JPH02214565A - Web coating device - Google Patents

Abstract

PURPOSE:To prevent the deposition of a coating film on a floating and supporting means by avoiding the start and finish of the rear coating when the part where the coating of a film on the front of a web is started or finished passes the floating and supporting means of a second coater. CONSTITUTION:A control means 23 is provided so that the coating of the rear is not started or finished when the part where the coating of a film on the web front 3a by a first coater 1 is started or finished passes the floating and supporting means 11 of the second coater 2. By such a structure, even if vibration is produced when the coating by the second coater 2 is started or finished, the deposition of an undried coating film on the web holding surface 11b of the means 11 is prevented, the coating process is stabilized, and the coating quality is maintained.

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 form 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 are 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 directly into contact with a support roll and continuously applying the coating to the opposite side (Special Publication No. 48-44171). ■Countless methods. A coating machine (coater) emits gas from the curved surface of the roll having small holes or slits to float the web.
Method of applying by pressing the tip of the
No. 9-17853) 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 a slide hopper, which are commonly used for coating photographic materials, cannot be applied.

For this reason, the present inventors have developed a first coater that applies the coating to the back surface of a continuously running web by contacting or supporting it with a floating support means, and a first coater that floats and supports the surface of the web using a floating support means and coats the back surface of the web. We have proposed a web coating device that coats one side with the first coater, and then coats the opposite side with the second coater while floatingly supporting the already coated side, and has put it into practical use. (Special request 1982)
-175801).

[Problem to be solved by the invention]

However, in the above-mentioned conventional web coating device, the behavior of the floating supported web becomes unstable at the start and end of coating, resulting in an accident in which the undried coating film on the floating supported surface adheres to the surface of the gas ejector. sometimes occurred.

That is, the continuously running web is deformed into an arc shape along the web bubble surface of the floating support means and is floated and supported. However, the flying height of the floating web changes greatly depending on whether or not the coating liquid from the second coater adheres to the back surface (see FIGS. 3(a) and 3(b)).

For this reason, large vibrations occur in the web at the start and end of coating, and if the amplitude is large, the coating film on the surface will come into contact with the gas ejector, and the undried coating will adhere to the surface of the gas ejector. There were times when I ended up doing this.

In view of the above points, it is an object of the present invention to provide a web coating device in which there is no risk of such contact accidents occurring at the start and end of coating.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a first coater that forms a coating film on the surface of a continuously running web whose back surface is in contact with or supported by a floating support means, and a first coater that forms a coating film on the surface of a continuously running web whose back surface is in contact with or is supported by a floating support means. A web coating apparatus comprising a second coater for forming a coating film on the back surface of the web, wherein coating start and end portions of the coating film on the surface of the web pass over floating support means of the second coater. A coating control means is provided to prevent the start or end of coating on the back side when the coating is on the opposite side ( The structure is such that large web vibrations do not occur due to the start and end of coating on the back side.

In general, for photographic materials that have coating films on both sides of the web, the start and end of coating are both on the front and back sides in order to increase production efficiency. It is generally known that the film is thicker than normal paint films.

However, as a result of the research conducted by the present inventors, it has not only become clear that the above-mentioned contact accidents can be prevented by avoiding the thick film parts and by adjusting the gas jet and coating conditions appropriately. , Start of coating on the front and back sides.
It was also found that by matching the ending, a large effect on warmth can be obtained.

〔Example〕

The present invention will be described below based on embodiments 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 change in the flying height of the web before and after the coating liquid is attached. 4 is a block diagram showing the system configuration of the coating control means, and FIG. 5 is a sectional view showing an example in which a gas ejector is constructed of a porous material.

In the figure, 1 is the first coater, 2 is the second coater,
The first and second coaters 1.2 are connected to the introduction section D of the web 3.
+ and the derivation section are provided in this order. The coater 1.2 is equipped with gushing slits la, lb and 2a, 2b, and is capable of performing two-layer coating with the coating liquid gushing out from the gushing slits la, lb and 2a, 2b. , the first coater 1 coats the surface 3a of the web 3 near the introduction part D1, and the second coater 2
The coating liquid is applied to the back surface 3b of the web 3 in the vicinity of the lead-out portion D2 to form a coating film, thereby realizing coating on both the front and back sides of the web 3.

The first coater 1 is configured to be able to move forward and backward by a drive means 21, and the second coater 2 is moved forward and backward by a drive means 22, and the driving timing thereof can be controlled by a coating control means 23, which will be described later.

