JPH11147061A - Coating device - Google Patents

Abstract

(57) [Summary] A coating apparatus capable of high-speed and thin-film coating even with a thin support, and even when the support has a film thickness variation or irregularities such as prints formed by pre-processing. The purpose is to provide. A pair of guide rolls for guiding a support member to an upstream side and a downstream side of a coater head, the coater head has an upstream lip and a downstream lip, and a slot portion capable of extruding a coating liquid between these lips. Form 4
A coating apparatus for applying a coating liquid 7 to a support 8 running opposite to the coater head 1, wherein a guide sheet 9 is provided between the upstream and downstream guide rolls on a side opposite to a coating surface of the support. .

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. In particular, 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 process of manufacturing a photographic light-sensitive material, a magnetic recording medium, a surface treatment of a steel plate, and the like, there is a step of applying a coating solution on a flexible support. This coating solution is prepared by mixing essential components such as photosensitive material or magnetic particles with a resin binder, and further adding various additives as necessary,
The one whose viscosity has been adjusted by dilution with an organic solvent or the like is used.

[0003] 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 is not exposed to air until just before coating, so there is no change in the coating liquid, excellent uniformity in the width direction of the coating film, and excellent smoothness of the coated surface. In recent years, its use has been increasing for such reasons. Therefore, its application has been attempted in fields such as pressure-sensitive adhesives and surface treatment agents in addition to the conventional coating field.

[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 uniformly and extruded directly from the coater head disposed between the guide rolls onto the surface of the support to apply the coating solution uniformly, smoothly, and thinly.

In this method, the lip at the tip of the die head, which pushes out the coating liquid, is pressed against a support running continuously between a pair of guide rolls, so that the coating liquid pushed out from the slot of the die head is pressed. Coating can be performed by changing the distance between the lip part at the tip of the die head and the surface of the support by the balance between the application pressure corresponding to the extrusion amount and the reaction force generated by the support being pressed and bent by the die head. Becomes

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 not stable. However, there is a disadvantage that the entire coating width is not applied uniformly, that is, air entrainment is likely to occur because the liquid pool of the coating liquid formed on the substrate is not stable.

Further, when the liquid pool becomes unstable, "transverse stripes" called step unevenness are generated intermittently in the width direction of the support in the running direction of the support. There is also a disadvantage that it is difficult to cope with the change.

In order to achieve a thin film and a high speed by the above-mentioned method, it is necessary to increase the tension of the support or the amount of pushing the coater head into the support to increase the amount of the support to the lip at 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 coating liquid pool formed between the tip of the coater head and the support increases, and the pressure of the liquid pool increases. I do. When the liquid pressure of the liquid pool increases, even if the reaction force from the support obtained by pushing the coater head into the support is constant, the distance between the tip of the coater head and the support increases. I will.

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 stripes 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 flexes 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, but is, for example, about 20 kgf / m or more when a PET film having a thickness of 20 μm is used.

When the amount of pushing of the coater head into the support is increased to increase the angle at which the support enters the lip at the tip of the coater head, the downstream lip and the upstream lip are required to maintain a stable coating state. In order to form an arcuate convex surface at the tip of the lip at an angle corresponding to the angle of entry or retreat of the support, it is necessary to form the lip into a shape having a certain curvature rather than a straight line. Was.

In the case where 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 some cases, a phenomenon in which the entering support comes into contact with the leading edge of the lip occurs, causing 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.

[0014] 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 the occurrence of scratches on the convex portion of the support, for example, a printed portion.

[0015]

In the conventional coating apparatus, when a thin support or the like is used as described above, it is difficult to increase the speed and reduce the film thickness. It was difficult to obtain a proper coated surface. The present invention has been made in view of the above circumstances, even if the support is thin, even if the surface of the support has irregularities such as variations in film thickness or printing formed by pre-processing, high speed and An object of the present invention is to provide a coating apparatus capable of coating a thin film.

[0016]

According to a first aspect of the present invention, there is provided a pair of guide rolls for guiding a support member upstream and downstream of a coater head, wherein the upstream guide roll and the downstream guide roll are provided. A coater head having an upstream lip and a downstream lip, and forming a slot portion capable of extruding the coating liquid between these lips, wherein the coater head has an upstream lip and a downstream lip, A coating apparatus for applying a coating liquid to a support running opposite to a coater head, wherein a guide sheet is provided between the upstream and downstream guide rolls on a side opposite to a coating surface of the support.

According to a second aspect of the present invention, the travel distance of the guide sheet is changed by moving to a travel path line of the guide sheet stretched between the upstream and downstream guide rolls. 2. The coating apparatus according to claim 1, further comprising an adjusting roll capable of freely adjusting the tension.

Further, according to the present invention, at least one of the upstream guide roll, the downstream guide roll, and the adjusting roll is driven at the same speed as the traveling speed of the support. Item 4. The coating device according to Item 2.

[0019]

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, and a support (8) for a coating liquid (7).
FIG. 9 is a cross-sectional view illustrating a use state in which a guide sheet (9) that travels together with the support while being in close contact with the side opposite to the application surface of the support (8) is disposed. The coating liquid is supplied to the inside of the coater head (1) from a supply system (not shown) by an upstream lip (3) and a downstream lip (2) with respect to the traveling direction of the support (8). It is divided into a manifold (5) provided as much as possible, and 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).

The cross section of the manifold (5) is circular or substantially circular, and is extended with the same or substantially the same cross-sectional shape in the width direction of the support body (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.

The supply of the coating liquid to the manifold (5) may be introduced from at least one of the opening ends.
Alternatively, at least one opening may be directly introduced from the coater head (1) through a supply port penetrating the manifold (5).

Further, the slot (4) has a width of 0.1 mm which is open from the manifold (5) to 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, similarly to the manifold.

At the extreme end of the slot (4) on the support side, there are an upstream lip (3) and a downstream lip (2) located respectively on the upstream side and the downstream side with respect to the running direction of the support. Are located. The relative positions of the upstream lip (3) and the downstream lip (2) are determined by setting the position of the distal end surface of the downstream lip (2) with respect to the distal end surface of the upstream lip (3) to -0.01 to It can be set freely within the range of 0.5 mm. Further, the width of each of the upstream lip (3) and the downstream lip (2) is independently 0.5 to 20 m.
It can be set freely within the range of m.

The coating liquid (7) is introduced from outside the coater head (1) to the manifold (5) via a supply system via a hose or a pipe. When the inside of the manifold (5) is filled with the coating liquid, the upstream lip (3) and the downstream lip have uniform pressure distribution and flow rate distribution in the width direction and pass through the slot (4) communicating with the manifold (5). (2) Further, a liquid pool (6) surrounded by the support (8) is formed.

The liquid pool (6) is formed by the properties such as the discharge pressure (amount) of the coating liquid extruded from the slot (4) and the viscosity of the coating liquid, the tension of the support (8) and the tension of the guide sheet (9). By the total balance of the size of
Its size is determined.

The coating film thickness is determined by the flow rate of the coating liquid to be discharged and the traveling speed of the support. 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 the uncoated portion may become streaks and defects may occur. is there. 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 coating conditions are constant except for the tension, by increasing the tension, the stable coating amount range in which no air entrainment occurs is expanded toward the low coating film thickness.

Further, the guide sheet (9) is running with a certain tension in the same direction as the running direction of the support (8) via the guide rolls (10, 11). The guide sheet (9) is preferably formed of a flexible material like the support body (8), and can stably reciprocate on the guide rolls (10, 11). Are more preferred. Further, the guide sheet (9) is 0.1 to 5.0 mm.
It is preferable that the thickness does not vary in both the width direction and the running direction, and more preferably the Young's modulus is the same.

The unevenness in the thickness of the guide sheet (9) and the unevenness of the Young's modulus, and the unevenness at the seam generated when the guide sheet is formed by joining the ends of two sheets, are caused by the aforementioned liquid pool. As a result of the application pressure of the coating solution and the reaction force from the support and the guide sheet, the state where the balance is maintained and stabilized is destroyed, and the coating stability is lost. There is a risk of damaging the uncoated surface. Therefore, the most preferable is a guide sheet formed by integral molding from a silicone resin or the like.

The operation of the guide sheet (9) is as follows.
Under coating conditions intended for high-speed thin film coating, where the thickness of the support usually needs to be increased when the film thickness is reduced, the support is flexed by applying the necessary tension like a thin support. Even under application conditions where "vertical stripes" are generated and are wavy in the width direction, the tension of the support is reduced to a tension at which "vertical stripes" are not generated (for example, if the PET film is 12 μm thick). 20 kgf / m or less). Instead, the tension shortage can be compensated for by the tension of the guide sheet which is in close contact with the support and travels in the same direction as the support.

Further, in addition to the guide rolls (10, 11) upstream and downstream of the coater head (1), an adjusting roll (12) for adjusting the length of the guide sheet pass line by moving the roll is added. This makes it possible to freely change the tension of the guide sheet (9).

FIGS. 3 and 4 show an example. The effect is to change the tension of the guide sheet (9) without changing the pushing amount of the coater head (1) into the support (8) and without changing the tension of the support (8). Thus, the stable coating area can be expanded to the low coating film thickness side. In other words, even if the amount of pushing of the coater head (1) into the support is made as small as possible, a sufficient reaction force from the support can be obtained. Therefore, by increasing the pushing amount, the coater head on the upstream side of the support can be obtained. There is no need to increase the angle of entry into the support, and it is possible to eliminate the occurrence of scratches on the support.

The running stability of the support (8) depends on the guide rolls (10, 11) or the adjusting rolls (12).
By driving at least one of the rolls at the same speed as the traveling speed of the support (8).

In the present coating method in which the coater head (1) is applied between the guide rolls on the upstream side and the downstream side of the coater head (1) by pressing the coater head (1) against the support (8),
The support body (8) is unstable, and a minute fluctuation in tension may cause intermittent streaks in the width direction of the support body in the running direction, which may be caused by the unevenness of the guide sheet as described above. The problem can be solved by running with a drive roll independently of the support.

[Example] Hereinafter, the present invention will be described in more detail with reference to examples. It was applied under the following conditions. (1) Support material: PET, thickness: 12 μm, width: 1000 mm Tension: 15 kgf / m (2) Guide sheet material: silicon resin, thickness: 1 mm, width: 1000 m
m tension: 5 kgf / m The tension of the guide sheet was determined by moving the adjusting roll. The downstream guide roll was driven at the same speed as the traveling speed of the support. (3) Coater head The structure is substantially the same as that of FIG. The pushing amount of the coater head into the support was 5 mm. (4) As the coating liquid, an acrylic resin dissolved with methyl ethyl ketone to obtain a solid content of 50 wt% was used. The viscosity at that time is 400 cps. (5) The coating speed was changed at 10 to 200 m / min. (6) The coating film thickness indicates the minimum film thickness that does not cause air entrainment, and a larger film thickness is shown in FIG. 5 as a stable coating region.

[Comparative Example] The coating was performed under the same coating conditions as those described in the above example without using a guide sheet. The results are also shown in FIG.

It can be seen that when the coating speed is changed, the coating stable region where no air entrainment occurs changes to the higher coating film thickness side as the speed increases. In the comparative example, the tension of the support was 15 kgf / m, and at a coating speed of 200 m / min, if the coating film thickness was not more than 18 μm, the film was cut off by air entrainment and a good coated surface could not be obtained.

In the embodiment of the present invention, the guide sheet is run at the same speed as the support on the opposite side to the coater head of the support, so that even if the coating speed is 200 m / min, the air is applied to the coating film thickness of 5 μm. Coating without entrainment became possible, and a stable coating area was expanded.

[0039]

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

[Brief description of the drawings]

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

FIG. 2 is a graph showing a film tension and a stable application area when applied by a conventional method.

FIG. 3 is an embodiment of a coating apparatus according to the present invention.

FIG. 4 is an embodiment of a coating apparatus according to the present invention.

FIG. 5 is a graph showing a coating speed and a stable coating area when the coating device of the present invention is used and when a conventional coating device is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Coater head 2 ... Downstream lip 3 ... Upstream lip 4 ... Slot 5 ... Manifold 6 ... Liquid pool 7 ... Coating liquid 8 ... Support body 9 ... Guide sheet 10 ... Upstream guide roll 11 ... Downstream guide roll 12 ... Adjusting roll A: Rotation direction of support and guide sheet

Claims (3)

[Claims] An apparatus is provided with a pair of guide rolls for guiding a support upstream and downstream of a coater head, and a coating liquid is applied directly to a support running between the upstream guide roll and the downstream guide roll. A coating device, wherein the coater head further includes 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 applied to a support running against the coater head. A coating apparatus for coating, wherein a guide sheet is provided between the upstream and downstream guide rolls on a side opposite to a coating surface of a support. 2. The tension can be freely adjusted by changing the travel distance of the guide sheet by moving to a travel path line of the guide sheet stretched between the upstream and downstream guide rolls. The coating device according to claim 1, further comprising an adjustment roll. 3. The apparatus according to claim 1, wherein at least one of the upstream guide roll, the downstream guide roll, and the adjusting roll is driven at the same speed as the traveling speed of the support. Coating device.