JPS62289264A - Method and device for coating - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of all parts of a membrane and to perform uniform coating by performing wind shielding just before the falling membrane in the upstream side of the advancing direction of a web and decompressing the vicinity of a collision point. CONSTITUTION:In coating a continuously running band-shaped support such as a film and photographic paper by liquid, both the part near to a point 20 wherein a coated membrane is allowed to fall and to collide from the part near to a lip 10 and the part exceeding the coated width are subjected to wind shielding in order to prevent the rocking of all parts of the membrane, and an implement 17 interrupting the air accompanied with the support 15 is set to the vicinity of the falling membrane 13. A suction apparatus 21 is provided in the implement 17 for preventing the rocking due to the air accompanied with the support 15 and the vicinity of the collision point is decompressed. Thereby the uniform coated membrane free from unevenness can be formed.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to photographic films, photographic paper, magnetic recording tapes, adhesive tapes, pressure-sensitive recording papers, offset plates, etc. During manufacturing, a continuously running strip support (hereinafter referred to as a "web") is used.
It is called. ) and relates to a method and apparatus for applying various liquid compositions to

[Prior art]

One typical method of coating a thin film-like coating liquid by colliding with a traveling band-shaped support is the curtain coating method.

The curtain coating method is a method in which a free-falling curtain made of one or more coating liquids is formed, and the curtain is collided with the object to be coated to form a coating film on the object. However, due to the demand for improved coating quality, high-precision coating has gradually become required, and in recent years, special public Akihiro Tar λ≠733, Akihiro Tar 3 and Reference 7 have been used. Attempts have been made to apply the curtain coating method, as disclosed in the above publication, to fields where precision is particularly required, such as the production of photographic light-sensitive materials.

In this method, stably forming a free-falling curtain is very important for uniform application. A device that distributes multiple perforated plates around a falling membrane to protect it from turbulence caused by nearby airflow is disclosed in the U.S. Patent No. ≠, Ko! 7. It is disclosed in Ko reference θ. It is said that this device can eliminate excess wind turbulence inside the building by diffusing the colliding winds. In addition, in order to prevent the film from shaking due to the air accompanying the web, there is a method of suctioning air before the falling point of the film, and a method of blowing gas onto the falling film after the falling point. Japanese Patent Publication No. Sho μr-3de No. 103 discloses a method of electrically carrying out the method using a charged substance.

[Problem that the invention seeks to solve]

However, with the method of surrounding the coating device with a plurality of perforated plates, it is difficult to prevent the film from being disturbed by entrained air near the web surface. In addition, in fields that require precision, such as in the production of photographic light-sensitive materials, simple suction or spraying before and after the drop point of the film cannot suppress the fluctuation of the upper part of the film, resulting in uneven coating. There is a problem.

An object of the present invention is to provide a method for uniform coating by preventing fluctuation of the entire film.

[Means for solving problems]

The above-mentioned object of the present invention is to provide a method of coating a continuously running web by colliding a coating liquid that falls freely in the form of a thin film, in which the upstream side of the web in the traveling direction is blocked from wind just before the falling film and the point of collision is This is achieved by a method and apparatus characterized by reducing the pressure in the vicinity.

The present invention will be explained in more detail below with reference to the drawings.

In FIGS. 1 and 2, / is a block including the lip 10f forming a curtain film, 2.3 is a block following it, and adjacent blocks have each slit ≠,! is formed. If the number of coated layers is three or more - it can be increased by adding more blocks. 2.7 is a cavity for distributing the liquid in the width direction, and the liquid feeding bag #♂,
It is filled with liquid supplied from there. Each liquid becomes a liquid film //, /2 and flows down, becoming a curtain film 13 held on both sides by an edge guide /2, colliding with a support /j running in the direction of the arrow, and becoming a coating film l≠ . In the above-mentioned apparatus, in order to prevent the entire film from shaking, the portion from near the lip /θ to near the coating film fall collision point 20 and beyond the coating area is covered with the wind shield i-1 support /! A device 17 for blocking the entrained air is placed in the vicinity of the falling film 13. In order to prevent the upper part of the membrane from swinging, the distance between the instrument/7 and the falling membrane/3 can be freely changed. The interval it is preferably 5~/! C
,,). Then, in order to prevent the support body /j from swinging due to the entrained air, the pressure inside the instrument /7 is reduced by the suction device 2/. The pressure at that time is -j to -7[u+H20:I, and the support l! The gap /9 between and the instrument /7 is o,
It is preferable that it is r~/o (,). By using this method and apparatus, it is possible not only to stably form the falling film /3 and enable uniform coating, but also to improve the effect of suppressing air entrainment between the coating film /≠ and the support 75.

Supports conveniently used in the present invention include 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 A, T, -nylon, and Otsu-nylon, polyethylene terephthalate, and polyethylene-X.
,! - Polyesters such as naphthalates, polycarbonates, cellulose acetates such as cellulose triacetate, cellulose diacetate, etc. are used. Further, the resin used for resin coated paper is typically polyolefin such as polyethylene, but is not necessarily limited thereto.

In addition, "coating liquid" includes liquids with various compositions depending on the application, such as those in photosensitive materials,
Coating liquids for photosensitive emulsion layers, undercoat layers, printing layers, back layers, etc.;
Coating liquids for magnetic J-1 undercoat layer, lubricating layer, enveloping layer, pack 1 cedar, etc. in magnetic recording bodies; coating liquids for adhesive layer, colored layer, anti-rust layer, etc. These coated AIs contain a water-soluble binder or an organic binder.

In order to further clarify the functions and effects of the present invention, some example data will be introduced below.

〔Example〕

Using the apparatus of the present invention shown in Figure 1, an aqueous alkaline gelatin solution (concentration: lo, O (wt)) was used as the coating liquid.
L4) K anionic surfactant /, JC9/l] and a blue dye added were used. The viscosity of the coating liquid is 4c
o('C:I was 00pr [poise]. The coating liquid was allowed to flow down from the coating die at a flow rate per coating die @/(ffi)/J (m//m·sec).

On a coating roll, gelatin was coated and applied to a support made of 93 vinegar cellulose. The falling distance from the tip of the coating die to the support is / 0 [cm]
Met.

First, when the coating was applied without using the anti-sway device 17, vertical streak-like unevenness was observed in the coating film l≠.

In addition, the limit speed due to air entrainment was 7 minutes].

Next, using the instrument 17, the inside is -2(ts I(20)
When the pressure was reduced, a uniform coating film with no unevenness could be formed. Also, the critical speed due to air entrainment at that time is 2
≠! [m/min]. In addition, the falling film at this time /3
The distance between and the device/7 is 10, the support/j and the device 1.
There is a gap between 7 and 7! It was [fin].

[Brief explanation of the drawing]

Ru.

Claims (2)

[Claims] (1) In a method of coating a continuously running web by colliding a coating liquid that falls freely in the form of a thin film, the wind is blocked just before the free-falling film on the upstream side in the direction of web travel, and the pressure near the collision point is reduced. A coating method characterized by: (2) In a device that coats a continuously running web by colliding a coating liquid that falls freely in the form of a thin film, the wind is blocked from the top of the thin film to near the drop point and over the entire coating width;
A coating device characterized by being equipped with a device for reducing pressure.