JPH0246523A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability of the magnetic layer without degrading the electromagnetic conversion characteristic as small as possible by incorporating a powder of tungsten compound as an additive into the magnetic layer. CONSTITUTION:The powder of tungsten compound with specific gravity between >=15 and <=18 is incorporated into the magnetic layer at the proportion of 20-80 pts.wt. of tungsten compound to 100 pts.wt. of magnetic powder. As the tungsten compound used as the additive has a specific gravity as large as 15 to 18, the volume fraction of the additive in the magnetic layer is small, which gives little influence to reduce the saturated magnetic flux density (Bm). Therefore, the tungsten compound powder can be incorporated as much as 20-80 pts.wt. into 100 pts.wt. of magnetic powder of the magnetic layer. Hardness of the tungsten compound is about 9 of Mohs hardness. It is hard enough that a proper polishing property can be obtained by selecting the mean particle size of the powder between 0.05-1.0mum, which can maintain a clean surface of a magnetic head. Thus, durability of the magnetic layer can be improved without degrading the electromagnetic conversion characteristics as small as possible.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and floppy disks used in audio equipment, video equipment, computer equipment, etc. [Summary of the Invention] The present invention relates to In magnetic recording media such as magnetic tapes and floppy disks used in audio equipment, video equipment, computer equipment, etc., electromagnetic conversion characteristics can be maximized by incorporating tungsten compound powder as an additive in the magnetic layer. The purpose is to improve the durability of the magnetic layer without reducing it.

[Conventional technology]

In recent years, in order to meet the increasing demand for high-density recording in magnetic recording technology, the surface of magnetic recording media such as magnetic tapes and floppy disks has been processed to have an ultra-smooth surface using a supercalender to reduce spacing loss. There is. In addition, based on the same request, efforts have been made to improve magnetic properties by making magnetic powder particles finer and changing from oxide-based magnetic materials to metal-based magnetic materials with lower hardness.

On the other hand, on the magnetic head side, the track width was set to 10 μm.
The intention is to achieve high-density recording by efficiently utilizing the area of the magnetic recording medium.

Furthermore, the relative speed between the magnetic recording medium and the magnetic head exceeds 1 meter per second, not only in video tape recorders but also in audio tape recorders, as recent digital audio tape recorders (DATs) employ rotating head mechanisms. Efforts are being made to speed up the process.

In response to these high-density recordings, the surface of the magnetic layer of a magnetic recording medium is easily damaged and its durability is reduced, and on the magnetic head side, the head is damaged due to deposits on the track surface. The chloragging phenomenon causes the playback output level to decrease. It is thought that the deposits on the track surface are mainly deposits from damaged parts of the magnetic layer surface.

Therefore, in order to improve durability, α was added to the magnetic layer in order to improve durability.
- Contain 10 parts by weight or less of non-magnetic additives with large Mohs hardness such as alumina (Japanese Patent Application Laid-open No. 60-177432) and nichrome trioxide (Japanese Patent Application Laid-open No. 60-209925) based on 100 parts by weight of magnetic powder. Things have been done.

Furthermore, it has been proposed to contain 1 to 10 parts by weight of at least one of titanium carbide, titanium nitride, silicon nitride, and tungsten carbide in the magnetic layer based on 100 parts by weight of magnetic powder (Japanese Unexamined Patent Application Publication No. 1983-1992-1). 212820).

However, even with these conventional techniques, it has not been possible to improve durability in still mode without deteriorating electromagnetic conversion characteristics such as reproduction output level. In other words, if the content of non-magnetic particles is small, the electromagnetic conversion characteristics are excellent but the durability is poor; on the other hand, if the content of non-magnetic particles is increased, the durability is improved but the electromagnetic conversion characteristics are poor. could not be satisfied.

[Problem to be solved by the invention]

In view of these problems, the problem to be solved by the present invention is to improve the durability of the magnetic layer in magnetic recording media such as magnetic tapes and floppy disks without impairing good electromagnetic conversion characteristics as much as possible. The purpose is to

[Means to solve the problem]

In order to solve the above-mentioned problems, a magnetic recording medium according to the present invention contains powder of a tungsten compound having a specific gravity of 15 or more and 18 or less in a magnetic layer. Examples of tungsten compounds that meet this condition are listed in Table 1.

The tungsten compound powder used in the present invention may be added in an amount of 20 to 80 parts by weight per 100 parts by weight of the magnetic powder, and preferably has an average particle size in the range of 0.05 to 1.0 μm.

