JPH0673181B2 - Method of manufacturing magnetic recording medium - 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 method for manufacturing 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 resin binder as a main component. However, in this coating type medium, it is difficult to manage the magnetic coating material for forming the magnetic layer, and Due to the limitation of the coating film forming technology 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, signal loss occurs due to adhesion of protrusions and dust on the surface of the magnetic layer, and due to uneven distribution of magnetic powder in the magnetic layer downward in the film direction, a binder resin-rich layer is formed on the surface of the magnetic layer. As a result, the electromagnetic conversion characteristics are impaired.

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 diagram showing an example of a conventional surface finishing process for a magnetic tape, in which 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.

The finishing process of the tape-shaped magnetic recording medium configured as described above is performed during the magnetic tape manufacturing process from the slitting of a wide original long medium into a tape shape and the winding of the medium into a cassette or reel. .

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 blade tip with R,
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 resin binder or the like is applied to the surface of the 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.

FIG. 4 and FIG. 5 are views showing an example of a surface finishing process of a conventional 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 undergone the surface treatment technology configured as described above is scraped off by the relatively large relative speed by contacting with the new surface of the polishing tape, the protrusions formed on the surface of the magnetic layer and the adhered foreign matter. As a result, excellent surface properties with few signal defects are 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, the ability to scrape scraps on the cutting edge of the blade is reduced, the limit of the scraping ability of the protrusion due to the relative speed and pressing force with the blade, the relative speed, and the scraping ability are increased by the pressing force. As a result, increase in change of the cutting edge with time, occurrence of scratches, and the like are included.

In the second example, better results were reported than in the first example due to changes in the abrasive grain size, changes in the abrasive tape feed rate, etc., but increased costs and stable contact between the abrasive tape and the magnetic medium. It is difficult to obtain sufficient reliability and merits in terms of the difficulty of polishing and variations in the quality of the polishing tape.

In view of the above problems, the present invention can stably maintain reduction of signal loss even under severe conditions in a high density recording area,
In addition, the present invention provides a method for manufacturing a magnetic recording medium in consideration of mass productivity.

Means for Solving the Problems In order to solve the above problems, the method for producing a magnetic recording medium of the present invention comprises applying and drying a magnetic layer containing a magnetic powder and a resin binder as a main component on a non-magnetic support. After being hardened by calendering, a blade with an edge made of sapphire or diamond is pressed against the surface of the magnetic layer, and diamond abrasive grains having a grain size of 0.5 to 4 μm are hardened with a metal binder. The surface of the magnetic layer is polished by rotating a cylindrical grindstone formed as described above.

Operation With the above configuration, it is possible to remove the protrusions on the surface of the magnetic layer that may cause signal defects. At this time,
Relatively large protrusions are scraped off with a sapphire or diamond blade, and fine protrusions that could not be removed at this time are removed with a grindstone using tire diamond abrasive grains having a grain size of 0.5 to 4 μm. At that time, since the large protrusions have already been removed by the blade, the contact between the grindstone and the magnetic layer surface is stable, and compared to the medium when processed only with the grindstone, the shavings of the protrusions are reduced, and the reliability is very high. Sex is obtained.
Even when the recording density is improved, the two-step surface treatment has an excellent surface profile, which improves not only the reliability but also the electromagnetic conversion characteristics and the output at high frequencies. To do. The grain size of the diamond abrasive grains is preferably 0.5 to 4 μm, and when the grain size is large, the grain size becomes coarse and the above effects are reduced, and when it is too small, polishing cannot be performed. A metal binder is preferable for the abrasive grains in this range from the viewpoint of strength.

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

FIG. 1 is a view showing the steps after slitting of the 8 mm VTR tape, and in FIG. 1, numeral 13 is a sapphire blade which is attached to the magnetic layer so as to be pressed against the edge portion or the magnetic layer. This may be a diamond blade. 14 is a cylindrical diamond grindstone, which is formed of abrasive grains having a particle size of 0.5 to 4 μm,
It is arranged so as to hit the surface of the magnetic layer. Further, independently of the slitter traveling system, it can be driven freely at any rotation speed in forward and reverse directions. Reference numeral 15 is an abrasive recording medium (raw material), 16 is an unwinding roll, 17 is an 8 mm tape winding roll, 18 is a nip roll, 19 is an 8 mm width slitter, 20 is a guide roll, 21 is a cleaning tissue running system, 22 Is an 8mm tape.

With this device, the original medium 15 attached to the original medium unwinding roll 16 is slit by the 8 mm width slitter 19 and then scraped off the protrusions and dust on the surface to some extent by the sapphire blade 13. It is further polished by a cylindrical diamond grindstone 14 and wound on an 8 mm tape winding roll 17.

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 disbar, and a sand mill were used as a paint-making device, and it was carried out for a sufficient time so that the paint was uniformly dispersed.

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 this, 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 going through the above process and slitting it into an 8 mm width.
Further, the tapes formed by the first example and the second example 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 per video signal was recorded and reproduced,
We compared the C / N values when recording and reproducing a 5MHz single sine wave. The equipment used is 8mm DECK MVS5000 (Kodak) NTSC signal generator VP8552A (Matsushita Electric) dropout counter VH01BZ (Shiba Soku) function generator 3225A (HP) spectrum analyzer 3585A (HP) Made). The results are shown in Table 1.

As is apparent from Table 1, sample # 3 according to the invention
The number of dropouts is 10 compared to the conventional examples # 1 and # 2.
It is shown 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 method of 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 embodiments, 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 a flexible disk. Is also applicable.

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

[Brief description of drawings]

FIG. 1 is a diagram showing a process after slitting an 8 mm video tape in an embodiment of the present invention, FIG. 2 is a diagram showing a conventional surface finishing process, and FIG. 3 is a knife-edge type cleaner used in FIG. Partially enlarged views, FIGS. 4 and 5 are views showing another example of the conventional surface finishing process. 13 …… Sapphire blade, 14 …… Cylindrical diamond whetstone, 15 …… Magnetic recording medium (texture), 16 …… Fabric roll, 17 …… 8mm tape winding roll, 22 …… 8
mm tape.

Claims (1)

[Claims] 1. A blade having an edge made of sapphire or diamond is formed by coating and drying a magnetic layer containing a magnetic powder and a resin binder as a main component on a non-magnetic support, followed by calendering and curing. Pressing against the surface of the running magnetic layer, further rotating a cylindrical grindstone formed by solidifying diamond abrasive grains having a grain size of 0.5 to 4 μm with a metal binder to polish the surface of the abrasive layer. And a method for manufacturing a magnetic recording medium.