JPH04366965A - Coating method for electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To form a photosensitive layer having a uniform film thickness without sticking a coating liquid at all on the inside wall of a cylindrical base body and to suppress the evaporation of the solvent of the coating liquid. CONSTITUTION:The bottom end of the cylindrical base body 5 is vertically moved along a shaft 3 and is subjected to a dip coating treatment. A coating chamber 7 is hermetically closed with a jig 1 for hermetically sealing the lower part of the cylindrical base body having the liquid repellent surface in tight contact with a hermetic closing upper holder 2 of the coating chamber to dip the cylindrical base body 5 into a photosensitive liquid essentially consisting of a photoconductive material in such a manner that both ends of the base body exist above and below, by which the base body is subjected to the dip coating treatment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating an electrophotographic photoreceptor in which the electrophotographic photoreceptor is uniformly and smoothly formed on the surface of a cylindrical substrate by a dip coating method.

0002

[Prior Art] Recording bodies such as electrophotographic photoreceptors have a charge generation layer using a condensed polycyclic pigment or an azo pigment and a charge transport layer using a hydrazone-based or arylamine-based material on the surface of a conductive substrate such as aluminum. It is formed by coating and laminating. Conventionally, in order to coat a cylindrical substrate with a coating liquid containing a photoconductive compound as a charge generating material and a charge transporting material, as shown in FIG. A method of applying a coating liquid to the surface of a cylindrical substrate is carried out by immersing the substrate in water and then pulling it up. In the above-described dip coating method, various measures have been taken to prevent the interior of the cylindrical substrate from being coated with the coating liquid.

For example, there is a method of adjusting the pressure of pressurized air introduced into the cylindrical substrate so that the coating liquid does not enter the cylindrical substrate and bubbles do not blow out into the coating liquid. 1986-80363, JP 60-499
65, Japanese Patent Application Laid-open No. 63-253365) and a method of sealing at least the lower end of both ends of a cylindrical substrate with a conical jig and dip coating (Japanese Patent Application Laid-open No. 63-58351).

0004

[Problems to be Solved by the Invention] However, in the conventional dip coating method, the air inside the cylindrical substrate expands during dipping and bubbles are generated, and these bubbles rise along the sides of the cylindrical substrate. The disadvantage is that air bubbles sometimes adhere to the surface of the cylindrical substrate, causing coating defects; the pressure must be balanced to prevent the coating liquid from entering the inside of the cylindrical substrate and to prevent air bubbles from ejecting into the coating liquid during immersion. The disadvantage is that it is difficult to
Alternatively, when a cylindrical substrate is immersed in a coating liquid, the cylindrical substrate is tilted or laterally shakes due to the buoyant force generated, resulting in non-uniformity of the coating film, that is, the photoreceptor layer.

In particular, an electrophotographic photoreceptor obtained by dip coating so that the coating liquid slightly enters the inside of a cylindrical substrate in order to prevent air bubbles from blowing out into the coating liquid is coated with a rotating jig. If it is rotatably supported and installed in a copying machine, laser printer, etc., problems with eccentricity may occur due to the coating liquid adhering to the rotating jig, or problems may occur between the rotating jig and the cylindrical base. Since the adhesive strength is weak, problems such as falling off during rotation or problems with grounding failure occur.

In order to eliminate the above-mentioned defects caused by the coating liquid adhering to the inner wall surface of the end of the cylindrical substrate, the inner wall surface of the end of the cylindrical substrate is dipped in a solvent or coated with a solvent after the coating process. The method of wiping it off with a sponge etc. is used, but
These methods require equipment for dipping or wiping, which increases manufacturing costs due to the increased number of steps, and the solvent vapor generated may have an adverse effect on the surface of the photoconductor, or the generation of solvent vapor during wiping may cause problems. There is a drawback that the solvent droplets attached to the photoreceptor surface cause image defects during image formation.

Furthermore, in conventional coating tanks, during and after coating a cylindrical substrate, the solvent in the coating solution evaporates from the opening of the coating tank, so the state of the coating solution (viscosity, concentration, etc.) changes over time, making it difficult to form a photoreceptor with a uniform film thickness. In order to form a photoreceptor with a uniform film thickness, it is necessary to measure the viscosity, add a solvent, and control the coating speed.

