JPH10199036A - Information recording medium and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to arbitrarily select an erasable recording method and unerasable recording method, by providing the information recording medium with a first dielectric layer having a m.p. higher than the m.p. of a phase transition recording layer and a second dielectric layer having a m.p. between the m.p. of the phase transition recording layer and the first dielectric layer. SOLUTION: The information recording medium 10 is irradiated with a laser beam 20 from a transparent substrate 11 side. The power of this laser beam 20 is adjusted to the extent of sufficiently melting the phase transition recording layer 12 and not melting the second dielectric layer or semiconductor layer 14. Then, the occurrence of evaporation or holding in the irradiated parts 21 of the molten phase transition recording layer 12 is averted. Next, the irradiated parts 21 are rapidly cooled and the phase transition from the crystalline to amorphous phase is induced by stopping the irradiation with the laser beam 20. The crystalline parts and amorphous parts are formed in the phase transition recording layer 12 to induce a difference in the reflectivity in such a manner, by which the erasable recording is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an information recording medium and a recording method, and more particularly to recording / erasing information by changing a phase between amorphous and crystalline by irradiation of light. The present invention relates to an information recording medium and a recording method thereof.

[0002]

2. Description of the Related Art In recent years, optical disks have attracted attention as large-capacity memories. This optical disc is a read-only type such as a CD that can only read information but cannot record information, a write-once type such as a CD-R that can record information only once, and can freely record and erase information. The rewritable type is widely classified into three types, namely, rewritable types used for external memories of computers and the like, and rewritable types are particularly attracting attention for their wide use.

There are mainly two rewritable optical disks, a magneto-optical disk and a phase-change optical disk. Of these, the phase-change type optical disc uses a recording layer that reversibly changes phase between amorphous and crystalline by irradiation with a laser beam or the like, thereby forming an amorphous recording mark and a crystalline background. The reproduction is performed using the difference in the reflectance between the two. This amorphous state is formed by heating the recording layer above its melting point and rapidly cooling it, and the crystalline state is formed by heating the recording layer above its crystallization temperature and below its melting point. Therefore, the phase change optical disk has an advantage that information can be freely rewritten by controlling the intensity of the laser beam applied to the recording layer.

FIG. 9 is a cross-sectional view of a general phase change optical disk. In this figure, a dielectric layer 93 made of a ZnS / SiO ₂ mixed film is formed on a transparent substrate 91 made of polycarbonate or glass, and an amorphous layer and a crystalline layer are formed thereon by irradiating a laser beam or the like. And a phase change recording layer 92 made of a ternary alloy of Ge ₂ Sb ₂ Te ₅ or the like, which changes phase reversibly between. On top of that, Z
a dielectric layer 94 made of an nS / SiO ₂ mixed film, and Al
A metal reflection layer 95 made of a Mo alloy is sequentially laminated to form a phase-change optical disc 90.

The phase change recording layer 92 is melted and quenched by laser light irradiation to become amorphous. Therefore,
The thickness of the phase change recording layer 92 is usually designed to be as thin as about 50 to 300 Å because it is necessary to easily melt the layer by irradiation with laser light. When the phase-change recording layer 92 is melted, there is a possibility that the laser-irradiated portion of the phase-change recording layer 92 may be evaporated and a hole may be formed. However, the dielectric layer 93 having a higher melting point than the phase-change recording layer 92 may be obtained. And the dielectric layer 94 sandwich the phase change recording layer 92,
Deterioration of the phase change recording layer 92 is prevented. That is, the dielectric layer 93 and the dielectric layer 94 serve to protect the phase-change recording layer 92 from heat.

[0006] The dielectric layer 93 provided on the transparent substrate 91 is provided so that the reflected light from the metal reflective layer 95 and the reflected light from the phase change recording layer 92 amplify each other during recording and reproduction. The thickness is designed. The dielectric layer 94 provided on the side of the metal reflection layer 95 has such a degree that the phase change recording layer 92 becomes amorphous, so that heat can be transmitted from the phase change recording layer 92 to the metal reflection layer 95 satisfactorily. Designed to be thin.

