JPH02119969A - Coater for web - Google Patents

Abstract

PURPOSE:To always maintain the temp. distribution of a gas ejector within a prescribed range by providing the flow passage of liquid whose temp. and flow rate have been controlled parallel to the width direction of a web to the outer shell of a web-nonheld face side of the gas ejector. CONSTITUTION:A plurality of flow passages 12 for regulating the temp. distribution of a gas ejector 11 are provided parallel to the width direction of a web 3 to the outer shell of a web-nonheld face 11b side opposite to a web holding face 11a of the gas ejector 11. The fluid R whose temp. and flow rate are previously controlled is passed therethrough. The web 3 is turned near to a second coater 2 by the gas ejector 11 while the surface 3a (already coated surface) of the web 3 is levitated, supported and protected thereby and coating liquid L is applied to the rear 3b (uncoated surface). Many fine jet holes F are provided to the web holding face 11a and the gas in the ejector 11 is jetted on the surface 3a of the web and thereby this web 3 is levitated and carried.

Description

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

[Prior Art] Conventionally, various means and methods have been known as techniques for coating both sides of a support.

For example, ■ A method in which the coating is applied to one side of the support, gelled, and then the gelled side is brought into direct contact with the support roll and applied continuously to the opposite side (Special Publication No. 4B-44171) ■ Small A method is known in which the support is floated by ejecting gas from the curved surface of a roll having holes or slits, and the coating is applied by pressing the tip of a coater against the support (Japanese Patent Publication No. 17853/1983).

However, with the above conventional technology, even if there is slight dust or scratches on the supporting 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 adhesion remains, and maintenance is extremely difficult. ■If the circumferential speed of the support roll deviates even slightly from the conveyance speed of the support, the gelled coating layer will be greatly disturbed. In the technology described in the -17853 publication,
■As the width of the support increases, the difference in the amount of floating in the center direction of the support increases, making it impossible to press the tip of the coating machine evenly against the support, making it difficult to obtain a uniform coating layer over the entire surface of the support. ■There is no consideration given to the vibration of the support before and after the coating machine, which tends to cause uneven coating.■Because the coating machine is pressed against the coating machine, it is difficult to use a slide hopper, etc. commonly used for coating photosensitive materials. There is a drawback that bead coating method cannot be applied.

For this reason, the present inventors installed a coater and a gas ejector at positions substantially facing each other across a continuously running support, and injected gas from the gas ejector toward the support. We have proposed and put into practical use a coating method and apparatus in which coating is carried out by the coater while supporting the support without contact by spraying (Japanese Patent Application No. 56-175).
801).

[Problem to be solved by the invention]

However, the conventional web coating apparatus described above has a phenomenon in which the gas jet is deformed due to heat transfer between the web and the coating layer (cooling in the cooling zone or heating by the coating liquid). Such thermal deformation of the gas jet is directly linked to deformation of the bead gap (the distance between the coater edge and the web, which has a large impact on the quality of coating) (particularly uneven distribution in the width direction of the web). This has the problem of causing non-uniformity and, in some cases, problems such as streak failures.

In view of the above-mentioned points, it is an object of the present invention to provide a web coating device that suppresses the occurrence of thermal deformation of a gas ejector.

[Means to solve the problem]

In order to achieve the above object, the present invention disposes a coater and a gas ejector at substantially opposite positions across a continuously running web, and directs gas toward the web from the gas ejector. In the web coating device in which the coating is carried out by the coater while floating and supporting the web by ejecting the gas, a flow path for a fluid whose temperature and flow rate are controlled is provided in the non-web-hugging outer shell of the gas ejector. It is provided parallel to the width direction of the web and is configured to maintain the temperature distribution of the gas jet within a predetermined range.

〔Example〕

The present invention will be described below with reference to an embodiment shown in the accompanying drawings.

Fig. 1 is a sectional view showing the overall configuration of the web coating device of the present invention, Fig. 2 is an enlarged perspective view of the gas ejector and the bead gap, and Fig. 3 is the thermal deformation of the gas ejector that affects the bead gap. FIG. 4 is a cross-sectional view showing another example of a gas ejector, and FIG. 5 is a cross-sectional view showing an example in which a porous body is used for the gas ejector.

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 inlet and outlet of the web 3, respectively.

