JPH05314552A - Magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] [Object] To provide a magneto-optical recording medium having high reproduction signal characteristics. [Structure] It has a structure of substrate / magnetic layer / high thermal conductive layer, the high thermal conductive layer is adjacent to the magnetic layer, and the high thermal conductive layer is 100 W.
/ M · K or more, a magneto-optical recording medium made of a simple substance or an alloy of the substance.

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 having high reproduction signal characteristics.

[0002]

2. Description of the Related Art As a recording medium having a recording layer (magnetic layer) on which information can be repeatedly recorded and reproduced, that is, information can be rewritten, a fine area of the magnetic layer is heated by light to a Curie point. A magneto-optical recording medium that records information by applying an external magnetic field and reversing the magnetization direction in a state where the coercive force of the area is extremely reduced has been put into practical use.

In such a magneto-optical recording medium, information is recorded as a repetition of a reversal area and a non-reversal area of the magnetization direction corresponding to 0 and 1. The recorded information uses, for example, the Kerr effect in which the deflection surface rotates in different directions depending on the direction of magnetization when the laser light is reflected on the surface of the recording layer, and the change in this rotation angle (Kerr rotation angle θκ) Is played by reading.

The Kerr rotation angle θκ of the magnetic layer has a great influence on the reproduction characteristic of recorded information. For example, the C / N ratio (reproduction signal characteristic) which is an index of readability of information is:
It increases as the Kerr rotation angle θκ increases. By improving the C / N ratio, accurate information reproduction can be performed and the reproduction speed can be increased even if the accuracy of the optical system of the information reproduction apparatus is lowered.

The magneto-optical recording medium as described above usually has a layer structure in which a first dielectric layer, a magnetic layer as a recording layer and a second dielectric layer are sequentially formed on a substrate (special feature). Kaihei 1-
263963, JP-A-62-209750 and JP-A-62
-217444 publication). The first dielectric layer has a role of protecting the magnetic layer, and prevents permeation of oxygen, water, etc. to the magnetic layer which is easily oxidized. Further, the first dielectric layer functions as an enhancement layer that enhances the Kerr effect, and utilizes multiple reflections to increase the apparent Kerr rotation angle and improve the reproduction signal characteristics. The second dielectric layer is provided to protect the magnetic layer.

More recently, research has been conducted on a magneto-optical recording medium having a reflective layer adjacent to the magnetic layer or outside the second dielectric layer in order to obtain a larger reproduction signal characteristic. (Japanese Patent Publication No. 62-27458,
JP-A-60-63747). This is in addition to the car effect
It is intended to utilize the Faraday effect due to reflection of light transmitted through the magnetic layer.

[0007]

However, in the magneto-optical recording medium having such a structure, if the thickness of the magnetic layer is reduced in order to increase the amount of transmitted light and sufficiently obtain the Faraday effect, write noise will occur. On the contrary, if the thickness of the magnetic layer is increased in order to reduce the write noise, a sufficient Faraday effect cannot be obtained this time, so that a high reproduction signal characteristic (C / N) can be obtained in any case. There was a problem of not having.

Therefore, an object of the present invention is to provide a magneto-optical recording medium having high reproduction signal characteristics.

[0009]

According to the present invention, in a magneto-optical recording medium having a magnetic layer provided on a transparent substrate, the magnetic layer is measured at room temperature on the side opposite to the substrate and adjacent to the magnetic layer. The present invention provides a magneto-optical recording medium characterized in that it is provided with a high thermal conductive layer made of a simple substance or an alloy of a substance having a thermal conductivity of 100 W / m · K or more. Here, it is necessary that the high thermal conductive layer made of a substance having high thermal conductivity as described above be present adjacent to the magnetic layer. This makes it easier for heat generated by laser irradiation during writing to escape in the thickness direction, forming rectangular pits,
It is considered that high reproduction signal characteristics can be obtained.

The magneto-optical recording medium of the present invention has a layer structure of substrate / magnetic layer / high heat conduction layer. Optionally, there can be a first dielectric layer between the substrate and the magnetic layer and a second dielectric layer outside the high thermal conductivity layer (opposite the substrate).

Specific examples of the material of the substrate include inorganic materials such as glass, resin materials such as polycarbonate, polymethylmethacrylate, and epoxy resin. The thickness of the substrate is not particularly limited and can be changed as needed.

The magnetic layer is a recording layer, and usually an alloy of a rare earth metal and a transition metal can be used. For example, TbFeCo
Examples thereof include amorphous alloys such as those based on GdFeCo, GdFeCo, DyFeCo, and PrFeCo. Preferably, the following formula: [T
b _X (Fe _1-Y Co _Y ) _1-X ] _100-Z M _Z (in the formula, M
Is selected from Cr, Ti, Zr, Pt, Pd, Rh, Nb, V and In, and X, Y and Z are each 0.19 ≦.
X ≦ 0.26, 0 ≦ Y ≦ 0.20, 0 ≦ Z ≦ 6, which is a rational number). The layer thickness is preferably 20
0 to 600 Angstroms. The magnetic layer may be formed by any known thin film forming method, for example, a sputtering method,
A vacuum deposition method, an ion plating method, a vapor phase growth method or the like can be used. Among them, the sputtering method is particularly preferable, and the DC sputtering method, the high frequency sputtering method, the reactive high frequency sputtering method and the like are preferably used.

