JP2604475B2 - Magneto-optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magneto-optical recording medium.

[Related Art] Magneto-optical recording media capable of recording new information in a superimposed manner regardless of the presence or absence of recorded information (overwrite) include a magnetic field modulation recording method and an optical recording medium. There is a modulation recording method.

The magnetic field modulation recording system modulates the magnetic field applied to the magneto-optical recording medium by modulating the magnetic field applied to the magneto-optical recording medium in accordance with the information to be recorded under irradiation of a laser beam of constant intensity, similarly to the ordinary magnetic recording system. This is for overwriting the magnetic recording medium. In order to perform overwriting by the magnetic field modulation recording method, the distance between the magnetic film of the magneto-optical recording medium and the recording head must be small, so that the magneto-optical recording medium to be used is a single plate having the magnetic film on only one side. Must be a structure. Further, the composition of the magnetic film needs to be such that the intensity of the magnetic field applied for recording is low.

The light modulation recording method is such that a protective film, two magnetic films having different magnetic properties and a protective film are sequentially laminated on a transparent substrate,
The material forming the upper magnetic film (hereinafter, referred to as an auxiliary layer) is a lower magnetic film (hereinafter, referred to as a recording layer).
Information to be recorded by applying an auxiliary magnetic field for initialization and a recording magnetic field in the opposite direction to a magneto-optical recording medium having a lower coercive force and a higher Curie temperature at room temperature than the material forming The overwriting is performed by modulating the intensity of the laser light to be irradiated in accordance with the method described in
-175948). More specifically, the direction of magnetization of the auxiliary layer is aligned with the erasing direction by applying an auxiliary magnetic field for initialization. When a laser beam having an erasing level is irradiated in this state, the magnetic field of the auxiliary layer is thermally transferred to the recording layer, and the magnetization of the recording layer is directed to the erasing direction. Here, if the high-intensity light at the writing level is irradiated in accordance with the information to be recorded, the magnetizations of the auxiliary layer and the recording layer disappear. If a storage magnetic field is applied to the magnetic film from which the magnetization has disappeared, the direction of the magnetization of the recording layer will be the recording direction opposite to the erasing direction, and thus new information will be recorded.

JP-A-63-64651 discloses that a protective film, a three-layer magnetic film having different magnetic properties and a protective film are sequentially laminated on a transparent substrate to form an upper magnetic film (auxiliary film). The material has a lower coercive force and a higher Kyrie temperature at room temperature than the material forming the magnetic film (recording film) of the intermediate layer, and the material forming the lower magnetic film (transfer layer) forms the upper magnetic film It is disclosed that overwriting is performed by a light modulation recording method using a magneto-optical recording medium having a lower coercive force and a higher Curie temperature at room temperature than the material to be used.

[Problems to be Solved by the Invention] The above-mentioned magnetic field modulation recording method cannot perform overwriting at high speed because it is difficult to modulate a magnetic field at high speed. Since it is limited to a plate structure and cannot be a laminated structure, there is a disadvantage that the amount of information to be recorded cannot be increased. In addition, the above-mentioned optical modulation recording method has a drawback that it is difficult to record high-density information because erasure unevenness is likely to occur.

An object of the present invention is to provide a magneto-optical recording medium capable of performing high-density overwriting at high speed.

[Means for Solving the Problems] According to the present invention, the above object is achieved by providing a protective film on a substrate, two magnetic films having different magnetic properties, a protective film, and a heat higher than the thermal conductivity of the protective film. A heat absorbing film having conductivity is sequentially laminated, and a material forming an upper magnetic film has lower coercive force and a higher Kyrie temperature at room temperature than a material forming a lower magnetic film. And a protective film, a three-layer magnetic film having different magnetic properties, a protective film, and a thermal conductivity higher than the thermal conductivity of the protective film. And a heat absorbing film having a high coercivity at room temperature and a higher Kyrie temperature at room temperature than the material forming the magnetic film of the intermediate layer. The material that forms the magnetic film is higher than the material that forms the upper magnetic film. This is achieved by providing a magneto-optical recording medium characterized by having a low coercive force and a high Curie temperature at room temperature.

