JPH0212155A - Dip coating method and coating device for photosensitive drum or the like - Google Patents

Abstract

PURPOSE:To prevent coating liquid from being dried on the upper end surface of a coating liquid tank and a solvent from vaporizing from the coating liquid surface by covering the coating liquid surface and the upper end surface of the coating liquid tank with a cover and pressing up the cover by the elevation of the liquid surface of the coating liquid when the coating liquid overflows. CONSTITUTION:The cover 3 which covers the surface of the coating liquid 4 and the upper end surface 11 of the coating liquid tank 1 is formed annularly of a lightweight member which floats on the surface of the coating liquid 4, e.g. styrolfoam. The cover 3 is supported by making its reverse surface abut on the upper end surface 11 of the coating liquid tank 1. The coating liquid 4, therefore, presses up the cover 3 slightly at the time of overflowing from the upper end surface 11 of the coating liquid tank 1 to flow out to a recovery tank 2. Consequently, the vaporization of the solvent and the drying of the coating liquid on the upper end surface of the coating liquid tank 1 where the coating liquid sticks by the overflowing can be prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for forming a coating film on the outer peripheral surface of a cylindrical substrate such as an electrophotographic photoreceptor drum, and in particular, immerses the substrate in a coating liquid, The present invention relates to a method and an apparatus that enable coating without coating unevenness and with uniform physical properties.

(Prior art) Conventionally, one of the methods for manufacturing photoreceptor drums for electrophotographic copying machines is to immerse a cylindrical substrate in a coating solution containing a photosensitive substance to apply the photosensitive substance to the outer peripheral surface of the substrate. A method for manufacturing photographic photosensitive drums is known as a dip coating method (see Japanese Patent Application Laid-open No. 130736/1984, etc.).

The dip coating method involves dipping the substrate into a pool of coating solution.
A volatile organic solvent such as tetrahydrofuran is used in the coating liquid used in manufacturing the photosensitive drum, and is obtained by dispersing or dissolving a photosensitive substance in this organic solvent.

Since the solvent is constantly evaporating from the coating solution, a film is formed on the liquid surface of the coating solution tank that stores the coating solution, and this film adheres to the peripheral surface of the substrate, and after the coating solution dries, the coating becomes uneven. There is a problem where it can become a hail.

Additionally, as the coating liquid decreases, the height of the rise in the coating liquid level as the substrate is immersed in the coating liquid tank changes, causing the troublesome problem of having to adjust the immersion depth of the substrate accordingly. there were.

Therefore, in order to eliminate the above drawbacks,
A dipping coating method has been proposed in which the coating liquid always overflows from the upper end surface of the coating liquid tank each time the photoconductor drum is immersed or during the manufacturing process of the photoreceptor drum.

(Problems to be Solved by the Invention) - In the case of a boat-type dip coating method, it is known that the surface of the coating solution is covered with a cover to prevent solvent evaporation at least when the substrate is immersed. . However, in the case of the above-mentioned dip coating method that causes overflow, even if only the surface of the coating liquid in the coating liquid tank is covered, when the apparatus is stopped (when the pump is stopped), the coating liquid adheres to the upper end surface of the coating liquid tank due to overflow. dries, and the height of the upper end surface of the coating liquid tank becomes uneven. As a result, the height of the coating film on the outer peripheral surface of the substrate during dipping is affected.

Furthermore, when the overflowing coating liquid is circulated within the apparatus, the coating liquid dried on the upper end surface of the coating liquid tank becomes an impurity, which affects the surface uniformity of the coating film.

Therefore, an object of the present invention is to prevent the coating liquid from drying on the upper end surface of the coating liquid tank by always covering the coating liquid surface and the upper end surface of the coating liquid tank in which the coating liquid is stored, with a cover.
Prevents solvent evaporation from above the coating liquid surface. As a result, it is an object of the present invention to provide a dip coating method for a photoreceptor drum and a coating method that can obtain a coating film having a uniform thickness on the outer peripheral surface of a substrate without coating unevenness.

