JP2002245663A - Optical recording medium - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a specific recording medium capable of performing high-density recording of the same capacity or more as a DVD-ROM and covering a recording linear velocity of 2 times or more (about 7 m / s or more). 3.0m / s to 20m / s
The present invention provides a phase-change type optical recording medium having good overwrite characteristics at a high recording linear velocity in the range described above and exhibiting sufficient reliability even when stored in a high-temperature environment. SOLUTION: An optical recording medium for recording information having a phase-change optical recording layer of a composition formula of XaSbxTey in which Sb and Te are essential elements and at least one kind of element X is added to SbTe in combination. And the CW of the laser light
The linear velocity range where the reflectivity changes from high level to low level by irradiation is in the range of 8 m / s to 30 m / s, and the recordable linear velocity range is 1.2 m / s to 30 m / s. The following optical recording medium is the main configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, and more particularly, to irradiating a light beam to cause an optical change in a material of a recording layer, thereby recording and reproducing information, and performing rewriting. It relates to a possible phase-change optical recording medium, and the linear velocity of a commercially available DVD-ROM is 2
The present invention relates to an optical recording medium capable of supporting a recording linear velocity twice or more.

[0002]

2. Description of the Related Art As a conventional technique, a rewritable optical disk corresponding to high linear velocity and high density recording generally includes Ge2S.
Using a recording material near the b2Te5 compound composition and Ag
Some recording materials use the SbTe eutectic composition represented by InSbTe as the main component, but due to their compatibility with high-density recording and good erasing characteristics during overwriting, they have already been commercialized and spread. The latter material is used for CD-RW.

[0003] JP-A-1-303643 discloses that Sb and
A recording material containing Te as a main component is disclosed, and when the recording material based on AgInSbTe has a Te content of 10 at% to 30 at% in Sb-Te as a recording material having a SbTe eutectic composition as a main component, It has been disclosed that it exhibits excellent overwrite characteristics. Experiments have confirmed that there are regions where high recording linear velocities can be obtained depending on the composition ratio of Sb-Te.However, the crystallization temperature of Sb-Te alone is generally low, and the recording mark crystallizes under high temperature and high humidity conditions. May disappear.

[0004] To prevent this, the present inventors use a small amount of
By adding various elements, typically Ag and In, the recording sensitivity is high even in the high linear velocity recording area, and 3.0 m / s
An AgInSbTe phase-change type optical recording medium has been developed which can realize overwrite repetition characteristics at a speed in the range of 1 to 20 m / s and good storage characteristics exhibiting sufficient reliability even in a high temperature environment.

[0005]

SUMMARY OF THE INVENTION The present invention provides a high-density recording of the same capacity or more as a DVD-ROM, and is capable of covering a recording linear velocity of 2 times or more (about 7 m / s or more). Provides a phase-change optical recording medium that has good overwrite characteristics at high recording linear velocities in the range of 3.0m / s to 20m / s and shows sufficient reliability even when stored in a high-temperature environment. I do.

[0006]

The above object of the present invention is achieved by the following means. According to the present invention, claim 1
Has a phase change optical recording layer of a composition formula of XaSbxTey in which Sb and Te are essential elements and at least one or more elements X are added to SbTe, and the recording layer is changed from a crystal phase by irradiation with laser light. An optical recording medium that records information by changing to an amorphous phase, and has a linear velocity range from 8 m / s to 30 m / s where the reflectance changes from high level to low level by CW irradiation of laser light. The main feature is that the linear velocity range is 1.2 m / s or more and 30 m / s or less.

Secondly, in the optical recording medium according to the first aspect, the composition ratio x / (x + y) of Sb and Te in XaSbxTey is 0.50-0.90 in atomic ratio.

Thirdly, in the optical recording medium according to any one of claims 1 and 2, the content a of the additional element is 0.15 or less in atomic ratio with respect to (Sb + Te).

Fourth, in the optical recording medium according to any one of claims 1 to 3, X is Ag, Au, Cu, Zn, B, Al, Ga, In, Si, G
It is characterized by one element selected from e, Sn, Pb, N, P, Bi, La, Ce, Gd, and Tb or a combination of a plurality of elements.

