JPH0515825A - Coating device for producing magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the coating device for producing magnetic recording media which allows high-speed coating and improves productivity by forming fine grooves on a roll in the direction inclining to the axial direction of this roll. CONSTITUTION:A coating liquid 4 in a coating liquid pan 6 is picked up by a graver roll 1 and is regulated to a specified amt. by a doctor blade 5. A nonmagnetic base 2 passes between a back up roll 3 and the qravure roll 1 and the coating material 4 is transferred onto the nonmagnetic base 2. The air in cells is efficiently released to the peak parts 9c of cell walls 9 by the fine grooves 10 inclined at 20 to 60 deg. to the axial direction of the roll 7 and the generation of vibrations is obviated even if the coating is increased. The splashing of the coating liquid 4 and the generation of skipping are obviated and the generation of unequal coating is obviated. Then, the uniform coating and the durability of the roll 7 are assured even if the coating speed is increased to as high as, for example, about 350m/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus for producing a magnetic recording medium for coating a non-magnetic support with a magnetic paint or a back coat paint, and more particularly to an improvement of a gravure roll.

[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. Further, in order to prevent winding disorder of the magnetic tape and to improve the surface property, running property, durability, etc., it is formed by applying a back coat paint to the back surface side of the non-magnetic support on which the magnetic layer is not provided. It is widely practiced to provide a back coat layer.

By the way, in order to apply these magnetic paints and back coat paints onto a non-magnetic support, there are, for example, a gravure coating method, a reverse roll coating method, a die coating method (extrusion method), etc. Among them, the gravure coating method is widely used from the viewpoint of high speed, operability, easy management, and low cost.

The gravure coating method uses a coating apparatus consisting of a gravure roll having a spiral cell pattern engraved on the surface thereof and a backup roll for press-bonding the nonmagnetic support to the gravure roll. This is a method of transferring liquid paint onto the top. That is, in order to transfer the coating material onto the non-magnetic support using this device, the non-magnetic support is pressure-bonded to the gravure roll with a backup roll made of an elastic material, and the roll surface is rotated by rotating these rolls. The paint in the coating liquid pan is picked up in each recess (cell) between the adjacent cell walls of the engraved cell pattern, and the paint filled in the cell is transferred to the web on the non-magnetic support. Good.

[0005]

However, in the transfer of the coating material onto the non-magnetic support by the gravure roll, the higher the coating speed, the more likely the coating unevenness will occur.
In other words, as the coating speed increases, paint lumps (hereinafter referred to as “beats”) generated by the doctor blade or backup roll pressure bonding violently vibrate in the cavitation inside the cells, causing paint scattering and skipping. Occurs and uneven coating occurs. Further, since the vibration at this time is a kind of ultrasonic vibration, the paint filled in the cell functions as an abrasive, and the surface of the gravure roll is abraded severely. Therefore, in the past, it has been necessary to suppress the coating speed in order to prevent these occurrences.

Therefore, the present invention has been proposed in order to solve the above-mentioned technical problems, and achieves uniform coating of the coating material, long life of the roll, high speed coating, and high productivity. It is an object of the present invention to provide a coating apparatus for manufacturing a magnetic recording medium, which can significantly improve the magnetic recording medium.

[0007]

In order to achieve the above-mentioned object, a coating apparatus for producing a magnetic recording medium of the present invention comprises a gravure roll having a spiral cell pattern engraved on its surface, and a non-magnetic support. A back-up roll for pressing the body onto the gravure roll, and at the top of the cell wall of the gravure roll, 20 ° to 6 ° with respect to the axial direction of the roll.
It is characterized in that a plurality of fine grooves are formed in the direction inclined by 0 °.

[0008]

For example, when fine grooves are formed on the top of the cell wall of the gravure roll along the axial direction of the roll, the direction of the fine grooves is orthogonal to the rotation direction of the roll. The air inside is difficult to escape to the outside and is not effectively released. However, in the present invention, since the fine groove is formed in a direction inclined by 20 ° to 60 ° with respect to the axial direction of the roll, the direction of the fine groove is oblique with respect to the rotation direction of the roll. The air in the cell is smoothly discharged to the outside as the roll rotates. Therefore, vibration within the cell is prevented and uniform coating can be performed.

