JPS61190027A - Alloy having variable spectral reflectance and recording material - Google Patents

Abstract

PURPOSE:To obtain a novel recording material applying a variable change of color or reflectance by transition between crystal structures by using an Au alloy contg. a specified amount of Cd and having variable spectral reflectance. CONSTITUTION:This alloy having variable spectral reflectance is an Au alloy contg. 40-60wt% Cd and having different crystal structures at the 1st temp. above room temp. and the 2nd temp. below the 1st temp. in the state of a solid soln. When part of the surface of the alloy is rapidly cooled from the 1st temp., the part has a crystal structure different from the crystal structure at the 2nd temp. The other part has the crystal structure at the 2nd temp. and is different from the rapidly cooled part in spectral reflectance. A novel recording material is made of the alloy having variable spectral reflectance.

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 Na.
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 allows writing only once and cannot be erased, while the latter 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. For this recording medium, it is generally known to use To or an alloy thereof, and to form irregularities by melting and sublimating the To. This type of medium has some problems such as toxicity. Magneto-optical materials are the mainstream for rewritable recording media, but the method uses optical energy to invert the local magnetic anisotropy of the medium at the Curie point or near the compensation point temperature, and record the area. Reproduction is performed using the amount of rotation of the plane of polarization due to the magnetic Faraday effect and magnetic Kerr effect of the polarized incident light. 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, National Tachnical
Report Vol. 129 & 5 (1983) describes an alloy in which small amounts of Ge and Sn are added to TaOx.

However, in this method, the crystallized portion of the amorphous phase is low.

The instability of the phase at room temperature is a major problem that 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%p
, n-(1-5) wt%Ni-remaining Cu, which takes advantage of the fact that it changes reversibly 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, it will undergo transformation 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. Can not,
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 consists of gold as a main component and 40 to 60% cadmium by weight.
Alloys containing 1A, 2A, and 4A.

5A, 6A, 7A, 8.1B, 2B, 3B, 4B.

The variable spectral reflectance alloy is characterized by being made of an alloy containing a total of 15% by weight or less of one or more of group 5B and rare earth elements. Cadmium is preferably 45 to 55%.

That is, 1 the present invention provides a first temperature higher than room temperature in a solid state (
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 at least two
It has phases with different crystal structures in two temperature ranges, and among these, 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 reversible change in reflectance of the alloy of the present invention will be explained with reference to FIG. The figure is a phase diagram of an X-Y binary alloy, in which an α solid solution and β and γ intermetallic compounds exist. Taking an alloy with composition A as an example, this alloy has the following properties in the solid state:
There are β single phase, (β+γ) phase and (α+γ) phase. The crystal structure is α, β.

The single phase state of γ is different, and the optical properties, such as spectral reflectance, are different in these single phase and mixed phase. Such alloys are stable in the (α+γ) phase at T, generally room temperature. When this is heated and rapidly cooled to T4 temperature, the β phase is rapidly cooled to T4 temperature. Since this state is different from the (α+γ) phase, the spectral reflectance is also different. When this rapidly cooled β-phase alloy is heated and cooled to a T2 temperature below the Ta temperature, the β phase transforms into an (α+γ) phase, and the spectral reflectance returns to its initial state. By repeating such two heating and cooling processes, it is possible to reversibly change the 1-spectral reflectance.

(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, gold is the main component and cadmium 4
Alloy compositions containing 0-60% are preferred.

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, 8.1B, 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, Group IA elements include lithium, Group 2A elements include magnesium and calcium, Group 4A elements include titanium, zirconium, and hafnium, Group 5A elements include vanadium, niobium, and tantalum, Group 6A elements include chromium, molybdenum, and tungsten, and Group 7A elements include manganese. , Group 8 is cobalt, rhodium, iridium,
iron.

Ruthenium, osmium, nickel, palladium.

Platinum, group IB is copper, silver, group 2B is zinc, group 3B is boron, aluminum, gallium, indium.

Group 4B is carbon, silicon, germanium, tin, lead, and 5B.
Particularly preferred are phosphorus, antimony, and bismuth, and among the rare earth elements are yttrium, lanthanum, cerium, samarium, gadolinium, terephium, dysprosium, and lutetium.