In such a phase-change type optical disk, higher recording density is required, and the recording density is increased by shortening the laser wavelength to reduce the diameter of the condensed spot. Further, conventionally, recording was performed only on the groove portion (groove) or only on the bank portion (land) of the disk. However, when the laser scans the groove, the recording of the land is not detected and the land is scanned. In such a case, the recording density is increased by optically adjusting the depth of the groove so as to prevent the recording of the groove from being detected, and by performing recording on both the groove and the land.

Usually, the above-mentioned optical disk has a fixed total storage capacity, and a header or address signal is embedded in the substrate in advance in the form of an emboss when the substrate is formed. Since the practically recordable capacity is a portion obtained by removing the emboss information from the total storage capacity, in order to increase the recordable capacity, a method of eliminating the emboss information and initializing it like a floppy disk That is, a so-called soft format has been proposed in which only grooves and lands are formed on a substrate without introducing emboss information, and headers and addresses are recorded by a drive while scanning only the grooves or lands with a laser beam.

However, the above-mentioned soft format has the following disadvantages. That is, if the header or address is
Since the information is recorded on the recording layer which reversibly changes in phase by the laser beam irradiation, there is a possibility that such information may be erased by mistake due to a drive failure or careless operation. When such information is erased, the header and address cannot be read, and therefore, it is impossible to access the sector in that part. Therefore, it becomes impossible to reproduce the information recorded in the sector.

As described above, the phase-change type optical disk can erase a record, but important information, for example, information that cannot be falsified, such as legal evidence, cannot be erased. May be more convenient.

[0011]

As described above, the conventional phase-change type optical disk cannot perform non-erasable recording. Even if possible, information cannot be erased after the phase-change optical disk is manufactured because the information is previously introduced into the substrate in the form of emboss. An object of the present invention is to provide an information recording medium and a recording method that can arbitrarily select erasable recording and non-erasable recording.

[0012]

Means for Solving the Problems The present invention (claim 1) provides:
A light-transmissive substrate, provided on the substrate, a phase-change recording layer that reversibly changes phase by light irradiation, provided on the phase-change recording layer, and having a higher melting point than the phase-change recording layer A first dielectric layer, provided between the substrate and the phase change recording layer, and having a melting point between the phase change recording layer and the first phase change recording layer;
A second dielectric layer or a semiconductor layer between the first and second dielectric layers,
An information recording medium comprising:

Further, the present invention (claim 2) provides a light-transmitting substrate, a phase-change recording layer provided on the substrate, and reversibly changing phase by light irradiation, the substrate and the phase-change recording layer And a first dielectric layer having a higher melting point than the phase change recording layer, and a first dielectric layer provided on the phase change recording layer, wherein the melting point is between the phase change recording layer and the first dielectric layer. There is provided an information recording medium comprising a second dielectric layer or a semiconductor layer between the recording medium and a body layer.

Further, according to the present invention (claim 3), in the information recording medium (claim 1), the first recording medium is provided between the phase change recording layer and the second dielectric layer or the semiconductor layer. A third dielectric layer made of the same material as the dielectric layer is provided.

Still further, according to the present invention (claim 4), in the information recording medium (claims 1 to 3), the phase change recording layer has a melting point of 600 ° C. to 700 ° C. The melting point of the layer is 1200 ° C. or higher, and the melting point of the second dielectric layer or the semiconductor layer is 800 ° C. to 1000 ° C.

Further, according to the present invention (claim 5), in the information recording medium (claim 4), the second dielectric layer or the semiconductor layer is made of Ge. further,
The present invention (claim 6) provides the information recording medium (claim 4).
In the above, a metal reflective layer is provided on the phase change recording layer, and the first dielectric film and the second dielectric film or the semiconductor film are arranged between the metal reflective layer and the substrate. It is characterized by having.

Still further, according to the present invention (claim 7), in the information recording medium (claim 4), the phase change recording layer is made of a ternary alloy of Ge, Sb and Te or a ternary alloy of In, Sb and Te. It is characterized by being composed of an original alloy.

