JP2506771B2 - Optical information recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable optical disc as a recording medium used in an information recording / reproducing apparatus using a laser beam, and provides a configuration for improving the rewriting characteristics thereof.

2. Description of the Related Art Phase change type optical disks and magneto-optical disks are known as optical disks capable of recording, reproducing and erasing signals. In the case of a phase change type optical disk, a signal is recorded by setting the crystalline state of the recording material to an unrecorded state and rapidly heating and chilling by irradiation of a laser spot to an amorphous state. Then, by rapid heating and slow cooling, the crystalline state is restored again and the recorded signal is erased. In addition, a transparent layer is provided adjacent to the recording layer for the purpose of protecting the recording layer from ambient components such as oxygen and water, adjusting the path length of light, and increasing the amount of change in reflected light before and after recording. Sometimes. Further, a reflective layer may be provided for the purpose of increasing the light absorption efficiency of the recording layer.

Problems to be Solved by the Invention Erasure of a recording signal in the above optical information recording medium is performed by continuously irradiating an erasing beam on a rotating recording medium. At this time, the recording medium may be damaged when the erasing beam passes over the address signals provided on the substrate in an uneven shape. For example, if the laser power of the erase beam changes accidentally, it will be damaged,
As a result, the address signal may not be recognized. This is because the concavo-convex portion is most likely to be destroyed due to the local stress caused by the temperature rise due to the beam irradiation. Therefore, it is not possible to obtain sufficient repetition of recording and erasing.

Means for Solving the Problems The present invention provides, as means for solving the above-mentioned problems,
A disk-shaped optical information recording that has a recording layer that absorbs light and causes a physical or chemical change on a substrate that has an address signal, and that irradiates a light beam to record / erase / reproduce information spirally or concentrically. In the medium, the absorption efficiency of the erase beam in the recording layer in the area where the address signal exists is made smaller than the light absorption efficiency of the erase beam in the recording layer in the area where the address signal does not exist.

Function In the disc-shaped optical information recording medium, the light absorption efficiency is made different in the circumferential direction of the recording medium, and the portion where the address signal is provided is the portion having the low light absorption efficiency. The existing local stress concentration disappears. As a result, the address signal is not damaged due to repeated recording / erasing, and the repeated life is remarkably improved.

EXAMPLES The present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of the optical information recording medium of the present invention.
FIGS. 1- (b) to (d) are enlarged cross-sectional views of the concentric AA 'portion shown in FIG. 1- (a). FIG. 1- (b) shows an example in which the film thickness of the recording layer is selectively different at a specific position in the circumferential direction of the recording medium, and FIG. 1- (c) shows the film thickness of the transparent layer in the circumferential direction of the recording medium. Example of selectively different in a specific place of
FIG. 9D shows an example in which the film thickness of the reflective layer is selectively different at a specific location in the circumferential direction of the recording medium.

As the substrate 1, a resin having a smooth surface such as resin such as PMMA or polycarbonate or glass is used. In the case of an optical disc, the substrate plane 8 is usually covered with spiral or concentric tracks to guide the laser light.

As the material of the recording layer 3, a substance such as a chalcogenide alloy based on Ge.Te, Se or the like that causes a reversible structural change between a crystalline state and an amorphous state based on a thermal process is used. be able to. When a substance that causes a reversible structural change between a crystalline state and an amorphous state based on a thermal process is used as the recording material, the recording material is in the unrecorded state when it is in the crystalline state, and when the laser spot is irradiated. A signal is recorded by rapidly quenching to an amorphous state. Next, rapid heating and rapid cooling results in a crystalline state, and the recorded signal is erased. Laser light for amorphizing the recording material and writing a signal is called a recording beam, and laser light for crystallizing and erasing a signal is called an erasing beam.

The materials for the transparent layers 2 and 4 are Al ₂ O ₃ , SiO, SiO ₂ , TeO ₂ and M.
_{oO 3, WO 3, BiF 3} , PbF 2, MgF 2, ZnS, choosing a dielectric or their suitable combination of SiN or the like. The function of these layers is 1
One is to prevent the recording layer 3 from being destroyed when recording and erasing are repeated, and one is to enhance the light absorption efficiency to the recording layer 3 by utilizing the multiple interference effect. At the same time, the amount of change in reflected light or transmitted light before and after recording is increased to obtain a high S / N.

The reflective layer 5 is made of a metal element such as Au, Ni, Fe, Cr, or an alloy thereof, and has a function of increasing the light absorption efficiency of the recording layer 3. The protective substrate 7 is formed by spin coating a resin,
A resin plate, a glass plate, a metal plate, or the like similar to the base material is formed by adhering it with the adhesive 6.

Furthermore, a structure capable of recording, reproducing, and erasing from both sides may be realized by bonding two sets of recording media with the intermediate substrate or the reflective layer inside, using an adhesive.

