JP2578631B2 - Coating device for magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an extrusion-type coating apparatus, and particularly when manufacturing a magnetic recording medium, can obtain a uniform film thickness distribution in the width direction of a support. The present invention relates to a coating device.

[Conventional technology]

It is well known that there are various coating methods such as roll coating, gravure coating, extrusion coating, slide bead coating, and curtain coating.

The magnetic recording medium is obtained by applying a magnetic coating solution on a support, and the coating method is generally a roll coating, a gravure coating, or an extrusion coating. Among them, the extrude coat is excellent since a uniform coating film thickness can be obtained.

By the way, as a conventional technique in an extrusion coating method mainly for the purpose of manufacturing a magnetic recording medium,
JP-A-57-84771, JP-A-58-104666, JP-A-60-238179
No. 6,069,098, in particular, those described in JP-A-62-183085 are known.

[Problems to be solved by the invention]

By the way, the uniformity of the film thickness of a magnetic recording medium formed by coating greatly affects recording / reproducing characteristics.

Basically, the thickness of the support in the running direction can be controlled by the coating speed (conveying speed of the support) and the supply speed of the coating liquid. The film thickness in the width direction should be uniform if the contact strength of the support to the coater head is constant in the width direction. However, in actuality, the running support has a different tension in the width direction. In addition, since the support has so-called "scratching" or "wrinkles", when applied, the film thickness often differs in the width direction. This leads to a decrease in yield as well as quality.

On the other hand, in consideration of the fact that the film thickness varies in the width direction in advance, a method of making the front edge surface and the back edge surface of the coater head uneven in the width direction is also conceivable. It must be changed, and if a film thickness variation factor is delicately added in a certain lot, this cannot be dealt with.

Furthermore, a method of adjusting the film thickness by generating a magnetic field is also known. However, since only the magnetic powder in the magnetic paint is attracted, aggregation of the magnetic powder is likely to occur.

Therefore, a main object of the present invention is to provide a coating apparatus for a magnetic recording medium capable of uniforming the film thickness distribution in the width direction using simple means and without adversely affecting the properties of the coating liquid. is there.

[Means for solving the problem]

The above object is achieved by continuously extruding a coating solution from a slit between the front edge surface and the back edge surface on a flexible support surface continuously running along a front edge surface and a back edge surface. A coating apparatus comprising: a coater head for applying a coating liquid on a surface; and a pair of guide rolls located upstream and downstream of the coater head and arranged to press the support against the coater head. This problem is solved by providing a tension adjusting unit between the head and at least one of the guide rolls for equalizing the tension applied to the support in the entire width direction.

[Action]

Generally, as long as the edge surface of the coater head is flat in the width direction, the tension of the support is strong at the center,
Tends to be weak on both sides. Therefore, according to the present invention, when the support is guided while traveling in a mountain shape toward the coater head as viewed in the traveling direction by tension adjusting means formed of, for example, a drum-shaped roll, the tension is strengthened on both sides of the support. Therefore, both sides of the slug come into contact with the coater head more strongly as compared to the case where it is flat. In this manner, unevenness in the width direction of the tension of the support can be eliminated.

On the other hand, it is conceivable to adjust the tension by moving or inclining the guide roll itself. However, it is impossible to accurately equalize the coating thickness in the width direction. The tension of the support can be directly made uniform over the entire width direction, and the coating film thickness can be made directly uniform.

Further, since the tension adjusting means can be constituted by, for example, a drum-shaped roll, it is practical in terms of apparatus cost and the like, and does not affect the properties of the coating liquid.
This is also advantageous.

[Specific configuration of the invention]

 Hereinafter, the present invention will be described in more detail.

The extruder coated CH shown in FIG. 1 is exemplarily shown and has a front edge surface 1 on an upstream surface and a back edge surface 2 on a downstream surface, and a coating solution pocket portion (shown in FIG. Slit 3 communicating below
have.

