JP2003248967A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a phase change recording medium and its material excellent in high density recording and shelf life. <P>SOLUTION: A lower protective layer 2, a second lower protective layer 3, a recording layer 4 making reversible phase change between amorphous and crystalline phases, a upper protective layer 5, and a reflection layer 6 mainly composed of Al are sequentially laminated on a transparent plate 1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a phase change optical disk,
The present invention relates to an optical recording medium such as a rewritable optical disc.

[0002]

2. Description of the Related Art So-called phase-change recording media using reversible phase changes of crystalline and amorphous phases are prevalent worldwide as rewritable recording media. With the spread of CD-R and CD-RW recording media, high-speed recording has been advanced, and high-speed recording is essential for phase change recording media. High speed recording
As the recording density increases, the pulse frequency of the laser light emission pulse increases, and it is necessary to control heating and quenching of the recording layer in a shorter time. Higher recording power is required for heating and rapid cooling in a short time, and rapid cooling requires a longer pulse off time, but linear velocity becomes faster and recording power is required. Ag-In-Sb
The Sb-Te eutectic phase-change recording material containing -Te has a high crystallization rate and enables high-speed erasing in high linear velocity recording. However, when the recording layer material and composition are selected and used with priority on high-speed erasing, the problem of lack of sensitivity and the amorphous phase due to high-speed crystallization, that is, recording marks are difficult to form due to the reasons described above. come. In addition, there is a side effect that storage characteristics in a high temperature environment deteriorate due to high-speed crystallization.

Therefore, it is necessary to improve not only the design based on the recording material and composition but also the protective layer and layer structure other than the recording material. In order to promote crystallization in a Ge ₂ Sb ₂ Te ₅ phase change recording material in which an amorphous phase is easily formed in high linear velocity recording, for example, Japanese Patent Laid-Open No. 2000-2
In Japanese Patent No. 98878, at least one of the recording layers has S
A configuration has been proposed in which layers such as i-C-O, Si-C-H, and Si-C-H-O are newly provided to enable high-speed erasing even when recording at a high linear velocity. In the Ge ₂ Sb ₂ Te ₅ phase change recording material, crystal nucleation occurs first at a temperature higher than the glass transition point, and then crystal growth occurs at a higher temperature. Therefore, it is provided in contact with one or both sides of the recording layer for the purpose of promoting nucleation.

Further, Ge ₂ Sb ₂ Te ₅ phase change recording material is mainly used, and ZrO ₂ , T is provided between the lower protective layer and the recording layer in contact with the recording layer.
There is a technique for promoting crystallization by providing at least one oxide layer of iO ₂ and Al ₂ O ₃ (see Japanese Patent Laid-Open No. 11-339332), but this technique aims at promoting crystallization in recording and reproduction. Rather, the purpose is to eliminate the so-called initialization step for crystallizing the recording layer, which is necessary for the production process of the phase change recording medium.

However, in any of the prior arts, when the recording linear velocity is recorded at a high linear velocity of about 3.5 m / s to 20 m / s, which is the linear velocity of DVD, sufficient characteristics are still obtained. It is in the present condition that has not been obtained.

[0006]

Problems to be Solved by the Invention Ag-In-Sb-T
The phase change recording material including the e and the Sb—Te eutectic system to which an additive element is added is an excellent phase change recording material because it has a high erasing ratio and can be erased at high speed. Therefore, sufficient characteristics can be obtained even at high linear velocity recording.

However, as the linear velocity becomes higher, giving priority to high-speed erasing, the storage property of data in a high temperature environment becomes insufficient, and an amorphous phase is hard to form, resulting in insufficient characteristics. You won't get it. By controlling the emission pulse of the semiconductor laser, it is easy to form an amorphous phase by heating rapidly to a high temperature (above the melting point) in a short time, turning the laser off immediately, and by making the medium structure a cooling priority structure. But,
It is difficult to crystallize (erase), resulting in poor sensitivity. The recording power may be simply increased, but the power is also limited.

Therefore, the present invention uses not only a material and a composition that can be erased at high speed and has good storage stability based on the Sb-Te eutectic phase change recording material, but also when recording at a high linear velocity. Another object of the present invention is to propose a protective layer material and a layer structure in which the cooling and crystallization rates are well balanced.

[0009]

According to the present invention, there is provided a structure and material of a phase change recording medium which is excellent in recording characteristics at high linear velocity and high density recording and can secure storage reliability. The invention according to relates to a lower protective layer, a second
An optical recording medium in which a lower protective layer, a recording layer that undergoes a reversible phase change between an amorphous phase and a crystalline phase, an upper protective layer, and a reflective layer containing Al as a main element are stacked in this order is the most important feature.

According to a second aspect of the present invention, a lower protective layer, a second lower protective layer, a recording layer having a reversible phase change between an amorphous phase and a crystalline phase, and an upper protective layer (sulfide) are formed on a transparent substrate. An optical recording medium in which an optical recording medium in which a layer not containing Pd) and a reflective layer containing Ag as a main element are laminated in this order is the most main feature.

According to a third aspect of the present invention, a lower protective layer, a second lower protective layer, a recording layer having a reversible phase change between an amorphous phase and a crystalline phase, and an upper protective layer (sulfide) are formed on a transparent substrate. An optical recording medium in which an optical recording medium is laminated in the order of a layer containing a), a sulfuration preventing layer, and a reflective layer containing Ag as a main element.

The invention according to claim 4 is mainly characterized in that the second lower protective layer according to any one of claims 1 to 3 is an oxide containing ZrO ₂ .

[0013] The invention according to claim 5, the recording layer according to any one of claims 1 to 3 _{Ga α Ge β In γ Sb δ} X ε T
e _{100- (α + β + γ + δ + ε)} , X is Ag, Cu, D
y, containing at least one of Mg, α, β,
The optical recording medium whose composition ratio (At%) of γ, δ, and ε is 0 <α <7 0 <β <10 0 <γ <5 60 <δ <800 <ε <5 is a main feature. .

The invention according to claim 6 is as follows.
The lower protective layer and the upper protective layer are made of a mixture of ZnS and SiO ₂ , and the sulfurization preventing layer is made of Si, SiC, Ge or GeCr.
The optical recording medium is a main feature.

According to a seventh aspect of the present invention, the second lower protective layer according to any one of the first to third aspects has a film thickness of 5 to 15 n.
The main feature is an optical recording medium of m.

The invention according to claim 8 is characterized mainly in an optical recording medium in which the film thickness of the sulfidation preventive layer according to claim 6 is 2 to 10 nm.

According to a ninth aspect of the present invention, there is provided an optical recording medium for recording at a linear velocity equal to or higher than the linear velocity at which the reflectance in the crystalline state of the recording layer obtained when the medium is erased with an optimum erasing power starts to sharply decrease. The main feature.

The tenth aspect of the invention is characterized mainly in an optical recording medium having a maximum recording linear velocity of 20 m / s in the medium according to any one of the first to ninth aspects.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first optical recording medium according to the present invention.
On the transparent substrate 1, a lower protective layer 2, a second lower protective layer 3, a recording layer 4 which undergoes a reversible phase change between an amorphous phase and a crystalline phase, and an upper protective layer 5 on the transparent substrate 1. , An optical recording medium in which a reflective layer 6 containing Al as a main element is sequentially stacked.

FIG. 2 shows a second embodiment of the optical recording medium according to the present invention, in which a lower protective layer 2, a second lower protective layer 3 and an amorphous phase are formed on a transparent substrate 1. The figure shows an optical recording medium in which a recording layer 4 that undergoes a reversible phase change of a crystal phase, an upper protective layer (a layer that does not contain sulfide) 5, and a reflective layer 6 that contains Ag as a main element are stacked in this order.

FIG. 3 shows a third embodiment of the optical recording medium according to the present invention, in which a lower protective layer 2, a second lower protective layer 3 and an amorphous phase are formed on a transparent substrate 1. An optical recording medium in which a recording layer 4 having a reversible phase change of a crystal phase, an upper protective layer (a layer containing a sulfide) 5, a sulfuration preventing layer 7, and a reflective layer 6 containing Ag as a main element are stacked in this order. Shows.

The lower protective layer 2 and the upper protective layer 5 are sulfides such as ZnS, Al ₂ O ₃ oxides such as SiO ₂ , In ₂ O ₃ and ZrO ₂ , nitrides such as SiN, GeN and AlN, and SiC. , Z
Carbides such as rC and mixtures thereof. Examples of the mixture include ZnS.SiO ₂ . It is preferable that these are transparent materials in which the wavelength of incident light is in the range of 400 to 780 nm and which has small absorption. Further, the refractive index is preferably around 2. The lower protective layer 2 is made of ZnS.SiO _{2 and} has a molar ratio of 50:50 to 90:10.
Around 0:20 is good. The film thickness of the lower protective layer 2 is required to maintain the environmental resistance of the recording layer 4, to prevent cracks from being generated in the film due to heat during film formation, and to prevent large substrate deformation. Is good.

The upper protection layer 5 may use the same ZnS · SiO ₂ with a lower protective layer 2 for the form of Figures 1 and 3. In the case of the configuration of FIG. 2, the upper protective layer 5 is made of ZnS.Si.
When O ₂ or sulfide is used, silver sulfide is formed in a high temperature and high humidity environment, errors during data reproduction increase due to an increase in medium defects, and recording characteristics are deteriorated. Sex decreases. Therefore, in the case of this structure, it is preferable to use oxides, carbides, and nitrides other than sulfides. The thickness of the upper protective layer 5 is preferably 3 to 20 nm. If it is too thin, the heat storage effect will decrease and the sensitivity will decrease, and if it is too thick, the sensitivity will improve but the cooling effect will decrease.
It becomes difficult to form a recording mark having a predetermined length and size.

The recording layer 4 is based on the eutectic composition near Sb ₁₀ Te ₃₀ . Composition segregation hardly occurs even after repeated recording, and excellent repeated recording characteristics. This alone increases the crystallization speed, that is, there is a limit to high-speed erasing, and the crystallization speed is high in a high temperature environment, and the crystallization temperature is about 100 ° C., so the mark disappears. Therefore, it is not enough to increase the Sb amount and enable high speed recording. Therefore, without increasing the Sb amount so much,
By adding a and In, the crystallization speed and the crystallization temperature can be increased. However, Ge is effective for improving storage stability. Basic elements Sb, T
This is because, among e, the binding energy with Te is high and the crystallization temperature rises. If Ga and In are added too much, the crystallization temperature becomes higher, so that the initialization is not sufficient in the initialization step for changing the phase of the recording layer 4 immediately after fabrication from the amorphous phase to the crystalline phase. Low reflectance,
The recording / reproducing characteristics are deteriorated such that uniform crystallization cannot be achieved. Further, if Ge is added too much, the crystallization rate becomes low. Therefore, Ga, Ge, In, S
b and Te, Ga _α Ge _β In _γ Sb _δ X _ε Te
_{For 100- (α + β + γ + δ + ε)} , 0 <α <7, 0 <β <
7, 0 <γ <5, 60 <δ <80 are preferable, and
At least one element of Ag, Cu, Dy, and Mg is added as X in order to increase the crystallization rate and improve the storage stability. The addition amount of these elements is preferably 0 <ε <5. Dy and Mg increase the crystallization rate, while A
g and Cu improve storability. Ag and Cu have a high coordination number with other elements in the amorphous state and have an effect of stabilizing the amorphous phase. The film thickness range of the recording layer 4 is 10 to 2
It is 5 nm. If it is too thin, the degree of modulation will be small, and if it is too thick, the recording sensitivity and repetitive recording characteristics will be poor.

