JPH1172932A - Immersion coating applicator for production of electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immersion coating applicator for production of electrophotographic photoreceptors capable of effectively preventing the occurrence of unequal coating application without the intrusion of air bubbles in the circulating system of a coating liquid. SOLUTION: This coating applicator for applying the coating liquid of a photoreceptor material on the surface of a cylindrical substrate by an immersion coating application method mainly comprises an immersion coating application tank 1, a coating liquid prepn. tank 2 and a circulator for the coating liquid, such as a circulating pump 3 and piping. A control means 9 included in the circulator of the coating liquid controls the opening and closing of a shut-off valve 8 interposed in the piping 55 for returning the coating liquid in accordance with the signal of a liquid level detecting means 7 and maintains the liquid level height of the coating liquid flowing over from an immersion coating application tank body 10 to a trough member 11 in a specified range, thereby preventing the advance of the air to the piping 55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dip coating apparatus for producing an electrophotographic photoreceptor, and more particularly, to a dip coating apparatus for circulating a coating liquid into a dip coating tank. The present invention relates to a dip coating apparatus for producing an electrophotographic photosensitive member which can effectively prevent the occurrence of coating unevenness.

[0002]

2. Description of the Related Art A drum-shaped electrophotographic photoreceptor is manufactured by forming a coating of a photoreceptor material on the surface of a cylindrical substrate. The coating is formed by containing a coating solution as a photoreceptor material. Further, a coating apparatus having a dip coating tank in which the substrate is immersed is used. In the treatment by the coating device, the substrate is immersed substantially vertically in the coating solution while overflowing the coating solution in the dip coating tank, and then pulled up substantially vertically to form a coating film of the photosensitive material on the surface of the substrate. Such a dip coating method is
This method is widely used because the composition of the coating liquid can be kept uniform.

In the dip coating method described above, it is important to prevent coating unevenness on the surface of the substrate in order to improve the smoothness of the photosensitive coating. One of the causes of application unevenness is the inclusion of air bubbles in a coating liquid circulation system that circulates and supplies the coating liquid to the dip coating tank. The mechanism by which bubbles are mixed in the coating liquid is as follows.

That is, in the above-described coating apparatus, the coating liquid overflowed from the dip coating tank main body to the gutter member on the outer peripheral side thereof is stored in a coating liquid preparation tank (liquid storage tank) via a lowered pipe. , In a coating liquid preparation tank. At this time, in the above-mentioned piping leading to the coating liquid preparation tank, air enters and the entered air is sent to the coating liquid preparation tank together with the coating liquid due to a change in the amount of overflow caused by immersion and pulling of the substrate. As a result, there is a problem that bubbles are mixed in the coating liquid supplied to the dip coating tank.

Therefore, as a means for preventing the mixing of air as described above, a technique has been proposed in which a gas-liquid separation pipe is provided at a stage subsequent to a pipe leading to a coating liquid preparation tank. Such a gas-liquid separation pipe is a vertical pipe whose upper end is connected to the upper space of the coating liquid preparation tank and whose lower end is connected to the liquid in the coating liquid preparation tank, and which is mixed with the coating liquid in the above-mentioned pipe. A structure for separating air (bubbles) with a specific gravity difference is provided (see Japanese Utility Model Laid-Open No. 2-147271).

[0006]

The coating liquid as a photoreceptor material has a relatively high viscosity, so that it has a property that the mixed air is difficult to separate. Moreover, as described above, since the overflow amount in the dip coating tank fluctuates, at the timing when the overflow amount increases,
There is a situation in which air once mixed in a coating liquid is sent to a coating liquid preparation tank without being sufficiently separated by a gas-liquid separation tube. In particular, the above-described separation operation is difficult for a high-viscosity charge transport coating solution used for a laminated electrophotographic photosensitive member.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to eliminate the incorporation of air bubbles in a coating liquid circulation system for circulating and supplying a coating liquid to a dip coating tank, thereby effectively preventing the occurrence of coating unevenness. It is another object of the present invention to provide a dip coating apparatus for producing an electrophotographic photosensitive member which can be prevented from occurring.

