JPH11169770A - Coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a stable coated area by providing an air blow-off device opposed to a coater head, on the opposite side to the coated face of a support between an upstream and downstream guide rolls, in a coating device which applies a coasting liquid to the support running between the upstream guide roll and the downstream guide roll. SOLUTION: When the interior of a manifold 5 in a coater head 1 is filled with a coating liquid 7, the coating liquid 7 passes through a slot 4 to form a liquid well 6 surrounded by upstream and downstream lips 2, 3 and a support 8. The size of the liquid well 6 is determined by the total balance of the spray pressure of the coating liquid 7 to be pushed out of the slot 4 and the physical properties such as viscosity of the coating liquid 7, the tension of the support 8 and the in blasting pressure by an air blasting device 9. The device 9 to be used is installed in opposition to the coater head 1, on the opposite side to the coated face of the support 8. Further, the length in the width direction of an air blow-off aperture is the same or larger than the coated width of the support 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for applying a coating liquid to a running support, and more particularly to an apparatus for applying a coating liquid to a flexible support using a die coater. Further, the present invention relates to a coating apparatus for performing high-speed and thin-film coating using a thin support.

[0002]

2. Description of the Related Art Conventionally, in a manufacturing process of a photographic light-sensitive material, a magnetic recording medium, a surface treatment of a steel plate, etc., there is a step of applying a coating liquid on a flexible support. This coating liquid is prepared by mixing essential components such as photosensitive material or magnetic particles with a resin binder, adding various additives as necessary, and diluting with an organic solvent or the like to adjust the viscosity.

As a method of applying such a coating solution to a flexible support, various coating methods such as a roll coater, a gravure coater, a knife coater, a die coater, and various reverse coaters have hitherto been used. Have been. Among these, the die coater has no change in the coating liquid because the coating liquid is not exposed to air until immediately before coating, has excellent uniformity in the width direction of the coating film, and has a smooth surface. In recent years, its use has been increasing because of its superiority. Therefore, in addition to the conventional coating field, its application has been attempted in fields such as pressure-sensitive adhesives and surface treatment materials.

[0004] As a typical method of such a coating method using a die coater, a support is continuously provided on a pair of guide rolls arranged at a predetermined interval on the upstream and downstream sides of a coater head. There is known a method in which a coating solution is guided and extruded directly from the coater head disposed between the guide rolls onto the surface of a support to apply the coating solution uniformly, smoothly, and thinly. In the case of this method, the amount of the coating solution pushed out from the slot of the die head is reduced by turning the lip portion at the tip of the die head that pushes the coating solution toward the support that continuously runs between the pair of guide rolls. Coating can be performed by changing the distance between the lip portion at the tip of the die head and the surface of the support by the balance between the corresponding application pressure and the reaction force generated by the support being pressed and bent by the die head.

The problem with the above coating method is that the balance between the coating pressure of the coating liquid extruded from the slot and the reaction force from the support obtained by the tension of the support is not stable, so that the distance between the tip of the coater head and the support is small. It is easy to change, and there is a disadvantage that the coating liquid formed between the tip of the coater head and the support is not stable, so that the entire coating width is not uniformly applied, that is, air entrainment is likely to occur. In addition, due to the instability of the liquid pool, there is also a defect that horizontal stripes called step unevenness occur in the width direction of the support intermittently in the running direction of the support. There is also the disadvantage of being difficult.

In order to achieve a thin film and a high speed by the above method, the tension of the support is increased, or the amount of pushing the coater head into the support is increased so that the support is applied to the lip of the tip of the coater head. Care must be taken to increase the approach angle and retreat angle of the support. The reason for increasing the tension is that the discharge amount of the application liquid pushed out from the slot of the coater head increases with the speeding up. The increase in the discharge amount means that the amount of the coating liquid supplied to the liquid pool of the coating liquid formed between the tip of the coater head and the support increases, and the pressure of the liquid pool increases.

When the pressure of the liquid pool increases, the distance between the tip of the coater head and the support increases even if the reaction force from the support obtained by pushing the coater head into the support until that time is constant. Would. An increase in the distance between the tip of the coater head and the support increases the instability of the coating behavior, easily causing air entrainment from the upstream lip side, and the generation of uncoated lines on the coating surface. Will happen. Therefore, in order to stabilize the coating state, it is necessary to increase the reaction force of the support as much as the pressure of the coating liquid and to reduce the distance between the tip of the die head and the support to a region where stable coating is possible.

