JPH0492234A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain the magneto-optical recording medium having high reliability by specifying the thermal conductivity at ordinary temp. of the magneto-optical recording film formed on a transparent substrate and a heat control layer formed on this magneto-optical recording film. CONSTITUTION:This recording medium has the transparent substrate 1, the magneto-optical recording film 4 formed on this transparent substrate 1, the heat control layer 6 which is formed on this recording film 4 and consists of, for example, an Al-Ti alloy or Cu-Ti alloy. The thermal conductivity K at ordinary temp. of this heat control layer is regulated to a 0.1 to 2.0 (W/cm.deg) range. The heat diffusion at the time of irradiation with a laser is adequately executed. There is, therefore, no need for increasing the laser power required for recording and erasing and the magneto-optical recording medium 4 which lessens the fall of the level of reproduced signals by the repetition of recording and erasing is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical-magnetic recording medium, and particularly to a thermal control layer formed on an optical-magnetic recording film thereof.

[Prior Art] Since optical-magnetic recording films containing rare earth elements are easily oxidized chemically, various proposals have been made to form chemically stable thin films on optical-magnetic recording films for the purpose of preserving ε. (For example, JP-A No. 58-60441, JP-A No. 60-60-3-65)
No. 9, JP-A-62-137743).

[Problems to be Solved by the Invention] However, these conventional proposals do not take into account the state of heat given by the incident laser beam, and in particular, the following problems occur when the metal protective film does not control the heat diffusion there. This may cause serious technical problems.

(2) If the thermal diffusion of the metal protective film is too fast, or if the heat capacity is too large, the laser power required for erasing must be increased.

1. If the thermal diffusion of the metal protective film is too slow, heat accumulation at the center of the laser spot increases, causing changes such as structural relaxation and crystallization in the recording film. Therefore, as recording and reproduction are repeated, the quality of the recording medium deteriorates, including a decrease in the level of the reproduced signal.

(2) If the heat capacity is too small and the heat diffusion of the metal protective film is too slow (Z), in addition to the disadvantages of (2) above, there is a fear that fluctuations in the reproduction output or data destruction due to temperature changes may occur.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
The object of the present invention is to provide a highly reliable optical-magnetic recording medium.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a transparent substrate, an optical-magnetic recording film formed above the transparent substrate, an optical-magnetic recording film, and a transparent substrate. For example, Al-
It has a thermal control layer made of Ti alloy, 0u-Ti alloy, etc., and the thermal conductivity of the thermal control layer at room temperature is 0.1 ~
It is characterized by being regulated within a range of 2.0 (W/Cm·deg).

[Function] As described above, in the present invention, by regulating the thermal conduction TcK of the thermal control layer, heat diffusion is properly performed during silent laser irradiation. Therefore, it is not necessary to increase the laser power required for recording and erasing, and it is possible to obtain an optical-magnetic recording medium in which the level of the reproduced signal is less likely to decrease due to repeated recording and erasing.

[Example code] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged sectional view of an opto-magnetic recording medium according to a second embodiment.

1 in the figure is a transparent substrate, for example transparent ceramics such as glass, polycarbonate, polymethylmethac? Lou
Transparent materials such as polymethylpentene, epoxy resin, etc.
IN material is used.

On the signal surface 2 of the second transparent substrate 1, desired preformat patterns such as guide grooves for guiding recording/reproducing light and various pre-pit rows are transferred.

3 is a first enhancement film that repeatedly reflects the reproduction light at the interface between the transparent substrate 1 and the optical-magnetic recording film 4 described later, and is apparently used to increase the Kerr rotation angle shown above. As the first enhancing film 3, a non-heating dielectric such as silicon nitride, aluminum nitride, silicon oxide, or aluminum oxide is used, and the film is formed to a thickness of about 700 to 1000 nm by sputtering or other means. Ru.

4 is an optical-magnetic recording film consisting of an amorphous perpendicular magnetization film;
An example of its composition is as follows.

% in the formula TbxFe+xoa-x-y-z+coyMz
g Y+ 2 is atomic %, 15≦, ≦30.5≦, ≦1
5.0 2 ≦10 M=Nbz Cr, Ptc 5 is the second process〉〉Hance absorption, which gives an enhancement effect to the transmitted light from the optical-magnetic=2 recording film 4 to further increase the Kerr rotation angle. It is formed for the purpose of The second enhancement film 5 is made of the same inorganic derivative as the first enhancement film 3.

