JPH0477748A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To decrease the residual charges of the electrophotographic sensitive body and to obtain good images which do not generate scumming in the images even if the photosensitive body is used in a high-speed copying machine by exposing a metal oxide at the free boundary of a protective layer formed by dispersing metal oxide particles into a binder resin. CONSTITUTION:The metal oxide powder is dispersed by a method, such as ball mill or bead mill, into the binder resin. Such binder resin is applied on a photoconductive layer and after the coating is dried and cured, the surface is subjected to finishing, such as lapping and polishing, by which the protective layer is formed. The surface roughness 15 of the protective layer formed in such a manner is specified to <=0.07mum center line average height, <=0.6mum max. height and <=0.5mum ten point average roughness. The metal oxide powder is exemplified by powders of ZnO, TiO2, SnO2, In2O3, Sb3O2-contg. SnO2, In2O3- contg. SnO2, V2O5, MoO3, NiO, etc. The electrophotographic sensitive body obtd. in such a manner prevents the accumulation of the charges at the free boundary of the protective layer and suppresses the residual potential in the copying machine and the scumming on the images. The good images are thus obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a surface protective layer in which metal oxide powder is dispersed in a binder resin. .

[Conventional technology]

Conventionally, electrophotographic photoreceptors include those in which a photoconductive layer mainly made of selenium or a selenium alloy is provided on a conductive support, and those in which an inorganic photoconductive material such as zinc oxide or cadmium oxide is dispersed in a binder. , those using organic photoconductive materials such as poly-h-vinylcarbazole, trinitrofluorenone, or azo pigments, and those using amorphous silicon are generally known.

For these photoreceptors, the demand for reliability that maintains high image quality for a long period of time is increasing year by year. However, when the photoconductive layer is exposed, damage caused by corona discharge during the charging process and physical or chemical damage caused by contact with other members during the copying process shorten the life of the photoreceptor.

As a method for eliminating such drawbacks, a technique is known in which a protective layer is provided on the surface of the photoreceptor. Specifically, a method of providing an organic film on the surface of a photosensitive layer (Japanese Patent Publication No. 38-1544
6), Method of providing inorganic oxide (Japanese Patent Publication No. 43-1451
7) After providing an adhesive layer, a-5i layer, a-5i:N:8 layer, a-5i layer, a-5i:N:8 layer,
a-5i: Method of laminating O:HM etc. (Japanese Unexamined Patent Publication No. 57-1
No. 7985'l, JP-A-59-58437) is disclosed.

However, the protective layer has high electrophotographic resistance (1014
Ω·011 or more), problems arise such as an increase in residual potential and accumulation during repetition, which is not preferred in practice.

As a technique to compensate for the above drawbacks, a method of using a photoconductive layer as a protective layer (Japanese Patent Publication No. 4B-38427, Japanese Patent Publication No. 43-16198,
Special Publication No. 49-10258, USP-2901348),
A method of adding a transfer agent such as a dye or a Lewis acid to the protective layer (Japanese Patent Publication No. 44-834, Japanese Patent Application Laid-Open No. 53-13344)
4), or a method of controlling the resistance of the protective layer by adding metal or metal oxide fine particles (Japanese Unexamined Patent Publication No. 53-3338) has been proposed.

However, in such a case, the protective layer absorbs light and the amount of light reaching the photoconductive layer decreases, resulting in a problem that the sensitivity of the electrophotographic photoreceptor decreases.

From this point of view, as disclosed in Japanese Patent Application Laid-Open No. 57-30846, the average particle size is 0.3. There is a method of making the surface substantially transparent to visible light by dispersing the following metal oxide fine particles as a resistance control agent in the surface protective layer. An electrophotographic photoreceptor having this surface protective layer exhibits little decrease in sensitivity, increases the mechanical strength of the surface protective layer, and improves durability. however.

When this photoreceptor is incorporated into an actual copying machine, there is a drawback that a residual potential is generated, causing background stains on the image. This residual potential is generated by residual charges accumulated on the surface protective layer, and increases significantly as the copying speed increases.

