JPH059846B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to magnetic recording media. More specifically, the present invention relates to a magnetic recording medium in which the abrasion resistance of a magnetic layer and the abrasion resistance of a magnetic head are improved. Magnetic recording media for audio, video, or computers are required to have a magnetic layer with excellent durability and little wear, because they come into intense sliding contact with a magnetic head during recording and reproduction. For this reason, non-magnetic powder such as Cr ₂ O ₃ powder and Al ₂ O ₃ powder, which is harder than magnetic powder and whose particle size is equal to or larger than magnetic particles, is mixed into the magnetic layer as a reinforcing additive. It is proposed to do so.
However, although the abrasion resistance is improved when these reinforcing additives are mixed, there is a risk that the magnetic head may be damaged by abrasion. On the other hand, the particle size is smaller than that of magnetic powder.
If non-magnetic powder such as Cr ₂ O ₃ powder or Al ₂ O ₃ powder is added, there is no risk of abrasion damage to the magnetic head, but the abrasion resistance of the magnetic layer will not be sufficiently improved. The first object of the present invention is to provide a magnetic recording medium in which the wear resistance of the magnetic layer is improved;
Another object of the present invention is to provide a magnetic recording medium that does not cause wear and tear on a magnetic head. The above object of the present invention is to contain 0.5 to 20 wt% of Al ₂ O ₃ powder of 0.005 to 0.1 μ and nonmagnetic powder of 0.3 to 2.0 μ with a Mohr hardness of 5 or more based on the magnetic powder. achieved by. As the mixing ratio of Al ₂ O ₃ powder to magnetic powder increases, the wear of the magnetic head decreases, but when the amount exceeds the same amount, the effect of improving the wear resistance of the magnetic recording medium decreases. For this reason, it is necessary to set the ratio of Al ₂ O ₃ powder and non-magnetic powder to 1:20 to 1:1.5 by weight, and the ratio of Al ₂ O ₃ powder and non-magnetic powder mixed at the above mixing ratio is required to be 1:20 to 1:1.5. Magnetic powder (e.g. Cr ₂ O ₃ , α−Fe ₂ O ₃ , α−
Excellent wear resistance of the magnetic layer can be obtained by adding _0.5 to 20 wt% of reinforcing additives ( _Al2O3 , SiC, _SiO2, etc.) to the magnetic powder. 20wt%
When the amount increases, head wear increases and electromagnetic conversion characteristics deteriorate. The magnetic layer of the present invention basically consists of a binder and magnetic powder dispersed in the binder, and the above-mentioned Al ₂ O ₃ and magnetic powder are contained in the binder. Here, the magnetic powder is not particularly limited. Specific examples of magnetic powder (ferromagnetic powder) include γ-Fe ₂ O ₃ , Fe ₃ O ₄ ,
Co-modified iron oxide, Fe-Co alloy, Ba ferrite,
There are Fe-Co-Ni alloy, Fe-Co-Cu alloy, etc.
Examples of binders include vinyl chloride-vinyl acetate copolymers, epoxy resins, polyamide resins, urea resins, melamine resins, phenolic resins, cellulose derivatives, and polyurethane resins. As a binder combination, the effects of the present invention are significantly exhibited when a vinyl chloride-vinyl acetate copolymer and a polyester urethane resin are combined. In other words, vinyl chloride-vinyl acetate copolymer has a high dispersion of magnetic powder and contributes to hardness, while polyester polyurethane resin is useful for imparting flexibility, but the magnetic layer plasticizes the coating and reduces still characteristics. Easy to deteriorate. This still characteristic can be improved by using a large amount of non-magnetic powder with a particle size of 0.3 to 2.0 μm and a Mohs hardness of 5 or more. However, if too much of this non-magnetic powder is added, head wear will increase too much. Therefore, by including fine particles of Al ₂ O ₃ within the above range, still characteristics and head wear can be solved at the same time. Regarding the magnetic layer, magnetic recording medium, and manufacturing method of the present invention, Japanese Patent Laid-Open No. 52-96505 may be followed. The magnetic recording medium of the present invention can be applied to video tape recorders, audio tape recorders, computers, etc. EXAMPLES The present invention will be explained in more detail by showing examples below. In the examples, "parts" indicate "parts by weight." Example 1 A magnetic layer coating solution was prepared by dispersing the following composition in a ball mill, and this was coated on a 15μ thick polyester base film to a dry thickness of 5μ and dried.
Furthermore, it was mirror-finished using a calendar roll and cut into a predetermined width to prepare a magnetic recording medium. Magnetic layer composition Cobalt-modified iron oxide 100 parts γ-Al ₂ O ₃ (particle size 0.05μ: Mohs hardness 8)
Quantity shown in Table 1 α-Al ₂ O ₃ (particle size 0.5μ: Mohs hardness 9)
Quantities shown in Table 1 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 parts Polyester polyurethane 10 parts Carbon black 8 parts Lubricant 9 parts Hardening agent 8 parts Solvent 130 parts Obtained samples 1 to 12 were recorded on a video tape recorder. The still characteristics were measured. In addition, the sample was run repeatedly in the regenerated state for 100 hours, and the amount of wear on the magnetic head was measured. Example 2 In Example 1, γ-Al ₂ O ₃ (particle size
Using α-Al ₂ O ₃ (particle size 0.08μ: Mohs hardness 9) instead of 0.05μ: Mohs hardness 9),
Sample 13 was prepared in the same manner as in Example 1 except that Cr ₂ O ₃ (particle size 0.4 μ: Mohs hardness 8.5) was used instead of Al ₂ O ₃ (particle size 0.5 μ: Mohs hardness 9).
The still characteristics and the amount of wear on the magnetic head were measured. The results are shown in Table 1. In the table, the still property is an index of abrasion resistance, and the longer the time, the better the abrasion resistance.

