JPH02143257A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the durability against the generation of wear and flaws on the surface by rubbing by incorporating polyethylene (PE) powder subjected to a surface oxidation treatment into the surface layer. CONSTITUTION:This photosensitive body is formed by incorporating the PE powder subjected to the surface oxidation treatment into the surface layer. Since the PE powder subjected to the surface oxidation treatment is uniformly dispersed into the coated film, there is no need for adding a large amt. of a surfactant thereto and the generation of bubbles in the coating liquid is obviated. The content of the PE powder to be dispersed into the surface layer is adequately 1 to 50wt.%, more particularly preferably 1 to 30wt.% by the weight of the solid content (exclusive of the PE powder) of the surface layer. The images having a high grade are obtd. at all times without generating flaws and image flow even after the repetitive use in this way. The effect of reforming the surface layer is insufficient if the content is below 1%. The light transmittability is degraded and the flowability of the carrier is degraded as well if the content exceeds 50wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to a highly durable electrophotographic photoreceptor with excellent moisture resistance and mechanical strength.

[Conventional technology]

Electrophotographic photoreceptors are required to have predetermined sensitivity, electrical properties, and optical properties depending on the electrophotographic process to which they are applied, but in addition, for photoreceptors that are used repeatedly, The surface layer of the photoreceptor, that is, the layer farthest from the substrate (hereinafter referred to as surface layer) K, is directly subjected to electrical and mechanical external forces such as corona charging, toner development 1 transfer to paper, and cleaning treatment. Therefore, durability against them is required.

Specifically, the occurrence of surface wear and scratches due to rubbing.

Additionally, durability against surface deterioration due to ozone generated during corona charging under high humidity conditions is required.

On the other hand, there are also problems such as toner scum and toner adhesion to the surface layer due to repeated cleaning, and to solve this problem, it is required to improve the cleaning performance of the surface layer.

In order to meet the characteristics required for the surface layer as described above, 1c
Several methods have been studied, among which the method of dispersing polyethylene powder in the surface layer is effective. The dispersion of the ethylene powder reduces the coefficient of friction of the surface layer, which improves cleaning performance and durability against wear and scratches.

Furthermore, since the water repellency and female moldability of the surface layer are improved, it is also effective in preventing surface deterioration under high humidity.

However, when dispersing polyethylene powder, there are problems with its dispersibility and cohesiveness, making it difficult to form a uniform and smooth film. It was inevitable that it would have defects.

Therefore, one method of uniformly dispersing polyethylene powder and forming a smooth film has been proposed to use a surfactant as a dispersion aid, and in recent years, the amount of polyethylene powder added has been increased. Studies are currently underway to further reduce the amount of wear on the photoreceptor and extend the life of the photoreceptor. Koo? As the amount of polyethylene powder increases, the amount of surfactant, which is a dispersion aid, must also be increased. This increase in the amount of surfactant caused the problem that the coating solution foamed and the foam that formed was difficult to disappear. Furthermore, electrophotographic photoreceptors with increased surfactant content have caused deterioration in electrophotographic properties, such as a decrease in sensitivity due to repeated use and a decrease in sensitivity under high temperature and high humidity environments.

Furthermore, in functionally separated photoreceptors that are formed by successively laminating a conductive support, a charge generation layer, and a charge transport layer, the charge transport layer, which is the surface layer, is subject to deterioration due to band formation products such as ozone and NOx. It has been proposed to add additives such as antioxidants to the charge transport layer in order to prevent this. Furthermore, it was found that it caused deterioration of electrophotographic properties.

As described above, electrophotographic photoreceptors to which polyethylene powder is added have various problems.

[Problem to be solved by the invention]

An object of the present invention is to provide an electrophotographic photoreceptor that meets the above-mentioned requirements.

That is, a first object of the present invention is to provide an electrophotographic photoreceptor that has durability against surface abrasion and scratches caused by rubbing.

The second objective is to provide an electrophotographic photoreceptor that can provide stable, high-quality images even under high humidity conditions.