(Non-bulk and manufacturing method thereof) In order to obtain reflectance variability, the alloy of the present invention must be able to form a supercooled 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, it is desirable to be a non-bulk material having a volume that allows substantially only a desired area portion to change to a crystal structure different from the standard crystal structure throughout the depth by energy input to a desired minute area. In order to produce high-density information in a desired micro area, it is desirable to use non-bulk materials such as foils, films, thin wires, or powders, which have a small heat capacity. 0.01~0.2μ for information production
It is preferable to set the film thickness to m. Generally, intermetallic compounds are difficult to plastically work.

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

There are chemical plating methods, etc. When using a film or powder material, it can be formed directly on the substrate, but it is more effective 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 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 preferred.

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 thickness of 0.1 μI or less, and 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 alloy as a whole is composed of intermetallic compounds. This intermetallic compound, which preferably has a composition forming a compound, is called an electronic compound, especially a 3/2 electron compound (average outer shell electron concentration e /
An alloy composition having a value of around 372) 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.

Furthermore, since the heat capacity of the film formed on the substrate is reduced, the film can be divided into the smallest recording units 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.

In addition, the difference in spectral reflectance obtained by quenching and non-quenching is preferably 5% or more, particularly preferably 10% or more. 6. 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 and displaying various information such as characters, figures and symbols, 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 devices 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,
Proton beams, laser beams such as argon lasers, semiconductor lasers, heat, etc.) can be used, and it is particularly preferable to utilize changes in spectral reflectance due to irradiation as a recording medium for optical disks. There are digital audio disks (DAD or compact disks), video disks, memory disks, etc., and by using the alloy of the present invention in the recording medium of optical disks, playback-only type and 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 principles of recording and reproduction in which the alloy of the present invention is used in the 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, particularly a short wavelength laser beam. Since the reflectance of the heated part and non-heated part of the present invention is greatest at a wavelength around 500 nm or 800 nm, it is possible to reproduce a laser beam having such a wavelength. The same laser source is preferably used for recording and reproducing, and it is preferable to irradiate erasing with another laser beam having a lower energy density than that for recording.

Furthermore, 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. can. 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.

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 1] An A u -Cd alloy was formed into a foil shape by a molten metal quenching method, and its color tone change, 1-spectral reflectance, etc. were examined.

Various alloys containing 40 to 60 wt% of Cd in Au were melted in a high frequency furnace in an argon atmosphere, solidified into rods with a diameter of about 4 m, and cut into pieces with a weight of about 5 to Log to prepare master alloys for rapidly cooling molten metal. Similarly, 50wt%Cd, Mg, Ti, Hf
An alloy containing 1 wt % of , Age Cr, and Y alone was prepared.

A commonly known single roll type device was used for the molten metal quenching method. The master alloy is charged into a quartz nozzle, remelted, and poured onto the outer periphery of a roll (300 mm φ) rotating at high speed to a thickness of approximately 50 mm.
A ribbon-shaped foil with a width of 5 m and 9 μm was produced. This foil was heated in an electric furnace for 2 minutes at each temperature and cooled with water, and the color of the foil was observed. The color of the foils was clearly different between those heat-treated at temperatures above about 400°C and those heat-treated below. These were golden yellow at room temperature and hotter, and white at lower temperatures.

A sufficient difference in spectral reflectance from visible light to near-infrared light was observed between the high-temperature color and the low-temperature color. In addition, foil that has been rapidly cooled from a high temperature area (over 400°C) to change its color is
When heat treated at a relatively high temperature below 'C (over 150°C), the color changes to a low temperature color. Thereafter, by repeating rapid cooling from a high temperature and heating and cooling at a low temperature, the color of the foil at room temperature changed reversibly. It was also confirmed that by locally heating a portion of the foil with a lighter or burner, the two colors can coexist, and that it can also be used as a display element.

[Example 2] An alloy was melted and solidified in the same manner as in Example 1, and then molded into powder by machining. When this powder was subjected to the same heat treatment as in Example 1, almost the same reversible color change was obtained, and the powder also showed the same phenomenon as the foil.

[Example 3] A disk having a thickness of 5 Illll and a diameter of 1100 nm was cut out from an ingot that was melted in the same manner as in Example 1 and solidified into a cylindrical shape of about 120 waφ, and used as a target for sputter deposition.