Further, in the present invention, since the fine grooves are filled with the coating material, the coating material is also coated on the non-magnetic support at the position where it contacts the top of the cell wall. Therefore, due to the synergistic effect of the cell and the minute cell by the minute groove,
The paint is evenly applied over the entire non-magnetic support.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described below with reference to the drawings. As shown in FIG. 1, the coating apparatus for manufacturing a magnetic recording medium of this embodiment comprises a gravure roll 1 having a cell pattern engraved on its surface, and a backup roll 3 for press-bonding a nonmagnetic support 2 to the gravure roll 1. And a doctor blade 5 for scraping the paint 4 such as a liquid magnetic paint or a back coat paint filled in a cell provided on the surface of the gravure roll 1 to a constant amount.

The gravure roll 1 picks up the coating material 4 stored in the coating liquid pan 6, fills it in the cells provided on the surface thereof, and transfers it onto the non-magnetic support 2. This gravure roll 1 is shown in FIG.
As shown in (1), it is composed of a cylindrical roll 7 made of Fe or the like having a relatively low hardness, and rotational shafts 8, 8 are press-fitted into the central hole 7a from both sides. In this embodiment, the roll 7 has a Rockwell hardness H _R C
STKM of 30 or Vickers hardness of about Hv300
The material (carbon steel pipe for machine structure) was used.

On the outer peripheral surface of the roll 7, as shown in FIG. 3, cell walls 9 for forming cells for filling the liquid paint 4 are formed as projections having a substantially trapezoidal cross section at a predetermined pitch along the axial direction. It is formed in a spiral shape. Therefore, between the adjoining cell walls 9 and 9 is formed a depression having a substantially trapezoidal cross section surrounded by the side walls 9a and 9b of the cell walls 9 and 9 and filled with the coating material 4. ..

Further, a fine groove 10 functioning as a fine cell is formed at the tip 9c which is the top of the peak of the cell wall 9. A plurality of the fine grooves 10 are formed at a predetermined pitch all around the surface of the gravure roll 1 and are inclined at an angle of 20 ° to 60 ° with respect to the axial direction of the roll in order to smoothly discharge the air in the cell to the outside. It is formed with an angle θ. When the inclination angle θ is smaller than 20 °, the air in the cell is not smoothly discharged to the outside, and the paint filling the cell, particularly the beat, is likely to vibrate, resulting in uneven coating. Similarly, when the inclination angle θ exceeds 60 °, the air in the cell cannot be smoothly discharged to the outside, resulting in uneven coating. The tilt angle θ
30 °, which allows the air in the cell to escape smoothly
It is desirable that the angle be ˜45 °. In addition, the fine groove 10
Is a minute cell that is filled with the paint 4, so it is preferable that the number thereof is as large as possible. For example, when the diameter of the gravure roll 1 is 250 to 350 mm, the fine grooves 10
The number of pitches (hereinafter referred to as the number of lines) is preferably 1400 or more. In this embodiment, the number is 2500.

The optimum shape of the fine groove 10 is determined from the viewpoint of smoothly escaping the air in the cell and the life of the fine groove 10. For example, as shown in FIG. It is desirable to use a groove having a substantially V-shaped cross section, where α is as large as possible. For example, the stylus angle α is preferably 90 ° to 160 °, which is an obtuse angle. If the stylus angle α is less than 90 °,
When recycled (re-plated), the fine grooves 10 are filled and the fine cells do not function. On the contrary, when the stylus angle α exceeds 160 °, the air in the cell is not smoothly discharged.

Further, the groove depth of the fine groove 10 is preferably deeper than the thickness of the plating layer described later. By doing so, even if the plating is lost due to wear, the fine grooves 10 function as cells, so that the life of the gravure roll 1 can be extended. It should be noted that the shape of the fine groove 10 is not limited to a groove having a substantially V-shaped cross-section and a bottom having a square shape, but may have a slightly arcuate shape.

In addition to the fine grooves 10, the surface of the roll 7 is plated with hard chrome for the purpose of forming fine cells for filling a small amount of the paint 4 and for improving durability. A layer (not shown) is formed. The plating layer is formed by electroplating on the surface of the roll 7 which has been made into a fine concavo-convex shape by honing, and the surface has a concavo-convex shape. Therefore, the depressions between the fine projections on the surface of the plating layer serve as fine cells filled with the coating material 4.

The gravure roll 1 is formed, for example, as follows. First, as shown in FIG.
Rotating shafts 8, 8 are press-fitted into the central hole 7a of the cylindrical roll 7 made of e or the like from both sides thereof. Next, as shown in FIG. 6, the rotating shafts 8 and 8 are welded to the roll 7 to be integrated. In the present embodiment, the roll 7 and the rotating shafts 8 and 8 are separate members, but they may be integrated.

