JP2587672B2 - Method and apparatus for manufacturing magnetic recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a magnetic recording medium, and more particularly, to a magnetic recording medium having good surface smoothness of a magnetic layer and excellent electromagnetic conversion characteristics. The present invention relates to an efficient manufacturing method and an apparatus therefor.

[Conventional technology]

Generally, a magnetic recording medium such as a magnetic tape is formed by applying a magnetic paint comprising a magnetic powder, a binder component, an organic solvent, and other necessary components onto a base film to form a magnetic layer, and performing a magnetic field orientation treatment and a drying treatment. After the surface is smoothed, it is cut into a desired shape.

In recent years, the demand for high-density recording for such magnetic recording media has increased, and in response to high-density recording, using ultrafine cobalt-containing γ-Fe ₂ O ₃ powder or ferromagnetic metal powder, The surface of the magnetic layer is smoothed together with the high coercive force.

However, ultrafine cobalt-containing γ-Fe ₂ O ₃ powder and ferromagnetic metal powder are more difficult to disperse as the particles become finer, and even if dispersed, they tend to re-agglomerate, A solid additive blended in the magnetic layer together with these magnetic powders has the same tendency. Then
When a magnetic paint containing such a magnetic powder or a solid additive that easily agglomerates is applied onto a base film, a magnetic layer having a convex portion on the surface is formed. There are drawbacks such as dropouts and many dropouts.

Therefore, in order to correct such protrusions on the surface of the magnetic layer and to suppress the occurrence of dropout, the surface of the magnetic layer formed on the substrate is subjected to a surface smoothing treatment, and then the magnetic recording medium is further rotated in a direction opposite to the running direction. The surface of the magnetic layer is polished, for example, by being wound around a polishing wheel. (Problems to be Solved by the Invention) However, if the magnetic recording medium is simply wound around the grinding wheel that rotates in the reverse direction and allowed to travel, the influence of the air layer entering along the surface layer of the magnetic recording medium can be reduced. As a result, a gap is formed between the polishing wheel and the magnetic recording medium, and the magnetic recording medium escapes, so that minute projections protruding from the surface of the magnetic layer cannot be cut off. In particular, when the magnetic layer has a relatively soft composition, this tendency is remarkable, and when the tension of the running magnetic recording medium is increased to drive out the air layer, permanent deformation of the magnetic recording medium occurs and the running becomes unstable, A skew problem or the like in which the reproducing magnetic head does not run accurately on the recorded track is likely to occur. Further, in the conventional polishing process, the winding is performed once after the frit, and the polishing process is performed again.

[Means for solving the problem]

The present invention was made as a result of conducting various studies in order to solve the drawbacks of the prior art, and applied a magnetic paint on a base film, and then smoothed a magnetic layer formed by the application. After that, the surface of the smoothed magnetic layer is polished by running while being pressed with a belt-shaped material having a tension of 50 to 1000 gf / 1 inch width on a polishing wheel whose peripheral surface is made of a high-hardness grinding material. In this manner, minute projections are sufficiently removed without increasing the tension of the magnetic recording medium, and the occurrence of dropout is effectively suppressed.

Further, after the surface smoothing treatment of the magnetic layer, the magnetic recording medium raw material is cut into a predetermined width, and at the same time, the tension of the magnetic recording medium is reduced by polishing the surfaces of the cut plurality of magnetic layers. The small projections are sufficiently cut off without increasing the height to suppress the occurrence of dropouts, and the polishing process can be performed with high efficiency.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a polishing wheel whose peripheral surface is made of a high-hardness grinding material, and a magnetic layer 4 formed on a base film 3 of a magnetic recording medium 2 has a predetermined thickness. 5 is a belt made of a woven or non-woven fabric that presses the magnetic recording medium 2 against the polishing wheel 1 and is applied with a predetermined tension indicated by an arrow T. Thus, the magnetic recording medium 2 running around the polishing wheel 1 is pressed from the base film 3 side. Reference numeral 6 denotes a leaf spring for further pressing the band 5 against the magnetic recording medium 2 and the grinding wheel 1, and is fixed by a support 7, and moves the magnetic recording medium 2 through the band 5 with a predetermined elastic force. Is pressed.