[0008]

In order to solve the above-mentioned problems, a dip coating apparatus for producing an electrophotographic photoreceptor according to the present invention comprises a dip coating method for applying a coating solution of a photoreceptor material onto the surface of a cylindrical substrate. A coating device for coating, a dip coating tank for coating a cylindrical substrate with a coating liquid, a coating liquid preparation tank for preparing a coating liquid, and circulating a coating liquid between the dip coating tank and the coating liquid preparation tank. The dip coating tank is mainly provided with a dip coating tank that contains the coating liquid in an overflow state and is immersed in the cylindrical substrate, and is provided on the upper outer peripheral side of the dip tank main body. And a gutter member for receiving the overflowed coating liquid, wherein the coating liquid circulation device includes a coating liquid return pipe having one end connected to the gutter member and the other end connected to the coating liquid preparation tank. For returning the coating liquid A shutoff valve interposed in the pipe, a liquid level detecting means for detecting a liquid level of the coating liquid retained in the gutter member, and the shutoff based on the liquid level detected by the liquid level detecting means. Control means for opening and closing a valve, wherein the control means controls the level of the coating liquid in the gutter member so as to keep the liquid level of the coating liquid in a predetermined range in a state where the opening of the pipe for returning the coating liquid is not exposed. It has a function of opening and closing the shutoff valve.

In the above dip coating apparatus, the specific control means adjusts a flow rate of the pipe for returning the coating liquid by opening and closing a shutoff valve, and controls an opening of the pipe attached to the gutter member. Is always located in the coating solution, thereby preventing air from entering the pipe.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a dip coating apparatus for producing an electrophotographic photosensitive member according to the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing main constituent members in the dip coating apparatus of the present invention, and is a diagram partially shown in a longitudinal section. FIG. 2 is a partial vertical cross-sectional view showing one embodiment of the liquid level detecting means in the gutter member of the dip coating tank. FIG. 3 is a partial longitudinal sectional view showing another embodiment of the liquid level detecting means in the gutter member of the dip coating tank. Hereinafter, in the description of the embodiments, the dip coating device is abbreviated as “coating device”, and the cylindrical substrate is abbreviated as “substrate”.

As shown in FIG. 1, the coating device of the present invention is a coating device for producing an electrophotographic photoreceptor for applying a coating solution of a photoreceptor material to the surface of a substrate (W) by a dip coating method.
A dip coating tank (1) for applying the coating liquid to the substrate (W), a coating liquid preparation tank (2) for preparing the coating liquid, and coating between the dip coating tank (1) and the coating liquid preparation tank (2). It mainly comprises a pump (3) for circulating the liquid and a coating liquid circulating device including piping.

In the present invention, the substrate (W) is, for example, a metal material such as aluminum, brass or stainless steel, a polymer material such as polyethylene terephthalate, polybutylene terephthalate, polypropylene, nylon, polystyrene, or phenol resin, or a hard material. An outer diameter of about 15 to 200 mm depending on the material such as paper is 200 to 100.
It refers to a conventionally known cylindrical substrate manufactured to a length of about 0 mm. When the surface of the base (W) is made of an insulating material, the conductive treatment is performed by impregnation of a conductive substance, lamination of a metal foil, vapor deposition of a metal, or the like.

The coating solution is a known coating solution comprising a photoreceptor material and one or more solvents. A coating solution of a photoreceptor material for producing a single-layer electrophotographic photoreceptor is prepared by mixing a charge generating substance, a charge transporting substance, a binder resin and a solvent. Further, a coating solution of a photoreceptor material in the case of manufacturing a laminated electrophotographic photoreceptor includes a coating solution for a charge generation layer comprising the charge generation material, a binder resin and a solvent, And a coating solution for a charge transport layer comprising a coating resin and a coating solvent are separately prepared.

Examples of the charge generating substance include azo pigments such as Sudan Red, Diane Blue, and Dienas Green B, disazo pigments, quinone pigments such as argol yellow and pyrenequinone, quinocyanine pigments, perylene pigments, and the like.
Examples include indigo pigments, bisbenzimidazole pigments such as indofast orange toner, phthalocyanine pigments such as copper phthalocyanine, quinacridone pigments, pyrylium salts, and azurenium salts.

As the charge transporting substance, polyaromatic compounds such as anthracene, pyrene, phenanthrene, coronene or indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, Examples thereof include compounds having a skeleton of a nitrogen-containing cyclic compound such as thiadiazole and triazole, and other hole transport substances such as hydrazone compounds.

As the binder resin, polycarbonate,
Polyarylate, polystyrene, polymethacrylates, styrene-methyl methacrylate copolymer, polyester, styrene-acrylonitrile copolymer,
And polysulfone. Further, as the solvent, n
-Butylamine, diethylamine, ethylenediamine,
Isopropanolamine, triethanolamine, N,
Solvents having high volatility and a higher vapor density than air, such as N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, and benzene, are suitably used.

