JP2732697B2 - Organic photoreceptor for electrophotography capable of both charging - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a dual-chargeable electrophotographic organic photoreceptor, and more particularly, to an organic photosensitive material containing a charge-generating substance and a charge-transporting substance in combination. It relates to improvement of a photoreceptor.

[Prior Art] In the field of electrophotographic photoreceptors, so-called function-separated organic photoreceptors in which a charge generation layer (CGL) and a charge transport layer (CTL) are laminated have been gradually used. Along with the laminated photoconductor, a single-layer dispersion type organic photoconductor in which a charge generating substance is dispersed in a medium of a charge transporting substance is already known.

As the charge transport substance of this type of photoreceptor, a substance having high carrier mobility is required. From a high molecular weight material such as polyvinyl carbazole (PVK) at the beginning to a low molecular weight compound material used in a resin dispersion system. It is moving. However, from the viewpoint of moldability, the charge transporting material is preferably a single film forming material that can be used. I mentioned earlier
PVK can be formed into a film, but there is a problem in that dimer sites formed by adjacent carbazole rings act as structural hole carrier traps, causing deterioration in electrophotographic characteristics of the photoreceptor.

Recently, Japanese Patent Application Laid-Open No. Sho 61-170747 proposes a photoreceptor containing organic polysilane as a hole transport material. It is also known that this organic polysilane can be formed into a film from a solution, and exhibits high hole drift mobility (1010 ⁻⁴ cm ² / V · sec) among amorphous polymer materials.

Most of the conventionally proposed charge transport materials generally have a hole transporting property, and as a few examples having an electron transporting ability, JP-A-1-206349 discloses that a compound having a diphenoquinone structure is an electrophotographic material. It has been proposed as a charge transport agent for photoreceptors.

[Problems to be Solved by the Invention] Most of the organic photoconductors conventionally used in the field of copying machines and the like are operated by negative charge, and have drawbacks such as generation of ozone. Therefore, a positively-charged organic photoreceptor has been eagerly desired.

Although the diphenoquinone derivative described above has good compatibility with the binder resin and is said to exhibit good electron transportability,
The laminated photoreceptor using the diphenoquinone derivative has a disadvantage that the residual potential is still high and the sensitivity in practical use is not sufficient.

On the other hand, regarding the charging polarity of the photoreceptor, it is advantageous that the application range of the photoreceptor can be further expanded if the photoreceptor can be used with both positive and negative charging polarities.

Therefore, an object of the present invention is to provide an organic photoreceptor containing a charge generating substance and a charge transporting substance, which can be charged with both polarities, the residual potential is suppressed to a low level, and the charging with both polarities is suppressed. An object of the present invention is to provide an organic photoreceptor that exhibits excellent sensitivity to the following.

Another object of the present invention is to provide an organic photoreceptor for electrophotography which has improved light fastness and excellent printing durability.

[Means for Solving the Problems] In an electrophotographic organic photoreceptor containing a charge-generating substance and a charge-transporting substance in a laminated type or a single-layer dispersed type, the charge transporting substance is represented by the following general formula (1): In the formula, each of R ₁ , R ₂ , R ₃ and R ₄ is a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, which contains a diphenoquinone derivative represented by Wherein the diphenoquinone derivative is contained in an amount of more than 30 parts by weight per 100 parts by weight of the hole transporting material. .

The diphenoquinone derivative is preferably used in an amount of 30 parts by weight or more, particularly 30 to 300 parts by weight per 100 parts by weight of the hole transporting substance, for the purpose of the present invention described above. The substance itself may also function as a resin, or may be used in combination with a resin, such as a low-molecular-weight hole transporting substance.

[Action] The present invention selects a diphenoquinone derivative from various electron transporting substances, and mixes it in a hole transporting substance in a certain amount or more. It is based on the finding that it shows excellent sensitivity.

FIG. 1 of the accompanying drawings plots the sensitivities at the time of positive charge and at the time of negative charge by changing the compounding ratio of the hole transport substance (tetraphenyl metaphenylenediamine compound) and the diphenoquinone derivative as the electron transport substance. It is a thing. Referring to FIG. 1, the unexpected fact that the charge-transporting material composed of both compositions shows excellent sensitivity to positive and negative charges within a fairly wide composition range. Becomes clear.

