JPS61194136A - Alloy having variable spectral reflectance and recording material - Google Patents

Abstract

PURPOSE:To obtain an information recording medium enabling recording and erasure by adding prescribed percentages of Zn, Ti and a rare earth element to Ag and allowing the resulting alloy to form phases having different crystal structures in two temp. ranges so as to change reversibly the spectral reflectance. CONSTITUTION:An alloy having variable spectral reflectance is composed of 30-46wt% Zn, <=10wt% Ti, <=15wt% in total of one or more kinds of elements selected among the elements belonging to the groups IA, IIA, IVA, VA, VIA, VIIA and VIII in the periodic table, the rare earth elements, etc., and the balance Ag. The alloy has different crystal structures at the 1st temp. above room temp. and a temp. below the 1st temp. in a solid state. When the alloy is rapidly cooled from the higher temp., the crystal structure changes to a structure different from a crystal structure formed by nonrapid cooling at the lower temp. Thus, two or more kinds of spectral reflectances are obtd. by heating and cooling in a solid state.

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. This invention relates to alloys that can be used as media for information recording, display, sensors, etc. that utilize 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. Especially for recording information using laser light energy.

The optical disc used for erasing and playing is made of industrial rare metal Nn.
As described in 80.1983 (Optical Disks and Materials), higher recording densities are possible than 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 recording method, a laser beam is used to destroy or shape the medium in the recording area 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 area 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. This method uses optical energy to invert and record the local magnetic anisotropy of the medium near the Curie point or the compensation point temperature, and the polarization plane of the polarized incident light at that part is caused by 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 methods utilize changes in reflectance caused by reversible phase changes between amorphous and crystalline recording media.1For example, National Technical Report Vol. 29, No. 5 (1983)
Chnical Report Vo129 IQ 5
(1983)) in which small amounts of Ge and S are added to TeOx.
There are alloys containing n.

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 one color tone change, JP-A-57-1
There is a base metal described in Publication No. 40845. This alloy is (1
2-15) wt%A Q-(1-5) wt%Ni
- This is an alloy made of residual Cu, which takes advantage of the fact that it reversibly changes from red to gold at the martensitic transformation temperature. Martensitic transformation is a transformation that inevitably occurs as the temperature decreases, so the color tone obtained when maintained above the martensitic transformation temperature cannot be brought below the martensitic modulation temperature, and conversely, martensitic transformation If a color tone that can be obtained at a temperature below this temperature is raised above the martensitic transformation temperature, the transformation will occur and change to a different color tone.Therefore, it is impossible to obtain two color tones that occur above and below the martensitic transformation at the same time 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 and a recording material that can maintain partially different spectral reflectances at the same temperature.

[Summary of the invention]

(Summary of the Invention) The present invention contains silver as a main component, 30 to 46% zinc and 10% or less titanium, and 1A, 2A, and 4A.

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

The variable spectral reflectance alloy is characterized by comprising an alloy containing one or more of group 5B and rare earth elements in a total amount of 15% by weight or less.

That is, the present invention provides a first temperature higher than room temperature (
An alloy having different crystal structures at a temperature lower than the first temperature (high temperature) and at a temperature lower than the first temperature (low temperature), characterized in that the alloy has a crystal structure different from that obtained by non-quenching at the low temperature due to quenching from the high temperature. It is an alloy with variable spectral reflectance.

The alloy of the present invention has at least two types of spectral reflectance at the same temperature due to heating and cooling treatment in a solid state.

The spectral reflectance can be changed reversibly.

That is, the alloy according to the present invention has a phase state of at least 2
It has phases with different crystal structures in two temperature regions, and among them, the spectral reflectance is different between the quenched state of the high temperature phase and the low temperature phase state of the non-quenched standard state. The spectral reflectance changes reversibly by heating and cooling in the low phase temperature region.

