JP2000268403A - Optical information recording medium and reproducing device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure good repetitive recording performance and to easily attain total erasure of information by forming a recording layer with a phase change material whose crystallization temperature is a specified value or below in measurement at a prescribed beating rate. SOLUTION: The recording layer of a rewritable optical information recording medium which records, erases or reproduces information by irradiation with laser light is formed with a phase change material whose crystallization temperature is <=130 deg.C in measurement at 10 deg.C/min heating rate. The phase change material is preferably based on a compound of the formula (where 0.65<=X<=0.8). A mark recorded on the resulting recording layer is erased with heat at about 80 deg.C in a relatively short time. The optical information recording medium has a mechanism by which it can be discriminated from another kind of optical information recording medium. A means of giving a user to understand that the temperature of a place in which the optical information recording medium is set approaches a temperature range in which the record may be erased is provided to the medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical information recording medium and an optical information recording / reproducing apparatus suitable for use thereof.

[0002]

2. Description of the Related Art Hitherto, there has been known a phase change type optical information recording medium (optical disk) utilizing a phase transition between an amorphous phase and a crystalline phase and utilizing the change in reflectivity resulting therefrom.
In this optical information recording medium, when information is to be written by amorphousization, the entire recording film must be in a state of being crystallized in advance. Here, at least a part of the recording film of the optical information recording medium immediately after being formed by the vacuum evaporation method or the sputtering method is in an amorphous state or in a metastable crystalline state. Therefore, it is necessary to completely crystallize the entire recording film (initial crystallinity) before writing information to this. Further, in order to completely erase the information once recorded on the recording film of the optical information recording medium, it is necessary to crystallize the entire recording film.

Japanese Patent Application Laid-Open No. 62-20153 discloses a method of heating the entire optical information recording medium using an oven or the like and crystallizing the recording film, or using a high-power laser such as an Ar laser. Irradiation heating of the recording film of the information recording medium,
A method for crystallizing the recording film is described.

When a track is erased one track at a time using a high-power laser in a normal optical information recording / reproducing apparatus (drive), a DVD has recently been put into practical use for about 30 minutes even with a CD.
In this case, it takes about 2 hours. In the future, development of optical information recording media having a larger capacity will be advanced, and the time required for full erasure will be further increased. Like an initialization device, which is one of the manufacturing devices for optical disks, it is possible to erase the entire surface in a relatively short time by using a wide laser,
Due to the cost, it is difficult for a user to own such a device. Therefore, when the number of optical information recording media on which unnecessary information is recorded is small, it is possible to erase the entire surface with the reproducing apparatus and reuse it. In many cases, the optical information recording medium is crushed or scratched to prevent data from being read, and is often discarded.

When data is erased by heating, the data is erased in a short time, so that it is heated at a high temperature, so that not only data is erased, but also the substrate is deformed and cannot be reused. Often done. It is not desirable from the viewpoint of resources, energy, and waste disposal that the optical information recording medium is originally discarded without being used up to its life.

To address these problems, Japanese Patent Laid-Open Publication No.
JP-A-52578 discloses that a heater film is provided on an optical information recording medium, and the initial crystallization of the recording film or the entire erasure of the recording is completed in an extremely short time as compared with the related art by heating the optical film. I have. However, in the present invention, since it is necessary to provide an insulating film and a heater film on the reflective film, the number of manufacturing steps increases, and the manufacturing cost increases.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide good repetitive recordability, easy erasure of all information,
An object of the present invention is to provide an optical information recording medium which can be used repeatedly even after erasing the entire surface, and an optical information recording / reproducing apparatus for using it with high reliability.

[0008]

SUMMARY OF THE INVENTION A first aspect of the present invention is to provide a rewritable optical information recording medium in which information is recorded, erased, and reproduced by irradiating a laser beam. Crystallization temperature of 130 ° C.
The present invention relates to an optical information recording medium characterized by being formed of a phase change material having a temperature of not more than ° C.

According to the present invention, the formed recording layer is kept at 10 ° C.
/ Min. When a phase change material having a crystallization temperature of 130 ° C. or less as measured by DSC (differential scanning calorimetry) is used, the recording mark disappears in a relatively short time with heat of about 80 ° C.

As such a phase change material, Sb_xT
e_(1-x), Sn₅Sb₇₀Te ₂₅(Tc = 123
℃), Au_3.5Sb₆₈Te_28.5(Tc = 121
℃), Ag_3.5Sb₆₈Te_28.5(Tc = 129
° C) and the like.
formula

Embedded image A compound represented by Sb _x Te _1-x (0.65 ≦ X ≦ 0.8) is preferable. By using such a phase-change material as the recording layer of the optical information recording medium of the present invention, the recording mark disappeared in a relatively short time with heat of about 80 ° C.

FIG. 1 shows a typical configuration example of the optical information recording medium of the present invention. This optical information recording medium comprises a heat-resistant protective layer 2, a recording layer 3, a heat-resistant protective layer 4, a reflective heat-radiating layer 5 on a substrate 1.
Is provided.

