JPH0589519A - Information recording medium and information recording method using this medium - Google Patents

Abstract

PURPOSE:To provide the reloadable information recording medium and information recording method which are high in recording sensitivity and erasing ratio and is not deteriorated in C/N. CONSTITUTION:This information recording medium has a recording layer 3, heat resistant protective layers 2 and 4 and an optical reflection layer 5 on a substrate 1. The material of particularly the heat resistant protective layer 4 is any among CuAlS2, CuAlSe2, CuGaS2, CuGaSe2, and CuInS2. The material of the recording layer is expressed by AgalphaInbetaTegammaSbdelta (where 5<=alpha<=17, 6<=beta<=18, 13<=gamma<=36, 33<=delta<=77, alpha+beta+gamma+delta=100).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, particularly a phase change type information recording medium, which causes a phase change in a recording layer material by irradiating a light beam to record and reproduce information. In addition, the present invention relates to a rewritable information recording medium, and is applied to optical memory-related equipment, particularly a rewritable compact disc (CD).

[0002]

2. Description of the Related Art As one of optical memory media capable of recording, reproducing and erasing information by irradiation of electromagnetic waves, especially laser beams, so-called phase change utilizing a transition between a crystal-amorphous phase or a crystal-crystal phase. A type optical information recording medium is well known. In particular, magneto-optical memory allows overwriting with a single beam, which is difficult, and the optical system on the drive side is simpler. Typical recording materials thereof are Ge-Te, Ge-Te-Sb-S and Ge-Te- as disclosed in USP 3,530,441.
S, Ge-Se-S, Ge-Se-Sb, Ge-As-
Examples include so-called chalcogen-based alloy materials such as Se, In-Te, Se-Te, and Se-As. Also stability,
Au was added to the Ge-Te system for the purpose of improving high-speed crystallization.
(Japanese Patent Laid-Open No. 61-219692), Sn and Au.
(JP-A-61-270190), Pd (JP-A-6-270190)
2-19490) and the like for the purpose of proposing a material added with etc. and improving the repetitive performance of recording / erasing.
A material with a specified composition ratio of Se-Sb (Japanese Patent Laid-Open No. 62-73)
No. 438) has been proposed. However, none of them can satisfy all of the characteristics required for the phase change type rewritable optical memory medium.

Further, Japanese Patent Laid-Open No. 63-251290 discloses an optical information recording medium having a recording layer formed of a multi-component compound single phase whose crystal state is substantially ternary or more (hereinafter abbreviated as "optical recording medium"). May be done) is proposed. Here, “substantially ternary or higher multi-component compound single phase” means a compound having a stoichiometric composition of ternary or higher (for example, In ₃ SbT).
e ₂ ) is contained in the recording layer in an amount of 90 atomic% or more. The use of such a recording layer enables high-speed recording and high-speed erasing. However, with this type, the laser power required for recording and erasing is not yet sufficient, and the erasing ratio is low (the unerased portion is large).
It has drawbacks such as Furthermore, JP-A-1-277338
The JP _{(Sb a Te 1-a)} 1-Y M Y ( here 0.4
≦ a <0.7, Y ≦ 0.2, and M is Ag, Al, A
s, Au, Bi, Cu, Ga, Ge, In, Pb, P
It is at least one selected from the group consisting of t, Se, Si, Sn and Zn. An optical recording medium having a recording layer made of an alloy having a composition represented by (4) has been proposed. The basis of this system is Sb ₂ Te ₃ , and excess Sb improves high-speed erasing and repetitive characteristics, and addition of M promotes high-speed erasing. In addition, the erasing rate by DC light is also high. However, in this document,
The erasing rate at the time of writing is not shown (results of erasure were found in the examination results of the present inventors), and the recording sensitivity is insufficient.

Similarly, in JP-A-60-177446, (In _1-X Sb _X ) _1-Y M _Y (0.55 ≦
X ≦ 0.80, 0 ≦ Y ≦ 0.20, M is Au, A
g, Cu, Pd, Pt, Al, Si, Ge, Ga, S
n, Te, Se, Bi. ) Alloy, and Ge in the recording layer in JP-A-63-228433.
Although using a Te-Sb ₂ Te ₃ -Sb (excessive) comprising alloy, both the sensitivity, it does not satisfy the characteristics such as erase ratio. As seen so far, in the optical recording medium, in particular, the recording sensitivity and the erasing sensitivity are improved, the reduction of the erasing ratio due to the unerased portion at the time of overwriting is prevented, and the life of the recorded portion and the unrecorded portion is extended. It is the most important issue to be solved. As one of means for solving these problems, there has been proposed a technique in which protective layers which are chemically stable and have good heat resistance are provided above and below the recording layer (JP-A-61-2450, 6).
3-259855). Functions required of the heat-resistant protective layer include transparency to laser light, high melting point at operating temperature, high mechanical strength, and high chemical stability. In the case of a recording layer, particularly a recording layer using a chalcogen compound, a chalcogen element is active, and therefore, a chemically inactive protective material is extremely important.

