxadiazole-based compounds, pyrazoline-based compounds, and hydrazone-based compounds have been proposed. Since these charge-transporting materials are hole-transporting materials, the charge-generating layer and charge-transporting layer are formed on the conductive substrate, which is one of the function-separated photoreceptors that are currently the mainstream of organic photoreceptors. A negative charging process is inevitably required for a laminated type photoreceptor of a system in which layers are sequentially laminated. However, with a negatively charged organic photoconductor, there is a risk that the environment will be polluted by the generation of ozone or the photoconductor will be oxidized and deteriorated. To prevent this, a system that does not generate ozone or an image forming apparatus There is a drawback that the process and the system are complicated because a system for discarding the ozone in the inside is required. Use of an electron transporting material as a charge transporting material has been studied in order to solve these drawbacks, and an electrophotographic photosensitive member using a compound having a diphenoquinone skeleton as the electron transporting material, which can be used in positive charging, is provided. Proposed (JP-A-1-206349)
Issue). The compound having a diphenoquinone skeleton,
It is an electron acceptor having a non-localized π-electron system, and can transport electrons by an electron transfer reaction involving an anion radical state. By the way, if a photoconductor having both positive charging property and negative charging property can be used, the application range of the photoconductor can be further expanded.
As such a photoreceptor, by containing an electron transporting material having a diphenoquinone structure as a charge transporting material and a polysilane-based hole transporting material in the photosensitive layer, it can be used in both positive and negative charging, and has high sensitivity and repetitive characteristics. It is also considered to obtain an excellent photoconductor.

However, a photoconductor using the above diphenoquinone compound as an electron transport material has a sensitivity because the diphenoquinone compound has sublimability and has low compatibility with the binder resin. However, when used repeatedly, the surface potential was lowered and the residual potential was increased, and the light resistance was insufficient. In addition, in order to create an organic photoconductor using various materials,
A material with good matching must be selected to satisfy the electrophotographic characteristics. For example, even if charge transporting materials having high charge transporting ability are combined, good electrophotographic characteristics are not always obtained, and in a system in which a hole transporting material and an electron transporting material coexist as charge transporting materials, Attention should be paid to the formation of the transfer complex. That is, when the charge transfer complex is formed, recombination occurs between the holes and the electrons, and the transfer of charges is reduced as a whole. Further, HOMO as a hole transport material and LUMO as an electron transport material.
If the energy gap of 1 corresponds to the wavelength energy of the main exposure and the static elimination light with which the photoconductor is irradiated, absorption of light by the charge transfer complex occurs, resulting in a drastic decrease in charge generation efficiency. It is inferred that the formation of the charge transfer complex has a causal relationship with the way in which the electron clouds of the hole transport material and the electron transport material overlap. The present invention is intended to solve the above-mentioned problems, and an object thereof is to provide an electrophotographic photosensitive member having high sensitivity, excellent repeating characteristics and light resistance.

Means and Actions for Solving the Problems On the conductive substrate, the following general formula (1) as an electron transport material:

[Chemical 3] (In the formula, R1, R2, R3, and R4 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group which may have a substituent, or a benzyl group.) A nonophene compound and the following general formula (2) as a hole transport material:

[Chemical 4] (Wherein R5, R6, R7, R8, R9 and R10
Are each independently an alkyl group or an alkoxy group, l, m, p, and q are integers of 0 to 5, and n and o are integers of 0 to 4. It was found that a photosensitive layer containing a compound represented by the formula (4) should be provided, and the present invention has been completed. In the electrophotographic photoreceptor of the present invention, the diphenoquinonophene compound represented by the general formula (1) used as an electron transport material has a wider conjugated system than conventional diphenoquinone compounds, and Mobility is improved. Further, since the compound (1) has an increased molecular weight as compared with the conventional diphenoquinone-based compound, it has excellent compatibility with the binder resin and can be contained in a large amount in the photosensitive layer. Therefore, the sensitivity of the photoconductor is improved. Further, since the compound (1) does not have a sublimation property unlike the diphenoquinone-based compound, the photoconductor has excellent light resistance and also has excellent repeating characteristics such as a stable potential during repeated use. Therefore, the inventors of the present invention selected a specific hole-transporting material for the above diphenoquinonophene-based compound and thought to obtain electrophotographic characteristics satisfying high performance. Various studies were conducted. Matching by selecting the compound represented by the general formula (1) as the specific electron transport material of the present invention and the compound represented by the general formula (2) as the specific hole transport material Although the effect of is not clear, it will be understood from the comparison of the examples and the comparative examples described later that the result is improvement in sensitivity, repeatability and light resistance. That is, it is presumed that problems such as fog do not occur even if the output of the exposure lamp that is standardly installed in the copying machine is not increased, which leads to a longer life of the exposure lamp and a reduction in power consumption. It

