JP2001167476A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a writable phase change optical recording medium excellent in repetitive durability and shelf durability without the degradation of jitter characteristics due to a number of repetitive overwrite, the lowering of signal amplitude and the occurrence of a burst defect and the like. SOLUTION: The optical recording medium has at least a recording layer and a reflecting layer provided on a substrate and can record, erase and reproduce information by irradiation with light. The recording and erasure of the information are carried out by a reversible phase change between amorphous and crystalline phases. A layer consisting of a carbon, nitrogen and/or oxygen is disposed between the substrate and the recording layer in contact with the recording layer.

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 provides a method for erasing recorded information,
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 rewritable function and capable of recording an information signal at high speed and high density.

[0002]

2. Description of the Related Art The technology of a conventional rewritable phase-change optical recording medium is as follows. These optical recording media have a recording layer mainly containing tellurium or the like, and at the time of recording, a focused laser light pulse is applied to the crystalline recording layer for a short time to partially melt the recording layer. 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 mark is irradiated with a laser beam and heated to a temperature below the melting point of the recording layer and above the crystallization temperature to crystallize the amorphous recording mark and return to the original unrecorded state. . As the material of 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. In
t.Symp.on Optical Memory 1987 pp. 61-66) is known.

[0003] These optical recording media using a Te alloy as a recording layer have a high crystallization speed, and high-speed overwriting with a single circular beam is possible 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 both sides of the recording layer one by one to prevent deformation and opening of the recording layer during recording. I'm preventing. Furthermore, 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.

[0004] Problems in the above-mentioned conventional rewritable phase-change optical recording medium are as follows. That is,
In the conventional disk structure, the repetition of overwriting causes deterioration in jitter characteristics, reduction in the amplitude of a reproduction signal (reduction in contrast), and the like. A possible cause of this is a change in the thickness of the recording layer due to mass transfer of the recording layer. In addition, burst defects may occur due to crack growth in the protective film.

Further, in the conventional configuration, if a disk on which a signal is already recorded is left for a long time and then overwriting is performed on a track on which a signal is recorded (hereinafter referred to as an overwrite shelf), the jitter characteristic is reduced. Has worsened, resulting in an error. For this reason, there was a problem in the storage durability of the disk.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rewritable phase-change type optical recording medium which causes little deterioration due to repetitive overwriting, such as deterioration of jitter characteristics, deterioration of contrast and occurrence of burst defects. It is in. Another object of the present invention is to provide a rewritable phase-change optical recording medium having excellent overwrite shelf characteristics.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to record, erase, and reproduce information by irradiating light, and to record and erase information between an amorphous phase and a crystalline phase. An optical recording medium which is performed by a reversible phase change and has at least a recording layer and a reflective layer on a substrate, wherein carbon and nitrogen and / or oxygen are used to contact the recording layer between the substrate and the recording layer. This is achieved by an optical recording medium characterized by having a layer formed of:

[0008]

DETAILED DESCRIPTION OF THE INVENTION The cause of the deterioration caused by repeated overwriting, that is, the deterioration of jitter characteristics and the decrease of contrast, which is the problem to be solved by the present invention, is that the recording layer material moves due to repeated melting and solidification. It is believed to be due to It is considered that the movement of the recording layer material is caused by an increase in volume due to melting of the recording layer, and elastic deformation and plastic deformation of the dielectric layer in contact with the recording layer. In addition, by overwrite shelf,
The reason why the jitter characteristic deteriorates is that the erasing characteristic deteriorates. The cause of the deterioration of the erasing characteristics is considered to be that the state of the atomic arrangement changes when the recording mark (amorphous phase) is left for a long time, or that the dielectric layer and the recording layer react. Can be

The present inventors have conducted intensive research and have found that a layer composed of carbon, nitrogen and / or oxygen is provided between the substrate and the recording layer so as to be in contact with the recording layer, so that the mass transfer of the recording layer is achieved. It has been found that deterioration due to repeated overwriting can be improved and deterioration of jitter characteristics due to overwriting shelf can be improved.

That is, a typical layer constitution of the constituent members of the optical recording medium of the present invention includes a first dielectric layer, a layer comprising carbon and nitrogen and / or oxygen, a recording layer, and a second dielectric layer on a transparent substrate.
The dielectric layer and the reflective layer are laminated in this order. Further, the layer composed of carbon and nitrogen and / or oxygen may be used as a layer between the recording layer in contact with the recording layer and the second dielectric layer,
A higher effect can be obtained by using it as a layer instead of the second dielectric layer. Further, a layer made of only carbon can be used as this layer. However, it is not limited to these.

