JPH0478038A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain the magneto-optical recording medium provided with a recording layer having high C/N by providing the recording layer consisting of an amorphous alloy having a specific compsn. CONSTITUTION:This medium has a substrate 1 and the recording layer 3 laminated on the substrate 1 and may further have an enhancement layer 5 laminated between the substrate 1 and the recording layer 3, a protective layer 7 laminated on the recording layer 3, etc. The amorphous alloy having the compsn. expressed by formula I is used as the recording material to form the recording layer 3. In the formula I, A to D denote the rational numbers satisfying O<A<=10, O<=B<=1, 20<=C<=26, 80<=D<=100. Consequently, the Kerr rotating angle thetakappa and signal component are large and noises are decreased. The magneto-optical recording medium provided with the recording layer which imparts the high C/N is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magneto-optical recording medium that can be repeatedly recorded and reproduced and has a recording layer with excellent reproduction characteristics.

Conventional technology: By repeatedly recording and reproducing information, in other words, as a recording medium with a recording layer that allows information to be rewritten, a minute area of the recording layer is heated to the Curie point with light, and the coercive force in this area is extremely high. Magneto-optical recording media have been put into practical use in which information is recorded by applying an external magnetic field in a state where the magnetic field is lowered to cause a reversal of the magnetization direction.

In a magneto-optical recording medium, information is recorded as repetitions of areas where the magnetization direction is reversed and areas where the magnetization direction is not reversed, corresponding to 0, 1-. When the recorded information is reflected from the laser tip or the surface of the recording layer, the Kerr effect rotates in different directions depending on the plane of polarization or the direction of magnetization, and this rotation angle (
It is reproduced by reading the change in the Kerr rotation angle θ).

Three Problems to be Solved by the Invention As a recording material forming the recording layer of such a magneto-optical recording medium, an amorphous alloy of rare earth-transition metals, such as Tb-Fe, has been used.

However, since the Tb--Fe type amorphous alloy has a small Kerr rotation angle .theta., the C/N ratio is low and there is a problem in that recording reproduction accuracy is low.

Conventionally, in order to increase the Kerr rotation angle θ and improve the C/N ratio, methods have been adopted in which CO is used as the transition metal or light rare earth elements are added. However, because
When such elements are used, although the Kerr rotation angle θ increases, the signal component decreases due to a decrease in reflectance, and noise increases due to the roughening of the recording film surface, so the C/N is still high. There was a problem in that it was not possible to obtain an amorphous alloy having a certain ratio.

The present invention aims to solve the problems associated with the prior art, and is based on an amorphous alloy that provides a large Kerr rotation angle θ and a large signal component, low noise, and a high C/N ratio. The object of the present invention is to provide a magneto-optical recording medium having a recording layer.

Means for Solving the Problems The magneto-optical recording medium according to the present invention has the following compositional formula;
, 0≦B≦too, 20≦C≦26.80≦D≦1
It is characterized by comprising a recording layer made of an amorphous alloy having a composition represented by (a rational number satisfying 00).

According to the magneto-optical recording medium of the present invention, since an amorphous alloy having the composition represented by the above compositional formula CIE is used as the recording material forming the recording layer, the Kerr rotation angle θ and the signal component are large, and It is possible to provide a magneto-optical recording medium with a recording layer that has less noise and provides a high C/N ratio.

Hereinafter, the magneto-optical recording medium according to the present invention will be explained in more detail.

The magneto-optical recording medium according to the present invention has a substrate 1 and a recording layer 3 laminated on the substrate 1, as shown in FIG. It may include an enhancement layer 5 laminated on the recording layer 3, a protective layer 7 laminated on the recording layer 3, and the like.

Specific examples of the material for the substrate 1 of such a magneto-optical recording medium include inorganic materials such as glass, as well as resin materials such as polycarbonate, polymethyl methacrylate, and epoxy resin.

The enhancement layer 5 is a dielectric layer that utilizes multiple reflections to enhance the Kerr effect and increase the Kerr rotation angle θ. As the dielectric material forming the enhancement layer 5, SiN, Sin, A
Examples include IN and ZnS.

Such an enhancement layer 5 may be formed by any known thin film forming method, such as a sputtering method, a vacuum evaporation method, an ion blasting method, a vapor phase growth method, or the like. Among these, sputtering is particularly preferred, and DC sputtering, high-frequency sputtering, reactive high-frequency sputtering, and the like are preferably used.

The thickness of the enhancement layer 5 is set to a value that maximizes the Kerr effect, or is usually 500 to 100 OA, preferably 600 to 800 Å.

The protective layer 7 is formed to prevent oxygen, water, etc. from permeating the recording layer 3, which is easily oxidized.

As a material for forming such a protective layer 7, Si3
N4, S t O, An N, ZnS, etc. can be used, and the protective layer 7 made of these materials can be formed by the same method as the enhancement layer 5.

The thickness of the protective layer 7 formed in this way is usually 50 mm.
It is 0-100OA, preferably 800-100OA.

