JPH11339315A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical recording medium which is free from deterioration by repetitive overwriting, such as the degradation in jitter characteristics, the deterioration at the beginning ends and terminals of sectors, the degradation in contrast and the occurrence of a burst defect and is excellent in an overwriting shelf characteristic and erasing characteristic by providing both sides or one side of the recording layer of the medium with a layer consisting of a carbide so as to bring this layer into contact therewith. SOLUTION: The representative constitution of the component members of the optical recording medium is obtd. by laminating a first dielectric layer, carbide layer, recording layer, second dielectric layer and reflection layer in this order on the transparent substrate. The mass transfer of the recording layer is suppressed and the diffusion of sulfur from the dielectric layers to the recording layer is prevented by forming the carbide in contact with the recording layer, by which the deterioration by the repetitive overwriting may be ameliorated. The reason thereof lies in that crystallization is accelerated by the carbide layer to enable the rapid crystallization of the recording layer. The layer consisting of the carbide is selected from silicon carbide, titanium carbide, tungsten carbide, and tantalum carbide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to an optical information recording medium capable of recording, erasing, and reproducing information.

In particular, the present invention relates to a rewritable phase-change optical recording medium, such as an optical disk, an optical card, or an optical tape, having a function of erasing and rewriting recorded information and capable of recording an information signal at high speed and high density. Things.

[0003]

2. Description of the Related Art The technology of a conventional rewritable phase-change optical recording medium is as follows.

[0004] These optical recording media have a recording layer mainly containing tellurium or the like. During recording, a focused laser light pulse is applied to the recording layer in a crystalline state for a short time to partially cover the recording layer. Melts. The melted portion is quenched by thermal diffusion and solidified to form an amorphous recording mark. The light reflectance of this recording mark is lower than that of the crystalline state and can be reproduced optically as a recording signal.

At the time of erasing, the recording marks are irradiated with a laser beam and heated to a temperature lower than the melting point of the recording layer and higher than the crystallization temperature to crystallize the recording marks in an amorphous state, and the original unrecorded data is recorded. Return to condition.

As a material for the recording layer of these rewritable phase-change optical recording media, alloys such as Ge ₂ Sb ₂ Te ₅ (N. Yamada et al. Proc. Int. Symp. On Optical Memory 1) are used.
987 p61-66) is known.

An optical recording medium having a Te alloy as a recording layer has a high crystallization speed and can perform high-speed overwriting with a single circular beam only by modulating the irradiation power. In an optical recording medium using these recording layers, usually, a heat-resistant and light-transmitting dielectric layer is provided on each side of the recording layer to prevent deformation and opening of the recording layer during recording. I'm preventing. Further, a technique is known in which a metal reflective layer such as light reflective Al is laminated on the dielectric layer on the opposite side to the light beam incident direction to improve the signal contrast during reproduction by an optical interference effect. I have.

The problems in the above-mentioned conventional rewritable phase-change type optical recording medium are as follows.

That is, in the conventional disk structure, the repetition of overwriting causes deterioration of jitter characteristics, deterioration of recording waveforms at the start and end ends of sector recording, and reduction of signal amplitude (reduction of contrast). . It is considered that this is caused by a change in the thickness of the recording layer due to mass transfer of the recording layer, and a change in optical characteristics due to the diffusion of sulfur in the protective layer into the recording layer. In addition, burst defects may occur due to crack growth in the protective layer.

[0010] Further, when overwriting is performed after leaving a disk on which a signal is already recorded for a long time (hereinafter referred to as an overwrite shelf), there has been a problem that jitter characteristics deteriorate and an error occurs. For this reason, there was a problem in the storage durability of the disk.

Further, as higher densities and higher speeds are demanded, higher densities and higher speeds are also being studied for phase change type optical recording media. Problems arise. This hinders stable recording and reproduction in mark length recording, and makes it difficult to achieve high density and high linear velocity.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
Second, there is little deterioration due to repeated overwriting, such as deterioration of jitter characteristics, deterioration of the start and end of the sector, deterioration of contrast, and occurrence of burst defects. Second, excellent overwrite shelf characteristics; An object of the present invention is to provide a rewritable phase-change type optical recording medium characterized by good erasing characteristics even under high-speed and high-density recording conditions.

