JPH0746230B2 - Organic photoconductor for electrophotography - 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.

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 an organic polysilane as a charge transport material (hole transport material), and to provide stable electrophotographic characteristics for a long period of time. Another object of the present invention is to provide a photoconductor for electrophotography, which is obtained.

(Means for Solving the Problems) According to the present invention, in an electrophotographic organic photoreceptor containing a charge-generating substance and a charge-transporting substance in a laminated type or a monolayer-dispersed type, the charge-transporting substance is a low-molecular-weight hole. It is composed of an organic polysilane containing a transport agent, and the organic polysilane has the following formula (1): In the formula, each of R ₁ and R ₂ is an alkyl group having 4 or less carbon atoms, or an aryl group or aralkyl group having 6 or more carbon atoms, and is composed of a repeating unit represented by: An organophotoreceptor for electrophotography is provided, wherein the agent is contained in an amount of 1 to 30 parts by weight per 100 parts by weight of organic polysilane.

(Function) In the present invention, when a low-molecular-weight hole transport agent is blended in an organic polysilane, the stability of the photoconductor when the charging-exposure operation is repeated is improved, and the increase in surface potential and residual potential is significantly suppressed. It is based on the knowledge to obtain.

As described above, when the charging-exposure operation is repeated on the photoreceptor using the organic polysilane as the charge transport material, both the surface potential and the residual potential increase considerably. This increase in surface potential and residual potential is due to the deterioration of the surface of the organic polysilane layer, which reduces the carrier transport ability of the surface portion,
The residual potential rises. The mechanism of this deterioration has not been fully clarified yet, but due to ultraviolet light or ozone generated during charging, or excitation-doublet oxygen, etc., the Si-Si main chain is broken and an insulating film is formed on the surface, resulting in a surface potential. It is considered that the residual potential rises due to the accumulation of electric charges in this insulating film due to repeated charging-exposure.

In the present invention, the stability of the above-mentioned charging-exposure process is improved by blending a low-molecular-weight hole-transporting agent in that the excited state of the organic polysilane is activated by the low-molecular-weight transporting agent. Therefore, it is considered that the deterioration of the surface of the photosensitive layer and the generation of radical species are suppressed. This idea is in good agreement with the fact that the fluorescence of the organic polysilane is quenched by the addition of the low molecular weight hole transporting agent. Further, by adding the low molecular weight hole transporting agent, the efficiency of injecting holes from the charge generation layer is improved, and this action can also reduce the residual potential.

(Preferred Embodiment) The organic polysilane used in the present invention is composed of the repeating unit represented by the above formula (1), and particularly preferred ones are methylphenylpolysilane, methylpropylpolysilane, methyl t-butylpolysilane, Examples thereof include diphenylpolysilane, methyltolylpolysilane, and 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.

As the low molecular weight hole transporting agent, any known per se, for example, 2,5-di (4-methylaminophenyl),
Oxadiazole compounds such as 1,3,4-oxadiazole, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, and pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline , Hydrazone compounds, triphenylamine compounds,
Examples thereof 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. The low molecular weight hole transport agent has the following formula In the formula, R is a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom.

The N, N, N ', N'-tetraphenyl m-phenylenediamine compound represented by

The low molecular weight hole transporting agent is preferably used in an amount of 1 to 30 parts by weight, particularly 5 to 15 parts by weight, based on 100 parts by weight of the organic polysilane. The effect of suppressing the increase in surface potential or residual potential tends to be inferior as compared with the case of being in the above range, while when it is more than the above range, the sensitivity tends to be lower as compared with the case of being in the above range. There is.

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-based polymers, acrylic polymers, styrene-acrylic copolymers, ethylene-
Vinyl acetate copolymer, polypropylene, olefin polymers such as ionomer, polyvinyl chloride, vinyl chloride-
Vinyl acetate copolymer, polyester, alkyd resin,
Various polymers such as polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, and photocurable resin such as epoxy acrylate can be used. It can be illustrated. 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 or an ultrasonic disperser, and a conventionally known method is used. Coating by coating means,
Just dry.

