JPS61107554A - Optomagnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the deformation of a disk with age by adhering a nonmagnetic metallic plate which is thin and strong to a disk substrate. CONSTITUTION:A recording layer 10 consisting successively of an underlying layer, magnetic layer formed with a ternary alloy film composed of Cd (cadmium), Tb (terbium) and Fe (iron) by sputtering and protective film layer is formed on the base of the hollow groove 8 of he acrylic substrate 2. A stainless steel plate 7 which is a nonmagnetic metal is adhered onto the layer 10 via a hollow part (air layer) 9 as an intermediate layer having low heat conductivity to constitute the above-mentioned medium. The deformation of the substrate with age is thus prevented even if the acrylic substrate which is a plastic substrate is used. The diffusion of heat in the stage of recording is prevented and the energy loss is prevented as well.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a magneto-optical recording medium, that is, a magneto-optical disk, and particularly relates to a laminated structure.

BACKGROUND OF THE INVENTION Generally, a magneto-optical disk has a structure as shown in FIG.

2 shows the entire magneto-optical disk, 2 is a substrate, 3 is an underlayer, 4 is a recording layer, 5 is a protective layer, 6 is an adhesive layer, and 7 is a backing plate.

On the disk substrate 2 of the disk, which is a magneto-optical recording medium,
Materials such as glass, acrylic, and polycarbonate are used, but glass has problems in terms of productivity, acrylic in terms of deformation over time due to hygroscopicity, and polycarbonate in terms of optical properties.

Among them, the most promising one is acrylic.
Although it is excellent in terms of productivity and optical properties, as mentioned above, it is prone to deformation over time, so there are problems with warping and surface wobbling in practical use, which is a problem with laser discs currently on the market. be. For this reason, especially in the case of acrylic substrates, an acrylic resin of the same thickness as the substrate is laminated as a backing plate, as shown in Figure 3, but in the case of magneto-optical disks, an auxiliary magnetic field is usually applied from the back side. Therefore, due to the thickness of the laminated plate (backing plate), the loss of the magnetic field is large, and the current flowing through the magnet is also very large.

Therefore, there was a desire for a magneto-optical disk that was thinner, stronger, did not deform over time, and could record with less auxiliary magnetic field current.

Purpose of the Invention The object of the present invention is to solve the above-mentioned problems and to provide an optical magnetic recording medium (hereinafter referred to as magneto-optical disk) which exhibits little deterioration over time and exhibits little warpage or surface wobbling during use. be.

Summary of the Invention The present invention prevents the disk from deforming over time by bonding a thin, strong non-magnetic metal plate to the disk substrate. Efforts have been made to prevent heat loss during recording by interposing a layer of a substance with low thermal conductivity, such as an air layer, a resin layer, or an adhesive layer, to the metal plate.

Example Hereinafter, the present invention will be specifically explained with reference to Examples.

In order to eliminate the above-mentioned drawbacks of the conventional method, it is best to use a thin and strong non-magnetic metal as the backing plate, but if such a metal plate directly touches the magnetic recording layer, the recording layer will be damaged during recording. Thermal energy of the laser beam irradiated on the recording layer may escape from the recording layer to the metal plate, and the temperature of the recording layer may not rise sufficiently and recording may not be performed successfully. Therefore, in the present invention, an intermediate layer with low thermal conductivity is provided between the metal plate and the recording layer in order to maintain strength and prevent energy loss during recording.

(Ml Embodiment) FIG. 1 is an enlarged sectional view of the main part showing a first embodiment of the magneto-optical disk of the present invention.

2 is a concave A8 disk with a thickness of 1.2 mm and an outer diameter of 200 mm.
On the bottom of the groove 8, a base layer, Cd (cadmium), Tb (terbium),
A recording layer 10 consisting of a magnetic layer formed by sputtering a ternary alloy film of Fe (iron) and a protective film layer is formed.

9 is a hollow intermediate layer, and 7 is a 0.6-thick stainless steel (
This is a backing plate made of SUS 304) disks attached with adhesive 6.

That is, a stainless steel plate made of a non-magnetic metal is bonded onto the recording layer IO via a hollow space (air layer) serving as an intermediate layer with low thermal conductivity.

This configuration prevents deformation over time even if an acrylic plastic substrate is used, and
Since a reinforcing non-magnetic metal backing plate is provided with an interlayer of air having low thermal conductivity interposed therebetween, heat diffusion during recording can be prevented and energy loss can also be prevented.

(Second Example) Fig. 2 shows a second example, in which a 0.6+pm thick stainless steel (SUS) is used on a substrate under the same conditions as the first example.
304), but instead of gluing the outer peripheral part and center part of the disc in the first embodiment,
The hollow portion formed by the groove 8, which forms the intermediate layer, is filled with a UV-curable adhesive that is an adhesive resin. That is, the adhesive 6 also serves as an intermediate layer.

By doing this, the backing board will be adhered via an adhesive layer (adhesive material) with relatively low thermal conductivity.
This provides the same effects as the first embodiment.