[Problem to be solved by the invention]

The present invention has been made in view of these circumstances, and it reduces the residual charge of an electrophotographic photoreceptor having a protective layer in which a metal oxide is dispersed in a binder resin, so that even when used in a high-speed copying machine, it is possible to obtain an image of a high quality image. A good image with no background stains can be obtained,
The purpose is to provide a highly reliable electrophotographic photoreceptor.

[Means to solve the problem]

As a result of various studies, the present inventors found that in an electrophotographic photoreceptor having a protective layer in which a metal oxide is dispersed in a binder resin, the metal oxide is completely covered by the binder resin at the free interface of the protective layer. If it is, the charge injection property is poor,
Residual charges accumulate at the free interface of the protective layer, causing surface stains on the image, but if metal oxides are exposed at the free interface of the protective layer, the injection of charged charges into the protective layer improves. They have also found that there is almost no residual charge on the free interface of the protective layer, and it is possible to prevent the occurrence of background stains and the like due to residual potential.

In addition, the surface of the protective layer was polished, and the surface roughness of the protective layer surface in the image area of the photoreceptor was adjusted to a center line average roughness of 0.07.
μm or less, maximum height 0.6. Below and ten point average roughness 0.
By setting it to 5 or less, it is possible to prevent the occurrence of residual potential and background stains caused by residual charges on the free interface of the protective layer.
Furthermore, mechanical strength deteriorates.

It was found that no abnormal images occurred.

The present invention has been made based on these findings.

That is, according to the present invention, in an electrophotographic photoreceptor in which a photoconductive layer and a protective layer in which metal oxide particles are dispersed in a binder resin are sequentially laminated on a conductive support, a metal layer is formed at the free interface of the protective layer. An electrophotographic photoreceptor characterized in that an oxide is exposed is provided, and further a photoconductive layer and a protective layer in which a metal oxide is dispersed in a binder resin are sequentially laminated on a conductive support. In an electrophotographic photoreceptor, the surface roughness of the protective layer has a center line average roughness of 0.07 prn or less and a maximum height of 0.6
Provided is an electrophotographic photoreceptor having a ten point average roughness of 0.5 or less and a ten point average roughness of 0.5 or less.

The present invention will be explained in more detail below.

The photoreceptor according to claim (1) of the present invention is characterized in that the metal compound is exposed at the free interface of the protective layer, and the photoreceptor according to claim (2) is characterized in that the surface roughness of the protective layer is It is characterized by having a center line average roughness of 0.077a or less, a maximum height of 0.6 tones or less, and a ten point average roughness of 0.5R or less.

To form such a protective layer, metal oxide powder is dispersed in a binder resin using a method such as a ball mill or bead mill, and this is applied onto the photoconductive layer. After drying and curing, the surface is rubbed and
It can be formed by applying processing means such as polishing. Specific surface treatment methods include, for example, a method in which a blade or brush-like object is brought into contact with the surface of the photoreceptor and the photoreceptor is rotated, a method in which the photoreceptor is rubbed by vibration and sliding of a grindstone, and a method in which the protective layer is coated with a puff cloth. Examples include a rubbing method, a rubbing method using a puff cloth impregnated with an abrasive, a method using fine particles of appropriate hardness, and a plasma etching method.

When a method using fine particles with appropriate hardness is adopted, fine particles with a Knoop hardness of 600 or more and a particle size of to, in or less, such as AQ203, TiO2, MgO, SiO□ (crystal)
,Si,CeO□,Fe2O,,Cr2O,,Si3N
4. It is desirable to use diamond or the like.

In addition, as a plasma etching method, the reaction chamber is evacuated, an etching gas is introduced, gas plasma is generated by high frequency, etc., and activated ions or neutral radicals are etched onto the surface of the protective layer. Coaxial electrostatic method, parallel plate electrode type single reactive ion etching method, etc. are adopted.

