JPH02211270A - Web coating device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of coating troubles by providing a curved edge which follows the deformation in the transversal direction of a web on a coater. CONSTITUTION:Uncoated web 3 is brought into an introducing port D1, being in contact with an auxiliary roller 4 and supported thereby, and then goes around the vicinity of a first coater 1, whereby its surface 3a is coated with two layers of coating liquid L coming through spout slits 1a, 1b, following which the web 3 is supported and carried by carrier rollers 9, while being subjected to cold air flow from a group of small holes 10 in a cold air flow zone 6, so that the web 3 is cooled and carried to a gas blow-off device 11. Further, the rear surface 3b is coated by means of a second coater 2, wherein a curved edge E2 and the web 3, facing each other, are curved in the same direction so as to form a curved bead gap B2. As a result, the coating process is stabilized and quality of coating can be improved.

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, the surface of a web of photographic material or the like opposite to the coated surface is continuously run while being supported in a floating manner.
The present invention relates to an apparatus for applying a seed or two or more types of coating liquids, and particularly to a web coating apparatus suitable for continuous double-sided coating.

[Conventional technology]

Conventionally, various means and methods have been known as techniques for coating both sides of a support (web). For example, (2) 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 a support roll and continuously applied to the opposite side (
(Japanese Patent Publication No. 48-44171) ■ A coating machine (coater) that floats the support by ejecting gas from the curved surface of the roll, which has numerous small holes or slits.
A method of applying by pressing the tip of the
-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 circumferential speed of the support roll deviates even slightly from the transport speed of the support, 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 support increases, the difference in float in the middle 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. .

■Since no consideration has been taken to suppress vibration of the support before and after the coating machine, uneven coating is likely to occur.

(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 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 floating and supporting the support by ejecting water (Japanese Patent Application No. 56-17580).
1).

[Problem to be solved by the invention]

In the conventional web coating apparatus described above, coating failures may occur due to non-uniformity of the bead gap.

That is, the web floatingly supported by the gas ejector deforms into a gentle concave or convex shape in the width direction of the web depending on the amount of ejected gas retained between the gas ejector and the web. There is a large amount of retained gas in the center (,
If the amount is small at both ends, the web deforms into a gentle convex shape (FIG. 6(b), when viewed in a horizontal cross-sectional view with the gas ejector facing downward).

However, the coater edge of conventional equipment is straight,
Since the bead gap is formed parallel to the straight edge of the gas ejector, deformation in the width direction of the web is directly linked to non-uniformity of the bead gap.
This was a cause of coating failure.

In view of the above points, the present invention provides a web coating device that can maintain a uniform bead gap and achieve uniform coating on a web that has been deformed due to the distribution in the width direction of the retained amount of gas ejected from a gas ejector. The purpose is to

[Means for Solving the Problem] In order to achieve the above object, the present invention disposes a coater and a gas jet at positions substantially opposite to each other across a continuously running web, and In a web coating device that performs coating by the coater while floating and supporting the web by jetting gas toward the web from a container, the coater is provided with a curved edge that follows the deformation of the web in the width direction. It is characterized by
The structure is such that the distance between the web and the coater edge is approximately constant at any location in the width direction.

[Example] The present invention will be described below based on an example shown in the accompanying drawings.

Fig. 1 is a vertical cross-sectional view showing the overall configuration of the web coating apparatus of the present application, Fig. 2 is a perspective view of a part of the second coater, Fig. 3(a),
) is a horizontal cross-sectional view showing the relationship between a coater with a curved edge, a web, and a gas ejector, FIG. 4 is a cross-sectional view showing another embodiment of the gas ejector, and FIG. FIG. 6 is a horizontal sectional view showing the relationship between a coater, a web, and a gas ejector in a conventional apparatus having a linear edge.

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 Dt of the web 3, respectively.

The coaters 1.2 are each provided with an outflow slit la, lb and 2a, 2b, the outflow slits la, lb and 2
The coating liquid gushing out from a and 2b enables two-layer coating (Figure 1.2).

Note that the number of slits in the first and second coaters 1.2 is not limited to this. Multilayer coating is possible with the coating liquid flowing out from each slit.

