JP2557436B2 - Coating device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a coating device for coating a thin film web typified by a film, paper, etc., with a uniform amount of a coating liquid at high speed and efficiently. Is.

BACKGROUND OF THE INVENTION Conventional coating methods such as gravure coating method, kiss coating method and die coating method have been used for coating thin film webs such as various photographic films, magnetic tapes and printing papers. The coating method is used, and it has been used properly according to each purpose of use. For example, a die coating type coating apparatus which is effective for coating a magnetic tape is configured as shown in FIG. In this device, as shown in FIG. 4, the coating liquid 31 is continuously extruded from the tip portion of the nozzle 32 to form a web.
Transferred to 33. On the other hand, the web 33 is in close contact with the backup roll 34 and is configured to continuously run in the direction of arrow F at a constant speed. Coating liquid transferred to web 33
31 is smoothed by a lower lip 35 and an upper lip 36 in the running direction of the web 33, and a predetermined coating film 27 is formed. FIG. 5 is an enlarged view of the portion indicated by the arrow II in FIG.
As shown in FIG. 5, on the upper lip 36, a coating liquid pool 39 is formed by the pressure difference between the pressure of the coating liquid 31 and the atmospheric pressure at the central portion 38 of the coating liquid jet.

Problems to be Solved by the Invention However, in the above-described coating apparatus, the air layer that adheres to and moves on the surface of the web 33 flows into the coating liquid pool 39 at substantially the same speed as the web 33. Therefore, there is a problem that air bubbles are mixed in the coating liquid 31 and various coating film defects described below occur. That is, a pinhole generated because the mixed air bubbles do not disappear, a vertical streak generated when the mixed air bubbles cause clogging between the lower lip 35 and the web 33, and the lower lip 35 due to the inclusion of the bubbles.
In addition, a coating film defect such as a minute surface disturbance of the coating film 37 caused by the flow of the coating liquid 31 between the upper lip 36 and the web 33 is disturbed. In particular, this phenomenon was remarkable in high-speed coating in which the moving speed of the web 33 was approximately 200 m / min or more.

Therefore, the present invention can prevent a moving air layer adhering to the web from being mixed in the coating liquid pool as much as possible, and can form a high-quality coating film without pinholes or vertical stripes even during high-speed coating. A coating device is provided.

Means for Solving the Problems In order to solve the above problems, the coating apparatus of the present invention is a web that continuously runs in close contact with a backup roll surface that rotates at a predetermined speed around a predetermined axis from a nozzle tip portion. A coating device for continuously extruding and coating a coating liquid, wherein the nozzle is provided with a lower lip and an upper lip provided at the tip to smooth the coating liquid to obtain a predetermined coating film. A rotary roll having an axis substantially parallel to the rotary axis of the backup roll is arranged on the upstream side of the upstream lip in the web running direction, and the outer peripheral surface of the rotary roll is brought close to the surface of the web. Is.

The air layer that adheres to the surface of the web and moves at approximately the same speed as the web is blocked by a rotating roll that is provided on the upper side of the upper lip in the web running direction and has an outer peripheral surface close to the web. The amount of air flowing into the coating liquid pool formed at the upper lip portion is reduced. Furthermore, by rotating this rotating roll so that its outer peripheral surface moves in the opposite direction to the web, the air layer adhering to the web and moving is forcibly removed, and the amount of air flowing into the coating liquid pool is increased. Is greatly reduced. As a result, even in the case of high-speed coating where the moving speed of the web greatly exceeds 200 m / min, it is possible to form a high-quality coating film without pinholes or vertical stripes, similar to the low-speed coating of conventional coating equipment. Becomes

Example Hereinafter, a coating apparatus in an example of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing the structure of the main part of a coating apparatus according to the first embodiment of the present invention. In FIG. 1, 1 is a backup roll having a substantially cylindrical shape, which is rotated around a predetermined axis at a predetermined speed. Reference numeral 2 denotes a thin film web, which is in close contact with the surface of the backup roll 1 and continuously runs in the direction of arrow A. Reference numeral 3 is a nozzle for applying the coating liquid 4 to the web 2. A lower lip 5 is formed on the lower end of the web 2 in the traveling direction of the web 2, and an upper lip is formed on the upper side of the web 2 in the traveling direction. 6 are integrally formed. Of course, each lip 5 and 6 may have a separate structure. Reference numeral 7 denotes a coating liquid pool formed between the upper lip 6 and the web 2 due to the pressure difference between the coating liquid pressure and the atmospheric pressure, and 8 denotes a coating film. 9 is a rotating roll made of hard rubber, which is arranged on the uppermost side in the running direction of the web of the upper lip 6, and this rotating roll 9 has its rotation axis substantially parallel to that of the backup roll 1 and The outer peripheral surface is arranged so as to be close to the web 2. Since the rotating roll 9 is arranged between the backup roll 1 and the upper lip 6, it has a smaller diameter than the backup roll 1. FIG. 2 is an enlarged view of the portion indicated by the arrow I in FIG. 1, in which the length 1 and the gap amount g of the upper lip 6 in the web running direction shown in FIG.
And the minimum gap amount between the web 2 and the web 2 are set to about 5 mm and about 50 μm, respectively, in this embodiment.

