JPS63181119A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an electromagnetic conversion characteristic and reliability in a high-density recording region by rotating a cylindrical grinding wheel which is formed by solidifying diamond abrasive grain by a metal binder and is specified in average surface roughness to a specific range, thereby polishing the surface of a magnetic layer. CONSTITUTION:The magnetic layer 14 mainly consisting of magnetic powder and resin binder is coated on a nonmagnetic base and is dried and after said layer is cured by subjecting the layer to a calender treatment, the cylindrical grinding wheel 13 which is formed by solidifying the diamond abrasive grain having 10-20mum grain size by the metal binder and is specified in the average surface roughness (Ra) to 0.6-1.2mum is rotated to polish the surface of the magnetic layer 14. Since the average surface roughness of the grinding wheel is previously adjusted, the generation of scratching flaws on the surface of the magnetic layer 14 by the abrasive grains constituting the grinding wheel is obviated. Such projections on the surface of the magnetic layer 14 which are the cause to generate signal defects are thereby surely removed. The medium which has less signal drop-outs even in the high-density recording region and have the improved reliability and electromagnetic conversion characteristic is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium such as a tape or flexible disk that can be used in video-related equipment, audio equipment, information-related equipment, etc. The present invention relates to a method of manufacturing a high-density recording medium with improved defects and electromagnetic characteristics.

Conventional technology With the increasing image quality in the video equipment field, digital signal processing in the audio equipment field, and the spread and diversification of computer equipment, these external memories are required to be smaller, larger in capacity, and higher in quality. It has become. Along with this, it has become necessary to improve the electromagnetic conversion characteristics and reliability of the magnetic recording media that are widely used as external memories in high-density recording areas.

Currently, the mainstream of these magnetic recording media is a coated type medium that is mainly made of magnetic powder and a resin binder. Due to the limitations of the coating film forming technology when forming the magnetic 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 the adhesion of protrusions and dust on the surface of the magnetic layer, and due to the uneven distribution of magnetic powder in the magnetic layer downward in the film thickness direction, a layer rich in binder resin is formed on the surface layer of the magnetic layer. For example, the electromagnetic conversion characteristics may be impaired due to the formation of

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

As a third example, a ceramic blade is used to clean the surface of a magnetic layer of a running tape-shaped magnetic recording medium by pushing it against the surface of the magnetic layer.

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

FIG. 2 is a diagram showing an example of a conventional magnetic tape surface finishing process, in which 1 is a knife type cleaner, 2 is a tape-shaped magnetic recording medium, and 3 is a guide roll. FIG. 3 is an enlarged view of the knife type cleaner, and 4 is a ceramic knife whose cutting edge has a radius of curvature Ri.

The finishing process of the tape-shaped magnetic recording medium configured as described above is carried out during the magnetic tape manufacturing process, after slitting a wide raw long medium into a tape shape and before winding it onto a cassette or reel. .

The tape-shaped magnetic recording medium produced by the above treatment has the following effects: When the Knifetsu type crease touches the surface of the magnetic layer during running,
Small protrusions and dirt on the surface are removed with the H-shaped cutting edge,
As a result, signal loss is reduced.

As a second example, an abrasive tape made of abrasive grains of alumina, chromium oxide, silicon carbide, etc. coated with a resin binder or the like is applied to the surface of a magnetic recording medium to scrape off protrusions, etc. on the surface of the medium.

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

FIGS. 4 and 5 are diagrams showing an example of a conventional surface finishing process for a magnetic recording medium. 5 is an abrasive tape, 6 is an abrasive tape unwinding roll, 7 is an abrasive tape winding roll, and 8 is an abrasive tape rolling roll. In addition, 9 in FIG. 2 is a tape-shaped magnetic medium.

1o is a guide roll. 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 process configured as described above comes into contact with the new surface of the abrasive tape at a relatively high relative speed, so that the protrusions formed on the surface of the magnetic layer and foreign matter adhering to it are scraped off. As a result, excellent surface properties with few signal defects can be obtained.

Problems to be Solved by the Invention However, the above-described configuration has a problem in that as the recording density increases, sufficient or stable signal loss reduction cannot be achieved. In the first example, ■ Decrease in ability due to shavings adhering to the cutting edge of the blade, ■ Limits in protrusion scraping ability due to relative speed with the blade and pressing force, ■ Scraping ability due to relative speed, pressing force, etc. Factors that can be cited for this include increased changes in the blade edge over time when the blade is raised, and the occurrence of scratches.

In the second example, better results than the first example have been reported due to changes in the abrasive grain size, ■ changes in the abrasive tape feeding speed, etc. However, there is an increase in cost, and ■ abrasive tape and magnetic media. The situation is such that sufficient reliability and benefits cannot be obtained due to difficulties in contact stability with the polishing chip, and variations in the quality of the polishing chip.

In view of the above-mentioned problems, the present invention can stably guarantee reduction of signal loss even under severe conditions in high-density recording areas.
The present invention also provides a method for manufacturing a magnetic recording medium that also takes mass production into consideration.

