JP3522937B2 - Optical disk signal recording / reproducing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc, and more particularly, to an optical disc having at least two or more layers capable of reading out a signal by irradiating a light beam in a direction perpendicular to a light beam incident surface. Signal of a partial ROM disc in which a RAM section capable of recording / reproducing / erasing an information signal and a ROM section capable of only reproducing are provided on the optical disc of FIG.
Recording / reproducing method .

[0002]

2. Description of the Related Art In recent years, RAM capable of recording / reproducing and erasing signals
A so-called partial ROM disc, which has a read-only portion, and a ROM portion in which a signal is recorded in advance and which can only read the signal, has been proposed and is generally used. According to Japanese Industrial Standard JIS X 6272 “90 mm rewritable and read-only optical disk cartridge”, the partially embossed disk corresponds to the partial ROM disk. (The international standard is ISO / IEC
Corresponding to 10090. In a conventional partial ROM disc, the information track of the RAM section is arranged on the inner peripheral side of the ROM as shown in FIG.
It is known that some information tracks have a structure in which they are located on the same layer on the outer peripheral side (for example, Japanese Patent Publication No.
(See Japanese Patent Publication No. 59494). In the figure, 901 is a partially embossed disk, 902 is a RAM section, that is, an area having an information track capable of recording / reproducing information signals, and 903 is R
An OM portion, that is, an area having a track in which information is recorded and which can only be reproduced is shown. A partial radial cross-section of such a disc is shown in FIG. 1001 is a substrate made of transparent resin such as polycarbonate or PMMA, 1
Reference numeral 002 denotes a RAM section having an information track capable of recording / reproducing information signals, 1003 denotes a ROM section having a pre-recorded information-only track, and 1004 denotes a protective layer.

Further, as shown in FIG. 11, a RAM disk having a RAM section capable of recording a signal and a ROM disk having a ROM section to which a signal is previously fixed are fitted through a hollow portion, and 1 There is an optical disc having a structure of one disc (for example, Japanese Patent Publication No. 44106/1993). In FIG. 11, reference numeral 1101 denotes a substantially transparent ROM disk having concave and convex pits with a reflectance of 3 to 4%, 1102 a RAM disk having a recording film 1104 containing Te, for example, and 1103 a hollow portion. The surfaces of the ROM disk 1101 and the RAM disk 1102 on which the information signals are recorded are opposed to each other, and the ROM disk and the RAM disk are connected to each other at the outer periphery and the inner peripheral edge via a hollow portion 1103. The ROM disk and the RAM disk are detachably configured and can be combined with various disks according to the application.

Further, as a well-known example that has been conventionally known, there is a multi-layer optical disk as shown in FIG. 12, in which two or more recording layers whose optical constants change by irradiation of a light beam are laminated. This is intended to improve the recording density.

[0005]

In the first known example among those described in the prior art, firstly, since the RAM portion and the ROM portion are provided on the same layer, one surface of the disc Storage capacity is RAM area or RO
Secondly, when the information relating to the information in the ROM portion is to be recorded in the RAM portion without going over the disk having the M portion, the track to the RAM portion at a position distant from the ROM portion in the radial direction is formed. There is a problem in that access is required and it takes time until a recordable state occurs due to this physical distance. This problem can be solved by using a linear motor for high-speed access in the optical disk recording / reproducing apparatus, but in that case, there is a problem that the apparatus becomes complicated and the cost becomes high.

In the second known example of the prior art, since the ROM part and the RAM part are manufactured separately, the structure is different from that of the present invention in that the structure is not multi-layered and complicated. However, the ROM disk and the R disk have a high manufacturing cost, and the ROM disk and the RAM disk are detachable.
When replacing the AM disk, there is a problem that dust may be mixed into the hollow portion.

In the third known example of the prior art, a multi-layered structure is used only for the purpose of improving the recording density, and a partial ROM disk using a RAM part and a ROM part together is used. It is needless to say that no means for solving the above-mentioned problem that track access from the ROM section to the RAM section takes time is not provided.

