JPS59227032A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide corrosion resistance superior to the existing medium without damaging the magnetic characteristic in writing and erasing from the substrate side in a transparent substrate and without damaging the magnetic characteristic in an oxidized state in writing and erasing from the magnetic recording layer side in an opaque substrate by oxidizing the surface of an amorphous magnetic thin film on heating, and forming a corrosion resistant layer thereon. CONSTITUTION:An amorphous magnetic film is provided on the surface thereof with a corrosion resistant layer formed by heating and oxidizing the surface at >=130 deg.C in an oxygen-contg. gas in a magnetic recording medium having a recording layer of said magnetic film formed on a substrate. Substrates consisting of glass, quartz, polycarbonate, metal, etc. are used as said substrate, and GdTbFe, GdTbFeCo, GdCoGdFe, TbFe, DyFe, TbDyFe, etc. are used as the amorphous magnetic film. Although the thickness of the corrosion resistant layer formed on the surface of the amorphous magnetic film by oxidation on heating may differ in accordance with the thickness of the amorphous magnetic film, the thickness is regulated preferably to 50-1,000 deg.C when the thickness of the film is 2,000 deg.C.

Description

[Detailed Description of the Invention] The present invention is applicable to magneto-optical memory, magnetic recording, display elements, etc. 1] This invention relates to magnetic recording media, and particularly relates to improvements in magneto-optical recording media that can be read using magneto-optical effects such as the magnetic Kerr effect or the Faraday effect.

Conventionally, for example, MnB1 has been used as a magneto-optical recording medium.

Polycrystalline thin films such as Mu Cu 11i, GdCo,
GdFe, TbFe.

I) yl'c, GdTbFe, T
I:+])yFe, GdFeCo,
TbFeCo.

Amorphous thin films such as (,id Tl)Co and single crystal thin films such as 0clIG are known.

Among these thin films, there are important factors 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 high efficiency compared to S. Considering the readout efficiency, the amorphous thin film is recently considered to be excellent as a photothermal recording medium. In particular, GdTbFe has a sharp Kerr rotation angle and a single Curie point of around 150° C., making it optimal as a photothermal magnetic recording medium.

However, amorphous magnetic materials generally used in magnetic recording media, including photothermal magnetic recording media such as Gd'l''bFc, have a drawback of poor rigidity.

In other words, when it comes into contact with the atmosphere or water vapor, its magnetic properties decrease,
Eventually, it will be completely oxidized and become transparent.

In order to eliminate such drawbacks, for example, in photothermal magnetic recording media, a protective cover made of a transparent material such as 5102 or SiO is provided on the recording layer, and a disk-shaped recording material sealed with an inert gas has been used. medium is proposed.

An object of the present invention is to provide a magnetic recording medium in which the corrosion resistance of the magnetic recording layer is improved without impairing the magnetic properties.

The object of the present invention is achieved by the following photothermal magnetic recording medium. In a magnetic recording medium having a recording layer of an amorphous magnetic film formed on a substrate, the magnetic film is formed by heating and oxidizing the surface of the magnetic film in an oxygen-containing gas at 160° C. or more at 5° C. 1. A magnetic recording medium, characterized in that the surface thereof is covered with a hanging layer.

The above substrates include glass, quartz, polycarbonate,
A metal substrate made of polyethylene terephthalate (for example, mylar) is used, and an example of an amorphous magnetic film is GdTbFc.

C; dTbFcco, GdCo, GdFe,
ThFe, DyFc, TbDyFe, etc. are used.

Thermal oxidation of the surface of the magnetic recording layer is carried out by forming an amorphous magnetic thin film on a substrate by a conventional method, and performing -C in an oxygen-containing gas, preferably air, at a temperature of 130 DEG C. or higher. Alternatively, after forming the magnetic recording layer by sputter straddling deposition, the substrate can be heated in the same vacuum chamber and oxidized by introducing oxygen gas. The upper limit of the heating temperature is preferably 400° C.; heating above this temperature is not preferable because crystallization occurs and the film is no longer a perpendicularly magnetized film.

Under particularly preferable heating conditions u13D to 250°C, 5
~120 minutes.

The thickness of the first-side layer formed on the surface of the amorphous magnetic film by thermal oxidation varies depending on the thickness of the amorphous magnetic thin film, but at 2000×, the thickness is preferably 50′ to 1000×.
It is X. If the thickness of the corrosion-resistant layer is smaller than the lower limit, corrosion of the magnetic recording layer cannot be prevented, and if it exceeds the upper limit by 1, write sensitivity and read sensitivity decrease.

