JPH06262113A - Coating device - Google Patents

Abstract

PURPOSE:To provide a coating device capable of uniformly forming a homogeneous coating film uniform in thickness on the surfaces of plural cylindrical substrates by dip coating. CONSTITUTION:This coating device is provided with a coating tank 1, a coating soln. tank 2, a coating soln. circulating mechanism for sending a coating soln. 3 from the tank 2 to the lower part of the coating tank 1 by a pump 5 through a feed pipeline 4 and a filter 8 in which the soln. is filtered, allowing the soln. to overflow the upper edge of the coating tank 1 into a receiving part 6 and returning the soln. to the tank 2 through a circulating pipeline 7 and a chucking mechanism 10 for dipping plural cylindrical substrates 9-1 to 9-n held by the chucks 11-1 to 11-n in the coating tank 1 and pulling up the substrate. In this case, the distance between the adjacent substrates to be dipped in the coating tank 1 is controlled to >=20mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus for forming a coating film by dip coating a coating liquid on the surface of a cylindrical substrate. More specifically, it relates to an apparatus for performing dip coating on the surfaces of a plurality of cylindrical substrates at the same time. For example, when manufacturing an organic photosensitive drum for electrophotography, a coating solution containing a photosensitive material is simultaneously dip-coated on the surfaces of a large number of cylindrical substrates for exposure. The present invention relates to a coating device suitable for forming a layer.

[0002]

2. Description of the Related Art An organic photosensitive drum for electrophotography is usually manufactured by applying a coating solution containing an organic photosensitive material onto the surface of a cylindrical substrate made of aluminum or the like to form a photosensitive layer. There are dip coating method, spray coating method, ring coating method, etc. as the coating method, but it is possible to obtain a coating film having an arbitrary film thickness relatively uniformly, and further, it is possible to simultaneously coat many substrates. The law is generally adopted.

FIG. 11 is a conceptual diagram showing an example of a conventional coating apparatus of the dip coating method. In FIG. 11, 1-1 to 1
-N is a coating tank, 2 is a coating liquid tank, and the coating liquid 3 is sent to each coating tank by a pump 5 through a feed pipe 4 connecting the bottom of the coating liquid tank 2 and the bottom of each coating tank. ,
It circulates in the coating tank by returning to the coating liquid tank 2 through the reflux pipe 7 through the receiving portions 6-1 to 6-n which overflows from the upper edge portion and receives the overflow. 8 is coating liquid 3
Is a filter for filtering. By moving the substrate chuck mechanism 10 up and down in each coating tank of such a coating device by an elevating means (not shown), the chuck 11-1 of the substrate chuck mechanism 10 is moved.
The cylindrical bases 9-1 to 9-n mounted on
Application is performed by dipping and pulling up. Reference numeral 12 is an air discharge pipe for discharging the air inside the base so that the compressed air inside the base does not expand abnormally and agitates the coating liquid when the base is pulled up, causing uneven coating. Yes, 13-1 to 13-n are needle valves for adjusting the discharge amount of air.

The dip coating method is a method of forming a uniform coating film having a uniform film thickness on the surface of a substrate by immersing the substrate in a coating tank and pulling it up at a constant speed. The amount of coating liquid equivalent to the volume of is added to the steady overflow amount and overflows,
When the liquid is pulled up, the liquid level fluctuates such that the liquid level drops. Therefore, it is necessary to increase the circulation amount of the coating liquid to prevent the liquid level from varying. Also, when pulling up,
The solvent of the applied liquid evaporates and the coating film dries,
This solvent may form a vapor layer around the substrate to disturb the air flow. When trying to perform dip coating on a large number of substrates at the same time in one coating tank, it is difficult to adjust the coating liquid circulation amount to prevent fluctuations in the liquid level, and the effect of the vapor layer is large.
It is difficult to form a good coating film due to the influence between adjacent substrates, and for that reason, the above-mentioned apparatus provided with a coating tank divided for each substrate has been used.

[0005]

However, in an apparatus having a coating tank divided for each substrate as described above, it is difficult to evenly circulate the coating solution in each coating tank, and the concentration of the coating solution is There is a problem that the viscosity and the like vary, and when the coating liquid is a dispersion liquid, the degree of dispersion also varies, the film thickness of the coating film differs between coating tanks, and the coating defects also vary. It was happening.

