JP2646725B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor having high sensitivity, high durability and high productivity.

2. Description of the Related Art Various proposals have been made to improve electrophotographic characteristics of electrophotographic photoreceptors. One of the improvements in characteristics is improvement in durability. Durability can be broadly divided into sensitivity, residual potential, chargeability, durability of electrophotographic physical surfaces such as image blur, and mechanical durability such as abrasion and scratches on the photoreceptor surface due to rubbing. Poor mechanical durability is a major factor in determining the life of a photoconductor, and development of a photoconductor having excellent mechanical durability has been desired.

In addition, the surface layer of the photoreceptor, particularly under high humidity, adhesion of a low-resistance substance generated by ozone generated during corona charging, or filming based on poor cleaning of toner,
It has a factor that causes image deterioration such as fusion, and therefore, in addition to the mechanical durability described above, releasability from various kinds of deposits is required.

In order to satisfy such demands, that is, to improve the mechanical durability against abrasion and scratches, and further to add releasability and water repellency, and to prevent toner fusion and the like, a lubricant is applied to the photoconductor surface layer. Is effective, and various proposals have been made. (JP-A-63-56658 and 63-61255)
Nos. 63-61256 and 63-113460) Problems to be Solved by the Invention However, in the technology proposed conventionally,
By dispersing the lubricant in the surface layer, the light transmittance is reduced, or the sensitivity is reduced due to the effect of the dispersant used to improve the dispersibility of the lubricant, and the charge exposure is repeated. In such a case, problems such as fluctuations in the light portion potential and lack of stability occur, and it is difficult to commercialize an electrophotographic photosensitive member having high durability, high sensitivity, and stable electrophotographic characteristics when repeatedly used. It is the current situation.

For example, when a fluororesin is used as a lubricant, the fluororesin powder has problems in dispersibility and cohesion, and it is difficult to form a uniform and smooth film. It is inevitable that image defects such as image unevenness and pinholes occur. As a method for improving this, a uniform method of dispersing the fluororesin powder by dispersing media such as glass beads and steel shots can be considered, but it has a disadvantage that electrophotographic characteristics are deteriorated due to contamination.

Another object of the present invention is to provide an electrophotographic photosensitive member having high durability that meets the above requirements. That is, an object of the present invention is to provide an electrophotographic photoreceptor which has durability against abrasion of a surface due to friction, generation of a scratch, and the like, and from which a high-quality image without image blur can be obtained. Another object of the present invention is to provide an electrophotographic photoreceptor having good cleaning properties and high durability without toner adhesion to the photoreceptor surface layer. Still another object of the present invention is to provide a highly durable electrophotographic photoreceptor capable of always obtaining a high-quality image without accumulation of residual potential in a repeated electrophotographic process.

Means for Solving the Problems The present inventors have found that the above objects can be achieved by using a specific resin and an organic compound on the surface of the photosensitive layer, and have completed the present invention.

That is, according to the present invention, in an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, a layer farthest from the conductive substrate is made of fine particles of a fluororesin, (Wherein R ₁ and R ₂ each represent a hydrogen atom or a methyl group, and R ₃ represents a hydrogen atom, a methyl group, an ethyl group or a chlorine atom) and a general formula (II) or (III) (Wherein, R ₄ represents a hydrogen atom, a methyl group, a bromine atom or a fluorine atom, R ₅ represents a methyl group, a phenyl group, a trifluoromethyl group or a cyano group, and R ₆ represents a methyl group, a phenyl group or a trifluoromethyl Wherein at least three kinds of polycarbonates each comprising a repeating unit represented by the formula (1) are contained, and the layer is prepared by dispersing a dispersion of a fluororesin in an organic solvent in the form of fine particles in advance in the form of tetraphenylbenzidine. It is formed by applying a coating solution obtained by mixing a compound and an organic solvent solution containing the polycarbonate.

Hereinafter, the electrophotographic photosensitive member of the present invention will be described in detail.