In this respect, the oxide-based dielectric materials and the like generally used cannot be said to sufficiently meet the demand. Further, the heat-resistant protective layer also has a function as a heat dissipation layer (heat transfer layer). Generally, if the thermal conductivity of the heat dissipation layer is too small, the quenching effect required for amorphization cannot be obtained, and if it is too large, the heat cannot be effectively utilized, that is, the slow cooling conditions required for crystallization are However, the recording and erasing sensitivity was lowered. Thus, the heat dissipation layer needs to be controlled to have a thermal conductivity adapted to the recording film. However, it has been difficult to control the thermal conductivity over a wide range with the above material group. For example, when the linear velocity is 3 m / s or less, particularly when the linear velocity is a low linear velocity of about 1.2 to 1.4 m / s, which is a standard for compact discs, the cooling rate of heat generated during recording (when absorbing laser light) is Insufficiency is likely to occur, and good recording marks cannot be obtained.

[0006]

[Problems to be Solved by the Invention]

(1) The present invention solves all of the above problems in the prior art, has a high recording sensitivity and an erasing ratio, and is capable of long-life recording without C / N deterioration due to repeated recording / erasing. An object of the present invention is to provide a rewritable information recording medium that does not require a complicated system and (2) a rewritable compact disc.

[0007]

The constitution of the present invention for solving the above-mentioned problems is an information recording medium as described in the claims and an information recording method using the same. Explaining the structure of this information recording medium, it is characterized in that a material having a relatively high thermal conductivity is used as the material of the upper heat-resistant protective layer. The chalcopyrite type compound containing Cu not only satisfies the basic physical properties (high melting point, translucency) required for the heat-resistant protective layer of the optical disk, but also has a higher thermal conductivity than that of general high melting point dielectric materials and It is suitable as a material for the upper heat-resistant protective layer because it has good compatibility with the recording layer material used for the variable disc, particularly the recording layer of the present invention.

Although the lower heat-resistant protective layer is not always necessary, the lower heat-resistant protective layer is necessary when the substrate is made of a material having low heat resistance such as polycarbonate resin. A material containing a quaternary phase-change recording material containing Ag, In, Te, Sb as a main component has extremely good recording (amorphization) sensitivity, erasing (crystallization) sensitivity / speed, and erasing ratio. Suitable as a material for the recording layer.

By combining the above recording layer and the upper heat-resistant protective layer laminated thereon, even under a low linear velocity of 1.2 to 1.4 m / sec, the quenching condition and erasing (crystal) at the time of recording (amorphization) are carried out. It is possible to satisfy the slow cooling conditions at the same time, and obtain good recording / reproducing characteristics. The heat-resistant protective layer preferably has a large optical energy gap (Eg. Opt), and is preferably 1.5 eV or more.
Particularly, it is preferable that this is large in order to improve the disc reflectance. The melting point of the heat-resistant protective layer is 800 ° C, preferably 1000 ° C or higher. Table A below shows the optical energy gaps and melting points of the materials for the heat-resistant protective layer of the present invention.

[0010]

[Table 1]

The recording layer of the present invention can be formed by various vapor phase growth methods such as vacuum vapor deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam vapor deposition method. Besides the vapor phase growth method, a wet process such as a sol-gel method can also be applied. The thickness of the recording layer is 200 to 10000Å, preferably 400 to 300
It is good to set it to 0Å. When the thickness is less than 200Å, the light absorption ability is remarkably lowered and the recording layer cannot serve as a recording layer. If it is thicker than 10000Å, uniform phase change at high speed is difficult to occur.

The substrate material is usually glass, ceramics,
Alternatively, it is a resin, and a resin substrate is preferable in terms of moldability, cost, and the like. Typical examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicon resin, fluorine resin, ABS resin, urethane resin and the like. , In terms of workability and optical properties, polycarbonate resin,
Acrylic resins are preferred.