Further, when the substrate becomes larger than the capacity of the coating tank, the overflow amount of the coating liquid when the substrate is dipped becomes much larger than the steady amount, and the feeding amount of the coating liquid during pulling up becomes insufficient. Surface variation occurs and uneven coating occurs. Therefore, there is a problem that it is necessary to thicken the pipe of the coating liquid circulation mechanism to increase the amount of the coating liquid to be circulated or to prepare an apparatus having coating tanks of various sizes according to the size of the substrate.

Furthermore, there is a drawback that the apparatus becomes complicated and large in size because a pipe for circulating the coating solution is required in each coating tank. Furthermore, the coating liquid overflowing from the upper edge of the coating tank is received by the receiving portion, but if the distance between the overflow surface and the coating liquid surface of the receiving portion at this time, that is, the difference in the coating liquid changes, the The amount of solvent volatilized from the coating liquid changes, and the state of vapor around the surface of the substrate changes. When forming an extremely thin film of micron order or submicron order like an organic photoconductor, there is a problem that uneven film formation occurs due to the influence and it is difficult to obtain a good photoconductor.

The present invention has been made in view of the above points, and provides a coating apparatus capable of dip-coating a uniform coating film having a uniform film thickness on the surfaces of a plurality of cylindrical substrates without unevenness of film formation. The purpose is to do.

[0009]

According to the present invention, there is provided a coating tank, a coating solution tank, and a coating solution fed from the coating solution tank to a lower portion of the coating tank through a filter.
A coating solution circulation mechanism that overflows from the upper edge of the coating tank and returns to the coating solution tank, and a substrate chuck mechanism that forms a coating film on the substrate surface by immersing and pulling up a plurality of cylindrical substrates in the coating tank In the coating device,
The problem can be solved by providing the coating apparatus in which the substrate chuck mechanism is configured so that the distance between the substrates to be dipped adjacent to each other is 20 mm or more.

Further, the above-mentioned problem is that the coating tank, the coating solution tank, and the coating solution are sent from the coating solution tank to the lower portion of the coating tank through a filter, overflow from the upper edge of the coating tank, and are returned to the coating solution tank. In a coating apparatus including a coating liquid circulation mechanism and a substrate chuck mechanism that forms a coating film on the surface of a substrate by immersing and pulling up a plurality of cylindrical substrates in a coating tank, the region in which the substrate is immersed is different for each substrate. The problem can also be solved by using a coating device that is divided into independent divided coating areas, and the coating liquid overflows from the upper edge of each divided coating area. In this case, the coating liquid circulating mechanism receives the overflowing coating liquid in the outer peripheral portion of the upper portion of the divided coating area and temporarily retains it, and the head constant mechanism that keeps the head between the liquid surface and the overflow surface. It is preferable to provide (1) and (2) because it is possible to suppress unevenness in film formation.

Further, an air discharge means for discharging the air in the cylindrical substrate when the substrate mounted on the substrate chuck mechanism is dipped in the coating liquid and pulled up, and the substrate internal pressure is monitored to discharge the air corresponding to the internal pressure. Providing an automatic discharge amount control mechanism for controlling the amount is also effective in suppressing the occurrence of uneven film formation.

[0012]

By setting a distance of 20 mm or more between the substrates to be immersed in the coating tank adjacent to each other, the swaying of the coating liquid surface caused by the dipping and pulling of the adjacent substrates, and the vapor layer of the solvent volatilized during the pulling The influence can be avoided, and even if dip coating is performed on a plurality of substrates in the same coating tank, it is possible to form a uniform and good coating film without being affected by each other. Unlike conventional devices, the coating tanks are not individually separated, so there is no variation in the concentration or viscosity of the coating liquid, or in the degree of dispersion when the coating liquid is a dispersion liquid. The variation is eliminated, and the problem that the coating film thickness varies between the substrates can be solved. In addition, the circulation amount of the coating liquid can be easily adjusted, fluctuations in the surface of the coating liquid can be reduced, and uneven coating can be prevented. Furthermore, piping for circulating the coating liquid individually in each coating tank is unnecessary.