The drawing is a schematic sectional view for explaining the layer constitution of the electrophotographic photosensitive member of the present invention. FIGS. 1 and 2 show a case where the photosensitive layer has a single-layer structure. In FIG. 1, a photosensitive layer 2 is provided on a conductive substrate 1, and in FIG. Subbing layer 3 between the photosensitive substrate 1 and the photosensitive substrate 2
Is provided. FIGS. 3 and 4 show a case where the photosensitive layer has a laminated structure in which a charge generation layer 21 and a charge transport layer 22 are functionally separated. In FIG. A generation layer 21 is formed, and a charge transport layer is formed thereon.
In FIG. 4, the undercoat layer 3 is provided between the conductive substrate 1 and the charge generation layer 21. Further, in FIG. 5, a charge transport layer 22 is formed on the conductive substrate 1, and a charge generation layer 21 is formed thereon.

In the electrophotographic photoreceptor of the present invention, when the photosensitive layer has a single-layer structure, the photosensitive layer itself is the layer most separated from the conductive substrate, and when the photosensitive layer has a laminated structure. Any of the charge transport layer and the charge generation layer may be the layer most separated from the conductive substrate.

As the conductive substrate in the electrophotographic photoreceptor of the present invention, any known conductive substrates used in electrophotographic photoreceptors can be used.

An undercoat layer having a barrier function and an undercoat function can be provided on the conductive substrate, if desired. The undercoat layer is formed for the purpose of improving the adhesiveness of the photosensitive layer, improving the coating property, protecting the substrate, covering defects on the substrate, improving the charge injection property from the substrate, and protecting the photosensitive layer from electrical breakdown. Is done.

As a material for forming the undercoat layer, polyvinyl butyral, polyvinyl acetal, silane coupling agent,
Polyvinyl pyridine, polyvinyl pyrrolidone, phenolic resin, polyvinyl alcohol, poly-N-vinyl imidazole, polyethylene oxide, ethyl cellulose,
Methyl cellulose, ethylene-acrylic acid copolymer, casein, polyamide, copolymerized nylon, glue, gelatin and the like can be used. They are dissolved in a suitable solvent and applied on a conductive substrate. The thickness of the undercoat layer is generally about 0.2 to 2 μm.

When the photosensitive layer has a laminated structure, a charge generation layer or a charge transport layer is formed on the conductive substrate or the undercoat layer.

The charge generation layer is obtained by dispersing a charge generation material in a binder resin, and as the charge generation material, trigonal selenium, bisazo pigment, condensed polycyclic pigment, phthalocyanine pigment, and the like are preferably used. . The charge generation pigment is preferably blended in an amount of 0.1 to 10 parts by weight based on 1 part by weight of the binder resin. On the other hand, as the binder resin, polystyrene,
Any conventionally known resin such as a silicone resin, a polycarbonate resin, an acrylic resin, a methacrylic resin, a polyester, a vinyl resin, a cellulose, and an alkyd resin can be used. When the charge generation layer is the most distant layer, the charge generation layer may contain fluorocarbon resin particles and a tetraphenylbenzidine compound, and the binder resin may be a polycarbonate resin. The thickness of the charge generation layer is generally set in the range of 0.05 to 5 μm.

The charge transport layer is one in which the charge transport agent is contained in the binder resin, but when the charge transport layer is provided as a layer most separated from the conductive substrate, fine particles of fluorine resin,
It is composed of a tetraphenylbenzidine compound represented by the general formula (I) and a polycarbonate comprising a repeating unit represented by the general formula (II) or (III).

As the fluororesin, for example, ethylene tetrafluoride resin powder, ethylene trifluoride chloride resin powder, hexafluoroethylene-propylene copolymer resin powder, vinyl fluoride resin powder, vinylidene fluoride resin powder, Fluorinated ethylene dichloride resin powder can be used.

The amount of the fluororesin is 1 to the total solid content of the coating solution.
A suitable range is from 30 to 30% by weight, preferably from 3 to 10% by weight. If the amount of the fluororesin is less than the above range, the desired high durability cannot be obtained. If the amount is more than the above range, the decrease in light transmittance and the deterioration of electrical characteristics ( (E.g., increase in residual potential and decrease in chargeability).

Examples of the tetraphenylbenzidine compound represented by the general formula (I), which is a charge transporting material, include those represented by the following structural formula.

Further, as the binder resin, the above-mentioned general formula (II) or (II)
Although a polycarbonate comprising a repeating unit represented by I) is used, a polycarbonate (III-a) comprising a repeating unit represented by the following structural formula is particularly preferred from the viewpoint of the stability over time of a coating solution.

