JPH03187039A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To generate large enhancing effect, to increase Kerr rotation angle and to improve recording density by providing a dielectric film, magnetic film and reflecting film on a transparent substrate arranged at the incident side of light, and forming the dielectric layer with amorphous material composed of SiC and SiN. CONSTITUTION:On a transparent substrate 1 such as glass and polycarbonate resin formed with guide grooves for tracking, dielectric film 2, magnetic film 3, dielectric film 4 composed of the same material as the film 2, and reflecting film 5 are successively formed to constitute the magneto-optical recording medium. Light 6 incident on the substrate 1 is made to reflect by the film 5. In this constitution, the amorphous material for the films 2, 4 has such a molar composition ratio of SiC:SiN = 20 - 80 : 80 - 20 with Si:N = 0.6 - 1.34 of SiN. The refractive index of the amorphous material is specified to 1.70 - 2.30, and the amorphous material is formed by sputtering in gaseous Ar atmosphere. Thereby, thermal diffusion of laser beam can be reduced to prevent expanding of recording bit diameter.

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 having a large Kerr rotation angle.
The present invention relates to a magneto-optical recording medium that has excellent optical transparency, good C/N, and can improve recording density.

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

[Problems to be Solved by the Invention] Therefore, in this type of magneto-optical recording medium, the surface of a conventionally known amorphous magnetic film is coated with Sin or SiN.

^IN, By forming a dielectric layer (film) such as 16N on 51 and setting the film thickness to /4n (λ is the laser wavelength, n is the refractive index), the apparent Kerr rotation angle is increased,
Efforts have been made to increase the C/N ratio (enhancement effect), but the improvement in properties by this is still insufficient, and a dielectric layer with an even higher refractive index and better transparency is required. .

Additionally, the amorphous magnetic film used here contains rare earth metals, but since these rare earth metals are extremely easily oxidized, their magnetic properties can easily be lost under high temperature and high humidity conditions. There is a problem that it deteriorates, and there is a proposal to give the above dielectric layer the role of a protective film, but Si
On the other hand, with oxides such as O, the rare earth elements reduce Si, so the effect is not sufficient, and SiN,
Since nitrides such as Ai'N have low reactivity, they are suitable for improving corrosion resistance, but they tend to crack when deposited on resin substrates and have poor mechanical strength. There is a problem.

It has also been proposed to use ON for this dielectric film [M, ^5ano et al, IEE
ETrans, Magn, MAG-23, 2820
, (1987)], it has a high refractive index, is transparent, and has excellent properties as a dielectric film, but even if it is formed by sputtering, it cannot be formed in a completely amorphous state. It is difficult, the composition is non-uniform, the surface becomes uneven, and there are problems in terms of durability.

[Means for Solving the Problems] The present invention relates to a magneto-optical recording medium that can solve the above problems, and consists of a dielectric layer and a magnetic film on a transparent substrate that is wrinkled 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 consisting of SiC and SiN.

That is, the present inventors conducted various studies to develop a magneto-optical recording medium that has a large Kerr rotation angle, excellent optical transparency, good C/N, and improved recording density. When the body layer is made of an amorphous material consisting of SiC and SiN (hereinafter abbreviated as amorphous 5iC-5iN II! material), l) I
! 2) Conventionally used Sin, SiN,
Compared to AIN, which has a refractive index of 1.4 to 1.13, this amorphous 5iC-5iN film has a refractive index of 1.7.
0 to 2.30, it has a large enhancement effect, and it also has good optical transparency, especially in the visible to infrared region, so it is suitable for magneto-optical recording media with a large C/H. 3) Amorphous 5iC-5
iN [l has low thermal conductivity, so the thermal diffusion of the irradiated laser is small, and the expansion of the recording bit diameter can be suppressed, so it is possible to improve the recording density.
They found that the above effect can be obtained, and conducted research on the method of forming this amorphous 5iC-5iN film, the molar ratio composition of SIC and SiN, etc., and completed the present invention.

This will be explained in further detail below.

