JPH0635219A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide the photosensitive body having a low residual potential without changing the content of the conductive fine powder in a binder resin of a protective layer by controlling the moisture content incorporated into the protective layer within a specific range. CONSTITUTION:This photosensitive body has a laminated structure and is laminated successively with an amorphous photoconductive layer 2 and a charge implantation blocking layer 3 on a conductive base 1. The surface thereof is provided with the protective layer 4. The charge implantation blocking layer 3 is formed by applying a soln. mixture composed of a zirconium chelate compd. or zirconium alkoxide and silane coupling agent and curing the coating. The protective layer 4 is formed by incorporating a compd. formed by making an electron-donating material conductive or incorporating conductive fine powder into a binder resin. The content in the protective layer 4 is required to be set in a 0.2 to 2.5wt.% range. The residual potential is too high if the moisture content is lower than 0.2wt.%. Resolving power is low and such low resolving power is undesirable if the content is higher than 2.5wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member having a low residual potential and a saturated residual potential.

[0002]

2. Description of the Related Art It is known that the life of an electrophotographic photosensitive member is mainly governed by factors such as deterioration in electrical characteristics, generation of scratches on the surface, and alteration (especially thermal change) of the photosensitive material itself. ing. When an amorphous photoconductive material such as amorphous selenium is used for the photoconductive layer, the surface of the photoconductive layer is easily scratched, and therefore, a protective layer is provided to extend the life. However, when the protective layer is provided, the residual potential tends to remain as compared with the electrophotographic photosensitive member without the protective layer, and the residual potential tends to accumulate due to repeated use, which causes fog in the background portion. It is also becoming. The accumulation of this residual potential is described in, for example, Japanese Patent Laid-Open No. 57-
Tin oxide, as disclosed in 128344.
Include conductive fine powder such as antimony oxide in the protective layer,
This can be solved by increasing the content of the conductive fine powder in the binder resin, but in this case, there is also a tradeoff with resolution, and in order to eliminate the accumulation of residual potential without reducing resolution. However, there is a problem that the selection range of the addition amount of the conductive fine powder is narrow.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned actual situation of the prior art. That is, an object of the present invention is to provide an electrophotographic photoreceptor having a low residual potential without changing the content of the conductive fine powder in the binder resin in the protective layer.

[0004]

As a result of various studies, the present inventors have found that the above object can be achieved by adjusting the amount of water contained in the protective layer within a certain range. It came to completion. That is, the electrophotographic photosensitive member of the present invention, an amorphous photoconductive layer, on the conductive support,
The charge injection blocking layer and the protective layer are sequentially laminated, and the water content of the protective layer is 0.2 to 2.5% by weight. The water content in the present invention is
It is a value obtained by the Karl Fischer method after removing the protective layer from the electrophotographic photoreceptor.

The present invention will be described in detail below. Figure 1
FIG. 3 is a schematic cross-sectional view of the electrophotographic photosensitive member of the present invention. The electrophotographic photosensitive member of the present invention has a laminated structure and has a conductive support 1
An amorphous photoconductive layer 2 and a charge injection blocking layer 3 are sequentially stacked on top of this, and a protective layer 4 is provided on the surface.

As the above-mentioned conductive support, any support can be used as long as it can be used as an electrophotographic photoreceptor. Specifically, in addition to metals such as aluminum, nickel, chromium, and stainless steel, plastic films coated with thin films of aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, ITO, etc. Etc. or paper and plastic film coated or impregnated with a conductivity-imparting agent. These conductive supports are used in a suitable shape such as a drum shape, a sheet shape, and a plate shape, but are not limited thereto. Further, if necessary, the surface of the conductive support may be subjected to various treatments within a range that does not affect the image quality, for example, surface oxidation treatment, chemical treatment and coloring treatment, or irregular reflection treatment such as graining. It can be performed.

In the present invention, the amorphous photoconductive layer can be formed using various known materials. For example,
Selenium and Se-Te alloy, Se-As alloy, Se-
Sb alloy, Se-Bi alloy and other selenium alloys or Cd
It can be formed by vapor-depositing a cadmium compound such as S, CdSSe, CdSe on the support. The thickness of the amorphous photoconductive layer is generally 20 to 80 μm.
It is set to the range of.

The charge injection blocking layer formed on the amorphous photoconductive layer can be formed by applying a mixed solution of a zirconium chelate compound or zirconium alkoxide and a silane coupling agent and curing it. The mixing ratio of the zirconium chelate compound or zirconium alkoxide and the silane coupling agent is Z
The r / Si molar ratio is preferably in the range of 2/1 to 4/1.

Specific examples of the zirconium chelate compound or zirconium alkoxide include zirconium tetraacetylacetonate, zirconium tetrabutoxide, and tributoxyzirconium acetylacetonate. As the silane coupling agent, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris-silane, etc.
2-methoxyethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane,
γ-methacryloxypropyltrimethoxysilane, γ-
Aminopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-2-aminoethylaminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, β-3,4-epoxycyclohexyl Examples thereof include ethyltrimethoxysilane.

Examples of the solvent for dissolving the zirconium compound and the silane coupling agent include alcohols such as ethanol, methanol, propanol, butanol and amyl alcohol, aromatic hydrocarbons such as toluene, ethyl acetate and cellosolve. Esters such as acetate can be used alone or in combination. The thickness of the charge injection blocking layer can be arbitrarily determined, but is usually set in the range of 0.1 to 0.5 μm.

The protective layer provided on the surface of the electrophotographic photosensitive member of the present invention is formed by containing a compound in which an electron-donating substance is made conductive or conductive fine powder in a binder resin.
As the electron-donating substance, a metallocene compound such as dimethylferrocene, an aromatic amino compound such as N, N′-diphenyl-N, N′-bis- (m-tolyl) benzidine,
Materials such as metal oxides such as antimony oxide, tin oxide, titanium oxide, indium oxide, and tin oxide-antimony oxide can be used as the conductive fine powder, but the conductive fine powder is not limited thereto. As the binder resin used for this protective layer, known resins such as polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin, polyvinylketone resin, polystyrene resin, and polyacrylamide resin can be used. However, a remarkable effect can be obtained especially with a protective layer using a polyurethane resin or a polycarbonate resin. The conductive fine powder has a primary particle diameter of 0.2 to 1.
Those having a range of 2 μm are used. The ratio of the conductive fine powder in the binder resin is 30% of the conductive fine powder with respect to the binder resin.
It is preferable to set it in the range of 60 wt%. These materials are dissolved and dispersed in an appropriate organic solvent to prepare a coating solution, which is coated on the charge injection blocking layer.

The coating method adopted when forming the above-mentioned protective layer is usually a blade coating method, a Mayer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method or the like. The method of can be used. The thickness of this protective layer is 0.5 to 20 μm.
m, preferably 1-10 μm.

In the present invention, the water content in the protective layer is
It is necessary to set in the range of 0.2 to 2.5% by weight. If the water content is less than 0.2% by weight, the residual potential will be too high, and if it is more than 2.5% by weight, the resolution will decrease, which is not preferable. The water content in the protective layer is adjusted by forming the protective layer using the above-mentioned material, and thereafter, for 12 hours to 24 hours under high temperature and high humidity at a temperature of 25 to 35 ° C. and a humidity of 80 to 90% RH.
It can be performed by leaving it to stand for a time.

[0014]

In the electrophotographic photoreceptor of the present invention, the reason why the residual potential is not accumulated when the protective layer contains a predetermined amount of water is presumed as follows. That is, an organic resin film made of conductive fine powder and a binder resin that forms a protective layer attracts water molecules into the polymer matrix, and the aspirated water dissolves impurities in the polymer matrix to form an organic resin. It is presumed that the resistance of the film is lowered, and as a result, the residual potential is not accumulated in the protective film. Moisture sucked into the polymer matrix is 50 ° C, 10% RH
No significant decrease is observed even after standing for 48 hours in the above environment. Next, when the photoconductor after being left standing for 24 hours in an environment of 80 ° C. and 5% RH was mounted on a copying machine, and a copy was taken, a slight fog was recognized in the background portion after about 7,000 continuous copies. Therefore, it is confirmed that the effect of reducing the residual potential due to the water content is reduced. As a result, water is not removed at the temperatures normally used in copying operations. The method of the present invention for reducing the residual potential by including the above-mentioned amount of water in the protective layer is applicable not only to the protective layer of the inorganic electrophotographic photoreceptor but also to the protective layer of the organic electrophotographic photoreceptor. Is also applicable.

[0015]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. Example 1 Arsenic selenide (As ₂ Se ₃ ) containing 1900 ppm of iodine and 37.5% by weight of arsenic (As ₂ Se ₃ ) was applied to an aluminum pipe having a diameter of 84 mm and a length of 410 mm under a vacuum of 10 ⁻⁵ Torr to have a film thickness of 60 μm. Thus, a selenium photosensitive layer was formed. Zirconium acetylacetonate and vinyltrimethoxysilane were added, an amyl alcohol was used as a solvent to prepare a coating solution, which was coated on the selenium photosensitive layer and dried to form a charge injection blocking layer having a thickness of about 0.1 μm. Formed. Further, an ultrafine powder of tin oxide having an average particle size of 0.7 μm was added to a polyurethane clear base and dispersed by a ball mill for 12 hours, and then an isocyanate cross-linking agent was added to the resulting dispersion to form a coating solution for forming a protective layer. Was prepared. This coating solution is applied on the charge injection blocking layer and dried to form a protective layer having a film thickness of about 7 μm, and the temperature is 30 ° C. and 90% R.
It was allowed to stand in the H environment for 24 hours. Next, the electrophotographic photosensitive member was taken out, the protective layer was peeled off, and the water content was measured by the Karl Fischer method. As a result, the water content was 2.5% by weight. This electrophotographic photoreceptor is used as a copying machine (FX47
It was mounted on a No. 00 Fuji Xerox Co., Ltd.), copying was performed, and the residual potential at the developing position was measured to be about 20V. Further, when copying was continued and the residual potential was measured at about 2000 sheets, the residual potential was about 50V.