The present invention has been made in view of the above problems of the prior art. The object of the present invention is to reduce the storage capacity of the disk and to provide a RAM portion for recording signals. A signal recording / reproducing method for an optical disc that shortens the recordable time, eliminates the possibility of dust and the like entering between layers of each RAM and ROM, and enables high-speed and stable recording / reproduction of signals with a large capacity.
It is an attempt to provide the law .

[0009]

In order to achieve the above object, an optical disk according to the present invention has a plurality of layers (ROM layer or RAM layer) from which a signal can be read by irradiating a light beam, At least one of the layers is a layer capable of recording / reproducing and erasing (RAM layer), and the other layer is a layer capable of only reproducing (ROM layer), and has a multilayer structure.

Then, a layer (R
As for the AM layer), since the energy of the light beam must be strong when recording and erasing the signal, the layer capable of recording / reproducing / erasing is a layer in which at least two or more layers are arranged in the direction perpendicular to the light beam incident surface. Of these, it is preferable to be provided at a position closest to the surface on which the light beam is incident.

The recording / reproducing erasable layer has a phase in which a crystalline state and an amorphous state undergo a reversible phase change due to heating or cooling, thereby changing an optical constant and recording or erasing information. A changing film can also be used.

When the phase change film as described above is used for the recording / reproducing / erasable layer, the recording / reproducing / erasable layer is previously formed on the entire surface of the layer for the reason described later.
It is desirable to record the signal. The information content of the signal may or may not have meaning.

Further, the layer capable of recording / reproducing / erasing a signal is
The magneto-optical film may be configured to change the optical characteristics by setting the direction of the magnetic poles upward or downward to enable recording / reproducing / erasing of signals.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Figure 1, this onset
FIG. 6 is a partial cross-sectional view of a first optical disc in the radial direction, which is a reference example according to the present invention. In the figure, 101 is polycarbonate or P
The substrate is made of a transparent resin such as MMA and has a thickness of about 0.58 mm. It should be noted that fine information pits are formed in advance on the surface of the substrate 101 on the 102 side by molding. 102 is formed on the information pit. Reference numeral 102 denotes a ROM layer made of a thin film such as aluminum or gold that can only reproduce a signal, and is formed by sputtering or vapor deposition. Reference numeral 105 denotes a protective layer, which is made of the same polycarbonate or PMMA as the substrate 101.
It is composed of transparent resin such as, and its thickness is about 0.58 mm
Is. When forming a guide groove (groove) for guiding the light beam to a predetermined position at the time of recording / reproducing / erasing an information signal on the surface of the protective layer 105, 10 of the protective layer 105 is formed.
The groove is formed in advance on the surface of the side 3 by molding. 103 is formed on such a protective layer 105. Reference numeral 103 is a RAM layer composed of a recording film capable of recording / reproducing / erasing a signal. Each of the RAM layer 103 and the ROM layer 102 has a very small thickness, which is on the order of nm. These are the transparent substrate 101 on which the ROM layer 102 is formed, and the RAM layer 103.
The protection layer 105 on which the ROM is formed, the ROM layer 102 and the RA
The M layer 103 is bonded so that it faces the M layer 103, and a single optical disc is formed. 104 is the ROM layer 1
02 is an intermediate layer for separating and adhering the RAM layer 103, and is formed of a transparent member having a high light beam transmittance,
The thickness is about 40 μm. An example of the transparent member is an ultraviolet curable resin. For example, an ultraviolet curable adhesive model number KZ8611J made by Japan Synthetic Rubber is used.
(For a light beam with a wavelength of 650 nm, its transmittance is 9
It is 9% or more. ) Is used. As described above, the respective layers are laminated to form a layered structure, and the total disc thickness is designed to be 1.2 mm. The ROM layer 102 and the RAM layer 103
The intermediate layer 104 is formed over the entire effective surface of the optical disc. Alternatively, a ROM section in which ROM data is previously recorded by information pits may be provided in a part of the RAM layer 103 to form a partial RAM layer.