(Means for Solving Problems) According to the present invention, in order to form a photoreceptor layer on the circumferential surface of a photoreceptor drum substrate, an overflow is caused in the final stage due to a rise in the liquid level of the coating liquid. In the dip coating method, the substrate is immersed in the coating liquid while keeping the liquid level constant, and after reaching a predetermined depth, the substrate is pulled up to form a photoreceptor layer on the peripheral surface of the substrate. The surface of the coating liquid and the upper end surface of the coating liquid tank are covered with a cover, and when the coating liquid overflows, the cover is pushed upward by the rise in the liquid level of the coating liquid, thereby achieving the above object. be done.

Further, the coating apparatus for carrying out the above-mentioned coating method includes a coating liquid tank in which a coating liquid for coating the circumferential surface of the substrate is stored, and a coating liquid tank for collecting the coating liquid flowing out from the upper end surface of the coating liquid tank. a recovery tank provided on the outer periphery of the coating liquid tank; a cover that substantially entirely covers the upper end opening of the recovery tank and the surface of the coating liquid, and has an opening through which the base body can pass;
The cover is supported by the upper end surface of the coating liquid tank and is guided vertically to the inner circumferential surface of the recovery tank, thereby achieving the above object.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described based on the accompanying drawings.

FIG. 1 is a schematic sectional view showing the state before the substrate is inserted into the coating liquid, and FIG. 2 is a schematic sectional view showing the state where the substrate is immersed in the coating liquid.

As shown in FIG. 1, the dip coating method for photoreceptor drums of the present invention includes a coating liquid tank 1 containing a volatile coating liquid 4, a recovery tank 2 provided on the outer periphery of the coating liquid tank 1, This is carried out using a cover 3 supported on the upper end surface 11 of the coating liquid tank 1 and disposed inside the recovery tank 2.

The recovery tank 2 is formed so that the outer periphery of the upper edge of the coating liquid tank 1 is annular, and the upper end surface of the outer wall of the recovery tank 2 is located higher than the upper end surface 11 of the coating liquid tank 1. The bottom of the recovery tank 2 is connected to a waste liquid tank (not shown) via a cock 5, and the bottom of the coating liquid tank 1 is connected to a replenishment tank (not shown) via a screwdriver. Therefore, the coating liquid 4 is injected into the coating liquid tank 1 from the supply tank through the conduit,
The coating liquid 4 overflowing from the coating liquid tank 1 is once
The liquid flows out into the recovery tank 2 and is recovered into the waste liquid tank via the cock 5.

Reference numeral 7 denotes a cylindrical base for the photosensitive drum, which is held by a holding means 8 disposed above the coating liquid tank 1 .

The holding means 8 (see FIG. 2) is disposed approximately vertically above the coating liquid 4, and its upper portion is connected to an elevating device (not shown). It is driven up and down while holding the In addition, as the above-mentioned holding means 8,
For example, the one disclosed in Japanese Unexamined Patent Application Publication No. 25660/1983 can be used. Therefore, even if the base body 7 is hollow, it can be immersed without the coating liquid 4 entering inside.

Although the shape of the coating liquid tank l is not particularly limited, it is preferably a cylindrical container, which has an inner diameter larger than the outer diameter of the base 7 and a depth larger than the axial length of the base 7. It has a certain quality.

As the coating liquid 4 contained in the coating liquid tank 1, for example, when manufacturing an electrophotographic photosensitive drum, a photosensitive substance dissolved in a volatile organic solvent such as tetrahydrofuran is used.

Further, the base body 7 is made of aluminum, for example.

Metals such as nickel, copper, zinc, palladium, silver, indium, tin, platinum, iron, stainless steel, and brass are used.

In addition, the cylindrical shape in the shape of the base body 7 is not particularly limited to the shape of both ends, as long as at least the body part is cylindrical.
For example, members or parts of other shapes may be added to both ends or one end thereof by means of fixing or fitting.

