JP3400832B2 - Information recording medium and information recording / reproducing system using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium suitable for optical video discs, digital audio discs, etc., and particularly suitable for information writable optical discs, and an information recording / reproducing system using the same. .

[0002]

2. Description of the Related Art As a conventional recordable optical disc in which information can be written using heating by a laser beam, there is one described in JP-A-57-186243. In the prior art disclosed in this prior application (hereinafter referred to as the first prior art), a disk structure has a layer that absorbs light and converts it into heat (heat conversion layer) and a layer that changes optical characteristics (optical A disc having a two-layer structure including a characteristic layer) is used. Then, the recording medium is irradiated with laser light to heat the optical characteristic layer by heat from the heat conversion layer, and the heat is used to perform recording mainly by utilizing the reflectance difference based on the change of the optical characteristic layer. . The recordable optical disc disclosed in the first conventional technique enables recording with low power by providing a layer that absorbs light in particular.

As another prior art, Japanese Patent Laid-Open No. 57-180
The optical information recording / reproducing method described in Japanese Patent No. 31 is cited. In the prior art disclosed in this prior application (hereinafter referred to as the second prior art), a metal film having a high reflectance and a low reflectance forming material which is alloyed with the metal film to form an alloy having a low reflectance are used. It has a two-layer structure. When recording, the recording beam is irradiated from the low-reflectance film side to form a low-reflection area between the low-reflectance film side and the high-reflection film side. On the contrary, when reading, the high-reflectance film side is read out. I have to. In the second conventional technique, information is recorded by lowering the reflectance at the recording point, as in the conventional read-only optical disc.

As an application example of the recordable disc,
Read-only area (ROM area) and recordable area (RA
A ROM-RAM mixed type optical disc provided with both of the M area) is known, and as a conventional technique of this ROM-RAM mixed type optical disc, there is a technique described in JP-A-2-42652. In the prior art disclosed in this prior application, an organic material is used for the recording film. In the prior art disclosed in this prior application, the RO is provided on the inner peripheral portion of the optical disc.
The M portion is provided, the outer peripheral portion is used as the RAM portion, and only the RAM portion is spin-coated with the organic material recording film to selectively apply and form the structure.

An optical disc having a prerecorded information portion (ROM portion) and a portion to be additionally recorded (RAM portion) is an optical disc as another known technique.
"JJAPProc. Int. Symp. On Optical Memory"; 19
91, 329-331. In the conventional technique disclosed in this known document, R
Pits are formed in the OM portion, and only tracking grooves are formed in the RAM portion. After that, an organic recording film is applied / formed on the entire surface by a spin coating technique, and a reflective film is vapor-deposited or formed on the entire surface by a sputtering ring to manufacture an optical disk.

[0006]

As is well known, read-only optical discs, which are now in widespread use in large quantities, record information by the irregularities (pits) of the substrate. In this method of forming pits, the reflectance is lowered at the recording points, that is, the positions of the pits, and information can be obtained by this. Hereinafter, the increase / decrease of the reflectance at the recording point will be referred to as recording polarity, and the decrease of the reflectance as in the case of pits will be referred to as positive polarity.

By the way, the above-mentioned first prior art has a characteristic that the reflectance at the recording point increases.
Recording polarity opposite to that of pit formation (reverse polarity)
Is. Therefore, when considering the compatibility of optical disks,
Since the recording polarity is opposite to that of a read-only optical disc based on the pit formation recording method, it is necessary to take measures such as performing inversion processing on the signal, and there is a problem in terms of optical disc compatibility.

Further, in the above-mentioned second prior art,
Although the recording polarity is the same as that of a read-only optical disk that adopts the pit-forming recording method, the beam incidence directions during recording and playback are different, so two beams are used or the disk is reversed between recording and playback. Operation is required. There is also a problem that a double-sided disk cannot be constructed.

In addition to the above, there is an organic material as a recording film material whose reflectance at the recording point decreases, but there is a problem that the organic material lacks long-term storage stability.