A DC-magnetron type sputter deposition method was used, and a hard glass disk with a diameter of 26a1 and a thickness of 1.2 m was used as the substrate. Substrate temperature 200℃, sputter power 150
A thin film with a thickness of about 1100 nm was fabricated by sputter deposition under conditions of W and a gas (Ar) partial pressure of 20 mTorr. In addition,
A Q x is applied to the film surface by RF sputtering as a protective film
Oa or S i O.

was deposited to a thickness of about 50 nm.

This alloy thin film was subjected to the same heat treatment as in Example 1. As a result, the color of the thin film at room temperature showed a reversible change similar to that in Example 1 depending on the heating and quenching conditions, and the spectral reflectance in the visible light and near-infrared regions also changed accordingly. Therefore, it was found that even in such a thin film, there is a reversible change in color tone and spectral reflectance.

[Example 4] A sputter-deposited alloy film produced in the same manner as in Example 3 was recorded, reproduced, and erased using a laser beam. As the laser light, a semiconductor laser (wavelength: 830 nm) or an Ar laser (wavelength: 488 nm) was used. The thin film after the low-temperature heat treatment was irradiated with laser light at a film surface power of 10 to 50 mW and a beam diameter of about 2 to 10 μm. As a result, the irradiated area changed to a color corresponding to when it was heated and rapidly cooled to a high temperature (400° C. or higher). As a result of scanning a line with a laser beam in this way, scanning a low-power laser across the line, and converting the change in reflectance into a DC voltage, a voltage change corresponding to li was observed, and an electrical It was confirmed that this characteristic is possible.

The lines drawn in this way disappeared when the entire film was heated to about 150° C. or when it was irradiated with a laser beam of low power density.

From the above, it was confirmed that this alloy thin film could be recorded, reproduced, and erased by laser light.

In addition, the recording portion heated by the laser beam has a different height of the laser beam reflecting surface than the non-recording portion, and the reflectance of the two portions differs.

〔Effect of the invention〕

According to the present invention, a novel recording material based on an Au-Cd alloy that utilizes a reversible change in color or reflectance due to crystal-crystal correlation transition can be obtained.

[Brief explanation of the drawing]

Figure 1 (a) is a binary phase diagram regarding the Au-Cd alloy, and Figure 1 (b) is a diagram showing the principle of recording and erasure. Breathe U

Claims (1)

[Scope of Claims] 1. A variable spectral reflectance alloy characterized by containing gold as a main component and 40 to 60% by weight of cadmium. 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 the solid phase transformation point. 5. A patent claim in which the difference between the spectral reflectance of a product having a crystal structure formed by the rapid cooling and the spectral reflectance of a product having a crystal structure at the low temperature formed by non-quenching is 5% or more. The variable spectral reflectance alloy according to any one of the ranges 1 to 4. 6. The spectral reflectance of the alloy is at a wavelength of 400 to 1000 nm.
10% or more of the variable spectral reflectance alloy according to any one of claims 1 to 5. 7. Claim 1, wherein the alloy is a non-bulk material.
The variable spectral reflectance alloy according to any one of items 6 to 6. 8. The variable spectral reflectance alloy according to any one of claims 1 to 7, wherein the alloy has a crystal grain size of 0.1 μm or less. 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. Main component is gold, 40-60% cadmium by weight
and 1A, 2A, 4A, 5A, 6A, 7A, 8, 1B, 2
A variable spectral reflectance alloy comprising an alloy containing a total of 15% by weight or less of one or more of B, 3B, 4B, 5B groups, and rare earth elements. 11. A recording material comprising an alloy containing gold as a main component and 40 to 60% by weight of cadmium. 12. 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. 12. The recording material according to claim 11, having an alloy composition that forms a crystal structure different from the crystal structure at the second temperature when quenched from the recording material. 13. The recording material according to claim 11 or 12, which is a foil or thin wire formed by pouring the molten metal of the alloy onto the circumferential surface of a rotating roll made of a highly thermally conductive member. 14. Claim 11 or 12, which is a thin film formed by depositing the alloy by vapor deposition or sputtering.
Recording materials listed in Section. 15. The recording material according to claim 11 or 12, which is a powder obtained by spraying the molten metal of the alloy using a liquid or gas cooling medium. 16. Main component is gold, 40-60% cadmium by weight
and 1A, 2A, 4A, 5A, 6A, 7A, 8, 1B, 2
A recording material comprising an alloy containing a total of 15% by weight or less of one or more of B, 3B, 4B, 5B groups, and rare earth elements.