JPH0929152A - Dip coating apparatus and coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a good coating film without any sagging or nonuniformity in thickness in the pulling up direction of a cylindrical substrate. SOLUTION: This coating apparatus consists of a dip tank 6 contg. a coating soln. and an overflow receiver 7 provided on the outer periphery of the tank and receiving the coating soln. overflowing the tank, and a cylindrical substrate 9 is dipped in the soln., pulled up and coated. Further, a first hood 11 covering the receiver 7 and having an opening 10 through which the substrate 9 is passed and a second hood 12 covering the first hood 11 and having an opening 14 through which the sibstrate 9 is passed are provided, and a clearance 15 is furnished between the lower outer periphery of the first hood 11 and the lower inner periphery of the second hood 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus and a coating method, and particularly to a dip coating apparatus and a coating method suitable for forming an organic photosensitive layer on the outer peripheral surface of a cylindrical substrate in the production of an electrophotographic photoreceptor. It is about.

[0002]

2. Description of the Related Art Various coating methods such as dip coating method, spray coating method, blade coating method, extrusion coating method and the like are known as a method for producing an organic photoconductor for electrophotography. A dip coating method is widely used as a method for forming a uniform photosensitive layer on the surface. In recent years, there has been a strong demand for downsizing and weight reduction of devices such as copying machines, printers, and facsimiles in which electrophotographic photoconductors are used, and along with this, electrophotographic photoconductors are being reduced in diameter year by year. There is. For example, when an electrophotographic photosensitive member is manufactured by applying a dip coating to a small-diameter cylindrical substrate having a diameter of 30 mmφ or less, it has been conventionally used for the purpose of supporting a variety of products in production and suppressing capital investment therefor. A coating apparatus for dip-coating a cylindrical substrate having a diameter of about 80 mmφ is commonly used. Further, a plurality of dipping tanks can be provided in one dipping tank for the purpose of downsizing the coating apparatus, simplifying the apparatus structure, or freely supporting the diameter and number of coated cylindrical substrates, that is, so-called multi-product production. The method of using a coating apparatus for simultaneously dip-coating the cylindrical substrate of 1) is adopted.

FIG. 4 is a schematic diagram showing an example of a conventional dip coating apparatus, and FIG. 5 is a schematic diagram showing an example of a conventional dip coating apparatus for simultaneously coating a plurality of cylindrical substrates. The drawing shows the state immediately after the substrate is pulled up from the dipping tank at the same time and the lower end of the cylindrical substrate leaves the surface of the coating liquid. In the figure, the coating liquid 1 is pumped from a tank 2 through a supply pipe 3 by a pump 4, and is supplied into a dipping tank 6 through a filter 5. The coating liquid 1 overflows from the upper part of the dipping tank 6, passes through the overflow receiver 7 and the return pipe 8 provided around the dipping tank 6, and is collected in the tank 2. A hood 16 is provided on an upper portion of the overflow receiver 7, and the cylindrical base 9 (9-1 to 9-
n) forms an opening through which n) passes.

However, when a small-diameter cylindrical substrate is coated by these coating devices or coating methods, the reduction of the cross-sectional area due to the reduction of the diameter of the cylindrical substrate is
Since the surface area of the coating liquid in the dipping tank increases, the evaporation amount of the solvent vapor from the coating liquid also increases. As a result, the concentration of solvent vapor around the cylindrical substrate during coating becomes high, so that the film coated on the outer peripheral surface of the cylindrical substrate becomes slow to dry and the time in which the film is kept in the wet state becomes long. As a result, there is a drawback that sagging occurs in the pulling direction of the cylindrical substrate. Furthermore, there is a drawback that the time that is affected by the surrounding wind also becomes long, and the film thickness unevenness in the circumferential direction of the cylindrical substrate is likely to occur. It is particularly remarkable when applied simultaneously.