Further, in the case of the ROM-RAM mixed type optical disk, the fact that the recording polarities are changed between the ROM section and the RAM section means that the tracking polarities must be changed even within the same disk, which is large. There is a problem. Therefore, in the conventional technology, the ROM section and the RAM are
In order to match the recording polarities of the parts, a positive polarity organic material whose reflectance at the recording point decreases is used as the recording film.
As described above, the organic material has a serious problem that it lacks long-term storage stability.

Furthermore, in the case where the recording film is formed also in the ROM portion in the ROM-RAM mixed type optical disc,
Since the reflectance before recording is low, there is a problem that the S / N of ROM data is lowered and the data cannot be read. Further, as described in the known example, since the pits are filled with the applied recording film, it is necessary to take measures such as enlarging the pit shape in advance. For this reason, there is a problem that the process becomes different from the normal ROM disk manufacturing process, causing confusion.

Therefore, the technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art.
It is an object of the present invention to provide a recordable optical disc which uses a recordable optical disc of a method of forming an alloy crystal and which has a lower reflectance at a recording point and which can be recorded / reproduced from one direction.

Further, also in the ROM-RAM mixed type optical disc, the reflectance before recording is high and the reflectance at the recording point is low in the RAM portion, and even if a recording film is formed on the ROM portion, the S in the ROM portion is reduced. / N does not decrease,
It is an object of the present invention to provide a recordable optical disk in which the ROM and RAM parts have the same tracking polarity and the ROM part can be formed under the same conditions as the conventional ROM (pit).

[0014]

In the conventional recording method for a recordable optical disc of the type that makes an alloy crystal, generally, before recording, the interference effect of the first layer is effectively used and the reflectance is substantially zero. After the recording, the first layer surface became a reflecting surface by crystallization of the alloy after recording, and the interference effect disappeared and the reflectance increased. Then, the difference in reflectance is associated with information for recording.

The present invention achieves the above object by providing an optical disc structure in which the interference effect is effectively utilized not only before alloy crystallization but also after recording. In other words, before recording, the film thickness is configured so that the reflectivity does not decrease due to the interference effect. After recording, not all the first layer is alloy crystallized, but part is made of alloy crystal, and the rest is the interference. The structure is such that it operates as a layer. By adopting a structure in which the interference layer after recording lowers the reflectance, a high reflectance can be obtained before recording and an reflectance can be reduced after recording.

Further, by using this structure, RO
Even if the recording film is formed on the M portion, the reflectance of the recording film before recording is high, so that the performance of the ROM portion is not impaired (S / N is lowered), and the film is formed by sputtering or the like. Since it does not damage the shape of the pit by doing,
Pits can be formed in the same way as in the conventional process, and R is the same as in the conventional process.
ROM-RAM having performance of OM section (pit formation section)
A mixed optical disc can be realized.

[0017]

A material having a small optical attenuation coefficient k is used for the first layer that operates as an interference layer even after recording, and the reflectance is changed by the interference effect by changing the film thickness of this layer. When the film thickness of the first layer is set to a certain value, the reflectance becomes almost zero, and the reflectance rises both before and after the film thickness where the reflectance is substantially zero. In the present invention, the first film thickness is larger than the film thickness at which the reflectance is substantially zero.
To form a layer of.

By irradiating this optical disk with laser light and heating it, the first layer and the second layer are melted to form alloy crystals. At this time, the thickness of the alloy crystal formed changes depending on the laser power. This is because alloy crystallization occurs from the interface between the first layer and the second layer, and the alloying amount of the first layer in the film thickness direction increases as the power becomes higher. Therefore, as the recording power increases, the film thickness of the non-alloyed portion of the first layer decreases.

The film thickness of the first layer in the initial state is thicker than the film thickness at which the reflectance becomes zero, and the film thickness of the non-alloyed portion decreases as the recording power increases, and the reflectance becomes zero. The film thickness approaches Then, ideally, at a certain recording power, the reflectance of the first layer becomes zero.

This makes it possible to perform recording in the direction in which the reflectance decreases at the recording point (recording with the positive polarity described above).

On the other hand, the S / N ratio of the ROM part is determined by the pit width, depth and shape and the reflectance of the ROM part. When the reflectance is low, the reflectance itself is small depending on the presence or absence of pits, so that the S / N is lowered after the pit signal is reproduced due to system noise or the like.

