JPH02211272A - Web coating device - Google Patents

Abstract

PURPOSE:To keep bead gap uniform to apply coating evenly by providing a means for restraining flotation of a web in a vacuum chamber under a coater. CONSTITUTION:There are vacuum chambers 7, 8, wherein a means for restraining flotation is provided in the chamber 8. The means for restraining flotation 12 prevents flotation and vibration of a web 3 from increasing in the chamber 8. The means 12 is made up of a cylindrical member having a smooth convex surface 12a on one side thereof, wherein the member is parallel to the width direction of the web 3 and disposed so that the convex surface 12a abuts the surface 3b of the web 3. Although the web 3 is subjected to the force due to the static pressure difference on the side of the chamber 8 in such a manner that flotation of the web is caused to increase, the surface 3a is restrained by the convex surface 12a of the means 12, thereby keeping the flotation of the web unchanged. As a result, coating can be applied evenly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an apparatus for floatingly supporting a web (band-shaped flexible support) and applying a coating liquid to a uniform film thickness.

More specifically, it relates to a device that applies one or more coating liquids to the surface of a web of photographic material, etc., opposite to the surface to be coated, by continuously moving the surface of the web while floating and supporting it. The present invention relates to a web coating device suitable for double-sided coating.

[Conventional technology]

Conventionally, various means and methods have been known as techniques for coating both sides of a web.

For example, ■Method of coating one side of the web, gelling it, and then bringing the gelled side into direct contact with a support roll and continuously applying the coating to the opposite side (Special Publication No. 48-44171) ■Small holes Alternatively, a method of ejecting gas from the curved surface of a roll having slits to float the web and pressing the tip of a coating machine (coater) against the web to coat the web (Special Publication No. 49-17
No. 853) are known.

However, with the above conventional technology, even if there is slight dust or scratches on the support roll that supports the gelled surface, the gelled coating surface will be disturbed, and a part of the coating layer may be left on the roll. The same problem occurs even if the adhesive remains, and maintenance is extremely difficult.

(2) If the peripheral speed of the support roll deviates even slightly from the conveyance speed of the web, the gelled coating layer will be greatly disturbed.

In addition, the technology described in Japanese Patent Publication No. 49-17853,
■As the width of the web increases, the difference in float in the middle direction of the web increases, making it impossible to press the tip of the coating machine evenly against the web, making it difficult to obtain a uniform coating layer over the entire surface of the web.

■ No consideration has been taken to suppress vibrations of the web before and after the coating machine, which tends to cause uneven coating.

(2) Since the method involves pressing the coating machine, there is a drawback that bead coating methods such as slide hoppers, which are generally used for coating photographic materials, cannot be applied.

For this reason, the present inventors installed a coater and a gas ejector at positions substantially facing each other across the continuously running web, and ejected gas from the gas ejector toward the web. proposed and put into practical use a coating method and an apparatus for coating the web using the coater while floating and supporting the web (Japanese Patent Application No. 175801/1983).
).

[Problem to be solved by the invention]

However, in the conventional web coating apparatus described above, vibration occurs in the web inside the vacuum chamber, and the amount of floating at the coating position changes due to the bulge of the web inside the vacuum chamber due to the suction of air by the vacuum chamber. As a result, coating failures such as streaks and unevenness may occur in the coating film.

That is, the web floatingly supported by the gas ejector deforms normally into an arc shape along the web-embracing surface of the gas ejector.

However, in the decompression chamber, the differential pressure between the static pressure on the side of the web holding surface and the pressure in the decompression chamber increases, so that the flying height of the web increases locally, resulting in a curved deformation as shown in FIG. Such deformation affects the amount of floating at the coating position, and vibrations at the deformed part tend to have large amplitudes and become unstable.Furthermore, when this vibration propagates to the bead gap, gap width fluctuations occur. This may cause coating failure (variation in coating film thickness).

However, conventional web floating type coating apparatuses have not taken any measures to prevent such phenomena.

In view of the above points, it is an object of the present invention to provide a web coating device that can maintain a uniform bead coating method by suppressing web deformation and abnormal vibrations in a vacuum chamber, and achieve stable and uniform coating. The purpose is

[Means for Solving the Problems] In order to achieve the above object, the present invention disposes a coater and a gas ejector at substantially opposite positions with a continuously running web in between, and the gas ejector In a web coating apparatus that performs coating by the coater while floating and supporting the web by jetting gas toward the web from the web, a means for regulating the flying height of the web is provided in a reduced pressure chamber below the coater. The structure is such that the floating amount of the web within the decompression chamber does not exceed a certain value and vibration of the web is suppressed.

〔Example〕

The present invention will be described below based on an embodiment shown in the accompanying drawings.

Fig. 1 is a vertical cross-sectional view showing the overall configuration of the web coating device of the present application, Fig. 2 is a perspective view of the gas jet and the vicinity of the second coater, and Fig. 3 is a depressurization showing an example in which a roll is used as a floating height regulating means. 4 is a sectional view of a decompression chamber showing an example of using a fixed rod, and FIG. 5 is a perspective view showing a floating height regulating means, (a) is a roll, (b) is a device with a bearing. (C) is a fixed rod, and FIG. 6 is a sectional view showing web deformation inside a decompression chamber in a conventional device.

