JPH0469835A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve mechanical strength and durability by using an amorphous material for a dielectric film and maintaining the refractive index of the film to a specified range. CONSTITUTION:The dielectric film 2 and/or 4 is an amorphous SiO:H film formed by sputtering. The dielectric film has small thermal conductivity and thermal diffusion when it contains hydrogen by 2 - 40 mol%. The molar ratio of Si to O is preferably in the range of (90 - 50):(10 - 50) since the excess amt. of O causes reaction with Tb and deterioration of the film. If the refractive index of the amorphous SiC:H film is <1.75, enough enhancing effect cannot be expected, while with >2.50 refractive index, transmittance and film property decrease. Thereby, the refractive index is specified to 1.75 - 2.50 to improve the mechanical strength and durability.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording medium, particularly a magneto-optical recording medium that has excellent chemical stability and optical transparency, has a good C/N, and can improve recording density. This relates to magneto-optical recording media that can be used.

[Prior Art] In recent years, with the advancement of the information society, rewritable magneto-optical memory has attracted attention, and rare earth element-transition metal element thin films such as TbFeCo are used as magnetic films for this magneto-optical memory. However, this method has the disadvantage that the obtained Kerr rotation angle is not very large and the C/N of the reproduced signal is not sufficient.

[Invention tries to solve! ! ! Problem] Therefore, for this type of magneto-optical recording medium, SiH4 SiN is used on the surface of a conventionally known amorphous magnetic film.

A dielectric layer (film) such as AiN is formed, and its thickness is set to λ/
4n (λ is the laser wavelength, n is the refractive index) to increase the apparent Kerr rotation angle and increase the C/N (enhancement effect), but the improvement in characteristics by this is still unresolved. This is sufficient, and this dielectric layer is required to have an even higher refractive index and better transparency.

Recently, with regard to magneto-optical recording media, the recording sensitivity of the disk has become a major problem as the demand for faster signal IA filling has become stronger, and in order to increase this recording sensitivity, the thermal conductivity of the dielectric film has been lowered. Attempts have been made to suppress the thermal diffusion and increase the thermal efficiency of the laser to reduce the power required for recording, but conventionally used dielectric films made of SiN, AJ2N, SiO, etc. have low thermal conductivity. This is difficult to suppress, and from this point of view, there is a need for the development of new membrane materials.

On the other hand, the amorphous magnetism film conventionally used here is said to contain rare earth metals, but since these rare earth metals are extremely easily oxidized, they cannot be used under high temperature and high humidity conditions. However, nitrides such as SiN and AjN have low reactivity, and there is a proposal to use the dielectric layer described above as a protective film. Therefore, although it is successful in improving corrosion resistance, it tends to crack when it is deposited on a resin substrate or the like, and there are problems with mechanical strength. Note that although oxides such as SiO are superior to nitrides in terms of mechanical strength, the excess 02 in the film reacts with the rare earths in the magnetic film and deteriorates the performance of the magnetic film. There was a drawback that it could be stored away.

[Means for Solving the Problems] The present invention relates to a magneto-optical recording medium that can solve the above problems, and includes a dielectric layer and a magnetic film on a transparent substrate placed on the light incident side. , a magneto-optical recording medium provided with a reflective film, characterized in that the dielectric layer is made of an amorphous material made of SiO containing H.

In other words, the present inventors found that the C/N
As a result of various studies aimed at developing a magneto-optical recording medium with improved B density, H
When made from an amorphous material 1I4 (hereinafter abbreviated as amorphous SiO:H film material) made of SiO containing
2) This amorphous SiO:) Ili contains H, so it has lower thermal conductivity than a SiO film that does not contain H. Thermal diffusion of the irradiating laser can be suppressed and the temperature can be raised efficiently, so recording sensitivity can be increased.The 3-layer film material contains H and thermal diffusion is small, suppressing the expansion of the recording bit diameter. 4) wA
Since it contains film material H, this material tends to become amorphous, and a film with excellent compositional uniformity and a smooth surface can be obtained.5) This material has excellent light transmittance;
In particular, it exhibits extremely high transparency in the visible-infrared region, so
The inventors discovered that it was possible to obtain a magneto-optical recording medium with a large C/N ratio, conducted research on methods for forming this amorphous material, and completed the present invention.

