JPH04105232A - Magneto-optical disk - Google Patents

Abstract

PURPOSE:To easily obtain the reflectivity required for a driving device by forming dielectric films consisting of a metal oxide or metal nitride by a sputtering method on a base body and forming the interference films consisting of the 1st and 2nd dielectric films varying in refractive index. CONSTITUTION:The interference film 21 consisting of the 1st dielectric film and the interference film 22 consisting of the 2nd dielectric film are laminated on the substrate 1. These films are the dielectric films consisting of the metal oxide or metal nitride and further, a magneto-optical recording medium 3, a protective film 4 and a UV curing resin 5 are laminated thereon. The interference films 21, 22 are formed by the sputtering method. Since the interference films are formed of the two layers; the 1st layer dielectric film 21 and the 2nd dielectric film 22 varying in the refractive index in such a manner, the film thicknesses of the two layers varying in the refractive index are respectively changed by the interference of light. The film formation of the dielectric films 21, 22 varying in the refractive index is also easily controlled by the presence or absence of nitrogen or oxygen during sputtering. The reflectivity required for the driving device is obtd. with the simple structure and film forming method in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dielectric film of a magneto-optical disk in which information is recorded, reproduced and erased using a light beam.

[Conventional technology]

Magneto-optical disks, in which information is recorded, reproduced, and erased using a light beam, are capable of recording rewritable information at high density, and are therefore expected to be used in a wide range of fields.

Conventionally, the structure of magneto-optical disks has been to use a transparent substrate made of glass, polycarbonate, etc. as the first layer of
Metal oxides such as Sin, /IN, metal nitrides such as SiN, metal sulfides such as ZnS, 5iAj! A dielectric film containing a metal mixture such as ON, a magneto-optical recording medium film as the second layer, and a dielectric film formed as the third layer, or a dielectric film as the first layer and the second layer as the dielectric film. A known disk structure includes a magneto-optical recording medium film, the dielectric film as the third layer, and a metal film such as AI, Bi, Ph, etc. as the fourth layer. The dielectric film serves as a protective film for the recording medium film, and in a three-layer structure, the first dielectric film serves as an interference film, and in a four-layer structure, the third dielectric film serves as an interference film. Usually, the reflectance of a disk is determined by the refractive index, light absorption coefficient, and film thickness of the dielectric film itself, which is this interference film.

[Problem to be solved by the invention]

However, these magneto-optical disks have a low reflectance of 10% to 40%, and CDs are expected to become a new field in the magneto-optical disk market in the future.
It is difficult to adapt to 1j conversion type magneto-optical disks.

The purpose of the present invention is to solve these problems and provide a magneto-optical disk that can be formed with a simple structure and film formation method, provides the reflectance required by drive devices, has excellent long-term durability, and is worthy of practical use. Our goal is to provide the following.

[Means to solve the problem]

To achieve the above object, the present invention has the structure of the conventional three-layer magneto-optical disk. The first dielectric film is formed by sputtering only the inert gas argon without oxygen or nitrogen on the interface and vicinity on the substrate side or the interface and vicinity on the recording medium side. This is a second dielectric film having a different coefficient.

[Effect]

The effects of the present invention will be explained below. In the disk structure as described above, in other words, the first layer dielectric film, which is an interference film, is formed of two layers of the same type of second dielectric film with different refractive indexes, so the refractive index differs due to light interference. A desired reflectance can be obtained by changing the film thicknesses of the two layers. Further, the formation of two dielectric films having different refractive indexes can be easily controlled by controlling the presence or absence of nitrogen or oxygen during dielectric film target sputtering. Therefore, with the above-described disk structure and film formation method, it is possible to easily provide a disk with a desired reflectance required by a drive device.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of a magneto-optical disk according to the present invention. That is, 1 is a polycarbonate substrate, on which are laminated the interference film 21 of the first dielectric film and the interference film W#22 of the second dielectric film. Metal nitrides such as Al1N and SiN,
5iAj! A dielectric film made of a metal mixture such as N, 5iAION, etc., and a magneto-optical recording medium.3. Protective film 4. An ultraviolet curing resin film (hereinafter referred to as UV resin) 5 was laminated. Here, the substrate 1 is not limited to polycarbonate, but may be PMMA,
Plastic materials such as polyolefin and epoxy, glass plates, etc. can be used. Magneto-optical recording medium 3 and Sin, Si
The interference films 21, 22 such as n, AIN, SiN, 5iAIN, 5iAjON, etc. and the protective film 4 are fabricated by sputtering, and the UV resin is spin coded by a spin code. Regarding the disk structure, a contact type double-sided recording type and an air sandwich type double-sided recording type are also possible.

