JPH0547040A - Optical recording medium - Google Patents

Abstract

PURPOSE: To prevent a light absorption track from being disordered in the protection zone of a recording medium and make it possible to record information afterward by making a 1st area less in reflectance factor than a 2nd area which is different in thickness. CONSTITUTION: The optical recording medium is formed by adhering a track layer 20 onto a light reflecting layer 16, boring the track layer 20, and adhering a light-absorbing layer 24 thereupon. In this case, the photosensitive layer 18 of the medium 1 has the track layer 20 which has >=1 hole and the light- absorbing layer which covers the track layer 20 and the holes in it, and consequently the 1st and 2nd areas which are different in reflectance factor are formed. Further, optical characteristics of >=1 part in the 1st area which is lower in reflection factor are made different from those of the remaining part to record information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and an information recording body having a photosensitive layer having spatially varying optical characteristics, which is useful for radial tracking of information, and a manufacturing method thereof.

[0002]

U.S. Pat. No. 4,097,895 discloses a two-layer optical recording medium having a light-reflecting layer coated with a light-absorbing layer. U.S. Pat. No. 4,216,501 discloses a three-layer optical recording medium in which a transparent interposing layer is sandwiched between the reflecting layer and the light absorbing layer. Information is recorded on both media by locally changing the optical characteristics of the medium by changing the optical characteristics of the light-absorbing layer by, for example, melting or ablating, and the transmittance of the medium at the exposed portion caused by this or The recorded information is read by detecting the change in reflectance.

Such recording media are substantially uniform in structure and optical properties prior to exposure and have no means of forming or tracking tracks prior to recording information. Although a recording medium having a groove formed in advance has such means, it does not have the freedom to change the arrangement of tracks or markers after manufacturing. The method of removing a part of the absorption layer with a laser beam to form a protective band between the absorption tracks has this degree of freedom, but the track may be damaged by the formation of this protective band, and it will be recorded on the protection band at a later date. It is not possible. Therefore, it is desirable that the light absorption track is not disturbed in the protective zone of the recording medium and information can be recorded at a later date.

[0004]

SUMMARY OF THE INVENTION In an improved optical recording medium according to the present invention, the photosensitive layer has a tracking layer having one or more apertures, a tracking layer and a light absorbing layer covering the apertures therein.
As a result, the first and second regions having different thicknesses are formed so that the reflectance of the first region is lower than that of the second region.

The method of the present invention comprises the steps of sequentially depositing a reflective layer and a tracking layer on a substrate, forming one or more holes in the tracking layer, and overlying the tracking layer and the holes. Depositing a light absorbing layer.

[0006]

DETAILED DESCRIPTION In FIG. 1, an optical recording medium 10 includes a substrate 12, an underlayer 14 that covers a flat surface of the substrate 12, a light reflection layer 16 that covers the surface of the underlayer 14, and a surface of the light reflection layer 16. A tracking layer 2 covering one or more apertures 22
0 and a light absorption layer 24 covering the tracking layer 20 and the reflection layer 16 in the opening 22.
6 and a photosensitive layer 18 forming a protective band 28.

The reference numerals of the respective parts of the optical recording medium 30 and the information recording bodies 40 and 50 of FIGS. 2 to 4 are the same as those of the corresponding parts of the optical recording medium 10 of FIG.

The optical recording medium 30 of FIG. 2 has an interposing layer 32 between the reflective layer 16 and the photosensitive layer 18, a barrier layer 34 on the light absorbing layer 24, and an overlayer 36 on the barrier layer 34. ..

Information recording bodies 40 and 5 shown in FIGS. 3 and 4.
0 is the optical recording medium 10 of FIG. 1 and FIG. 2 in which information is recorded in a format in which one or more regions 42 of the light absorbing layer 24 in the recording track 26 have different optical characteristics from the remaining regions. It comprises a recording medium 30. The difference in the optical characteristics of each region 42 of the photosensitive layer 18 may be due to irreversible deformation such as pores and bubbles of the light absorbing layer 24, and, for example, US Pat. No. 2,544,469 of April 16, 1981.
It may be due to a reversible change of the optical constant of the light absorption layer 24, such as a change in the crystallinity of the light absorption layer as disclosed in the specification.
The reflectance of the recording medium changes depending on whether or not the optical characteristics of the photosensitive layer 18 change, and the length and interval of the region 42 display the recorded information.

