JPH091027A - Coating device - Google Patents

Abstract

PURPOSE: To form a coating film without a defect line and a uniform thickness even when the coating speed is increased by forming a tapered face at the apex end of the slit side of the upstream side lip, and making an angle formed by this tapered face and the slit side face satisfy a specified condition. CONSTITUTION: An extrusion type coating apparatus applies a coating 10 on a flexible substrate 7 running continuously along the apex face between the upstream side lip 5 and the downstream side lip 6 of the apex of a die 1 while the coating 10 is extruded from a slit 4 provided between the upstream side lip 5 and the downstream side lip 6. In addition, a tapered face 5a is formed at the apex of the slit side of the upstream side lip 5 in such a way that the angle θformed by this tapered face 5a and the face 5 of the slit 4 side satisfies a condition of 0 deg.<=θ<=45 deg.. The coating 10 extruded from the slit 4 forms thereby a storage 11 of the coating in the space between the tapered face 5a and the substrate 7 and the substrate is made to float up from the apex face of the upstream side lip 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating device of so-called eclectic type.

[0002]

2. Description of the Related Art Generally, audio tapes and video tapes are coated with a magnetic paint prepared by dispersing and kneading a ferromagnetic powder, a binder, a dispersant, a lubricant, etc. in an organic solvent on a non-magnetic support such as a polyester film. By doing so, the magnetic layer is formed.

As a method for coating the magnetic coating material on the support in this way, a roll coating method using a roll is predominant, as represented by a gravure roll method and a reverse roll method. However, these roll coating methods have problems such as poor paint transfer from the roll to the support, paint splashes, and deterioration of paint quality due to excess supply paint being returned to the mixing process. Is a cause of impairing the characteristics of.
For example, if the coating thickness of the magnetic coating film is uneven, this causes the output fluctuation. Further, if the paint is scattered on the magnetic coating film, this causes dropout. Problems such as coating thickness unevenness tend to become more prominent particularly as the coating speed is increased, so that there is a disadvantage that the coating speed is limited.

Therefore, in recent years, as a new coating method capable of solving these problems, an extrusion (die) method has been attracting attention and has already been partially put into practical use. As shown in FIG. 3, the extrusion type applicator has an upstream end lip 25 and a downstream end lip 26, and a wide slit 24 between the upstream lip 25 and the downstream lip 26. The coating material, which has a die 28 and is continuously extruded from the slit 24, is applied to the surface of the support 27 running along the tip surfaces of the upstream lip 25 and the downstream lip 26 with a uniform thickness. It is a thing.

Here, in such a die 28,
The shapes of the tip surfaces of the upstream lip 25 and the downstream lip 26 greatly affect the contact with the support 27, the paint flow, and the like. Conventionally, the shape of this tip surface is the upstream lip 25.
Has a slanted surface inclined with respect to a tangent line drawn from the upstream lip 25 to the downstream lip 26, and the downstream lip 26 has a curved surface having a predetermined curvature. In the die having such a tip end surface shape, the paint extruded from the slit 24 has a support 27 and a downstream lip 26.
In the substantially wedge-shaped space formed between the curved surface and the curved surface, the paint is accumulated and adheres to the support 27.

[0006]

However, in the die 28 having such a tip surface shape, the upstream side lip 2 is used.
There is a high possibility that the slit-side tip portion 25a of No. 5 will come into contact with the coating surface, and it is often found that the slit-side tip portion 25a comes into contact with scratches on the coating surface.

As a method of preventing the generation of such scratch lines, as shown in FIG. 4, the entire upstream lip 25 is retracted with respect to the support 27, and the tip 25a of the upstream lip 25 is applied to the coating surface. It is also possible to separate it from. However, when the upstream lip 25 is retracted with respect to the support 27, a step is generated between the tip surface of the downstream lip 26 and the tip surface of the upstream lip 25, and the paint between the downstream lip 26 and the support 27 is removed. The pressure between the downstream lip 25 and the support 27 facilitates overflow to the upstream side. In particular, such an overflow becomes more remarkable as the coating speed becomes higher, which hinders the higher coating speed.

Therefore, the present invention has been proposed in view of such conventional circumstances, and provides a coating apparatus capable of forming a coating film having no scratch line with a uniform thickness even when the coating speed is increased. The purpose is to provide.