[0013]

According to the present invention, information can be recorded, erased, and reproduced by irradiating a recording layer formed on a substrate with light.
An optical recording medium in which at least a recording layer and a reflective layer are laminated on a substrate in this order by a phase change between an amorphous phase and a crystalline phase, and both sides or one side thereof are in contact with the recording layer. The present invention relates to an optical recording medium provided with a layer made of a carbide.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Deterioration due to repetitive overwriting, which is a problem to be solved by the present invention, that is, deterioration of jitter characteristics, deterioration of the beginning and end of a sector, and reduction of amplitude, are caused by mass transfer of a recording layer material, dielectric layer, It is thought to be due to the diffusion of sulfur in the recording layer. Further, the deterioration of the overwrite shelf characteristic is caused by the deterioration of the erasing characteristic. This may be because the state of the atomic arrangement or the like changes when the recording mark (amorphous layer) is left for a long time, or the dielectric layer reacts with the recording layer. Furthermore, in realizing high linear velocity and high density, it is considered that the problem of deterioration of the erasing characteristics is caused by a reduction in the time for which the recording layer is maintained at a temperature higher than the crystallization temperature. Can be

The present inventors have conducted intensive experiments,
It has been found that when the carbide layer is provided so as to be in contact with the recording layer, problems such as deterioration due to repeated overwriting, deterioration of overwrite shelf characteristics, and deterioration of erasing characteristics at high linear velocity and high density can be improved.

That is, a typical layer constitution of the constituent members of the optical recording medium of the present invention is that a first dielectric layer, a carbide layer, a recording layer, a second dielectric layer, and a reflective layer are laminated in this order on a transparent substrate. It was done. However, it is not limited to this.

In the optical recording medium of the present invention, it is necessary to form a carbide layer in contact with the recording layer. This has the following effects.

First, deterioration due to repeated overwriting can be improved by suppressing mass transfer of the recording layer and preventing diffusion of sulfur from the dielectric layer to the recording layer. Second, the deterioration of the overwrite shelf characteristics can be improved. This is considered to be due to the effect of preventing a change in the atomic arrangement of the recording marks (amorphous) and a reaction between the dielectric layer and the recording layer even after being left for a long time.

Third, the erasure characteristics at high linear velocity and high density are prevented from deteriorating. This is because the carbide layer promotes crystallization,
This is probably because the recording layer can be crystallized in a short time.

As the carbide, silicon carbide, titanium carbide, tungsten carbide, tantalum carbide and the like are preferable, and a mixture containing two or more of these materials may be used. However, it is preferable not to contain sulfide. Further, it may contain oxygen and nitrogen. A more preferable material is silicon carbide, and a mixture with other materials may be used. However, in order to obtain good characteristics, it is preferable that silicon carbide is contained in a proportion of 60 mol% or more.

The thickness of the carbide layer should be not less than 0.5 nm and not more than 300 n in consideration of the difficulty of peeling and optical conditions.
m or less is preferable. From the viewpoint of productivity and ease of film formation, the thickness is more preferably 1 nm or more and 10 nm or less.

The material of the first dielectric layer is preferably substantially transparent at the wavelength of the recording light, and has a refractive index larger than that of the transparent substrate and smaller than that of the recording layer. Specifically, a thin film of ZnS, Si, Ge,
Thin films of oxides of metals such as Ti, Zr, Ta, Nb,
A thin film of a nitride such as Si or Ge, a thin film of a carbide such as Zr or Hf, and a film of a mixture of these compounds are preferable because of high heat resistance. In particular, a film made of a mixture of ZnS and SiO2 is preferable because deterioration due to repeated overwriting hardly occurs. In particular, ZnS and SiO
The mixture of 2 and carbon is preferable because the residual stress of the film is small, and the recording sensitivity, carrier-to-noise ratio (C / N), erasure rate, and the like are unlikely to be deteriorated even by repeated recording and erasing. The thickness of the film is preferably from 10 to 500 nm from the viewpoint of optical conditions and productivity.

The recording layer of the present invention is not particularly limited, but may be a Ge—Te alloy, an In—Se alloy, a Ge
-Sb-Te alloy, In-Sb-Te alloy, Pd-Ge
-Sb-Te alloy, Pt-Ge-Sb-Te alloy, Nb
-Ge-Sb-Te alloy, Ni-Ge-Sb-Te alloy, Co-Ge-Sb-Te alloy, Ag-In-Sb-
Te alloy, Ag-V-In-Sb-Te alloy, Ag-G
e-Sb-Te alloy, Ag-Pd-Ge-Sb-Te alloy, Pd-Nb-Ge-Sb-Te alloy, and the like.

