JP3010063B2 - Electrophotographic photoreceptor having photosensitive layer containing polysilane compound - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having an organic photoconductor of a polysilane compound, which gives improved electrophotographic properties. It is.

[Description of Prior Art]

Conventionally, as a photoconductive material used in an electrophotographic photoreceptor, various organic photoconductive polymers such as polyvinyl carbazole have been proposed.
Despite being superior to inorganic photoconductive materials in terms of film-forming properties and lightness, it has been difficult to put it to practical use until today because sufficient film-forming properties have not yet been obtained. In addition, sensitivity, durability and stability due to environmental changes are inferior to inorganic photoconductive materials. Further, hydrazone compounds disclosed in U.S. Pat.No. 4,150,987, etc., triarylpyrazoline compounds described in U.S. Pat.
Low molecular weight organic photoconductors such as a 9-styrylanthracene compound described in 4829 and the like have been proposed.
Such a low-molecular organic photoconductor, by appropriately changing the binder to be used, it has become possible to eliminate the drawback of the film-forming property which has been a problem in the field of organic photoconductive polymers, It is not enough in terms of sensitivity.

In recent years, use of polysilane compounds has been studied to solve these problems.

By the way, it was reported that polysilane was insoluble in solvents [The Journal of American Chemical Society, 125 , 2291 pp (1924)]. Thereafter, it was reported that polysilane was soluble in solvents and easy to form a film. [The Journal of American Ceramic Society, 61 , 504 pp (1978)] and gained attention.

In addition, polysilane has the property of an optical semiconductor capable of transferring charges by a σ-bond of the main chain [Physical Review, B, 35 , 2818pp (1987)], and is expected to be applied to an electrophotographic photoreceptor. Became. However, for application to such electrophotographic photoreceptors, it is necessary that the polysilane compound not only has a solvent-soluble and film-forming ability, but also can form a film without fine defects and can form a film with high homogeneity. Becomes Since fine defects are not allowed in the electrophotosensitive material, a high-quality polysilane compound which has a clear substituent structure and does not cause an abnormality in film formation is required.

There have been various reports on synthesis studies of polysilane compounds, but there are still problems in using them for electrophotographic photoreceptors. A low molecular weight polysilane compound having a structure in which all Si groups are substituted with organic groups has been reported [The Journal of American Chemical Society, 94 , (1)
1), 3806pp (1972), JP-B-63-38033].

The former publication has a structure in which a terminal group of dimethylsilane is substituted with a methyl group, and the latter publication has a structure in which a terminal group of dimethylsilane is substituted with an alkoxy group. Also have a degree of polymerization of 2 to 6 and do not exhibit the characteristics of a polymer. That is, because of its low molecular weight, it has no film forming ability as it is, and is difficult to use industrially. Recently, a high molecular weight polysilane compound having a structure in which all Si groups are substituted with organic groups has been reported [Nikkei New Materials, 8/15, p. 46 (1988)]. However, since the reaction proceeds via a special reaction intermediate, a decrease in the synthesis yield is expected, and industrial mass production is difficult.

Also, the synthesis method of the polysilane compound is described in The Journal of Organometallic Chemistry, 198pp, C27
(1980) or The Journal of Polymer Science, Polymer Chemistry Edition, Vol. 22,
159-170pp (1984). However, in any of the reported synthesis methods, only the condensation reaction of the polysilane main chain is performed, and there is no mention of a terminal group. In any of the synthesis methods, unreacted chloro groups and by-products are produced by side reactions, and it is difficult to constantly obtain a desired polysilane compound.

Examples of using the above-mentioned polysilane compounds as photoconductors have also been reported (U.S. Pat. No. 4,618,551, U.S. Pat. No. 4,772,525, JP-A-62-269964).
JP-A No. 2000-209, and the effects of unreacted chloro groups and by-products due to side reactions are presumed.

In U.S. Pat.No. 4,618,551, the above-described polysilane compound is used as an electrophotographic photoreceptor, but in a general copying machine, the absolute value of the surface potential may be 500 to 800 V,
Abnormally high surface potential -1000V is used. This is presumably because, at a normal potential, a defect occurs in the electrophotographic photosensitive member due to a structural defect of the polysilane, and a spot-like abnormal phenomenon on an image disappears. In Japanese Patent Application Laid-Open No. 62-269964, an electrophotographic photoreceptor is manufactured using the above-mentioned polysilane compound, and the photosensitivity is measured. Has no advantage over photoreceptors.