[Effect]

Since these tungsten compounds have a high Mohs hardness of about 9, they have a moderate abrasive action and are effective in keeping the magnetic head surface always clean and avoiding the head crawling phenomenon. In addition, these tungsten compound powders exhibit the effect of reinforcing the magnetic layer coating by being uniformly dispersed in the magnetic layer, and prevent scratches on the surface of the magnetic layer that are likely to occur when sliding on magnetic heads, drums, tape guides, etc. It has the effect of preventing All of these effects enable long-time playback in still mode and work toward improving durability.

Furthermore, these tungsten compounds have a specific gravity of 15°3~
It is in the range of 17.2, which is about 3 to 4 times higher than that of α-alumina, which is 3.94, and nichrome dioxide, which is 5.21.

Therefore, these tungsten compounds have a small volume per unit weight, and even if they are added in an amount necessary and sufficient to improve the durability of the magnetic layer, they have little effect on lowering the saturation magnetic flux density (Bm). This is the reason why the electromagnetic conversion characteristics of the magnetic recording medium according to the present invention are maintained well.

〔Example〕

The present invention will be described below based on Examples and Comparative Examples.

Real fan open up First, a magnetic paint was prepared with the following composition.

Co-containing 7-Fe203
----------400 parts by weight (specific surface area 40m2
/g) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer resin
----40 parts by weight (VAGH manufactured by UCC) Polyurethane resin------------
-----40 parts by weight (N-2 manufactured by Nippon Polyurethane Industries)
304) Carbon black---------
−−−−−−−−−−−−−・−−−−−−−2 parts by weight (Harkan XC-72, manufactured by Cabot Corporation) Butyl stearate −−−−−−−−−−−−−− −−−−−−−−
---2 parts by weight of methyl ethyl ketone ---
-----420 parts by weight methyl isobutyl ketone---
-m------------60 parts by weight of toluene-----
−−−−−−−−−−=−−−60 parts by weight 20 parts by weight of monotungsten monocarbide powder with an average particle size of 0.4 μm was added to the above composition as an additive, and mixed in a ball mill for 48 hours. After dispersion, 2 parts by weight of isocyanate (Coronate, manufactured by Nippon Polyurethane Industries) was added and mixed as a hardening agent, and the mixture was filtered through a filter to obtain a magnetic paint.

Next, the above magnetic paint was applied onto a polyethylene terephthalate film having a thickness of 14 μm and dried, and the magnetic layer was subjected to ultra-smooth surface processing by supercalendering, and then hardened to obtain a jumbo roll.

The thickness of the magnetic layer was set to 6 μm. The jumbo roll was cut into 2-inch widths and loaded into a video cassette case to form a sample tape.

Fruit 1 Sub-Shishi X4 Average particle size 0.4 which is the additive used in Example 1
Example 1 except that μm monotungsten carbide powder was used as it was and the content was changed to 25.30 or 35 parts by weight.
Three types of sample tapes were created in the same manner.

The average particle size of the monotungsten monocarbide powder as the flaming additive was selected to be 0.2, 0.6 or 0.8 μm, and the contents were all kept constant at 25 parts by weight. Other than that, three types of sample tapes were prepared in the same manner as in Example 1.

In place of the tungsten monocarbide powder used in Example 1, tungsten boride powder was used as the additive. The average particle size was selected to be 0.32 μm,
Two types of sample tapes were prepared in the same manner as in Example 1 except that the content was 25 or 35 parts by weight.

Example 2 was prepared in the same manner as in Example 1, except that boride-tungsten powder was selected as the additive, the average particle size was 0.41 μm or 0.48 μm, and the contents were both 25 parts by weight. We created different types of sample tapes.

Monotungsten monocarbide powder, which is a tungsten compound, was used as the bifurcated additive, and the average particle size was 0.4 μm, and the content was 15 or 5 parts by weight.

Other than that, two types of sample tapes were created in the same manner as in Example 1.

Tungsten boride powder was used as the main additive for Hokukai coal, and the average particle size was 0.32 μm and the content was 15 parts by weight. A sample tape was produced in the same manner as in Example 1 in other respects.

α-Alumina, which has been conventionally used as a comparative coal soil additive, was used. 2 was prepared in the same manner as in Example 1, except that the average particle size was selected to be 0.4 μm or 0.6 μm, and the contents were both 10 parts by weight.
We created different types of sample tapes.

Northern comparison ±52 (3) Nichrome dioxide, which has been conventionally used as an additive, was used. The average particle size is 0.28 μm, and the content is 5.1
0 or 15 parts by weight. Other than that, three types of sample tapes were prepared in the same manner as in Example 1.

