JPH01249170A - Coating method - Google Patents

Abstract

PURPOSE:To prevent the staining of rolls and the adhesion of a product by leveling a thick coated part with a coating bar while a coating liq. on a web on the downstream side of a coating device is in an undried state. CONSTITUTION:A polyethylene terephthalate film is travelled as a web 1 at a constant speed. Immediately after the beginning of coating with a bar coating device 9, the action of the coating bar 11 for leveling is started and then the bar 11 is moved down through a stand for moving up and down the bar 11 to finish leveling operation. Thus, coating rate and yield can be increased. Paper, an Al web or a plastic film may be used as the web and the pref. thickness is 0.01-1.0mm.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to photographic materials such as photographic film and photographic paper, photolithographic materials, magnetic recording materials such as magnetic recording tape, pressure-sensitive recording paper, and heat-sensitive recording paper. This invention relates to an improvement in the process of applying a liquid coating composition to a continuously running long flexible support (hereinafter referred to as "web") in the production of recording materials, and in particular to improved bar coating methods and roller coating methods. It is something.

[Prior Art] Various methods have been proposed for applying a coating liquid to a continuously running web. Generally, the coating process involves the part where the coating liquid is transferred to the web (hereinafter referred to as [
"Application system". ) and the coating liquid transferred to the web to the desired coating amount! Since the application method is considered to be divided into two parts (hereinafter referred to as "measuring system"), the application method has been classified according to the difference between the application system and the measurement system.

Based on the difference in application system, roller coating method,
Known methods include dip coating, fountain coating, and air knife coating, blade coating, bar coating, etc. based on differences in metering systems.

Further, as methods in which the application and measurement are performed in the same part, the Extru-silane coating method, the bead coating method, and the curtain coating method are known.

Among these coating methods, the bar coating method or the roller coating method transfers excess coating liquid onto the web, and then uses a bar or roller that is stationary or rotating at a slower circumferential speed in the opposite direction to the web to transfer the excess coating liquid onto the web. It scrapes off the coating liquid to achieve the desired amount of coating, and has been widely used because it has the feature of being able to coat a thin layer at high speed with a simple device and operation.

For example, FIG. 4 shows an example of a bar coating device using a coating rod for a conventional coating device (for example, Japanese Patent Laid-Open No. 53-225
43), in which a coating rod 2 is rotated in the same direction or in the opposite direction as the web 1, which is continuously running. A bar support member 3 is provided over the entire length of the bar 2, and has the function of preventing the bar 2 from being bent and serving as a liquid supply device for supplying the coating liquid 4 to the bar 2. That is, the coating liquid 4 is supplied from the liquid supply port 5 provided in the bar support member 3 into the liquid supply guide groove 7 formed between the bar support member 3 and the weir member 6, and is picked up by the rotating bar 2 and applied to the web l. However, at this time, the coating liquid 4 is measured at the contact area between the web 1 and the bar 2, and only the desired coating amount is applied to the web 1, while the rest flows down and the newly supplied coating liquid 4 is applied. At the same time, a liquid reservoir 8 is formed. Therefore, in a steady state, the coating liquid 4 is applied to the web 1 via the liquid reservoir 8.

[Problem to be solved by the invention]

However, at the start and end of coating, when the coating rod or roller and the web come into contact with or separate from each other by raising or lowering the coater upper and lower tables, etc., the liquid on the coating rod or roller is not measured, resulting in a significant amount of liquid being applied onto the web. There was a problem with thick coating. Incidentally, this phenomenon is caused by the formation of coating liquid bridges.
This can also occur in the case of a heat coating device. This extremely thick coating varies depending on the physical properties of the coating liquid, the shape of the coating rod or roller, and the type of web, but it may be more than 5 times thicker than the steady area, so be careful not to dry in the drying zone. If countermeasures were not taken, the subsequent rollers would be significantly contaminated, which would adhere to the products that were subsequently passed through, resulting in loss of products.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a stable coating method that eliminates roller dirt and product adhesion.

C! Means and operation for solving problem i] The object of the present invention is to provide a method for coating a continuously running long flexible support by forming a coating liquid bridge between the support and the support.
When the coating liquid on the web on the downstream side of the coating device is at least not dry, the thickly coated area is smoothed using a smoothing coating bar or coating roller when coating with the coating device or at the end of coating. This is achieved by a coating method characterized by:

The continuously running web in the present invention includes paper, plastic film, resin coated paper, aluminum web, 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, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polycarbonates, and cellulose acetates such as cellulose triacetate and cellulose diacetate are used. Further, the resin used for resin coated paper is typically polyolefin such as polyethylene, but is not necessarily limited thereto.

The thickness of the web is also not particularly limited, but is 0.01 m111
A length of about 1.0 m is advantageous in terms of handling and versatility.

In the present invention, the method of coating by forming a coating liquid bridge between the support and the web includes all coating methods, but especially when performing Fi\ layer coating, the bar coating method, Examples include roller coating method and extrusion type bead coating.