In the conventional optical disc whose reflectance increases after recording (recording with the reverse polarity described above), since the reflectance of the recording film before recording is low, this recording film is used as a conventional aluminum film on the ROM section. When used in place of a reflective film such as gold, the S / N is significantly reduced. On the other hand, the above-mentioned two-layer structure recording film according to the present invention has a high reflectance before recording, so that the S / N is not significantly reduced even when used as a reflecting film.

Therefore, when the recording film according to the present invention is formed on the entire area of the disk, it functions as a reflective film in the ROM section and functions as a recording film in the RAM section. And RA
Guide groove (groove) provided in advance in the M section
Record the data according to.

As a result, while the performance of the ROM part is ensured, the tracking of the ROM and the RAM part has the same polarity RO.
An M-RAM mixed type optical disc can be realized.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an enlarged cross section of a main part of a recordable optical disk according to the first embodiment of the present invention. FIG. 1 (a) shows a state before recording and FIG. 1 (b) shows a state after recording. Are shown respectively. In FIG. 1, 1 is a polycarbonate substrate (hereinafter referred to as a substrate) which is a transparent substrate, 2 is a first layer which is an interference film, and 3 is a second layer which is a reflective film.

On the substrate 1, the interference film as the first layer 2 is formed of the Sb ₂ Se ₃ film, and subsequently, the reflection film as the second layer 3 is formed of the Bi film. Each of these films is formed by sputtering. After forming the Bi film of the second layer 3, although not shown, a protective film is formed on the second layer 3. An ultraviolet curable resin was used for this protective film.

The optical characteristics of the Sb ₂ Se ₃ film of the first layer 2 are n * = 3.8-i0.4 using the complex index of refraction n *, and the attenuation coefficient k is small and the laser light having a wavelength of 780 nm is used. There is no absorption in. The optical characteristics of the Bi film of the second layer 3 are n * = 2.6-i4.5, which is a metallic material having a large attenuation coefficient k.

FIG. 2 is a graph showing the calculation result of the reflectance change with respect to the film thickness of the first layer 2 when the two-layer film composed of the Sb ₂ Se ₃ film and the Bi film is used. . Figure 2
The characteristic curve of is that the film thickness of the second layer (Bi film) 3 is 25 n
The figure shows a case where the film thickness of the first layer (Sb ₂ Se ₃ film; interference film) 2 is changed in a state where m is kept constant. As is clear from FIG. 2, the film thickness of the first layer (interference film) 2 is 35 n.
When the thickness is m, the reflectance becomes zero, and before and after this film thickness, the reflectance becomes large.

In this embodiment, the film thickness of the first layer 2 is 55n.
m, and the film thickness of the second layer 3 is 25 nm.

As shown in FIG. 1 (b) showing the state after recording, when the laser beam focused from the substrate 1 side is irradiated, the light absorption / heating action of the second layer 3 causes the first layer 2 to absorb.
The Sb ₂ Se ₃ film, which is the barrel, and the Bi film, which is the second layer 3, react to form an alloy crystal layer 4 having different optical characteristics between Sb—Se—Bi. The optical characteristic of the alloy crystal layer 4 is n * = 4.5-i3.0, which is a characteristic close to that of a metal material. In this embodiment, since the thickness of the first layer 2 is as thick as 55 nm, the first layer 2 and the second layer 2
Layer 3 does not completely form alloy crystals, part of the first layer 2 becomes alloy crystals, and the rest remains in the initial state. As a result, the film thickness of the Sb ₂ Se ₃ film of the first layer 2 in the recording portion becomes thin, and the interference effect differs from the initial state.

That is, in FIG. 2, the film thickness of the first layer 2 was 55 nm in the initial state, which was point “A” in the figure, but the film thickness of the first layer 2 was changed after recording. Thinning,
It approaches the point where the reflectance becomes zero (“O” point). This enables recording in the direction in which the reflectance at the recording point decreases, in other words, recording with the positive polarity described above.

Using the optical disc manufactured in this example, the reflectance of the optical disc before recording was measured and found to be 28%. Then, as a result of actually irradiating this optical disk with a laser to perform recording, the reflectance at the recording point becomes about 8%,
The C / N after recording was 50 dB or more.