In the figure, 1 is the first coater, 2 is the second coater,
The first and second coaters 1.2 are provided in this order at the introduction section and the exit section D2 of the web 3, respectively. The coater 1.2 is provided with gushing slits la, lb and 2a, 2b, respectively, and is capable of performing two-layer coating using the coating liquid gushing out from the gushing slits la, lb and 2a, 2b. That is, the first coater 1 has an introduction section and applies the coating liquid to the front surface 3a of the web 3 in the vicinity, and the second coater 2 has a discharge section and applies the coating liquid to the back surface 3b of the web 3 in the vicinity, thereby coating both sides of the web 3. It is structured so that it can be realized.

The web 3 is supported in contact with the auxiliary roller 4 and is moved to the introduction section D.
After being carried into the first coater 1, it is supported in contact with the main roller 5 and goes around, and when passing near the first coater 1, the coater 1
It is applied to the surface 3a and then transported to the cold air zone 6.

Reference numeral 7.8 denotes a vacuum chamber, and the vacuum chamber 7.8 appropriately sucks the bead of coating liquid from each coater 1 and 2 (coating liquid cross-linked from the coater to the web surface), and removes the coating liquid. The purpose is to stabilize the transfer of the material to the web surface. Among the vacuum chambers 7.8, one chamber 7 is provided below the bead gap B of the first coater 1, and the other chamber 8 is provided below the bead gap B2 of the second coater 2. This chamber 8
is internally equipped with a flying height regulating means 12, which will be described later.

The cold air zone 6 is for cooling the coating liquid applied to the surface 3a of the web 3 to promote gelation, and supports the back surface 3b (uncoated surface) of the web 3 while cooling it. Conveyance roller group 9 to be conveyed and surface 3a of web 3
It is equipped with a small hole (or) slit group IO that cools the (already coated surface) by applying cold air to it. The temperature in this cold air zone 6 depends on coating conditions (temperature of coating solution, coating thickness, coating speed, etc.) and web running conditions (web temperature, web thickness, web running speed, etc.), but usually, The temperature of the web 3 when it leaves the cold air zone 6 and is conveyed to the second coater 2 is 10°C.
It is adjusted so that it goes back and forth.

Reference numeral 11 denotes a gas ejector, and the gas ejector 11 floats and supports the web 3 to protect its front surface 3a (already coated surface), and then allows the web 3 to pass around near the second coater 2 and sprays the back surface 3b (coated surface).
This is for applying the coating liquid to the uncoated surface. That is, the web holding surface 11a of the outer shell of the gas ejector 1 is provided with a large number of fine gas ejection holes F, and the gas in the gas ejector 11 is ejected toward the surface 3a of the web 3, and the coater 2
The web 3 can be floated and conveyed while being coated.

The gas used for floating support here may be any gas, such as Nt gas or air, as long as it does not pose a safety problem, but air is most commonly used. The coated web coated on the opposite side in the floating support section is then exposed to cold air on both sides without contact in a cold air zone (not shown) to gel the coating layer. It is conveyed to the contact drying zone, but even if the coated web fluctuates (or vibrates) in the direction perpendicular to the running direction in the non-contact gelling part or the non-contact drying zone, the floating support section It is designed to be able to be applied uniformly without being absorbed and propagated.

The web flying height regulating means 12 is for preventing the flying height and vibration of the web 3 from increasing within the decompression chamber 8. The floating height regulating means 12 (FIG. 4) is
It is made of a rod-shaped member with a smooth convex surface 12a on at least one side, and is placed in the vacuum chamber 8 so that it is parallel to the width direction of the web 3 and that the convex surface 12a is in contact with the surface 3b (uncoated surface) of the web 3. It is provided. This floating height regulating means 12 includes a fixed rod B equipped with a rotatable roller r such as a cylindrical roll R1 as shown in FIG.
Alternatively, it may be constructed of a fixed rod K having at least one side surface convex over the entire width, as shown in FIG. 3(C).

Here, the cylindrical roll R of (a) may be rotatably supported or may be fixed.

The fixed rod B in b) is equipped with one or more rolls r each rotatably supported by a shaft, and each roll r contacts the surface of the web 3 with as little load as possible, and It is configured to be able to rotate.

In addition, the fixing rod (C) has at least a surface made of a material softer than the web, so that the surface facing the web 3 is formed into a smooth convex surface 12a, so that the surface of the web 3 is not damaged. The deformation vibration can be controlled.

In addition, even when the floating height regulating means 12 is composed of a cylindrical roll R or a fixed rod B1 with a roll or a fixed rod K, it can be appropriately arranged not only at a location but also at a plurality of locations as shown in the third figure. In this way, the deformation vibration of the web 3 may be restricted from multiple directions.

The web 3, which has not been coated on both sides, is carried into the introduction part D1 while being supported in contact with the auxiliary roller 4, and passed around the vicinity of the first coater 1 while being supported in contact with the main roller 5, and the sulfur sulfur is gushed out from the sulfur la and lb. Two layers of coating liquid are applied to the surface 3a.

