JPH05128510A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate the difficulty of adjustment and to eliminate the low durability of components constituting a coating apparatus by a method wherein a paint in a definite quantity can be filled into cells without using a doctor blade. CONSTITUTION:In a gravure coating system, the filling operation of a paint into cells 8 formed on the surface of a gravure roll 1 is performed by supplying the paint between the gravure roll 1 being turned and a furnisher roll 9 nipped by said gravure roll 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnetic recording medium in which a magnetic coating material is applied by a gravure coating method.

[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.

For coating these magnetic coatings on a non-magnetic support, there have been known, for example, a gravure coating method, a reverse roll coating method, a die coating method (extrusion method), among others, but among them, high speed and operability are preferable. The gravure method is often used because it is easy to manage and inexpensive.

The gravure coating method uses a coating device consisting of a gravure roll having a 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 the paint. That is, in order to apply a magnetic coating material onto a non-magnetic support using this device, the non-magnetic support is pressure-bonded to a gravure roll with a backup roll made of an elastic material, and the roll surface is rotated by rotating these rolls. By picking up the paint in the coating liquid pan into each depression (cell) between the adjacent cell walls of the cell pattern engraved in the cell pattern and transferring the paint filled in the cell onto the non-magnetic support Paint is applied.

Also, in this gravure coating apparatus, normally,
It has a doctor blade for filling the cells with a fixed amount of the paint picked up from the coating liquid pan by the rotation of the gravure roll. That is, this doctor blade is a rectangular plate made of spring steel, stainless steel, plastic, etc., one end of which is supported, one end of which is a free end, and the free end side of which is in contact with the outer peripheral surface of the gravure roll. Is provided. Then, the free end of the doctor blade slides the outer peripheral surface of the gravure roll to scrape off excess paint from the picked-up paint, and a fixed amount of paint is filled in the cell. ..

[0006]

However, when the width of the gravure roll is small, the doctor blade exhibits a good scraping action, but when the width of the gravure roll is wide, it does not exhibit a sufficient action. However, it has a drawback that the amount of paint filled in the cell becomes non-uniform. Further, since the position of the gravure roll greatly affects the scraping action of the doctor blade, it is necessary to pay close attention to the position adjustment, and it is difficult to obtain a stable scraping action.

Moreover, when the coating apparatus having the doctor blade is used for a long period of time, the free end of the doctor blade is always in sliding contact with the surface of the gravure roll having irregularities, so that it is gradually damaged. When the free end is damaged,
The scraping effect of the doctor blade is reduced, the amount of paint filled in the cell is not constant, and the film thickness of the coating film becomes uneven. Further, if the doctor blade whose free end is damaged is continuously used, the surface of the gravure roll that is brought into sliding contact is also scraped off, causing scratches and wear. Furthermore, due to the wear of the doctor blade and gravure roll, if the generated metal powder falls into the paint pan,
When the gravure roll and the backup roll are pressure-bonded with each other, the metal powder in the paint may damage the gravure roll. In order to prevent such an inconvenience, it is necessary to replace the doctor blade and the gravure roll quite frequently, resulting in a huge maintenance cost.

Therefore, the present invention has been proposed in view of such a conventional situation, and it is possible to secure the durability of the parts constituting the coating apparatus and to provide a coating film having a uniform film thickness for a long period of time. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium in which a magnetic recording medium is formed.

[0009]

In order to achieve the above-mentioned object, a method of manufacturing a magnetic recording medium according to the present invention provides a coating between a rotating gravure roll and a finisher roll nipping the gravure roll. It is characterized in that after supplying and filling the paint in the cells provided on the surface of the gravure roll, the paint is transferred onto a non-magnetic support that continuously runs between the gravure roll and a backup roll that is in pressure contact with the gravure roll. To do.

Further, the JIS of the above-mentioned finisher roll
The hardness measured by a -A hardness meter is 60 ° to 85 °. Furthermore, the surface roughness of the finisher roll is 5 to 10 μm in terms of ten-point average roughness Rz.

[0011]

When the paint is supplied to the contact portion between the rotating gravure roll and the furnisher roll that nips the gravure roll, a fixed amount of the paint is sequentially filled in the cells provided on the outer peripheral surface of the gravure roll. Then, when the non-magnetic support is continuously run through between the gravure roll filled with the paint in the cell and the backup roll pressed against the gravure roll, the paint in the cell is uniformly distributed on the non-magnetic support. Transferred to form a coating film having no coating unevenness.