Example 2 An electrophotographic photosensitive member having a protective layer formed was prepared in the same manner as in Example 1, and this electrophotographic photosensitive member was prepared in the same manner as in Example 1 under the environment of 22 ° C. and 70% RH. It was allowed to stand for 24 hours, the water content was adjusted, and the water content was measured.
It was 1.0% by weight. This electrophotographic photosensitive member was used in Example 1.
The residual potential was measured in the same manner as in. The initial residual potential at the developing position was about 70V, and the residual potential after continuous copying of about 3000 sheets was about 120V. At this point, no fog on the background was observed. In addition,
The developing bias in this copying was 350V.

Example 3 An electrophotographic photosensitive member on which a protective layer was formed was prepared in the same manner as in Example 1, and the electrophotographic photosensitive member was processed in the same manner as in Example 1 under the environment of 20 ° C. and 40% RH. Let stand for 24 hours,
When the water content was adjusted and the water content was measured, the water content was
It was 0.2% by weight. This electrophotographic photosensitive member was used in Example 1.
The residual potential was measured in the same manner as in. The residual potential at the first developing position was about 95V, and the residual potential after continuous copying of about 5000 sheets was about 160V. At this point, no fog on the background was observed. In addition,
The developing bias in this copying was 400V.

Comparative Example 1 An electrophotographic photosensitive member having a protective layer formed thereon was prepared in the same manner as in Example 1, and the electrophotographic photosensitive member was immersed in pure water at 80 ° C.
It was immersed for a period of time to adjust the water content. When the water content was measured in the same manner as in Example 1, the water content was 3.2% by weight. Next, the electrophotographic photosensitive member is transferred to a copying machine (FX470
(0 Fuji Xerox Co., Ltd.), copying was performed and a copy was taken. As a result, a reduction in resolution was observed, and the resolution of 5 lines / mm was insufficient, resulting in a poorly sharp image overall. When the residual potential at the developing position was measured,
It was about 20V. After that, about 5,000 sheets were continuously copied, and the residual potential was measured.
It remained V.

Comparative Example 2 An electrophotographic photosensitive member having a protective layer was prepared in the same manner as in Example 1 except that the water content was not adjusted, and the water content was measured. The water content was 0. It was 0.1% by weight. This electrophotographic photosensitive member was mounted on a copying machine (FX4700, manufactured by Fuji Xerox Co., Ltd.), copying was performed, and the residual potential at the developing position was measured. As a result, a residual potential of about 100 V was observed. Next, when it was mounted on a developing machine and about 5,000 sheets were continuously copied, some fog was generated in the background portion around the 4,000th sheet, and this fog could not be suppressed by adjusting the developing bias. When the residual potential at the developing position at this time was measured, it was about 170V. Further, even after copying up to 100 sheets in succession, there was no change in the fog condition of the background portion.

The following Table 1 shows the relationship between the water content conditions for containing the protective layer described in the above Examples and Comparative Examples, the water content of the produced electrophotographic photosensitive member, the residual potential and the resolution. . Further, FIG. 2 is a plot of the water content and the residual potential (RP) in the protective layer shown in Table 1. As is clear from the description in Table 1 and FIG. 2, the residual potential tends to increase as the water content decreases, while the residual potential decreases as the water content increases, but the resolution tends to deteriorate. The water content is preferably in the range of 0.2 to 2.5% by weight from the viewpoint of balance between residual potential and resolution.

[0021]

[Table 1]

[0022]

EFFECTS OF THE INVENTION The electrophotographic photosensitive member of the present invention having the above-mentioned structure has a low residual potential level when used for image formation, and the residual potential increases with repeated copying. There is no. Therefore, even if copying is repeated, a sufficient electric potential is secured in the background cleaning field, and fog does not occur in the background even if the performance of the developer deteriorates.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an electrophotographic photosensitive member of the present invention.

FIG. 2 is a graph showing the relationship between the water content in the protective layer and the residual potential in the electrophotographic photosensitive member of the present invention.

[Explanation of symbols]

1 ... Conductive support, 2 ... Amorphous photoconductive layer, 3 ... Charge injection blocking layer, 4 ... Protective layer

Claims (1)

[Claims] 1. An electrophotographic photoreceptor comprising a conductive support, and an amorphous photoconductive layer, a charge injection blocking layer and a protective layer, which are laminated in this order, and the protective layer has a water content of 0.2 to 2. An electrophotographic photosensitive member characterized by being 0.5% by weight.