JPH03151A - Thin film coating device - Google Patents

Abstract

PURPOSE:To prevent nonuniform coating by providing a port for exhausting a solvent vapor in a vapor storage tank and an exhaust control mechanism to the tank. CONSTITUTION:A shutter 6 is closed, and coating is started when the concn. of the solvent vapor in the vapor tank 2 practically reaches the concn. of the vapor from a coating soln. 8 overflowing the coating tank 1. The concn. of the solvent vapor in the tank 2 increases and coating proceeds. Accordingly, the shutter 6 is opened or closed at this time to exhaust the solvent vapor in the tank 2 from an exhaust port 5 by an exhaust fan 7, hence the concn. of the solvent vapor in the tank 2 is controlled in a specified concn. range, and coating is continued. A homogeneous coating thin film having excellent appearance and uniform thickness is formed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film coating device for forming a thin film on the surface of an object.

[Conventional technology]

In recent years, thin films on the order of microns or less, such as surface protective films of magnetic recording media, photosensitive layers of electrophotographic photoreceptors, flux coating films on printed circuit boards, and resist If cloth films on IC boards, have been developed. BACKGROUND OF THE INVENTION An increasing number of technical fields require membranes with specific functions.

Such a film is required to have uniform functionality, but since it is a thin film, a slight difference in film thickness will cause large variations in functionality. A thick film is desired. For this reason, conventional coating film formation methods such as brush coating and spray gun coating cannot be applied, and spin cord methods and dipping methods are used, which can obtain a coating film with a more uniform thickness. However, the spin code method requires a high-speed rotating drive system, which makes coating difficult or impossible when the surface area of the object to be coated is large or the surface shape is complex. Dipping methods have been widely used.

In the dipping method, a functional material is dissolved or dispersed in an organic solvent, and in some cases adhesives, plasticizers, etc. are added to form a coating solution, which is then filled into a coating funnel, and the object to be coated is immersed in this coating solution. In this method, the object to be coated is pulled up and dried to form a coating film. This method is simple and allows a thin film to be obtained relatively easily by adjusting the viscosity of the coating liquid and the rate at which the object to be coated is lifted from the coating liquid.

Such a dipping method or a similar coating method is used, in which the coating surface of the object to be coated and the coating liquid in the coating liquid reservoir are moved relative to each other in the vertical direction while they are in contact with each other. In the method of forming a coating film on the coating film formation surface by pulling upward from the coating solution, if the evaporation rate of the coating solution solvent is fast, the relative movement of the coating solution solvent and the coating film formation surface that comes out from the coating solution. Rapid evaporation of the solvent occurs from the paint film, resulting in a significantly poor appearance of the paint film! ! ! (Pear ground) Therefore, there has been a drawback that coating conditions such as the type of solvent in the coating liquid and the relative movement speed between the object to be coated and the coating liquid storage tank are limited. Conventionally, in order to eliminate these drawbacks, solvent vapor is placed around the upper opening of the coating liquid reservoir so that the solvent vapor, which has a higher specific gravity than the air that evaporates from the coating liquid and the coating film, is retained around the object to be coated. Additional steam storage tanks were being added.

[Problem to be solved by the invention]

However, in conventional thin film coating equipment, the concentration of solvent vapor in the vapor storage tank is not constant, and the vapor concentration is particularly low immediately after the start of coating, so that the solvent evaporates from the coating film quickly, leaving the coating film with no spots. The concentration increases as the coating time progresses, and solvent vapor from the coating film is suppressed, resulting in problems such as changes in coating thickness. Furthermore, at the end of coating, the object to be coated comes out of the coating liquid into the air, which disturbs the solvent vapor flow, resulting in uneven coating at the lower end of the coating surface.

The present invention eliminates these drawbacks and does not impose any restrictions on the type of solvent used in the coating solution or the coating conditions.
Prevents the formation of blank spots on the coating object,
Another object of the present invention is to provide a thin film coating device that can prevent coating unevenness that occurs at the lower end of the coating film formation surface at the time of completion of coating.

[Means to solve the problem]

According to the present invention, the above problem can be solved by moving the coating film forming surface of the object to be coated upwardly from the coating solution by moving the coating film forming surface of the object to be coated and the coating solution in the coating solution reservoir in contact with each other in the vertical direction. A thin film coating device that forms a thin film of the coating liquid on the coating film forming surface by separating the coating liquid from the coating liquid is wiped onto a device having a vapor storage tank for solvent vapor of the coating liquid in an upper opening of the coating liquid storage tank. This problem can be solved by using a thin film coating apparatus in which the steam storage tank is provided with an exhaust port for exhausting the steam in the tank from near the bottom of the tank, and a forced exhaust control mechanism connected to the exhaust port.

