JPS62164244A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled medium having excellent weatherability by forming a photomagnetic recording layer on a spacer formed on a discoid transparent substrate, further forming a protective layer thereon, and allowing the protective layer to cover the side surfaces of the photomagnetic recording layer. CONSTITUTION:The spacer 2 is formed on the substrate 1, and the photomagnetic recording layer 3 and the protective layer 4 are successively formed thereon. A glass disk, etc., are used as the substrate 1, and a groove 11 for laser beam tracking is previously formed on the substrate 1. A material such as SiO2 and AlN which is optically homogeneous and transparent, having no anisotropy, and capable of shielding water and oxygen is used as the material of the protective film 4 and the spacer 2, and the protective layer 4 is formed to cover also the side surfaces op the photomagnetic recording layer 3. Consequently, the infiltration of water and the intrusion of oxygen from the side surfaces of the photomagnetic recording layer 3 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magneto-optical recording medium that records, reproduces and erases information using laser light.

(Prior Art) Optical disk memory is considered as a new memory to replace the current magnetic disk memory because it is capable of high density, large capacity, and high speed access. Among them, magneto-optical disks using magneto-optical recording media have attracted the most attention because they are rewritable, and research and development have been actively conducted in recent years.

The configuration of a conventionally known magneto-optical recording medium is as shown in FIG. A magneto-optical recording layer 3 made of a magnetized film is formed. As the magneto-optical recording layer, MnB1. MnCuB
1. MnTiB1. Crystalline magnetic thin films such as MnAlGe and PtCo, or Gd, Tb, Dy, Ho, Sm,
Amorphous magnetic thin films obtained as alloys of rare earths such as Nd and transition metals such as Fe, Co, and Ni are known. Further, as shown in FIG.
A medium configuration is also known in which grooves 11 with a pitch of 0 to 1000 and a period of 1.6 to 2.5 pm are formed in a thinly wound or concentric shape, and a magneto-optical recording layer 3 is formed on the substrate 1. The groove 11 formed here is used for recording information on a recording medium.
Alternatively, it is used for tracking access of a focused laser beam used for reproduction/erasing.

In addition, the seventh type of conventionally known magneto-optical recording medium
As shown in the figure, there is a type in which a magneto-optical recording layer 3 is sandwiched between a spacer 2 and a protective layer 4. This configuration can be seen, for example, in Japanese Patent Application Laid-Open No. 59-110052. Since the magneto-optical recording layer 3 is sandwiched between the spacer 2 and the protective layer 4, moisture and oxygen are prevented from penetrating into the magneto-optical recording layer 3 from the substrate side and the film side, and the aging of the magneto-optical recording layer 3 is prevented. Change and deterioration can be prevented. Also known is a medium having this structure, as shown in FIG. 8, which uses a substrate 1 having thinly wound or concentric grooves 11, similar to that shown in FIG.

(Problems to be Solved by the Invention) Amorphous magnetic thin films of rare earth transition metal alloys currently used as magneto-optical recording layers are highly susceptible to oxidation and deteriorate rapidly due to penetration of moisture or oxygen from the outside. do. In known magneto-optical recording media, as shown in FIGS. 7 and 8, a protective layer 4 and a spacer 2 are provided on the two layers and the lower layer of the magneto-optical recording layer 3 to prevent penetration of moisture and oxygen. It is provided. However, no measures have been taken to protect the side surfaces of the magneto-optical recording layer, and there has been a drawback in that changes over time and deterioration progress from the side surfaces of the magneto-optical recording layer.

An object of the present invention is to solve the drawbacks of the conventional magneto-optical recording medium and to provide a novel magneto-optical recording medium with a simple structure and excellent weather resistance.

(Means for Solving the Problems) According to the present invention, in a magneto-optical recording medium in which information is recorded, reproduced and erased using a laser beam, a disc-shaped transparent substrate, a spacer formed on the substrate, It is characterized by comprising a magneto-optical recording layer formed on the spacer and a protective layer formed on the magneto-optical recording layer, the protective layer being formed in a shape to cover a side surface of the magneto-optical recording layer. A magneto-optical recording medium is obtained.

