JP2003151175A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium adopting a recording material on the basis of a Sb-Te eutectic phase change type optical recording material capable of fast erasing and having high storage property and adopting a protective layer material and a layer structure which can improve the sensitivity and reduces deterioration by fast rapid cooling or fast heating. SOLUTION: (1) The optical recording medium has a lower protective layer, a recording layer which reversibly changes between an amorphous phase and a crystalline phase, an upper protective layer made of ZnS, ZrO2 , Y2 O3 or SiO2 , and a reflecting layer containing Al as the main element successively deposited on a transparent substrate. (2) The optical recording medium further has a sulfuration preventing layer on the upper part of the protective layer and has a reflecting layer containing Ag as the main element. (3) The optical recording medium further has a lower second protective layer made of ZnS, ZrO2 , Y2 O3 or SiO2 on the lower protective layer.

Description

Detailed Description of the Invention

The present invention relates to a phase change type optical recording medium which has excellent recording characteristics in high linear velocity or high density recording and can secure storage reliability.

[0002]

2. Description of the Related Art A so-called phase change type optical recording medium utilizing reversible phase change between a crystalline phase and an amorphous phase is prevailing worldwide as a rewritable optical recording medium. CD-R, C
With the spread of D-RW recording media, high-speed recording is progressing, and high-speed recording is also essential for phase-change optical recording media. In high-speed recording, as the recording density increases, the pulse frequency of the laser light emission pulse also increases, and it is necessary to control heating and rapid cooling of the recording layer in a shorter time. In order to heat and quench in a short time, apply higher recording power,
The rapid cooling requires a long pulse off time, but the recording power is required as the linear velocity becomes faster. A
Sb-Te eutectic phase change optical recording materials such as g-In-Sb-Te have a high crystallization rate and can be erased at high speed in high linear velocity recording. However, when a recording layer material and composition that prioritize high speed erasing are used, the amorphous phase,
That is, it becomes difficult to form recording marks. Further, when high-speed recording and repeated recording are performed, high temperature heating and cooling are repeated in a short time, so that not only the recording layer but also the protective layer between the recording layer and the reflective layer is more likely to deteriorate. Therefore, in order to increase the heat resistance of the protective layer, conventional ZnS,
As a technique using an oxide having a high melting point other than SiO ₂ ,
JP-A-8-180458 and JP-A-8-28751
No. 5 (when the recording layer is a Ge—Sb—Te compound),
JP, 9-138947, A (recording layer is Ag-In-
Sb-Te system).

[0003]

Problems to be Solved by the Invention Ag-In-Sb-T
The phase-change optical recording materials including the e and the Sb-Te eutectic system to which an additive element is added have a high erasing ratio and can be erased at a high speed, and thus are superior to the rewritable phase-change optical recording medium. It is a material. Therefore, sufficient repetitive recording characteristics can be obtained even in high linear velocity recording. However, as the linear velocity becomes higher, if high-speed erasing is given priority,
Storability of data in a high temperature environment becomes insufficient, and it becomes difficult to form an amorphous phase, and sufficient characteristics cannot be obtained. Further, in the case of high-speed recording, in order to form an amorphous phase, it is necessary to heat to a high temperature (above the melting point) in a short time and then rapidly cool. For rapid cooling, the laser may be turned off in a short time, and the medium structure may have a cooling structure in order to improve heat dissipation. In this case, however, higher recording power is required, and the sensitivity deteriorates. As a countermeasure, the laser power should be increased, but the laser power is limited. Therefore, the present invention provides
A recording material based on an Sb-Te eutectic phase-change optical recording material, which enables high-speed erasing and has good storage stability, and a protective layer material and layer capable of improving sensitivity and reducing deterioration due to rapid quenching and rapid heating. An object is to provide an optical recording medium having the configuration.