Fifth, in the optical recording medium according to any one of claims 1 to 4, when two or more of the above-mentioned additional elements are added, N is an essential element to be added.

Sixth, in the optical recording medium according to any one of the first to fifth aspects, the linear velocity range at which the reflectance changes from a high level to a low level by CW irradiation of a laser beam on the recording medium is defined by the line according to the first aspect. The maximum linear velocity is in the range of 1 to 1.5 times the maximum linear velocity used by the combination of elements according to claim 4.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. As a characteristic of the phase change recording material used for the optical recording medium, there is a range of linear velocity (hereinafter referred to as transition linear velocity) in which the reflectance of the medium changes from a high level to a low level by CW irradiation of a laser beam. It has been confirmed by experiments that the range varies depending on the type of the element X in the phase-change optical recording layer and its composition ratio. As a result of evaluating the recording characteristics of these materials, it was also found that in the recording linear velocity region equal to or lower than the transition linear velocity, good characteristics can be obtained without largely changing the recording method from the conventional one.

FIG. 1 shows a change in reflectivity due to CW irradiation of a laser beam to an SbTe optical recording medium. The linear velocity range in which the reflectivity decreases is not an absolute value because it depends on the power density of the laser beam. However, at least in the optical system used in the recording system,
By measuring, it becomes a reference amount in the system, and can be used as a design standard of the recording linear velocity region of the optical disk based on this numerical value.

FIG. 2 shows the reflectivity of a phase change optical recording material of the composition formula XaSbxTey in which 5% of Ag, Ge, Sn and In elements are added alone to SbTe having a Te content of 25%. The rate change is shown.

The transition linear velocity range in which the reflectivity decreases due to the characteristics of the added element includes those that shift to a slow region and those that shift to a fast region. Ag, Au, Cu, Zn, Ga, G
e, N, etc. lower the transition linear velocity, Pb, In, La, Ce, Gd,
Tb and the like are a group of elements that increase the transition linear velocity.
Bi, B, S that do not change the transition linear velocity very much
n, Si, B, Al, P, and the like.

From these results, the transition linear velocity range can be freely set depending on the composition ratio of SbTe and the content and combination of each additive element. In particular, the transition linear velocity range from 8 m / s to 25 m / s can be set. The material has high linear velocity recording.

When an optical recording medium is manufactured using a material having a certain transition speed, the recording characteristics of the optical recording medium are slower than the transition speed (the linear velocity range is from 1 time to 1.times. The maximum linear velocity used). Experiments have also confirmed that good recording characteristics can be obtained by performing recording in a linear velocity range of preferably 1.5 m / s or less. The result is shown in FIG. In the case of an optical disk using a recording material having a transition linear velocity of 8 m / s or more and 30 m / s, an optical recording medium having a recordable linear velocity range of 1.2 m / s or more and 30 m / s or less is obtained.

In XSbTe having the composition adjusted as described above, not only the transition linear velocity needs to be matched, but also in order to obtain good recording characteristics, particularly overwrite characteristics, it is necessary to use XaSbxTey of Sb and Te. Composition ratio x / (x + y) is the atomic ratio
It must be 0.50-0.90.

FIG. 4 shows the overwrite characteristics of SbTe as the main component. This is because the remaining Sb / (Te
+ Sb) ratio is considered to be equivalent to the overwrite characteristic, and it was found that a good overwrite characteristic was obtained when the Sb / (Te + Sb) ratio r was around 0.75. XaSbxT
If the composition ratio x / (x + y) of Sb and Te in ey is 0.50-0.90 in atomic ratio, the residual Sb / (Te + Sb) ratio r can be designed to be around 0.75.

Further, in the optical disk, the transition linear velocity is reduced from the viewpoint of reducing jitter and securing reliability.
Ag, Ge, N, etc. need to be added as essential elements. In particular, the effect of adding N element is remarkable.

However, since it is necessary to increase the transition linear velocity for an optical disk corresponding to a high linear velocity, it is necessary to add an element such as In to In, such as In, to Ag, Ge, N and the like. Occurs. However, it has been confirmed by experiments that the reproduction light stability becomes a problem when excessive In is added. The results are as shown in Table 1.

