JP2000343830A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium having good repeating characteristics, good preserving characteristics and high recoding sensitivity. SOLUTION: A recording material of a recording layer contains Sb and Te as main components. A phase change material in which one type or above selected from B, C, N, Ag, In, P and Ge is added as an adding element is used. In this layer, in a structure of the state of a crystal, its diffraction spectrum is exhibited at any of two positions of spacing d of lattice planes (unit: A) of 5.09±0.03, 3.48±0.03, 3.09±0.03, 2.17±0.03, 1.78±0.03, 1.55±0.03, and 1.38±0.03.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change optical recording medium applicable to the field of rewritable optical recording media.

[0002]

2. Description of the Related Art As one of optical recording media capable of recording, reproducing and erasing information by irradiating a laser beam, so-called phase-change optical recording utilizing a transition between a crystal and an amorphous phase or between a crystal and a crystal phase. The medium is well known.
It can be overwritten with a single beam,
The drive-side optical system is also characterized by being simpler, and has been applied as a computer-related or audio-visual recording medium. The recording materials include GeTe, GeT
eSe, GeTeS, GeSeS, GeSeSb, Ge
AsSe, InTe, SeTe, SeAs, Ge-Te
-(Sn, Au, Pd), GeTeSeSb, GeTe
Sb, Ag-In-Sb-Te and the like. Further, as disclosed in JP-A-57-208648,
There has also been proposed a recording layer in which a recording layer is embedded in a base material such as SiO ₂ to suppress irreversible changes in the recording material. Also,
Ag-In-Sb-Te has high sensitivity and a feature in which an amorphous portion has a clear contour, and has been developed as a recording layer for mark edge recording. (JP-A-2-37466,
JP-A-2-171325, JP-A-2-415581
No., JP-A-4-141485). Further, a (Sb-Ag-Te) (Ge-Te) system corresponding to high speed has been developed (Japanese Patent Laid-Open No. Hei 10-10438).

As an optical recording medium using these recording layers, there is a multi-layered structure having a reflective layer, a first protective layer and a second protective layer. An important issue is to balance the characteristics with other characteristics, such as a modulation factor and a predetermined reflectance.
Regarding this problem, the addition of nitrogen or the like to the recording layer suppresses the flow of the recording layer and contributes to the improvement of the repetitive recording characteristics.
These are disclosed in JP-A-4-11336, JP-A-4-10980, JP-A-4-16383, JP-A-4-10979, JP-A-4-52188, and JP-A-4-52189. Japanese Patent Application Laid-Open No. 1-303643 discloses a structure based on X-ray diffraction in the Sb-Te system.
Is disclosed.

[0004] However, in an optical recording system which is inexpensive and has a relatively low recording linear velocity or an optical recording medium used as an optical recording medium (CD-RW) which is reproduction-compatible with a CD, a recording layer is still required. Due to problems such as fluid flow, film peeling due to thermal shock at the time of laser irradiation, or deterioration of the metal used for the reflective layer, the number of repetitive recordings remains at a level of several thousand times, and frequent rewriting is performed by computer peripheral equipment etc. In some cases there was a problem. Further, in order to further reduce the price of the drive, it is required to improve the recording sensitivity. Furthermore, the conventional recording medium does not consider the easiness of initial crystallization very much, and has a problem that the characteristics such as jitters are deteriorated because repetition characteristics and recording sensitivity are good but initialization is difficult.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above circumstances, and a first object of the present invention is to provide an optical recording medium having good repetition characteristics. It is in. A second object of the present invention is to provide an optical recording medium having good repetition characteristics. It is a further object of the present invention to provide an optical recording medium having good storage characteristics, good repetition characteristics, and high recording sensitivity.

