JPS60191423A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which has superior characteristics as a recording medium and high corrosion resistance by forming a magnetic thin film layer which contains a specific amount of oxygen atoms to specific layer thickness adjacently to a magnetic thin-film recording layer. CONSTITUTION:Recording and reproduction which use a laser beam are performed from an upper substrate surface 1 as shown by an arrow. The content percentage of oxygen atoms in the magnetic thin film layer 4 containing oxygen is so set as to obtain the best effect on prevention against the deterioration of the magnetic thin film recording layer 3 due to oxygen or water, etc., in air passed through an adhesive layer, and its value is normally 0.1-20at%. When this magnetic thin film layer 4 is too thin, water or oxygen is not prevented from entering the layer sufficiently and when too thick, evil influence is exerted upon the characteristics of the magnetic recording layer 4 ro entail a decrease in S/N ratio or recording sensitivity because of the reduction of magnetic effect when this medium is used as, for example, an optical thermomagnetic recording medium. For the purpose, the layer thickness is set normally to 30-1,000Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a magneto-optical memory.
This invention relates to improvements in magnetic recording media used in photothermal magnetic recording media, etc., which are used in magnetic recording, display elements, etc., and which can be read using magneto-optic effects such as the magnetic Kerr effect or the Faraday effect.

Conventionally, MnB1. Polycrystalline thin films such as MnCuBi, GdCo, GdFe, TbFe, DyFeXG
dTbFe, TbDyFe, GdFeCo.

Amorphous thin films such as GdTbCo and single crystal thin films such as GdIG are known.

Among these thin films, there are various issues such as film formability when manufacturing large-area thin films at temperatures near room temperature, writing efficiency for writing signals with small photothermal energy, and readout of written signals with a good S/N ratio. In consideration of read efficiency and the like, the amorphous thin film has recently been considered to be excellent for use in photothermal magnetic recording media. In particular, GdTdFe has a large Kerr rotation angle and a single Curie point of around 150° C., making it ideal for photothermal magnetic recording media.

However, magnetic materials generally used as recording layers, including amorphous magnetic materials such as GdTbFe, have poor corrosion resistance and are corroded in a humid atmosphere, resulting in deterioration of magnetic properties. Si, Cr, T
Addition of elements such as i improves corrosion resistance, but has the disadvantage that the Curie point increases and recording sensitivity decreases.

In order to eliminate these drawbacks, various protective layers have been conventionally provided on the recording magnetic layer made of an amorphous magnetic material, or air sandwich structures or bonded structures in which the recording magnetic layer is sealed with an inert gas have been developed. Disc-shaped photothermal magnetic recording media have been proposed, but it cannot be said that their functions are fully fulfilled.

An object of the present invention is to provide a recording medium with excellent characteristics, and
An object of the present invention is to provide a magnetic recording medium with excellent corrosion resistance.

This objective is achieved by the following magnetic recording medium.

In a magnetic recording medium in which a magnetic thin film recording bag layer and an auxiliary layer are sequentially provided on a substrate, a magnetic thin film layer containing oxygen atoms is provided adjacent to the magnetic thin film recording layer. Features of magnetic recording media.

The coercive force of the magnetic thin film recording layer in the present invention is ],004
Particularly preferred is 0000e.

Furthermore, C01Bi, Cr, Ge, Si, Ti, N
It is particularly preferable to contain at least one element such as i.

Here, the magnetic thin film recording layer usually consists of a group of rare earth elements such as Gd, Tb, and Dy and a group of transition metal elements such as FeXCo, and each is formed to a thickness of 0.01 to 02 μm by sputtering using a high-frequency spacing device. .

The magnetic thin film layer containing oxygen atoms in the present invention can be formed, for example, by the following method. For example, if a sputtering device is used, a magnetic material is used as a target, and oxygen gas is mixed into Ar gas for causing glow discharge. Alternatively, this can be achieved by adding a magnetic oxide to the magnetic material used as the target. As the target material, the same material as the magnetic thin film recording layer may be used, or a different type of magnetic material may be used depending on the situation. The oxide added to the magnetic thin film layer containing oxygen atoms may be the same type of material as the magnetic thin film recording layer and containing oxygen atoms, such as Cry,
NiONlol(i),,O,-,,,Fe5o4,
Co11.83- Fe2.20. etc. can be used.

