JP2567274B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, more specifically, humidity resistance,
The present invention relates to a highly durable electrophotographic photoreceptor having excellent mechanical strength.

[Prior Art] An electrophotographic photosensitive member is required to have predetermined sensitivity, electrical characteristics, and optical characteristics according to an electrophotographic process to be applied. As for the surface layer of the photoreceptor, that is, the layer most distant from the support, electrical and mechanical external forces such as corona charging, toner development, transfer to paper, and cleaning treatment are directly applied, Durability against them is required.

Specifically, durability is required against abrasion and scratches on the surface due to rubbing, or deterioration of the surface due to ozone generated during corona charging under high humidity.

On the other hand, there is a problem that the toner adheres to the surface layer due to repeated toner development and cleaning processes, and it is required to improve the cleaning property of the surface layer.

Various methods have been investigated in order to satisfy the properties required for the surface layer as described above, and among them, the means of dispersing the fluororesin powder in the surface layer is effective.

Dispersion of the fluororesin powder reduces the friction coefficient of the surface layer, which improves the cleaning property and the durability against wear and scratches.

Further, since the water repellency and the releasability of the surface layer are improved, it is also effective for preventing the surface deterioration under high humidity.

However, in the fluororesin powder dispersion, there is a problem in dispersibility and cohesiveness, and it is difficult to form a uniform and smooth film. Therefore, the obtained surface layer has an image such as image unevenness or pinholes. It was unavoidable to have defects.

Therefore, it has been proposed to use a surfactant as a dispersion aid as one of the methods for uniformly dispersing the fluororesin powder and forming a smooth film. It has been studied to further reduce the amount of abrasion of the photoconductor and increase the life of the photoconductor by increasing the addition amount.

Along with the increase in the amount of the fluororesin powder, the amount of the surfactant, which is a dispersion aid, must be increased. Due to the increase in the amount of the surfactant, there arises a problem that the coating liquid foams and the generated foam is hard to disappear.

In addition, the electrophotographic photosensitive member containing the increased amount of the surfactant causes deterioration of the electrophotographic characteristics such as a decrease in sensitivity due to kickback use and a decrease in sensitivity in a high temperature and high humidity environment.

Furthermore, in the case of a function-separated type photoreceptor in which a conductive support, a charge generation layer, and a charge transport layer are sequentially laminated, oxidation is performed in order to prevent deterioration of the surface charge transport layer due to ozone, NOx, and other charged products. It has been proposed to add an additive such as an inhibitor to the charge transport layer, and the coexistence of this additive and the above-mentioned surfactant, which is a dispersion aid of the fluorine-based resin powder, further improves the electron emission. It has been found that it causes deterioration of photographic characteristics.

As described above, the electrophotographic photosensitive member to which the fluorine-based resin powder is added has various problems.

[Problems to be Solved by the Invention] The present invention is to provide an electrophotographic photosensitive member which should meet the above-mentioned requirements.

That is, the first purpose is to provide an electrophotographic photosensitive member having durability against surface abrasion and scratches caused by rubbing.
The second purpose is to provide an electrophotographic photosensitive member that can obtain a stable and high-quality image even under high humidity, and the third purpose is an electrophotographic photosensitive member that has good cleaning properties and does not have toner adhered to the surface layer. The fourth purpose of providing a body is to provide an electrophotographic photosensitive member that does not have coating unevenness or pinholes on the surface, and does not accumulate residual potential in a repeated electrophotographic process and can always obtain a high-quality image. Fifth, to provide an electrophotographic photoreceptor without deterioration of electrophotographic characteristics due to the dispersion aid.

[Means and Actions for Solving the Problems] As a result of earnest studies in accordance with the above-mentioned object, the present inventor has found that the electrophotographic photoreceptor having the surface layer in which the fluorine-based resin powder subjected to the surface oxidation treatment is dispersed has the above-mentioned requirements. The present invention has been completed by discovering that it answers the above.

That is, the present invention relates to an electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the surface layer contains a surface-oxidation-treated fluororesin powder. Composed.

In the present invention, since the surface-oxidized fluororesin powder is uniformly dispersed in the coating film, it is not necessary to add a large amount of the surfactant, and bubbles are not generated in the coating material.

The fluororesin powder applied to the present invention is tetrafluoroethylene resin, trifluoroethylene chloride resin, tetrafluoroethylene hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorochloroethylene resin. One or more of these and copolymers are appropriately selected, and tetrafluoroethylene resin and trifluorochloroethylene resin are particularly preferable. The molecular weight and powder particle size of the resin can be appropriately selected and used from commercially available grades.