As a means to improve these, Japanese Patent Laid-Open No.
According to Japanese Patent No. 80383, a hood having an opening through which a cylindrical substrate is passed is provided on a lid provided on the dip, and a gap, a hole, a net or the like for allowing solvent vapor to escape is provided under the hood. Proposed. However, in this coating apparatus, since gaps, holes, nets, etc. for letting out solvent vapor are provided adjacent to the cylindrical substrate, it is said that it is affected by wind from the outside and uneven film thickness occurs. There's a problem.

[0006] Further, as another one, Japanese Patent Laid-Open No. 5-337.
Japanese Patent No. 430 proposes a dip coating method that regulates the height of the solvent vapor layer on the dipping tank. According to this method, a hood having an opening through which a cylindrical substrate passes is provided on the upper surface of an overflow receiver that surrounds the outer periphery of the immersion tank, and the height of this hood is set to 30 mm or less, so that the liquid surface of the immersion tank is The height of the solvent vapor layer generated is 30 mm or less. However, when coating a small-diameter cylindrical substrate, it is unavoidable that the solvent vapor concentration around the substrate during coating increases due to an increase in the surface area of the coating solution in the dipping tank, and further coating was repeated. In this case, in addition to the solvent vapor that evaporates from the surface of the coating liquid in the dipping tank, the solvent vapor that evaporates from the film applied to the outer peripheral surface of the cylindrical substrate also accumulates and stays in the hood, so in continuous production, It turned out that it is difficult to suppress the sagging stably. Also, when the height of the solvent vapor layer generated on the liquid surface of the immersion tank is set to 30 mm or less due to the height of the hood, the film applied to the outer peripheral surface of the cylindrical substrate has almost the same wetness as immediately after application. Since it goes out of the hood as it is, it is apt to be affected by a slight air flow in the surroundings, and the film thickness unevenness of the circumferential method becomes large.

Further, when a plurality of cylindrical substrates are simultaneously coated in one dipping tank, a hood having an opening through which the cylindrical substrate passes is provided on the upper surface of the overflow receiver surrounding the outer periphery of the dipping tank. Since the concentration distribution of the solvent vapor in the hood tends to be uneven, there is a drawback that the coating film thickness varies between the cylindrical substrates.
In order to prevent this, even when a plurality of cylindrical substrates are coated at the same time, it is conceivable to provide dip coating tanks separately for the number of cylindrical substrates. It is disadvantageous for the simplification of the structure and the support for various kinds of production.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art. That is, the object of the present invention is, in a dip coating apparatus having a dipping tank in which the surface area of the coating liquid in the dipping tank is large and the evaporation amount of the solvent is relatively large as compared with the cross-sectional area of the cylindrical substrate, It is an object of the present invention to provide a dip coating apparatus capable of forming a good coating film without sagging and uneven film thickness, and a coating method using the same. Another object of the present invention is to provide a dip coating apparatus that can cope with a change in the diameter of a cylindrical substrate without switching the dipping tank, and a coating method using the same. Still another object of the present invention is, even in an immersion coating apparatus for simultaneously coating a plurality of cylindrical substrates in a single immersion tank, solvent vapor evaporating from the surface of the coating solution in the immersion tank, or on the outer peripheral surface of the cylindrical substrate. Immersion coating device with a small size and simple structure that can form a good coating film without sagging or film thickness unevenness caused by solvent vapor evaporating from the coated film and surrounding wind, and coating using it To provide a method.

[0009]

The present invention comprises a dipping tank for containing a coating liquid, and an overflow receiver provided on the outer periphery of the dipping tank for collecting the coating liquid overflowing from the dipping tank. Dipping the substrate in the coating solution,
In a coating apparatus for pulling up and coating, a first hood that covers the overflow receiver and has an opening through which a cylindrical base body passes, and a second hood that covers the first hood and has an opening through which the cylindrical base body passes. And a gap is provided between the outer periphery of the lower end of the first hood and the inner periphery of the lower end of the second hood.

