JP2796574B2 - Magneto-optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a high-sensitivity, high-density magneto-optical recording medium.

[Conventional technology]

A magneto-optical recording medium utilizes perpendicular magnetic recording and a magneto-optical effect (Kerr effect, Faraday effect, etc.), and uses a laser beam to record information,
Since reproduction is performed, the recording capacity is large and rewritable. Further, recording and reproduction can be performed without contact between the head and the medium, and the recording medium is not affected by dust, so that the stability is excellent. This magneto-optical recording medium is currently being actively studied, and is expected to be used for document information files, video / still image files, memory for computers, or to replace floppy disks and hard disks. Has been reached.

Various amorphous magnetic alloy films combining transition metals (Fe, Co) and rare earth metals (Tb, Dy, Gd, Ho, Er, etc.) have been proposed for the recording layer of such a magneto-optical recording medium. Have been. A magnetic alloy film formed on a substrate by sputtering or vapor deposition by combining one or more transition metals and rare earth metals, respectively, is an amorphous perpendicular magnetization film (easy magnetization in the direction perpendicular to the film surface) near the compensation composition. (A magnetic film having an axis), and can be applied to a magneto-optical recording medium.

[Problems to be solved by the invention]

On the other hand, from the viewpoint of speeding up information processing and alternatives such as a hard disk, it is very important to achieve higher speed and higher density of recording in a magneto-optical recording medium. For high-speed and high-density recording, the recording laser power needs to be small, and the recording bit length must be short and the shape must be sharp.
If the recording bit length is long, it will hinder high density, and if the recording bit shape is disturbed, noise will increase and the reproduction C / N will deteriorate. The magneto-optical recording medium uses thermo-magnetic recording, and the recording material has a multilayer structure because it is easily oxidized and deteriorated. It greatly depends on the bit length and shape. However, in the conventional magneto-optical recording medium, studies and proposals have been made to improve the characteristics of individual layers including thermal conductivity (for example, see Japanese Patent Application Laid-Open No. Sho 62-62).
-226449, 56-74844, etc.).
Actually, the magneto-optical recording medium has a multilayer structure, and the respective components are complementarily related to each other. At present, sufficiently satisfactory characteristics have not been obtained by examining each layer alone.

An object of the present invention is to provide a high-speed, high-density magneto-optical recording medium having good recording sensitivity in view of the situation of the related art.

[Means for solving the problem]

To achieve the above object, according to the present invention, a recording layer composed of an amorphous rare earth metal-transition metal alloy thin film is provided on a transparent substrate via a first dielectric layer, and a second dielectric layer is further formed thereon.
It has a configuration in which a dielectric layer and a heat absorbing layer are sequentially provided, and the first dielectric layer and the second dielectric layer have a thermal conductivity of 0.03 cal · c.
m / s · cm ² · ° C. (room temperature) or less, and the recording layer and the heat absorbing layer are 0.20 cal · cm / s · cm ² · ° C.
(Room temperature) A magneto-optical recording medium comprising the following material is provided.

 Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of a layer structure of a magneto-optical recording medium according to the present invention. In FIG. 1, reference numeral 1 denotes a transparent substrate, on which a first dielectric layer (enhancement layer) 2, a recording layer 3 , A second dielectric layer (heat insulating layer) 4 and a heat absorbing layer (heat sink layer) 5 are sequentially laminated. Then, an organic protective layer or a bonding layer 6 is formed as necessary.

First, as a material for the substrate 1, an optically transparent plastic such as polycarbonate, methyl methacrylate, polyolefin, epoxy resin, or glass is used. A guide track and a preformat may be formed on the substrate 1 in advance. Further, the laser light incident surface of the substrate 1 may be covered with a dielectric layer, a hydrophobic layer, a gas-resistant layer (for example, a fluororesin layer) or the like to prevent H ₂ O and O ₂ from entering.

The first dielectric layer 2 prevents the magnetic properties of the recording layer 3 from deteriorating due to the intrusion of H ₂ O and O ₂ from the outside of the substrate, and the magneto-optical effect (Kerr rotation angle θ _K ) by multiple reflection of light. Plays a role of enhancement. For this reason, the material used for the first dielectric layer 2 has a refractive index n of 2.0 or more and a thermal conductivity at room temperature of 0.03 cal · cm / cm ² · s · ° C. or less. The thermal conductivity of the first dielectric layer 2 is 0.03 cal · cm / s
-If it is larger than cm ² , heat loss due to heat conduction increases, which is not preferable. The first dielectric layer, SiN _X, ZrT _X, Si
ZrN _X , CrN, SmN, NdN, V ₂ N, TaN, SbN, BN, HfN, TiN,
One or a combination of two or more of nitrides such as GeN is used, and is formed to a thickness of 800 to 1300 ° by a sputtering method, a vapor deposition method, an ion plating method, or the like.

For the recording layer 3, amorphous TbDyFeCo or GdDyFoCo is preferably used, and its compensation temperature Tcomp is higher than room temperature, and the thermal conductivity at room temperature is preferably 0.20 cal · cm / cm ² · s · ° C. or less. . The thermal conductivity of the recording layer 3 is 0.20 cal · cm /
If it is larger than cm ² · s · ° C., the recording mark (bit) becomes large. The recording layer 3 is formed to a thickness of 200 to 700 ° by a film forming method such as a sputtering method and a vapor deposition method.

The second dielectric layer 4 plays a role of collecting heat in the recording layer 3 without diffusing heat generated in the recording layer 3 by laser irradiation at the time of recording, and using the H ₂ O and O ₂ in the atmosphere to record the heat.
Plays a role in preventing oxidation and corrosion. For this reason,
The thermal conductivity of the second dielectric layer 4 is preferably 0.2 cal · cm / cm ² · s · ° C or less. The thermal conductivity of the layer 4 is 0.2 cal
If the temperature is higher than cm / cm ² · s · ° C., heat diffusion increases, and the effect of storing heat in the recording layer 3 decreases, which is not preferable. As the material of the second dielectric layer 4, the same material as that of the first dielectric layer 2 is used.
It is formed to a thickness of about 800 mm.