It is preferable that the material of the first dielectric layer is 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 film of oxide of metal such as Ti, Zr, Ta, Nb, S
A thin film of a nitride such as i 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 SiO ₂ is preferable because deterioration due to repeated overwriting hardly occurs. In particular, ZnS and SiO ₂
The mixture of and carbon has low residual stress in the film,
This is preferable because the recording sensitivity, the carrier-to-noise ratio (C / N), the erasing rate, and the like are unlikely to be deteriorated by repeated erasing. The thickness of the film is determined by optical conditions, but is preferably from 10 to 500 nm. If it is thicker than this,
Cracks and the like may occur. If the thickness is smaller than this, the substrate is easily damaged by heat due to repetition of overwriting, and the repetition characteristics deteriorate. A particularly preferred range of the film thickness is 50 nm or more and 200 nm or less.

The present invention is characterized in that a layer made of carbon, nitrogen and / or oxygen is provided between the substrate and the recording layer so as to be in contact with the recording layer. By providing this, it is possible to prevent deterioration of jitter due to repetition of overwriting and a decrease in amplitude of a reproduced signal. This is considered to be because the influence of the elastic deformation and the plastic deformation of the first dielectric layer can be reduced by providing this film. Further, by providing a layer composed of carbon, nitrogen and / or oxygen, deterioration of jitter characteristics due to the overwrite shelf can be improved. This is presumably because even if left for a long time, a change in the state of the atomic arrangement or the like and a reaction between the dielectric layer and the recording layer can be prevented.

The layer composed of carbon, nitrogen and / or oxygen is a layer composed of any of carbon and nitrogen, carbon and oxygen, carbon, oxygen and nitrogen. The thickness of the layer composed of carbon and nitrogen and / or oxygen is as follows:
From the viewpoint of difficulty in peeling and optical conditions, the thickness is preferably 0.5 nm or more and 10 nm or less. If the thickness exceeds 10 nm, it is easy to peel off. On the other hand, if the thickness is less than 0.5 nm, it is difficult to deposit the film to a uniform thickness, and the effect of providing a layer composed of carbon and nitrogen and / or oxygen may not be obtained. Considering the deposition rate of a layer composed of carbon, nitrogen and / or oxygen, the thickness is particularly preferably 1 nm or more and 8 nm or less.

The recording layer of the present invention is not particularly limited, but may be a Ge-Te alloy, a Ge-Sb-Te alloy, a Pd-Ge-Sb-Te alloy, a Nb-Ge-Sb-
Te alloy, Pd-Nb-Ge-Sb-Te alloy, Pt-
Ge-Sb-Te alloy, Co-Ge-Sb-Te alloy,
In-Sb-Te alloy, Ag-In-Sb-Te alloy,
Ag-V-In-Sb-Te alloy, In-Se alloy, and the like. Among them, those containing Ge, Sb, and Te as main components are short in erasing time and excellent in many times of recording. Further, among these, in order to achieve both excellent overwrite shelf characteristics and excellent long-term storage characteristics (archival characteristics) of recording marks, carbon and nitrogen and / or oxygen are contacted between the substrate and the recording layer so as to be in contact with the recording layer. In the case where a layer composed of the following is provided, the composition of the recording layer is preferably within the range of the following formula (I). In _{{(Ge 0.5 Te 0.5) x} (Sb 0.4 Te 0.6) 1-x} 1-yz Sb y A z (I) formula, A is a Group 3A of the sixth period of the second period in the periodic table of the elements Elements other than Ge, Sb, and Te belonging to Group 6B, and are Al, Si, Sc, Ti, V, Cr, Mn, and F.
e, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr,
Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, S
n, La, Hf, Ta, W, Re, Ir, Pt, Au,
Represents at least one selected from Tl and Pb, and x,
y and z represent numbers and satisfy the following relational expression. 0.2 ≦ x ≦ 0.8, 0.01 ≦ y ≦ 0.07, z = 0 or 0.2 ≦ x ≦ 0.8, 0 ≦ y ≦ 0.07, 0
<Z ≦ 0.2.

When x <0.2, the contrast becomes too small and a sufficient signal intensity may not be obtained.
In the case of 0.8, the crystallization speed becomes slow, the erasing characteristics are deteriorated, and direct overwriting may become difficult under the condition that the linear velocity is 5 m / s or more and the shortest mark length is 0.7 μm or less. When z = 0 and y <0.01, the stability of the amorphous is low, and the archival characteristics are poor.
If y> 0.07, overwriting after long-term storage may be difficult. When z> 0.2, the crystallization speed is reduced, the erasing characteristics are deteriorated, and it becomes difficult to perform direct overwriting or phase separation under the condition that the linear velocity is 5 m / s or more and the shortest mark length is 0.7 μm or less. In some cases, the repetition characteristics may be greatly deteriorated, or overwriting after long-term storage may be difficult. When z = 0, the stability of the amorphous may be low and the archival characteristics may be deteriorated.