The concentration of each component in the coating solution is appropriately set according to a known technique. The concentration of solids is mainly
It is determined according to the thickness of the layer to be formed, but in the case of a coating solution for producing a single-layer type electrophotographic photoreceptor, and for a charge transport layer when producing a laminated type electrophotographic photoreceptor. In the case of a coating solution, 40% by weight or less, preferably 10 to 35% by weight
It is prepared as follows. In the case of these coating solutions, the viscosity is 50 to 350 cps, preferably 70 to 250 cps.
s, and the dry film thickness is 15 to 40 μm.
Further, in the case of a coating solution for a charge generation layer when producing a laminated electrophotographic photosensitive member, the solid content concentration is adjusted to 15% by weight or less, preferably 1 to 10% by weight. The coating solution for the charge generation layer has a viscosity of 1 to 5 cps, and a dry film thickness of 0.1 to 1 μm.

In the coating apparatus of the present invention, as the dip coating tank (1), a coating tank having a structure in which a coating solution is processed while overflowing the coating liquid is used. That is, the dip coating tank (1) is provided on the outer peripheral side of the upper part of the dip tank main body (10), which stores the coating liquid in the overflow state and in which the base (W) is immersed. And a gutter member (11) for receiving the applied coating liquid.

The immersion tank main body (10) has a structure in which an upper end is opened and a coating liquid is supplied from a lower end side, and a pipe (branch) for supplying the coating liquid is provided at a lower end of the immersion tank main body (10). The pipe (54) is connected. The body of the immersion tank main body (10) for accommodating the base (W) is formed in a substantially cylindrical shape and the bottom is formed in an inverted conical shape in order to eliminate partial stagnation of the coating liquid. The immersion tank body (10) may be provided alone, but for efficient operation, usually a plurality of immersion tank bodies are provided in parallel.

The gutter member (11) is formed, for example, in a cylindrical shape with a short axis and a bottom, and the immersion tank body (1) is formed from the bottom surface thereof.
0) is configured such that the upper portion protrudes. Gutter member (1
In 1), in order to return the coating liquid overflowing from the immersion tank main body (10) to the coating liquid preparation tank (2), a pipe for returning the coating liquid described below (hereinafter simply referred to as “pipe”) (5).
One end of 5) is connected. A flexible hood (12) that expands and contracts as the base (W) is immersed and pulled up is attached to the upper part of the gutter member (11).
The method 2) reduces the evaporation of the solvent in the coating liquid and adjusts the drying speed of the coating liquid applied to the surface of the substrate (W).

A so-called robot hand or the like having a chuck mechanism is provided inside the hood (12) for vertically and vertically raising and lowering the base (W) with respect to the dip coating tank (1) from above. Holding device (6) is provided. The holding device (6) is composed of, for example, a vertical elevating shaft inserted from the upper end of the base (W) and a balloon as a holding member attached to the elevating shaft, and moves up and down on the base (W). This is a device in which a shaft is inserted and the balloon body is inflated in the radial direction of the base (W) by pressurized air, thereby holding the base (W) from its inner peripheral surface. In addition, as the above-mentioned holding member, a member made of an elastic material such as foamed rubber that is compressed in the axial direction of the elevating shaft and expands in the radial direction is used.

The coating liquid preparation tank (2) is a dip coating tank (1)
This is provided in order to accommodate and re-prepare the overflowing coating liquid and to always supply a sufficient amount of the coating liquid to the dip coating tank (1). The inside of the coating liquid preparation tank (2) is set to have substantially the same height as the bottom of the gutter member (11) in order to mix and prepare the coating liquid flowing out of the dip coating tank (1) into a predetermined composition and to store it. Mixing tank by partition wall (21)
And a storage tank (22).

The other end of the pipe (55) is connected to the mixing tank (21) for introducing the coating liquid overflowing into the gutter member (11). A pipe (57) for supplying a liquid is inserted. Further, the mixing tank (21) is provided with a stirring blade (23) for uniformly stirring and mixing the application liquid. The storage tank (22) is connected to a pipe (51) for supplying the prepared coating liquid flowing over the partition wall to the dip coating tank (1).

The circulating device for the coating solution is a coating solution preparation tank (2)
Piping (51, 52, 54, 5)
5) and a circulation pump (3). The pipe (51) extends from the storage tank (22) of the coating liquid preparation tank (2) and is connected to the suction side of the circulation pump (3).
Pipe (52) extended from the discharge side of the circulation pump (3)
Is connected to the immersion tank body (10) via the filter (4) and the branch pipe (54).