Further, the film quality of these polysilanes was poor in solubility and abrasion resistance, and when used as an electrophotographic photosensitive member, the durability was extremely poor.

In actuality, polysilane organic photoconductors that can be used industrially have not yet been provided, in that many problems still remain for use in such electronic materials.

[Object of the invention]

An object of the present invention is to solve the above-mentioned problems and to provide an electrophotographic photosensitive member having excellent electrophotographic characteristics, durability, and repetition characteristics.

[Structure and effect of the invention]

An object of the present invention is to provide an electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer has a polysilane compound represented by the following general formula (I) and a solubility parameter δ of 8.0 to 10.0. This is achieved by forming a layer containing a certain polymer resin compound.

Wherein R ₁ is an alkyl group having 1 or 2 carbon atoms, R ₂ is an alkyl group having 3 to 8 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms. And the group R ₄ represents an alkyl group having 1 to ₄ carbon atoms. A and A 'each represent an alkyl group having 4 to 12 carbon atoms;
It is a cycloalkyl group, an aryl group or an aralkyl group, both of which may be the same or different. n and m are molar ratios indicating the ratio of the number of each monomer to the total monomers in the polymer, and n + m = 1,
0 <n ≦ 1 and 0 ≦ m <1. The conventionally known polysilane is obtained by synthesizing a polymer by subjecting a dichlorosilane monomer to halogen elimination using a Na catalyst, so that a halogen residue remains at the terminal. If the terminal of the polysilane is a halogen group, it becomes a trap for charge transfer in the photoconductor,
This causes a residual potential. When repeated charging and exposure are performed, the residual potential increases, and the bright portion potential increases,
It was found that the durability was poor. Further, if the C group remains at the terminal, it is decomposed by moisture or the like to generate HCl gas, and corrodes the conductive portion of the substrate in the photoconductor, so that an image defect due to poor conduction occurs.

The present inventors have found that an electrophotographic photoreceptor having high sensitivity and high durability can be formed by shielding the terminal group of polysilane with an alkyl group, a cycloalkyl group, an aryl group, and an aralkyl group. This is considered as follows. That is, when an active C group remains at the terminal group of the polysilane, the generated carrier charge is trapped by the C group upon exposure as a photoreceptor, and a residual potential is generated. Therefore, by eliminating the C group at the terminal group of the polysilane and shielding it with an organic substituent, traps in the photoreceptor can be reduced and the residual potential at the time of exposure can be significantly reduced. Further, the potential is stable even after repeated charging and exposure.

However, these polysilane films are insufficient in solubility and abrasion resistance, and when used for an electrophotographic photoreceptor having contact with a developer, paper, and a cleaning member, the durability of the polysilane alone film is insufficient. Become. So, after careful examination,
When a polymer resin having a solubility parameter similar to the value of the solubility parameter δ of polysilane is well compatible with the polysilane, and when the compatible film is used as an electrophotographic photosensitive member, excellent electrophotographic properties are obtained. And sufficient durability.

The “dissolution parameter δ” is determined by the Fedors formula described in Yuji Harazaki, “Basic Chemistry of Coatings”, pp. 5 to 57 (published by Maki Shoten in 1977).

Specifically, when the value of the solubility parameter δ of polysilane is concentrated in the range of 8 to 10, such polysilane is compatible with many of the polymer resin compounds having the same value and can form a film. Becomes These resins are polystyrene, polymethyl methacrylate, polyvinyl acetate, polycarbonate and the like, and all have a solubility parameter δ in the range of 8 to 10. Two or more of these resins may be mixed depending on the case, and the types are not limited to these. Solvents for dissolving these polysilanes and resins having specific solubility parameter δ values include aromatic solvents such as toluene, benzene and xylene, and halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform and carbon tetrachloride. The system, its tetrahydrofuran, dioxane and the like are used.

The layer constitution of the electrophotographic photoreceptor of the present invention may be either a lamination type photoreceptor or a single-layer type photoreceptor.

The laminated photoreceptor comprises at least a charge generation layer and a charge transport layer. In this case, the charge generation layer is formed by depositing the charge generation substance or dispersing the charge generation substance in a binder resin, applying the obtained dispersion, and drying. Examples of the charge generating material include selenium-tellurium, pyrylium, thiopyrylium dyes, phthalocyanine pigments, anthantrone pigments, dibenzopyrene quinone pigments, pyranthrone pigments, trisazo pigments, disazo pigments, azo pigments, indigo pigments, quinacridone pigments,
Asymmetric quinocyanines, quinocyanines and the like can be used.