The substrate 1 used is polycarbonate (P
C), a plastic substrate such as polymethacrylic acid (PMMA), or a transparent substrate such as glass is used.

The reflective layer 6 is made of Al, Ag, Cu, Au, P.
A metal such as t or Pd or an alloy thereof is used. In high linear velocity recording, it is preferable to use a metal or alloy having higher thermal conductivity. Al or Al alloy, or Ag or Ag with higher thermal conductivity than these, small amount of Cu, Ni
Is used to increase the environmental resistance of the alloy. Film thickness is 50
To 200 nm, preferably 100 to 15
It is 0 nm. If it is thin, the heat dissipation effect will deteriorate and the degree of modulation will decrease.

In the present invention, in order to obtain sufficient recording characteristics at a higher linear velocity, when the medium design is mainly focused on high-speed crystallization, it is difficult to form recording marks and the data storability in a high temperature environment is poor. Therefore, the second lower protective layer 3 is replaced with the lower protective layer 2 by giving priority to the formation of recording marks and data storability.
It is provided between the recording layer 4 and the recording layer 4 to sufficiently promote erasing, that is, crystallization, in repetitive recording at a high linear velocity, and widen the erase recording power margin. In particular, when a linear velocity of 10 m / s or less is set to a low linear velocity, crystallization is sufficiently performed with the optimum erasing power,
It is effective in the case where a higher linear velocity of 10 to 20 m / s or more cannot sufficiently crystallize and therefore the reflectance also becomes low.

The second lower protective layer 3 preferably has a lower thermal conductivity than the lower protective layer 2, is transparent, and has a melting point higher than that of the recording layer 4. Therefore, in the present invention, a material containing ZrO ₂ as a main oxide is used. ZrO ₂ has a low thermal conductivity among other ceramics in a bulk crystal. Relatively high thermal conductivity is 500 W / each for SiC, AlN, and Al ₂ O _3.
While mK, 200 mW / mK and 40 mW / mK, ZrO ₂ is 5 W / mK or less. Moreover, the melting point is as high as 2000 ° C. or higher, the refractive index is 2.0 or higher, and the absorption is small. Therefore, it can also be used as the lower protective layer 2 and the upper protective layer 5. In the present invention, it is mainly used between the recording layer 4 and the lower protective layer 2. The recording layer material uses a phase change material that can be erased at high speed.
Since the record mark data storage property tends to deteriorate,
There is a limit only in the recording layer material. Moreover, the recording linear velocity is 2
At 0 m / s, it becomes difficult to achieve both good properties and good storability. When ZrO ₂ is used for the upper protective layer, ZnS · S
The erasing speed is almost the same as that of iO ₂ . Therefore,
The use of ZrO ₂ hardly reduces the crystallization rate. By using this material, which has low thermal conductivity and acceleration of crystallization, as a main material, high-speed erasing is possible even when recording is performed at a high linear velocity, and repetitive recording characteristics are improved.
When laser light of a certain size necessary for recording or erasing is irradiated from the substrate 1 side, a temperature gradient is generated between the upper protective layer 5 side and the lower protective layer 2 side of the recording layer 4. Upper protective layer 5
On the side, there is the reflective layer 6 on it, and since the metal or alloy having high thermal conductivity is used, the heat is lower in the upper protective layer 5 and the temperature in the lower protective layer 2 is higher than that. Crystallization occurs below the melting point and above the crystallization temperature. Therefore, when crystallization is performed by irradiating light during erasing, the recording layer 4
Is crystallized from the lower protective layer 2 side. The thermal conductivity between the recording layer 4 and the lower protective layer 2 is lower than that of ZnS.SiO ₂ ,
By using an oxide containing ZrO ₂ as a main component, crystallization is further promoted and the margin of low erasing power is widened. Therefore, even when the erasing speed of the recording layer material is relatively low, repeated recording can be performed at a higher speed, and a recording medium having high storage reliability can be obtained. When the erasing speed of the recording layer material is lower than the recording linear velocity, sufficient crystallization does not easily occur on the side where the linear velocity is high. This is because an amorphous phase is likely to be formed when the erasing power is increased. Therefore, the erasing power cannot be increased so much. If it is too low, the temperature required for crystallization cannot be obtained, and as a result, the margin for the erase power becomes narrow. Zr between the lower protective layer 2 and the recording layer 4
By providing an oxide containing O ₂ as a main component, the repetitive recording characteristics at high speed can be improved. However, when this material is used for the lower protective layer 2, the film formation rate is slower than that of ZnS.SiO ₂ (twice or more), so it takes time to form a film having the same thickness as the lower protective layer 2. Moreover, the temperature of the film rises. Since the upper protective layer 5 has a film thickness of 30% of that of the lower protective layer 2, it can be used for the upper protective layer 5.