Information such as the track identification number may be recorded on the protective band 28 before or after the information is recorded on the recording track 26. Such information may include one or more areas 44 having different optical properties from the rest of the guard band 28.
Can be composed of

Substrate 12 can be made of glass, a plastic material such as polyvinyl chloride or polymethylmethacrylate, or a metal such as aluminum. The underlayer 14 is a non-conformal coating of a plastic material such as epoxy or acrylic resin, which has a microscopically smooth surface and is applied to the surface of the substrate 12 prior to the application of the reflective layer 16.

The reflective layer 16 reflects a substantial portion of the incident light of the wavelength of the recording light beam, preferably at least 50%,
It is composed of a metal such as aluminum or gold or a multilayer dielectric reflective film.

The interposing layer 32 of the recording medium 30 is substantially transparent and non-scattering at the recording and reading wavelengths,
Suitable materials for this layer include organic materials such as fluorocarbon and hydrocarbon polymers and inorganic materials such as oxides of silicon, titanium, magnesium and aluminum. These materials can be deposited on the reflective layer 16 using deposition methods known to those skilled in the art.

The tracking layer 20 is light absorbing at the wavelengths used to form the apertures and may be formed of organic or inorganic materials, with suitable inorganic materials including bismuth, titanium, rhodium, tellurium, selenium and tellurium or selenium. There is a chalcogenide alloy. The thickness of the tracking layer 20 may be about 20 to 150 nm, but is preferably such that the combined reflectance of the reflective layer and the tracking layer decreases at the wavelength for forming the apertures 22. The shape of the apertures 22 may be continuous or intermittent circular or spiral groove.

The light absorbing layer 24 is made of a material that is sensitive to the recording light beam, and the material can be an organic or inorganic material. Suitable inorganic materials include bismuth, rhodium, titanium, tellurium, selenium and chalcogenide alloys of tellurium and selenium. The light absorption layer 24 in the recording track 26 has a reflectance of the optical recording medium 10 or 30 which is the track 2
It has a thickness that decreases according to the anti-reflective state in 6 and is preferably the minimum. In the case of the optical recording medium 10, the optimum thickness can be determined from the optical constants at specific wavelengths of the reflective layer 16, the light absorbing layer 24 and all overlayers by methods known to those skilled in the art, generally at about 20-100 nm. is there. The sum of the thicknesses of the tracking layer 20 and the light absorbing layer 24 in the protective band 28 is selected so that the reflectance at that specific wavelength is higher than that of the recording track 26.

In the case of the optical recording medium 30, the thickness of the light absorbing layer 24 can be determined from the thickness of the interposing layer 32 and the optical constants of the reflecting layer 16, the interposing layer 32, the light absorbing layer 24 and all the upper layers. , Generally about 3-100 nm.

The barrier layer 34 is made of a translucent material that forms a thermochemical barrier between the light absorbing layer 24 and the overlayer 36, and is an oxide of aluminum, magnesium, silicon or titanium having a thickness of about 50 to 500 nm. It is preferably composed of a thing.
The overlayer 36 preferably comprises a light transmissive material such as silicone rubber having a thickness of 500-1500μ. Such a combination of barrier layer and overlayer is disclosed in US Pat. No. 4,101,907.

The present invention provides a recording medium having a thick portion and a thin portion in its photosensitive layer, and exhibiting different reflectances due to the difference in the thickness. The embodiment described above has a thickness such that the light-absorbing layer in the recording track has a lower reflectance than that in the protective zone. The reverse structure, which includes a tracking layer and a light-absorbing layer with optical constants and thicknesses such that the recording track and protective band are opposite and the reflectance in the protective band is lower than that in the recording track, is also useful. However, since the amount of the material in the recording track that should be changed into the recording information by melting, ablation, etc. is small, the first embodiment is recommended. Also, information is recorded on the material layer without disturbance after deposition, but the tracking layer may be damaged during the groove formation process.

