JPH0365266A - Coating method and device - Google Patents

Abstract

PURPOSE:To interrupt accompanying air of a web and form a uniform film without generating marks or scratches on the surface of the web by spraying the air, in the direction opposite to the travelling direction of the web, to the web surface to be coated just before coating uniformly in the width direction of the web. CONSTITUTION:A single or a plurality of layers of coating solution 4 are jetted out of a slot 5S and an injector 5 to a continuously travelling web 2 and are made in collision with the web 2 as self-fallen coating solution films. Then, air in the direction oppose to the travelling direction of the web is sprayed onto a web coating surface just before coating uniformly in the width direction of the web 2 by means of an accompanying air interrupting tool 8. As a result, even if the web is not supported by a backup roller, a uniform film can be formed without making marks or scratches on the surface of the web by interrupting the air accompanying the web.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to continuous running paper in the production of photographic film, photographic paper, magnetic recording tape, adhesive tape, pressure-sensitive recording paper, offset plate, etc. The present invention relates to a method and apparatus for applying various liquid materials to a strip-shaped support (hereinafter referred to as a "web").

More specifically, the present invention relates to a method and apparatus for applying a thin film of free-falling coating liquid by colliding with a running web.

[Conventional technology]

The curtain coating method is a method in which a free-falling curtain film made of one or more coating liquids is formed, and the curtain film is made to collide with the object to be coated to form a coating film on the object. It has been used for coating iron plates, etc., but due to the demand for improved coating quality, high-precision coating is gradually required, and in recent years, Japanese Patent Publication Nos. 49-24133 and 4
As disclosed in Japanese Patent Publication No. 9-35447, curtain coating methods have come to be applied to fields where precision is particularly required, such as the production of photographic light-sensitive materials.

The method disclosed in Japanese Patent Publication Nos. 49-24133 and 49-35477 involves applying one or more types of coating liquid to two support members ( (hereinafter referred to as "edge guide") to form a thin film-like free-falling curtain,
It is applied to a continuously running web.

Obtaining a coated product of the same quality by increasing the coating speed than before is an extremely important technique in the manufacturing process of photosensitive materials and magnetic recording media, which require high coating quality.

One of the problems in increasing the coating speed in such a high-quality coating process is that the running of the web causes so-called wind, which entrains air and causes the falling curtain film to sway, causing damage to the coated product. There is a phenomenon where it remains as a uniform spot. That is, the air flow carried by the running web collides with the curtain membrane and the contact line between the curtain membrane and the web (hereinafter referred to as the "dynamic contact line"), causing the curtain membrane and the dynamic contact line to swing. This is a phenomenon that occurs as the web travels faster.
The direction is around 1, where the amount of entrained air increases and occurs.

Since defects such as spots are fatal in photosensitive materials and magnetic recording media, suppressing the occurrence of this phenomenon is an important issue in speeding up coating.

As a method of suppressing the adverse effects caused by the entrained wind of a running web, there is a method of providing an air shield in front of the dynamic contact line of the curtain film, as disclosed in Japanese Patent Publication No. 49-24133.

FIG. 3 shows a side view of an example of a curtain coating device comprising a conventional slide hopper type liquid supply device, in which a shield plate 1 is installed in front of a dynamic contact line 10 of the curtain film. Fourth
The figure shows a side view of an example of a curtain coating device consisting of an extrusion type liquid injector. An air suction port 3 for an air shield is installed in front of the dynamic contact line 10 of the curtain membrane, and the air suction port 3 is installed in front of the dynamic contact line 10 of the curtain membrane. The entrained wind of the web is sucked to prevent damage to the curtain membrane due to the entrained wind of the web.

[Problem to be solved by the invention]

However, the tip of the shield plate 1 shown in FIG. 3 and the air suction port 3 shown in FIG. 4 must be placed close to the web 2 shown so as not to come into contact with it. That is, if the gap between the shield plate 1l and the web 2 and the gap between the air suction port 3 and the web 2 are large, the entrained wind of the web will not be blocked or suctioned and will collide with the curtain membrane, causing the curtain membrane to be damaged. This is because the oscillation causes non-uniformity of the coating film.

In particular, the gap between the shield [1] and the web 2 needs to be small enough to make contact with the web or not, so that vertical vibrations of the web, such as when the web 2 is running supported by a backup roll, are prevented. Unless it is installed in a completely free area, the web surface will be damaged in areas where the web vibrates up and down.