Next, the sulfidation preventive layer 7 in the case of the embodiment shown in FIG.
I will describe. When the upper protective layer 5 is ZnS.SiO ₂ , it is necessary to provide the layer 7 for preventing sulfidation when Ag or Ag alloy is used for the reflective layer 6. When the film thickness of this sulfurization preventing layer 7 becomes thick, the efficiency of radiating the heat accumulated in the upper protective layer 5 to the reflecting layer 6 becomes poor, but if it is too thin, the film may not be evenly attached. Partial sulfurization occurs. Materials used include oxides, nitrides, carbides, metals and alloys. The thermal conductivity is preferably higher than that of the upper protective layer 5, has a high melting point, and does not change with time. SiN, AlN, Al ₂ O ₃ , SiO ₂ ,
SiC oxide, nitride, carbide, Si, Ge, GeC
r etc. Among these materials, when oxides and nitrides are left to stand for a long time in a high temperature and high humidity environment, when the film thickness is 4 nm, defects occur to some extent, although there are some differences. Among them, SiC, Si, Ge and GeCr had almost no problem. However, since light absorption of these materials is higher than that of nitrides and oxides, 3 to 7 nm is preferable.

In the above structure, the recording linear velocity is set within a range in which the crystallization speed is sufficiently high, and recording is performed, but the linear velocity is 20.
Near m / s, even if a recording layer material with an optimum erasing power and a sufficient crystallization rate is selected, uniform and sufficient reflectance cannot be obtained at the initialization stage, or the data disappears at high temperature. As a result, the storability deteriorates. Therefore, in high-speed recording, in order to improve the balance of these characteristics, it is necessary to be able to use even when sufficient erasing is not performed when erasing with high power at high linear velocity. In the present invention, even under these conditions, the characteristics are not improved as compared with the conventional structure. However, the erasing power used at the time of recording is lower than the conventional value. In this case, even if the recording power is changed, the erasing power is kept constant for recording. The second lower protective layer 3 has the effect of speeding up crystallization even with a low erase power.

The phase-change recording medium of the present invention can record and reproduce in the recording wavelength range of 400 to 780 nm. To increase the recording density, the aperture ratio of the objective lens is set to 0.60.
As described above, the beam diameter of incident light is reduced. Wavelength 650
nm, the numerical aperture of the objective lens is 0.6 to 0.65, the thickness of the substrate 1 is 0.6 mm, the track pitch of the substrate 1 is 0.74 μm or less, and the groove depth is 15 to 60 nm.
The groove width is 0.2 to 0.3 μm. When high-speed and high-density recording is performed using this recording medium, the laser light emission pulse has three levels of recording, erasing, and bias. The recording and erasing power is higher than the reproducing power, and the bias power is reproducing. Be less than or equal to power. The bias power is the power after the recording power is applied and is necessary for forming the amorphous phase. This pulse is further the first pulse (1 pulse), multiple pulse trains, cooling pulse (1 pulse)
These light emitting patterns are necessary for sharpening the edge portion of the recording mark and for making the recorded position and the length of the recorded mark accurate. The recording linear velocity is 20 m / s at maximum, and the recording frequency is linear density 0.267.
The maximum is about 150 MHz in μm / bit.