In the coating apparatus of the present invention, it is preferable that the lower end of the second hood is located lower than the liquid level of the dipping tank. Further, it is preferable that the opening of the first hood is provided in the vicinity of the coating liquid surface of the dipping tank. The coating apparatus of the present invention may be configured so that a plurality of cylindrical substrates can be simultaneously dip coated. In that case, there are a plurality of openings of the first hood and a plurality of openings of the second hood,
In addition, the structure may be provided so as to allow the cylindrical substrate to pass therethrough. Also, the opening of the first hood and the second
It is preferable that the openings of the hood are provided at equal intervals.

Further, according to the present invention, in the coating method in which the cylindrical substrate is dipped in the coating liquid for the dipping layer and is pulled up and coated by using the above-mentioned coating device, the outer periphery of the lower end of the first hood and the second The solvent vapor of the coating liquid is exhausted through a gap between the inner periphery of the lower end of the hood. INDUSTRIAL APPLICABILITY The present invention is effective when a solvent having a specific gravity of solvent vapor that is heavier than air is used as the solvent in the coating liquid. Alternatively, a plurality of cylindrical substrates may be dipped in the coating solution at the same time and simultaneously pulled up for coating. Further, the present invention is preferably applied to the case of forming a photosensitive layer on a cylindrical support using a photosensitive layer forming coating liquid.

As the cylindrical substrate used in the present invention, a known conductive substrate used for an electrophotographic photosensitive member is used. The coating liquid used in the present invention may be a known coating liquid used for coating the outer peripheral surface of a cylindrical substrate, and particularly, a charge generation layer, a charge transport layer, an undercoat layer of an electrophotographic photoreceptor. It is preferable to use a known coating liquid that is applied to form the layer and the protective layer, and any of these coating liquids can be used.

Examples of the solvent used for the coating liquid include alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as hexane, octane and cyclohexane, benzene and toluene,
Aromatic hydrocarbons such as xylene, dichloromethane, dichloroethane, carbon tetrachloride, halogenated hydrocarbons such as chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, ethers such as ethylene glycol,
Ketones such as acetone, methyl ethyl ketone, anone,
Esters such as methyl acetate, ethyl acetate, butyl acetate,
Examples thereof include dimethylformaldehyde, dimethylformamide, dimethylsulfoxide and the like. These solvents are
Both have a specific gravity heavier than air. The viscosity of the coating liquid is preferably 0.01 mPas to 1000 mPas, more preferably 1 mPas to 600 mPas.
However, depending on the coating thickness and coating speed,
It is preferable to select an appropriate one. Any known material can be used as the coating liquid for forming the photosensitive layer on the cylindrical substrate.

In the coating apparatus of the present invention, the first hood is provided in the vicinity of the liquid surface of the dipping tank and at a position where it does not come into contact with the coating liquid, so that the solvent vapor evaporated from the surface of the coating liquid in the dipping tank is evaporated. The amount can be reduced. This allows
The solvent vapor concentration around the substrate during coating can be kept low, and solvent evaporation from the film coated on the outer peripheral surface of the cylindrical substrate is not suppressed. Furthermore, the gap between the lower end of the second hood surrounding the dip tank and the outer circumference of the lower end of the first hood that covers the overflow receiver of the dip tank is opened downward to form a coating solution for the dip tank. The solvent vapor that evaporates from the wet film applied to the outer surface of the cylindrical substrate and the outer peripheral surface of the cylindrical substrate naturally flows out of the second hood due to its own weight to the outside of the second hood, and the solvent vapor in the second hood Accumulation and retention can be prevented, and the solvent vapor concentration in the second hood can be further reduced.
Thereby, the restriction on the height of the second hood is relaxed, and the wet film applied to the outer peripheral surface of the cylindrical substrate is
The solvent evaporation can be promoted in the second hood until it is less affected by the slight air flow around, and a good coating film without sagging or film thickness unevenness is formed. In a dipping coating device that simultaneously coats a plurality of cylindrical substrates in one dipping tank, the same action works, and
Since the top plate on the upper part of the second hood has the opening only in the portion through which the cylindrical base body passes, it is not easily affected by the wind from the outside of the second hood.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an example of the dip coating device of the present invention. In the drawing, a coating liquid 1 is supplied from a tank 2 to a supply pipe 3
Through the filter 4 and is supplied into the dipping bath 6 through the filter 5. The coating liquid 1 overflows from the upper part of the dipping tank 6, passes through the overflow receiver 7 and the return pipe 8 provided around the dipping tank 6, and is collected in the tank 2. The upper part of the overflow receiver 7 is covered with a first hood 11 having an opening 10 through which the cylindrical substrate 9 passes, whereby the liquid surface of the coating liquid 1 in the dipping tank 6 is covered. In addition, the second hood 12 surrounds the cylindrical base body 9 and the overflow receiver 7.
Is provided. The second hood 12 has an opening 14 through which the cylindrical substrate passes, and a gap 15 is opened downward between the inner periphery of the lower end of the second hood 12 and the outer periphery of the lower end of the first hood 11. Is provided. Cylindrical substrate 9
Is immersed in the coating liquid 1 in the dipping tank 6 by a gripping tool (not shown) directly connected to the lifting device, and then pulled up at a predetermined speed.