The material of the substrate is usually glass, ceramics or resin, and a resin substrate is suitable in terms of moldability and cost. Representative examples of the resin, polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin,
Polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin and the like are mentioned, but polycarbonate resin and acrylic resin are preferable in view of workability, optical characteristics and the like.

The material of the heat-resistant protective layer is Si
O, SiO ₂ , ZnO · SnO ₂ , Al ₂ O ₃ , TiO
₂ , metal oxides such as In ₂ O ₃ , MgO, ZrO ₂ ,
Nitrides such as Si ₂ N ₄ , AlN, TiN, BN, and ZrN; sulfides such as ZnS, In ₂ S ₃ and TaS ₄ ;
Examples thereof include carbides such as C, TaC, B ₄ C, WC, TiC, and ZrC, diamond-like carbon, and mixtures thereof. These materials can be used alone as a protective layer, or as a mixture of each other. Further, it may contain impurities as needed. However, the melting point of the heat-resistant protective layer needs to be higher than the melting point of the recording layer. In addition, the protective layer can be multi-layered as necessary. The film thickness is 10 to 500 nm, preferably 20 to 300 nm.
nm. When the thickness is less than 10 nm, the layer does not function as a heat-resistant protective layer.
When the thickness is larger than the above, the sensitivity may be lowered, and the interface peeling may easily occur.

Since the reflective heat radiation layer must have both roles of the reflection layer and the heat radiation layer, it is formed of a material having high reflectance and high thermal conductivity to some extent. Specifically, a metal material such as Al, Au, Ag, or an alloy thereof can be used, and among them, Ti,
An Al alloy containing 1 to 3 wt% of Si, Cr and the like is suitable. The film thickness is 30 to 300 nm, preferably 50 to 2
00 nm.

Such a heat-resistant protective layer, reflective heat dissipation layer and recording layer are formed by various vapor phase growth methods, for example, a vacuum evaporation method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam evaporation method. And the like.

The optical information recording medium of the present invention is not limited to those having various layers as described above. For example, an organic protective film may be provided on a reflective heat radiation layer. Alternatively, they may be bonded by using an adhesive.

As described above, the optical information recording medium of the present invention has such a characteristic that the recording is lost only by being exposed to the heat of about 80 ° C. for a short time, so that it can be distinguished from other types of optical information recording medium. It is preferable that the optical information recording medium itself has various mechanisms. As a mechanism that can be distinguished from other types of optical information recording media, for example, holes, irregularities, marks, printing, or the like can be provided as marks on portions that are not related to recording, such as near the center of the substrate or on the outer periphery. In some cases, the mechanism may be an electrically or mechanically identifiable mechanism.

Therefore, when it is desired to perform confidential processing of recorded data on the optical information recording medium of the present invention, 5 m at 80 ° C.
In may be maintained. If there are a large number of information recording media to be subjected to confidential processing, they can be put together in a constant temperature bath and processed collectively. Further, in the case of a few sheets, it is difficult to reproduce the recording only by heating the information recording medium with a household iron or dryer.

A second aspect of the present invention is that when the temperature of the place where the optical information recording medium is set becomes a temperature area where the recording of the optical information recording medium is likely to be lost or approaches the temperature area, The present invention relates to an optical information recording / reproducing device provided with means for informing a user.
The overall playback device is not particularly limited,
What is necessary is just to add the said means to a well-known reproducing | regenerating apparatus. Known playback devices are disclosed in JP-A-9-91704 and JP-A-9-91704.
Nos. 73632 and 5-182929.

As described above, the optical information recording medium of the present invention has the property of erasing recording at a temperature of about 80 ° C. in a short time, so that a reproducing apparatus using the optical information recording medium of the present invention has such a property. It is preferable to provide a safety means for preventing any disappearance.

The temperature close to the temperature range where the recording of the optical information recording medium is likely to be lost is 50 ° C.
It is one measure.

Accordingly, one specific safety measure is to provide a warning when the temperature of the place where the optical information recording medium is set is in a temperature range where recording may be lost or approaches the temperature range. Safety measures such as notifying the user by a lamp or a buzzer can be given.

As another safety means, there is provided a means for discharging the optical information recording medium to the outside when the temperature of the place where the optical information recording medium is set reaches or approaches the temperature range. Can be mentioned.

Further, when such a condition is satisfied,
If means for reading, overwriting, and discharging data recorded on the optical information recording medium is provided, clearer recording can be maintained. These safety means can be used in combination of two or more as necessary.

