JPH1176913A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a downward hole and the splashing, abnormal flow or the like of liquid when pulling out a cylindrical base material by supplying solvent saturated gas whose pressure is adjusted by immersing a pipe in a liquid column of coating liquid below a gripping part inside a cylindrical base material and making the depth of the pipe in the liquid column approximately equal to or a little smaller than the immersion depth. SOLUTION: Gas such as air and nitrogen is blown in from gas blowing line 14 in coating liquid adjusting solvent 10 of a cylindrical vessel 12 to make small bubbles by a porous substance 13 of a tip part and pass them through the solvent 10, thereby obtaining solvent saturated gas. By immersion depth 'h' changed by moving a pipe 18 communicating with a solvent saturated gas supply pipe 24 in coating liquid 15 of a vessel 17 by a linear way 21, pressure is adjusted. The depth 'h' is made approximately equal to or a little smaller than immersion depth 'h0 ' of a cylindrical base material 1. Pressure of gas 5 is adjusted with the coating liquid height 'h' by a pressure adjusting means 16. Downward holes by leaking of the gas 5 and liquid sagging of coating liquid 6 when pulling out the cylindrical base material 1 from a coating liquid surface 4 are prevented. Without providing a complicated mechanism such as pressure measurement, uniform coating can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a tubular body having a coating film. More specifically, for example, OPC used in PPC copiers and laser beam printers
The present invention relates to a coating method for forming a coating film having no coating unevenness and defects on a cylindrical substrate used for a photosensitive drum or the like.

[0002]

2. Description of the Related Art As a method of forming a coating film on the surface of a cylindrical body, various methods are known, but a dip coating method is employed particularly when importance is placed on the smoothness of the coating film. .
In a general immersion method, a cylinder is immersed in a coating solution, and then pulled up at an appropriate speed to form a coating film on the outer surface of the cylinder. In this method, the viscosity of the coating liquid,
By setting the pulling speed and the like as appropriate, a substantially uniform coating film can be formed on the outer surface of the cylindrical body. However, in the case of a cylindrical body whose both ends in the longitudinal direction are open, the coating liquid also penetrates into the cylindrical body when the cylindrical body is immersed in the coating liquid, so that a coating film is formed on the inner surface. In addition, not only is the coating liquid wasted, but also the inner surface of the cylinder is difficult to dry, and there are problems such as contamination.

In order to solve this problem, a lid is attached to the end (lower part) of the cylindrical body which is immersed in the coating liquid, and when the cylindrical body is immersed in the coating liquid, the coating liquid penetrates into the inner surface of the cylindrical body. Prevent,
A method for preventing the application liquid from adhering to the inner surface of the cylinder has been proposed. However, in this method, the work is inferior because it takes time to attach the lid, and when the cylinder is immersed in the coating liquid, the coating liquid also adheres to the surface of the lid. In addition, there is a problem that maintenance work is complicated.

On the other hand, by closing the end (upper portion) of the cylindrical body that is not immersed in the coating liquid, air is trapped inside the cylindrical body when the cylindrical body is immersed in the coating liquid. A method for preventing the intrusion of the coating solution into the coating has also been proposed. However, this method also has the following disadvantages.

[0005] It is because the pressure of gas such as air confined inside the cylindrical base increases with the evaporation of the solvent constituting the coating solution, and the pressure of the confined space acts from the outside of the cylindrical body. If the diameter becomes larger, the gas cannot be confined and placed inside the substrate, and a phenomenon (hereinafter, referred to as a “bottom phenomenon”) in which the gas floats from the lower end of the cylindrical body to the coating liquid surface as bubbles. During the floating of the air bubbles, the air bubbles come into contact with the outer surface of the cylindrical body or pop off on the surface of the coating liquid to disturb the surface of the coating liquid.

For the purpose of controlling the floating of such bubbles, for example, a method of extracting gas such as air trapped inside a cylinder as described in Japanese Patent Publication No. 62-4187. Has been proposed. Japanese Patent Publication No. Sho 62-29106 discloses a method for sealing and gripping the inner surface of a cylindrical body with the cylindrical body open at both ends. 28665 and the like. Although these do have means for adjusting the pressure, they detect the internal pressure and open the valve of the high-pressure original gas, or detect the liquid level in the enclosed space, and The troublesome measurement and operation such as opening the valve of the original gas were required.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the pressure in a closed space formed by tightly gripping a substrate having both ends opened and immersing the substrate in a coating solution is disclosed. The simple operation is undoubtedly followed by the change associated with the immersion pull-out operation, and is changed to prevent the occurrence of a lower bulge and to prevent the liquid scattering, abnormal flow, etc. generated when the tubular base is pulled out from the liquid. Things.

