JPS62112742A - Spectral reflectivity variable alloy - Google Patents

Abstract

PURPOSE:To provide a spectral reflectivity variable alloy which permits recording and erasing as a recording medium for information by incorporating a prescribed ratio each of Zn, Be, Al,and further specific elements including rare earths into Ag which is an essential component. CONSTITUTION:This alloy consists of Ag as the essential component and contains, by weight, 30-46% Zn, <=10% Be, <=2.5% Al and <=15% >=1 kinds among 1A, 2A, 4A, 5A, 6A, 7A, 8, 1B, 2B, 3B, 4B, 5B groups, and rare earths. This alloy has different crystal structures in high- and low-temp. states. The quickly cooled crystal structure is obtd. by quick cooling from a high-temp. and further the phase formed by the quick cooling is changed to the crystal structure in the low-temp. state by the heating at a prescribed temp. Since the color or spectral reflectivity by the crystal-crystal phase transfer can be reversibly changed, the above-mentioned alloy is effectively usable as the medium for information recording, display, sensor, etc., for which light and heat energy is used.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a novel alloy with variable spectral reflectance and a recording material, and in particular to a novel alloy with variable spectral reflectance and a recording material, and in particular, the spectral reflectance of the alloy changes as the crystal structure of the alloy changes due to the application of light and thermal energy. The present invention relates to an alloy with variable spectral reflectance that can be used as a medium for information recording, display, sensors, etc. that utilizes change.

[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 industrial rare metal Nα80, 1983 (
As described in ``Optical Disks and Materials'', they are capable of higher recording densities than magnetic disks, and 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 destroys or forms a recording portion of the medium to make it uneven, 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.

For this recording medium, it is generally known that Te or its alloy is used to form irregularities by melting and sublimating Te. This type of medium has some problems such as toxicity. Magneto-optical materials are the mainstream for rewritable recording media.

In this method, optical energy is used to invert the local magnetic anisotropy of the medium near the compensation point temperature and record the magnetic Faraday effect and magnetic force effect of the polarized incident light in that area. Reproduction is performed using the amount of rotation of the plane of polarization.

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 that has a large amount of rotation of the plane of polarization, and even with various efforts such as multilayer film formation, the S/N and C/H
A major problem is that the output level is low. Other rewritable systems utilize reflectance changes due to reversible phase changes between amorphous and crystalline recording media. For example, National Technical R
eport Vo129, Na 5 (1983)
There is an alloy in which small amounts of Ge and Sn are added to TeOx.

However, this method has a major problem in that the crystallization portion 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 with martensitic transformation temperature as the boundary.

It takes advantage of the reversible change from red to gold. Martensitic transformation is a transformation that inevitably occurs as the temperature decreases, so the color tone obtained when the temperature is maintained above the martensitic transformation temperature cannot be brought below the martensitic modulation temperature6.And conversely, martensitic transformation If a color tone obtained at a temperature below this temperature is heated above the martensitic transformation temperature, the color tone will undergo transformation and change to a different color tone. Therefore, the two color tones occurring above and below the martensitic transformation cannot be obtained simultaneously at the same temperature. Therefore, this principle cannot be applied as a recording material.

[Purpose of the invention]

An object of the present invention is to provide a variable spectral reflectance alloy that can maintain partially different spectral reflectances at the same temperature.

[Summary of the invention]

The main component of the present invention is silver, 30 to 46% zinc, 1110% or less beryllium, and 2.5% or less aluminum by weight.

7A, 8. A variable spectral reflectance alloy comprising an alloy containing a total of 15% or less of one or more of iB, 2B, 3B, 4B, 5B groups, and rare earth elements.

The present invention provides a first temperature higher than room temperature (high temperature) in a solid state.
and an alloy having a different crystal structure at a temperature lower than the first temperature (low temperature), characterized in that the alloy has a crystal structure different from that obtained by quenching from the high temperature than that obtained by non-quenching at the low temperature. Located in alloys with variable spectral reflectance.

