JPS63271744A - Magneto-optical disk medium - Google Patents

Abstract

PURPOSE:To suppress diffusion of heat and to improve recording sensitivity without degrading C/N by alternately laminating recording films and dielectric films having a low heat conductivity. CONSTITUTION:The magneto-optical recording medium consisting of rare earth metals (RE)-transition metals (TM) is formed into the structure in which the RE-TM films and the dielectric films having the low heat conductivity of <=5J/M.S.K heat conductivity are alternately laminated at prescribed layer thickness ratios by respectively at least two layers each, more preferably 3-6 layers each. For example, ZnS is used as an upper layer protective film 2 and a lower layer protective film 3, and the recording films 6 consisting of TbFeCo and the dielectric films 7 consisting of ZnS are successively and alternately laminated as the recording layer 4. The recording sensitivity is improved without degrading the C/N by forming the recording layer into the laminated structure in such a manner.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a magneto-optical disk medium in which the recording layer is composed of multiple layers of a rare earth metal-transition metal recording film and a dielectric film having low thermal conductivity in order to improve recording sensitivity. The layered structure suppresses heat conduction in the recording layer, lowers the recording power, and enables the disk to rotate at high speed.

[Industrial application field]

The present invention relates to magneto-optical disk media. Magneto-optical disks are expected to be used as file memory because they do not have a large capacity and are less affected by dust, but for this purpose, high-speed data transfer is required, and improved recording sensitivity is desired. It is an object of the present invention to provide a magneto-optical disk medium in which recording sensitivity is improved without reducing the C/N ratio.

[Conventional technology]

Conventional magneto-optical disks have an underlayer (e.g. 5tot, 5iO1SiJ4, ZnS, AIN) on a substrate made of polycarbonate resin, glass-photopolymer, PMMA, etc.
), Record Ji! (For example, TbFe, TbFeCo,
GdFbFeSTbCo), and the upper layer (e.g. 5
iOz, 5iO1Si3N4, ZnS.

It is constructed by laminating layers of AIN) in this order, and efficiently utilizes heat by utilizing light interference from the underlayer.

In a magneto-optical disk with such a structure, the recording sensitivity of the medium itself is determined by the thermal conductivity and heat capacity, which are the physical properties of the constituent materials, and the recording sensitivity of the medium is increased by making the underlayer thick enough to reduce reflection due to optical interference. . however,
A magneto-optical disk medium having such a structure has insufficient recording sensitivity when the disk is rotated at high speed, for example.

[Problem that the invention seeks to solve]

As mentioned above, conventional magneto-optical disks have a problem in that the recording sensitivity is insufficient when the disk is rotated at high speed.

Therefore, the present invention provides sufficient C/
An object of the present invention is to provide a magneto-optical disk medium having a high N ratio and improved recording sensitivity.

[Means for solving problems]

According to the present invention, in a rare earth metal-transition metal magneto-optical disk medium, a rare earth metal-transition metal recording film and a dielectric film having a low thermal conductivity of 5 J/M·S·K or less are provided. A magneto-optical disk medium is provided in which at least two layers are alternately laminated at a film thickness ratio of .

[For production]

The present invention will be explained in more detail below with reference to the accompanying drawings.

According to the present invention, as described above, a rare earth metal (RE)-transition metal (TM) magneto-optical recording medium has an RE-7M film and a low thermal conductivity of 5 J/M-3 K or less. At least 2 layers each, preferably 3 to 6 dielectric films.
The above object can be achieved by forming a structure in which layers are alternately laminated.

In the present invention, any conventionally known RE-
7M film, e.g. TbFeCo, TbFe, TbGd
Fe.

TbGdFeCo, TbCo, etc. can be used, and the magneto-optical disk medium of the present invention preferably has a film thickness per IN of 100 to 300, more preferably 100 to 2.
It can be produced by laminating two or more layers, preferably three to six layers, of the recording film 6 of 0.000000000000000 films, preferably 3 to 6 layers, alternately with the dielectric film 7 according to a conventional method.

On the other hand, the dielectric film 7 that constitutes the recording layer 4 by alternately laminating the recording films 6 is made of a material having a low thermal conductivity, preferably a thermal conductivity of 5 J/M・S・K or less (for example, ZnS, Sin, etc.).
5iO1ZrO,), the film thickness per layer is preferably 10
~300 people, more preferably 50-200 people dielectric film 7
It can be produced by laminating two or more layers, preferably three to six layers, alternately with the recording layer 6.

