JPH07265773A - Coating apparatus - Google Patents

Abstract

PURPOSE:To uniformize a coating thickness distribution in the width direction of the coating independently of the types of coating materials and form a coating film with high quality. CONSTITUTION:Regarding an extrusion type coating apparatus which is provided with a die 4 having a paint storage 3 to which a paint 1 is supplied to carry out coating while extruding a paint 1 through a slit 5 formed at the time end of the die 4 to a continuously running supporting body 6, a cylindrical filtering part 7 whose thickness continuously changes in the coating width direction is inserted into the inside of the paint storage 3 of the die 4 and the paint 1 is supplied through the filtering part 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called extrusion type coating apparatus, and more particularly to a coating apparatus suitable for coating a magnetic paint or the like when manufacturing a magnetic recording medium.

[0002]

2. Description of the Related Art Generally, as an audio tape or a video tape, a magnetic coating material prepared by dispersing and kneading a magnetic powder, a binder, a dispersant, a lubricant, etc. in an organic solvent is coated on a non-magnetic support such as a polyester film. A so-called coating type magnetic recording medium in which a magnetic layer is formed by doing so is used.

In producing this coating type magnetic recording medium, as a method for coating a magnetic coating on a non-magnetic support,
An extrusion method using an extrusion (die) type coating apparatus has been drawing attention and has been partially put into practical use. The extrusion type coating apparatus has a wide slit facing the tip surface and is provided with a die having a doctor edge in the vicinity of the tip portion, and is directed toward the surface of the running non-magnetic support. The magnetic coating material extruded continuously is applied to the non-magnetic support with a uniform thickness by the doctor edge.

In this extrusion type coating apparatus, the coating material is supplied from both sides of the die into the coating liquid reservoir provided on the back side of the slit. And
This paint is sent out into the slit through the coating liquid reservoir, extruded from the tip of the slit, and applied onto the non-magnetic support. Such an extrusion type coating apparatus can easily form a coating film having a uniform film thickness, and since it does not use a roll having a large diameter, the apparatus is low in cost and small in size. Is advantageous,
Further, since the coating material supplied to the die is entirely applied, it is not necessary to circulate the coating material around the die, and thus it has been used in the fields of photographic film, photographic paper and the like.

By the way, in recent years, in the above-mentioned coating type magnetic recording medium, improvement of the magnetic recording medium itself has been rapidly advanced, and for example, high B as a magnetic powder constituting a magnetic layer.
A method of using magnetic oxide powder or barium ferrite powder having an ET value is widely used. In such a magnetic recording medium, the viscosity of the coating liquid has been increased, and accordingly, the high-viscosity magnetic paint can be favorably applied, and further, the thin film and high-speed coating are required for improving the productivity. It is desired to develop a coating technology that can fully cope with this.

Therefore, in the above-mentioned extrusion type coating apparatus, for example, JP-A-57-84771, JP-A-58-104666, and JP-A-60-238179.
Methods such as those disclosed in Japanese Laid-Open Publications have been proposed. However, with these coating devices, although it is possible to obtain a uniform coating film thickness, good coating can be carried out only in a relatively narrow viscosity range. Under the conditions described above, it is difficult to obtain the desired coating state. In particular, when a thin film having a thickness of the magnetic layer of 30 μm or less (wet film thickness) is applied, the resulting coating film has uneven film thickness.

It is known that the unevenness of the film thickness is caused by various factors such as die dimensional accuracy, edge shape, coating solution pool shape, base tension, and physical properties of the coating solution in a complicated relationship. Therefore, it is an important issue for the coating apparatus to obtain a uniform film thickness distribution without being affected by these factors.

For example, according to EDI Company, USA, it has been reported that it is possible to improve the coating thickness distribution by controlling the shape of the paint flow path in the die. However, in this method, since a suitable slit shape is different depending on the viscosity characteristic of the coating material, the coating material which can be handled by one die is limited, and therefore it is necessary to replace the die depending on the coating material. Further, in the design of the slit shape, advanced flow analysis technology and processing technology are inevitable, which is not practical.