(Function) FIG. 1 shows an example of a magneto-optical recording medium according to the present invention.
FIG. A spacer 2 is formed on a substrate 1, a magneto-optical recording layer 3 is further formed on the spacer 2, and a protective layer 4 is further formed on the negative side of the magneto-optical recording layer 3. The substrate 1 is glass molded into a disk shape,
Polycarbonate resin, polymethyl methacrylate resin, epoxy resin, etc. are used. Further, as shown in FIG. 2, a groove 11 for laser beam tracking may be formed in advance. As the protective film 4 and the spacer 2, a material is used that is optically homogeneous, has no anisotropy, is transparent, and can block moisture and oxygen. parable
For example, SiO, AIN, Si3N4. ZnS, Sb2S3.
CdS, ThF4. MgF2゜LaF3. NdF3. C
eF3. PbF2, 8i, Ge, etc. are used. As the magneto-optical recording layer 3, an amorphous magnetic thin film made of an alloy of rare earth metals such as Gd, Tb, Dy, and Ho and transition metals such as Fe, Co, and Ni is used. For example, G
dCo.

GdTbCo, GdTbFeCo, TbFe, TbFe
Co, TbDyFeCo.

GdTbFe, GdTbDyFe, TbCo, TbDy
Co, TbFeNi, etc.

In FIGS. 1 and 2, the protective layer 4 is formed to cover the side surface of the magneto-optical recording layer 3. As shown in FIG. In conventional magneto-optical recording media, as shown in Figs. 7 and 8, the sides of the magneto-optical recording layer formed on the base (1), the root soil, that is, the side surfaces of the outer circumference and the side surfaces of the inner circumference are exposed. However, as in the present invention, the magneto-optical recording layer in the outer and inner circumferential areas has the disadvantage that moisture and oxygen infiltrate from the sides, causing deterioration and deterioration of the magneto-optical recording layer over time. By forming a protective layer to completely cover the magneto-optical recording layer, deterioration of the magneto-optical recording layer can be prevented and weather resistance can be improved.

The magneto-optical recording layer 3, protective layer 4, and sparser 2 are continuously formed by sputtering or vacuum evaporation without breaking the vacuum. At this time, the protective layer 4 needs to be formed to cover the magneto-optical recording layer 3. Therefore, when forming the magneto-optical recording layer, a shutter with a ring-shaped opening is inserted between the sputtering target or vapor deposition source and the disc-shaped support substrate as shown in Figure 3, but when forming the protective layer, the shutter is not inserted. Adopt. FIG. 4 is a schematic diagram of a film forming apparatus used for forming a film of a magneto-optical recording medium according to the present invention. In FIG. 4, the shutter 25 has the same shape as in FIG. 3, and has a movable unit 21 so that it can be inserted between the disk-shaped support substrate and the sputter target or vapor deposition source. The disc-shaped support substrate rotates during film formation. Due to the use of the shutter, the area in which the magneto-optical recording layer 3 is formed is limited to the shutter opening. On the other hand, since no shutter is used when forming the protective layer 4, the protective layer 4 is formed over a wider area than the magneto-optical recording layer. Thereby, the side surfaces of the magneto-optical recording layer 3 are covered and protected by the protective layer 4. Although the present invention has been described with respect to the case where there is a spacer layer, it is clear that the same effect can be obtained even when there is no spacer layer.

(Example-1) A polycarbonate substrate (130 mm
Two sheets (diameter and thickness 1.2 mm) were prepared, and a magneto-optical recording medium was created by sputtering. In both cases, Si3N4 was used as a spacer, and T was used as a magneto-optical recording layer.
1000 bFeCo, 1 Si3N4 as a protective film
This is a configuration in which 1,000 films were deposited directly. The first magneto-optical recording medium (medium 1) was produced by inserting a shutter having a ring-shaped opening with an inner diameter of 25 mm and an outer diameter of 120 mm at a position 1Q mm from the substrate during film formation of the magneto-optical recording layer. The spacer layer and the protective layer were formed to have an inner diameter of 20 mm and an outer diameter of 125 mm. On the other sheet (medium 2), each layer was formed in a range from an inner diameter of 20 mm to an outer diameter of 125 mm without using the shutter.

Next, to examine the weather resistance of the magneto-optical recording medium, we conducted an accelerated environmental test under high temperature and high humidity conditions. The two magneto-optical recording media described above were left in an environment of 60° C. and 80% humidity for 300 hours, and changes in the Kerr rotation angle, coercive force, and recording/reproducing characteristics before and after the test were examined.

