JPH08215626A - Method and apparatus for coating - Google Patents

Abstract

PURPOSE: To prevent the generation of defects on a coated surface and to keep quality constant in the application of coating liquid containing a filler which precipitates easily by applying the liquid while generating a flow in the width direction of a coated surface in the liquid in a manifold in a coating head. CONSTITUTION: A coating liquid supply port 5 and a coating liquid discharge opening 7 are formed in a coating head 1, and part of coating liquid is extracted from a manifold 2 to be circulated to generate a flow in the width direction of a coated surface in the liquid in the manifold 2. For example, with the newly supplied liquid sent to the port 5 in the middle of the manifold 2, a coating liquid supply port 8 and the opening 7 are installed on both sides of a die head connected with both ends of the manifold 2, and the liquid is circulated through a tank 10 by a circulating pump 9 so that the flow of the coating liquid is generated in the width direction of the coated surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is particularly suitable for applying a coating liquid containing a filler which easily sediments to a coating liquid (coating) using a coating head such as a die coating head or a fountain head. The present invention relates to a coating method and a coating apparatus capable of making the quality of a coating film, particularly the content of a filler, uniform and suppressing the occurrence of defects such as spots and streaks.

[0002]

2. Description of the Related Art When applying a coating liquid containing a filler which easily sediments, it is necessary to prevent the defects on the coated surface and to make the quality uniform by applying the coating liquid containing no filler. It was technically more difficult than it was. For example, when coating with the gravure coating method, the coating liquid is supplied and stored in the ink pan, but gradually the filler is settled in the ink pan and the transfer of the liquid to the gravure roll becomes unstable, Defects such as streaks and bubbles were generated on the coated surface, and the quality of the coating film in the width direction (content of filler, etc.) was uneven.

Further, also in the case of the slit reverse coating method using an ink pan, the transfer of the liquid to the coater roll becomes unstable due to the sedimentation of the filler in the ink pan, which causes defects and quality problems. did. In particular, when the content of the filler in the ink jet base material or the like affects print density, ink absorbency, and other qualities, it becomes a serious problem.

As described above, the coating method using an ink pan has a problem of filler sedimentation, and in order to solve the problem, a method of coating using a coating head such as a die coat head or a fountain head has been proposed. . For example, there are a die coating method on a backup roll, a die coating method on a roll span, and a reverse roll method of supplying a liquid by a fountain head instead of an ink pan.

[0005]

The method using these heads has a manifold in the coating head in order to make the coating thickness in the width direction uniform, that is, to make the flow rate of the coating liquid in the width direction uniform. Is generally set. Compared to the coating method using an ink pan, the above-mentioned problems such as uneven coating surface and bubble omission are less likely to occur, but in the case of a liquid containing a filler that easily sediments or when coating for a long time, the inside of the manifold In addition, sedimentation of the filler occurs, which causes a problem that the coating thickness in the width direction of the coating surface becomes uneven.

[0006]

An object of the present invention is to provide a coating method which, when coating a coating liquid containing a filler which easily sediments, has uniform quality without causing defects on the coated surface. It is the one we are trying to provide. According to the study of the present inventors, by causing the coating liquid to have a special behavior in the manifold of the coating head, the coating liquid can be uniformly supplied in the width direction of the coating surface. It was found that the above was achieved and the present invention was completed.

That is, the gist of the present invention is to supply a coating liquid from a coating head having a manifold through a slit to an object to be coated, to the coating liquid in the manifold in a direction along the width direction of the coating surface. The coating method is characterized in that the coating is performed while generating the flow of The coating head 1 such as a die coat head or a fountain head has a manifold 2, and the coating liquid supplied to the manifold 2 is applied to an object to be coated 4 through a slit 3.