A layer composed of carbon and nitrogen and / or oxygen between the substrate and the recording layer so as to be in contact with the recording layer, and carbon or carbon and nitrogen and / or between the reflective layer and the recording layer so as to be in contact with the recording layer. Alternatively, when both layers composed of oxygen are provided, the composition of the recording layer is preferably in the range of the following formula (II). _{{(Ge 0.5 Te 0.5) x} (Sb 0.4 Te 0.6) 1-x} 1-yz Sb y A z (II) ( wherein, A represents, Ge, Sb, second period of the periodic Table, except for Te Represents the elements belonging to groups 3A to 6B of the sixth period, x, y, and z represent numbers and satisfy the following relational expressions: 0.2 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.08, z =
0 or 0.2 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.08,
0 <z ≦ 0.2.

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. The thickness of the recording layer is preferably from 10 nm to 35 nm, more preferably from 10 nm to 24 nm.
nm.

The material of the second dielectric layer of the present invention may be the same as the material 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, SiO _2, and carbon has low residual stress in the film and hardly causes deterioration in recording sensitivity, carrier-to-noise ratio (C / N), erasure rate, and the like even when recording and erasing are repeated. preferable.

As a material of the reflection layer, a metal such as Al or Au having light reflectivity, containing these as a main component, Ti, C
alloys containing additional elements such as r and Hf, and metals such as Al and Au, metal nitrides such as Al and Si, metal oxides,
What mixed the metal compound, such as a metal chalcogenide, is mentioned. Metals such as Al and Au and alloys containing these as main components are preferable because of their high light reflectivity and high thermal conductivity. Taking the above alloy as an example, A
l is Si, Mg, Cu, Pd, Ti, Cr, Hf, T
a, Nb, Mn and other at least one element in total of 5
Atomic% or less, 1 atomic% or more added, or Au
To which at least one element such as Cr, Ag, Cu, Pd, Pt, and Ni is added in a total amount of 1 at% to 20 at%. In particular, Al or an alloy containing Al as a main component is preferable because the material is inexpensive.
i, Cr, Ta, Hf, Zr, Mn, and at least one metal selected from Pd in a total content of at least 0.5 at.
Alloys containing at most atomic% are preferred. Furthermore, since corrosion resistance is good and hillocks and the like hardly occur, Al-Hf-Pd alloys, Al-Hf alloys, Al-Hf alloys containing a total of 0.5 to 5 atomic% of additional elements. T
i-alloy, Al-Ti-Hf alloy, Al-Cr alloy, Al
-Ta alloy, Al-Ti-Cr alloy, Al-Si-Mn
It is preferable to use one of the alloys containing Al as a main component. Among these Al alloys, an Al-Hf-Pd alloy having a composition represented by the following formula has particularly excellent thermal stability, so that the recording characteristics are less likely to deteriorate during repeated recording and erasing many times. can do. Pd _j Hf _k Al _1-jk 0.001 <j <0.01 0.005 <k <0.10 where j and k are the number of atoms of each element (the number of moles of each element)
Represents

The thickness of the above-mentioned reflective layer is approximately 10 nm or more and 200 nm in any case made of any alloy.
Hereinafter, the thickness is more preferably set to 50 to 200 nm.

Next, a method for manufacturing the optical recording medium of the present invention will be described. As a method for forming the first dielectric layer, the carbon layer, the recording layer, the second dielectric layer, the reflective layer, and the like on the substrate, a thin film forming method in a vacuum, for example, a vacuum deposition method, an ion plating method, a sputtering method, Law. 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.

When a layer made of carbon, nitrogen and / or oxygen is formed by sputtering, the layer is easily formed by using a carbon target as a sputtering gas with nitrogen gas, oxygen gas, Ar gas or a mixed gas thereof. Can be. Alternatively, a hydrogen gas may be mixed with these gases to form a hydrogen-containing layer.

After forming the reflective layer, a dielectric layer of ZnS, SiO ₂ , ZnS—SiO ₂ , or the like, or ultraviolet curing may be used after forming the reflective layer within a range that does not significantly impair the effects of the present invention. A protective layer such as a resin may be provided as necessary.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. (Analysis and Measurement Method) 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 reflective layer was monitored with a quartz crystal 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.

In Examples 1 to 23 and Comparative Examples 1 and 2, the recording characteristics were measured under the following condition 1.
The recording characteristics of Nos. 4 and 25 were measured under condition 2.