The metal oxide powder according to the present invention is ZnO1Tie.
2.5n02, In2O,,sb, o2-containing SnO□
, In2O3 containing 5n02, ■206, Mob, , Ni
An example is powder such as 01CuO. Two or more of these metal oxides may be mixed.

The binder resin for the surface protective layer according to the present invention is preferably one that is substantially transparent to visible light and has excellent electrical insulation, strength, and adhesive properties. For example, polystyrene, MMA,
n-BMA, polyamide, polyester.

Polyurethane, polycarbonate, polyvinyl acetal, polysilicone, polyvinyl acetal, polyvinyl butyral, ethyl cellulose, melamine resin, and copolymers and mixtures thereof are used.

Furthermore, various additives may be added to the surface protective layer for the purpose of improving adhesion and the like.

The specific resistance of the surface protective layer is 109-1013Ω・Cl1l,
It is preferably 1010 to 1012 Ω·cm, and the optimum mixing weight ratio of the resin and metal oxide powder varies depending on the combination of the selected resin, metal oxide powder, and average particle size thereof.

The thickness of the protective layer according to the present invention is preferably 10 tones or less,
Furthermore, from the viewpoint of passability and strength, 1 to 5 flaws are more preferable.

As the constituent material of the photoconductive layer according to the present invention, Se or Se-based alloys such as 5e-Te, As2Se, etc.; ZnO-
Systems in which particles of II-VI group compounds such as CdS and CdSe are dispersed in resin; organic photoconductive materials such as polyvinylcarbazole and anthracene; and amorphous 51 are used.

Further, as a method for forming the photoconductive layer, methods such as vapor deposition, sputtering, and coating are appropriately selected depending on the material used. The structure of the photoconductive layer is not particularly limited, and may be a single phase or a laminated layer of a charge generation layer containing the photoconductive material as a main component and a charge transport layer containing a donor or acceptor as a main component.

The thickness is 3 to 1001 seconds for a single-layer photoconductive layer, and 0.05 to 3μ for a charge generation layer in a multilayer photoconductive layer.
m, a range of 3 to 100R is appropriate for the charge transport layer.

Additionally, there is an adhesive layer between the surface protective layer and the photoconductive layer to increase adhesion, an electrical barrier layer to prevent charge injection, and an organic photoconductive layer that is attacked by the solvent in the surface protective layer forming solution. A solvent-resistant layer may be provided to prevent this.

As the conductive support according to the present invention, A1. Ni,F
e. Metal or alloy such as Cu-Au: A1. Examples include those provided with a metal film such as Ag or Au or a metal oxide film such as In2O, SnO2, etc.; electrically conductive treated paper, etc. Although the shape is not particularly limited, it is usually plate-shaped, drum-shaped, or belt-shaped.

〔Example〕

The present invention will be explained below by way of examples.

Example 1 An A1 drum support of 80 mmφ x 340 m+n (length) was set in a vacuum evaporation apparatus, and 7s2Se and alloy were placed in the evaporation source boat of this apparatus, and the vacuum degree was 3 x 10.
-' Torr, support temperature 200°C, boat temperature 45
Vapor deposition was performed at 0° C. to form a photoconductive layer with a thickness of 60 mm on the support.

Next, on top of this, a) a polysiloxane containing an alkoxy group, b) a polysiloxane containing a hydroxyl group, and C) at least one amino group, imino group, or nitrile group bonded to the carbon atom.
Silicone resin A (
AY42-440) manufactured by Toray Silicone Co., Ltd. and the above a),
Which equivalent amount (weight) of silicone resin B (AV42-441 manufactured by Toray Silicone Co., Ltd.) with different component ratios of b) and C)
A groin solution of the mixture was applied and dried at 120° C. for 1 hour to form an electrical barrier layer with a thickness of 0.15 mm. Next, 30 parts by weight of a 40vt% toluene-butanol (9:1 ratio) solution of styrene-methacrylic acid-acrylic acid-N-methylol acrylamide copolymer and a resistance control agent SnO
□ (S-1 manufactured by Mitsubishi Metals) 18 parts by weight and an appropriate amount of toluene-butanol (9:l ratio) mixed solvent were mixed in a ball mill.
Dispersed for 6 hours, coated on the electrical barrier layer,
Drying was performed at 30° C. for 30 minutes to form a protective layer with a thickness of 4 ptn. Next, an electrophotographic photoreceptor was obtained in which this protective layer was formed, a urethane rubber node was brought into contact with the photoreceptor, and the photoreceptor was rotated to atomize SnO2 onto the free interface of the protective layer.

Example 2 An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the metal oxide in the protective layer was changed from SnO□ to In2O3.

Example 3 An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the metal oxide in the protective layer was changed from 5nO7 to NjO.

Comparative Example 1 An electrophotographic photoreceptor was produced in exactly the same manner as in Example 1, except that the step of exposing SnO to the free interface of the protective layer was not performed.

Comparative Example 2 An electrophotographic photoreceptor was produced in exactly the same manner as in Example 2, except that the step of exposing In, , O3 to the free interface of the protective layer was not performed.

Comparative Example 3 An electrophotographic photoreceptor was produced in exactly the same manner as in Example 3, except that the step of exposing NiO to the free interface of the protective layer was not performed.

The electrophotographic photoreceptor produced as described above is used in an actual copying machine (
It was installed in Ricoh's FT6550) and the residual potential inside the actual machine and the background stain were evaluated. The results are shown in Table-1. In addition,
The residual potential is the potential measured after charging and Isis exposure. In addition, skin stains were visually observed.

Table 1 As is clear from Table 1, the electrophotographic photoreceptor of the comparative example in which the metal oxide was not exposed on the free interface of the protective layer had a high residual potential and had severe background staining, whereas the photoreceptor of the present invention It can be seen that the electrophotographic photoreceptor has a low residual potential because the metal oxide is exposed at the free interface of the protective layer, and is good in that it does not cause background stains.

The protective layers of Examples 1 to 3 and Comparative Examples 1 to 3 were peeled off and the cross sections were examined using a transmission electron microscope! When tested, it was found that in Examples 1 to 3, the metal oxide was exposed at the free interface of the protective layer, whereas in Comparative Examples 1 to 3, the metal oxide was completely covered at the free interface of the protective layer. It turns out.

Example 4 An A1 drum support of 80 mm φ x 340 mm (length) was set in a vacuum evaporation apparatus, and As2Se3 alloy was put in the evaporation source bow 1 of this apparatus, and the vacuum degree was 3 x 10.
'Torr, support temperature 200℃, port temperature 450℃
Vapor deposition was carried out at 0.degree. C. to form a photoconductive layer with a thickness of 60 Aun on the support.

Next, on top of this, a) a polysiloxane containing an alkoxy group, b) a polysiloxane containing a hydroxyl group, and C) at least one amino group, imino group, or nitrile group bonded to the carbon atom.
Silicone resin A (
AY42440 manufactured by Tone Silicone Co., Ltd.) and the above a) and b
) and silicone resin B (AY42-441 manufactured by Tone Silicone Co., Ltd.) having different component ratios. An electrical barrier layer was formed. Next, 30 parts by weight of a 40 wt% toluene-butanol (9:1 ratio) solution of styrene-methacrylic acid-acrylic acid-N-methylolacrylamide copolymer and 5 n of a resistance control agent.
02 (S-1 manufactured by Mitsubishi Metals) and an appropriate amount of toluene-butanol (9:1 ratio) mixed solvent were dispersed in a ball mill for 96 hours, and this was applied onto the electrical barrier layer.
Drying was performed at 130° C. for 30 minutes to form a protective layer with a thickness of 4 square meters. Next, this photoconductor was installed in a copying machine (Ref-type FT6550) in which a polyurethane cleaning blade and a polyester cleaning brush are brought into contact with the photoconductor, and the photoconductor was rubbed for 2 hours in non-sheet copy mode to protect it. An electrophotographic photoreceptor was produced in which the surface roughness of the layer was 0.047× in center line average roughness, 0.57 m in maximum height, and 0.45 μm in 10-point average width.