A third objective is to provide an electrophotographic photoreceptor that has good cleaning properties and does not have toner attached to its surface layer.

The fourth objective is to provide an electrophotographic photoreceptor that has no coating unevenness or pinholes on one surface, and that does not accumulate residual potential during repeated electrophotographic processes and can always produce high-quality images.

A fifth objective is to provide an electrophotographic photoreceptor whose electrophotographic properties are not degraded by a dispersion aid.

[Means to solve the problem]

As a result of extensive studies in accordance with the above objectives, the present inventors discovered that an electrophotographic photoreceptor having a surface layer in which polyethylene powder subjected to surface oxidation treatment was dispersed satisfies the above requirements, and completed the present invention. Nine.

That is, the present invention is an electrophotographic photoreceptor having a photosensitive layer on a conductive support, characterized in that the surface layer contains polyethylene powder subjected to surface oxidation treatment.

In the present invention, since the surface-oxidized polyethylene powder is uniformly dispersed in the coating film, there is no need to add a large amount of surfactant, and no bubbles are generated in the blood.

The molecular weight and powder particle size of the polyethylene powder applied to the present invention can be appropriately selected from commercially available blades.

The content of polyethylene powder dispersed in the surface layer is 1 to 1 based on the weight of the surface layer solid content (excluding polyethylene powder).
50 weight ratio, and preferably VC1 to 30 weight ratio. If the content is less than 1%, the effect of modifying the surface layer by the polyethylene powder will not be sufficient, while if it exceeds 5atin, the light transmittance and carrier mobility will decrease.

Furthermore, as the method for surface oxidation treatment of polyethylene powder in the present invention, it is possible to use surface treatment methods such as corona discharge treatment, ozone treatment, and chemical treatment. The binder resin for forming the surface layer may be any polymer with film-forming properties, but from the viewpoints of having a certain degree of hardness even when used alone and not interfering with carrier transport, we use I-remethacrylic acid ester, polymer, etc. Styrene, methacrylate ester/
Styrene copolymers, /recarnates, polyarylates, polyesters, Irisulfone, etc. are preferred.

When producing the electrophotographic photoreceptor of the present invention, the support may be metal such as aluminum or stainless steel, paper, f')
Cylindrical cylinders or films such as styrene are used.

A subbing layer (adhesive layer) having a rear function and a subbing function can be provided on these supports.

The subbing layer is used to improve adhesion of the photosensitive layer, improve coating properties, protect the support, cover defects on the support, improve charge injection from the support, protect the photosensitive layer from electrical damage, etc. It is formed. Materials for the undercoat layer include polyvinyl alcohol, poly-N-vinylimidazole, I-lyethylene oxide, ethylcellulose λ, methylcellulose, ethylene-
Known examples include acrylic acid copolymers, casein, polyamides, copolymerized nylons, glue, and gelatin.

Each of these is dissolved in a suitable solvent and applied onto the support. The film thickness is about 0.2 to 2 μm.

The charge generating substances include cyanine dyes, azulene dyes, scuparylium dyes, pyrylicum dyes, thiapyrylium dyes, 7-thalocyanine pigments, anthorone pigments, dibenzpyrenequinone pigments, -lanthrone pigments, monoazo pigments, Azo pigments such as disazo pigments and trisazo pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric kickanine, quinocyanine, and the like can be used.

As the charge transport substance, N-isopropylcarbazole, N-methane? N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, carbazole-based compounds, p-diethylaminobenzaldehyde-N-α-su7 N-phenylhydrazone, p-pyrrolidinobenzaldehyde-N,N-diphenylhydrazone, 1,3.3-) dimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone,
hydrazone compounds such as p-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone;
1-[pyridyl(2)]-3-(p-diethylaminostyryl)-4-methyl-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl(2))
-3-(α-methyl-P-diethylaminostyryl)-
Pyrazoline compounds such as 5-(p-diethylaminophenyl)pyrazoline, 2-(p-diethylaminostyryl)-6-dinithylaminobenzoxazole, 2-(
Oxazole compounds such as p-diethylamino7enyl)-4-(p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2-(p-diethylaminostyryl)-6-//ethylaminobenzthiazole thiazole compounds such as, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)phenylmethane, 1,1-bis(4-N,N-
diethylamine-2-methylphenyl)heptane, 1
, 1,2.2-tetrakis(4-N,N--/methylamino-2-methylphenyl)ethane and other polyarylalkanes 5-(4-diphenylaminobenzylidene)-5'-dipenzo[tame,d]cycloheptene , 1.2
Stilbene compounds* such as -benzo-3-(α-7enylstyryl)-9-, -butylcar-1zole, etc. can be used.