The pipe (55) is provided with a gutter member (1).
The mixing tank (2) of the coating liquid preparation tank (2) extended from 1)
The other end is connected to 1). And in the pipe (55),
In order to control the flow rate of the application liquid returned by the pipe, a shutoff valve (8) described later is interposed. In addition, the code | symbol (55c) in a figure shows the opening part at one end side of the piping (55) opened to the bottom part of the gutter member (11). Further, as the circulation pump (3), a pump capable of controlling rotation is suitable, and specifically, for example, a quantitative rotary pump such as an Ibex MOG pump (trade name) manufactured by Toko Sangyo is used. You.

In the above-mentioned coating liquid circulation apparatus, the circulation pump (3) sucks the coating liquid from the storage tank (22) of the coating liquid preparation tank (2) through the pipe (51), and draws the pipe (5).
2) through the filter (4) and the branch pipe (54)
A coating liquid is supplied to each immersion tank main body (10) of the immersion coating tank (1). Then, the coating liquid continuously supplied to each immersion tank body (10) overflows from the immersion tank body (10) to the gutter member (11), and then again through the pipe (55) to the coating liquid preparation tank (2). Is returned to the mixing tank (21).

In the coating apparatus of the present invention, in order to prevent air from being mixed in the pipe (55), the coating liquid circulating apparatus includes, in addition to the circulating pump (3) and pipes as described above, Liquid level detecting means (7) for detecting the liquid level of the coating liquid retained in the gutter member (11), and a shutoff valve (8) based on the liquid level detected by the liquid level detecting means (7) Control means (9) for opening and closing the device.

The liquid level detecting means (7) includes a float (70) disposed in the gutter member (11), and a float (70).
And a sensor (71) for detecting the flying height. As the sensor (71), an appropriate sensor such as an electromagnetic induction type or a light reflection type can be used as long as the float (70) can be detected without malfunction. The upper and lower limits of the liquid level of the coating liquid in the gutter member (11) are detected by the liquid level detecting means (7). In addition, as the liquid level detecting means, a float and a sensor are integrated, for example, a pair of donut-shaped floats in which a magnet is buried are vertically mounted on a support shaft in which a pair of proximity switches are vertically installed. A so-called float switch which is arranged so as to be swingable may be used.

The shutoff valve (8) is provided for regulating the flow rate of the coating liquid in the pipe (55) and controlling the liquid level of the gutter member (11). An explosion-proof solenoid valve or an air-operated valve is used as the shutoff valve (8). Such a shutoff valve (8)
May have a structure capable of adjusting the flow rate, but an on-off valve is usually sufficient for simple control.

The control means (9) includes equipment and a circulating pump (3) associated with the dip coating tank (1) and the coating liquid preparation tank (2).
And a control device such as a program controller provided separately for collectively controlling the entire device including the device. And
The control means (9) has a function of opening and closing the shut-off valve (8) in the gutter member (11) so as to maintain the liquid level of the application liquid in a predetermined range so that the opening of the pipe (55) is not exposed. It is necessary to have.

Next, the coating operation in the coating apparatus of the present invention will be described. In the coating apparatus of the present invention, as described above, the coating liquid is usually circulated in a constant amount between the dip coating tank (1) and the coating liquid preparation tank (2) by the circulation device as described above. Then, first, the holding device (6) is lowered, and the held substrate (W) is immersed in the coating liquid in the immersion tank body (10). At this time, the gutter member (11) is moved from the immersion tank body (10).
The overflow amount of the coating liquid to the substrate temporarily increases with the dipping operation of the substrate (W), and returns to a steady state when the dipping operation is completed.

After the substrate (W) is substantially entirely immersed in the coating solution, the holding device (6) is raised while the coating solution overflows from the immersion tank body (10), so that the substrate (W) is immersed. Pull up from the tank body (10). that time,
The overflow amount of the coating liquid from the immersion tank main body (10) to the gutter member (11) temporarily decreases as the substrate (W) is pulled up, and returns to a steady state with the completion of the pulling up operation.