At this time, the finisher roll has a hardness of 60 ° to 85 measured by a JIS-A hardness meter.
When the surface roughness Rz of 5 to 10 μm is used, the amount of the paint filled in the cell becomes more precise and constant, and the magnetic coating film formed on the non-magnetic support is more uniform. Becomes

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings.

In the present invention, a non-magnetic paint such as a magnetic paint or a back coat paint is applied onto the non-magnetic support.

In the former case, for example, a magnetic coating film is formed by applying a liquid magnetic coating material composed of magnetic powder, a binder, a solvent and the like onto a non-magnetic support. The magnetic powder, binder, and solvent used in the magnetic paint may be any of those commonly used as magnetic paint materials in coating-type magnetic recording media. As an oxide magnetic powder such as γ-Fe ₂ O ₃ or Fe, Co
Examples thereof include metal-based magnetic powders, polyvinyl chloride-based copolymers and polyurethane resins as binders, and methyl ethyl ketone, toluene, cyclohexanone, etc. as solvents. Further, a lubricant, an abrasive, a dispersant, etc. may be added to the magnetic paint.

In the latter case, a back coat paint consisting of carbon black, a binder, a solvent and the like is applied to the surface opposite to the magnetic paint to form a back coat layer. As the binder and the solvent, any of those used in magnetic paints can be used.

To apply the above-mentioned paint, for example, the application device shown in FIG. 1 is used.

The coating apparatus comprises a gravure roll 1 having a cell pattern engraved on the surface thereof, a backup roll 2 for pressing the non-magnetic support 4 onto the gravure roll 1, and a cell provided on the surface of the gravure roll 1. 8 and a finisher roll 9 for supplying a fixed amount of paint.

The gravure roll 1 transfers the paint filled in the cells 8 onto the non-magnetic support 4. The gravure roll 1 is a cylindrical roll made of Fe or the like having a relatively low hardness.
A large number of the cells 8 are formed as, for example, quadrangular pyramid-shaped recesses.

The backup roll 2 is formed by pressing a long non-magnetic support 4 such as a polyester film onto the surface of the gravure roll 1 to fill the coating material filled in the cells 8 provided in the gravure roll 1. Magnetic support 4
For good transfer onto the top, it is made of an elastic roll of rubber or the like. Therefore, the elastic force of this roll causes the non-magnetic support 4 to come into close contact with the cells 8 on the surface of the gravure roll 1, and the paint filled in the cells 8 can be satisfactorily transferred to the non-magnetic support 4. The backup roll 2 is provided so as to face the gravure roll 1 and sends the non-magnetic support 4 in the direction of arrow X in the figure in synchronization with the gravure roll 1.

Further, in the above coating apparatus, a smoothing device 5 for smoothing the transferred magnetic coating film is provided on the downstream side of the gravure roll 1 so that the cell pattern of the gravure roll 1 is transferred. The unevenness of the applied paint is leveled to form a smooth magnetic coating film. The smoothing device 5 may be a film smoother type device made of a flexible film or the like, or a bar smoother type device made of a cylindrical rigid material.

Further, in the above coating apparatus, the cell 8 provided on the surface of the gravure roll 1 is provided with a finisher roll 9 on the delivery side of the non-magnetic support 4 for filling a predetermined amount of paint. It is provided at a position close to the gravure roll 1.

That is, the finisher roll 9
Is provided in contact with the gravure roll 1, and the nozzle 10 is provided in the wedge-shaped space formed by the paint 10 coming into contact with the furnisher roll 9 and the gravure roll 1.
Supplied at 1. A part of the supplied paint 10 drops into the coating liquid pan 12, but the gravure roll 1 is held in this wedge-shaped space and rotates in an amount according to its viscosity and the like.
Each cell 8 provided on the surface is sequentially filled.

Here, when the gravure roll is simply dipped in the coating liquid pan in which the coating material is stored to pick up the coating material, the coating material is supplied to the cells in an amount larger than the volume of the cells due to the surface tension of the coating material. Therefore, in order to make the paint in the cell constant, it is necessary to scrape off the excess paint with a doctor blade. However, in the method using the finisher roll 9, the finisher roll 9 also functions as a scraping device, and the paint 10 in the cell in contact with the finisher roll 9 has only the volume of the cell 8. Since the amount is constantly filled, the doctor blade can be dispensed with, and the inconvenience caused by using the doctor blade, that is, the wear of the device, the difficulty of position adjustment, and the like can be prevented.

In addition, in the case of using the finisher roll 9, since the new coating material 10 is always supplied into the cell 8, the characteristics of the coating film to be formed can always be good. ..

