JPS59112427A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having high coercive force and square ratio with good productivity without using diagonal vapor deposition by providing the 1st underlying layer consisting essentially of Ti or Cr on a non- magnetic base and the 2nd underlying layer consisting of Bi thereon and further forming a thin magnetic metallic film thereon. CONSTITUTION:Ti or Cr or an alloy consisting essentially thereof and contg. Zr, Hf, etc. is formed as the 1st underlying layer on a non-magnetic base to 50- 100Angstrom thickness. The surface layer of the layer 2 is oxidized by using a bombarding electrode in an O2 atmosphere maintained under the reduced pressure. Bi is then deposited by evaporation to 10-1,000Angstrom thickness to form the 2nd underlying layer 3. The layer 3 is also subjected to the bombarding treatment. A thin magnetic metallic film 4 of an Ni-Co alloy, etc. is deposited by evaporation on the layer 3 whereby a magnetic recording medium is obtd. The medium has good adhesion strength of the base 1 and the layers 2-4, is free from exfoliation, etc., excells in a magnetic characteristic, mechanical strength, etc. and has a long still life.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium in which a metal magnetic thin film is deposited on a non-magnetic support.

Conventionally, general magnetic recording media are made by applying a magnetic coating material mainly consisting of acicular magnetic powder and a polymeric binder to a non-magnetic support using a so-called physical vapor deposition technique such as air vapor deposition, sputtering, or ion blating. The metal thin film type magnetic recording medium, which is coated on top to form a metal magnetic thin film, is different from the above-mentioned coating type magnetic recording medium because a non-magnetic polymeric binder is not used. Since a high residual magnetic flux density can be obtained and the magnetic layer can be formed extremely thin, it has the advantage of high output and excellent short wavelength response.

However, when forming this metal magnetic thin film, a magnetic recording medium having a large coercive force cannot be obtained by simply depositing the magnetic metal, such as Co, on a non-magnetic support.

In order to obtain high coercive force in such metal magnetic thin film type magnetic recording media, it is possible to apply an oblique deposition method in which the magnetic metal is deposited from an oblique direction, but in this case, the deposition efficiency is low. The disadvantage is that the productivity is low.

On the other hand, the present application proposes a metal thin film magnetic recording medium that exhibits sufficiently high coercive force and can obtain a high squareness ratio even when a method using almost perpendicular evaporation is adopted instead of using oblique evaporation. It was first suggested by someone. In this magnetic recording medium, a Bi thin film is deposited as an underlayer on a non-magnetic support, and then a magnetic thin film of metal such as CO is deposited thereon by vapor deposition or the like.

The present invention aims to further improve the durability of this type of metal thin film magnetic recording medium. That is, in the present invention, as shown in FIG.
), a base layer (2) mainly made of Ti or Cr, which has a particularly high affinity for oxygen, is deposited as a first base layer, and on top of this, the second base layer of Bi mentioned above is applied. A metal magnetic thin film (4) such as Co or Co--Ni alloy is formed by vapor deposition.

The nonmagnetic support (1) is, for example, a polymer film such as polyethylene terephrate, polyamide, polyamideimide, polyimide, or glass ceramic.

Alternatively, a metal plate or the like whose surface is oxidized can be used.

In addition, the first base layer (2) has a high affinity for oxygen.
Mainly composed of i or Cr, but also Zr, Hf
.

This first underlayer (
The film thickness of 2) is desirably selected to be about 50 to 100X.

Further, the Bi thin film as the second underlayer (3) formed on the first underlayer (2) has a thickness of 10 to 100 mm.
0X, and is formed as a continuous or discontinuous film.

The metal magnetic thin film formed on the second underlayer is made of Co or Co-Ni alloy and has a thickness of 100 to 10
00X, preferably 200-500X.