The heat absorbing layer 5 functions to prevent heat diffusion in the second dielectric layer 4. That is, the heat generated in the recording layer 3 by the laser irradiation at the time of recording is conducted to the second dielectric layer 4 and is conducted to the heat absorbing layer 5 of the second dielectric layer 4 so that the second
Thermal diffusion in the dielectric layer 4 is prevented. As a result, the trailing edge of the recording bit is short and the bit shape is sharp and faithful to the laser spot diameter. On the other hand, when the heat absorbing layer 5 is not provided, heat diffusion occurs in the second dielectric layer 4, and the trailing edge of the recording bit is long, and its shape is smaller than the laser spot diameter. Therefore, the heat absorption layer 5 has a lower thermal conductivity than the second dielectric film 4 and a thermal conductivity of 0.20 ca at room temperature.
Materials less than l · cm / cm ² · s · ° C, such as Zr, Pt, Cr, A
At least one of g, Au, and Rh or an alloy thereof is preferably used. Then, it is formed to a thickness of 300 to 700 ° by a film forming method such as a sputtering method and a vapor deposition method.

An organic protective layer or a bonding layer 6 is provided on the heat absorbing layer 5 if necessary. The organic protective layer protects the lower layer below the heat absorbing layer 5, and the bonding layer is used for bonding in a double-sided recording type medium. Do. The organic protective layer or the bonding layer 6 is made of a UV curable resin (UV resin), a thermoplastic resin, a plasma polymerized resin, or the like, and is formed to a thickness of 1 μm by a method such as spinner coating.
The film is formed to a thickness of 100 μm.

When the two disks having the above-described configuration are bonded to each other to form a double-sided recording type magneto-optical disk, it is preferable that the ends of the disks are joined with a dielectric material or plastic.

Although the present invention has been described based on one configuration example, the layer configuration of the present invention is not limited to this example.
Various modifications and changes are possible, such as a structure in which only one of the first dielectric film 2 and the second dielectric film 4 is provided, and a structure in which the recording layer 3 has a two-layer structure.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example 1) A polycarbonate plate having an outer diameter of 130 mm, an inner diameter of 15 mm, and a thickness of 1.2 mm was used as a substrate, and an N ₂ + Ar gas was flowed while using a Si target in an RF magnetron sputtering apparatus.
The SiN film was formed 1000Å thick by sputtering as a first dielectric layer on the substrate, then _{Tb 0 · 12 Dy 0 · 12} Fe as the recording layer in the same RF magnetron sputtered onto the
The _{0 · 68} Co _{0 · 08} film is formed 250Å thick was further formed thereon a second dielectric layer made of SiN film in the same manner as the first dielectric layer formed on the 300Å thick. Next, DC is placed on the second dielectric layer.
After forming Al-Zr to a thickness of 600 mm by sputtering, a UV resin (trade name: EH214, manufactured by Yokohama Rubber Co., Ltd.) is formed to a thickness of about 4 μm by a spinner coating method, and then cured to form an organic protective layer. A magnetic disk was obtained. The material of each element and the thickness of each layer are shown in Table 1 below, and the value of the thermal conductivity of each layer is shown in Table 2 below.

(Examples 2 to 8) In the same manner as in Example 1, the materials shown in Table 1 were used as the materials for the substrate, the first dielectric layer, the recording layer, the second dielectric layer, the heat conductive layer, and the organic protective layer. Thus, a magneto-optical recording medium was obtained. The thickness of each layer and the thermal conductivity of each layer are as shown in Tables 1 and 2, respectively.

(Comparative Example) A magneto-optical disk was manufactured in the same manner as in Example 1, except that the materials shown in Table 1 were used as the materials for the components. The thickness and thermal conductivity of each layer are as shown in Tables 1 and 2, respectively.

The recording and reproduction characteristics of each magneto-optical disk manufactured as described above were evaluated under the following conditions. Table 3 shows the results.
Shown in

・ Laser wavelength 790nm ・ NA = 0.53 ・ Line speed 7m / sec ・ Recording frequency 4MHz [Effects of the Invention] As described above in detail, according to the present invention, since the thermal conductivity of each layer is specified as described above, the recording bit length is short, the bit shape is sharp, and the recording / reproducing characteristics are improved. In addition, higher speed and higher density of recording can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the layer structure of the magneto-optical recording medium of the present invention. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... 1st dielectric layer 3 ... Recording layer 4 ... 2nd dielectric layer 5 ... Heat absorption layer

Continuing on the front page (72) Inventor Fumiya Omi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Yasuo Sawada 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company (72) Inventor Isao Miyamoto 1-3-6 Nakamagome, Ota-ku, Tokyo In-house Ricoh Company (56) References JP-A-62-226449 (JP, A) JP-A-1-315049 ( JP, A) JP-A-62-172545 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 11/10 521

Claims (1)

(57) [Claims] 1. A recording layer comprising an amorphous rare earth metal-transition metal alloy thin film is provided on a transparent substrate via a first dielectric layer, and a second dielectric layer and a heat absorbing layer are sequentially formed thereon. The first dielectric layer and the second dielectric layer are made of a material having a thermal conductivity of 0.03 cal · cm / s · cm ² · ° C. (room temperature) or less. Heat absorption layer is 0.
A magneto-optical recording medium comprising a material having a temperature of ²⁰ cal · cm / s · cm ² · ° C (room temperature) or less.