The coating liquid in the present invention is not particularly limited, and may be a water or organic solvent liquid of a polymer compound.

Targets include αnn ice water dispersion, colloidal solutions, etc. In addition, the physical properties of the coating liquid are not particularly limited, and are 0,
5 cps to several 100 cps O liquid can be used.

In the present invention, the thickly coated area during coating by the coating device or at the end of coating refers to the area where the coating may be five times or more thicker than the steady area, which is the problem to be solved by the invention. say.

In the present invention, smoothing means bringing a coating bar or coating roller into contact with the thickly coated area,
This refers to transferring the coating liquid in thickly coated areas to a coating bar or coating roller, thereby smoothing it.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1.2 or 3 is a layout diagram of the coating apparatus of each embodiment for explaining the coating method according to the present invention.

In the first inspection, the bar code 9 is a coating device, and a coating bar wound with a wire of about 0.1 to 0.8 strands, for example, is installed in this coating device. A coating bar 11 for smoothing is also installed. Considering the purpose of the coating bar used for smoothing, it is preferable to use a bar with a smooth surface, and at least when using a wire bar, it is preferable to use a wire smaller than the wire bar of the coating device. Further, in the coating bar 11 for smoothing, a component solvent contained in the coating liquid applied by the barcode coating device 9 may be supplied, or no solvent may be supplied at all. In the latter case, the wire of the coating bar used for smoothing can be larger than the coating bar code 9.

In FIG. 2, the coating device 12 is a forward or reverse roll coating device W12, and the coating bar 11 for smoothing is the same as in FIG.

In this case as well, the coating bar 11 for smoothing can apply an amount smaller than the amount applied by the roll coater 12 (although it is not actually applied).
. It is preferable to use a coating bar for smoothing, and it is more preferable to use a coating bar with a smooth surface.

Further, in FIG. 3, the coating device is an example of a so-called bead coat type coating device that forms a coating liquid bridge between the web and the coating device, and is provided with a coating bar 11 for smoothing.

Example-1 Coating liquid: Viscosity 5 cps solution with the following components Acrylic acid copolymer: 10 parts Methyl glycol: 78.8 parts Methanol: 10 parts Dye = 0.1 part Using the apparatus shown in Figure 1 A polyethylene terephthalate film was run as a web at a coating speed of 70 m/11 inch, and a smoothing coating bar was started on the coating device 1 sec after the start of coating. In this case, no coating liquid was used on the smooth portion. Thereafter, the smoothing coating bar lowered the upper and lower tables after 1 See, and the smoothing operation was completed. The pattern at the beginning of coating had a thick coating area as shown in FIG. 5(b) below, and the maximum thick coating rate of the thick coating area was 10% as shown in (al).

The definition of thick coating rate is as follows.

Next, during steady coating, the upper and lower tables of the coating section were lowered and at the same time the upper and lower tables of the smoothing coating bar were raised. The finished pattern at that time is shown in Figure 5 (b2).
The Iv coating area had a thick coating ratio of 1°15 as shown in (a).

Comparative Example-1 Using the same coating equipment as in Example-1, the application of the same coating liquid was started and completed under the same conditions except that the smoothing coating bar was not used. At this time, the distribution of thick coating in the longitudinal direction is as shown in Figure 6, and the thick coating rate is 2.0 at the beginning of coating as shown in (a,).
．． At the end of painting, as shown in (a2), the result was much larger by 2 or 3.

〔Effect of the invention〕

The present invention provides a method for coating a continuously running long flexible support by forming a coating liquid bridge between the support and the coating liquid on the web downstream of a coating device. Excessive thick coating is removed using a coating method characterized by smoothing the coated area using a coating bar or coating roller when coating with a coating device or at the end of coating in a dry state. This eliminates accidents such as the adhesion of dirty reweb to the rollers, contributing to increased productivity and yield of coating/drying equipment.

[Brief explanation of the drawing]

Fig. 1.2.3 is a layout diagram of a coating apparatus according to an embodiment of the coating method of the present invention, Fig. 4 is a cross-sectional view of a coating bar according to the present invention, and Fig. 5 is a diagram of a coating device according to an embodiment of the coating method of the present invention. Web top view at the start of coating when coating smoothing measures are taken (b,), relationship graph between thick coating rate and distance (a,),
Flat surface of the web at the end of coating 2...Coating rod 3...Bar support member 4...Coating liquid 5...Supply port 6...Dish portion 7...Liquid supply guide groove 8... Liquid pool 9...Barcode coating device 10...Coated web 11...Smoothing coating bar 12...Roll coat coating device I3...Bead coat coating device (3 idiots) Fig. 4 Figure 5! I! Hawk II (k,,,) (b2) W electric (-)

Claims (1)

[Claims] In a method of coating a continuously running long flexible support by forming a coating liquid bridge between the support and the coating liquid, the coating liquid on the web on the downstream side of the coating device is at least in an undried state. A coating method characterized by smoothing thickly coated areas using a coating device or at the end of coating using a smoothing coating bar or coating roller.