JP3484475B2 - Electrophotographic photoreceptor and electrophotographic apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor and an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic photosensitive member, a photoconductive layer mainly composed of selenium or a selenium alloy is provided on a conductive support, or an inorganic photoconductive material such as zinc oxide or cadmium oxide is used as a binder. Dispersed in poly-N
Those using an organic photoconductive material such as vinylcarbazole and trinitrofluorenone or an azo pigment, and those using amorphous silicon are generally known. The demand for reliability of keeping high image quality for a long time is increasing for these photoconductors year by year. However, when the photoconductive layer is exposed, damage due to corona discharge during the charging process and physical or chemical damage due to contact with other members during the copying process impairs the life of the photoconductor. As a method of solving such a defect, a technique of providing a protective layer on the surface of the photoconductor is known. Specifically, a method of providing an organic film on the surface of the photosensitive layer (Japanese Patent Publication No. 38-15446), a method of providing an inorganic oxide (Japanese Patent Publication No. 43-14517), a method of laminating an insulating layer after providing an adhesive layer ( JP-B-43-275
91), or an a-Si layer, an a-Si: N: H layer, an a-Si: O: by a plasma CVD method, a photo CVD method, or the like.
Methods for laminating H layers and the like (JP-A-57-179859 and JP-A-59-58437) are disclosed. However, when the protective layer becomes electrophotographically high in resistance (10 ¹⁴ Ω · cm or more), the residual potential increases, accumulation during repetition and the like become problems, which is not preferable in practice. As a technique for compensating the above-mentioned drawbacks, a method in which a protective layer is a photoconductive layer (Japanese Patent Publication No. 48-384)
27, Japanese Patent Publication 43-16198, Japanese Patent Publication 49-1025
8, USP-2901348), a method of adding a transfer agent typified by a dye or a Lewis acid into the protective layer (Japanese Patent Publication No. 44-44-
834, JP-A-53-133444), or a method of controlling the resistance of the protective layer by adding metal or metal oxide fine particles (JP-A-53-3338). However, in such a case, the light absorption by the protective layer occurs and the amount of light reaching the photoconductive layer is reduced, resulting in a problem that the sensitivity of the electrophotographic photoreceptor is lowered. From such a viewpoint, as disclosed in JP-A-57-30846, by dispersing metal oxide fine particles having an average particle diameter of 0.3 μm or less as a resistance control agent in the surface protective layer, it is possible to prevent visible light. There is a method of making it substantially transparent. The electrophotographic photosensitive member having the surface protective layer has less deterioration in sensitivity, the mechanical strength of the surface protective layer is increased, and the durability is improved. However, when this photoconductor is incorporated into an actual copying machine, there is a drawback that a residual potential is generated and a background stain is generated on an image. This residual potential is generated by the residual charges accumulated on the surface protective layer, and remarkably increases as the copying speed increases.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of these circumstances, and reduces the residual charge of an electrophotographic photoreceptor having a protective layer in which a metal oxide is dispersed in a binder resin, An object of the present invention is to provide a highly reliable electrophotographic photoreceptor which can obtain a good image without causing background stains even when used in a high speed copying machine.

[0004]

As a result of various investigations by the present inventors, in an electrophotographic photoreceptor having a protective layer in which a metal oxide is dispersed in a binder resin, the metal oxide is contained in the binder resin. By rubbing or polishing the surface of the protective layer in which the particles are dispersed, the surface roughness of the protective layer surface is center line average roughness 0.07 μm or less, maximum height 0.6 μm or less, and ten-point average. When smoothing to a roughness of 0.5 μm or less,
Residual potential due to residual charge on the free interface of the protective layer, generation of stains on the ground surface, etc. can be prevented, and further deterioration of mechanical strength,
It was found that no abnormal image was generated at all.