The method and apparatus of the present invention are devised so that the coating liquid supplied in the width direction of the coating surface is made uniform in the manifold 2. For example, in the case of the head shown in FIGS. 1 and 2, the coating liquid is supplied into the manifold 2 from the coating liquid supply port 5 in the central portion of the manifold 2, and then the liquid is supplied along the manifold 2. It can be spread across the width of the head. Next, the coating liquid passes through the slit 3 and exits from the tip of the lip portion 6 to be applied (applied) to the object to be coated 4.

When the coating liquid contains a filler or the like that is prone to settle, the filler settles at the bottom of the manifold 2 and the filler concentration in the coating liquid becomes unstable, resulting in a non-uniform coating composition. Will be. Hereinafter, an example of the method and apparatus of the present invention will be further described with reference to the drawings. FIG.
2 is an explanatory view of an example of an apparatus used in the method of the present invention, FIG. 2 is a vertical sectional view of an example of a coating head portion, and FIGS. 3 and 4 are explanatory views showing other connection examples of a circulation system.

A feature of the method and apparatus of the present invention is that a coating film in the width direction of the coated surface can be uniformly formed even when a coating liquid in which a solid substance such as a filler is dispersed is used.
For that purpose, it is important to prevent the precipitation of the solid matter in the coating liquid during the coating operation. Sedimentation of solid substances such as fillers is most likely to occur when the liquid is allowed to stand, but this can be suppressed by causing the liquid to flow.

In the present invention, a method of suppressing sedimentation of solid matters such as fillers by causing the coating liquid in the manifold 2 of the coating head 1 to flow in the width direction of the coating surface is used. Specifically, for example, the coating head 1 as shown in FIGS. 1 and 2 is normally provided with only one coating liquid supply port 5, but in the present invention, The liquid discharge port 7 is provided at least at one or more places, and a part of the coating liquid is extracted from the manifold 2 to the external circulation device and is circulated to the manifold 2 again to circulate in the manifold 2. Generates a flow along the width of the coated surface. In this way, by keeping the coating liquid constantly flowing, sedimentation of the filler and the like is prevented.

The shape of the manifold 2 may be appropriately changed depending on the viscosity of the coating liquid used. If the shape is inappropriate, the coating liquid supply amount in the width direction becomes non-uniform, and the thickness of the coating film may become non-uniform. For example, when the viscosity is high (usually 5,000-5
20,000 cps at 25 ° C) is suitable for a coat hanger type manifold, and when the viscosity is low (usually 2 to 5,000 cps at 25 ° C)
Is preferably a straight manifold type.

As an example of the installation positions of the coating liquid supply port 5 and the discharge port 7, the configurations shown in FIGS. 1, 3 and 4 can be considered. FIG. 1 shows a circulation pump in which a coating liquid supply port 8 and a discharge port 7 are installed on both side surfaces of a die head in a position connected to both ends of a manifold while feeding a coating liquid newly supplied to a supply port 5 in a central portion of a manifold. At 9, the liquid is circulated through the tank 10 to generate a flow in the width direction of the coated surface.

If necessary, a filter 11 may be provided in the circulation line.
Alternatively, the defoamer 12 may be installed on the way. In the apparatus of FIG. 1, the supply of the coating liquid is provided from the tank 13 through the pump 14, the filter 15, and the defoamer 16 to a line separate from the circulation line, but the tank 10 and the tank 13 are the same tank, Of course, the sharable devices may be integrated into one line. What is indicated by PG in the middle of the line is a pressure gauge.

The coating liquid thus supplied to the coating head 1 is supplied to the surface of the object 4 to be coated which is wound around the coating roll 17, and coating (coating) is performed to form a coating film 19. To be done. Since a substantially constant flow of the coating liquid occurs in the coating head 1, sedimentation of the filler in the coating liquid does not occur and uniform coating (application) can be performed. FIG. 3 shows an example in which the circulation line B is connected in the middle of the supply line A (the reverse connection is also possible).

FIG. 4 shows a case where the coating head 1 is supplied from both ends (two locations) of the head and the central hole is used as the discharge line C. Conversely, it is also possible to supply from the central part and discharge from both ends. In addition, the connection of the supply line A, the circulation line B, and the discharge line C can be such that the coating liquid does not stay in the coating head 1 and always flows in the width direction of the head 1. Of course, any connection may be made.