The binder resin for dispersing the charge generating substance is selected from a wide range of insulating resins or organic photoconductive polymers, but includes polyvinyl butyral, polyvinyl benzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulosic resin, and acrylic resin. Resins, polyurethane and polysilane compounds are preferred,
The amount used is 80% by weight or less, preferably 40% by weight or less in terms of the content in the charge generation layer.

The solvent used is preferably selected from those which dissolve the resin and do not dissolve the charge transport layer and the undercoat layer described below.

Specifically, tetrahydrofuran, ethers such as 1,4-dioxane, cyclohexanone, ketones such as methyl ethyl ketone, amides such as N, N-dimethylformamide, methyl acetate, esters such as ethyl acetate, toluene, xylene, Aromatics such as chlorobenzene, alcohols such as methanol, ethanol and 2-propanol;
Examples thereof include aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene.

The charge generation layer, the charge generation material is dispersed well by a method such as a homogenizer, an ultrasonic wave, a ball mill, a vibration ball mill, a sand mill, an attritor, and a roll mill together with a binder resin and a solvent in an amount of 0.3 to 4 times, and then coated. It is formed by drying. Its thickness is about 0.1-1 μm.

The coating can be performed using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a wire bar coating method, a blade coating method, a roller coating method, and a curtain coating method. Drying is preferably performed by touch drying at room temperature and then heating and drying. The heating and drying can be performed at 30 to 200 ° C. for 5 minutes to 2 hours in a still or blowing condition.

The charge transport layer is made of the specific polysilane compound described above and a polymer resin compound having a solubility parameter δ of 8.0 to 10.0. Examples of the polysilane compound to be used include the following.

Examples of polysilane compounds Note): X and Y in the above structural formula each represent a monomer polymerization unit. And n is X / (X + Y), and m is Y /
Each is obtained by the calculation formula of (X + Y).

Examples of the polymer resin compound include polystyrene, polymethyl methacrylate, polyvinyl acetate, and polycarbonate. The mixing ratio of the polysilane compound and the polymer resin compound is preferably such that the polysilane ratio is 20% to 80%. When the proportion of the polysilane compound is less than 20%, the charge transport function becomes insufficient, and when it exceeds 80%, the abrasion resistance becomes insufficient. A more preferred ratio of the polysilane compound is 40% to 70%.

As a solvent for dissolving the polysilane compound and the polymer resin compound, benzene, toluene, xylene, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, tetrahydrofuran, dioxane and the like are used. As a coating method for forming the charge transport layer using the obtained liquid, the same means as in the case of forming the charge generation layer described above can be employed. The thickness of the charge transport layer is preferably 5 μm to 35 μm.

In the case of a single-layer type photoreceptor, the above-mentioned charge generating substance is dispersed in the above-mentioned polysilane compound and polymer resin compound, and the resulting dispersion is applied and dried. The mixing ratio of each substance in the dispersion is preferably 3 to 7 parts by weight of a polysilane compound and 3 to 7 parts by weight of a polymer resin compound per 1 to 10 parts by weight of a charge generating substance. The single-layer type photoreceptor is obtained as follows.

First, a charge generating substance is dispersed together with an organic solvent and a polymer resin compound using a dispersing machine such as a ball mill, a sand mill, and an attritor.

Next, a polysilane compound and, if necessary, an organic solvent are added to prepare a charge-generating substance-dispersed polysilane solution. This solution is applied on a substrate and dried to obtain a single-layer photoreceptor. In this case, the film thickness is preferably 5 μm to 35 μm.

As the conductive support used in the present invention, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, titanium, nickel, indium, gold, platinum and the like are used. In addition, plastics (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, etc.) formed by coating these metals or alloys by a vacuum evaporation method, and conductive particles (for example, carbon black, silver particles, etc.) are suitable. A support coated on a plastic or metal substrate together with a suitable binder resin or a support in which conductive particles are impregnated in plastic or paper can be used.

In the electrophotographic photoreceptor of the present invention, an undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer.

The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide, or the like.

The thickness of the undercoat layer is 5 μm or less, preferably 0.1 to 3 μm.
Is appropriate.

The electrophotographic photoreceptor of the present invention can be widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 An aluminum substrate was prepared. Next, 10 parts by weight (hereinafter, parts) of chloroaluminum phthalocyanine and 5 parts of polyvinyl butyral were added to 90 parts of MEK, dispersed by a ball mill for 2 hours, coated on an aluminum substrate with a wire bar, dried, and dried at 200 mg / m ^2. Was provided.