[Examples] Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Embodiment 1 FIG. 1 shows a schematic partial cross-sectional view of one example of the magneto-optical recording medium of the present invention. This magneto-optical recording medium has a protective film 2 made of Si ₅₁ N ₄₉ (atomic ratio) on a polycarbonate resin substrate 1.
, A magnetic film 3 composed of Gd ₄ Tb ₁₉ Fe ₇₇ (atomic ratio) (hereinafter referred to as a recording layer), and Tb ₂₉ Fe ₆₁ Co ₁₀ (atomic ratio)
A magnetic film (hereinafter referred to as an auxiliary layer) 4 comprising
A protective film 5 made of Si ₅₁ N ₄₉ (atomic ratio) and a heat absorbing film 6 made of Al ₉₇ Ti ₃ (atomic ratio) are each composed of a protective film 1100 Å, a recording layer 1100 補助, and an auxiliary layer having lower film thicknesses. 500 mm, the upper protective film 350 mm, and the heat absorbing film 500 mm. The coercive force of the material forming the above auxiliary layer is 3KOe,
The Curie temperature is 220 ° C., the holding power of the material forming the recording layer is 7 KOe, and the Curie temperature is 150 ° C.

Using this magneto-optical recording medium, the erasing level output of the laser beam irradiated from the substrate side is 8 mW, and the writing level output is 12 mW.
W, the recording magnetic field was 0.3 KOe, the initialization magnetic field was 5 KOe, and the information was recorded by performing the overwriting of the light modulation recording method under the condition that the rotation speed was 1800 rpm.
Frequency and C / N in the signal obtained by reproducing this information
Is shown by a solid line in FIG.

Further, using this magneto-optical recording medium, the output of the erasing level of the irradiated laser beam is 8 mW, the recording magnetic field is 0.3 KOe, the initialization magnetic field is 5 KOe, and the rotation speed is 1800 rpm. The information was recorded by changing the output of the writing level in the range of 7 to 15 mW and performing overwriting of the light modulation recording method. The relationship between the output of the laser light at the write level and the C / N in the signal obtained by reproducing this information is shown in FIG.
This is shown by a solid line in the figure.

Comparative Example 1 The relationship between the frequency and C / N measured under the same conditions using a magneto-optical recording medium having the same structure as in Example 1 except that the heat absorbing film was not provided is shown in FIG. The relationship between the laser light output and C / N is shown by broken lines in FIG.

As is clear from FIG. 2, the magneto-optical recording medium of Example 1 has a higher C / N at a higher frequency than the magneto-optical recording medium of Comparative Example 1, so that overwriting can be performed at high speed. it can. As is clear from FIG. 3, the magneto-optical recording medium of Example 1 has a wider allowable range of the output of the laser beam irradiated for recording than the magneto-optical recording medium of Comparative Example 1, so that the information recording time can be reduced. This indicates that the heat generated by the irradiating laser light hardly remains in the magnetic film. Therefore, the magneto-optical recording medium of Example 1 can record information at a higher density than the magneto-optical recording medium of Comparative Example 1.

Embodiment 2 FIG. 4 is a partial schematic sectional view of another example of the magneto-optical recording medium of the present invention. In this magneto-optical recording medium, a protective film 2 (thickness: 1000 mm) made of Si ₄₈ N ₅₂ (atomic ratio) and a magnetic film (thickness: Gd ₂₂ Fe ₅₅ Co ₂₃ (atomic ratio)) are formed on a polycarbonate resin substrate 1. Hereinafter, this is referred to as a transfer layer.
0Å), a magnetic film made of Gd ₂₃ Tb ₃ Fe ₇₄ (atomic ratio) (hereinafter referred to as a recording layer) 8 (500Å in thickness), Tb ₂₈ Fe
_A magnetic film made of ₆₅ Co ₇ (atomic ratio) (hereinafter referred to as an auxiliary layer) 9 (500 Å in thickness), a protective film 5 made of Si ₄₈ N ₅₂ (atomic ratio) (thickness: 300 お よ び) and A heat absorbing film 6 (thickness: 450 °) made of Al ₉₀ Ti ₁₀ (atomic ratio) is sequentially laminated. The coercive force of the material forming the transfer layer is 0.1 KO
e, the Kyuri temperature is 380 ° C, the coercive force of the material forming the recording layer is 8 kOe, the Kyuri temperature is 150 ° C, the coercive force of the material forming the auxiliary layer is 3KOe, and the Kyuri temperature is 200 ° C
It is.