[0004]

[Means for Solving the Problems] The above problems are solved in the following 1) to
It is solved by the invention of 8) (hereinafter, referred to as the present inventions 1 to 8). 1) On a transparent substrate, a lower protective layer, a recording layer that undergoes a reversible phase change between an amorphous phase and a crystalline phase, ZnS, ZrO ₂ ,
An optical recording medium in which an upper protective layer made of Y ₂ O ₃ , SiO ₂ and a reflective layer containing Al as a main element are laminated in this order. 2) On the transparent substrate, a lower protective layer, a recording layer that undergoes a reversible phase change between an amorphous phase and a crystalline phase, ZnS, ZrO ₂ ,
An upper protective layer made of Y ₂ O ₃ and SiO ₂ , a sulfidation prevention layer,
An optical recording medium in which a reflective layer containing Ag as a main element is laminated in this order. 3) On the transparent substrate, a lower protective layer, ZnS, ZrO ₂ ,
A lower second protective layer made of Y ₂ O ₃ and SiO ₂ , a recording layer that undergoes a reversible phase change between an amorphous phase and a crystalline phase, ZnS,
An optical recording medium in which an upper protective layer made of ZrO ₂ , Y ₂ O ₃ , SiO ₂ or ZnS, SiO ₂ , an anti-sulfur layer, and a reflective layer containing Ag as a main element are laminated in this order. 4) The film thickness of the lower second protective layer is 3 to 10 nm 3)
The optical recording medium described. 5) The optical recording medium according to any one of 2) to 4), wherein the sulfuration preventing layer is any one of SiC, Si, and Ge. 6) The film thickness of the sulfuration prevention layer is 3 to 10 nm 2) to
The recording medium according to any one of 5). 7) The composition formula of the upper protective layer made of ZnS, ZrO ₂ , Y ₂ O ₃ , and SiO ₂ is (ZrO ₂ ) a (Y ₂ O ₃ ) b.
As (SiO ₂ ) c (ZnS) 100- (a + b + c) (a, b, and c in the formula are mol% of each component), the condition of 5 <a <702 <b <80 <c <20 is satisfied. The optical recording medium according to any one of 1) to 6). 8) The composition formula of the recording layer is GaαGeβSbδXεTe100− (α + β + δ +
ε) (X in the formula is Ag, Cu, Dy, Mg, C
at least one of a and Mn, α, β, δ, ε is at% of each component), and 0 <α <10 0 <β <10 60 <δ <80 0 <ε <10 is satisfied 1). The optical recording medium according to any one of to 7).

The present invention will be described in detail below. As shown in FIG. 1, the layer structure of the present invention 1 includes a lower protective layer, a recording layer that undergoes a reversible phase change between an amorphous phase and a crystalline phase, ZnS, ZrO ₂ , and Y on a transparent substrate. ₂ O ₃ , Si
An upper protective layer made of O ₂ and a reflective layer containing Al as a main element are laminated in this order. It should be noted that “having Al as a main element” means that Al is contained most in the constituent elements, and also includes the case of Al alone. The layer structure of the present invention 2 is, as shown in FIG. 2, on a transparent substrate,
Lower protective layer, recording layer that undergoes reversible phase change between amorphous phase and crystalline phase, upper protective layer composed of ZnS, ZrO ₂ , Y ₂ O ₃ , and SiO ₂ , anti-sulfurization layer, and Ag as the main element The reflective layer is laminated in this order. It should be noted that “having Ag as a main element” means that Ag is contained most in the constituent elements, and also includes the case of Ag alone. As shown in FIG. 3, the layer structure of the present invention 3 has a lower protective layer, ZnS, ZrO ₂ , Y ₂ O ₃ , and Si on a transparent substrate.
Lower second protective layer made of O _2, recording layer having reversible phase change between amorphous phase and crystalline phase, ZnS, ZrO ₂ , Y ₂
An upper protective layer made of O ₃ , SiO ₂ or ZnS, SiO ₂ , a sulfidation prevention layer, and a reflective layer containing Ag as a main element are laminated in this order. The definition of "using Ag as a main element" is the same as above.