Next, it has the following structural formula (A) and has a number average molecular weight of 23000
5 parts of a polysilane compound and 5 parts of a polystyrene having a number average molecular weight of 98,000 and a solubility parameter δ of 9.37 (a value of the solubility parameter δ: 9.0) were dissolved in toluene (a value of the solubility parameter δ: 8.9), The obtained liquid is applied on the charge generation layer with a wire bar, and dried to form a film.
Photoconductor No. 1 was obtained by forming a polysilane content of 18 μm.

The electrophotographic photoreceptor was -5 kV in a static manner using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.
After charging for 1 second in a dark place, exposure was performed at an illuminance of 2.5 lux, and the charging characteristics were evaluated. Further, the residual potential after strong exposure (illuminance: 20 lux / sec) was examined.

As the charging characteristics, the exposure amount (E) required to attenuate the surface potential (V ₀ ) and the potential (V ₁ ) when dark attenuated for 1 second (1/2) is used.
1/2) was measured. Further, the residual potential _VSL was measured.

Further, the photoreceptor is mounted on a PPC copier ND manufactured by Canon Inc.
Affixed to the photosensitive drum cylinder of −3825, made 10,000 copies with the same machine, and after copying 10,000 sheets, residual potential V _SL
Was measured. The results are shown in Table 1.

Table 1 also shows the initial film thickness and the film thickness after 10,000 copies.

Comparative Example 1 A photoconductor was prepared in exactly the same manner as in Example 1 except that polystyrene was not contained in the polysilane-containing layer.
No. 1.

The same evaluation as in Example 1 was performed, and the results are shown in Table 1.

Examples 2 to 4 A φ80 aluminum cylinder was prepared as a substrate. As the undercoat layer, a polyamide resin (6-66-610-12,
One part of a quaternary nylon copolymer) and 3 parts of an 8 nylon resin (methoxymethylated 6 nylon) are dissolved in a solvent composed of 50 parts of methanol and 40 parts of butanol to obtain a coating solution, which is then dried by a dip coating method. A 0.5 μm undercoat layer was formed on the substrate.

Next, a disazo pigment 10 having the following structural formula (B)
Department, And 5 parts of polyvinyl butyral with cyclohexanone 100
In addition, the mixture was dispersed in a ball mill for 2 hours, diluted appropriately with methyl ethyl ketone to obtain a coating solution for the charge generation layer, dried on the undercoat layer by a dip coating method, and applied to a thickness of 180 mg / m ² to form a charge generation layer. Formed.

Next, it has the following structural formula (C) and has a number average molecular weight of 28
000 polysilane compound (value of solubility parameter δ:
9.37) 4 copies, And 1 part, 4 parts and 16 parts of polymethyl methacrylate (number average molecular weight 9800, value of solubility parameter δ: 9.3) are each dissolved in toluene, appropriately diluted with the same solvent, and charged by a dip coating method as a coating solution. Coated on the generating layer and dried
An 18 μm polysilane-containing layer was formed to obtain a photoreceptor. The obtained photoreceptor was composed of 1 part of polymethyl methacrylate, 4 parts,
These photoconductors are No.2, No.3,
No. 4.

Each of the photoreceptor resulting Nanba2～4, deposited Canon KK copier NP3825, light-area potential (V _l) is 150V when set to the dark potential (V _d) 650V Exposure amount (ux · sec) required for (EΔ500V) was obtained. In addition, 10,000 copies were actually made, and the changes in V _d and V _l at that time were also determined. Further, changes in the initial film thickness and the film thickness of the 10,000-sheet copying machine were also obtained, and these are shown in Table 2.

Comparative Examples 2 to 4 Photoconductors were prepared in the same manner as in Examples 2 to 5, except that the mixing number of polymethyl methacrylate in the polysilane-containing layer was changed to 0 part, 0.5 part, and 20 parts, respectively. Photoconductors No. 2, No. 3, and No. 4 were used.

For each of these comparative photoreceptors, Examples 2 to
The evaluation was performed in the same manner as in the case of No. 4, and the results are shown in Table 2.

Examples 5 to 7 The procedure up to the charge generation layer was performed in the same manner as in Examples 2 to 4. Thereafter, a polysilane compound having the following structural formula (D) and having a number average molecular weight of 18000 (dissolution parameter δ)
Value: 8.3) to 4 parts, And 1 part of bisphenol Z-type polycarbonate (number average molecular weight 22000, value of solubility parameter δ: 8.2), 4 parts, 1 part
Each of the 6 parts was dissolved in a solvent having a mixing ratio of toluene / dichloromethane and 1/1, appropriately diluted with the same solvent, and applied as a coating liquid on the charge generation layer by a dip coating method.
A polysilane-containing layer having a thickness of μm was formed to obtain a photoreceptor. The obtained photoreceptors were one part, 4 parts, and 16 parts of polycarbonate, and these photoreceptors were designated as photoreceptors No. 5, No. 6, and No. 7, respectively. These photoconductors were evaluated in the same manner as in Examples 2 to 4, and the results are shown in Table 2.