Condition 1: A random pattern of 8/16 modulation was recorded at a mark length of 10 by using an optical head having a numerical aperture of an objective lens of 0.6 and a wavelength of 660 nm of a semiconductor laser under the condition of a linear velocity of 6 m / sec. Overwritten 10,000 times. At this time, the recording laser waveform used was a general multi-pulse. The window width at this time is 34 ns
(The shortest mark length in this case was 0.63 μm). Recording power and erasing power were optimized for each disk. Jitter was measured by a time interval analyzer. The decrease in the amplitude of the signal waveform and the presence or absence of a burst defect were observed with an oscilloscope.

Condition 2: At a linear velocity of 8.2 m / sec, the numerical aperture of the objective lens is 0.6, and the wavelength of the semiconductor laser is 660 n.
The mark length of a random pattern of 8/16 modulation was recorded using an optical head of m length. At this time, the recording laser waveform used was a general multi-pulse. The window width at this time was 17 ns (the shortest mark length in this case was 0.42 μm). Recording power and erasing power were optimized for each disk. Jitter was measured by a time interval analyzer.

(Example 1) thickness 0.6 mm, diameter 12c
Sputtering was performed while rotating a polycarbonate substrate with a spiral groove having a pitch of 1.48 μm (land width 0.74 μm, groove width 0.74 μm) at 30 revolutions per minute. First, after the inside of the vacuum vessel is evacuated to 1 × 10 ^-3 Pa, the pressure in the Ar gas atmosphere of 2 × 10 ^-1 Pa is increased.
ZnS to which 20 mol% of iO ₂ was added was sputtered to form a first dielectric layer having a thickness of 92 nm on the substrate. Next, a carbon target was sputtered with nitrogen gas to form a carbon layer and a layer made of nitrogen to a thickness of 2 nm. Then, Ge, Sb, Te
Sputtering an alloy target consisting of
m, composition Nb _0.4 Ge _17.0 Sb _27.9 Te _54.7 [that is, {(Ge _0.5 Te _0.5 ) _0.351 (Sb _0.4 Te _0.6 ) _0.649 }
_0.968 obtain a coating layer of Sb _0.028 Nb _{0.00 4].} Furthermore, the same ZnS.SiO ₂ as the first dielectric layer is used as the second dielectric layer.
Is formed to a thickness of 16 nm, and Al-H
An f-Pd alloy was sputtered to form a 120 nm-thick reflective layer, and an optical recording medium of the present invention was obtained.

When the jitter after 100,000 times of overwriting was measured, it was 3.06 ns, which was 9% of the window width, which was confirmed to be 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. Further, recording was performed once on this disk, and the byte error rate at that time was measured to be 2.5 × 10 ⁻⁵ . In the recorded state, the substrate was dried (in air without special humidity control or the like) and allowed to stand at 80 ° C. for 100 hours. Thereafter, when the byte error rate of the same part was measured, it was 3.0.
There was almost no change at ^10-5 . Furthermore, when this portion was overwritten once, it was confirmed that the byte error rate (BER) was 4.1 × 10 ⁻⁵ and hardly changed. The jitter at this time was 3.38 ns, which was a good value of 10% of the window width.

(Example 2) An optical recording medium was manufactured in the same manner as in Example 1 except that an Al-Cr alloy was used instead of the Al-Hf-Pd alloy. The recording characteristics were almost the same as in Example 1 and were as follows.

When the jitter after overwriting 100,000 times was measured, it was 3.05 ns, which was 9% of the window width, which was confirmed to be 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. Further, recording was performed once on this disk, and the byte error rate at that time was measured to be 2.5 × 10 ⁻⁵ . In the recorded state, the substrate was dried (in air without special humidity control or the like) and allowed to stand at 80 ° C. for 100 hours. After that, when the byte error rate of the same part was measured, it was 2.9.
There was almost no change at ^10-5 . Furthermore, when this portion was overwritten once, it was confirmed that the byte error rate was 4.0 × 10 ⁻⁵ and hardly changed. The jitter at this time was 3.38 ns, which was a good value of 10% of the window width.

Example 3 The composition of the recording layer was Ge _17.1 Sb
_28.0 Te _54.9 [that is, ｛(Ge _0.5 Te _0.5 )
Except that the _{0. 351 (Sb 0.4 Te 0.6)} 0.649} 0.968 Sb 0.032] in the same manner as in Example 1 was applied.
The recording characteristics were almost the same as in Example 1.

When the jitter after 100,000 times of overwriting was measured, it was 3.06 ns, which was 9% of the window width, which was confirmed to be 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. Further, recording was performed once on this disk, and the byte error rate at that time was measured to be 2.5 × 10 ⁻⁵ . Dry as recorded (in air without special humidity control), 8
It was left for 100 hours at 0 ° C. After that, when the byte error rate of the same portion was measured, it was 3.0 × 10 ^−5.
And there was almost no change. Furthermore, when this portion is overwritten once, the byte error rate becomes 4.
It was confirmed that there was almost no change at 1 × 10 ⁻⁵ . The jitter at this time was 3.38 ns, which was a good value of 10% of the window width.

