JP2002045753A - Application device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of bubbles in a coating liquid when the overflowing coating liquid is recovered or the coating liquid is supplied and minimize the migration of the generated bubbles into a post-process and thus enable a thin coating film which has no irregularities in the film formation with sufficient film thickness uniformity and homogeneity and is in the submicron order, to be applied to the outer surface of a cylindrical base, in an immersion application method. SOLUTION: In the application device which applies the coating liquid to the outer surface of the cylindrical base by immersing the cylindrical base in the coating liquid in such a state that the cylindrical shaft of the base is retained almost vertically and pulling the cylindrical base out of the coating liquid, a coating liquid circulation mechanism which comprises a coating tank in which the coating liquid is stored and the cylindrical base is immersed, a circulation tank which circulates the coating liquid into the coating tank and feeds the coating liquid into the lower part of the coating tank from the lower part of the circulation tank by means of a pressure feed pump and makes the coating liquid overflow from the upper edge part of the coating tank to send the coating liquid into the circulation tank is provided. In addition, a filter is arranged, facing the upstream side of the coating liquid flow, in piping which guides the overflowing coating liquid to the circulation tank. Besides, the filter is arranged in such a way that it blocks the upper part of the inside diameter of the piping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing an electrophotographic photosensitive drum by applying a photosensitive substance to a drum outer peripheral surface by a dip coating method.

[0002]

2. Description of the Related Art In an electrophotographic photosensitive drum, a photosensitive layer is formed by applying a coating solution containing an organic photosensitive material to an outer peripheral surface of a cylindrical substrate usually made of aluminum or the like. As a coating method, there are a dip coating method, a spray coating method, a ring coating method and the like, and a dip coating method capable of obtaining a relatively uniform film pressure and a coating film and having high productivity is generally adopted.
In a general dip coating method, a cylindrical substrate is immersed in a coating tank containing a coating liquid, and then pulled up again to apply the coating liquid to its outer peripheral surface. This is a circulation type in which the coating liquid overflowing from the upper edge is collected and returned to the coating tank via the circulation tank.

[0003] A conventional apparatus of the circulation type dip coating method will be briefly described. FIG. 2 is a conceptual diagram illustrating an example of a conventional coating apparatus using a dip coating method. In FIG. 2, 1 is a coating liquid 3
Is a coating tank in which the cylindrical substrate 10 is immersed and pulled up, 2 is a circulation tank for storing the coating liquid 3 and sending the coating liquid 3 to the coating tank 1, and the coating liquid 3 is a coating liquid. It is sent to the lower part of the coating tank 1 by a pressure pump 6 through a pipe 4 connecting the lower part of the tank 2 and the lower part of the coating tank 1, and flows through a gutter 9 which overflows from its upper edge and receives it. 7 and circulates back to the coating liquid tank 2.

Using such a coating apparatus, a cylindrical substrate 10 provided with a mechanism for preventing the coating liquid from entering the inside of the cylinder is placed in the coating tank 1 while the coating liquid 3 is circulated. By holding the tube almost vertically and immersing it in the direction of the cylinder axis, and then pulling it up at a predetermined speed, a uniform and uniform coating film is formed on the outer surface of the cylindrical substrate 10.
In this case, when the cylindrical substrate 10 is immersed in the coating tank 1, an amount of the coating liquid corresponding to the volume of the substrate is added to the steady overflow amount and overflows. , The liquid level changes. For this reason, the pulling speed of the substrate with respect to the coating liquid level changes, and the coating liquid cannot be uniformly applied to the outer surface of the substrate. In order to minimize the influence of such liquid level fluctuation, a method is adopted in which the amount of circulation of the coating liquid is adjusted, and the liquid is applied while the coating liquid overflows without interruption when lifting the substrate.

[0005]

In such a circulation type coating apparatus, as a method for collecting the overflowed liquid, there is a free fall method in which the coating liquid is collected by utilizing the height difference between the circulation tank and the coating tank. , There is a method of collecting with a pump.

[0006] Each of these recovery methods has the following problems. That is, the free fall method is a simple method that does not require driving of a pump or the like, but it is necessary to consider the positional relationship between the coating tank and the circulation tank. In addition, when the collected coating liquid is stored in the circulation tank, bubbles are generated due to an impact caused by falling on the coating liquid surface. Although it is not necessary to consider the positional relationship between the coating tank and the circulating tank when collecting with a pump, bubbles may be caught at the time of liquid feeding depending on the type of pump and the driving method. If these bubbles are present in the coating liquid, they adhere to the coated photosensitive layer of the photosensitive drum, resulting in defective products and a reduction in yield. In particular, when the cylindrical substrate is lifted from the coating tank, bubbles are generated on the liquid surface when the cylindrical substrate separates from the coating liquid, and are transferred to the circulation tank through a pipe together with the overflow of the coating liquid. When the viscosity of the coating liquid is high, the bubbles circulate in the coating device without disappearing, and if the bubbles are present in the coating liquid, they adhere to the photosensitive layer of the coated photosensitive drum in the same manner, resulting in a defective product and yield. May cause a drop.

[0007]

According to the present invention, in order to solve the above-mentioned problems, a cylindrical substrate is immersed in a coating solution with its cylindrical axis held substantially vertically, and pulled up from the coating solution to the outside. In a coating apparatus for coating a coating liquid on the outer surface of the cylindrical substrate, a coating tank containing the coating liquid and immersing the cylindrical substrate, and a circulation tank for circulating the coating liquid to the coating tank A coating liquid circulating mechanism that feeds the coating liquid from the lower part of the circulation tank to the lower part of the coating tank by a pressure pump, overflows from the upper edge of the coating tank, and sends the coating liquid to the circulation tank. This is achieved by arranging a filter on the pipe leading to the upstream of the flow of the coating liquid. Further, this is achieved by providing an air vent mechanism near the filter. In addition, the filter is achieved by disposing the filter so as to close an upper portion of the inner diameter of the pipe. Further, the opening degree of the filter is 50 to 10
This is achieved by being 0 μm.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of an example of a coating apparatus according to the present invention, wherein 1 is a coating tank and 2 is a circulation tank. The coating liquid 3 is connected to a pipe 4 connecting the lower part of the circulation tank 2 and the lower part of the coating tank 1.
Is fed into the coating tank 1 by the pressure feed pump 6, overflows from the upper edge thereof, passes through the gutter 9 which receives the overflow, and is sent to the circulation tank 2 through the pipe 7 to circulate in the coating apparatus. In the middle of the pipe 7, there is provided a filter 8 which is inclined toward the upstream side of the flow of the overflowing coating liquid 3 from the gutter 9 to the circulation tank 2. An air release mechanism 11 is provided near the filter 8.

As shown in FIG. 3, the filter 8 is provided with a mesh at the top of the pipe 7 and at least an arrow B
Is made to exist below the surface of the coating liquid 3 flowing in the direction of. The filter 8 is inclined such that its upper part is located above the horizontal plane, though it is related to the inclination angle of the pipe as shown in FIG.

Using such an apparatus, while circulating the coating liquid 3, the cylindrical substrate 10 provided with a mechanism for preventing the coating liquid from entering the inside of the cylinder is moved by a bidirectional arrow A by a lifting means (not shown). Move vertically in the axial direction like
The coating is performed by dipping in the coating tank 1 and lifting it up. When the cylindrical substrate 10 is immersed, the amount of the coating liquid overflowing from the upper edge of the coating tank 1 increases.

In particular, when the cylindrical substrate 10 is lifted, excess coating liquid drops on the coating liquid surface in the coating tank 1, and bubbles are generated due to the impact or a sudden change in the liquid level. The overflowed coating liquid 3 is collected in a gutter 9 as a receiving tray and flows through the pipe 7. Bubbles generally have a low density and concentrate in the upper layer of the coating liquid 3, and therefore flow on the surface of the coating liquid flowing in the pipe 7. Therefore, the bubbles are crushed or captured by the filter 8 provided in the pipe 7, and the movement of the bubbles into the circulation tank 2 is blocked.