The cover 3 that completely covers the surface of the coating liquid 4 and the upper end surface 11 of the coating liquid tank 1 is preferably formed into an annular shape using a lightweight member (eg, styrene foam, etc.) that can float above the surface of the coating liquid 4. The cover 3 is supported by its lower surface coming into contact with the upper end surface 11 of the coating liquid tank 1. Therefore, when the coating liquid 4 overflows from the upper end surface 11 of the coating liquid tank 1, it flows out into the recovery tank 2 by pushing up the cover 3 slightly upward.

Further, if the diameter of the opening 31 of the cover 3 is larger than the outer diameter of the base 7, or if it is too large, the problem of evaporation of the coating liquid 4 occurs, which is not preferable. On the other hand, if it is made smaller, there is a possibility that it will hit the cover 3 when lowering the base 7, and if the coating liquid has a high viscosity, it will pass through the gap D (see Figure 2) between the base 7 and the cover 3 when it is raised. Coating on the top surface of cover 3 along with base 7? (! 4 overflows. Therefore, the diameter of the opening 31 and the outer diameter of the base body 7 should be determined respectively so that the inside of the gap is 2 to 3 mm or less.The outer diameter of the cover 3 is Specifically, the gap between the outer circumferential surface 32 of one cover 3 and the inner circumferential surface 21 of the collection tank 2 (see FIG. 1) is smaller than the middle of the gap, preferably there is no gap. It is better.And the outer peripheral surface 32 of the cover 3
is opposed to the inner circumferential surface 21 of the collection tank 2, so that the vertical movement of the cover 3 is guided by the inner circumferential surface 21. That is, the inner peripheral surface 21 functions as a guide for the cover 3. With the above configuration, the upper end opening 22 of the recovery tank 2 is also substantially entirely covered by the cover 3.

In the above apparatus configuration, the method of the present invention is implemented as follows.

First, as shown in FIG. 1, the lid is opened and the coating liquid 4 is constantly injected into the coating liquid tank 1 so that the coating liquid 4 overflows from the upper end surface 11 of the coating liquid tank 1 to the recovery tank 2 side. Next, the substrate 7 held by the holding means 8 is inserted into the coating liquid tank 1 as shown in FIG. 2 and immersed. At this time, coating liquid 4
is displaced by the volume of the substrate 7, and a larger amount of the coating liquid 4 overflows from the upper end surface 11 of the coating liquid tank 1 than the amount of overflow accompanying the injection of the coating liquid 4, and flows out into the recovery tank 2. The cover 3 is guided by the inner circumferential surface 21 of the recovery tank 2 and moves in the vertical direction as the overflow occurs. and,
When the substrate 7 is pulled up, coating is completed and the next substrate 7 is dipped.

When the base body 7 is pulled up, the overflow amount pushed away by the base body 7 and the coating liquid 4 coated on the base body 7 disappear from the coating liquid tank 1, so that the liquid level of the coating liquid 4 falls.

However, if the injection amount is set so that the coating liquid 4 is injected from a replenishment tank (not shown) via a droplet in an amount that exceeds the amount of drop in the liquid level due to the rate at which the substrate 7 is pulled up, overflow will always occur even when the substrate 7 is pulled up. The state can be maintained.

If it always overflows as above, apply liquid 4.
The supply speed of the coating liquid becomes considerably high, and the turbulence caused by the waving of the liquid surface on the surface of the coating liquid 4 increases accordingly. However, since the cover 3 absorbs the turbulence of the coating liquid 4, variations in the thickness and height of the coating film on the outer peripheral surface of the base body 7 are prevented.

If the apparatus is stopped here and there is no overflow, if the liquid level of the coating liquid 4 is equal to the upper end surface 11, then
When the cover 3 comes into contact with the upper end surface 11, the coating liquid 4 is always present in the gap between the lower surface of the cover 3 and the upper end surface 11 due to capillary action. I have no contact with you. Therefore, the upper end surface ll
Drying of the coating liquid 4 on the surface is suppressed.