[Function] The magneto-optical recording medium of the present invention is a magneto-optical recording medium in which a dielectric layer, a magnetic film, and a reflective film are provided on a transparent substrate, and the dielectric layer is an amorphous 51--3IN film.

The structure of this magneto-optical recording medium is known, and as shown in FIG. A dielectric film 2, a magnetic WA 3, and a dielectric WA are formed on the substrate 1.
2, a dielectric film 4 and a reflective film 5 of the same quality as those of 2 are sequentially laminated, and as shown in FIG. It may also have a three-layered structure, in which when light 6.11 enters from the light incident side of the transparent substrate 1.7, the light 6 is reflected by the reflective film 5, and the thickness of the magnetic film increases. In the diagram 's2 with thicker, the incident light 11 is magnetic
reflected.

In the magneto-optical recording medium of the present invention, the dielectric material 1112°8 and/or 4.10 is the amorphous 5iC-
5iN fl! However, this dielectric film can be formed by sputtering using a mixture of SiC and SiN, a mixture of Si and C, or a mixture of Si and SiC as a target. Since these targets are insulators, a high frequency is used as a power source, and the inside of the vacuum equipment is heated in an inert gas atmosphere (0,
When the target is a mixture of SiC and SiN, this atmosphere is an argon gas atmosphere.
In the case of a mixture of SiC and SiC, the film may be formed on the substrate by reactive sputtering in an argon-nitrogen mixed gas atmosphere.

Moreover, SiC in the dielectric film formed in this way
There is no particular restriction on the composition ratio between SiN and SiN, but if the refractive index is less than 1.70, an apparent increase in θ (enhancement effect) due to multiple reflections of light on the medium surface cannot be expected. If the refractive index is larger than 2.30, the film quality will deteriorate and the mechanical strength and durability will be adversely affected. Therefore, it is preferable that the refractive index is 1.70 or more and 2.30 or less. From this point of view, SiC The molar composition ratio of SiC and SiN is preferably in the range of SiC:SiN -20 to 80:80 to 20, and for this SiN, the composition ratio Si:N is 0.6 to 1.34. It is good to do.

In addition, in the magneto-optical recording medium of the present invention, a magnetic film and a reflective film are formed on the dielectric layer 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 Co 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 1,000 mm.
It is sufficient to provide a metal film such as G with a thickness of about 200 to 1,000.

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

Examples 1 to 3, Comparative Examples 1 to 2 110 with glass substrate set in sputtering equipment
℃, a mixture of SiC and SiN was placed as a target in the device, the device was made into an argon gas atmosphere of 4 × 10-' Torr, and a high frequency wave with an output of 600 W was applied to sputter the mixture onto a glass substrate. An amorphous dielectric layer made of amorphous 5iC-5iN was provided to a thickness of 0.2 μm (Example 1.2). A mixture of 51 and C was used as the target, and the inside of the apparatus was heated at a gas pressure of 8×10-” A dielectric layer was similarly prepared by sputtering in an atmosphere of 80%-N220% (Example 3).For comparison, the targets were boron nitride (BN) and silicon dioxide (Si(h)). ) as BN
(Comparative Example 1), 5t(h (Comparative Example 2)) was made as a dielectric layer, and the molar composition ratio, refractive index, and transmittance of this dielectric layer were measured, as shown in Table 1. The results were obtained.

Table 1 Also, when we investigated the relationship between the film thickness and visible light transmittance of this dielectric film made of amorphous 5iC-5IN, we found that the light transmittance at a wavelength of 633 na was
The results shown in the figure were obtained, and when the molar ratio of SiC and SiN in this dielectric layer and the film formation rate were investigated, the results shown in Figure 4 were obtained. The transmittance of the film increases as the film thickness becomes thinner.
The film formation rate is faster when SiC:5iN=50:50.
It was confirmed that it is advantageous for mass production.

This dielectric film was made with a molar ratio of SiC and SiN of 50:5Q, and various film thicknesses were made for the BN and 5ift films, and the film thickness and Kerr rotation angle were When we investigated the relationship, we obtained the results shown in Figure 5, and found that θk reached its maximum value of 2.0 at around 8 Onm, where the film thickness d was d = λ/4n, indicating a sufficient enhancement effect. was confirmed.