FIG. 1 shows an example of a configuration in which the present invention is applied to a photothermal magnetic recording medium.

In FIG. 1, 1 is a substrate glass, 2 is an antireflection layer made of a dielectric layer or a multilayer structure, 3 is a magnetic thin film recording layer,
4 is a magnetic thin film layer containing oxygen atoms, 5 is a protective layer, 6 is an adhesive layer 1, and 7 is a protective substrate. Recording and reproduction using a laser beam is performed from the upper substrate surface as indicated by the arrow in FIG. Magnetic thin film layer 4 containing oxygen
The content of oxygen atoms in the layer is the most effective in preventing the magnetic thin film recording layer 3 from being deteriorated by oxygen or moisture in the air through the adhesive layer 6. is set to Its value is usually between 01at% and 2at%.
It is in the range of 0 at %. Furthermore, if the layer thickness of the oxygen-containing magnetic thin film layer is too thin, it will not be sufficient to prevent moisture or oxygen from entering, and if it is too thick, it will affect the characteristics of the magnetic recording layer, such as photothermal magnetism. When used as a recording medium, a decrease in the magnetic effect causes a decrease in the S/N ratio or a decrease in recording sensitivity of 4-. Therefore, the above layer thickness is usually 30A to 1
000 people, preferably in the range of 50X to 500 people.

As shown in FIG. 2 as another structural example of the recording medium according to the present invention, by providing a reflective film 9, it is possible to increase the magnetic effect and improve the S/N ratio. Second
In the figure, oxygen-containing magnetic thin film layers 4' and 4'' are provided on both sides of a magnetic thin film recording layer 3''. 5' is a protective layer, 6 is an adhesive layer, and 7 is a protective substrate. An intermediate layer 8 is made of an inorganic transparent material such as 5iO1SiO2, and its thickness is set so that the S/N ratio of the magneto-optical signal is optimized.

9 is a reflective film made of aluminum, copper, gold, silver, or the like.

The present invention can be applied to a photothermal magnetic recording medium having an air sandwich structure or a laminated structure. In addition, between the writing side substrate and the photothermal magnetic recording layer, a heat insulating layer such as an organic resin, a layer made of a dye or pigment that is transparent to the light used and has a high refractive index when formed, or a layer made of a Ti , Cr
, Zn, AI, si nanometal or Tie,...
AI, 03.5IO3, Cr20. A protective layer made of an oxide such as , etc. can be formed. Furthermore, it is possible to provide various auxiliary layers such as a layer on which index marks and tracking marks are written, or to use a write-side substrate whose surface is processed into a porous layer. The adhesive layer for bonding the substrate with the recording layer and the protective substrate is Diana [Ryoe Chemical ■], Coal Top [Nippon Kako Paper ■], V, P, M.
Anti-corrosion layers containing volatile rust preventive agents such as [Nihon Kagaku Sangyo ■], Ferroguard [Ronco Laboratories, Inc., USA], Zelast [Taiyo Liquefied Gas], Killesgard [Nippon Kagaku Sangyo ■], Metal Guard [Mobil Oil ■] , Ruston [Tobi Chemical ■L C, R, C, Dialate [Rhiko Chemical ■]
Corrosion protection layer containing oil-soluble rust preventive agents such as AI, Sn, Zn
, Goj, , Metal fine powder containing layer containing metal fine powder such as Cr, MgO, BadXCab, AI, 03, CaC
12KO sandwich Na OH, Ca'sO4, 3AH20, S
i O,, xH,,01P20s, activated alumina,
Mg (CIO4L, desiccant-containing layer containing a desiccant such as ZnBr2, 2,4.6-)limethylpyridine, sodium dimethylglycine, tris(hydroxymethyl)
It can also be replaced with a basic organic substance-containing layer containing a basic organic substance such as amitumekune, 2-amino-2-methyl-1,3-propanediol, or the like.