[0032]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Example 1-6 A polycarbonate substrate 1 (FIG. 1) having a groove pitch of 0.74 μm, a groove width of 0.25 μm, a groove depth of 25 nm, and a thickness of 0.6 mm was used. Each layer is laminated. The lower protective layer 2 is
A target of ZnS: SiO ₂ = 80: 20 (mol%) was used and the film thickness was set to 60 nm. Next, as shown in Table 1, a second lower protective layer 3 and a recording layer 4 capable of recording at a predetermined recording linear velocity were formed with a film thickness of 17 nm, in that order. Second
The target of the lower protective layer 3 contains 3% by weight of Y ₂ O ₃ . Same as the lower protective layer 2 ZnS: SiO ₂ = 8
0:20 (mol%) was used as the upper protective layer 5 with a film thickness of 10 nm. Next, an AlTi alloy having a film thickness of 160 nm was used as the reflective layer 6. A UV curable resin was applied to a thickness of 2 μm for protection. Finally, another substrate having no film was attached with an ultraviolet curable resin to a thickness of 1.2 mm to obtain a recording medium. After that, large-diameter LD (1μm × 100μ
m) was used to crystallize the recording layer 4 at a linear velocity of 3.5 m / s and a power of 850 mW. Recording / reproduction was performed using a pickup head with a wavelength of 655 nm and an objective lens NA of 0.65.
Recording density is 0.267 μm / at a given linear velocity (CLV)
It was recorded so as to be a bit. The recording data modulation method is (8, 16) modulation. Recording power is 15mW to 20m
W, bias power is 0.1 mW, and erasing power is half or less of recording power. Laser emission waveform is recording layer 4
The on-pulse width for heating and the off-pulse width for contributing to cooling were set arbitrarily. The number of pulses is the recording mark length nT
(N is an integer of 2 or more, T is the clock frequency),
(N-1). In Table 1, jitter values after 1000 times of repeated recording at the optimum power are shown.

[0033]

[Table 1]

[Embodiment 7-12] The groove pitch of the substrate was set to 0.
A polycarbonate substrate 1 (FIG. 2) having a thickness of 74 μm, a groove width of 0.25 μm, a groove depth of 25 nm, and a thickness of 0.6 mm is used, and each layer is laminated thereon by a sputtering method. The lower protective layer 2 is ZnS: SiO ₂ = 80: 20.
(Mol%) of target was used and the film thickness was set to 60 nm. Next, as shown in Table 2, the second lower protective layer 3 and the recording layer 4 capable of recording at a predetermined recording linear velocity were formed with a film thickness of 17 nm in order. The target of the second lower protective layer 3 contains 3% by weight of Y ₂ O ₃ . Next, ZrO ₂ 6
0At%. An upper protective layer 5 having a film thickness of 10 nm was formed using a target having a ratio of SiO _{2 of} 40 At%. However,
The target contains 3% by weight of Y ₂ O ₃ . Next, the Ag alloy was formed to a film thickness of 140 nm to form the reflective layer 6. A UV curable resin was applied to a thickness of 2 μm for protection. Finally, another substrate having no film was attached with an ultraviolet curable resin to a thickness of 1.2 mm to obtain a recording medium. After that, the recording layer 4 was crystallized using a large-diameter LD (1 μm × 100 μm) at a linear velocity of 3.5 m / s and a power of 850 mW. Recording / reproduction has a wavelength of 655 nm and objective lens NA0.
With a pickup head of 65, a predetermined linear velocity (C
LV) so that the recording density was 0.267 μm / bit. The recording data modulation method is (8, 16) modulation. The recording power is 15 mW to 20 mW, the bias power is 0.1 mW, and the erasing power is half or less of the recording power. Regarding the laser emission waveform, the on-pulse width for heating the recording layer 4 and the off-pulse width for contributing to cooling were set arbitrarily. The number of pulses was (n-1) with respect to the recording mark length nT (n is an integer of 2 or more, T is a clock frequency).
Table 2 shows the jitter values after 1000 times of repeated recording at the optimum power.