This magneto-optical recording medium also has a high C / N at a high frequency, and has a feature that the allowable range of the output of the laser beam irradiated for recording is wide.

The heat absorbing film of the present invention is made of one element selected from the group consisting of Al, Au, Ag, Pt and CU, or one element selected from the above group and a group consisting of Cr, Ti, Ge and Si. It is preferable that the composition and the film thickness be appropriately set in accordance with the thermal characteristics of the protective film and the magnetic film, which is an alloy with at least one element selected from the group consisting of:

As the above substrate, a polymethyl methacrylate resin, an epoxy resin, glass, or the like can be used in addition to the polycarbonate resin. The magnetic film has a two-layer structure or a three-layer structure.
It has a layer structure, and as a material of the magnetic film forming the two-layer structure, GdDyFe-GdTbFe, TbFe-GdTbFe, TbDyFe-
A combination such as GdDyFe can be used, and the magnetic film is 3
In the case of having a layer, the material of the magnetic film forming the three-layer structure is GdFeCo-GdDyFe-GdTbFe, GdFeCo-TbFe-GdTb
A combination such as Fe, TbDyFe-GdDYFe-GdFeCo can be used. As a material for forming the protective film, AlN, AlSiN, or the like can be used in addition to SiN.

The thickness of the protective film, the magnetic film, etc. can be determined according to their optical characteristics and thermal conductivity. Usually, each film thickness is 400 to 1200 mm of the lower protective film and the magnetic film (recording layer + auxiliary layer). Or the total thickness of transfer layer + recording layer + auxiliary layer) is 600 ~ 2300mm, upper protective film is 300 ~ 1200mm, heat absorption rate
Preferably it is in the range of 200 to 1500 °. Each of the above films can be formed by a sputtering method.

[Effect of the Invention] According to the present invention, a magneto-optical recording medium capable of performing high-density information overwriting at high speed is provided.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view of one example of a magneto-optical recording medium of the present invention, FIG. 2 is a characteristic diagram showing the relationship between the frequency and C / N of the magneto-optical recording medium, and FIG. FIG. 4 is a characteristic diagram showing the relationship between the output of the laser light at the write level and the C / N ratio, and FIG. 4 is a schematic partial sectional view of another example of the magneto-optical recording medium of the present invention. DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... protective film, 3 ... magnetic film (recording film), 4 ... magnetic film (auxiliary layer), 5 ... protective film, 6 ... heat absorption film, 7 ... magnetic film ( Transfer layer), 8 ... magnetic film (recording layer), 9 ... magnetic film (auxiliary layer).

Claims (2)

(57) [Claims] A protective film, a two-layer magnetic film having different magnetic properties, a protective film, and a heat absorbing film having a thermal conductivity higher than the thermal conductivity of the protective film are sequentially laminated on a substrate; A magneto-optical recording medium, characterized in that the material forming the upper magnetic film has lower coercive force and higher Curie temperature at room temperature than the material forming the lower magnetic film. 2. A protective film, a magnetic film of three layers having different magnetic properties, a protective film, and a heat absorbing film having a thermal conductivity higher than that of the protective film are sequentially laminated on a substrate, The material forming the upper magnetic film has a lower coercive force and a higher temperature at room temperature than the material forming the magnetic film of the intermediate layer, and the material forming the lower magnetic film forms the upper magnetic film. A magneto-optical recording medium having a lower coercive force and a higher Curie temperature at room temperature than a material.