[Preferable Embodiment] As the charge generating material , conventionally known materials can be used, and examples thereof include selenium, selenium-tellurium, selenium-arsenic, amorphous silicon, pyrylium salts, azo pigments, perylene pigments, Ansanthuron-based pigments, phthalocyanine-based pigments, indigo-based pigments, triphenylmethane-based pigments, slene-based pigments, toluidine-based pigments, pyrazoline-based pigments, quinacridone-based pigments, pyrrolopyrrole-based pigments, and the like, preferably metal-free phthalocyanine ,
Examples thereof include copper phthalocyanine and oxotitanyl phthalocyanine. Charge Transport Material The electron transport material represented by the general formula (1) and the hole transport material represented by the general formula (2) are used. In the diphenoquinonophene compound represented by the general formula (1), examples of the alkyl group corresponding to R1, R2, R3 and R4 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group and isobutyl. Group, t-butyl group, pentyl group, hexyl group and the like. Examples of the alkoxy group include a methoxy group, an ethoxy group,
Examples include propoxy group, isopropoxy group, butoxy group, t-butoxy group, hexyloxy group and the like. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, a naphthyl group, an anthryl group and a phenanthryl group. Examples of the substituent that substitutes the aryl group and the benzyl group include a methyl group, an ethyl group, an isopropyl group, a propyl group, a butyl group, an isobutyl group,
t-butyl group, pentyl group, methoxy group, ethoxy group,
Examples include propoxy group, isopropoxy group, butoxy group, isobutoxy group, t-butoxy group and the like. Specific examples of the diphenoquinonophene compound represented by the general formula (1) include those represented by the following formulas (A1) to (A9).

[Chemical 5]

[Chemical 6]

[Chemical 7] The diphenoquinonophene compound of the present invention can be synthesized by various methods (for example, Chemisto).
ry Letters, pp. 1461-1464 (1991)). In the hole transport material represented by the above general formula (2), R5, R6, R7, R
Examples of the alkyl group and alkoxy group corresponding to 8, R9 and R10 include the same as those in the above general formula (1). Specific examples of the compound represented by the general formula (2) include compounds represented by the following formulas (B1) to (B16).

[Chemical 8]

[Chemical 9]

[Chemical 10]