The principle of the reversible change in reflectance of the alloy of the present invention will be explained with reference to FIG. 1, taking as an example the alloy having the composition (, f) in FIG. 6. This alloy is in the ζ phase at equilibrium. The color of this phase is silvery white, and a curve corresponding to the 1-spectral reflectance is obtained. When this alloy is heated to the stable temperature region (T4) of the β phase, which is a high temperature phase, and then rapidly cooled, the β phase is appropriately cooled and becomes a β' phase having an ordered crystal structure. The color tone of the alloy in this properly cooled state is pink, and the 1-spectral reflectance is also significantly different from that in the ζ phase state. This alloy is in the ζ-phase stable temperature region (T
When heated (T2) at (below e), β' transforms into ζ phase,
Along with this, the color tone of the alloy changes reversibly from pink to silvery white, and the spectral reflectance returns to its original value.

Thereafter, this process can be repeated.The spectral reflectance change of 0 or more can be applied to recording, reproducing, and erasing information. It is valid.

Regeneration is at T8 temperature, generally at room temperature. T.

Energy is selectively applied to the silvery white material in the ζ phase at T4.
Heat until cool and then cool quickly. 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 a different density of energy to this pink colored part and heating and rapidly cooling it to T2, the phase transforms from β' to ζ and returns to silvery white. This corresponds to erasing records. The above-mentioned recording, reproducing and erasing processes can also be performed by completely opposite color tone changes. That is, β′
The pink color of the phase is recorded as a silvery white color 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. ranging from ultraviolet to infrared are suitable. Furthermore, since it can be recognized as a change in color, it can also be used as a display element.

(Alloy Composition) The alloy of the present invention must have different crystal structures at high and low temperatures, and the rapidly cooled crystal structure must be formed by rapid cooling from a high temperature.
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 zinc is 30 to 4 by weight.
Alloy compositions comprising 6% titanium and 10% titanium or less are preferred.
Titanium has a Zn content of 3 in the A g -Z n binary system.
At 6% or less, the β' phase (pink) changes over time and becomes β'.
→ It becomes a ζ phase, and the pink color becomes silvery white. Adding titanium has the effect of preventing this change over time. A particularly preferred amount of titanium is 0.2 to 7.5% by weight.

Furthermore, the high-temperature intermetallic compounds are stable, and the temperature at which the spectral reflectance changes, that is, the in-phase transformation point, can be controlled arbitrarily depending on the application, such as 1A or 2A.

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

An alloy containing a total of 15% by weight or less of one or more elements of groups 4B and 5B and rare earth elements is good. Specifically, the LA group elements include lithium, the 2A groups include magnesium and calcium, the 4A groups include zirconium and hafnium, the 5A groups include vanadium, niobium, and tantalum, the 6A groups include chromium, molybdenum, and tungsten, and the 7A groups include manganese and 8 The groups are cobalt, rhodium, iridium, iron, ruthenium, osmium, nickel, palladium, platinum, I
Group B is steel, gold, Group 2B is cadmium, Group 3B is boron,
Aluminum, gallium, indium, group 4B is carbon,
Particularly preferred are silicon, germanium, tin, and lead, phosphorus, antimony, and bismuth for Group 5B, and yttrium, lanthanum, cerium, samarium, gadolinium, terephium, dysprosium, and lutetium as rare earth elements.

(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.In other words, the energy applied to a desired minute area allows the depth of only the desired area to be reduced. It is desirable that the foil be a non-bulk material that has a volume that can change to a crystal structure different from the reference crystal structure throughout. Therefore, in order to produce high-density information in a desired small area, a non-bulk material with a small heat capacity is required. , film, thin wire, powder, etc. are preferable. The recording density is 0.01 to 0.2 for producing information in a minute area such as 20 megabits/a# or more.
It is preferable to have a film thickness of μm. In general, intermetallic compounds are difficult to plastically work.

Therefore, foil, membrane 1. An effective way to make thin wires or powder is to directly rapidly cool and solidify the material from the gas or liquid phase to form it into a predetermined shape. These methods include PVD
method (vapor deposition, sputtering method, etc.), CVD method, and a member with high thermal conductivity that rotates molten metal at high speed. In particular, molten metal quenching method in which molten metal is poured onto the circumferential surface of a metal roll and rapidly solidified.
electroplating.