[0025]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Examples 1-3, Comparative Examples 1-2 Diameter 12 cm, thickness 0.6 mm, track pitch 0.7
₂₀ (ZnS) ₈₀ (SiO ₂ ) ₂₀ as a lower heat-resistant protective layer was formed on a polycarbonate substrate having 4 μm grooves (guide grooves provided for performing tracking).
0 nm, the recording layer made of Sb _x Te _1-x (0.65 ≦ X ≦ 0.8) is 20 nm, and the upper heat-resistant protective layer is (Z
nS) ₈₀ (SiO ₂ ) ₂₀ was deposited to a thickness of 25 nm, and an Al alloy film as a reflective heat dissipation layer was deposited to a thickness of 120 nm in this order by sputtering. Further, an organic protective film made of an acrylic ultraviolet curable resin is formed on the reflective heat radiation layer by a spinner.
The composition was applied to a thickness of 10 μm to 10 μm and cured by ultraviolet rays. A polycarbonate disk having a diameter of 12 cm and a thickness of 0.6 mm was further adhered to this surface with an adhesive sheet to obtain a sample.

After the recording layer of the sample is crystallized (initialized) by a semiconductor laser, a linear density of 0.267 μm is obtained.
An amorphous mark having a random pattern of 3T to 14T was recorded, and the change over time in jitter was evaluated. Evaluation,
A pickup having a wavelength of 635 nm and an NA of 0.6 was used.
Since the optimum recording linear velocity differs depending on the recording film composition,
Recording was performed with a strategy and recording power such that the initial jitter σ was smaller than 3.5 ns in all cases at an optimum linear velocity in the range of 9.0 to 9.0 m / s. All reproductions are performed at a linear speed of 3.
The test was performed at 5 m / s.

Table 1 shows the composition of the recording layer of the present embodiment, the composition of the recording layer for comparison, and the value of the jitter σ after the optical information recording media of the examples and comparative examples were held in a constant temperature bath at 80 ° C. Is shown. In the comparative example, little change was observed in the jitter, whereas in the case of the example, 5 min. It can be seen that the jitter increases sharply even to the extent that reproduction is difficult. From a security standpoint, it is sufficient to erase this level. As a precaution, when it is desired to completely crystallize and erase the recording mark, it is achieved by holding the recording mark for a longer time. When the recording mark was kept for 24 hours, it was confirmed that the recording mark was completely crystallized and was erased, but it is presumed that the recording mark was actually completely crystallized in several hours. In the case of the comparative example, almost no change in jitter was observed even after 24 hours. In any of the examples, no increase in jitter was observed when the measurement was carried out after being left at room temperature for 6 months. Therefore, in normal use, there is no problem in normal use if care is taken in storage temperature control.

[0029]

[Table 1]

[0030]

According to the present invention, the recording layer is crystallized by performing the heat treatment at a temperature of about 80 ° C. for several minutes, thereby making it difficult to reproduce data easily. In contrast to the second aspect, the recording performance is good, and there is no problem in rewriting after erasing by heat. According to the third aspect, the safety management of the optical information recording medium during storage or use can be easily performed. Appropriate processing can be performed so that data is not lost during recording and reproduction by the optical information recording medium reproducing apparatus. As compared with claim 5, it is easy to use and can reliably hold data. The data can always be kept in a clear state. According to the seventh aspect, the optical information recording medium of the present invention can be selected to ensure safety during use.

[Brief description of the drawings]

FIG. 1 shows a configuration example of an optical information recording medium of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 substrate 2 heat-resistant protective layer 3 recording layer 4 heat-resistant protective layer 5 reflective heat dissipation layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/00 656 G11B 19/04 501Q 19/04 501 B41M 5/26 X F-term (Reference) 2H111 EA12 EA23 EA47 FB09 FB12 FB30 5D029 JA01 JC09 MA13 PA01 5D090 AA01 BB05 CC12 DD01 DD05 EE20 FF09 HH01 HH10 JJ07

Claims (7)

[Claims] 1. A rewritable optical information recording medium in which information is recorded, erased, and reproduced by irradiating a laser beam, the recording layer has a crystallization temperature of 130 ° C. when measured at a temperature rise of 10 ° C./min. An optical information recording medium characterized by being formed of a phase change material having a temperature of not more than ° C. 2. The recording layer according to claim 1, wherein the recording layer is mainly composed of a compound represented by the following general formula: Sb _x Te _1-x (0.65 ≦ X ≦ 0.8). Optical information recording medium. 3. The optical information recording medium according to claim 1, wherein the optical information recording medium has a mechanism that can be distinguished from another type of optical information recording medium. 4. A system for notifying a user when a temperature of a place where an optical information recording medium is set has reached or approached a temperature region where the recording of the optical information recording medium may be lost. An optical information recording / reproducing apparatus characterized by comprising means. 5. When the temperature of the place where the optical information recording medium is set reaches or approaches a temperature area where the recording of the optical information recording medium may be lost, the optical information recording medium is turned off. An optical information recording / reproducing apparatus characterized by comprising a mechanism for discharging to the outside. 6. When the temperature of a place where an optical information recording medium is set becomes 50 ° C. or higher, data is read into and overwritten on the optical information recording medium, and the optical information recording medium is removed. An optical information recording / reproducing apparatus, characterized in that a mechanism for discharging the information is provided. 7. The optical information recording / reproducing apparatus according to claim 4, further comprising a mechanism for distinguishing the optical information recording medium according to claim 1 from another type of optical information recording medium.