Note that the intermediate layer may be filled with a resin having low thermal conductivity and the backing plate may be bonded to the intermediate layer using an adhesive.

Above, we have explained the case where stainless steel is used as the backing plate, but AM aluminum), IVLg (magnesium)
, Ti (titanium), etc., any non-magnetic and highly rigid metal alloy can be used as the backing plate of the present invention.

Next, experimental results of the magneto-optical disk according to the present invention will be explained.

The experimental conditions were that three types of disks based on the first and second examples of the present invention and two types of comparative samples were left in an atmosphere with a temperature of 60 ° C. and a humidity of 90% for 24 hours, and then
The amount of surface runout and warpage of the disc was measured.

(Table) Sample (1)...First example (plate thickness 0, 6 mm)
Sample (2) - Second example (plate thickness 0, 6 n+m
) Sample (3)...Produced based on the second example (however, plate thickness 0.3 mm) Comparative example (1)... Produced based on the first example (however, plate thickness 1.2 mm) Comparison Example (2): Manufactured based on the first example (however, the backing plate was acrylic) As a result of the experiment, remarkable effects were observed as shown in the table.

Sample (1) and sample (backed with plate thickness 0 and 6 mm)
Sample (3), in which the plate thickness was half as thick as 0.3 mm compared to 2), had a slightly larger surface runout, but compared to comparative example (2), in which the backing plate was a conventional acrylic plate, the surface runout and The improvement effect on warping is fully recognized.

In Comparative Example (1), although the surface runout was slightly large, the warp was smaller than that of the third sample.

This changes the backing plate in sample (1) from 0.6 to 1.
・The thickness was increased to 3.2+nm, which is a natural result.

However, if we compare Comparative Example (1) with Sample (3), which has a plate thickness of 0 and 3 mm, the latter (Sample (3)) has a plate thickness half that of the former (Comparative Example (1)). Despite this, there was no significant change in surface runout or warpage that would pose a practical problem, and considering the disadvantage of increasing the plate thickness and weakening the magnetic field during disk recording, an appropriate value for the plate thickness was found. is determined by itself.

Further, regarding recording sensitivity, no particular difference was observed among the three samples.

As described in detail, the present invention prevents the plastic substrate of a magneto-optical disk from deforming over time, reduces surface wobbling in practical use, and provides a disk with high strength and low energy loss during recording. It has the effect of being able to obtain.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of the main part of the first embodiment of the present invention, FIG. 2 is an enlarged sectional view of the main part of the second embodiment, and FIG. 3 is an enlarged sectional view of the main part of a conventional magneto-optical disk. It is. 2...Substrate 6...Adhesive material 7...Backing plate 8...Concave groove lO...Recording layer Patent applicant Olympus Optical Industry Co., Ltd. ) December 5, 1980 Manabu Shiga, Commissioner of the Patent Office 2 Name of the invention Magneto-optical recording medium 3 Relationship to the case of the person making the amendment Patent applicant address 2-43-2 Hatagaya, Shibuya-ku, Tokyo 4. Agent 1, tl is also 1 VNOY] (1) The statements from the table on page 7 of the specification to line 8 on page 9 of the specification are amended as follows. (Table) Sample (1)...First example (plate thickness Q, (3mm)
Sample (2)...Second example (plate thickness Q, (3mm
>Sample (3)...Produced based on the second example (However, the plate thickness is 0, 3 mm) Comparative example (1)... Produced based on the first example (However, the plate thickness is 1.2 mm.) (acrylic plate) Comparative example (2)...Manufactured based on the first example (acrylic plate with a plate thickness of 0 and 6 mw+) As a result of the experiment, remarkable effects were observed as shown in the table. Sample (1) and sample (2) lined with plate thickness 0.6 mm
Sample (3) with half the thickness of 0.3 mm compared to
Although the surface run-out is somewhat large, the improvement effect on surface run-out and warpage is sufficiently greater than that of Comparative Examples (1) and (2) in which the backing plate was a conventional acrylic plate. In other words, even when the plate is as thin as 0.3 mm, the effect of significantly reducing surface and warpage is obtained compared to the plate using an acrylic plate. The thickness of the plate in the present invention does not need to be particularly limited, but if it is too thick, the magnetic field will be weakened, so there will be some restrictions from that point of view. Moreover, if it is too thin, the effect of the lining will be meaningless. Therefore, the range of thickness is a range of design matters determined by itself. It should be noted that no particular difference in recording sensitivity was observed among the three types of samples. 1

Claims (4)

[Claims] (1) A magneto-optical recording medium characterized in that a disk has a magnetic recording layer formed on a plastic substrate, and a non-magnetic metal plate is adhered onto the recording layer via an intermediate layer with low thermal conductivity. (2) The magneto-optical recording medium according to claim 1, wherein the intermediate layer is air. (3) The magneto-optical recording medium according to claim 2, wherein the substance with low thermal conductivity is a resin. (4) The magneto-optical recording medium according to claim 2, wherein the substance with low thermal conductivity is an adhesive.