JPH0352651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a novel rewritable optical disk recording medium for writing and reading.

<Prior Art> Optical disks originally used as a recording layer an uneven pit array formed on a substrate according to information, and reproduced information by optically picking up the pit array. However, with the development of a recording method that utilizes the phase transition of solids, it is possible to do more than just playback.
By using laser light to both write and reproduce information, it is possible to write one bit on an approximately 2μ square, making it possible to achieve a recording density that is more than an order of magnitude higher than current high-density magnetic disks. . Furthermore, unlike magnetic disks, information can be written, read, and accessed randomly at high speed without contact, so there is no risk of deteriorating the recording surface of the disk. Further, it has the advantage that the recording surface can be easily sealed and protected, and it can be prevented from being affected by dust, scratches, etc.

Te or TeO _x (where 0<x<2) has been known as a rewritable recording medium for write/read optical discs. When these recording media are irradiated for a short period of time so that the temperature of the irradiated part of the laser beam rises above the melting point, the irradiated part is recorded as an amorphous state, and the laser irradiated part is heated to a temperature slightly above the crystallization temperature. If it is irradiated for a long time so that it returns to a crystalline state, the record can be erased and rewritten. However, Te
Since its crystallization temperature is 10°C to 60°C, the amorphous state is not stable, which poses a problem in terms of preservation of recorded information. On the other hand, TeO _X (where 0<x<2.)
To stabilize the amorphous phase, they added impurities such as Sn and Ge, controlled the crystallization temperature, and stabilized it by increasing the activation energy. However, TeO _X has the disadvantage that it is difficult to control the oxygen concentration and that different elements are added, resulting in poor manufacturing reproducibility. Furthermore, these materials have a high vapor pressure in their molten state, and when used as recording media for optical disks, the materials scatter every time they are written, reproduced, or rewritten, resulting in a disadvantage in repeated use.

In view of the above-mentioned circumstances regarding conventional optical disc recording media, the inventors have conducted repeated research on optical disc recording _media and have developed an (In _{1 - X Sb} Au, Ag, Cu, Pd, Pt, Al, Si,
At least one selected from Ge, Ga, Sn, Te, Se and Bi. ) from molten state to room temperature
When rapidly cooled at a cooling rate of 10 ⁶ °C/sec or higher, it becomes a pseudo-stable phase (hereinafter referred to as the "π phase"), but when slowly cooled, it transforms to a mixed phase of InSb and Sb (equilibrium phase), and the π When it is in phase, the reflectance is higher than when it is in mixed phase.
We learned that not only is the price higher by 10 to 20%, but the π phase itself is more stable. Furthermore, the (In _{1 - X Sb}
The present invention was completed by discovering that written information can be easily erased and rewritten (rewritten).

<Objective of the Invention> That is, the present invention provides an optical disk recording medium in which information can be easily written, reproduced, and erased, the recording state has high phase stability, and furthermore, writing, reproduction, and erasing can be repeated. The purpose is to

<Structure of the Invention> The optical disc recording medium of the present invention for achieving the above object has an alloy film having a composition represented by the general formula (In _1-X Sb _X ) _{1-Y MY} in the recording layer. This is a characteristic feature. However, in the above general formula, X and Y are respectively 55% by weight≦X≦80% by weight and 0% by weight≦Y≦20% by weight, and M is Au, Ag, Cu, Pd, Pt, Al, Si,
Represents at least one selected from Ge, Ga, Sn, Te, Se and Bi.

In _addition , _the recording layer has _an alloy film having _a composition represented by the general formula ₍ In _{1 - X Sb 2} ,
Another feature is that at least one selected from oxides such as SiO ₂ or fluorides such as MgF ₂ , CeF ₃ and AlF ₃ is laminated as a protective film. However, in the general formula, X and Y are respectively 55% by weight≦X≦80% by weight and 0% by weight≦Y≦20% by weight, and M is Au, Ag, Cu, Pd, Pt, Al, Si,
Represents at least one selected from Ge, Ga, Sn, Te, Se and Bi.