According to the magnetic recording medium polishing apparatus 8 configured as described above, the base film 3 of the magnetic recording medium 2 can be used.
The magnetic layer 4 formed thereon is polished by the polishing wheel 1 whose peripheral surface is made of a high-hardness grinding material while being sufficiently pressed against the polishing wheel 1 by the strip 5 and the leaf spring 7. Then, minute projections on the magnetic layer 4 formed of the agglomerated magnetic powder or the like are sufficiently cut off, and the surface of the magnetic layer is polished. As a result, a magnetic layer having excellent surface smoothness is formed, and a magnetic recording medium having excellent electromagnetic conversion characteristics can be obtained.

Here, the polishing wheel 1 of the polishing apparatus 8 preferably has a peripheral surface hardness of 9 or more and a Mohs hardness of 8 or less, and shows almost no polishing effect on a magnetic layer containing an additive such as alumina. I can't. Further, the peripheral surface of the polishing wheel 1 is preferably formed of abrasive grains having a grain size of # 1500 to # 4000. If the grain size is less than # 1500, the surface roughness becomes too large and the magnetic layer is damaged. When the particle size exceeds # 4000, the polishing effect is extremely reduced. The peripheral surface of the polishing wheel 1 may be formed by integrally molding a ceramic having a Mohs hardness of 9 or more and a particle size of # 1500 to # 4000 on the peripheral surface of the polishing wheel body, or a Mohs hardness of 9 or more and a particle size of # 1500. ~ 4000 abrasive grains are sintered on the peripheral surface of the polishing wheel body, and the Mohs hardness is 9
As described above, abrasive grains having a particle size of # 1500 to # 4000 are formed by applying a binder resin to the peripheral surface of the polishing wheel body, and examples of the abrasive grains include diamond, boron carbide, silicon carbide, and aluminum oxide. And the like are preferably used.

Further, the magnetic recording medium 2 includes a polishing layer 1 and a magnetic layer 4.
Of the woven or non-woven fabric for pressing the magnetic recording medium 2 against the grinding wheel 1 in the direction indicated by the arrow T. It is preferable that the magnetic layer 4 of the magnetic recording medium 2 is pressed by applying a tension of 50 to 1000 gf / 1 inch width. If the winding angle θ of the magnetic recording medium 2 is smaller than 30 degrees, the polishing of the magnetic layer 4 is difficult. It cannot be performed well, and it is physically difficult to make the angle larger than 300 degrees due to a guide roll and the like, and the meandering of the magnetic recording medium also becomes large. If the tension of the strip is less than 50 gf / 1 inch width, there is no polishing effect. If the tension is more than 1000 gf / 1 inch width, a large tension is required for the magnetic recording medium 2 to travel and permanent deformation may occur. is there.

Further, the leaf spring 6 for further pressing the woven or non-woven band 5 for pressing the magnetic recording medium 2 against the polishing wheel 1 is preferably pressed with a pressing force of 10 to 100 gf / 1 inch width, preferably 10 gf / inch. When the pressing force is smaller than 1 inch width, the polishing effect is small, and when the pressing force is larger than 100 gf / 1 inch width, the magnetic layer 4 is easily damaged.

In addition, with the belt-shaped material 5 which consists of a woven fabric or a nonwoven fabric,
When the magnetic recording medium 2 can be sufficiently pressed against the polishing wheel 1, the leaf spring 6 is not necessarily required.

The polishing wheel 1 may be rotated. For example, when the polishing wheel 1 is rotated in a direction opposite to the running direction A of the magnetic recording medium 2 as shown by an arrow B, the polishing process on the surface of the magnetic layer 4 can be performed more favorably. Results are obtained.

