JP2814601B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention performs magneto-optical recording media, that is, magneto-optical (thermal) magnetic recording by, for example, irradiation of a semiconductor laser beam, and reads the recording by detecting the Kerr rotation angle. The present invention relates to a magneto-optical recording medium adapted to perform the above-described operations.

SUMMARY OF THE INVENTION The present invention relates to a magneto-optical recording medium, and is formed on a dielectric film, a reflective magneto-optical recording film, a protective film, a resin protective film, and a dielectric film provided on a light-transmitting substrate. 25 to 200 mm thick
By adopting a configuration in which the resin protective film is formed via an aluminum thin film less than the aluminum thin film, by providing the aluminum film, the reliability is improved and the reduction in the recording sensitivity is avoided.

[Conventional technology]

A magneto-optical recording medium that forms an information bit, ie, a magnetic domain by local heating by laser beam irradiation and reads it out by magneto-optical interaction, ie, the Kerr effect, is, for example, a third magnetic recording medium.
As shown in the figure, a dielectric film (12) such as Si ₃ N ₄ and a TbFeC are placed on a light transmitting substrate (11) such as a polycarbonate (PC) substrate.
a magneto-optical recording film (13) made of o, etc., that is, a perpendicular magnetization film, a dielectric film (14) made of, for example, Si ₃ N _4, and a resin protective film (15) made of, for example, an ultraviolet curing resin. .

In such a magneto-optical recording medium, in an operation mode such as when the magneto-optical recording film (13) has a thickness in an optically transparent state, for example, a thickness of about 400 ° or less, the effective mode is effective. In order to obtain the Kerr effect, an aluminum Al film is formed on the back of the magnetic recording film (13), that is, on the opposite side of the light transmitting substrate (11), for example, between the dielectric film (14) and the resin protective film (15). In some cases, a configuration in which the components are stacked and arranged therebetween is adopted. In some cases, an Al film may be disposed to obtain a heat sink effect. The thickness of the Al film for these purposes needs to be selected to be 400 mm or more.

However, recently, as a magneto-optical recording perpendicular magnetization film (13), a reflective magneto-optical recording medium film which performs reading by the Kerr effect in this film by reflection on the film itself,
That is, when the thickness exceeds 400 mm, or when the thickness of the magneto-optical recording film is large as in a recording medium for light intensity modulation overwriting, or when the magneto-optical recording film has In a magneto-optical recording medium that does not require the enhancement effect of the Al film as in a magneto-optical recording medium having a configuration of more than a layer film, the above-described arrangement of the thick Al film can reduce the recording sensitivity due to the heat dissipation effect due to this. Therefore, the arrangement of the Al film tends to be excluded because of lowering of the Al film. However,
In such a magneto-optical recording medium from which the Al film has been eliminated, the problem of corrosion (pitting) of the magneto-optical recording film due to erosion from the resin protective film (15) side by the ultraviolet curable resin, that is, a decrease in S / N, There is a problem of reduced reliability.

[Problems to be solved by the invention]

The present invention relates to a magneto-optical recording medium as described above, particularly a magneto-optical recording medium having a reflective magneto-optical recording film having a thickness of more than 400 mm, for example, having a thickness of 600 mm or more, which exhibits reflectivity to a semiconductor laser beam of 780 nm. In a recording medium, reliability is improved without lowering recording sensitivity.

[Means for solving the problem]

According to the present invention, a dielectric film (2) is sequentially formed on a light-transmitting substrate (1) as shown in FIG.
The reflective magneto-optical recording film (3) having a thickness of 400 mm or more, that is, the thickness of the reflective magneto-optical recording film (3) is so large that the magneto-optical interaction of the light reflected on the magneto-optical recording film (3) is detected and the recording is read out. A perpendicular magnetic film, a protective film (4), and a resin protective film (5) are laminated on a magneto-optical recording medium, and aluminum (Al) having a thickness of 25 to less than 200 mm is formed on the protective film (4). The configuration is such that the resin protective film (5) is formed via the thin film (6).

[Action]

According to the configuration of the present invention described above, the Al thin film (6) is interposed between the protective film (4) and the resin protective film (5). In this case, the film of the Al thin film (6) is particularly used. 25 ~ 20 thick
When the recording laser beam is applied to the magneto-optical recording film (3) due to the existence of the Al thin film (6) due to the selection of less than 0 °, the heat dissipation by the Al thin film (6) increases the recording laser power required for recording. It was confirmed that the pitting corrosion of the recording film (3) could be effectively avoided by the Al thin film (6) having such a thickness without causing the reduction in the sensitivity, that is, lowering the sensitivity.