FIG. 3 shows the reproduced waveform of the actual recording result.
Vertical axis of (a) to (d) of FIG. 3 (vertical axis of oscilloscope)
Indicates a voltage, which corresponds to the reflectance, and the higher the voltage, the higher the reflectance. 3A shows a case where recording is performed with a slightly low recording power, FIG. 3B shows a case where recording is performed with an optimum recording power, and FIG. 3C shows a recording with slightly over recording power. 3d in FIG.
Indicates the case where the recording is completely performed with the over recording power. The recording power is small (a) in FIG.
In, the reflectance at the recording point is lower, but the amount of decrease is smaller than the optimum value in the case of FIG. 3B. In the optimum recording power (b) of FIG. 3, the reflectance at the recording point is substantially uniformly and greatly reduced, and the signal can be reproduced properly. On the other hand, in (c) and (d) of FIG.
The reflectance at the recording point is higher than in the case of the optimum value in FIG. 3B. Particularly, in FIG. 3D, the reflectance is higher than the initial value. This is because the alloy crystallization of the first layer 2 further progresses, and the film thickness of the first layer 2 becomes thinner than the film thickness of the reflectance of zero (point “O” in FIG. 2) described above. This is because the point reaches the point “B” in FIG. 2 and thus the reflectance is increased more than the initial film thickness (the point “A” in FIG. 2). Therefore, in this embodiment, it is necessary to optimally set the recording power.

Further, the optical disc of this embodiment is provided with a tracking groove for controlling the laser beam to a predetermined position, as in a general optical disc. The record is
Usually, it is performed either in the groove (groove) or between the grooves (land). In this example, recording was performed on the land. Since the reproduction light forms a spot larger than this tracking groove, one side (land) during reproduction
The laser beam is radiated to the other side (groove) even when the data is reproduced. Therefore, in land recording, not only the recording point but also the return light from the groove determines the overall reflectance.

At this time, when the reflectance change at the recording point and the phase change between the land and groove act in the same direction, the reflectance change before and after recording is emphasized, and a large signal change can be obtained. If the phase change is opposite, the signal will be smaller. Therefore, it is desirable to record in the direction in which the phase is strengthened, and land recording is used in this embodiment.

As described above, according to the present embodiment, since the reflectance at the recording point after recording is lowered, reflection is performed with the same recording polarity as that of a read-only optical disc such as a laser disc adopting a recording system by pit formation. The rate changes, and it becomes possible to realize a recordable optical disc that is compatible with conventional read-only optical discs. Moreover, recording and reproduction can be performed by laser irradiation from one direction.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is an enlarged cross-sectional view of a main part of the recordable optical disc according to the present embodiment. FIG. 4A shows a state before recording,
FIG. 4B shows the state after recording. The present example is different from the first example in that a two-layer film of an Sb ₂ Se ₃ film and a ZnS film is used as the first layer 2 in the present example, and the second layer 3 Is B as in the first embodiment.
i film is used.

In this embodiment, as shown in FIG.
On the substrate 1, a ZnS film which is difficult to react with Bi is first formed as a first unrecorded layer 21 by sputtering, and an Sb ₂ Se ₃ layer is similarly formed as a first recording layer 22 on the ZnS film by sputtering. The first layer unrecorded layer 21 and the first layer recording layer 22 form the first layer 2. And
A Bi film is formed as the second layer 3 on the first layer 2 (first layer recording layer 22) as in the first embodiment, and a protective film made of an ultraviolet curable resin is further formed on the Bi film. It is formed and manufactured as an optical disc.

In this embodiment, at the time of recording, the first layer recording layer (Sb ₂ Se ₃ film) 22 and the second layer (Bi) in the first layer 2 are recorded.
Only the film 3) reacts to form the alloy crystal layer 4, and the first unrecorded layer (ZnS film) 21 in the first layer 2 remains unreacted and remains as an interference film. work. In this embodiment, the ZnS film at this time has a film thickness such that the reflectance becomes substantially zero due to the interference effect (that is, the Sb ₂ Se ₃ film is in a state before alloy crystallization of the Sb ₂ Se ₃ film). The reflectance by the interference film when only the ZnS film is made smaller than the reflectance by the interference film in the two-layer structure of the ZnS film). Therefore, as in the first embodiment, the structure has a low reflectance at the recording point after recording.