[0006]

According to the present invention, there is provided an optical recording medium having a recording layer on a substrate on which information can be recorded by a phase change between a crystal and an amorphous phase. The material is composed of a phase change material containing Sb and Te as main components, and at least one element as an additive element, and the structure of the recording layer in a crystalline state is determined by X-ray diffraction.
The diffraction spectrum has a lattice spacing d (unit Å) of 5.
09 ± 0.03, 3.48 ± 0.03, 3.09 ± 0.
03, 2.17 ± 0.03, 1.78 ± 0.03, 1.
An optical recording medium is provided which appears at any one of at least two positions of 55 ± 0.03 and 1.38 ± 0.03.

Preferred elements used as the additional elements in the recording material constituting the recording medium are B, C, N,
Among Ag, In, P, and Ge, C, N, B, and Ge are particularly preferable in terms of improving the storage characteristics of the recording medium, Ag is preferable in terms of preventing deterioration with respect to reproduction light, and In and P are high in linear velocity. It is preferable to improve the recording and erasing characteristics when performing recording / reproduction by the above method. These can also obtain a synergistic effect by adding each element in combination.

In the present invention, the recording layer is made of a conventional Sb.
Unlike a multi-component composition containing Ti and Te, the above-described element is added to a Sb-Te alloy near the eutectic composition of Sb and Te to form an alloy, and the alloy is formed by a method such as evaporation. Obtainable. The eutectic composition is S
b The composition of ₇₀ Te ₃₀ is referred to, and the vicinity is ± 5 of the composition.
% (Each represents at%). The recording layer is preferably formed at a substrate temperature of 40 ° C. to 80 ° C., preferably 50 ° C. to 60 ° C., and a film is formed at a sputtering rate of 3 ° to 5 ° per second.

The crystallization temperature of the recording material constituting the recording medium is preferably 160 ° C. or more and 210 ° C. or less, more preferably 180 ° C., more preferably 190 ° C., and most preferably 185 ° C. It is.

[0010] The activation energy of the recording material constituting the recording medium is preferably 2.5 eV or more, more preferably 2.65 eV, most preferably 2.80 eV, and more preferably 3 eV. .3e
In V, the most preferable upper limit is 3.0 eV.

The melting point of the recording material constituting the recording medium is preferably 551 ° C. or more and 556 ° C. or less, more preferably 553 ° C., and more preferably 5%.
54 ° C.

The optical gap of the recording material constituting the recording medium in the amorphous state is preferably from 0.1 eV to 0.6 eV, more preferably 0.4 eV.
The most preferred upper limit is 0.3 eV. The various physical properties described above can be determined by a known measurement method.

Further, since the optical gap of the amorphous phase of the recording material of the present invention is between 0.1 eV and 0.6 eV, the light absorption efficiency becomes good, and the recording medium having good recording sensitivity and erasing sensitivity is obtained. Is realized. The optical gap of the Sb-Te recording material has a very narrow gap of less than 0.1 eV when no other element is added. However, when an element having a high coordination number is added thereto, the optical gap is widened. , 0.1
Since the absorption efficiency is between eV and 0.6 eV, the absorption efficiency is not reduced, so that a recording medium having good recording sensitivity and erasing sensitivity is realized. Here, the cause of widening the optical gap by adding an element having a high coordination number is unknown, but it is conceivable that the lattice constant of the crystal structure became small due to the strong covalent bond.

The structure of the optical recording medium of the present invention is preferably such that a lower heat-resistant protective layer, a recording layer, an upper heat-resistant protective layer, a reflective heat dissipation layer, and an overcoat layer are provided on a substrate having a guide groove. As the material of the substrate, glass, ceramics, or resin is usually used, and a resin substrate is preferable in terms of moldability. Representative examples include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, polyethylene resin, polypropylene resin, silicone resin, fluorine-based resin, ABS resin, urethane resin, and the like. Resins are preferred. Further, the shape of the substrate may be a disk shape, a card shape or a sheet shape.