The alloy of the present invention has at least two types of spectral reflectance at the same temperature and can reversibly change the spectral reflectance by heating and cooling treatment in a solid state. That is, the alloy according to the present invention has phases with different crystal structures in at least two temperature ranges in a solid state, and among these, a state in which the high temperature phase is quenched and a low G + 71 phase state in which the high temperature phase is quenched and a non-quenched standard 1ψ state. The spectral reflectivity is different between the two, and the spectral reflectance changes reversibly by heating and cooling in the material temperature range and heating and cooling in the low-temperature range.

The principle of reversible change in reflectance of the alloy of the present invention will be explained with reference to FIG. Let us take the alloy with composition (1) in the figure as an example. This alloy is in the ζ phase at equilibrium. The color of this phase is silvery white, and a corresponding curve is obtained in the spectral reflectance. When this alloy is heated to the β-phase stable temperature region (T4), which is a high sum, and then rapidly cooled, the β-phase cools appropriately and becomes a β' phase with an ordered crystal structure. The color tone of the alloy in this moderately cooled state is pink, and the spectral reflectance is also significantly different from that in the ζ phase state. This alloy is in the ζ-phase stable temperature region (Te
In heating (T2) (below), β' transforms into the ζ phase, and accordingly, the color tone of the alloy changes reversibly from pink to silvery white, and the spectral reflectance returns to its original value. This process can then be repeated. The above changes in spectral reflectance can be used to record, reproduce, and record information.
Applicable to erasure. The present invention is effective as a recording material that utilizes changes in reflectance and color tone due to phase transition between different types of crystals.

Regeneration is at T1 temperature, generally at room temperature. Energy is selectively applied to the silvery-white material in the ζ phase at Tl, and after heating to Tl, it is rapidly cooled. Then, that part becomes β' phase and changes color to pink. This corresponds to a record. The recorded portion can be reproduced by comparing this portion with other portions. By applying energy of a different density to this pink-colored part and heating and cooling it to T2, β'
It undergoes a phase transformation from to ζ and returns to silvery white. This corresponds to erasing the record. The above-mentioned recording, reproducing and erasing processes can also be performed by completely opposite color tone changes. That is, the pink color of the β' phase is recorded as silvery white by utilizing the β' ζ transformation. This is distinguished from the pink color and reproduced. Furthermore, it can be eliminated by changing the ζ phase to the β' phase.

Generally, electromagnetic waves are suitable as the above-mentioned energy. Specifically, various laser beams, electron beams, etc. are also suitable. For reproduction, light of any wavelength that shows a difference in spectral reflectance may be used.

That is, lasers, lamps, etc. in the ultraviolet to infrared region are suitable. Furthermore, since it can be recognized as a change in one color, it can also be used as a display element.

(Alloy Composition) The alloy of the present invention has different crystal structures at high and low temperatures, and the rapidly cooled crystal structure must be formed by rapid cooling from a high temperature. Furthermore,
The phase formed by this rapid cooling must be able to change into a crystalline structure at a low temperature by heating at a predetermined temperature.

From these points of view, silver is the main component and the weight is 7130 ~
An alloy composition of 46%, BelO% or less, and AQ of 2.5% or less is desirable. In the Ag-Zn binary system, Be is
When ZnJl is less than 36%, the β' phase (pink color) changes over time to a β'→ζ phase, and the pink color becomes silvery white, which becomes a problem. The addition of Be has the effect of preventing changes over time. The amount of Be is 1.
Particularly preferred is 5-8%. Further, An has the effect of increasing the temperature of the β phase. In other words, in the A g -Z n binary system, the boundary temperature at which the color changes to pink due to rapid heating and cooling is 275°C.
The temperature at which the color changes from pink to silvery white is 135°C, and the difference therebetween is 140°C.