In addition, even if the web is supported by a backup roll, if thick webs are joined and coated by continuous running, it is necessary to install the shield plate 1 based on the thick web. In that case, a sufficient air shield effect could not be produced.

In the method of installing the air suction port 3 to suck the entrained wind of the web, unless the web is supported by a backup roll, if the gap between the air suction port 3 and the web 2 is made small, the air suction port There was a problem in that the web 2 was attracted to the web 2 and the surface of the web was damaged.

When the web is not supported by a backup roll, Japanese Patent Application Laid-Open Nos. 53-115754 and 53-11
5759, when curtain coating is performed while supporting the back side of the web by gas pressure, or when curtain coating is performed at a location away from the backup roll, that is, at the midpoint between the rolls.

An object of the present invention is to solve the above-mentioned problems, and in a method of performing curtain coating using a slide hopper type liquid injection device or an extrusion type liquid injection device, even when the web is not supported by a backup roller, the web surface can be To provide a coating method and apparatus capable of obtaining a uniform coating film by blocking entrained wind of a web without worrying about damaging the web.

[! ! [Means for Solving a Problem] The above objects of the present invention are as follows: (1) A single layer or multiple layers of coating liquid are flowed out from a slot of a liquid injector onto a continuously running web, and the coating liquid is free-falling. A coating method in which the web is impinged on the web as a film, characterized in that air is sprayed uniformly across the width of the web in a direction opposite to the running direction of the web onto the coated surface of the web immediately before coating.

(2) In a curtain coating device that applies a coating liquid to a continuously running web, a coating liquid is placed on the upstream side of the curtain film at a position adjacent to the curtain film and close to the web for the entire length of the web in the radial direction. 1. A coating device comprising an entrainment air blocking device having an air blowing slit that opens in a direction opposite to the running direction of the web.

achieved by

In the present invention, spraying air uniformly across the width of the web in the opposite direction to the running direction of the web on the coating surface of the web immediately before coating means, specifically, that air is sprayed onto the coating surface of the web immediately before coating, in the upstream side of the curtain film of the coating liquid, adjacent to the curtain film. In addition, this is carried out using an entrained air blocking device having an air blowing slit that opens in a direction opposite to the running direction of the web over the entire width of the web at a position close to the web, but the curtain film of the air blowing slot of the entrained air blocking device The distance between the upstream side of the curtain film and the curtain film is preferably within 40 degrees.

When the distance between adjacent devices exceeds 40 m, the effect rapidly weakens.

Also, as the location of the air blowing slot close to the web, it is optimal to be within 3 tm from the web.

The angle of the air blowing loss slot in the direction opposite to the running direction of the web is preferably in the range of 45 to 55 degrees, and in order to spray uniformly across the width of the web, it is necessary to set the air blowing slot sufficiently uniformly across the width in the entrained air blocking device. Preferably, measures are taken to ensure a uniform pressure distribution, and the slot clearance is narrowly narrowed to 0.3 to 0.7 wa.

The blowing speed is preferably 5 to 14 m/sec. To further explain the present invention, the web in the present invention includes paper, plastic film, metal, resin coated paper, synthetic paper, etc. The material of the plastic film is, for example, polyolefin such as polyethylene or polypropylene, polyvinyl acetate, or polyvinyl chloride.

Vinyl polymers such as polystyrene, 6.6-nylon, 6
- Polyamides such as nylon, polyesters such as polyethylene terephthalate and polyethylene-2-6-naphthalate, polycarbonates, cellulose triacetate,
Cellulose acetates such as cellulose diacetate are used.

Further, the resin used for the resin coated paper is typically polyolefin, but is not necessarily limited thereto, and the metal web includes, for example, an aluminum web.

In addition, the "coating liquid" in the present invention refers to various liquids and! depending on the application. I include certain things, for example, light-sensitive emulsion layers, subbing layers, as in photographic light-sensitive materials.

Coating liquid for protective layer, back layer, etc.; magnetic layer, undercoat layer, lubricating layer, protective layer as in magnetic recording media.

Coating liquid for back layer, etc.; Other adhesive layer 1 colored layer.

Examples include coating liquids for rust prevention layers, etc., and these coating liquids must contain a water-soluble binder or an organic binder.