A light beam 106 is emitted from the substrate 101 side. When the signal is reproduced by the ROM layer 102, the light beam 106 is controlled so as to focus on the ROM layer 102. Further, when recording, reproducing, or erasing a signal in the RAM layer 103, the light beam 106 is controlled so as to focus on the RAM layer 103.

FIG. 2 shows the RA of the optical disc of FIG.
When recording, reproducing, or erasing a signal in the M layer,
It is a figure which shows the state of irradiation of a light beam at the time of reproducing a signal by an OM layer. The state of FIG. 2 (a) is RO
The case of reproducing the M layer is shown, and the state of FIG.
The case of recording, reproducing, or erasing on a layer is shown. 2 in the figure
01 is a substrate, 202 is a ROM layer, 203 is a RAM layer, 2
Reference numeral 04 is an intermediate layer, 205 is a protective layer, and 206 is a light beam, and the characteristics of the respective constituent elements are the same as in the case of FIG.

The reproduction of the signal by the ROM layer is shown in FIG.
As shown in FIG. 3, by focusing the light beam 206 on the information track of the ROM layer 202 and reproducing the modulated data obtained from the information pits formed on the information track of the ROM layer 202, Reproduce the information signal. In addition, recording / erasing or reproducing to / from the RAM layer is performed as shown in FIG.
As shown in (b), the light beam 206 is focused on the information track of the RAM layer 203 via the ROM layer 202 and the intermediate layer 204. When reproducing from the RAM layer 203, the light beam focused on the RAM layer is reflected,
This is performed by detecting an optical signal returning via the intermediate layer 204 and the ROM layer 202.

The light beam 206 is emitted from the ROM layer 2 of FIG.
In the process of reproducing the information track No. 02 and processing the data of the reproduced signal, when the related data is recorded in the RAM layer 203, the focus of the light beam 206 is moved between layers, and In this state, the information is recorded on the information track on the RAM layer 203 located at the substantially same radius of the ROM layer 202. By performing such processing, the moving distance of the light beam can be set to several tens of μm at most, and the track access between the information track of the ROM layer and the information track of the related RAM layer can be performed in a short time. . And
In this case, it is not necessary to use a linear motor for high speed access as in a conventional partial ROM disc having a ROM section and a RAM section in the same plane.

As a method of using the RAM layer, the data relating to the data of the reproduction signal from the information track of the ROM layer as described above is located at substantially the same radius of the ROM layer.
In addition to recording in the information track of the AM layer, the versioned data can be stored in the RAM layer when the computer software is upgraded.

FIG. 3 shows a second light according to the embodiment of the present invention .
FIG. 7 is a partial cross-sectional view of the disc in the radial direction. 301 in the figure
Is a transparent substrate made of a transparent resin capable of transmitting a light beam, 3
02 is an R composed of a recording film capable of recording / reproducing and erasing signals
AM layer, 303 is a first ROM that can only reproduce signals
A layer, 304 is a first intermediate layer for separating the RAM layer 302 and the first ROM layer 303, 305 is a second ROM layer capable of only reproducing signals, and 306 is a first ROM layer 303.
And a second intermediate layer 307 that separates the second ROM layer 305 from the second ROM layer 305, and a third ROM layer 307 that can only reproduce signals.
Reference numeral 08 is a third intermediate layer that separates the second ROM layer 305 and the third ROM layer 307, and 309 is a protective layer.
A light beam 310 is emitted from the substrate 301 side.

