JP2912725B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium in which a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are sequentially laminated on a substrate. The present invention relates to a novel magneto-optical recording medium using yttrium sialon.

[0002]

2. Description of the Related Art A magneto-optical recording medium for performing recording, reproduction, erasing, and the like using a laser beam has a first dielectric layer, a recording layer, a second dielectric layer, In general, a four-layer structure in which a reflection layer and a reflection layer are sequentially stacked is provided, and the first and second dielectric layers are provided to increase a car rotation angle by a car enhancement effect.

[0003] In particular, the second dielectric layer serves to increase the Kerr rotation angle by a car enhancement effect between the recording layer and the reflective layer, thereby improving read performance, and also functions as a protective layer for the recording layer. In addition, the heat insulating effect on the reflective layer prevents the heat of the laser light from escaping to the reflective layer as much as possible, and plays an important role such as improving the writing performance by using the laser light without waste.

[0004] However, when the second dielectric layer is considered as a heat insulating layer, the thicker the better, the better the thermal conductivity is. The lower the thermal conductivity, the better. When light interferes multiplexly in the layer, light is absorbed in the layer, and a problem arises that the amount of reflected light decreases.
On the other hand, if the thickness is too small, the heat insulating effect becomes insufficient even if it is optically good, and there is a problem that the recording sensitivity of the magneto-optical recording medium is greatly reduced. Therefore, if the AlN film is conventionally used as the second dielectric layer, at most.
It is effective only in a narrow range of about 200 to 300 mm,
Even within that range, there is a problem that the recording power margin is insufficient.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above problems,
It is an object of the present invention to provide a magneto-optical recording medium having a high heat insulating effect, a high C / N value, and a high sensitivity.

[0006]

In order to achieve the above object, a magneto-optical recording medium of the present invention comprises a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer on a light-transmitting substrate. Are sequentially laminated, the second dielectric layer is formed of yttrium sialon having a thickness of 150 to 400 °, and the reflection layer is formed of Al, Ti, Cr,
It is characterized by being composed of a single metal of Cu, Ag, and Au and an alloy thereof, or a low oxide thereof.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, a magneto-optical recording medium R applied to the present embodiment has a first dielectric layer 2, a recording layer 3, and a second dielectric layer on a disk-shaped translucent substrate 1 having a diameter of about 130 mm. It has at least a four-layer structure in which a layer 4 and a reflective layer 5 are sequentially laminated. Each of the above layers was formed using a magnetron sputtering apparatus at an Ar pressure of 0.40 to 0.65 Pa.

Here, the substrate 1 is a polycarbonate resin substrate having a thickness of about 1.2 mm, and a glass substrate such as a tempered glass can also be used.

The first dielectric layer 2 is an amorphous yttrium sialon having a thickness of about 1100 °. This yttrium
Sialon is represented by _{Y a · Si b · Al c} · O d · N e, 0 <a <0.5, 0.1 <b <0.8, 0 <c <0.5,
0 <d <0.5, 0.1 <e <0.7, a + b + c + d + e =
The composition satisfies the condition of 1. In this embodiment, a = 0.04,
b = 0.60, c = 0.04, d = 0.07, and e = 0.25. The first dielectric layer 2 is made of SiO ₂ or Si in addition to the above materials.
O, CeO ₂ , ZrO ₂ , TiO ₂ , Bi ₂ O ₃ , Zn
S, Sb ₂ S ₃ , Si ₃ N _{4 and the} like can also be used.

The recording layer 3 is a perpendicular magnetization film having a magnetization direction perpendicular to the surface of the substrate 1. An amorphous alloy mainly composed of a rare earth element and an iron group element is used. GdDyFe of about 200 ° is used. The recording layer is T
b, Dy, Gd, Ho, at least one kind of element;
It contains one or both elements of Fe and Co. For example, GdDyFeTi, GdDyFe,
GdTbFe, TbFeCo, DyFeCo, GdTb
DyFe, GdTbFeCo, TbDyFeCo, Gd
DyFeCo, NdGdDyFe, NdDyFeCo,
It has a composition such as NdGdDyFeCo.