The method for producing an electrophotographic photoreceptor of the present invention will be explained using an example of a functionally separated photoreceptor in which a charge transport layer is laminated on a charge generation layer.

The above charge generating substance is mixed with a binder resin and a solvent in an amount of 0.3 to 109 times using a homogenizer, ultrasonic waves, d-lumin, vibration? - Disperses well using methods such as lumill, sand mill, attritor roll mill, etc.

This dispersion is applied onto the substrate coated with the undercoat layer and dried to form a coating film of about 0.1 to 1 μm.

In this flI, polyethylene powder is dispersed in the surface layer as it becomes a charge transport layer, but prior to dispersion, this polyethylene powder is subjected to the corona discharge treatment as described above.
Use those whose surface has been modified by methods such as ozone treatment or chemical treatment. The surface-treated polyethylene powder is dispersed together with the binder resin, polyethylene powder, and solvent using a homogenizer, ultrasonic wave, ball mill, sand mill, attritor roll mill, etc., and a solution of the charge transport substance and binder resin is added to this. and prepare the desired charge transport layer liquid.

The mixing ratio of charge transport material and binder resin is 2:1~
l: about 4.

Solvents include aromatic hydrocarbons such as toluene and xylene, dichloromethane, and chlorpe/zene.

Chlorinated hydrocarbons such as chloroform and carbon tetracarbons are used. When applying this solution.

For example, dip coating method, spray coating method,
Coating methods such as spinner coating method, pea coating method, blade coating method, and curtain coating method can be used, and drying time is 10 to 20 minutes.
5 minutes to 0°C, preferably at a temperature in the range of 20 to 150°C
The drying can be carried out for 5 hours, preferably from 10 minutes to 2 hours, under blow drying or stationary drying. The thickness of the formed charge transport layer is about 10 to 30 μm.

Also, place the charge generation layer on the charge transport layer! ! ! In the case of a photoconductor to be installed, KF′i,! Since the load-generating layer becomes the surface layer, the surface oxidized polyethylene powder is contained therein. This charge generation layer dispersion is prepared by adding a dispersion of surface oxidized polyethylene powder dispersed in a binder resin used for the charge generation layer to a charge generation material dispersion prepared as described above.
It can be prepared by a mixing method, and a photoreceptor for Himi use can be obtained by coating this dispersion on a charge transport layer.

Further, when a protective layer is provided on the photosensitive layer and the protective layer serves as a surface layer, this protective layer contains polyethylene powder subjected to surface oxidation treatment. This protective layer was subjected to surface oxidation treatment in the resin forming the protective layer as described above. d It can be obtained by coating a dispersion liquid containing polyethylene powder on the photosensitive layer.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example D Surface oxidation treatment method for polyethylene powder.

1) Corona discharge treatment Polyethylene powder (trade name = 70-sen UF.

Sprinkle Seitetsu Kagaku Co., Ltd.) evenly onto a stainless steel container to a thickness of approximately 2cm, and then sprinkle a 25cm wide layer over it.
A corona charger made of stainless steel with a height of 15m and a length of 340m is connected to a tungsten wire with a thickness of 60μm.The applied voltage is -6kV and the total current is 200μ.
Corona discharge treatment was performed under discharge conditions A while maintaining the distance between the tungsten wire and the polyethylene powder at about 20 mm. In addition, in order to perform the treatment uniformly, the stainless steel container should be 20mm/ml! The corona discharge treatment was carried out by moving the sample back and forth at a speed of 1, so that the corona discharge time per unit area was 2 minutes/2 minutes. The polyethylene powder subjected to this surface oxidation treatment is referred to as Mu1.

