JP2908826B2 - Information recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an information recording medium, in particular, a phase change type information recording medium, which irradiates a light beam to cause a phase change in a recording layer material, and The present invention relates to an information recording medium capable of recording, reproducing, and rewriting information, and is applied to an optical memory related device.

[Prior art] Recording and recording of information by irradiation of electromagnetic waves, especially laser beams
As one of the rewritable and erasable optical memory media, utilizing a transition between a crystal and an amorphous phase or between a crystal and a crystal phase,
So-called phase change recording media are well known. In particular, overwriting with a single beam, which is difficult with a magneto-optical memory, is possible, and the drive-side optical system is simpler. Typical examples of the material include Ge-Te, Ge-Te-Sb-S, Ge-Te-S, Ge-Se-S, and Ge as disclosed in US Pat. No. 3,530,441.
So-called chalcogen-based alloy materials such as -Se-Sb, Ge-As-Se, In-Te, Se-Te, and Se-As. For the purpose of improving stability, high-speed crystallization, etc., Au (Japanese Patent Application Laid-Open No. 61-219692)
And the composition ratio of Ge-Te-Se-Sb with the aim of proposing materials to which Au (Japanese Patent Application Laid-Open No. 61-270190), Pd (Japanese Patent Application Laid-open No. 62-19490), etc. were added, and improving the recording / erasing repeatability There is also a proposal of a material (JP-A-62-73438) specifying the above. However,
None of them can satisfy all of the properties required for a phase-change rewritable optical memory medium.

Japanese Patent Application Laid-Open No. 63-251290 proposes an optical recording medium having a recording layer composed of a single phase of a multicomponent compound having a crystalline state of substantially three or more. Here, a ternary or higher ternary compound single phase is defined as a compound having a ternary or higher stoichiometric composition (eg, In ₃ SbTe ₂ ) in a recording layer of 90 atomic% or more.

By using such a recording layer, high-speed recording and high-speed erasing can be performed.

However, the laser power required for recording and erasing is not yet sufficient, and the erasing ratio is low (the erasure remains large).
And the like.

Further, Japanese Patent Application Laid-Open No. 1-277338 discloses that (Sb _X Te _1-X ) _1- YM
_Y (where 0.4 ≦ a <0.7, y ≦ 0.2, M is Ag, Al, As, A
optical recording medium having a recording layer composed of an alloy having a composition represented by at least one selected from the group consisting of u, Bi, Cu, Ga, Ge, In, Pb, Pt, Se, Si, Sn and Zn) Has been proposed.

The basis of this system is Sb ₂ Te ₃ , and when Sb is excessive, high-speed erasing and repetition characteristics are improved, and addition of M promotes high-speed erasing. It also states that the erasing rate by DC light is large.

However, the erasing rate at the time of overwriting is not shown (results of study by the present inventors have left unerased data), and the recording sensitivity is also insufficient.

Similarly, in JP-A-60-177446, (In _1-X Sb _X ) _1-Y
An alloy of M _Y (0.55 ≦ X ≦ 0.80, 0 ≦ Y ≦ 0.20)
Japanese Patent Application Laid-Open No. 63-228433 uses GeTe-Sb ₂ Te ₃ -Sb (excess) alloy for the recording layer, but does not satisfy characteristics such as sensitivity and erasing ratio.

In particular, improvement of recording sensitivity and erasing sensitivity, prevention of a decrease in erasing ratio due to unerased portion at the time of overwriting, and extension of life of a recorded portion and an unrecorded portion are the most important issues to be solved.

In particular, as for the laser writing power on the medium surface under the condition that the laser irradiation time is 100 nsec or less, all of the reported examples up to now require a power of about 15 mW or more, which is a major barrier to improving the transfer speed. ing. Also, due to the heat generated when recording / erasing is repeated,
Since the recording layer, the heat-resistant protective layer, and the like are damaged and the characteristics are deteriorated, it is a great obstacle to the improvement of the repetition performance.

[Problems to be Solved by the Invention] An object of the present invention is to provide an information recording medium in which the following points are improved as compared with the above-mentioned conventional technology.

(1) Improvement of laser writing (recording) sensitivity, (2) Improvement of erasing sensitivity, (3) Improvement of repetition performance of recording-erasing, (4) Improvement of erasing ratio [Means for solving the problem] To solve the problem, by using a material represented by the following general formula as a main component as a recording layer material,
It has been found that very large improvements are possible.

That is, the constitution of the present invention is as follows: (1) The main component of the recording layer provided on the substrate is represented by the following general formula, and the presence state in the recording layer is a mixed phase of XYZ _two phase and M phase. Characteristic information recording medium.

