JPH03116565A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain the magneto-optical recording medium having high recording sensitivity and without generating any recording error due to the heat produced by the irradiation with laser light in recording by forming a reflecting film from an Al alloy and gradually reducing its heat conductivity in the film thick ness direction from the protecting film side. CONSTITUTION:The reflecting film 5 is made of an Al alloy, and its heat con ductivity is gradually reduced in the film thickness direction from the protecting film 4 side. In this case, the alloy consists of Al and at least one element selected from a group consisting of Cr, Ti, Pt, V, Ge and Si, and the Al content is gradually reduced in the film thickness direction from the protecting film 4 side. Consequently, the heat produced by irradiating a magneto-optical record ing medium with laser light for recording information is not left in the magnetic film 3, any recording error is not caused, and the heat conductivity of the reflecting film is appropriately adjusted to prevent a decrease in recording sensitivity due to the release of heat from the magnetic film 3. As a result, high recording sensitivity is imparted, and any recording error due to the heat produced by the laserlight for irradiation in recording is not caused.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magneto-optical recording medium.

[Prior Art] Magneto-optical recording media on which information can be erased and rewritten are
In general, it has a structure in which a protective film, a magnetic film having perpendicular magnetic anisotropy, and a protective film are laminated in this order on a transparent substrate, or a reflective film is further laminated on the above-mentioned protective film. There is. The above magnetic film is preferably an amorphous alloy of rare earth elements and transition metals, such as T
bFeCo.

Alloys such as NdDyFeCo5GdTbFe are used.

These alloys have problems such as being very easily oxidized and having a small magneto-optic effect. In order to compensate for this problem with the magnetic film, the materials forming the upper and lower protective films must have properties that prevent the intrusion of oxygen and water, and the protective film and reflective film must not interfere with each other. It is necessary to have a film thickness and refractive index that enhances the effect.

The material for forming the protective film is SiOx 5iOt, S
iN.

Materials with high refractive index such as Al25iN and AlN are used. In addition, the materials for forming the reflective film include:
＾u, A(!, Cu5A12 1'+alloy, Al-C
r alloy etc. are used.

It is known that high recording sensitivity can be obtained when the protective film and reflective film are made of a material with low thermal conductivity. Among the above-mentioned protective film materials, SiN has a low thermal conductivity, and among reflective film materials, Al-Ti alloys and Cr alloys have low thermal conductivities. The magneto-optical recording medium has high recording sensitivity.Also, even when the magnetic film has a low Curie temperature, the magneto-optical recording medium has high recording sensitivity.

[Problem to be solved by the invention] When the thermal conductivity of the material forming the protective film is low, the heat generated when irradiating the magneto-optical recording medium with laser light to record information is It tends to remain in the magnetic film. Since recording errors may occur due to this heat, the output of the laser beam cannot be increased, and information cannot be recorded at a high density. A lower protective film (thickness:
1,100 people), magnetic film made of TbFeCo (film thickness,
250 people), each with a composition of A121Ads-Tit
(atomic ratio), ^f! , Ti, (atomic ratio) in the magneto-optical recording media (a), (b) and (c), the output of the laser beam irradiated for recording and the recording sensitivity (R
Fig. 4 shows the relationship with F amplitude). However, the Ti contents in the magneto-optical recording media (a), (b) and (c) are 8%, 2% and 0%, respectively. As is clear from FIG. 4, when the thermal conductivity of the reflective film is reduced by adding Ti element, the output of the laser beam cannot be increased, and the permissible range of the output of the laser beam is It gets narrower.

When the magnetic film has a low key temperature, the magneto-optical effect of the magnetic film is small, resulting in a disadvantage that the intensity of the signal obtained when recording information becomes small. The composition of each magnetic film is Tbt+Fe7tCOt (atomic ratio) s
Tbt+Fe74COs (atomic ratio) and Tbt+
Irradiation for recording in magneto-optical recording media (d), (e) and (f) having the same structure as the magneto-optical recording medium (a) above except that Fe71cOs (atomic ratio) FIG. 5 shows the relationship between the output of the laser beam and the recording sensitivity (RF amplitude). However, magneto-optical recording media (d), (e
The Curie temperatures of the magnetic films in ) and (f) are 160°C, 180°C and 200°C, respectively. As is clear from FIG. 5, when the Curie temperature of the magnetic film is low, the recording sensitivity of the magneto-optical recording medium decreases.

An object of the present invention is to provide a magneto-optical recording medium that has high recording sensitivity and does not cause recording errors due to the influence of heat generated by laser beam irradiation during recording.

In a magneto-optical recording medium in which a film, a magnetic film, a protective film, and a reflective film are sequentially laminated, the reflective film is made of an AC alloy, and its thermal conductivity gradually decreases from the protective film side in the film thickness direction. This is achieved by providing a magneto-optical recording medium characterized by the following.

