JP2670910B2 - Application method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method, and particularly in the production of photographic light-sensitive materials such as photographic films and printing papers, photoengraving materials, magnetic recording materials, pressure-sensitive copying papers and heat-sensitive copying papers. The present invention relates to a method for coating a running long strip-shaped support (hereinafter referred to as "web") with a coating solution such as a photographic emulsion and a magnetic agent, and more particularly to a high-speed coating method therefor.

[0002]

2. Description of the Related Art Conventionally, as a method of applying a coating liquid on a continuously running web at a high speed, a decompression chamber is divided into three parts along the web into which a web to be applied enters a liquid injector. A method is provided in which a liquid such as water is put in the central chamber to evaporate, and air containing a large amount of vaporized gas or a large amount of water vapor is passed at high speed in the gap between the central chamber and the object to be coated during decompression exhaust ( (Japanese Patent Laid-Open No. 48-32923), a method of spraying and adhering a spray liquid previously atomized by using ultrasonic vibration to the surface of a web to start coating (Japanese Patent Laid-Open No. 52-31727). Furthermore, after the surface of the support is subjected to a hydrophilic treatment in advance, the surface is pre-moistened, and a coating solution is applied to the surface before the surface is completely dried (JP-A-104376). There is a method of applying by electrification (Japanese Patent Publication No. 57-167750).

[0003]

However, in the method of (1), if the liquid which is vaporized and solidified or atomized is condensed on the web, or the coarse droplets directly generated adhere to the web to cause coating failure. There is a drawback to say. In the method of (1), it is actually difficult to uniformly charge the entire surface of the web, and there is a drawback that coating unevenness easily occurs due to uneven charging. The present invention eliminates the above-mentioned conventional defects, without causing dew condensation around the web or causing coating failure due to coarse droplets,
Another object is to provide a coating method capable of increasing the coating speed without causing coating unevenness due to charging unevenness.

[0004]

The above object of the present invention is to provide a coating solution on a continuously running long strip-shaped support, in which a charger is provided on the long strip-shaped support immediately before coating. Use it to charge, then the relative humidity 75% to 95
The solution is provided by a coating method, characterized in that the coating is carried out after spraying% air. In the present invention, charging using a charger immediately before coating means that a ground roller is installed on the back surface of the web immediately before coating, and an electrode is installed facing the ground roller away from the web, and the charge amount of the web is 5
A voltage in the range of 0.1 to 7 kv / cm is applied to the electrodes so that the voltage is 00 v or less, preferably 300 v or less. One charger may be used, but it is preferable to install two or more chargers if possible. The reason is that it is more preferable to provide two or more units in series to reduce the amount of charge per unit for uniform charging.

In the present invention, the related temperature is 75% to 95%.
Spraying the air of means that water is in the moisture state in the air and is sprayed to prevent the formation of dew condensation or coarse droplets, while the high humidity air and the web make contact with the web. The effect is that the equilibrium water content is increased and the charge distribution of the web is made uniform while the equilibrium water content is increased. A relative humidity of 75% to 95% can be used, preferably 80% to 90%. Even if air having a relative humidity of 75% to 95% is blown, there is almost no decrease in the amount of charge.

An embodiment of the present invention will be described with reference to FIG. In the method of applying the coating liquid 2 from the liquid injector 3 onto the web 1 which continuously runs in FIG. 1, the back surface of the web 1 is supported by the earth roll 4 immediately before the coating, and the charging electrode 5 and the high voltage power supply 6 It receives a voltage and is discharged. After that, the relative humidity from the blowing chamber 7 to the coated surface is 75% to 9%.
After spraying 5% of air at a blowing air velocity of about 10 m / sec, the coating liquid 2 is applied onto the web 1 from the coating liquid injector 3.

The present invention will be further described. The material of the corona discharge electrode in the present invention is metal, carbon fiber or the like, and the shape is fine wire, brush shape, knife edge shape,
A flat plate shape or the like can be used. In addition, as the web used in the present invention, paper, plastic film,
Resin coated paper, synthetic paper and the like are included. The material of the plastic film is, for example, polyolefin such as polyethylene or polypropylene, vinyl polymer such as polyvinyl acetate, polyvinyl chloride or polystyrene, or 6,6.
-Polyamide such as nylon and 6-nylon, polyester such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polycarbonate, cellulose acetate such as cellulose triacetate and cellulose diacetate and the like are used. The resin used for the resin-coated paper is typically a polyolefin such as polyethylene, and may be one-sided or two-sided laminated. However, it is not necessarily limited to these. Further, the "coating liquid" includes various liquid compositions depending on its use, and for example, a coating liquid for a photosensitive emulsion layer, an undercoat layer, a protective layer, a back layer, etc. in a photographic light-sensitive material; Coating solutions for magnetic layers, undercoat layers, lubricating layers, protective layers, back layers, etc. for magnetic recording media; other coating solutions for adhesive layers, colored layers, rust preventive layers, etc. It is made of a conductive binder or an organic binder. As a method for applying the above-mentioned coating liquid onto the support, slide coating, roller bead coating, spray coating,
Extrusion coating, curtain coating, etc. can be used, and other methods are also possible.

[0008]

[Examples] When 100 μm of polyethylene terephthalate film was applied from an extrusion coater 3 to a coating solution of 11% gelatin solution having a viscosity of 30 cp at a coating amount of 50 cc / m ² , it was charged. The application was performed by blowing high-humidity air at a blowing speed of 10 m / sec. The conditions and results are shown in Table 1.

[0009]

[Table 1]

[0010]

According to the coating method of the present invention, the coating speed can be increased without the occurrence of the conventional dew condensation, droplet failure and uneven coating due to uneven charging.

[Brief description of the drawings]

FIG. 1 is a side view of one example for explaining an embodiment of a coating method of the present invention.

[Explanation of symbols] 1 web 2 coating liquid 3 liquid injector 4 earth roller 5 electrode 6 high voltage power supply 7 high humidity air blowing chamber

Claims (1)

(57) [Claims] 1. A method for applying a coating solution onto a continuous strip-shaped support, which comprises charging the strip-shaped support with a charger immediately before coating, and then applying relative humidity to the coated surface. A coating method, characterized in that the coating is performed after blowing 75% to 95% of air.