Generally, when an electron-accepting substance is added to a hole-transporting substance, an interaction such as charge transfer between the two causes a decrease in charge mobility as a whole, thereby lowering the sensitivity of the photoreceptor. . However, the diphenoquinone derivative used in the present invention exhibits an exceptional effect that the charge mobility does not decrease due to the interaction, even when added at a concentration higher than the concentration at which electron transport occurs efficiently, and thus, the negative charge It shows good sensitivity even at the time of positive charging without deteriorating the sensitivity.

In addition, the diphenoquinone derivative used in the present invention is, among various electron-accepting substances, particularly effective in suppressing the rise in surface potential and residual potential during repeated charge-exposure, and has a good quenching effect. Therefore, the light resistance of the photoreceptor to ultraviolet light can also be improved.
This is a specific chemical structure of the diphenoquinone derivative,
That is, it is recognized that it is related to the conjugate bond structure.

The diphenoquinone derivative used in the present invention is excellent in compatibility with various hole transporting substances, and has a high electron transporting ability itself. Therefore, the diphenoquinone derivative advantageously prevents charge accumulation in the hole transporting substance layer. To bring about various effects.

Further, when the composition is used in a single-layer dispersion type, charge transport is performed by both holes and electrons, so that the sensitivity is improved and the content of the charge generating agent can be reduced.

[Preferred Aspect] The present invention can be applied to a laminated electrophotographic photoconductor and a monolayer electrophotographic photoconductor. For example, the second
As shown in the figure, a charge generation layer (CGL) is formed on a conductive substrate 1.
2 and a charge transport layer (CT) composed of the composition of the hole transport material and the diphenoquinone derivative is formed on the charge generation layer.
L) 3 can be provided.

In the case of positive charging (FIG. 2A), of the pairs of holes and electrons generated in CGL2, electrons are injected into CTL3, and an electrostatic image is formed by electron transport by the diphenoquinone derivative in CTL. In the case of negative charging (FIG. 2B), holes generated in CGL2 are injected into CTL3, and an electrostatic image is formed by hole transport by a hole transporting substance in CTL.

Alternatively, conversely, as shown in FIG. 3, a charge transport layer 3 made of a composition of the hole transport substance and the diphenoquinone derivative is provided on a conductive substrate 1, and a charge generation layer 2 is provided on the charge transport layer. Can also be provided. In the case of positive charging (third
Figure A), of the pairs of holes and electrons generated in CGL2, holes are injected into CTL3, energization is performed by hole transport by the hole transport material in CTL, and an electrostatic image is formed. Will be In the case of negative charging (FIG. 3B), conversely, electrons generated in CGL are injected into CTL3, and an electron image is formed by electron transport by the diphenoquinone derivative in CTL.

Further, as shown in FIG. 4, a photosensitive material 4 in which a charge generating substance is dispersed in a charge transporting medium of a hole transporting substance and a diphenoquinone derivative is provided in a single layer on the conductive substrate 1. In this case, in the case of positive charging (FIG. 4A), of the pairs of holes and electrons generated by the charge generating substance, the hole transporting substance transfers the hole to the conductive substrate 1 side. In charge of transport, the diphenoquinone derivative is responsible for transport of electrons to the surface side to form an electrostatic latent image. Conversely, for negative charging (FIG. 4B), the diphenoquinone derivative is responsible for transporting electrons to the conductive substrate 1, the hole transporting substance is responsible for transporting holes to the surface side, and the electrostatic latent An image is formed.

That is, in the case of a single-layer type photoreceptor, all charges generated in the photosensitive layer 4 can be efficiently transported, leading to an improvement in sensitivity.