Example 5 The same procedure was used as in Example 1 except that the rubbing time in Example 1 was changed to 10 hours, and the surface roughness of the protective layer was set to 0.00000.
03 houses, maximum height 0.3 pxl, ten point average roughness 0.36
A unique electrophotographic photoreceptor was fabricated.

Example 6 A protective layer was prepared in the same manner as in Example 4, except that the polishing step was replaced with rubbing with 2000-grit sandpaper. An electrophotographic photoreceptor having a cape of .32 and a ten-point average roughness of 0.34 was produced.

Comparative Example 4 The same procedure as Example 4 was carried out except that the polyester cleaning brush was replaced with a stainless steel loop-shaped cleaning brush, and the surface roughness of the protective layer was 0.08p in center line average roughness.
An electrophotographic photoreceptor having a maximum height of 1.2 and a ten-point average roughness of 0.8 prn was produced.

Comparative Example 5 The same procedure as in Example 6 was carried out except that the 2000 grit sandpaper was replaced with the 100 grit sandpaper, and the surface roughness of the protective layer was set to a center line average roughness of 0.1.0/ja and a maximum height. 0.
No. 8, an electrophotographic photoreceptor having a ten-point average roughness of 0.867 m was produced.

The electrophotographic photoreceptor produced as described above is used in an actual copying machine (
It was incorporated into a ref-type FT-6550), and the residual potential in the actual machine, background stains, uniformity of halftone images, cleanability, and pencil hardness of the protective layer were evaluated. Table 2 of the results
Shown below.

Residual potential: Charging - Evaluate the potential after exposure to Isis Cleanability: Evaluate the amount of toner remaining on the photoreceptor after copying Background stain: Evaluate the background stain of the copied image by visual inspection Halftone image uniformity: Half of the copied image Visually evaluate the uniformity of tone Pencil hardness: Under a load of 100 g As is clear from evaluation table 2, the surface roughness of the protective layer is 0.07 degrees or less in center line average roughness and 0.6 degrees or less in maximum height. If the condition of 10-point average roughness of 0.5 or less is not satisfied, even if it is possible to prevent surface staining due to residual potential, surface staining occurs due to poor cleaning, and furthermore, the strength of the coating film is significantly reduced. On the contrary, the electrophotographic photoreceptors of Examples 4 to 6 according to the present invention not only suppressed background stains caused by residual potential, but also
It has good cleaning properties and coating strength, with no side effects.

After carrying out a copying test of 50,000 sheets each for the electrophotographic photoreceptors of Example 4 and Comparative Example 4, the wear amount of the protective layer was evaluated, and it was found that the average decrease in film thickness of Comparative Example 4 was 0. It was found that the thickness of Example 1 according to the present invention was 0, and that it was also excellent in abrasion resistance in a copying machine.

〔Effect of the invention〕

As explained above, the electrophotographic photoreceptor of claim (1) can prevent the accumulation of charge at the free interface of the protective layer, and can suppress residual potential in the copying machine and background stains on the image. ,
It is highly reliable as it provides good images. In addition, the electrophotographic photoreceptor of claim (2) can prevent the accumulation of charges at the free interface of the protective layer, suppress residual potential in a copying machine, and background stains on images, as well as It is extremely reliable as it allows good images to be obtained without impairing coating film strength or abrasion resistance.

Patent applicant Rico Co., Ltd.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor in which a photoconductive layer and a protective layer in which metal oxide particles are dispersed in a binder resin are sequentially laminated on a conductive support, the metal oxide is exposed at the free interface of the protective layer. An electrophotographic photoreceptor characterized by: (2) In an electrophotographic photoreceptor in which a photoconductive layer and a protective layer in which metal oxide particles are dispersed in a binder resin are sequentially laminated on a conductive support, the surface roughness of the protective layer is center line average roughness. A photoreceptor for electrophotography, characterized in that the height is 0.07 μm or less, the maximum height is 0.6 μm or less, and the ten-point average roughness is 0.5 μm or less.