JPH0194976A - Coating method - Google Patents

Abstract

PURPOSE:To prevent the back-turning of a coating liquid and the thick coating thereof at the edge part of a web and to perform high speed coating and drying, by sucking the coating liquid on a coating rod outside from the edge part of a support by a suction nozzle. CONSTITUTION:In a method for coating a long flexible support such as a photographic film or printing paper with a liquid coating composition, a suction nozzle 13 is provided above a coating rod (bar) 2. The built-up part on the coating rod 2 of the liquid sump 8 of a coating liquid 4 formed by the coating rod 2 outside from the support 1 and a weir member 6 is sucked. By this method, the back-turning of the coating liquid at the edge of the web 1 and the thick coating of the edge part are prevented and high speed coating and drying becomes possible and quality is also enhanced.

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. Regarding improvements 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, more specifically, improved bar coating methods and roller coating. It is about the method.

[Conventional technology]

Conventionally, various methods have been proposed as methods 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 "
The coating method can be divided into two parts: the application system (hereinafter referred to as the "application system") and the part that measures the coating liquid transferred to the web to the desired coating amount (hereinafter referred to as the "measuring system"). They were classified based on their differences.

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.

In addition, extrusion coating methods, bead coating methods, and curtain coating methods are known as methods in which application and measurement are performed in the same part.

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 is a schematic diagram showing an example of a bar coating device using a coating rod for a conventional coating device according to the present invention. Rod 2 is rotated. 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 flows from the liquid supply port 5 provided in the bar support member 3 to the liquid supply guide groove 7 formed between the weir member 6 and the liquid supply port 5.
The rotating bar 2 picks up the material and applies it to the web 1, but at this time, the web 1 and the bar 2
The coating liquid 4 is measured at the contact portion with the web 1, and only the desired coating amount is applied to the web 1, and the rest flows down to form a liquid pool 8 together with the newly supplied coating liquid 4. Therefore, in a steady state, the coating liquid 4 is applied to the web 1 via the liquid reservoir 8.

In the case of this coating method, the edges of the web 1 are coated thickly, so the following method has been disclosed as a measure to prevent thick coating.

That is, a method of scraping off the coating liquid with a blade to prevent the thickly coated portion of the web from becoming thickly coated (Japanese Patent Laid-Open No. 60-225
669 (Japanese Patent Application Laid-open No. 142248/1983), or a method of scraping off thickly coated areas with air after coating (Japanese Patent Application Laid-open No. 142248/1983).

[Problem that the invention seeks to solve]

However, as the coating speed increases or the flow rate increases, the coating liquid 4 may bulge on the end surface 11 of the web 1 at the upper part of the liquid pool 8 as shown in FIG. As shown in FIG. 6, the coating liquid 4 also adheres to the edge 9 of the reverse fabric surface 12 of the web 1 (referred to as the back side). Therefore, the end face 1 of the coated web 10
As shown in FIG. 7, a large amount of the coating liquid 4 adheres to the fabric surface 12, and further, as shown in FIG.

In the latter case, the downstream pass roll will naturally be contaminated, and in the former case, the coating liquid will rise up the end surface 11 due to surface tension effects, etc., and the opposite surface 1 will be contaminated as shown in FIG.
If the liquid spreads to the 2 side or rises to the reverse side 12, it will stain the subsequent bath roll and the back side of the support, or if excess coating liquid adheres to the edge of the web. This will result in thickening of the web edges.

These phenomena contaminate the manufacturing process, stain the back edge of the support, and lower the commercial value, which is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a coating method that solves the above-mentioned problems, prevents web edges from rolling back, prevents thick coating on edges, and enables high-speed coating.

[Means for solving problems]

The object of the present invention is to apply a coating liquid to a continuously running support using a coating rod or a coating roller, in which coating is applied on the outer side of the support from the edge of the support where the coating rod or coating roller contacts the support. This is achieved by a coating method characterized by sucking the coating liquid on a rod or coating roller using a suction nozzle.

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

Pigment aqueous dispersions, colloidal solutions, etc. can be used. Further, the physical properties of the coating liquid are not particularly limited, but the coating liquid sucked from the support through the suction port has a lower viscosity, and a coating liquid of 100 cp or less, particularly 50 cp or less, passes through. Surface tension is also not particularly limited, but 50 dyn
Particularly preferable results can be obtained at less than e/cm.