FIG. 2 is a schematic view showing another example of the coating apparatus of the present invention. A state immediately after a plurality of cylindrical substrates are pulled out of the dipping tank at the same time and the lower end of the cylindrical substrates leaves the coating liquid surface. Is shown. In the overflow receiver 7 provided around the dipping tank 6 of the coating apparatus, the cylindrical substrate 9 (9
-1 to 9-n) passes through the opening 10 (10-1 to 10).
The first hood 11 having -n) is arranged so as to surround the overflow receiver 7, and covers the liquid surface of the coating liquid 1 in the dipping tank 6. In addition, the dip tank 6 and the overflow receiver 7 provided around the dip tank 6 have a second
Hood 12 is provided, and an opening 14 through which the cylindrical substrate 9 passes is further provided on the second hood 12.
A top plate 13 having (14-1 to 14-n) is provided. A gap 15 is formed downward in the inner circumference of the lower end of the second hood 12 and the outer circumference of the lower end of the first hood that covers the overflow receiver 7. The cylindrical substrate 9 is configured to be dipped in the coating liquid 1 in the dipping tank 6 by a holding tool (not shown) directly connected to the elevating device and then pulled up at a predetermined speed.

The openings 10 of the first hood are individually provided so as to correspond to the cylindrical base body, and it is preferable that the opening has a small hole diameter in order to suppress the rise of solvent vapor. A suitable hole diameter is selected depending on the above, but the distance between the surface of the cylindrical substrate and the open end is preferably in the range of 2 mm to 20 mm. For example, in the case of a 30 mmφ cylindrical substrate, the hole diameter of the first hood is preferably in the range of 34 mmφ to 70 mmφ. Further, in order to prevent the occurrence of surface defects such as orange peel, the distance between the first hood 11 and the surface of the coating solution in the dipping tank is preferably in the range of 4 mm to 50 mm. Further, a gap 15 that is opened downward between the lower end outer circumference of the first hood and the lower end inner circumference of the second hood 12 that covers the overflow receiver 7 that surrounds the dipping tank is formed in the second hood. It is necessary that the cylindrical substrate 9 is not affected by the surrounding wind and that the solvent vapor in the second hood 12 is naturally exhausted by its own weight, and it is selected in the range of 1 mm to 30 mm. be able to. The lower end of the gap 15 is preferably located below the liquid surface of the coating liquid. The height of the second hood 12 is such that the wet film immediately after application is
The distance between the upper end of the second hood and the liquid surface is preferably in the range of 10 mm to 500 mm, more preferably 20 mm, although it should be determined considering the influence of the surrounding wind. The range is 200 mm. However, these dimensions are not limited to the above values, and may be appropriately selected depending on the length of the cylindrical substrate, the coating speed, the coating liquid temperature, the evaporation rate of the solvent in the coating liquid, the wet film thickness, and the like. preferable.