There are chemical plating methods, etc. 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 coating, it is best to use a binder that does not cause a reaction even when the powder is heated.Also, to prevent oxidation of the material due to heating,
It is also effective to coat the surface of a film or coating layer formed on the substrate.

The foil or thin wire is preferably formed by a molten metal quenching method, and preferably has a thickness or diameter of 0.1 m or less.

In particular, in order to produce foil or thin wire with a crystal grain size of 0.1 μm or less, a thickness or diameter of 0.05 m or less is preferable.

The powder is preferably formed by the Gaia atomization method in which molten metal is sprayed with a gaseous or liquid refrigerant and then poured into water for rapid cooling.The particle size is preferably 0.1 m or less, particularly ultrafine powder with a particle size of 1 μm or less. is preferred.

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.

(Structure) The alloy of the present invention has different crystal structures at high and low temperatures, and must have a composition of a quenched phase in which the crystal structure at high temperature is maintained at low temperature by quenching from high temperature, and is irregular at high temperature. It has a lattice crystal structure, but
For example, the quenched phase is preferably an intermetallic compound having a regular lattice.As the optical properties can be greatly changed, the alloy of the present invention is preferably an alloy that mainly forms this intermetallic compound.In particular, the entire alloy is made of metal. Preferably, the composition forms an intermetallic compound. This intermetallic compound is called an electronic compound, and especially a 3/2 electron compound (average outer shell electron concentration a
/a is around 372) alloy composition is good.

Further, the alloy of the present invention preferably has an alloy composition having in-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.

In addition, since the heat capacity of the film formed on the substrate is reduced, the film can be divided into the minimum size of the recording unit by etching or the like.

(Characteristic) The variable spectral reflectance alloy and recording material of the present invention are as follows.

At least two types of spectral reflectance in the visible light region can be formed 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 the spectral reflectance of a material having a crystal structure (structure) formed by non-quenching.

In addition, the difference in spectral reflectance obtained by quenching and non-quenching is preferably 5% or more, particularly preferably 10% or more.0 If the difference in spectral reflectance is large, it is easy to visually identify the color, It has remarkable effects in various applications 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, optical refractive index, optical polarization index, and optical transmittance, which can be changed reversibly in the same way as spectral reflectance, and can be used to change signals.

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

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 can be heated and rapidly cooled to partially or entirely change its physical or electrical properties such as spectral reflectance of electromagnetic waves, electrical resistivity, refractive index, polarization index, and transmittance due to a change in crystal structure. By utilizing changes in these characteristics, it can be used for elements such as recording, display, and sensors.

Electric energy in the form of voltage and current, electromagnetic waves (visible light, radiant heat) are used as a means of recording information, etc.

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 (DAC or compact discs), video discs, memory discs, etc. By using the alloy of the present invention in the recording medium of optical discs, playback-only type and additional recording type can be created. .

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 used as a base to locally heat the recording medium. 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, and a short wavelength laser is particularly preferable.6 Since the reflectance between the heated part and the non-heated part of the present invention is greatest at a wavelength around 500 nm or 800 nm, a laser beam having such a wavelength can be used for reproduction. Preferably, the same laser source is used for recording and reproducing, and another laser beam having a lower energy density than that for recording is irradiated for erasing.

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 of visible light, so it is possible to record characters, figures, symbols, etc. 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. A sensor using the alloy of the present invention, whose temperature at which it changes to a high-temperature phase is known in advance, is held in the temperature range to be measured.

Approximate temperature detection can be performed by maintaining an appropriate cooling phase through appropriate cooling.

(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. and forming a region having a crystal structure formed by the rapid cooling and forming a different spectral reflectance between the region having the crystal structure formed by the rapid cooling and the region having the crystal structure at the second temperature. It is in the manufacturing method of the alloy.

Furthermore, one aspect of the present invention provides that the entire surface of the alloy having the aforementioned chemical composition having a different crystal structure at a first temperature higher than room temperature and a second temperature lower than the first temperature in a solid state is heated at the first temperature. 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. be.

