JPH0770052B2 - 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 containing magnetic powder and a binder resin as a main component. However, in this coating type medium, it is difficult to control the production of the magnetic coating material for forming the magnetic layer and the magnetic layer is difficult to manage. Due to the limitation of the coating film forming technology for forming the magnetic recording layer, the surface condition after forming the magnetic layer did not satisfy the electromagnetic conversion characteristics and reliability in the high density recording area. Specifically, signal loss occurs due to protrusions, foreign matter on the surface of the magnetic layer, and dust attached during cutting, and the magnetic powder in the magnetic layer is unevenly distributed downward in the film thickness direction. For example, the resin-rich layer impairs electromagnetic conversion characteristics.

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) variation in polishing tape quality, 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, a magnetic recording medium polishing apparatus according to the present invention comprises a rotatable rotatable diamond abrasive grain having a grain size of 0.5 to 20 μm, which is solidified with a binder. It has a cylindrical grindstone.

Action With the above structure, almost all of the protrusions that cause signal loss, including fine protrusions on the magnetic coating film, which are difficult to remove by the conventional method, can be removed. Furthermore, dust adhering to the magnetic layer surface during the magnetic layer forming process,
It is also possible to remove or reduce the binder resin-based layer containing no magnetic powder on the surface of the magnetic layer.

By thus improving the surface property and surface configuration of the magnetic layer, excellent electromagnetic conversion characteristics can be obtained even in the high-density recording area, and signal defects are reduced and reliability is improved.

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, 14 is a magnetic recording medium (original fabric), 15 is an original fabric medium unwinding roll, 16 Is a 8 mm tape take-up roll, 17 is a nip roll, 18 is an 8 mm width slitter, 19 is a guide roll, 20 is a cleaning tissue running system, and 21 is an 8 mm tape.

Here, the cylindrical diamond grindstone 13 is made of diamond abrasive grains with a grain size of 0.5 to 4 μm that fits the 8 mm VTR tape,
It is arranged so as to come into contact with the magnetic layer side of the medium, and is independently and independently driven by the slitter traveling system at any rotational speed. The raw fabric medium 14 attached to the raw fabric medium unwinding roll 15 is slit by an 8 mm slitter 18 and then subjected to a polishing process which is a feature of the present invention by a cylindrical diamond grindstone 13 rotating at 4000 to 6000 rpm. After that, it is taken up by the 8 mm tape take-up roll 15. The particle size of diamond is preferably 0.5 to 20 μm, and particularly preferably 0.5 to 4 μm for high density recording tape such as 8 mm tape. 10 for regular tapes and audio tapes
A size of up to 20 μm is suitable. When it is larger than 20 μm, it is too rough and scratches easily occur on the magnetic layer.
If the size is too small (5 mm or less), clogging occurs and polishing becomes difficult.

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 treatment process 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 of 1 is reduced to 1/8 of that of the conventional examples # 1 and # 2, which shows that the effect is high. In addition, as the surface property is improved, the electromagnetic conversion characteristics are also improved by about 0.5 to 1.0 dB in C / N value as compared with 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, the magnetic recording medium processed according to the present invention can obtain high reliability in which a signal loss is extremely small even in a high-density recording area, and further can improve electromagnetic conversion characteristics. Further, such excellent effects can be semi-permanently connected, and large effects can be obtained in mass productivity and low cost.

[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 polishing apparatus for a magnetic recording medium, comprising a rotatable cylindrical grindstone formed by hardening diamond abrasive grains having a grain size of 0.5 to 20 μm with a binder.