In the method using the finisher roll 9, in order to form a coating film having a uniform film thickness with no coating unevenness by precisely controlling the amount of the coating material 10 with which the cells 8 are filled, It is necessary that the surface hardness of the roll 9 measured by the JIS-A hardness meter is 60 ° to 85 ° and the surface roughness Rz is 5 to 10 μm.

The surface hardness of the finisher roll 9 is 60.
If it is less than °, the scraping action is too strong and coating unevenness occurs on the magnetic coating film. If it exceeds 85 °, the coating material does not move smoothly and thick streaky unevenness occurs on the magnetic coating film.

The surface roughness R of the finisher roll 9
If z is less than 5 μm, stick slip occurs,
When it exceeds 10 μm, the scraping action is too strong, and uneven coating occurs in any case. The surface roughness Rz referred to here is a ten-point average roughness Rz defined by JIS-B0601 and is an index of two-dimensional surface roughness.

The above-mentioned furnisher roll 9 is provided with a rotation driving device, and the rotation direction of the gravure roll 1 (in the figure, a
Direction) may be rotated in the positive direction (direction b in the drawing) with an arbitrary peripheral speed difference. The mobility of the paint maintained in the wedge-shaped space varies depending on its viscosity, and if the viscosity of the paint is too high or too low, streak unevenness occurs, but by adjusting the peripheral speed difference, The mobility can be adjusted, and the streak unevenness and the like due to the viscosity of the paint can be suppressed. Further, by providing the peripheral speed difference, it is possible to prevent the coating material from scattering when the peripheral speed of the gravure roll is set to a high speed, and it is possible to increase the limit film formation speed.

It is important that the surface hardness and the surface roughness Rz of the finisher roll 9 are within the above ranges. It is desirable that friction and wear do not occur even when sliding. Further, since the solvent contained in the magnetic paint is methyl ethyl ketone (MEK), toluene (TOL), cyclohexanone, etc.,
It is necessary to have solvent resistance to these organic solvents. For example, when the finisher roll 9 is made of only a material such as a rubber-based material having insufficient solvent resistance to the solvent, the finisher roll is gradually expanded and deformed by the organic solvent, Function deteriorates.

As shown in FIG. 2, for example, the finisher roll 9 satisfying these requirements has a cylindrical shape having a hole portion 31 through which a rotary shaft is inserted, and the hole portion 3
1 includes an iron layer 32, a rubber elastic layer 33, and a fluorocarbon resin layer 34 in the order of 1. In the finisher roll 9 having this structure, the surface of the fluorocarbon resin layer 34 is subjected to a surface roughening treatment to obtain a predetermined surface roughness, and the material used for the rubber elastic layer 33 is selected. To give a predetermined surface hardness. Further, the solvent resistance is ensured by the fluorocarbon resin layer 34, and the wear resistance and abrasion resistance with respect to the central axis are ensured by the iron layer 32 in contact with the central axis.

As the fluorocarbon resin used in the fluorocarbon resin layer, polytetrafluoroethylene (Teflon), tetrafluoroethylene hexafluoropropylene copolymer (FEP), perfluoroalkoxy fluororesin (PFA) and the like are used. Examples of the material used for the rubber elastic layer include ethylene-propylene copolymer (EPT)
Etc.

Further, as another example of the finisher roll 9 having the other structure, the finisher roll 9 including the iron layer 32 and the urethane elastomer layer 35 provided around the iron layer 32 can be mentioned. The urethane elastomer layer 35 has solvent resistance and has a predetermined surface hardness depending on the surface roughening treatment and material selection.
It can be surface roughness. The finisher roll 9 having this configuration is particularly suitable for applying a low-viscosity paint and when the layer to be formed is a thin film.

In the manufacturing method of the present invention, a magnetic coating is first applied and dried on the non-magnetic support by the coating apparatus having such a structure to form a magnetic layer, and then the non-magnetic support is coated. A back coat paint is applied to the surface opposite to the magnetic layer side and dried to manufacture a magnetic recording medium.

In the magnetic recording medium thus manufactured, both the magnetic layer and the back coat layer are formed to have a uniform film thickness without coating unevenness, and are used for forming the magnetic layer and the back coat layer. The above-mentioned coating device has high durability, with its components being hardly worn even after long-term use.