[Chemical 11] The compounds represented by the above general formulas (1) and (2), which are charge transport materials, can be used in combination with other conventionally known charge transport materials. As the conventionally known charge transport material, various electron-withdrawing compounds and electron-donating compounds can be used. As the electron-withdrawing compounds, e.g., ^{2,6-dimethyl-2,, 6,} - di tert- dibutyl phenoxide diphenoquinone derivatives non like, malononitrile, thiopyran compounds, tetracyanoethylene, 2,4,8-tri Nitrothioxanthone, 3,4
5,7-tetranitro-9-fluorenone, dinitrobenzene, dinitroanthracene, dinitroacridine,
Examples thereof include nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Further, as the electron donating compound, 2,
Oxadiazole compounds such as 5-di (4-methylaminophenyl) and 1,3,4-oxadiazole, 9-
Styryl compounds such as (4-diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds Examples include nitrogen-containing cyclic compounds such as indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds, and condensed polycyclic compounds. There is. These charge transport materials are used alone or in combination of two or more. When using a charge transport material having film-forming properties such as polyvinylcarbazole, the binder resin is not always necessary. Binder Resin Various resins can be used as the binder resin. For example, styrene-based polymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer , Chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester alkyd resin, polyamide, polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, Thermoplastic resin such as polyester resin, silicone resin, epoxy resin,
Examples thereof include phenol resins, urea resins, melamine resins, other crosslinkable thermosetting resins, and photocurable resins such as epoxy acrylate and urethane-acrylate.
These binder resins can be used alone or in combination of two or more. As the conductive substrate on which the conductive substrate photosensitive layer is formed, various materials having conductivity can be used, for example, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, Examples include simple metals such as nickel, palladium, indium, stainless steel, and brass, plastic materials in which the above metals are vapor-deposited or laminated, and glass coated with aluminum iodide, tin oxide, indium oxide, or the like. The conductive substrate is a sheet,
It may have any shape such as a drum shape, as long as the substrate itself has conductivity or the surface of the substrate has conductivity. Further, it is preferable that the conductive substrate has sufficient mechanical strength when used. Additives The organic photosensitive layer may contain additives such as a sensitizer, a fluorene compound, an antioxidant, a deterioration inhibitor such as an ultraviolet absorber, and a plasticizer. Further, in order to improve the sensitivity of the charge generation layer, known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generation material. Structure of Photoreceptor The photoconductor of the present invention can be applied to either a single layer type or a laminated type as a photosensitive layer. However, the effect of the combination of the electron transporting material and the hole transporting material becomes more remarkable particularly in the single-layer type photosensitive layer in which both materials are contained in the same layer. It can be said that it is more preferable to apply it to an electrophotographic photoreceptor having a photosensitive layer. In order to obtain a single-layer type photoreceptor, a charge generating material, a compound represented by the general formula (1) which is an electron transporting material, and a general formula (2) which is a hole transporting material are represented. A photosensitive layer containing the compound and a binder resin may be formed on the conductive substrate by means of coating or the like. That is, the principle of charge image generation in the above-mentioned single layer system is that the charge generation material is exposed to charges (holes / electrons) by exposure.
Electron is injected into the electron transporting material, holes are injected into the hole transporting material, and the respective charges (holes / electrons) injected thereafter are not trapped in the middle of the respective transporting material. It is delivered and received inside and finally transported to the surface of the photosensitive layer or the surface of the conductive substrate. That is,
The single-layer type photoconductor as described above has a wide range of applications since it can be used as a dual charging photoconductor in addition to suppressing charge trapping and improving sensitivity. Further, since the single-layer type photoreceptor does not need to be coated twice on the photosensitive layer due to its constitution, the productivity is improved. Further, in order to obtain a laminated type photoreceptor, a charge generating layer containing a charge generating material is formed on a conductive substrate by means such as vapor deposition or coating, and the electron transporting material is formed on the charge generating layer. A compound represented by the general formula (1) and a compound represented by the general formula (2), which is a hole transport material,
A charge transport layer containing a binder resin may be formed. Alternatively, conversely to the above, the charge transport layer may be formed on the conductive substrate, and then the charge generation layer may be formed. The above-mentioned laminated type photoconductor can be used as a dual charging photoconductor and has a wide range of applications. In addition, a hole transport layer containing a compound represented by the general formula (2), which is a hole transport material, and a binder resin is formed on a conductive substrate, and vapor deposition is performed on the hole transport layer. Alternatively, a charge generating layer containing a charge generating material is formed by means such as coating, and the compound represented by the general formula (1), which is an electron transporting material, and a binder resin are formed on the charge generating layer. An electron transport layer may be formed. The above-mentioned laminated type photoreceptor is a positively charged type. Alternatively, conversely to the above, an electron transport layer may be formed on a conductive substrate, and then a charge generation layer and a hole transport layer may be sequentially laminated. The laminated type photoreceptor of the above type is a negative charging type.
