JPH11160895A - Electrophotographic photoreceptor, its production and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an electrophotographic photoreceptor suitable to be used in a contact electrification type copying machine. SOLUTION: This electrophotographic photoreceptor possesses a photoreceptive film formed on a base substance by immersing and coating. In the image forming area of the photoreceptive film, the film thickness A of a lower end part positioned at the lower part at the time of immersing and coating is larger than the film thickness B of an upper end part positioned at the upper part at the time of immersing and coating. In such a case, it is desirable that a difference between the film thickness A and the film thickness B is within the range of 0.5 μm to 0.3 μm. A method in which the drawing-up speed at the time of finishing drawing-up the base substance is made higher than that at the time of starting drawing-up the base substance in the case of forming the photoreceptive film by immersing and coating is adopted as the producing method of the photoreceptor.

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 used for an electrophotographic printer, a copying machine, and the like, a method for manufacturing the same, and an image forming apparatus. It relates to a manufacturing method.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member (OPC) used in an electrophotographic printer or a copying machine has an undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL) on an aluminum tube. Layered ones are the mainstream.

In recent years, in an electrophotographic apparatus, a contact charging method is used for a photosensitive drum in order to reduce the amount of generated ozone, reduce costs by not using a high-voltage power supply, and reduce the size of a charger. It became so. Contact charging does not require a high-voltage power supply such as 4 to 6 kV in the case of corona charging, and is usually performed by applying a voltage of 1 to 2 kV. However, when the photosensitive drum is used in the contact charging method, there is a problem that charge leakage occurs due to concentration of charges. The cause is roughly divided into the following two. (A) There are minute convex defects on the surface of the aluminum tube. (B) Fine defects such as dust are present in the photosensitive film of the electrophotographic photosensitive member.

[0004] As means for improving (A), several methods have been proposed. Specific methods include, for example, (1) a method of shaving off a convex defective portion with a burnishing roll (Japanese Patent Laid-Open No. 3-149180). No.),
(2) A method of grinding a convex defect using a grindstone
JP-A-167824), and (3) a method of dissolving and removing convex defects chemically (JP-A-6-148921) and the like have been proposed.

As described above, various remedies have been proposed for minute convex defects on the surface of an aluminum tube. However, effective means for completely resolving the problem (B) has been found. There is no present. The reason is that no matter what kind of clean room the electrophotographic photosensitive member is manufactured, it is impossible to eliminate submicron-order fine dust and the like. As a result, the yield in production is reduced, and the cost is increased.

The above problem is remarkable in the case of the contact charging method. However, even in the case of the conventional non-contact charging method using corona discharge, there is a problem that the minute defective portion becomes an image defect such as a black point or a white point. Existed.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems in the prior art. That is, an object of the present invention is to provide an electrophotographic photoreceptor suitable for electrophotographic printers and copiers, thereby obtaining a high-quality image free from black spots or white spots regardless of the charging method. It is an object of the present invention to provide a photographic photosensitive member and a method for efficiently manufacturing the electrophotographic photosensitive member. Another object of the present invention is to provide an image forming apparatus capable of forming a high-quality image using the above electrophotographic photosensitive member.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems in the prior art, and as a result, the dust in the photosensitive film of the electrophotographic photosensitive member (B) has been found. Focusing on the fact that many charge leaks due to charge concentration caused by the presence of minute defects such as those occurring in the lower part during the production of the electrophotographic photoreceptor, as a result of further exploring the causes, It has been found that fine defects such as dust in the photosensitive film occupy the majority due to the following three factors.