Further, the coater 1.2 has gushing slits la and lb, respectively.
, and 2a, 2b, and the coating liquid gushing out from the slits la, lb, and 2a, 2b enables 2N coating. That is, the first coater 1 applies the coating liquid to the front surface 3a of the web 3 near the introduction section D1, and the second coater 2 applies the coating liquid to the back surface 3b of the web 3 near the exit section D2, thereby coating both sides of the web 3. It is structured so that it can be achieved.

The web 3 is carried into the introduction section D1 while being supported in contact with the auxiliary roller 4, and then rotated around while being supported in contact with the main roller 5, passing near the first coater 1, and passing through the vicinity of the first coater 1.
After being applied to the surface 3a, it is conveyed to the cold air zone 6.

Reference numeral 7.8 is a reduced pressure chamber, and the chamber 7.8 appropriately suctions a bead of coating liquid from each coater 1.2 (coating liquid cross-linked from the coater to the web surface).
This is to stabilize the transfer of the coating liquid to the web surface. The chamber 7 is provided below the bead gap B1 of the first coater 1, and the chamber 8 is provided below the bead gap B2 of the second coater 2.

The cold air zone 6 is for cooling the coating liquid applied to the front surface 3a of the web 3 to promote gelation, and cools it by contacting and supporting the back surface 3b (uncoated surface) of the web 3. The conveying roller group 9 conveys the web 3 while conveying the surface 3 of the web 3.
A (already coated surface) is provided with a group of small holes (or slits) 10 that cool the surface by applying cold air to it. The temperature in the cold air zone 6 depends on the coating conditions (temperature of the coating solution, coating thickness, coating speed, etc.) and web running conditions (web temperature, web thickness, web running speed, etc.), but usually the cold air The temperature of the web 3 when it leaves the zone 6 and is conveyed to the second coater 2 is 2~
It is adjusted to be around 15°C.

Reference numeral 11 denotes a gas ejector, and the ejector 11
The web 3 is rotated around the second coater 2 while a (already coated surface) is supported and protected by floating, and the coating liquid is applied to the back surface 3b (uncoated surface). That is, the web holding surface 11a of the outer shell of the gas ejector 11 is provided with a large number of micro ejection holes F, and the gas in the ejector 11 is ejected toward the surface 3a of the web 3, and the coating is performed by the coater 2. The web 3 can be transported while floating.

12 is a flow path, and the flow path I2 is for adjusting the temperature distribution of the gas ejector 11. A plurality of flow passages 12 are provided in the outer shell on the non-web holding surface 11b side opposite to the web holding surface 12a of the gas ejector 11 in parallel with the width direction of the web 3, and the temperature and flow rate are controlled in advance. It is designed to allow fluid R to flow through it. That is, the temperature and flow rate of the fluid R can be appropriately controlled by web conveyance conditions (web running speed, web thickness, web temperature, etc.) and coating conditions (coating liquid temperature, coating film thickness, etc.).

Further, the temperature and flow rate of the fluid R are also controlled depending on whether coating is being performed or not. The type of fluid R to be passed through the flow path 12 is not particularly limited, but it is generally desirable to use air if it is a gas, and water if it is a liquid. In addition to this, anything can be used as long as it does not cause problems in equipment maintenance or safety, such as N□ gas, chlorofluorocarbon gas, and oil. For example, if water at a temperature of 3 to 5°C is appropriately distributed as the fluid R through the flow path 12, the thermal deformation of the gas ejector 11 due to heat transfer between the web and the coating layer can be reduced by the cooling effect of the fluid R. It can be suppressed by

On the other hand, the gas used for floating support in the present invention may be any gas, such as N2 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 in a non-contact state in a cold air zone (not shown) to gel the coated layer, and then transported to a non-contact drying zone. However, in this invention, in this non-contact gelling part or non-contact drying zone,
It has been found that even if the support to be coated changes (or vibrates) in a direction perpendicular to the running direction, it is absorbed by the floating support and does not propagate, allowing for uniform coating.

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 of the web-closing surface that serves as 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 wire or stainless steel with hard chrome plating on the surface is preferable. When providing a through hole as in the above, plastic materials such as Bakelite or acrylic resin can also be used in view of ease of drilling.

Furthermore, in carrying out the present invention, in order to prevent gas from colliding with the gelled coating layer in the floating support section and preventing the coating layer from being disturbed by the dynamic pressure of this gas, the gas enters the floating support section. The temperature of the coating layer immediately before is 2 to 15 degrees.
It is desirable to increase the gel strength of the coating layer by using C.