For example, the surface of the non-magnetic material (1) made of plastic paste or polyethylene terephthalate is subjected to so-called bombardment treatment, in which oxygen ions are bombarded with oxygen or an atmosphere containing oxygen, prior to forming the first underlayer (2). Furthermore, the surface of the first base layer (2) formed thereon is also subjected to a so-called bombardment process in which oxygen ions are removed in the same manner. It is desirable to form an oxide film with a thickness of 50 to 100 times. These bombardment treatments can be performed by applying a DC voltage IK to the bombardment electrode under an oxygen pressure of 0.07 Torr, for example.

Further, a first base layer (2) mainly composed of Ti or Cr
The deposition may be formed by vapor deposition under a vacuum of I x 10"" Torr.

Furthermore, in the deposition of the Bi layer as the second underlayer (3) and the Co or Co-Ni as the metal magnetic thin film (4) thereon, each deposition was performed under a vacuum of I x 10'' Torr. It can be formed by processing. Moreover, the metal magnetic thin film (4) is not limited to a single layer structure, but as shown in FIG. (In the example shown, it can be made into a laminated structure of two layers of metal magnetic thin films (4a) and (4b)), and in this case as well, the surface of the lower layer metal magnetic thin film (4a) is coated with the same structure as described above. A bombardment process is performed, and an upper metal magnetic thin film (4b) is formed on this through the Bi of the second underlayer (2).

Example 1 [Direct current I
After performing oxygen bombardment treatment by applying KV for 30 seconds, the temperature of this support (1) was set to 60C and the tenth underlayer (
A Cr layer as 2) was deposited to a thickness of 200X.

Furthermore, the surface of this base layer (2) is heated to an oxygen pressure of 0.07 Torr.
Similarly, a DC voltage IKV was applied to the bombarded electrode for 30 seconds to carry out bombardment treatment, and then B was applied as a second underlayer at the temperature of the support (1), that is, the substrate temperature of 150C.
Then, 35% Ni--Co alloy was deposited to a thickness of 300X to form a metal magnetic thin film (4). Then, the surface of this metal magnetic thin film (4a) was subjected to bombardment treatment under the same conditions as described above, and then a second underlayer of Bi (
2) was formed, and a similar magnetic layer (4b) was deposited thereon with the same thickness and deposition conditions as the metal magnetic thin film (4a). Then, this surface was further subjected to bombardment [2] under the same bombardment conditions as described above. The magnetic recording medium thus obtained is referred to as sample tape A.

Example 2 In place of Cr in the underlayer (2) in Example IK, Ti was evaporated at 200X under the same conditions. The magnetic recording medium thus obtained is referred to as Tape B.

Comparative Example 1 Bombardment treatment of the non-magnetic support (1) in Examples 1 and 2 described above and Ti or C of the first underlayer
By omitting the underlayer r and forming a Bi layer (2) as a second underlayer directly on the non-magnetic support (1), magnetic recording is performed in the same manner as in Examples 1 and 2. Got the medium. The magnetic recording medium thus obtained was referred to as Tape C, and the results of measuring the magnetic properties and mechanical properties of each of these sample tapes A to C are shown in Table 1.

Table 1 Here, the still life is measured by attaching each sample tape to a home video tape recorder. characteristic, that is, coercive force Hc,
It was confirmed that the still life, that is, the durability, was significantly improved with respect to the squareness ratio Rs and the like.

As described above, according to the magnetic recording medium of the present invention, it is possible to improve the short still life caused by damage such as peeling of the metal magnetic thin film due to contact with the magnetic head. The adhesion strength to the body (1) is improved, the durability and hence the lifespan are improved, and the benefits of this are obvious when put to practical use.

[Brief explanation of the drawing]

1 and 2 are enlarged cross-sectional views of each side of a magnetic recording medium according to the present invention. (1) is a non-magnetic support, (2) is a first underlayer, (3)
is the second underlayer, and (41, (4a) and (4b) are metal magnetic thin films.

Claims (1)

[Claims] A magnetic recording medium comprising a first underlayer mainly made of Ti or Cr on a nonmagnetic support, and a metal magnetic thin film adhered to the first underlayer via a Bi layer.