An example of a method of manufacturing the optical disc shown in FIG. 3 will be described below. First, the substrate 301 is made of transparent resin such as polycarbonate or PMMA to a thickness of about 0.54 mm. R of the substrate 301
When the above-mentioned guide groove (groove) is provided on the surface of the AM layer 302 side, the groove is previously formed on the surface by molding. On such a transparent substrate 301, RA
The M layer 302 is formed. Subsequently, an intermediate layer 304 made of photopolymer having fine information pits formed on the ROM layer 303 side is formed on the RAM layer 302 by the 2P (photopolymer) method. Then, the intermediate layer 304
The ROM layer 303 is formed thereon. A member of the optical disc manufactured in this manner is referred to as a member A. on the other hand,
The protective layer 309 is made of the same transparent resin as the substrate 301 and has a thickness of about 0.54 mm. Its protective layer 3
On the surface of the 09 of the ROM layer 307 side, fine information pits are formed in advance by embossing by molding. Then, the ROM layer 307 is formed on the information pit. Then, an intermediate layer 308 having fine information pits formed on the ROM layer 305 side is formed on the ROM layer 307 by the same 2P method as described above. And the intermediate layer 30
The ROM layer 305 is formed on the upper surface 8. The member of the optical disc manufactured in this manner is referred to as member B. The member A and the member B are adhered to each other by the intermediate layer 306 made of the ultraviolet curable resin to manufacture one optical disk. The intermediate layers 304, 306, and 3 described above are used.
08 is made to have a thickness of about 40 μm. Also, R
The OM layers 303, 305, and 307 are made of a thin film of aluminum or gold and are produced by sputtering or vapor deposition. RAM layer 302 and 303, 305, 30
The thickness of each ROM layer of No. 7 is very small and is on the order of nm. Each of these layers described above is laminated to form a layered structure and is designed so that the total disc thickness is 1.2 mm. In the optical disc configured as described above, it is possible to record the information related to the data reproduced from the information tracks on the first, second and third ROM layers on the RAM layer 302 at substantially the same radius. Become.

FIG. 4 shows a third light according to the embodiment of the present invention .
FIG. 7 is a partial cross-sectional view of the disc in the radial direction. 401 in the figure
Is a substrate made of transparent resin such as polycarbonate or PMMA, and the thickness of the layer is about 0.58 mm. When the above-mentioned guide groove (groove) is formed on the surface of the transparent substrate 401 on the 402 side, it is formed beforehand by molding.
The groove is formed. On the substrate 401, a RAM layer 4 composed of a recording film capable of recording / reproducing and erasing signals
02 is formed. A protective layer 405 has a thickness of about 0.58 mm and is made of the same material as the substrate 401. In addition, fine information pits are formed in advance on the surface of the protective layer 405 on the 403 side by molding. A ROM layer 403 capable of only reproducing a signal is formed on the information pit. Each of the ROM layer 403 and the RAM layer 402 has a thickness of nm.
The thickness is very small on the order. RAM of these
The transparent substrate 401 on which the layer 402 is formed, and the ROM layer 40
3 is formed on the RAM layer 402 and R
Adhesion is performed by 404 so as to face the OM layer 403. Reference numeral 404 denotes an intermediate layer that adheres the RAM layer 402 and the ROM layer 403 to each other and separates them from each other. The intermediate layer 404 is formed of a transparent member such as an ultraviolet curable resin and has a thickness of about 40 μm. Of the layers arranged in the direction perpendicular to the light beam incident surface as shown in FIG. 4, by setting the position of the RAM layer at a position close to the light beam incident surface, the energy of the strong light beam is generally increased. It is possible to efficiently record information on the required information track of the RAM layer. The RAM layer 402, the ROM layer 403, and the intermediate layer 404 are formed over the entire effective surface of the optical disc. Alternatively, a ROM section in which ROM data is previously recorded by information pits may be provided in a part of the RAM layer 402 to form a partial RAM layer. A light beam 406 is emitted from the substrate 401 side. RAM layer 402
The light beam 406 is controlled to focus on the RAM layer 402 when recording, reproducing, or erasing a signal. Further, when the signal is reproduced by the ROM layer 403, the light beam 406 is controlled so as to focus on the ROM layer 403.