The diphenoquinone derivative used in the present invention has the following general formula In the formula, each of R ₁ , R ₂ , R ₃ and R ₄ is a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group. Suitable examples thereof include, but are not limited to, 2,6-dimethyl-2 ', 6'-di-t-
Butyl diphenoquinone, 2,2'-dimethyl-6,6'-di-t
-Butyl diphenoquinone, 2,6'-dimethyl-2 ', 6'
-Di-t-butyldiphenoquinone, 2,6,2 ', 6'-tetramethyldiphenoquinone, 2,6,2', 6'-tetrat-butyldiphenoquinone, 2,6,2 ', 6'-tetraphenyldiphenoquinone, 2,6,2 ', 6'-tetracyclohexyldiphenoquinone and the like can be mentioned, but they have the following formula [I]
Alternatively, a diphenoquinone derivative having a substituent that satisfies the relationship of the formula [II] is preferable because of low molecular symmetry, small interaction between molecules, and excellent solubility.

(R ₁ carbon number = number of carbon atoms of R _2)> (R ₃ carbon atoms = number of carbon atoms of _{R 4) ... [I] (} R 1 carbon number = number of carbon atoms of R _3)> (the R ₂ carbon Number = carbon number of R ₄ ) [II] As the hole transporting material, a low molecular weight hole transporting material or a high molecular weight hole transporting material is used, and the low molecular weight hole transporting material is a binder described later. Used in combination with
As such a hole transport material, for example, 2,5-di (4-
Methylaminophenyl), 1,3,4-oxadiazole,
Such as oxadiazole-based compounds, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, carbazole-based compounds such as polyvinylcarbazole, organic polysilane compounds, and 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline. Nitrogen-containing cyclic compounds such as pyrazoline compounds, hydrazone compounds, triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds. Compounds and condensed polycyclic compounds are exemplified.

Polysilane can also be used as a high molecular weight hole transport material. This polysilane may be any known per se, but the main chain is composed of a chain of silicon, and has an organic group, particularly a monovalent hydrocarbon group in a side chain,
The following formula In the formula, each of R ₁ and R ₂ is a monovalent hydrocarbon group, particularly an alkyl group having 4 or less carbon atoms, an aryl group having 6 or more carbon atoms, or an aralkyl group. Suitable organic polysilanes include methylphenyl polysilane, methylpropyl polysilane, methyl t-butyl polysilane, diphenyl polysilane, methyltolyl polysilane, or copolymers thereof.

The organic polysilane used should have a molecular weight sufficient to form a so-called film, and is generally 5,000 to 5,000.
It preferably has a weight average molecular weight ( _w ) of 0, especially 5000 to 20000.

The terminal of the organic polysilane may be a silanol group, an alkoxy group, or the like.

In the present invention, the hole transport substance and the diphenoquinone derivative should be used in the above-mentioned quantitative ratio.

Examples of the charge generation material include selenium, selenium-tellurium, amorphous silicon, pyrylium salts, azo pigments, disazo pigments, anthanthrone pigments, phthalocyanine pigments, indigo pigments, slen pigments, toluidine pigments, and pyrazoline. Pigments, perylene pigments, quinacridone pigments and the like are exemplified, and one kind or a mixture of two or more kinds is used so as to have an absorption wavelength range in a desired region.

This charge generation material can be applied in the form of a layer by means such as vapor deposition, or can be applied as a layer in a form dispersed in a binder resin. Various resins can be used as such a binder resin, for example, olefins such as styrene polymers, acrylic polymers, styrene-acrylic copolymers, ethylene-vinyl acetate copolymers, polypropylene, and ionomers. -Based polymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, Various polymers such as a polyether resin, a phenol resin, and a photocurable resin such as an epoxy acrylate can be exemplified. These binder resins may be used alone or in combination of two or more.

In addition, as a solvent used to form a coating solution,
Various organic solvents can be used, such as methanol, ethanol,
Alcohols such as isopropanol and butanol, n-
Hekinsan, octane, aliphatic hydrocarbons such as cyclohexane, benzene, toluene, aromatic hydrocarbons such as xylene, dichloromethane, dichloroethane, carbon tetrachloride,
Halogenated hydrocarbons such as chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone and cyclohexane; esters such as ethyl acetate and methyl acetate; dimethylformamide and dimethyl Various solvents such as sulfoxide are exemplified,
One type or a mixture of two or more types is used.