The above general formula (In _{1 - X Sb} composition within the range of A shown in the figure) will no longer be formed,
If it exceeds 80% by weight, a single phase c of Sb will be formed and no mixed phase will be formed, making it impossible to write, reproduce, and rewrite information using the phase transition between the π phase and the mixed phase.

₍ In _{1 - X Sb} You will no longer be able to write, play, or rewrite information. Furthermore, as shown in Figure 2, the relationship between the additive metal M composition and the phase transition temperature shows that Te, Se and
In the case of Bi, within the range I between curves a and b,
These metals can be varied in various combinations depending on the combination of metals; in the case of Au, Ag, Cu, Pd and Pt, they can be varied within the range between curves e and f; for Al, Si, Ge, Ga and Sn. can be changed within the range between curves c and d. Furthermore, by changing the combination of metals belonging to different ranges among the metals in each group showing phase transition temperatures of 120 to 160℃
An alloy having a transition temperature within a suitable range can be obtained within the range of .

When writing information on the above-mentioned optical disk recording medium, the recording layer is irradiated with a high-power laser beam to melt it and then allowed to cool naturally to room temperature ^.
When rapidly cooled at a cooling rate of ℃/sec or higher, it transitions to the π phase, allowing information to be written on it.If a π-phase medium is irradiated with a low-power laser beam, it undergoes a phase transition to a mixed phase and information can be erased. can be rewritten.

<Examples> Hereinafter, typical examples of the present invention will be described.

Example 1 Production of optical disk recording medium A material in which In and Sb were mixed at a ratio of 30% by weight and 70% by weight, respectively, was placed in a quartz crucible, heated and melted at 645°C in a high-frequency heating furnace, and then heated in the furnace. After natural cooling, an In _0.3 Sb _0.7 material could be obtained.

Next, as shown in FIG. 3, a polymethyl acrylate (hereinafter referred to as "PMMA") disc 2 with a diameter of 20 cm is attached to the support 3 at the top inside the bell gear 1.
At the same time, a zirconia crucible 5 containing the In _0.3 Sb _0.7 material 4 obtained in the above process and an electron beam source 6 are placed inside the bell gear 1, and the inside of the bell gear 1 is heated to 1×10 ^-4 ~1×
After evacuation to 10 ^-5 Torr, an electron beam is irradiated from the electron beam source 6 to the In _0.3 Sb _0.7 material 4 in the crucible 5 to evaporate the In _0.3 Sb _0.7 and deposit In _0.3 on the surface of the disk 2.
A Sb _0.7 alloy film was deposited. Then, the inside of the bell gear 1 was returned to normal pressure, and the disc 2 was allowed to cool naturally.

The obtained PMMA disk 2 (hereinafter referred to as “Sample No. 1”)
That's what it means. ) The film thickness of the In _0.3 Sb _0.7 alloy film was measured and was 250 Å.

Performance of optical disk recording medium In _0.3 of sample No. 1 obtained by the above process
The performance was measured with the Sb _0.7 alloy film facing upward using the writing/reproducing device shown in FIG.

In the writing/reproducing device shown in FIG.
The writing side consists of an information input source 10, a writing control device 11, a GaAs semiconductor laser 12, a condensing lens 13, and a mirror 14. The optical output of the GaAs semiconductor laser when writing onto a sample is 8.
I went with mW.

The reproduction side consists of a GaAs semiconductor laser 15, a condensing lens 16, a beam splitter 17, a tracking mirror 18, a photodetector 19, a reproduction output control device 20, and a television monitor 21.
The record written with the optical output of the GaAs semiconductor laser 12 is set to 0.8 mW, and the reproduced signal obtained by the photodetector 19 is transmitted via the reproducing device 20 to the carrier wave-to-noise ratio ( The C/N ratio (hereinafter referred to as "C/N ratio") was 55%.

