JP2597237B2 - Application method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coating method. Particularly, in the production of photographic photosensitive materials such as photographic films and photographic papers, photoengraving materials, magnetic recording materials, pressure-sensitive copying papers, and thermosensitive copying papers, etc., a long strip-shaped support (hereinafter, referred to as a "high speed continuous running"). (Hereinafter referred to as "web"), and applying a coating solution such as a photographic emulsion or a magnetic agent to form a bead.

[0002]

2. Description of the Related Art Conventionally, in the application of photographic light-sensitive materials, magnetic recording materials, recording paper, etc., a method of forming a bead and applying a coating solution after charging a continuously running web at a high speed is widely known. I have. That is, a coating method in which a discharge treatment is performed only at the start of coating and / or at a joint portion (Japanese Patent Application Laid-Open
-142565). A method in which a potential of 0.1 KV or more is applied to the bead forming portion of the coating solution or the surface of the support immediately before reaching the portion (JP-A-61-146369). Before coating, the support is charged at a constant charging potential and the degree of depressurization is kept at or below the steady-state depressurizing degree.After coating, the depressurizing degree is kept at or above the steady-state depressurizing degree for a certain period of time, and then the coating method shifts to the steady-state depressurizing degree. (JP-A-1-258772
Publication).

[0003]

However, this method is useful for preventing the occurrence of thick coating and streak failure at the start of coating and at the time of joining the web, but it is not useful for high-speed coating at a steady state. When such a voltage is applied, there is a problem that a repelling failure occurs. The other method is useful for preventing cissing at the time of steady state. However, when the required high charge is applied to the unsteady part such as the joint at the start of coating, the streak and unevenness of the steady part tends to occur. If the charge amount was low enough not to cause streak and unevenness failure in the steady part, it was insufficient for stabilizing the unsteady part. Further, in the other method, since charging is performed at a constant charging potential which is reached at the time of steady state, uniformity during coating and passing through the joint is dealt with by keeping the degree of decompression higher than the degree of decompression for a certain period of time.

[0004] An object of the present invention is to eliminate the problems of the above-mentioned various methods, to eliminate the occurrence of thick coating and streak failure at the start of coating and at the time of joining the web, and to cause the occurrence of streak, unevenness, cissing and the like even in a steady state. It is another object of the present invention to provide a coating method capable of performing uniform production at high speed.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for forming a bead by applying a coating solution after charging the surface of a long strip-shaped support continuously at a high speed. This is achieved by a coating method characterized in that the charge amount at the start and when the web passes through the bonding is higher than the charge amount at the time of steady application.

[0006] In the present invention, continuous application at a high speed requires a large number of web joining points. Therefore, it is necessary to shorten the thick coating and the streak failure of the portion corresponding to the downstream of the joining point as short as possible. In the present invention, the fact that the charge amount at the start of coating and at the time of passing through the bonding of the web is higher than the charge amount at the time of steady coating means that, specifically, at the start of coating and at the time of passing through the bonding of the web, the charging amount is 1K.
V or more, that is, 0.1 to 0.5 KV in the steady portion. The value of 1 KV or more at the start of coating and at the time when the web has passed through the joint means that the thick coating rate (the coating amount of the thick coating portion /
It is necessary to keep the amount of coating in a normal part) to 130% or less, and the upper limit is preferably raised to such an extent that spark discharge does not occur. Also, 0.1
The value of 0.5 KV means that a repelling failure easily occurs at 0.1 KV or less, and charging unevenness at 0.5 KV or more easily occurs as coating unevenness.

In the present invention, the adjustment of the charge amount is shown by the applied voltage with respect to the coating time, as shown in FIG. 1, at the start of coating and at the time of passing through the junction, an applied voltage of, for example, 8 KV is applied and the web charge amount at that time becomes 1000 V. Normally 5K
This means that the charged amount of the web becomes 150 V when the applied voltage of V is applied.