As the conductive substrate, various materials having conductivity can be used, for example, aluminum, copper, tin, platinum, gold,
Coated with silver, panadium, molybdenum, chromium, cadmium, titanium, nickel, indium, stainless steel, brass, or a plastic material on which the above metal is deposited or laminated, aluminum iodide, tin oxide, indium oxide, etc. Glass etc. are illustrated.

In addition, in order to form a coating liquid, a charge generation material and the like and a binder resin and the like are adjusted using a conventionally known method, for example, using a roll mill, a ball mill, an attritor, a paint shaker, an ultrasonic disperser, or the like, and a conventionally known method is used. May be applied and dried by the application means.

In the case of the substrate / CGL / CTL photoreceptor of FIG. 2, the CGL ranges from 0.01 to 0.05 μm for vapor deposition to 0.01 to 0.05 μm for coating.
μm, but CTL is 5-40 μm, especially 10-25
It is preferably in the range of μm. In the case of the substrate / CTL / CGL photoreceptor of FIG. 3, the CTL preferably has a thickness of 5 to 40 μm, especially 10 to 25 μm, while the CGL has a thickness of 0.1 to 0.5 μm. Also, in the CTM and CGM dispersion type photoreceptor of FIG. 4,
The charge generating material is preferably present in the photosensitive layer in an amount of 1 to 15 parts by weight, especially 5 to 10 parts by weight, based on 100 parts by weight of the organic polysilane, and the photosensitive layer is 10 to 40 μm, particularly 15 to 30 μm.
Preferably, it has a thickness of m.

[Effects of the Invention] According to the present invention, in a photoreceptor using a combination of a charge generating substance and a charge transporting substance, by using a combination of a hole transporting substance and a specific amount of diphenoquinone derivative as a charge transporting substance, It has become possible to provide a photosensitive member that operates with both negative and positive charges.

Further, the accumulation of electric charge was eliminated, and the stability and printing durability during repeated use were improved. Further, the diphenoquinone derivative in the charge transporting material worked as a quencher, and the light fastness was improved. In the case of a single-layer type photoreceptor, the content of the charge generating pigment can be reduced with a small amount, and high sensitivity can be obtained.

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples.

(Example 1) 100 parts by weight of α-oxotitanyl phthalocyanine as a charge generating substance and tetrahydrofuran 4000 as a solvent
Parts by weight in a ball mill, stirred for 24 hours, added with 100 parts by weight of polyvinyl butyral (Sekisui Chemical Co., Ltd., trade name: SREC BM-3), and further stirred and mixed for 1 hour to form a coating solution for the charge generation layer. After applying this adjustment liquid on aluminum foil with a wire bar (No.5),
The resultant was dried with hot air at 100 ° C. for 30 minutes and cured to form a charge generation layer having a thickness of about 0.5 μm.

Next, 30 parts by weight of N, N, N ', N'-tetrakis (3-tolyl) -1,3-phenylenediamine as a hole transporting substance and 2,6-dimethyl- as a diphenoquinone derivative
70 parts by weight of 2 ', 6'-ditert-dibutyldiphenoquinone,
100 parts by weight of a polycarbonate (manufactured by Mitsubishi Gas Chemical Company, trade name Z200) as a binder resin and 900 parts by weight of tetrahydrofuran as a solvent were stirred and mixed with a homomixer to prepare a coating solution for a charge transport layer. After applying this coating solution on the charge generation layer with a wire bar (No. 60),
The resultant was dried with hot air for 30 minutes to form a charge transporting layer having a thickness of about 15 μm, thereby producing a laminated electrophotographic photoreceptor.

Example 2 In the preparation of the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
Example 1 was repeated except that 40 parts by weight of phenylenediamine and 60 parts by weight of 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative were used.
In the same manner as in the above, a laminated electrophotographic photosensitive member was produced.

Example 3 In the preparation of the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
Example 1 was repeated except that 60 parts by weight of phenylenediamine and 40 parts by weight of 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative were used.
In the same manner as in the above, a laminated electrophotographic photosensitive member was produced.

Example 4 In the preparation of the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
Example 1 was repeated except that 60 parts by weight of phenylenediamine and 80 parts by weight of 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative were used.
In the same manner as in the above, a laminated electrophotographic photosensitive member was produced.