Further, even when the liquid level of the coating liquid 4 does not reach the upper end surface 11 of the coating liquid tank l, the coating liquid 4 interposed at the abutting portion between the lower surface of the cover 3 and the upper end surface 11 does not have the cover 3. than time,
Drying of the coating liquid 4 is extremely suppressed.

Furthermore, since the cover 3 completely covers the upper end opening 22 of the recovery tank 2, the internal space becomes saturated with solvent vapor, and the recovery tank 2 becomes saturated.
Evaporation of the coating liquid 4 adhering to the inside and the solvent of the recovered coating liquid 4 is also suppressed. Therefore, the upper end surface 11 of the coating liquid tank 1
The film of the coating liquid 4 does not adhere to the surface and its height becomes non-uniform, and even if the collected coating liquid 4 is circulated within the apparatus, the uniform physical properties of the coating film are maintained.

Although specific examples of the apparatus for carrying out the dip coating method according to the present invention have been described above, the present invention is not limited to these specific examples and can be modified in various ways.

For example, the opening 31 of the cover 3 may be provided with a lid before the substrate 7 is immersed in order to more effectively prevent evaporation. Further, the opening 31 of the cover 3 may have a shutter structure so that when the base 7 is immersed, it opens in the side direction to form the same opening 31 as described above.

Incidentally, as a dipping method, the substrate 7 can be fixed and the coating liquid tank 1 can be raised and lowered for dipping.

(Effects of the Invention) As described above, the present invention suppresses evaporation of the solvent by covering almost the entire opening of the upper end surface of the device with a cover supported by the upper end surface of the coating liquid tank, and in particular prevents the coating liquid from overflowing. It is possible to prevent the coating liquid from drying on the top and end surfaces of the coating liquid tank to which it adheres. As a result, no liquid surface film of the coating liquid remains, and there is no possibility that it will adhere to the circumferential surface of the substrate, thereby making it possible to obtain a coating film with no uneven coating and uniform physical properties.

Furthermore, since the recovery tank is also covered, evaporation of the solvent from the recovery tank is also suppressed.

Note that the cover absorbs disturbances caused by undulating the liquid surface and has the effect of forming a uniform coating film.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a coating device showing an embodiment of the present invention, showing a state before a substrate is inserted into a coating solution, and FIG. 2 is a schematic sectional view of a coating device showing a state in which a substrate is immersed in a coating solution. FIG.・Coating liquid tank ・Collection tank ・Cover ・Coating liquid ・Substrate Utility model registration applicant Sanda Kogyo Co., Ltd.

Claims (2)

[Claims] (1) In order to form a photoreceptor layer on the circumferential surface of the photoreceptor drum substrate, as the liquid level of the coating liquid rises, an overflow is caused in the final stage to keep the liquid level constant; In a dip coating method in which the substrate is immersed in a liquid, the substrate is pulled up after reaching a predetermined depth, and a photoreceptor layer is formed on the circumferential surface of the substrate, the surface of the coating liquid and the upper end surface of the coating liquid tank are covered. A dip coating method for photoreceptor drums, etc., characterized in that when the coating liquid overflows, the cover is pushed upward by the rising liquid level of the coating liquid. (2) A coating liquid tank containing a coating liquid for coating on the circumferential surface of the substrate, and a coating liquid tank provided on the outer periphery of the coating liquid tank to collect the coating liquid flowing out from the upper end surface of the coating liquid tank. a recovery tank; and a cover that substantially entirely covers an upper end opening of the recovery tank and the surface of the coating solution, and is formed with an opening through which the base body can penetrate, A coating device for a photoreceptor drum or the like, characterized in that it is supported by an upper end surface of a liquid tank and is guided vertically to an inner circumferential surface of the recovery tank.