In particular, Ge-Sb-Te alloy, Pd-Ge-
Sb-Te alloy, Pt-Ge-Sb-Te alloy, Nb-
Ge-Sb-Te alloy, Pd-Nb-Ge-Sb-Te
The alloy has a short erasing time and can be repeatedly recorded and erased many times, and has a carrier-to-noise ratio (C / N),
It is preferable because recording characteristics such as an erasing ratio are excellent.

The thickness of the recording layer of the present invention is preferably from 5 nm to 40 nm. When the thickness of the recording layer is smaller than the above, the recording characteristics are significantly degraded due to repeated overwriting, and when the recording layer is thicker than the above, the recording layer is likely to move due to repeated overwriting. Jitter becomes worse. In particular, when mark length recording is adopted, the recording layer is more likely to move due to recording and erasing than when pit position recording is used.To prevent this, it is necessary to further increase the cooling of the recording layer during recording. And the thickness of the recording layer is 10 nm to 35 nm.
Is more preferable, and since the recording characteristics such as the carrier-to-noise ratio (C / N) and the erasing ratio are excellent, the ratio is more preferably 1.
0 nm to 24 nm.

The material of the second dielectric layer of the present invention may be the same as that of the first dielectric layer,
Different materials may be used. Thickness is 3nm or more and 50n
m or less is preferable. If the thickness of the second dielectric layer is smaller than the above, defects such as cracks occur, and the durability of the second dielectric layer is undesirably reduced. Further, the thickness of the second dielectric layer is
If the thickness is larger than the above, the cooling degree of the recording layer becomes low, which is not preferable. The thickness of the second dielectric layer has a more direct effect on the cooling of the recording layer, and in order to obtain better erasure characteristics and repetition durability, and particularly to achieve good recording in the case of mark length recording. -In order to obtain erasing characteristics, 30 nm or less is more effective. Since it absorbs light and can be efficiently used as thermal energy for recording and erasing, it is also preferable to be formed from a non-transparent material. For example,
The mixture of ZnS, SiO2 and carbon is preferable because the residual stress of the film is small, and the recording sensitivity, the carrier-to-noise ratio (C / N), the erasing rate, and the like are hardly deteriorated even when recording and erasing are repeated. .

Examples of the material of the reflective layer include metals, alloys, and mixtures of metals and metal compounds having light reflectivity. Specifically, a metal having a high reflectivity, such as Al, Au, Ag, or Cu, an alloy containing the same as a main component, Al, S
Metal compounds such as nitrides, oxides, and chalcogenides such as i are preferable. Metals such as Al and Au and alloys containing these as main components are particularly preferable because of their high light reflectivity and high thermal conductivity. The thickness of the reflective layer is generally about 10 nm or more and 300 nm or less. The thickness is preferably 30 nm or more and 200 nm or less because the recording sensitivity is high and the reproduction signal intensity can be increased.

As the material of the substrate of the present invention, various transparent synthetic resins, transparent glass and the like can be used. For the purpose of avoiding the effects of dust and scratches on the substrate, it is preferable to use a transparent substrate and perform recording from the substrate side with a focused light beam.As such a transparent substrate material, glass, polycarbonate, polymethyl methacrylate, Polyolefin resin, epoxy resin, polyimide resin and the like can be mentioned. In particular, a polycarbonate resin and an amorphous polyolefin resin are preferable because they have low optical birefringence, low hygroscopicity, and are easy to mold. When heat resistance is required, an epoxy resin is preferred.

Although the thickness of the substrate is not particularly limited, it is practically 0.01 mm to 5 mm. 0.01m
If it is less than m, even when recording with a light beam focused from the substrate side, it is susceptible to dust, and if it is 5 mm or more,
It becomes difficult to increase the numerical aperture of the objective lens, and the spot size of the irradiation light beam becomes large, so that it becomes difficult to increase the recording density.

Next, a method for manufacturing the optical recording medium of the present invention will be described. As a method of forming a first dielectric layer, a carbide layer, a recording layer, a second dielectric layer, a reflective layer, and the like on a substrate,
A method of forming a thin film in a vacuum, for example, a vacuum deposition method, an ion plating method, a sputtering method and the like can be mentioned. In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled. The thickness of the recording layer or the like to be formed can be easily controlled by monitoring the deposited state with a quartz crystal film thickness meter or the like.

