JPS59175049A - Substrate for photomagnetic disc - Google Patents

Abstract

PURPOSE:To obtain a substrate for a photomagnetic disc which is highly mechanically strong and is thermally stable by forming an SiO2 layer and an a-SiO layer respectively to prescribed thicknesses on a metallic substrate. CONSTITUTION:A substrate for a photomagnetic disc which is highly mechanically strong and is thermally stable is obtd. by forming an SiO2 film 2 having >=1,200Angstrom film thickness and an a-SiO film 1 having >=500Angstrom film thickness on an Al disc 3. A Gd20Tb7Fe73 film is formed on the film 1 of such substrate to 1.2mum thickness, by which the photomagnetic disc is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a substrate used in a magneto-optical disk in which information is recorded, reproduced, and erased on an amorphous perpendicularly magnetized film using a laser beam.

Conventionally, research has been actively conducted on substrates used in magneto-optical disks that record, reproduce, and erase information by irradiating a laser beam onto a rare earth-transition metal amorphous perpendicularly magnetized film. υ with a dielectric layer formed on it, or polymer substrates such as acrylic or polycarbonate have been used. However, conventional glass substrates are difficult to process and have weak mechanical strength against impact forces, and polymer substrates such as acrylic and polycarbonate have thermal problems. When forming a film, it has the disadvantage that a great deal of effort is required to prevent thermal decomposition of the polymer substrate surface.

The present invention eliminates the drawbacks of the glass substrate, which is difficult to process, and has low mechanical strength against impact forces, and the thermal drawbacks of the polymer substrate, and provides a magneto-optical disk that has excellent mechanical strength against impact forces and is thermally stable. The purpose is to provide a substrate for

The magneto-optical disk substrate according to the present invention is A4. Or O
A first layer such as a 5in2 film on a metal disk such as N, S
Form a ninth layer of 10 films, especially 5102 of the first layer.
The thickness of the film is 1200 A or more, and the thickness of the 810 film of the second scrap is 500 A or more, so it has excellent mechanical strength against impact force and is thermally decomposed when forming a perpendicular magnetization film by sputtering. We solved the above problems by creating a substrate that does not have any problems.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magneto-optical disk substrate according to the present invention will be described based on embodiments with reference to the drawings.

FIG. 1 is a configuration diagram of a magneto-optical disk substrate according to the present invention, where 1 is a SiO film, 2 is a 5in2 film, and 3 is an At
It is a disk. The 5102 film 2, the Sin film, and the Sin film 1 were sequentially formed on the AA disk 3 by sputtering.

The At disk 3 used was a press-cut At disk with a thickness of 1 mm, which was chamfered, mechanically polished, and then electrolytically polished.

In order to investigate the mechanical strength against impact force of the magneto-optical disk substrate prepared as above, im and 3
As a result of repeating the drop test 20 times from a height of m and 5 rn, there was no peeling of the SiO2 film 2 and the SiO film 1 formed on the M disk 3-A in any case.

Next, we investigated the recording, reproducing, and erasing characteristics when an amorphous perpendicularly magnetized film is actually formed on the substrate, which is the most important property for a magneto-optical disk substrate, and whether it is possible to actually form an amorphous perpendicularly magnetized film. .

FIG. 2 is a block diagram of a magneto-optical disk manufactured using the magneto-optical disk substrate according to the present invention, in which 1 is a Si film, 2 is an SiO2 film, 3 is an M disk, and 4 is a Gd2oTb7
Fe, 3 film. G d2oT b, Fe, and the film thickness of the film 4 were set to 1·2 μm. This EliO[1 and 5i
FIG. 6 shows whether the G4oTb7FeIs film 4 becomes amorphous when the thickness of the n2 film 2 is changed, and the shaded area in FIG. 6 is the amorphous region. Note: Tb, Fe7. Whether or not it is amorphous was determined by X-ray diffraction. Figure 3 p G
51 for d2oTb7Fe to become amorphous
The thickness of the 02 film must be 650X or more, 'S i
It has been found that if the thickness of the O film is above 1oooX and B, it has almost no relation to the thickness of the 810 film.

Next, the recording, reproducing and erasing characteristics of information were investigated using the magneto-optical disk shown in FIG. 2 o' for recording/erasing
m W He-'Nθ laser, 5 m W H for playback
Using an e-Nθ laser, the characteristics were evaluated by measuring the magnitude of the magnetic Kerr rotation angle.