The web 3, which has not been coated on both sides, is carried into the introduction section while being supported in contact with the auxiliary roller 4. The web 3, which has not been coated on both sides, is carried into the introduction section while being supported in contact with the main roller 5, and passes around the first coater l while being supported in contact with the main opening roller 5. Two layers are applied to the surface 3a by the coating liquid gushing out from the surface. Next, the web 3 is placed in the cold air zone 6
While receiving cold air from the small hole group IO, the material is conveyed in contact with conveyance rollers 9 and cooled to around 2 to 15°C.
The gas is transported 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 ejector 11. Here, the already applied layer on the surface 3a is the gas ejector surface 1.
1a, and there is heat transfer between the two through radiation and conduction.

Therefore, before and after the coating liquid adheres to the back surface 3b, the surface 3a
The temperature of the upper coating layer changes and the temperature changes to the gas injector.
The fluid R whose temperature and flow rate are changed as appropriate depending on coating conditions and web conveyance conditions, which affects the temperature distribution above, is in the flow path 1.
2, the temperature distribution on the gas jet rtll is appropriately adjusted. Therefore, thermal deformation of the gas ejector 11 is significantly suppressed, and the amount of deformation of the bead gap Bz is maintained within 50 μm at most. 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.

Although the present invention has been described above, the embodiments of the present invention are not limited thereto, and the gas ejector has a continuous curved surface in the floating support part in order to maintain high static pressure in the gap with the web, and the curved surface Any material may be used as long as the gas can be ejected from the gas ejector and the conditions of the present invention are satisfied, and the outer shape may be a roll shape, or the portion that allows gas to pass from the inside of the gas ejector to the outside may be a through hole. It is not necessary, 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 semi-cylindrical or elliptical, and as shown in Fig. 4, which shows another example of the gas ejector, only the floating support part has a curvature on the outer surface, and the other parts are flat. It is also possible to have a form composed of . On the other hand, this is the part that allows the gas supplied inside the gas ejector to pass to the outside, and its major role is to allow the gas to pass and provide pressure loss.

Any format is fine as long as this condition is met,
In the case of a through hole, the shape may be a round hole or a polygonal hole, and as shown in FIG.
Alternatively, the outer shell of the gas ejector of the floating support section may be configured. Furthermore, instead of making the gas ejector hollow, it is also possible to construct the gas ejector from the gas inlet to the outer surface of the non-contact support part entirely from a porous body as described above.

In addition, as a method for coating one side and the opposite side of the support to be coated, conventionally known methods such as bead coating method and extrusion coating method can be used.

〔Effect of the invention〕

As described above, the present invention includes disposing a coater and a gas ejector at substantially opposite positions across a continuously running web, and ejecting gas toward the web from the gas ejector. Accordingly, in the web coating device in which coating is performed by the coater while floating and supporting the web, a flow path for a fluid whose temperature and flow rate are controlled is provided in the web holding surface of the ejector in the width direction of the web. Since they are arranged in parallel, the temperature distribution of the gas ejector can be maintained within a predetermined range at all times by appropriately adjusting the heat transfer around the gas ejector.

Therefore, deformation of the gas ejector due to temperature changes is suppressed,
The bead gap can be maintained within an acceptable range.

As a result, uniform coating on both sides can always be achieved regardless of changes in coating conditions or web conveyance conditions, which has a great effect on stabilizing the web manufacturing process and improving quality.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the overall configuration of the web coating device of the present invention, Fig. 2 is an enlarged perspective view of the gas ejector and the bead gap, and Fig. 3 is the effect of thermal deformation of the gas ejector on the bead gap. FIG. 4 is a cross-sectional view in the horizontal direction showing the influence, FIG. 4 is a cross-sectional view showing another example of the gas ejector, and FIG. 5 is a cross-sectional view showing an example in which a porous body is used for the gas ejector. l.--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--Transportation Roller group 10 - Small hole group 11 - Gas ejector 11 a - Web holding surface 11b - Non-web holding surface 12 - Distribution path, - m - Inlet part D2 - Outlet part B+, Bz L - Coating liquid F - Nozzle Bead Gap Fluid Co., Ltd. Figure 3 ■ Figure Figure

Claims (1)

[Claims] By arranging a coater and a gas ejector at positions substantially facing each other across a continuously running web, and ejecting gas toward the web from the expected ejector,
In a web coating device that performs coating by the coater while floating and supporting the web, a fluid flow passage whose temperature and flow rate are controlled is provided in the outer shell on the non-web-hugging surface side opposite to the web-hugging surface of the ejector; A web coating device, characterized in that it is provided parallel to the width direction of the web.