In order to eliminate the above-mentioned drawbacks, the inventors of the present invention first developed a cylindrical substrate whose lower end can be moved up and down along the shaft and which can be brought into close contact with the upper holder of the coating tank after the coating process. It has been found that when the substrate is sealed with a sealing jig at the bottom of the cylindrical substrate, the coating process can be performed without any coating liquid adhering to the inner wall of the cylindrical substrate, and without the cylindrical substrate tilting or wobbling laterally during the dip coating process. I found it.

When an electrophotographic photoreceptor is produced for a long period of time using this previously proposed method, (1) the half-dried coating liquid adhering to the sealing jig is coated every time the cylindrical substrate is dip-coated; Since the sealing jig is immersed in the coating solution in the coating tank, the viscosity of the coating solution in the coating tank may increase due to re-dissolution of the half-dried coating solution that has adhered to the sealing jig. (2) The coating liquid adhering to the sealing jig will gradually grow (become thicker) depending on the number of dip coatings, so the sealing jig may deteriorate. (3) When the sealing jig is separated from the cylindrical base after coating, the sealing jig may be subject to heavy loads. A stringing phenomenon occurs in the applied and half-dried coating liquid, and the half-dried coating liquid on the sealing jig sticks to the cylindrical substrate and rises like strings, damaging the surface of the photoreceptor. It has its drawbacks.

0010

[Means for Solving the Problems] In order to solve the drawbacks of such long-term dip coating processing, as a result of intensive research by the present inventors, the lower end of the cylindrical base is moved up and down along the shaft, and If a sealing jig with a liquid-repellent surface is used as a sealing jig for the lower part of the cylindrical substrate that is tightly attached to the upper holder of the coating tank after the coating process, the coating solution will not deteriorate even after 1000 or more dip coating processes. It has been discovered that an electrophotographic photoreceptor of excellent quality can be formed without causing any damage, and based on this knowledge, the present invention has been accomplished.

[0011]

[Function] The structure of the present invention is that a cylindrical photoreceptor is coated in a coating method for an electrophotographic photoreceptor, which consists of dipping a cylindrical substrate in a coating solution containing a photoconductive compound so that both ends of the cylindrical substrate are in the vertical direction. An electronic method consisting of a dip coating process in which the lower end of the substrate is sealed with a liquid-repellent cylindrical substrate lower sealing jig that moves up and down along a shaft and that comes into close contact with the sealed upper holder of the coating tank after coating. This is a coating method for photographic photoreceptors.

FIG. 1 is a diagram schematically showing a coating method for an electrophotographic photoreceptor according to the present invention. In FIG. 1(A), the force of the spring 4 causes the sealing flange 1 of the cylindrical base lower sealing jig whose surface is liquid-repellent, which is in close contact with the sealing flange holder 2 of the sealing upper holder, to drive the cylindrical base lifting device. It comes into close contact with the lower part of the cylindrical substrate 5 that has descended, and is immersed in the coating liquid 6 in the coating tank 7 . In FIG. 1(B),
A cylindrical base body 5 sealed with a sealing flange 1 having a liquid-repellent surface is smoothly and vertically downwardly immersed in the coating liquid to the deepest point along a sealing flange moving shaft 3. At this time, since the sealing flange 1 whose surface is liquid-repellent is in close contact with the cylindrical base 5 by the force of the spring 4, the coating liquid 6 does not enter the inside of the cylindrical base 5. In FIG. 1(C),
The cylindrical substrate 5 is pulled up from the coating solution to obtain a cylindrical substrate with a photoreceptor layer 9 formed on its surface. When the cylindrical base 5 is pulled up, the liquid-repellent sealing flange 1 rises together with the cylindrical base 5 due to the force of the spring 4, but stops when it comes into contact with the upper sealing holder 2, and the seal with the cylindrical base 5 is released. . Furthermore, the sealing flange 1 with a liquid-repellent surface is kept in the sealing upper holder 2 until the next dip coating process is performed.
Since the coating liquid 6 is in close contact with the coating liquid 6, evaporation of the solvent in the coating liquid 6 in the coating tank 7 can be suppressed.

