JPH04184730A - Optical recording medium and stamper for its manufacture - Google Patents

Abstract

PURPOSE:To eliminate a multilayer laminated structure and, further, obtain a high CNR (carrier to noise ratio) by a method wherein a substrate and a recording film are provided and the surface of the substrate on the recording film side has a center line average roughness in a range of 0.3-0.7mum. CONSTITUTION:A protective film 2 made of dielectric, a recording film 3 containing rare-earth element and transition metal, a protective film 4 made of dielectric and a reflective film 5 are successively built up on a substrate 1. In order to record, reproduce and erase information, a light beam is applied to the substrate 1 side. The surface 2a of the protective film 2 which is built up on the substrate 1 and brought into contact with the recording film 3 has a center line average toughness in a range of 0.3-0.7mum. With this constitution, a multilayer laminated structure is not necessary and, further, a high CNR can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical recording medium and a stamper used for manufacturing the same.
Regarding.

[Prior Art] Optical recording media that reproduce recorded information by irradiation with focused light include read-only types, write-once types, and rewritable types.

A magneto-optical recording medium, which is one type of rewritable optical recording medium, generally has a structure in which a protective film, a recording film having perpendicular magnetic anisotropy, and a protective film are laminated in this order on a transparent substrate. Alternatively, it has a structure in which a reflective film is further laminated on the upper protective film. The material for forming the recording film is preferably an amorphous alloy of rare earth elements and transition metals, such as TbFeCo%NdDyFeCo,
Alloys such as GdTbFe are used.

CNR (Carri
er to noise ratio). CNR
Various improvements have been made in the past in order to increase the magnetic field. For example, a magneto-optical recording medium having a recording film formed by laminating two layers of magnetic films with different magnetic properties has been developed. Since this magneto-optical recording medium has a large Kerr rotation angle and an improved carrier level, this magneto-optical recording medium has a high CNR.

[Problems to be Solved by the Invention] In order to increase the CNR of an optical recording medium by improving the carrier level, it is necessary to multilayer the laminated structure of the optical recording medium as described above. For this reason, the number of manufacturing steps for the optical recording medium is increased, which may lower the yield.

One object of the present invention is to provide an optical recording medium that does not have a multilayered structure and has a high CNR. Another object of the present invention is to provide a stamper for use in manufacturing the above-mentioned optical recording medium.

[Means for Solving the Problems] According to the present invention, one of the above objects is to provide a substrate having a substrate and a recording film, and having a center line average roughness of 0.3 to 0.7 μm on the substrate surface on the recording film side. or has a structure in which a substrate, a protective film, and a recording film are sequentially laminated, and the center line average roughness of the surface of the protective film in contact with the recording film is 0.5 to 1.
This is achieved by providing an optical recording medium characterized in that it is in the range of 5 um.

The center line average roughness of the above substrate surface is 0.3 to 0.
The optical recording medium of the present invention having a center line average roughness of 7 μm and a centerline average roughness of 0.5 to 1.5 μl on the surface of the protective film is particularly preferable because it has a high CNR.

According to the present invention, another object of the above is that the centerline average roughness of the transfer surface of the optical recording medium 9 to the substrate is 0.
This is achieved by providing a stamper used for manufacturing the above-mentioned optical recording medium, which is characterized in that it has a thickness of 5 μm or less.

The center line average roughness used in this specification is JIS standard B
0601, and its cutoff value is 5 μm.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 FIG. 1 shows a schematic cross-sectional view of a magneto-optical recording medium as an example of the optical recording medium of the present invention. A magneto-optical recording medium having the cross-sectional structure shown in FIG. 1 includes a substrate 1, a protective film 2 made of a dielectric, a recording film 3 containing a rare earth element and a transition metal, a protection 14 made of a dielectric, and a reflective film. 5 are sequentially stacked. Light is irradiated from the substrate 1 side to record, reproduce, or erase information.

Sis on a substrate l made of polycarbonate resin. N
Protective film 2 (film thickness: 1100
recording film 3 (thickness: 250) consisting of Tb+JessCOsCrs (atomic ratio), Sis. N.

The cross-sectional structure shown in FIG. 1 is made up of a protective film 4 (thickness: 350 layers) made of A12SDI3 (atomic ratio) and a reflective film 5 (thickness: 500 layers) made of A12sdi3 (atomic ratio). The relationship between the center line average roughness of the substrate surface 1a on the side of the recording film 3 and the noise level of the magneto-optical recording medium was measured in the optical recording medium, and the results are shown in FIG. In addition, in this magneto-optical recording medium, the surface 2 of the protective film 2 that is laminated on the substrate l and in contact with the recording film 3 is
The center line average roughness of a was 1°0 μm.

As is clear from FIG. 2, the magneto-optical recording medium in which the surface 18 of the substrate has a centerline average roughness of 0.71 or less has a low noise level, and the above-mentioned centerline average roughness having a high CNR A magneto-optical recording medium with a roughness of less than 0.3 μm is not preferred because the protective film 2 is likely to peel off and the durability is poor.

Example 2 In a magneto-optical recording medium having the same structure as in Example 1, 1. Surface 2a of the protective film 2 in contact with the above-mentioned recording film 3
The relationship between the centerline average roughness of the magneto-optical recording medium and the noise level of the magneto-optical recording medium was measured, and the results are shown in FIG. In this magneto-optical recording medium, the center line average roughness of the substrate surface 1a on the side of the recording film 3 is 1.0μ.
■It was.

As is clear from FIG. 3, a magneto-optical recording medium in which the center line average roughness of the protective film surface 2a is 1.5 μm or less has a low noise level and a high CNR.

