JPS62170390A - Recording material - Google Patents

Abstract

PURPOSE:To obtain a recording material superior in information recording/ erasing properties, by using a material wherein a change in optical characteristics is locally induced by an endothermic reaction. CONSTITUTION:As a concrete material, a metal and an alloy of semimetal element ranging from Ib to IVb in the periodic table, especially an alloy of 1.45 or more average electron concentration, is used. Particularly, a beta' phase (an order phase of CsCl type) formed in an alloy of Ag-Zn series produces a pink, thus resulting in a remarkable change in an optical characteristics from a zeta phase (silverwhite) existing in the aforesaid alloy series. With an initial state of the zeta phase in the alloy, a transformation zeta beta' corresponds to a recording, and a transformation beta' zeta is an erasing. In this relation, since the transformation zeta beta' is quenched after completion of a transformation zeta betato establish the beta' phase, it is desirable that the transformation zeta beta is substan tially endothermic. It is the most desirable, however, as a recording material that both the above transformations are made endothermic by adding Al, Ga, In, Sn, Sb in the range of 10wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a recording material, and more particularly to a material capable of recording and erasing information as the optical properties of the alloy change upon application of light or thermal energy.

[Background of the invention]

In recent years, as information recording becomes more dense and digital, various information recording and reproducing methods are being developed. In particular, optical discs that use laser light energy for recording, erasing, and reproducing information are manufactured using industrial rare metals Ha 80, 1.98
As described in Section 3 (Optical disks and materials), higher recording densities are possible than with magnetic disks, and this will be a promising method for information recording in the future. Among these, laser playback devices have been put into practical use as compact discs (CDs).

On the other hand, recordable methods can be broadly divided into two types: write-once type and rewritable type. The former can only be written once and cannot be erased. The latter is a method that allows repeated recording and erasing. In the write-once type recording method, a laser beam is used to destroy or shape the recording portion of the medium to create unevenness, and for reproduction, a change in the amount of light reflected due to the interference of the laser beam at the uneven portion is used for reproduction. This type of recording medium is generally known to use Te or its alloy to form irregularities by dissolving and sublimating it, but this type of medium has some problems such as toxicity. Magneto-optical materials are the mainstream for rewritable recording media. This method utilizes optical energy to invert and record the local magnetic anisotropy of the medium near the Curie point or compensation point temperature, and the polarization plane of the polarized incident light at that part due to the magnetic Faraday effect and magnetic Kerr effect. Play with the amount of rotation. This method is considered to be the most promising rewritable method, and active research and development is underway with the aim of putting it into practical use in the next few years. However, there is currently no material with a large amount of rotation of the plane of polarization, and even with various measures such as multilayer film formation, there is a big problem that output levels such as S/N and C/N are low.

Other rewritable systems utilize reflectance changes due to reversible phase changes between amorphous and crystalline recording media. For example, the National Technical Report (Nat
ional Tschnieal Report Vo
129 Nu 5 (1983)), there is a material in which small amounts of Ge and Sn are added to TeOx.

However, this method has a major problem in that the crystallization temperature of the amorphous phase is low, and the instability of the phase at room temperature affects the reliability of the disk.

On the other hand, as an alloy utilizing color tone change, JP-A-57-1
There are 40845. This alloy is (12-15)wt%A
Q - (1 to 5) wt% Ni-remaining Cu alloy at the martensitic transformation temperature.

It takes advantage of the reversible change from red to gold. Since martensitic transformation is a transformation that inevitably occurs as the temperature decreases, the color tone obtained when the temperature is maintained above the martensitic transformation temperature cannot be brought below the martensitic modulation temperature. On the other hand, if a color tone obtained at a temperature of 1 to full tensile transformation temperature is heated to a temperature higher than the martensitic transformation temperature, the color tone will undergo transformation and change to a different color tone. Therefore, the two shades that occur under L of the full-strength 1-transformation cannot be obtained simultaneously at the same temperature. Therefore, this principle cannot be applied as a recording material.7 [Object of the Invention] An object of the present invention is to provide a recording material that has excellent recording and erasing characteristics and has variable optical characteristics.