Further, according to the present invention (claim 8), by irradiating light of a first power, the phase change recording layer is caused to have a melting point of the phase change recording layer and the second dielectric layer or the semiconductor layer. Erasing the recording medium by heating to a temperature between the melting point of the phase change recording layer and the second dielectric layer by irradiating light having a second power higher than the first power. Alternatively, the melting point of the phase change recording layer and the second
The recording method of the information recording medium (one of claims 1 to 3), wherein the recording is performed by heating to a temperature between the melting point of the dielectric layer and the semiconductor layer. provide.

Further, according to the present invention (claim 9), the phase-change recording layer is irradiated with light of a first power so that
Perform erasable recording by heating to 00 ° C to 700 ° C,
By irradiating light of a second power higher than the first power, the phase change recording layer and the second dielectric layer or the semiconductor layer are heated to 800 ° C. to 1000 ° C. to make it impossible to erase. A recording method for the information recording medium (claim 4), characterized by performing recording.

Hereinafter, the information recording medium of the present invention will be described in more detail. Examples of the light-transmitting substrate used in the present invention include a synthetic resin substrate such as a polycarbonate and a glass substrate.

Further, the phase change recording layer used in the present invention needs to be made of a material which reversibly changes between amorphous and crystalline phases by light irradiation. As a material constituting the phase change recording layer, a ternary alloy of Ge, Sb, and Te, a ternary alloy of In, Sb, and Te, and the like can be given. The thickness of this phase change recording layer is 50-30.
Preferably, it is 0 Å.

The first dielectric layer formed on the phase change recording layer or between the substrate and the phase change recording layer is made of a material having a higher melting point than the material forming the phase change recording layer. Need to be configured. This melting point is preferably 1200 ° C. or higher, and ZnS / SiO ₂ , SiO ₂ , TiO ₂ , Al ₂ O
Light-transmissive dielectrics such as ₃ and SiN ₄ / Ta ₂ O ₅ can be used.

The melting point of the second dielectric layer or the semiconductor layer formed between the substrate and the phase change recording layer or on the phase change recording layer is determined by comparing the melting point of the phase change recording layer with the first melting point. It must be between the melting point of the dielectric layer and 700-100
Preferably it is 0 ° C. Ge, GeO, PbO, or the like can be used as a material forming the second dielectric layer or the semiconductor layer.

When the first dielectric layer and the second dielectric layer or the semiconductor layer are provided on the substrate side, 500 to
It is preferable that the thickness is 3000 Å, and when it is provided on the metal reflection layer side, it is 50 to 300 Å.
Preferably, the thickness is Å.

In the information recording medium according to the present invention, a third dielectric layer can be provided between the second dielectric layer and the semiconductor layer. Is composed of the same material as the dielectric layer. Preferably, the thickness of the third dielectric layer is between 30 and 200 angstroms.

In the information recording medium of the present invention, a metal reflective layer can be provided as the uppermost layer. This metal reflective layer is made of Al
It can be made of Mo, Au, Al, Cu or the like.
The thickness of the metal reflection film is preferably 500 to 3000 Å.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of an information recording medium according to an embodiment of the present invention. As shown in FIG. 1, a second dielectric layer or semiconductor layer 14, a phase change recording layer 12, a first dielectric layer 1
3 and the metal reflective layer 15 are sequentially laminated, and the information recording medium 1
0 is configured. Second dielectric layer or semiconductor layer 1
4. The melting points of the phase change recording layer 12 and the first dielectric layer 13 are, in order from the highest, the first dielectric layer 13, the second dielectric or semiconductor layer 14, and the phase change recording layer 12. ing.

Next, an erasable recording method for the above-mentioned information recording medium will be described with reference to FIG. First, the information recording medium 10 is irradiated with the laser beam 20 from the transparent substrate 11 side. The power of the laser beam 20 is adjusted so that the phase change recording layer 12 is sufficiently melted and the second dielectric layer or semiconductor layer 14 is not melted. Therefore, evaporation and perforation do not occur in the irradiated portion 21 of the melted phase change recording layer 12.