Example 4 Instead of sputtering the carbon target with nitrogen gas in Example 1, Ar 90%, oxygen 1
An optical recording medium was manufactured in the same manner as in Example 1 except that a layer composed of carbon and oxygen was formed by sputtering with a mixed gas of 0%. When the jitter after 100,000 times of overwriting was measured, it was 3.05 ns, which was confirmed to be 9% of the window width and sufficiently small for practical use. The amplitude of the signal hardly changes compared to the amplitude of the signal after overwriting 10 times,
No burst defects were seen. Further, recording was performed once on this disk, and the byte error rate at that time was measured to be 1.0 × 10 ⁻⁵ . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, it was almost unchanged at 1.0 × 10 ⁻⁵ . Further, when this portion was overwritten once, it was confirmed that the byte error rate was 1.2 × 10 ^-5 and hardly changed. The jitter at this time was 3.41 ns, which was a good value of 10% of the window width.

Example 5 Instead of sputtering a carbon target with nitrogen gas in Example 1, 80% Ar and 1% nitrogen were used.
An optical recording medium was produced in the same manner as in Example 1 except that a layer composed of carbon, nitrogen and oxygen was formed by sputtering with a mixed gas of 0% and 10% oxygen. When the jitter after 100,000 times of overwriting was measured, it was 3.23 ns, and it was confirmed that the window width was 9.5%, 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. Further, recording was performed once on this disk, and the byte error rate at that time was measured to be 2.0 × 10 ⁻⁵ . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, it was almost unchanged at 2.0 × 10 ⁻⁵ . Furthermore, when this portion was overwritten once, the byte error rate was 2.1 × 1
That there is little change between 0 ^-5 it could be confirmed. The jitter at this time is 3.33 ns, which is 9.8% of the window width.
And good values.

(Examples 6 to 8) Thickness 0.6 mm, diameter 1
2 cm, 1.48 μm pitch (land width 0.74 μm,
Sputtering was performed while rotating a polycarbonate substrate with a spiral groove having a groove width of 0.74 μm) at 30 revolutions per minute. First, the inside of the vacuum vessel is 1 × 10 ^-3
After evacuation to Pa, ZnS to which 20 mol% of SiO ₂ was added was sputtered in an Ar gas atmosphere of 2 × 10 ^-1 Pa to form a first dielectric layer with a thickness of 92 nm on the substrate.
Next, a carbon target was sputtered with nitrogen gas to form a carbon layer and a layer made of nitrogen to a thickness of 2 nm. Then Ge, S
An alloy target composed of b and Te is sputtered to have a thickness of 19 nm and a composition of Nb _0.4 Ge _17.0 Sb _27.9 Te _54.7 [that is, ｛(Ge _0.5 Te _0.5 ) _0.351 (Sb _0.4 Te _0.6 ).
_0.649} to obtain a coating layer of _0.968 Sb _0.028 Nb _{0.00 4],} again, a carbon target was sputtered in nitrogen gas, was 2nm form a layer composed of a carbon layer and nitrogen. Further, as the second dielectric layer, the same ZnS · SiO ₂ as the first dielectric layer is sputtered to form a 14 nm layer, and an Al—Cr alloy is sputtered thereon to form a 120 nm thick reflective layer. An optical recording medium of the invention was obtained.

The jitter after overwriting 100,000 times was 3.07 ns, which was 9% of the window width.
It was confirmed that it was small enough for practical use. The signal amplitude is 10
There was almost no change in the amplitude of the signal after the overwrite, and no burst defect was observed.

The disk was recorded once, and the byte error rate (BER at the time of recording once) was measured to be 2.4 × 10 ^-5 . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate (BER after storage under moist heat) of the same portion was measured, there was almost no change of 2.9 × 10 ⁻⁵ . Further, when this portion was overwritten once, it was confirmed that the byte error rate (overwrite BER after storage under moist heat) was 3.9 × 10 ⁻⁵ and hardly changed. The jitter at this time (overwrite jitter after storage under moist heat) was 3.37 ns, which was a good value of 9.9% of the window width (Example 6).

When the layer between the first dielectric layer and the recording layer is replaced with a layer made of carbon and oxygen (Example 7), and when the layer made of carbon, nitrogen and oxygen is replaced (Example 8) Table 1 shows the recording characteristics. In each case, the recording characteristics were almost the same as those in Example 6.