The mixing ratio of the above-mentioned tetraphenylbenzidine compound and polycarbonate is suitably in the range of 3: 1 to 1: 3.

The thickness of the charge transport layer is generally set at 5 to 50 μm.

When the photosensitive layer has a single-layer structure, the photosensitive layer is made of fine particles of a fluororesin, a tetraphenylbenzidine compound represented by the formula (I), a compound of the formula (II) or (III).
And a charge generation pigment. In that case, the mixing ratio of each component can be appropriately set according to the above. Further, the film thickness is generally set to 5 to 30 μm.

In the present invention, the layer most separated from the conductive substrate,
It must be formed as follows. That is, first, a dispersion liquid is prepared by dispersing fluororesin fine particles in an organic solvent in a fine particle state. This dispersion has an average particle size
It contains fluororesin fine particles of 0.1 to 16 μm, preferably 0.3 to 7 μm. As organic solvents, aromatic halogenated solvents,
Aliphatic halogenated solvents, ethers, ketones, cellosolves, esters, etc. can be used. Is preferred.

The dispersion liquid of the fluororesin fine particles is an organic solvent solution containing the above-mentioned tetraphenylbenzidine compound and the above-mentioned polycarbonate, or the charge generation pigment is dispersed therein and mixed with the dispersion to prepare a coating liquid. Examples of the organic solvent in this case include ketones such as cyclohexanone and methyl ethyl ketone, alcohols such as methyl alcohol, ethyl alcohol and butyl alcohol, amides such as N, N-dimethylformamide, tetrahydrofuran, dioxane, and ethylene. Ethers such as glycol monobutyl ether, halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene; and aromatic hydrocarbons such as benzene, toluene, xylene, monochlorobenzene, and dichlorobenzene And the like.

The obtained coating liquid can be applied by a coating method such as a dip coating method, a spray coating method, a blade coating method, a spinner coating method, a bead coating method, and a curtain coating method. After coating, dry the coating, but dry 10-150
C., preferably at a temperature in the range of 20-100.degree. C., for 5 minutes to 5 hours, preferably 10 minutes to 2 hours, by air drying or still drying.

The layer farthest from the conductive substrate formed by the above method in the present invention is extremely uniform and smooth, and does not cause image quality defects such as uneven image quality and pinholes.

Examples Hereinafter, the present invention will be described with reference to examples.

Example 1 An aluminum pipe (outside diameter: 84 mm, length: 360 mm) was used as a conductive substrate, and a 5% n-propyl alcohol / water mixed solution of polyvinyl acetal resin represented by the following structural formula was applied thereon by dip coating. An undercoat layer having a thickness of 0.5 μm was formed.

l = 30-36, m = 63-69, n = 0.5-3.0 (all are mol%) 87 parts by weight of granular trigonal selenium and vinyl chloride-vinyl acetate copolymer (trade name: Solution Vinyl VMCH) ,
A solution in which 13 parts by weight of Union Carbide Co., Ltd.) was dissolved in 200 parts by weight of n-butyl acetate was subjected to a dispersion treatment with an attritor for 24 hours. Next, 57 parts by weight of n-butyl acetate was added to 30 parts by weight of the obtained dispersion to dilute it to obtain a dip coating solution.

Using this dip coating solution, dip coating was performed on an undercoat layer on an aluminum pipe. That is, the aluminum pipe on which the undercoat layer is formed is immersed in the coating solution in the dip coating tank, pulled up at a speed of 100 mm / min, and dried by heating at 100 ° C. for 5 minutes to generate a charge of about 0.1 μm in thickness. A layer was formed.

Next, as a fluororesin, a polytetrafluoroethylene Freon TF dispersion (trade name: VYDAX AR, solid content: 20%, manufactured by DuPont), a tetraphenylbenzidine compound, the above-mentioned exemplary compound (I-a), and a polycarbonate The exemplary resin (III-a) was prepared. 8 parts by weight of the exemplary compound (Ia) and 12 parts by weight of the exemplary resin (III-a) are dissolved in 80 parts by weight of monochlorobenzene, and 10 parts by weight of the above-mentioned polytetrafluoroethylene dispersion of Freon TF is added thereto. Thus, a coating solution for forming a charge transport layer was prepared.