The larger this temperature difference is, the more advantageous it becomes during erasing (from pink to silvery white). The addition of AQ does not change the erasing temperature, but has the effect of increasing the recording temperature (from silvery white to pink) and increasing the temperature difference between recording and erasing.

The amount of AQ is preferably 2.5% or less, and if it exceeds this, the color tone will fade.

Furthermore, LA and 2A are suitable for use because high-temperature intermetallic compounds are stable and the temperature at which the spectral reflectance changes, that is, the solid phase transformation point, can be controlled arbitrarily depending on the application.

4A, 5A, 6A, 7A, 8. IB, 2B, 3B.

An alloy containing one or more elements of group 4B and 5B elements and rare earth elements in a total amount of 1 giant weight % or less is good. Specifically, the LA group elements include lithium, the 2A groups include magnesium and calcium, the 4A groups include zirconium, the 11.5A groups include vanadium, niobium, and tantalum, the 6A groups include chromium, molybdenum, and tungsten, and the 7A groups include manganese and 8 Groups are cobalt, rhodium, iridium 1%, iron, ruthenium, osmila lx, nickel, palladium, platinum, group IB is copper and gold, group 2B is cadmium, group 3B is boron, gallium, indium, group 4B is carbon.

Silicon, germanium, tin, lead, and group 5B is phosphorus.

Antimony, bismuth, rare earths include yztrium,
Particularly preferred are lanthanum, cerium, samarium, gadolinium, terbium, dysprosium, and lutetium.

(Non-bulk and manufacturing method thereof) In order to obtain reflectance variability, the alloy of the present invention must be capable of forming an appropriately cooled phase by heating and rapidly cooling the material. In order to create and store information at high speed, it is desirable to use a non-bulk material with a high rapid heating and cooling effect and a small heat capacity. That is, it is desirable to be a non-bulk material having a volume that allows substantially only a desired area portion to be changed to a crystal structure different from a reference crystal structure throughout the depth by energy input to a desired minute area. Therefore, in order to produce high-density information in a desired small area, foreign customers I11. A non-bulk m + Ilq l MN wire or powder with a small amount is desirable. For producing information in a very small area with a recording density of 20 megabits/d or more, it is preferable to use a film of 0.0Y to 0.2 μm. In general, intermetallic compounds are difficult to plastically work. Therefore, it is effective to directly rapidly cool and solidify the material from the gas or liquid phase to form it into a predetermined shape in order to make it into a shape, film, thin wire, or powder. These methods include PVD methods (vapor deposition, sputtering methods, etc.).

CVD method, consisting of a member with high thermal conductivity that rotates molten metal at high speed. In particular, there are a molten metal quenching method in which molten metal is poured onto the circumferential surface of a metal roll and rapidly solidified, and an electroplating method and a chemical plating method. When using a film or powder material, it is effective to form it directly on the substrate or to apply it and adhere it to the substrate. When applying, a binder that does not cause any reaction even when the powder is heated is preferred. Furthermore, in order to prevent oxidation of the material due to heating, it is also effective to coat the surface of the material, the film formed on the substrate, or the surface of the coating layer.

The bamboo or thin wire is preferably formed by the molten metal Koi-rei method, and preferably has a thickness or diameter of 0.1 mm or less.

Thicknesses or diameters of 0.05 mm or less are particularly preferred for producing foils or trainings with grain sizes of 0.1 μm or less.

The powder is preferably formed by a Gaia atomization method in which molten metal is atomized together with a gaseous or liquid refrigerant and then poured into water to be rapidly cooled. The particle size is preferably 0.0, Lnwu or less, and ultrafine powder with a particle size of 1 μm or less is particularly preferable.

The film can be formed by vapor deposition, sputtering, CVD electroplating, chemical plating, etc., as described above.

In particular, sputtering is preferable to form a film with a thickness of 0.1 μm or less. Sputtering allows easy control of the target alloy composition.