[Examples and comparative examples]

The present invention will be described in more detail below with reference to Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples.

A photopolymer (2P)-glass substrate (5"
A sample of a magneto-optical medium having the structure shown in FIGS. 1(a) and (b) was prepared on φ)1. Note that ZnS was used as the upper protective film 2 and the lower protective film 3, and rbpeco and ZnS were laminated as the recording layer 4.

The vacuum chamber 5 was evacuated to lXIQ-'Pa, and Ar gas was introduced into the vacuum chamber 5 under a vacuum of 0.2 Pa.
Each film was formed. Upper and lower layer protection 1g (Zn
S) The thickness of layers 2 and 3 is 800, and the thickness of recording layer 4 is 800.
The TbFeCo recording film 6 was sequentially and alternately laminated by 100 people and the ZnS dielectric film 7 by 50 people, so that the total thickness of the recording layer 4 was 900 people. The films were stacked alternately by rotating the substrate 1. Disc A was produced in this way. In FIG. 2, 8 is a substrate holder, 9 is a shutter, and 10 is a window.

Next, as a comparative example, disk B with a conventional structure (simple three-layer structure) was coated with a ZnS protective film of 800 layers and a TbFeCo recording layer of 9 layers.
A ZnS protective film of 0.00 and a ZnS protective film of 800 were sequentially formed by sputtering.

As another comparative example, a disk C was prepared in which the recording layer was simply thin (that is, a ZnS protective film of 800 layers, a TbFeCo recording layer of 300 layers, and a ZnS protective layer of 800 layers).

Each disk A was produced in this way.

The recording and reproducing characteristics of B and C were measured, and the optimum recording power (recording power when the second harmonic is the lowest), which is a guideline for recording sensitivity, and C, , C2, and N were determined.

Note that the recording and reproducing characteristics are 90 m at a radius R = 46 m.
Measurements were made at 0 rpm and a recording frequency of I MHz. The results obtained are shown in FIG.

As is clear from the results shown in Figure 3, even with a disk in which only the recording layer is simply thinned (disk C), the optimum recording power is approximately 3.5 mW, and the recording sensitivity is improved to the same extent as disk A of the present invention. However, C/N (C.

-N) has decreased significantly. On the other hand, in the disc A of the present invention, the optimum recording power is reduced without reducing the C/N ratio. As described above, by forming the recording layer into a laminated structure according to the present invention, recording sensitivity can be improved without reducing the C/N ratio.

〔Effect of the invention〕

As explained above, according to the present invention, recording films and dielectric films with low thermal conductivity are alternately laminated to suppress heat diffusion and improve recording sensitivity without reducing the C/N ratio. You can force it.

[Brief explanation of the drawing]

1(a) and (b) are cross-sectional views schematically showing the structure of the magneto-optical disk medium of the present invention, and FIGS. 2(a) and (b) are cross-sectional views of the magneto-optical disk medium of the present invention. FIG. 3 is a schematic diagram showing an RF magnetron sputtering apparatus that can be used for manufacturing, and FIG. 3 is a graph diagram showing the results of Examples and Comparative Examples. DESCRIPTION OF SYMBOLS 1... Base, 2... Upper layer protective film, 3... Lower layer protective film, 4... Recording layer, 5... Vacuum chamber, 6... Recording film, 7... Dielectric film , 8... Board holder, 9... Shutter, 10... Window. (a) (b) Figure 1 (a) 2... Upper protective film 7... Dielectric film recording power (mW) Figure 3 C1: Carrier level C2: Second harmonic level N: Noise level

Claims (1)

[Claims] 1. In a rare earth metal-transition metal magneto-optical disk medium, the rare earth metal-transition metal recording film has a thermal conductivity of 5 J/M.
- A magneto-optical disk medium in which at least two dielectric films each having a low thermal conductivity of S.K or less are laminated alternately at a predetermined film thickness ratio. 2. The thickness of one recording film is 100 to 300 Å, and 1
2. The magneto-optical disk medium according to claim 1, wherein the dielectric film of the layer has a thickness of 10 to 300 Å.