The first coater 1 applies the coating liquid to the front surface 3a of the web 3 near the introduction section, and the second coater 2 applies the coating liquid to the back surface 3b of the web 3 near the exit section D2, thereby realizing double-sided coating of the web 3. It is configured so that it can be done. The straight edge El of the first coater 1 is a straight line, and the bead gap B is straight and parallel to the web 3 that is supported in contact with the main roller 5.
, has come to form.

On the other hand, the curved edge E2 of the second coater 2 has a gently curved shape that follows the deformation of the web 3 in the width direction. That is, the curved edge E2 is connected to the gas ejector 11, which will be described later.
A bead gap B2 having a constant distance in the width direction is formed along the slightly curved web 3 which is floated and supported by the web 3 (FIG. 3). The curved edge ExO has a gas ejector 11 and a web in which the direction and amount of curvature in the width direction are influenced by the width, thickness, elasticity of the web 3, the ejection pressure of the gas ejector 11, the degree of pressure reduction of the decompression chamber, etc. Of course, this depends on the distribution of the amount of gas retained between 3 and 3, and depending on these conditions, a convex edge or a concave edge is formed.

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

Reference numeral 7.8 denotes a vacuum chamber, and the vacuum chamber 7.8 properly suctions the bead (coating solution cross-linked from the coater to the web surface) of the coating liquid from each coater 1.2 to remove 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 B1 of the first coater 1, and 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 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 web 3 includes a group of conveying rollers 9 that convey the web 3 while conveying the web 3, and a group of small holes (or slits) 10 that cool the surface 3a (already coated surface) of the web 3 by applying cold air to it. The temperature in the cold air zone 6 depends on the coating conditions (temperature of the coating liquid, thickness of the coating film, etc.) and web running conditions (web temperature, web thickness, web running speed, etc.), but usually the temperature in the cold air zone 6 is The temperature of the web 3 when it comes out and is conveyed to the second coater 2 is adjusted to be around 10°C.

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, thereby spraying the back surface 3b.
This is for applying coating liquid to (uncoated surface).

That is, a large number of fine gas ejection holes F are arranged in the web-closing surface 11a of the outer shell of the gas ejector 11, and the gas ejector 11
The gas inside is ejected toward the surface 3a of the web 3, so that the web 3 can be floated and conveyed while being coated by the coater 2.

The gas used for non-contact support in this invention is N
2 Gas, air, etc. can be used as long as there is no 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 is then conveyed to a non-contact drying zone. However, according to the present invention, even if the coated web fluctuates (or vibrates) in the direction perpendicular to the running direction in the non-contact gelling area or the non-contact drying zone, the fluctuation or vibration is caused by the floating support. It was found that uniform application was possible without being absorbed and propagating in the area.

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 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.

In carrying out the present invention, in the sense that gas collides with the gelled coating layer in the floating support part and the coating layer is not 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 setting the temperature of the coating layer immediately before entering the coating layer to 2 to 10'' C1, preferably 2 to 5 degrees Celsius.

Thus, 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, goes around the vicinity of the first coater 1 while being supported in contact with the main roller 4, and is gushed out from the gushing slits la and 1b. Two layers are applied to the surface 3a using a coating liquid. At this time, the straight edge E and the web 3 face each other, forming a straight and parallel slit-like bead gap B.

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 is 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 curved edges E2 and the web 3, which are opposed to each other, are curved in the same direction to form curved bead gaps Bz at regular intervals.

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 one embodiment has been described above, the present invention is not limited to the above embodiment, and as a gas ejector, the non-contact support part has a continuous curved surface as its outer surface in order to maintain high static pressure in the gap with the support body. Any material may be used as long as the curved surface is capable of ejecting gas and satisfies the conditions of the present invention, and may have a roll-like outer shape or a portion that allows gas to pass from the inside to the outside of the gas ejector. There is no need for the through hole to be 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 semi-cylindrical or elliptical, and only the floating support part has a curvature on the outer surface, as shown in Fig. 4, which shows another example of the gas ejector. It may also have a shape composed of a plane.

