JPH0448113B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for recording and erasing information using a new recording medium for an information recording/reproducing device, and in particular, the present invention relates to a method for recording and erasing information using a recording medium for an information recording/reproducing device. The present invention relates to a method for recording and erasing information using an information recording/reproducing device that utilizes changes in spectral reflectance due to changes in structure.

[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 disks that use laser light energy to record, erase, and reproduce information are capable of higher recording densities than magnetic disks, as stated in Industrial Rare Metal No. 80, 1983 (Optical Disks and Materials). This is a promising method for recording information 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 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 that Te or its alloy is used 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 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 Faraday effect and magnetic force 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 efforts such as multilayer film formation, there is a major problem in 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
Described in Technical Report Vol. 29 No. 5 (1983)
There is an alloy in which small amounts of Ge and Sn are added to TeOx.

However, this method has a major problem in that the crystallization temperature of the amorphous phase is low and the instability of the phase at room temperature is linked to the reliability of Dake.

On the other hand, as an alloy that utilizes color tone change,
There is 57−140845. This alloy is (12-15) wt%
It is an alloy consisting of Al-(1 to 5)wt% Ni-remaining Cu, and 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 maintained below the martensitic modulation temperature. Conversely, if a color tone obtained at a temperature below the martensitic transformation temperature is heated above the martensitic transformation temperature, the color tone will undergo transformation and change to a different color tone. Therefore, the two color tones occurring above and below the martensitic transformation cannot be obtained simultaneously at the same temperature. Therefore, this principle cannot be applied as a recording material.

[Purpose of the invention]

An object of the present invention is to provide a method for recording and erasing information using an information recording medium equipped with a recording layer that utilizes a phase change between crystals with high energy incidence efficiency.

[Summary of the invention]

(Summary of the Invention) The present invention provides an optical recording medium having a recording layer made of an alloy and a layer that reduces the surface reflectance of the recording layer.
A method of recording or erasing information by irradiating light energy and heating the recording layer, the light energy being incident on the recording layer through a layer that reduces the surface reflectance of the recording layer. a first crystal formed by heating to a high phase temperature region and rapidly cooling; and the first crystal formed by heating and cooling to a low phase temperature region and having an intermetallic compound. Information is recorded or erased by reversibly changing the phase of the recording layer with a second crystal different from the recording layer and changing the reflectance of the alloy forming the recording layer. .

As the layer for reducing the surface reflectance of the recording layer, it is preferable to use at least one of an absorption layer and an interference layer.

If the reflected energy from the information recording medium can be reduced by some means, the amount of heat input to the recording layer will increase, the temperature of the recording layer will rise rapidly, and high-speed writing will be possible, as well as writing with less incident energy. Alternatively, since erasing becomes possible, the writing sensitivity or erasing sensitivity of the information recording/reproducing medium increases.

(Absorption Layer, Interference Layer) As shown in FIG. It is absorbed and changed into thermal energy, and the temperature of the absorption layer 3 rises rapidly. As a result, much thermal energy is transferred from the absorption layer 3 to the recording layer 1 by thermal conduction, and the temperature of the recording layer 1 also decreases.
The temperature rises rapidly and to a higher temperature than in the case without the absorption layer 3. The thickness of this absorption layer 3 is determined by the surface reflectance (reflected energy/
It is desirable that the thickness be such that the ratio of incident energy is 5% to 80%. When the reflectance is less than 5%,
Since the intensity of the reflected light decreases, the signal-to-noise ratio (S/N ratio) during playback of the recorded signal, in which the recorded signal is read by comparing the reflected light intensity of the recorded and unrecorded areas, deteriorates, which is disadvantageous. be. Furthermore, when the reflectance exceeds 80%, most of the incident energy is reflected by the absorption layer 3 without being converted into thermal energy, so that the temperature of the absorption layer 3 does not rise. As a result, almost no thermal energy is transmitted to the recording layer 1, and no increase in the writing sensitivity or erasing sensitivity of the information recording/reproducing medium can be expected. As an absorption layer, it converts electromagnetic waves (for example, laser light/light) into thermal energy.

One way to reduce the surface reflectance of an information recording/reproducing medium is to utilize the interference effect of incident energy.

Preferably, the film is made of tantalum oxide, alumina, or the like and has an energy transmittance of 50% or more. Its thickness is
50 to 500 nm is preferable, and colorless is preferable. For example, if a colorless and transparent interference layer 2 of an appropriate thickness is provided on the energy incident side of the recording layer 1 as shown in FIG. The remaining incident energy penetrates into the interference layer 2 and reaches the recording layer 1. Some percentage of this incident energy is reflected by the surface of the recording layer 1, passes through the interference layer 2 in the opposite direction, and reaches the surface of the interference layer 2. At this time, if the incident energy has wave properties like electromagnetic waves, the reflected energy waves on the surface of the interference layer 2,
Energy waves reflected from the surface of the recording layer 1 cause interference. When the phases of the two energy waves are shifted by half the wavelength of the energy waves, the peaks and troughs of the energy waves cancel each other out, and the amplitude of the energy waves decreases. This means that the energy reflected back from the surface of the information recording/reproducing medium is substantially reduced. That is, by setting the thickness of the interference layer 2 to an appropriate value, the energy reflectance can be lowered. In this case, since the absorption of light in the interference layer 2 is extremely small, the remaining energy after subtracting the reflected energy from the incident energy is all absorbed by the recording layer 1, and the temperature of the recording layer 1 is the same as that without the interference layer 2. In comparison, it rises to high temperatures more rapidly.