The web in the present invention includes paper, plastic film, resin coated paper, aluminum web, synthetic paper and the like. 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, polycarbonate, and cellulose triacetate.

Cellulose acetates such as 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 may range from 0.01 to 1.
Those with about 0 fins are available and are advantageous in terms of versatility.

Although the coating rod or coating roller in the present invention is rotated in the same direction as the web in FIG. 1, it may be rotated in the opposite direction.

[For production]

In the method of applying a coating liquid to a continuously running support using the coating rod or coating roller of the present invention, the coating rod or coating roller is located outside the edge of the support where the coating rod or coating roller contacts the support. By suctioning the upper coating liquid with a suction nozzle, it is possible to remove the coating liquid that has climbed up to the web end surface or that is running around the web edge, so that the coating liquid that remains on the edge end surface after coating can be removed. It can also prevent thick coating on the back and edges of the product.

[Embodiment]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a side partial end view of a coating device showing one embodiment of the present invention. A support 1 is placed on the top of the coating rod 2.
There is a suction nozzle 13 for suctioning the swell on the base of the liquid pool 8 of the coating liquid 4 formed by the outer coating rod 2 and the weir member 6. Various types of suction nozzles can be used, but for example,
The nozzle etc. illustrated in 6-73579 can be used. The suction nozzle 13 is supported by a support 14 and connected via a tube 15 to suction means such as a vacuum pump.

That is, various diameters of the suction nozzle 13 can be selected depending on the diameter of the rod or the structure of the coater, but for example, when using a rod with a diameter of φ15,
Preferably, a 0 mm suction nozzle is used. It is preferable to set the adhesive clearance between the suction nozzle and the rod surface in a range of about 1 to 5 degrees. Suction pressure is 50-50
0 cmHg is preferred.

Further, the position of the suction nozzle relative to the support is preferably set within a range of about 2 to 10 degrees outward from the edge of the support. If it is placed too close to the support, thin coating will occur at the edge of the support 1 on the coated side. Also, if it is too far from the support 1, the coating liquid 4 in FIG.

It becomes impossible to suction the swelling of the coating liquid 4 as shown in FIG. If a suction nozzle is installed in the above-mentioned range, it is possible to suction the bulge 4 of the coating liquid as shown in FIGS. 5 and 6 formed by the rod and weir member, and the liquid as shown in The swelling can be reduced as shown in FIG. As shown in FIG. 3, the amount of adhesion on the end face after coating is also extremely small.

〔Effect of the invention〕

The present invention relates to a method of applying a coating liquid to a continuously running support using a coating rod or a coating roller, in which the coating rod or coating is applied outside the edge of the support where the coating rod or coating roller contacts the support. The coating method, which is characterized by sucking the coating liquid on the roller with a suction nozzle, prevents the coating liquid from running behind the edges of the web, prevents thick coating on the edges, and enables high-speed coating and drying. The quality has also improved.

[Brief explanation of the drawing]

FIG. 1 is a side partial cross-sectional view of one embodiment of a coating apparatus according to the coating method of the present invention, FIG. 4 is a sectional view of the edge after coating, FIG. 4 is a side sectional view of the coating device related to the conventional coating method, FIGS. 5 and 6 are sectional views of the web edge directly above the coating rod, and FIGS. FIG. 8 is a cross-sectional view of the web edge after application of FIGS. 5 and 6, respectively. 1... Web 2... Coating rod (bar) 3... Bar support member 4... Coating liquid 5... Supply port 6... Layer portion 7... Liquid supply guide groove 8...・Liquid pool 9
...Edge 10...Pa coated web 11...End surface 12...Reverse cloth surface 13...
Suction nozzle 14... Support 15... Tube (other 3
Figure 1

Claims (1)

[Claims] In a method of applying a coating liquid to a continuously running support using a coating rod or coating roller, the coating liquid on the coating rod or coating roller outside the edge of the support where the coating rod or coating roller and the support come in contact with each other. A coating method characterized by sucking the coating liquid using a suction nozzle.