6 is a heat control layer that also serves as a reflective film and a protective film.

AJ One or more metal elements selected from the group of Ag, Au, Cu, and Be, and Cr and Ti.

Tar Sn, Si, Rh, Pe, Nb, Mo.

Li,: 1 selected from the group of \iH, W, Zr
It is composed of an alloy with more than one gold element.

In particular, it contained 6 to 10 at% of Ti. b. It is preferable to use a Q-Ti alloy with a film thickness regulated within the range of 500 to 1000.

When forming recording pits using a Tb-Fe-Co alloy as the material for the optical-magnetic recording film 4, the Curie point of the alloy with the above composition is about 200°C, so the temperature inside the film in the laser beam irradiation area is set to 200°C. When the optical-magnetic recording film 4 reaches that thermal state due to the recording laser beam, which requires raising the temperature to a temperature above .degree. C., the temperature at the center of the laser beam irradiation becomes the highest within the film. That is, 1. For example, in the case of forming a recording pit of a certain size (for example, 0.8 μm in diameter) as shown in FIG. 2, it is necessary to raise the temperature inside the diameter to 200° C. or higher. In other words, a circumferential line with a diameter of 0.8 μm becomes a 200°C equimixture line, and the temperature inside the line is inevitably higher than 200°C. There will be a difference in temperature.

The curves in the figure schematically show temperature distribution, and the one-dot curve B is for thermal control layer 6 with relatively good thermal conductivity, and the solid curve A is for thermal control layer 6 with relatively poor thermal conductivity. This is a characteristic curve when layer 6 is used. As is clear from the second figure, the difference in thermal conductivity of the thermal control layer 6 causes a difference in temperature at the center of the laser beam irradiated area. In other words, the maximum temperature of the recording film 4 can be controlled by the thermal conductivity (thermal conductivity, film thickness, etc.) of the thermal control N6.

When the temperature of the above-mentioned optical-magnetic recording mound 4 is raised above 300''C, the structure becomes loose (1r:i) and crystallization occurs, which deteriorates the recording and reproducing characteristics. It is necessary to control so that such a situation does not occur.

As mentioned above, a Tb-Fe-Co alloy is used as the optical-magnetic recording film, and an A, fl-Ti alloy is used as the protective film on gold, so that the Ti in the thermal control layer with respect to the maximum temperature of the optical-magnetic recording film is Figure 3 shows the results of examining the dependence on content.

The horizontal axis in the figure represents the T-containing space in the 〇-Ti alloy.
The central temperature of the laser beam irradiation area is shown on the cherry blossom axis. Note that this center temperature is equal to the film surface temperature of 2.
This is the temperature at the center when the area above 00'C is 1 μm in diameter.

As mentioned above, Tlg;F e+xoa-x-y-z+c
In OyMz-based opto-magnetic recording films, if the temperature of the laser beam irradiated area exceeds 300°C, crystallization will proceed and adversely affect the recording and reproduction characteristics, so it is necessary to control the temperature so that the temperature does not exceed 300°C. be. For this purpose, as is clear from Figure 3.

It is necessary to control the Ti content in the 8.λQ-Ti alloy to 20.7% or less.

FIG. 4 is a diagram showing the relationship between the Ti content in an Al-Ti alloy and the thermal conductivity of that alloy at room temperature. As is clear from this figure, depending on the Ti content, Ω−r=
The thermal conductivity of the alloy changes, and the Ti content increases to 10yK%.
The following means that the thermal conductivity is 0.13 [W/cm
-deg or more.

From the results of various experiments conducted by the present inventors, we found that the temperature of the second thermal control layer? ,
In this case, the thermal conductivity is 2.0≧≧0゜1[W/
It has been clarified that it is necessary to regulate it within the cm/degE range. The thermal conduction history of the thermal control layer is 2°Q [W/cm-d
If it exceeds eg, heat diffusion is too rapid and high laser power is required for recording and erasing, which is uneconomical. On the other hand, the thermal conductivity of the thermal control layer is 0.1 [W/cm-
On the contrary, when the temperature is less than 1 degree, thermal diffusion is too slow, and as recording and reproduction are repeated, the amorphous structure of the recording film is relaxed and crystallized. Therefore, the thermal conduction of the thermal control layer at room temperature is Rates include 2.0≧ to ≧0.1rW/c
m-d eg], especially 0.
It is preferable that the range is regulated to 25≧ and ≧0.14 [W/cm-deg].