(Embodiment 9) Between the recording layer and the second dielectric layer
Instead of sputtering the carbon target with nitrogen gas
Is sputtered with a mixed gas of 90% Ar and 10% oxygen.
The same optical recording as in Example 6 except that a layer composed of carbon and oxygen was used.
A recording medium was obtained, and the same measurement as in Example 6 was performed. 100,000 times
The jitter after overwriting was measured to be 3.07 n
s, which is 9% of the window width and sufficiently small for practical use.
It was recognized. The signal amplitude after overwriting 10 times
There is almost no change compared to the signal amplitude, and burst defects
I couldn't see it. Also, record once on this disc.
I measured the byte error rate at that time.
6 × 10^-FiveMet. 80 ° C, phase as recorded
It was left for 100 hours under the condition of 80% relative humidity. After this,
When the byte error rate of the same part was measured, it was 2.8.
× 10^-FiveAnd there was almost no change. Furthermore, this part
Is overwritten once, the byte error rate
Is 3.8 × 10 ^-FiveConfirm that there is almost no change
Came. The jitter at this time is 3.37 ns,
This was a good value of 9.9% of the dough width.

(Embodiments 10 to 12) The layer between the recording layer and the second dielectric layer was sputtered with a mixed gas of 80% Ar, 10% nitrogen, and 10% oxygen instead of sputtering a carbon target with a nitrogen gas. An optical recording medium was obtained in the same manner as in Example 6, except that the layer was made of carbon, nitrogen and oxygen. When the jitter after overwriting 100,000 times was measured in the same manner as in Example 6, it was 3.06 ns, which was 9% of the window width and was confirmed to be 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. Further, recording was performed once on this disk, and the byte error rate at that time was measured to be 2.3 × 10 ⁻⁵ . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, there was almost no change of 2.4 × 10 ⁻⁵ .
Further, when this portion was overwritten once, it was confirmed that the byte error rate was 3.3 × 10 ⁻⁵ and hardly changed. The jitter at this time is 3.33n
s, which was a good value of 9.8% of the window width (Example 10).

When the layer between the first dielectric layer and the recording layer is replaced with a layer made of carbon and oxygen (Example 11), and when the layer made of carbon, nitrogen and oxygen is replaced (Example 12) Table 1 shows the recording characteristics. In each case, the recording characteristics were almost the same as those in Example 10.

(Examples 13 to 15) Example 6 was repeated except that the layer between the recording layer and the second dielectric layer was sputtered with an Ar gas instead of a carbon target with a nitrogen gas to form a carbon layer. An optical recording medium similar to the above was obtained. When the jitter after overwriting 100,000 times was measured in the same manner as in Example 6, it was 3.06 ns, which was 9% of the window width and was confirmed to be sufficiently small for practical use. The amplitude of the signal hardly changes compared to the amplitude of the signal after overwriting 10 times,
No burst defects were seen. Further, recording was performed once on this disk, and the byte error rate at that time was 2.1 × 10 ⁻⁵ . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. After that, when the byte error rate of the same portion was measured, it was 2.2 × 10 ^-5 and there was almost no change. Further, when this portion was overwritten once, it was confirmed that the byte error rate was 3.0 × 10 ⁻⁵ and hardly changed. The jitter at this time is 3.16 ns
And a good value of 9.3% of the window width (Example 13).

When the layer between the first dielectric layer and the recording layer is replaced with a layer made of carbon and oxygen (Example 14), and when the layer made of carbon, nitrogen and oxygen is replaced (Example 15) Table 1 shows the recording characteristics. In each case, the recording characteristics were almost the same as those in Example 13.

(Comparative Example 1) An optical recording medium similar to that of Example 1 was obtained except that the layer composed of carbon and nitrogen was omitted. Example 1
The same measurement was performed, and the jitter after overwriting 100,000 times was 4.76 ns, which was as large as 14%. The amplitude of the signal was 70% of the amplitude after overwriting 10 times, and the contrast was reduced. I was

The error rate when recording was performed once was 4.0 × 10 ⁻⁵ . 80 as in the first embodiment.
C. and 80% relative humidity for 100 hours. After that, when the byte error rate of the same part was measured,
There was almost no change to 3.0 × 10 ⁻⁵ . However,
When this portion was overwritten once, an error occurred and the byte error rate deteriorated so 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 6.13 ns, which was about 18% of the window width.

(Comparative Example 2) The layer made of carbon and nitrogen was omitted, and the second dielectric layer was made of carbon and oxygen by sputtering a carbon target with a mixed gas of 95% Ar and 10% oxygen at a pressure of 0.2 Pa. An optical recording medium similar to that of Example 1 was obtained except that the layer had a thickness of 18 nm. When the same measurement as in Example 1 was performed, the amplitude of the signal after overwriting 20,000 times was 80% of the amplitude after overwriting 10 times, and the contrast was low. 80 ° C., relative humidity 80
%, The disk was delaminated on the disk for 100 hours.