Next, when the irradiation of the laser beam 20 is stopped, the irradiated portion 21 is rapidly cooled, and changes its phase from crystalline to amorphous. As described above, the phase change recording layer 12
Then, by forming a crystalline portion and an amorphous portion to cause a difference in reflectance, erasable recording can be performed.

Referring to FIG. 3, a non-erasable recording method for this information recording medium will be described. First, as shown in FIG. 3A, the information recording medium 10 is irradiated with a laser beam 30, as in the erasable recording method described above. Unlike the erasable recording method described above, the power of the laser beam 30 is sufficient to melt the phase change recording layer 12 and the second dielectric layer or semiconductor layer 14 and to melt the first dielectric layer 13. It is adjusted to the extent that it does not.

At this time, the irradiated portion 31 of the phase change recording layer 12 and the irradiated portion 32 of the second dielectric layer or semiconductor layer 14 which have been irradiated with the laser beam are both melted, and these melts are melted. Are mixed. In addition, by irradiation of laser light,
If the transparent substrate 11 is heated above its melting point,
As shown in (b), the interface 33 between the transparent substrate 11 and the irradiated part 32 is deformed.

Next, by stopping the irradiation of the laser beam 30, the irradiated portion 31 and the irradiated portion 32 are solidified in a state where the respective materials are mixed and the interface 33 is deformed. The recording thus formed is irreversible, and the reflectance of this recorded portion is much smaller than the reflectance of the erasable amorphous portion described above. Therefore, even if the above-described erasable recording is attempted on this recording portion, the information is not erased.

As described above, by performing recording that is irreversible and whose reflectance is greatly reduced, it is possible to perform recording that cannot be erased. As described above, the case where the first dielectric layer having the highest melting point is formed on the phase change recording layer has been described, but the arrangement may be different from this. For example, a first dielectric layer can be formed between the phase change recording layer and the substrate.

FIG. 4 is a sectional view of an information recording medium according to another embodiment of the present invention. In this figure, a first dielectric layer 43, a phase change recording layer 42, a second
The information recording medium 40 is formed by laminating the dielectric layer or semiconductor layer 44 and the metal reflection layer 45 of FIG. The melting points of the first dielectric layer 43, the phase-change recording layer 42, and the second dielectric layer or the semiconductor layer 44 are, in ascending order, the first dielectric layer 43, the second dielectric layer or the semiconductor layer. 44, a phase change recording layer 42.

The erasable recording on the information recording medium 40 is performed by the same method as described with reference to FIG. With reference to FIG. 5, a non-erasable recording method for this information recording medium will be described.

First, similarly to the above-described erasable recording method, the information recording medium 40 is irradiated with a laser beam (not shown). Unlike the erasable recording method described above, the power of the laser beam sufficiently melts the phase change recording layer 42 and the second dielectric layer or semiconductor layer 44 and does not melt the first dielectric layer 43. It has been adjusted to a degree.

At this time, the irradiated portion 51 of the phase change recording layer 42 and the irradiated portion 52 of the second dielectric layer or semiconductor layer 44, both of which have been irradiated with the laser beam, are melted together. Are mixed.

Next, by stopping the irradiation of the laser beam, the irradiated portion 51 and the irradiated portion 52 are solidified in a state where the respective materials are mixed. The recording thus formed is irreversible, and the reflectance of this recorded portion is much smaller than the reflectance of the erasable amorphous portion described above. Therefore, even if the above-described erasable recording is attempted on this recording portion, the information is not erased.

As described above, irreversible and irreversible recording can be performed by performing recording in which the reflectance is greatly reduced. In the above information recording medium, the phase change recording layer and the second dielectric layer or the semiconductor layer are provided in contact with each other, but the second dielectric layer or the semiconductor layer has a lower melting point than the first dielectric layer. Is low, the recording / erasing is repeated, so that the second dielectric layer or the semiconductor layer is deteriorated,
It is conceivable that evaporation or perforation of the phase change recording layer occurs, and the durability of the phase change recording layer decreases.

Therefore, by providing a layer having a high melting point between the phase change recording layer and the second dielectric layer or the semiconductor layer, it is possible to prevent a decrease in the durability of the phase change recording layer. FIG. 6 is a sectional view of an information recording medium according to still another embodiment of the present invention.