[Effect]

By providing a forced exhaust mechanism and turning it on and off, it becomes possible to control the concentration of solvent vapor in the vapor storage tank. By performing coating while maintaining the concentration of solvent vapor within a required range, a coated thin film with uniform thickness, homogeneity, and good appearance can be obtained. Furthermore, when the solvent vapor flow is likely to be disturbed at the end of coating, the solvent vapor can be forcibly exhausted to prevent uneven coating at the lower end of the coating surface.

〔Example〕

FIG. 1 shows a schematic cross section of an embodiment of a thin film coating apparatus according to the present invention. In FIG. 1, 1 is a coating liquid storage tank and a coating tank, and the coating liquid 8 is supplied to a circulation pump 4.
As shown by the arrow, the water flows into the coating tank 1 from the lower part, overflows from the upper opening, flows into the auxiliary tank 3 from the upper part, and circulates back into the coating tank 1 from the lower part. A steam tank 2, which is a tank for storing steam, is provided so as to surround the upper opening of the coating tank l from the side.
The steam tank 2 is provided with an exhaust port 5 equipped with an exhaust fan 7 near the bottom of the tank, and the solvent vapor in the steam tank 2 can be forcibly exhausted to the outside through the exhaust port 5 by the exhaust fan 7. It has become. Furthermore, a shutter 6 is attached to the exhaust port 5, and the concentration of solvent vapor in the steam tank 2 is controlled by opening and closing the shutter 6 mechanically or electrically from the outside.

When forming a coating film using the thin film coating apparatus of this embodiment, first, with the shutter 6 closed, the concentration of solvent vapor in the steam tank 2 is reduced from the coating liquid 8 overflowing from the coating tank 1. Coating is started when the concentration reaches a level where the evaporated solvent vapor does not cause pear spots on the coating film.

As coating progresses, the concentration of solvent vapor in the vapor tank 2 increases due to solvent vapor that evaporates from the coating film on the coating surface that is pulled up from the coating solution in the coating tank 1. When the shutter 6 is opened and closed, the solvent vapor in the steam tank 2 is exhausted from the exhaust port 5 by the exhaust fan 7, or the exhaust is stopped, and the concentration of the solvent vapor in the steam tank 2 is kept within a required constant concentration range. Apply while controlling. In this way, a coated thin film with uniform thickness, homogeneity, and good appearance can be formed.

In addition, when the solvent vapor flow is likely to be disturbed at the end of coating, the shutter 6 can be opened to exhaust the solvent vapor.
It is possible to prevent uneven coating from occurring at the lower end of the coating film forming surface.

〔Effect of the invention〕

According to the present invention, a thin film coating apparatus using a dipping method or a similar method is equipped with a mechanism that can forcibly exhaust the solvent vapor inside the vapor storage tank provided at the upper opening of the coating liquid storage tank. establish.

By using the thin film coating device according to the present invention, it is possible to control the concentration of solvent vapor in the vapor storage tank within the required range, without particularly limiting the type of solvent used in the coating liquid and the coating conditions. It is possible to form a homogeneous coated thin film with a good appearance without the appearance of pear spots, and a uniform thickness.

Further, by forcibly exhausting the steam that is disturbed when the lower end of the coating film forming surface of the object to be coated leaves the coating liquid, it becomes possible to eliminate uneven coating at the lower end of the coating film forming surface of the object.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an embodiment of a thin film coating apparatus according to the present invention. 1- coating tank, 2 steam tank, 5 exhaust port, 6 shutter, 7 exhaust fan, 8 coating liquid. Figure 1

Claims (1)

[Claims] 1) The coating film is formed by moving the coating film forming surface of the object to be coated and the coating liquid in the coating liquid storage tank in contact with each other in the vertical direction and separating the coating film forming surface upward from the coating liquid. A thin film coating device for forming a thin film of the coating liquid on a forming surface is provided with a vapor storage tank for solvent vapor of the coating liquid at an upper opening of the coating liquid storage tank, and a vapor storage tank for solvent vapor of the coating liquid is placed in the vapor storage tank. A thin film coating device characterized by being equipped with an exhaust port for exhausting solvent vapor from near the bottom of the tank, and a forced exhaust control mechanism connected to the exhaust port.