However, when the tension of the support is increased, "vertical stripes" in which the support is bent in the width direction occur, and the uniformity of the coating film in the width direction is lost. Become. The magnitude of the tension at which the "vertical streaks" occur varies depending on the type and thickness of the support. For example, when a PET film having a thickness of 20 μm is used, it is about 20 kgf / m or more.

In order to maintain a stable coating state, the downstream lip and the upstream lip are required to maintain a stable coating state when the pushing amount of the support into the coater head support is increased to increase the angle at which the support enters the lip at the tip of the coater head. In order to form an arc-shaped convex surface on the lip, and to form an angle corresponding to the entering angle or retreat angle of the support at the leading edge of the lip, it is necessary to form the lip not a straight line but a shape with a certain curvature there were.

Further, when the approach angle of the support and the curvature of the upstream lip are changed by changing the application conditions, the angle of the leading edge of the lip often becomes smaller than the approach angle of the support. In such a case, a phenomenon occurs in which the entering support comes into contact with the lip tip edge, which may cause a problem that the support is damaged. Therefore, in order to solve these problems, a coater head has to be created again by changing the radius of curvature of the lip, which increases time and cost.

[0011] In particular, the above problems are caused when the support is thin,
The effect is large when there is unevenness on the support, especially when the support is printed as pre-processing, and the support is applied with a higher tension than before, such as when high-speed and thin film coating is required. When transported, expansion of the support due to heat in the dryer and subsequent cooling may cause the pre-printed printing pitch to exceed the allowable range, and may cause partial contact due to contact with the lip tip when the support enters. It has been difficult to obtain a good coated surface, such as a scratch on a convex portion of the support, for example, a printed portion.

[0012]

SUMMARY OF THE INVENTION In a conventional coating apparatus,
When a thin support is used as described above, the speed is increased,
It was difficult to cope with thinning, and it was difficult to make the coating film pressure uniform and obtain a good coating surface. However, the present invention has been made in consideration of the above-described circumstances, and even when a thin support is used, the thickness of the support may be “varied” or “unevenness” such as a print formed by pre-processing may be applied. And to provide a coating apparatus capable of high-speed and thin-film coating.

[0013]

Means for Solving the Problems In order to achieve the above object in the present invention, first, in the first aspect, a pair of guide rolls for guiding a support member upstream and downstream of a coater head are provided, A coating apparatus for directly applying a coating solution to a support running between the upstream guide roll and the downstream guide roll, wherein the coater includes an upstream lip and a downstream lip, and coats between these lips. Forming a slot portion capable of extruding the liquid, in a coating apparatus that applies a coating liquid to a support that runs opposite the coater head, between the upstream and downstream guide rolls on the opposite side to the coating surface of the support. An application device characterized by providing an air blowing device facing the coater head.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. FIG. 1 shows a coater head (1) used in the coating apparatus of the present invention. The coater head (1) is provided on the side opposite to the coating surface of the support (8) with a coating solution (7) and a support (8). It is sectional drawing which shows the use condition when the air blowing device (9) is arrange | positioned facing. In the coater head (1), the coating liquid is supplied into the coater head (1) from a supply system (not shown) with an upstream lip (2) and a downstream lip (3) with respect to the traveling direction of the support (8). The manifold (5) is provided with a slot (4) which is a passage for pushing out the coating liquid from the manifold (5) to the lip portion. Guide rolls (10, 11) are arranged before and after the coater head (1). FIG. 2 is a diagram showing one embodiment.

The cross section of the manifold (5) is circular or elliptical, and is extended with the same or substantially the same cross-sectional shape in the width direction of the support (8). It is longer than or equal to the width of the support (8). The inside diameter of the manifold (5) is 5
The best size may be set to about 50 mm depending on the properties, viscosity, etc. of the coating liquid, and the open ends of the coating liquid are prevented from leaking to the outside of the coater head (1) by seal plates or the like. I have. Further, the supply of the coating liquid to the manifold (5) may be introduced from at least one of the opening ends, or at least one of the openings directly penetrates from the coater head (1) to the manifold (5). It may be introduced from the supply port.

Further, the slot (4) has a width of 0.1 mm which opens from the manifold (5) toward the support (8).
It is a slit-shaped coating liquid passage of 0.5 to 0.5 mm, and the distance from the manifold (5) to the tip of the lip is 5 to 10
0 mm. The width and distance of the slot (4) are also determined by the operating conditions such as the properties of the coating solution, the coating speed and the coating film thickness.