In this figure, the second substrate is arranged in order from the transparent substrate 61 side.
A third dielectric layer 66, a phase change recording layer 62, a first dielectric layer 63, and a metal reflective layer 65, which are made of the same material as the first dielectric layer, An information recording medium 60 is formed. The first dielectric layer 63 and the third dielectric layer 66 have the same melting point, and are higher than the melting points of the phase change recording layer 62 and the second dielectric layer or the semiconductor layer 64. Further, the melting point of the second dielectric layer or the semiconductor layer 64 is higher than that of the phase change recording layer 62.

The erasable recording on the information recording medium 60 is performed by the same method as described with reference to FIG. At this time, since the third dielectric layer 66 is provided between the phase change recording layer 62 and the second dielectric layer or the semiconductor layer 64, the recording / erasing of the phase change recording layer 62 is repeated. No evaporation or perforation occurs.

Next, a method of non-erasable recording on the information recording medium will be described. First, similarly to the above-described erasable recording method, the information recording medium 60 is irradiated with a laser beam (not shown). Unlike the erasable recording method described above, the power of the laser light sufficiently melts the phase change recording layer 62 and the second dielectric layer or semiconductor layer 64 and does not melt the first dielectric layer 63. It has been adjusted to a degree.

Phase change recording layer 6 irradiated with laser light
The irradiated portion 2 and the irradiated portion of the second dielectric layer or semiconductor layer 64 are both melted. At this time, the third dielectric layer 66 is broken because it is formed to be very thin, and the third dielectric layer 66 is irradiated with the irradiated portion of the phase change recording layer 62 and the second dielectric layer or the irradiated portion of the semiconductor layer 64. The respective melts are mixed. When the transparent substrate 61 is heated to a temperature equal to or higher than its melting point by laser light irradiation, as described with reference to the information recording medium of FIG. The interface irradiated with the laser light is deformed.

Next, by stopping the irradiation of the laser beam, the irradiated portion of the phase change recording layer 62 and the irradiated portion of the second dielectric layer or the semiconductor layer 64 are mixed with each other. In the state, and the interface solidifies in a deformed state. The record thus formed is irreversible,
Further, the reflectance of the recording portion is much smaller than the reflectance of the erasable amorphous portion. Therefore, even if the above-described erasable recording is attempted on this recording portion, the information is not erased. As described above, by performing recording that is irreversible and whose reflectance is greatly reduced, erasable recording can be performed.

[0046]

Embodiments of the present invention will be described below. (Example 1) The information recording medium shown in FIG. 1 was manufactured by the following method.

First, the diameter is 120 mm and the thickness is 0.6 m
A semiconductor layer having a thickness of 1500 angstroms was laminated on a transparent substrate made of polycarbonate with a melting point of 940 ° C. using a vacuum sputtering apparatus. Next, a Ge ₂ Sb ₂ T film having a thickness of 200 Å was formed on the Ge semiconductor layer by a vacuum sputtering apparatus.
phase change recording layer made of e _5, first dielectric layer thickness is a ZnS / SiO ₂ at 200 angstroms, and the thickness was successively laminating a metal reflective layer of AlMo 1000 Angstroms.

Further, a UV curable resin was spin-coated thereon by using a UV spin coater, and further, 800
By irradiating ultraviolet rays with a kW UV lamp to cure the UV resin and form a 10 μm thick UV resin film,
An information recording medium was obtained. The UV resin film is a generally known passivation film that is provided to prevent scratches or the like generated during handling of the information recording medium.

A spiral continuous groove is formed in the information recording medium thus obtained, and no header or address information by emboss is introduced. That is, it is a soft format. In addition, this information recording medium has an L / G recording specification in which the width of the groove and the land forming the groove are both 0.74 μm, and recording is possible on both the groove and the land.

This information recording medium was initialized by a drive. That is, Ge ₂ Sb ₂ Te ₅ having a crystallization temperature of 165 ° C.
A phase change recording layer made of and a semiconductor layer made of Ge having a crystallization temperature of 180 ° C. are crystallized by irradiating a laser beam set to a power of 7 mW, and a laser beam set to a power of 16 mW is irradiated. As a result, Ge having a melting point of 940 ° C. and the phase change recording layer were melted and mixed, and header and address information were recorded in an erasable manner.