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 +, it is supported in contact with the main roller 5, which is a contact support means, and turns around, and when passing the first coater 1,
A coating film is formed on the surface 3a by the coater 1, and the cold air zone 6
It is now being transported to.

Reference numeral 7.8 denotes a vacuum chamber, and the vacuum 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) to remove the coating liquid. This is to stabilize the transfer of the material to the surface (or back surface) of the web. One of the vacuum chambers 7.8 is the bead gap B of the first coater 1.

The other 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 surface 3a of the web 3 and promoting gelation of the coating film,
A group of conveying rollers 9 that transport the web 3 while cooling it by contacting and supporting the back surface 3b (uncoated surface), and a small hole (or) slit that cools the front surface 3a (already coated surface) of the web 3 by applying cold air to it. Group 10. This cold air zone 6
Although the temperature within 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.), it is usually cold air zone 6.
The temperature of the web 3 is adjusted to be around 10°C when it leaves the web and is conveyed to the second coater 2.

11 is a gas ejector used as a web floating support means;
The gas ejector 11 floats and supports the web 3 so that its surface 3
a (already coated surface) without protecting the web 3 from the second coater 2
This is for applying the coating liquid to the back surface 3b (uncoated surface) by passing it around near the surface. That is, the web holding surface 11a of the outer shell of the gas ejector 11 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 conveyed floating while being coated.

The timing of forward and backward movement of the coater 2 can be controlled by a coating control means 23. The coating control means 23 includes a coating film detection means 24 and a timing command means 2.
5 and the driving means 22.

At the start of coating, this coating control means 23 detects the approach of the coating film on the surface 3a of the web 3 by means of a coating film detection means 24, and sends a command from the commanding means 23 at a timing when the coating starting portion passes over the gas ejector 11. The second coater 2 is moved forward by the driving means 22 driven by the command of
The coating is now starting. On the other hand, at the end of coating, the coating film detecting means 24 detects the timing at which the finished part of the coating film on the back surface 3b passes over the gas jetter 11, and the driving means 22, which is also driven by a command from the commanding means 23, applies the coating. When the end portion of the second coater 2 is not on the gas ejector 11, the second coater 2 can be moved back to finish coating the back surface 3b.

Here, the coating film detection means 24 electrically detects a signal instructing the start of the forward and backward movement of the drive means 21 corresponding to the start of coating by the first coater 1, and thereafter, the timing command means 25 counts a certain period of time or If the configuration is such that the second coater is driven by arithmetic processing, a special sensor can be omitted. However, since the coating start portion of the surface 3a is not necessarily a straight line in the width direction but often has a certain width in the direction in which the web travels, a non-contact object detection sensor is used as the coating film detection means 24. It is desirable to provide a plurality of sensors in the width direction near the surface 3a of 3 to directly detect the coating film.

The timing command means 25 consists of some signal processing and arithmetic processing circuits. It should be noted that the timing command means 25 can be replaced by human judgment if the timing of passage over the gas ejector 11 at the start and end of coating is made known by an alarm or the like.

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, passes around the first coater 1 while being supported in contact with the main roller 5, and passes through the cold air zone 6. , the web holding surface 1 of the gas ejector 11
It goes around the vicinity of the second coater 2 while being floated and supported by 1a.

Next, coating is started, and the second coater 2 starts forming a coating film with the coating start portion of the coating film on the surface 3a of the web 3 facing the web holding surface 11a of the gas jetter 11. It will not be done.

That is, one method is to first move the second coater 2 forward using the drive means 22 to start coating the back surface 3b, and then move the first coater 1 forward using the drive means 21 to start coating the front surface 3a. A film is formed. On the contrary, when the first coater 1 forms the coating film on the surface 3a first, the coating film detection means 24 detects the coating film on the surface 3a, and the coating start part of the coating film is detected by the gas injector lI. The command means 25 causes the second coater 2 to move forward using the drive means 22 to form a coating film on the back surface 3b while avoiding the timing when the second coater 2 passes over the surface.

In the first and second coaters, there is a gushing slit la.

The front surface 3a and the back surface 3b are each coated with two layers by the coating liquid gushing out from 1b, 2a, and 2b.

At the end of the application, as at the start, the second coater 2 does not end the application on the back surface 3b while the end of application of the coating film on the front surface 3a faces the web holding surface 11a of the gas jetter 11. . That is, the coating film detection means 24 detects the timing at which the end portion of the coating film on the surface 3a passes over the gas ejector 11, and the drive means 22 moves the second coater 2 backward according to the command means 25 to avoid this timing. Then, the coating on the back surface 3b is completed. Therefore, even if the web vibrates greatly at the start and end of coating, the thicker part than usual is not on the gas ejector 11, so the gas ejector 11
If the coating conditions are appropriately set, there is no risk that the coating film on the surface 3a will adhere.