Example 5 In the preparation of the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
Example 1 was repeated except that 80 parts by weight of phenylenediamine and 60 parts by weight of 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative were used.
In the same manner as in the above, a laminated electrophotographic photosensitive member was produced.

Example 6 In the preparation of the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
The same procedure as in Example 1 was repeated except that 170 parts by weight of phenylenediamine and 50 parts by weight of 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative were used. A photoreceptor was prepared.

(Comparative Example 1) In the preparation of the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
Laminated electrophotography in the same manner as in Example 1 except that phenylenediamine was used in an amount of 100 parts by weight and 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone was not used as a diphenoquinone derivative. A photoreceptor was produced.

(Comparative Example 2) In adjusting the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
Example 1 was repeated except that phenylenediamine was not used and 100 parts by weight of 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative was used.
In the same manner as in the above, a laminated electrophotographic photosensitive member was produced.

(Comparative Example 3) In preparing the coating solution for the charge transport layer, N, N, N ', N'-tetrakis (3-tolyl) -1,3- as a hole transport material was used.
Example 1 was repeated except that 80 parts by weight of phenylenediamine and 20 parts by weight of 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative were used.
In the same manner as in the above, a laminated electrophotographic photosensitive member was produced.

(Example 7) 0.5 part by weight of X-type metal-free phthalocyanine as a charge generating substance, and 60 parts by weight of N, N, N ', N'-tetrakis (3-tolyl) -1,3-phenylenediamine as a hole transporting substance Part, 2,6-dimethyl- as diphenoquinone derivative
80 parts by weight of 2 ', 6'-ditert-dibutyldiphenoquinone,
100 parts by weight of polycarbonate (manufactured by Mitsubishi Gas Chemical Company, trade name Z200) as a binder resin and 900 parts by weight of tetrahydrofuran as a solvent were mixed and dispersed with an ultrasonic disperser to prepare a coating solution for a single-layer type photosensitive layer. After applying this adjustment liquid on an aluminum foil with a wire bar (No. 60),
By drying with hot air at 30 ° C. for 30 minutes, a single-layer type electrophotographic photoreceptor having a thickness of about 15 μm was prepared.

(Comparative Example 4) N, N, N ', N'-tetrakis (3
-Tolyl) -1,3-phenylenediamine in 100 parts by weight and 2,6-dimethyl 2 ',
A single-layer electrophotographic photosensitive member was prepared in the same manner as in Example 7, except that 6'-ditert-dibutyldiphenoquinone was not used.

(Comparative Example 5) N, N, N ', N'-tetrakis (3
2,3-dimethyl-2 ', 6'- as a diphenoquinone derivative without using -tolyl) -1,3-phenylenediamine
A single-layer electrophotographic photosensitive member was prepared in the same manner as in Example 7, except that 100 parts by weight of ditert-dibutyldiphenoquinone was used.

(Example 8) [Synthesis of phenylmethylpolysilane] 100 g of methylphenyldichlorosilane, sodium metal 2
6 g is added to 400 ml of dry toluene, heated to 130 ° C., stirred for 11 hours, and then cooled. Ethanol was added to the resulting reaction solution (solution containing dark purple) to convert unreacted sodium into ethoxide. The precipitate was separated by filtration, dried, dissolved in toluene, re-precipitated in ethanol, and re-precipitated in white phenylmethyl. Polysilane was obtained (yield 22.0 g: 34%).

[Adjustment of Electrophotographic Photoreceptor] 0.5 part by weight of X-type metal-free phthalocyanine as a charge generating substance, 100 parts by weight of phenylmethylpolysilane as a hole transporting substance, 2,6 as a diphenoquinone derivative
-Dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone (100 parts by weight) and tetrahydrofuran 1000 as a solvent
Parts by weight were mixed and dispersed with an ultrasonic disperser to prepare a coating solution for a single-layer type photosensitive layer. This coating solution was applied on an aluminum foil with a wire bar (No. 60). By drying with hot air for 1 minute, a single-layer type electrophotographic photoreceptor having a film thickness of about 10 μm was prepared.

(Comparative Example 6) 2,6-dimethyl-2 ', as a diphenoquinone derivative
A single-layer electrophotographic photosensitive member was prepared in the same manner as in Example 8, except that 6'-ditert-dibutyldiphenoquinone was not used.