At this time, the linear velocity of the disk is 6 m.
/ S, the wavelength of the laser is 680 nm, and the NA of the lens
Was 0.63. Next, in the initialized information recording medium, the frequency is set to 9.7 MHz corresponding to the (8, 16) modulation closest-packed recording pattern (3T) at a single frequency of 50% duty, and the power is set to 12 mW. By irradiating the laser light, erasable recording was performed. After erasing the recording by irradiating a laser beam set to a power of 6 mW, the frequency is changed to 2.1 MHz corresponding to the sparsest recording pattern (14T), erasable recording is performed, and recording is performed again. Was erased.

Recording / erasing was performed in the above two types of recording patterns, and each time recording was performed in each pattern, a reproduced signal of each recording was measured. That is, in each recording pattern, the information recording medium is irradiated with a laser beam set to a power of 0.8 mW, and the recording / reproduction is performed by performing automatic focus / tracking adjustment. C / N was measured. Further, the recorded portion was erased, the wavelength was changed, and the erasure rate of the first recording remaining when the information was further recorded thereon was measured.

As a result, C / N is 5 in the sparsest pattern.
5 dB, and 53 dB for the densest pattern.
33 dB for the sparsest pattern, 30 dB for the densest pattern
Met.

In addition, the reflectance of each of the recording patterns of the non-erasably recorded portion and the erasably recorded portion is lower than that of the erasable portion. The signal amplitude was nearly four times higher in the unrecorded portion.

Further, the above-described erasable recording was performed on the non-erasable portion of the information recording medium where the header and address were recorded. As a result, the recording of the header and address introduced by the initialization remained without being erased, and a signal amplitude nearly four times as large as that of newly recorded erasable recording could be obtained. Therefore, even if erasable recording is performed on a part that has been recorded erasably, signals can be easily separated due to a large difference in signal amplitude.

Next, on the information recording medium initialized as described above, recording / erasing is alternately repeated with the above-described two types of recording patterns. The reproduced signal was measured.

FIG. 7 shows the result. In FIG. 7, the horizontal axis indicates the number of recordings (the sum of the number of recordings in the sparsest pattern and the densest pattern), and the ordinate indicates C / N (dB) and erasure rate (dB).
Is shown. In addition, data on the sparsest pattern is indicated by a solid line, and data on the densest pattern is indicated by a broken line.

In this figure, C / N is maintained at 50 dB or more for both the sparsest pattern and the densest pattern in the range where the number of recordings is up to 1000, but the number of recordings is 2 or less.
When the number of times exceeds 000, the temperature rapidly decreases. This tendency is the same for the erasure rate. This is because, in the information recording medium of the present embodiment, the phase change recording layer and the semiconductor layer made of Ge are provided in contact with each other. This is considered to be due to mixing with the recording layer.

Example 2 The information recording medium shown in FIG. 6 was manufactured by the following method. That is, between a semiconductor layer made of Ge and a phase-change recording layer, ZnS / Si is deposited at a thickness of 100 Å by a vacuum sputtering apparatus.
An information recording medium was manufactured in the same manner as in Example 1 except that a third dielectric layer made of O ₂ was provided.

This information recording medium was initialized in the same manner as in Example 1 except that the power of the laser beam used for non-erasable recording was set to 18 mW to perform non-erasable recording. In the same manner as in Example 1, the reflectance, signal amplitude, C / N, and erasure rate were measured.

As a result, the reflectivity of both the non-erasably recorded portion and the erasable recorded portion is lower in each of the recording patterns, and the erasable portions are smaller than the erasable portions. The signal amplitude was nearly three times higher in the proper recording portion.

At this time, the C / N is 55 dB for the sparsest pattern and 53 dB for the densest pattern, and the erasing rate is 33 dB for the sparsest pattern and 3 for the densest pattern.
It was 0 dB.