Means for Solving the Problems In order to solve the above problems, the method for producing a magnetic recording medium of the present invention involves coating and drying a magnetic layer containing magnetic powder and a resin binder as main ingredients on a non-magnetic support. After hardening by calendering, a diamond grindstone with a grain size of 10 to 20 μm is hardened with a metal binder, and a cylindrical grindstone with an average surface roughness (Ra) of Ooθ to 1.2 μm is rotated. The surface of the magnetic layer is then polished.

Effect: With the above configuration, protrusions on the surface of the magnetic layer that may cause signal defects can be reliably removed. At that time, by adjusting the average surface roughness of the grinding wheel,
The abrasive grains constituting the grindstone do not cause scratches on the surface of the magnetic layer. Further, there is a large degree of freedom in the contact conditions between the grindstone and the medium, and the present invention can be applied to various types of media.

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 diagram showing the steps after slitting the BonmVTR tape. In FIG. 1, 13 is a cylindrical diamond grindstone for polishing the surface of the magnetic layer;
It is formed of abrasive grains with a particle size of 20 μm, and the average surface roughness (RZL) is adjusted to be 0.6 to 1.2 μm. Also, independently of the slitter running system, the slitter is driven freely in forward and reverse directions at arbitrary rotational speeds. 14 is a magnetic recording medium (original roll); 15 is a roll for unwinding the original roll; 1
6 is smmmm chi removal roll, 17 is nip roll,
18I/'18mm width slitter, 19 is guide roll, 20 is cleaning tissue running system, 21 is 8mm
It's a tape.

With this device, the original web medium 14 attached to the original web medium unwinding roll 15 is slit by an 8ou++ width slitter 18, and then subjected to the polishing process that is a feature of the present invention using a cylindrical diamond grindstone 13. The 8ffIm tape is wound onto the take-up roll 16. A metal binder is preferable for fixing the diamond abrasive grains from the viewpoint of strength, and the particle size of the abrasive grains is preferably 10 to 20 μm. If it is too small, the polishing effect will be small, and if it exceeds 20 μm, it will be too rough and the surface will be damaged.For the same reason, the average surface roughness is preferably 0.6 to 1.2 μm.

Example 1 A magnetic paint with the following composition? Created.

・Acicular alloy magnetic powder 100 parts by weight ・Binder resin 22 〃・Dispersant
2.6〃・Lubricant
2 〃・Alumina 7
Parts by weight: Carbon 1 Incyanate 4 When making the paint, the solid content concentration was adjusted to approximately 26% using the following solvent ratio. As the coating equipment, a kneader, a disper, and a sand mill were used, and sufficient time was taken to ensure that the J coating material was uniformly dispersed.

The thus prepared magnetic paint was coated onto a 10 μm thick polyethylene terephthalate film to a dry film thickness of 4 μm. A gravure coating method was used as the coating method.

The coated magnetic coating film was subjected to a mirror polishing treatment, and then the coating film was cured.

After this, a back coat layer composed of polyurethane, vinyl chloride, carbon, alumina, and a hardening agent was formed on the back side of the magnetic layer to a thickness of about 0.6 μTIJ.

The entire cassette produced through the above process was slit into a width of 8 mm and was designated as sample i sample #0. Further, the tapes made 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 recording and reproducing an NTSC full color bar video signal and the C/N value when recording and reproducing an sMIIz single sine wave were compared. The equipment that was replaced is. Table 1 shows the results.

(Left below) Table 1 As is clear from Table 1, sample #3 based on the present invention
The number of dropouts is reduced to one-tenth of that of conventional examples #1 and #2, indicating that the effect is high. Furthermore, along with the improvement in surface properties, the electromagnetic conversion characteristics also show an improvement in C/N value of about 0.4 to 0.8 dB compared to the conventional example.

The method of the present invention can be carried out by simply adding a simple device to a commonly used slitter device, and there are no consumables such as the polishing tape shown in the conventional example, making it excellent in terms of mass production.

Although the above embodiment describes an 8mm V'l'R tape, it can also be applied to other VTR tapes, magnetic tapes, etc. Also, by processing the original magnetic medium and punching it into a disk shape, it can be used to create flexible disks, etc. It can also be applied to other magnetic disks.

Effects of the Invention As described above, according to the present invention, it is possible to obtain a highly reliable medium with extremely little signal loss even in a high-density recording area, and with improved electromagnetic conversion characteristics.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the process after slitting the AMM videotape in an embodiment of the present invention, Fig. 2 is a diagram showing the conventional surface finishing process, and Fig. 3 is a partial enlargement of the knife-type cleaner used in Fig. 2. 4 and 5 are views showing other examples of the conventional surface finishing process. 13... Cylindrical diamond grindstone, 14...
...magnetic recording medium (original film), 15...original medium unwinding roll, 16...8mm tape winding roll,
21...8mn+tape. 1-74 Fezzu Type Cleaner 3-Katana Z Troll Happy 2 Figure 4-℃ Ramic's 74 Fezzi Figure 3 IO-Force Odoror

Claims (1)

[Claims] A magnetic layer containing magnetic powder and a resin binder as main ingredients is coated on a non-magnetic support, dried, hardened by calendering, and then diamond abrasive grains having a particle size of 10 to 20 μm are hardened with a metal binder. The average surface roughness (R
A method for manufacturing a magnetic recording medium, characterized in that a) the surface of the magnetic layer is polished by rotating a cylindrical grindstone having a diameter of 0.6 to 1.2 μm.