This will be explained in further detail below.

[Function] In the magneto-optical recording medium of the present invention, the dielectric film in the magneto-optical recording medium is formed by providing a dielectric layer, a magnetic film, and a reflective film on a transparent substrate using amorphous SiO:)! It is made into a membrane.

The structure of this magneto-optical recording medium is known, and as shown in FIG. A dielectric @ 2, a magnetic film 3, an 8-electric material 1]i4 of the same quality as the dielectric film 2, and a reflective film 5 are sequentially laminated on a substrate 1, as shown in Fig. 2. It may also have a three-layer structure in which a dielectric film 8, a magnetic film 9, and a dielectric film 10 are sequentially laminated on the transparent substrate 7, and in these, light is transmitted from the light incident side of the transparent substrate 1.7. 6.11 is incident, the light 6 is reflected by the reflective film 5, and in the case of FIG. 2 in which the thickness of the magnetic film is increased, the incident light 11 is reflected by the magnetic film 9.

In the magneto-optical recording medium of the present invention, the dielectric film 28 and/or
Alternatively, 4 and 10 are formed from the amorphous SiO: Since this improves the recording sensitivity and provides a film with a smooth surface, it is often made to contain hydrogen in a molar ratio of 2 to 40%, and when the amount of SiO is in excess, it is difficult to form a magnetic film. The molar ratio of Si and 0 is preferably in the range of 90 to 50 and 10 to 50, since it reacts with Tb in the silicon and deteriorates its properties. Also, this amorphous Sin:
) For IIIM, if the refractive index is less than 175, a sufficient enhancement effect cannot be expected, and attempts to make it larger than 2.50 result in a decrease in transmittance and film quality, resulting in C/
This value is preferably in the range of 1.75 to 2.50 since this may reduce N and adversely affect mechanical strength and durability.

Note that this amorphous SiO:H film may be formed by plasma CVD or sputtering.

In this plasma CVD method, SiH and N20 gases are introduced into a reaction apparatus, and these are excited and decomposed by plasma to form a Sin:H film on the substrate.
Since it is possible to form a film even at a low temperature of 00° C. or lower, it is advantageous in cases where heat resistance is a problem, such as in the case of resin substrates. In addition, this sputtering method uses SiO as a target and performs sputtering using high-frequency power in an argon-hydrogen mixed gas atmosphere. Alternatively, amorphous SiO:Hm may be formed by a method.

Incidentally, in the magneto-optical recording medium of the present invention, a magnetic film and a reflective film are formed on the dielectric film formed on the substrate, and both of these may be of known type. consisting of a rare earth element-transition metal element film, therefore T
b, Rare earth elements such as Dy, Gd, and Nd and Fe,
Made of transition metal elements such as Go and Ni, for example T
bFe, TbFeCo, GdTbFe, GdDy
An amorphous metal film made of FeCo or the like with the structure shown in Figure 1 requires 200 to 500 people, and with the structure shown in Figure 2 it requires 80 people.
The reflective layer may be formed by sputtering to a thickness of about 0 to 1, CIoO.
A metal film such as A3 may be provided with a thickness of about 200 to 1,000.

[Example code] Next, examples of the present invention and comparative examples will be given.

Examples, Comparative Examples 1 and 2 SiO as a target was placed on a glass substrate, and an amorphous SiO:H film was formed by sputtering using a high frequency with an output of 300 m in a mixed gas atmosphere of 8G% argon gas and 20% SiH4 gas. was formed, and the molar composition ratio, refractive index, and transmittance of the film were investigated.
The results shown in the table were obtained.