The content of the fluorine-based resin powder dispersed in the surface layer is appropriately 1 to 50% based on the weight of the solid content of the surface layer, and particularly preferably 2 to 30%.

If the content is less than 1%, the effect of modifying the surface layer by the fluororesin powder is not sufficient, whereas if it exceeds 50%, the light transmittance is reduced and the mobility of the carrier is also reduced.

Further, as the surface oxidation treatment method of the fluorine-based resin powder in the present invention, a surface treatment method such as corona discharge treatment, ozone treatment, and chemical treatment can be used.

As the corona discharge treatment method, the AC corona charging is preferably performed by negative charging.

As the ozone treatment method, treatment by irradiation with ultraviolet light is preferable.

As a chemical treatment method, it is preferable to treat with a mixed acid of sulfuric acid / chromic acid, a liquid obtained by adding sodium to liquid ammonia, or the like.

The binder resin for forming the surface layer may be a polymer substance having a film-forming property, but even if it is used alone, it has a certain degree of hardness and does not interfere with carrier transportation. Ester, polystyrene,
Methacrylic acid ester / styrene copolymer, polycarbonate, polyarylate, polyester, polysulfone and the like are preferable.

When the electrophotographic photosensitive member of the present invention is produced, a metal such as aluminum or stainless steel, a cylindrical cylinder or a film such as paper or plastic is used as the support.

An undercoat layer (adhesive layer) having a barrier function and an undercoat function can be provided on these supports.

The undercoat layer is for improving the adhesion of the photosensitive layer, improving the coating property, protecting the support, covering defects on the support, improving the charge injection property from the support, protecting the photosensitive layer against electrical breakdown, etc. Is formed.

As materials for the undercoat layer, polyvinyl alcohol, poly-N-vinylimidazole, polyethylenelenoxide, erylcellulose, methylcellulose, ethylene / acrylic acid copolymer, casein, polyamide, copolymerized nylon, glue, gelatin and the like are known. . These are dissolved in a suitable solvent and coated on a support. The film thickness is about 0.2 to 2 μm.

As the charge generating substance, cyanine dyes, azolene dyes, squavalium dyes, pyrylium dyes, thiapyrylium dyes, phthalocyanine pigments, anthanthrone pigments, dibenzpyrenequinone pigments, pyranthrone pigments, monoazo pigments Azo pigments such as disazo pigments and trisazo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanines and quinocyanines can be used.

Examples of the charge transport material include carbazole compounds such as N-isopropylcarbazole, N-methyl-N-phenylhydrazino-3-methylden-9-ethylcarbazole and N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole. Compound, p-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, p-pyrrolidinobenzaldehyde-N, N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-
Aldehyde-N, N-diphenylhydrazone, p-diethylbenzaldehyde-3-methylbenzthiazolinone-
Hydrazone compounds such as 2-hydrazone, 1- [pyridyl (2)]-3- (p-diethylaminostyryl)-
4-methyl-5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (α-methyl-
a pyrazoline-based compound such as p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline,
2- (p-diethylaminostyryl) -6-diethylaminobenzoxazole, 2- (p-diethylaminostyryl) -4- (p-dimethylaminophenyl) -5-
Oxazole-based compounds such as (2-chlorophenyl) oxazole, 2- (p-diethylaminostyryl) -6
-Thiazole compounds such as diethylaminobenzthiazole, triarylmethane compounds such as bis (4-diethylamino-2-methylphenyl) phenylmethane, 1,1-bis (4-N, N-diethylamino-2-methylphenyl) Heptane, 1,1,2,2-tetrakis (4-N, N-
Polyarylalkanes such as dimethylamino-2-methylphenyl) ethane, 5- (4-diphenylaminobenzylidene) -5Hdibenzo [a, d] cycloheptene,
1,2-benzo-3- (α-phenylstyryl) -9-n
A stilbene compound such as -butylcarbazole can be used.

The preparation of the electrophotographic photoreceptor of the present invention will be described by taking a case of a function-separated photoreceptor in which a charge transport layer is laminated on a charge generation layer as an example.

The above charge generating substance is well dispersed together with a binder resin and a solvent in an amount of 0.3 to 10 times by a method such as a homogenizer, ultrasonic wave, ball mill, vibrating ball mill, sand mill, attritor or roll mill. This dispersion is applied onto the support coated with the undercoat layer and dried to give 0.1 to 1 μm.
Form a coating film of a certain degree.