Upper protective layer and lower portion of phase change type optical recording medium
Conventionally, ZnS and SiO are used for the protective layer. _TwoWith a mixture of
The mixing ratio is ZnS: SiO._Two= 80: 20 (mode
Ratio). The refractive index is 2.0 to 2.1. This
The material has a higher melting point than the recording layer and_TwoAdd
This reduces the coefficient of thermal expansion. Thermal conductivity
Is smaller than ZnS alone, so the recording
Deformation due to repeated recording and Zn without decreasing sensitivity
The change in optical constants due to crystallization of S can be reduced.
Since then, it has been used so far. Especially recording layer and reflection
The upper protective layer between the layers increases the number of repeated recordings.
And easily deteriorates. If you want to record faster,
The layer is heated at a high speed and cooled rapidly, so thermal shock is also large.
It In addition, the pulse width of the light emission pulse irradiating the medium is high.
As the speed increases, the reference clock (T) becomes smaller
Because it becomes narrow. Wider width provides more pulses for cooling
The area and length of the amorphous phase are shortened because the time of no light emission is shortened.
Becomes smaller and it becomes difficult to form a mark having a predetermined length.
That is, higher emission power is required.

Therefore, as the thermophysical properties of the upper protective layer, not only the melting point is high, but also the thermal conductivity is smaller, the coefficient of thermal expansion is smaller, cracks are less likely to be generated by thermal shock, and the elasticity is high. Materials are needed. ZrO ₂ is a dielectric material having a low thermal conductivity, and bulk crystals have a low thermal conductivity among other ceramics. 500 W for SiC, AlN, and Al ₂ O ₃ , which have relatively high thermal conductivity
/ MK, 200 W / mK, 40 W / mK, while 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 be used for the upper protective layer. When the upper protective layer made of ZnS, ZrO ₂ , Y ₂ O ₃ , and SiO ₂ is used, the erasing speed is almost the same as that of ZnS.SiO _2, and the crystallization speed is reduced by replacing the protective layer. There is no. However, from a practical point of view, when the film is formed by the sputtering method, the film formation speed is slower than half that of ZnS.SiO ₂ , and therefore the thicker the film, the longer it takes.
Also, as the film thickness increases, the absorption increases and the reflectance of the medium decreases. Further, since the film is in a crystalline state, if it is left in a high temperature environment for a long time, the mark is easily deteriorated (crystallized) and the characteristics are deteriorated, so that it has an action of promoting crystallization.

Therefore, in the present invention 1, it has been decided to use a mixture of these materials which makes use of the characteristics of ZrO _{2 and has} the features of high refractive index of ZnS and high practical thin film formation speed. Mixing ZrO ₂ with another dielectric also has the effect of lowering the thermal conductivity, and it is possible to lower the thermal conductivity than a conventional mixture of ZnS and SiO ₂ . Furthermore, Y ₂ is added to the target material so that the target material used when forming a thin film of these mixtures does not crack.
The O ₃ is added. In addition, by adding SiO ₂ , ZnS,
Crystallization of ZrO ₂ by repeated recording is suppressed. The ratio of each component of this protective layer material is determined by the composition formula (ZrO ₂ ) a
_{(Y 2 O 3) b (} SiO 2) c (ZnS) 100- (a
As + b + c) (in the formula, a, b, and c are mol%), those satisfying the following conditions are preferable. 5 <a <702 <b <80 <c <20 The optimum range of the film thickness of the upper protective layer is 5 to 20 nm.
If it is too thin, the sensitivity will be poor, and if it is too thick, the cooling rate will be slow, making it difficult to form an amorphous phase and reducing the area of the mark. The lower protective layer is made of conventional ZnS and SiO.
A mixture of ₂ was used, the ratio of which was ZnS: SiO ₂ = 50:
It is 50 to 85:15.

In the phase-change optical recording layer, Ga, Ge and In are added based on the eutectic composition near Sb ₇₀ Te ₃₀ , and the composition formula is GaαGeβSbδXεTe100- (α + β + δ).
+ (Ε) (wherein α, β, δ, ε are at% of each element, X is Ag, Cu, Dy, Mg, Ca,
It is at least one element of Mn. It is preferable that the composition ratio of each element satisfies the following conditions. 0 <α <10 0 <β <10 60 <δ <800 0 <ε <10 Sb, Te The eutectic composition of the recording layer does not easily cause composition segregation even after repeated recording, and has excellent repeated recording characteristics. However, there is a limit to the improvement of crystallization speed, that is, high-speed erasing, and even if the crystallization speed is increased only by the Sb amount,
Since the crystallization temperature is about 100 ° C. in a high temperature environment, the mark disappears at a higher temperature, and there is a problem that it cannot be used as an optical recording medium.