(1) Fine dust existing in the air in a clean room, which is fine, but due to its own weight,
Since a relatively large amount is present at a low position, a large amount is generated at a lower end portion when an electrophotographic photosensitive member is manufactured. (2) The unnecessary portion of the lower end of the photoreceptor is wiped off with a solvent, a brush, or the like. Occurs frequently in the film. (3) The photosensitive film of the electrophotographic photoreceptor is formed by successively dip-coating an undercoat layer, a charge generation layer, a charge transport layer, and the like to produce an electrophotographic photoreceptor. The pallet and the electrophotographic photoreceptor are rubbed on a moving means called a pallet in order to move between the apparatuses for applying the respective layers and in the dryer. When the next layer is applied, a large amount of the metal powder is generated in the lower photosensitive film when the electrophotographic photosensitive member is manufactured. For all of the above three factors, the rate of occurrence can be reduced by improvement, but it is impossible to eliminate the occurrence at all from the viewpoint of the mechanism of occurrence.

Therefore, even if a fine defect such as dust is present in the photosensitive film of the electrophotographic photosensitive member, the electrophotographic photosensitive member does not cause charge leakage due to charge concentration and does not affect image quality. The manufacturing method was developed.

That is, the electrophotographic photoreceptor of the present invention has a photosensitive film formed on a substrate by dip coating, and a lower end of an image forming area of the photosensitive film which is located below during dip coating. The film thickness A of the portion is larger than the film thickness B of the upper end portion located above at the time of dip coating. In the case of the present invention, the difference between the film thickness A and the film thickness B is 0.5
It is preferably in the range from μm to 3.0 μm. It is preferable that the thickness of the photosensitive film in the image forming region gradually increases from one end of the image forming region located at the time of dip coating to one end of the image forming region located at the time of dip coating.

The electrophotographic photoreceptor of the present invention is manufactured by immersing a substrate in a coating solution held in a coating tank and pulling up the substrate to form a photosensitive film. The method is characterized in that the application speed at the end of pulling is higher than the application speed at the start of pulling of the substrate. In this case, it is preferable that the application speed by pulling up the substrate is gradually increased from the start of pulling to the end of pulling. The production method of the electrophotographic photoreceptor of the present invention,
It is preferably applied to the case where the substrate is placed on a pallet and transported.

Further, the image forming apparatus of the present invention comprises a photoconductor, a charging unit for charging the photoconductor, an exposing unit for exposing the charged photoconductor to form an electrostatic latent image, and a photoconductor. Developing means for visualizing the latent image, wherein the photosensitive member is the above-described electrophotographic photosensitive member, and the charging means is a charger which contacts and charges the photosensitive member.

[0014]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a photosensitive film thickness distribution of the electrophotographic photosensitive member. As shown in the drawing, the image area of the electrophotographic photosensitive member has a film thickness A at a lower portion located below at the time of dip coating. Sometimes it is thicker than the film thickness B at the upper end located above.

In the present invention, the photosensitive film is formed of an undercoat layer, a charge generation layer, and a charge transport layer. In any one of the layers, the photosensitive film is formed so that the film thickness A is larger than the film thickness B. However, it is particularly desirable that the charge transport layer has the above thickness. The reason is that the charge transport layer is often made relatively thickest, so that it is easy to provide a film thickness difference.

In the electrophotographic photoreceptor of the present invention, a conductive substrate such as an aluminum or aluminum alloy substrate is used as the substrate. An undercoat layer is formed on the conductive substrate as required. The undercoat layer is formed using a known resin or a coupling agent, and has a thickness of 0.05 μm to 10 μm, particularly 0.1 μm to
It is preferable to set it in the range of 2 μm. When the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer, any of them may be provided on the undercoat layer. The charge generation layer is formed using a known material such as phthalocyanine, and has a thickness in the range of 0.05 μm to 1 μm, particularly 0.1 μm.
It is preferable to set the range of μm to 0.5 μm. The charge transport layer is formed by incorporating a known charge transport material into a known binder resin such as polycarbonate, and preferably has an average film thickness in the range of 15 μm to 30 μm.

It is preferable to make the film thickness A larger than the film thickness B for the charge transport layer as described above. The coating speed at the lower end of the electrophotographic photosensitive member is higher than that at the upper end of the electrophotographic photosensitive member in the effective image area. However, if the coating speed is suddenly changed in the middle, the photosensitive film thickness also changes abruptly, and as a result, the difference in the density of the image printed on the photoreceptor is recognized in that part, and it is not practical, It is preferable to gradually increase the application speed when applying the photosensitive film and to gradually increase the photosensitive film thickness.