From the results, the content a of the additional element is (Sb + Te)
By setting the atomic ratio to 0.15 or less, and particularly desirably, to 10% or less for elements that increase the transition linear velocity such as In, a reliable optical recording medium can be realized.

The prescription other than the recording layer is as follows.
FIG. 5 shows the layer configuration of the optical recording medium. The upper protective layer and the lower protective layer can be formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method, an electron beam deposition method, or the like. The thickness of the lower protective layer depends on its function, that is, the function as a heat-resistant layer and a multiple interference layer.
110 nm or 170 nm to 230 nm is good. If it is less than 50 nm, the function of protecting the recording layer from the influence of the substrate will not work, and if it is more than 300 nm, interface peeling is likely to occur. Also, the upper protective layer is preferably 10 to 35 nm. If it is less than 10 nm, the recording sensitivity will be poor, and if it is more than 35 nm, the heat will be excessive.

The recording layer of the present invention is generally formed by a sputtering method, and its thickness is preferably 10 to 30 nm. 10nm
If the thickness is smaller, the light absorbing ability is reduced and the function as a recording layer is lost. On the other hand, if the thickness exceeds 30 nm, the recording sensitivity becomes poor.

Although various metals can be used for the reflective heat dissipation layer, in particular, Al-Ti, Al-Ni, Al-Mn, Al-Cr, Al-Zr, A
Al alloys such as l-Si and Ag alloys such as Ag-Pd are desirable. These layers are formed by a vacuum evaporation method, a sputtering method, an electron beam method, or the like, and the thickness thereof is preferably 20 to 300 nm. If it is less than 20 nm, the heat radiation effect cannot be obtained. On the other hand, if the thickness is 300 nm or more, interface peeling tends to occur.

On a polycarbonate substrate 1 having a guide groove, a lower protective layer 2 containing ZnS-SiO ₂ , an XSbTe recording layer 3 on this first protective layer, and a ZnS-SiO ₂ on this recording layer are deposited by sputtering. An upper protective layer 4 containing the Al-Ti reflective heat radiation layer 5 on the upper protective layer is formed, and an environmental protection layer 6 having a UV curable resin applied by spin coating is laminated on the reflective heat radiation layer. I have. The film forming conditions for each layer were ZnS-
SiO ₂ film: input power 3kW, Ar gas pressure (film forming chamber pressure) 2E-3To
rr, AgInSbTe film: input power 1 kW, Ar gas pressure (deposition chamber pressure) 2E-3 Torr, ZnS-SiO ₂ film: input power 3 kW, Ar
Gas pressure (film forming chamber pressure) 2E-3Torr, Al film: input power 9k
The W and Ar gas pressures (the film forming chamber pressure) were set at 2 mTorr.

Table 1 shows a recording linear velocity of the optical recording medium of the present invention of 8 m.
The number of times of repetition recording at / s was examined together with a comparative example. The number of repetitive recordings is determined by the maximum number of times that the value σ / Tw of the shutter normalized by the window width Tw satisfies the standard value. The track pitch is 0.74 μm.

(Examples) Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples.

Example 1 The recording layer having the composition shown in Table 1 was 20 nm, and the first dielectric layer was 70 nm.
The characteristics of an optical recording medium formed by sputtering on a polycarbonate substrate with the second dielectric layer being 20 nm for the second dielectric layer and the reflecting layer being 140 nm for a recording layer having a recording linear velocity of 8 m / s which is more than twice the speed of 4.7 GB DVD-ROM As a result, good characteristics as shown in Table 1 were obtained.

Example 2 As a result of evaluating a recording medium in which the composition of the recording layer was changed as shown in Table 1 with respect to Example 1, almost the same results as in Example 1 were obtained. Except for the composition of the recording layer, it is the same as Example 1.

Example 3 This is an example in which a recording layer having the same composition as in Example 1 was formed using an argon / nitrogen mixed gas containing about 3% of nitrogen.
Except for the composition of the recording layer, it is the same as Example 1. The storage reliability was improved as compared with the example.

Comparative Example 1 This is an example using a recording layer in which the composition ratio of the recording layer is changed and the transition linear velocity is lower than the recording linear velocity. Other configurations are the same as those of the first embodiment. In this case, the overwrite characteristics were worse than those of the examples, and the effect of the recording layer composition of the present invention was confirmed.

