JPH0588385A - Dip coating equipment - Google Patents

Abstract

PURPOSE:To obtain dip coating equipment where a film with little sagging is formed and simultaneously the scattering of the sagging values generated when dip coating a lot of cylindrical substrates at the same time is made small. CONSTITUTION:In dip coating equipment provided with a dip tank 1 and a means 11 for movably in the vertical direction supporting a cylindrical material to be coated 12, a rising air flow blowoff device 5 laving air blowoff slits 4 is installed above the dip tank 1 and a lower air blowoff device 21 is installed below the rising air flow blowoff device 5.

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 suitable for forming an electrophotographic photoreceptor. More specifically, the present invention relates to a dip coating device that controls touch-drying to form a coating film having a uniform and constant film thickness on the surface of a substrate.

[0002]

2. Description of the Related Art Conventionally, various methods and apparatuses have been proposed for the purpose of preventing so-called sagging, in which the thickness of a coating film becomes thin in the vicinity of the upper end of an object to be coated during dip coating. For example, it has been attempted to form a uniform coating film by applying an air flow to the outer surface of a cylindrical object to exert an air doctor effect and a drying effect, prevent sagging of the upper end portion of the coating film, and form a uniform coating film. There is. (For example, JP-A-59-225771). In this method, the flow velocity of the blown air may be uneven in the circumferential direction due to an error in manufacturing the air blower. The blowing unevenness has a drawback that even if it is minute, unevenness in film thickness occurs in the coating film. Since various conventionally proposed dip coating devices that prevent sagging by blowing air have the above-mentioned drawbacks, they are not stable against the occurrence of uneven film thickness. Had a problem that was difficult to introduce.

In order to improve this point, the present inventors have
First, a method and an apparatus for controlling the touch-drying to prevent film thickness sagging near the upper end of the coating film have been proposed (Japanese Patent Application No. 2-2079).
90 and 2-411660). In one of them, in an apparatus provided with rising air blowing means having an air blowing slit above the immersion tank and an air intake means having an air intake opening at the bottom of the air blowing means, the air is blown from the air blowing slit. By generating a negative pressure near the liquid surface and sucking air from the lower air intake tool opening based on the negative pressure, it is possible to stably form a uniform coating film with little film thickness sag. There is.

[0004]

In recent years, for the purpose of improving productivity, so-called multiple simultaneous dip coating, in which a large number of cylindrical substrates are simultaneously dip coated, has been carried out. However, it is required to simultaneously apply a large number of cylindrical substrates by dip coating to create an electrophotographic photosensitive member. In that case, the sag value is stably reduced, but the external air sucked based on negative pressure is used. However, since it is difficult to hit all of the cylindrical substrates uniformly in the circumferential direction, the sag value in the circumferential direction of one cylindrical substrate varies, leaving room for improvement in quality. ing.

FIG. 8 shows a dip coating apparatus for simultaneously dip coating a large number by the method previously proposed by the present inventors. A lid 3 is placed on an overflow receiver 2 provided at the upper part of the plurality of immersion tanks 1, and an ascending airflow generator 5 having a ring-shaped air blowing slit 4 is provided thereon. The opening degree of the opening b of the lid 3 can be adjusted by the opening adjusting screw 6. The coating liquid is held in the dipping tank and is circulated by the pipes 7 and 8, the circulation tank 9 and the circulation pump 10. The cylindrical substrate 12 supported by the chucking device 11 is lowered by an elevating device to be dipped in the coating liquid in the coating tank and then pulled up. Due to the negative pressure near the surface, the outside air is sucked through the opening b, and the preliminary drying effect thereby contributes to the prevention of film thickness sag.
However, the amount of sucked outside air is large in a portion close to the opening on the surface of the cylindrical substrate, and the sag value is small, but deteriorates in a portion where the sucked outside air is hard to reach. FIG. 9 illustrates the case where the state of sagging is examined at intervals of 90 ° on the peripheral surface of each cylindrical substrate. Black dots are points where the film thickness sagging value is small, and open circles are films. This is a part with a large thickness sag value. This phenomenon becomes remarkable when a large number of cylindrical substrates are simultaneously applied by dip coating, so that the product quality varies.

The present invention has been made in view of the above circumstances, and its purpose is to form a coating film with less sagging and to simultaneously apply a large number of cylindrical substrates by dip coating. It is an object of the present invention to provide a dip coating device that reduces variations in sagging value.