Formula _{(XYZ 2) 1-a M} a XYZ 2 is Ib-IIIb-VIb of the periodic table ₂ or IIb-IVb-Vb ₂
In chalcopyrite-type compound represented, M is Sb and / or Bi when the XYZ ₂ is Ib-IIIb-VIb _2, when XYZ ₂ is _{IIb-IVb-Vb 2 S,} Se, from the Te One or more elements selected.

0.30 ≦ a ≦ 0.92.

(2) The information recording medium according to the above (1), wherein XYZ ₂ is AgInTe ₂ and M is Se or Bi.

If a is less than 0.3 or more than 0.92, there is no effect on improving the sensitivity, the erasing ratio, and the contrast.

Further, the recording layer may contain trace amounts (1% or less) of other impurities and the like.

Specific examples of XYZ ₂ include: Ib-IIIb-VIb ₂ ; AgInTe ₂ , AgInSe ₂ , AgGaSe ₂ , AgInS ₂ , Cu
InTe ₂ , CuInSe ₂ IIb-IVb-Vb ₂ ; ZnSnSb ₂ , ZnSnAs ₂ , ZnSnP ₂ , ZnGeAs ₂ , CdS
nP ₂ , CdSnAs _{2 and the} like.

XYZ ₂ preferably has a stoichiometric composition, but each may have a slight composition deviation.

Specifically, when irradiating a laser beam to the recording layer of the X _o Y _p Z when the _{q 0.2 ≦ o ≦ 0.3 0.2 ≦} p ≦ 0.3 0.4 ≦ q ≦ 0.6 o + p + q = 1.0 [ Operation] The present invention, by irradiation conditions It is considered that the following phase transition occurs.

For simplicity, take AgInTe ₂ as XYZ ₂ and
Sb will be described as an example.

(1) Crystal phase transition between AgInTe ₂ Chalcopyrite-type structure and Zincblende-type structure (M facilitates and stabilizes the transition) (2) Chalcopyrite-type structure and / or Zincb of AgInTe ₂
Lende-type crystal-to-coarse crystal transition (M facilitates and stabilizes the transition) (3) Crystal-crystal of M in amorphous and / or Chalcopyrite-type and / or Zincblende-type structure of AgInTe ₂ Intercrystalline and / or crystalline-amorphous and / or microcrystalline-coarse crystalline transitions.

(4) Complex transition of (1), (2) and (3).

The information currently available alone cannot clearly identify the mechanism of the phase transition, but in any case AgInTe ₂ and S
The following points were found to be particularly excellent as compared with the case where b exists alone.

(1) The light absorptivity is increased, and the recording / erasing sensitivity is improved.

(2) The optical contrast before and after the transition increases and C /
N improves.

(3) The erasing ratio during overwriting is dramatically improved.

In particular, as for the erasing characteristics, surprisingly, almost complete erasing was possible not only in simple erasing with DC light but also in one-beam overwrite mode.

This is a performance not found at all in any material known to date.

The information recording medium of the present invention may be provided with auxiliary layers such as a heat-resistant protective layer, a surface protective layer, a reflective layer, a heat dissipation layer, and an adhesive layer, if necessary. The substrate used in the present invention is usually glass, ceramic or resin, and a resin substrate is suitable in terms of moldability, cost, and the like. Typical examples of resins include polycarbonate resin, acrylic resin, epoxy resin,
Polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, etc. Resins are preferred. The shape of the substrate may be a disk shape, a card shape or a sheet shape.

Materials for the heat-resistant protective layer include SiO, SiO ₂ , ZnO, and Sn.
Metal oxides such as O ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂ , nitrides such as Si ₃ N ₄ , AlN, TiN, BN, ZrN, ZnS, In ₂
S _3, TaS sulfides such as _{4, SiC, TaC, B 4} C, WC, TiC, ZrC
And diamond-like carbon or a mixture thereof. Further, it may contain impurities as needed. Such a heat-resistant protective layer can be formed by various vapor deposition methods,
For example, vacuum evaporation, sputtering, plasma CVD, optical C
It can be formed by a VD method, an ion plating method, an electron beam evaporation method, or the like.

The thickness of the heat-resistant protective layer is 200 to 5000 mm, preferably 5
It is good to be 00-3000Å. When the thickness is less than 200 mm, the layer does not function as a heat-resistant protective layer. On the other hand, when the thickness is more than 5000 mm, the sensitivity is lowered and the interface is apt to be peeled off. Further, if necessary, the protective layer can be multi-layered.

The phase-change material is not limited to a single layer, but may be a multilayer film or an ultra-fine particle in which the phase-change material according to claim 1 is dispersed in a heat-resistant matrix.

As a method of producing the recording film as the latter, a wet process such as a sol-gel method can be applied in addition to the vapor phase film formation.

Among the vapor deposition methods, a high frequency (rf) sputtering method is a preferable method in terms of film characteristics, ease of film formation, and the like.