Evaluation of electrophotographic photoreceptor Using an electrostatic copying tester (Model-8100, manufactured by Kawaguchi Electric Co., Ltd.), the voltage applied to the photoreceptor obtained in each example was ± 6.0 KV.
, And the electrophotographic characteristics were measured under the following conditions. The results are shown in Tables 1 to 3.

Exposure time: 10 seconds Irradiation light: 780 nm monochromatic light Exposure intensity: 0.1 mW / cm ^{2 In} the table, V ₁ (V) is the initial value of the photosensitive member when the photosensitive member is charged by applying a voltage under the above conditions. Indicates surface potential V ₁ (V), and E ₁ 1/2 (μJ / cm ² ) is a half calculated from the time required for the surface potential to become 1/2 of the original surface potential V ₁ (V) Indicates the amount of exposure. V _1rp (V) in the table is obtained by measuring the surface potential 5 seconds after the start of exposure as a residual potential.

Further, charge-exposure was repeated 1000 times, and the surface potential V ₂ (V) of the photoreceptor at that time, the half-exposure amount E ₂ 1/2 (μJ /
cm ² ) and residual potential V _2rp (V) were measured.

On the other hand, the photosensitive members obtained in Example 5 and Comparative Example 1 were irradiated with ultraviolet rays (300 to 400 nm, 600 mW / cm ⁻² ) for 10 minutes, and the surface potential V ₁₀ (V) of the photosensitive members and the half-life exposure amount E ₁₀ 1/2 (μJ / c
m ² ) and the residual potential V _10rp were measured, and the results are shown in Table 4.

According to the results of Tables 1 to 3, the electrophotographic photoreceptors of Examples 1 to 8 in which the charge transporting substance contained the diphenoquinone derivative in an amount of more than 30 parts by weight per 100 parts by weight of the hole transporting substance, It was also found that both exhibited good both-charging properties and showed small changes in surface potential, sensitivity and residual potential even after repeated charging and exposure, and had excellent repetition characteristics. On the other hand, as is clear from Comparative Examples 3 and 1, when the amount of the diphenoquinone derivative decreases, the sensitivity and residual potential in positive charging tend to deteriorate,
In the case where the diphenoquinone derivative was not contained, even light decay due to positive charge did not occur. Further, as is apparent from Comparative Example 2, when only the diphenoquinone derivative was contained, no light decay occurred in negative charging.

Further, from the results in Table 4, it was found that the electrophotographic photoreceptor of Example 5 containing the diphenoquinone derivative had a small change in surface potential and residual potential even when irradiated with ultraviolet light, and also had excellent light resistance. .

[Brief description of the drawings]

FIG. 1 shows a change in the blending ratio of a tetraphenyl metaphenylenediamine compound as a hole transporting substance and a diphenoquinone derivative as an electron transporting substance, using a laminated electrophotographic photosensitive member having the structure shown in FIG. Then, the reciprocal of the sensitivity at the time of positive charging and at the time of negative charging is plotted.
FIG. 2 is a sectional view of the negatively charged photoreceptor of the present invention. FIG. 3 is a cross-sectional view of the positively charged photoreceptor of the present invention. 4th
The figure is a cross-sectional view of the single-layer type photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1 ... Conductive substrate, 2 ... Charge generation layer, 3 ... Charge transport layer, 4 ... Single layer type photosensitive layer

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Kakui 1-2-2, Tamazo, Chuo-ku, Osaka-shi, Osaka Mita Kogyo Co., Ltd. (56) References JP-A-55-11545 (JP, A) JP-A Hei 1-206349 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic organic photoreceptor containing a charge generating substance and a charge transporting substance in a laminated type or a monolayer dispersed type, wherein the charge transporting substance is represented by the following general formula (1): In the formula, each of R ₁ , R ₂ , R ₃ and R ₄ is a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, which contains a diphenoquinone derivative represented by A chargeable electrophotographic organic photoreceptor, wherein the diphenoquinone derivative is contained in an amount of more than 30 parts by weight per 100 parts by weight of the hole transport material.