The above AC alloys are AC, Cr, Ti, Pt, VS
It consists of at least EEi-1 elements selected from the group consisting of Ge and 6-Si, and by gradually decreasing the Al content from the protective film side in the film thickness direction, a magneto-optical system is used to record information. To prevent the heat generated by irradiating the recording medium with laser light from remaining in the magnetic film and causing recording errors, and to prevent the recording sensitivity from decreasing due to heat being released from the magnetic film. It is preferable to adjust the thermal conductivity of the reflective film as appropriate.

[Example code] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A schematic partial cross-sectional view of an example of the magneto-optical recording medium of the present invention is shown in the first example.
As shown in the figure. This magneto-optical recording medium has a polycarbonate resin substrate 1, a protective film 2 made of 5151N411 (atomic ratio), a magnetic film 3 made of Tt+2+FetsCOa (atomic ratio) (Curie temperature = 170°C), and S
A protective film 4 consisting of i,,N,-(atomic ratio) and A(1
- reflective films 5 made of Ti alloy are sequentially laminated,
The thickness of each layer is 1,100 for the lower protective film, 250 for the magnetic film, 350 for the upper protective film, and 700 for the reflective film.

The Ti content in the reflective film 5 is shown in FIG. Reflective film 5
The Ti content (atomic ratio) is 200 mm thick from the upper protective film.
It is 0% in the human range, and the film thickness is 200 to 70%.
It gradually increases in the range of 0 people, and on the surface side (film thickness 70
0 person) Ti content is 5%. With this configuration, the thermal conductivity of the reflective film gradually decreases in the film thickness direction from the upper protective film side.

FIG. 3 shows the relationship between the output of the laser beam irradiated to the magneto-optical recording medium for recording and the recording sensitivity.

Comparing Figure 3 with Figures 4 and 5, it is clear that the above-mentioned magneto-optical recording medium has high recording sensitivity and has a wide tolerance range for the output of the laser beam irradiated for recording. It is.

The reflective film in the present invention is made of Cr, Ti5Pt1V, Ge
It is preferable that the film be made of an alloy of Man Q and at least one element selected from the group consisting of Si and Si, and the composition ratio and composition distribution may be appropriately set according to the thermal characteristics of the protective film and the magnetic film.

In addition to polycarbonate resin, polymethyl methacrylate resin, epoxy resin, glass, etc. can be used as the above-mentioned substrate. In addition to TbFeCo, NdDyFeCo is also used as a material for forming the magnetic film.

An amorphous alloy material of a rare earth element and a transition metal such as GdTbFe can be used. The thickness of the protective film, magnetic film, etc. can be determined depending on their optical properties, but usually the thickness of the lower protective film is 800 to 160 mm.
0 people, magnetic film 2oO~4oo people, upper layer protective film 30 people
It is preferable that the number of participants is 0 to 800, and the number of reflective films is 300 to 700.

The above six films can be formed by sputtering. Furthermore, by adjusting the power applied to the target during the formation of the reflective film, a composition distribution that provides a desired thermal conductivity can be obtained.

[Effects of the Invention] According to the present invention, it is possible to obtain a magneto-optical recording medium which has high recording sensitivity and does not cause recording errors due to the influence of heat generated by laser light irradiated during recording.

[Brief explanation of drawings]

FIG. 1 is a schematic partial cross-sectional view of an example of the magneto-optical recording medium of the present invention, FIG. 2 is a diagram showing the Ti content in the reflective film of Example 1, and FIG. 3 is a diagram showing the Ti content of the magneto-optical recording medium of Example 1. Figure 4 is a characteristic diagram showing the relationship between the output of the irradiated laser beam and recording sensitivity, Figure 4 is a characteristic diagram showing the relationship between Ti content and recording sensitivity, and Figure 5 is a diagram showing the relationship between the Curie temperature of the magnetic film and recording sensitivity. It is a characteristic diagram showing a relationship. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Protective film, 3... Magnetic film, 4... Protective film, 5... Reflective film.

Claims (2)

[Claims] 1. In a magneto-optical recording medium in which a protective film, a magnetic film, a protective film, and a reflective film are sequentially laminated on a substrate, the reflective film is made of an Al alloy, and its thermal conductivity gradually increases from the protective film side in the film thickness direction. A magneto-optical recording medium characterized by a magnetic field. 2. The Al alloy consists of Al and at least one element selected from the group consisting of Cr, Ti, Pt, V, Ge, and Si, and the Al content gradually decreases from the protective film side in the film thickness direction. The magneto-optical recording medium according to claim 1, characterized in that: