JPH03123657A - Coating apparatus - Google Patents

Abstract

PURPOSE:To remove the accompanied air of a web and to prevent coating irregularity by providing a vacuum chamber at the position opposed to a backup roller and respectively setting the gap between the vacuum chamber and the web and the distance between the vacuum chamber and a free falling coating solution film collision part to specific numerical values. CONSTITUTION:The coating solution 2 from a curtain coating die 1 is formed into a free falling coating solution film 4 which in turn collides with a web to coat the same. Herein, the vacuum chamber 8 connected to a suction apparatus 7 is provided at the position opposed to the backup roller 5 on the upstream side of a free falling coating solution film collision part 9. The gap between the peripheral wall of the vacuum chamber 8 and the web 3 is set to a range of 1mm or less not coming into contact with the web 3 and the distance between the downstream end of the vacuum chamber 8 and the free falling coating solution film collision part 9 along the web 3 is set to 10 - 100 mm. Further, the vacuum degree of the vacuum chamber 8 is set to 10 mm H2O or less. Since the accompanied air of the web 3 can sufficiently be blocked by this constitution, the disturbance of the free falling coating solution film 4 and the fluttering of the web 3 are not generated and good coating quality is obtained even at a high speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coating device, and in particular to a coating device for film for photographic photosensitive materials, photographic paper, magnetic recording tape, adhesive tape, pressure-sensitive recording paper, offset plate, etc. This invention relates to a device that applies various liquid compositions to a continuously running web (band-shaped support) used in manufacturing using a curtain coating method.

(Prior Art) In a device that applies a thin film of free-falling coating liquid by colliding with a continuously running web, that is, in a curtain coating device, it is important to keep the thin film of freely falling coating liquid stable. In particular, it is necessary to prevent the thin film of the coating liquid from being disturbed by air flow entrained by the support being conveyed at high speed.

Therefore, various wind shielding or membrane stabilizing means have been proposed.

As a means for this purpose, (1) a coating device having a slit-shaped suction port on the upstream side of the free-falling coating liquid film and provided with a suction device for sucking the entrained air on the web (see Japanese Patent Publication No. 49-24133);

■ A method of sucking the entrained air on the web using a box-shaped suction port and reducing the pressure near the collision point (Japanese Patent Laid-Open No. 62-2892
(see Publication No. 64).

[Problem to be solved by the invention]

However, with the method (2), a large amount of suction is used to remove the entrained air, and the falling film itself is disturbed by the flow of surrounding air, so it is difficult to say that it can produce a sufficient wind effect. , If the amount of suction is too large, the free-falling coating film itself may be attracted, or air flow may occur in the narrow gap between the suction device and the falling film, disturbing the free-falling coating film. Therefore, it may not be possible to find the optimal conditions. In addition, the method of suctioning on a horizontally conveyed web as in (1) and (2) may cause the web to flap, which may induce other secondary failures.

The present invention solves the above problems and prevents uneven coating by removing entrained air from the web without disturbing the free-falling coating liquid film or inducing flutter of the web in a curtain coating device. An object of the present invention is to provide a coating device using a suction type entrained wind removal device.

[Means and effects for solving the problems] The above-mentioned objects of the present invention are as follows: (1) In an apparatus that applies a thin free-falling coating liquid film by colliding it onto a continuously running web, the free-falling coating liquid film is A decompression chamber facing the back unroller on the upstream side of the collision part is provided, and the gap between the peripheral wall of the decompression chamber and the web is 1 m.
m or less and not in contact with the web, the distance along the web between the downstream end of the vacuum chamber and the free-falling coating liquid film collision part is 10 to 100 cm, and the degree of vacuum in the vacuum chamber is 10 cm in water column.
A coating device characterized in that the coating thickness is less than mm.

(2) The coating device according to claim 1, further comprising a partition wall that divides the vacuum chamber into two, and a suction device performs suction from the vacuum chamber on the upstream side.

achieved by

In the present invention, a vacuum chamber is provided opposite to a backup roller on the upstream side of a free-falling coating liquid film collision part, and the gap between the vacuum chamber and the web is 1 mm or less in a range that does not contact the web, and the downstream end of the vacuum chamber and the web are free from contact. By setting the distance along the web to the colliding part of the falling coating liquid film to 10 to 100 m, and the degree of decompression in the decompression chamber to be less than 10 gm of water, the above-mentioned uneven coating can be prevented without causing other secondary failures. can do. Further, by dividing this decompression chamber into two units and suctioning from the upstream side using a suction device, further effects can be achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A more detailed description of embodiments of the present invention will be given below with reference to the drawings.

In FIG. 1, 1 is a curtain coating goo, 3 is a web, and the coating liquid 2 forms a free-falling coating liquid film 4, collides with the web 3, and is applied. Reference numeral 5 denotes a backup roller, and here an example is shown where the falling film collides with the apex of the backup roller, but the collision part 9 may be on the upstream side of the apex of the backup roller on the Puffquano propeller, or the colliding portion 9 may be on the upstream side of the apex of the backup roller, or It may also be located on the downstream side.

6 is a decompression chamber, which is connected to a suction device (blower) 7. FIG. 2 shows an example in which the decompression chamber is partitioned into two by a partition wall.