As described above, when rotating the polishing wheel 1, it is preferable to rotate the polishing wheel 1 at a peripheral speed of 1 to 700 m / min and run the magnetic recording medium 2 at a traveling speed of 20 to 500 m / min. Polishing wheel 1 and magnetic recording medium 2
When the speed is lower than this range, the polishing effect is small, and when the speed is higher, the air layer interposed therebetween becomes too thick and polishing cannot be performed.

FIG. 2 shows an example in which such a polishing apparatus 8 for a magnetic recording medium is attached to a cutting apparatus, and the magnetic recording medium raw 21 wound around the raw roll 9 is cut. Device 10
After being cut into a predetermined width by a pair of cutters 11, it is divided into two groups by a pair of guide rolls 12, and several magnetic tapes 22 are respectively guided to the polishing device 8 and polished, and are taken up by the winding roll 13. It is wound up. However, in this case, after the magnetic tape 22 is cut and polished, the magnetic tape 22 is subsequently polished, so that the polishing treatment of the magnetic tape 22 can be performed efficiently, and the surface smoothness of the magnetic layer is good, and The magnetic tape 22 having excellent conversion characteristics can be obtained efficiently.

Examples of the magnetic powder used in the present invention include:
γ-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, Co
Various known magnetic powders such as Fe ₃ O ₄ powder, CrO ₂ powder, Fe powder, and Co powder are widely included, and as a binder resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, cellulose Conventionally widely used binder resins such as base resins, polyurethane resins, polyester resins, and isocyanate compounds are widely used.

Further, as the organic solvent, conventionally used organic solvents such as toluene, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, and ethyl acetate are used alone or in combination of two or more.

Further, a coating machine for applying a magnetic paint prepared by mixing and dispersing these magnetic powders, a binder resin, an organic solvent, and the like on a base film is a knife coater, a gravure coater, a reverse roll coater, a bead coater, Any of those conventionally used such as a kiss coater, a die coater, and a curtain coater are preferably used.

In the magnetic paint, various commonly used additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent may be optionally added and used.

〔Example〕

 Next, an embodiment of the present invention will be described.

Example 1 Co-containing γ-Fe ₂ O ₃ magnetic powder 100 parts by weight Powder (specific surface area: 40 m ² / g) Nitrocellulose (Asahi Kasei Co., Ltd., 10 kg, HIG1) Polyurethane (Goodrich Co., Ltd., 9 kg, Estane 5702) Polyisocyanate (Nippon Poly 1 Co., Ltd. Urethane Co., Coronate L) α-alumina 2 carbon black 5 zinc stearate 0.5 zinc n-butyl stearate 0.5 cyclohexanone 80 methyl ethyl ketone 80 toluene 80 And sufficiently kneaded and dispersed to obtain a magnetic coating material A. Further, the kneading and dispersing time was slightly shortened with the same composition to obtain a magnetic coating material B in which aggregates remained. Next, the magnetic coating material A and the magnetic coating material B were mixed to obtain a magnetic coating material C in which a little aggregate was intentionally left. This magnetic coating material C is coated on a polyethylene terephthalate film support having a thickness of 14 μm by a gravure roll coater so that the magnetic layer has a thickness of 5 μm, and is subjected to an orientation treatment. To obtain a raw magnetic tape.

Next, as shown in FIG. 2, this magnetic tape material is transferred from the material roll 9 to the cutting device 10 and the polishing treatment device 8 by a distance of 15 mm.
Run at a running speed of 0 m / min.
The magnetic tape 22 was cut into 12.65 mm widths and divided into two groups. Polishing by this polishing device 8 is performed using a diamond having a particle size of # 2000 and a diameter of 10 mm.
The 0 mm polishing wheel 1 is rotated in the direction of arrow B at a peripheral speed of 360 m / min, and the magnetic tape 22 is run in the direction of arrow A at a tension of 100 gf / 1 inch width and a winding angle of θ60 °. The magnetic layer 4 was pressed against the polishing wheel 1 with a tension of / 1 inch width, and the pressing by the leaf spring 6 was omitted.