Further, the area where the substrate is dipped in the upper part of the coating tank is divided into independent divided coating areas for each substrate, and the coating liquid overflows from the upper edge of each divided coating area. In the case of a device, since the lower region of the coating tank is not divided, the coating liquid fed into it is homogeneous as a whole, and since the coating liquid overflows from the upper edge of each divided coating region, it is divided into each divided coating region. The coating solution will flow into the substrate uniformly, and there will be no variation in film thickness or variation in film quality between the substrates. Moreover, since the coating film is formed on each substrate in the divided coating regions, it is possible to form a uniform and excellent coating film without being influenced by each other. In such an apparatus, the overflowing coating liquid is received by the receiving portion, but if the distance between the overflow surface at this time and the coating liquid surface of the receiving portion, that is, the difference in the coating liquid changes, the coating liquid will fall during the fall. The amount of solvent volatilized from the substrate changes, the state of the vapor around the surface of the substrate changes, and uneven film formation occurs. Such a phenomenon can be avoided by providing the receiving part with a constant drop mechanism, and an extremely thin film of submicron order can be formed uniformly and satisfactorily.

Further, the chuck of the substrate chuck mechanism is designed to prevent the coating liquid from entering the cylindrical substrate and forming a coating film on the inner surface of the substrate when the substrate is immersed in the coating liquid. It has a structure that prevents air from leaking. Therefore, when dipping the substrate in the coating solution,
While the internal pressure of the substrate is balanced as the pressure of the coating liquid in contact with the air in the substrate at the lower end of the substrate increases, an example of FIG.
As shown in (a), it rises. Subsequently, when the substrate is pulled up, the pressure of the coating liquid in contact with the air in the substrate decreases as the substrate is pulled up. Therefore, it is necessary to discharge the air in the substrate accordingly and maintain the pressure balance. For this reason, the substrate chuck mechanism is usually provided with an air discharge pipe and a needle valve for discharging the air inside the substrate, and when pulling up, the needle valve is opened to discharge the air inside the substrate so as to discharge the air inside the substrate. Make sure that the internal pressure drops smoothly as shown in. Although the air discharge amount is controlled by adjusting the degree of opening and closing of the needle valve to adjust the internal pressure of the base body, if the air discharge amount is not appropriate, the pressure balance will be lost, and FIG.
As shown in (b), the internal pressure may fluctuate abnormally and the coating liquid may be disturbed, resulting in uneven coating. In the present invention, a pressure gauge is further attached to the air discharge pipe, and the discharge pressure automatic control mechanism for adjusting the discharge amount of air by automatically opening and closing the needle valve by monitoring the internal pressure by the pressure gauge is attached. By providing this mechanism, the internal pressure of the substrate can be adjusted more accurately than in the past, and the occurrence of uneven film formation can be further reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a conceptual diagram of an embodiment of the coating apparatus of the present invention. In FIG. 1, reference numeral 1 is a coating tank, 2 is a coating solution tank, and a coating solution 3 is applied by a pump 5 through a feed pipe 4 that connects the bottom of the coating solution tank 2 to the bottom of the coating tank.
Is circulated in the coating tank by being returned to the coating liquid tank 2 through the reflux pipe 7 through the receiving portion 6 that receives the overflow from the upper edge portion thereof. Reference numeral 8 is a filter for filtering the coating liquid 3. Reference numerals 9-1 to 9-n are cylindrical bases, and the base chuck mechanism 10 is composed of chucks 11-1 to 11-n for mounting the bases and an air exhaust pipe 12, and the chucks 11-1 to 11-n are The distance between adjacent substrates is 20 mm when the substrates are mounted on the chuck.
It is configured to be arranged at intervals as described above. Further, the air discharge pipe 12 is provided with needle valves 13-1 to 13-n corresponding to each base, and each needle valve is opened so that the internal pressure of each base does not fluctuate abnormally when the base is pulled up. It is configured so that an appropriate amount of air inside each substrate can be discharged.
With such an apparatus, while circulating the coating liquid 3, the substrate chuck mechanism 10 is vertically moved by an elevating means (not shown) as indicated by a double-headed arrow A to coat the mounted cylindrical substrate. Application is performed by immersing in the tank 1 and pulling it up.

In the coating apparatus as described above, the size of the coating tank is 20 mm between the bases adjacent to each other in width and depth and between the base and the wall of the coating tank.
And the depth from the length of the substrate is 4
Design to be 0 mm longer. In this case, in order to simultaneously coat n substrates having an outer diameter of φmm, it is assumed that a lines are arranged in the width direction of the coating tank and b lines are arranged in the depth direction (a × b =
n), the width and depth of the coating tank are given by the following formula (unit: mm).