When the present invention is used in a photothermal magnetic recording medium, after forming four corrosion layers by thermal oxidation as described above, a well-known retention layer or a reflective layer that also serves as a protective layer, an antireflection layer, Corrosion resistance can be further improved by providing a heat insulating layer or the like. A heat insulating layer and an antireflection layer can also be provided between the twisted substrate and the magnetic recording layer in this order from the substrate side. Furthermore, in the amorphous wire f1 alloy, C, Si or .1.1
Excellent surface 1 corrosion resistance can be achieved by containing elements such as 2 dimensions or Sl, L ('I゛, 1dCr and A/!).

A photothermal magnetic recording medium id1 formed based on the present invention,
Well-known air sand winch structure and bonding +j7
Any type of I structure may be used, but in the case of an opaque substrate,
Air Sandwich structure is good.

According to the present invention, by heating and oxidizing the surface of an amorphous magnetic thin film to form a surface 1 corrosion layer, for example, in the case of a photothermal magnetic recording medium, in the case of a transparent substrate, magnetic properties are In an opaque substrate, writing and erasing from the magnetic recording layer side can be performed without impairing the magnetic properties of the oxidized structure. A photothermal magnetic recording medium made of a magnetic material is provided.

The present invention will be described in more detail below by showing examples in which it is used in a photothermal magnetic recording medium.

Example 1 Using a high frequency sputtering device on a glass substrate (,1d
Tl) FeCo was formed into a film with a thickness of 1500X to prepare 10 samples. Nine of these samples were heated in air at 80°C, 90°C, ioo°C, 110°C,
120℃, 160℃, 140℃, 150℃ and 160℃
The magnetic recording layer was oxidized by heating for 60 minutes to form a corrosion-resistant layer on the surface of the magnetic recording layer. These trials, together with the trials that were not subjected to heating and oxidation treatment, were subjected to corrosion resistance tests in a constant temperature and humidity chamber at 70°C and relative humidity of 85 degrees. The results are shown in Table 1. 1 Figure 1 shows the results of measuring the Kerr rotation angle of each sample from the glass surface side after the corrosion resistance test (100 hours later).The horizontal axis represents the heating temperature of each sample, and the vertical axis represents the heating temperature of each sample. Figure 1 shows the change in the Kerr rotation angle as a ratio to the value before heating and oxidation.As is clear from Figure 1, the sample heated at a temperature of 160°C or higher has a surface area of 1 even after heating and oxidation. Even after the corrosion test, no change was observed in the Kerr rotation angle from the glass surface side.

Example 2 A 7000× thick heat insulating layer made of polyarylate (trade name IJ-100, manufactured by Unitika) was provided on a glass substrate, and an antireflection layer made of SiO and 900× thick was further provided thereon. Gd was applied onto the antireflection layer using a high frequency sputtering device.1. 1) Fe was formed into a film with a thickness of 2000X. Then, it was heated at 140°C in air for 6
A surface corrosion layer was formed on the surface of the 0dTl)Fc film by heating for 0 minutes.

The photothermal magnetic recording medium thus obtained was heated at 70°C.
A one-sided layer eclipse test was conducted at a relative humidity of 85%. 10
No pinholes were observed even after 0 hours.

Example 6 An aluminum plate with a thickness of 1.5 mm was used as a substrate, and on top of this was an i-thermal layer with a thickness of 2 μm made of polyimide (manufactured by Hitachi Chemical Co., Ltd., trade name PIQ), and on top of that was a high-frequency sputtering device.
Therefore, a film of Cd Co was formed to a thickness of 15 ooX, and an antireflection layer made of SiO was further provided. Same r'c sky 4
; In IJ, ((1) The leaked photothermal recording medium was heated to 160° C., and oxygen gas was introduced to 309 mTorr to oxidize the surface of the magnetic recording layer.

The photothermal recording medium thus treated was heated to 70°C and relative humidity was 85°C.
%, a 100 hour corrosion resistance test was conducted, but no pinhole-like corrosion was observed.

[Brief explanation of drawings]

Figure 1 shows Example 1 after the 1li11 mystery food test for 100 hours.
FIG. 2 is a chart showing the relationship between the heating temperature of each sample and the change in Kerr rotation angle before heating oxidation and after the surface corrosion test. FIG. Canon Co., Ltd., 3-30-2 Shimomaruko, Ota-ku, Tokyo Inventor: Susumu Ito, Canon Co., Ltd., 3-30-2 Shimomaruko, Ota-ku, Tokyo

Claims (1)

[Claims] 1. A magnetic recording medium comprising a corrosion-resistant layer formed by heating and oxidizing a recording layer of an amorphous magnetic film formed on a substrate.