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 charging a low molecular weight hole-transporting agent in an organic polysilane as a hole-transporting material, charging-
It became possible to suppress the rise of surface potential and residual potential during repeated exposure and obtain stable electrophotographic characteristics for a long period of time. Further, the injection efficiency from the charge generating agent is improved, the sensitivity of the photoconductor is improved, and the residual potential can be suppressed to a low value. 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 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 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 S-REC BM-3) (100 parts by weight), and the mixture is stirred and mixed for 1 hour to prepare a coating solution for the charge generation layer, which is coated on an aluminum foil with a wire bar (No. 5). After 100
A 5 μm-thick charge generation layer was formed by drying in hot air at 30 ° C. for 30 minutes to cure.

Next, phenylmethylpolysilane as a charge transport material
100 parts by weight, N, N, N ', N'-as a low molecular weight hole transport agent
Tetrakis (3-tolyl) -1,3-phenylenediamine 1
A coating solution for the charge transport layer was prepared by stirring and mixing 0 part by weight and 1000 parts by weight of tetrahydrofuran as a solvent with a homomixer. 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) N, N, N ', N'-tetrakis (3-tolyl) -as a low molecular weight hole transport agent in the preparation of the coating liquid for the charge transport layer
Instead of 1,3-phenylenediamine, N-ethyl-3-
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that carbazolylaldehyde N, N-diphenylhydrazone 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 N, N, as a low molecular weight hole transport agent.
10 parts by weight of N ', N'-tetrakis (3-tolyl) -1,3-phenylenediamine and 1000 parts by weight of tetrahydrofuran as a solvent are mixed by stirring in a ball mill for 24 hours to prepare a coating solution for a single-layer type photosensitive layer. did. Apply this coating solution on aluminum foil with a wire bar (No.60), then at 100 ℃
A single-layer type photosensitive layer having a film thickness of about 10 μm was formed by drying with hot air for 30 minutes to prepare an electrophotographic photoreceptor.

(Comparative Example 1) N, N, N ', N'-tetrakis (3-tolyl) -as a low molecular weight hole transport agent in the preparation of the coating liquid for the charge transport layer
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 1,3-phenylenediamine was not added.

(Comparative Example 2) N, N, N ', N'-tetrakis (3-tolyl) -as a low molecular weight hole transport agent in the preparation of the coating liquid for the charge transport layer
An electrophotographic photoreceptor was prepared in the same manner as in Example 3 except that 1,3-phenylenediamine was not added.

[Evaluation of electrophotographic photoreceptor]

Using an electrostatic copying tester (Kawaguchi Denki Co., Model-8100), 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 and 2. It was shown to.

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 surface potential V ₁ (V) of the photoconductor when E ₁ 1/2 (μJ / cm ² ) is the initial surface potential
The half-exposure amount calculated from the exposure time required to become 1/2 of V ₁ (V) 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,
Surface potential V _2s (V) of the photoconductor at that time, half exposure amount E ₂ 1/2
(ΜJ / cm ² ), the residual potential V ₂ rp (V) and the attenuation rate% were measured.

From the results in the above table, the electrophotographic photoreceptors of Comparative Examples 1 and 2 to which the low molecular weight hole transporting agent was not added showed a large increase in surface potential and residual potential due to repeated charging-exposure. On the other hand, the electrophotographic photoconductors of Examples 1, 2, and 3 to which the low-molecular-weight hole transporting agent was added showed small changes in the surface potential and the residual potential even after repeated charging-exposure, and showed good repeatability. Turned out to have.

[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 (1)

[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 comprises an organic polysilane containing a low-molecular-weight hole-transporting agent. The organic polysilane has the following formula (1): In the formula, each of R ₁ and R ₂ is an alkyl group having 4 or less carbon atoms, or an aryl group or aralkyl group having 6 or more carbon atoms, and is composed of a repeating unit represented by: An organic photoconductor for electrophotography, wherein the agent is contained in an amount of 1 to 30 parts by weight per 100 parts by weight of organic polysilane.