In this way, the web 3 with the coating film formed on the surface 3a is conveyed in contact with the conveyor rollers 9 while receiving cold air from the small hole group 10 in the cold air zone 6, and is cooled to around 10°C, and gas is ejected. It is transported to the container 11. Here, the web 3 with the coating film formed on the back surface 3b is led out from the lead-out portion Dt and conveyed to a cooling/drying process.

Note that the ejected gas used for floating and supporting the gas ejector may be any gas such as N, gas, air, etc. as long as it does not pose a safety problem, but air is most commonly used. The coated web with a coating film formed on the opposite side at the floating support section is then
After gelling the coating layer while applying cold air to both surfaces without contact in a cold air zone (not shown), the extraction portion D! However, even if the coated web fluctuates (or vibrates) in the direction perpendicular to the running direction in this non-contact gelling area or the non-contact drying zone, , it is configured so that it is absorbed by the floating support portion and does not propagate, allowing for uniform application.

Further, as the coated web used in the present invention, plastic films such as polyethylene terephthalate and cellulose triacetate, webs for photographic light-sensitive materials such as paper, etc. can be used.

Furthermore, there are no particular restrictions on the material that constitutes the curved surface of the floating support part, and any material may 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 this case, plastic materials such as Bakelite or acrylic resin can also be used in view of ease of drilling.

Further, 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, it is necessary to It is desirable to increase the gel strength of the coating layer by lowering the temperature of the coating layer to about 10°C.

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 (such as a roll-shaped outer shape or a part that allows gas to pass from the inside of the gas ejector to the outside). The gas ejector does not need to be a through hole, and may be a coating device equipped with a gas ejector of another configuration.For example, the shape of the gas ejector may be semi-cylindrical or elliptical, or the floating support Only the outer surface may have a curvature, and the rest may be flat.

On the other hand, the part that allows the gas supplied inside the gas ejector to pass to the outside has a major role in allowing the gas to pass through as well as providing pressure loss, so the cross-sectional shape of the through hole may be round or polygonal. Alternatively, as shown in FIG. 5, the outer shell of the gas ejector of the floating support section may be constructed of a porous material 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.

[Effects of the Invention] As described above, the present invention includes a first coater that forms a coating film on the surface of a continuously running web whose back surface is in contact with or is supported by a floating support means, and a first coater that forms a coating film on the surface of a continuous web that is supported by a floating support means. and a second coater for forming a coating film on the back surface of the web, when the application start and end portions of the coating film on the web surface pass over the floating support means, The present invention is characterized by having a coating control means that prevents the start and end of coating.
Even if vibrations occur at the beginning and end of coating, there is no risk of undried coating film adhering to the web-closing surface of the gas jet. Therefore, it is highly effective in stabilizing the coating process and maintaining coating quality.

[Brief explanation of the drawing]

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 change in the flying height of the web before and after the coating liquid is attached. 4 is a block diagram showing the system configuration of the coating control means, and FIG. 5 is a sectional view showing an example in which a gas ejector is constructed of a porous material. 1-First coater 2-Second coater 3...Web 3a--Web front surface 3b--Web back surface 4-Auxiliary roller 5--Main roller (contact support means) 6-Cold air zone 7.8-- - Decompression chamber 9 - Conveyance roller group 10 - Small hole group 11 - Gas ejector (floating support means) 11a - Web holding surface 11b - Non-steep holding surface 21.22 - Drive means 23 -Coating control means 24--Coating film detection means 25-Timing command means Dr'--Introduction part D! ---Derivation part B. B, ---Bead gap L--Coating liquid--Gas nozzle hole Patent applicant Coca Co., Ltd. Figure 3 (b) Figure 4 Section

Claims (1)

[Claims] a first coater that forms a coating film on the surface of the continuous running web whose back surface is in contact with or supported by a floating support means; and a second coater that forms a coating film on the back surface of the web that is floated and supported by the floating support means. In a web coating apparatus equipped with a second coater, when the coating start or finish portion of the coating film on the surface of the web passes over the floating support means of the second coater, the coating start and finish of the back side are controlled. A web coating device characterized in that it is provided with a coating control means for preventing coating from occurring.