JPH1110060A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily coat thin film without narrowing clearance unnecessarily by lowering the viscosity of coating liquid to be applied on the lowest layer of a multilayer membrane rather than the viscosity of coating liquid to be applied on an adjacent upper layer. SOLUTION: A die coater 3 is arranged proximately to a support 1 to be wound around a backup roll 2 almost in half, the die coater 3 has plural slits 3a, the coating liquid is successively applied from these slits 3a to the support 1, and a multilayer coating membrane 4 is formed over the support 1. Then, the viscosity of coating liquid to be applied on the lowest layer of that multilayer coating membrane 4 is lowered rather than the viscosity of coating liquid to be applied on the adjacent upper layer. Thus, thin film coating on the upper layer is easily enabled without narrowing clearance unnecessarily and further, thin filming is enabled even as the total membrane thickness of upper and lower layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coating method capable of coating a thin film using a die coater coating apparatus having a plurality of slits.

[0002]

2. Description of the Related Art Conventionally, various coating methods have been proposed as a method of applying a coating solution to a running support.
Among them, the die coater has been widely used as a highly accurate coating method in which the film thickness is determined only by the flow rate of the liquid. Further, as a method for forming a multilayer coating film, there is a simultaneous multilayer coating method in which coating is simultaneously performed using a die coater having a plurality of slits. This method has an advantage that the production efficiency is superior to that of successive coating and drying.

[0003]

In a normal coating, a thick wet coating causes an increase in drying load.
Thin film application is desired. In order to perform thin film coating in die coater coating, it is necessary to narrow the clearance between the support and the tip surface of the coater lip, but as the thin film coating becomes more demanding, the precision of the equipment becomes more stringent . However, there is a limit to narrowing this clearance.

In view of such a problem, it is an object of the present invention to propose a coating method capable of easily applying a thin film without narrowing the above clearance in a thin film coating using a die coater having a plurality of slits. This is one issue. It is a second object of the present invention to propose a coating method having a good coating surface.

[0005]

SUMMARY OF THE INVENTION The first object of the present invention is to provide a multi-layer coating by moving a support close to a die coater having a plurality of slits and applying a plurality of coating liquids to the support. In a coating method for forming a film, the problem is solved by a coating method in which the viscosity of a coating liquid applied to the lowermost layer of the multilayer coating film is lower than the viscosity of a coating liquid applied to an adjacent upper layer.

[0006] The second object is to provide a coating method for forming a multilayer coating film by moving a support close to a die coater having a plurality of slits and applying a plurality of coating liquids to the support. In the method, the surface tension of the coating liquid applied to the lower layer is made higher than the surface tension of the coating liquid applied to the upper layer, of the two adjacent coating films in the multilayer coating film.

The first problem and the second problem are that the support is run close to a die coater having a plurality of slits, and a plurality of coating liquids are applied to the support to form a multilayer coating. In the coating method for forming a film, the viscosity of the coating liquid applied to the lowermost layer in the multilayer coating film is lower than the viscosity of the coating liquid applied to the adjacent upper layer, and the coating film of the two adjacent layers The problem is solved by a coating method in which the surface tension of the coating liquid applied to the lower layer is higher than the surface tension of the coating liquid applied to the upper layer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the coating method of the present invention will be described.

First, a structure for forming a thin film using a die coater will be described with reference to a sectional view of the die coater shown in FIG.

In FIG. 1, a support 1 is wound around a backup roll 2 for about a half turn and travels in a direction indicated by an arrow.
A die coater 3 is arranged close to the support 1. The die coater 3 has a plurality of slits 3a, and a coating solution is sequentially applied to the support 1 from the slits 3a, and a multilayer coating film 4 is formed on the support.

In such a coating method using a die coater having a plurality of slits, the present inventors have made intensive studies on thin film coating, and as a result, have come to invent the following coating method.

That is, by making the viscosity of the coating liquid applied to the lowermost layer of the multilayer coating film lower than the viscosity of the coating liquid applied to the adjacent upper layer, the upper layer can be applied as a thin film, and the upper and lower layers can be further coated. It has been found that the total film thickness can be reduced.

In addition, by applying the present invention, a low-viscosity solvent having no solid content is applied to the lower layer when the coating liquid has a relatively high viscosity although the function of the coating film is a single layer. The multi-layer coating makes it possible to apply a thin film, and after drying, a substantially single-layer coating film is obtained.

Incidentally, the solvent of the lower layer provided in the coating film may remain as a residual solvent in the dried coating film, and this may rarely affect the function of the coating film.
In such a case, it is desirable to use the solvent contained in the upper layer as the lower layer solvent to be applied.