The upper and / or lower heat-resistant protective layer can be formed by various vapor phase growth methods, for example, a vacuum deposition method, a sputtering method, an electron beam method and the like. Further, the thickness of the lower heat-resistant protective layer is preferably 500 to 3000, preferably 800 to 2000, although it depends on its function, that is, the function as a heat-resistant layer and a multiple interference layer. Further, the upper heat-resistant protective layer has a thickness of 100 to 1000 °, preferably 150 to 1000 °.
It is good to be 350 degrees.

Various metals and alloys can be used for the reflective heat radiation layer, and in particular, Al-Ti, Al-Ni, Al-Mn, A
Al alloys such as l-Cr, Al-Zr, Al-Si and Ag
-An Ag alloy such as Pd is desirable. These layers are formed by a vacuum deposition method, a sputtering method, an electron beam method, or the like, and have a thickness of 200 to 3000 °, preferably 500
~ 2000Å is good.

It is desirable to have an overcoat layer 7. As the overcoat layer, an ultraviolet curable resin produced by spin coating is generally used.
μm is appropriate. When a printing layer is provided on the overcoat layer, the thickness is preferably 7 μm or more in order to prevent occurrence of an error during recording and reproduction.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically by way of examples. Example 1 On a polycarbonate substrate having a track pitch of 1.0 μm, a depth of 500 mm, a grooved thickness of 1.2 mm, and a diameter of 120 mm, a lower heat-resistant protective layer, a recording layer, an upper heat-resistant protective layer and a reflection heat radiation having the configuration shown in Table 1 The layers were sequentially laminated by a sputtering method to prepare a phase change recording medium. The substrate temperature is 5
All layers were formed at 5 ° C. and a sputter rate of 5 ° / sec. The thickness of each layer is 800 ° for the lower protective layer, 200 ° for the recording layer, 300 ° for the upper protective layer, and 100 for the reflective heat dissipation layer.
0 °.

At this time, the heat-resistant protective layer is made of (ZnS) ₈₀ (Si
O ₂ ) ₂₀ , the reflective heat radiation layer was made of an Al alloy, and the recording layer was made of Sb ₇₅ Te ₂₅ alloy according to the present invention as a target, and N ₂ was flowed at 1 SCCM during sputtering (Sb ₇₅ Te).
Was formed a recording layer of _{25) 95} N _5. Here, CD-R
Evaluate the characteristics as W, but of course DVD-RAM
It can also be used as Samples for measuring the structure, crystallization temperature, melting point, activation energy, and optical gap of the recording layer single film were also prepared. The lattice spacing was 3.10 and 2.18.

Example 2 The recording layer was made of Sb ₇₅ Te ₂₅ alloy as a target, and N ₂ was flowed at ₂ SCCM during sputtering (Sb ₇₅ Te ₂₅ ).
Except that was formed a recording layer of ₉₀ N ₁₀ created the recording medium in the same manner as in Example 1. The lattice spacing was the same as in Example 1.

Example 3 The recording layer was made of Sb ₇₅ Te ₂₅ alloy as a target, and N ₂ was flowed at 3 SCCM during sputtering (Sb ₇₅ Te ₂₅ ).
Except that was formed a recording layer of ₈₅ N ₁₅ created the recording medium in the same manner as in Example 1. The lattice spacing was the same as in Example 1.

Example 4 A recording medium was prepared in exactly the same manner as in Example 1 except that a target obtained by adding 5 at% of Ge to an Sb ₇₅ Te ₂₅ alloy was used as a recording layer. The lattice spacing is 3.10,
2.18, 1.55 and 1.38.

Example 5 A recording medium was prepared in exactly the same manner as in Example 1 except that 5 at% of B was added to an Sb ₇₅ Te ₂₅ alloy as a recording layer. The lattice spacing is 5.10, 3.10, 2.16.
Met.

Example 6 A recording medium was prepared in exactly the same manner as in Example 1 except that 5 at% of P was added to an Sb ₇₅ Te ₂₅ alloy as a recording layer. The lattice spacing is 3.11, 2.18, 1.78.
Met.