Conventionally, in order to prevent uneven coating due to entrained air, it has been thought that it is necessary to block entrained air in the close vicinity of the collision point 9 of the free-falling coating liquid film. However, research has revealed that in reality, it is not the entrained airflow itself, but the turbulence components contained within it that are causing the uneven coating.

After cutting off the entrained air, it takes a very short distance for the air boundary layer to be formed again, but it usually takes a distance of several centimeters for turbulence to occur. Therefore, if the effect of removing the entrained wind is sufficient, the effect of preventing uneven coating can be obtained without reducing the pressure including the collision part 9, and it is also possible to obtain sufficient entrained air without disturbing the free-falling coating liquid film 4. can be removed by suction. Specifically, the free-falling coating liquid film 4 and the decompression chamber 5
The distance along the web 3 should be IOM or more and 100 mm or less, preferably 10 ma+ or more and 50 InI11 or less, and in order to sufficiently remove the entrained air by suction, the gap between the decompression chamber 6 and the web 3 should be very narrow. It is necessary to set the pressure to be less than 0.5 fan, preferably less than 0.5 so that it does not come into contact with the web, and to have a high degree of vacuum. However, if an extremely large degree of vacuum is used, the air volume will be large (and will easily disturb the free-falling coating film 4), so the degree of vacuum must be 10 mm or less in the water column, preferably 0.5 to 5 mm in the water column. Furthermore, in places where the web runs in a straight line, the suction may cause the web to flutter, or the web may be pulled in and come into contact with the walls of the decompression chamber, causing other failures. By providing a vacuum chamber opposite the backup roller, such problems can be eliminated and the web can be sufficiently removed by entrained air.

Incidentally, it is preferable that the decompression chamber is partitioned into two by a wall because the decompression effect becomes even more effective.

The web used in the present invention includes paper, plastic film, resin coated paper, synthetic paper, and the like. Examples of the material of the plastic film include polyolefins such as polyethylene and polypropylene, vinyl polymers such as polyvinyl acetate, polyvinyl chloride, and polystyrene, polyamides such as 6,6-nylon and 6-nylon, and polyethylene terephthalate and polyethylene-2,6. Polyesters such as naphthalate, polycarbonates, cellulose acetates such as cellulose triacetate, cellulose diacetate, etc. are used. Further, the resin used for resin coachitic paper is typically polyolefin such as polyethylene, but is not necessarily limited thereto. Further, the paper may include one laminated with polyolefin, and the surface thereof may be flat or embossed.

Furthermore, the coating liquid includes various liquid compositions depending on the application, such as coating liquids for photosensitive emulsion layers, undercoat layers, protective layers, bank layers, etc. in photographic light-sensitive materials, magnetic recording Examples include coating liquids for magnetic layers, undercoat layers, lubricating layers, protective layers, bank layers, etc., as well as coating liquids for adhesive layers, colored layers, anti-rust layers, etc., as in media, and these coating liquids are water-soluble. It contains a synthetic binder or an organic binder.

〔Example〕

As a coating solution, 0.0% of an anionic surfactant is added to an 8% aqueous solution of alkali-treated gelatin for photography. 1 wt% and a water-soluble dye was used.

The viscosity of the liquid was adjusted to 0.4 poise at 40°C by adding a water-soluble thickener. Using a curtain coating device as shown in Fig. 1, apply this liquid at a flow rate per width of 3 CC/CI sec at a distance of 200 cm horizontally 10 cm below the tip of the die.
It was coated on a gelatin-subbed cellulose triacetate film running at a speed of m/win.

First, when coating was performed without using a suction device, streak-like coating unevenness that was parallel to or slightly deviated from parallel to the direction of travel occurred. Next, a decompression chamber that sucks up to the upstream side of the 30 cylinder from the falling film landing point is placed opposite the backup roller,
Installed with a minimum gap of 0.3 rrm to the web, 2an
When the vacuum was applied to the vacuum level of the water column, no similar coating unevenness was observed, and the coating speed was increased to 400.
It was possible to increase it to m/l 1in.

〔Effect of the invention〕

According to the coating device of the present invention, it is possible to sufficiently block wind entrained in the web without disturbing the free-falling coating liquid film or causing web flapping, and good coating quality can be achieved even at high speeds. This greatly contributed to speeding up the process.

[Brief explanation of drawings]

FIG. 1 is a side view of an embodiment of the coating device according to the present invention;
FIG. 2 is a side view of another embodiment of the present invention in which the vacuum chamber is divided into two parts. ■ Curtain coating die 2 Coating liquid 3 Web 4 Free-fall coating liquid film 5 Backup roller 6 Decompression chamber 7 Suction blower 8 Decompression chamber dividing wall 9 point of collision

Claims (2)

[Claims] (1) In an apparatus that applies a thin free-falling coating liquid film by colliding it onto a continuously running web, a decompression chamber is provided opposite to a backup roller on the upstream side of the free-falling coating liquid film collision part, and the depressurization The gap between the room surrounding wall and the web is 1mm.
The distance along the web between the downstream end of the vacuum chamber and the collision part of the free-falling coating liquid film is 10 to 100 mm, and the degree of vacuum in the vacuum chamber is 10 m in water column.
A coating device characterized in that the coating thickness is less than m. (2) The application according to claim (1), wherein the reduced pressure chamber has a partition wall that divides the inside of the reduced pressure chamber into two, and suction is performed from the upstream reduced pressure chamber by a suction device. Device.