Further, in not significantly impaired range the effects of the present invention, after forming the reflective layer, flaws, such as for prevention of deformation, ZnS, dielectric layers or ultraviolet, such as SiO _2, ZnS and mixtures SiO ₂ A protective layer such as a cured resin may be provided as necessary.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

(Analysis and Measurement Methods) The compositions of the reflective layer and the recording layer were confirmed by ICP emission analysis (manufactured by Seiko Instruments Inc.).

The film thickness during the formation of the recording layer, the dielectric layer, and the reflection layer was monitored by a quartz oscillator film thickness meter. The thickness of each layer was measured by observing the cross section with a scanning or transmission electron microscope.

In the optical recording medium formed by sputtering, the recording layer on the entire surface of the disk was crystallized and initialized with a beam of a semiconductor laser having a wavelength of 830 nm before recording.

Next, under the condition that the recording track has a linear velocity of 6 m / sec, using an optical disc evaluation apparatus having an optical head having a numerical aperture of an objective lens of 0.6 and a wavelength of a semiconductor laser of 680 nm, 8/16 modulation is performed. The random pattern was overwritten 100,000 times by mark length recording. At this time, a multi-pulse was used as the recording laser waveform. The window width at this time was 34 ns. Recording power and erasing power were optimized for each disk.

At the time of overwriting, the start and end of writing of a data group (recording mark) are fixed to one point on the disk. The distance between the data write start portion and the data write end portion was 1 cm, and only this portion was overwritten.

Jitter was measured by a time interval analyzer. The deterioration distance (collapse of the waveform) at the beginning and end of the recording area, the decrease in the amplitude of the signal waveform, and the presence or absence of a burst defect were observed with an oscilloscope.

Subsequently, recording is performed once on another track, and the byte error rate at that time is measured.
It was left in a drying oven at 100 ° C. for 100 hours. After that, the byte error rate of the same part was measured, and
The overwrite shelf characteristics were evaluated by overwriting once and measuring the byte error rate again.

The erasing characteristics were evaluated by recording on a recording track under the following conditions using an optical disk evaluation apparatus having an optical head having a numerical aperture of an objective lens of 0.6 and a semiconductor laser having a wavelength of 638 nm.

(Condition a) At a linear velocity of 6 m / sec, the recording frequency f
Recording was performed 10 times at 1 = 1.1 MHz (long recording mark), and overwriting was performed once at f2 = 4.9 MHz (short recording mark). The duty was 50% and the window width was 34 ns. An erasing ratio is defined as a ratio of a carrier of a long recording mark before and after overwriting a short recording mark, and an effective erasing ratio is defined as a ratio of a carrier of a short recording mark to a carrier of a long recording mark after overwriting. Was measured by a spectrum analyzer under the following conditions.

(Condition b) At a linear velocity of 9 m / sec and a recording frequency f
Recording was performed 10 times at 3 = 2.4 MHz (long recording mark), and overwriting was performed once at f4 = 10.6 MHz (short recording mark). The duty was 50% and the window width was 16 ns. The erasing rate and the effective erasing rate were measured in the same manner as in (condition a).

In both cases (condition a) and (condition b), the lengths of the long recording mark and the short recording mark are 13 times and 3 times the window width, respectively, and the recording linear density in the case of (condition b) Is
It is about 1.5 times that in the case of (condition a). In addition, the recording power and the erasing power were optimized for each disk.

(Example 1) A polycarbonate substrate with a guide groove having a thickness of 0.6 mm, a diameter of 12 cm, and a pitch of 1.48 μm (land width 0.74 μm, groove width 0.1 mm) rotated at 30 revolutions per minute. 74 μm), the following sputtering film formation was performed.

First, the inside of the vacuum vessel was evacuated to 1 × 10 ^-3 Pa, and then SiO 2 was evacuated in an Ar gas atmosphere of 2 × 10 ^-1 Pa.
_A first dielectric layer having a thickness of 95 nm was formed on the substrate by sputtering ZnS to which 20 mol% of ₂ was added. Next, silicon carbide was sputtered to form a carbide layer having a thickness of 5 nm. Subsequently, an alloy target made of Ge, Sb, and Te was sputtered to obtain a recording layer having a thickness of 20 nm. Further, as the second dielectric layer, the same ZnS.SiO as the first dielectric layer is used.
₂ was formed to a thickness of 16 nm, and an Al-Hf-Pd alloy was sputtered thereon to form a reflective layer having a thickness of 150 nm, thereby obtaining an optical recording medium of the present invention.