In the coating operation as described above, generally, the dipping of the coating liquid from the dipping tank body (10) to the gutter member (11) is accompanied by the dipping of the base (W) and the lifting of the base (W). The amount of overflow increases or decreases. In that case, in the coating apparatus of the present invention, the liquid level detecting means (7) detects the liquid level of the coating liquid in the gutter member (11), and when the liquid level of the coating liquid reaches the lower limit, the specific control means (7). (9) Closes the shut-off valve (8) based on the detection signal of the sensor (71), and connects the pipe (55).
The liquid surface of the coating liquid is maintained in a state where the opening of the coating liquid is not exposed.
When the level of the coating liquid in the gutter member (11) reaches the upper limit, the shut-off valve (8) is opened.

That is, the control means (9) operates the shutoff valve (8) based on the detection signal of the liquid level detection means (7) to adjust the flow rate of the coating liquid return pipe (55). The liquid level of the coating liquid in the gutter member (11) is maintained within a certain range. Even when the overflow amount is small, the opening (5) of the pipe (55) attached to the gutter member (11)
5c) is always positioned in the coating solution to prevent air from entering the pipe (55). Therefore, in the coating apparatus of the present invention, air (bubbles) is not sent into the coating liquid preparation tank (2), and no bubbles are mixed in the coating liquid in the dip coating tank (1). Application unevenness on the surface can be effectively prevented, and a suitable coating film can be formed.

As described above, in the coating apparatus of the present invention, the flow of the coating liquid in the pipe (55) is regulated so that the opening (55c) of the pipe (55) is not exposed. 2) is used to control the liquid level.
Alternatively, as shown in FIG. 3, the liquid level detecting means (7) is provided with an opening degree adjusting function for the opening (55c) of the pipe (55), so that the responsiveness can be further improved and the mixing of air can be further reduced. It can be reliably prevented.

The liquid level detecting means (7) shown in FIG. 2 has a structure for opening and closing the opening (55c) of the pipe (55) by the float (70). That is, the float (7
A spherical float is used as 0), and the float (70) is suspended vertically so that the bar (72) protruding upward is supported by a guide so that it can swing vertically. ) Is pivotally supported on one end of a support bar (73) rotatably supported up and down on the gutter member (11) side. Such a float (70) seals the opening (55c) of the pipe (55) when the level of the coating liquid in the gutter member (11) drops. A sensor (71) for detecting the floating height of the float (70) is provided on the support bar (7).
The height of the detected portion (74) attached to the other end of 3) is detected.

That is, the opening (55) of the pipe (55)
c) is configured to be openable and closable by the float (70) of the liquid level detecting means (7), and in such an embodiment,
The control means (9) includes a sensor (7) of the liquid level detection means (7).
Based on the detection signal of 1), the shutoff valve (8) is closed when the opening (55c) is closed by the float (70), and shut off when the opening (55c) is opened by the float (70). It has a function to open the valve (8).

Accordingly, in the coating apparatus of the embodiment shown in FIG. 2, the opening (55c) of the pipe (55) can be opened and closed together with the opening and closing operation of the shut-off valve (8). And a quick response is obtained, and even if the coating liquid runs out of the gutter member (11), the opening (55
Since c) can be sealed, entry of air into the pipe (55) can be more reliably prevented.

The liquid level detecting means (7) shown in FIG. 3 has a structure for adjusting the opening at the opening (55c) of the pipe (55) by the float (70). In particular,
As the float (70), a cylindrical float that is supported by a guide and floated vertically and swingably is used. On the other hand, the opening (55) of the pipe (55)
In (c), for example, a disk-shaped damper (77) is rotatably provided, and the end of the connecting bar (76) extending from the upper part of the damper (77) is located at the lower end of the float (70). Be pivoted.

When the level of the coating liquid in the gutter member (11) drops, the float (70) lowers its floating height, so that the float (70) is connected to the damper (7) through the connecting bar (76).
7) is rotated to narrow the opening of the opening (55c) of the pipe (55). Then, a sensor (71) for detecting the floating height of the float (70) detects the height of an instruction bar (75) as a detection target attached to the upper end of the float (70).

That is, the opening (55) of the pipe (55)
c) is configured such that the degree of opening can be adjusted by a damper (77) that rotates in conjunction with the float (70) of the liquid level detection means (7), and the damper (77) is provided with a float (7).
0) increases the opening of the opening (55c), and lowers the float (70) to increase the opening (55c).
In such an embodiment, the control means (9) controls the opening (55 c) to float () based on the detection signal of the sensor (71) of the liquid level detection means (7). When the opening is reduced by 70), the shut-off valve (8) is closed, and the opening (55c) is closed by the float (7).
It has a function of opening the shut-off valve (8) when the opening is increased by 0).