Therefore, in the present invention 1, the recording linear velocity is 20 m.
Ga is added without increasing the Sb amount so much as to correspond to high-speed recording of / s or more. When Ga is used, the crystallization rate can be increased and the crystallization temperature can be increased with a small addition amount. As a result, the stability of the mark when placed in a high temperature environment can be improved. However, if the amount of Ga is too large, the crystallization temperature becomes too high, and a uniform and high reflectance is obtained at the time of initialization in which the amorphous phase is changed to the crystalline phase in advance in the production process. Becomes difficult to do. The preferable addition amount range of Ga is 1 to 4 at.
%, And the preferable range of the Sb amount is 65 to 75 at%.
Is. In has the same effect as Ga, but since it does not raise the crystallization temperature as much as Ga, it is effective in supplementing Ga. However, if too much is added, the repetitive recording characteristics deteriorate. In addition to Ga, D is an additional element that increases the crystallization rate and does not increase the crystallization temperature as much as Ga.
y, Mg, Ca, and Mn are used.

In order to improve the reliability including the data storability after repeated recording, addition of Ge is more effective. The optimum addition amount range is 2 to 5 at%. Further, since Ge has a low crystallization rate when added in a large amount, Cu or Ag is used as an element to supplement this. C
The preferred addition amount of u and Ag is 2 at% or less. The film thickness range of the recording layer is 10 to 25 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. Polycarbonate (PC),
A transparent substrate made of plastic such as polymethylmethacrylate (PMMA) or glass is used.
The reflective layer is made of Al, Ag, Cu, Pd, Cr, Ta, Ti.
A metal material such as is used. The film thickness is preferably 50 to 250 nm. Furthermore, in order to protect the reflective layer, if necessary,
A protective layer made of an ultraviolet curable resin or the like may be provided on the reflective layer.

The second aspect of the present invention is the same as the first aspect of the present invention, except for the presence or absence of the sulfidation preventive layer and the material of the reflective layer. Invention 2 is suitable for recording at a higher linear velocity than Invention 1. Since the reflective layer containing Ag as the main element is used, the thermal conductivity of the reflective layer is higher and the quenching effect is higher than that in the case of using Al of the present invention 1 as the main element. However, in the case of Ag, when the alloy has a large amount of additional elements, the thermal conductivity tends to decrease sharply as compared with pure Ag as the amount of additional elements increases, so it cannot be added in a too large amount. Therefore, the amount of added elements is several w
t% is preferred. In the second aspect of the invention, since the reflective layer has Ag as a main element, Ag reacts easily with S of the upper protective layer to form AgS. This reaction is further accelerated under a high temperature and high humidity environment to generate a defect and increase the data error rate. Therefore, when Ag or an Ag alloy is used for the reflective layer, it is necessary to provide a layer for preventing sulfidation (sulfidation prevention layer). However, if the thickness of this layer becomes thicker, the efficiency of the heat accumulated in the upper protective layer being dissipated in the reflecting layer will deteriorate, and conversely, if the thickness is too thin, the film will not adhere evenly. Be careful because partial sulfidation occurs due to such a phenomenon. The preferable film thickness range is 3 to 10 nm. If it is thinner than 3 nm, it is easily sulfided, and if it is thicker than 10 nm, the reflectance is remarkably lowered, which is not preferable (invention 6).

Materials used for the sulfidation prevention layer include oxides, nitrides, carbides, metals and alloys. It is preferable that the thermal conductivity is higher than that of the upper protective layer, the melting point is higher, and it does not change with time. As a specific example, SiN, AlN,
Al ₂ O ₃ , SiO ₂ , SiC and other oxides, nitrides,
Carbides, Si, Ge and the like can be mentioned. Of these materials, oxides and nitrides, when left to stand in a high temperature and high humidity environment for a long time, have defects to some extent when the film thickness is set to 4 nm, although to some extent. On the other hand, SiC, Si, Ge
Is preferable because there are almost no such problems. However, S
Since iC, Si, and Ge have larger light absorption than nitrides and oxides, iC, Si, and Ge have a film thickness of 3 to 10 nm, preferably 3 to
7 nm. By providing a sulfidation prevention layer, 80
Even if it is exposed to an environment of ℃ and relative humidity of 85% for a long time, the sulfidation reaction does not occur, and the error rate can be kept within the allowable range.