For the second dielectric layer 4, a material having the same composition as that of the first dielectric layer 2 can be used.
Using _{0.04 · Si 0.56 · Al 0.04 ·} O 0.07 · N 0.29, the characteristics were measured by changing the thickness of the 100 to 600 Å. The refractive index of the second dielectric layer 4 having the above composition is about 2.3, and the absorption coefficient is about 0.01. Although these characteristic values slightly change mainly depending on the composition ratio of Si and N, the best composition ratio is set in consideration of film stress, reliability, and the like.

The reflection layer 5 is made of Al having a thickness of about 500.degree., And may be made of a single metal such as Ti, Cr, Cu, Ag, or Au, an alloy thereof, or a low oxide thereof.

Next, FIG. 2 shows the results of measuring the characteristics while changing the thickness of the second dielectric layer 4 variously. A position 30 mm from the center of the magneto-optical recording medium R is set as a measurement position, and the number of rotations is 2400 rpm,
Under the conditions of a recording frequency of 4.9 MHz and a recording duty of 33%, C /
When the N value and the recording power of the laser were measured, C / N
48 dB or more (ISO standard requires 45 dB or more)
It was found that the thickness of the second dielectric layer 4 capable of realizing a practical recording power of 8 mW or less was 100 to 500 mm. More preferably, the second dielectric layer 4 can realize a C / N value of 50 dB or more and a practical recording power of 8 mW or less.
Has a thickness of 100 to 400 mm.

For comparison, the second dielectric layer 4 has a refractive index of about
FIG. 3 shows the measurement results obtained when Al _0.6 N _0.4 having an absorption coefficient of about 2.0 and an absorption coefficient of about 0.05 was used. The other components are the same as described above, and the description is omitted. As is clear from this figure, the AlN film capable of realizing a C / N value of 48 dB or more and a recording power of 8 mW or less is 200 to 300 °, and is a film in a considerably narrower range than the yttrium sialon of this embodiment. Limited to thickness.

In practice, it is desirable that the C / N value rises at a low recording power and does not decrease to a high recording power. However, as shown in FIG. 4, a C / N value of 48 dB or more is required. Assuming that the range of the recording power to be taken is ΔP (= P2−P1), as shown in FIG. 5, when the second dielectric layer 4 is yttrium sialon, the film thickness range where ΔP is 3.5 mW or more is 150 to A wide range of 500 m2 is possible. On the other hand, when the second dielectric layer 4 is made of AlN, under the above conditions, 250 to 45
It is limited to a narrow film thickness range of 0 mm. Further, when this layer is yttrium sialon, it is possible even if {P is 4 mW or more, and its film thickness range is 250 to 350}.

[0016]

According to the magneto-optical recording medium of the present invention, since the yttrium sialon having a thickness of 100 to 400.degree. Is used as the second dielectric layer, it has a high heat insulating effect and a high C of 50 dB or more. / N value and a high sensitivity of 8 mW or less in recording power can be realized, and a highly reliable magneto-optical recording medium having a wide recording power margin can be provided.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a magneto-optical recording medium according to the present invention.

FIG. 2 is a diagram showing measurement results of a C / N value and a recording power when yttrium sialon having various thicknesses is used as a second dielectric layer.

FIG. 3 shows AlN of various thicknesses as a second dielectric layer
FIG. 4 is a diagram showing measurement results of a C / N value and a recording power in the case of using.

FIG. 4 is a diagram illustrating a range of recording power in which a C / N value is equal to or more than 48 dB.

FIG. 5 is a diagram showing the relationship between the film thickness and ΔP when the second dielectric layer is yttrium sialon or AlN.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... 1st dielectric layer 3 ... Recording layer 4 ... 2nd dielectric layer 5 ... Reflective layer R ... Magneto-optical recording body

Claims (1)

(57) [Claims] A first dielectric layer, a recording layer,
A magneto-optical recording medium in which a second dielectric layer and a reflective layer are sequentially laminated, wherein the second dielectric layer is formed of yttrium sialon having a thickness of 150 to 400 °, and the reflective layer is formed of A
1. A magneto-optical recording medium comprising a single metal of 1, 1, Ti, Cr, Cu, Ag, and Au and an alloy thereof, or a low oxide thereof.