[Summary of the invention]

The present invention relates to a recording material that can record and erase information by changing local optical properties using light and thermal energy,
This is especially true for materials in which optical property changes occur due to endothermic reactions in the material. Recording media such as optical disks change local optical characteristics mainly by the energy of laser light. In the present invention, the light/thermal energy may broadly be electromagnetic waves, but laser light is generally preferred.The optical property is the refractive index of the material, and the transmittance, reflectance, etc. determined by this are also directly recorded as information. This is preferable as a characteristic that can be changed. The material of the present invention converts the above energy into heat, and its optical properties change upon heating. In this case, if the material itself is in a solid state rather than in a liquid state, the distortion caused by the change is small and the material is excellent in recording and erasing repeatability as a recording material.

The present invention exhibits at least two optical properties at the temperature of use of the recording material, generally room temperature. This is mainly achieved by differences in atomic arrangement corresponding to each state, generally the crystal structure9 organization, etc. Therefore, these tissues change due to light and thermal energy. For example, assume that two states corresponding to optical characteristics are A and B. If the initial state of the recording material is A, a change to A-+B corresponds to recording, and a change to B-)A corresponds to erasing. The present invention is characterized in that at least one of these two changes, preferably both, involves an endothermic reaction. Since this material achieves recording and erasing by heating, the fact that these changes are endothermic reactions causes A#B changes to occur quickly, resulting in a marked improvement in recording and erasing sensitivity.

The specific material of the present invention is an alloy of metals and metalloid elements from rb to iib in the periodic table of elements. In particular, the alloy has an average electron concentration of 1.45 or more. The average electron concentration is expressed as the total value of the Ib group as 1, nb as 2, below (2) b as 8, and (2) as O, and the values are proportionally blended according to the alloy composition (at%). This value particularly affects the electronic structure of the alloy and is important as a factor determining optical properties. Among these, the intermetallic compounds of these alloys have unique optical properties and are therefore suitable as those corresponding to the A or B state. The amorphous state is also good. Among these, some compounds mainly of group Ib have a unique color tone, and when used, the optical properties in the visible region change significantly. this house.

Ag-based alloys are also optimal for this color tone change.

In particular, the β' phase (CsC
The Q-shaped ordered phase) exhibits a pink color, and the ζ that appears in the same alloy system.
A remarkable change in photoconstancy corresponding to A and B mentioned above appears between the phase (silver white). If the initial state of these alloys is the ζ phase, the ζ→β' transformation corresponds to recording, and the β'→ζ transformation corresponds to erasure. Among these transformations, the ζ→β' transformation is rapidly cooled to become β' after the ζ→β transformation, so it is desirable that the ζ→β transformation is essentially endothermic. It is most desirable for recording materials that both of these transformations are endothermic;
Ga.

This can be achieved by adding In, Sn, and Sb in a range of 10 wt%. Therefore, when these are used as recording materials, very good characteristics can be obtained.

In solid phase transformation, lattice strain between different types of crystals becomes a problem during the endothermic reaction. Therefore, in order to facilitate the reaction, a structure that softens this strain as much as possible is desired. Regarding this point, the material of the present invention has equiaxed crystals with an average grain size of 0.5
It is desirable that the thickness be less than μm. The equiaxed product is preferably one in which the ratio of the major axis to the minor axis of the grain is twice or less.

When the above materials are used as recording materials, they are used substantially in a thin film state. This manufacturing method is common PVD, C
A DVD or the like is fine. As the PVD, sputtering method, vacuum evaporation method, etc. are suitable.

[Embodiments of the invention]

Example I A g -Z n binary alloy foil was produced by a liquid quenching method, and its phase transformation corresponding to recording and erasing was investigated using a differential scanning calorimeter (DSC). A single roll type device was used for the liquid quenching method. A master alloy was prepared by melting an Ag-30 to 45 wt% Zn alloy in a high frequency furnace in an argon atmosphere. This was made into a ribbon-like foil with a thickness of about 8 Q ALm and a width of 5 nn using a single roll quenching device. The manufacturing conditions are roll (material:
Approximately 1.0 kg/mm of master alloy was remelted in a quartz nozzle by rotating tool steel (diameter: 300 ma) at approximately 1100 Orp.
Ar gas at cn pressure was ejected directly above the roll.

This ribbon-shaped foil was heated at 350°C for 10 minutes and then cooled with water to obtain β'
I made it pink (pink). A piece of about 1 mg was cut out from this and subjected to thermal analysis by DSC. Figure 2 shows changes in the DSC curve depending on the amount of Zn6.
A peak appears around 0°C. The low-temperature peak corresponds to the β′→ζ transformation, and the high-temperature peak corresponds to the ζ→β transformation, and the former disappears.
The latter corresponds to records. Both ζ → β are endothermic reactions, but β' → ζ changes from exothermic to endothermic 1 as the amount of Zn increases.
It turns into an exothermic mixed peak. Therefore, it can be seen that the higher the Zn level is, the better the erasing characteristic is, and the higher the Zn content, the better the recording material.