The third aspect of the present invention is that a lower second protective layer is provided,
And ZnS and ZrO as upper protective layer materials_Two, Y
_TwoO_Three, SiO_TwoIn addition to materials consisting of ZnS, SiO
_TwoThe present invention, except that a material consisting of
Same as 2. Upper protective layer material used in the present invention 1 and 2
ZnS / SiO_TwoLower part between the lower protective layer and the recording layer
2 When used as a protective layer, further improves repetitive recording characteristics.
You can However, if it is too thick, the heat dissipation will be poor.
Therefore, the upper limit of the film thickness of the lower second protective layer is about 10 nm.
It is degree. If the thickness is less than 3 nm, the film will have a uniform thickness.
As a result, cracks and cracks tend to occur from the grain boundary part.
Therefore, the preferable range of film thickness is 3 to 10 nm (
Ming 4). Furthermore, ZrO_TwoProtective layer containing crystallization effect
Therefore, high speed crystallization is possible especially in high speed recording.
Become. However, ZrO_TwoCrystallization-promoting effect with large addition
However, the composition of the lower second protective layer is deteriorated because it deteriorates storage stability.
The formula is (ZrO_Two) A (Y _TwoO_Three) B (SiO_Two) C (Z
nS) 100- (a + b + c) (wherein a, b,
c is mol% of each component), and those satisfying the following conditions are preferable.
Good 10 <a <30 2 <b <8 5 <c <10

The optical recording medium of the present invention has a recording wavelength of 400 to
Recording and reproduction is possible in the range of 780 nm. In order to increase the recording density, the aperture ratio of the objective lens is set to 0.60 or more and the beam diameter of incident light is reduced. For example, the recording wavelength is 650 nm, the aperture ratio of the objective lens is 0.6 to 0.65, the thickness of the substrate is 0.6 mm, and the track pitch of the substrate is 0.
74 μm or less, the groove depth is 15 to 60 nm, and the groove width is 0.
2 to 0.3 μm. When recording at high speed and high density using the optical recording medium of the present invention, the pulse width of laser light is modulated. The power level of the light emission pulse is recorded, erased,
It consists of three levels of bias. The recording / erasing power is higher than the reproducing power, and the bias power is lower than the reproducing power. The bias power is the power after the recording power is applied and is necessary for forming the amorphous phase.

When forming a mark in which the time length of the recording mark is nT (n is an integer of 2 or more, T is a reference clock time), the recording power and bias power irradiation times are OPn and FPn, respectively. As (n is the number of pulses), light is emitted in a pulse pattern in which the number m of pulses is n-1. The sum of OPn and FPn is 0.5T <OPn +
FPn <1.5T. This pulse further consists of a head pulse (1 pulse), a plurality of pulse trains, and a final pulse (1 pulse). These light emission patterns sharpen the edge portion of the recording mark, and also the recording position and the length of the recording mark. It is necessary to record the length in a predetermined length. As shown in FIG. 4, of OPn and FPn, the head portion is OP1, FP1, and the intermediate pulse is OPj, FPj.
(J = 2 to m−1), the final pulse is divided into OPm and FPm. The maximum recording linear velocity is 20 m / s in the case of a DVD having a capacity of 4.7 GB, and the recording clock has a linear density of 0.
267 μm / bit. , The maximum is 150 MHz, and the recording data modulation method is the (8, 16) modulation method.

[0017]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, in the example and the comparative example, each pulse time in FIG. 4 was set as follows. OP1 4.5 nsec. FP1 4.3 nsec. OPj 3.5 nsec. FPj 4.4 nsec. OPm 3.5 nsec. FPm 2.0 nsec.