Typical recording layer preparation conditions for rf sputtering include: target: XYZ ₂ + M (for example, AgInTe ₂ + Sb); sputtering (reaction) pressure: 0.5 to 20 Pa; rf power: 20 W to 1 kW; sputtering gas: Ar + ( (O ₂ : at the time of controlling the amount of oxygen in the film) Sputtering time: 10 seconds to 20 minutes, but the production method and conditions are not limited at all.

The thickness of the recording layer is 200 to 10,000Å, preferably 500 to
3000Å, optimally 700-2000Å.

Various types of electromagnetic waves such as laser light, electron beam, X-ray, ultraviolet ray, visible light, infrared ray, and microwave can be used for recording, reproduction, and erasing, but when mounted on a drive, a small and compact semiconductor is used. The laser beam is optimal.

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples. However, these examples do not limit the present invention at all.

Example 1 A groove having a pitch of 1.6 μm and a depth of 700 mm, a thickness of 1.2 mm, and a diameter of 86 m
A heat-resistant protective layer, a recording layer, a heat-resistant protective layer, and a reflective layer were sequentially laminated on an mφ polycarbonate substrate by an rf sputtering method to produce an optical disc for evaluation.

 The material and film thickness used for each layer are shown in Table 1 below.

The evaluation of the optical disk was conducted using a 830 nm semiconductor laser
This was performed by narrowing down to a spot diameter of 1 μmφ on the medium surface through the above lens and irradiating from the substrate side.

Although the recording film after the film formation was amorphous, at the time of measurement, the entire surface of the disk was first sufficiently crystallized with 4 to 10 mW DC light on the medium surface, and was brought into an initial (unrecorded) state.

 The linear velocity of the disk was 7 m / s.

The writing conditions for recording were such that the linear velocity was 7 m / s and the frequency was constant at 3.7 MHz, and the laser power (P _W ) was varied from 7-14 mW.

The reading power (P _R ) was 1.0 mW. Table 1 shows the laser power (P _W ) and the optimum erase power (P _E ) when the C / N (carrier-to-noise ratio) value is saturated or maximum, and the obtained C / N value and erase ratio. Show.

Further, for a disk having a C / N value of 45 dB or more and an erasing ratio of 35 dB or more, two writing frequencies (f ₁ = 3.7 MHz)
(z, f ₂ = 4.5 MHz), and an overwrite test was performed alternately.

The optimum values of the write power (P _W ) and the erase power (P _E ) during overwriting were selected depending on the disk.

Linear velocity, P _R or the like, the other conditions were the same as when writing test.

 The results of overwrite performance are shown in Table 2 below.

From Tables 1 and 2, it is confirmed that the phase-change type optical recording medium according to the present invention has excellent performance, and particularly high recording sensitivity has been achieved.

Example 2 The write performance was tested under the same conditions as in Example 1 except that the layer configuration was changed. The results are shown in Table 3 below.

The overwrite performance was tested under the same conditions as in Example 1. The results are shown in Table 4 below.

Example 3 As in Example 2, the write performance was tested under the same conditions as Example 1 except that the layer configuration of Example 1 was changed. The results are shown in Table 5 below.

The overwrite performance was tested under the same conditions as in Example 1. The results are shown in Table 6 below.

[Effects of the Invention] As described above, the effects of the present invention are summarized as follows.

(1) The heating temperature required for recording / erasing is low.
Further, since the material of the present invention has a high light absorptivity, the recording layer heating efficiency during laser beam absorption is also high. For the above reasons,
The required laser power can be reduced.

 That is, the recording / erasing sensitivity is greatly improved.

(2) Since the required laser power can be reduced, a commercially available inexpensive and stable semiconductor laser can be used.

(3) Since the temperature of the laser irradiation part can be kept low, characteristic deterioration due to thermal damage can be reduced.

(4) The erasing ratio during overwriting can be dramatically increased.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukio Ide 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-64-10439 (JP, A) 1-94545 (JP, A) JP-A-2-178086 (JP, A) JP-A-2-150384 (JP, A) JP-A-2-175285 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/26

Claims (2)

(57) [Claims] 1. A main component of the recording layer provided on the substrate is represented by the following general formula, and present state of the recording layer is XYZ ₂ phase and M
An information recording medium characterized by being a mixed phase with a phase. Formula (XYZ ₂ ) _1-a M _a XYZ ₂ is _a chalcopyrite-type compound represented by Ib-IIIb-VIb ₂ or IIb-IVb-Vb ₂ in the periodic table, and M is Xb ₂ of Ib-IIIb-VIb a Sb and / or Bi at _2, one or more elements selected from among S, Se, Te when the XYZ ₂ is IIb-IVb-Vb _2. 0.30 ≦ a ≦ 0.92 2. The information recording medium according to claim 1, wherein XYZ ₂ is AgInTe ₂ and M is Sb or Bi.