In addition, for comparison, the above atmosphere was changed to 100% argon gas, but the same process as above was used to produce a SiC film that does not contain H (Comparative Example 1). When the refractive index and transmittance of the film (Comparative Example 2) were examined, the results shown in Table 1 were obtained.

Next, in order to make a magneto-optical recording medium as shown in Figure 1, amorphous SiO:Htm was formed on a polycarbonate substrate to a thickness of 1,000 mm by sputtering, and argon gas pressure was applied to this layer. 7m tall, high frequency power 20
Under the condition of 0 W, a 200-thick TbFe magnetic film, a 300-thick SiO:)l film, and a 500-thick aluminum reflective film were formed, and their H%i: ! When the optimum recording power was measured, the results shown in FIG. 3 were slightly hit.

Moreover, for this magneto-optical recording medium, 85°C, 85%R
After conducting a durability test on H, the results shown in Figure 4 were obtained, indicating that this product had extremely excellent corrosion resistance. As shown in FIG. 4, the performance of the devices using SiC and SiN deteriorated during testing due to peeling of the 8-electrode film and occurrence of cranks.

Summary (Effects of the Invention) The present invention relates to an optical 6n optical recording medium, which is a magneto-optical recording medium in which a substrate is provided with an 8-electroelectric film, a magnetic film, and a reflective film. is made of an amorphous M layer made of SiO containing H. According to this, this 8-electrode film has a refractive index of 1.75 to 2.50, so it has a large enhancement effect. In addition, the C/N ratio is increased due to its excellent light transmittance, and since this amorphous film contains H, the film surface becomes smooth, which also improves mechanical strength and durability. Since the thermal conductivity is low, the thermal diffusion of the laser is reduced, and the expansion of the diameter of the recording bit is suppressed, so that the recording density is improved.

[Brief explanation of drawings]

Figures 1 and 2 are configuration diagrams of magneto-optical recording media, Figure 3 is a graph of the relationship between hydrogen I and optimum recording power variation of the magneto-optical recording medium in the example, and Figure 4 is the example and comparative example. This is a graph showing the results of a durability test of a magneto-optical recording medium at 85° C. and 85% RH. 1.7... Transparent substrate 2.4.8.10... Dielectric film (ffi) 3.9...
・Magnetic film 5... Reflective film Patent applicant: Shin-Etsu Chemical Co., Ltd. Kane Arai 1-Biki Chu, - -to4 Quantity (al °X) Figure 3

Claims (1)

[Claims] 1. A magneto-optical recording medium in which a dielectric layer, a magnetic film, and a reflective film are provided on a transparent substrate placed on the light incident side, in which the dielectric layer is a non-containing material made of SiO containing H. A magneto-optical recording medium characterized by being made of a crystalline material. 2. The magneto-optical recording medium according to claim 1, wherein the amorphous material made of SiO containing H contains H in a molar ratio of 2 to 40%. 3. SiO in an amorphous material made of SiO containing H
The molar ratio of Si and O is Si:O (molar ratio) = 90 to 50
2. The magneto-optical recording medium according to claim 1, wherein: 4. An amorphous material made of SiO containing H has a refractive index (n)
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium has a value of 1.75 to 2.50. 5. Amorphous material made of SiO containing H is plasma CV
2. The magneto-optical recording medium according to claim 1, which is formed by the D method or the sputtering method. 6. The magneto-optical recording medium according to claim 1, wherein the amorphous material made of SiO containing H is formed by sputtering using SiO as a target in an argon-H_2 mixed gas atmosphere. 7. The amorphous material made of SiO containing H is formed by sputtering using SiO or SiO_2 as a target in an SiH_4 gas atmosphere or an argon-SiH_4 mixed gas atmosphere. Magneto-optical recording medium. 8. The magneto-optical recording medium according to claim 1, wherein the amorphous material made of SiO containing H is formed by a plasma CVD method using SiH_4 gas and N_2O gas as raw materials.