The liquid injection device in the present invention refers to a slide hopper type liquid injection device, an extrusion type liquid injection device, or a slide extrusion type liquid injection device that is a mixture of both.

Implementation of the present invention based on the drawings below! ! I will explain this in more detail.

Figure 1 shows the implementation of the present invention! ! FIG. 2 is a schematic side sectional view of the curtain coating device. The coating liquid 4 is sent to the extrusion type liquid injector 5 by a pump (not shown), and is discharged from the slot 5S between the edge guides 6a and 6b.
A curtain film 4C is formed and applied by falling onto the web 2 which is supported by rollers 7a and 7b and is running in the direction of the arrow.

The entrained air barrier 8 is disposed adjacent to and in front of the dynamic contact line 10 where the curtain membrane 4C collides with the web, and air is fed into the entrained air barrier 8 by a blower (not shown) and blown out. Surin) is ejected from 8s.

Here, since the flow of air ejected from the entrained air cutoff M8 needs to be ejected uniformly and without disturbance across the width direction of the entrained air cutoff device 8, the entrained air cutoff R8 has two slits 9s in the air chamber 9. and blur) 9p
is provided to make the dynamic pressure distribution uniform in the width direction and to keep the amount of air discharged in the width direction constant. Slit blowout angle α-45° to 55° of entrained air blocking device 8, blowout slit 8s
Gap between tip of web 2 and web 2 y-2 to 3-9 Blowout slit 8
The gap between the blowing tip and the curtain membrane 4c is within x-40mm,
conditions are most suitable.

[For production]

Next, the operation of the present coating method and apparatus configured as described above will be explained.

The coating liquid 4 discharged from the slot 5S of the liquid injector 5 becomes a free-falling curtain film 4C while the width of the free-falling coating liquid film is regulated by a pair of edge guides 6a and 6b, and is supported by rollers 7a and 7b. The liquid flows down onto the surface of the running web 2 to form a coating film.

At this time, as shown in FIG.
c, an upward airflow is generated along the curtain membrane 4c, and the surface of the curtain membrane 4c is swayed. In addition, near the dynamic contact line IO, the air flow generated when the curtain 114c freely falls and the entrained wind due to the running of the web 2 collide, creating an air vortex, and the dynamic contact line IO is near the curtain 114c.
The coating is not uniform in the width direction, and the oscillation is severe, resulting in an inability to obtain a uniform coating film. Naturally, as the running speed of the web increases, the curtain film 4c and the dynamic contact line 1
At 0, the fluctuation is large, and when the flow rate of the coating liquid is relatively low, the dynamic contact line 10 is destroyed by the entrained wind, making the coating operation difficult.

As shown in FIG.
is placed adjacent to the curtain membrane 4c before the dynamic contact line 10 that collides with the web 2, and uniform air is blown out from the blow-off slit 8g to form an air curtain. The entrained air is blocked by the entrained air blocker 8, and the flow flows along the front surface of the entrained air blocker 8, and the influence of the entrained wind on the web is eliminated by the entrained air blocker 8.

Here, the wind-shielding effect of the air curtain is determined by the clearance of the blow-off slit 8S and the blow-off wind speed from the slit 8S, and the value of the clearance is 0.
3 to 0.7 m/sec, and the wind speed is more preferably 5 m/sec to 3 m/sec.

The gap y between the outlet of the blow-off slit 8S and the web 2 is 2 to 5 m.
It is preferable that the web 2 is in the range of
Since it works in the direction of pressing, it does not damage the surface of the web.

Although the above description is based on the embodiments of the present invention, the present invention is not limited to such embodiments, and modifications as shown in FIG. 2 are possible.

FIG. 2 further shows an air suction pipe 1 between the blowout slit 8s of the entrained air blocking device 8 of the present invention and the curtain 114e.
1. In this case, the amount of suction from the air suction pipe 11 is very small, and the air carried by the curtain 114c is removed, thereby further stabilizing the dynamic contact wAlo.

Further, the entrained air blocking device of the present invention can be used when coating is carried out while a running web is supported by a backup roll, or by coating methods such as those disclosed in JP-A-53-11574 and JP-A-53-115759. and equipment.

〔Example〕

Example 1 A coating solution having the composition and physical properties shown in Table 1 was coated with an extrusion type curtain coating device as shown in Figure 1.
Thickness 11001J being conveyed at a speed of 00rn/min
, was coated at a coating weight of 60 cc/rrf (wet state) on a polyethylene terephthalate film provided with a gelatin layer having a width of 1 Bcm.