By the method explained above, sample tapes according to 11 types of examples according to the present invention and sample tapes according to 8 types of comparative examples were created. These are shown in Tables 2 and 3 together with the measurement and evaluation results using a home video tape recorder.

Margin Table 2 Below Table 2 In Tables 2 and 3 above, the content of the additive is expressed in parts by weight of the additive based on 100 parts by weight of the magnetic powder. In addition, the playback output was shown by recording a 4.5 MHz test signal on a sample tape and comparing the playback output with the playback output of a standard tape. The still characteristics are shown in 4. on the sample tape.
A 2 MHz test signal was recorded, the same track on the magnetic tape was continuously reproduced in still mode, and the time required for the reproduction output to attenuate to 50% of the initial reproduction output was expressed.

Comparative Examples 1 to 8 in Table 3 failed to satisfy both the reproduction output of 068 or more and still characteristics of 120 minutes or more, whereas in Examples 1 to 11 according to the present invention in Table 2, all samples Tape playback output 06
8 or more and still characteristics of 120 minutes or more.

In this example, monotungsten monocarbide powder with an average particle size of 0.4 μm was used as an additive, and the content was 10% magnetic powder.
Nine types of magnetic paints were prepared in the same manner as in Example 1 except that 10 to 90 parts by weight were selected every 10 parts by weight relative to 0 parts by weight. Each magnetic paint was applied to both sides of a polyethylene terephthalate base film, dried, surface treated, and then hardened. Each was cut into a predetermined shape and stored in a floppy jacket to make a sample floppy disk. When standard signals were recorded on these nine types of sample floppy disks and the playback output was compared with the playback output of the standard floppy disk, it was found that for each sample floppy disk containing 80 parts by weight or less of additives, the playback output was changed by more than 0clB. . For durability, additive content 20-9
0 parts by weight of each sample floppy disk met the standard time.

In Examples 1 to 12 and Comparative Examples 1 to 3, -tungsten carbide (WC) or -tungsten boride (WB) powder was exemplified;
Tungsten compounds of above 18 or less, such as - ditungsten carbide (W2C), - ditungsten boride (W2B)
), -Similar measurement results were obtained for the powder of ditungsten nitride (wzN). Similar measurement results were obtained using a mixture of two or more of these tungsten compound powders.

Furthermore, as is clear from Examples 1 to 12 and Comparative Examples 1 to 3, the content of these tungsten compound powders can be selected between 20 and 80 parts by weight per 100 parts by weight of the magnetic powder to produce a reproduction output. Results were obtained that satisfied both properties and durability. Furthermore, if the average particle size of these tungsten compounds is smaller than 0.05 μm, durability deteriorates;
When the thickness exceeded 0 μm, a decrease in electromagnetic conversion characteristics was observed.

In this example, CO-containing 7-F was used as the magnetic powder.
Although e2O3 was used, 7-Fezes, Fe1O4
It is possible to use ferromagnetic powders such as ferromagnetic powders having an isospinel structure, barium ferrite powders having a magnetoblumbite structure, chromium dioxide powders, and metal-based powders. Further, as the binder, in addition to the vinyl resin and polyurethane resin used in this example, polyester resin, nitrocellulose resin, polyacecool resin, polyvinyl butyral resin, etc. may be used.

〔Effect of the invention〕

As detailed above, the magnetic recording medium according to the present invention has
Since a tungsten compound having a high specific gravity of 15 or more and 18 or less is used as an additive, the volume fraction of the additive in the magnetic layer is small, and the effect of lowering the saturation magnetic flux density (Bm) is small. Therefore, the tungsten compound powder used in the present invention can be contained in an amount of 20 to 80 parts by weight per 100 parts by weight of the magnetic powder in the magnetic layer. In addition, these tungsten compounds have a high Mohs hardness of about 9, so by selecting the average particle size in the range of 0.05 to 1.0 μm, an appropriate polishing effect can be obtained, which is effective in keeping the magnetic head surface always clean. It has both. Furthermore, by being uniformly dispersed in the magnetic layer, these tungsten compound powders exert a reinforcing effect on the magnetic layer coating, and prevent the surface of the magnetic layer from forming when sliding on magnetic heads, drums, tape guides, etc. It also has the effect of preventing scratches. As a comprehensive result of these effects, a magnetic recording medium with improved durability without impairing electromagnetic conversion characteristics as much as possible can be obtained, and its industrial utility value is great.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a binder is formed on a non-magnetic support, a tungsten compound powder having a specific gravity of 15 or more and 18 or less is added to the magnetic layer in an amount equal to 100% by weight of the magnetic powder. 20 to 80 parts by weight per part of the magnetic recording medium.