[0008]

The object of the present invention is to provide a coating method for forming a coating film on the outer surface of a cylindrical substrate by holding an inner surface of the cylindrical substrate in an airtight manner and immersing a coating solution tank in the coating method. Gas saturated with the vapor of the solvent used in the process (liquid medium saturated gas)
The solvent-saturated gas, the pressure of which is adjusted by a pressure adjusting means having a structure in which a pipe is immersed in a coating liquid itself or a liquid column having the same specific gravity as the coating liquid, is applied to the lower portion of the gripping portion inside the cylindrical substrate. supplied, the depth of the pipe in the liquid column of the pressure regulating means h, and immersion depth of the coating fluid bath of the cylindrical body is taken as h _0, immersing the cylindrical substrate in the coating liquid tank In this case, h can be set to be substantially the same as h ₀ , and when the cylindrical substrate is extracted from the coating liquid tank, h can be adjusted to be equal to or slightly smaller than h ₀ to solve the problem.

[0009]

According to the present invention, first, the pressure change in the closed space (hereinafter simply referred to as the "closed space") below the gripping portion inside the cylindrical base is determined by the immersion depth of the cylindrical base. In order to be determined by the following formula, means is provided for preventing the solvent of the coating liquid from evaporating into the closed space. Specifically, it is a means for always saturating the gas supplied to the closed space with the solvent vapor for adjusting the coating liquid, and sufficiently replacing the unsaturated gas in the closed space with the solvent saturated gas. Further, a gas used for adjusting the pressure in the closed space is a solvent-saturated gas.

Second, a liquid column is formed using the coating liquid itself, and the pressure of the saturated gas supplied to the vapor-tight space is adjusted by the liquid column. Specifically, using a bottomed pipe-shaped container or the like, a liquid column composed of the coating liquid itself is formed, and a hype communicating with the supply pipe for supplying the solvent-saturated gas is immersed vertically from above the liquid column, and is constantly immersed. This is a pressure adjusting mechanism having a structure for releasing a solvent-saturated gas from the tip of the pipe, and adjusts the pressure in the pipe for supplying the solvent-saturated vapor by the immersion depth h of the pipe.

At this time, the immersion depth of the pipe is set to be substantially equal to or slightly smaller than the immersion depth in the coating operation. When the immersion depth increases, the liquid column depth is set so that the coating liquid does not enter the enclosed space. When extracting the substrate while supplying the solvent saturated gas while increasing the pressure, reduce the immersion depth of the pipe, and the pressure in the enclosed space will become too large, causing lower dents or becoming too small The pressure in the closed space is adjusted so that the application liquid does not enter into the closed space and the liquid does not splash when the drum end leaves the liquid surface.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 is an overall view showing one embodiment of the present invention. The method of the present invention is applied to a cylindrical substrate 1 having both ends in the longitudinal direction opened. For example, when the use of the cylindrical substrate 1 is a support for an electrophotographic photosensitive member, any of the well-known electrophotographic photosensitive members can be used. Specifically, for example, a metal drum of aluminum, stainless steel, copper, or the like, or a laminate or a vapor-deposit of these metal foils may be used. Further, plastic drums, paper tubes, and the like, which have been subjected to a conductive treatment by applying a conductive substance such as metal powder, carbon black, copper iodide, and a polymer electrolyte together with a suitable binder, may be mentioned. Further, a plastic drum which contains a conductive substance such as metal powder, carbon black, and carbon fiber and is made conductive may be used. Further, a charge generation layer, an undercoat layer and the like may be provided on these supports. Cylindrical substrate 1
The size can be appropriately selected according to the use of the tubular substrate, but it is particularly effective to select the outer diameter in the range of 30 mm to 140 mm and the length to be 200 mm or more.

First, the dip coating performed in the present invention will be described. The inside of the cylindrical substrate 1 is hermetically sealed and gripped by an airtight gripping member 2 so that the axis of the cylindrical substrate 1 is perpendicular or substantially perpendicular to the coating liquid surface 4 by the support member 3. It is attached. The sealing by the sealing gripping member 2 is performed to prevent the gas 5 trapped in the tubular base 1 from leaking when the tubular base 1 is immersed in the coating solution. There is no limitation on the structure of the sealing member as long as it can be achieved. Although FIG. 1 shows an example in which the sealing member and the gripping member are used, the sealing member and the gripping member may be separated.

As a preferred embodiment of the closed gripping member 2, a rubber tube or the like, which is inserted into the upper part of the cylindrical base in a reduced state, and then expanded to contact the inner wall and hermetically seal, can be exemplified. Specifically, compressed air is sent to the rubber tube-shaped closed gripping member 2 through the pipe 9 to expand the closed gripping member 2 and make the inside of the tubular base 1 airtight. In FIG.
The support member 3 also serves as a pipe for the solvent-saturated gas. Although the support member and the pipe for the solvent-saturated gas may be provided separately, it is more preferable to use both of them because the structure is simplified. The support member (solvent-saturated gas pipe) 3 is sealed with 3a at the time of use. Before immersing the cylindrical substrate 1, a solvent-saturated gas is supplied through the pipe 3 and the gas 5 inside the cylindrical substrate 1 is supplied.
Is replaced with a solvent saturated gas.