The method for producing an electrophotographic photosensitive member according to the present invention is particularly effective when a pallet is used for transportation. That is, when a cylindrical substrate is used, the substrate is transported to a coating tank of a dip coating apparatus, and after the coating operation is completed, the coated substrate is transported from the coating tank to a next step, for example, a step of washing, coating, or the like. However, in this case, when a pallet is used for transportation, when the cylindrical base is attached to or detached from the convex holder provided on the base of the pallet, the holder of the pallet comes into contact with the inside of the cylindrical base. Fine shavings are generated, which mainly adhere to the lower end of the base. However, when the above method of the present invention is adopted, the film thickness A at the lower end of the image forming region becomes larger than the film thickness B at the upper end of the image forming region, and even if there is a fine chip attached thereto, , Thereby offsetting the decrease in insulation resistance. Therefore, the manufacturing method of the present invention is particularly effective when a transport method using a pallet is employed.

Next, the image forming apparatus of the present invention will be described. FIG. 2 is a schematic diagram of an example of the image forming apparatus of the present invention. The photoreceptor 1 has a photosensitive film produced as described above, and is arranged such that a charging roll 3 to which a voltage is supplied from a power supply 2 provided outside the apparatus is in contact with the surface thereof. Has been established. Around the photoreceptor 1, an image input device 4, a developing device 5, a pressure transfer device 6 or an electrostatic transfer device, a cleaner device 7, and a charge removing device 8 are provided. As the contact charger, a known charger is used, and a charging roll is shown in the figure. However, a charging brush or a blade-type film charger may be used. The charging roll, for example, a conductive roller having a conductive foam rubber layer and a surface layer made of a conductive rubber tube around a conductive shaft, for example, the electrical resistance of 10 ⁴ -
Those having a resistance of 10 ⁶ Ω can be suitably used.

In the above-described image forming apparatus, for example, a direct current of 1 to 2 kV or a superimposed current of direct current and alternating current is applied to the contact charger, whereby the photosensitive member is uniformly charged. Next, the image input device 4 exposes the image, and the formed electrostatic latent image is developed by the developing device 5 to form a toner image. The formed toner image is transferred onto the sheet 9 by the pressure transfer device 6 or the electrostatic transfer device, and then fixed by the fixing device 10. On the other hand, the toner remaining on the surface of the photoconductor 1 after the transfer is transferred to a cleaner device 7.
, And the electric charge slightly remaining on the surface of the photoconductor 1 is erased by the charge removing device 8.

[0021]

The present invention will be further described below with reference to examples. Examples 1 to 5 and Comparative Example 1 As a conductive substrate, 0.90 mm thick × 30.3 mmφ ×
A 340 mm long aluminum tube (A6063 alloy) is 0.75 mm thick x 30 mm using a diamond tool.
After mirror cutting to φ × 340mm length, the surface is Ra
The surface was finished to a smooth surface of 0.03 to 0.04 μm. The surface of this aluminum tube was roughened by a liquid honing device. The surface roughening treatment is performed using the abrasive 1
8.9 kg is suspended in 51 liters of water, sent to a gun at a flow rate of 21 liters / minute, and sprayed at a predetermined compressed air pressure (0.1 to 0.2 MPa), so that the substrate surface has a desired surface. The surface roughness (Ra: 0.1 to 0.5 μm) was set. As the abrasive, aluminum oxide: alumina beads (CB-A) manufactured by Showa Titanium Co., Ltd.
30S; particle size is 27 μm).