Next, as shown in FIG. 7, spiral grooves are cut on the outer peripheral surface of the roll 7 along the axial direction at a predetermined pitch. As a result, the depressions between the cell walls 9 that have a substantially trapezoidal cross section and project on both sides of the groove become cells. As a method for forming the cell pattern, there is a so-called knurling process in which the roll 7 is rotated and the roll 7 is pressed by the die.

Next, a plurality of fine grooves 10 are formed on the crests 9c of the crests of the cell wall 9 in the direction of 20 ° to 60 ° with respect to the axial direction of the roll 7. To form the fine grooves 10, a jig formed by forming a plurality of protrusions having a shape opposite to the groove shape of the fine grooves 10 at a predetermined pitch on the surface of the cylindrical roller is pressed against the surface of the roll 7. Form by applying. That is, it is manufactured by rolling.

Next, the surface of the roll 7 on which the cell walls 9 and the fine grooves 10 are formed is roughened by liquid honing. The liquid honing is a method in which fine abrasive grains are mixed with a liquid and the liquid is sprayed onto the surface of the roll 7 by using air pressure to roughen the surface of the roll 7. The surface roughness value here is the type of paint 4 used,
The thickness is appropriately set according to the film thickness of the coating film.
When forming a coating film having a thickness of 1 μm or more, the surface roughness is 3 to 5 μm in terms of ten-point average roughness Rz (value specified by JIS B 0601), and when forming a coating film having a thickness of less than 1 μm. Is preferably 2 to 3 μm.

Next, hard chrome is electroplated on this for the purpose of improving the durability of the roll 7 and forming microcells. As a result, as shown in FIG. 9, a plated layer 11 having a surface with irregularities is formed. It should be noted that a small amount of the coating material 4 is filled in the depressions between the minute protrusions provided on the surface of the plating layer 11.

On the other hand, the backup roll 3 is obtained by pressing the long non-magnetic support 2 such as a polyester film onto the surface of the gravure roll 1 and applying the paint 4 filled in the cells provided in the gravure roll 1. It is for favorably transferring onto the non-magnetic support 2, and is made of an elastic roll such as rubber. Therefore, this roll 3
The non-magnetic support 2 comes into close contact with the apex 9c of the cell wall 9 on the surface of the gravure roll 1 by the elastic force of, and the paint 4 filled in the cell is satisfactorily transferred to the non-magnetic support 2. The backup roll 3 is provided so as to face the gravure roll 1, and the gravure roll 1 is provided.
The non-magnetic support 4 is sent out in the direction of arrow X in FIG.

The doctor blade 5 is for scraping the coating material 4 picked up from the coating liquid pan 6 and filled in the cell so that the coating material 4 has a constant amount. The doctor blade 5 is provided at a position close to the gravure roll 1 on the supply side of the non-magnetic support 2.

In the coating device constructed as described above, the coating liquid 4 stored in the coating liquid pan 6 is picked up by the gravure roll 1, and the coating liquid 4 filled in the cells is fixed by the doctor blade 5. After being made with quantity
When the non-magnetic support 4 passes between the backup roll 3 and the gravure roll 1, the paint 4 is applied onto the non-magnetic support 2.
Is transcribed. By the way, when the coating speed is gradually increased, a beat is generated due to pressure bonding of the backup roll 3 and the doctor blade 5, and violent vibration occurs in the cavitation in the cell. However, in the above-mentioned apparatus, even if the coating speed is increased, the roll 7 is applied to the top portion 9c of the cell wall 9.
Since the fine grooves 10 that are inclined with respect to the axial direction are provided, the air in the cells is smoothly and efficiently discharged to the outside, and vibration does not occur. Therefore, the coating liquid 4 does not scatter or skip, and uneven coating does not occur. Also, coating liquid 4
Does not vibrate, the coating liquid 4 does not function as an abrasive and the surface of the gravure roll 1 is not abraded. Therefore, the coating speed is, for example, 350 m /
Even at a high speed, uniform coating and durability of the roll 7 can be ensured. Also, from low viscosity to high viscosity, that is, solid content 10 to 50%, viscosity 10 to 7000c
It is possible to coat in a very wide range of ps and coating thickness of 0.5 to 6.0 μm.

The coating material 4 applied on the non-magnetic support 2 at this time is applied substantially uniformly over the entire surface of the non-magnetic support 2, as shown in FIG. This is because the cells formed between the cell walls 9 of the gravure roll 1 that are in contact with the non-magnetic support 2, the fine cells formed by a plurality of fine grooves 10 provided on the tops 9c of the cell walls 9, and the plating layer This is because of the synergistic action with the fine cells formed of fine depressions formed on the surface.