[0017]

[Equation 1]

Width: (φ + 20) × a + 20 Depth: (φ + 20) × b + 20 By the way, when pulling up the immersed substrate, coating is performed.
If the bath is not replenished with coating liquid, it will adhere to the substrate surface.
Depending on the amount of coating liquid and the volume of the substrate drawn from the coating liquid,
At the same time, the coating liquid level is lowered. The coating liquid is always
To prevent overflow and fluctuation of the coating liquid level
For this purpose, make sure to circulate more than the above two amounts of coating liquid.
And are required. Volume of n substrates V (mm³) Is
(Φ / 2) ²× π × L × n, and the pulling rate is v
(Mm / sec) Time required to pull up the substrate
(Coating time) is L / v (sec)
In order to eliminate the drop in the coating liquid level corresponding to the volume of the body,
Amount of coating liquid replenishment (mm³/ Sec) as (φ / 2)²× π ×
n × v is required. Therefore, the circulation amount of the coating liquid (mm³
/ Sec), this amount is further applied to the substrate surface
It is necessary to add more than the amount of coating liquid.

Using the coating apparatus having the above structure,
A coating film was simultaneously formed on the surface of 20 aluminum alloy cylindrical substrates having an outer diameter of 30 mm, a wall thickness of 1 mm and a length of 260 mm. Four substrates were arranged in the width direction of the coating tank, and five substrates were arranged in the depth direction. FIG. 2 is a conceptual view of such an arrayed state of the substrates as seen from the upper surface of the coating tank. The thickness of the coating film thus obtained on each of the coated substrate examples 1-1 to 1-20 was measured. The results are shown in Table 1.

[0020]

[Table 1]

Comparative Example 1 For comparison, a conventional coating apparatus (10 coating tanks) as shown in FIG. 11 was used to coat 10 substrates.
The coated substrates of Comparative Examples 1-1 to 1-20 were obtained, and the film thickness thereof was measured. The results are shown in Table 2.

[0022]

[Table 2]

As can be seen from Tables 1 and 2, the variation in the film thickness of the coating film is smaller than the comparative example by 1/2 or less in both the standard deviation and the difference between the maximum and the minimum. 1
The effect of the device is clear. Embodiment 2 FIG. 3 shows a conceptual diagram of a different embodiment of the coating apparatus of the present invention. 1 is different from FIG. 1 in that the area in which the substrates are immersed in the coating tank 1 is divided for each substrate instead of setting the interval between the substrates adjacent to each other to be 20 mm or more, and the divided coating regions 1 ₁ to 1
_n is provided, the coating liquid overflows from the upper edge portion of each divided coating area, and the receiving portions 6-
1 to 6-n, and is returned to the coating liquid tank via the reflux pipe 7.

According to the first embodiment, a coating apparatus having 20 divided coating areas is used according to the first embodiment.
When the coated substrate bases of Examples 2-1 to 2-20 were prepared and the film thickness thereof was measured, the film thickness variation was about the same as that prepared in Example 1, and the coating apparatus of Example 2 was also used. It was found to be effective in forming a uniform coating film. Embodiment 3 FIG. 4 shows an air discharge pipe 12 of the coating apparatus of FIG. 1 or 3 as a further different embodiment of the coating apparatus of the present invention.
In addition, a pressure gauge is attached to each of the bases, and a means for automatically controlling the discharge amount according to the internal pressure of each base monitored by each pressure gauge when the base is pulled up is required. FIG. 9 is a conceptual diagram of a main part showing a part as a representative of a base chuck mechanism part of a base 9-1. In FIG. 4, a pressure gauge 14-1 and a needle valve 13-1 are attached to an air discharge pipe 12 penetrating a chuck 11-1 on which a cylindrical substrate 9-1 is mounted, and 15-1 is a pressure gauge. 14-1 is an automatic discharge amount controller that automatically controls the opening / closing degree of the needle valve 13-1 in accordance with the substrate internal pressure monitored by 14-1 to automatically adjust the discharge amount of air. By further adding such a discharge amount automatic control means to the apparatus of FIG. 1 or FIG. 3, it becomes possible to more accurately eliminate abnormal fluctuations in the internal pressure of the substrate when pulling up the substrate, and uneven film formation. Can be less.

Embodiment 4 FIG. 5 shows, as a further different embodiment of the coating apparatus of the present invention, a receiving portion provided in each divided coating area of the coating apparatus of FIG. 3 and further from the upper edge portion of the divided coating area. FIG. 5A is a conceptual view showing _a main part of an apparatus to which a means for making the head of overflowing coating solution constant is added is represented by _a part of _a divided coating area 1 _a . FIG. ) Is a vertical sectional view. In FIG. 5, a shield plate 16-1 having a function of making the head of the coating liquid constant is provided on the inner lower surface of the receiving portion 6-1 provided at the upper end of the divided coating area 1 _a .