As a material for the lower heat-resistant protective layer, Si is used.
O, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ ,
In ₂ O ₃ , MgO, ZrO _{2 and} other metal oxides, Si
Nitride such as ₃ N ₄ , AlN, TiN, BN, ZrN, Z
Sulfides such as nS, In ₂ S ₃ , TaS ₄ , SiC, Ta
Examples thereof include carbides such as C, B ₄ C, WC, TiC, and ZrC, diamond-like carbon, and mixtures thereof. These materials may be used alone as the protective layer, but may also be a mixture with each other. In addition, impurities may be included if necessary.

However, the melting point of the heat-resistant protective layer must be higher than that of the recording layer. Such a heat-resistant protective layer may be formed by various vapor deposition methods such as vacuum deposition, sputtering,
It can be formed by a plasma CVD method, a photo CVD method, an ion plating method, an electron beam evaporation method, or the like. The thickness of the heat resistant protective layer is 200 to 5000Å, preferably 500 to 3000Å
It is good to say When the thickness is less than 200Å, the function as a heat resistant protective layer is not achieved, and when the thickness is more than 5000Å, the sensitivity is lowered and the interfacial peeling is likely to occur. Further, the protective layer may be multi-layered if necessary.

For the reflective layer, a metal material such as Al or Au, or an alloy thereof can be used. High thermal conductivity (preferably 2.0 W / cm · d)
(eg or higher) material such as Ag, Au, Cu, Al is preferable, and Ag (4.2 W / cm · deg), Au (3.0 W)
/ Cm · deg) or alloys thereof are particularly preferred. In this case, the reflective layer also functions as a heat dissipation layer. The thickness of the reflective layer is 200 to 3000Å, preferably 50
0 ~ 2000Å is good. Such a reflective layer can be formed by various vapor deposition methods, for example, a vacuum vapor deposition method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam vapor deposition method and the like.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples. Example I-1 Pitch of 1.6 μm, groove of 700 Å depth, thickness of 1.2
mm, the diameter is 1200 mmφ, and the lower heat-resistant protective layer, the recording layer, and the structure shown in Table I-1 are formed on the polycarbonate substrate.
The upper heat-resistant protective layer and the reflective layer were sequentially laminated.

[0017]

[Table 2]

The evaluation of the optical disk was carried out by using a semiconductor laser beam of 780 nm with N.V. A. The irradiation was performed from the substrate side through the objective lens of 0.5, and the spot diameter was narrowed down to about 1 μmφ on the medium surface. The recording film immediately after film formation is amorphous. In the measurement, first, the entire surface of the disk was sufficiently crystallized by DC light of 3 mW on the medium surface to make it into an initial (unrecorded) state. The rotational linear velocity of the disk at this time is 1.
It was kept constant at 3 m / s. Next, write power 3 to 10 mW
The recording performance was evaluated with a pulse width of 690 ns while varying by 1 mW each. The reproduction light was constant at 0.6 mW. As a result, a signal of C / N of 45 dB or more was obtained at 4 to 10 mW. When the recording mark was further erased with DC light of 3 mW, the recording mark was almost completely erased, and no unerased residue was observed.

Example I-2 A disk was prepared in the same manner as in Example I-1 except that the composition of the recording layer material was changed to Ag ₈ In ₈ Te ₁₆ Sb ₆₈ and the reflective layer material was changed to Ag. An evaluation was made. Comparative Example I-1 The same layer constitution as in Example I-1 was used except that the composition of the recording layer material was Ag ₅ In ₅ Te ₁₀ Sb _80, and the same evaluation was performed. Comparative Example I-2 A layer similar to Example I-1 except that the recording layer was Ag ₁₀ In ₁₀ Te ₂₀ Sb ₆₀ and the upper protective layer was the same [ZnS + SiO ₂ (20%)] composite dielectric layer as the lower protective layer. A disk having the constitution was prepared and the same evaluation was performed. Comparative Example I-3 The same evaluations as in Example I-1 were made, except that the recording layer was Ag ₂₀ In ₂₀ Te ₃₀ Sb ₃₀ . The results are summarized in Table I-2.

[0020]

[Table 3]

Further, with respect to the samples of Examples I-1 and I-2, one-beam overwriting was attempted under the following conditions.
Very good results have been obtained. - linear velocity ... 1.3 m / S-recording power (Pw) ... 7 mW, erase power (PE) ... in the right column of 3 mW, the recording frequency _{... f 1 = 0.65MHz f 2 =} 0.85MHz Table I-2 , C / N and erase ratio when a track previously recorded at f ₁ is overwritten at f ₂ . No deterioration of characteristics was observed in both Examples I-1 and 2 even when overwriting was repeated 1000 times or more.