FIG. 5 shows the RA of the optical disk of FIG.
When recording, reproducing, or erasing a signal in the M layer,
It is a figure which shows the irradiation state of a light beam at the time of reproducing a signal by an OM layer. The state of FIG. 5A shows the case where the signal is reproduced by the ROM layer, and the state of FIG. 5B shows the case where the signal is recorded, reproduced, or erased in the RAM layer. In the figure, 501 is a substrate, 502 is a RAM layer, 503.
Is a ROM layer, 504 is an intermediate layer, 505 is a protective layer, 506
Is a light beam, and the characteristics of each component are the same as in the case of FIG.

The reproduction of the signal by the ROM layer is shown in FIG.
As shown in FIG. 7, the light beam 506 is focused on the information track of the ROM layer 503 through the RAM layer 502 and the intermediate layer 504, and reflected from the information pit formed on the information track of the ROM layer 503. The detected optical signal is detected via the intermediate layer 504 and the RAM layer 502, and the modulated data is reproduced to reproduce the information signal from the ROM layer 503. Further, recording / erasing or reproduction of a signal to / from the RAM layer is performed by focusing the light beam 506 on the information track of the RAM layer 502, as shown in FIG. 5B. RA
The reproduction of the signal from the M layer 502 is performed by detecting the optical signal that returns when the light beam focused on the RAM layer is reflected.

Of the layers arranged at least two or more in the direction perpendicular to the light beam incident surface, the recording / reproducing / erasable layer is
By providing the position closest to the light beam incident surface,
It is possible to accurately record a signal in a layer capable of recording / reproducing and erasing.

The light beam 506 is emitted from the ROM layer 5 of FIG.
In the process of reproducing the signal of the information track No. 03 and processing the data of this reproduced signal, the related data is recorded in the RAM layer 50.
In the case of recording to No. 2, the focal point of the light beam 506 is subjected to interlayer movement processing so as to be in the state of FIG. 5B, and recording is performed to the information track on the RAM layer 502 located at substantially the same radius of the ROM layer 503. By performing such processing, the moving distance of the light beam can be set to several tens of μm at most, and the track access between the information track of the ROM layer and the information track of the related RAM layer can be performed in a short time. .

As described above, among the layers arranged at least two or more in the direction perpendicular to the light beam incident surface, the recording / reproducing erasable layer is provided at the position closest to the light beam incident surface, thereby recording / reproducing / erasing. It is possible to efficiently record a signal on a possible layer.

FIG. 6 shows a fourth light according to the embodiment of the present invention .
FIG. 7 is a partial cross-sectional view of the disc in the radial direction. Figure 6 (a)
In the figure, 601 is a substrate made of transparent resin such as polycarbonate or PMMA, 602 is a RAM layer capable of recording / reproducing and erasing signals, and 603 is a ROM capable of only reproducing signals.
A layer 604 is an intermediate layer separating the RAM layer 602 and the ROM layer 603, and 605 is a protective layer. A characteristic of this figure is that the RAM layer 602 is formed of a phase change film. This phase change film causes a reversible phase change between, for example, a crystalline state and an amorphous state by heating and cooling by irradiation of a light beam with output control, and changes optical constants such as reflectance. As a result, signals can be recorded and erased. When reading a signal, the output of the light beam is reduced to about 1/10 of that at the time of recording. When this phase change film is used as a RAM layer, the phase change film has a high CN ratio even when a light beam of a short wavelength is used, and a magnetic field required when a magneto-optical film or the like is used as a RAM layer. Since the generation device is not required, the structure of the optical disk recording / reproducing device can be simplified, and the operation of recording another signal in the RAM layer in which the signal is recorded is performed only by controlling the output of the light beam. It becomes possible to make it easy. The features of the other components are the same as those in the case of FIG. A light beam 606 is emitted from the substrate 601 side. RAM layer 6
If you want to record, play, or erase the signal in 02,
The light beam 606 is controlled to focus on the RAM layer 602. Further, when the signal is reproduced by the ROM layer 603, the light beam 606 is controlled so as to focus on the ROM layer 603.

