JPH06103397B2 - Organic photoconductor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic organic photoconductor used in a copying machine, a laser printer, etc., and more specifically, improved stability during repeated use. And an organic photoconductor for electrophotography.

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

As the charge transport material for this type of photoconductor, one having a high carrier mobility is required, and from a high molecular weight material such as polyvinylcarbazole (PVK) at an early stage to a low molecular weight compound material used in a resin dispersion system. It is migrating. However, from the viewpoint of moldability, it is desirable that the charge transport material is a film-forming material that can be used alone. Mentioned above
Although PVK can be formed into a film, it has a problem that the dimer site formed by the adjacent carbazole ring acts as a structural hole carrier trap and causes deterioration of electrophotographic characteristics of the photoconductor.

Recently, Japanese Unexamined Patent Publication (Kokai) No. 61-170747 proposes a photoreceptor containing organic polysilane as a hole transport material. It is known that this organic polysilane can be formed into a film from a solution and exhibits a high hole drift mobility (up to 10 ⁻⁴ cm ² / V · sec) among amorphous polymer materials.

(Problems to be Solved by the Invention) As a photoreceptor to be mounted on a copying machine, not only initial characteristics but also stability upon repeated use are required, but a photoreceptor using an organic polysilane is not yet available. It seems that this stability has not been fully investigated.

The present inventors have made a study to apply the organic polysilane to a commercial electrophotographic photoreceptor, and when charging-exposure is repeated on this photoreceptor, the surface potential of the photoreceptor and the residual potential increase, It has been found that the density change and the fog of the copied image are accompanied with this. Such an increase in surface potential and an increase in residual potential during repeated charging-exposure are particularly remarkable in the organic polysilane, but are also similarly observed in the case of using another hole transporting substance.

Therefore, an object of the present invention is to suppress an increase in surface potential or residual potential during repeated charging-exposure in a photoreceptor using a hole transporting material, particularly organic polysilane, and to obtain stable electrophotographic characteristics for a long period of time. The present invention provides an electrophotographic photosensitive member.

(Means for Solving the Problems) According to the present invention, in an electrophotographic photoreceptor containing a charge generating substance and a charge transporting substance in a laminated type or a monolayer dispersion type, the charge transporting substance contains a diphenoquinone derivative. There is provided an organophotoreceptor for electrophotography, which comprises a hole transporting material composition.

Diphenoquinone derivative per 100 parts by weight of hole transport material
It is preferable to contain it in an amount of 0.1 to 30 parts by weight, particularly 1 to 15 parts by weight. The effect of the present invention is particularly remarkable when the hole transport material is organic polysilane.

(Function) The present invention provides the following in a hole transport material such as an organic polysilane.
It is based on the finding that the incorporation of the diphenoquinone derivative improves the stability of the photoconductor when the charging-exposure operation is repeated, and can markedly suppress the rise of the surface potential and the residual potential.

As described above, the photoreceptor using the hole transport material is charged-
When the exposure operation is repeated, both the surface potential and the residual potential increase considerably. The increase in the surface potential and the residual potential is due to the deterioration of the hole transport layer or the surface of the hole transport layer, and the carrier transport ability of the surface portion decreases, and the surface potential and the residual potential increase. The mechanism of this deterioration has not been fully clarified yet, but the ultraviolet light generated at the time of charging, ozone, excited singlet oxygen, etc. forms an insulating film on the surface to increase the surface potential, and charging-exposure is repeated. It is considered that the residual potential rises due to the accumulation of charges in this insulating film. With organopolysilanes, which are particularly notable for these drawbacks,
It is recognized that an insulating film such as siloxane is formed on the surface by cutting the Si-Si main chain.

On the other hand, according to the present invention, when the diphenoquinone derivative is blended in the hole-transporting substance, its electron-accepting property causes
It is considered that the hole transporting substance in the excited state is deactivated, which suppresses its deterioration and the generation of radical species. This can also be confirmed from the fact that diphenoquinone effectively deactivates the fluorescence of the organic polysilane. Further, since the diphenoquinone derivative itself is stable, it is considered to have a remarkable effect.

The diphenoquinone derivative used in the present invention is, among various electron-accepting substances, an effect of suppressing an increase in surface potential and residual potential during repeated charging-exposure is particularly outstanding, and in addition, because of a good quenching effect, It is also possible to improve the light resistance of the photoconductor to ultraviolet light. It is recognized that this is related to a specific chemical structure possessed by the diphenoquinone derivative, that is, a conjugated bond structure.

