JPS61131235A - Information recording method - Google Patents

Abstract

PURPOSE:To improve reproducting sensitivity and facilitate rewriting by setting the spectral reflection factor of a recording part in a state obtained by quenching higher after high-energy application than in low-energy application. CONSTITUTION:When information is recorded on a recording medium which has different crystal structures in a cooling state after specific-intensity high energy is applied and in a cooling state after energy with lower intensity is applied, the spectral reflection factor in the cooling state after the high energy is applied is set higher than that in the cooling state after the low energy is applied. The recording medium has at least two kinds of reflection factors at the same temperature according to energy applied in a solid state and varies in spectral reflection factor reversibly; the spectral reflection factor RW in the cooling state, specially, after the high energy is applied is set higher than the reflection factor RE after the low energy is applied. Further, when RE<RW<gammaRE +(1-gamma), the recording and erasure of the recording medium are possible (gamma : effective energy ratio required to obtain a high and a low reflection factor state).

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a novel information recording method, in particular a method in which the spectral reflectance in a state in which high energy is applied changes higher than the spectral reflectance in a state in which low energy is applied. The present invention relates to an erasable information recording method for recording information.

[Background of the invention]

In recent years, as information recording becomes more dense and digital, various information recording and reproducing methods are being developed. In particular, optical discs that use laser light energy to record, erase, and reproduce information are capable of higher recording densities than magnetic discs, as stated in the Mining Rare Metals ISO, 1983 (Optical discs and materials), and future information This is a powerful method of recording. Among these, laser playback devices have been put into practical use as compact discs (CDs).

Recordable formats can be broadly divided into two types: write-once type and rewritable type. The former can only be soaked once and cannot be erased. The latter is a method that allows repeated recording and erasing.

In the write-once type recording method, a laser beam is used to destroy or shape the recording portion of the medium to create unevenness, and for reproduction, a change in the amount of light reflected due to the interference of the laser beam at the uneven portion is used for reproduction.

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

This method utilizes optical energy to invert and record the local magnetic anisotropy of the medium near the carry point or compensation point temperature, and the polarization plane of the polarized incident light at that part due to the magnetic Faraday effect and magnetic Kerr effect. Play with the amount of rotation.

This method is also promising in terms of the amount of rewritable data, and active research and development is underway with the aim of putting it into practical use in the next few years. However, there is currently no material that has a large amount of rotation of the plane of polarization, and even with various efforts such as multi-acoustic membranes, the S/N and C/
There is a big problem that the output level of N etc. is small.

Other rewritable systems utilize reflectance changes due to reversible phase changes between amorphous and crystalline recording media.

For example, National Technical Rep.
ort Vol.

29, A5' (1983) p. 82, a thin film of TeOx doped with a small amount of germanium (Ge) and (Sn) is made amorphous by irradiation with a laser beam of high power density and short pulses, and becomes laser beam-resistant. It is used by irradiating it with a low-strength laser beam to crystallize it and make it have a higher reflectance than the recording part.

In the case of recording in a state where the reflectance is low, for example, if dirt or dust adheres to the disk, these will work to lower the reflectance. Therefore, the signal level of the recorded signal will be lowered due to dirt, dust, etc.

[Purpose of the invention]

An object of the present invention is to provide an information recording method that uses a recording medium that utilizes crystal structure changes, has high reflectance after high energy input, and enables highly sensitive reproduction.

[Summary of the invention]

The present invention provides a method for recording on a recording medium having different crystal structures in a state in which high energy of a predetermined intensity is applied and then cooled, and a state in which low energy with an intensity lower than the intensity is applied and cooled. There is an information recording method characterized in that information is recorded by changing the spectral reflectance in a state where the information is cooled after being inputted to be higher than the spectral reflectance in a state where the spectral reflectance is cooled after being inputted with low energy.

The recording medium according to the present invention has at least two types of reflectance at the same temperature by inputting energy in a solid state, and can reversibly change the spectral reflectance. It is a recording medium whose spectral reflectance in a state where it is cooled after being charged with low energy can change higher than the reflectance in a state where it is cooled down after being charged with low energy.

In addition, in the present invention, the reflectance RW after high energy input is
In a recording medium in which the reflectance RΣ is larger than the reflectance RΣ after low energy input, Rx<RW<γRz+(1-r), O<7"<1-"
(1) When formula (1) is satisfied, the recording medium becomes recordable and erasable. However, γ is the ratio of effective energy required to obtain a low reflectance state and a high reflectance state.

This relationship can be derived as follows. That is, there is a relationship expressed by equation (2) between the energy P input from the outside and the effective energy Q actually input into the medium.

P(1-几)=Q ・・・・・・(2)
In a medium with a low reflectance, the PR energy is reflected,
It is not actually put into the media. Therefore, equation (3) holds true between the high reflectance RW when high energy is input and the low reflectance Rm when low energy is input.Here, since Pw>Pz, equation (1) is obtained from equation (3). can get.

The range obtained from equation (1) is shown in FIG. The shaded area in FIG. 1 is the state in which recording and erasure are possible.