Further, in the above-mentioned extrusion type coating apparatus, there occurs a phenomenon that the residue produced by the retention of the coating material in the coating liquid reservoir or the slit to which the coating material is supplied hardens in a cake form, and There is a problem that the uniformity of coating in the width direction is impaired, a part of the above-mentioned residue is peeled off and coated, and streak unevenness occurs. This is because, when used for a long period of time, the paint in the coating liquid pool is particularly retained, and for example, the dispersant in the magnetic coating material is agglomerated and accumulated in the coating liquid pool or adheres to the slit opening. This is because. As described above, the stagnation of the paint causes unevenness of the coating film thickness in the width direction and non-uniformity of the performance, and has a serious adverse effect on the obtained product.

In order to solve this problem, a method of arranging a spacer in the slit has been proposed as described in, for example, Japanese Patent Application Laid-Open No. 64-18467 and Japanese Patent Application Laid-Open No. 5-104053. There is.

However, in these methods,
The spacer of the appropriate shape differs depending on the viscosity characteristics of the paint, but replacement of the spacer requires disassembly of the die.
Even if the spacer can be replaced only by partially disassembling the die, a change in the die assembling accuracy and a deterioration in the coating quality due to the drying of the paint in the slit portion are inevitable due to the replacement.

In addition, as shown in FIG. 8, a filter member 34 is inserted into a coating liquid reservoir 33 provided as an orifice-like space inside a die 31 having a wide slit 32 facing the tip end surface. A method for obtaining a uniform coating thickness distribution by increasing the pressure loss has been studied. However, in this method, the pressure loss (rectifying effect) may be insufficient depending on the viscosity characteristics of the coating material, and the method of only increasing the pressure loss causes the coating material supply pressure to rise too much, and the life of the filtering member also shortens. There is a problem.

Further, in this method, as shown in FIG. 9, the element holder 37 supporting the filtering member 34 is fixed to the side plates 36 having the paint supply ports 35 attached to both sides of the die 31. It has been configured. Therefore, when replacing the filter member 34,
It is necessary to disassemble the die 31.

[0014]

As described above, in the conventional coating apparatus, the uniform coating film thickness over the entire coating width and the satisfactory effect of preventing the generation of the residue due to the retention are not obtained. is there. Therefore, the present invention has been proposed in view of such circumstances, and provides a coating apparatus capable of forming a uniform coating thickness distribution in the coating width direction and forming a good coating film. To aim.

[0015]

The present invention has been proposed to achieve the above object. That is, the present invention is an extrusion type which is provided with a die having a paint reservoir to which the paint is supplied, and which is applied on a continuously running support while extruding the paint through a slit provided at the tip of the die. In the coating apparatus, the cylindrical filter member whose wall thickness continuously changes in the coating width direction is inserted into the paint reservoir of the die, and the paint is supplied through the filter member. It is a thing.

The extrusion type coating device uses a die in which a slit is formed facing the front end surface and the vicinity of the front end surface is doctor-edged, and is directed to the surface of a running support. Is a coating device for coating the above-mentioned support with a uniform thickness by the doctor edge.

In the present invention, a cylindrical filter member whose wall thickness continuously changes in the coating width direction is inserted into the paint reservoir of the die, and the paint is supplied through the filter member. The filter member functions so as to rectify the flow of the paint by causing the pressure of the paint in the paint reservoir to be lost and to make the coating thickness of the paint uniform. In the present invention, the filter member has a cylindrical shape whose wall thickness changes continuously in the coating width direction.

When a filter member having a constant wall thickness in the coating width direction is used, for example, when a highly viscous coating material is applied, the coating thickness becomes thicker at the edge, and the coating film cross section has a dish shape. Tends to be. On the other hand, if a filter member whose wall thickness continuously changes in the coating width direction is used, a pressure loss effect corresponding to the characteristics of the coating material can be obtained, and a coating film with a uniform film thickness can be obtained regardless of the type of coating material. Can be formed.

In the above filtering member, the supporting portion may be formed independently of the die side plate so as to be detachable so that the filtering member can be easily replaced.

[0020]

When a coating material is formed on a continuously running support by a die to form a coating film, a cylindrical filter whose wall thickness continuously changes in the coating width direction in the coating liquid reservoir of the die. When a member is inserted and the above coating material is supplied through the filtration member, pressure loss (rectifying effect) that matches the characteristics of the coating material in the coating width direction
Is obtained, and a coating film having a uniform coating thickness distribution is formed regardless of the type of coating material.