The diphenoquinone derivative used in the present invention has excellent compatibility with various hole-transporting substances and also has a high electron-transporting ability by itself, which is advantageous in that it prevents the accumulation of charges in the hole-transporting substance layer. Bring about the action.

(Preferred Embodiment) 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 preferably a hydrogen atom, an alkyl group, a siliroalkyl group, an aryl group, an aralkyl group, or the like. Suitable examples include, but are not limited to, 2,6-dimethyl-2 ', 6'.
-Di-t-butyldiphenoquinone, 2,2'-dimethyl-6,
6'-di-t-butyldiphenoquinone, 2,6'-dimethyl-
2 ', 6'-di-t-butyldiphenoquinone, 2,6,2', 6 '
-Tetramethyldiphenoquinone, 2,6,2 ', 6'-tetra-t-butyldiphenoquinone, 2,6,2', 6'-tetraphenyldiphenoquinone, 2,6,2 ', 6' -Tetracyclohexyldiphenoquinone and the like.

As the hole transporting substance, a low molecular weight hole transporting substance or a high molecular weight hole transporting substance is used, and the low molecular weight hole transporting substance is used in combination with a binder described later. Examples of the hole transport material include oxadiazole compounds such as 2,5-di (4-methylaminophenyl) and 1,3,4-oxadiazole, 9- (4-diethylaminostyryl) anthracene. And other styryl compounds, polyvinylcarbazole and other carbazole compounds, organic polysilane compounds, 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline and other pyrazoline compounds, hydrazone compounds, triphenylamine compounds, indole compounds, oxazole Examples thereof include nitrogen-containing cyclic compounds and condensed polycyclic compounds such as system compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

The present invention is particularly useful when organic polysilane is used. This organic 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 the side chain, and has 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 are 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, generally 5,000 to 50,000,
It is particularly preferable to have a weight average molecular weight ( _w ) of 5,000 to 20,000.

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

Diphenoquinone derivative per 100 parts by weight of hole transport material
It is preferably used in an amount of 0.1 to 30 parts by weight, particularly 1 to 15 parts by weight. When the amount is less than the above range, the effect of suppressing the increase of surface potential and residual potential during repeated charging-exposure is within the above range. When it is more than the above range, the sensitivity tends to be lower than when it is in the above range.

INDUSTRIAL APPLICABILITY The present invention can be applied to a laminated type electrophotographic photoreceptor or a single-layer dispersion type electrophotographic photoreceptor. For example, as shown in FIG. 1, a charge generation layer (CGL) 2 is formed on a conductive substrate 1.
And a charge transport layer (CTL) 3 composed of the organic polysilane composition can be provided on the charge generation layer. Alternatively, conversely, as shown in FIG. 2, the charge transport layer 3 made of the organic polysilane composition may be provided on the conductive substrate 1, and the charge generation layer 2 may be provided on the charge transport layer. Further, as shown in FIG. 3, on the conductive substrate 1,
A single layer may be provided as the photosensitive layer 4 in which the charge generating substance 2'is dispersed in the charge transport medium 3'made of an organic polysilane composition.

Examples of the charge generation material include selenium and selenium-
Tellurium, amorphous silicon, pyrylium salts, azo pigments, disazo pigments, ansanthrone pigments, phthalocyanine pigments, indigo pigments, slene pigments, toluidine pigments, pyrazoline pigments, perylene pigments, quinacridone pigments, etc. For example, one kind or a mixture of two or more kinds is used so as to have an absorption wavelength region in a desired region.

This charge generating material can be applied in the form of a layer by means such as vapor deposition, or can be applied as a layer in the form of being dispersed in a binder resin. As such a binder resin, various resins can be used, and examples thereof include styrene polymers, acrylic polymers, styrene-acrylic copolymers, ethylene-vinyl acetate copolymers, polypropylene, and olefins such as ionomers. 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 polyether resin, phenol resin, and photocurable resin such as epoxy acrylate can be exemplified. These binder resins may be used alone or in combination of two or more.