Each layer is formed by an electron beam evaporation method, a sputtering method, an ion plating method, a CVD method, or the like. FIG. 2 shows an outline of film formation. The substrate 1 is fixed to the substrate supporting jig 9, and vapor deposition is performed from the vapor deposition source 10 while rotating to obtain a desired film on the substrate 1. At this time, the film thickness of the vapor deposition film can be selectively changed at a specific location in the circumferential direction by devising the shape of the substrate supporting jig. For example, a substrate supporting jig 11 as shown in FIG. 3 is used. No film is formed on a portion of the substrate which is in the shadow of the mask 12, and a mask 14 having a large number of holes 13 is formed.
A film is formed in a shadowed area of the mask thinner than in a shadowed area of the mask.

Using the above-mentioned substrate supporting jig with a mask, a disc-shaped optical information recording medium having different light absorption efficiencies in the recording layer at a specific position in the circumferential direction was prepared, and repeated recording / erasing tests were conducted. However, by lowering the light absorption efficiency in the recording layer where the address signal is provided compared to other areas, damage to the address signal due to repeated recording and erasing does not occur, and the repeated life can be significantly improved. It was confirmed experimentally.

 The present invention will be described in detail below with reference to specific examples.

Example 1 As shown in FIGS. 4- (a) and (b), recording media having different recording layer 17 film thicknesses were prepared at specific circumferential positions. 1.2 mm thick polycarbonate resin as the substrate 15, ZnS as the material of the first transparent body layer 16 and the second transparent body layer 18, (Te ₆₅ Ge ₂₅ Se ₁₀ ) ₇₀ Sb ₃₀ as the material of the recording layer 17, reflection Ni-40% Cr is used as the material of the layer 19.

A first transparent layer, a recording layer, a second transparent layer, and a reflective layer are sequentially formed on a substrate by an electron beam evaporation method. The film thickness of each layer depends on the wavelength λ (83
0 nm) and the refractive index n of each layer. The film thickness of the first transparent body layer is 5λ / 16n, the film thickness of the second transparent body layer is λ / 2n, and the film thickness of the reflective layer is 40 nm. The thickness of the recording layer is 4- (b)
Only the part of the address signal area I shown in the figure is 30 nm, the address signal area I
At other locations including I, the thickness was 40 nm. Repeat the recording and erasing of the obtained recording medium by changing the location one million times 5
I went to 0 places. As a result, in the area I, the damage of the address signal part did not occur after repeating 1 million times in all 50 places, whereas in the region II, the address signal part was damaged in 7 places out of 50, and the address recognition was unsuccessful. It became possible, and recording / erasing could not be repeated up to 1 million times.

Next, the optical characteristics will be described. The refractive index n and the extinction coefficient k of each layer are obtained in advance by an experimental method, and by giving these values and the film thickness of each layer, the light of the laser beam having a wavelength of 830 nm in the recording layer of the recording medium having the above-described structure is obtained. The absorption efficiency was calculated. In Table 1, n of each layer used for calculation,
k, Table 2 shows the calculation results.

From the above results, when the portion where the address signal is provided is the thin portion of the recording layer-that is, the portion where the light absorption efficiency in the recording layer is low-there is no damage to the signal portion after 1 million repetitions. On the other hand, when the light absorption efficiency in the recording layer is sufficiently high even in the area where the address signal is provided, it can be seen that the address signal is damaged after 1 million repetitions. That is, by making the portion where the address signal is provided a portion having a low light absorption efficiency, the local stress concentration existing in the address signal portion in the conventional structure is eliminated, and as a result,
Distortion of the address signal portion due to repeated erasing is eliminated, and repeated life and reliability are significantly improved.

Example 2 As shown in FIGS. 4- (a) and (c), recording media having different transparent layer 18 film thicknesses were prepared at specific circumferential positions.
1.2 mm thick polycarbonate resin as the substrate 15, ZnS as the material of the first transparent body layer 16 and the second transparent body layer 18, (Te ₆₅ Ge ₂₅ Se ₁₀ ) ₇₀ Sb ₃₀ as the material of the recording layer 17, reflection Ni-40% Cr is used as the material of the layer 19.

A first transparent layer, a recording layer, a second transparent layer, and a reflective layer are sequentially formed on a substrate by an electron beam evaporation method. The film thickness of each layer depends on the wavelength λ (83
0 nm) and the refractive index n of each layer. The thickness of the first transparent layer is 5λ / 16n, the thickness of the recording layer is 40 nm, and the thickness of the reflective layer is 40 nm. The thickness of the second transparent layer is λ / 4n only in the address signal area I shown in FIG. 4- (c), and the address signal area II.
In other places including, it was set to λ / 2n. Recording and erasing of the obtained recording medium were performed 1 million times at 50 locations by changing locations. The shape of the recording beam was circular and the power was 8 mW, and the shape of the erasing beam was elliptical and the power was 18 mW. As a result, in the area I, the damage of the address signal did not occur after repeating 1 million times at 50 points, but in the area II, the address signal part was damaged at 11 points of the 50 points and the address recognition was impossible. Therefore, recording / erasing could not be repeated up to 1 million times.