An upstream lip (2) and a downstream lip (3) located at the upstream and downstream sides with respect to the running direction of the support, respectively, are provided at the end of the slot (4) on the support side. Are located. The relative positions of the upstream lip (2) and the downstream lip (3) are set such that the position of the downstream lip (3) with respect to the upstream lip (2) is -0.0.
It can be set freely within the range of 01 to 0.5 mm. Further, the widths of the upstream lip (2) and the downstream lip (3) can be freely set independently in the range of 0.5 to 20 mm.

The coating liquid (7) is introduced from the outside of the coater head (1) into the manifold (5) by a hose or a pipe via a supply system. When the inside of the manifold (5) is filled with the coating liquid, the upstream lip (2) and the downstream lip pass through the slot (4) communicating with the manifold (5) with uniform pressure distribution and flow rate distribution in the width direction. (3) Further, a liquid pool (6) surrounded by the support (8) is formed. The liquid pool (6) is formed by applying pressure (amount) of the coating liquid extruded from the slot (4) and physical properties such as viscosity of the coating liquid, tension of the support (8), and air blowing pressure by an air blowing device (9). The size is determined by the total balance of the above, and the distance between the upstream lip (2) and the downstream lip (3) and the support (8) is determined.

The coating liquid having the liquid pool (6) is applied to the surface of the running support and the coating process is completed. The coating film thickness is determined by the flow rate of the coating liquid to be discharged and the running speed of the support. You. However, the applied coating solution does not necessarily spread in the width direction of the support, and a uniform film thickness distribution is not obtained. In some cases, air entrainment may occur, and uncoated portions may become streaks and defects may occur. . In such a case, since the distance between the lip and the support is too large, it is necessary to increase the tension of the support and reduce the liquid pool. This state will be described with reference to FIG. If the application conditions are constant except for the tension, by increasing the tension, the stable application region free of air entrainment will be extended to the low application film thickness side.

An air spraying device (9) is installed on the opposite side of the coating surface of the support from the coater head (1),
The width of the air blowing port of the air blowing device (9) in the width direction is equal to or longer than the coating width of the support, and the length of the support in the running direction is 0.05 to 1
It can be set freely within the range of 0 mm. further,
The air blowing device 9 blows uniform air in the width direction.

The operation of the above-mentioned air blowing device is such that, under coating conditions for high-speed thin film coating, the tension of the support must be increased when the film thickness is normally reduced. By applying the necessary tension, the support flexes and vertical streaks occur,
Even under coating conditions that cause waving in the width direction, the tension of the support is reduced to a tension that does not cause vertical streaks (for example, 20 kgf / m or less for a PET film having a thickness of 20 μm). The shortage of tension can be compensated by blowing air from the opposite side to the application surface with an air blowing device.

Further, by adjusting the air volume of the air blowing device, the distance between the lip and the support can be reduced without changing the amount of pushing of the coater head into the support and without changing the tension of the support. However, it is possible to expand the stable application region to the low application film thickness side.

[0023]

As described above, by using the coating apparatus according to the present invention, when performing thin-film coating at a high speed using a thin support, a high tension is not applied to the support, and a stable air-free entrainment is performed. An enlargement of the application area can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a coater head of a coating apparatus according to the present invention.

FIG. 2 is an embodiment of a coating apparatus of the present invention.

FIG. 3 is a graph showing a film tension and a stable application area when applied by a conventional method.

[Explanation of symbols]

 1 Coater head 2 Upstream lip 3 Downstream lip 4 Slot 5 Manifold 6 Liquid pool 7 Coating liquid 8 Support 9 Air blowing device 10 Upstream Side guide roll 11 ‥‥ Downstream side guide roll A 走 行 Support direction of travel B 体 Air

Claims (1)

[Claims] 1. A coating liquid is applied directly to a support running between an upstream guide roll and a downstream guide roll, comprising a pair of guide rolls for guiding a support upstream and downstream of a coater head. A coating device, wherein the coater further comprises an upstream lip and a downstream lip, and a slot portion capable of extruding the coating liquid is formed between these lips, and the coating liquid is formed on a support running against the coater head. A coating device, wherein an air blowing device is provided between the upstream side guide roll and the downstream side guide roll on a side opposite to a coating surface of a support so as to face a coater head.