[0009]

To achieve the above objects, the present invention provides a flexible support which runs continuously along the tip surfaces of the upstream and downstream lips of the die tip. In the extrusion type coating device for applying the coating material while extruding the coating material from the slit provided between the upstream lip and the downstream lip, a taper surface is formed at the slit side tip of the upstream lip, and the upstream lip is formed. The angle θ between the taper surface and the slit side surface is 0 ° <θ
It is characterized by satisfying the condition of ≦ 45 °.

The coating apparatus can be used in various fields. For example, when it is used for forming a magnetic coating film on a magnetic recording medium,
It is possible to obtain a magnetic recording medium having excellent characteristics in which output fluctuation and dropout are suppressed.

[0011]

The coating material is applied from the slits provided between the upstream lip and the downstream lip on the flexible support that continuously runs along the tip surfaces of the upstream lip and the downstream lip of the die tip. In the extrusion type coating apparatus that applies while extruding, if the slit side tip of the upstream lip is a tapered surface, the paint extruded from the slit is between the tapered surface of the upstream lip and the support. Form a paint puddle in space. In such a case, the coating material floats the support from the tip surface of the upstream lip. Therefore, it is possible to prevent the generation of scratch lines and the adhesion of foreign matter from the lip due to the contact of the tip end surface of the upstream lip with the coating surface.

Further, such a paint pool is stably held between the upstream side lip, the downstream side lip and the non-magnetic support, and does not overflow to the upstream side. Therefore, even if the coating speed is increased to 500 m / min or more, a good magnetic coating film on the coated surface can be formed with a uniform film thickness.

In order to form a coating film having a uniform thickness, the angle θ between the taper surface of the upstream lip and the slit surface is θ.
Is 0 ° <θ ≦ 45 °, more preferably 5 ° ≦ θ ≦ 35 °
It is necessary to be. When θ exceeds 45 °, the space between the taper surface of the upstream lip and the non-magnetic support becomes too large, so that air is likely to flow into this space and the coating film becomes chipped. Further, the fact that the angle θ between the taper surface of the upstream lip and the slit surface exceeds 45 ° means that the angle θ ′ between the taper surface and the non-magnetic support is in the range of 45 °> θ ′> 0 °. . When θ ′ is a small angle as described above, the interface between the air and the paint on the upstream side tends to fluctuate, resulting in uneven coating.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described below with reference to the drawings.

In the coating apparatus according to this embodiment, it is the magnetic coating material that is coated on the non-magnetic support. That is, a magnetic coating film is formed by applying a liquid magnetic paint containing a magnetic powder, a binder, a solvent and the like onto a non-magnetic support. In addition,
As the magnetic powder, binder, and solvent used in the magnetic coating, any of those generally used as a material for the magnetic coating in the coating type magnetic recording medium may be used. -Oxide magnetic powder such as Fe ₂ O ₃ or metal magnetic powder such as Fe or Co, polyvinyl chloride copolymer as binder, polyurethane resin, etc., methyl ethyl ketone, toluene, cyclohexanone etc. as solvent To be Further, a lubricant, an abrasive, a dispersant, etc. may be added to the magnetic paint.

FIG. 1 shows a coating apparatus for coating such a magnetic paint.

That is, in this coating apparatus, as shown in FIG. 1, the coating material 10 is supplied into the pocket (coating material reservoir) 3 of the die (extruder) 1 and pushed out from the slit 4, and the guide rollers 8 and 9 are used. Support 7
It is applied on top.

The die 1 is a metal block having a substantially rectangular parallelepiped shape with a predetermined width, and its tip is divided into an upstream lip 5 and a downstream lip 6, and the upstream lip 5 and the downstream lip 5 are separated. The slit 4 is formed between the side lips 6.

The slit 4 is a gap through which the paint is extruded, and is formed with a width corresponding to the coating width so as to face the tip surface of the die 1. In addition, the slit 4
Is usually a very narrow gap of about 100 to 400 μm.

On the back side of the slit 4, a pocket 3 communicating with the slit 4 is formed as a cylindrical space having a length substantially equal to the width of the slit 4. A paint supply port having an inner diameter smaller than that of the pocket 3 is provided at both ends of the pocket 3 so as to open on both side surfaces of the die, and the paint 10 is supplied into the pocket 3 from here. It is done like this. Therefore,
The pocket 3 serves as a space for receiving the paint 10 pressure-fed from the paint supply device 2 and has a function of an accumulator.