EXAMPLES The present invention will be specifically described below with reference to Examples.

Example 1 A photothermal magnetic recording medium having the structure shown in FIG. 1 was manufactured as follows.

A flat glass plate having a diameter of 20 mm and a thickness of 1.5 mm was used as a substrate 1, and an antireflection layer 2 was formed thereon by vapor deposition to a thickness of 01 .mu.m by ZrO2 electron beam heating using a vacuum evaporation apparatus. Next, as the magnetic thin film recording layer 3, Fe760d12Tb12 was formed into a film with a thickness of 009 μm by sputtering using a high frequency shatter device. The coercive force was adjusted to 20,000e. Next, the substrate was moved to another chamber, and while oxygen gas was flowing at a flow rate of 20 SCCM, Fe76Gd, 2Tb
Sputtering is performed using , , as a target: r
A magnetic thin film layer 4 containing oxygen of ooX was formed. Further, as a protective layer 5, SiO was deposited to a thickness of 02 μm by electron beam heating using a vacuum deposition apparatus. Adhesive layer 6
A photothermal magnetic recording medium was manufactured by bonding it with a protective glass substrate 7. In order to evaluate the magneto-optic effect of this photothermal magnetic recording medium, the Kerr rotation angle was measured. In addition, for evaluation of recording sensitivity and readout efficiency, recording frequency 511
The quality of the SIN ratio was determined by measuring the bias magnetic field necessary for recording at /IHz and analyzing the waveform of the reproduced signal. Recording was performed using the following device. Optical head output] 5
The light source was a mW semiconductor laser (820 nm) that could irradiate the surface of the recording layer as a minute spot of ~12 μm96, and had an electromagnet that could apply a magnetic field in the perpendicular direction to the recording layer. The photothermal magnetic recording medium was rotated at 80° p11 to uniformly magnetize the recording layer, and a laser was pulsed to record pits at a frequency of 50°.

In addition, a bias magnetic field was applied using electromagnetic force.

For reading and playback, 4. A mW semiconductor laser was used as a light source, and during recording, the open recording layer was irradiated, and the reflected light was detected by a detector via a polarizer. Further, this photothermal magnetic recording medium was placed in a constant temperature and humidity chamber at 65° C. and relative humidity of 85° C., and a corrosion resistance test was conducted for 1,000 hours, and the change in the Kerr rotation angle was determined as a ratio to the initial value.

The results obtained are shown in Table 1.

Comparative Example 1 Example 1 except that the magnetic thin film layer containing oxygen atoms is not provided.
Two types of photothermal magnetic recording media manufactured in the same manner were tested in the same manner as in Example 1. The results obtained are shown in Table 1.

10-

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining the structure of one embodiment of the magnetic recording medium of the present invention, and FIG. 2 is a schematic diagram for explaining the structure of another embodiment of the magnetic recording medium of the present invention. It is a diagram. １・・・・・・・・・・・・・・・・・・Board 2
・・・・・・・・・・・・・・・・・・ Antireflection layer 3.3' ・・・・・・・・・・・・・・・ Magnetic thin film recording layer 4, 4: 4//... Magnetic thin film layer containing oxygen atoms 5.5'...
・・・Protection layer 6・・・・・・・・・・・・・・・
・・・・・・Adhesive layer 7 ・・・・・・・・・・・・・・・
・・・・・・Protective board 8・・・・・・・・・・・・・・・
・・・・・・Middle layer 9・・・・・・・・・・・・
...Reflective film patent applicant Canon Co., Ltd. 11-

Claims (3)

[Claims] (1) In a magnetic recording medium comprising a magnetic thin film recording layer and, if necessary, an auxiliary layer provided on a substrate, a magnetic thin film layer containing oxygen atoms is provided adjacent to the magnetic thin film recording layer. Features of magnetic recording media. (2) The amount of oxygen atoms contained in the magnetic thin film layer is Q
, lat% to 20at. (3) The thickness of the magnetic thin film layer containing oxygen atoms is 30A
The magnetic recording medium according to claim 1 or 2, wherein the magnetic recording medium has a capacity of 1,000 to 1,000 people.