[0026] By providing such a shielding plate 16-1, the coating liquid 3 which is received by the overflow receiving unit 6-1 from the upper edge of the divided coating region 1 _a causes flow into the return line 7 as soon Instead, it stays and reaches the amount exceeding the upper edge of the shielding plate 16-1, and then flows into the reflux pipe 7. The overflow of the coating liquid is constant because it is determined by the height difference between the upper edge of the divided coating area 1 _{a and} the upper edge of the shielding plate 16-1. As a result, the amount of solvent that volatilizes from the coating liquid during the drop changes, and the state of the vapor around the surface of the substrate changes, which can avoid the problem of uneven film formation. It can be formed well.

The means for making the head of the coating liquid constant is not limited to the above-mentioned shield plate, but various means can be considered. For example, a method using two shield plates as shown in FIG. 6 may be used. 6A is a top view and FIG. 6B is a vertical cross-sectional view, the shield plate 1 provided on the top surface of the receiving portion 6-1.
7-1 and the shielding plate 18-1 provided on the lower surface are the shielding plate 1
The lower edge of 7-1 reaches below the upper edge of the shielding plate 18-1, and the two are parallel to each other so that a gap is formed therebetween. The coating liquid 3 will flow into the reflux pipe 7 through this gap, and the drop of the coating liquid that overflows is determined by the height difference between the upper edge of the divided coating area 1 _{a and} the upper edge of the shield plate 18-1. And becomes constant. Further, as shown in FIG. 7, the receiving portion 6 of the return pipe 7 is
Alternatively, the opening to -1 may be provided at a position apart from the bottom surface of the side wall of the receiving portion 6-1. In this case, drop is determined by the difference in height between the upper edge and the opening of the divided coating region 1 _a. Further, as shown in FIG. 8, the reflux pipe 7 may be bent to form a portion higher than the opening. In this case, the drop is determined by the height difference between where it becomes most high bent and the upper edge portion of the divided coating region 1 ₁ a reflux pipe 7. Furthermore, as shown in FIG. 9, an opening to the receiving portion 6-1 of the reflux pipe 7 is formed on the lower surface of the receiving portion 6-1 and the reflux pipe 7 is bent to form a portion higher than the opening. May be. Also in this case, the drop is determined by the height difference between the upper edge of the divided coating area 1 _a and the highest point where the reflux pipe 7 is bent.

[0028]

According to the present invention, the coating bath, the coating liquid tank, and the coating liquid are sent from the coating liquid tank through the filter to the lower portion of the coating bath, and are overflowed from the upper edge of the coating bath to flow back to the coating liquid tank. In a coating apparatus having a coating liquid circulating mechanism for allowing the coating liquid to circulate, and a substrate chuck mechanism for forming a coating film on the surface of the substrate by immersing and pulling up a plurality of cylindrical substrates in the coating tank, the substrates are immersed adjacent to each other. The coating device is configured so that the distance between the substrate and the substrate is 20 mm or more. In this way, by providing a distance of 20 mm or more between the substrates to be dipped in the coating tank adjacent to each other, even if the dipping coating is performed on a plurality of substrates at the same time in the same coating tank, they are uniform without being affected by each other. It becomes possible to form a good coating film. Since the coating tanks are not individually separated as in the conventional apparatus, the problem that the film thickness of the coating film between the substrates varies can be solved. In addition, the circulation amount of the coating liquid can be easily adjusted, fluctuations in the surface of the coating liquid can be reduced, and uneven coating can be prevented. Furthermore, there is an advantage that a pipe for circulating the coating solution individually in each coating tank is unnecessary.

Further, in the present invention, the coating tank, the coating liquid tank, and the coating liquid are sent from the coating liquid tank to the lower portion of the coating tank through a filter, overflow from the upper edge of the coating tank, and are returned to the coating liquid tank. In a coating apparatus provided with a coating liquid circulating mechanism for allowing a plurality of cylindrical substrates to be dipped in a coating tank and pulled up to form a coating film on the substrate surface, The coating apparatus is divided into independent divided coating areas for each substrate, and the coating liquid overflows from the upper edge of each divided coating area. With the device having such a configuration, since the lower region of the coating tank is not divided, the coating liquid fed therein is uniform as a whole, and the coating liquid is applied from the upper edge of each divided coating region. Since the liquid overflows, the coating liquid uniformly flows into each of the divided coating regions, so that the variation in the film thickness and the variation in the film quality between the substrates are eliminated. Moreover, since the coating film is formed on each substrate in the divided coating regions, it is possible to form a uniform and excellent coating film without being influenced by each other. Furthermore, the coating liquid that overflows from the upper edge of the divided coating area is received by the receiving portion, but the amount of the solvent that volatilizes from the coating liquid during the fall is provided by providing a coating liquid drop constant mechanism in the receiving portion. It is possible to avoid the problem that the state of vapor changes around the substrate surface and the unevenness of film formation occurs, and even a very thin film of submicron order can be formed uniformly and satisfactorily.