On the other hand, the tip end surface of the die 1 is an inclined surface which is inclined with respect to the tangent line drawn from the upstream lip 5 to the downstream lip 6 at the upstream lip 5, and the downstream lip 6 is provided.
In, the curved surface has a predetermined curvature. And
In particular, in this coating device, the upstream end of the upstream lip 5 is notched to form a tapered surface 5a, and the angle θ of the tapered surface 5a with respect to the slit surface 5b is regulated.

That is, as for the angle θ, as shown in an enlarged view in FIG. 2, a line drawn on the slit surface 5b of the upstream lip 5 is drawn on the line L and a tapered surface 5a of the upstream lip 5. When a line is a line N, it is defined as an angle formed by the line L and the line N, and this θ is in the range of 0 ° <θ ≦ 45 °.

In the coating apparatus having such a structure, the support 7 is continuously run while being held along the tip surfaces of the upstream lip 5 and the downstream lip 6 at the tip of the die 1. . On the other hand, the paint 10 supplied from the paint supply device 2 to the pocket 3 of the die 1 has a uniform paint pressure due to the accumulator effect, and is uniformly extruded from the slit 4.

Here, in this coating apparatus, the slit side tip portion of the upstream lip 5 is cut out to form a tapered surface 5a, and the tapered surface 5a and the curved surface 6a of the downstream lip 6 and the non-magnetic support. A space is formed by the body 7. In such a case, the paint extruded from the slit 4 forms a paint pool 11 in this space,
This paint pool 11 causes the support 7 to move to the upstream lip 5
Is levitated from the tip surface of. Therefore, it is possible to prevent a scratch line from being generated due to the tip of the upstream lip 5 coming into contact with the coating surface.

The paint pool 11 is stably held between the upstream side lip 5, the downstream side lip 6 and the non-magnetic support, and does not overflow to the upstream side. Therefore, even if the coating speed is increased to 500 m / min or more, a good magnetic coating film on the coated surface can be formed with a uniform film thickness.

In order to form a coating film having a uniform thickness, the angle θ formed by the taper surface 5a of the upstream lip 5 and the slit surface 5b is 0 ° <θ ≦ 45 °, as in this coating apparatus.
More preferably, it is necessary that 5 ° ≦ θ ≦ 35 °.

A coating apparatus having a θ exceeding 45 ° is disclosed in Japanese Patent Laid-Open No.
No. 154690. An example of this coating device is shown in FIG. 5. In this case, the upstream lip 3
Since the angle θ formed by the tapered surface 35a and the slit surface 35b of No. 5 is large, inflow of air is likely to occur in this space, and the coating film is likely to be striped.

Further, the taper surface 35 of the upstream lip 35
The angle θ formed by a and the slit surface 35b exceeds 45 ° means that the non-magnetic support 37 of the tapered surface 35a is formed.
The angle θ ′ formed by is in the range of 45 °> θ ′> 0 °. When θ ′ is a small angle as described above, the interface between the air and the paint on the upstream side tends to fluctuate, resulting in uneven coating. It should be noted that the above-mentioned streak-like defects and the coating unevenness are all 50
It becomes remarkable in the high speed range of 0 m / min or more.

The above is the basic structure of the coating apparatus.
In this coating device, a magnet may be arranged on the back surface side of the non-magnetic support at a position corresponding to the slit 4 of the coating device. By the magnetic force of this magnet,
The paint pool 11 is stably held by the space between the taper surface of the upstream lip 5 and the curved surface of the downstream lip 6 and the non-magnetic support, so that the paint can be applied uniformly.

Next, the following experiment was conducted to confirm the effect of restricting the angle θ formed by the taper surface of the upstream lip and the slit surface.

The angle θ formed by the taper surface of the upstream lip and the slit surface is 0 °, 15 °, 30 °, 45 °, 60 °, that is, the coating device of the type shown in FIG. 4 (θ =
0 °), a coating device of the type shown in FIG. 1 (θ = 15 °, 3
0 °, 45 °), a coating device of the type shown in FIG. 5 (θ = 6
0 °) was prepared. However, in these coating devices, the slit width 1 is 250 μm, and the step d between the upstream lip and the downstream lip is 25 μm. Then, the magnetic coating material was applied onto the support by these coating devices, and the coating state was examined.