[0007]

DISCLOSURE OF THE INVENTION As a result of investigations, the inventors of the present invention conducted dip coating below the rising air flow blowing device by forcibly blowing out an amount of air equal to or more than the amount of sucked air from the outside. As a result, they have found that the above problems can be improved, and have completed the present invention. The present invention, in a dipping tank, and a dip coating apparatus having means for supporting a cylindrical object to be moved in the vertical direction, providing an ascending air flow blowing means having an air blowing slit above the dipping tank, A lower air blowing means is provided below the rising air flow blowing means. In the present invention, the means for supporting the cylindrical object to be moved in the vertical direction includes a cylindrical chuck device support having an outer diameter that is the same as the outer diameter of the cylindrical object, and the chuck device support. A chuck device is provided at the lower end of the tool, and when a cylindrical object is supported by the chuck device, a step is formed between the outer circumference of the cylindrical chuck device support tool and the outer circumference of the cylindrical object. Is preferably prevented.
The present invention will be described in more detail with reference to FIG. 1, which is one embodiment thereof. In the dip coating apparatus of the present invention, an overflow receiver 2 is provided on an upper portion of a coating tank 1, and a lid 3 is placed on the overflow receiver 2. There is. A lower air blowing device 21 is provided on the lid, and an ascending air blowing device 5 is provided thereon.
Is provided.

[0008]

In the dip coating device shown in FIG. 1, the chucking device 11 supports the cylindrical substrate 12, moves it downward to immerse it in the coating liquid in the coating tank, and then pulls it up to perform coating. Be seen. In that case, air is blown upward from the ring-shaped slit 4 of the upper rising air blowing device 5 to form a rising air flow and hit the surface of the cylindrical substrate. On the other hand, the lower air blowing device 21 also ejects an air flow. As a result, the negative pressure generated by the rising air flow is eliminated, and the air flow is evenly applied in the circumferential direction of all of the plurality of cylindrical substrates, preventing sagging and evenly coating the film. You can maintain your sex. In the present invention, the cylindrical chuck device supporting member in the chucking device is, as shown in FIG.
When the outer diameter of the cylindrical object to be coated is the same as that of the object to be coated, when the object to be coated is supported by the chuck device, the object to be coated and the cylindrical chuck device support on it are the same on the same axis. Since they are arranged as cylinders having an outer diameter, no step is formed at the joint. Therefore, when the coating object is pulled up from the coating tank, there is no powder that causes fluctuations in the flow velocity of the rising air flow, fine film thickness unevenness does not occur at the coating film upper end portion of the coating object, and the upper end of the coating film The uniformity of the part can be maintained even better.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of the dip coating device of the present invention, and FIG. 2 is a sectional view of the main part thereof. An overflow receiver 2 for receiving an overflowing coating solution is provided on the upper portion of the coating tank 1, and a lid 3 is placed on the overflow receiver 2. A lower air blowing device 21 is provided on the lid, and a rising air blowing device 5 is provided on the lower air blowing device 21. The coating tank is filled with the coating solution, and the overflowing coating solution is sent to the circulation tank 9 through the pipe 7 and further sent to the bottom of the coating tank through the pipe 8 by the circulation pump 10 for circulation. It is supposed to do. A chucking device 11 for supporting the cylindrical substrate 12 is arranged above the coating tank so as to be movable in the vertical direction by a known means (not shown).

As shown in FIG. 2, the rising air blowing device 5 comprises a hollow air jacket 13 having a slit 4 so that air is supplied from an air supply port 14 into the air jacket. Is becoming The slit 4 is formed in a ring shape on the surface facing the cylindrical substrate 12 that is the object to be coated, and is 30 to 80 ° with respect to the horizontal plane.
Slit angle θ = 30 so that the air flow is jetted upward
It opens at an angle of ~ 80 °.

The lower air blowing device 21 is composed of a hollow cylindrical air jacket 22 having an air blowing surface 23, and air is supplied from the air supply port 24 into the air jacket. There is. In the present invention, the air blowing surface 23 is located below the overflow surface of the dipping tank so that the air blown from the air blowing surface 23 does not directly hit the cylindrical substrate immediately after coating and cause unevenness in film thickness. Therefore, it is necessary to make it possible to perform uniform blowing over the entire surface in the circumferential direction. Therefore, it is preferable that the air blowing surface 24 is formed of, for example, a sintered mesh made of stainless steel or a perforated plate over the entire circumference of the lower portion of the cylindrical air jacket 22.

A specific example of the case where an electrophotographic photosensitive member having a photosensitive layer provided on a cylindrical substrate is produced by the above dip coating apparatus will be described. Example 1 As a cylindrical substrate, 84 mmφ × 340 mmL × 1 mm
An electrophotographic photoreceptor having a charge injection blocking layer made of a zirconium compound and having a thickness of 0.1 μm, and a charge generation layer having a thickness of 0.1 μm and containing 65% by volume of trigonal selenium is provided on an aluminum pipe of t. An intermediate product was used. Also,
As the coating liquid, the charge transport material 4 represented by the following structural formula is used.
Department,

[Chemical 1] What was obtained by dissolving 6 parts of a polycarbonate resin having a viscosity average molecular weight of 39000 in 47 parts of monochlorobenzene was used.