As described above, also in this embodiment, the reflectivity changes with the same recording polarity (positive polarity) as the read-only optical disk such as the laser disk which adopts the recording method by the pit formation, and the read-only optical disk which is conventionally used. It becomes possible to realize a recordable optical disc compatible with. Furthermore, in this embodiment, the first layer which is hard to react with the second layer 3 during recording is used.
Since the layer unrecorded layer (ZnS film) 21 is used in the first layer 2, it is possible to realize a recordable optical disc with little recording power dependency. Although ZnS is used for the first layer unrecorded layer 21 in the present embodiment, the first layer unrecorded layer 21 is not limited to this and any material that does not react with Bi and is unlikely to form alloy crystals can be used. It is possible to use it as the layer 21.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is an enlarged cross-sectional view of a main part of the recordable optical disc according to the present embodiment. FIG. 5A shows a state before recording,
FIG. 5B shows the state after recording. In this embodiment, the first layer 2 is formed from the substrate 1 side by Sb ₂
A three-layer film structure is formed by sequentially forming an Se ₃ film, a SiO ₂ film, and an Sb ₂ Se ₃ film. In this embodiment, the thickness of the entire first layer 2 is set to 60 nm, and the thickness of the first unrecorded layer (Sb ₂ Se ₃ film) 23 on the substrate 1 side is set to 37 to 3.
8 nm, the thickness of the intermediate first layer intermediate layer (SiO ₂ film) 24 is 2 to 3 nm, the first layer recording layer (Sb ₂ S ₂ ) on the second layer 3 side.
The film thickness of the e ₃ film) 25 is set to 20 nm. The structure of the other parts is the same as that of the first embodiment.

In this embodiment, since the alloy crystallization stops at the first intermediate layer (SiO ₂ film) 24 portion during recording,
Only the first recording layer (Sb ₂ Se ₃ film) 25 and the second layer (Bi film) 3 in the first layer 2 react to form an alloy crystal layer 4, The first unrecorded layer (Sb
₂ Se ₃ ) 23 does not react and remains in the initial state and functions as an interference film.

Therefore, also in this embodiment, the reflectance changes with the same recording polarity (positive polarity) as the read-only optical disk such as the laser disk which adopts the recording method by the pit formation, and is compatible with the conventional read-only optical disk. It becomes possible to realize a recordable optical disc with a certain level. Further, in the present embodiment, as in the second embodiment, it is possible to realize a recordable optical disc with little dependence on recording power.

In each of the embodiments described above, the first layer 2
It was shown that a part of the sample remained completely in the initial state, and the interference effect of this layer allowed the signal to be recorded from a high reflectivity to a low reflectivity positive polarity. In each of these embodiments, the recordable optical disk is taken as an example of the information recording medium according to the present invention, but the present invention can be applied to other information recording media such as tapes and cards in addition to the optical disk. Needless to say.

Next, an embodiment of the ROM-RAM mixed type optical disk according to the present invention will be described.

FIG. 6 shows a ROM-ROM according to the fourth embodiment of the present invention.
FIG. 3 is a plan view of a RAM mixed type optical disc 5. As shown in the figure, in this embodiment, a RAM section 51 is provided on the outer peripheral portion and a ROM section 52 is provided on the inner peripheral portion. 7 and 8
5 shows a schematic sectional structure taken along the line AA ′ in FIG. 5, in which a RAM groove 51 for the outer peripheral portion is formed with a tracking groove 53, and a ROM portion 52 for the inner peripheral portion.
Only pits 54 are formed in the pits. The recording film 60 used in the optical disc 5 of the present embodiment has a two-layer structure of a first layer 2 made of an Sb ₂ Se ₃ film and a second layer 3 made of a Bi film. Groove part, pit part (R
The entire area of the AM section 51 and the ROM section 52) is formed by sputtering. In addition, in FIG.
55 indicates a land.