As the solvent used to form the coating liquid, various organic solvents can be used, alcohols such as methanol, ethanol, isopropanol, butanol, and aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, Benzene, toluene, aromatic hydrocarbons such as xylene, dichloromethane, dichloroethane, carbon tetrachloride, halogenated hydrocarbons such as chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethers such as diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, Ketones such as cyclohexane, ethyl acetate,
Examples of various solvents include esters such as methyl acetate, dimethylformamide, dimethylsulfoxide, and the like, and one kind or a mixture of two or more kinds is used.

As the conductive substrate, various materials having conductivity can be used, and examples thereof include aluminum, copper, tin, platinum, gold, silver,
Single metal of vanadium, molybdenum, chromium, cadmium, titanium, nickel, indium, stainless steel, brass, plastic material in which the above metal is vapor-deposited or laminated, glass coated with aluminum iodide, tin oxide, indium oxide, etc. Is exemplified.

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

In the case of the substrate / CGL / CTL photoreceptor of FIG. 1, CGL is 0.01 to 0.05 μm in the case of vapor deposition to 0.1 to 0.5 μm in the case of coating.
CTL varies from 5 to 40 μm, especially from 10 to 25 μm
It should be in the range of. For the substrate / CTL / CGL photoreceptor of FIG. 2, the CTL should have a thickness of 5 to 40 μm, especially 10 to 25 μm, while the CGL should have a thickness of 0.1 to 0.5 μm. Further, in the CTL and CGL dispersion type photoreceptor of FIG. 3, the charge generating material is present in the photosensitive layer in an amount of 1 to 15 parts by weight, particularly 5 to 10 parts by weight, based on 100 parts by weight of the organic polysilane. Well, the photosensitive layer preferably has a thickness of 10 to 40 μm, particularly 15 to 30 μm.

(Effects of the Invention) According to the present invention, by incorporating a diphenoquinone derivative in a hole transport material, it is possible to suppress an increase in surface potential or residual potential during repeated charging-exposure and prevent deterioration by ultraviolet rays for a long period of time. It has become possible to obtain stable electrophotographic characteristics. Further, since the high hole drift mobility originally possessed by the organic polysilane is maintained as it is, a photoconductor for a copying machine or a laser printer having high sensitivity and stable electrophotographic characteristics is provided.

<Example> Hereinafter, the present invention will be described in more detail based on Examples.

(Example 1) [Synthesis of phenylmethylpolysilane] 100 g of methylphenyldichlorosilane, 26 sodium metal
g was 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 a dark purple precipitate) to convert unreacted sodium into ethoxide, the precipitate was filtered off, dried, dissolved in toluene and added dropwise to ethanol to reprecipitate a white precipitate. Phenylmethylpolysilane was obtained (22.0 g: 34% yield).

[Preparation of Electrophotographic Photoreceptor] 100 parts by weight of α-type oxotitanyl phthalocyanine as a charge generating material and 4000 parts by weight of tetrahydrofuran as a solvent were charged in a ball mill and stirred for 24 hours, and then polyvinyl butyral (Sekisui Chemical Co., Ltd.) was used as a binder. Manufactured by Eslec BM-3) (100 parts by weight) and further mixed by stirring for 1 hour to prepare a coating solution for the charge generation layer, and the coating solution was applied onto an aluminum foil with a wire bar (No. 5). After 100 ℃
Then, the charge generation layer having a thickness of 5 μm was formed by drying in a hot air for 30 minutes and curing.

Next, phenylmethylpolysilane as a charge transport material
100 parts by weight, 10 parts by weight of 2.6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative, and 1000 parts by weight of tetrahydrofuran as a solvent are mixed by stirring with a homomixer to apply a charge transport layer. The liquid was adjusted. This coating solution is applied on the charge generation layer with a wire bar (No. 60) and then dried with hot air at 100 ° C. for 30 minutes to form a charge transport layer having a thickness of about 5 μm. It was created.

(Example 2) In the preparation of the coating liquid for the charge transport layer, 2,2'-dimethyl-6,6'-dimethyl-6 ', 6'-di-tert-butyldiphenoquinone was used instead of 2,6-dimethyl-2', 6'-ditert-butyldiphenoquinone as the diphenoquinone derivative. 6 ',-
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that ditert-butyldiphenoquinone was used.