Table 1 Here the curtain height is 10c++,! ! ! The cloth is 15c
m, and the entrained air blocker 8 with a width of 18 cm is connected to the dynamic contact line 1.
Before 0, the distance x between the curtain 114c and the blowout slit 8S
=40m, distance My between blowout slit 8S and web surface 2
=3txm, blowout angle α-45 of blowout slit 8S
5.5 m/s
It was supplied from a blower so that ea.

During the coating operation, there was almost no fluctuation of the curtain film 4C and the dynamic contact line 10, and the surface condition of the coating film after drying was uniform.

In addition, when the blower was stopped in this state and the coating was applied, fluctuations occurred in the curtain film 4c and the dynamic contact line 10, and the surface condition of the coating film after drying was streaky and uneven.

Furthermore, using the above coating liquid and curtain coating device, the web speed was adjusted to 150 n/e+in and 200 n/wi.
After coating with a large value of n, we compared and observed the surface condition of the coating film with and without the air blown from the entrained air blocker, and found that a uniform coated surface was maintained when air was blown out from the entrained air blocker. When the blower was stopped, the streaks became more numerous and more obvious as the web speed increased.

Example 2 The relationship between the coating speed and the flow rate per unit width that can be coated when the coating method of the present invention and the conventional coating method are performed using the same coating device, coating liquid, and physical properties is as follows. The 0 curve (a) shown in FIG. 5 is based on the present invention, the 1 curve (c) is based on the conventional coating method, and the coating method is based on the conventional coating method.

■ With this invention, the lowest flow rate per unit width is 0.7
cc/C1-5ec was 0.6CC/CI
It was possible to reduce the amount to -5ec and apply it. That is,
The present invention enables thinner coating.

- The present invention has made it possible to coat up to 250 m/win, whereas conventionally it was only possible to coat up to about 200 m/sin. In other words, it has become possible to increase the maximum coating speed.

The above values vary depending on the concentration of the coating solution, the height of the support, the curtain film, additives to the coating solution, etc., but the effect of the wind shield device under certain conditions is clear.

〔Effect of the invention〕

As shown above, the coating method and apparatus of the present invention make it possible to block web-entrained wind and eliminate diversion of the web and curtain film, eliminate the fear of damaging the web surface, and eliminate the fear of spots. A uniform coating film could be obtained, and coating quality and yield could be improved.

Furthermore, it is now possible to further lower the minimum possible flow rate per unit width than before, and increase the maximum coating speed by 20 to 30%, greatly contributing to improved coating quality and productivity. is possible

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an extrusion-type curtain coating device equipped with an entrainment air barrier, which is an embodiment of the coating method and device of the present invention, and FIG. FIGS. 3 and 4 are schematic side views of a coating device with an air suction pipe attached to an entrainment air cutoff device, which is an embodiment of the present invention, and FIGS. FIG. 5 is a diagram showing the relationship between the flow rate per unit width and the coating speed when using the coating device of the present invention and when using the conventional coating device. 1...Shield plate 2...Web 3...Air suction port 4...Coating liquid 4c...Curtain membrane 5...Extrusion type liquid injector 5s...Slots 6a, 6b ...Edge guide 7a. 8 ・ ・ 8 s ・ 9 ・ ・ 9 S ・ 10 ・ 11 ・ 7b...Roller・Entrained air blocker・・Blowout slit・Air chamber・・Slit・・Dynamic contact line・・Air suction pipe 9P・・Pocket (3 others) W4Afr Yachiri>it (CC/c = sec,) Procedural Amendment October 16, 1999

Claims (2)

[Claims] (1) Web coating immediately before coating in a coating method in which a single layer or multiple layers of coating solution flow out from a slot of a liquid injector onto a continuously running web and collide with the web as a self-falling coating liquid film. A coating method characterized by spraying air uniformly across the width of the web in a direction opposite to the running direction of the web. (2) In a curtain coating device that applies a coating liquid to a continuously running web, a coating liquid is placed on the upstream side of the curtain film at a position adjacent to the curtain film and close to the web along the entire width direction of the web. What is claimed is: 1. A coating device comprising an entrainment air blocker having an air blowing slit that opens in the direction opposite to the running direction of the web.