[0033]

[Table 1]

[0034]

According to the first aspect, SbTe is an essential element,
In the phase-change optical recording layer of the composition formula of XaSbxTey, which is obtained by adding at least one or more elements and the element X in combination, the transition linear velocity range is set to a range of 8 m / s to 30 m / s, and Good recording characteristics are realized in the recording linear velocity range of not less than m / s and not more than 30 m / s.

According to the second aspect of the present invention, the composition ratio of x / (x + y) of Sb and Te in XaSbxTey is set to 0.50-0.90 in atomic ratio. can get.

The content a of the additional element according to claim 3 is (Sb +
By setting the atomic ratio to 0.15 or less with respect to (Te), an optical recording medium having excellent reliability such as reproduction light stability can be obtained.

In the fourth aspect, X is Ag, Au, Cu, Zn, B, A
l, Ga, In, Si, Ge, Sn, Pb, N, P, Bi, La, Ce, Gd,
The transition linear velocity range of claim 1 can be realized by one element selected from Tb or a combination of plural elements.

In the case of adding two or more of the above-mentioned additional elements, an optical recording medium with high storage speed and high linear velocity with high storage reliability can be obtained by using N among the additional elements as an essential element.

According to a sixth aspect of the present invention, an optical recording medium having excellent recording characteristics can be obtained by setting the transition linear velocity range of the recording medium to a range of 1 to 1.5 times the maximum recording linear velocity.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a change in reflectance of SbTe due to laser CW irradiation according to the present invention.

FIG. 2 is an explanatory diagram showing a change in reflectance due to addition of Ag, Ge, Sn, In, and 5% to SbTe in the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a transition linear velocity to a recording medium of the present invention and a recording linear velocity.

FIG. 4 is an explanatory diagram showing that the repetitive recording characteristics are good at 25% of SbTe of the present invention.

FIG. 5 is a cross-sectional view showing a layer configuration of the optical recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower protective layer 3 Recording layer 4 Upper protective layer 5 Reflection heat dissipation layer 6 Environmental protection layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hajime Yonehara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Eiko Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Share Inside Ricoh Company (72) Inventor Nobuaki Onagi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Hiroko Tashiro 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F Terms (reference) 2H111 EA04 EA12 EA23 EA31 EA32 EA40 FA01 FB04 FB05 FB06 FB07 FB09 FB10 FB12 FB17 FB19 FB20 FB21 FB24 FB30 5D029 JA01 JB18 JB35 JC02 5D090 AA01 BB05 CC01 CC02 DD01

Claims (6)

[Claims] 1. A phase change optical recording layer having a composition formula of X _a Sb _x Te _y obtained by adding Sb and Te as essential elements and adding at least one or more elements X to SbTe in combination, An optical recording medium that records information by changing the recording layer from a crystalline phase to an amorphous phase by laser light irradiation, and the medium changes the reflectance from high level to low level by CW irradiation of laser light. The linear velocity range is 8m / s or more and 30m / s or less, and the recordable linear velocity range is 1.2m
An optical recording medium having a speed of not less than / s and not more than 30 m / s. 2. The composition ratio x / (x + y) of Sb and Te is 0.50 in atomic ratio.
2. The optical recording medium according to claim 1, wherein the value is -0.90. 3. The method according to claim 1, wherein the content a of the additional element is 0.15 or less in atomic ratio with respect to (Sb + Te).
Or the optical recording medium according to item 2. 4. X is Ag, Au, Cu, Zn, B, Al, Ga, In,
The method according to any one of claims 1 to 3, wherein one element selected from Si, Ge, Sn, Pb, N, P, Bi, La, Ce, Gd, and Tb or a combination of a plurality of elements is used. The optical recording medium according to the above. 5. When a plurality of elements are employed as X,
The optical recording medium according to claim 1, wherein at least one is N. 6. The recording medium according to claim 1, wherein a linear velocity range at which the reflectance changes from a high level to a low level by CW irradiation of a laser beam is set to a linear velocity range. An optical recording medium set to a range of 1 to 1.5 times the maximum linear velocity.