Furthermore, a protective layer may be provided on the organic photosensitive layer, or an intermediate layer may be provided between the organic photosensitive layer and the conductive substrate. When the organic photosensitive layer is formed of a single layer, the thickness of the organic photosensitive layer is preferably 10 to 50 μm,
More preferably, it is 15 to 30 μm. The content of the charge generating material is preferably in the range of 1 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the binder resin in the organic photosensitive layer. When the content of the charge generating material is less than 1 part by weight, the resulting photoreceptor has a low charge generating ability. On the other hand, if the content of the charge generating material exceeds 20 parts by weight, the abrasion resistance of the obtained photoreceptor may be reduced. The content of the electron transporting material represented by the above general formula (1) is preferably is contained in a range of 10 to 100 by weight parts of the binder resin 100 parts by weight of an organic photosensitive layer, more preferably is a 20 to 70 by weight part. If the content of the electron transporting material is less than 10 parts by weight, the sensitivity and repeatability of the resulting photoreceptor will be poor.
On the other hand, if the content of the electron transport material exceeds 100 parts by weight, the abrasion resistance of the obtained photoreceptor may be reduced. The content of the hole transport material represented by the general formula (2) is 10 to 100 parts by weight of the binder resin of the organic photosensitive layer.
The content is preferably 100 parts by weight, more preferably 20 to 70 parts by weight. When the content of the hole transport material is less than 10 parts by weight, the sensitivity of the resulting photoreceptor becomes poor. On the contrary, the content of the hole transport material is 1
If it exceeds 100 parts by weight, the abrasion resistance of the resulting photoreceptor may be reduced. The content of the electron transport material represented by the general formula (1) is 20 to 8 in the charge transport material.
It is contained in an amount of 0% by weight, preferably 30 to 70% by weight. If the content of the electron transporting material in the charge transporting material is less than 20% by weight, the sensitivity and repeatability of the obtained photoreceptor will be poor. On the contrary, when the content of the electron transporting material exceeds 80% by weight, the sensitivity of the obtained photoreceptor becomes poor. When the organic photosensitive layer is composed of a charge generation layer and a charge transport layer, the thickness of the charge generation layer is preferably 0.1 to 5 μm, more preferably 0.5.
~ 2 μm. The thickness of the charge transport layer is preferably 10 to 50 μm, more preferably 15 to 30 μm. The content of the above charge generation material is the binder resin 10 of the charge generation layer.
It is preferably contained in the range of 50 to 500 parts by weight, more preferably 100 to 300, relative to 0 parts by weight.
Parts by weight. When the content of the charge generating material is less than 50 parts by weight, the charge generating ability of the obtained photoreceptor is small, and conversely, when the content of the charge generating material exceeds 500 parts by weight, the mechanical strength of the obtained photoreceptor is low. It may decrease. The content of the electron transport material represented by the general formula (1) is 10 to 100 parts by weight based on 100 parts by weight of the binder resin in the charge transport layer.
It is preferable to be contained in an amount ranging unit, more preferably from 20 to 70 by weight part. When the content of the electron transporting material is less than 10 parts by weight, the sensitivity of the obtained photoreceptor,
Repeatability deteriorates. On the other hand, if the content of the electron transport material exceeds 100 parts by weight, the abrasion resistance of the obtained photoreceptor may be reduced. The content of the hole transport material represented by the general formula (2) is determined by the binder resin 10 of the charge transport layer.
The content is preferably 10 to 100 parts by weight, more preferably 20 to 70 parts by weight, based on 0 parts by weight. When the content of the hole transport material is less than 10 parts by weight, the sensitivity of the resulting photoreceptor becomes poor. On the other hand, if the content of the hole transport material exceeds 100 parts by weight, the abrasion resistance of the resulting photoreceptor may be reduced. Further, the content of the electron transport material represented by the general formula (1) is 20 to 80% by weight, and particularly preferably 30 to 70% by weight in the charge transport material. If the content of the electron transporting material in the charge transporting material is less than 20% by weight, the sensitivity and repeatability of the obtained photoreceptor will be poor. On the contrary, when the content of the electron transporting material exceeds 80% by weight, the sensitivity of the obtained photoreceptor becomes poor. Preparation of Photoreceptor When forming each of the above layers by a coating method, the charge generation material, charge transport material, binder resin and the like exemplified above, together with a suitable solvent, in a known method, for example, a roll mill,
Prepare a coating solution by dispersing and mixing with a ball mill, attritor, paint shaker or ultrasonic disperser.
This may be applied and dried by a known means. As the solvent for forming the coating liquid, various organic solvents can be used, for example, alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, benzene, Aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride and chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, cyclohexanone, etc. Examples thereof include ketones, esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide, dimethylsulfoxide and the like.
These solvents can be used alone or in combination of two or more. Furthermore, in order to improve the dispersibility of the charge transport material and the charge generating material and the smoothness of the photosensitive layer surface, a surfactant,
A leveling agent or the like may be used. Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