Furthermore, after the above C/N ratio measurement was completed, the information writing surface of sample No. 1 was scanned with a GaAs semiconductor laser beam with an output of 4 mW, and the written information could be erased.

Example 2 A 250 Å thick film was deposited on a PMMA disk in the same manner as in Example 1 except that In _0.45 Sb _0.55 material was used as the evaporation source.
A sample was obtained in which an In _0.45 Sb _0.55 alloy film was formed. Regarding this sample No. 2, the C/N ratio was measured according to the same method as in Example 1, and the value was 55%. Furthermore, the information written on this sample No. 2 could be erased by scanning the sample surface with a 5 mW GaAs semiconductor laser beam.

Example 3 As evaporation sources, (In _0.45 Sb _0.55 ) _0.9
Au _0.1 , (In _0.3 Sb _0.7 ) _0.9 Au _0.1 , (In _0.2 Sb _0.8 ) _0.8 Au
_0.2 ),
(In _0.45 Sb _0.55 ) _0.9 Au _0.1 , (In _0.3 Sb _0.7 ) _0.8 Ag _0.2 )
,
(In _0.2 Sb _0.8 ) _0.8 Ag _0.2 ), (In _0.45 Sb _0.55 ) _0.8 Cu _0.2
,
(In _0.3 Sb _0.7 ) _0.8 Ag _0.2 ), (In _0.2 Sb _0.8 ) _0.8 Ag _0.2 ,
(In _0.45
Sb _0.55 ) _0.8 Pd _0.2 , (In _0.3 Sb _0.7 ) _0.8 Pd _0.2 , (In _0.2 S
b _0.8 ) _0.
8 Pd _0.2 , (In _0.45 Sb _0.55 ) _0.9 Pt _0.1 , (In _0.3 Sb _0.7 ) _0
.9 Pt _0.1 ,
(In _0.2 Sb _0.8 ) _0.9 Pt _0.1 , (In _0.45 Sb _0.55 ) _0.9 Al _0.1 ,
(In _0.3
Sb _0.7 ) _0.9 Al _0.1 , (In _0.2 Sb _0.8 ) _0.9 Al _0.1 , (In _0.45 S
b _0.55 ) _0.
9 Si _0.1 , (In _0.3 Sb _0.7 ) _0.9 Si _0.1 , (In _0.2 Sb _0.8 ) _0.9
Si _0.1 ,
(In _0.45 Sb _0.55 ) _0.9 Ge _0.1 , (In _0.3 Sb _0.7 ) _0.9 Ge _0.1 ,
(In _0.2
Sb _0.8 ) _0.9 Ge _0.1 , (In _0.45 Sb _0.55 ) _0.9 Ga _0.1 , (In _0.3
Sb _0.7 )
_0.9 Ga _0.1 , (In _0.2 Sb _0.8 ) _0.9 Ga _0.1 , (In _0.45 Sb _0.55 )
_0.9
Sn _0.1 , (In _0.3 Sb _0.7 ) _0.9 Sn _0.1 , (In _0.2 Sb _0.8 ) _0.9 Sn
_0.1 ,
(In _0.45 Sb _0.55 ) _0.9 Te _0.1 , (In _0.3 Sb _0.7 ) _0.9 Te _0.1 ,
(In _0.2
Sb _0.8 ) _0.9 Te _0.1 , (In _0.45 Sb _0.55 ) _0.9 Bi _0.1 , (In _0.3
Sb _0.7 )
The C/N ratio was measured by the same alloy film deposition method and C/N ratio measurement method as in Example 1, except that _0.9 Bi _0.1 and (In _0.2 Sb _0.8 ) _0.9 Bi _0.1 were used, and the values were the same in both cases. was 55%.

Example 4 The alloy films of each sample prepared in Examples 1, 2, and 3 were prepared using the same apparatus and method as in FIG. 3, except that MgF ₂ was used as the vapor deposition source material 4. A 1000Å evaporated film of MgF ₂ is applied as a protective film on top.
When deposited to a thickness of ~2000 Å and measured the C/N ratio using the apparatus shown in Figure 4, the writing laser output was 10 to 13 mW, 5 to 8 mW during erasing, and 1 to 1.5 mW for recording and reproduction. It was found that it was necessary.