Therefore, in the coating apparatus of the embodiment shown in FIG. 3, the opening degree of the opening (55c) of the pipe (55) can be adjusted together with the opening / closing operation of the shut-off valve (8). A quick response can be obtained according to the liquid level of the gutter member (11), and abrupt fluctuation of the coating liquid in the gutter member (11) can be prevented, so that the entry of air into the pipe (55) can be more reliably prevented. it can.

Further, in the coating apparatus of the present invention, in order to further stabilize the level of the coating liquid in the gutter member (11), the flow rate of the circulation pump (3) is controlled in addition to the operation of the shut-off valve (8). You can do it. When the rotation of the circulation pump (3) is controlled based on the detected liquid level, the fluctuation of the liquid level in the gutter member (11) is further reduced, so that the intrusion of air can be more reliably prevented. The coating apparatus of the present invention can be more suitably used for a high-viscosity charge transport coating liquid in which bubbles are difficult to remove.

[0044]

As described above, according to the dip coating apparatus for producing an electrophotographic photoreceptor according to the present invention, the coating liquid in the gutter member is prevented from exposing the opening of the pipe for returning the coating liquid. Since the liquid level is controlled, no air is sent into the coating liquid preparation tank. Therefore, no bubbles are mixed in the coating solution in the dip coating tank, and coating unevenness on the surface of the cylindrical substrate can be effectively prevented, and a suitable coating film can be formed.

[Brief description of the drawings]

FIG. 1 is a system diagram showing main components in a dip coating apparatus of the present invention.

FIG. 2 is a partial longitudinal sectional view showing one embodiment of a liquid level detecting means in a gutter member of the dip coating tank.

FIG. 3 is a partial longitudinal sectional view showing another embodiment of the liquid level detecting means in the gutter member of the dip coating tank.

[Explanation of symbols]

 1: immersion coating tank 10: immersion tank main body 11: gutter member 2: coating liquid preparation tank 3: pump 55: pipe for returning coating liquid 55c: opening of pipe for returning coating liquid 7: liquid level detecting means 70: float 71: sensor 77: damper 8: shut-off valve 9: control means W: cylindrical base

Claims (5)

[Claims] 1. A coating apparatus for applying a coating solution of a photoreceptor material to the surface of a cylindrical substrate by a dip coating method, comprising: a dip coating tank for applying the coating liquid to the cylindrical substrate; A liquid preparation tank, and a coating liquid circulation device that circulates the coating liquid between the dip coating tank and the coating liquid preparation tank. The dip coating tank contains the coating liquid in an overflow state and has a cylindrical shape. A immersion tank body in which the substrate is immersed, and a gutter member attached to the upper outer peripheral side of the immersion tank body and receiving an overflowed coating solution,
The coating liquid circulation device is provided with a coating liquid return pipe having one end connected to the gutter member and the other end connected to the coating liquid preparation tank, and a coating liquid return pipe. A shutoff valve, a liquid level detecting means for detecting the liquid level of the coating liquid retained in the gutter member, and opening and closing the shutoff valve based on the liquid level detected by the liquid level detecting means. Control means, wherein the control means opens and closes the shut-off valve in the gutter member so as to keep the liquid level of the coating liquid within a predetermined range so that the opening of the pipe for returning the coating liquid is not exposed. A dip coating apparatus for producing an electrophotographic photoreceptor, the dip coating apparatus having a function of performing the following. 2. The dip coating apparatus according to claim 1, wherein the liquid level detecting means comprises a float disposed in the gutter member, and a sensor for detecting a floating height of the float. 3. An opening of a pipe for returning a coating liquid is configured to be openable and closable by a float of a liquid level detecting means, and the control means sets the opening based on a detection signal of a sensor of the liquid level detecting means. The dip coating apparatus according to claim 2, further comprising a function of closing a shut-off valve when closed by the float and opening the shut-off valve when the opening is opened by the float. 4. An opening of a pipe for returning a coating liquid is configured so that an opening thereof can be adjusted by a damper which rotates in conjunction with a float of a liquid level detecting means, and the damper is provided with a float of the float. A structure is provided in which the opening degree of the opening is increased by ascending, and the opening degree of the opening is decreased by lowering of the float, and the control means controls the opening based on a detection signal of a sensor of a liquid level detecting means. The immersion apparatus according to claim 2, further comprising a function of closing the shut-off valve when the opening is reduced by the float and opening the shut-off valve when the opening is increased by the float. Coating device. 5. The dip coating apparatus according to claim 1, wherein the coating liquid is a charge transport coating liquid.