The coating speed is 300 m / min, 400 m / min.
Min, 500 m / min or 600 m / min. Other coating conditions are as follows.

Coating conditions Support: polyethylene terephthalate film for video (thickness 12 μm, width 620 mm) coating width: 610 mm coating thickness: 2.5 μm Table 1 shows the evaluation results of the coating conditions in each case. In Table 1, ◯, Δ, and x represent coating levels, respectively. ○ indicates a good coating level, △ indicates some instability in coating, but × indicates a practical coating level, × indicates scratches and the like on the coated surface, and coating is below the practical level. Each case is shown.

[0034]

[Table 1]

First, in the coating device (θ = 0 °) in which the upstream lip does not have a tapered surface, 300 to 400 m
When the coating speed is about / minute, a good level of coating is performed. However, when the coating speed is 500 m / min or more, the coating material extruded from the slit overflows to the upstream lip and the coating becomes unstable. In this case, when the support is brought close to the upstream lip, the overflow is alleviated, but the slit-side tip portion of the upstream lip comes into contact with the coating film, causing scratches or foreign matter on the coating film.

On the other hand, in the coating apparatus in which the angle θ formed by the taper surface of the upstream lip and the slit surface is larger than 45 °, streak-like defects are observed in the coating film as the coating speed is increased. Become. For example, when the angle θ between the taper surface of the upstream lip and the slit surface is 60 °, the coating property is already at a poor level at a coating speed of 400 m / min.

On the other hand, in the coating apparatus in which the angle θ formed by the taper surface of the upstream lip and the slit surface is 0 ° <θ ≦ 45 °, not only in the low speed region but also in the high speed region of 500 m / min or more. Also provides a good level of coatability.

From the above results, it is necessary to form a taper surface at the slit side tip of the upstream lip and regulate the angle θ formed by the taper surface and the slit surface within the range of 0 ° <θ ≦ 45 °. It was confirmed that it is effective in improving the coating property in the high speed region of not less than / min. At the angle θ between the taper surface of the upstream lip and the slit surface,
A more preferable range is 5 ° ≦ θ ≦ 35 °.

[0039]

As is apparent from the above description, in the present invention, in the extrusion type coating apparatus, the slit side tip portion of the upstream lip is cut out to form a tapered surface, and the tapered surface and the slit are formed. Since the angle θ formed by the surface is restricted to a relatively small angle range of 0 ° <θ ≦ 45 °, a coating film having a good coating surface can be formed with a uniform film thickness even when the coating speed is increased. .

Therefore, according to the coating apparatus of the present invention,
For example, when the magnetic layer of a coating type magnetic recording medium is formed, it is possible to obtain a magnetic recording medium with excellent characteristics in which output fluctuation and dropout are suppressed.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram for explaining an angle θ formed by a taper surface of an upstream lip and a slit surface.

FIG. 3 is a schematic view showing an example of a coating apparatus of a type that does not have a taper surface on a slit-side tip portion of an upstream lip.

FIG. 4 is a schematic view showing another example of a coating apparatus of a type in which the slit side tip portion of the upstream lip does not have a tapered surface.

FIG. 5 is a schematic diagram showing a coating apparatus in which an angle θ formed by a taper surface of an upstream lip and a slit surface exceeds a predetermined range.

[Explanation of symbols]

 1 Die 4 Slit 5 Upstream Lip 6 Downstream Lip 7 Support 10 Paint

Claims (2)

[Claims] 1. A flexible support that continuously runs along the tip surfaces of the upstream lip and the downstream lip of the die tip,
In an extrusion type coating apparatus that applies coating while extruding paint from a slit provided between the upstream lip and the downstream lip, a taper surface is formed at the slit-side tip of the upstream lip, An application apparatus characterized in that an angle θ formed by a taper surface and a surface on a slit side satisfies a condition of 0 ° <θ ≦ 45 °. 2. The coating apparatus according to claim 1, wherein the coating material to be coated is a magnetic coating material, and a magnetic layer of a coating type magnetic recording medium is formed.