[0018]

EXAMPLES The present invention will now be described with reference to more detailed examples. Example 1 In the coating apparatus of FIG. 1, the distance (c) from the upper surface of the first hood 11 to the liquid surface of the coating liquid is 25 mm, the diameter of the opening 10 of the first hood 11 is 40 mmφ, and the second hood is The diameter of the upper opening 14 of 12 is 37 mmφ, and the distance (a) between the upper end of the second hood 12 and the lower part (A) of the second hood 12 is 85.
mm, lower part of the first hood 11 and the second hood 12 (A)
(B) is 10 mm, and the gap 15 between the inner circumference of the lower end of the second hood and the outer circumference of the lower end of the first hood is 12 mm. As the coating liquid, N, N'-diphenyl-N, N'-
Bis (3-biphenyl)-[1,1'-biphenyl]-
A coating solution was prepared by dissolving 10 parts of 4,4 ′ diamine and 13 parts of poly (4,4-cyclohexylidenediphenylene carbonate) resin in a mixture of 23 parts of monochlorobenzene and 54 parts of tetrahydrofuran. As the cylindrical substrate 9, an aluminum pipe (0.75 mmt × 30 mmφ)
X 340 mm), and was held by a holding device (not shown), dipped in the coating liquid 1 by an elevating device (not shown), and then pulled up at a speed of 200 mm / min. After air drying,
The film was placed in a hot air dryer at 110 ° C. for 40 minutes and dried by heating to form a charge transport layer having a film thickness of 24 μm. Moreover, in order to confirm the stability of coating, coating was continuously performed on 14 aluminum pipes under the same conditions at intervals of 5 minutes. Table 1 shows the measurement results of the obtained coating film thickness. The coating film thickness is 20 mm, 50 mm, 160 mm, 30 from the beginning of coating.
Measurements were made at a total of 16 locations of 4 locations (90 ° intervals) in the circumferential direction at each location of 0 mm, the average was taken as the average film thickness, and the difference between the maximum and minimum values at the 16 locations was taken as the film thickness unevenness. . In addition, the difference between the minimum film thickness and the average film thickness at four locations (intervals of 90 °) in the circumferential direction at 20 mm from the beginning of coating was defined as sag.

[0019]

[Table 1]

Example 2 In the coating apparatus of FIG. 2, the distance from the liquid surface of the first hood 11 was 25 mm, and the diameter of the opening 10 of the first hood 11 was 40 mm.
mmφ, opening 14 of the top plate 13 above the second hood 12
Has a diameter of 37 mm, the distance between the top plate 13 and the first hood 11 is 85 mm, and the gap 15 between the inner periphery of the lower end of the second hood and the outer periphery of the lower end of the first hood is 12 mm. As the cylindrical substrate 9, the same aluminum pipe as in Example 1 was used, and as shown in the schematic diagram of FIG. 3, 14 pieces were arranged in an equilateral triangle shape at equal intervals. The same coating liquid as in Example 1 was used, and the conditions for dip coating and the method for evaluating the coating film thickness were the same as in Example 1. Table 2 shows the measurement results of the obtained coating film thickness.

[Table 2]

Comparative Example 1 For comparison, except using the coating apparatus shown in FIG.
A coating film was formed under the same conditions as in Example 1. In FIG. 4, the diameter of the upper opening of the hood 16 is 40 mm, the distance between the lower end of the hood 16 and the liquid surface is 25 mm, the distance between the upper end of the hood 16 and the liquid surface is 110 mm, and the distance is continuous at 5 minute intervals. Application was performed on 14 aluminum pipes.
Table 3 shows the measurement results of the obtained coating film thickness.

[Table 3]

Comparative Example 2 Further, for comparison of an apparatus for simultaneously dip-coating a plurality of cylindrical substrates in one dipping tank, coating was performed under the same conditions as in Example 2 except that the coating apparatus shown in FIG. 5 was used. A film was formed. In FIG. 5, the distance between the lower end of the hood 16 and the liquid surface is 25 mm, and the distance between the upper end of the hood 16 and the liquid surface is 11 mm.
0 mm. Table 4 shows the measurement results of the obtained coating film thickness.