The present invention has been made based on these findings. According to the present invention, the following inventions are provided. 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 of the protective layer is rubbed against the surface of the protective layer. Alternatively, the surface roughness of the protective layer surface is smoothed to a center line average roughness of 0.07 μm or less, a maximum height of 0.6 μm or less, and a ten-point average roughness of 0.5 μm or less by performing a polishing process. An electrophotographic photoreceptor characterized by: In an electrophotographic apparatus including at least an electrophotographic photosensitive member,
An electrophotographic apparatus comprising the electrophotographic photosensitive member described above as an electrophotographic photosensitive member.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION To form a protective layer of the present invention, a metal oxide powder is dispersed in a binder resin by a method such as a ball mill or a bead mill, coated on a photoconductive layer, dried and cured, It can be formed by applying processing means such as rubbing or polishing the surface. Specific surface processing means include, for example, a method in which a blade or a brush-shaped object is brought into contact with the surface of the photoconductor and the photoconductor is rotated, a method of rubbing with the vibration and sliding of a grindstone, and a protective layer with a buff cloth. Examples thereof include a method of rubbing, a method of rubbing a buff cloth with an abrasive, a method of using fine particles having an appropriate hardness, and a method of using a plasma etching method. When the method using fine particles of appropriate hardness is adopted, Knoop hardness is 600 or more and particle diameter is 10μ.
fine particles of m or less such as Al ₂ O ₃ , TiO ₂ , MgO,
SiO ₂ (crystal), Si, CeO ₂ , Fe ₂ O ₃ , Cr
It is desirable to use ₂ O ₃ , Si ₃ N 4, diamond or the like. Further, as the plasma etching method, after the reaction chamber is evacuated, an etching gas is introduced, a gas plasma is generated by a high frequency or the like, and an activated ion or neutral radical is etched on the protective layer surface,
For example, a coaxial electrostatic system, a parallel plate electrode type, a reactive ion etching method, etc. are adopted.

As a metal oxide powder used in the present invention
Is ZnO, TiO₂, SnO₂, In ₂O₃, Sb₃O₂Inclusion
SnO₂, In₂O₃Contained SnO₂, V₂O₃, MoO₃, N
The powder of iO, CuO, etc. can be illustrated. Oxidation of these metals
Two or more kinds of materials may be mixed.

The binder resin for the surface protective layer according to the present invention is substantially transparent to visible light and has electrical insulation, strength, and
Those with excellent adhesiveness are desirable. For example, polystyrene, MMA, n-BMA, polyamide, polyester,
Polyurethane, polycarbonate, polyvinylholimal, polysilicone, polyvinyl acetal, polyvinyl butyral, ethyl cellulose, melamine resin and copolymers and mixtures thereof are used. Further, various additives may be added to the surface protective layer for the purpose of improving adhesiveness and the like.

The specific resistance of the surface protective layer is 10 ⁹ to 10 ¹³ Ω.
cm, preferably 10 ¹⁰ to 10 ¹² Ω · cm, and the optimum mixing weight ratio of the resin and the metal oxide powder varies depending on the combination of the selected resin, the metal oxide powder and the average particle size thereof.

The thickness of the protective layer of the present invention is preferably 10 μm or less, and more preferably 1 to 5 μm from the viewpoints of superpermeability and strength. As the constituent material of the photoconductive layer according to the present invention, Se or Se-based alloys such as Se to Te and As ₂ Se ₃ ; particles of II-VI group compounds such as ZnO, CdS, and CdSe are dispersed in a resin. A system; organic photoconductive materials such as polyvinylcarbazole and anthracene; amorphous Si and the like are used. Further, as a method for forming the photoconductive layer, a method such as vapor deposition, sputtering or coating is appropriately selected depending on the material used. The structure of the photoconductive layer is not particularly limited, and it may be a single phase or a stacked layer of a charge generation layer containing the photoconductive material as a main component and a charge transport layer containing a donor or an acceptor as a main component. The thickness of the single-layer photoconductive layer is preferably 3 to 100 μm, the thickness of the multilayer photoconductive layer is 0.05 to 3 μm for the charge generation layer, and the charge transport layer is preferably 3 to 100 μm. Furthermore, the organic photoconductive layer is attacked by an adhesive layer for enhancing the adhesiveness between the surface protective layer and the photoconductive layer, an electrical barrier layer for preventing charge injection, and a solvent in the surface protective layer forming liquid. You may provide the solvent resistant layer which prevents that.

As the conductive support of the present invention, Al, N
Metals or alloys such as i, Fe, Cu and Au: Metal films such as Al, Ag and Au or metals such as In ₂ O ₃ and SnO ₂ on an insulating substrate such as plastic or glass such as polyester, polycarbonate and polyimide. The one provided with an oxide film; conductive treated paper and the like can be exemplified. The shape is not particularly limited, but is usually a plate shape, a drum shape or a belt shape.