During the operation of the optical recording, reproducing or erasing method, a recording, reproducing or erasing light beam is focused on the track. Since the reflectances of the two regions of the optical recording medium and the information recording medium of the present invention are different, the radial displacement of this beam or the track sensing beam is detected as a change in the reflection intensity of the beam. This change can be converted into an electric signal proportional to the displacement of the beam with respect to the track and used for position correction of the recording, reproducing or erasing light beam.

The method for producing an optical medium of the present invention comprises the steps of applying an undercoat layer to the surface of a substrate, applying a light reflecting layer to the surface of the undercoat layer, and applying the light reflecting layer onto the light reflecting layer. Depositing a tracking layer of light absorbing material, forming one or more apertures in the tracking layer, depositing a light absorbing layer on and in the tracer layer, The step of depositing a barrier layer and an overlayer over the light absorbing layer. The openings can also be formed by ablation using a laser light beam having the same wavelength as or a wavelength different from the wavelength used for recording information later, or by melting and pulling back the material, and a photoengraving method or a chemical etching method known to those skilled in the art. Can also be formed.

[Brief description of drawings]

FIG. 1 is a perspective view of a part of a two-layer optical recording medium of the present invention.

FIG. 2 is a partial sectional view of a three-layer optical recording medium of the present invention.

FIG. 3 is a partial sectional view of an embodiment of the information recording medium of the present invention.

FIG. 4 is a partial cross-sectional view of another embodiment of the information recording medium of the present invention.

[Explanation of symbols]

 12 substrate 16 light reflecting layer 18 photosensitive layer 20 tracking layer 22 apertures 24 light absorbing layer

Claims (12)

[Claims] 1. A planar light-reflecting layer, a tracking layer that covers the light-reflecting layer and has one or more openings, and the light-reflecting layer portion within the openings of the tracking layer and the tracking layer. And a light-absorbing layer having a substantially uniform thickness for covering the concave-convex shape and the light-absorbing layer and the tracking layer each having a thickness of the first region of the optical recording medium at a specific wavelength. The reflectance is selected to be smaller than the reflectance of the second region, and the optical characteristics of one or more portions in the first region are different from those of the rest of the first region. An optical recording medium on which information is recorded. 2. A transparent interposing layer is disposed between the light reflecting layer and the light absorbing layer, and the thicknesses of the light reflecting layer, the light absorbing layer and the interposing layer are the above at a specific wavelength. The optical recording medium according to claim 1, wherein the reflectance of the first region is selected to be smaller than the reflectance of the second region. 3. The optical recording medium according to claim 2, wherein the interposing layer is disposed between the light reflecting layer and the tracking layer. 4. The first region comprises an optical recording medium portion including an opening of the tracking layer, and the thickness of the light absorption layer in the first region is the first region at a specific wavelength. The optical recording medium according to claim 1, wherein the optical recording medium is selected so as to have a minimum reflectance and an antireflection state. 5. A transparent interposing layer is disposed between the light reflecting layer and the light absorbing layer, and the thicknesses of the light reflecting layer, the light absorbing layer and the interposing layer are the above at a specific wavelength. The optical recording medium according to claim 4, wherein the optical recording medium is selected so that the reflectance of the first region is minimized to provide an antireflection state. 6. The optical recording medium according to claim 5, wherein the interposing layer is disposed between the light reflecting layer and the tracking layer. 7. The optical recording medium according to claim 1, wherein each of the one or more portions in the first region includes pores in the light absorption layer. 8. The method of claim 1, wherein each of the one or more portions in the first region comprises a material having an optical constant different from that of the material forming the remainder of the first region. Optical recording medium. 9. Information is recorded in the second area by one or more portions of the second area having different optical properties than the rest of the second area. The optical recording medium according to claim 1, wherein 10. A light reflection layer is deposited on the surface of a substrate, a tracking layer having openings is formed on the light reflection layer, and the light reflection in the tracking layer and the openings of the tracking layer is performed. A method of manufacturing an optical recording medium, which comprises the step of forming a light absorption layer that covers the layer portion in conformity with the concavo-convex shape. 11. The method according to claim 1, further comprising the step of forming a transparent interposing layer covering the light reflecting layer before forming the light absorbing layer.
0. The manufacturing method as described in 0. 12. The manufacturing method according to claim 11, wherein the holes in the tracking layer are formed by irradiating a light beam to ablate the tracking layer.