The aluminum tube prepared as described above is first sprayed with well water at 3 L / min for 20 seconds, and then with a nylon brush (φ6) while spraying well water at 3 L / min.
5 μm) is pressed with a brush for 10 seconds while rotating in the same direction at 200 rpm with an aluminum tube, and then pure water (conductivity 0.1 to 1.0 μS / c)
m, temperature 18-18 ° C.), oscillating at 30 times / minute for 5 minutes, rinsing with warm pure water (conductivity 0.1-1.0 μS / c)
m, at a temperature of 48 to 55 ° C.) for 30 seconds, then 200 mm
After slowly pulling up at / min, drying with hot air at 135 ° C. was performed for 3 minutes to complete the washing.

As the undercoat layer (UCL), a 50% toluene solution of tributoxy zirconium acetylacetonate (ZC540, manufactured by Matsumoto Kosho Co., Ltd.) as a zirconium compound was placed on the aluminum tube prepared as described above.
00 parts, γ-aminopropyltriethoxysilane (A1100, manufactured by Nippon Unicar) 10 as a silane compound
Parts, 10 parts of polyvinyl butyral resin (BM-S, manufactured by Sekisui Chemical Co., Ltd.) and 130 parts of n-butanol were mixed, and the obtained coating solution was applied by a dip coating method.
By heating for 0 minutes, an undercoat layer having a thickness of 1.0 μm was formed.

Next, a charge generation layer (CGL) was formed.
That is, a vinyl chloride-vinyl acetate copolymer (trade name:
A hydroxygallium phthalocyanine pigment (described in JP-A-5-263007) was mixed with a 2% cyclohexanone solution of VMCH (manufactured by Union Carbide Co.) so that the ratio of pigment to resin was 1: 1. Dispersion treatment was performed for 3 hours by a sand mill. The obtained dispersion was further diluted with n-butyl acetate and dip-coated on the surface of an aluminum tube to form a charge generation layer having a thickness of 0.25 μm.

Further, a charge transport layer (CTL) was formed.
That is, N, N'-diphenyl-N, N'-bis (m
A solution prepared by dissolving 4 parts of tolyl) benzidine and 6 parts of polycarbonate Z resin in 9 parts of monochlorobenzene and 27 parts of tetrahydrofuran (THF) was dip-coated on the charge generation layer. At this time, coating was performed under the following dip coating conditions. Thereafter, the resultant was dried at 115 ° C. for 40 minutes to form a charge transport layer having an average film thickness of 24 μm, which was used as a photosensitive drum.

(Comparative Example 1) Coating speed 200 mm / min
The aluminum tube was pulled up at a constant speed of for coating.

(Example 1) Coating speed 200 mm / min
Then, the application was started by pulling up the aluminum tube, the application speed was gradually increased, and at the end of the application, the application was performed such that the application speed was 203 mm / min.

(Example 2) Coating speed 200 mm / min
Then, the application was started by raising the aluminum tube, and the application speed was gradually increased. At the end of the application, the application was performed such that the application speed was 205 mm / min.

(Example 3) Coating speed 200 mm / min
The application was started by pulling up the aluminum tube, the application speed was gradually increased, and at the end of the application, the application was performed so that the application speed became 210 mm / min.

(Example 4) Coating speed 200 mm / min
The aluminum tube is pulled up to start coating, and the coating speed is set to 210 mm / mi at a position substantially at the center of the photoconductor.
n, and the lifting was continued in that state.

(Example 5) Coating speed 200 mm / min
Then, the application was started by pulling up the aluminum tube, the application speed was gradually increased, and at the end of the application, the application was performed such that the application speed was 230 mm / min, and application was performed.

Each photosensitive drum obtained as described above was examined by the following method for the rate of occurrence of charge leakage due to concentration of charges. As a contact charging roll, a conductive roll having an electrical resistance of 10 ⁶ Ω and a rubber hardness of 55 degrees (JIS A) provided with a conductive foam rubber layer and a surface layer made of a conductive rubber tube around a conductive shaft is used. The charge leakage was evaluated under the applied voltage of -4 kV. Table 1 shows the results. In addition, the image quality is a multi-functional printer (Able-332
1, Fuji Xerox) and evaluated the density difference of image quality.