Example 2 In the polishing processing by the polishing apparatus 8 in Example 1,
Instead of the grinding wheel 1 having a diameter of 100 mm and using a diamond having a grain size of # 2000, an Al ₂ O ₃ powder having an average grain size of 5 μm is formed on the peripheral surface of the grinding wheel body to a thickness of 0.3 mm by thermal spraying to reduce the surface roughness. Using a grinding wheel 1 having a center line average roughness of 1 μmRa and a grain size of # 2000 and a diameter of 100 mm, using a nylon woven fabric instead of a non-woven fabric, and applying the magnetic layer 4 to the grinding wheel 1 with the same tension. Example 1 except for pressing
Polishing treatment was performed in the same manner as described above.

Example 3 In the polishing processing by the polishing apparatus 8 in Example 1,
Except that the tension of the nonwoven fabric 5 was changed from 400 gf / 1 inch width to 200 gf / 1 inch width, and the nonwoven fabric 5 was pressed at a tension of 20 gf / 1 inch with a leaf spring 6 made of 0.2 mm thick polyester film. Polishing was performed in the same manner as in Example 1.

Example 4 In Example 1, the magnetic tape cut by the cutter 11 of the cutting device 10 was wound around a raw roll, and the magnetic tape 22 wound around this raw roll 91 was polished as shown in FIG. And polished in the same manner as in Example 1.

Comparative Example 1 In the polishing processing by the polishing apparatus 8 in Example 1,
Polishing was performed in the same manner as in Example 1 except that the use of the nonwoven fabric was omitted.

Comparative Example 2 In the polishing processing by the polishing apparatus 8 in Example 1,
Polishing was performed in the same manner as in Example 1 except that the use of the nonwoven fabric was omitted and the tension of the magnetic tape was changed to 1000 gf / 1 inch.

With respect to the magnetic tapes obtained in each of the examples and the comparative examples, the protrusion resection rate, the number of dropouts, and the skew fluctuation were examined. The ratio of excision of the protrusion having a diameter of 20 μm or more was examined by a polarizing microscope. In addition, the number of dropouts was as follows: A 2000 m pancake obtained by winding a take-up roll 13 from a raw magnetic recording medium into a VHS cassette was recorded and regenerated using a VTR, VT-8000 manufactured by Hitachi, Ltd. The number of dropouts was examined. Furthermore, the skew fluctuation was recorded by a Hitachi VTR, VT-8000 under conditions of 40 ° C. and 80% RH, and after being sufficiently left under conditions of 5 ° C. and 40% RH, reproduced and monitored. Measured on TV.

 The following table shows the results.

[Effects of the Invention] As is clear from the above table, the magnetic tape obtained in the present invention (Examples 1 to 4) has a higher protrusion removal rate than the magnetic tape obtained in Comparative Examples 1 and 2. Therefore, according to the manufacturing method and the apparatus of the present invention, a magnetic recording medium having a good magnetic layer with excellent surface smoothness and excellent electromagnetic conversion characteristics can be efficiently obtained with low dropout and low skew fluctuation. I understand.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of a polishing apparatus for a magnetic recording medium according to the present invention, and FIG. 2 is a view showing a manufacturing process in which the polishing apparatus for a magnetic recording medium according to the present invention is attached to a cutting apparatus. FIG. 3 is an explanatory view showing an outline, and FIG. 3 is an explanatory view showing an outline of another example of the polishing treatment step of the magnetic layer of the present invention. DESCRIPTION OF SYMBOLS 1 ... Polishing wheel, 2 ... Magnetic recording medium, 3 ... Base film, 4 ... Magnetic layer, 5 ... Strip, 6 ... Spring plate, 8 ... Polishing device, 10 ... Cutting device, 21 …… Magnetic recording media, 22 …… Magnetic tape

Claims (34)