11) Spread the polyethylene powder used for ozone treatment uniformly on a stainless steel container for several minutes to a thickness of about 5 m and place it in an ozone atmosphere bath (Model 0-3-2 manufactured by Kaneda Rika Kogyo Co., Ltd.). Ozone treatment was performed for 20 minutes at an ozone concentration of 300 ppm with K added. The polyethylene powder subjected to this surface oxidation treatment is referred to as Mu2.

111) Put 200I of the above polyethylene powder into a chemically treated glass beaker and add sulfuric acid-chromic acid mixture (K2Cr2O7; 1(2
0; H2BO3-4,4: 88.5: 7.1 weight ratio) 500.d was added, stirred lightly with a glass rod, kept quiet for 30 seconds, and then filtered to separate polyethylene.

The chemically treated polyethylene was then heated to 800℃ and dried for 3 hours using a specific hot air dryer. The polyethylene powder subjected to this surface oxidation treatment is referred to as a flat plate 3.

Example 2 An aluminum cylinder of 80φ x 360m was used as a base, and polyamide (trade name: Amilan CM-4000,
Toshishiku Co., Ltd.) 5-time methanol solution was immersed and sprayed.
A micrometer-thick subbing layer was provided.

Next, 10 parts (parts by weight, same hereinafter) and 70 to 120 parts (appropriate) of a cis-azo pigment having the following structural formula were added and coated on the undercoat layer to form a charge generation layer with a thickness of 0.201 tm. .

Next, 10 parts of polymethyl methacrylate (trade name: Dianal BR-85 manufactured by Mitsubishi Rayon) and 10 parts of the polyethylene powder of the above AX were dissolved in 40 parts of monochlorobenzene and 30 parts of buto2hydrof2fu, and stainless steel MyW −
The mixture was dispersed in Lumil for 48 hours. To 10 parts of the resulting dispersion, 5 parts of polyvinyl butyral (trade name: Kosuretsu BM-2, manufactured by Tanezu Kagaku Co., Ltd.) and 50 parts of cyclohexanone were dispersed for 200 hours in a sand mill using 1φ glass beads. In this dispersion, 10 parts of a hydrazone compound having the structural formula represented by methylethylke and 10 parts of the above polymethyl methacrylate were dissolved in 60 parts of monochlorobenzene.
, 70 parts were mixed to prepare a charge transport layer solution. This solution was coated on the charge generation layer and dried under heat at 110° C. for 90 minutes to form a charge transport layer of 18 μm. The surface of the charge transport layer obtained was uniform, smooth and uneven (average surface area 0.2
μm). This is designated as sample 1. For comparison, a photoreceptor was prepared in the same manner as above using polyethylene powder that had not been subjected to the surface treatment, and this was designated as Sample 2.

In sample 2, the cohesive force of the polyethylene powder in the surface layer was extremely strong.
The condition was not worthy of image evaluation. On the other hand, a sample without the addition of polyethylene powder was prepared in the same manner as above. This is designated as sample 3.

Each of these samples is transferred to an electrophotographic copying machine that has an electrophotographic process consisting of primary charging, image exposure, dry toner development, transfer of the toner image to transfer paper, separation of the transfer paper from the photoreceptor, creaming, and pre-exposure. Evaluations were made on NP-3725 machine (manufactured by Canon Inc.) with respect to initial printability and durability. First, regarding the initial image characteristics, the photoreceptor surface potential at the previous developing device position is -650V for the black background part of the original O, and -650V for the white background part.
Before the voltage reaches 30V, adjust the lighting voltage of the Halodan Lang used in the gIN light device for each position of the discharge wire of the primary charger to vI4 so that each sample has the same latent image potential. Got the image. In addition, regarding durability characteristics, after the initial image evaluation, it was tested under the same conditions at room temperature and humidity at 23℃.
℃, 55 Excellent Rf (.