After the gas 5 has been sufficiently replaced with a solvent-saturated gas, the cylindrical substrate 1 is immersed in the coating liquid 6 while keeping it perpendicular or almost perpendicular to the coating liquid surface 4 from the lower end which is the open end. At this time, the pressure of the gas 5 is adjusted by the communication between the pressure adjusting means for the solvent-saturated gas described later and the space below the closed gripping member via the pipe 3. The coating liquid 6 overflows from the coating tank 7 due to the volume of the cylindrical substrate 1 immersed therein, and is stored in the overflow tank 8. The coating liquid stored in the overflow tank 8 is
It is collected in a storage tank (not shown) and circulated again to the coating tank 7.

Next, a method for preparing a solvent-saturated gas will be described. The solvent 10 used for preparing the coating liquid is placed in a cylindrical container 12 having an appropriate length, and the tip of the gas blowing pipe 14 is introduced into the solvent. Porous 13 is attached to the tip of the gas blowing pipe 14 in order to convert the gas into small bubbles. When a mixed solvent is used for preparing the coating solution, a mixed solvent having the same composition is used as the solvent 10. Injection of gas such as air or nitrogen from the pipe 14;
By passing the solvent 10 as small bubbles in the porous material 13 and collecting it on the liquid surface of the solvent, a solvent-saturated gas is obtained.

Next, the pressure adjusting means will be described. Vessel 17 capable of taking a depth larger than the immersion depth of cylindrical base 1
, A coating liquid 15 is put therein, and a pipe 18 is introduced into the coating liquid. The pipe 18 communicates with a solvent-saturated gas supply pipe 24 via a flexible tube 20. The pressure is adjusted by the immersion depth h of the pipe 18. Changing the immersion depth h involves moving the pipe 18 (FIGS. 1 and 2).
And a method of changing the height of the coating liquid 15 (FIG. 3).

In the method of FIG. 1, the pipe 18 is fixed on the linear way 21 and moved by the motor 22 to change the immersion depth h. In the method of FIG.
A magnet 26 is attached to the tip of the
The magnet 27 having the opposite polarity is attached to a ball screw block, and the block is moved by a motor 28 to change the immersion depth. In the method of FIG. 3, the pipe 18 is fixed, the container 17 and the coating liquid storage tank 28 are connected via the pump 29, and the immersion depth h is changed by adjusting the amount of liquid to be charged into the container 17. The immersion depth h of the pipe is substantially the same as or slightly smaller than the immersion depth h ₀ of the cylindrical base 1. Specifically, h is equal to or slightly smaller than h ₀ , for example, h is h ₀ to h ₀ -20 mm, preferably h ₀ to h ₀ -10 mm, and particularly h = h ₀ -5 mm
Near is preferred.

Since the gas 5 is replaced with a solvent-saturated gas below the grip portion inside the cylindrical base 1, there is no increase in pressure due to evaporation of the coating liquid. The pressure of the gas 5 is adjusted by the pressure adjusting means 16 to a pressure equal to the height h of the coating liquid, and h is adjusted to be substantially the same as or slightly smaller than the immersion depth h ₀ of the cylindrical substrate 1. Therefore, the pressure of the coating liquid 6 and the pressure of the gas 5 are balanced, so that the gas 5 does not leak out to cause the generation of a downward bulge. No dripping occurs when 1 is pulled out of the coating liquid surface 4.

[0020]

According to the method of the present invention, the pressure in the closed space inside the cylindrical base 1 can be adjusted without providing a complicated mechanism such as pressure measurement, so that malfunctions and erroneous operations are reduced. , Uniform coating can be performed.

[Brief description of the drawings]

FIG. 1 is an overall explanatory view of one embodiment of the present invention;

FIG. 2 is an explanatory view of another embodiment of the pressure adjusting means used in the present invention.

FIG. 3 is an explanatory view of still another embodiment of the pressure adjusting means used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical base 2 Sealing holding member 3 Supporting member (solvent-saturated gas pipe) 6 Coating liquid 10 Solvent 13 Porous body 14 Gas blowing pipe 15 Coating liquid 16 Pressure control means 18 Pipe 21 Linear way 22 Motor 23 Exhaust gas surplus Outlet 24 Solvent-saturated gas supply pipe 26 Magnet 27 Magnet 28 Storage tank

Claims (1)

[Claims] 1. A coating method in which an inner surface of a cylindrical substrate is air-tightly gripped and immersed in a coating solution tank to form a coating film on an outer surface of the cylindrical substrate, wherein the coating film is saturated with a vapor of a solvent used for preparing a coating solution. Gas (hereinafter, referred to as
A liquid-saturated gas), a pressure adjusting means for the solvent-saturated gas having a structure in which a pipe is immersed in a liquid column of the coating liquid itself, and a closed space below a grip portion inside the cylindrical base. adjusting the pressure in the enclosed space of the gripping subordinate side made to communicate with the, and the depth of the pipe in the liquid column of the pressure regulating means h, and immersion depth of the coating fluid bath of the tubular substrate and h ₀ H is h ₀
A coating method characterized by being adjusted to be the same as or slightly smaller than the above.