Example 7 A recording medium was prepared in exactly the same manner as in Example 1 except that 5 at% of Ag was added to a Sb ₇₅ Te ₂₅ alloy as a recording layer. Note that the lattice spacing is 3.08, 2.17, 1.55.
Met.

Comparative Example A recording medium was prepared in exactly the same manner as in Example 1 except that the Sb ₇₅ Te ₂₅ alloy was used as the recording layer.

Evaluation The crystallization temperature obtained by changing the X-ray diffraction of the recording layer obtained as described above, the crystallization temperature by a differential scanning calorimeter, and the heating rate was determined, and the Kissinger plot method was performed. The optical gap was determined from the activation energy, melting point, and the spectral absorption of the amorphous film. 1 and 2,
3, 4, 5, and 6 show diffraction spectra by X-ray diffraction, and Table 1 shows crystallization temperature, activation energy, melting point, and optical gap. The desk characteristics were evaluated by initializing the recording medium, repeatedly performing overwriting repeatedly with an EFM random pattern at a linear velocity of 1.4 m / s, and evaluating the recording power dependence of the jitter of the 3T signal at that time. Note that the linear velocity during reproduction is 2.8 m / s. The results are shown in Tables 2 to 9. The storage was evaluated by archival and shelf after 100 hours in an atmosphere of 80 ° C. and 70%. ○ is good.
Δ indicates that the jitter is slightly higher. × indicates failure.

[0028]

[Table 1] The crystallization temperature in Table 1 is a value at a temperature rise of 10 ° C./min.

From Table 1, it can be seen that, by adding the additives of Examples 1 to 7 to Comparative Example 1, the crystallization temperature became 50%.
Temperature rises from 80 ° C to 80 ° C and activation energy is 1 eV
From 2 eV. Also, the optical gap is double to 4
About twice as wide. In addition, in the X-ray diffraction spectrum, the diffraction peak partially disappeared with respect to the comparative example due to the additive, but the basic structure was the same, and the growth of the crystal plane was different depending on the additive. It is considered to be for. Regarding the desk characteristics, the comparative example has good recording sensitivity and repetition characteristics, but has extremely poor storage characteristics. This is considered to be because the crystallization temperature is low in the comparative example, so that the crystallization proceeds and the recording mark disappears. On the other hand, the crystallization temperature is increased by the additive to improve the storage characteristics. In this case, in order to maintain the recording sensitivity and the repetition characteristics, the additive changes the structure and does not change the melting point. Must be done. For example, when the structure changes and the melting point increases, the sensitivity decreases. However, in the case of the recording material of the present invention, a large change in the melting point due to the additive was not recognized, and it was found that when the melting point was within the range of the present invention, good recording sensitivity and good repetition characteristics were obtained. Further, the optical gap is about two to four times wider than the additive. However, since the original gap is small, it does not impair the light absorption efficiency and does not lower the optical recording sensitivity. That is, if the optical gap is within this range, high recording sensitivity is obtained. In order to have these favorable characteristics, the recording material must have a structure in which a diffraction spectrum in X-ray diffraction appears at the position of the lattice spacing d of the present invention.

[0030]

[Table 2] Example 1

[Table 3] Example 2

[Table 4] Example 3

[Table 5] Example 4

[Table 6] Example 5

[Table 7] Example 6

[Table 8] Example 7

[Table 9] Comparative Example 1

[0031]

According to the optical recording medium of the present invention, the recording material is mainly composed of Sb and Te, and B, C, N, Ag, I, and B have a large number of bonding coordinations to increase the crystallization temperature.
The structure obtained by adding n, P, and Ge and crystallizing the same is X-ray diffraction, and the diffraction spectrum shows the lattice spacing d.
5.09 ± 0.03, 3.48 ± 0.0 (unit Å)
3, 3.09 ± 0.03, 2.17 ± 0.03, 1.7
8 ± 0.03, 1.55 ± 0.03, 1.38 ± 0.0
By appearing in at least one of two or more positions of 3, the recording sensitivity is high and the repetition characteristics are excellent.