FIG. 5 is a diagram showing the relationship between the T1 content in the 80-Ti alloy and the decrease in carrier wave level after recording and erasing cycles. Note that the film thickness of the Al-Ti alloy is 7
This figure shows how the carrier wave level of the recorded and reproduced signals decreased after recording and erasing were repeated 10,000 times with 50 people.

As is clear from this figure, Ti in the Al-T1 unit
When the content exceeds a little over 10 atomic %, the carrier wave level decreases, and this is presumed to be due to relaxation of the amorphous structure of the recording film and progress of crystallization.

In this optical-magnetic recording medium, the thickness of the winter coat on the substrate is usually as follows.

1st enhancement film...600-100 OA light-Koiki B film...200-500 2nd enhancement film...0-40 Constructed like OA2 In the case of an optical-magnetic recording medium, the laser power required in the recording and erasing processes can be controlled by Iff of the thermal control layer.

Laser power reaching the film surface is 5 to 10 mW [5-inch optical-magnetic disk at 2400 rpm (linear velocity 7.5 to
Recording and erasing are performed by rotating at a speed of 15 m/s), and
In order to perform reproduction with a laser power of 3 mW, the film thickness of the thermal control layer and the Ti content in the An-Ti alloy need to be in the region ▪ in FIG. 10. Above the upper limit of this region 7, a laser power of 10 mW or more is required for erasing at an I&S speed of 15 m/sec (taking into account the track offset margin). Further, below the lower limit of the region (■), there is a risk that data will be destroyed when a signal is reproduced with a laser power of 1 to 3 mW.

The thermal control layer also has the function of protecting the second recording film, and its effectiveness varies depending on the composition and thickness of the thermal control layer. In An-Ti alloy.

The composition and film thickness are in the range of the composition and film thickness in which the error rate remains below UXIO~C for 1000 hours under the ffl condition of 80'C590%RH. , in the region where the Ti content in the Ω-Ti alloy is 6 at% or more,
It has been confirmed that if the thickness of the thermal control layer is equal to or greater than OOA, it has a stable protective effect. , this is a manifestation of the anti-corrosion effect of Ti.

If the Ti content is less than 6 atoms and 92, the corrosion prevention effect is not necessarily sufficient. Therefore, Ti in the An-Ti alloy
It is necessary to control the content to 6 atomic % or more and the film thickness to 500 Å or more.

From the above two points, T in the Al-Ti alloy of the thermal control layer is
By regulating the i content to 6 to 10 i% and the film thickness to 500 Å or more, a light beam with excellent recording and erasing cycle durability, recording, erasing, and reproducing power characteristics, and recording film storage efficiency can be obtained. A magnetic recording medium can be obtained.

FIG. 6 and FIG. 7 are diagrams showing specific examples of the present invention,
Figure 6 shows a closely bonded type optical-magnetic recording medium, and Figure 7 shows an air sandwich type optical-magnetic recording medium.
1.12 is a recording disk, 13 is winter clothes 3~ shown in Figure 1.
Product W with 6! 14 is an adhesive layer, iDL inner spacer, 16 is outer spacer, and 17 is a gap.

In the above embodiments, the thermal control layer is made of an Al-Ti alloy.
Cr, Ti, Ta, Sn+Si, Rb, Pt, Nb, M
In an alloy with at least one metal element selected from the group consisting of o, Mg, W, and Zr, the thermal conductivity is 0.1≦
As long as the thermal control layer has a temperature of ≦2.0, the same effects as in the above embodiment can be obtained.

Next, a performance comparison between each example will be explained regarding specific examples.

(Example 1) First enhancement film (SiN) 800 people Optical-magnetic recording FA (Tb-Fe-Co) 400 people Second enhancement film (SiN) 200 people Thermal control, fi
i' (Al-Ti alloy with Ti content of 7 at%)
750 people (Example 2) First enhancement film (SiN) 800 people Optical-magnetic recording film (Tb-Fe-Co) 400 people Second enhancement film (SiN) 200 people Thermal control layer (Ti content 1o atoms % Al-Ti alloy)
750 people (Example 3) First enhancement film (S i N) B Q O
Human optical-magnetic recording film (Tb-Fe-Co) 400 people 2nd enhancement film (SUN) 200A thermal control JW
(Al-Ti alloy with Ti content of 12 at%)
750 people Figure 11 is a characteristic diagram showing the relationship between the Al1-Ag alloy composition to which the present invention can be applied and the thermal conductivity of that alloy, and Figure 12 further shows the relationship between the Cu-Ti alloy composition and the thermal conductivity of that alloy. FIG.