Therefore, the supply port and the discharge port of the head may be used in reverse. As a method of adjusting the coating width (coating width) of the coating head 1, a width adjusting plate 18 made of a metal plate or a synthetic resin plate having substantially the same thickness as the slit thickness is formed at the end of the slit 3 of the coating head 1 or the like. By sandwiching and adjusting the coating width, coating of various widths can be performed, and the width of the coating film 17 can be adjusted.

As described above, a flow in the width direction of the coating surface is generated in the manifold 2 to suppress the sedimentation of the filler in the liquid, whereby a coating film of good quality can be obtained. The flow velocity of the coating liquid in the width direction in the manifold 2 depends on the coating speed of the object to be coated, but the coating speed is 5 to 20 m /
Minutes, 0.3 m / min or more, preferably 0.4 to
The effect becomes remarkable when the speed is 5 m / min.

When the speed is lower than that, the effect of suppressing the sedimentation of the filler becomes small. Further, this effect is great in the case of a coating liquid in which the sedimentation time of the filler is 2 minutes or less, preferably 30 seconds to 1 minute, that is, a liquid which easily sediments. The sedimentation time is measured by the method described below. That is, the coating liquid is added to a cylindrical container having an inner diameter of 100 mm and a depth of 150 mm in an amount of 100
The container is sealed to the depth of mm (the liquid should not leak when the container is turned upside down).

The container is turned upside down and the liquid is stirred.
This operation is performed 10 times and left still. After the lapse of 2 minutes, 20 mm of the lower side of the liquid is left and sampling is performed to measure the amount of solid matter such as filler contained in the upper side of 80 mm as the solid content concentration. The time when the amount becomes 10% of the amount of solids contained in the entire liquid used first is defined as the sedimentation time.

The liquid which is particularly effective in the present invention is a liquid having a sedimentation time of 2 minutes or less, and 2 minutes or less, preferably 30 seconds to
90% or more of the amount of solid matter in the liquid in 1 minute, preferably 93%
The coating liquid is such that ˜97% of it settles on the lower 20 mm of the liquid. The coating liquid used in the present invention has an average particle size of 0.
A slurry containing 1 to 50 μm, preferably 1 to 15 μm, of filler in an amount of 1 to 50% by weight, preferably 3 to 20% by weight is suitable. Viscosity at 25 ° C is 3-10 cp
s, preferably 5 to 8 cps is more suitable.

As the filler, for example, natural zeolite, synthetic zeolite, calcium carbonate, diatomaceous earth, fine silica (average particle size 1 μm or less), silica (average particle size 2)
5 μm or less) and the like. These fillers are used alone or in combination of several kinds. Examples of the solvent of the coating liquid include water, isopropyl alcohol, toluene, methyl ethyl ketone, ethyl acetate, butyl acetate and the like. These are used alone or in combination of several kinds.

[0023]

EXAMPLES Next, the present invention will be described more specifically by way of examples. The parts or percentages in the text are based on weight unless otherwise specified.

Example 1 Coating was carried out by a die coating method using a coating head having a width of 1000 mm in which coating liquid supply lines A and B and a discharge line C were installed at the positions shown in FIG. The liquid used has the following composition. 85 parts of water, polyvinyl alcohol (trade name:
Gohsenol NL-05, a product of Nippon Gosei Co., Ltd. 6
And 9 parts of powdered silica (trade name: Nipseal E200A, manufactured by Nippon Silica Company) were mixed and dispersed by a homomixer. The sedimentation time of the obtained liquid was 1 minute.