In this example, the surface layer is the charge transport layer, so
Fluorine-based resin powder is dispersed here, and the fluorine-based resin powder is surface-modified by the above-described corona discharge treatment, ozone treatment, chemical treatment method or the like prior to dispersion.

The surface-treated fluororesin powder is dispersed with a binder resin, fluororesin powder and solvent in a homogenizer, ultrasonic wave, ball mill, vibrating ball mill, sand mill, attritor, roll mill, etc. A solution of a binder resin is added to prepare a desired charge transport layer coating solution.

Mixing ratio of charge transport material and binder resin is 2: 1 ~
It is about 1: 4.

As the solvent, aromatic hydrocarbon compounds such as toluene and xylene, chlorine-based hydrocarbon compounds such as dichloromethane, chlorobenzene, chloroform and carbon tetrachloride are used.

When applying this solution, for example, dip coating method, spray coating method, spinner coating method, bead coating method, blade coating method,
A coating method such as a curtain coating method can be used, and drying is 10 to 200 ° C, preferably 20 to 150 ° C.
Can be carried out at a temperature in the range of 5 minutes to 5 hours, preferably under static drying.

 The thickness of the formed charge transport layer is about 10 to 30 μm.

Further, in the case of a photoreceptor in which the charge generation layer is coated on the charge transport layer, the charge generation layer serves as the surface layer, and therefore the surface-oxidized fluorine resin powder is contained therein.

This charge generation layer coating liquid is prepared by adding and mixing the dispersion liquid in which the surface-oxidized fluororesin powder is dispersed in the binder resin used for the charge generation layer, to the dispersion liquid of the charge generation substance prepared as described above. The electrophotographic photosensitive member of the present invention can be prepared by applying the prepared coating liquid on the charge transport layer to form a charge generating layer.

When a protective layer is provided on the photosensitive layer and the protective layer serves as the surface layer, the surface-oxidized fluorine-based resin powder is contained in the protective layer.

This protective layer can be formed by coating the photosensitive layer with a protective layer coating solution obtained by adding and mixing a dispersion liquid of the surface-oxidized fluorine-based resin powder in the resin forming the protective layer as described above.

[Example] Example 1 Surface oxidation treatment method for fluororesin powder (i) Corona discharge treatment Polytetrafluoroethylene (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) powder as fluororesin powder Using a body, spread this evenly on a stainless steel container to a thickness of about 2 mm, and from above on a charger housing made of stainless steel with a width of 25 mm, height of 15 mm, length of 340 mm, thickness 60
The distance between the tungsten wire and the above polytetrafluoroethylene was approximately reduced under the discharge conditions of an applied voltage of -6KV and a total current of -200μA using a corona charger equipped with a tungsten wire of μm.
Corona discharge treatment was performed while keeping the distance to 20 mm. In order to perform uniform treatment, move the stainless steel container back and forth at a speed of 20 cm / mh, and set the corona discharge time per unit area to 2
Corona discharge was performed at a rate of min / cm ² .

The fluororesin powder that has been subjected to this surface oxidation treatment is referred to as No. 1.

(Ii) Ozone treatment Polytetrafluoroethylene powder was used as the fluorine-based resin powder, and this was evenly dispersed on a stainless steel container to a thickness of about 5 mm, and the ozone atmosphere tank (type 0-3 −2
1, put in Kaneda Rika Kogyo Co., Ltd., ozone concentration 300ppm
Was treated with ozone for 20 minutes.

The fluororesin powder that has been subjected to this surface oxidation treatment is designated as No. 2.

(Iii) Chemical treatment 200g of polytetrafluoroethylene powder was put into a glass beaker, and sulfuric acid / chromic acid mixed liquid (K ₂ Cr ₂ O ₇ ; H ₂ O; H ₂ SO ₄
(4.4: 88.5; 7.1 weight ratio), 500 ml was added, lightly stirred with a glass rod, allowed to stand for 30 seconds and then filtered to separate polytetrafluoroethylene.

Then, this chemically treated polytetrafluoroethylene was dried for 3 hours by a hot air dryer heated to 80 ° C.

The fluororesin powder subjected to this surface oxidation treatment is designated as No. 3.