(57) [Claims] (1) A magnetic paint is applied on a base film, and the magnetic layer formed by the application is smoothed. Then, the surface of the smoothed magnetic layer is removed. A method for manufacturing a magnetic recording medium, wherein the polishing is performed by running while being pressed with a belt-like material having a tension of 50 to 1000 gf / 1 inch applied to a polishing wheel made of a grinding material. 2. A method for manufacturing a magnetic recording medium according to claim 1, wherein the magnetic layer pressed against the polishing wheel by the belt-like material is polished by being wound around the polishing wheel at a winding angle of 30 to 300 degrees. 3. The polishing wheel according to claim 1, wherein a polishing wheel whose peripheral surface is made of a high-hardness grinding material is rotated in a direction reverse to the running direction of the magnetic recording medium on which the magnetic layer is formed. Manufacturing method of magnetic recording medium 4. A grinding wheel whose peripheral surface is made of a grinding material having high hardness is rotated at a peripheral speed of 0 to 700 m / min, and a running speed of a magnetic recording medium having a magnetic layer formed thereon is 20 to 500 m / min. 4. The method for manufacturing a magnetic recording medium according to claim 3, wherein the magnetic recording medium is polished by running. 5. The polishing wheel according to claim 1, wherein the peripheral surface of the polishing wheel is formed of abrasive grains having a Mohs hardness of 9 or more and a particle size of # 1500 to # 4000.
A method for manufacturing a magnetic recording medium according to claim 2, 3 or 4. 6. The abrasive grains forming the peripheral surface of the polishing wheel,
6. The method according to claim 5, wherein the magnetic recording medium is diamond. 7. The magnetic recording medium according to claim 1, wherein a peripheral surface of the polishing wheel is formed of ceramic having a Mohs hardness of 9 or more and a particle size of # 1500 to # 4000. Production method 8. The method according to claim 1, wherein the strip is a woven fabric.
A method for manufacturing a magnetic recording medium according to any one of claims 3, 4, 5, 6, and 7. 9. The method for manufacturing a magnetic recording medium according to claim 1, wherein the strip is a non-woven fabric. 10. The belt-shaped material is further pressed by a leaf spring. Method of manufacturing magnetic recording medium 11. The method for manufacturing a magnetic recording medium according to claim 10, wherein the leaf spring is pressed with a pressing force having a width of 10 to 100 gf / 1 inch. 12. A magnetic paint is applied on a base film, and then the magnetic layer formed by the application is smoothed, and then cut into a predetermined width and simultaneously smoothed and cut into a plurality of pieces. The surface of the magnetic layer is polished by running while pressing the surface of the magnetic layer with a strip having a tension of 50 to 1000 gf / 1 inch applied to a polishing wheel whose peripheral surface is made of a high-hardness grinding material. Manufacturing method of magnetic recording medium 13. The method for manufacturing a magnetic recording medium according to claim 12, wherein the magnetic layer pressed against the polishing wheel by the belt-like material is polished by being wound around the polishing wheel at a winding angle of 30 to 300 degrees. 14. The polishing method according to claim 12, wherein a polishing wheel whose peripheral surface is formed of a high-hardness grinding material is rotated in a direction reverse to the running direction of the magnetic recording medium on which the magnetic layer is formed. Manufacturing method of magnetic recording medium 15. A running speed of a magnetic recording medium, on which a magnetic layer is formed, of 20 to 500 m / min by rotating a polishing wheel having a peripheral surface made of a grinding material having a high hardness at a peripheral speed of 0 to 700 m / min. 15. The method for producing a magnetic recording medium according to claim 14, wherein the polishing is performed by running the magnetic recording medium. 16. A polishing wheel having a Mohs hardness of 9
As described above, the abrasive grains having a particle size of # 1500 to # 4000 are formed.