[0021]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

In this example, a magnetic coating was applied onto a polyethylene terephthalate film, which is a non-magnetic support, by using a coating device in which a filter member was inserted into a coating liquid reservoir of a die to form a magnetic layer. Is. First, in the present embodiment, the configuration of the coating device used for coating and forming the magnetic coating material will be described.

That is, in this coating apparatus, as shown in FIG. 1, a substantially rectangular parallelepiped having a predetermined width is provided in the middle part where the non-magnetic support 6 is sequentially run from the unwinding side to the winding side. A die (extruder) 4 made of a metal block is arranged. The die 4 is disposed laterally of the non-magnetic support 6 which runs upward from below in FIG. 1, and the tip surface 4a of the die 4 faces the surface of the non-magnetic support 6. Is installed in.

The die 4 has a so-called wedge shape in which the vicinity of the tip surface 4a is linearly and obliquely scraped off, and a slit 5 having a width corresponding to the coating width is formed facing the tip surface 4a. Has been done. The slit 5 is a gap through which the paint 1 made of a magnetic material is extruded,
Usually, it is set to a very narrow gap of about 0.01 to 2.0 mm.

On the back side of the slit 5, a pocket (coating liquid reservoir) 3 communicating with the slit 5 is formed. The pocket 3 has a length substantially equal to the width of the slit 5 and is formed as an orifice-shaped space. As shown in FIG. 2, a cylindrical filtering member 7 having a width substantially equal to the coating width is inserted into the pocket 3. The filter member 7 has a pressure loss, and the paint 1 supplied into the pocket 3 via the filter member 7 causes the slit 5 to pass.
Supplied within. As a result, a pressure loss (rectifying effect) that matches the characteristics of the coating material in the coating width direction is obtained, and it is possible to form a coating film having a uniform coating thickness distribution in the coating width direction. Examples of the material of the filter member 7 include a stainless sintered body and the like.

As shown in FIG. 3, the filter member 7 is formed so that the wall thickness continuously changes in the coating width direction. As a result, it is possible to perform good coating on a coating having a wide range of viscosity characteristics, and it is possible to obtain a uniform coating thickness distribution in the width direction even for a coating that was conventionally considered to have a poor coating thickness distribution.

The filter member 7 is supported by element holders 9 fitted and arranged at both ends thereof. The element holder 9 is disposed by being inserted into the openings 8a formed in the side plates 8 attached to both sides of the die 4, and is formed independently of the side plates 8. As a result, the filter member 7 can be removed together with the element holder 9, and the filter member 7 can be easily replaced without disassembling the die 4.

A coating liquid supply port 11 is provided on the outer side of the element holder 9 so as to open on both end faces of the die 4, and the coating liquid 1 is introduced into the coating liquid supply port 11. A coating liquid supply pipe (not shown) for connection is connected.

A pump (not shown) is attached to an intermediate portion of the coating liquid supply pipe, so that the coating material 1 is supplied from the coating liquid supply pipe into the pocket 3 through the filtering member. It is designed to be sent under pressure. Therefore, the pocket 3 serves as a space for receiving the paint 1 to be pumped, and has a function of an accumulator.

The paint 1 pumped into the pocket 3 is
It is supplied into the slit 5 through the filter member 7,
Further, it is extruded from the front end of the slit 5 onto the surface of the non-magnetic support 6 and formed as a coating film.
At this time, since the coating material 1 is supplied into the slit 5 through the filtering member 7, a pressure loss (rectifying effect) matching the characteristics of the coating material 1 in the coating width direction can be obtained and a uniform coating width can be obtained. The coating thickness distribution in the direction is obtained.

On the other hand, the non-magnetic support 6 which is moved and run from the unwinding side to the winding side is the guide roll 1
0a, 10b and the support rolls 2 are made to run, and the guide rolls 10a, 10b
The appropriate tension is applied to ensure smooth running.

Therefore, in this coating apparatus, the tip surface 4a of the die 4 is fed to the surface of the non-magnetic support 6 which is fed from the unwinding side and travels in the direction of arrow A in FIG.
Is abutted, and the paint 1 is extruded from the slit 5 formed on the abutting surface to face the tip end surface 4a of the die 4 to form a coating film.

