JPS6119748A - Spectral reflectance variable alloy and recording material - Google Patents

Abstract

PURPOSE:To enable the adaptation to a material capable of recording and erasing information, by preparing an alloy, which takes different spectral reflectances on the basis of the change in a crystal structure by quenching and heating, by compounding Cu and In being main component in a specific ratio. CONSTITUTION:A Cu-In alloy containing 20-40wt% of In is formed into a foil shape. This foil shows a light brown color and changes to a silver white color upon heating and air-cooling. When this silver white substrate is scanned by laser beam, a brown color line can be drawn on the silver white substrate. When this line part is irradiated with low output laser beam, the light brown color changes to the original silver white color. That is, this alloy has different crystal structures and spectral reflectances between first temp. higher than room temp. and second temp. lower than room temp. This change in the reflectance can be discriminated in a wavelength region excepting the vicinity of about 570 nm. The recording material utilizing this alloy is enabled in the recording and erasion of information and the operation thereof can be performed repeatedly.

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 erasure and playback is industrial rare metal A8.
0, 1983 (Optical Disks and Materials), it is possible to achieve a higher recording density 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 is used to destroy or shape the medium in the paper-recorded 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. Optical-air 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 compensation point temperature, and the polarized incident light is polarized at that part due to the magnetic 7 Alladay effect and magnetic Kerr effect. Play based on the amount of rotation of the surface. 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 'rechnica
lReport Vol 29 A 5 (1983)
There is an alloy in which small amounts of Ge and Sn are added to TeQx described in .

However, this method has a major problem in that the source of crystallization 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
It is 40845. This alloy is (12-15)wt%A
This is an alloy consisting of 4-(1 to 5) wt% Ni and residual 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 the temperature is maintained above the martensitic transformation temperature cannot be brought below the martensitic modulation temperature. Conversely, if a color tone obtained at a temperature below the martensite transformation temperature is heated to a temperature higher than the martensite transformation temperature, the color tone will undergo transformation and change to a different color tone. Therefore, the two color tones above and below the martensitic transformation cannot be obtained 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 has copper (Cu) as its main component and indium (I).
n) 20 to 40% by weight of a variable spectral reflectance alloy.

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 by heating and cooling treatment in a solid state, and the spectral reflectance can be changed reversibly. 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, the high temperature phase is quenched and the low temperature phase is a non-quenched standard state. The spectral reflectance is different, and the spectral reflectance changes reversibly by heating and cooling in the high temperature phase region and heating and cooling in the low phase temperature region. Also, by utilizing this reversible change,
Information such as one signal, one figure, one symbol, etc. can be recorded, reproduced, and erased, and it is effective as a recording material.

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 a Cu-In alloy. In the alloy with composition (A), there are two phase states in the solid phase state. That is, there are β single phase, β+δ phase, and α10δ phase. The crystal structure differs depending on the single phase states of β, α, and δ, and therefore, although it is natural when these are used alone, their optical properties also change depending on their mixed phase. Optical properties also change due to differences in crystal structure. Spectral reflectance will be explained as a difference in optical properties due to a difference in crystal structure. TI means the temperature at which what is recorded can be read, and it can be considered room temperature.In the equilibrium state at T1, δ-richα+
Since it is a δ phase, the spectral reflectance of the alloy is close to δ. This is T
When heated to 4 and rapidly cooled, the β phase is maintained at T1. ,
The spectral reflectance of the β phase at T1 is different from that of the α+δ phase.

Therefore, both phases can be distinguished. To describe general color tone characteristics, the β phase at T1 when rapidly cooled after holding is a pale reddish copper color, and the α+δ phase is silvery white. That is, α+
For example, the alloy in the δ phase state is irradiated with a laser beam having a diameter of several μm to locally heat it to T4, and then the laser irradiation is stopped. The irradiated area is rapidly cooled, and in TI, only the laser irradiated area becomes β phase. Since the portion that is not irradiated with the laser remains in the α+δ phase, the spectral reflectance of the laser irradiated portion differs from that of the other portions in TI, making it possible to distinguish between the two. This state corresponds to the recording state. On the other hand, if the β-phase state held at T1 is heated to T2 higher than T1 by rapid cooling after heating to T4, the β phase changes to α+β phase, and even if the temperature is returned to TI, the α+β phase remains. Therefore, when a laser beam is irradiated to a portion locally made into a β phase by laser irradiation and heated to a temperature of T2 as described above, the β phase changes to an α+δ phase. Even after the temperature is returned to T1, the α10δ phase state is maintained. In other words, this corresponds to erasure. Note that in order to change the β phase to the α+β phase, it is sufficient to heat it to a temperature higher than T1, but the upper limit temperature is the temperature at which the β phase does not precipitate while being maintained at a high temperature, Te in Fig. 1, that is, This is the eutectoid temperature. The above process can be repeated and can be applied as a so-called rewritable recording medium.