The sputtering device may be a commonly used device, so although it is not shown in the figure, the substrate 1 is first placed in a vacuum chamber,
After evacuation to 0-' Pa), the interference films 21 and 22, the magneto-optical recording medium film 3, and the protective film 4 are formed on the substrate 1 in the same vacuum chamber.For example, when using a SiN film as the interference film, Ar+N, By reactive sputtering using Si, N, and a target in an ambient atmosphere, the refractive index n is low (in this case n = 1.7
5) Form the SiN film 21, then block the reaction gas N2, and form the SiN film 2 with a high refractive index n (n-2,2 in this case).
2 is formed into a film. Alternatively, for example, a SiN film with a high refractive index n is formed first, and then a reactive gas N2 is introduced into the SiN film with a low refractive index n.
iNWi! It is also possible to form a film.

The relationship between the film thickness and reflectance of the disk obtained by such a method is shown in FIGS. 2 and 3. This is an example in which the sputtering target is Si, N, or oxide, and the dielectric film is a SiN film. In FIG. 2, the interference film 21 is made of Si having a low refractive index n.
N film (500 people), the interference film 22 is StN with a high refractive index n.
@, and on top of that, the thickness of the magneto-optical recording medium film 3 is 900mm, and the protective film 4 is 5iNIll with a low refractive index n! (1000
When the film thickness of the interference film 22 is used as a parameter in a disc structure with a disc structure of 100%, the disc reflectance changes between 20% and 43%. In FIG. 3, the interference film 21 is made of Si having a high refractive index n.
The N film and the interference film 22 are replaced by a SiN film with a low refractive index n (1000
400 people), the film thickness of the magneto-optical recording medium film 3 is 400 people, and the protective film 4 is
In a disk structure in which a SiN film (600) having a high refractive index n is used, and when the thickness of the interference film 21 is used as a parameter, the disk reflectance changes between 44 and 70%. In this way, various reflectances can be obtained with a simple disk structure and film formation method, and SiO, SiO□, AIN, A
l0N, 5iAI! The same can be said of other dielectric films such as N, 5iAi'ON, etc.

〔Effect of the invention〕

The magneto-optical disk according to the present invention has a simple structure in which the interference film is a stack of two dielectric films of the same type with different refractive indexes, and a magneto-optical recording medium film and a protective film are further stacked. Since two layers with greatly different refractive indexes can be easily formed depending on the presence or absence of a reactive gas during sputtering, various reflectances can be obtained by light interference by changing the thickness of the interference film.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a magneto-optical disk according to the present invention, and FIGS. 2 and 3 are examples of changes in disk reflectance due to changes in the thickness of the interference film and the structure of the disk at that time. 1... Substrate 3... Magneto-optical recording medium film (RE-TM) 4... Protective film 5... UV resin film 21.22... 1st. This is the second interference film.

Claims (1)

[Claims] In magneto-optical disks, in which dielectric films are laminated on both sides of a magneto-optical recording medium film, and information is recorded, reproduced, and erased by irradiating the medium film with a light beam, both dielectric films are formed by sputtering. A film made of a metal oxide or a metal nitride, in which the dielectric film formed on the substrate has a laminated structure of a first dielectric film and a second dielectric film having different refractive indexes. A magneto-optical disk characterized in that it has an interference film consisting of.