[Table] As is clear from Table 1, γ-Al ₂ O ₃ and α-
A magnetic recording medium using Al ₂ O ₃ in combination has excellent still characteristics and has less head wear than one using only α-Al ₂ O ₃ . Furthermore, among the magnetic recording media of the present invention, still characteristics are better when the amount of γ-Al ₂ O ₃ is smaller than the amount of α-Al ₂ O ₃ . Further, a similar effect is obtained when fine particles of α-Al ₂ O ₃ and Cr ₂ O ₃ are used together. Example 3 In Example 1, γ-Al ₂ O ₃ and α-Al ₂ O ₃
Sample No. 14 was prepared in the same manner as in Example 1, except that the total content of these substances was changed as shown in Table 2.
~20 was obtained, and the still characteristics and the amount of wear of the magnetic head were measured. The results are shown in Table 2.

【table】

[Table] As is clear from Table 2, Al ₂ O ₃ , (γ-
It can be seen that good head wear and still characteristics can be obtained when the total content of Al ₂ O ₃ ) and non-magnetic powder (α-Al ₂ O ₃ ) is 0.5 to 20 wt%. As is common to the results in Tables 1 and 2, if the amount of head wear is too large, the head will be severely scraped, which is a problem.On the other hand, if the head wear is too small, the cleaning effect on the head will be lost, so moderate head wear is required. It is necessary to have a quantity. Furthermore, from the results in Tables 1 and 2, vinyl chloride-
The combination of vinyl acetate copolymer and polyester polyurethane resin provides good head wear and still durability, and eliminates the need for extreme caution to avoid the risk of explosion, which was required when using nitrocellulose. ,preferable.

Claims (1)

[Claims] 1 Consisting of a support and a magnetic layer provided on it, the magnetic layer consists of (1) magnetic powder, (2) particle size 0.005~
Contains 0.1 μ of Al ₂ O ₃ , (3) non-magnetic powder with a particle size of 0.3 to 2.0 μ and a Mohs hardness of 5 or more, (3) vinyl chloride-vinyl acetate copolymer, (4) polyester polyurethane resin, and The ratio of ₂ O ₃ and non-magnetic powder is 1:20 to 1:1.5 by weight, and the total content of Al ₂ O ₃ and non-magnetic powder is 0.5 to 20 wt% relative to the magnetic powder. magnetic recording media.