JPH0770051B2 - Polishing device for magnetic recording media - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a tape or a flexible disk which can be used in video-related equipment, audio equipment, information-related equipment, and the like. The present invention relates to a polishing apparatus for a high density recording medium with improved defects and electromagnetic conversion characteristics.

2. Description of the Related Art With the improvement in image quality in the field of video equipment, digital signal processing in the field of audio equipment, and the spread and diversification of computer equipment, these external memories are required to be small in size, large in capacity, and high in quality. Has become. Along with this, it has become necessary to improve the electromagnetic conversion characteristics and reliability of the magnetic recording medium widely used as these external memories in the high density recording area.

Currently, the mainstream of these magnetic recording media is a coating-type medium mainly composed of magnetic powder and a binder resin. However, in this coating-type medium, it is difficult to control the production of the magnetic coating material for forming the magnetic layer, and Due to the limitation of the coating film forming technique when forming the layer, the surface condition after forming the magnetic layer did not satisfy the electromagnetic conversion characteristics and reliability in the high density recording region. Specifically, protrusions and foreign matter on the surface of the magnetic layer,
The signal loss occurs due to the adhesion of dust during cutting, and the magnetic powder in the magnetic layer is unevenly distributed downward in the film thickness direction, and the accompanying binder resin-rich layer on the surface of the magnetic layer impairs electromagnetic conversion characteristics. To be

As a means for improving these, the following examples are known in the prior art.

As a first example, a ceramic blade is pressed against the surface of a magnetic layer of a tape-shaped magnetic recording medium to be cleaned for cleaning.

Hereinafter, the above-mentioned conventional example will be described with reference to the drawings.

FIG. 2 is a view showing an example of a conventional magnetic tape surface finishing apparatus, wherein 1 is a knife-edge type cleaner, 2 is a tape-shaped magnetic recording medium, and 3 is a guide roll. FIG. 3 is an enlarged view of a knife edge type cleaner, and 4 is a ceramic knife edge, the cutting edge of which has a radius of curvature R. R
Is generally smaller than 1 mm.

The tape-shaped magnetic recording medium finishing device configured as described above is used during the magnetic tape manufacturing process from the time when a wide raw fabric long medium is slit into a tape shape to the time when it is wound on a cassette or a reel. ing.

The tape-shaped magnetic recording medium by the above treatment, the knife edge type cleaner touches the magnetic layer surface during running,
Small protrusions and dust on the surface are removed with a small R edge,
As a result, signal loss is reduced.

As a second example, a polishing tape obtained by coating and hardening abrasive grains of alumina, chromium oxide, silicon carbide or the like with a binder resin is applied to the surface of a magnetic recording medium to scrape off protrusions and the like on the medium surface.

The second conventional example will be described below with reference to the drawings.

4 and 5 are views showing an example of a conventional surface finishing apparatus for a magnetic recording medium. 5 is a polishing tape, 6 is a polishing tape unwinding roll, 7 is a polishing tape winding roll, and 8 is a polishing tape touching roll. In FIG. 4, 9 is a tape-shaped magnetic medium and 10 is a guide roll. Fifth
In the figure, 11 is a disk-shaped magnetic medium, and 12 is a disk rotation system.

The magnetic recording medium that has passed through the surface treatment device configured as described above is scraped off by the relatively large relative speed by contacting with the new surface of the polishing tape, the projections formed on the surface of the magnetic layer, the adhered foreign matter, etc. As a result, excellent surface properties with few signal defects can be obtained.

Problems to be Solved by the Invention However, the above-mentioned configuration has a problem that sufficient or stable reduction of signal loss cannot be obtained as the recording density is improved. In the first example, (1) a decrease in the ability due to the adhesion of shavings to the cutting edge of the blade, (2) the limit of the scraping ability due to the relative speed with the blade and the pressing force, (3) the relative speed, the pressing Increased scraping ability due to force or the like increases the change over time in the cutting edge, and (4) scratches are the causes.

In the second example, better results were reported than in the first example due to changes in the abrasive grain size, changes in the polishing tape feed rate, etc., but (1) increase in cost, (2) polishing tape and magnetic medium In terms of difficulty in contact stability with (3) variations in polishing tape quality, etc., sufficient reliability and merits cannot be obtained.

In view of the above problems, the present invention can stably guarantee reduction of signal loss even under severe conditions in a high density recording area.
In addition, the present invention provides a polishing apparatus for a magnetic recording medium, which also takes mass productivity into consideration.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium polishing apparatus of the present invention comprises diamond abrasive grains having a grain size of 10 to 20 μm, which are solidified with a metal binder to form a center line average. Roughness (R
It has a rotatable grindstone in which a) is adjusted to 0.6 to 1.2 μm.

Effects With the above configuration, it is possible to reliably remove the protrusion on the surface of the magnetic layer that may cause a signal defect. At that time, by adjusting the center line average roughness of the grindstone, even if the size of the abrasive grains constituting the grindstone is 10 to 20 μm, scratches are not generated on the surface of the magnetic layer. Further, the degree of freedom of the contact condition between the grindstone and the medium is large, and the present invention can be applied to various types of medium.