The operation of the coating apparatus of the first embodiment constructed as above will be described with reference to FIG. The coating liquid 4 transferred from the tip of the nozzle 3 to the web 2 which is in close contact with the backup roll 1 and continuously runs is smoothed by the lower lip 5 and the upper lip 6 provided at the tip of the nozzle 3. Then, a predetermined coating film 8 is formed on the surface of the web 2. By the way, in the case of high-speed coating in which the moving speed of the web 2 exceeds 200 m / min, the amount of air that adheres to the web 2 and moves in the direction of arrow B increases. However, the air that adheres to and moves on the web 2 is provided on the uppermost side of the upper lip 6 in the moving direction of the web 2, and its rotation axis is substantially parallel to the rotation axis of the backup roll 1 and The outer peripheral surface is blocked by the rotating roll 9 close to the web 2, and the amount of air flowing into the coating liquid pool 7 is reduced. Further, by rotating this rotating roll 9 in the direction of arrow C in FIG. 1 so that its outer peripheral surface moves in the direction opposite to that of the web 2, the air layer adhering to and moving on the web 2 is indicated by the arrow D. In this case, the amount of air flowing into the coating liquid reservoir 7 is significantly reduced. As a result, it is possible to form a high-quality coating film 8 without pinholes or vertical stripes even during high-speed coating. Actually, the length 1 and the gap amount g shown in FIG.
When a regular coating of video tape was applied at a coating speed of 300 m / min with m set to about 50 μm, the occurrence of coating film defects changed with and without the rotating roll 9. That is, by installing the rotating roll 9,
The surface roughness of the coating film 8 after drying was improved and the number of vertical stripes was also reduced. Then, the rotating roll 9 was rotated in the direction of arrow C in FIG. 1 so that the moving speed of the outer peripheral surface thereof was substantially the same as the moving speed of the web 2 of 300 m / min. The situation has changed significantly. That is, the surface roughness and glossiness of the coating film 8 after drying were greatly improved, and the number of vertical stripes and pinholes was drastically reduced.

As described above, according to the present embodiment, in the die coating type coating apparatus, the rotary roll having the axis substantially parallel to the rotation axis of the backup roll is arranged on the uppermost side in the web running direction of the upper lip. In addition, the outer peripheral surface of the rotating roll is brought close to the web, and by rotating the rotating roll so that the outer peripheral surface of the rotating roll moves in the opposite direction to the web surface, even during high-speed coating, It is possible to forcibly eliminate the air layer that adheres to the web and moves, and to prevent it from entering the coating liquid pool as much as possible, and to form a high-quality coating film without pinholes or vertical stripes.

Next, a coating apparatus according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a sectional view showing the structure of the main part of a coating apparatus according to the second embodiment of the present invention. In FIG. 3, 11 is a backup roll, 12 is a web, 13 is a nozzle, 14 is a coating liquid, 15 is a lower lip, 16 is an upper lip, 17 is a coating liquid pool, 18 is a coating film, and 19 is a rotating roll. The above is the same as the configuration of the first embodiment (FIG. 1). Length l'of the upper lip 16 in the web running direction and gap amount g '(minimum gap amount between the rotating roll 19 and the web 12)
As for the first embodiment, each of them is approximately 5 mm,
It is set to about 50 μm. The difference from the configuration of the first embodiment is that a blade 20 is provided on the web side of the nozzle 13 and on the uppermost side in the web running direction.
The tip of 20 is in contact with or close to the outer peripheral surface of the rotating roll 19. That is, with this blade 20,
The gap 21 formed between the outer peripheral surface of the rotating roll 19 and the nozzle 13 can be closed or extremely narrowed.