[Table 4]

[0023]

As is clear from the above comparison, according to the coating apparatus of the present invention, even in the dip coating of a plurality of cylindrical substrates in one dipping tank, the surface of the coating liquid in the dipping tank and the overflow receiver is obtained. A first hood that reduces the amount of evaporation of solvent vapor from the tank is provided, and a second hood that surrounds the immersion tank is provided.
Between the inner circumference of the lower end of the hood and the outer circumference of the lower end of the first hood,
By opening the gap downward, it is possible to prevent the influence of a slight flow of air around and to prevent the accumulation and retention of solvent vapor in the second hood, so that there is no sagging or uneven film thickness. A good coating film can be formed, and even in continuous coating, a coating layer having a very stable film thickness can be formed. Therefore, the present invention is extremely suitable for manufacturing an electrophotographic photoreceptor.

[Brief description of drawings]

FIG. 1 is a schematic view showing a state during coating by a coating apparatus of the present invention.

FIG. 2 is a schematic view showing another example of the coating apparatus of the present invention.

FIG. 3 is a schematic top view showing an arrangement example of cylindrical substrates when a plurality of cylindrical substrates are simultaneously dip-coated in one dipping tank by using the coating apparatus of the present invention.

FIG. 4 is a schematic view showing an example of a conventional dip coating device.

FIG. 5 is a schematic view showing another example of a conventional dip coating device.

[Explanation of symbols]

1 ... Coating liquid, 2 ... Tank, 3 ... Supply pipe, 4 ... Pump,
5 ... Filter, 6 ... Immersion tank, 7 ... Overflow receiver, 8 ... Return piping, 9, 9-1 to 9-n ... Cylindrical substrate,
10, 10-1 to 10-n ... opening of the first hood, 1
1 ... 1st hood, 12 ... 2nd hood, 13 ... Top plate,
14, 14-1 to 14-n ... second hood opening, 1
5 ... A gap between the inner circumference of the lower end of the second hood and the outer circumference of the lower end of the first hood, 16 ... Hood.

Claims (9)

[Claims] 1. A dipping tank for containing a coating liquid, and an overflow receiver provided on the outer periphery of the dipping tank for collecting the coating liquid overflowing from the dipping tank, wherein the cylindrical substrate is dipped in the coating liquid. Then, in the coating device for pulling up and coating, there is a first hood that covers the overflow receiver and has an opening through which the cylindrical substrate passes, and an opening that covers the first hood and through which the cylindrical substrate passes. A second hood, wherein a gap is provided between a lower end outer circumference of the first hood and a lower end inner circumference of the second hood. 2. The coating apparatus according to claim 1, wherein the lower end of the second hood is located at a position lower than the liquid surface of the dipping tank. 3. The coating apparatus according to claim 1, wherein the opening of the first hood is provided near the coating liquid surface of the dipping tank. 4. A plurality of openings of the first hood and openings of the second hood are provided, respectively, and are provided so as to allow the cylindrical substrate to pass therethrough. Item 1. The coating apparatus according to Item 1. 5. The coating apparatus according to claim 1, wherein the openings of the first hood and the openings of the second hood are provided at equal intervals. 6. A coating liquid of a coating device comprising: a dipping tank for containing the coating liquid; and an overflow receiver provided on the outer periphery of the dipping tank for collecting the coating liquid overflowing from the dipping tank. In a coating method in which a substrate is dipped, pulled up and coated, the coating device covers the overflow receiver, a first hood having a first opening through which a cylindrical substrate passes, and a first hood. A second hood having an opening through which the cylindrical base body passes, and a gap is provided between the outer periphery of the lower end of the first hood and the inner periphery of the lower end of the second hood, A coating method, wherein the solvent vapor of the coating liquid is exhausted through the gap. 7. The coating method according to claim 6, wherein the specific gravity of the solvent vapor of the coating liquid is heavier than that of air. 8. The coating method according to claim 6, wherein a plurality of cylindrical substrates are simultaneously immersed in the coating solution and simultaneously pulled up for coating. 9. The coating method according to claim 6, wherein the coating liquid is a photosensitive layer forming coating liquid.