JPH0793810A - Optical disk - Google Patents

Abstract

PURPOSE:To prohibit erasing and alteration of once recorded data by changing the reflectivity of both of pit forming parts and non-pit forming parts at the time of writing so that the temp. of s recording film do not rise up to a pit forming temp. at the time of the next irradiation with a writing laser beam. CONSTITUTION:This optical disk is composed of a substrate 101 consisting of glass, plastic, etc., an amorphous thin film 102 consisting of As-S-Te, Ge-Sb- Te, etc., a metallic thin film 103 consisting of Ag, Al, etc., a buffer film 104 consisting of SiO2, ZnS, etc., a reflection film 105 consisting of Ag and a protective film 106 consisting of plastic. The temp. of the film 102 rises up to about 1200 deg.C and the films 102, 103, 104, 105 melt and are bored with holes when the films are irradiated with an irradiation light quantity P3 from the substrate 101 side at the time of an initial state. The reflectivity decreases as low as 5% viewed from the substrate side and writing is executed. The temp. in the irradiated parts does not rise up to the pit forming temp. even if these parts are irradiated again with the irradiation light quantity P3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc having a recording film laminated on a substrate made of glass or synthetic resin for irradiating laser light to record and reproduce information.

[0002]

2. Description of the Related Art Various recording / reproducing optical discs have been conventionally known. In general, an optical disk is provided on a transparent substrate made of glass or synthetic resin having a flat plate or a guide groove, or a low melting point metal such as tellurium, selenium or bismuth, or a composite material of these metals and an organic substance as a recording layer by vapor deposition or sputtering. It is a thing. This recording layer is irradiated with modulated laser light, the layer is altered on the irradiation spot, and the reflectance is changed. As a result, pits are formed in the recording layer. When recording on such an optical disc, the laser light for reading is irradiated to search for an unrecorded portion while reading out the signals of the pits in the recording layer and the portions where the pits are not formed, and record there. Go. When reproducing, the pits formed in the recording layer are read by using the reading laser light whose output is weaker than that of the writing laser light.

[0003]

In the conventional recording / reproducing optical disk of this kind, the output of the reading laser light is sufficiently weaker than that of the writing laser light to form pits in the recording layer. I try not to record the parts that have not been recorded. Further, a circuit protects the laser light for reading and writing at a predetermined place so as not to exceed a predetermined light amount. However, the data can be erased by intentionally irradiating the portion where the data is recorded with the laser light for writing. WORM (write once optical disk) is characterized in that it can be written only once and data cannot be tampered with. However, in a rewritable optical disk, if the same laser light as that at the time of writing is applied to the recording portion, the data can be tampered with. -The data can be broken or tampered with. That is, when recording data of 1 and 0, at the time of recording, data 1 is laser light for writing and data 0 is reading laser light.
In order to apply the light (to apply the servo), the data 1 part of the already recorded part is the writing
The light hits and pits are formed in the recording layer,
Since the data 0 part is exposed to the reading laser light,
If laser light for writing is applied again, pits will be formed in the recording layer. Therefore, it is possible to destroy or falsify the data even in the already recorded part.
Therefore, there is a problem in storing official documents.

According to the present invention, the laser light for reading and writing is a recorded portion, and even if the laser light exceeds a predetermined light amount
It is an object of the present invention to provide a recordable / reproducible optical disc that cannot be erased or tampered with.

[0005]

According to the present invention, the reflectance of both the pit formation portion (recording with the second irradiation light amount) and the non-pit formation portion (recording with the first irradiation light amount) is changed during writing on the optical disk. By so doing, the temperature reached by the recording film at the irradiated portion does not rise to the temperature at which the pits are formed even when the writing laser light is irradiated next. The reproduction of information from the optical disc is performed with a light beam that is smaller than the first irradiation light amount.

[0006]

According to the present invention, once data is written on an optical disk, the data cannot be erased or tampered with by laser light irradiation, and can be used for storing an official document which must not be tampered with.