FIG. 2 is a diagram schematically showing a conventional coating method. In FIG. 2A, as the cylindrical substrate 5 is immersed in the coating liquid, the cylindrical shape is Pressurized air is introduced into the interior of the base body 5. At this time, in order to prevent the introduced air from forming bubbles from the bottom of the opening of the cylindrical substrate 5 and ejecting into the coating liquid 6, the coating liquid is allowed to enter the inside of the cylindrical substrate 5 slightly. In FIG. 2C, the cylindrical substrate 5 immersed in the coating liquid 6 is pulled up to obtain a cylindrical substrate on which a photoreceptor layer 9 is formed on the surface and the inner wall surface of the lower end. Furthermore, when the cylindrical coating tank 7 is used, during the dip coating process shown in FIGS. 2(A) and 2(B), the area [( X/2)2 π-(y/2)2
The solvent evaporates from the surface of the coating solution shown as
After the coating process in C), the inner area of the coating tank 7 [(x/2)2
The solvent evaporates from the surface of the coating liquid 6 indicated by π].

FIG. 3 is a diagram showing a cross section of the lower part of the cylindrical substrate 5 after coating according to the method of the present invention in FIG. 1 and a lower cross section of the cylindrical substrate 5 after coating according to the conventional method shown in FIG. Figure 3 (
In A), by the method of the present invention, the sealing flange with a liquid-repellent surface is in close contact with the lower part of the cylindrical substrate 5 during the dip coating process, so that the spigot part 8 of the cylindrical substrate 5 (for rotation when completed) No photoreceptor layer is formed on the end inner wall surface processed portion of the cylindrical base 5 provided for mounting the jig. On the other hand, in FIG. 3(B), the coating liquid 6 slightly enters the inside of the cylindrical base 5 due to the internal pressure control in the conventional method, so that the photoreceptor layer reaches the spigot part 8 and the lower inner wall of the cylindrical base 5. 9 is formed.

The cylindrical substrate bottom sealing jig with a liquid-repellent surface used in the present invention is one in which the surface tension of the sealing jig is smaller than the surface tension of the coating liquid, preferably a liquid-repellent surface. The surface tension of the sealing jig is 75% of the surface tension of the coating liquid.
The following are desirable.

The cylindrical base bottom sealing jig with a liquid-repellent surface used in the present invention includes a stainless steel sealing jig whose surface is coated with Teflon.

As described above, in the present invention, the cylindrical substrate 5 is immersed in the coating liquid 6 of the coating tank 7 and is in close contact with the lower part of the cylindrical substrate 5 while being pulled up, and after the cylindrical substrate 5 is pulled up, that is, After the dip coating process is completed, a cylindrical base lower sealing jig 1 whose surface is liquid repellent and comes into close contact with the coating tank upper holder 2; a liquid repellent surface to prevent the cylindrical base 5 from tilting or lateral wobbling; Shaft 3 for vertically moving the cylindrical base lower sealing jig 1 with liquid repellency; During the dip coating process, the cylindrical base lower sealing jig 1 with a liquid-repellent surface is brought into close contact with the cylindrical base 5, and after the dip coating process , a coating device for an electrophotographic photoreceptor, comprising a spring for tightly contacting a cylindrical substrate lower sealing jig 1 with a liquid-repellent surface to a coating tank upper holder 2; and a drive device for vertically moving the cylindrical substrate 5. using the cylindrical base 5
By performing a dip coating process, an electrophotographic photoreceptor having a uniform film thickness and excellent image forming ability can be manufactured continuously over a long period of time, for example, 1000 times, without any coating liquid adhering to the inner wall of the cylindrical substrate 5. In addition to being able to
Evaporation of the solvent during and after the coating process can be significantly suppressed, and the coating liquid will not adhere to the cylindrical substrate lower sealing jig 1 even during long-term continuous dip coating process.
Deterioration of the coating liquid can be suppressed.

[0018]

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples.

Example Using a Teflon-coated stainless steel sealing flange 1, the following liquid A was applied to the surface of a cylindrical substrate 5 to a dry film thickness of 0.5 μm by the method shown in FIG. It was applied by dip coating and dried at a temperature of 80° C. for 1 hour. Furthermore, using the same method using a Teflon-coated stainless steel sealing flange 1, the following liquid B was immersed onto the surface of the cylindrical substrate 5 coated with liquid A so that the film thickness after drying was 20 μm. The coating was applied and dried at a temperature of 70° C. for 1 hour to continuously produce 1000 electrophotographic photoreceptors.