Another recording method uses a sample in a β-phase state at a temperature Tl. When this is irradiated with a laser beam having a diameter of, for example, several μm and heated to T2, the laser irradiated part changes to an α+β phase. Even after cooling to a temperature of T1, the laser irradiated part is in the α+β phase, which can be distinguished from the β phase in the non-laser irradiated part by having a different spectral reflectance. Therefore, it can be recorded. Erasing can be done by heating the entire surface of the sample to T2 and then cooling it. This is because when such a treatment is performed, the entire surface changes to α+β phase at temperature T1.

(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. The alloy in which a supercooled phase is formed by rapid cooling from a high temperature must contain from 40% by weight of In2O, preferably from 25 to 35% by weight.

(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. 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 minute area, non-bulk materials such as foils, films, thin wires, or powders with low heat capacity are desirable. The recording density is 20 m□gabits/cr! To produce information in a micro area such as the above, 0.01~
The film thickness is preferably 0.2 μm. 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 PVD method (vapor deposition, sputtering method, etc.),
There are CVD methods, molten metal quenching methods in which molten metal is rotated at high speed and made of a member having high thermal conductivity, especially by pouring the molten metal onto the circumferential surface of a metal roll and rapidly solidifying it, electroplating, and chemical plating methods. If a film or powder material is used (3.1), 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 foil or thin wire is preferably formed by a molten metal quenching method, and preferably has a thickness or diameter of 0.1 wax or less.

In particular, for producing foil or thin wire with a crystal grain size of 0.1 μm or less, a thickness or diameter of 0.05 mm or less is preferred.

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 0.1 rtm 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.

In addition, it is recommended that the film formed on the substrate be divided into pieces as large as recording units by etching to reduce the heat capacity of each film.

(Structure) The alloy of the present invention has different crystal structures at high and low temperatures, and must have a composition of an undercooled phase that maintains the crystal structure at high temperature at low temperature by rapid cooling from high temperature. At high temperatures, it has an irregular lattice crystal structure, but
The supercooled phase is preferably an intermetallic compound having a cs-ct type or DOs type regular 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, and those having an alloy composition close to a 3/2 electron compound (average outer shell electron concentration e/a of 3/2) are particularly good.

Further, the alloy of the present invention preferably has an alloy composition having solid phase transformation, particularly eutectoid transformation, and the alloy has 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.

(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, optical refractive index, optical polarization rate, optical transmittance, etc., which can be changed reversibly in the same way as spectral reflectance.
It can be used as a regeneration and detection means for sensors, etc.

Spectral reflectance is related to the surface roughness of the alloy, so
As mentioned above, it is preferable that at least the target portion has a mirror surface so that the surface has a mirror surface of at least 10% in the visible light region.

(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.

As a means of recording information, etc., electrical energy in the form of voltage and current, electromagnetic waves (visible light, radiant heat, infrared rays, ultraviolet rays, light from photographic flash lamps, electron beams, proton beams, lasers such as argon lasers, semiconductor lasers, etc.) are used. (light, heat, etc.), and it is particularly preferable to utilize the change in spectral reflectance caused by the irradiation for use in optical disc recording media. Optical discs include digital audio discs (D
AD or compact discs), video discs, memory discs, etc., and can be used for these. By using the alloy of the present invention in the recording medium of an optical disc, it can be used in read-only type, additional recording type, and rewritable type disc devices, and is particularly effective in rewritable type disc 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 friend 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 of the heated portion and non-heated portion of the present invention is large at wavelengths around 500 nm or Fi800 nm, it is preferable to use laser light having such wavelengths for reproduction.

It is preferable that the same laser source be used for recording and reproducing, and for erasing, a different laser beam having a lower energy density than that for recording is irradiated.

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 identified visually. . 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 hotbed detection can be performed by holding a centimeter in the temperature range to be measured using the alloy of the present invention, whose temperature at which it changes to a high temperature phase is known in advance, and maintaining an 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 different crystal structure at a second temperature lower than the temperature of spectral reflectance, characterized in that a region having a crystal structure formed by the quenching and a region having a crystal structure at the second temperature form different spectral reflectances. It is in the manufacturing method of variable alloys.

Furthermore, the present invention provides a method for applying the first temperature to the entire surface of the alloy having the chemical composition described above, which has 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. to form a crystal structure different from the crystal structure at the second temperature, and then heat a portion 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.

Is the cooling rate from the first temperature 102t? /second or more, more preferably 10"tl:'/second or more.