Further, in the present invention, a pressure gauge is attached to the air discharge pipe of the substrate chuck mechanism so that the pressure inside the substrate when the substrate is pulled up can be monitored by the pressure gauge.
An exhaust amount automatic control mechanism for automatically adjusting the exhaust amount of air from the base body according to the internal pressure is attached. By providing this mechanism, it becomes possible to more accurately adjust the internal pressure of the substrate when the substrate is pulled up, and it is possible to further reduce the occurrence of uneven film formation.

[Brief description of drawings]

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

FIG. 2 is a conceptual diagram showing an example of an arrangement state of substrates during coating in the apparatus of FIG. 1 as seen from the top of a coating tank.

FIG. 3 is a conceptual diagram of a different embodiment of the coating apparatus of the present invention.

FIG. 4 is a conceptual diagram of an example of means for automatically controlling the internal pressure of the substrate during pulling up.

FIG. 5 is a conceptual diagram of an example of means for stabilizing the head.

FIG. 6 is a conceptual diagram of an example in which the means for stabilizing the head is different.

FIG. 7 is a conceptual diagram of still another example of the means for stabilizing the head.

FIG. 8 is a conceptual diagram of still another example of the means for stabilizing the head.

FIG. 9 is a conceptual diagram of a different example of the means for stabilizing the head.

FIG. 10 is a diagram showing an example of changes in the substrate internal pressure during coating.

FIG. 11 is a conceptual diagram of an example of a conventional coating device.

[Explanation of symbols]

1,1-1~1-n coating tank 1 _a to 1 _n divided coating region 2 coating solution tank 3 the coating liquid 4 infeed pipe 5 pump 6,6-1~6-n receiving unit 7 return line 8 filter 9 1-9-n base | substrate 10 base | substrate chuck mechanism 11-1 to 11-n chuck 12 air discharge piping 13-1 to 13-n needle valve 14-1 pressure gauge 15-1 discharge | emission amount automatic controller 16-1,17- 1,18-1 Shield plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Megumi Kurokawa 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Fuji Electric Co., Ltd.

Claims (4)

[Claims] 1. A coating tank, a coating solution tank, and a coating solution circulating mechanism for feeding the coating solution from the coating solution tank to a lower portion of the coating tank through a filter, causing the coating solution to overflow from the upper edge of the coating tank and flowing back to the coating solution tank. And a substrate chuck mechanism for forming a coating film on the substrate surface by immersing and pulling up a plurality of cylindrical substrates in a coating tank, wherein the substrate chuck mechanism is a substrate to be immersed adjacent to each other. A coating apparatus having a structure such that a space between the substrate and the substrate is 20 mm or more. 2. A coating bath, a coating liquid tank, and a coating liquid circulating mechanism for feeding the coating liquid from the coating liquid tank to a lower portion of the coating bath through a filter, causing the coating liquid to overflow from the upper edge portion of the coating bath and flowing back to the coating liquid tank. And a substrate chuck mechanism that forms a coating film on the surface of a substrate by immersing and pulling up a plurality of cylindrical substrates in a coating tank. The coating device is divided into regions, and the coating liquid overflows from the upper edge of each divided coating region. 3. A coating liquid circulation mechanism, a receiving portion for temporarily retaining the overflowed coating liquid in the upper outer peripheral portion of each divided coating region, and a constant drop difference for keeping a constant difference between the liquid surface staying here and the overflow surface. The coating device according to claim 2, further comprising: 4. A substrate chuck mechanism is provided with air discharging means for discharging air in a cylindrical substrate when the substrate mounted thereon is dipped in a coating liquid and pulled up, and the substrate internal pressure is monitored to correspond to the internal pressure. The coating apparatus according to any one of claims 1 to 3, further comprising an automatic discharge amount control mechanism that controls the amount of discharged air.