The recording layer 3 used in the magneto-optical recording medium according to the present invention is
Pr as a light rare earth and Tb and D as rare earths
at least one of y and Fe as a transition metal
and CO in a specific composition ratio, and is represented by the above compositional formula [I].

In an amorphous alloy having a composition represented by the composition formula CI),
Since it contains Pr in the above amount, it is possible to improve the Kerr effect due to pr, and there is no problem such as demagnetizing field, and a recording layer 3 with sufficient reflectance and high C/N ratio can be formed. I can do it. In addition, in an amorphous alloy having such a composition, there is a compensation temperature at which the magnetization appears to be 0 and the coercive force becomes very large, and since this compensation temperature is close to room temperature, the coercive force at room temperature is An information recording medium having a large and stable recording layer can be provided.

As a method for forming such a recording layer 3, any known thin film forming method may be adopted, such as a sputtering method, a CVD method, a PVD method, an ion brate ink method, a vapor phase growth method, etc. be able to. Among these, the sputtering method is particularly preferred, and DC sputtering, high frequency sputtering, reactive high frequency sputtering, etc. are preferably used.

The film thickness of the recording layer 3 obtained in this way is associative 11,
The magneto-optical recording medium according to the present invention has been described by exemplifying the case where the enhancement layer 5, the recording layer 3, and the protective layer 7 are sequentially laminated in this order on the substrate.

However, in the present invention, it is possible to have any layer structure including a recording layer, for example, a reflective layer is provided between a protective layer and a recording layer so that the Faraday effect can also be utilized. It's okay.

Effects of the Invention The magneto-optical recording medium according to the present invention includes a recording layer made of an amorphous alloy having a composition represented by the above compositional formula [T]. It is possible to provide a magneto-optical recording medium having a recording layer that is large, has low noise, and provides a high C/N ratio.

Hereinafter, the magneto-optical recording medium according to the present invention will be explained in more detail with reference to Examples, but the present invention should not be construed as being limited to these Examples.

Example 1 S was deposited on a polycarbonate substrate by a reactive high-frequency sputter link using a Si target in an atmosphere of Ar + N2 at an ultimate vacuum of 2 x 1.0'Torr or less.
An enhancement layer made of iN was formed. Further, the film thickness of the enhancement layer was set to 800A so that the obtained magneto-optical recording medium had a maximum C/N ratio.

Next, this enhancement layer was coated with a film thickness having the composition shown in Table 1 by direct current sputtering using a PrTbFeCo composite target under an Ar atmosphere at an ultimate vacuum of IX1O'Torr or less. A recording layer A was formed. Next, a film made of SiN with a thickness of 800 mm was formed on this recording layer in the same manner as when forming the enhancement layer.
A protective layer of A was formed.

The C/N ratio of the magneto-optical recording medium obtained in this way is
Disc rotation speed 180 orpm, recording frequency 3.7M)
fz, resolution bandwidth 30kHz, laser wavelength 830nm
Measurements were taken at the inner circumference of the disk. The results obtained are shown in Table 1.

Examples 2 to 5 Except for changing the composition of the recording layer to the composition shown in Table 1,
A magneto-optical recording medium was manufactured in the same manner as in Example 1, and the C/N
The ratio was measured. The composition of the recording layer was changed by placing an appropriate alloy or metal chip on the reference L target.

The results obtained are shown in Table 1.

Example 6-lO A magneto-optical recording medium was manufactured in the same manner as in Example 1, except that the composition of the recording layer to be formed was changed to the composition shown in Table 2 by changing the reference target, and C /N ratio was measured.

The results obtained are shown in Table 2.

Comparative Examples 1 to 4 Magneto-optical recording media were manufactured in the same manner as in Examples, except that a recording layer containing Pr, Tb, Fe, and Co and having a composition ratio different from that of the present invention as shown in Table 3 was formed. C/N
The ratio was measured.

The results obtained are shown in Table 3.

Comparative Examples 5 to 10 Magneto-optical recording media were manufactured in the same manner as in Examples, except that a recording layer containing no Pr and having the composition shown in Table 3 was formed.
The C/N ratio was measured.

The results obtained are shown in Table 3.

[Brief explanation of the drawing]

FIG. 1 attached herewith is a sectional view showing one preferred embodiment of the magneto-optical recording medium according to the present invention. 1...Substrate 3...Recording layer 5...
Enhancement layer 7...Protective layer a) ÷〈I Procedural amendment dated February S, 1991

Claims (1)

[Claims] The following compositional formula; {Pr_A(Tb_BDy_1_0_0_-_B)_1
_0_0_-_A}_C(Fe_DCo_1_0_0_
-_D)_1_0_0_-_C...[I] (In the formula, A, B, C and D are 0<A≦10, 0≦B≦
100, 20≦C≦26, and 80≦D≦100) A magneto-optical recording medium comprising a recording layer made of an amorphous alloy having the following composition.