[0007]

EXAMPLES Examples of the present invention will be described below. The film structure of the optical disk is shown in FIG. A substrate 101 made of glass, plastic, etc., an amorphous thin film 102 made of As-S-Te, Ge-Sb-Te, etc., a metal thin film 103 made of Ag, Al, etc., a buffer film 104 made of SiO, ZnS, etc.,
The reflective film 105 is made of Ag and the protective film 106 is made of plastic. When the reflectance of the amorphous thin film 102 viewed from the substrate 101 side is in the initial state r1 of about 10%, the substrate 101
Amount of irradiation light when irradiated with light from the side and the amorphous thin film 102
The relationship with the ultimate temperature of is shown in FIG. FIG. 3 shows the relationship between the amount of light applied to the amorphous thin film 102 and the reflectance. Amount of irradiation light to the amorphous thin film 102, the amorphous thin film 102 and the reflective film 10
FIG. 4 shows the relationship with the total film thickness of No. 5. Once, the temperature T2 of the amorphous thin film 102 is raised to about 600 [° C.], and the reflectance r2 of the amorphous thin film 102 viewed from the substrate 101 side is about 9
FIG. 5 shows the relationship between the amount of irradiation light and the ultimate temperature of the amorphous thin film 102 when light is irradiated from the substrate 101 side in a state where the temperature is lowered after changing to 0%.

In the initial state, the reflectance when viewed from the substrate 101 side is r1, and the total film thickness L1 of the amorphous thin film 102, the metal thin film 103, the buffer film 104, the reflective film 105, and the protective layer 106 is about 0. .1 [μm]. In the initial state, when the irradiation light amount P1 is applied from the substrate 101 side, the temperature of the amorphous thin film 102 rises to about 100 [° C.] T1 as shown in FIG. Does not diffuse rapidly, and the reflectance when viewed from the substrate 101 side does not change. In the initial state, when the irradiation amount of light P2 is applied from the substrate 101 side, the temperature of the amorphous thin film 102 rises to T2 as shown in FIG.
Spreads rapidly inside. In the portion where the metal is diffused, the reflectance is lower than the original laminated film and the transmittance is as high as about 90%.
When the irradiation is stopped in this state, the reflectance of the reflection film 105 on the metal thin film 103 becomes the reflectance as viewed from the substrate 101 side, and the reflectance at that time is r2 as shown in FIG.

In the initial state, when the irradiation amount of light P3 is applied from the substrate 101 side, the temperature of the amorphous thin film 102 is as shown in FIG.
As shown in FIG. 3, T3 rises to about 1200 [° C.], and the amorphous thin film 102, the metal thin film 103, the buffer film 104, and the reflective film 10
No. 5 melts, and a hole is formed by being pulled to the periphery by the surface tension, and the reflectance when viewed from the substrate 101 side has a low r0 of about 5% as shown in FIG. On the other hand, in the portion irradiated with the irradiation light amount P2, the reflectance of the irradiation portion is as high as r2 even if the light is irradiated again with the irradiation light amount P3 from the substrate 101 side. Therefore, as shown in FIG. Does not rise. Therefore, the amorphous thin film 102 and the metal thin film 1
03, the buffer film 104, and the reflective film 105 do not melt and have no holes. The portion irradiated with the irradiation light amount P3 is the substrate 10
Even if the light is irradiated again with the irradiation light amount P2 or P3 from the 1 side, holes are already formed in the amorphous thin film 102, the metal thin film 103, the buffer film 104, and the reflection film 105 in the irradiated portion, so that from the substrate 101 side. The reflectance when viewed is unchanged from r0.