[0035]

[Table 2]

[Example 13-21] A polycarbonate substrate 1 (FIG. 3) having a groove pitch of 0.74 μm, a groove width of 0.25 μm, a groove depth of 25 nm and a thickness of 0.6 mm was used. Each layer is laminated by a sputtering method. The lower protective layer 2 is ZnS: SiO ₂ = 80: 20.
(Mol%) of target was used and the film thickness was set to 60 nm. Next, as shown in Table 3, a second lower protective layer 3 and a recording layer 4 capable of recording at a predetermined recording linear velocity were formed with a film thickness of 17 nm in order. The target of the second lower protective layer 3 contains 3% by weight of Y ₂ O ₃ . The same ZnS: SiO ₂ = 80: 20 (mol%) as the lower protective layer 2 is formed to a film thickness of 1
It was set to 0 nm and was used as the upper protective layer 5. Next, the sulfuration prevention layer 7
Was applied with the materials and film thicknesses shown in Table 3. Further, Ag was formed to have a film thickness of 160 nm to form the reflective layer 6. A UV curable resin was applied to a thickness of 2 μm for protection. Finally, another substrate having no film was attached with an ultraviolet curable resin to a thickness of 1.2 mm to obtain a recording medium. After that, large-diameter LD
(1 μm × 100 μm) was used to crystallize the recording layer 4 at a linear velocity of 3.5 m / s and a power of 850 mW. Recording / reproduction was performed using a pickup head having a wavelength of 655 nm and an objective lens NA of 0.65 so that the recording density was 0.267 μm / bit at a predetermined linear velocity (CLV). The recording data modulation method is (8, 16) modulation. Recording power is 1
The bias power is 5 mW to 20 mW, the bias power is 0.1 mW, and the erasing power is half or less of the recording power. Regarding the laser emission waveform, the on-pulse width for heating the recording layer 4 and the off-pulse width for contributing to cooling were set arbitrarily. The number of pulses was (n-1) with respect to the recording mark length nT (n is an integer of 2 or more, T is a clock frequency). Table 3 shows the jitter values after 1000 times of repeated recording at the optimum power.

[0037]

[Table 3]

[Comparative Example] In Examples 13 to 16,
In the case where the sulfidation preventive layer was not provided, when it was left standing for 100 hours in an environment of 80 ° C. and 85%, defects due to sulfides were noticeably visible. On the other hand, in Examples 13 to 16, no defects were found at all under the same conditions. In Examples 18 and 20, recording was performed in the case where the second lower protective layer was not provided and the other configurations were the same, and the film thickness of the lower protective layer 2 was 70 nm. As a result, at the linear velocity of 18 to 20 m / s, the jitter after 1000 times of repeated recording was about 3% higher than that of the example.

[0039]

According to the constitutions of claims 1 to 3, it is possible to provide a phase change type optical recording medium having excellent recording characteristics when recording at a high linear velocity.

By using the protective layer material according to the fourth aspect, it is possible to provide a phase change type optical recording medium having excellent recording characteristics when recording at a high linear velocity.

By using the recording layer material according to the fifth aspect, it is possible to provide a reflective layer material of a phase change type optical recording medium which is excellent in recording characteristics and storage characteristics when recording at a high linear velocity.

By using the sulfurization preventive layer according to the sixth aspect, it is possible to provide a phase change type optical recording medium having excellent recording characteristics and storage characteristics when recording is performed at a high linear velocity.

By setting the film thickness range according to claims 7 and 8, when recording at high density and high linear velocity, the recording characteristics,
A phase change type optical recording medium having excellent storage characteristics can be provided.