【Example】

Examples 1 to 9 and Comparative Examples 1 to 10 As a charge generating material, 5 parts by weight of metal-free phthalocyanine, 40 parts by weight of electron transporting material, 40 parts by weight of hole transporting material, 100 parts by weight of polycarbonate resin as a binder resin, and as a solvent. 800 parts by weight of dichloromethane was mixed and dispersed with a paint shaker to prepare a coating solution for a single-layer type photosensitive layer. The prepared solution was applied onto an aluminum sheet with a wire bar and then dried by heating at 60 ° C. for 120 minutes to obtain an electrophotographic photosensitive member having a single-layer type photosensitive layer having a film thickness of 15 to 20 μm. The electron transport material used is
Compound numbers of the following formulas (a) to (d)

[Chemical 12] The hole transport material is a compound number of the following formulas (A) to (F)

[Chemical 13]

[Chemical 14] Are specifically shown in Table 1. The following tests were carried out on the electrophotographic photoreceptors of the above-mentioned respective Examples and Comparative Examples, and their characteristics were evaluated. Electrical characteristics Electrostatic copying tester (EPA-810, Kawaguchi Denki KK)
0), an applied voltage of ± 7 KV was applied to the surface of the sheet-shaped electrophotographic photoconductors prepared in Examples and Comparative Examples to positively or negatively charge the surface potential to obtain an initial surface potential V1.
(V) was measured. Then, using a halogen lamp as an exposure light source, white halogen light was irradiated for an exposure time of 6 seconds to measure the half-dose exposure amount. That is, the initial surface potential V1
The half-exposure dose (μJ / cm ² ) was determined by determining the time until (V) became 1/2. Further, the surface potential at a time point 5 seconds after the start of exposure was determined as an initial residual potential V2 (V). The above results are shown in Table 1. Repetitive characteristics The electrophotographic photoreceptors obtained in each of the above Examples and Comparative Examples,
Each of them was attached on an aluminum cylinder with an adhesive tape and then mounted on an electrostatic copying machine DC-1656 (manufactured by Mita Industry Co., Ltd.). Next, copying was repeated 1000 times, and the surface potential V1 ′ (V) and the post-exposure potential V2 ′ (V) were measured in the same manner as above, and the difference between the initial surface potential and the initial residual potential was calculated by the following formula. It was calculated using.

[Equation 1] The above results are shown in Table 2.

[Table 1]

[Table 2] As is clear from Tables 1 and 2, the electrophotographic photoconductors of the present invention represented by Examples 1 to 9 are excellent in post-exposure potential, half-exposure amount and repetitive characteristics. It can be seen that the characteristics show high performance. In comparison with this, the electrophotographic photosensitive members represented by Comparative Examples 1 to 10 are
The potential after exposure was high, the sensitivity was poor, and the surface potential was extremely lowered by repeated use.

According to the present invention, the diphenoquinonophene compound represented by the general formula (1) as the electron transport material and the compound represented by the general formula (2) as the hole transport material are selected. By doing so, it was possible to provide an organic photoreceptor having excellent electrophotographic characteristics.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideo Nakamori 1-2-2 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka Mita Industry Co., Ltd.

Claims (1)

[Claims] 1. A compound represented by the following general formula (1) as an electron transport material on a conductive substrate: (In the formula, R1, R2, R3, and R4 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group which may have a substituent, or a benzyl group.) A nonophene compound and the following general formula (2) as a hole transport material: (Wherein R5, R6, R7, R8, R9 and R10
Each independently represents an alkyl group or an alkoxy group, l, m, p, and q are integers of 0 to 5, and n and o are integers of 0 to 4. An electrophotographic photosensitive member comprising a photosensitive layer containing a compound represented by the formula (1).