Here, the magnetic coating material was actually coated on the non-magnetic support under the following conditions by using the coating apparatus described above, and the coating unevenness was observed. Coating Conditions In Examples 1 to 3, the inclination angle θ of the fine groove 10 with respect to the axial direction of the roller 7 was 45 °, and in Comparative Examples 1 to 3, the inclination angle θ of the fine groove 10 was 0.5 °. did. In Examples 1 and 2 and Comparative Examples 1 and 2, the capacity of the gravure roll 1 was 1.5 mm ² / inch, the width W of the top 9c of the helical cell wall 9 was 30 μm, and the groove depth H was 30 mm.
₁ was 100 μm. Further, the stylus angle α of the fine groove 10 was 60 °, the groove depth H ₂ was 15 μm, and the number of lines was 1400. On the other hand, in Example 3 and Comparative Example 3,
The capacity of the gravure roll 1 is 0.2 mm ² / inch, and the width W of the top portion 9c of the helical cell wall 9 is 25 μm.
m and the groove depth H ₁ was 15 μm. The stylus angle α of the fine groove 10 was 150 °, the groove depth H ₂ was 20 μm, and the number of lines was 2100.

On the other hand, the magnetic paint is prepared by mixing Co-coated γ-Fe ₂ O ₃ as magnetic powder, vinyl chloride copolymer polyurethane resin as binder, methyl ethyl ketone or anone as solvent, and lecithin as additive, and mixing them. Then, it was prepared by adjusting so as to have a predetermined viscosity. Also,
The non-magnetic paint was manufactured in the same manner as the magnetic paint except that carbon black was used instead of the magnetic powder.

The coating material 4 was applied on the non-magnetic support 2 based on the above conditions, and the applied state was evaluated by visual observation or photograph observation. The results are shown in the table. In addition, when there is no coating unevenness, it is ◯, when uneven coating is slightly observed, △,
The case where uneven coating was clearly observed was evaluated by x.

[0029]

[Table 1]

As can be seen from these results, in the comparative examples in which the inclination angle θ of the fine groove 10 with respect to the axial direction of the roll 7 is small, uneven coating occurs at high speed coating (350 m / min), and uniform coating is possible. You can see that it is gone. On the other hand, in the examples in which the inclination angle θ of the fine groove 10 is large, it can be seen that there is no coating unevenness even at high speed coating. Further, it can be seen that regardless of whether the viscosity of the paint is low or high, the paint is applied uniformly over a wide range. Similarly, it can be seen that the coating is applied uniformly over a wide range regardless of the thickness of the coating.

[0031]

As is apparent from the above description, in the apparatus of the present invention, fine grooves to be fine cells are formed in the axial direction of the roll in the top portion of the cell wall of the gravure roll which is in contact with the non-magnetic support. The air inside the cells is smoothly discharged to the outside, so that vibration does not occur. Therefore, the coating material can be applied uniformly on the non-magnetic support at a high speed, and the quality and productivity can be greatly improved. Also, the life of the gravure roll can be significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a coating apparatus for manufacturing a magnetic recording medium to which the present invention is applied.

FIG. 2 is a schematic perspective view of a gravure roll.

FIG. 3 is an enlarged perspective view of an essential part showing an enlarged roll surface.

FIG. 4 is an enlarged perspective view of an essential part showing an enlarged fine groove.

FIG. 5 is a schematic perspective view showing a rotary shaft press-fitting step, showing a gravure roll manufacturing step in the order of steps.

FIG. 6 is a schematic perspective view showing a welding process.

FIG. 7 is a schematic perspective view showing a cell pattern forming step.

FIG. 8 is a schematic perspective view showing a fine groove forming step.

FIG. 9 is an enlarged sectional view of an essential part showing an electroplating process.

FIG. 10 is an enlarged cross-sectional view of an essential part showing a non-magnetic support body to which a coating material has been applied by the application device according to the present embodiment in an enlarged manner.

[Explanation of symbols]

 1 ... Gravure roll 2 ... Non-magnetic support 3 ... Backup roll 4 ... Paint (magnetic paint, back coat paint) 9 ... Cell wall 10 ... Fine grooves

Claims (1)

Claim: What is claimed is: 1. A cell of the gravure roll, comprising: a gravure roll having a spiral cell pattern engraved on a surface thereof; and a backup roll for press-bonding a nonmagnetic support to the gravure roll. A coating apparatus for manufacturing a magnetic recording medium, wherein a plurality of fine grooves are formed on the top of the wall in a direction inclined by 20 ° to 60 ° with respect to the axial direction of the roll.