Comparative Examples 5 to 7 In the polysilane-containing layer, Examples 5 to 5 except that the number of mixed parts of polycarbonate was set to 0 part, 0.5 part, and 20 parts, respectively.
7 and photoreceptors were obtained in the same manner as in Comparative Photoreceptor N.
o.5, No.6 and No.7.

These photoconductors were evaluated in the same manner as in Examples 2 to 4, and the results are shown in Table 2.

Example 8 The same procedure as in Examples 2 to 4 was performed up to the undercoat layer. Next, 2 parts of a disazo pigment having the following structural formula (E), 5 parts of polyvinyl acetate (number average molecular weight 30,000, value of dissolution parameter δ: 9.4) was added to 70 parts of toluene, dispersed by a ball mill for 4 hours, and 5 parts of the same polysilane compound as used in Example 1 was dispersed in this dispersion. Was added to form a coating liquid, and a photosensitive layer having a thickness of 20 μm was formed on the undercoat layer after drying by a dip coating method to obtain a photosensitive member. The photoreceptor was mounted on a Canon copier NP-3825, when V _D -650 V, was measured exposure amount when V _L is set to be -150 V, a 3.5ux · sec, 1 million in There was no change in the potential after copying, and excellent characteristics were exhibited.

Comparative Examples 8 to 9 A photoconductor was prepared in the same manner as in Example 8, except that the amount of the polysilane compound in the photosensitive layer was changed to 1 part and 17 parts, and the same evaluation as in Example 8 was performed.

As a result, in the case of 1 part of the polysilane compound, the _VL after 10,000 copies was changed to -280 V, and the image was ground fog on the image.

In the case of 17 parts of the polysilane compound, copying was impossible due to scraping of the photosensitive layer after copying 5,000 sheets.

[Summary of Effects of the Invention] As is clear from Examples and Comparative Examples, when used alone in the photosensitive layer, it is a polysilane compound showing excellent electrophotographic properties. Insufficient strength leads to poor durability. However, according to the present invention,
It is possible to impart sufficient mechanical strength to the polysilane-containing photoconductor without impairing the electrophotographic properties. this is,
This can be achieved by dissolving a polymer resin compound having a solubility parameter (SP value) that is very close to that of the polysilane compound.

Continuation of the front page (56) References JP-A-2-263831 (JP, A) JP-A-1-319044 (JP, A) JP-A-4-245250 (JP, A) JP-A-4-338968 (JP) , A) JP-A-63-313167 (JP, A) JP-A-63-271451 (JP, A) U.S. Pat. No. 4,265,990 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/00

Claims (4)

(57) [Claims] In an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer has a polysilane compound represented by the following general formula [I] and a solubility parameter δ of 8.
An electrophotographic photoreceptor comprising a polymer resin compound having a molecular weight of 0 to 10.0. Wherein R ₁ is an alkyl group having 1 or 2 carbon atoms, R ₂ is an alkyl group having 3 to 8 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms. And the group R ₄ represents an alkyl group having 1 to ₄ carbon atoms. A and A 'each represent an alkyl group having 4 to 12 carbon atoms;
It is a cycloalkyl group, an aryl group or an aralkyl group, both of which may be the same or different. n and m are molar ratios indicating the ratio of the number of each monomer to the total monomers in the polymer, and n + m = 1,
0 <n ≦ 1 and 0 ≦ m <1. ] 2. The method according to claim 1, wherein the value of the solubility parameter δ is 8.0 to 10.
The electrophotography according to claim 1, wherein the polymer resin compound 0 is a mixture of one or more of polystyrene, polymethyl methacrylate, polyvinyl acetate, and polycarbonate. Photoconductor. 3. The photosensitive layer is of a laminated type, and the polysilane compound contained in the layer has a polysilane ratio of 20 to 80.
% Of the electrophotographic photoreceptor according to claim 1. 4. The photosensitive layer is of a single-layer type, and the polysilane compound contained in the layer has a polysilane ratio of 15 to 70.
% Of the electrophotographic photoreceptor according to claim 1.