Next, in order to confirm the effect obtained by using the finisher roll having a predetermined surface hardness and surface roughness, in the above-mentioned coating apparatus, the finisher roll was subjected to the surface hardness and Those having the surface roughness shown in Table 2 (the specific constitution and material of the finisher roll are also shown in Table 1 and Table 2. The materials are in order from the innermost layer of the finisher roll. In place of the above described), a magnetic layer is formed to form a magnetic tape (sample tape 1 to sample tape 4, comparative tape 1 to comparative tape 1).
0) was prepared. Then, the swelling state of the paint on the gravure roll, the filling state of the paint in the cells, the uniformity of the formed coating film, and the limit coating speed were investigated. The results are also shown in Tables 1 and 2.

The above magnetic paint contains C as magnetic powder.
o Adhesion γ-Fe ₂ O ₃ , vinyl chloride copolymer, polyurethane resin as a binder, methyl ethyl ketone, toluene, cyclohexanone as a solvent, and additives such as lecithin were added.

In the above coating apparatus, the peripheral speed of the gravure roll is set to 250 m / min and the peripheral speed of the finisher roll is set to 50 m / min, so that a peripheral speed difference is generated between the gravure roll and the finisher roll. did.

The surface roughness Rz was measured according to the method specified in JIS-B0601.

The swelling state of the coating material on the gravure roll, the filling state and the coating state of the coating material in the cells are good when it is ○, when it is at the practical limit, it is △, when there is a problem in practice, it is ×. Was expressed.

[0041]

[Table 1]

[0042]

[Table 2]

As can be seen from Tables 1 and 2, in Comparative Tape 1 to Comparative Tape 10 prepared by using the finisher rolls whose surface hardness and surface roughness deviate from the predetermined ranges, when applying the magnetic coating material, However, the paint on the gravure roll is swelled, the paint is not sufficiently filled in the cells, and a magnetic layer having a uniform thickness is not formed.

On the other hand, in the sample tapes 1 to 4 prepared by using the finisher rolls having the surface hardness and the surface roughness within the predetermined ranges, when the magnetic coating material is applied, the coating material on the gravure roll is swelled. The cell is filled with a fixed amount of the coating material, and the formed magnetic layer is also formed with a uniform film thickness without coating unevenness.

For reference, a magnetic tape was prepared by a method of picking up the paint from the coating liquid pan without using the finisher roll. However, when the magnetic layer was applied, the paint turbulently flowed on the gravure roll, The filling amount of the paint in the cell was insufficient, and the limiting speed was as low as 250 m / min, so that good results were not obtained.

Therefore, it was found from the above that the use of a finisher roll having a predetermined surface hardness and surface roughness Rz is effective in forming a coating film having a uniform film thickness. .. Also, given surface hardness,
It has been found that when a furnisher roll having a surface roughness Rz is used, the coating limit speed is high and high-speed film formation is possible.

In this example, two types of finisher rolls to which the present invention was applied were used to fabricate magnetic tapes. Among them, an iron layer, a rubber elastic layer and an EPT layer were prepared. Furnisher rolls consisting of a Teflon fluorocarbon layer form a thick film layer such as a magnetic layer, and a furnisher roll consisting of an iron layer and a urethane elastomer layer form a thin film layer such as a back coat layer. It has been shown to be suitable when formed.

[0048]

As is apparent from the above description, in the manufacturing method of the present invention, by supplying the coating material to the contact portion of the rotating gravure roll and the finisher roll nipping the gravure roll, the gravure Since the paint is filled in the cells provided on the surface of the roll, the paint of the volume of the cells is always constantly filled in the cells. Therefore, unlike the case of simply immersing the gravure roll in the coating liquid pan and picking up the paint in the cell, the scraping operation by the doctor blade is not necessary, so the inconvenience caused by using the doctor blade, that is, the adjustment And the problem of low durability of the coating apparatus are solved, a uniform coating film can be formed, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a smoothing device to which the present invention is applied.

FIG. 2 is a schematic perspective view showing a configuration example of a finisher roll.

FIG. 3 is a schematic perspective view showing another configuration example of a finisher roll.

[Explanation of symbols]

 1 ... gravure roll 2 ... backup roll 9 ... furniture roll

Claims (3)

[Claims] 1. A paint is supplied between a rotating gravure roll and a furnisher roll nipping the gravure roll to fill the paint in the cells provided on the surface of the gravure roll, and then the gravure roll and the A method for producing a magnetic recording medium, characterized in that a coating material is transferred onto a non-magnetic support that continuously runs between backup rolls that are pressed against a gravure roll. 2. The JIS-A of the finisher roll
The method for producing a magnetic recording medium according to claim 1, wherein the hardness measured by a hardness meter is 60 ° to 85 °. 3. The method of manufacturing a magnetic recording medium according to claim 1, wherein the surface roughness of the finisher roll is 5 to 10 μm in ten-point average roughness Rz.