The present invention will be described in further detail. The material of the corona discharge electrode in the present invention may be metal, carbon fiber, or the like, and the shape may be a thin wire, brush, tough edge, flat plate, or the like. In addition, examples of the support used in the present invention include paper, plastic film, resin-coated paper, and synthetic paper. The material of the plastic film is, for example, polyethylene,
Polyolefins such as polypropylene, polyvinyl acetate,
Vinyl polymers such as polyvinyl chloride and polystyrene, 6,
Polyamides such as 6-nylon and 6-nylon, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polycarbonates, and cellulose acetates such as cellulose triacetate and cellulose diacetate 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. The term "coating solution" includes those having various liquid compositions depending on the intended use. For example, coating solutions for photosensitive emulsion layers, undercoat layers, protective layers, back layers, etc., as in photographic materials. Coating liquids for magnetic layers, undercoat layers, lubricating layers, protective layers, back layers, etc. as in magnetic recording media; and coating liquids for other adhesive layers, coloring layers, rust-preventive layers, etc .; It comprises a water-soluble binder or an organic binder. As a method of applying the coating liquid on the support, a slide coat, a roller bead coat, an extrusion coat, a curtain coat, or the like can be used, and other methods are also possible.

An embodiment of the present invention will be described with reference to the drawings. In FIG. 2, a coating liquid 6a is supplied to a liquid injector 1 by a pump 2
The liquid 6 is supplied to the cavity 3, is spread over the entire coating width in the cavity 3, flows from the slot 4 to the slide surface 5, and is also applied to the slide surface at the same time.
A coating liquid bead 8 is formed in a superimposed relationship with b, and is coated on the support 7 supported by the backing roller 9.
At the start of coating and at the time of passing through the joining portion, the coating liquid bead 8 tends to generate a thicker coating than usual at the time of contact with the web 7. The electrode 11 is installed, and corona discharge is performed at a voltage from the high-voltage power supply 15 to increase the adhesion of the coating solution to the web surface. On the other hand, the decompression chamber 10 for depressurizing the part before application of the liquid injector by the decompression pump 14 performs a constant decompression for increasing the application speed in response to the increase in the application speed. The present invention is a coating method characterized in that the voltage is changed so that the charge amount at the start of coating and when the web passes through the bonding is higher than the charge amount at the time of steady coating.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment will be described to clarify the effects of the present invention. However, the present invention is not limited to this embodiment. 5% gelatin solution as coating solution, viscosity 2
In applying the material having a pressure of 0 cp from a liquid injector to a slide bead coater having the above-described decompression chamber, the degree of decompression in the decompression chamber was kept constant at −50 mmH ₂ O, and the application speed was 150 m / m.
The coating surface conditions at the start of coating, at the time of steady state, and at the time of passing through the bonding were compared depending on the charge amount at in and 300 m / min. Table 1 shows the results.

[0011]

[Table 1]

As shown in Table 1, the coating speed is 150 m / mi.
In the case of n, the change of the thick coating rate at the start of coating is shown. At a coating speed of 300 m / min, the charge amount is preferably 1000 V or more at the start of coating and at the time of passing through the joint.
In normal times, about 200 V is preferable, and it is clear that a change in the charge amount is desired.

[0013]

According to the coating method of the present invention in which the charge amount at the start of coating and at the time of passing through the joint is higher than the charge amount at steady state,
This eliminates the occurrence of thick coating, streak failure, unevenness during normal operation, and cissing failure at the start of coating and at the time of passing through bonding during high-speed continuous coating, and uniform production can be efficiently performed.

[Brief description of the drawings]

FIG. 1 is a chart showing how an applied voltage is applied to a continuous coating time in a coating method of the present invention.

FIG. 2 is a side view of a coating apparatus according to one embodiment for performing the coating method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injector 2 Pump 3 Cavity 4 Slot 5 Slide surface 6a, 6b Coating liquid 7 Support 8 Coating liquid bead 9 Backing roller 10 Decompression chamber 11 Electrode 12 Earth roller 13 Charging part 14 Decompression pump 15 High pressure power supply

Claims (1)

(57) [Claims] 1. A method for applying a coating solution by forming a bead after charging the surface of a long strip-shaped support that runs continuously at a high speed, wherein the charging is performed at the start of coating and at the time of passing a web. A coating method characterized in that the amount is higher than the charge amount during steady application.