2. A method for manufacturing a magnetic recording medium according to claim 13, claim 14, or claim 15. 17. The method for producing a magnetic recording medium according to claim 16, wherein the abrasive grains forming the peripheral surface of the polishing wheel are diamond. 18. A polishing wheel having a Mohs hardness of 9
The method for manufacturing a magnetic recording medium according to claim 12, claim 13, claim 14, or claim 15, wherein the magnetic recording medium is formed of ceramic having a particle size of # 1500 to # 4000. 19. The method according to claim 12, wherein the band is a woven fabric.
3. A method for manufacturing a magnetic recording medium according to claim 14, claim 15, claim 16, claim 17, or claim 18. 20. The method according to claim 12, wherein the band is a non-woven fabric.
A method for manufacturing a magnetic recording medium according to claim 13, claim 14, claim 15, claim 16, claim 17, or claim 18. 21. A belt-shaped object further pressed by a leaf spring.
12, claim 13, claim 14, claim 15, claim 16, claim
17. A method for manufacturing a magnetic recording medium according to claim 18, claim 19, or claim 20. 22. The method for manufacturing a magnetic recording medium according to claim 21, wherein the leaf spring is pressed with a pressing force having a width of 10 to 100 gf / 1 inch. 23. A smoothed magnetic layer of a magnetic recording medium is pressed against a polishing wheel whose peripheral surface is made of a high-hardness grinding material with a belt-like material having a tension of 50 to 1000 gf / 1 inch width applied thereto. A magnetic recording medium manufacturing apparatus, comprising: a polishing apparatus for polishing while running. 24. The apparatus for manufacturing a magnetic recording medium according to claim 23, wherein the polishing apparatus is attached to a cutting apparatus for the magnetic recording medium. 25. The apparatus for manufacturing a magnetic recording medium according to claim 23, wherein the magnetic layer pressed against the polishing wheel by the strip is wound around the polishing wheel at a winding angle of 30 to 300 degrees. 26. The polishing wheel according to claim 23, 24 or 25, wherein the polishing wheel whose peripheral surface is made of a high-hardness grinding material is reversely rotated with respect to the running direction of the magnetic recording medium on which the magnetic layer is formed. Magnetic recording medium manufacturing equipment 27. A polishing wheel whose peripheral surface is made of a high-hardness grinding material is rotated at a peripheral speed of 0 to 700 m / min to run a magnetic recording medium having a magnetic layer formed thereon for 20 to 500 m / min. 27. The apparatus for manufacturing a magnetic recording medium according to claim 26, wherein the apparatus runs at a speed. 28. A polishing wheel having a Mohs hardness of 9
As described above, claim 2 formed of abrasive grains having a grain size of # 1500 to # 4000.
3. An apparatus for manufacturing a magnetic recording medium according to claim 24, claim 25, claim 26 or claim 27. 29. The apparatus for manufacturing a magnetic recording medium according to claim 28, wherein the abrasive grains forming the peripheral surface of the polishing wheel are diamond. 30. A grinding wheel having a Mohs hardness of 9
As set forth above, claim 23, claim 24, claim 25, claim 26 or claim 27 formed of ceramic having a particle size of # 1500 to # 4000.
Manufacturing apparatus for magnetic recording medium 31. The belt-shaped material is a woven fabric.
4, claim 25, claim 26, claim 27, claim 28, claim 2
An apparatus for manufacturing a magnetic recording medium according to claim 9 or 30. 32. The method according to claim 23, wherein the band is a non-woven fabric.
24, Claim 25, Claim 26, Claim 27, Claim 28, Claim
An apparatus for manufacturing a magnetic recording medium according to claim 29 or claim 30. 33. The belt-shaped object is further pressed by a leaf spring.
23, Claim 24, Claim 25, Claim 26, Claim 27, Claim
An apparatus for manufacturing a magnetic recording medium according to claim 28, claim 29, claim 30, or claim 31 or claim 32. 34. The apparatus for manufacturing a magnetic recording medium according to claim 33, wherein the leaf spring is pressed with a pressing force having a width of 10 to 100 gf / 1 inch.