(Example 3) 100 parts by weight of phenylmethylpolysilane as a charge transport material, 4 parts by weight of α-type oxotitanyl phthalocyanine as a charge generation material, and 2,6 as a diphenoquinone derivative.
-Dimethyl-2 ', 6'-ditert-butyldiphenoquinone and 1000 parts by weight of tetrahydrofuran as a solvent were mixed by stirring in a ball mill for 24 hours to prepare a coating solution for a single-layer type photosensitive layer. After coating this coating solution on an aluminum foil with a wire bar (No.60), it is dried with hot air at 100 ° C for 30 minutes to form a single-layer type photosensitive layer with a film thickness of about 10 µm.
An electrophotographic photoreceptor was created.

Comparative Example 1 Example 1 was repeated except that 2,6-dimethyl-2 ′, 6′-ditert-dibutyldiphenoquinone as a diphenoquinone derivative was not added in the preparation of the coating liquid for the charge transport layer.
An electrophotographic photoreceptor was prepared in the same manner as in.

(Comparative Example 2) Comparative Example 2 was the same as Example 3 except that 2,6-dimethyl-2 ', 6'-ditert-dibutyldiphenoquinone as a diphenoquinone derivative was not added in the preparation of the coating liquid for the charge transport layer. An electrophotographic photoreceptor was prepared in the same manner.

[Evaluation of Electrophotographic Photosensitive Member] Using an electrostatic copying tester (Model-8100, manufactured by Kawaguchi Electric Co., Ltd.), the photosensitive member obtained in each example was positively or negatively charged with an applied voltage of ± 6.0 kv, The electrophotographic characteristics were measured under the following conditions, and the results are shown in Tables 1, 2 and 3.

Exposure time: 10 seconds Irradiation light: Wavelength 780 nm Exposure intensity: 10 μW / cm ² Dark decay after charging: 2 seconds In addition, V ₁ (V) in the table applies voltage under the above conditions to charge the photoreceptor. Shows the initial specific surface potential V ₁ (V) of the photoconductor at the time, and E ₁ 1/2 (μJ / cm ² ) is half the initial surface potential V ₁ (V) The half-exposure amount calculated from the required exposure time is shown. Further, V ₁ rp (V) in the table is the surface potential measured 5 seconds after the start of exposure as the residual potential, and the attenuation rate% is calculated by the following formula.

Further, in the above conditions, the exposure time was changed to 3 seconds, the dark decay after charging was changed to 1 second, and charging-exposure was repeated 100 times. At that time, the surface potential V ₂ (V) of the photoconductor and the half-exposure amount E ₂ 1/2
(ΜJ / cm ² ), the residual potential V ₂ rp (V) and the attenuation rate% were measured.

On the other hand, the photoconductors obtained in the respective examples were exposed to ultraviolet rays (300 to 400n
m, 60mW / cm ² ) after 10 minutes of irradiation, the surface potential V of the photoconductor
₁₀ (V), half exposure E ₁₀ 1/2 (μJ / cm ² ), residual potential V ₁₀
rp (V), and% attenuation were measured.

According to the results in the above table, the electrophotographic photosensitive members of Comparative Examples 1 and 2 in which the diphenoquinone derivative was not added were both charged-
The surface potential and the residual potential greatly increased due to repeated exposure and irradiation with ultraviolet rays. On the other hand, the electrophotographic photoconductors of Examples 1 to 3 to which the diphenoquinone derivative was added, even after repeated charging-exposure and irradiation with ultraviolet rays,
It was found that the amount of change in the surface potential and the residual potential was small, and that it had excellent repeatability and light resistance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a negative charging type laminated photoreceptor of the present invention. FIG. 2 is a cross-sectional view of the positive charging type laminated photoreceptor of the present invention. FIG. 3 is a cross-sectional view of the positive charging type single layer photoreceptor of the present invention. 1 ... Substrate, 2 ... Charge generation layer, 3 ... Charge transport layer, 4
...... Single layer type photosensitive layer.

Claims (3)

[Claims] 1. An organic photoreceptor for electrophotography, which comprises a charge-generating substance and a charge-transporting substance in a laminated type or in a monolayer-dispersed type, wherein the charge-transporting substance comprises a hole-transporting substance composition containing a diphenoquinone derivative. An organic photoconductor for electrophotography, which is characterized by: 2. The diphenoquinone derivative is a hole transport material 100.
A content of 0.1 to 30 parts by weight per part by weight.
The described photoreceptor. 3. The photoreceptor according to claim 1, wherein the hole transport material is an organic polysilane.