Next, the web 3 is conveyed with contact support by conveying rollers 9 while receiving cold air from the small hole group 10 in the cold air zone 6.
It is cooled down to around °C and conveyed to the gas ejector 11. The second coater 2 coats the back surface 3b of the web 3, whose coated surface 3a is floated and supported by the web holding surface 11a of the gas ejector 11. At this time, the web 3 in the decompression chamber 8 receives pressure in the direction of increasing its flying height due to the static pressure difference between the gas ejector side and the decompression chamber side. Since it is smoothly regulated, the flying height hardly changes.

Therefore, changes in the floating amount distribution at the coating position due to increased flying height and increases in amplitude during vibration are also suppressed.

The web 3, which has been uniformly coated on both sides, is led out from the lead-out section D2 and transported to the cooling and drying process, where the both-side coating process is completed.

The web to be coated used in the present invention may be a plastic film such as polyethylene terephthalate or cellulose triacetate, or a web for photosensitive materials such as paper.

There are no particular restrictions on the material that makes up the curved surface of the floating support part, and any material can be used as long as it can withstand the internal pressure of the hollow part, but brass steel or stainless steel with hard chrome plating on the surface is preferable. When providing a through hole as in the case, plastic materials such as Bakelite or acrylic resin can also be used in view of ease of drilling.

Although the embodiments have been described above, the embodiments of the present invention are not limited thereto, and the gas ejector has a continuous curved surface as the outer surface of the non-contact support part in order to maintain high static pressure in the gap with the web. Any material may be used as long as it has a curved surface, allows gas to be ejected from the surface, and satisfies the conditions of the present invention, and may have a roll-like outer shape or a part that allows gas to pass from the inside to the outside of the gas ejector. There is no need to use a through hole, and a coating device equipped with a gas ejector of another configuration may be used. For example, the shape of the gas ejector may be a semi-cylindrical shape, an elliptical shape, or a shape in which only the floating support part has a curvature on the outer surface, and the other parts are flat.

On the other hand, the main role of the part that allows the gas supplied inside the gas ejector to pass outside is to allow the gas to pass through as well as to provide pressure loss, so the cross-sectional shape of the through hole may be round or polygonal. It may be a hole, or it may be of a type in which the outer shell of the gas ejector of the floating support portion is constituted by a porous body P made of sintered metal or the like.

Furthermore, instead of making the gas ejector hollow, it is also possible to construct the entire structure from the gas inlet to the outer surface of the floating support part from a porous body as described above.

[Experiment example]

Regarding the web coating device of the present invention, flying height regulating means 1
What kind of change occurs in the web flying height at the bead gap when 2 is used and when it is not used? Measurements were made for each case of B. As a result, as shown in Table 1, it was confirmed that the web flying height could be significantly stabilized by using the flying height regulating means 12.

Table 1 [Effects of the Invention] As described above, the present invention provides a coater and a gas ejector that are disposed at positions substantially facing each other across a continuously running web, and a coater and a gas ejector are disposed at positions substantially opposite to each other with a continuously running web interposed therebetween. A web coating device that performs coating by the coater while floating and supporting the web by blowing out gas, characterized in that means for regulating the flying height of the web is provided in a reduced pressure chamber below the coater. Therefore, the flying height of the web in the decompression chamber does not exceed a certain value. This makes the floating amount distribution in the width direction of the coating position uniform, and also significantly suppresses the increase in amplitude when vibration occurs, achieving a uniform bead gap, and coating while always maintaining a constant coating thickness. This has an outstanding effect on stabilizing the coating process and improving coating quality.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing the overall configuration of the web coating device of the present invention, Fig. 2 is a perspective view of the gas jet and the vicinity of the second coater, and Fig. 3 is a reduced pressure showing an example in which a roll is used as a floating height regulating means. 4 is a sectional view of a decompression chamber showing an example of using a fixed rod, and FIG. 5 is a perspective view showing a floating height regulating means. , (C) is a fixed rod, and FIG. 6 is a sectional view showing web deformation inside a decompression chamber in a conventional device. 1.--First coater 2--Second coater 3--Web 3a--Web front surface 3b--Web back surface 4--Auxiliary roller 5--Main roller 6--Cold air zone 7 .8-Decompression chamber 9--Transport roller group 10--Small hole group 11--Gas jetter 11 a-Web holding surface 1 l b-Non-nib holding surface 12--Web floating height regulating means 12a-- -Convex surface R-m-Roll (web flying height regulating means) B -Bearing (〃) K -Fixing rod (〃) D, -Introduction part Dt'-m-Derivation part B+, 13z-・-Bead gap L・- Coating liquid F-・-spout hole Fig. 2 Fig. 3 Fig. 4 Fig. 6 Fig. Fig.

Claims (1)

[Claims] A coater and a gas ejector are disposed at positions substantially facing each other across the continuously running web, and the gas is ejected from the gas ejector toward the web, thereby supporting the web while floating. A web coating apparatus that performs coating using the coater, characterized in that a web flying height regulating means is provided in a reduced pressure chamber below the coater.