Example 2 An 80 mmφ × 360 mm aluminum cylinder was used as a support, and a 5% methanol solution of polyamide (trade name: Amilan CM-4000, manufactured by Toray Industries, Inc.) was applied onto the support by dip coating to give 1 μm.
An undercoat layer was provided. Next, a disazo pigment of the following structural formula
Parts (weight ratio, the same below) 5 parts of polyvinyl butyral (trade name ESLEK BM-2, manufactured by Sekisui Chemical Co., Ltd.) and 50 parts of cyclohexanone
It was dispersed for 20 hours by a sand mill using 1 mmφ glass beads. Methyl ethyl ketone 70-120 (appropriate) in this dispersion
Parts were added and coated on the undercoat layer to form a charge generation layer having a thickness of 0.20 μm.

Next, 10 parts of polymethylmethacrylate (trade name of Dianal BR-85, manufactured by Mitsubishi Rayon Co., Ltd.) and 10 parts of the No. 1 fluororesin powder were dissolved in 40 parts of chlorobenzene and 30 parts of tetrahydrofuran, With a stainless steel ball mill
Dispersed for 48 hours. To 10 parts of the obtained dispersion liquid, p-diethylaminobenzaldehyde-N-α-naphthyl-N
-A resin solution prepared by dissolving 10 parts of phenylhydrazone and 10 parts of polymethylmethacrylate (described above) in 60 parts of chlorobenzene.
70 parts were mixed to prepare a charge transport layer coating solution.

The average particle size of the polytetrafluoroethylene powder in this charge transport layer coating liquid is a particle size distribution measuring device (trade name CAPA-500,
When measured by Horiba, Ltd., it was 0.46 μm.

This coating solution was applied on the charge generation layer and dried with hot air at 110 ° C. for 90 minutes to form a charge transport layer of 18 μm.

The surface of the obtained charge transport layer was uniform and smooth, and the average surface roughness was 0.2 μm.

 The electrophotographic photosensitive member thus prepared is referred to as Sample 1.

For comparison, an electrophotographic photosensitive member was prepared in the same manner as above using the fluorine-based resin powder (polytetrafluoroethylene powder) that had not been subjected to the surface oxidation treatment, and this is designated as Sample 2.

In Sample 2, the polytetrafluoroethylene powder in the surface layer was extremely agglomerated, and was in a state unworthy of image evaluation.

Further, an electrophotographic photosensitive member was prepared in the same manner as above except that the fluorine-based resin powder was not added.

 This is designated as Sample 3.

An electrophotographic copying machine having an electrophotographic process including primary charging, image exposure, dry toner development, transfer of a toner image to transfer paper, separation of transfer paper from a photoconductor, cleaning, and pre-exposure of each of these samples (commodity). Initial image characteristics and durability characteristics were evaluated by NP-3725, manufactured by Canon Inc.

First, the initial image characteristics were used for the position of the discharge wire of the primary charger and the image exposure device so that the surface potential of the photoconductor at the position of the developing device was −650 V on the black background and −130 V on the white background of the original. The initial voltage was obtained by adjusting the lighting voltage of each halogen lamp so that each sample had the same latent image potential.

Regarding the durability characteristics, after the initial image evaluation, room temperature and normal humidity 23 ℃, 55% RH, high temperature and high humidity 32.5 ℃, under the same conditions.
Durability evaluation of 30,000 sheets was performed under each environment of 90% RH. The results are shown.

Sample initial image 1 Good 2 White spot 3 Good Sample 23 ° C, 55% RH endurance 1 High quality and stable image up to 30,000 sheets 2 Not worthy of evaluation 3 Scratches on 16,000 sheets 35,000 Toner fusion on the surface Sample 32.5 ° C, 90% RH endurance 1 High quality and stable image up to 130,000 sheets 2 Not worthy of evaluation 3 Image deletion occurred at 4000 sheets Example 3 Same material and method as in Example 2 To form a subbing layer and then a charge generation layer on the support.

Next, 10 parts of bisphenol Z type polycarbonate (manufactured by Mitsubishi Gas Chemical Co., Inc.) and the above No. 2 fluororesin powder 20
Part was dissolved in 50 parts of cyclohexanone and 20 parts of tetrahydrofuran, and dispersed for 20 hours in a sand mill using 1 mmφ glass beads.

To 10 parts of the obtained dispersion liquid, 12 parts of the pyrazoline compound having the following structural formula and the above bisphenol Z type polycarbonate
40 parts of cyclohexanone and 10 parts of a resin solution dissolved in 20 parts of tetrahydrofuran are mixed, A charge transport layer coating solution was prepared.

The average particle size of the polytetrafluoroethylene powder in this coating solution was 0.45 μm.

This charge transport layer coating liquid is applied on the charge generation layer,
It was dried with hot air at 110 ° C. for 90 minutes to form a 20 μm charge transport layer. The surface roughness was 0.2 μm or less.

 The electrophotographic photosensitive member thus created is referred to as Sample 4.

For comparison, an electrophotographic photosensitive member was prepared in the same manner as above using the fluorine-based resin powder (polytetrafluoroethylene powder) that had not been subjected to the surface oxidation treatment, and this was designated as Sample 5.

In sample 5, the polytetrafluoroethylene powder in the surface layer was extremely agglomerated and was in a state unworthy of image evaluation.

Further, an electrophotographic photosensitive member was prepared in the same manner as above except that the fluorine-based resin powder was not added.

 This is designated as Sample 6.

For each sample, the durability of 30,000 sheets was evaluated in the same manner as in Example 2. The results are shown.

Sample initial image 4 Good 5 White spots 6 Good 23 ° C, 55% RH durability 4 High quality and stable image up to 30,000 sheets 5 Not worth evaluation 6 Toner fusion at 6,000 sheets Sample 32.5 ° C, 90% RH endurance 4 High-quality and stable image up to 30,000 sheets 5 Not worth evaluation 6 Image bleeding occurred at 5,000 sheets Example 4 0.5 μm on a support using the same material and method as in Example 2.
m undercoat layer was formed.

Next, 10 parts of a disazo pigment having the following structural formula, polyvinyl butyral (trade name: Eslek BL-S, Sekisui Chemical Co., Ltd.)
6 parts) and 50 parts of cyclohexanone were dispersed in a sand mill using 1 mmφ glass beads for 20 hours.

To this dispersion, 100 parts of tetrahydrofuran was added and coated on the undercoat layer to form a charge generation layer having a thickness of 0.2 μm.

Next, 10 parts of the bisphenol Z-type polycarbonate used in Example 2 and 10 parts of the No. 3 fluororesin powder were dissolved in 50 parts of dichloromethane and 10 parts of chlorobenzene to give 1 mmφ.
It was dispersed for 20 hours in a sand mill using the glass beads of.

With respect to 10 parts of the resulting dispersion, 10 parts of a stilbene compound having the following structural formula Resin solution prepared by dissolving 10 parts of the above bisphenol Z type polycarbonate in 50 parts of dichloromethane and 10 parts of chlorobenzene.
70 parts were mixed to prepare a charge transport layer coating solution, and 1,3,
0.3 part of 5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene was added, coated on the charge generation layer, and dried with hot air at 110 ° C for 90 minutes. To form a 20 μm charge transport layer.

 This electrophotographic photosensitive member is referred to as Sample 7.

For comparison, an electrophotographic photosensitive member was prepared in the same manner as above using the fluorine-based resin powder (polytetrafluoroethylene powder) that had not been subjected to the surface oxidation treatment, and this is designated as Sample 8.

In Sample 8, the polytetrafluoroethylene powder in the surface layer was extremely agglomerated and was in a state unworthy of image evaluation.

Further, an electrophotographic photosensitive member was prepared in the same manner as above except that the fluorine-based resin powder was not added.

 This is designated as Sample 9.

For each sample, the durability of 30,000 sheets was evaluated in the same manner as in Example 2. The results are shown.

Sample initial image 7 Good 8 Full white spot 9 Good Sample 23 ℃, 55% RH endurance 7 High quality and stable image up to 30,000 sheets 8 Not worth evaluation 9 9 000 sheets toner fusion sample 32.5 ℃, 90% RH durability 7 High-quality and stable image up to 30,000 sheets 8 Not worth evaluation 9 Image bleeding occurred on 5,000 sheets Example 5 10 parts of the stilbene compound used in Example 4 and Example 2
10 parts of polycarbonate used in 50 parts of dichloromethane,
It was dissolved in 10 parts of chlorobenzene. This solution was applied onto an 80 mmφ × 360 mm aluminum cylinder coated with an undercoat layer by dip coating in the same manner as in Example 3 and dried at 100 ° C. for 1 hour to form a 12 μm charge transport layer.

Next, the surface oxidation treatment applied to the No. 1 fluororesin powder was performed using polytrifluoroethylene chloride powder (Daikin Co., Ltd.).
10 parts of the resulting fluororesin powder, 10 parts of the disazo pigment used in Example 3, and the additive 1,3,5-trimethyl-2,4,6-tris used in Example 3 as well. (3,5-di-tert
-Butyl-4-hydroxybenzyl) benzene (0.6 parts) with 10 wt% of the above polycarbonate, cyclohexane solution
It was added to 100 parts and dispersed in a stainless ball mill for 50 hours.