FIG. 6 shows the configuration of a light source control circuit when a semiconductor laser (hereinafter referred to as LD 612) is used as a light source for recording / reproducing. The recording data 601 enters the recording signal processing circuit 602. The recording data 601 is modulated by the recording signal processing circuit 602 and converted into data to be actually recorded, and at the same time, a recording gate signal is generated by a recording gate generation circuit 603 which indicates a recording period and is output. The signal converted by the recording signal processing circuit 602 and the recording gate signal enter the LD light amount switching circuit 604. The LD light amount switching circuit 604 includes a switch 1 608 and a switch 2
609 and the switch 3 610 are controlled to switch the light amount setting value entering the LD drive circuit 611. FIG. 7 shows the waveform of each part of the light source control circuit. Switch 160 during playback
Only 8 is turned on, the output from the LD light amount P1 setting circuit 605 enters the LD drive circuit 611, and the irradiation light amount of the LD 612 becomes P1. When the signal converted by the recording signal processing circuit 602 and the recording gate signal are input, the switch 2 is activated when the signal converted by the recording signal processing circuit 602 is at a low level.
Only 609 is turned on, and the LD drive circuit 611 has an LD
The output from the light amount P2 setting circuit 606 is input to the LD 612.
The irradiation light amount of P2 is P2, and at the time of high level, switch 3 610
Only the light is turned on, and the LD drive circuit 611 outputs the LD light amount P
3 The output from the setting circuit 607 is input, and the irradiation light amount of the LD 612 becomes P3. As described above, by controlling the irradiation light amount of the light source, for example, the data of 1 and 0 converted by the recording signal processing circuit 602 is recorded. When the data 0 is irradiated with the irradiation light amount P3 and the data 1 is irradiated with the irradiation light amount P2, the portion of the data 1 has the reflectance r2 and the portion of the data 0 has the reflectance r0. Normally, this data is irradiated with the irradiation light amount P1 to detect the change in the light amount and reproduce it.

[0011]

As described above, according to the present invention, the data recorded in this way is used for reading and writing.
There is almost no change in reflectance even when the light is increased as the irradiation light amounts P2 and P3. Therefore, even if a large amount of laser light is intentionally applied to the portion where the data is recorded, the data cannot be erased or tampered with. Can be used for storage.

[Brief description of drawings]

FIG. 1 is a diagram showing a film structure of a disc of the present invention.

FIG. 2 is a diagram showing a relationship between an irradiation light amount in an initial state and a temperature of an amorphous thin film.

FIG. 3 is a diagram showing the relationship between the temperature and the reflectance of an amorphous thin film.

FIG. 4 is a diagram showing the relationship between the temperature of the amorphous thin film and the total film thickness of the amorphous thin film, the metal thin film, the buffer film, and the reflective film.

FIG. 5 is a graph showing the relationship between the amount of irradiation light and the temperature of the amorphous thin film in the state of reflectance r2.

FIG. 6 is a diagram showing the configuration of a light source control circuit for performing recording and reproduction on an optical disc according to the present invention.

7 is a diagram showing the waveform of each part of the light source control circuit of FIG.

[Explanation of symbols]

 101 ... Substrate 102 ... Amorphous thin film 103 ... Metal thin film 104 ... Buffer film 105 ... Reflective film 106 ... Protective film

Claims (2)

[Claims] 1. A substrate and a first irradiation light amount which is laminated on the substrate and whose reflectance does not change with a light beam having an irradiation light amount smaller than a first irradiation light amount according to information from the substrate side. Up to the light beam, the reflectance changes, and a recording film is dissolved when irradiated with a light beam having a second irradiation light amount larger than the first irradiation light amount; With a light beam up to the irradiation light amount, a reflection film that reflects the light beam toward the substrate and dissolves when irradiated with the second irradiation light beam is laminated on the reflection film, and at least the recording film is formed. An optical disk comprising a protective film that protects a film and a reflective film and that transmits the light beam. 2. An optical disk substrate and a recording film laminated on the substrate, and by irradiating the recording film with light to heat it, the reflectance and the film thickness of the recording film change, and The relationship between temperature, reflectance change, and film thickness change is the initial reflectance r1
, The temperature reached by the light irradiation during reproduction is T1, the temperature at which the reflectance is r2 (where r2> r1) is T2, and the initial film thickness of the recording film is L1. When the temperature at which (L2 <L1) is T3, the temperatures T1, T2 and T3 satisfy the condition of T1 <T2 <T3 and the recording film is irradiated with light and heated when the reflectance is r1. When the relationship between the quantity of light and the ultimate temperature is the quantity of light P1, the ultimate temperature T1, the temperature T2 when the quantity of light P2, the ultimate temperature T3 when the quantity of light P3 (where P1 <P2 <P3, T1 <
T2 <T3), the temperature of the recording film reaches T2 by light irradiation, the recording film changes to the reflectance r2, and once cooled, the relation between the light amount and the temperature reaches the light amount P3. An optical disk having a temperature <T3, wherein the reflectance of the recording film is changed from the initial reflectance r1 to the reflectances r2 and r0 (however, r0 by irradiating and heating the recording film. An optical disc on which information is recorded in a state of <r1 <r2).