[0033]

[Table 1]

Charge leakage ratio (when the photoreceptor is mounted):…: less than 5%, Δ: 5% or more and less than 10%, ×: 10%
Above Image quality (density difference): ○: no problem in particular, Δ ^{* 1} : slight difference in density at center, Δ ^{* 2} : slight difference in density when comparing upper and lower parts of photoconductor, ×: density of photoconductor There is a difference.

As is clear from Table 1, in the case of Examples 1 to 5, the ratio of charge leakage is 10% or less, and particularly in the case of Examples 2 to 5, it is less than 5%. The defect rate in performing is decreasing. As a result, production costs can be reduced. On the other hand, Comparative Example 1
In the case of (1), the rate of charge leakage is 10% or more, the defect rate in production is high, and as a result, not only the production cost is increased but also the production is more It is very wasteful in terms of resources.

It should be noted that the density difference of the image quality is described in the fourth embodiment.
In the case of the above, the portion where the density difference occurs corresponds to the central portion of the photoreceptor, which is considered to be caused by suddenly changing the coating speed.

[0037]

As described above, in the electrophotographic photoreceptor of the present invention, the film thickness A at the lower end of the charged area is formed larger than the film thickness B at the lower end of the image area. Even if a minute defect such as dust is present, the insulation resistance value of the defect is increased to prevent the occurrence of charge leakage due to charge concentration, and does not affect the image quality of an image. Therefore, the electrophotographic photoreceptor of the present invention is excellent in chargeability and can obtain a high-quality image free from image defects such as black spots and white spots regardless of the charging method. Further, the electrophotographic photoreceptor of the present invention is particularly suitable for use in a contact charging method for realizing reduction of ozone generation amount, reduction of cost by not using a high-voltage power supply, miniaturization of a charger, and the like. Thus, by using a printer and a copier using a contact charging system, it is possible to stably provide good image quality.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a photosensitive film thickness distribution of an electrophotographic photosensitive member of the present invention.

FIG. 2 is a schematic configuration diagram of an example of an image forming apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Power supply, 3 ... Charging roll, 4 ... Image input device, 5 ... Developing device, 6 ... Pressure transfer device, 7 ... Cleaner device, 8 ... Static elimination device, 9 ... Paper, 10 ... Fixing device.

Claims (7)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive film formed by dip coating on a substrate, wherein a film thickness A at a lower end portion of an image forming region of the photosensitive film located below at the time of dip coating is Thickness B of upper end located above during dip coating
An electrophotographic photoreceptor characterized by being larger than 2. The electrophotographic photosensitive member according to claim 1, wherein a difference between the film thickness A and the film thickness B is in a range of 0.5 μm to 3.0 μm. 3. The film thickness of a photosensitive film in an image forming area is:
2. The electrophotographic photoreceptor according to claim 1, wherein the thickness gradually increases from one end of the image forming region located above during dip coating to one end of the image forming region located below during dip coating. 4. In a method for manufacturing an electrophotographic photoreceptor in which a photosensitive film is formed by immersing a substrate in a coating solution held in a coating tank and lifting the substrate, the time of completion of the pulling is higher than the speed of application when the substrate is pulled. A method for producing an electrophotographic photoreceptor, comprising increasing the application speed of an electrophotographic photosensitive member. 5. The method of manufacturing an electrophotographic photosensitive member according to claim 4, wherein the application speed by pulling up the substrate is gradually increased from the start of pulling to the end of pulling. 6. A method for forming a photosensitive film by immersing a substrate in a coating liquid held in a coating tank, wherein the transfer of the substrate to and from the coating tank is performed by a pallet. The method for producing an electrophotographic photosensitive member according to claim 4. 7. A photoreceptor, charging means for charging the photoreceptor, exposure means for exposing the charged photoreceptor to form an electrostatic latent image, and developing means for visualizing the electrostatic latent image Wherein the photosensitive member is the electrophotographic photosensitive member according to any one of claims 1 to 3, and the charging means is a charger which contacts and charges the photosensitive member. An image forming apparatus comprising: