JPH10272397A - Method and device for immersing coating of cylindrical body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the formation of uneven film thickness in the circumferential direction of a substrate and improve the film thickness uniformity by a simple method. SOLUTION: When a coating liquid is fed from a lower section and a cylindrical substrate is immersed in a coating tank overflowing from its upper section and then the cylindrical base is lifted up to carry out the immersion coating of the cylindrical substrate, a body with a helical rib 4 formed on the inner wall is used as the coating tank 1. The cylindrical substrate can be lifted while a swirl flowing is generated in a coating liquid between the cylindrical substrate and a coating tank inner wall by the arrangement, and as a result, when a coated layer of film thickness of 10 μm or more is formed on the surface of the cylindrical substrate, the uniform film without the uneven film thickness can be formed. As for the cylindrical substrate, a photoreceptor drum substrate and a development sleeve substrate are used suitably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dip-coating method for a cylindrical substrate such as a photosensitive drum, and more particularly to a dip-coating method capable of easily and largely reducing circumferential thickness unevenness.

[0002]

2. Description of the Related Art Conventionally, a photosensitive drum has been widely manufactured by applying a photosensitive coating solution or the like to the surface of a cylindrical substrate. The coating method is described, for example, in JP-A-59-906.
As described in Japanese Patent Publication No. 67, a method of dip coating a substrate while overflowing and circulating a coating solution from the upper portion of a coating tank is generally used. The photosensitive drum is charged,
Processes such as exposure, development, transfer, and cleaning of residual toner are added, but their characteristics depend on the film thickness, and important characteristics such as chargeability and sensitivity are sensitively affected by the film thickness. In particular, in a color image output apparatus, the uniformity of halftone density is very important, and in a photosensitive drum used in the color image output apparatus, the uniformity of the thickness of a photosensitive layer is more strictly required than before.

However, when the photosensitive drum is manufactured by the dip coating method, there is a disadvantage that the film thickness tends to be uneven in the axial direction or circumferential direction of the cylindrical substrate. As the film thickness unevenness in the axial direction, a so-called edge portion at the upper end portion of the coating film is typical. As countermeasures against this, for example, as described in JP-A-59-73074, an air stream is applied to the coating to promote drying,
As described in JP-A-9-127049 and the like, a method for promoting drying by sucking a solvent vapor near a coating film is known.

On the other hand, film thickness unevenness in the circumferential direction is caused by an uneven amount of overflow of the coating liquid in the circumferential direction or an uneven flow path of the overflow flow. Regarding technology to prevent this, Japanese Patent Publication No. 3-22
As described in Japanese Patent Publication No. 226, there is known a method of rotating a spiral blade provided in a coating tank to swirl the coating liquid to homogenize the coating liquid. FIG. 5 is a view for explaining such a case. In FIG.
A spiral blade 22 is rotatably provided in the coating tank 20 holding the coating liquid. A gear 24 is attached to the upper end of the spiral blade 22, and by driving a drive mechanism 23, bevel gears 25, 26
And a gear 27. However, in the case of this publication, a driving mechanism and a gear mechanism for rotating the spiral blade are required, and there is a disadvantage that the structure of the coating apparatus is complicated. Further, in the case of the above publication, the spiral blade has an upper end protruding from the upper edge of the coating tank, so that when the spiral blade is applied to a dip coating apparatus, the overflow is not uniform, and the blade is easily rotated. In order to achieve this, it is necessary to provide a sufficient distance between the coating tank and the blade and between the blade and the substrate, which causes a problem that a sufficient swirling flow does not occur.

In addition, as described in JP-A-64-75064 and JP-A-3-20748, a method of stirring a coating liquid by providing a circumferential flow generating means below a coating tank,
As described in JP-A-2-9472 and JP-A-3-27048, there is known a method in which a coating solution is supplied from the lower portion of a coating tank while being swirled. Although it occurs in the lower part of the tank, there is a problem that the swirling effect is weakened in the overflow part in the upper part of the coating tank. Instead of swirling the coating solution, there is also known a method of pulling up while rotating the substrate by a substrate support having a rotation drive unit as described in JP-A-1-171672, but the coating device is also complicated. There was a problem of becoming.

[0006]

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 a dip coating method for a cylindrical substrate, which can eliminate unevenness in the thickness of a coating layer in the circumferential direction and improve the uniformity of the thickness. Another object of the present invention is to provide a dip coating apparatus having a simple structure capable of eliminating unevenness in circumferential thickness and improving uniformity of thickness.

[0007]

According to the dip coating method for a cylindrical substrate of the present invention, the cylindrical substrate is immersed in a coating tank which is supplied with a coating liquid from the lower part and overflows from the upper part, and then is lifted up. A method for applying a coating liquid, wherein a coating tank having a spiral rib on an inner wall is used, and the substrate is pulled up while causing a swirling flow in the coating liquid between the substrate and the inner wall of the coating tank. I do. At that time, it is also effective to lift the substrate while applying an air current to the coating layer. The dip coating method of the present invention can be effectively applied particularly to dip coating of a cylindrical substrate used for applications in which the occurrence of uneven film thickness in the circumferential direction becomes a problem, such as a photosensitive drum and a developing sleeve.

The dip coating apparatus of the present invention has a support member for vertically moving a cylindrical substrate and supporting it so that it can be inserted into a coating tank, a coating liquid supply port at a lower part, and a coating liquid overflowing at an upper part is collected. And a circulating means for circulating the recovered coating liquid, wherein the coating tank has a spiral rib on the inner wall.

[0009]

FIG. 4 is a schematic diagram showing an example of a dip coating apparatus according to the present invention. The dip coating apparatus comprises a coating tank 1 having an inner wall provided with spiral ribs, and a guide tube 11. A coating liquid circulating means including a coating liquid recovery tank 12, a pump 13, and a pipe 14, and a support member for vertically supporting the cylindrical substrate 7, which is an object to be coated. The coating tank 1 is provided with a spiral rib on its inner wall as described later, and a supply port for supplying the coating liquid 6 is provided below the rib. It communicates with the liquid recovery tank 12. A receiver 3 for holding the overflowing coating liquid is formed on the upper outer peripheral surface of the coating tank. The receiver 3 is provided with a discharge port connected to the guide tube 11 so that the recovered coating liquid passes through the guide tube and is recovered in the coating liquid recovery tank. On the other hand, the cylindrical base 7 is supported by a support member 8 and is configured to move up and down by a motor 15 and a ball screw 16.

FIG. 1 is a schematic view of an example of a coating tank used in the present invention. The coating tank 1 is provided with a supply port 2 for supplying a coating liquid at a lower part, and is provided at an upper outer peripheral surface. ,
A receiver 3 for holding the overflowing coating liquid is provided. A spiral rib 4 is provided on the inner wall of the coating tank. In this coating tank, the coating liquid is supplied from a supply port at the lower part of the coating tank, overflows from the upper edge, is collected by the receiver 3, is discharged from the discharge port 5, and is circulated.

The inner diameter of the coating tank is 20 to 10 times smaller than the outer diameter of the substrate.
What is necessary is just to be 0 mm larger. As the spiral rib 4 provided on the inner wall of the coating tank, two or more plate-shaped ribs may be used, and the inclination thereof can be arbitrarily set. Regarding the setting position of the rib, the upper end of the rib is 1
It is preferable to form it so as to be located at 0 to 20 mm below. If the upper end of the rib protrudes from the upper edge of the coating tank, the overflow of the coating liquid is blocked at that portion, and if the rib is located immediately below the upper edge of the coating tank, the flow of the coating liquid is disturbed. Because. The position of the rib lower end is arbitrary.

FIG. 2 is a sectional view of the coating tank showing a state where the cylindrical substrate is immersed in a coating liquid. In the figure, reference numeral 6 denotes a coating solution, 7 denotes a cylindrical base, 8 denotes a support member, and other reference numerals mean the same as those in FIG. The dip coating is performed by attaching the cylindrical substrate 7 to the support member 8 and immersing it in the coating liquid 6 and then pulling it up at a predetermined speed. However, when the cylindrical substrate is not immersed, the coating liquid flows through the center of the coating tank. It does not turn especially. However, when the cylindrical base 7 is immersed and pulled up, the coating liquid 6 flows through the gap between the cylindrical base and the inner wall of the coating tank, and the spiral rib 4
Is present, the coating liquid flows while spiraling. Therefore, in order to promote the rotation of the coating liquid, it is preferable that the interval between the rib and the cylindrical base is small,
Usually, about 1 to 5 mm is preferable. At the time of dip coating, the larger the supply amount of the coating liquid, the stronger the swirling of the coating liquid by the ribs, and the coating liquid is homogenized. However, if the supply amount of the coating liquid is too large, the overflow surface is wavy, so that it is not wavy. It is preferable to increase the supply amount within the range.

FIG. 3 is an explanatory view of a coating tank showing another embodiment of the present invention. In this embodiment, instead of forming the rib directly on the inner wall of the coating tank, an annular swirling flow generating jig 9 having the rib 4 attached to the inner wall is fitted inside the upper part of the coating tank 1 so that the inner wall of the coating tank is formed. A helical rib is provided. In the case of this embodiment, a conventional coating tank having no rib can be used as the coating tank.

Generally, circumferential unevenness is 10 μm thick.
Such a coating layer is likely to occur in the above-mentioned coating layer.
L) is representative. The CTL is formed on a charge generation layer (CGL) by dissolving a charge transport material such as a benzidine compound or a hydrazone compound in a solvent together with a film-forming resin such as polycarbonate or polyarylate. CGL is formed by dispersing a charge-generating pigment such as phthalocyanine or perylene in a binder resin solution such as polyvinyl butyral or polyester to form a coating solution and, if necessary, on a cylindrical substrate having an undercoat layer formed thereon. The thickness of the CGL is generally 0.05 to 0.5 μm, and the viscosity of the coating solution is low. Therefore, even if it is well flow-stirred and immersion-coated, the circumferential unevenness does not cause much problem. The thickness of the coating solution is usually as thick as 10 to 35 μm, and the viscosity of the coating solution is high, so that it is difficult to stir, and there is a problem of unevenness.
According to the method of the present invention, the required value for the film thickness unevenness is 1 μm.
Even in the case of m or less, the required value can be satisfied.

As another coating layer having a film thickness of 10 μm or more that can be suitably used in the dip coating method of the present invention, for example, a resin layer containing conductive fine particles such as carbon (Japanese Patent Laid-Open No. 1-27-27)
No. 6174), and a coating layer of a developing sleeve (coat sleeve) in which a film is formed on the surface of a cylindrical substrate, such as a film containing molybdenum disulfide (see Japanese Patent Application Laid-Open No. 3-1380). These coating layers are provided in order to prevent development ghosts and have a film thickness of usually 5 to 50 μm, but it is preferable to apply the present invention when the thickness is 10 μm or more.

In the present invention, it is also effective to raise the cylindrical substrate while applying an air current in order to promote drying of the coating layer and reduce dripping. When applying airflow, if the method of applying as a circumferential flow in the tangential direction of the cylindrical substrate,
There is also an advantage that unevenness in film thickness in the circumferential direction of the substrate can be prevented. (JP-A-3-213171, JP-A-4
-29773)

[0017]

【Example】

Example 1 The surface of an aluminum cylindrical substrate having an outer diameter of 30 mm, an inner diameter of 28.5 mm, and a length of 258 mm was roughened by honing, and a subbing layer of type 8 nylon resin having a thickness of 1 μm was formed. On the other hand, 1 part (parts by weight, hereinafter the same) of a polyvinyl butyral resin (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) was dissolved in 19 parts of cyclohexanone, and 3 parts of chlorogallium phthalocyanine was added and dispersed by a sand mill.
Further, 20 parts of 2-butanone was added to prepare a coating solution, which was dip-coated on the undercoat layer, dried at 100 ° C. for 5 minutes, and dried at 0.1 ° C.
An m-thick CGL was formed. Since the undercoat layer and the CGL are thin, there is no problem of unevenness in the circumferential direction. Therefore, dip coating was performed by a usual method.

Next, N, N'-diphenyl-N, N '
36 parts of (m-tolyl) benzidine and 64 parts of polycarbonate Z resin were dissolved in 300 parts of monochlorobenzene to prepare a coating liquid for CTL formation. This coating liquid was circulated in the dip coating apparatus at a supply rate of 1.5 liter / min. The coating tank is a cylindrical one with a height of 350 mm and an inner diameter of 60 mm.
Spiral ribs with a width of 13 mm on the inner wall, 20 mm from the upper edge
Three pieces were formed at a position from the position of mm to 200 mm.
The cylindrical substrate on which each layer up to the CGL was formed was chucked to a support member, immersed in a coating solution, and pulled up at a rate of 150 mm / min for coating. The interval between the cylindrical substrate and the spiral rib was 2 mm, and the coating liquid mainly flowed between the ribs and overflowed while generating a swirling flow. After the application, the coating was dried at 115 ° C. for 40 minutes to form CTL. When the thickness of the CTL was measured, it was found to be approximately 20 μm in the circumferential direction.
m, and no unevenness occurred. When the photosensitive drum was mounted on a color copying machine and subjected to an image copying test, no unevenness was observed, and an image of good quality was obtained.

Comparative Example 1 An OPC photosensitive drum was manufactured in the same manner as in Example 1, except that a coating tank having no spiral rib was used when applying CTL. After CTL formation,
When the film thickness was measured, unevenness of 1.5 μm was recognized in the circumferential direction.

When the photosensitive drum was mounted on a color copying machine and subjected to an image copying test, a slight density unevenness occurred in the halftone image corresponding to the uneven thickness of the CTL.
However, when this photosensitive drum was used in a laser printer that mainly outputs character images, unevenness did not cause a problem. Conventionally, since the OPC photosensitive drum was rarely used in a color copying apparatus, it is considered that density unevenness due to uneven film thickness was not detected.

Embodiment 2 As shown in FIG. 3, an annular swirling flow generating jig having a rib 4 attached to an inner wall thereof is provided in a cylindrical coating tank 1 having a height of 350 mm and an inner diameter of 60 mm without a spiral rib. The tool 9 was fitted. As the swirling flow generating jig, one having twelve ribs formed from a position 20 mm from the upper edge to 100 mm from the upper edge was used. Using this coating tank, C
When TL was applied and formed, no unevenness in film thickness similarly occurred.

[0022]

According to the dip coating method of the present invention, by using a dip coating apparatus having a simple structure having a coating tank provided with helical ribs on the inner wall, dip coating of a thick film coating liquid on a cylindrical substrate is performed. Is performed, it is possible to prevent the occurrence of uneven film thickness in the circumferential direction, and it is possible to form a coating film having a uniform thickness even when a thick film having a thickness of 10 μm or more is formed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a coating tank used in a dip coating method of the present invention.

FIG. 2 is a cross-sectional view showing a coating tank in a state where a cylindrical substrate is immersed in a coating liquid in the present invention.

FIG. 3 is a schematic configuration diagram of another embodiment of a coating tank in the present invention.

FIG. 4 is a schematic configuration diagram of an example of a dip coating apparatus of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional coating tank.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Application tank, 2 ... Supply port, 3 ... Receiver, 4 ... Rib, 5 ...
Discharge port, 6: coating liquid, 7: cylindrical substrate, 8: support member, 9
... Swirl flow generating jig, 11 ... Guide tube, 12 ... Coating liquid recovery tank, 13 ... Pump, 14 ... Piping, 15 ... Motor, 1
6 ball screw, 20 coating tank, 21 seal member,
22: spiral blade, 23: drive mechanism, 24: gear,
25, 26: bevel gear, 27: gear.

Claims (4)

[Claims] 1. A dip coating method in which a coating liquid is supplied from a lower part and is immersed in a coating liquid in a coating tank overflowing from an upper part and then pulled up to apply the coating liquid to the cylindrical base. A dip coating method comprising using a coating tank having spiral ribs and raising the base while causing a swirling flow in the coating liquid between the base and the inner wall of the coating tank. 2. The dip coating method according to claim 1, wherein the cylindrical substrate is a substrate for a photosensitive drum. 3. The dip coating method according to claim 1, wherein the cylindrical substrate is a substrate for a developing sleeve. 4. A support member for vertically moving a cylindrical substrate and supporting it so as to be insertable into a coating tank, and a receiver having a coating liquid supply port at a lower part and collecting an overflowing coating liquid at an upper part. In a dip coating apparatus having a coating tank having, and a circulating means for circulating the collected coating liquid,
A dip coating apparatus, wherein the coating tank has a spiral rib on an inner wall.