In the information recording medium of the present embodiment, the signal amplitude of the non-erasable recording portion was about ／ of that of the information recording medium of the first embodiment. This is because the third dielectric layer is formed between the phase change recording layer and the semiconductor layer made of Ge, so that the phase change recording layer and the semiconductor layer made of Ge are hardly mixed. It is believed that there is.

Next, in the same manner as in Example 1, the changes in the C / N and the erasure ratio with respect to the repetition of the recording were measured. FIG. 8 shows the result.

As is apparent from this figure, in the information recording medium of this embodiment, the C / N and the erasing rate hardly decrease until about 50,000 times. This is because the phase change recording layer and Ge
This is because the third dielectric layer having a high melting point is formed between the semiconductor layer made of Ge and the phase change recording layer and the semiconductor layer made of Ge due to repetition of recording / erasing. is there.

Example 3 The information recording medium shown in FIG. 4 was manufactured by the following method. That is, on a transparent substrate,
Except that the first dielectric layer was formed with a thickness of 1800 angstroms, the phase change recording layer was formed with a thickness of 200 angstroms, and the Ge semiconductor layer was formed sequentially with a thickness of 200 angstroms. An information recording medium was produced in the same manner as in Example 1.

This information recording medium is initialized in the same manner as in the first embodiment to perform non-erasable recording.
The reflectance, the signal amplitude, the C / N, and the erasure rate were measured in the same manner as described above.

As a result, the reflectance decreased in the erasable recording portion, but increased in the non-erasable recording portion. This is considered for the following reasons.
That is, the phase change recording layer made of Ge ₂ Sb ₂ Te ₅ and the Ge semiconductor layer are heated to the melting point of Ge or more,
The function of protecting the phase change recording layer of the Ge semiconductor layer is lost,
The phase change recording layer and the semiconductor layer are mixed. As a result, the optical conditions change and the reflection at the interface between the mixed layer and the first dielectric layer increases, so that the reflectance increases.

Further, a signal amplitude about twice as large was obtained in a non-erasable recording portion as compared to an erasable portion. C / N
Is 54 dB for the sparsest pattern and 53 for the densest pattern.
The erasing rate was 32 dB for the sparsest pattern and 29 dB for the densest pattern.

Further, in the same manner as in Example 1, erasable recording was performed on the portion of the information recording medium where the header and address were recorded so as not to be erased. As a result, the record of the header and address introduced by the initialization remains without being erased, and as described above, the reflectivity has increased in the non-erasable recording part, so that the non-erasable recording is clearly discriminated. We were able to.

In Examples 1 to 3, the phase change recording layer
Although the case of being composed of a ternary alloy consisting of e, Sb, and Te has been described, In, which have almost the same melting points as these,
It goes without saying that the phase change recording layer can be constituted by a ternary alloy composed of Sb and Te. In the above embodiment, the semiconductor layer made of Ge is exemplified as the second dielectric layer or the semiconductor layer. However, the melting point is between the melting point of the first dielectric layer and the melting point of the phase change recording layer. It is also possible to use another dielectric or semiconductor.

[0072]

According to the present invention, in addition to the phase change recording layer having a relatively low melting point and the first dielectric layer having a high melting point, a phase change recording layer having a melting point between the phase change recording layer and the first dielectric layer is provided. An information recording medium and a recording method having a certain second dielectric layer or semiconductor layer are provided, and erasable recording is performed by a reversible phase change of the phase change recording layer, and the phase change recording layer and the second dielectric layer are provided. Non-erasable recording is performed due to irreversible mixing with the body layer or the semiconductor layer, and further, since these recording methods are controlled only by changing the power of irradiated light, erasing is possible. Recording and non-erasable recording can be arbitrarily selected.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an information recording medium according to an embodiment of the present invention.

FIG. 2 is a sectional view for explaining a recording method of the information recording medium according to one embodiment of the present invention.

FIG. 3 is a sectional view for explaining a recording method of the information recording medium according to one embodiment of the present invention.

FIG. 4 is a sectional view showing an information recording medium according to one embodiment of the present invention.

FIG. 5 is a sectional view for explaining a recording method of the information recording medium according to one embodiment of the present invention.

