JPH03278317A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To avoid wearing of cleaning sheet fibers and to improve reliability by incorporating a solid additive comprising inorg. solid additive and org. solid additive by 2 - 30 wt.% in the magnetic material and selecting these two kinds of additives so that the particle size differs from each other and the particle size of the org. solid additive is larger than that of the inorg. solid additive. CONSTITUTION:Two kinds of solid additives having different average particle sizes are used as the solid additive to be incorporated to the magnetic coating film. The solid additive of rather small particle size of 0.2 - 0.7mum consists of such as alumina Al2O3, while the larger particles of 0.5 - 1.5 mum particle size is carbon black or zinc stearate. By this constitution, the org. solid additive directly comes into contact with a cleaning sheet during the magnetic disk is rotated, which reduces wearing of the cleaning sheet. Thus, the magnetic recording medium has high durability and reliability, causing little wearing of a cleaning sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media, and more particularly to improvements in isomorphic additives contained in magnetic layers.

[Conventional technology]

In conventional magnetic recording media, solid additives such as alumina are contained in magnetic paints for the purpose of improving durability.

[Problem to be solved by the invention]

However, while these solid additives have excellent durability, they also cause significant abrasion of the cleaning sheet fibers inside the disk cartridge when the magnetic disk rotates, and furthermore, the abrasion powder adheres to the surface of the magnetic recording medium, causing dropouts. There was a problem with becoming.

The object of the present invention is to solve the drawback of the above-mentioned conventional products, such as abrasion of the cleaning sheet fibers, and thereby provide a highly reliable magnetic recording medium.

[Means to solve the problem]

The above object is to provide a magnetic recording medium in which a magnetic layer is formed by coating a magnetic material on a support substrate, in which a solid additive consisting of an inorganic solid additive and an organic solid additive with different particle sizes is applied to the magnetic material in a range of 2 to 30%. This is achieved by including the organic solid additive in the magnetic layer in a proportion of 30 to 30% by weight, and by making the particle size of the organic solid additive larger than the particle size of the inorganic solid additive.

[Effect]

Two types of solid additives with different average particle sizes are used for the solid additives contained in the magnetic coating film, and the particle size is 0°2 to 0.7μ.
The solid additive with a relatively small particle size of m is an inorganic substance such as alumina (Aj!zo,), and the relatively large solid additive with a particle size of 0.5 to 1.5 μm is an organic substance such as carbon black or zinc stearate. When the magnetic disk rotates, the organic solid additive comes into direct sliding contact with the cleaning sheet, thereby reducing wear on the cleaning sheet fibers.

〔Example〕

EXAMPLES The present invention will be explained in detail by describing examples below.

1) Example 1 Metal magnetic powder (specific surface area: 42 m"/g, holding crab 16
500e, saturation magnetization: 133emu/g)
100 parts by weight Vinyl chloride acetate-viny(1-arbourethane) copolymer 14 parts by weight Polyurethane resin 8.5 parts by weight Trifunctional isocyanate crosslinking agent 5.5 parts by weight Alumina (AI!z)
O:+: Average particle size 0.43. cam) 20 parts by weight graphitized carphone black (GCB#401.0BS
) 2 parts by weight 2-hebutyl undecyl oleate 6.5 parts by weight cyclohexanone
1801i lid toluene
180 parts by weight of the above composition was mixed and dispersed in a ball mill to prepare a magnetic paint.
A magnetic layer was formed on both sides of a 2 μm polyethylene terephthalate film so that the film thickness after dry calendering was 2.5 μm, dried, and then calendered. Next, this was heat cured for 64 hours in an 80° C. constant temperature bath, and then punched out into a disk shape with a diameter of 130.2 mm and polished to produce a magnetic disk.

The thus obtained magnetic disk was assembled into a disk cartridge with Kendall Co., Ltd. 149-246 cleaning sheets adhered to both surfaces to produce a floppy disk.

2) Example 2 A magnetic disk was produced in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 1, the same amount of zinc stearate was used instead of graphitized carbon black.

3) Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1, except that alumina was used alone as the solid additive in the composition of the magnetic paint in Example 1.

3) Comparative Example 2 A magnetic disk was produced in the same manner as in Example 1, except that graphitized carbon black alone was used as the solid additive in the composition of the magnetic paint in Example 1.

Regarding the magnetic disks obtained in the above Examples and Comparative Examples, the state of wear of the cleaning sheet fibers was examined.

To remove the wear of the cleaning sheet fibers, insert the magnetic disk into the disk cartridge, load it into the drive,
After running for 1 hour at room temperature, the wear of the cleaning sheet fibers in the portion of the cartridge that was in contact with the lifter was observed using a microscope.

The results are shown in Table 1 below.

Table 1 [Effects of the Invention] As explained above, in the present invention, by mixing inorganic solid additives and organic solid additives in the magnetic layer, the cleaning sheet fibers have less abrasion and are highly durable. It is possible to provide a magnetic recording medium with high performance.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer is formed by coating a magnetic material on a support substrate, a solid additive consisting of an inorganic solid additive and an organic solid additive with different particle sizes is added to the magnetic material in a ratio of 2 to 30%.
1. A magnetic recording medium characterized in that the particle size of the organic solid additive is larger than that of the inorganic solid additive, and the particle size of the organic solid additive is larger than that of the inorganic solid additive.