FIG. 6B shows an embodiment in which FIG. 6A is put to practical use. In FIG. 6B, R
The AM layer 602 is accompanied by a protective layer 607 and a reflective layer 608 formed by sputtering or vapor deposition to form a RAM layer having a multilayer structure. ZnS is used as the protective layer 607.
-SiO2 or the like, the reflective layer 608 is an aluminum alloy or the like, and the phase change film 602 is Ge2Sb2Te5 or the like.
For example, use.

As described above, by using the phase change film as the recordable / erasable layer, the CN ratio is high even when a light beam of a short wavelength is used, and a magneto-optical film or the like is used as the RAM layer. When used, a necessary magnetic field generator is not required, so that the structure of the optical disk recording / reproducing apparatus can be simplified and the RA in which a signal is recorded is used.
The operation of further recording a signal in the M layer can be easily performed only by controlling the output of the light beam.

Next, referring to FIG . 7, the embodiment shown in FIG.
The reproduction signal level from the ROM layer in the case of the state will be described.
The vertical axis of FIG. 7 represents the HF reproduction signal level reproduced from the ROM layer via the RAM layer, and the horizontal axis represents time. Figure 7 (a)
Is R when the information signal is recorded only on a part of the RAM layer.
An example of the OM layer reproduction signal level is shown. In addition, FIG.
Shows an example of the ROM layer reproduction signal level when a random information signal is recorded in advance on the entire surface of the RAM layer. As shown in FIG. 7A, when the information signal is recorded only on a part of the RAM layer, the transmittance changes when passing through the RAM layer on which the information signal is recorded, and the ROM layer reproduction signal is generated. The level changes, which makes stable signal reproduction difficult. On the other hand, when an information signal is recorded on the entire surface of the RAM layer, as shown in FIG. 7B, the transmittance does not change and the ROM layer reproduction signal level does not change and is stable. Signal reproduction is possible. Therefore,
As described in claim 5, the optical disc shown in FIG. 6 has a meaningless signal over the entire surface of the rewritable / erasable layer when the optical disc is first used by a person who uses the optical disc for the first time. Has already been recorded, in other words, before the information signal is reproduced or recorded / erased from the optical disc, meaningless data in the RAM layer, for example, a signal or an irregular pattern that repeats the minimum mark is recorded. RA for random signals that have no meaning
The data is recorded on the entire surface of the M layer and is overwritten on the prerecorded data only when it is necessary to record information on the RAM layer. The meaningless data signal may be a data signal having meaningful information property, for example, when the RAM layer is used as a temporary ROM layer.

As described above, when the recording / reproducing / erasable layer is composed of the phase change film, the signal from the layer only capable of reproducing the signal by previously recording the signal on the entire surface of the layer. Can be detected stably and accurately.

FIG. 8 shows a fifth light according to the embodiment of the present invention .
FIG. 7 is a partial cross-sectional view of the disc in the radial direction. 801 in the figure
Is a substrate made of transparent resin such as polycarbonate or PMMA, 802 is a RAM layer capable of recording / reproducing and erasing signals.
Reference numeral 803 is a ROM layer capable of only reproducing signals, and 804 is RA.
805 is a protective layer which is an intermediate layer for adhering and separating the M layer 802 and the ROM layer 803. A feature of FIG. 8 is that the RAM layer 802 is composed of a magneto-optical film. The magneto-optical film can reproduce or record / erase information by setting the direction of its magnetic pole upward or downward. The features of the other constituent elements are the same as those in FIG.