The degree of opening of the filter 8 depends on the viscosity of the coating liquid 3 and the lifting speed of the cylindrical substrate 10, and depends on the size of the generated bubbles. 50-100μ because the diameter is about 0.1-2mm
With a mesh of m, bubbles can be captured. The filter 8 is arranged so as to go back to the flow, and scoops bubbles from the application liquid flow. Since the upper part of the filter 8 is slightly inclined from the horizontal plane in a direction away from the liquid surface, the scooped bubbles move to the upper part of the filter 8 and are crushed by the wall surfaces of the filter 8 and the pipe 7.

Although the inclination angle of the filter 8 is related to the inclination of the pipe 7, the pipe 7 has a gentle inclination in order to return the overflowing coating liquid 3 to the circulation tank 2. As shown in FIG. 4, when the angle between the filter 8 and the horizontal plane is α and the angle between the pipe 7 and the horizontal plane is β, the pipe 7 for allowing the overflowing coating liquid 3 to flow naturally and gently into the circulation tank 2 is formed. The angle β is 5 to 30 degrees, while the angle of the filter 8 is desirably 0 to 30 degrees in order to scoop the bubbles and trap the bubbles in the filter 8. Angle, ie, 180- (α
+ Β) degree is desirably about 130 to 175 degrees in order to effectively scoop up the bubbles while suppressing the generation of bubbles by the filter 8.

Further, an air bleeding mechanism for discharging the clogged foam to the outside is provided near the filter 8, so that the foam does not stay in the pipe for a long time.

[0015]

According to the present invention, a cylindrical substrate is immersed in a coating solution while its cylindrical axis is held substantially vertically.
In a coating apparatus for applying a coating liquid to the outer surface of the cylindrical substrate by pulling up the coating liquid to the outside, a coating tank containing the coating liquid and immersing the cylindrical substrate, and coating the coating liquid It has a circulation tank that circulates through the tank, and has a coating liquid circulation mechanism that sends the coating liquid from the lower part of the circulation tank to the lower part of the coating tank with a pressure pump, overflows from the upper edge of the coating tank, and sends it to the circulation tank A filter is arranged in a pipe for guiding the coating liquid to the circulation tank toward an upstream side of the flow of the coating liquid. Further, the filter is arranged so as to close an upper portion of the inner diameter of the pipe. The filter has an aperture of 50 to 100 μm.

With the coating apparatus having such a configuration, the generation of bubbles in the coating liquid is reduced, and the movement of the generated bubbles to a subsequent process is reduced, so that a film is formed on the outer surface of the cylindrical substrate. It is possible to dip-coat a submicron-order thin film having a uniform thickness and a uniform thickness without unevenness.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of one embodiment of a coating apparatus of the present invention.

FIG. 2 is a conceptual diagram of an example of a conventional coating apparatus.

FIG. 3 is a conceptual diagram showing a relationship between a pipe and a filter.

FIG. 4 is a conceptual diagram showing a state of capturing bubbles in a coating solution.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coating tank 2 Circulation tank 3 Coating liquid 4, 7 Piping 6 Pressure pump 8 Filter 9 Gutter 10 Cylindrical base 11 Air release mechanism

Claims (4)

[Claims] A coating apparatus for applying a coating liquid to an outer surface of a cylindrical substrate by immersing the cylindrical substrate in a coating liquid while keeping its cylindrical axis substantially vertical, and pulling the coating liquid out of the coating liquid. In the above, there is provided a coating tank containing the coating liquid and immersed in the cylindrical substrate, and a circulation tank for circulating the coating liquid to the coating tank, and coating the coating liquid from the lower part of the circulation tank by a pressure pump. Equipped with a coating liquid circulation mechanism that feeds into the lower part of the tank, overflows from the upper edge of the coating tank and sends it to the circulation tank, and arranges a filter on the pipe that guides the overflowing coating liquid to the circulation tank toward the upstream side of the flow of the coating liquid A coating device, characterized in that: 2. The coating apparatus according to claim 1, wherein the filter is disposed so as to close an upper portion of an inner diameter of the pipe. 3. The coating apparatus according to claim 2, wherein an air release mechanism is provided in the vicinity of the pipe where the filter is provided. 4. The filter has an aperture of 50 to 100.
2. The coating device according to claim 1, wherein the thickness is μm.