Regarding the film thickness of the recording film 60 of the present embodiment, the second layer 3 (Bi film) is 30 nm and the first layer 2 (Sb ₂ Se).
₃ film) is 90 nm. Under this condition, since the reflectance before recording is about 40%, the S / N ratio in the ROM section 54 is sufficient. FIG. 9 shows an eye pattern (reproduced signal waveform) in the ROM section of this embodiment. As is clear from the figure, the open state of the eye pattern has no problem in practical use.

Here, in the present embodiment, a Bi film, Sb ₂ Se ₃
The recording film of the film is formed by sputtering as described above. Therefore, since the original pits 54 are transferred to the ROM section 52 as they are, the conditions for forming the ROM section 52 may be the same as those for the conventional CD or the like. The ROM section 52
The position of may be inside or outside, or may be a part of the circumference.

As described above, according to this embodiment, the recording film 60
Has a high reflectance in the initial state, so even if the recording film is formed over the entire area including the ROM part, the S / N ratio of the ROM part is
Can be taken sufficiently. Furthermore, ROM forming conditions,
The degree of freedom of the forming position is great.

Next, a fifth embodiment of the present invention will be described with reference to FIG. ROM-R as shown in the fourth embodiment
In the AM-mixed optical disc, when the ROM portion 52 is irradiated with the laser light for recording in the RAM portion 51,
The reflectance of the ROM section 52 is lowered, and the characteristics of that portion are deteriorated. As a countermeasure against this, as shown in FIG. 10, a metal film 61 made of a metal material having a high thermal conductivity is formed only on the ROM portion 52 in the recording film 60 (the first layer 2 similar to the fourth embodiment). Sb ₂ Se ₃ film as B and B as the second layer 3
It is formed on the i-film and a two-layer structure film). In this embodiment, the metal film 61 is an Al film, and the film thickness of the Al film is 100 nm. ROM section 52 at this time
The laser light power required for alloy crystallization of the Sb ₂ Se ₃ film and the Bi film is about 3 in the case of no Al.
Doubled. As a result, even when the ROM portion 52 is irradiated with laser light, the Sb ₂ Se ₃ film and the Bi film do not react with each other, and the reflectance does not change. Therefore, even when the recording laser beam is irradiated on the ROM section 52 due to a malfunction, the ROM section 52
It is possible to prevent the S / N from decreasing. Note that Au, Cu, SUS, or the like can be used as the metal film 61 having excellent thermal conductivity.

Further, the metal film 61 is formed on the ROM portion 52 on which the metal film 61 made of a metal material having excellent thermal conductivity is formed.
When a laser beam having the same power as the optimum recording power in the RAM section 51 in which the laser beam is not formed is irradiated, the temperature at that point is the temperature at the time of irradiation of the reproduction power in the RAM section 51,
If the film thickness of the metal film 61 is set so as to be approximately the same, the recording laser light will be emitted from the ROM section 52 due to a malfunction.
There is no possibility of alloy crystallization of the Sb ₂ Se ₃ film and the Bi film in the ROM portion 52 even when the irradiation is performed on the substrate.

Next, a pseudo ROM optical disk using an optical disk similar to the optical disk used in the fifth embodiment and a system using the same will be described.
FIG. 11 shows an optical disk according to the sixth embodiment of the present invention. This embodiment is the ROM shown in the fifth embodiment of FIG.
-RO of a RAM mixed type optical disk (ROM-RAM mixed type optical disk in which erroneous recording prevention measures are implemented in the ROM section 52)
A RAM area (pseudo ROM section 52
A) is provided. In the optical disc of this embodiment,
Since the metal film 61 (for example, Al film) having excellent thermal conductivity is formed on the ROM portion 52, Al is not formed on this portion.
Since the thermal conductivity of the film is high, it cannot be recorded by a normal recording device. However, by using a dedicated large-sized laser irradiation device, it is possible to perform recording in the ROM part 52 by alloying the Sb ₂ Se ₃ film and the Bi film. In this embodiment, at the CD linear velocity (1.3 m / s), the laser power on the film surface is 0.3 mW for the reproducing light, and the RAM section 51.
The recording power was set to 4.5 mW, and the pseudo ROM section 52A was recorded at a recording power of 13 mW.