A light beam 806 is emitted from the substrate 801 side. When recording, reproducing, or erasing a signal in the RAM layer 802, the light beam 806 emits light to the RAM layer 8.
Controlled to focus on 02. Further, when the signal is reproduced by the ROM layer 803, the light beam 806 is controlled so as to focus on the ROM layer 803. When the RAM layer 802 formed of a magneto-optical film is used, the transmittance and the reflectance of the RAM layer 802 hardly change between the case where information is recorded and the case where information is not recorded, and the ROM The information reproduction signal of the layer 803 is hardly affected.

By thus forming the recording / reproducing / erasable layer with the magneto-optical film, it is possible to record a signal in the recording / reproducing / erasable layer in advance, which is required in the case of the phase change film. It is possible to stably read a signal from a layer that can only reproduce the signal.

[0036]

Since the present invention is constructed as described above, it has the following effects. In a multilayer optical disc in which at least two layers (RAM layer or ROM layer) capable of reading a signal by irradiating a light beam are arranged in a direction perpendicular to the light beam incident surface, the above signal can be read. At least one recording / reproducing / erasable layer (RAM layer) capable of recording and erasing a signal in addition to reading a signal from a possible layer (RAM layer or ROM layer), and reading a signal. By configuring with a layer that can only be read (ROM layer), the recording capacity from the ROM layer to the RAM layer for recording signals can be shortened without reducing the storage capacity of the disk, and further, each RAM Layer and R
It is possible to eliminate the risk of dust and the like being mixed between the OM layers, and to perform high-speed and stable recording / reproduction / erasure of a signal with a large capacity.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the present invention, particularly according to claim 1;

FIG. 2 is a diagram for explaining reproduction of an optical disc according to an embodiment of the present invention, particularly claim 1;

FIG. 3 is a sectional view showing an embodiment of the present invention, particularly according to claims 11 and 12;

FIG. 4 is a sectional view showing an embodiment according to claim 2 of the present invention.

FIG. 5 is a diagram for explaining reproduction of an optical disc according to an embodiment of the present invention, particularly claim 2;

FIG. 6 is a sectional view showing an embodiment according to claim 4 of the present invention.

FIG. 7 is a diagram for explaining signal reproduction in an embodiment according to claim 5 of the present invention;

FIG. 8 is a sectional view showing an embodiment according to claim 7 of the present invention.

FIG. 9 is a schematic diagram showing a first conventional example.

FIG. 10 is a partial sectional view showing a first conventional example.

FIG. 11 is a partial sectional view showing a second conventional example.

FIG. 12 is a partial sectional view showing a third conventional example.

[Explanation of symbols]

101, 401, 1001, 1203 Substrate 102, 303, 403 RO
M layer 103, 302, 402 RA
M layer 104, 304, 404, 1202 Intermediate layer 105, 405, 607, 1004, 1204 Protective layer 608 Reflective layer 106, 310, 406 Light beam 901 Partial ROM disk 902, 1002 RA
M section 903, 1003 RO
M section 1101 RO
M disk 1102 RA
M disk 1103 Hollow part 1104, 1201 Recording film

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 00-7/0065 G11B 7/24

Claims (2)

(57) [Claims] 1. A first layer composed of a phase change film in which a signal is recorded, reproduced and erased by being irradiated with a light beam, and a signal is previously recorded and the light beam is passed through the first layer. Is a signal recording / reproducing method for an optical disc having a second layer from which the pre-recorded signal is read, and a random information signal is previously recorded on the entire surface of the first layer, A signal recording / reproducing method for an optical disc, characterized in that the signal is read from the second layer or the signal is recorded in the first layer. 2. A first layer composed of a phase change film in which a signal is recorded, reproduced, and erased by being irradiated with a light beam, and a signal is recorded in advance through the first layer, and the light beam is passed through the first layer. Is a signal recording / reproducing method for an optical disc having a second layer from which the prerecorded signal is read by irradiating with a laser beam, the signal being a repetitive pattern of minimum marks on the entire surface of the first layer. A signal recording / reproducing method for an optical disc, which comprises: recording, and thereafter, reading a signal from the second layer or recording a signal to the first layer.