Examples 1 to 5 A polycarbonate substrate 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 is used as a guide groove, on which each layer is sequentially formed by a sputtering method. Laminated. ZnS: SiO ₂ = 8 for the lower protective layer
A target of 0:20 (mol%) is used, and the film thickness is 7
It was set to 0 nm. The material having the composition shown in Table 1 below was used for the recording layer, and the film thickness was set to 17 nm. Y is used for the upper protective layer.
ZnS, ZrO ₂ , SiO containing ₃ mol% of ₂ O _3
Two- mixture target was used and the film thickness was 7 nm. An AlTi alloy was used for the reflective layer, and the film thickness was set to 180 nm. Further, a protective UV curable resin having a film thickness of 2 μm was applied on the reflective layer. Finally, another substrate that has not been film-formed is attached with an ultraviolet curing resin, and the thickness is 1.2 m.
m optical recording medium. After that, a large-diameter LD (1 μm x
100 μm), linear velocity 3.5 m / s, power 850
The recording layer was crystallized at mW. Recording / reproduction was performed using a pickup head having a laser wavelength of 655 nm and an NA of 0.65 as an objective lens so that the recording density was 0.267 μm / bit at a recording linear velocity of 14 m / s. The recording data modulation method is (8, 16) modulation, and the recording power is 20.
mW, bias power 0.1 mW, erase power 6 mW
And Table 1 shows the jitter after the first and 1000th repeated recording (DOW1000).

[0019]

[Table 1]

Examples 6 to 10 A polycarbonate substrate 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 is used as a guide groove, on which each layer is sequentially formed by a sputtering method. Laminated. ZnS: SiO ₂ = 8 for the lower protective layer
A target of 0:20 (mol%) is used, and the film thickness is 7
It was set to 0 nm. The material having the composition shown in Table 2 below was used for the recording layer, and the film thickness was set to 17 nm. Y ₂ is used as the upper protective layer.
ZnS, ZrO ₂ , SiO ₂ containing ₃ mol% of O _3.
A mixture target was used and the film thickness was 7 nm. For the sulfidation prevention layer, the materials shown in Table 2 below are used, and the film thickness is 4n.
m. Ag is used for the reflective layer, and the film thickness is 160 nm.
And Further, a protective UV curable resin having a film thickness of 2 μm was applied on the reflective layer. Finally, another substrate that has not been film-formed is attached with an ultraviolet curable resin to a thickness of 1.2.
mm optical recording medium. After that, a large-diameter LD (1 μm
× 100 μm), linear velocity 3.5 m / s, power 85
The recording layer was crystallized at 0 mW. Recording / reproduction was performed using a pickup head having a laser wavelength of 655 nm and an NA of 0.65 as an objective lens so that the recording density was 0.267 μm / bit at a recording linear velocity of 17 m / s. The modulation method of the recording data was (8,16) modulation. FIG. 5 shows the dependence of jitter on the number of times of repeated recording (DOW) when the recording power (Pw) was 20 mW in Example 10. The erasing power was 6 mW. Moreover, in FIG.
The recording power dependency at the time of the first recording of is shown. Table 2 shows the jitter after the initial recording and after 1000 repeated recordings (DOW1000).

[0021]

[Table 2]

Examples 11 to 15 A polycarbonate substrate 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 as a guide groove, on which each layer was sequentially formed by a sputtering method. Laminated. ZnS: SiO ₂ = 8 for the lower protective layer
A target of 0:20 (mol%) is used and a film thickness is 6
It was set to 0 nm. The lower second protective layer had a composition shown in Table 3 below and a film thickness of 5 nm. For the recording layer, a material having a composition shown in Table 3 which enables recording at a predetermined recording linear velocity was used, and the film thickness was set to 17 nm. In the upper protective layer, Z shown in Table 3 below is used.
nS, ZrO ₂ , SiO ₂ , Y ₂ O ₃ mixture, or Z
nS: SiO ₂ = 80: 20 (mol%) was used and the film thickness was set to 10 nm. For the sulfidation prevention layer, the materials shown in Table 3 below were used and the film thickness was set to 4 nm. Ag was used for the reflective layer, and the film thickness was set to 160 nm. Furthermore, on the reflective layer,
A protective UV curable resin having a film thickness of 2 μm was applied. Finally, another substrate on which no film was formed was attached with an ultraviolet curable resin to obtain an optical recording medium having a thickness of 1.2 mm.
Then, using a large-diameter LD (1 μm × 100 μm), the recording layer was crystallized at a linear velocity of 3.5 m / s and a power of 850 mW. Recording and reproduction were performed using a pickup head having a laser wavelength of 655 nm and an objective lens NA of 0.65 so that the recording density was 267 μm / bit at a recording linear velocity of 17 m / s. The erasing power was 6 mW. The modulation method of the recording data was (8,16) modulation. Table 3 shows the jitter after the first and 1000th repeated recording (DOW1000). After recording on these optical recording media, 80
Even when left in an environment of 85 ° C. and 85% RH for 300 hours, there was almost no deterioration of jitter.

