JPH10290945A - Die coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable thin-film state even at the time of a high speed by forming the upstream side lip of a die for a coating liquid in the moving direction of a base to a curved surface by chamfering the upstream side in the moving direction of the base, thereby preventing the chipping of the base and the trapping of foreign matter at the front end of the front lip edge to be even in the thickness of the solvent layer. SOLUTION: The coating liquid 5 is applied on the precoated base 11 by the die 7 for the coating liquid. The stable coating application state is maintained by applying the precoating liquid 2 in excess of the amt. at which the liquid passes between the base 1 and the front edge 3a existing on the upstream side in the moving direction of the base of the front lip 3 and applying the coating liquid 6 thereon while scrapping the excess precoating liquid by means of the front edge 3a. At this time, the excess precoating liquid 2 falls by gravity. Then, the front edge 3a is chamfered to the curved surface in order to prevent the chipping of the base and the trapping of the foreign matter at the front edge 3a and to obtain a stable coating state with, the die coating device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion die for continuously applying a coating liquid onto a surface of a continuously running support and applying the coating liquid at a uniform thickness at a high speed. It relates to a coating device.

[0002]

2. Description of the Related Art JP-A-63-88080 and JP-A-2-1980 disclose a coating apparatus for forming a coating layer by applying one or a plurality of coating liquids on a support which continuously runs at high speed.
No. 7971 discloses this. These are called support pressurized extrusion coating heads, and have a coating lip for coating the coating liquid on the downstream side in the support moving direction with respect to the coating liquid discharge slit at the tip of the coating head. The support is pressed against the coating lip side to apply the coating solution between the lip edge and the support under pressure.

[0003] This support pressurizing type coating head is excellent in high-speed thin layer properties, but since the coating is performed by the balance between the pressing force of the support and the pressure of the coating liquid, unevenness in rigidity and the like of the support may occur. In some cases, application unevenness occurs, causing a problem.

Here, the coating liquid refers to a back coating or the like on the back surface of the magnetic recording layer of a magnetic recording medium such as a magnetic disk or a magnetic tape.

Under these circumstances, a non-pressurizing type coating apparatus which improves the above-mentioned coating unevenness and avoids fluctuations in the coating film thickness due to streak failure and unevenness of the thickness of the support, Young's modulus, etc. Have been proposed in JP-A-63-20069, JP-A-5-293420 and the like.

FIG. 5 shows the basic structure of these coating apparatuses.

FIG. 5 is an enlarged sectional view showing the tip of an extrusion die in which a coating liquid 16 is stored and a slit 15 for discharging the coating liquid 16 is provided.

A precoating liquid 12 mainly composed of an organic solvent is previously applied to the coating surface of the support 11.

The front lip 13 is located on the upstream side in the support moving direction from the exit of the slit 15 and protrudes closer to the support than the tip of the coating lip 14 disposed on the downstream side. Further, the coating lip 14 is disposed such that the tip end thereof retreats in the direction opposite to the support body with respect to a tangent line at the outlet of the slit of the front lip 13.

According to this apparatus, first, a precoat liquid 12 mainly composed of an organic solvent is applied to a coating surface of a support 11 by a gravure coater, a roll coater, a blade coater, and the like.
It is applied by a known coating device such as an extrusion coater. This pre-coat liquid layer prevents entrained air from entering the coating layer from the upstream side of the front lip, and enables high-speed coating in which a defect-free coating state is maintained.

That is, since the coating lip 14 is retracted from the front lip 13 with respect to the support 11, no pressure is exerted on the coating lip 14 by the support 11, so that foreign matter is present at the tip of the coating lip 14. It can be prevented from being trapped. Furthermore, even if the behavior of the support in the vicinity of the coating head becomes unstable due to the variation in the elastic modulus of the support or the poor surface properties of the support, the coating method should not use the pressing force of the support. Therefore, it is hard to be affected by the unstable behavior, and it is possible to obtain a coated product excellent in preventing the occurrence of thickness unevenness such as a wavy coating film.

[0012]

However, when single-layer or multi-layer simultaneous coating is performed using this non-pressurizing type coating apparatus, the support body may be cut off at the front edge 13a of the front lip of the front lip of the coating die head. It has been found that there is a trap of foreign matter.

As a result, streaks are generated in the solvent layer, and the streaks cause disturbance in the upper layer, resulting in streak-like disturbance at the interface between the solvent layer and the upper coating layer. This streak-like disturbance causes disturbance of the entire coating layer, which causes a streak failure on the surface of the coating layer. For example, when the streak-like disturbance is present in the magnetic recording layer, there arises a problem that it hinders the improvement of the electromagnetic conversion characteristics.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and it is intended to prevent shaving of the support at the tip of the front lip edge and trapping of foreign matter, to make the solvent layer uniform in thickness, and It is another object of the present invention to provide a die coating apparatus capable of obtaining a stable thin film state.