By recording under the conditions defined in claim 9, it is possible to provide a structure of a phase change type optical recording medium which is excellent in recording characteristics when recording at high density and high linear velocity.

By recording at the recording linear velocity according to the tenth aspect, it is possible to provide a phase change type optical recording medium capable of recording at high density and high linear velocity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first form of an optical recording medium according to the present invention.

FIG. 2 is a sectional view showing a second form of the optical recording medium according to the present invention.

FIG. 3 is a sectional view showing a third mode of the optical recording medium according to the present invention.

[Explanation of symbols]

1 Substrate 2 Lower Protective Layer 3 Lower Second Protective Layer 4 Recording Layer 5 Upper Protective Layer 6 Reflective Layer (Al or Al Alloy Reflective Layer, Silver or Silver Alloy Reflective Layer) 7 Sulfidation Prevention Layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 G11B 7/24 534N 535 535 535G 535H 538 538E B41M 5/26 7/0045 Z G11B 7/0045 B41M 5/26 X (72) Inventor Yoshiyuki Kageyama 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Inventor Yuji Miura 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh, Inc. (72) Inventor Mirai Mizutani, 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor, Eiko Suzuki 1-3-3, Nakamagome, Ota-ku, Tokyo (72) Invention, Ricoh Co., Ltd. Person Hiroko Tashiro 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H111 EA03 EA04 EA12 EA23 EA36 E A40 FA11 FA12 FA14 FA23 FA25 FA27 FB05 FB09 FB12 FB17 FB18 FB20 FB21 FB30 5D029 HA06 JA01 JB18 LA14 LA15 LA17 LB07 MA13 NA13 5D090 AA01 BB05 CC01 DD01 EE01

Claims (10)

[Claims] 1. A lower protective layer, a second lower protective layer, a recording layer having a reversible phase change between an amorphous phase and a crystalline phase, an upper protective layer, and a reflective layer containing Al as a main element on a transparent substrate. An optical recording medium characterized by being laminated in this order. 2. A transparent substrate on which a lower protective layer, a second lower protective layer, a recording layer which undergoes a reversible phase change between an amorphous phase and a crystalline phase, and an upper protective layer (which does not contain sulfide). layer),
An optical recording medium in which a reflective layer containing Ag as a main element is laminated in this order. 3. A lower protective layer, a second lower protective layer, a recording layer having a reversible phase change between an amorphous phase and a crystalline phase, and an upper protective layer (a layer containing a sulfide) on a transparent substrate. ), An anti-sulfurization layer, and a reflection layer containing Ag as a main element in that order. 4. The optical recording medium according to claim 1, wherein the second lower protective layer is an oxide containing ZrO ₂ . 5. The recording layer is Ga _α Ge _β In _γ Sb _δ X _ε.
For Te _{100- (α + β + γ + δ + ε)} , X is Ag, Cu, D
y, containing at least one of Mg, α, β,
The composition ratio (At%) of γ, δ, and ε is 0 <α <7 0 <β <10 0 <γ <5 60 <δ <80 0 <ε <5. 3. The optical recording medium according to any one of 3 above. 6. The lower protective layer and the upper protective layer are ZnS and Si.
A mixture of O ₂ is used, and the sulfurization prevention layer is made of Si, SiC, Ge.
Or it is GeCr, The optical recording medium of Claim 3 characterized by the above-mentioned. 7. The second lower protective layer has a film thickness of 5 to 15 n.
The optical recording medium according to claim 1, wherein the optical recording medium is m. 8. The optical recording medium according to claim 6, wherein the film thickness of the sulfuration preventing layer is 2 to 10 nm. 9. An optical recording medium characterized by recording at a linear velocity not lower than a linear velocity at which the reflectance in a crystalline state of a recording layer obtained when the medium is erased with an optimum erasing power starts to drop sharply. 10. The recording linear velocity of the medium is up to 20 m / s.
The optical recording medium according to any one of claims 1 to 9, wherein