A magneto-optical recording medium having the above-mentioned center line average roughness smaller than 0.5 μm is not preferred because the recording film 3 is likely to peel off and the durability is poor.

Embodiment 3 FIG. 4 shows a schematic cross-sectional view of a read-only optical recording medium as another example of the optical recording medium of the present invention. The optical recording medium having the cross-sectional structure shown in FIG. 4 has a reflective film (recording film) on the substrate 6.
7 is formed, and light is irradiated from the substrate 6 side to reproduce information.

In the read-only optical recording medium shown in FIG. 4, in which a reflective film 7 made of A12 (thickness: 100 mm) is formed on a substrate 6 made of polycarbonate resin, the center line of the substrate surface 6a on the side of the reflective film 7 The relationship between the average roughness and the noise level of the read-only optical recording medium was measured, and the results are shown in FIG.

As is clear from FIG. 5, a read-only optical recording medium in which the center line average roughness of the surface 6a of the substrate is 0.7 μm or less has a low noise level and a high CNR. Similarly, read-only optical recording media having a center line average roughness of less than 0.3 .mu.m are inferior in durability.

Example 4 In a stamper used to mold the substrate l of a magneto-optical recording medium having the same structure as in Example 1, the center line average roughness of the transfer surface to the substrate l and the magneto-optical recording medium have The relationship with the noise level was measured and the results are shown in FIG. In this magneto-optical recording medium, the center line average roughness of the substrate surface 1a on the side of the recording film 3 is 0.5 μm1 The center line roughness of the surface 2a of the protective film 2 in contact with the recording film 3 was 1.0 μm.

As is clear from FIG. 6, the magneto-optical recording medium manufactured using a stamper whose center line average roughness of the transfer surface to the substrate l is 0.5 μm or less has a low noise level and a high jCNR. have

In Examples 1.2 and 4, a magneto-optical recording medium was used which was initialized by applying a bias magnetic field of 5000e and rotating it at a linear velocity of 10 m/s before irradiating it with laser light (intensity: 9 mW). The nozzle level was measured. In Example 3, a read-only optical recording medium was rotated at a linear velocity of 1.2 m/s, and the noise level was measured for a signal of 780 k[Iz].

The center line average roughness was measured using a scanning tunneling microscope (STM: Sca
nnning Tunnelling Microsco
pe) was used.

As the substrate l in the magneto-optical recording medium having the cross-sectional structure shown in FIG. 1, amorphous polyolefin resin, polymethyl methacrylate resin, epoxy resin, glass, etc. can also be used. The materials constituting the protective film 2 and the protective film 4 include SiN, AffN, and A12.
It may also be SiN, Al25iON%Sin, ZnS, or the like. The recording film 3 is TbFe, TbDyF.
e.

It is preferable to use an amorphous alloy consisting of a rare earth element such as GdDyFe, GdTbFe, or GdFeCo and a transition metal. The reflective film 5 is Au, Ag5
Made of Pt etc. or Ti5Cr, In, C
It consists of an alloy made by adding u etc. to these. The thickness of the protective film, recording film, etc. can be determined depending on their optical properties, but usually the lower protective film 2 has a thickness of HO to 16DO, the recording film 3 has a thickness of 200 to 400, and the upper layer has a thickness of HO to 16DO. 300 to 800 people for film 4 and 300 for reflective film 5
The preferred range is 700 people. Each of the above films can be formed by sputtering.

The magneto-optical recording medium has been explained in detail above, but the optical recording medium according to the present invention includes a phase change type rewritable type,
Includes write-once type and read-only type. For phase change type rewritable optical recording media, In5bTeSG
Chalcogenite-based amorphous metals such as eTeSb are used as recording films, and in write-once optical recording media, anine dyes and TeC are used.

Te01TeSePb or the like is used as the recording film.

In a read-only optical recording medium, a recording film consisting of ^a in which information is recorded as pits is usually used.

[Effects of the Invention] According to the invention, an optical recording medium can be obtained that does not have a multilayered structure and has a high CNR. Also, a stamper for use in manufacturing the above-mentioned optical recording medium can be obtained.

[Brief explanation of drawings]

1st EiU is a schematic cross-sectional view showing one example of the optical recording medium of the present invention, FIG. 2 is a diagram showing the relationship between the center line average roughness of the substrate surface on the recording film side and the noise level of the magneto-optical recording medium, FIG. 3 is a diagram showing the relationship between the center line average roughness of the surface of the protective film in contact with the recording film and the noise level of the magneto-optical recording medium, and FIG. 4 is another example of the optical recording medium of the present invention.
A schematic cross-sectional view showing an example, FIG. 5 is a diagram showing the relationship between the center line average roughness of the substrate surface on the reflective film side and the noise level of the read-only optical recording medium, and FIG. 6 is the substrate surface of the stamper. FIG. 3 is a diagram showing the relationship between the center line average roughness of the transfer surface and the noise level of the magneto-optical recording medium. 1.6...Substrate, 2.4...Protective film, 3
...recording film, 5 ...reflection film, 7 ...
Reflective film (recording film). Patent applicant RiRa Shi Co., Ltd.

Claims (1)

[Claims] 1. An optical recording medium comprising a substrate and a recording film, characterized in that the centerline average roughness of the substrate surface on the recording film side is in the range of 0.3 to 0.7 μm. 2. It has a structure in which a substrate, a protective film, and a recording film are sequentially laminated, and is characterized in that the center line average roughness of the surface of the protective film in contact with the recording film is in the range of 0.5 to 1.5 μm. optical recording medium. 3. The stamper used for manufacturing an optical recording medium according to claim 1 or 2, wherein the center line average roughness of the transfer surface of the optical recording medium to the substrate is 0.5 μm or less.