The crystallization temperature of the recording material is in the range of 160 ° C. to 210 ° C., and the activation energy is 2.5 eV
By being in the above range, the storage characteristics are excellent.

The melting point of the recording material is 551 ° C. to 5 ° C.
When the temperature is within the range of 56 ° C., the recording sensitivity becomes excellent.

Further, since the optical gap of the recording material is between 0.1 eV and 0.6 eV, the recording sensitivity becomes excellent.

[Brief description of the drawings]

FIG. 1 shows an X-ray diffraction spectrum of a comparative example.

FIG. 2 shows an X-ray diffraction spectrum of Example 1.

FIG. 3 shows an X-ray diffraction spectrum of Example 4.

FIG. 4 shows an X-ray diffraction spectrum of Example 5.

FIG. 5 shows an X-ray diffraction spectrum of Example 6.

FIG. 6 shows an X-ray diffraction spectrum of Example 7.

Continued on the front page F term (reference) 2H111 EA04 EA12 EA23 EA33 EA41 FB05 FB09 FB12 FB17 FB20 FB21 FB28 FB29 5D029 JA01 JC11 JC17 JC18 JC18

Claims (14)

[Claims] 1. An optical recording medium having a recording layer capable of recording information by a phase change between a crystal and an amorphous phase provided on a substrate, wherein a recording material constituting the recording layer contains Sb and Te as main components, The recording layer is made of a phase-change material to which at least one element is added as an additional element, and the structure of the recording layer in a crystalline state is X-ray diffraction, and the diffraction spectrum is 5.09 ± 5 of lattice spacing d (unit Å). 0.03, 3.48 ± 0.
03, 3.09 ± 0.03, 2.17 ± 0.03, 1.
78 ± 0.03, 1.55 ± 0.03, 1.38 ± 0.
03. An optical recording medium, wherein the optical recording medium appears in at least one of two or more positions. 2. The additive element is B, C, N, Ag, In,
2. The optical recording medium according to claim 1, comprising at least one selected from P and Ge. 3. The optical recording medium according to claim 1, wherein the additional element is Ge. 4. The optical recording medium according to claim 1, wherein the additional element is B. 5. The optical recording medium according to claim 1, wherein the crystallization temperature of the phase change material is 160 ° C. or more and 210 ° C. or less. 6. The optical recording medium according to claim 1, wherein the crystallization temperature of the phase change material is 180 ° C. or more and 190 ° C. or less. 7. The optical recording medium according to claim 1, wherein the crystallization temperature of the phase change material is 180 ° C. or more and 185 ° C. or less. 8. The optical recording medium according to claim 1, wherein the activation energy for crystallization of the phase change material is 2.5 eV or more. 9. The optical recording medium according to claim 1, wherein the activation energy for crystallization of the phase change material is 2.65 eV or more and 3.3 eV or less. 10. The optical recording medium according to claim 1, wherein the activation energy of crystallization of the phase change material is 2.80 eV or more and 3.0 eV or less. 11. The phase change material having a melting point of 551 ° C. or more and 55 ° C.
2. The optical recording medium according to claim 1, wherein the temperature is 6 [deg.] C. or lower. 12. The melting point of the phase change material is at least 553 ° C.
2. The optical recording medium according to claim 1, wherein the temperature is 6 [deg.] C. or lower. 13. The phase change material having a melting point of at least 553 ° C.
2. The optical recording medium according to claim 1, wherein the temperature is 4 [deg.] C. or lower. 14. The optical gap of the amorphous phase is 0.1 eV.
An optical recording medium, which is between 0.6 and 0.6 eV.