Example II-1 The material for the upper heat-resistant protective layer in Example I-1 was CuAl.
An optical disk was produced under the same conditions as in Example I-1 except that Se ₂ was used, and the test was performed under the same conditions.
As with 1, good results were obtained. Example II-2 The composition of the recording layer material of Example II-1 was changed to Ag ₈ In ₈ T.
e ₁₆ Sb ₆₈ , Example I except that the reflective layer material was changed to Ag
A disk was prepared and tested in the same manner as in I-1. The results of the above examples are shown in Table II-1 below.

[0023]

[Table 4]

Further, in both Examples II-1 and II, no deterioration in characteristics was observed even after overwriting was repeated 1000 times or more. Example III-1 The material of the upper heat-resistant protective layer in Example I-1 was CuGa.
Results except for changing the S ₂ will produce an optical disc under the same conditions as in Example I-1, was tested under the same conditions, Example I-1
As with, good results were obtained. Example III-2 The composition of the recording layer material of Example III-1 was changed to Ag ₈ In ₈
A disc was prepared and tested in the same manner as in Example III-1 except that Te ₁₆ Sb ₆₈ and the reflective layer material were changed to Ag. The results of the above examples are shown in Table III-1 below.

[0025]

[Table 5]

Further, in both Examples III-1 and II, 1000
No deterioration in characteristics was observed even when overwriting was repeated more than once. Example IV-1 The material of the upper heat-resistant protective layer in Example I-1 was CuGa.
An optical disk was produced under the same conditions as in Example I-1 except that Se ₂ was used, and the test was performed under the same conditions.
As with 1, good results were obtained. Example IV-2 The composition of the recording layer material of Example IV-1 was changed to Ag ₈ In ₈ T.
e ₁₆ Sb ₆₈ , Example I except that the reflective layer material was changed to Ag
A disk was prepared and tested in the same manner as V-1. The results of the above examples are shown in Table IV-1 below.

[0027]

[Table 6]

Further, in Examples IV-1 and 2 as well, no deterioration of characteristics was observed even after overwriting was repeated 1000 times or more. Example V-1 The material of the upper heat-resistant protective layer in Example I-1 was CuIn.
Results except for changing the S ₂ will produce an optical disc under the same conditions as in Example I-1, was tested under the same conditions, Example I-1
As with, good results were obtained. Example V-2 The composition of the recording layer material of Example V-1 was changed to Ag ₈ In ₈ Te.
₁₆ Sb ₆₈ , Example V-except that the reflective layer material was changed to Ag
A disk was prepared in exactly the same manner as 1 and the same test was performed. The results of the above examples are shown in Table V-1 below.

[0029]

[Table 7] Table V-1 Furthermore, in both Examples V-1 and 2, no deterioration in characteristics was observed even after overwriting was repeated 1000 times or more.

[0030]

The effects of the present invention described above are summarized as follows. (1) A phase change type information recording medium having excellent recording / erasing performance even at a low linear velocity by combining a recording layer material having a good crystal-amorphous transition characteristic and an upper heat-resistant protective layer having a good thermal conductivity. Was obtained. (2) A rewritable compact disc can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an information recording medium of the present invention.

[Explanation of symbols]

 1 substrate 2 lower heat-resistant protective layer 3 recording layer 4 upper heat-resistant protective layer 5 optical reflection layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroko Iwasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (4)

[Claims] 1. A rewritable information recording medium for recording, erasing and reproducing information by irradiating a laser beam, wherein a recording layer, an upper heat-resistant protective layer and an optical reflection layer are sequentially laminated on a substrate. , The material of this upper heat-resistant protective layer is Cu
An information recording medium, which is a chalcopyrite type compound containing, and whose recording layer contains a quaternary phase-change recording material containing Ag, In, Te, and Sb as a main component. 2. The material of the upper heat-resistant protective layer is CuAl.
S ₂ , CuAlSe ₂ , CuGaS ₂ , CuGaSe ₂ , C
2. The information recording medium according to claim 1, wherein the recording layer is any one of uInS ₂ and the recording layer contains a phase change type recording material represented by the following general formula as a main component. General formula Ag _α In _β Te _γ Sb _δ However, 5 ≦ α ≦ 17 6 ≦ β ≦ 18 13 ≦ γ ≦ 36 33 ≦ δ ≦ 77 α + β + γ + δ = 100 3. The information recording medium according to claim 1, further comprising a lower heat-resistant protective layer between the substrate and the recording layer. 4. The recording layer is irradiated with laser light from the substrate side while rotating the information recording medium according to claim 1 at a constant linear velocity of 1.2 to 1.4 m / sec. An information recording method characterized by recording a signal.