[0023]

[Table 3]

Comparative Examples 1 to 5 A polycarbonate substrate 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 is used, and each layer is sequentially formed on this by a sputtering method. Laminated. ZnS: SiO ₂ = 8 for the lower protective layer
A target of 0:20 (mol%) is used, and the film thickness is 7
It was set to 0 nm. The lower second protective layer had the composition shown in Table 3 and had a film thickness of 5 nm. The recording layer was made of a material having the composition shown in Table 3 and capable of recording at a predetermined recording linear velocity, and had a film thickness of 17 nm. ZnS: SiO is used for the upper protective layer.
₂ = 80: 20 (mol%) mixture was used and the film thickness was 1
It was set to 2 nm. SiC was used for the sulfidation prevention layer, and the film thickness was 4 nm. Ag is used for the reflective layer, and the film thickness is 16
It was set to 0 nm. Further, a protective UV curable resin having a film thickness of 2 μm was applied on the reflective layer. Finally, another substrate on which no film was formed was attached with an ultraviolet curable resin to obtain an optical recording medium having a thickness of 1.2 mm. After that, large-diameter LD
Using (1 μm × 100 μm), the recording layer was crystallized at a linear velocity of 3.5 m / s and a power of 750 mW. Recording and playback
Recording was performed at a recording linear velocity of 14 m / s and a recording density of 0.267 μm / bit using a pickup head having a laser wavelength of 655 nm and an NA of 0.65 for the objective lens. The modulation method of the recording data was (8,16) modulation.
For comparison with Example 10, FIG. 5 shows the dependence of jitter on the number of times of repeated recording (DOW) when the recording power (Pw) of Comparative Example 5 was 20 mW. The erasing power is 6mW
And Similarly, FIG. 6 shows the recording power dependency at the time of the first recording in Comparative Example 5.

As is clear from the results shown in FIGS. 5 and 6,
The optical recording medium of Example 10 has improved jitter after 1000 times of repeated recording (DOW1000) and also improved jitter at low recording power, as compared with the comparative example. That is, in the present invention, as a result of devising the material and composition of the protective layer and the recording layer, when recording at a high linear velocity, the characteristics at low recording power are particularly improved as compared with the conventional medium, and the number of times of repeated recording is increased. An optical recording medium having improved characteristics after 1000 times (DOW1000) could be obtained.

[0026]

According to the present inventions 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. According to the present inventions 4 and 6, it is possible to provide a phase change type optical recording medium having excellent recording characteristics and storage characteristics when recording is performed at high density and high linear velocity. Invention 5
According to this, 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. According to the present invention 7, it is possible to provide a phase change type optical recording medium having excellent recording characteristics when recording at a high linear velocity. According to the present invention 8, it is possible to provide a phase change type optical recording medium which is excellent in recording characteristics and storage characteristics when recording is performed at a high linear velocity.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic layer structure of an optical recording medium according to the present invention 1.

FIG. 2 is a diagram showing a basic layer structure of an optical recording medium according to the present invention 2.

FIG. 3 is a diagram showing a basic layer structure of an optical recording medium according to the present invention 3.

FIG. 4 is a diagram showing an example of a recording power and a bias power irradiation time when recording is performed by pulse-width-modulating a laser beam.