From the above results, when the part where the address signal is provided is the thin part of the second transparent body layer-that is, the part where the light absorption efficiency in the recording layer is low-the damage of the signal part is seen after 1 million repetitions. On the other hand, if the light absorption efficiency in the recording layer is sufficiently high, the area where the address signal is provided is 10
It can be seen that the address signal is damaged after repeating 0,000 times. That is, by making the portion where the address signal is provided a portion having low light absorption efficiency, the local stress concentration existing in the address signal portion in the conventional structure is eliminated, and as a result, the distortion due to repeated recording and erasing is eliminated. The address signal part is not damaged, and the life and reliability are remarkably improved.

Example 3 As shown in FIGS. 4- (a) and (d), recording media having different film layers of the reflective layer 19 were prepared at specific locations in the circumferential direction. 1.2 mm thick polycarbonate resin as the substrate 15, ZnS as the material of the first transparent body layer 16 and the second transparent body layer 18, (Te ₆₅ Ge ₂₅ Se ₁₀ ) ₇₀ Sb ₃₀ as the material of the recording layer 17, reflection Ni-40% Cr is used as the material of the layer 19.

A first transparent layer, a recording layer, a second transparent layer, and a reflective layer are sequentially formed on a substrate by an electron beam evaporation method. The film thickness of each layer depends on the wavelength λ (83
0 nm) and the refractive index n of each layer. The film thickness of the first transparent body layer is 5λ / 16n, the film thickness of the recording layer is 40 nm, and the film thickness of the second transparent body layer is λ / 2n. The thickness of the reflective layer is 4- (d)
Only the address signal area I shown in the figure is 0 nm, address signal area II
In other places including, it was set to 40 nm. Repeat the recording and erasing of the obtained recording medium by changing the location by 1 million times 50
Went in places. The recording beam has a circular shape with a power of 8 mW,
The shape of the erase beam was elliptical and the power was 18 mW. As a result, in the area I, the damage of the address signal part did not occur after repeating 1 million times in 50 locations, whereas in the area II,
The address signal part was damaged at 11 of the locations, making it impossible to recognize the address, and recording / erasing could not be repeated up to 1 million times. From the above results, when the part where the address signal is provided is the thin part of the reflection layer-that is, the part where the light absorption efficiency in the recording layer is low-there is no damage to the signal part after 1 million repetitions. On the other hand, when the light absorption efficiency in the recording layer is sufficiently high even in the area where the address signal is provided, it can be seen that the address signal is damaged after 1 million repetitions. That is, by making the portion provided with the address signal a portion having low light absorption efficiency, the local stress concentration existing in the address signal portion in the conventional structure is eliminated, and as a result, distortion due to repeated recording and erasing is eliminated. The address signal part is not damaged, and the life and reliability are remarkably improved.

EFFECTS OF THE INVENTION As described above, according to the present invention, a recording medium having an excellent repeated life of recording / erasing as compared with the conventional optical information recording medium is provided.

Based on this effect, it can be applied to, for example, a computer file / memory for image processing.

[Brief description of drawings]

FIG. 1 (a) is a plan view of the optical information recording medium of the present invention, FIGS. 1 (b), (c) and (d) are sectional views of the same medium, and FIG. 2 is an optical information recording medium of the present invention. FIG. 3 is a schematic view of an apparatus for manufacturing, FIG. 3 is a plan view of a substrate supporting jig used in manufacturing the optical information recording medium of the present invention, and FIG. 4 (a) is subjected to repeated recording / erasing test. FIGS. 3A and 3B are views showing recording media having various configurations, and FIGS. 6B, 6C, and 6D are cross-sectional views of the media. 20: adhesive, 21: protective substrate, 22: information recording signal,
23 …… Bell jar, 24 …… Exhaust device, 25 …… Address signal.

Claims (4)

(57) [Claims] 1. A recording layer which absorbs light and causes a physical or chemical change is provided on a substrate having an address signal, and a light beam is irradiated to record / erase information in a spiral or concentric pattern.
In the disc-shaped optical information recording medium to be reproduced, the absorption efficiency of the erasing beam in the recording layer in the area where the address signal exists is smaller than the light absorption efficiency of the erasing beam in the recording layer in the area where the address signal does not exist. An optical information recording medium characterized by: 2. The film thickness of the recording layer is selectively different in the area where the address signal is present.
An optical information recording medium according to the item. 3. An optical information recording medium having a transparent body layer for adjusting the optical path length of light so as to increase the amount of change in reflected light before and after recording, wherein the transparent body layer has a film thickness and an address signal exists. The optical information recording medium according to claim 1, wherein the optical information recording medium is selectively different in the area. 4. An optical information recording medium having a reflective layer for increasing the light absorption efficiency to the recording layer, wherein the thickness of the reflective layer is selectively different in the area where the address signal exists. The optical information recording medium according to claim 1.