As shown in FIG. 1, the above coating solution was supplied to a coating tank of a dip coating apparatus for simultaneous coating of eight lines to form a charge transport layer on the charge generation layer of the intermediate product. The conditions of the dipping coating device at that time were set as follows. The lower air blowing device uses an air blowing surface 23 made of a sintered mesh of 5 μm stainless steel, and the height h =
50 mm, the distance i from the upper end of the lower air blowing surface to the liquid surface of the dipping tank was i = 20 mm, the inner diameter of the dipping tank was 110 mmφ, the inner diameter of the lower air blowing device was j = 135 mmφ, and the height of the lower air blowing surface was g = 25 mm. Regarding the rising airflow generator 5, the slit spacing d = 1.0 mm, the slit angle θ = 60 °, and the rising airflow generator inner diameter f = 115.
mmφ and the distance a between the immersion tank liquid surface and the slit a = 25 mm.

As operating conditions, the amount of air supplied to the rising air flow generator 5 is 16 Nm ³ / hr per coating tank, and the air supplied to the lower air blowing device 21 is 12 Nm per coating tank.
Dip coating was performed under the coating conditions of ³ / hr and a coating speed of 120 mm / min. Also, the supply air has a dew point of -1 at normal pressure
Compressed air at 7 ° C was used. In addition, as the supply air,
The dehumidified air as described above may be used, or the air containing a solvent gas used in the coating liquid or another solvent gas may be used.

Comparative Example 1 For comparison, dip coating was carried out using the dip coating apparatus for simultaneous coating of eight lines shown in FIG. In that case, 300 cm ² was set as the opening b, and the coating conditions were all set to be the same except for the condition related to the lower air blowing in Example 1.

Comparative Example 2 Immersion coating was carried out using the same dipping coating device as in Example 1 except that the rising airflow generator and the lower air blowing device were not used, except for the air blowing conditions.

The film thickness of the charge transport layer formed in Example 1 and Comparative Examples 1 and 2 was measured by an interference film thickness meter, and the relationship between the distance from the beginning of coating and the film thickness was investigated. The results are shown in Table 1. The film thickness measurement points were unified to the positions shown by the black dots in FIG.

[0018]

[Table 1]

From the results shown in Table 1, in the case of Example 1 and Comparative Example 1, as compared with the case of Comparative Example 2, the film thickness is large at a short distance from the start of coating, that is, the film thickness sag. You can see that there are few.

Next, in the case of Example 1 and Comparative Example 1, the film thickness at the position of 15 mm from the beginning of coating was measured at 90 ° intervals in four places in each dipping tank. The result is shown in FIG. Note that FIG. 4A shows the results of Example 1, and FIG.
(B) shows the results of Comparative Example 1. In these figures, black dots indicate measurement positions, and each numerical value means film thickness (μm). From the results shown in FIG. 4, it can be seen that in Example 1, the film thickness uniformity was maintained as compared with Comparative Example 1.

FIG. 5 shows another preferred embodiment of the present invention. In this embodiment, the means for supporting the cylindrical object to be moved in the vertical direction has an outer diameter of the cylindrical substrate 12. n has a cylindrical chuck device support 15 having the same outer diameter m as n, and a chuck device 17 is attached to a chuck device mounting portion 16 provided at the lower end of the chuck device support.
Is attached. Then, the chuck device 17
When the cylindrical substrate 12 is supported by, the cylindrical chuck device support tool and the cylindrical substrate are aligned on the same axis,
There is no step at the joint between the two. In the above case, the fact that the outer diameter n of the cylindrical substrate 12 and the outer diameter m of the cylindrical chuck device support 15 are the same means that the difference between them is within ± 1.0 mm. still,
Other symbols in FIG. 5 are synonymous with those shown in FIGS.

The dip coating apparatus shown in FIG. 5 is also dip coated in the same manner as the dip coating apparatus shown in FIG. 1, but in this case, the cylindrical substrate supported by the chuck device 17 is supported by the cylindrical chuck device. Since it is lined up on the same axis as the ingredients,
There is no step between the two. FIG. 6 is an enlarged cross-sectional view of a joint portion between the cylindrical base body and the cylindrical chuck device support tool in FIG. 5, and since the chuck device mounting portion 16 is attached, the outer periphery of the cylindrical base body 12 has a cylindrical shape. It is possible to accurately match the outer circumference of the chuck device support tool 15. When there is a step between the outer circumference of the cylindrical substrate and the outer circumference of the cylindrical chuck device support, before and after passing through the slit 4 portion of the rising air flow generator 5 when pulling up the cylindrical substrate from the coating tank 1. Then, there is a case where the flow velocity of the rising air flow changes, and a fine film thickness unevenness may occur at the upper end of the coating film formed on the cylindrical substrate.
In the case shown in FIG. 5, since there is no step at the joint between the cylindrical substrate and the cylindrical chuck device support, there is no change in the velocity of the rising air flow during pulling. Therefore, it becomes possible to form a coating film having even better uniformity.