Next, on the dielectric film thus obtained, a TbFe magnetic film with a thickness of 20 nm is deposited by a conventional method, and an amorphous Sl (nee S) film with a film thickness of 2 On is deposited on top of this by the same method as described above.
An iN B electric film is provided, and a high frequency output of 20
A magneto-optical recording medium as shown in Fig. 1 was prepared by sputtering under conditions of 0W and argon gas pressure of 7xlO-'Torr to form an aluminum-based reflective film with a film thickness of 40rv. When we conducted a durability test at RH, we obtained the results shown in Figure 6 regarding the retention force change and retention time (hrs), and the amorphous 5iC-5iN dielectric layer as an example was compared. It is superior to the example in which BN and 5102 are used as the dielectric layer, and the holding force of the example shows almost no decrease even after 500 hours, whereas BN and Sin
, it was confirmed that this decreases considerably.

[Effects of the Invention] The present invention relates to a magneto-optical recording medium in which a dielectric film, a magnetic film, and a reflective film are provided on a substrate as described above. According to this method, this dielectric film has a refractive index of 1.70 to 2.30, which has a large enhancement effect, and increases the Kerr rotation angle. In addition, this amorphous film has a smooth film surface, excellent mechanical strength and durability, and has excellent thermal conductivity. Since this is small, the thermal diffusion of the laser is reduced, and the expansion of the diameter of the recording bit is suppressed, giving the advantage that the recording density is improved.

[Brief explanation of drawings]

Figures 1 and 2 are configuration diagrams of the magneto-optical recording medium, Figure 3 is a graph of the relationship between the molar ratio of SiC and SiN of an amorphous 5iC-5iN dielectric film and visible light transmittance, and Figure 4 is the same. A graph of the relationship between the molar ratio of SiC and SiN and the film formation rate, FIG. 5 is a graph of the relationship between the film thickness of the dielectric film and the Kerr rotation angle in Examples and Comparative Examples, and FIG. 6 is a graph of the relationship between the Example and Comparative Examples. This is a graph showing the relationship between retention time and coercive force. Codes in the figure: 1.7...Transparent substrate 2.4, 8.10...Dielectric film (layer) 3.9...Magnetic film reflective film 5llN4 SiC+431. N4 (Morschitsu diagram +00 00 00 00 00 Holding time (11) Diagram Kerr rotation angle (degrees) To # Speed (blade/now) Procedural amendment October 16, 1990 Patent application No. 325208 of 1999 2゜Name of invention Magneto-optical recording medium name (206) Shin-Etsu Chemical Co., Ltd. 4゜

Claims (1)

[Claims] 1. A magneto-optical recording medium comprising a dielectric layer, a magnetic film, and a reflective film on a transparent substrate placed on the light incident side, in which the dielectric layer is a non-containing material made of SiC and SiN. A magneto-optical recording medium characterized by being made of a crystalline material. 2. The amorphous material has a molar composition ratio of SiC:SiN=20~
80:80~20, SiN=0.6~1.3
4. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is 3. The magneto-optical recording medium according to claim 1 or 2, wherein the amorphous material has a refractive index (n) of 1.70 to 2.30. 4. The magneto-optical recording medium according to claim 1, 2 or 3, wherein the dielectric layer is formed by a sputtering method. 5. The magneto-optical recording medium according to claim 1, 2 or 3, wherein the dielectric layer is formed by sputtering in an argon gas atmosphere using a mixture of SiC and SiN as a target. 6. The dielectric layer targets a mixture of Si and C,
2. The magneto-optical recording medium according to claim 1, which is formed by sputtering in an argon-nitrogen mixed gas atmosphere. 7. The magneto-optical recording medium according to claim 1, 2 or 3, wherein the dielectric layer is formed by sputtering using a mixture of Si and SiC as a target in an argon-nitrogen mixed gas atmosphere.