Further, it was found that the C/N ratio was 55%, which is the same as that without a protective film.

Furthermore, although the protective film in this example uses MgF ₂ , other fluorides such as CeF ₃ and AlF ₃ can also be used.
Similar results were also obtained when an oxide film of TeO ₂ , V ₂ O ₃ , V ₃ O ₅ , TiO ₂ , SiO ₂ or the like was formed as a protective film.

In the above example _, the method of depositing the (In _{1 - X} Sb , or may be formed by a sputtering method. In addition, although the substrate used was shown to be made of PMMA, materials such as acrylic, glass, and Al may also be used, but when using highly thermally conductive materials such as glass and Al, the substrate and alloy layer may be used. It is better to form a thermal insulating layer with a thickness of about 500 Å to 0.2 mm between the two.

<Effects of the Invention> As is clear from the above explanation, the optical disc recording medium according to the present invention has a low phase transition temperature of 10°C to 60°C, which is lower than that of conventional optical disc recording media such as Te and _TeO Written information will be erased even if the temperature rises during use or the ambient temperature rises while not in use, but in the optical disk recording medium of the present invention, the π-phase, Only a phase transition between mixed phases occurs. Therefore,
High stability of written information. Furthermore, the phase transition temperature can be freely selected between 120° C. and 160° C. by appropriately selecting the type and combination ratio of the materials of the recording medium used, depending on the usage conditions of the optical disk recording medium.

Information can be written with an optical output of 8 to 13 mW from a GaAs semiconductor laser (other lasers may be used), and the C/N ratio of the resulting reproduced signal is
This is about 55%, which cannot necessarily be said to be higher than the C/N ratio of conventional optical disk recording media using Te and _TeOx , which is about 60%.
The written information is highly stable and can be played repeatedly.

[Brief explanation of drawings]

Figure 1 shows In _1-X of the optical disc recording medium of the present invention.
A characteristic diagram showing _{the relationship} between the compositional dependence during the formation of the _π phase in the Sb _X alloy and the phase transition temperature from the π phase to _the mixed phase. A characteristic diagram showing the relationship between the composition dependence of phase formation and the phase transition temperature from π phase to mixed phase. FIG. 3 is a schematic diagram of the vacuum apparatus used for manufacturing the optical disk recording medium of the example. FIG. 4
The figure is a schematic configuration diagram of a writing/reproducing device used to measure the performance of the optical disk recording medium of the example. In the drawing, 1... Belgear, 2... PMMA substrate,
4... Vapor deposition material, 10... Information input source, 12,1
5...GaAs semiconductor laser, 17...beam splitter, 19...photodetector, 20...reproduction output control device, 21...television monitor.

Claims (1)

[Claims] 1. An optical disk recording medium characterized in that the recording layer has an alloy film having a composition represented by the general formula (In _1-X Sb _X ) _{1-Y MY} . However, in the general formula, X and Y are respectively 55% by weight≦X≦80% by weight, 0% by weight≦Y≦20% by weight, and M is Au, Ag, Cu, Pd, Pt, Al, Si,
Represents at least one selected from Ge, Ga, Sn, Te, Se and Bi. 2 The recording _{layer has an} alloy _film having _{a composition} represented by the general formula ₍ In _{1 -X Sb} ,
1. An optical disc recording medium characterized in that at least one kind selected from oxides such as SiO ₂ or fluorides such as MgF ₂ , CeF ₃ and AlF ₃ is laminated as a protective film. However, in the general formula, X and Y are respectively 55% by weight≦X≦80% by weight and 0% by weight≦Y≦20% by weight, and M is Au, Ag, Cu, Pd, Pt, Al, Si,
Represents at least one selected from Ge, Ga, Sn, Te, Se and Bi.