[0012]

EXAMPLES The present invention will be described below with reference to examples. Reference Example 1 An 80 mmφ × 340 mm (length) Al drum support was set in a vacuum vapor deposition apparatus, an As ₂ Se ₃ alloy was placed in a vapor deposition source boat of this apparatus, and a vacuum degree was 3 × 10 ⁻⁶ To.
Vapor deposition was performed under the conditions of rr, the support temperature of 200 ° C., and the boat temperature of 450 ° C. to form a photoconductive layer having a thickness of 60 μm on the support. Next, a) an alkoxy group-containing polysiloxane, b) a hydroxyl group-containing polysiloxane, and c) at least one amino group, imino group or nitrile group bonded to a carbon atom, and two or three alkoxy groups bonded thereto. Silicone resin A (AY42-440 manufactured by Toray Silicone Co., Ltd.) containing a silicon atom-containing organosilicon compound as a main component and silicone resin B having a different component ratio of a), b) and c)
A ligroin solution of an equal amount (weight) mixture with (Toray Silicone AY42-441) was applied and dried at 120 ° C. for 1 hour to form an electric barrier layer having a thickness of 0.15 μm. Next, styrene-methacrylic acid-acrylic acid-N
30 parts by weight of a 40 wt% toluene-butanol (9: 1 ratio) solution of a methylol acrylamide copolymer, 18 parts by weight of a resistance control agent SnO ₂ (S-1 manufactured by Mitsubishi Metals) and an appropriate amount of toluene-butanol (9: 1). (Ratio) The mixed solvent was dispersed in a ball mill for 96 hours, and this was applied onto the electrical barrier layer and dried at 130 ° C. for 30 minutes to form a protective layer having a thickness of 4 μm. Next, a urethane rubber blade was brought into contact with the photoconductor on which the protective layer was formed, and the photoconductor was rotated to obtain an electrophotographic photoconductor in which SnO ₂ was exposed at the free interface of the protective layer.

Reference Example 2 An electrophotographic photosensitive member was produced in exactly the same manner as in Reference Example 1 except that the metal oxide in the protective layer was changed from SnO ₂ to In ₂ O ₃ .

Reference Example 3 An electrophotographic photoreceptor was prepared in exactly the same manner as in Reference Example 1 , except that the metal oxide in the protective layer was changed from SnO ₂ to NiO.

Comparative Example 1 An electrophotographic photoreceptor was prepared in exactly the same manner as in Reference Example 1 except that the step of exposing SnO ₂ to the free interface of the protective layer was not performed.

Comparative Example 2 An electrophotographic photosensitive member was produced in exactly the same manner as Reference Example 2 except that the step of exposing In ₂ O ₃ to the free interface of the protective layer was not performed.

Comparative Example 3 An electrophotographic photosensitive member was manufactured in exactly the same manner as Reference Example 3 except that the step of exposing NiO to the free interface of the protective layer was not performed. The electrophotographic photosensitive member produced as described above was incorporated into an actual copying machine (FT6550 manufactured by Ricoh Co., Ltd.), and the residual potential in the actual machine and the background stain were evaluated. The results are shown in Table-1. The residual potential is a potential measured after charging / erasing exposure. The background stain was visually observed.

[0018]

[Table 1]

As is clear from Table 1, the electrophotographic photosensitive member of the comparative example in which the metal oxide is not exposed at the free interface of the protective layer has a high residual potential and therefore has a large background stain. Since the metal oxide is exposed at the free interface of the protective layer, the photoconductor for photographic use has a low residual potential and is a good one without causing background stain. When the protective layers of Reference Examples 1 to 3 and Comparative Examples 1 to 3 were peeled off and their cross sections were observed with a transmission electron microscope, the metal oxides were exposed at the free interfaces of the protective layers in Reference Examples 1 to 3. On the other hand, in Comparative Examples 1 to 3, it was found that the free oxide of the protective layer was completely covered with the metal oxide.

Example 4 An 80 mmφ × 340 mm (length) Al drum support was set in a vacuum vapor deposition apparatus, and a vapor deposition source boat of this apparatus was charged with As ₂ Se ₃ alloy, and the degree of vacuum was 3 × 10 ^−6. Tor
r, the substrate temperature was 200 ° C., and the boat temperature was 450 ° C. to perform vapor deposition to form a photoconductive layer having a thickness of 60 μm on the substrate. Next, a) an alkoxy group-containing polysiloxane, b) a hydroxyl group-containing polysiloxane, and c) at least one amino group, imino group or nitrile group bonded to a carbon atom, and two or three alkoxy groups bonded thereto. Silicone resin A (AY42-440 manufactured by Toray Silicone Co., Ltd.) containing a silicon atom-containing organosilicon compound as a main component and silicone resin B having a different component ratio of a), b) and c)
A ligroin solution of an equal amount (weight) mixture with (Toray Silicone AY42-441) was applied and dried at 120 ° C. for 1 hour to form an electric barrier layer having a thickness of 0.15 μm. Next, styrene-methacrylic acid-acrylic acid-N
30 parts by weight of a 40 wt% toluene-butanol (9: 1 ratio) solution of a methylol acrylamide copolymer, 18 parts by weight of a resistance control agent SnO ₂ (S-1 manufactured by Mitsubishi Metals) and an appropriate amount of toluene-butanol (9: 1). (Ratio) The mixed solvent was dispersed in a ball mill for 96 hours, and this was applied onto the electrical barrier layer and dried at 130 ° C. for 30 minutes to form a protective layer having a thickness of 4 μm. Next, a copier (a FT655 manufactured by Ricoh Co., Ltd.) in which a cleaning blade made of polyutalen and a cleaning brush made of polyester are brought into contact with the photosensitive body
0) and rubbed for 2 hours in non-paper copy mode, and the surface roughness of the protective layer is center line average roughness 0.04μ.
m, the maximum height was 0.5 μm, and the ten-point average roughness was 0.45 μm to prepare an electrophotographic photoreceptor.