Then, using the coating device having the above-mentioned constitution, the magnetic coating material was coated on a polyethylene terephthalate film (width: 620 mm) having a thickness of 12 μm to produce an audio tape. As the above magnetic paint, three kinds of paints A having different viscosities, as shown in Table 1 below,
Using B and C (the same kind of magnetic paint was used for both), coating was performed so that the coating thickness was 4 to 6 μm and the coating width was 610 mm.

The coating speed was 250 m / min.

Then, with respect to the obtained magnetic tape, the coating thickness distribution of the magnetic layer was examined when the wall thickness of the filtering member was continuously changed (tapered) in the coating width direction. The results are shown in Table 1 below. Evaluation is shown in Figure 5.
The magnetic layer 2 formed on the non-magnetic support 21 as shown in FIG.
When the surface of No. 2 bulges in a mountain shape, it is ◯, when the surface of the magnetic layer 22 is flat as shown in FIG. 6, ◎, and the surface of the magnetic layer 22 is dish-shaped as shown in FIG. The case of depression was visually evaluated as × to Δ according to the degree of depression.

The taper size of the filter member is defined as the difference between the wall thickness A at the end and the wall thickness B at the center of the filter member, as shown in FIG.

[0037]

[Table 1]

As shown in Table 1, in this embodiment,
It was found that by continuously changing the wall thickness of the filtering member in the coating width direction, a good coating film having a uniform coating thickness distribution can be obtained for magnetic coating materials having a wide viscosity range of 2000 to 8000 cps. It was

[0039]

As is apparent from the above description, according to the present invention, the cylindrical filter member whose wall thickness continuously changes in the coating width direction is inserted in the coating liquid reservoir of the die. Also, it is possible to handle paints with a wide range of viscosity, and it is possible to perform good coating even for paints that were conventionally considered to have a poor coating thickness distribution in the coating width direction.

As a result, the manufacturing process can be simplified, and it is possible to sufficiently deal with materials that have been conventionally unusable, which is advantageous for cost reduction.

Further, by replacing the supporting portion (element holder) of the filtering member with the die side plate as an independent component, the filtering member can be easily replaced, and the accuracy of the die and the paint accumulation due to this replacement can be changed. Also, there is no risk that the paint will dry in the paint flow path in the slit.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a coating apparatus according to the present invention.

FIG. 2 is an enlarged perspective view of an essential part showing the configuration of a die of the coating apparatus.

FIG. 3 is an enlarged sectional view of an essential part showing a configuration of a filtering member inserted into a coating liquid reservoir of the die and a supporting portion (element holder) of the filtering member.

FIG. 4 is an enlarged cross-sectional view of an essential part for explaining the degree of change in wall thickness (taper size) of the filtering member in the width direction.

FIG. 5 is a diagram for explaining a method for evaluating a coating thickness distribution of a magnetic layer formed on a support, and a cross-sectional view showing a case where the coating thickness distribution has a mountain shape.

FIG. 6 is a diagram for explaining a method for evaluating a coating thickness distribution of a magnetic layer formed on a support, and a cross-sectional view showing a case where the coating thickness distribution is flat.

FIG. 7 is a diagram for explaining a method for evaluating a coating thickness distribution of a magnetic layer formed on a support, and is a cross-sectional view showing a case where the coating thickness distribution is dish-shaped.

FIG. 8 is a perspective view showing a configuration example of a die in a conventional coating apparatus.

FIG. 9 is a cross-sectional view showing a configuration of a filtering member and a supporting portion (element holder) of the filtering member inserted into a coating liquid reservoir of a die in a conventional coating device.

[Explanation of symbols]

 1 Paint 3 Pocket (Coating Liquid Reservoir) 4 Die 5 Slit 6 Nonmagnetic Support 7 Filtering Member 8 Side Plate 9 Element Holder 11 Paint Supply Port

Claims (2)

[Claims] 1. An extrusion type die, which comprises a die having a paint reservoir to which the paint is supplied, and which applies the paint while pushing it out through a slit provided at the tip of the die on a continuously running support. In the coating device, a cylindrical filter member whose wall thickness continuously changes in the coating width direction is inserted into the coating material reservoir of the die, and the coating material is supplied through the filtering member. apparatus. 2. The coating apparatus according to claim 1, wherein the supporting portion of the filtering member is formed independently of the die side plate and is detachable.