A soft polyvinyl chloride sheet having a thickness of 100 μm is used as a substrate, and a vinyl chloride resin (trade name: VYNC, manufactured by Union Carbide Co.) as an anchor layer is applied to this as a dry thickness of 3 μm. The liquid was applied to a dry thickness of 20 μm to obtain a recording material for inkjet. At this time, the flow velocity in the width direction inside the manifold was 0.5 m / min. After 500 m ^{2 of} coating, the coating head was disassembled to check the condition inside the manifold, but there was almost no sedimentation of the filler.

The surface of this recording material was good without coating defects such as gear marks and streaks in the length direction. or,
A color image was formed on the obtained recording material using an inkjet printer (trade name: IO-735, manufactured by Sharp Corporation). Check the density unevenness with a solid blue print to confirm the presence or absence of image defects (Reflective color densitometer (manufactured by Sakata Inx, Macbeth densitometer RD-91
8) was used to measure the density unevenness in the width direction of the solid printed product, but it was uniform and there was no abnormality.

Example 2 Example 2 except that the coating was performed by the die coating method using a coating head having a width of 1000 mm in which both the coating liquid supply line A and the discharge line B were installed at the positions shown in FIG. The same procedure as 1 was performed. Similar to Example 1, the obtained recording material was good without defects on the coated surface and image unevenness.

Comparative Example 1 A recording material was obtained in the same manner as in Example 1 except that the method was carried out by the gravure coating method with a width of 1000 mm, but spot-like defects on the coated surface occurred. It was found that a large amount of filler had settled in the ink pan.

Example 3 The same procedure as in Example 1 was carried out except that the flow velocity in the width direction inside the manifold was 0.3 m / min. No defects were found on the painted surface. In addition, when the density unevenness was checked by solid printing, streak-shaped coating defects occurred in the lengthwise direction at the center in the width direction at the last part of the coated surface (streaks with high density occurred). It was on the coated surface 95
% Was a good coating state.

Comparative Example 2 The same coating head as in Example 1 was used except that the supply port B
(Circulation) and using a coating head having no outlet C,
The same procedure as in Example 1 was performed except that the coating liquid was supplied from the supply port A. Although there were no defects on the coated surface, when density unevenness was checked with a solid print, in this example,
A coating defect having a high concentration was formed in stripes in the central portion in the width direction over the entire length from the initial stage to the end of supplying the coating liquid from the coating head to the object to be coated.

[0031]

EFFECTS OF THE INVENTION According to the present invention, when a coating liquid containing a filler that easily sediments is coated using a coating head such as a die coating head or fountain head, The quality, especially the content of the filler can be made uniform, and a coating method without defects such as stripes can be provided. For example, it is very effective when coating and manufacturing a recording material for an inkjet method using a coating liquid in which a filler easily precipitates.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example of an apparatus used in the method of the present invention.

FIG. 2 is a vertical sectional view of an example of a coating head section.

FIG. 3 is an explanatory diagram showing another connection example of the circulation system.

FIG. 4 is an explanatory diagram showing another connection example of the circulation system.

[Explanation of symbols]

 1 Coating Head 2 Manifold 3 Slit 4 Object to be coated 5 Coating Liquid Supply Port 6 Lip 7 Coating Liquid Discharge Port 8 Circulating Liquid Supply Port

Claims (5)

[Claims] 1. When supplying a coating liquid from a coating head having a manifold to a coating object through a slit, the coating liquid in the manifold is caused to flow in a direction along a width direction of a coating surface. A coating method characterized by applying while. 2. The flow velocity of the coating liquid in the manifold of the coating head in the width direction of the coating surface is 0.3 m /
The coating method according to claim 1, which is not less than a minute. 3. The coating method according to claim 1, wherein the coating liquid is a filler-containing slurry having a sedimentation time of 2 minutes or less. 4. The coating method according to claim 1, wherein the coating liquid is a slurry containing 3 to 20% by weight of a filler having an average particle diameter of 0.1 to 15 μm. 5. A coating consisting of a manifold, a coating head in which a slit portion extending from the manifold to the lip portion is formed, and a circulation device for extracting a part of the coating liquid from the manifold of the coating head and circulating it to the manifold again. apparatus.