Further, when performing multi-layer coating, of the two adjacent coating films, the surface tension of the coating solution applied to the lower layer is made higher than the surface tension of the coating solution applied to the upper layer, whereby the coating is stabilized. It was found that coating was possible. When the relationship of the surface tension is reversed, a repelling or mottled coating pattern is likely to be generated, and a good coating surface is not always obtained.

In a coating method using a die coater, it is known to reduce the pressure on the upstream side of the support of the die coater in order to realize high-speed coating. Is effective.

The support applied in the coating method of the present invention is not particularly limited, and can be applied to supports such as paper, plastic, and metal. Examples of polyethylene terephthalate and metals include aluminum.

[0018]

【Example】

<Example 1> Using a 300 mm wide die coater coating apparatus having two slits, a width of 250 mm and a thickness of 10
Coating was performed on a 0 μm polyethylene terephthalate support at a coating speed of 10 m / min. At that time, die
The gap between the lip tip and the support was set to 0.1 mm.
Using a coating liquid having a liquid viscosity of 5 cp and a surface tension of 25 dyne / cm for the upper layer, changing the lower layer coating liquid as follows, fixing the wet film thickness of each lower layer coating liquid, The lower limit of the wet film thickness was investigated. This is shown in Table 1 below.

[0019]

[Table 1]

As a result, it can be seen that the upper layer can be made thinner than the comparative example, and that the total thickness can be made thinner. Furthermore, the total film thickness can be reduced as compared with a single-layer coating of only the upper layer of the comparative example.

<Embodiment 2> Width 3 having two slits
Using a 00 mm die coater coating device, width 250 m
m and a 100 μm-thick polyethylene terephthalate support at a coating speed of 10 m / min. At that time, the gap between the die lip tip and the support was 0.1 mm
Set to. Liquid viscosity 5cp, surface tension 25dyn in upper layer
The lower layer coating solution was changed as follows using an e / cm coating solution. Then, the wet film thickness is set to 20 μm for the lower layer,
The thickness was set to 0 μm, and the state of the coating film surface was observed. This is shown in Table 2.
Shown in

[0022]

[Table 2]

As a result, it can be seen that the higher the surface tension of the lower layer coating solution is, the better the surface tension of the lower layer coating solution is compared with the surface tension of the upper layer coating solution.

[0024]

According to the coating method of the present invention, the thickness of the upper layer can be easily reduced, and the total thickness can be reduced.

According to the coating method of the second aspect, a repelling or mottled coating pattern does not occur, and a good coating surface can be obtained.

According to the coating method of the present invention, the thickness of the upper layer can be easily reduced, and the total thickness can be reduced. Further, a repelling or mottled coating pattern is not generated. A good coated surface is obtained.

According to the coating method of the fourth aspect, even if the coating solution has a high viscosity in a single-layer coating film, a thin film can be applied.

According to the coating method of the present invention, it is possible to apply a thin film even if the coating solution has a high viscosity in a single-layer coating film, and does not affect the coating film function.

[Brief description of the drawings]

FIG. 1 is a sectional view of a die coater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support 2 Backup roll 3 Die coater 4 Coating

Claims (5)

[Claims] 1. A coating method for forming a multi-layer coating film by moving a support close to a die coater having a plurality of slits and applying a plurality of coating liquids to the support, wherein: A coating method, wherein the viscosity of a coating liquid applied to the lowermost layer of a coating film is lower than the viscosity of a coating liquid applied to an adjacent upper layer. 2. A coating method in which a support is run close to a die coater having a plurality of slits, and a plurality of coating liquids are applied to the support to form a multilayer coating film. A coating method characterized in that, of two adjacent coating films in a coating film, the surface tension of a coating solution applied to a lower layer is higher than the surface tension of a coating solution applied to an upper layer. 3. A coating method in which a support is run close to a die coater having a plurality of slits, and a plurality of coating liquids are applied to the support to form a multilayer coating film. The viscosity of the coating liquid applied to the lowermost layer of the coating film is lower than the viscosity of the coating liquid applied to the adjacent upper layer, and the surface tension of the coating liquid applied to the lower layer of the two adjacent coating films Is higher than the surface tension of the coating liquid applied to the upper layer. 4. The coating method according to claim 1, wherein the coating liquid applied to the lowermost layer is a solvent having no solid content. 5. The coating method according to claim 4, wherein the coating liquid applied to the lowermost layer is a solvent contained in a coating liquid applied to an adjacent upper layer.