(mklt) The alloy of the present invention has different crystal structures at high and low temperatures, and must have a suitable cooling phase composition that allows the crystal structure at high temperature to be maintained at low temperature by rapid cooling from high temperature. At high temperatures, it has an irregular lattice crystal structure, but
The quenching phase is preferably an intermetallic compound having a conventional lattice, for example. As the alloy of the present invention is capable of greatly changing optical properties, it is preferable that the alloy mainly forms this intermetallic compound, and a composition in which the entire alloy forms an intermetallic compound is particularly preferable. This intermetallic compound is called an electronic compound, especially a 372-electron compound (average outer shell electron concentration e /
An alloy composition in the vicinity of a=3/2) is good.

Further, the alloy of the present invention preferably has an alloy composition having solid phase transformation, particularly eutectoid transformation or enveloping transformation, and the alloy can be obtained with a large difference in spectral reflectance by quenching from high temperature and non-quenching.

The alloy of the present invention preferably has ultrafine crystal grains, and particularly preferably has a crystal grain size of 0.1 μm or less.

That is, the crystal grains are preferably smaller than the wavelength of visible light, but may be smaller than the wavelength of semiconductor laser light.

Furthermore, in order to reduce the external μ of the film formed on the plate, it is possible to divide the film into a size as small as 111 by etching or the like.

(Characteristics) The variable spectral reflectance alloy and recording material of the present invention can form at least two types of spectral reflectance in the visible light region at the same temperature. That is, it is necessary that the spectral reflectance of a material having a crystal structure (structure) formed by rapid cooling from a high temperature is different from that of a material having a crystal structure (structure) formed by non-quenching.

Further, the difference in spectral reflectance obtained by quenching and non-quenching is preferably 5% or more, particularly preferably 10% or more. If the difference in spectral reflectance is large, it is easy to visually identify the color, and this has a significant effect in various uses described later.

As a light source for spectrally reflecting, electromagnetic waves other than visible light can be used, and infrared rays, ultraviolet rays, etc. can also be used.

Other properties of the alloy of the present invention include electrical resistivity.

The refractive index of light, the polarization rate of light, and the transmittance of light can be changed reversibly in the same way as the spectral reflectance, and the signals can be changed.

It can be used as a means for recording, reproducing, erasing and displaying various information such as letters, figures, symbols, etc., reproducing sensors, etc., and detecting means.

Since the spectral reflectance is related to the surface roughness of the alloy, it is preferable that at least the intended portion has a mirror surface so as to have 10% or more in the visible light region as described above.

(Applications) The alloy of the present invention has a spectral reflectance of electromagnetic waves due to a partial or total change in crystal structure due to heating and rapid cooling.

Physical or electrical properties such as electrical resistivity, refractive index, polarization index, transmittance, etc. can be changed, and changes in these properties can be utilized for use in elements such as recording, display, and sensors.

As a means of recording information, etc., electrical energy in the form of voltage and current, electromagnetic waves (visible light, @ heat radiation) are used.

Infrared rays, ultraviolet rays, photographic flash lamp light, electron beams,
A proton beam, a laser beam such as an argon laser, a semiconductor laser, heat, etc.) can be used, and it is particularly preferable to utilize the change in spectral reflectance caused by the irradiation in the recording medium of an optical disk. Optical discs include digital audio discs (DAD or compact discs), video discs, memory discs, and the like, and can be used for these. By using the alloy of the present invention in the recording medium of an optical disk, a read-only type and an additional recording type can be produced.

It can be used in any rewritable disk device, and is particularly effective in rewritable disk devices.

An example of the principle of recording and reproduction when the alloy of the present invention is used in a recording medium of an optical disk is as follows.

First, the recording medium is locally heated and then rapidly cooled to maintain the crystal structure in the high temperature region in the low temperature region to record predetermined information, or the high temperature phase is locally heated as a base. recorded locally by a low temperature phase during the high temperature phase,
Information can be reproduced by irradiating the recorded portion with light and detecting the difference in optical characteristics between the heated portion and the non-heated portion. Furthermore, the recorded information can be erased by heating the portion recorded as information at a temperature lower or higher than the heating temperature at the time of recording. The light is preferably a laser beam, particularly a short wavelength laser. Since the reflectance between the heated portion and the non-heated portion of the present invention is greatest at a wavelength around 500 nm or 800 nm, it is preferable to use a laser beam having such a wavelength for reproduction. The same laser source is used for recording and playback.