In the ROM-RAM mixed optical disc, software or the like is generally put in the ROM portion which can be mass-produced.
The user inserts and uses his / her own data in the RAM portion. As an example, the pseudo ROM unit 52A described above is used to write a different data such as a serial number and a personal identification number for each disc at the time of shipment, and to operate a protection mechanism such that the software does not operate unless the number is read. In this case, it is desirable that the means for recording data in the pseudo ROM unit 52A be limited. In the case of this embodiment, C
D-WO (Compact Disk Write-Once) is assumed, and the recording power (recording power of the RAM section 51) is 4 to 8 mW according to the CD-WO standard, and the actual device has no more power. I assumed. Therefore, the pseudo ROM
A dedicated recording device is required for recording in the section 52A,
The general user cannot write. Naturally, the values of the recording powers described above vary depending on the system, and accordingly, it is necessary to change the above-mentioned film thicknesses of the optical disk to appropriate values.

A system using the optical disk of the sixth embodiment of FIG. 11 will be described with reference to FIG. In FIG.
Reference numeral 70 is a pickup, 71 is a preamplifier, 72 is a code detector, 73 is a comparator, and 74 is a control unit. When reading the software of the ROM section 52 of the optical disk, first, the code number of the pseudo ROM section 52A of the ROM section 52 is read by the code detector 72 through the pickup 70 and the preamplifier 71, and the code number read by the comparator 73 is read. It is determined whether the entered personal identification number matches, and the determination result is output to the control unit 74. Then, the pseudo ROM section 52A
Only when the personal identification number and the input personal identification number match, the control unit 74 executes the process of reading the software of the ROM unit 52 of the optical disc. It should be noted that it does not operate on an optical disc with a mismatched secret code or without a secret code, and even if data is written to an optical disc without a secret code, recording cannot be performed from the viewpoint of system power. In this embodiment, other data on the optical disk can be read only when the personal identification numbers match, but this pseudo R
In addition to the personal identification number, the OM unit 52A can record in advance data such as the registrant name and the limiting conditions of the device used, and the software protection function can be activated by the data of the pseudo ROM unit 52A. .

The optical disk having the pseudo ROM portion of the sixth embodiment is not limited to the optical disk using the material proposed in the present invention, but may be a commercially available disk with only RAM such as a magneto-optical disk. Is also applicable, and has a feature that a ROM-RAM mixed optical disk can be manufactured in a pseudo manner.

[0057]

As is apparent from the above description, the present invention has the following effects. That is, the reflectance due to the interference effect is controlled by controlling the film thickness of the alloy crystallized in the first layer (in other words, the film thickness remaining without being crystallized, which functions as an interference film even after recording). Can be utilized after recording, and a recordable optical disc having a lower reflectance at the recording point than before recording can be provided. As a result, since the recording polarities are the same as those of the conventional read-only disc, a recordable optical disc having high compatibility can be realized. Furthermore, ROM-RAM
Even in a mixed optical disc, the condition that the reflectance before recording is high and the reflectance decreases at the recording point and the condition that the tracking polarities are the same in the ROM part and the RAM are satisfied, and the S / N in the ROM part is reduced. There is no ROM
There is an advantage that the portion can be formed under the same conditions as the conventional ROM portion (pit portion).

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part showing a structure before and after recording of a recordable optical disc according to a first embodiment of the invention.

FIG. 2 is an explanatory diagram showing the relationship between the film thickness of the first layer and the reflectance according to the first example of the present invention.

FIG. 3 is an explanatory diagram showing reproduction waveforms of the recordable optical disc according to the first embodiment of the present invention.

FIG. 4 is an enlarged sectional view of an essential part showing a structure before and after recording of a recordable optical disc according to a second embodiment of the invention.

FIG. 5 is an enlarged sectional view of an essential part showing the structure of a recordable optical disc according to a third embodiment of the present invention before and after recording.

FIG. 6 is a plan view of a ROM-RAM mixed type recordable optical disc according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a ROM-RAM mixed type recordable optical disk according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a ROM-RAM mixed type recordable optical disk according to a fourth embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an eye pattern of a ROM section of a ROM-RAM mixed type recordable optical disk according to a fourth example of the present invention.