〔Example〕

As shown in FIG. 1, for example, an 800 mm thick S is formed on a light transmitting substrate (1) made of a resin substrate such as a PC or a glass substrate.
a dielectric film (2) made of i ₃ N _{4 having a} thickness of, for example, 400
A reflective magneto-optical recording film (3) consisting of a perpendicular magnetization film of Tb Fe Co of 600 ° or more, for example, 800 °
Protective film (4) made of 800Å Si ₃ N ₄ and thickness 25Å-20
A magneto-optical recording medium is formed by sequentially laminating an Al thin film (6) of less than 0 ° and a protective film (5) made of, for example, an ultraviolet curable resin.

In this magneto-optical recording medium, each magneto-optical recording medium in which the film thickness of the Al thin film (6) was changed was manufactured, and the relationship between the recording laser power and the film thickness was measured. The result is shown in FIG. The measurement conditions in this case are as follows: a semiconductor laser having a wavelength of 780 nm is used as a recording laser beam, the relative speed with respect to the magneto-optical recording medium, that is, the linear velocity is 10 m / s, the recording magnetic field is 300 (Oe), and the recording frequency is 5 MHz. It is. In this case, the recording laser power, that is, the recording power at which the second harmonic level was minimized, was measured. In this case, as clearly shown in FIG. 2, the recording power was not more than about 200 °, and as clearly apparent from FIG. Is less than 200 [deg.] And the recording laser power is hardly increased when the Al thin film is not provided, that is, when the thickness of the Al thin film is 0. That is, a decrease in sensitivity is suppressed.

On the other hand, the number of pits on the Al thin film in this case, that is, the number of corrosions of the magnetic recording medium due to corrosion was measured. Table 1 shows the results.

In this case, each film thickness t (Å) is defined as t = 0Å, 50Å, 100Å, 20
The average value of the results obtained by leaving each of the 16 magneto-optical disks in total at 16 ° C. for 1000 hours in a thermo-hygrostat at a temperature of 80 ° C. and a humidity of 85% RH for a total of 16 magneto-optical disks is shown. As is apparent from this, when the Al film (6) is provided, the occurrence of pitting corrosion is remarkably avoided when the Al film (6) is provided, irrespective of the thickness t <200 °. I understand. By the way, with this thickness of the Al thin film, there is almost no light reflection effect.

In the above-described example, the case where the perpendicular magnetic film of the magneto-optical recording film (3) is made of TbFeCo has been described. However, various kinds of other perpendicular magnetic films such as a rare earth-transition metal alloy thin film and the like may be used. The present invention can be applied not only to a thin film or a single layer but also to a multilayer thin film.

〔The invention's effect〕

As is apparent from the above, according to the present invention,
By arranging the thin Al thin film (6) having a thickness of less than 25 ° to less than 200 °, it is possible to effectively avoid a decrease in reliability due to the occurrence of pitting corrosion. An increase in laser power, that is, a decrease in sensitivity can be avoided, and a magneto-optical recording medium having excellent recording characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic enlarged cross-sectional view of an example of a magneto-optical recording medium according to the present invention, FIG. 2 is a diagram showing the measurement results of the dependence of the recording laser power on the thickness of an Al thin film, and FIG. FIG. 2 is a schematic enlarged cross-sectional view of an example of the magneto-optical recording medium of FIG. (1) is a light transmitting substrate, (2) is a dielectric film, (3) is a magneto-optical recording film, (4) is a protective film, (5) is a resin protective film,
(6) is an aluminum (Al) thin film.

Continuation of the front page (72) Inventor Yukatsu Nakaoki 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-2-105352 (JP, A) JP-A-2 -239446 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 11/10 521 F G11B 11/10 506 Z

Claims (1)

(57) [Claims] A dielectric film and a thickness are sequentially formed on a light-transmitting substrate.
In a magneto-optical recording medium in which a magneto-optical recording film of 400 mm or more, a protective film, and a resin protective film are laminated and reproduced by reflection on the magneto-optical recording film, a thickness of 25 to 200 mm is formed on the protective film. A magneto-optical recording medium comprising the above-mentioned resin protective film formed via a thin aluminum thin film having a thickness of less than.