In this case, considering that the playback output will be good, R
It is desirable that the difference in reflectance between W and RE is large. ! In the case of RW≧1.3 Rv, particularly good reproduction output can be obtained and a large S/N ratio can be obtained. This range is shown by the light section in Figure 1. Although r is the ratio of Q and Qw, it can be substantially approximated to the heating temperature of the recording medium at which the reflectance of 'RW and R, w collapses. It can be approximated as a temperature that can substantially cause a change in reflectance.

The recording medium of the present invention is suitable for materials that satisfy the above relationship, but among these materials, materials having a crystal-crystal phase transition are also suitable.

The recording medium of the present invention is preferably made of an alloy of at least one element selected from Group Ib elements of the periodic table and at least one element selected from Group 11) Group B, Group IIb, and Group Vb. . Among these alloys, copper is the main component, A,! ,
Alloys with Ga, In, ()e, and Sn are preferred, and alloys containing Ni, Mn, Fe, and Cr as third elements in these alloys are also preferred.

Further, alloys containing silver as a main component and containing At, Cd, and Zn are preferable, and Cu, Cu, and Zn are further added to these alloys as a third element.
An alloy containing At and Au is preferred.

An alloy containing gold as a main component and containing At is preferable.

The alloy of the present invention includes the above-mentioned group Ib elements, group Hb, [[group b].

(2) Those having intermetallic compounds with group b and group Vb elements are preferred.

That is, the alloy according to the present invention has phases with different crystal structures in at least two temperature regions in a solid state, and can exhibit at least two different reflectances at the same temperature by heating and cooling in the solid state. The reflectance can be changed reversibly.

The present invention can be applied to a device in which a thin film of a recording medium is provided on a substrate provided with tracking grooves.

The recording medium has different crystal structures in a solid state at a first temperature higher than room temperature (high temperature) and at a temperature lower than the first temperature (low temperature), and is in an equilibrium phase at room temperature by rapid cooling from the high temperature. A metal or an alloy having a crystal structure different from the crystal structure is preferred.

The alloy according to the present invention has a spectral reflectance of at least 2 products at the same temperature by rapid cooling from a high-temperature solid state, and can reversibly change the spectral reflectance. 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 second spectral reflectance changes by heating and cooling in the temperature range where the high temperature phase is rapidly cooled. It changes reversibly.

The principle of the reversible change in reflectance according to the present invention will be explained using FIG. 7. The figure is a phase diagram of an X-Y binary alloy, in which an α solid solution and β, r intermetallic compounds exist. Taking an alloy with composition A as an example, this alloy has a β single phase, a (β+r) phase, and an (α+γ) phase in the same phase state. The crystal structure is different in the single phase state of α, β, and r, and the optical properties, such as spectral reflectance, are different in each of these single phases and mixed phases. In such alloys, the (α+γ) phase is stable at T1 temperature, 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 temperature below T, 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 spectral reflectance.

Examples of the alloy of the recording medium of the present invention are as follows.

Alloy containing silver as the main component, 30-46 wt% zinc, 6-1Qwt% aluminum, copper as the main component, 10-20wt% aluminum, 20-dQw indium
An alloy containing one of the following: 16 to 35 wt % of tin, an alloy containing gold as a main component and 2.5 to 5 wt % of aluminum, or a small amount of 1, Ib, Ib, II [b,
■b, vb.

(1) It can contain one or more of the elements of group (1)a and (2) group a. Its content is preferably 10wt or less.

The recording density is between 0.01 and 0.01 to produce information in a micro area of 20 megapixels/cm2 or more.
The film thickness is preferably 2 μm. It is effective to form the recording layer into a predetermined shape by directly rapidly cooling and solidifying it from the gas or liquid phase. 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, there are a molten metal quenching method in which molten metal is poured onto the circumferential surface of a metal roll and rapidly solidified, electroplating, chemical plating, and the like. When using powdered materials, the base □
It is effective to apply it on a plate 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 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 σ1 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. Substitution rings allow for easy control of the target alloy composition.

(Applications) Electrical energy in the form of voltage and current, electromagnetic waves (visible light, radiant heat, infrared rays, ultraviolet rays, photographic flash lamp light, electron beams, proton beams, argon lasers, semiconductor lasers) as a means of recording information, etc. (e.g., laser beams, heat, etc.), and it is particularly preferable to use it for optical discs that take advantage of changes in spectral reflectance caused by irradiation. Optical discs include digital audio discs (DAD or compact discs), video discs, memory discs, etc., and can be used for these. The recording medium of the present invention can be used in read-only type, additional recording type, and rewritable type disk devices, and is particularly effective in rewritable type disk devices.

An example of the principle of recording and reproducing an optical disc according to the present invention 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. Information can be reproduced by recording locally using a low-temperature phase during high-temperature curing, and by irradiating the recorded portion with light and detecting the difference in optical properties 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.

The reflectance of the heated part and non-heated part of the present invention is 500 nm
It is largest at a wavelength around 800 nm, so it is preferable to use a laser beam having such a wavelength 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.