Example 5 The surface roughness of the protective layer was the same as in Example 4 except that the rubbing time in Example 4 was 10 hours.
03 μm, maximum height 0.3 μm, ten-point average roughness 0.36
An electrophotographic photosensitive member of μm was manufactured.

Example 6 The surface roughness of the protective layer was 0.04 μm in center line average roughness and maximum height in exactly the same manner as in Example 4 except that the polishing step of the protective layer was changed to rubbing with No. 2000 sandpaper. 0.32
A photoconductor for electrophotography having a thickness of 10 μm and a ten-point average roughness of 0.34 μm was produced.

Comparative Example 4 The surface roughness of the protective layer was the center line average roughness of 0.08 μm in exactly the same manner as in Example 4 except that the polyester cleaning brush was replaced with a stainless loop cleaning brush.
m, the maximum height was 1.2 μm, and the ten-point average roughness was 0.8 μm.

Comparative Example 5 The surface roughness of the protective layer was 0.10 μm in center line average and 0 in maximum height in the same manner as in Example 6 except that the sandpaper No. 2000 was replaced with the sandpaper No. 100. .8μ
m, and a ten-point average roughness of 0.86 μm to prepare an electrophotographic photoreceptor. The electrophotographic photoreceptor prepared as described above is incorporated into an actual copying machine (FT-6550 manufactured by Ricoh), and residual potential in the actual machine, background stain, uniformity of halftone image, cleaning property, and pencil for the protective layer The hardness was evaluated. The results are shown in Table 2. Residual potential: Charge-Evaluation of potential after erase exposure Cleaning property: Evaluation of residual toner amount on photoconductor after copying Background stain: Visual evaluation of background stain of copied image Halftone image uniformity: Half of copied image Visual evaluation of tone uniformity Pencil hardness: Evaluation with a load of 100 g

[0025]

[Table 2]

As is clear from Table 2, the surface roughness of the protective layer is not more than 0.07 μm in the center line average roughness and the maximum height is 0.6 μm.
Those that do not satisfy the conditions of m or less and ten-point average roughness of 0.5 μm or less can prevent the background stain due to the residual potential, but cause the background stain due to poor cleaning and further significantly reduce the strength of the coating film. . On the contrary, Example 4 according to the present invention
The electrophotographic photoconductors of Nos. 6 to 6 are good ones that not only suppress the background stain caused by the residual potential but also have no side effects such as cleaning property and coating film strength. The electrophotographic photoreceptors of Example 4 and Comparative Example 4 were each subjected to a copying test of 50,000 sheets, and the abrasion loss of the protective layer was evaluated. While it was 3 μm, Example 1 according to the present invention was 0 μm, and it was found that the abrasion resistance in the copying machine was excellent.

[0027]

The electrophotographic photoreceptor of the present invention is capable of preventing the accumulation of electric charge at the free interface of the protective layer, suppressing the residual potential in the copying machine, and the background stain on the image, and of course, the original of the protective layer. Since a good image can be obtained without impairing the coating film strength and abrasion resistance, the reliability is extremely high.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-77748 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/00

Claims (2)

(57) [Claims] 1. An electrophotographic photosensitive member comprising a conductive support, a photoconductive layer, and a protective layer in which metal oxide particles are dispersed in a binder resin, which are sequentially laminated on the surface of the protective layer. By performing the processing, the surface roughness of the protective layer surface is a center line average roughness of 0.07 μm or less and a maximum height of 0.6 μm.
The following, and an electrophotographic photosensitive member characterized by being smoothed to a ten-point average roughness of 0.5 μm or less. 2. An electrophotographic apparatus comprising at least an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member according to claim 1 is mounted as the electrophotographic photosensitive member.