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

More preferably, it is 103° C./second or higher.

[Embodiments of the invention]

[Example 1] A g -35wt%Zn-Ti alloy was formed into a foil shape by a molten metal quenching method, and its color change, spectral reflectance, etc. were investigated. Ag, Zn35wt%, Ti1.7w2.8,3
．． The alloy containing 5 and 7.0 wt% was melted in an argon atmosphere and solidified into a rod shape of about 4 φ. Add this to 5~Lo
It was cut into pieces weighing approximately 1.5 g to prepare a mother alloy for rapidly cooling the molten metal.

For the molten metal quenching method, the master alloy is charged into an 8-quartz nozzle using a commonly known single roll type device, remelted, and then poured onto the outer periphery of a roll (300 φ) rotating at high speed to a thickness of 50 μm.
An Ag-Zn-Ti alloy foil with a width of 5 m was produced. This foil was heated in an electric furnace for 2 minutes at each temperature, then cooled with water, and the color change and spectral reflectance of the foil were measured. Figure 2 shows the color change of the foil after heating and quenching; the * mark is pink and the 0 mark is silvery white. The boundary of color change in the Ag-35% Zn alloy containing no Ti is 275° C., and this temperature hardly changes even if Ti is added.

Figure 3 shows the color of the pink foil when it was heat treated at temperatures below 200°C for 2 minutes and then air cooled.

The temperature at which the A g -35% Zn alloy that does not contain Ti changes from pink to silvery white is approximately 135°C;
This temperature does not change even if Ti is added. The above color change is thought to be caused by the β' phase, which caused the pink color due to rapid cooling from high temperature, and the change from pink to silvery white to be caused by the β'→ζ transformation.

Figure 4 shows 10% of Ag-35%Zn-3,5%Ti alloy foil.
450 and 600 nm showing spectral reflectance after 0 hours
A remarkable difference in reflectance is observed except in the wavelength region. The color change between pink and silvery white as described above occurs at 350℃ and 20℃.
By repeating heating and quenching at 0°C, the change occurred 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.

FIG. 5 shows the Ag-35Zn binary alloy and the Ag-35Zn of the present invention in the 830 nm wavelength region.

3.5 This figure shows the difference in spectral reflection between a foil that has changed to a pink color and a foil that has changed to a silvery white color as the Ti alloy changes over time. In the case of the Ag-35Zn binary alloy that does not contain Ti, the difference in spectral reflectance decreases over time.

This is because the β' phase (pink color) due to heating and rapid cooling changes from pink to six colors of silver over time, and the difference in spectral reflectance with the foil that changes to silvery white becomes smaller. .

On the other hand, Ti-added A g -35Z n -3,5
Ti alloys do not change over time, and the effects of Ti are produced.

[Example 2] An Ag-35% Zn-3,5% Ti alloy was melted in an argon atmosphere and solidified into a cylindrical shape with a diameter of about 120 mm. A disk with a thickness of 5 mm and a diameter of 100 mm 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 mm. The above alloy was deposited to a thickness of approximately 80 nm at a substrate temperature of 200°C and a sputter power of 150 mW. Sputter deposited. Ar gas was used at 20 mTorr. The film surface was further coated with Al1,0. Or S i Ol
was deposited to a thickness of about 20 nm as a protective film.

In the sputter-deposited state, the film was silvery white. When this substrate was heat treated at 350° C. for 2 minutes and then cooled with water, it turned pink. When this was further heat-treated at 200° C. under the same conditions, the color returned to silvery white. In this way, the sputtered film also showed the same color change as the foil.

[Example 3] Ag-35%Zn produced by the same method as Example 2
Recording, reproduction, and erasing were performed on the -3.5% Ti sputtered film using laser light. As a laser beam, a semiconductor laser (wavelength 830 nm) or an Ar laser (wavelength 488 nm) is used.
was used. Laser light beam.