For erasing, it is preferable to irradiate another laser beam with a lower energy density than that for recording.

Further, a disk using the alloy of the present invention as a recording medium has a great advantage in that it can be visually determined whether information is recorded or not.

As a display, it is possible to partially change the spectral reflectance in visible light, so characters, shapes, symbols, etc. can be recorded without using paint, and these displays can be visually identified. . Furthermore, this information can be erased, and in addition to being used repeatedly by recording and erasing, it is also possible to store it permanently. Examples of its applications include clock faces and accessories.

As a sensor, there is a temperature sensor that utilizes changes in spectral reflectance, especially in visible light. Approximate temperature detection can be made by holding a sensor using the alloy of the present invention, whose temperature at which it changes to a high temperature phase is known in advance, in the temperature range to be measured, and maintaining the appropriate cool phase by cooling it appropriately.

(Production method) The present invention provides a first temperature higher than room temperature in a solid state and a first temperature higher than room temperature in a solid state.
A part of the surface of the alloy having the chemical composition described above, which has a crystal structure different from that at the second temperature lower than the temperature, is rapidly cooled from the first temperature to form a crystal structure different from the crystal structure at the second temperature. spectral reflectance, characterized in that the region having a crystal structure formed by the rapid cooling and the region having the crystal structure at the second temperature form different spectral reflectances. It is in the manufacturing method of variable alloys.

Further, the present invention provides a method for applying the first chemical composition to the entire surface of the above-described chemical composition 1 alloy having different crystal structures at a first temperature higher than room temperature and a second temperature lower than the first temperature in a solid state.
to form a crystal structure different from the crystal structure at the second temperature, and then heat a part of the alloy surface to the second temperature to form a region having the crystal structure at the second temperature. and forming different spectral reflectances in the region having the crystal structure formed by the rapid cooling and the region having the crystal structure at the second temperature. It's in the law.

The cooling rate from the first temperature is preferably 102° C./second or more, more preferably 103° C./second or more.

[Embodiments of the invention]

Example l Ag-352nAQ alloy and Ag-35Z n-I
An AQ-Be (wt%) alloy was formed into a foil by a molten metal quenching method, and its color tone change, 1-spectral reflectance, etc. were investigated. The above alloy was melted in an argon atmosphere and solidified into a rod shape of about 4Iφ. This was cut into pieces with a weight of about 5 to Log to prepare a mother alloy for rapidly cooling the molten metal.

A commonly known single roll type device was used for the molten metal quenching method. The master alloy was charged into a quartz nozzle, remelted, and poured onto the outer periphery of a roll (300+nmφ) rotating at high speed to produce the above alloy foil having a length of 5 μm and a width of 5 m. This basket was heated in an electric furnace for 2 minutes at each temperature and then cooled with water to determine the color change and light reflectance of the foil. Figure 2 shows A g that has been heated and rapidly cooled.
-352n -A Q Shows color change of alloy foil.・The mark is pink and the O mark is silvery white.

Figure 3 shows the color of the pink foil when it was heat treated at temperatures below 250°C for 3 minutes and then air cooled.

The temperature at which the Ag-35% Zn alloy without AQ changes from pink to silvery white is approximately 135°C, and this temperature does not change even when AQ is added. The above color change is caused by the β′ phase, which causes the pink color due to rapid cooling from high temperature.
The change from pink to silvery white is thought to be due to the β'→ζ change 7ffl.