On the other hand, as shown in FIG.
Guide rolls 4 and 5 are arranged on the upstream side and the downstream side, and the support 6 passes through the upstream guide roll 4, along the front edge surface 1 and the back edge surface 2, and then passes through the downstream guide roll 5. , And are guided downstream.

At this time, since the coater head CH protrudes from between the guide rolls 4 and 5, conversely, the support 6 is
And against the back edge surface 2.

In the present invention, for example, a drum-shaped tension adjusting roll 7 is provided between the coater head CH and the upstream guide roll 4, and the support 6 is guided by being pushed by the adjusting roll 7.

When the support 6 passes through the adjustment roll 7, the support 6
The tension on both sides is stronger than the tension on the center. Therefore, the coating film thickness tends to be thinner on both sides.

When the edge surfaces 1 and 2 of the coater head CH are flat in the width direction, the center tends to be thinner and the both sides tend to be thicker. However, when the adjusting roll 7 is used, the tension of the support is reduced in the width direction. Thus, the coating film thickness is also made uniform.

Instead of the above drum-shaped adjusting roll 7, as shown in FIG.
The unit adjusting rolls 7A and 7B in a valley shape may be pushed into the support 6.

Further, the above-mentioned drum-shaped adjusting roll 7 and the drum-shaped adjusting roll 7 ′ shown in FIG. 4 are arranged side by side along the running direction with the support 6, and when guided to them, one adjusting roll is used. As a result, more delicate tension control in the width direction can be performed.

On the other hand, when the edge surface of the coater head CH has, for example, a valley shape, the drum-shaped adjusting roll 7 'can be used alone.

Further, if these rolls are made movable and the degree of pushing into the support can be adjusted, it is possible to sufficiently cope with a lot difference and a film thickness variation factor within a lot. Further, by pressing these rolls obliquely with respect to the support, it is possible to cope with uneven film thickness in the width direction of the support.

The adjustment roll described above may be located between the coater head CH and the downstream guide roll 5. The tension adjusting means is
It is not necessary to be a roll, and the lower surface of the non-rotating block may be formed in a mountain shape or the like. In this case, the support 6 travels while sliding on the lower surface thereof.

〔Example〕

 Next, the effects of the present invention will be clarified in Examples.

Metal powder (BET value 60m ³ /
g) with a magnetic coating solution of 3000 cps at a wet film thickness of 15
μm to obtain a magnetic recording medium sheet.

In this case, the film thickness distribution in the width direction when each of the coating apparatus of FIGS. 1 and 2 according to the present invention and the same coating apparatus except that the tension adjusting means is not provided is used. As a result of comparison, the results shown in FIG. 5 were obtained.

According to these results, the effect of uniforming the film thickness in the width direction by the device of the present invention is apparent.

〔The invention's effect〕

As described above, according to the present invention, the film thickness can be easily made uniform in the width direction.

[Brief description of the drawings]

FIG. 1 is an overall view of a coating apparatus of the present invention, FIG. 2 is a perspective view of an example of the tension adjusting roll, FIGS. 3 and 4 are front and perspective views of another example of the tension adjusting roll, and FIG.
The figure is a graph of an example of the optimization of the thickness distribution in the width direction. DESCRIPTION OF SYMBOLS 1 ... Front edge surface, 2 ... Back edge surface, 3 ... Slit, 6 ... Support, 7,7A, 7B, 7 '... Tension adjustment roll.

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein a coating solution is continuously extruded from a slit formed between the front edge surface and the back edge surface on a surface of a flexible support that runs continuously along the front edge surface and the back edge surface. A coating apparatus comprising: a coater head for applying a coating solution to a body surface; and a pair of guide rolls located upstream and downstream of the coater head and arranged to press the support against the coater head. A coating apparatus for a magnetic recording medium, comprising: a tension adjusting means provided between the coater head and at least one guide roll to make the tension applied to the support uniform in the entire width direction.