EXAMPLE A magnetic recording medium polishing apparatus according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the steps after slitting of the 8 mm VTR tape. In FIG. 1, 13 is a cylindrical diamond grindstone for polishing the surface of the magnetic layer. Formed, centerline average roughness (Ra) of 0.6
It is adjusted to be ~ 1.2 μm. Further, independently of the slitter traveling system, it can be freely driven in forward and reverse directions at an arbitrary rotational speed. 14 is a magnetic recording medium (original), 15 is an unrolling medium winding roll, 16 is an 8 mm tape winding roll, 17 is a nip roll, 18 is an 8 mm width slitter, 1
9 is a guide roll, 20 is a cleaning tissue running system, and 21 is an 8 mm tape.

With this device, the original medium 14 attached to the original medium unwinding roll 15 is slit by an 8 mm width slitter 18 and then subjected to a polishing process which is a feature of the present invention by a cylindrical diamond grindstone 13 and then 8 mm. Tape winding roll 16
To be wound up. A metal binder is preferred for fixing the diamond abrasive grains in terms of strength. With an organic binder, there is a concern that the abrasive grains may fall off, and in order to avoid the adverse effects of the dropped abrasive grains, it is possible to obtain high reliability by using a metal binder. The grain size of the abrasive grains is preferably 10 to 20 μm.

Although the cleaning effect can be obtained with abrasive particles smaller than 10 μm, it is necessary to use 10 μm in order to increase the contact area with the magnetic layer and the frequency.
It is effective that it is m or more.

At that time, it is important to adjust the center line average roughness of the surface of the grindstone to 0.6 to 1.2 μm, which is more likely to cause clogging of polishing debris smaller than this, and if rougher than this, scratches the magnetic layer surface easily .

On the other hand, if the abrasive grain size exceeds 20 μm, even if the surface roughness is adjusted, scratches are severely generated or the polishing effect is low, so that excellent performance cannot be obtained.

Example 1 A magnetic paint having the following composition was prepared.

When converting to paint, The solid content concentration was adjusted to about 26% under the solvent ratio of. A kneader, a disper, and a sand mill were used as a paint-making device, and it was carried out for a sufficient time so that the dispersed state of the paint was uniform.

The magnetic coating material thus prepared was coated on a polyethylene terephthalate film having a thickness of 10 μm so as to have a dry film thickness of 4 μm. The coating method used was the gravure coating method.

The magnetic coating film after coating was subjected to a mirror finishing treatment and then cured.

After that, a back coat layer composed of polyurethane, vinyl chloride, carbon, alumina, and a curing agent was formed on the back side of the magnetic layer to a thickness of about 0.5 μm.

Sample # 0 is a cassette produced by directly slitting the finished product through the above process to a width of 8 mm. or,
Tapes prepared by the first and second examples described in the conventional example are referred to as samples # 1 and # 2, respectively.

On the other hand, the tape according to the present invention obtained through the surface polishing apparatus shown in FIG. 1 is designated as sample # 3.

For the above samples # 0 to # 3, the number of dropouts when the NTSC full color bar video signal was recorded and reproduced,
The C / N values when recording and reproducing a 5 MHz single sine wave were compared. The equipment used is Is. The results are shown in Table 1.

As is apparent from Table 1, sample # 3 according to the invention
The number of dropouts in
It has been reduced to one tenth, indicating that the effect is high. In addition, as the surface property is improved, the electromagnetic conversion characteristics are also improved by about 0.4 to 0.8 dB in C / N value compared to the conventional example. The present invention can be carried out by simply adding a simple device to the commonly used slitter device, and is not consumable like the polishing tape shown in the conventional example, and is excellent in terms of mass production.

In the above example, the 8 mm VTR tape is described, but it can be applied to other VTR tapes, magnetic tapes, etc., and after being processed in the original state of the magnetic medium, it is punched into a disk shape to make a magnetic disk such as flexible disk. Is also applicable.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to obtain a medium which has very few signal loss even in a high density recording area and which has high reliability and excellent electromagnetic conversion characteristics.

In particular, by using a metal binder as the abrasive grain binder, the accuracy of the cylindrical shape is high, so that stable processing can be performed even when it is added to an existing medium running system.

Furthermore, since the grindstone itself has high durability, it can be readjusted even when the surface roughness of the grindstone changes over time, and the effect is semipermanently obtained, and the cost effect is also great.

[Brief description of drawings]

FIG. 1 is a view showing a slitting device of an 8 mm video tape in which an embodiment of the present invention is mounted, FIG. 2 is a view showing a conventional surface finishing device, and FIG. 3 is a portion of a knife edge type cleaner used in FIG. Enlarged views, FIG. 4 and FIG. 5 are views showing another example of the conventional surface finishing apparatus. 13 …… Cylindrical diamond grindstone, 14 …… Magnetic recording medium (texture), 15 …… Fabric medium unwinding roll, 16 …… 8mm tape winding roll, 21 …… 8mm tape.

Claims (1)

[Claims] 1. A rotatable grindstone having a center line average roughness (Ra) of 0.6 to 1.2 μm, which is formed by solidifying diamond abrasive grains having a particle size of 10 to 20 μm with a metal binder. A polishing apparatus for a magnetic recording medium characterized by the above.