The present invention is characterized in that a high thermal conductive layer is provided on the opposite side of the magnetic layer from the substrate and adjacent to the magnetic layer. As the material of the high thermal conductive layer, a simple substance or an alloy of a substance having a thermal conductivity measured at room temperature of 100 W / m · K or more, preferably 110 W / m · K or more is used. Specific examples thereof include Ir, Mo, Rh, R
u, W, Zn and other metals alone or alloys of these metals; these metals and other metals such as Al, Au, A
g, alloy with Cu, etc .; or diamond-like carbon (carbon partially containing diamond structure), B
Inorganic substances such as N may be used. The layer thickness of the high thermal conductive layer is 20
It is preferably from 0 to 600 angstroms. Such a high thermal conductive layer may be formed by any known thin film forming method. Among them, the sputtering method is particularly preferable, and the DC sputtering method, the high frequency sputtering method, the reactive high frequency sputtering method and the like are preferably used.

The first and second dielectric layers each have Z
Sulfides such as nS, SiO, SiO ₂ , In ₂ O ₃ , Sn
Oxides such as O ₂ and nitrides such as AlN and silicon nitride can be used. Preferred is silicon nitride, for example SiN,
_{Si 2 N 3, Si 3 N} 4 and the like. The layer thickness of each dielectric layer is preferably 300 to 1000 angstroms. Such a dielectric layer may be formed by any known thin film forming method, like the magnetic layer described above. Among them, the sputtering method is particularly preferable, and the direct current sputtering method, the high frequency sputtering method,
A reactive high frequency sputtering method or the like is preferably used.

[0015]

In the magneto-optical recording medium of the present invention, since the high thermal conductive layer is adjacent to the magnetic layer, the heat generated by the laser irradiation during writing easily escapes in the thickness direction, and a rectangular pit is formed. Therefore, it is considered that high reproduction signal characteristics can be obtained.

[0016]

The present invention will be described in more detail with reference to the following examples.
explain.Examples 1-9 and Comparative Examples 1-3  Polycarbonate (hereinafter sometimes referred to as PC) substrate
On top, in order, SiN (first dielectric layer), Tb_{twenty one}Fe₇₁Co₈of
Magnetic layer with composition, material and thermal conductivity shown in the table
High thermal conductivity layer (measured at room temperature), and SiN (second invitation)
Each layer of (electrical layer) was formed. The formation of each layer is a planar
Magnetron sputtering equipment (Substrate rotation type, ULVAC
(Manufactured by the same company) in the same batch under the following conditions:
It was.Initial vacuum degree When forming the first dielectric layer and the second dielectric layer: 2 × 10^-6Torr
Below, when forming magnetic layer: 5 x 10^-7Torr or less, when forming high thermal conductivity layer: 2 × 10^-6Below TorrSputter gas and gas pressure When forming the first dielectric layer and the second dielectric layer: Ar + N₂,
10 x 10^-3Torr, when forming magnetic layer: Ar, 5 × 10^-3Torr, when forming high thermal conductivity layer: Ar, 1 × 10^-3Torr thus substrate / first dielectric layer / magnetic layer / high thermal conductivity layer /
A magneto-optical recording medium having the layer structure of the second dielectric layer was prepared.
It was The layer thickness of each layer is 800 Å for the first and second dielectric layers.
Ngstrom, magnetic layer 400 angstrom,
And the high thermal conductivity layer was 300 Å.

Reproduction signal characteristic C of the obtained magneto-optical recording medium
/ N ratio, disk rotation speed at the measurement position of radius 30 mm
1800 rpm, recording frequency 3.7 MHz, resolution bandwidth 30
The measurement was performed at the inner circumference of the disk at KHz and a laser wavelength of 830 nm. The results are shown in the table below.

[0018]

【table】

[0019]

According to the present invention, it is possible to provide a magneto-optical recording medium having high reproduction signal characteristics. Therefore, the magneto-optical recording medium of the present invention is industrially useful.

Claims (2)

[Claims] 1. In a magneto-optical recording medium having a magnetic layer provided on a transparent substrate, the thermal conductivity measured at room temperature is 100 W / m on the side of the magnetic layer opposite to the substrate and adjacent to the magnetic layer.
A magneto-optical recording medium provided with a high thermal conductive layer made of a simple substance or an alloy of a substance of K or more. 2. The high thermal conductive layer is made of Ir, Mo, Rh, R.
The magneto-optical recording according to claim 1, comprising a simple substance of a metal selected from u, W and Zn, an alloy of these metals, an alloy of these metals and Al, Au, Ag or Cu, diamond-like carbon, or BN. Medium.