[0015]

In order to solve the above-mentioned problems, a die coating apparatus according to the present invention comprises: a precoat die for applying a precoat liquid onto a continuously running support; A coating liquid die for scraping off a part of the pre-coat liquid applied by the coating liquid and applying a further coating liquid thereon, and a support moving direction upstream lip of the coating liquid die is disposed in the support moving direction upstream. The side edge is chamfered to be a curved surface.

By chamfering the front edge on the upstream side of the front lip, it becomes possible to stably supply the precoat liquid to the front lip, prevent contact of the support with the lip, and maintain a stable coating state without stripe disturbance. Will be obtained.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a structural example of a die coating apparatus to which the present invention is applied.

The die coating apparatus includes a coating liquid die 7 for applying a coating liquid and a precoat liquid die 8.
The support 1 is guided by guide rolls 9 and 10.

The coating surface of the support 1 is preliminarily coated with a precoat liquid 2 mainly composed of an organic solvent by a precoat die 8.

The coating liquid die 7 is an extrusion die in which a coating liquid 6 is stored and a slit 5 serving as a discharge port for discharging the coating liquid 6 is provided. The coating liquid die 7 is disposed to face the surface of the support 1 that runs continuously from right to left in FIG. The tip surface of the coating liquid die 7 is constituted by a pair of lips including a front lip 3 and a coating lip 4,
The lip is disposed so as to face the surface of the support 1.

The front lip 3 is located on the upstream side in the support moving direction from the exit of the slit 5, and protrudes closer to the support than the tip of the coating lip 4 arranged on the downstream side. Further, the coating lip 4 is disposed such that its tip is retracted in the direction opposite to the support body with respect to the tangent at the exit of the slit of the front lip 3.

The coating liquid die 7 is provided between the two guide rolls 9 and 10. FIG. 1 shows an example in which the pre-coating is performed in such a manner that the support 1 runs from the upper side to the lower side. In this case, the precoat liquid die 8 is installed on the upstream side of the guide roll 9, and the running direction of the support 1 can be changed by the guide roll 9.
However, the present invention is not limited to this, and the pre-coat liquid die 8 may be provided between the coating liquid die 7 and the guide roll 9 on the upstream side thereof.

An extrusion type die 8 for discharging the precoat liquid from the slit at a high speed to form a uniform film of the precoat liquid in a coating width and applying the coating on the support without contacting the support is used as the die 8 for the precoat liquid. Dies are preferred. However, the present invention is not limited to this, and a known coating device that is generally used such as a gravure coater, a roll coater, or a blade coater may be used.

The pre-coated support 1 is subsequently coated with a coating liquid 5 by a coating liquid die 7. At this time, the upstream side of the front lip is
As a result, the liquid is sealed by the pre-coat liquid 2 applied, thereby preventing entry of entrained air. In order to maintain a stable application state, the precoat liquid 2 is applied in excess of the amount that passes between the support 1 and the front edge 3a located on the upstream side of the front lip 3 in the support movement direction, It is necessary to apply the coating liquid 6 while scraping off the excess precoat liquid at the front edge 3a. At this time, the excess precoat liquid falls by its own weight. Further, the liquid thickness is optimally 3 μm or less in a wet state.

However, if the front edge 3a is a sharp edge, the support may be scraped or foreign matter may be trapped when the precoat liquid is scraped off, resulting in streak-like disturbance.

Therefore, in the die coating apparatus to which the present invention is applied, the support body is cut off at the front edge 3a,
Front edge 3a to prevent trapping of foreign matter, make the precoat liquid layer uniform, and obtain a stable coating state
Is chamfered to a curved surface.

FIG. 2 is an enlarged sectional view showing a front edge 3a of the front lip 3. As shown in FIG. The front edge 3a is chamfered. The shape is constituted by, for example, an arcuate curved surface. When the front edge shape is an arc-shaped curved surface, the radius R of the curved surface and the central angle α are important.
Specifically, as can be seen from the experimental results described later, the radius R of the curved surface is preferably 0.01 mm or more and 0.1 mm or less. Also, the central angle α of the curved surface is 30 ° or more,
It is preferable that the angle is 120 ° or less.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a coating experiment performed using a coating apparatus having the above-described configuration will be described.

An extrusion die was used for both the precoat liquid die and the coating liquid die.

Here, the die for the precoat liquid is made of stainless steel, and the die width for the precoat liquid is 160 mm. 0.03mm slit gap, 120mm coating width
Set to.

The pre-coating solution contains methyl ethyl ketone, toluene and cyclohexanone in a ratio of 5: 3: 2, respectively.
, And the thickness of the precoat liquid was adjusted to 20 to 40 µm.