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. . This information can be erased, and in addition to being recorded and erased repeatedly, it is also possible to store it permanently.

[Embodiments of the invention]

(Example 1) A recording medium having a thickness of about 10 mm was fabricated on a 5 tot glass substrate having a thickness of 1 or 2 rrm t by sputtering. This 2
The layer film was recorded using a laser beam from the recording medium film side, and then erased. After recording and erasing, 200~
An example of the spectral reflectance at a wavelength of 1500 nm is shown in FIG. 2, and Table 1 shows the results of measuring the reflectance (h) of various alloy thin films during recording and erasing at a light source wavelength of 830 nm. A high recording temperature corresponds to inputting high energy, and a low erasing temperature corresponds to inputting low energy, but all the alloy thin films shown in Table 1 satisfied the recording and erasing conditions. Alloy compositions in the table are in weight percent. The power of the laser beam was adjusted so that the recording temperature was 350c, and the erasing temperature was adjusted by defocusing the laser beam so that it was 1'50tZ'. According to this embodiment, a high S/N ratio can be obtained.

(Example 2) A disk was produced with the film configuration shown in Table 2 using an A, g-40Wt'% Zn alloy thin film as a recording medium. Recording and erasing were performed using a semiconductor laser with a wavelength of 830 nm, and the reflectance after recording and erasing was measured at a light source wavelength of 83 Q nm. The results are shown in FIG. 3, and the recording and erasing conditions were satisfied for volumes 1 to 12. Among these, especially J
Optimal characteristics were shown from f6.8 to A12. In addition, j
f613 satisfied the recording conditions but did not satisfy the erasing conditions. However, even in this case, Ta20116! can be used as a laser beam interference film! :I If the thickness of the film is modified to create a situation like A5, the erasing condition can be satisfied. In this case, by optimizing the film thicknesses of 'ra and o, it was possible to cause interference as shown in FIG. 4 and reduce the reflectance after recording and erasing. In addition, A10 to 1 of Table 2
The Cr OX film shown in Table 12 as the heat absorption film satisfies the recording and erasing conditions due to the effect of lowering the reflectance and the effect of heat absorption, as shown in FIG.

The recording and erasing temperatures were controlled by adjusting the laser beam so as to maintain the same temperature as in Example 1.

(Example 3) Glass with a diameter of 1.2 mm was used as the substrate, and glass with a diameter of 7 mm was used as the recording film.
An Ag-40 wt% Zn film with a thickness of 0 nm was used as a heat absorption layer, and a transparent layer of CrOx with a thickness of 1 Q nm was used as a heat absorption layer.
A disk as shown in FIG. 6 with a thickness of 200 nm was prepared, and a recording medium formed on a glass substrate 1 using a semiconductor laser 5 was recorded and erased as described in the recording method of the present invention. As a result of repeated testing, it was confirmed that the initial characteristics were maintained without any problems even after repeated testing. In the figure, 1 is a glass substrate, 2 is a recording medium, 3 is a heat absorption layer, and 4 is a transparent layer as a protective film.

〔Effect of the invention〕

According to the present invention, it is possible to obtain an information recording method that has high sensitivity in reproduction and can be easily rewritten.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between spectral reflectance during recording and erasing, FIG. 2 is a diagram showing spectral reflectance characteristics according to the recording method of the present invention, and FIG. 3 is a diagram showing the relationship between recording and erasing of the alloy film according to the present invention. A diagram showing the relationship between spectral reflectance during erasing, FIG. 4 is a diagram showing spectral reflectance characteristics according to the recording method of the present invention with an interference film, and FIG. 5 is a diagram showing the recording of the present invention with a heat absorption film. 6 is a cross-sectional view showing an example of a disk used in the recording method of the present invention, and FIG. 7 is a diagram showing an example of the alloy of the recording medium used in the recording method of the present invention. FIG. 1... Substrate, 2... Recording medium, 3... Heat absorption layer,
4...Transparent layer, 5...Laser light.

Claims (1)

[Claims] 1. A method for recording information on a recording medium that has different crystal structures in a state in which it is cooled after inputting high energy with a predetermined intensity and in a state in which it is cooled after inputting low energy with an intensity lower than the intensity. . An information recording method, characterized in that the spectral reflectance of the recording portion in a state obtained by cooling after inputting high energy is made higher than the spectral reflectance in a state obtained by cooling after inputting low energy. 2. The information recording method according to claim 1, wherein the following relationship is satisfied between the spectral reflectance (R_W) of the recorded portion and the spectral reflectance (R_E) of the unrecorded portion. R_W<γR_E+(1-γ) (However, this is the ratio of input energy during recording to input energy during non-recording.) 3. Claim 2 that satisfies the relationship R_W≧1.3R_E Information recording method described. 4. The information recording medium according to any one of claims 1 to 3, wherein the recording medium is made of a metal or an alloy that forms a crystal structure different from an equilibrium phase at room temperature by rapid cooling from a high-temperature solid state. Method.