FIG. 6 is a sectional view showing an information recording medium according to an embodiment of the present invention.

FIG. 7 is a graph showing a change in recording characteristics with respect to the number of recordings of the information recording medium according to one embodiment of the present invention.

FIG. 8 is a graph showing a change in recording characteristics with respect to the number of recordings of the information recording medium according to one embodiment of the present invention.

FIG. 9 is a sectional view showing a conventional information recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Information recording medium 11 ... Transparent substrate 12 ... Phase change recording layer 13 ... 1st dielectric layer 14 ... 2nd dielectric layer 15 ... Metal reflection layer 20 ... Laser beam 21 ... Irradiation part 30 ... Laser beam 31 ... Irradiated part 32 ... Irradiated part 33 ... Interface 40 ... Information recording medium 41 ... Transparent substrate 42 ... Phase change recording layer 43 ... First dielectric layer 44 ... Second dielectric layer 45 ... Metal reflective layer 51 ... Irradiated section 52 Irradiated section 60 Information recording medium 61 Transparent substrate 62 Phase change recording layer 63 First dielectric layer 64 Second dielectric layer 65 Metal reflective layer 66 Third dielectric Body layer 90 Information recording medium 91 Transparent substrate 92 Phase change recording layer 93 Dielectric layer 94 Dielectric layer 95 Metal reflective layer

Claims (9)

[Claims] 1. A light-transmissive substrate, a phase change recording layer provided on the substrate and reversibly changing phase by light irradiation, provided on the phase change recording layer, A first dielectric layer having a high melting point, and a second dielectric layer provided between the substrate and the phase change recording layer and having a melting point between the phase change recording layer and the first dielectric layer. An information recording medium comprising: a dielectric layer or a semiconductor layer. 2. A light-transmissive substrate, a phase-change recording layer provided on the substrate and reversibly changing phase by light irradiation, provided between the substrate and the phase-change recording layer, A first dielectric layer having a higher melting point than the phase change recording layer; and a second dielectric layer provided on the phase change recording layer and having a melting point between the phase change recording layer and the first dielectric layer. An information recording medium comprising: a dielectric layer or a semiconductor layer. 3. A semiconductor device comprising a third dielectric layer made of the same material as the first dielectric layer between the phase change recording layer and the second dielectric layer or the semiconductor layer. The information recording medium according to claim 1, wherein 4. The melting point of the phase change recording layer is from 600 ° C. to 7 ° C.
00 ° C., and the melting point of the first dielectric layer is 1200 ° C.
The melting point of the second dielectric layer or the semiconductor layer is 800 ° C. to 1000 ° C.
4. The information recording medium according to any one of items 3 to 3. 5. The semiconductor device according to claim 1, wherein said second dielectric layer or semiconductor layer is
5. The information recording medium according to claim 4, comprising e. 6. A metal reflection layer is provided on the phase change recording layer, and the first dielectric film and the second dielectric film or the semiconductor film are provided between the metal reflection layer and the substrate. The information recording medium according to claim 4, wherein is arranged. 7. The phase change recording layer according to claim 1, wherein the phase change recording layer is formed of Ge, Sb,
The information recording medium according to claim 4, comprising a ternary alloy of e or a ternary alloy of In, Sb, and Te. 8. The phase change recording layer is heated to a temperature between a melting point of the phase change recording layer and a melting point of the second dielectric layer or the semiconductor layer by irradiating light of a first power. By performing erasable recording by irradiating light having a second power higher than the first power, the phase change recording layer and the second dielectric layer or the semiconductor layer are subjected to the phase change recording. The non-erasable recording is performed by heating to a temperature between the melting point of a layer and the melting point of the second dielectric layer or the semiconductor layer. Recording method of information recording medium. 9. Irradiating light of a first power to heat the phase change recording layer to 600 ° C. to 700 ° C. to perform erasable recording, and a second power higher than the first power The non-erasable recording is performed by heating the phase change recording layer and the second dielectric layer or the semiconductor layer to 800 ° C. to 1000 ° C. by irradiating the light. Recording method of the information recording medium according to the item 1.