This coating solution was applied on the charge generation layer formed as described above by dip coating, and dried with hot air at 100 ° C. for 60 minutes to form a charge transport layer having a thickness of 25 μm.

The electrophotographic photoreceptor thus manufactured is mounted on a copying machine (FX4700 modified machine, manufactured by Fuji Xerox Co., Ltd.),
After adjusting the dark portion potential VD to be -800 V, ² erg / cm ²
The light portion potential VL when the exposure was given was measured. afterwards,
An endurance test was performed on 100,000 copies, and changes in the dark part potential VD and the light part potential VL were measured. At the same time, the image quality was evaluated.

Example 2 Instead of the fluororesin of Example 1, a dispersion of polytetrafluoroethylene particles in Diflon Solvent S3 (trade name:
Lubron LD-1, solid weight 6%, manufactured by Daikin Industries, Ltd.)
And an electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that 33 parts by weight of this dispersion was added and mixed.

Example 3 Instead of the fluororesin of Example 1, a Freon TF dispersion of polyvinylidene fluoride particles (trade name: Kynar 202,
80% solid content, manufactured by Pennwalt)
An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1 except that 2.5 parts by weight were added and mixed.

Comparative Example 1 An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1, except that the dispersion of polytetrafluoroethylene particles was not added.

Comparative Example 2 Instead of the dispersion of the fluororesin of Example 1, polytetrafluoroethylene powder (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) was used, except that 2 parts by weight of this powder was added and mixed. In the same manner as in Example 1, an electrophotographic photosensitive member was produced and evaluated.

Comparative Example 3 Instead of the fluororesin dispersion of Example 1, polytetrafluoroethylene powder (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) was used, and 2 parts by weight of this powder was added. Using the mixed liquid as a dispersion medium, add a stainless steel steel shot and use a stainless steel ball mill.
The mixture was dispersed for 50 hours to prepare a coating solution for forming a charge transport layer.
Using this solution, an electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1.

Table 1 shows the evaluation results of Examples 1 to 3 and Comparative Examples 1 to 3.

Effect of the Invention In the electrophotographic photoreceptor of the present invention, the layer farthest from the conductive substrate is made of fine particles of a fluororesin, a tetraphenylbenzidine compound represented by the above general formula (I), and the above general formula (II) or (III) Containing the polycarbonate represented by the above, and formed by the above specific method, the surface of the electrophotographic photoreceptor is a layer that is uniform, smooth and free of coating film defects, and has high durability . Therefore,
The electrophotographic photoreceptor of the present invention has durability against abrasion of the surface due to friction, generation of scratches, etc., good cleaning properties, no toner adhesion to the photoreceptor surface layer, and repetitive electrophotography. In the process, there is no accumulation of residual potential, and a high-quality image without blur is always obtained.

[Brief description of the drawings]

1 to 5 are schematic cross-sectional views of the electrophotographic photosensitive member of the present invention. 1 ... conductive substrate, 2 ... photosensitive layer, 21 ... charge generation layer,
22 ... Charge transport layer, 3 ... Undercoat layer.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G03G 5/147 504 G03G 5/147 504

Claims (1)

(57) [Claims] In an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, a layer most distant from the conductive substrate is made of fine particles of a fluororesin, represented by the general formula (I): (Wherein R ₁ and R ₂ each represent a hydrogen atom or a methyl group, and R ₃ represents a hydrogen atom, a methyl group, an ethyl group or a chlorine atom) and a general formula (II) or (III) (Wherein, R ₄ represents a hydrogen atom, a methyl group, a bromine atom or a fluorine atom, R ₅ represents a methyl group, a phenyl group, a trifluoromethyl group or a cyano group, and R ₆ represents a methyl group, a phenyl group or a trifluoromethyl Wherein the layer comprises at least three kinds of polycarbonates each comprising a repeating unit represented by the formula: and the layer is prepared by dispersing a dispersion of a fluororesin in an organic solvent in the form of fine particles in advance in the form of tetraphenylbenzidine. An electrophotographic photoreceptor formed by applying a coating solution obtained by mixing a compound and an organic solvent solution containing the polycarbonate.