The operation of the coating apparatus according to the second embodiment having the above structure will be described with reference to FIG. In the case of high-speed coating in which the moving speed of the web 12 exceeds 200 m / min, the amount of air that adheres to the web 12 and moves in the direction of arrow B increases, but the upper lip 16 moves to the uppermost side in the moving direction of the web 12. Is provided,
Rotating roll 19 whose outer peripheral surface is close to the web 12,
The outer peripheral surface of the web 12 is rotated in the direction of arrow C in FIG.
The air layer adhering to and moving in the direction of arrow D can be forcibly removed, and as a result, the air adhering to and moving on the web 12 can be eliminated to the utmost as much as possible. On the other hand, an air layer is attached to the outer peripheral surface of the rotating roll 19, and when the rotating roll 19 is rotated in the direction of arrow C, a part of the air layer attached to the outer peripheral surface of the rotating roll 19 is rotated. An attempt is made to flow into the coating liquid pool 17 through the gap 21 between the outer peripheral surface of the roll 19 and the nozzle 13. But the nozzle
By the blade 20 provided between the 13 and the rotating roll 19, the air trying to flow into the gap 21 is blocked,
As indicated by the arrow E, the liquid is forcibly removed and the coating liquid pool 17
It is possible to further reduce the amount of air flowing into the. As a result, it becomes possible to form a high-quality coating film 18 without pinholes or vertical stripes even during high-speed coating.

As described above, according to the present embodiment, in the die coating type coating apparatus, the rotary roll forcibly removing the air layer attached to and moving on the web and the rotary roll attached to the outer peripheral surface of the rotary roll. By providing a blade that forcibly eliminates the air layer, even during high-speed coating, it is possible to prevent air from entering the coating liquid pool more efficiently, and to ensure high quality with no pinholes or vertical lines. A coating film can be formed.

In the first and second embodiments of the present invention, the lengths l and l '(see FIG. 2) of the upper lip 6 and 16 are set to approximately 5 mm, but the coating liquid pools 7 and 17 are stabilized. Although it may have any size as long as it can be formed by the above, it is preferably 10 mm or less in order to prevent dripping due to gravity.

Also, in the first and second embodiments, the gap amounts g, g '
Was set to approximately 50 μm, but in order to efficiently scrape the air layer that adheres to the webs 2 and 12 and moves, 150 μm
The following is desirable.

Further, in the first and second embodiments, the material of the rotating rolls 9, 19 is hard rubber, but any material may be used as long as the same effect can be obtained.

As described above, according to the configuration of the present invention, the coating liquid is continuously extruded from the nozzle tip portion to be applied to the continuously running web in close contact with the backup roll surface rotating at a predetermined speed, and the nozzle tip is applied. Is a coating device for smoothing a coating liquid applied by a lower side lip and an upper side lip provided in a portion to obtain a predetermined coating film, wherein the backup roll is provided on the upper side of the upper side lip in the web running direction. By disposing a rotating roll having an axis substantially parallel to the rotating axis of, and bringing the outer peripheral surface of the rotating roll close to the web, an air layer that adheres to the web and moves even during high-speed coating. It is possible to form a high-quality coating film that does not have pinholes or vertical streaks by preventing it from entering the coating liquid pool as much as possible, and its practical effect is great. There is

[Brief description of drawings]

FIG. 1 is a sectional view showing the constitution of a coating apparatus according to a first embodiment of the present invention, FIG. 2 is an enlarged view of a portion indicated by an arrow I in FIG. 1, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a sectional view showing the structure of the coating apparatus of FIG. 4, FIG. 4 is a sectional view showing the structure of the conventional coating apparatus, and FIG. 5 is an enlarged view of the portion indicated by the arrow II in FIG. 1,11 …… Backup roll, 2,12 …… Web, 3,13…
… Nozzle, 5,15 …… Lower lip, 6,16 …… Upper lip, 9,19… Rotating roll, 20 …… Blade.

Claims (5)

(57) [Claims] 1. A web continuously running in close contact with the surface of a backup roll that rotates at a predetermined speed around a predetermined axis.
With a coating device that continuously extrudes the coating liquid from the tip of the nozzle to apply, and smoothes the coating liquid applied by the lower lip and the upper lip of the nozzle to obtain a predetermined coating film. There, a rotating roll having an axis substantially parallel to the rotating shaft of the backup roll is arranged on the upper side of the upper lip in the web running direction, and the outer peripheral surface of the rotating roll is placed on the surface of the web. Coater placed close to each other. 2. The coating apparatus according to claim 1, wherein the rotating roll is rotated so that the outer peripheral surface of the rotating roll moves in directions opposite to the web surface. 3. The coating apparatus according to claim 1, wherein a blade is arranged on the upstream side of the nozzle tip portion in the web traveling direction, and the tip is arranged so as to come into contact with or come close to the outer peripheral surface of the rotary roll. 4. The coating apparatus according to claim 1, wherein the length 1 of the upper lip in the web running direction is 1 ≦ 10 mm or less. 5. The coating apparatus according to claim 1, wherein the minimum gap amount g between the rotating roll and the web is g ≦ 150 μm.