Example 2 Using the dip coating apparatus shown in FIG. 5, the same intermediate product as in Example 1 was used, and dip coating was performed using the same coating solution. The coating conditions were the same as in Example 1 except for the following points. Outer diameter of cylindrical substrate: n = 84 mm, outer diameter of cylindrical chuck device support: m = 84 mm, distance between slit and outer periphery of cylindrical chuck device: k = 10 mm, rising air flow rate:
12 Nm ³ / hr (dew point at normal pressure: -17 ° C. air), pulling rate: 110 mm / min, width of uncoated part: p = 2 m
m. The formed film was dried at 135 ° C. for 60 minutes, and the state of the film thickness was measured with a dial gauge (Mitutoyo). The result is shown in FIG. 7. For reference, the outer diameter is 90
Immersion coating was performed in the same manner as described above except that a cylindrical chuck device of mm was used. The result is shown in FIG. 7.

In the present invention, the apparatus and various operating conditions described in the examples are arbitrarily set depending on the physical properties of the materials used, but the coating speed is usually 50 to 50.
The range of 400 mm / min is set, and the amount of air supplied to the lower air blowing device is usually set to 30 to 100% of the amount of air supplied to the rising air generator. In addition,
In the above example, the lower air blowing device has a cylindrical mesh type, but any shape can be used as long as it is uniform around the cylindrical substrate and a predetermined amount of air flows.

[0025]

As described above in detail, the dip coating apparatus of the present invention is provided with the rising air flow blowing means and the lower air blowing means below the rising air flow blowing means. In addition, it is possible to prevent the film thickness from sagging and to prevent the sag value from varying in each cylindrical substrate, which has occurred when a large number of organic photoconductors are manufactured at the same time. Therefore, according to the dip coating device of the present invention, the variation in the film thickness sagging in one cylindrical substrate is reduced, and the yield in mass production is increased,
Since it is advantageous in terms of cost, it is very effective for mass production of organic electrophotographic photoreceptors with stable quality. Further, when a cylindrical chuck device support tool having the same outer diameter as that of the cylindrical object to be coated is used, the joint between the cylindrical object to be coated and the cylindrical chuck device support tool is used. Since no step is formed, fine coating unevenness does not occur at the upper end portion of the coating film.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of a dip coating device of the present invention.

FIG. 2 is a sectional view of a main part of the dip coating device of FIG.

FIG. 3 is a diagram showing measurement points of film thickness in Example 1 and Comparative Examples 1 and 2.

FIG. 4 is a diagram showing a film thickness at a position of 15 mm from the beginning of coating in Example 1 and Comparative Example 1.

FIG. 5 is a sectional view of a main part of another example of the dip coating device of the present invention.

FIG. 6 is an enlarged cross-sectional view of a joint portion between the cylindrical base body and the cylindrical chuck device support tool of FIG.

FIG. 7 is a diagram showing a film thickness state of a coating film obtained in Example 2.

FIG. 8 is a schematic configuration diagram of a dip coating device of a comparative example.

FIG. 9 is a diagram illustrating the state of the sagging of the end portion of the coating film formed by the dip coating device of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Immersion tank, 2 ... Overflow receiver, 3 ... Lid, 4 ... Slit, 5 ... Ascending air flow generator, 6 ... Opening adjusting screw, 7 ... Piping, 8 ... Piping, 9 ... Circulation tank, 10 ... Circulation Pump, 11 ... Chucking device, 12 ... Cylindrical substrate,
13 ... Air jacket, 14 ... Air supply port, 15 ... Cylindrical chuck device support. , 16 ... Chuck device attachment part, 17 ... Chuck device, 21 ... Lower air blowing device, 22 ... Air jacket, 23 ... Air blowing surface,
24 ... Air supply port.

Claims (2)

[Claims] 1. An immersion coating apparatus comprising a dipping tank and a means for vertically movably supporting an object to be coated, wherein ascending air flow blowing means having an air blowing slit is provided above the dipping tank. And a lower air blowing unit provided below the rising air flow blowing unit. 2. A cylindrical chuck device supporter having means for supporting a cylindrical object to be moved in the vertical direction and having the same outer diameter as the outer diameter of the object to be coated, and the chuck device. Between the outer periphery of the cylindrical chuck device support and the outer periphery of the cylindrical object to be coated, when the cylindrical object is supported by the chuck device, the chuck device is provided at the lower end of the holder. The dip coating device according to claim 1, wherein no step is formed on the surface.