[Embodiments of the invention]

(Example 1) A ribbon with a thickness of approximately 40 μm was prepared by making a Cu-31 wt % In alloy into a molten state and pouring the molten metal onto the outer periphery of a roll rotating at high speed, which is the so-called liquid quenching method. did. The ribbon was a pale coppery color at room temperature. When this ribbon was heated for 55,002 ml and then air cooled, the color changed to silvery white. Furthermore, this ribbon is 65002
When heated and cooled with water, the color tone changed to a light reddish copper color. As a result of measuring the spectral reflectance of both of them, as shown in FIG. 2, each exhibited a unique change in reflectance, and it was possible to distinguish them in the wavelength range except around 57 Q nm. Thereafter, even if these two heating and quenching processes were repeated, this difference hardly changed, and the reproducibility of the reversible change was confirmed.

(Example 2) A 50 nm thick alloy thin film having the same composition as in Example 1 was prepared on a glass substrate by sputter deposition, and At503 or 8iCh was coated thereon as a protective film to a thickness of 5Q nm by sputter deposition. The produced film exhibited a pale reddish copper color. Next, this film was heated to 55 CI' for 2 minutes and air cooled, resulting in
The color tone changed to silvery white. This spectral reflectance was almost the same as the result shown in FIG. A semiconductor laser with a spot diameter of approximately 2 μm is applied to a sample whose entire surface is silver-white with an output of 30 m.
Scanning was performed at W or less. As a result of observing the laser irradiated area at room temperature, it was found that a thin copper-colored line with a width of about 2 μm was drawn on the silver-white base. That is, it was confirmed that the color was changed by local heating with laser light, and that laser irradiation was recorded by the color change. Next, reduce the laser power or
When the laser beam was irradiated onto the discolored area while the focus of the laser beam was slightly shifted from the film surface, the line portion that had changed to a pale reddish copper color reversibly changed to the silvery white color of the base. That is,
It was confirmed that it was possible to erase what was recorded in a pale reddish copper color. It was also confirmed that this reversible change is possible even if it is repeated thereafter.

It was confirmed that the above results can also be obtained using an Ar laser.

(Example 3) A semiconductor laser (output 20 mW) was applied to a sample prepared in the same manner as in Example 2, that is, a sample whose entire surface was a pale copper color at room temperature.
was scanned. The laser scanning part turned silvery white at room temperature and could be distinguished from the color of the base.

In other words, laser recording was possible. Thereafter, when the whole was heated to 550C for 2 minutes, the whole turned silvery white, and the recorded portion could be erased.

The results obtained on tatami could also be achieved using an At laser.

[Effect of Gyomei]

According to the present invention, it is possible to obtain an alloy whose spectral reflectance is variable based on a phase change between sand crystals and crystals when thermal energy such as light is applied.

[Brief explanation of the drawing]

Figure 1 is a schematic binary alloy phase diagram showing changes in crystal structure due to phase transformation of Cu-In alloy, and Figure 2 is a diagram of the Cu-In alloy of the present invention.
-1l121 Cu-r/? showing the spectral reflectance of In alloy foil. No 1
2 Figure epithelium long (ga angle)

Claims (1)

[Scope of Claims] 1. An alloy with variable spectral reflectance, characterized in that it consists of an alloy containing copper as a main component and 20 to 40% indium. 2. A part of the alloy surface that has a different crystal structure at a first temperature higher than room temperature and at a second temperature lower than the first temperature in a solid state is quenched by rapid cooling from the first temperature. It has a crystal structure different from the crystal structure at the temperature of 2,
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. An alloy consisting of an alloy containing copper as a main component and 20 to 40% by weight of indium, which has a different crystal structure in a solid state at a temperature higher than room temperature and at a second temperature lower than the first temperature. A region having a crystal structure different from the crystal structure at the second temperature is formed on a part of the surface by being rapidly cooled from the first temperature, and a region having the crystal structure formed by the rapid cooling and the second 1. A method for producing an alloy with variable spectral reflectance, characterized in that different spectral reflectances are formed in regions having a crystal structure at a temperature of . 11. An alloy consisting of an alloy containing copper as a main component and 20 to 40% by weight of indium, which has different crystal structures in a solid state at a first temperature higher than room temperature and at a second temperature lower than the first temperature. The entire surface is rapidly cooled from the first temperature to form a crystal structure different from the crystal structure at the second temperature, and then a portion of the alloy surface is heated to the second temperature to form the second crystal structure. A region having a crystal structure at a temperature of A method for manufacturing alloys with variable spectral reflectance. 12. A recording material comprising an alloy containing copper as a main component and 20 to 40% by weight of indium. 13. 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. 13. The recording material according to claim 12, having an alloy composition that forms a crystal structure different from the crystal structure at the second temperature when quenched from the recording material. 14. The recording material according to claim 12 or 13, 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. 15. Claim 12 or 13, which is a thin film formed by depositing the alloy by vapor deposition or sputtering.
Recording materials listed in Section. 16. The recording material according to claim 12 or 13, which is a powder obtained by spraying the molten metal of the alloy using a liquid or gas cooling medium.