JPS63224020A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To stabilize the contact of magnetic layer with a magnetic head and to improve the mechanical durability of the magnetic layer by forming an under coat layer of an org. substance contg. hard nonmagnetic particles on a nonmagnetic substrate and by laminating the magnetic layer on the under cat layer. CONSTITUTION:An under coat layer of an org. substance contg. nonmagnetic particles having >=3 Moh's hardness is formed the surface of a nonmagnetic substrate as an underlayer for a magnetic layer. The org. substance is flexible and causes elastic deformation relatively easily according to stress produced by contact with a magnetic head, so that travelling performing performance of the resulting magnetic recording medium is improved. Since the under coat layer contains the hard nonmagnetic particles having >=3 Moh's hardness, even though the edge of a magnetic head collides against the surface of the recording medium by accident, the edge is prevented from penetrating into the medium and superior mechanical durability is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium. More particularly, the present invention relates to improvements in that underlayer.

[Prior Art] As the demand for high-density magnetic recording increases, new high-density recording media such as Go-Ni-P plating film and γ-Fe2
Research and development of thin film media such as 03 sputtered film, Co--Ni obliquely evaporated film, and co-Cr sputtered film has become active.

Although these thin film media have excellent high-density recording characteristics, they have the following drawbacks. Firstly, there are problems such as poor mechanical durability, and secondly, if the surface smoothness of the recording medium is insufficient, stable contact with the magnetic head is difficult.

If a hard underlayer is provided on the substrate and a magnetic layer is laminated on top of this, the presence of the hard underlayer will make the magnetic layer less likely to deform (or be damaged) when it comes into contact with the head. However, on the other hand, since the contact area with the head becomes very small, even if a lubricating layer is provided on the magnetic layer, a large external force is locally applied, resulting in poor running performance.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the drawbacks of the prior art and thereby provide a magnetic recording medium with excellent durability and runnability.

[Means for Solving the Problems] In order to achieve the following two objectives, the inventors have proposed
By providing an organic undercoat layer containing nonmagnetic fine particles with a Mohs hardness of 3 or more on the surface of the nonmagnetic substrate as a substratum, the durability of the recording medium and the contact with the magnetic head are significantly improved.

The reason why a recording medium having such an F coating layer is excellent in durability and contactability with a magnetic head is that the organic substance in the undercoat layer has high accessibility, so when it comes into contact with a magnetic head, it can be relatively easily adjusted to the stress. This is because it is elastically deformed. In addition, since the undercoat layer contains hard non-magnetic particles with a Mohs hardness of 3 or more, even if the edge of the magnetic head accidentally collides with the surface of the recording medium, the penetration of the edge is suppressed, which improves mechanical durability. But it's excellent.

Therefore, the undercoat layer of the present invention differs from conventional hard underlayers in that it uses organic matter to provide flexibility and non-magnetic particles to provide hardness.
It has a unique configuration that combines both functions.

The organic substance used in the undercoat layer is vinyl chloride.
Vinyl acetate copolymer, styrene-butadiene copolymer,
Examples include epoxy resin and polyurethane resin.

The hard nonmagnetic particles contained in the undercoat layer preferably have a Mohs hardness of 3 or more. Specifically, 5iC
)+t ZrO2, A120at BaTiO3, Ca
These include TiO3, ZnFe0q, etc.

If the Mohs hardness is less than 3, the effect of improving mechanical durability will be insufficient.

The thickness of the organic undercoat layer is at least 0.1μ.
It is preferable that the distance is greater than or equal to m, and if it is less than this, no significant improvement in contact with the magnetic head will be observed. on the other hand,
The thickness of the undercoat layer is preferably 100 μm or less. If the thickness increases beyond this point, the flexibility of the entire medium will decrease.

Furthermore, it is preferable that the average particle diameter of the non-magnetic particles is at least equal to or less than the film thickness of the undercoat layer.If this film thickness value is exceeded, particle protrusions will appear on the surface of the undercoat layer, which will eventually result in the formation of particles during recording and reproduction. increase the spacing loss. Furthermore, the preferred impregnation rate of the non-magnetic particles in the undercoat layer is 5 to 85.
If it is less than 5%, the durability will be poor, and if it is more than 66%, the medium will have poor accessibility, causing problems in contact with the magnetic head.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

5i02 on a polyimide film substrate with a thickness of 40 μm.
A coating film of vinyl chloride binder in which particles are dispersed is formed, and Co16Cr2t with a film thickness of 0.20 μm is applied on this coating film.
The film was formed by vacuum evaporation.

In order to find the optimal conditions for the undercoat layer, we changed the average particle size of 5i02 and the thickness of the undercoat layer to improve the recording and reproducing characteristics.
The contact with the magnetic head and the durability of the recording medium were evaluated. The magnetic head used in the evaluation was a barium titanate slider with a curvature of 30 m and an amorphous-ferrite composite head (gap length 0.3 μm) embedded therein. The recording density was 80 kBPI, and the peripheral speed was 4 m/s.

Further, the stable contact between the magnetic head and the recording medium was evaluated based on the modulation of the Il+ raw output amplitude. That is, those with envelope homogeneity within 10% were considered to have good contact, and those exceeding that value were considered poor.

Furthermore, durability was evaluated by the number of times the magnetic head was passed until the reproduction output decreased to 80% of the initial value.

The above results are summarized in Table 1 below.

As is clear from the above results, when the thickness of the undercoat layer is 0.
1 μm or more, the average particle size of the non-magnetic fine particles is smaller than the film thickness of the undercoat layer, and the blending ratio of the non-magnetic fine particles is 5 to 65 vol.
It is understood that samples within the 1% range are satisfactory in terms of both reproduction collar durability and head touch.

[Effects of the Invention] As explained in L1 below, by providing an organic undercoat layer containing hard nonmagnetic particles on a nonmagnetic substrate and laminating a thin magnetic layer thereon, stable contact between the magnetic layer and the magnetic head is achieved. The properties and mechanical durability of the magnetic layer can be greatly improved.

Claims (3)

[Claims] (1) A magnetic recording medium characterized in that an organic undercoat layer containing nonmagnetic fine particles having a Mohs hardness of 3 or more is provided on a nonmagnetic substrate, and a thin magnetic layer is provided on the layer. (2) A magnetic recording medium according to claim 1, characterized in that the average particle diameter of the non-magnetic fine particles contained in the organic undercoat layer is at least smaller than the thickness of the organic undercoat layer. Medium. (3) In the magnetic recording medium according to claim 1 or 2, the non-magnetic fine particles having a Mohs hardness of 3 or more are Si.
O_2, ZrO_2, Al_2O_3, BaTiO_3
, CaTiO_3, and ZnFeO_4.