Example 2 A g -50at%Zn(3
A 9.7wt%Zn)-1at%X ternary alloy foil was produced, and its DSC curve was examined. The heat treatment of the measurement sample was also the same as in Example 1. X elements include AQ, Ga, In,
Periodic Table of Elements 1b~■ of Sn, sb, pb, Bi, Te
Each element of group b. Figure 3 shows A g -50at%Z
n D of each lat%pb and lat%Bi ternary alloy
It is an SC curve. The DSC curves of these two alloys are A g
-Zn This is a pattern showing endothermic peaks at low temperatures and endothermic peaks at high temperatures, similar to the high Zn composition of binary alloys, and is a relatively good pattern as a recording material.

FIG. 1 shows Ag-50at%Zn-1. at%AQ, la
t%Ga.

3 each of lat%In, lat%Sn and lat%sb
2 shows a DSC curve of a base alloy foil. A feature of each alloy system is that the low-temperature peak, that is, the peak corresponding to the β'→ζ transformation, becomes an endothermic peak. Therefore, as a recording material, both recording and erasing properties are significantly improved.

Example 3 Thin films of Ag-Zn alloy and Ag-Zn-X alloy (or the same as in Example 2) were produced by sputtering, and their recording and erasing characteristics with a semiconductor laser were investigated.

A DC-magnetron type sputtering device was used to prepare the thin film. The target used was a 100Iφ alloy target made by a melting method, and the sputtering substrate was 26N*φ,
A 1.2 m thick quartz glass was used. FIG. 4 shows the structure of the produced membrane. Approximately 60 nm of CrxO on a glass substrate
After forming the S film by RF-sputtering, the alloy is formed thereon to a thickness of about 30 to 50 nm. Furthermore, a Ta 20δ film of about 580 nm was deposited as a protective film on top of it by RF-sputtering.
m was formed.

Recording and erasing using a laser is performed from the glass substrate side (in the direction of the arrow in the figure). CrzOa film reduces reflectance.

It plays the role of effectively converting the irradiated laser light into heat.

The semiconductor laser used was one with a power of 30 mW and a wavelength of 830 nm. Recording and playback are performed by changing the amount of reflected light from a laser, and converting the amount of reflected light into voltage for recording and playback.

Confirmed deletion. At the film surface, the laser beam is approximately 1-06 μm.
narrowed down to the diameter. All of the Ag-based alloy films were kept in the ζ phase (silver white) state, and pulsed laser light was irradiated, and the amount of reflected light was recorded as a voltage. As a result A g
- In the Zn binary system, the erasing laser pulse width becomes smaller as the amount of Zn1l increases, and furthermore, in the alloy system shown in Figure 1, erasing is possible with a pulse width that is about one order of magnitude smaller than this, and there is a remarkable difference in erasing characteristics. It was observed.

Example 4 AK-based gold alloy film 3Ta 20 having the film configuration shown in Example 3
A film of a material that causes an exothermic reaction was formed between the 15 films 4. This material is an amorphous film or the like whose crystallization temperature is near the endothermic peak generation temperature of the Ag-based alloy. This material undergoes an exothermic reaction when heated by laser light, which promotes heating of the Ag-based alloy and improves recording and erasing characteristics. If this material is transparent, Cr203g2 and Ag-based alloy film:
It is also effective to form it between 3 and 3.

〔Effect of the invention〕

According to the present invention, a novel recording material with excellent recording and erasing properties can be obtained.

[Brief explanation of drawings]

FIG. 1 shows Ag-50at%Zn-1 according to an embodiment of the present invention.
at%
A diagram showing the Z n amount dependence of the DSC curve of the base alloy foil,
Figure 3 shows Ag 50at%Zn-1at%X (X=
Pd, Bi) Alloy Foil (7) DSC Curve Diagram FIG. 4 is a cross-sectional view showing the film structure of a thin film produced by a sputtering method. ]...Quartz glass, 2...GrzOs film, 3...
Ag-based alloy film, Figure 1 Degrees (°C) Figure 2

Claims (1)

[Claims] 1. In a recording material where local optical properties are different from other parts and information is recorded and erased by changes in the difference, the local change in optical properties is characterized by an endothermic reaction. Recording materials.