FIG. 4 shows the Si
It is a diagram showing the change in the magnitude of the magnetic Kerr rotation angle of the G (120T'b7Fe, 3 films) when the film thickness of the S i O film is changed with the film thickness of the n film being 1500X.

From FIG. 4, if the film thickness of the 5102 film is 1200X or more, the magnetic Kerr rotation angle is constant at 052 degrees, which is about the same size as when a conventional magneto-optical disk substrate is used. Furthermore, when the film thickness of the 5in2 film is 650X, the magnitude of the magnetic Kerr rotation angle suddenly changes at 2°T.
b? F e7. This is because this is the point at which the structure changes from amorphous to polycrystalline.

FIG. 5 is a diagram showing changes in the magnetic Kerr rotation angle when the thickness of the 5102 film is kept constant at 200 OA and the thickness of the Sin film is varied. As is clear from Figure 5, S
It has been found that if the thickness of the in film is 500 mm or more, the magnetic Kerr rotation angle can be 0.32 degrees, which is comparable to that obtained when a conventional magneto-optical disk substrate is used.

Next, in the magneto-optical disk substrate according to the present invention, when the material of the metal disk is changed, the Gd2oTb7 formed on it is
Table 1 shows how the magnetic Kerr rotation angle of the Fe73 film changes.

The values in Table 1 are M as the interest rate of the metal disk.

Ou, Fe, SU8.316 (78% by weight 'F
e -18%0r-10wt%Ni), select Ni,
On top of that, a 2060X SiO□ film and a 1500X S
On top of the in film formed, Gd2oTh6;"" 01 film? , (, is the magnitude of the magnetic Kerr rotation angle in degrees when formed with a thickness of 1 or 2 μm.

Table 1 As is clear from Table 1, the magnitude of the magnetic Kerr rotation angle of the G d2o' T b7,7 e 3 films formed on the magneto-optical disk substrate according to the present invention using M or Cu as the metal disk The magnetic Kerr rotation angle is comparable to that of the Gd2oTb7Fe73 film formed using a conventional magneto-optical disk substrate, but when other materials are used as the metal disk, the magnetic Kerr rotation angle is It was found that the size of the disk was reduced by about 30% compared to when a conventional magneto-optical disk substrate was used.

As described above, the magneto-optical disk substrate according to the present invention has a first layer made of an 8102 film and a second layer made of an S10 film on a disk made of metal such as M or Cu. By making the thickness of the 5in2 film 1200X or more and the thickness of the second layer SiO film 500X or more, information recording, reproduction, and information recording performance comparable to that of a magneto-optical disk made using a conventional magneto-optical disk substrate can be achieved. This method has the advantage that a magneto-optical disk having erasing properties can be produced, and a substrate that has excellent mechanical strength against impact force and that does not undergo thermal decomposition during the production of a perpendicularly magnetized film by sputtering can be produced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the structure of a magneto-optical disk substrate according to the present invention, and FIG. 2 is a cross-sectional view of the structure of a magneto-optical disk using the magneto-optical disk substrate according to the present invention. 1...SiO film, 2...5102 film, 3...
・・M disk, 4-・-G eL2o'I'
b7F e73 film, FIG. 6, shows Gd2OTb? when the EliO film and 5102 film are changed in the magneto-optical disk shown in FIG. This is a graph examining whether the F"73 film is amorphous. In the figure, the shaded area is the amorphous region. Figure 4 shows the Si film in the magneto-optical disk shown in Figure 2.
G (12o-T b7 ”
7 is a graph showing changes in the magnetic Kerr rotation angle of a 7g film. FIG. 5 shows 51
2 is a graph showing the magnitude of the magnetic Kerr rotation angle of the Gd2o-Tb7Fe film when the film thickness of the SiO film is changed while the film thickness of the 02 film is kept constant at 200 OA. Applicant Daini Seikosha Co., Ltd. 23 Figure 1 □ 3 Figure 3 Sl0M Sarano

Claims (4)

[Claims] (1) A substrate used for a magneto-optical disk that records, reproduces, and erases information using laser light on an amorphous perpendicularly magnetized film, characterized in that a second layer of 5in2 is formed on a metal disk. A substrate for magneto-optical disks. (2) The magneto-optical disk substrate according to claim 1, wherein the metal substrate is AA or Ou. (3) The magneto-optical disk substrate according to claim 2, wherein the film thickness of S 1o is 120 (111 or more). (4) The magneto-optical disk substrate according to claim 3, wherein the SiO2 film thickness is 500X or more.