The viscosity increase of liquid A after continuous dip coating treatment of 50 cylindrical substrates was 0 mpa·s, the viscosity increase of liquid B was 1 mpa·s, and after continuous dip coating treatment of 200 cylindrical substrates. The viscosity increase of liquid A was 1 mpa·s, and the viscosity increase of liquid B was 3 mpa·s.

Furthermore, A of the 1000th cylindrical substrate surface
No coating defects such as uneven coating or white spots were found in the liquid coating layer and the liquid B coating layer, and good coating layers were formed.

Furthermore, the obtained electrophotographic photoreceptor was mounted on a rotating jig and mounted on a copying machine [SF-8100, manufactured by Sharp Corporation] to make copies and perform image evaluation.
A uniform image with no unevenness was obtained. Also, 20,000
Even when a copy test was performed, high-quality images were obtained without any problems such as misalignment of the rotating jig, falling off, or poor grounding.

2 parts by weight of liquid A dibrome anthron, butyral resin [
A liquid obtained by dispersing 2 parts by weight of S-LEC BM-2 manufactured by Sekisui Kagaku Co., Ltd. and 230 parts by weight of cyclohexanone in a ball mill for 8 hours.

B liquid hydrazone charge transport material [ABPH, manufactured by Nippon Kayaku Co., Ltd.] 1 part by weight, polycarbonate resin [Panlite L-1]
250, manufactured by Teijin Chemicals Ltd.] in 8 parts by weight of dichloroethane.

Comparative Example According to the method shown in FIG. 2, liquid A was applied to the surface of the cylindrical substrate 5 in the same manner as in the example so that the film thickness after drying was 0.5 μm, and dried at 80° C. for 1 hour. Further, liquid B was applied thereon so that the film thickness after drying was 20 μm, and dried at 70° C. for 1 hour to obtain an electrophotographic photoreceptor. This electrophotographic photoreceptor was attached to a rotating jig and installed in a copying machine [SF-8100, manufactured by Sharp Corporation], and a 20,000-copy test was performed, and the number of copies exceeded 14,000. However, the image became blurred. When the machine was stopped and investigated, it was found that the dried paint film that had adhered to the inner wall surface of the end of the cylindrical base (spigot part) had come off, and the rotating jig was spinning idly.

After dip coating 50 cylindrical substrates, the increase in viscosity of liquid A was 2 mpa·s, and the increase in the viscosity of liquid B was 11 mpa·s.

[0027]

[Effects of the Invention] As described above, the method of the present invention prevents the cylindrical substrate from tilting or lateral wobbling, so that a photoreceptor with a uniform film thickness can be formed on the surface of the cylindrical substrate. In addition, since the coating liquid does not adhere to the inner wall of the cylindrical substrate at all, wiping operations and the like are not necessary, and it is possible to obtain uniform images without unevenness even during continuous copying over a long period of time. Furthermore, even during long-term dip coating treatment, evaporation of the solvent in the coating solution and deterioration of the coating solution can be suppressed, so the coating solution can be stabilized and there is no need to adjust the viscosity of the coating solution or control the coating speed. It is.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the dip coating method of the present invention.

FIG. 2 is a schematic diagram of a conventional dip coating method.

FIG. 3 is a cross-sectional view of the lower end of a cylindrical substrate coated by the present invention and a conventional dip coating method.

[Explanation of symbols]

1 Sealing flange 2 Sealing flange holder 3 Sealed flange moving shaft 4 Spring 5 Cylindrical base 6 Coating liquid 7 Coating tank

Claims (1)

[Claims] 1. A method for coating an electrophotographic photoreceptor, which comprises immersing a cylindrical substrate in a photosensitive liquid containing a photoconductive substance as a main component, with both ends of the cylindrical substrate facing up and down. Electrophotography characterized in that dip coating is performed by sealing the lower end of the substrate with a cylindrical substrate lower sealing jig that moves up and down along the shaft and has a liquid-repellent surface that comes into close contact with the upper holder of the coating tank after coating. How to apply photoreceptor.