Durability evaluation was carried out on 30,000 sheets under environments of high temperature, high humidity, 32.5° C., and 904 RH.

The results are shown in Table IK.

Example 3 An 80φ x 360mm aluminum cylinder was used as a support, and polyamide (trade name Amilan CM-8000) was applied to this.
, manufactured by Toshiku Co., Ltd.) by dip coating,
A subbing layer with a thickness of 1 μm was provided.

Next, a charge generation layer was formed using the same materials and method as in Example 2. Next, bisphenol type 2 polycargonate (
(manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 20 parts of the 4-reproduced tyrene powder of No. 42 above were dissolved in 50 parts of cyclohexanone and 20 parts of tetrahydrofuran, and dispersed for 20 hours in a sand mill apparatus using 1 mφ glass beads. To 10 parts of the obtained dispersion, 12 parts of a pyrazoline compound having the following structural formula and 10 parts of the above polycarbonate resin were added to 24 parts of cyclohexane.
0 parts, and 70 parts of the resin solution dissolved in 20 parts of tetrahydrofuran are mixed to form a charge transport layer solution of 1! Jim did it. This solution was applied onto the charge generation layer and dried with hot air at 110° C. for 90 minutes to form a charge transport layer with a thickness of 20 μm. The surface roughness was 0.2 μm or less.

This is designated as sample 4.

For comparison, a photoreceptor was prepared in the same manner as above using polyethylene powder that had not been subjected to the surface treatment, and this was designated as Sample 5.

Sample 5 had severe agglomeration of polyethylene powder in the surface layer.
The condition was not worthy of image evaluation.

On the other hand, a sample without adding polyethylene was prepared in the same manner as above. This is designated as sample 6.

Durability evaluation was performed on each of these samples in the same manner as in Example 2. The results are shown in Table 2.

Example 4 An aluminum cylinder of 80φ x 360mm was used as a support, and polyamide (trade name Amilan CM-8000
．． 5-time methanol solution (manufactured by Toshishiku Co., Ltd.) was applied by dip coating,
A separate layer with a thickness of 0.5 μm was provided.

Next, 10 parts of a disazo pigment having the following structural formula was dispersed for 20 hours in a sand mill using a sand mill.

To 10 parts of the obtained dispersion, 10 parts of a stilbene compound having the following structural formula, 6 parts of the polycarbonate tree polyvinyl butyral 6 resin (trade name: S-LEC BL-8, manufactured by Sekisui Chemical), and 50 parts of cyclohexanone were added. Dispersion was carried out for 20 hours using a sand mill device using 1 φ glass beads.

100 parts of Tetrahydro 7ran was added to this dispersion and applied onto the undercoat layer to form a charge generation layer with a thickness of 0.2 μm.

Next, 10 parts of the bisphenol z type I recarmenate used in Example 2, 10 parts of monoethylene powder of &3 above, 50 parts of dichloromethane, and 10 parts of monochlorobenzene were dissolved, and 10 parts of glass bee fat of 1 φ was added. dichloromethane 5
Resin solution 7 dissolved in 0 parts and 10 parts of monochlorobenzene
0 parts were mixed to prepare a charge transport layer solution. As an antioxidant, 1,3,5-) listyl-2,4,6-)
0.3 part of lith(3,5-J-t@rtf-thyl-4-hydroxybenzyl)benzene was added and applied onto the charge generation layer, and dried with hot air at 110°C for 90 minutes to form a charge transport layer of 20 μm. Formed. This is designated as sample 7.

For comparison, a photoreceptor was prepared in the same manner as above using polyethylene powder that had not been subjected to the # surface treatment, and this was designated as Sample 8.

Sample 8 had severe agglomeration of polyethylene powder in the surface layer.
The condition was not worthy of image evaluation.

On the other hand, a sample without adding polyethylene was prepared in the same manner as above. This is designated as sample 9.

Durability evaluation was performed on each of these samples in the same manner as in Example 2. The results are shown in Table 3.

Example 5 10 parts of the stilbene compound used in Example M1914 and 10 parts of the polycargonate resin used in Example 2 were dissolved in 50 parts of dichloromethane and 10 parts of monochlorobenzene. An undercoat layer was applied using this solution in the same manner as in Example 3. 80
It was applied by dip coating onto a 4×360 m aluminum cylinder and dried at 100° C. for several hours to form a charge transport layer of 12 μm.

Next, 10 parts of the above-mentioned bulk ethylene powder, 10 parts of the disazo pigment used in Example 4, and 0.6 parts of the same antioxidant used in Example 4 were added to 100 parts of the cyclohexanone solution based on 10 parts by weight of the polycarbonate. and dispersed in a stainless steel ball mill for 50 hours. This solution was applied onto the charge transport layer and dried at 100° C. for 20 minutes to form a charge generation layer with a thickness of 3 μm. The surface roughness was O84 or less. The prepared photoreceptor is referred to as sample 10.

For comparison, a photoreceptor was prepared in the same manner as above using polyethylene powder that had not been subjected to the surface treatment, and this was designated as Sample 11.

Sample 11 had severe agglomeration of the polyethylene powder in the surface layer, and was not worthy of image evaluation.

On the other hand, 4! A sample without the addition of recycled tyrene powder was prepared in the same manner as above. This is designated as sample 12.

Electrophotocopying machine NP using these samples in Example 2
-The polarity of the primary charging and transfer charging of the NP-3725 machine was changed to the external power supply, and the polarity of the developing noquis applied to the developing device was also changed, and the toner was also of opposite polarity.The NP-7550 machine (
In the same manner as in Example 2, the durability of initial images and 10,000 sheets was evaluated, except for the one used in Canon (manufactured by Canon). The results are shown in Table 4.

Example 6 An aluminum cylinder of 80φ x 360m was used as a support, and I-lyamide (trade name Amilan CM-8000) was applied to it.
, manufactured by Toshiku Co., Ltd.) was applied by dip coating,
A subbing layer with a thickness of 0.5 μm was provided.

Next, on top of this, a charge generation layer similar to that in Example 3 was applied with a thickness of 0.2 μm.
It was applied to a thickness of m. Furthermore, bisphenol A type I is added to this.
A solution prepared by dissolving 10 parts of liquorinate in 60 parts of a mixed solvent of dioxane and dichloromethane, and further dissolving 10 parts of the charge transport substance used in Example 4 and 0.3 parts of antioxidant was applied to a thickness of 18 μm by dip coating. , and dried at 100° C. for 1 hour to form a charge transport layer. This is designated as sample 13.

Furthermore, on top of this charge transport layer, 2 parts of the bisphenol 2 type polycarbonate used in Example 2 was added with 3 parts of dichloromethane.
Dissolve 0 parts in 42. jf! J ethylene powder 1
A protective layer having a thickness of 1 μm was formed by applying the dispersion solution for 50 hours using a stainless steel hole mill. This is designated as sample 14.

For comparison, a photoreceptor was prepared in the same manner as above using polyethylene powder that had not been subjected to the surface treatment, and this was designated as Sample 15.

Sample 15 was in a state where the agglomeration of the polyethylene powder in the surface layer was so severe that it was not worthy of image evaluation.

Durability evaluation was performed on each of these samples in the same manner as in Example 2. The results are shown in Table 5LK-.

〔Effect of the invention〕

As described above, the electrophotographic photoreceptor containing polyethylene powder subjected to surface oxidation treatment in the surface layer according to the present invention always has a uniform surface because the polyethylene powder is uniformly dispersed and its dispersion stability is improved. As a result, not only initial images but also scratches and image deletion do not occur even after repeated durability, and high-quality images can always be obtained.

By using surface oxidized 7'11-/IJ ethylene powder, no surfactant is required, and bubbles are no longer generated in the coating solution, so the resulting photoreceptor 91
It can provide high image quality without image defects.

Agent Patent Attorney Johei Yamashita

Claims (1)

[Claims] An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the surface layer contains polyethylene powder subjected to surface oxidation treatment.