Observation of the waveform collapse at the data write start portion and the data write end portion after overwriting 100,000 times revealed that they were 3 μm and 10 μm, respectively, and it was confirmed that there was no practical problem. Further, when the jitter of this portion was measured, it was confirmed that it was 9% of the window width, which was sufficiently small for practical use. The amplitude of the signal hardly changed compared to the amplitude of the signal after 10 times of overwriting, and no burst defect was observed.

The byte error rate when recording was performed once on this disk was 3.0 × 10 ^-5 . After leaving it in the drying oven and measuring the same part again,
There was almost no change at 3.5 × 10 ⁻⁵ . When this part was overwritten once and the byte error rate was measured, it was 4.0 × 10 ^-5 and there was almost no change, indicating good overwrite shelf characteristics. The jitter at this time was a good value of 9% of the window width.

Further, a pitch of 1.2 μm (land width of 0.
The same sputtering film formation as above was performed on a polycarbonate substrate having a thickness of 6 μm and a groove width of 0.6 μm), and the erasing characteristics were evaluated.

When the erasure rate under (condition a) was measured, it was 4
0 dB and the effective erasing rate was 30 dB. Next, when the erasing rate under (condition b) was measured, the erasing rate was 38 dB and the effective erasing rate was 26 dB, and practically sufficient erasing characteristics were obtained even under high linear velocity and high density recording conditions.

Example 2 A disk similar to that of Example 1 was produced except that titanium carbide was formed to a thickness of 5 nm as a carbide layer.

The same measurement as in Example 1 was performed.
The collapse of the waveform at the writing start portion and the writing end portion after the overwriting of 10,000 times was 5 μm and 10 μm, respectively, which were confirmed to be sufficiently small for practical use. Also, it was confirmed that the jitter in this portion was 11% of the window width and was sufficiently small for practical use. The amplitude of the signal is about 90% of the amplitude after 10 overwrites, which is a level that does not cause any practical problem. Also, no burst defects occurred.

The byte error rate when recording was performed once on this disk was 3.5 × 10 ^-5 . After being left in a drying oven under the same conditions as in Example 1, the same portion was measured again and found to be 3.8 × 10 ^-5 with little change. When this part was overwritten once and the byte error rate was measured, it was 4.2 × 10 ^-5 and there was almost no change, indicating good overwrite shelf characteristics. The jitter at this time was a good value of 10% of the window width.

When the erasing rate was measured in the same manner as in Example 1 (condition a), the erasing rate was 40 dB and the effective erasing rate was 28 dB. Next, when the erasing rate under (condition b) was measured, the erasing rate was 36 dB and the effective erasing rate was 24 dB. Under any of the conditions, practically sufficient erasing characteristics were obtained.

(Example 3) A disk was manufactured in the same manner as in Example 1 except that tungsten carbide was formed to a thickness of 5 nm as a carbide layer.

The same measurement as in Example 1 was performed.
The collapse of the waveform at the writing start portion and the writing end portion after the overwriting of 10,000 times was 8 μm and 10 μm, respectively, which were confirmed to be sufficiently small for practical use. Also, it was confirmed that the jitter in this portion was 12% of the window width and was sufficiently small for practical use. The amplitude of the signal is about 90% of the amplitude after 10 overwrites, which is a level that does not cause any practical problem. Also, no burst defects occurred.

The byte error rate when recording was performed once on this disk was 3.5 × 10 ^-5 . After being left in a drying oven under the same conditions as in Example 1, the same portion was measured again. As a result, there was almost no change at 3.7 × 10 ⁻⁵ . When this portion was overwritten once and the byte error rate was measured, it was 4.3 × 10 ⁻⁵ , there was almost no change, and good overwrite shelf characteristics were exhibited. The jitter at this time was a good value of 10% of the window width.

When the erasing rate was measured in the same manner as in Example 1 (condition a), the erasing rate was 39 dB, and the effective erasing rate was 27 dB. Next, when the erasing rate under (condition b) was measured, the erasing rate was 35 dB and the effective erasing rate was 22 dB. Under all the conditions, practically sufficient erasing characteristics were obtained.

Example 4 A disk similar to that of Example 1 was produced except that tantalum carbide was formed to a thickness of 5 nm as a carbide layer.