Similar effects can be obtained by using these Aρ-Ag alloys and Cu-Ti alloys as a thermal control layer and regulating the range of their thermal conductivity.

[Effects of the Invention] FIG. 8 shows the erasing characteristics of the opto-magnetic disk in each of the above embodiments. As is clear from this figure, low laser power is sufficient for both the opto-magnetic disks in each embodiment.

FIG. 9 is a characteristic diagram of the carrier level of the opto-magnetic disk in Example 1. As is clear from this box, in the present invention, even if recording and erasing are repeated many times, signal attenuation hardly occurs, and a highly reliable optical-magnetic recording medium can be provided.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of an opto-magnetic recording medium according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the temperature distribution when the optical-magnetic recording film is irradiated with a laser beam. FIG. 3 is a characteristic diagram showing the relationship between the Ti content in the A11-Ti alloy and the central temperature when the opto-magnetic recording film is irradiated with a laser beam. Fig. 4 is a characteristic diagram showing the relationship between the Ti content in the Aff-Ti alloy and the thermal conductivity of the alloy, and Fig. 5 is a characteristic diagram showing the relationship between the Ti content in the Aff-Ti alloy and the thermal conductivity of the alloy.
FIGS. 6 and 7 are characteristic diagrams showing the relationship between the Ti content in the Ti alloy and the decrease in the nib carrier wave level after recording and reproducing cycles. FIG. 8 is a cross-sectional view, and FIG. 8 is a reproduction signal output characteristic diagram of the optical-magnetic recording medium in each embodiment of the present invention. FIG. 9 is a characteristic diagram of the carrier level of the opto-magnetic recording medium in Example 1 of the present invention. FIG. 10 is a graph showing the Ti content in the Al-Ti alloy, the thermal conductivity of the alloy, and the film thickness. 11th is a characteristic diagram showing the relationship between the Ω-Ag alloy composition and the thermal conductivity of the alloy. FIG. 12 is a characteristic diagram showing the relationship between the Cu-Ti alloy composition and the thermal conductivity of the alloy. Fig. 1 1...Transparent substrate, 2...Signal surface, 3.
・・ First enhancement film, 4. Optical-magnetic recording film, 5.
...Second enhancement film, 6...Temperature control layer. 1゜2゜3. 4. 5. 6. , transparent substrate, signal surface, first enhancement layer, optical-magnetic recording layer, second enhancement film, thermal control layer. 3 Figure Figure Figure Figure Erasing laser power (mW) Figure Number of recording and erasing repetitions (B) Figure T1 content (0%) + 0.50.30.2 0.15 0.1 Thermal conductivity K [W/crrrdegko

Claims (5)

[Claims] (1) It has a transparent substrate, an optical-magnetic recording film formed above the transparent substrate, and a thermal control layer formed above the optical-magnetic recording film, and the thermal control layer is kept at room temperature. An optical-magnetic recording medium characterized in that its thermal conductivity is regulated within a range of 0.1 to 2.0 [W/Cm·deg]. (2) In claim (1), the thermal control layer comprises A
one or more metal elements selected from the group consisting of 1, Ag, Au, Cu, and Be, and Cr, Ti, Ta, Sn, and Si.
, Rb, Pe, Nb, Mo, Li, Mg, W, and Zr. (3) In claim (2), the thermal control layer is made of Al.
- An optical-magnetic recording medium comprising an alloy of Ti, wherein the content of Ti in the alloy is regulated within a range of 6 to 10 at.%. (4) Claim (1), Claim (2) or Claim (3)
In the description, the thickness of the thermal control layer is 500 to 1000.
An optical-magnetic recording medium characterized in that the recording medium is regulated within a range of Å. (5) In claim (1), claim (2), claim (3), or claim (4), the optical-magnetic recording film is composed of an amorphous perpendicularly magnetized film, and has a composition of the following formula: An optical-magnetic recording medium comprising: Tb_XFe_(_1_0_0_-_X_-_Y_-_
Z_)Co_YM_Z In the formula, X, Y, and Z are atomic %, and 1
5≦X≦30, 5≦Y≦15, 0≦Z≦10 M=Nb, Cr, Pt.