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. As long as this condition is met, any type of hole may be used, and in the case of a through hole, the shape may be round or polygonal.Also, as shown in Figure 5, a porous material such as sintered metal may be used. A type in which P constitutes the outer shell of the gas ejector of the floating support section may also be used.

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.

In addition, methods for coating on one side and the opposite side of the substrate to be coated include bead coating method, extrusion coating method, etc.
This invention brings about great effects in methods where it is necessary to precisely define the distance between the coater and the web.

[Experiment example]

FIG. 3(a) shows Experimental Example A in which the web is deformed into a convex shape (with the coater at the top and the gas ejector at the bottom).

Here, the web conveyance conditions are web width = 200 cm.

Web conveyance speed = 150 cm/sec, degree of vacuum in vacuum chamber = 15 mmAq, web center static pressure = 200
mmAq, open end static pressure -100 mmAq, etc. In this case, the web 3 and the gas ejector 11 are deformed into a gentle convex shape with a distance of 800 μm at the center and 300 μm at both ends.

The curved edge E2 of the second coater 2 is curved inward at the center by 500 μm from both ends along this deformation, so that the distance between the curved edge Ex and the web 3 is constant at any position in the width direction. It has become.

FIG. 3(b) shows Experimental Example B in which the web deforms into a concave shape (with the coater at the top and the gas ejector at the bottom), contrary to FIG. 3(a).

Here, the web conveyance conditions are web width = 200 cm.

Web conveyance speed = 150 cm/see S vacuum chamber vacuum degree = 30 mmAq, web center static pressure = 150
mmAq, open end static pressure = 100 mmAq, etc. In this case, the web 3 is deformed into a gentle concave shape in which the spacing between the gas ejectors 11 is 200 μm at the center and 500 μm at both ends.

The curved edge E2 of the second coater 2 is curved so that the center part protrudes outward by 300 μm from both ends along this deformation, and the distance between the curved edge E2 and the web 3 is constant at any position in the width direction. It's supposed to be.

Therefore, in both of the above experimental examples A and B, the bead gap is constant at any position in the width direction of the application position, corresponding to the gas retention amount distribution in the width direction of the gap between the gas ejector and the web. It was found that uniform coating could always be achieved because of the formation of .

〔Effect of the invention〕

As described above, the present invention includes disposing a coater and a gas ejector at positions substantially facing each other across a continuously running web, and ejecting gas from the gas ejector toward the web. In the web coating apparatus which performs coating by the coater while floating and supporting the web, the coater is provided with a curved edge that follows the deformation of the web in the width direction, so that the distance between the web and the coater edge is reduced. The distance between them is constant across the width direction. Therefore, coating is always achieved with a uniform bead gap, which has a great effect on stabilizing the coating process and improving coating quality.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing the overall configuration of the web coating apparatus of the present application, FIG. 2 is a perspective view of a part of the second coater, FIG. 3(a),
(b) is a horizontal sectional view showing the relationship between a coater with a curved edge, a web, and a gas ejector, FIG. 4 is a sectional view showing another embodiment of the gas ejector, and FIG. 5 is a porous body. Explanatory diagram showing an example of the configured gas ejector, FIGS. 6(a) and (b)
1 is a horizontal cross-sectional view showing the relationship between a coater, a web, and a gas ejector of a conventional apparatus having a straight edge; FIG. 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 ejector 11a--Web holding surface 1 l b-Non-nib holding surface, ...Introduction part D2...-Derivation part E, ...-Straight edge E2-- Curved edge B+, Bz...-Bead gap L--Coating liquid F...-Minute nozzle hole patent Applicant Konica Corporation Fig. 3 (Q) (b) Fig. Fig. 6 (b) )

Claims (2)

[Claims] (1) A coater and a gas ejector are disposed at positions substantially facing each other across a continuously running web, and the gas is ejected from the gas ejector toward the web. A web coating device that performs coating with the coater while floating and supporting the web, wherein the coater is provided with a curved edge that follows the deformation of the web in the width direction. (2) The web coating device according to claim 1, wherein the difference between the most convex part and the most concave part in the width direction of the edge of the coater is 30 μm or more.