JPH03123672A - Coating method - Google Patents

Abstract

PURPOSE:To perform the curtain coating of a low viscosity coating solution low in its flow rate by increasing the liquid resistance of the coating solution having a free falling coating solution film flow down rate of 0.5cc/cm sec or less and viscosity of 20 cps or less in a slot to coat a web. CONSTITUTION:Coating solutions having viscosity of 20 cps or less are applied to a web at a flow rate wherein the flow-down rate of a free falling coating solution film is 0.5cc/cm sec or less from an extrusion type liquid injector 3 whose slots 5, 6 are present above a liquid sump part while the liquid resistances in the slots are increased. At this time, it is pref. to set the clearance of each of the slots to 0.5mm or less because the resistances of the coating solutions 1, 2 in the respective slot parts 5, 6 are increased in order to prevent the falling of the coating solutions in a cavity part 4 being the defect of the extrusion type liquid injector 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a curtain coating method, and more particularly to a curtain coating method using a low viscosity and low flow rate coating liquid from an extrusion type liquid injection device.

[Conventional technology]

Conventionally, curtain coating methods using an extrusion type liquid injection device have been disclosed in Japanese Patent Application Laid-open Nos. 48-34946 and 1972.
There are various publications such as No.-69946.

[The invention tries to solve i! ! ! 9) However,
In the coating device disclosed in Japanese Patent Application Laid-Open No. 48-34946, referring to FIG. 1 to explain the liquid dispenser, when coating with low viscosity and low flow rate, a liquid pool (cavity) 4 is formed from slots 5 and 6. exists at the top, so if the slot clearance D,,D, is wide or the viscosity of the liquid is low.

The coating 11.2 flows down from the slot 5.6 when the inside of the cavity is not sufficiently filled with liquid, and a space is created within the cavity 4.

Coating defects such as streaks and unevenness occur when the coating surface requires a homogeneous material, such as photographic light-sensitive materials.

For this reason, the Extru-silane type liquid injection device is difficult to use, and is generally a slide hombar type (for example,
No. 33) Coating devices using liquid pourers are often used for coating photographic photosensitive agents.

JP-A-52-69946 discloses an example of countermeasures using double slots and cavities, but there are many structural difficulties.

In addition, the curtain coating method using a slide hopper type liquid injection device is suitable for multilayer coating, but since the entire coating device becomes large, on the other hand, an extrusion type liquid injection device is suitable for coating a single layer or several layers. It's more compact and better.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a coating method in which a low flow rate, low viscosity coating liquid can be applied using an extrusion type liquid injection device.

[Means and effects for solving the problems] The above-mentioned objects of the present invention are as follows: (1) Coating with a free-falling coating liquid film onto the web from an extrusion type liquid injection device in which a liquid pool is located above the slot. In the method, a coating liquid having a viscosity of 20 cps or less is applied at a flow rate of 0.5 cc/cm-see or less of the free-falling coating liquid film by increasing the coating liquid resistance of the slot. Characteristic application method.

(2) The clearance of the slot is 0.5 m or less.
The coating method according to claim 1, characterized in that:

achieved by

Increasing the coating liquid resistance of the slot clearance in the present invention is achieved by narrowing the slot clearance or increasing the length. It can also be achieved by increasing the viscosity of the coating solution to a limit level.

The present invention will be explained using figures. FIG. 1 is a cross-sectional view of an extrusion device using the coating method of the present invention.

In FIG. 1, reducing the slot clearance to 0.5 mm or less means that the application Ml, 2
each slot part 5.6 to prevent it from falling.
This is to increase the resistance of coating liquid 1.2. The clearances D- and Db of each slot 56 are preferably 0.5mm or less, preferably 0.3mm or less, although this depends on the flow rate and viscosity of the free-falling coating liquid film.

Also, as shown in Figure 2, the slot clearance D.

In addition to D, making the slot length Pa as long as zb will further help the above effect. Slot length is 5
A value of 0++a or more is preferable, but this is naturally limited due to constraints from the size of the device.

7 is the web.

〔Example〕

Comparative Example 1 As a curtain coating method using an extrusion type liquid injection device as shown in Figure 1, an extrusion type coating device with a slot clearance of 0.8 was used to apply a liquid containing an antihalation dye and a protective layer. When applying, I tried to apply the protective layer as thinly as possible due to the dry load, but
In order to coat at a coating speed of 100 III/win, a protective layer of 60 cc/rrr (free-falling coating liquid film flow rate I
ce/cm・sec), satisfactory coating could not be achieved. The viscosity of the coating solution is 40°C and the solution containing dye is 4
5 cps, and the protective layer was 10 cps.

Example 1 Using the same type of coating device as Comparative Example 1, the clearance of the slot on the protective layer side was increased to 0.3 arm, and the rest was coated under the same conditions as Comparative Example 1. , protective layer coating amount 6 cc/po (free fall coating liquid film flow rate Q,
A film was sufficiently formed at lee/c [sec] and coating was possible.

Example-2 Using the coating device of Example-1, the viscosity of only the protective layer was set to 20.
When the cps was increased with a thickener and applied, the application amount was further increased to 4.2cc/rrr (free falling application liquid flow down iQ,
07 cc/cya-see).

The above results are compared in Table 1.

Table 1 Example-3 The coating liquid was not a protective layer, but a coating liquid in which a metal oxide was dispersed in a binder and a solvent was adjusted to a viscosity of 10 cps, and extrusion was performed in the same manner as in Example-1 using the coating liquid as the lower layer. When coating was carried out using a mold pourer, it was possible to coat at a coating speed of 200 m/min with a coating amount of 6 cc/po (natural fall coating liquid film flow rate: 0.2 cc/cm·sec).

〔Effect of the invention〕

The coating method of the present invention makes it possible to use a curtain coating method using an extrusion type liquid injector even when using low flow rate and low viscosity coating liquids, making it possible to coat an even thinner layer, thereby improving quality. This has a significant effect, as well as an increase in production efficiency due to the fact that high-speed coating is now possible.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of the coating method of the present invention, and FIG.
The figure is a cross-sectional view showing another embodiment of the invention. 1.2...Coating liquid 3...Extrusion type liquid injector 4...Cavity 5.6...Thrower]・1 p, a. D. C. Slot Clearance Slot Length Map Procedure Amendment September 13, 1990

Claims (2)

[Claims] (1) In a method of coating the web with a free-falling coating liquid film from an extrusion-type liquid injection device in which a liquid pool exists above a slot, the flow rate of the free-falling coating liquid film is 0.5 cc/ At a flow rate of cm・sec or less, 2
A coating method characterized in that a coating liquid having a viscosity of 0 cps or less is applied by increasing liquid resistance in the slot. (2) The coating method according to claim (1), characterized in that the clearance of the slot is set to 0.5 mm or less.