On the other hand, the front lip and the coating lip of the coating liquid die are made of cemented carbide, and the width of the coating liquid die is 160 mm. The slit gap was set to 0.1 mm, and the coating width was set to 110 mm.

The coating solution used was a coating material for the back surface of a magnetic recording medium, and the coating thickness was set to 0.5 to 0.9 μm.

A coating experiment was carried out using polyethylene terephthalate having a width of 125 mm and a thickness of 9 μm as a substrate to be coated, and applying a tension of 2 to 4 kgw to the entire width.

<Experimental Example 1> The front edge shape was an arc-shaped curved surface, and the central angle α was set to 30 °. The radius R of the front edge curved surface is 0.005 mm, 0.01 mm,
0.03 mm, 0.1 mm, 0.2 mm, and 0.3 mm, and the coating speed was 100 m / min, 20 for each of them.
0 m / min, 300 m / min, 400 m / min, 500 m / min
The coating experiment was performed under various conditions of 600 m / min, 700 m / min, and 800 m / min. FIG. 3 shows an example of the front edge shape, and Table 1 shows the results of the coating experiment.

[0037]

[Table 1]

The evaluation of the coating experiment was carried out based on the abrasion state of the support during the coating and the presence or absence of the coating streaks.

From these results, it was found that the thickness of the precoat liquid on the front lip can be controlled by changing the radius R of the curved surface. Specifically, when the radius R of the curved surface is 0.01 mm or more and 0.1 mm or less, 50
A good coating state was obtained even at a high speed of 0 m / min.

<Experimental Example 2> The front edge shape was an arc-shaped curved surface, and the radius R was set to 0.03 mm. The center angle α of the front edge curved surface is 20 °, 25 °, 30 °,
90 °, 120 °, and the coating speed was changed to 100 m / min, 200 m / min, 300 m / min, 400 m for each of them.
/ Min, 500m / min, 600m / min, 700m / min, 8
A coating experiment was performed under each condition of 00 m / min. FIG. 4 shows an example of the front edge shape, and Table 2 shows the results of the coating experiment.

[0041]

[Table 2]

The evaluation of the coating experiment was carried out based on the abrasion state of the support during the coating and the presence or absence of the coating streaks.

When the central angle was 25 ° or less, a phenomenon occurred in which the precoat liquid scraped off at the front edge was wound up again on the support, and abnormalities were found in the scraping state. No abnormality was observed at an angle of 30 ° or more.

From the results of these experiments, it was found that by chamfering the front edge to form a curved surface, stable scraping without shaving of the support or coating streaks was performed.
Specifically, when the front edge shape is an arc-shaped curved surface, it is preferable that the radius R be 0.01 mm or more and 0.1 mm or less, and the central angle α be 30 ° or more and 120 ° or less.

When the front edge shape is an arc-shaped curved surface, if the central angle α is 120 ° or more, machining is difficult,
It is difficult to get the accuracy of the curved surface. However, the central angle α may be 120 ° or more if sufficient processing accuracy is obtained.

[0046]

As is apparent from the above description, in the die coating apparatus according to the present invention, the occurrence of shaving of the support at the front edge and the trapping of foreign matter are eliminated. As a result, streaks and defects in scraping were eliminated, and a stable coating state from low speed to high speed (800 m / min) became possible, leading to stable quality. Furthermore,
The roll shape after winding was improved, and the yield after cutting was improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one configuration example of a die coating apparatus to which the present invention is applied.

FIG. 2 is an enlarged sectional view showing an example of a front edge portion of a coating liquid die used in a die coating apparatus to which the present invention is applied.

FIG. 3 is an enlarged sectional view showing an example of a front edge portion of a coating liquid die used in a die coating apparatus to which the present invention is applied.

FIG. 4 is an enlarged sectional view showing an example of a front edge portion of a coating liquid die used in a die coating apparatus to which the present invention is applied.

FIG. 5 is an enlarged sectional view showing a part of a die used in a conventional die coating apparatus.

[Explanation of symbols]

Reference Signs List 1 support, 2 pre-coating liquid, 3 front lip, 3a front edge, 4 coating lip, 6 coating liquid, 7 coating liquid die, 8
Die for pre-coating liquid

Claims (3)

[Claims] 1. A pre-coating die for applying a pre-coating liquid onto a continuously running support, and a part of the pre-coating liquid applied by the pre-coating die is scraped off and at least one more coating liquid is applied. A die coating apparatus comprising: a coating liquid die; and an upstream lip of the coating liquid die in a support moving direction has a chamfered edge on an upstream edge in the support moving direction. 2. The curved surface has an arc shape with a radius of 0.
2. The die coating apparatus according to claim 1, wherein the diameter is from 0.1 mm to 0.1 mm. 3. The curved surface has an arc shape, and its central angle is 3
2. The method according to claim 1, wherein the angle is not less than 0 ° and not more than 120 °.
The die coating apparatus as described.