FIG. 5 is a diagram showing the dependence of jitter on the number of repeated recordings (DOW) when the recording power (Pw) is 20 mW in the optical recording media of Example 10 and Comparative Example 5.

FIG. 6 is a graph showing the recording power dependence of the optical recording media of Example 10 and Comparative Example 5 at the time of initial recording.

[Explanation of symbols]

1 substrate 2 Lower protective layer 3 recording layers 4 Upper protective layer 5 Al or Al alloy reflective layer 6 Sulfidation prevention layer 7 Ag or Ag alloy reflective layer 8 Lower second protective layer Clock time as the reference OP1 Time to irradiate the recording power of the first pulse OPj Time to irradiate recording power of intermediate pulse OPm Time to irradiate the recording power of the last pulse FP1 Lead pulse bias power irradiation time FPj Time for applying intermediate pulse bias power FPm Time to irradiate the bias power of the final pulse

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 G11B 7/24 535H 538 538E B41M 5/26 B41M 5/26 X (72) Inventor Masato Hariya 1-6-3 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Eiko Suzuki Inc. 1-3-6 Nakamagome, Ota-ku Tokyo (72) Inventor Hiroko Tashiro Ota-ku, Tokyo Nakamagome 1-3-6, Ricoh Co., Ltd. (72) Inventor Mirai Mizutani 1-3-6 Nakamagome, Rita, Tokyo (72) Inventor Yoshiyuki Kageyama 1-chome Nakamagome, Ota-ku, Tokyo No. 3-6 F-term in Ricoh Co., Ltd. (reference) 2H111 EA04 EA23 EA36 EA40 FA01 FA11 FA12 FA14 FA23 FA25 FA27 FB05 FB09 FB12 FB16 FB17 FB18 FB19 FB2 0 FB21 FB30 5D029 JA01 LA14 LA15 LA19 LB01 LB07 NA13

Claims (8)

[Claims] 1. A lower protective layer, a recording layer having a reversible phase change between an amorphous phase and a crystalline phase, ZnS, Z on a transparent substrate.
An upper protective layer made of rO ₂ , Y ₂ O ₃ , and SiO ₂ , Al
An optical recording medium in which a reflective layer containing, as a main element, is laminated in this order. 2. A lower protective layer, a recording layer which undergoes a reversible phase change between an amorphous phase and a crystalline phase, ZnS, Z on a transparent substrate.
_{rO 2, Y 2 O 3,} SiO 2 upper protective layer made of, preventing sulfide layer, an optical recording medium are laminated in this order on the reflective layer to major elements of Ag. 3. A lower protective layer, ZnS, Z on a transparent substrate.
a lower second protective layer made of rO ₂ , Y ₂ O ₃ and SiO ₂ ,
A recording layer that undergoes a reversible phase change between an amorphous phase and a crystalline phase,
ZnS, ZrO ₂ , Y ₂ O ₃ , SiO ₂ or ZnS, S
upper protective layer made of iO _2, anti-sulfide layer, an optical recording medium are laminated in this order on the reflective layer to major elements of Ag. 4. The optical recording medium according to claim 3, wherein the film thickness of the lower second protective layer is 3 to 10 nm. 5. The optical recording medium according to claim 2, wherein the sulfidation prevention layer is one of SiC, Si and Ge. 6. The optical recording medium according to claim 2, wherein the sulfidation preventive layer has a film thickness of 3 to 10 nm. 7. ZnS, ZrO ₂ , Y ₂ O ₃ , SiO ₂
The composition formula of the upper protective layer made of (ZrO ₂ ) a (Y ₂ O ₃ ) b (SiO ₂ ) c (Zn
S) 100- (a + b + c) (where a, b, and c are mol% of each component in the formula), 5 <a <70 2 <b <80 0 ≦ c <20 being satisfied. The optical recording medium according to any one of 1. 8. The composition formula of the recording layer is GaαGeβSbδXεTe100− (α + β + δ +
ε) (X in the formula is Ag, Cu, Dy, Mg, C
at least one of a and Mn, α, β, δ, and ε are at% of each component), and 0 <α <10 0 <β <10 60 <δ <800 <ε <10 are satisfied. The optical recording medium according to any one of 1 to 7.