Example 16 The composition of the recording layer was Ge _33.9 S
b _15.6 Te _50.5 [i.e. _{{(Ge 0.5 Te 0.5) 0.} 710
(Sb _0.4 Te _0.6 ) A disk having a six-layer structure similar to that of Example 6 was prepared except that _0.290 { _0.955 Sb _0.045 ].

Recording was performed once on this disk, and the byte error rate at that time was 2.8 × 10 ⁻⁵ . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, it was almost unchanged at 4.5 × 10 ⁻⁵ . Furthermore, when this portion was overwritten once, the byte error rate was 1.8 × 1
^0-4 was confirmed to be practically ^acceptable . The jitter at this time was 3.5 ns, which was a good value of 10.3% of the window width.

Example 17 The composition of the recording layer was Ge _34.1 S
b _15.3 Te _50.6 [i.e. _{{(Ge 0.5 Te 0.5) 0.} 706
Is _{(Sb 0.4 Te 0.6) 0.294}} 0.980 except that the Sb _0.0 35], to prepare a disk having the same six-layer structure as in Example 6.

Recording was performed once on this disk, and the byte error rate at that time was 3.8 × 10 ^-5 . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, it was almost unchanged at 1.2 × 10 ⁻⁴ . Furthermore, when this portion was overwritten once, the byte error rate was 4.2 × 1
^0-4 was confirmed to be practically ^acceptable . The jitter at this time was 3.6 ns, a favorable value of 10.6% of the window width.

Example 18 The composition of the recording layer was Ge _36.2 S
b _13.0 Te _50.8 [i.e. _{{(Ge 0.5 Te 0.5) 0.} 747
It is (Sb _0.4 Te _{0.6) 0.253}} except that the _0.9 68Sb _0.0 32], to prepare a disk having the same six-layer structure as in Example 6.

Recording was performed once on this disk, and the byte error rate at that time was 2.5 × 10 ⁻⁴ . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, it was confirmed that there was no practical problem of 3.2 × 10 ⁻⁴ . Furthermore, when this part is overwritten once, the byte error rate becomes
It was confirmed that there was no practical problem of 4.4 × 10 ⁻⁴ . The jitter at this time is 3.9 ns, and the window width is 1
1.5%.

Example 19 The composition of the recording layer was Ge _39.6 S
b _10.2 Te ₅ 0 _.2 [i.e. _{{(Ge 0.5 Te 0.5) 0.} 818
(Sb _0.4 Te _0.6 ) A disk having a six-layer structure similar to that of Example 6 was prepared except that _0.182 { _0.969 Sb _0.031 ].

Recording was performed once on this disk, and the byte error rate at that time was 1.7 × 10 ⁻³ . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, it was 2.0 × 10 ⁻³ . Further, when this portion was overwritten once, the byte error rate was 2.0 × 10 ^−3, and the error rate before and after overwriting did not deteriorate. The jitter at this time was 4.4 ns, which was 12.9% of the window width.

Example 20 The composition of the recording layer was Ge _27.0 S
b _20.0 Te _53.0 [i.e. _{{(Ge 0.5 Te 0.5) 0.} 555
(Sb _0.4 Te _0.6 ) A disk having a six-layer structure similar to that of Example 6 was prepared except that _0.445 { _0.973 Sb _0.027 ].

Recording was performed once on this disk, and the byte error rate at that time was measured to be 3.7 × 10 ^-5 . The recording was left for 100 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, a slight increase of 4.3 × 10 ⁻⁴ was observed. Furthermore, when this portion was overwritten once, the byte error rate was 7.1 × 10
^-5 , the error rate did not deteriorate before and after overwriting. The jitter at this time was 3.1 ns, which was 9.1% of the window width.

(Examples 21 to 22) The composition of the recording layer was changed to Ge.
₂ Sb ₂ Te ₅ [that is, (Ge _0.5 Te _0.5 ) _0.444 (Sb
Except that the _{0. 4} Te _{0.6) 0.556],} thereby obtaining the 6-layer disc the same manner as in Example 6.

Recording was performed once on this disk, and the byte error rate at that time was 3.1 × 10 ^-5 . The recording was left for 40 hours at 80 ° C. and 80% relative humidity. Thereafter, when the byte error rate of the same portion was measured, it was found to be 2.8 × 10 ⁻³ (Example 21). When the reproduced waveform was observed, it was presumed that the amplitude was reduced and a part of the amorphous part was crystallized.

The composition of the recording layer was Ge ₁ Sb ₂ Te
₄ [ie (Ge _0.5 Te _0.5 ) _0.287 (Sb _0.4 T
e _0.6 ) _0.714 ], the byte error rate is 5.9 when left for 40 hours at 80 ° C. and 80% relative humidity.
From × 10 ^-4 to 6.9 × 10 ^-2 (Example 22).