The same measurement as in Example 1 was performed.
The collapse of the waveform at the writing start portion and the writing end portion after the overwriting of 10,000 times was 8 μm and 12 μm, respectively, which were confirmed to be sufficiently small for practical use. Also, it was confirmed that the jitter in this portion was 11% of the window width and was sufficiently small for practical use. The amplitude of the signal is about 90% of the amplitude after 10 overwrites, which is a level that does not cause any practical problem. Also, no burst defects occurred.

The byte error rate when recording was performed once on this disk was 3.4 × 10 ^-5 . After being left in a drying oven under the same conditions as in Example 1, the same portion was measured again. As a result, there was almost no change at 3.9 × 10 ⁻⁵ . When this portion was overwritten once and the byte error rate was measured, it was 4.3 × 10 ⁻⁵ , there was almost no change, and good overwrite shelf characteristics were exhibited. The jitter at this time was a good value of 10% of the window width.

When the erasing rate was measured in the same manner as in Example 1 (condition a), the erasing rate was 38 dB, and the effective erasing rate was 28 dB. Next, when the erasing rate under (condition b) was measured, the erasing rate was 35 dB and the effective erasing rate was 22 dB. Under all the conditions, practically sufficient erasing characteristics were obtained.

Comparative Example 1 A disk similar to that of Example 1 was obtained except that the carbide layer was omitted.

The same measurement as in Example 1 was performed.
The jitter after 100,000 times overwriting is 14 times the window width.
%, And the collapse of the waveform at the start of writing and at the end of writing was observed to be 200 μm,
As large as 50 μm, it was found that accurate data reproduction was difficult. Further, the amplitude of the signal was 75% of the amplitude after overwriting 10 times, and the contrast was low.

The byte error rate when recording was performed once on this disk was 4.0 × 10 ^-5 . When the same portion was measured again after being left in a drying oven under the same conditions as in Example 1, there was almost no change at 3.5 × 10 ⁻⁵ , but this portion was overwritten once to reduce the byte error rate. The measurement resulted in an error, and the overwrite shelf characteristics were so deteriorated that the byte error rate could not be measured. The cause of the error was due to the deterioration of the jitter. At this time, the jitter was about 18% of the window width.

When the erasing rate was measured in the same manner as in Example 1 (condition a), the erasing rate was 38 dB, the effective erasing rate was 24 dB, and the erasing characteristics were good. However, when the erase ratio under (condition b) was measured, it was 28 dB, and the effective erase ratio was 14 dB.
dB, and the erasing characteristics deteriorated under the conditions of high linear velocity and high density.

[0066]

According to the optical recording medium of the present invention, the following effects can be obtained.

(1) Even if recording / erasing is performed many times, a decrease in signal amplitude is small.

(2) Even if recording / erasing is performed a large number of times, the start and end of the sector are hardly degraded. (3) Good jitter characteristics can be obtained even if recording / erasing is performed many times.

(4) Burst defects do not occur even if recording / erasing is performed many times.

(5) Good storage durability.

(6) Good erasing characteristics can be obtained even under high linear velocity and high density recording conditions.

(7) It can be easily manufactured by the sputtering method.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hitoshi Nosumasa 1-1-1 Sonoyama, Otsu City, Shiga Prefecture Toray Industries, Inc. Shiga Plant

Claims (6)

[Claims] An information recording, erasing, and reproducing operation can be performed by irradiating a recording layer with light, and information recording and erasing are performed by a phase change between an amorphous phase and a crystalline phase. An optical recording medium comprising at least a recording layer and a reflective layer laminated in this order, wherein a layer made of carbide is provided on one or both sides thereof so as to be in contact with the recording layer. 2. The optical recording medium according to claim 1, wherein a layer made of carbide is provided between the substrate and the recording layer. 3. The optical recording medium according to claim 1, wherein a dielectric layer containing ZnS and SiO 2 is provided between at least one of the substrate and the recording layer and between the recording layer and the reflection layer. 4. An average film thickness of a layer made of carbide is 0.5
2. The optical recording medium according to claim 1, wherein the thickness is not less than 300 nm and not more than 300 nm. 5. The light according to claim 1, wherein the layer made of carbide is at least one selected from silicon carbide, titanium carbide, tungsten carbide, and tantalum carbide. recoding media. 6. The optical recording medium according to claim 1, wherein the layer made of carbide is a mixture containing silicon carbide as a main component.