This dispersion is pushed up onto the charge transport layer and coated at 100 ° C.
And dried for 20 minutes to form a charge generation layer having a thickness of 3 μm. The polytrifluoroethylene chloride powder in this charge generation layer had an average particle size of 0.5 μm and a surface roughness of 0.2 μm or less.

 The prepared electrophotographic photosensitive member is referred to as Sample 10.

For comparison, using the fluorine-based resin powder (polytrifluoroethylene chloride powder) not subjected to the surface oxidation treatment,
An electrophotographic photoreceptor was prepared in the same manner as above, and this was used as a sample.
11

In Sample 11, the aggregation of the polytrifluoroethylene chloride powder in the surface layer was so severe that the image was not worth evaluating.

Further, an electrophotographic photosensitive member was prepared in the same manner as above except that the fluorine-based resin powder was not added.

 This is designated as Sample 12.

For each sample, the polarity of the primary charging and transfer charging of the electrophotographic copying machine used in Example 2 was changed to the positive polarity by an external power source, and the toner was of the opposite polarity. NP-7500 machine (Canon Co., Ltd.) The initial image and 10,000 sheets were subjected to durability evaluation in the same manner as in Example 2 instead of the one used in Example 2. The results are shown.

Sample initial image 10 Good 11 White spot 12 Good sample 23 ℃, 55% RH Durability 10 High-quality and stable image up to 10,000 sheets 11 Not worthy of evaluation 12 Scratch on 3,000 sheets Sample 32.5 ℃, 90% RH Durability 10 High-quality and stable images up to 10,000 sheets 11 Image deterioration occurred at 12 thousand sheets not worthy of evaluation Example 6 0.5 μm on a support using the same material and method as in Example 2.
m undercoat layer was formed.

Next, a charge generation layer similar to that of the third embodiment is formed thereon by 0.2 μm.
It was applied thickly.

Further, 10 parts of bisphenol A type polycarbonate was dissolved in 60 parts of a mixed solvent of dioxane and dichloromethane, and 10 parts of the charge transport material used in Example 3 and the additive 1,3,5-trimethyl-2,4, 6-tris (3,5-di-tert
-Butyl-4-hydroxybenzyl) benzene solution 0.3 parts was applied by dip coating to a thickness of 18 μm,
The charge transport layer was formed by drying at ℃ for 1 hour. The electrophotographic photosensitive member thus created is referred to as Sample 13.

Further, 2 parts of the bisphenol Z-type polycarbonate used in Example 2 was dissolved in 30 parts of dichloromethane, and 1 part of the fluororesin powder No. 2 was added to the upper part of the charge transport layer.
Part of the solution was added and dispersed with a stainless steel ball mill for 50 hours to apply the solution to form a protective layer having a thickness of 1 μm.

 This electrophotographic photosensitive member is referred to as Sample 14.

For comparison, an electrophotographic photosensitive member was prepared in the same manner as above using the fluorine-based resin powder (polytetrafluoroethylene powder) that had not been subjected to the surface oxidation treatment, and this is designated as Sample 15.

In Sample 15, the polytetrafluoroethylene powder in the surface layer was extremely agglomerated and was in a state unworthy of image evaluation.

For each sample, the durability of 30,000 sheets was evaluated in the same manner as in Example 2. The results are shown.

Sample initial image 13 Good 14 Good 15 All white spots Sample 23 ℃, 55% RH endurance 13 Toner fusion at 7,000 sheets 14 High quality and stable image up to 30,000 sheets 15 Not worthy of evaluation Sample 32.5 ° C, 90% RH endurance 13 Image loss occurred at 6,000 sheets 14 High-quality and stable image up to 30,000 sheets 15 Not worthy of evaluation [Effect of the invention] Fluorine-based resin powder surface-treated according to the present invention was used as the surface layer. The electrophotographic photoreceptor containing the fluorine-based resin powder is uniformly dispersed, the dispersion stability is improved,
A uniform surface layer is always obtained, and as a result, not only the initial image but also scratches and image deletion do not occur after repeated durability, and a high quality image can always be obtained.

By using the surface-oxidized fluorine-based resin powder, a surfactant is not required, so that bubbles are not generated in the paint, and high image quality without image defects can be provided.

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the surface layer contains a surface-oxidized fluorine-based resin powder.