As a result of scanning the silvery-white film surface with a power of 10 to 50 mW on the film surface and a beam source varying from about 1 μm to about 10 μm, a line that turned pink 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 are drawn and a semiconductor laser is scanned across the lines, the reflectance changes, resulting in approximately 20
It was possible to convert the color change into an electrical signal as a change in DC voltage level of %.

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

[Brief explanation of drawings]

Figure 1(a) is an equilibrium phase diagram of the Ag-Zn binary system, Figure 1(b) is an explanatory diagram showing the principle of recording and erasing by the heating and quenching process of the alloy of the present invention, and Figures 2 and 3 are Characteristic diagrams showing color changes due to heat treatment of the molten rapidly cooled Ag-Zn-Ti alloy foil of the present invention. Figure 4 shows pink color (air cooled at 350°C for 2 minutes) and silvery white (2 complete water cooling at 350°C → 200°C for 2 minutes). It is a diagram showing the spectral reflectance of A, -35% Z n -3,5% Ti alloy foil which has been air-cooled. Figure 5 shows A g -35Z n
FIG. 2 is a characteristic diagram showing changes in spectral reflectance difference over time between a binary alloy and an Ag-35Zn-3,5Ti alloy.

Claims (1)

[Claims] 1. The main component is silver, 30 to 46% zinc and 10% or less titanium, and 1A, 2A, 4A, 5A, 6A, 7A,
A variable spectral reflectance alloy comprising an alloy containing a total of 15% or less of one or more of Group 8, 1B, 2B, 3B, 4B, 5B, and rare earth elements. 2. A part of the alloy surface having a different crystal structure at a first temperature higher than room temperature and a second temperature lower than the first temperature in the solid state is formed by rapid cooling from the first temperature. having a crystal structure different from the crystal structure at the second temperature,
2. The variable spectral reflectance alloy according to claim 1, wherein the other alloy has a crystal structure at the second temperature and has a spectral reflectance different from that of the rapidly cooled crystal structure. 3. The variable spectral reflectance alloy according to claim 1 or 2, wherein the alloy contains an intermetallic compound. 4. The variable spectral reflectance alloy according to any one of claims 1 to 3, wherein the first temperature is higher than a solid phase transformation point. 5. The difference between the spectral reflectance of the material having a crystal structure formed by the rapid cooling and the spectral reflectance of the material having the crystal structure at the low temperature formed by non-quenching is 5% or more. Claims 1 to 4, which are
The variable spectral reflectance alloy according to any one of the items. 6. Claim 1, characterized in that the spectral reflectance of the alloy is 10% or more at a wavelength of 400 to 1000 nm.
The variable spectral reflectance alloy according to any one of Items 1 to 5. 7. The variable spectral reflectance alloy according to any one of claims 1 to 6, wherein the alloy is a non-bulk material. 8. Any one of claims 1 to 7, wherein the alloy has a crystal grain size of 0.1 μm or less.
The variable spectral reflectance alloy described in . 9. The variable spectral reflectance alloy according to any one of claims 1 to 8, wherein the alloy is any one of a thin film, foil, strip, powder, and thin wire. 10. Silver as the main component, 30 to 46% zinc and 10% or less titanium by weight, 1A, 2A, 4A, 5A, 6A, 7A
, 8, 1B, 2B, 3B, 4B, 5B groups, and rare earth elements in a total of 15% or less. 11. An alloy having different crystal structures in a solid state at a first temperature higher than room temperature and a second temperature lower than the first temperature, wherein at least a part of the alloy surface is at the first temperature. 11. The recording material according to claim 10, wherein the recording material has an alloy composition that forms a crystal structure different from the crystal structure at the second temperature when quenched from the temperature. 12. It is a foil or thin wire formed by pouring the molten metal of the alloy onto the circumferential surface of a roll made of a rotating highly thermally conductive member, according to claim 10 or 11. Recording materials. 13. The recording material according to claim 10 or 11, which is a thin film formed by depositing the alloy by vapor deposition or sputtering. 14. The recording material according to claim 10 or 11, which is a powder obtained by spraying the molten metal of the alloy using a liquid or gas cooling medium.