FIG. 10 is a sectional view of a ROM-RAM mixed type recordable optical disk according to a fifth embodiment of the present invention.

FIG. 11 is a sectional view of a ROM-RAM mixed type recordable optical disk according to a sixth embodiment of the present invention.

FIG. 12 is a block diagram showing a system using an optical disc according to a sixth embodiment of the present invention.

[Explanation of symbols]

1 Polycarbonate substrate (substrate) 2 First layer 3 Second layer 4 Alloy crystal layer 21 First layer Unrecorded layer 22 First layer Recording layer 23 First layer Unrecorded layer 24 First layer Middle layer 25 First layer Recording layer 51 RAM section 52 ROM section 52A Pseudo ROM section 53 Groove 54 pits 60 recording film 61 Metal film

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junmi Suzuki, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi Video Media Research Laboratory (72) Inventor Koichi Moriya 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Visual Media Research Laboratory (72) Inventor Shin Miyamoto 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi Ltd. Visual Media Research Laboratory (56) Reference JP-A-63-281234 (JP, A) Special Kai 61-130093 (JP, A) JP 61-115252 (JP, A) JP 60-28045 (JP, A) JP 60-160036 (JP, A) JP 6-309667 ( JP, A) JP 5-128589 (JP, A) JP 4-296593 (JP, A) JP 2-40142 (JP, A) JP 2-306430 (JP, A) Kaihei 2-302943 (JP, A) JP-A-2-232832 (JP, A) JP-A-2-246032 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 7 /twenty four

Claims (7)

(57) [Claims] 1. A first layer, which is a single layer for controlling optical characteristics, and a second layer for absorbing and heating light are sequentially formed on a substrate, and the reflectance before recording is the first layer. By irradiating the information recording medium having a structure having optical characteristics that changes depending on the change in the film thickness of the layer with laser light and heating the alloy, the first layer and the second layer are alloyed and crystallized. In an information recording medium in which optical characteristics are changed so that information can be recorded, the film thickness of the first layer on the substrate is made thicker than the film thickness at which reflectance is zero before recording. The information recording medium is formed in such a manner that after recording, at least a part of the first layer does not form an alloy crystal and remains in the initial state, and the reflectance at the recording point is lowered. _{2. The} Sb ₂ film according to claim 1, wherein Sb ₂ is present in at least a portion of the first layer where alloy crystals are formed.
An information recording medium characterized by using Se ₃ and using Bi for the second layer. 3. A ROM area in which read-only data is recorded in advance and an R capable of recording data
In a ROM-RAM mixed type information recording medium comprising an AM area, after forming ROM data by pits, the first layer according to claim 1 or 2 is formed on the entire one surface of the information recording medium including the ROM area. An information recording medium, comprising a recording film formed of: and a second layer. 4. A according to any one of claims 1 to 3, on the opposite side to the laser beam incident surface of the portion of the recordable region, a metal film made of a metal material having excellent thermal conductivity formed Then, when the laser beam having the same power as the optimum recording power at the position where the metal film is not formed is irradiated to the position where the metal film is formed, the state of the first layer is not changed. And an information recording medium. 5. The recording film according to claim 3, wherein the ROM film is formed after the ROM data is formed by the pits.
An information recording medium, characterized in that it is formed on the entire one surface of the information recording medium including the M region, and a metal film made of a metal material having excellent thermal conductivity is formed on the ROM region. 6. The laser beam according to claim 4 or 5 , having the same power as the optimum recording power at the position where the metal film made of the metal material having excellent thermal conductivity is formed, at the position where the metal film is not formed. The information recording medium is characterized in that the film thickness of the metal film is set such that the temperature at that point is matched with the temperature at the time of reproducing power irradiation at the position where the metal film is not formed, when the film is irradiated with. 7. An information recording / reproducing system using the information recording medium according to claim 4 , wherein information on a predetermined portion of a portion of the recordable portion on the information recording medium where the metal film is formed is recorded. An information recording / reproducing system, wherein first, reading is performed, and only when the read information satisfies a predetermined condition, other information on the information recording medium can be read.