Kerr rotation angle and coercive force at the position of inner diameter 3Qmm and outer diameter 1
Measurement was made at a position of 15 mm. For medium 1, there was no change in the Kerr rotation angle before and after the test, and the change in coercive force was 5.
It was ~10%. On the other hand, for medium 2, the Kerr rotation angle after the test decreased to 70% of that before the test, and the coercive force changed by 40~
It was 50%.

Next, the recording and reproducing characteristics before and after the test were investigated using the magneto-optical disk head. C/ of the reproduced signal with an outer diameter of 115 mm
N (frequency IMHz, linear velocity 10 m, /s) did not change before and after the test in medium 1, but in medium 2 there was a 3 dB C/N drop due to the environmental test.

(Example 2) A polymethyl methacrylate substrate (
Two sheets (130 mm in diameter, 1 in thickness, 2 mm) were prepared, and a magneto-optical recording medium was produced by electron beam evaporation. In each case, 700 layers of ZnS were used as a spacer, 1000 layers of TbFeCo were used as a magneto-optical recording layer, and 7 layers of ZnS were used as a protective layer.
00 people continuously deposited films. The first magneto-optical recording medium (medium 3
) has a circular diameter of 25 mm and an outer diameter of 120 mm when forming the magneto-optical recording layer.
It was created by inserting a shutter with a ring-shaped opening at a position 1Qmm from the substrate. The spacer and protective layer were formed in a range from an inner diameter of 20 mm to an outer diameter of 125 mm. In the other one (medium 4), each layer was continuously formed in a range from an inner diameter of 20 mm to an outer diameter of 125 mm without using the shutter.

Next, to examine the weather resistance of the magneto-optical recording medium, we conducted an accelerated environmental test under high temperature and high humidity conditions. medium 3 and medium 4 to 6
It was left for 100 hours in an environment of 0°C and 80% humidity, and the change in Kerr rotation angle before and after the test was measured. The Kerr rotation angle at an outer diameter of 115 mm did not change for medium 3, whereas for medium 4 it decreased to a value of 40 to 50% of the value before the test.

(Effects of the Invention) As described above, it can be seen that the magneto-optical recording medium according to the present invention has excellent weather resistance compared to conventional media. In particular, the weather resistance at the inner and outer circumferential portions of the medium is significantly improved compared to conventional media.

Since the protective layer completely shields the side surfaces of the magneto-optical recording layer, the present invention is effective in preventing deterioration from the side surfaces of the magneto-optical recording layer.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the structure of a magneto-optical recording medium to which the present invention is applied; FIG. 3 is a view showing the structure of a shutter used in producing the magneto-optical recording medium according to the present invention; FIG. 4 is a block diagram of a film forming apparatus for producing a magneto-optical recording medium according to the present invention, and FIGS. 5, 6, 7 and 8 are cross-sectional views showing the structure of a conventional magneto-optical recording medium. It is a diagram. In the figure, 1...substrate, 2...spacer, 3...
Magneto-optical recording layer, 4... protective layer, 11... groove. FIG. 1 16 Substrate 2, spacer 3, magneto-optical recording layer 4, protective layer FIG. 2 FIG. 1, substrate 2, spacer 3, magneto-optical recording layer 4, protective layer 11, groove FIG. 3 FIG. 4 FIG. Substrate 27. Chamber 251.
Yatta 28. Sputter gas inlet 2
9. Vacuum exhaust unit FIG. 5 1, Substrate 3, Magneto-optical recording layer 6 FIG. 1, Substrate 3, Magneto-optical recording layer 11, Groove 7 FIG. 1, Substrate 2, Spacer 3, Magneto-optical recording layer 4, Protection layer

Claims (1)

[Claims] A magneto-optical recording medium in which information is recorded, read and erased using a laser beam, includes a disc-shaped transparent substrate, a spacer formed on the substrate, a magneto-optical recording layer formed on the spacer, and the magneto-optical recording layer. 1. A magneto-optical recording medium, comprising: a protective layer formed on the magneto-optical recording layer, the protective layer having a shape that covers a side surface of the magneto-optical recording layer.