Example 23 The composition of the recording layer was Ge _0.5 T
e _0.5 [i.e. _{{(Ge 0.5 Te 0.5) 1.00} (Sb 0. 4 T
e _0.6 ) _0.00 ｝ _1.00 Sb _0.00 ]
A 6-layer disc similar to the above was produced.

Recording was performed once on this disk, and the byte error rate at that time was 2.5 × 10−2. (Example 24) Thickness 0.6 mm, diameter 12 cm, 1.2
Sputtering was performed while rotating a polycarbonate substrate with a spiral groove having a pitch of 3 μm (land width 0.615 μm, groove width 0.615 μm) at 30 revolutions per minute. First, after evacuating the inside of the vacuum vessel to 1 × 10 −3 Pa, S 2 gas was discharged in an Ar gas atmosphere of 2 × 10 −1 Pa
ZnS to which 20 mol% of iO2 was added was sputtered to form a first dielectric layer having a thickness of 92 nm on the substrate. Next, a carbon target was sputtered with nitrogen gas to form a carbon layer and a layer made of nitrogen to a thickness of 2 nm. Then, Ge, Sb, Te
Sputtering alloy target consisting of 12n thickness
m, composition Ge27.6Sb18.5Te53.9 [that is, ｛(Ge0.5Te0.5) 0.558 (Sb0.
4Te0.6) 0.442 {0.99 Sb0.01]. Further, a carbon target was sputtered with a nitrogen gas to form a layer of carbon and nitrogen having a thickness of 2 nm. The same ZnS · S as the first dielectric layer as the second dielectric layer
iO ₂ is sputtered to form a film having a thickness of 23 nm.
Sputtering 198.0Cr2.0 alloy to 90nm film thickness
Was formed. After taking out the disk from the vacuum container, an acrylic UV curable resin (SD-101 manufactured by Dainippon Ink and Chemicals Co., Ltd.) is spin-coated on the reflective layer, and cured by UV irradiation to form a resin layer having a thickness of 3 μm. Was formed, and then a slow-acting ultraviolet curable resin was applied using a screen printing machine, and after irradiating with ultraviolet rays, two disks produced in the same manner were adhered to obtain an optical recording medium of the present invention.

The recording characteristics of this disk were evaluated under condition 2. The overwrite recording was performed 10 times, and the jitter was measured.
The value was as good as 1%. While recording, in the air without humidity control such as humidification, 1
It was left for 00 hours. After that, when the jitter of the same portion was measured, there was no change at 1.55 ns. Furthermore, when this portion was overwritten once, the jitter was 2.
At 2 ns, it was confirmed that there was no practical problem with a good value of 12.9% of the window width. Example 25 A recording layer and a second dielectric layer in contact with a recording layer were formed in the same manner as in Example 1 except that a Ge target was sputtered with a mixed gas of 41% nitrogen and 59% argon to form GeN1.2 with a thickness of 2 nm. A disk was produced in the same manner.

The recording characteristics of this disk were evaluated under condition 2. When overwrite recording was performed 10 times and the jitter was measured, it was 1.52 ns, and the window width was 8.
It was a good value of 9%. As recorded, in air without humidity control such as humidification, 80 ° C
Left for 0 hours. Thereafter, when the jitter of the same portion was measured, there was no change at 1.52 ns. Furthermore, when this portion was overwritten once, the jitter was 1.9.
At 9 ns, it was confirmed that there was no practical problem with a favorable value of 11.7% of the window width.

[0066]

[Table 1]

[0067]

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) Good storage durability.

Claims (6)

[Claims] An information recording, erasing, and reproducing operation can be performed by irradiating light, and information recording and erasing are performed by a reversible phase change between an amorphous phase and a crystalline phase. An optical recording medium comprising at least a recording layer and a reflective layer, wherein a layer made of carbon, nitrogen and / or oxygen is provided between the substrate and the recording layer so as to be in contact with the recording layer. Medium. 2. The optical recording medium according to claim 1, wherein a layer made of carbon or carbon and nitrogen and / or oxygen is provided between the recording layer and the reflection layer so as to be in contact with the recording layer. 3. The optical recording medium according to claim 1, wherein a first dielectric layer is provided between the substrate and the recording layer. 4. The optical recording medium according to claim 3, wherein the first dielectric layer contains ZnS and SiO ₂ . 5. The optical recording medium according to claim 1, wherein a second dielectric layer is provided between the recording layer and the reflection layer. 6. The optical recording medium according to claim 1, wherein the layer comprising carbon, nitrogen and / or oxygen has a thickness of 0.5 nm or more and 10 nm or less.