Figure 4 shows Ag-35%Z n -1%AQ, 5 of alloy foil.
The spectral reflectance after 0 hours is shown. 450 and 600nm
Except for the wavelength region, there is a remarkable difference in reflectance of 1. I can be praised. The color change between pink and silvery white as shown above is 350'C.
By repeating heating and quenching at 200° C., the spectral reflectance changed reversibly, and the spectral reflectance also changed almost reversibly.

Furthermore, when the silver-white foil was locally heated and rapidly cooled with a lighter, only those areas became pink, and the boundaries between the colors were very clear. Conversely, when the pink foil was locally heated, some parts became silvery white.

Figure 5 shows Ag-35%Zn in the 830nm wavelength region.
-1% AQ alloy and A g of the present invention -35% Zn -1%
This figure shows the difference in spectral reflectance between the Afl-5%Be alloy foil that changed over time, and the foil that turned pink and the foil that turned silver white.

In the case of the Ag-35%Zn, -1%AQ alloy that does not contain Be, the difference in spectral reflectance becomes smaller as time passes (after 100 hours). This is because the β' phase (pink color) due to heating and rapid cooling changes from pink to silvery white over time, so the difference in spectral reflection from the silvery white color becomes smaller. On the other hand, this alloy has B
(A g −35%Z n −]%ΔQ with addition of !
-5%13e alloy does not change over time, and the effect of ne appears. As shown in I- below, the alloy of the present invention is a new alloy system that prevents aging due to the increase in recording temperature due to AQ and the addition of Be.

Example 2 An Ag-35%Zn-1%AQ-5%Be alloy was melted in an argon atmosphere and solidified into a cylindrical shape with a diameter of about 120 plates. A disk with a thickness of 5 rm+ and a diameter of 100 mφ was cut out from this and used as a target for sputter deposition.

A DC-magnetron type sputter deposition method was used, and the substrate was made of hard glass with a diameter of approximately 26 mm and a thickness of 1.2 m. The above alloy was deposited to a thickness of approximately 80 nm under conditions of a substrate temperature of 200"C and a sputter power of 150 mW. Sputter deposition was carried out.Ar gas was used at 20 mTorr.The film surface was further coated with Al2203 or 5iOz by R,F sputtering.
was deposited as a protective film to a thickness of about 20 nm.

In the sputter-deposited state, the film was silvery white. This is 1+
(For each plate: After heat treatment at 350°C for 2 minutes and cooling with water, it turned pink. When it was further heat-treated at 200°C under the same conditions, it returned to a silvery white color. In this way, the sputtered film also showed the same color change as the foil. Ta.

Example 3 Ag-35%Zn-1 produced by the same method as Example 2
%Al2-5%Be alloy sputtered film was subjected to recording, reproduction, and erasing using a laser beam. As a laser beam, a semiconductor laser (wavelength 830 nm) or an Ar laser (wavelength 48 nm) is used.
8 nm) was used. The power of the laser beam is 10 on the film surface.
~50 mW, the beam diameter was varied from about 1 μm to about 10 μm, and as a result of scanning the silvery white film surface, a pink colored line could be drawn. This line width could be varied from about 1 μm to 20 μm depending on the laser output. When several such lines were drawn and a semiconductor laser was scanned across the lines, the change in reflectance enabled the color change to be converted into an electrical signal as a change in the DC voltage level of approximately 20%.

The lines drawn in this way could be easily restored to their original silvery white color by heating the entire film to nearly 200°C or by scanning it with a laser beam of low power density.

〔Effect of the invention〕

According to the present invention, the color or spectral reflectance due to crystal-crystal phase transition can be reversibly changed, so that a remarkable effect can be obtained in which recording and erasing can be performed as an information recording medium.

[Brief explanation of drawings]

Claims (1)

[Claims] 1. 1A with silver as the main component, 30 to 46% zinc, 10% or less beryllium, and 2.5% or less aluminum by weight;
2A, 4A, 5A, 6A, 7A, 8, 1B, 2B, 3B
, 4B, 5B groups, and rare earth elements in an amount of 15% or less in total.