The optimal thickness of the interference layer can be determined by the following equation derived from the theory of interference.

d=λ/4n ₁ (2m+1) ...(1) (m=0, 1, 2, 3...) Here, d: Thickness of the interference layer, n ₁ : Refractive index of the interference layer λ: Wavelength of the energy wave Further, the optimum value n ₁ ' of the refractive index of the interference film is similarly derived from the theory of interference and is expressed by the following equation.

n ₁ ′=√ ₂ ...(2) where, n ₂ : refractive index of recording layer 1 The layer that reduces the reflectance described above has an independent function as an incident energy absorption layer or an interference layer. However, it is also possible to provide one layer with the functions of an interference layer and an absorption layer at the same time.

As the absorption layer, a thin film of titanium oxide, chromium oxide, copper oxide, triiron tetroxide, etc. can be used.
Semi-transparent is preferred. Especially colored ones,
It is preferable to use a black body, which has a resistance of 10 to light.
Those with an energy absorption of ~30% and a transparency of 50% or less are preferred. Thickness is less than 50nm,
More preferably, it is 30 to 50 nm.

When using a colored absorption layer, it is preferable to reproduce information from the side opposite to the information recording side.

If such an interference/absorption layer 2' is formed on the energy incident side of the recording layer 1 as shown in FIG. can be improved.

All of the antireflection films described so far have a single-layer structure, but it is also possible to have a two-layer structure using separate layers for the absorption layer 3 and the interference layer 2, as shown in FIG. 2d.

Until now, it has been possible to rapidly raise the temperature of the recording layer 1 to a high temperature by forming an antireflection layer on the front surface of the recording layer 1 and substantially increasing the thermal energy input to the recording layer 1. However, there is a means to further increase the temperature of the recording layer. This is a method of forming a thermal insulating layer 5 so as to surround the recording layer 1 as shown in FIG. 3a. Since the recording layer is generally thin and has low mechanical strength by itself, it is often formed on a support layer 7 such as a metal plate, glass plate, or plastic plate, as shown in FIG. 3c.
In such a structure, thermal energy flows from the recording layer to the support layer, and the support layer 7 acts as a cooling body for the recording layer 1. Therefore, the temperature of the recording layer 1 becomes difficult to rise. In order to prevent this loss of thermal energy, it is effective to provide a thermal insulating layer 5 between the recording layer and the support layer. Further, since thermal energy flows from the recording layer to the opposite side of the support layer in the opposite direction to that described above, it is more effective if this flow is also prevented. When an interference layer is provided on the upper surface of the recording layer, a thermal insulating layer is provided to surround the interference layer and the recording layer. When the heat absorption layer is on the upper surface (energy incidence side) of the recording layer, in order to prevent the loss of thermal energy from the heat absorption layer, heat is placed on the energy incidence side of the heat absorption layer 3 as shown in Figure 3a. Providing the insulating layer 5 is effective.

Thermal insulation layer is for keeping heat out.
Oxides such as SiO ₂ glass and alumina are preferred.

By the way, the support layer that supports the recording layer is
Although the support layer (substrate) was considered to be on the side opposite to the energy incidence side, it is also possible to provide the support layer (substrate) on the energy incidence side. In such a structure, the support layer is a colorless transparent film that transmits incident energy;
For example, a glass plate or a plastic plate is used. By the way, providing a transparent layer between the recording layer and the energy incidence surface has another effect. That is, since information recording media are exposed to the outside air, dust in the air and human fingerprints often adhere to them. If recorded data is reproduced in such a state, noise will increase and the S/N ratio will decrease. However, as shown in Figure 1e, 0.5~2.0mm
If the transparent layer 4 is on the upper surface of the recording layer, dust and fingerprints will adhere to the surface of the transparent layer 4 (away from the recording layer 1). A device for reproducing recorded data on an information recording/reproducing medium has an optical system similar to a microscope, observes a minute area of the recording layer, observes changes in reflectance depending on the location of the recording layer 1, and reproduces the recorded data. Reproduce. At this time, when the optical system is focused on the recording layer 1, dust and fingerprints on the surface of the transparent layer 4 are out of the depth of focus range, resulting in a blurred image, which does not adversely affect the reproduced signal. There is no decrease in N ratio.

When the support layer is on the energy incidence side of the recording layer as described above, a thermal insulation layer is provided on the lower surface of the recording layer (the side opposite to the energy incidence surface) to prevent heat loss into the air. Furthermore, if a material with high thermal insulation is used as the interference layer or absorption layer, the film structure can be simplified.

Glass, ceramics, plastics such as polymethyl methacrylate, polystyrene, polycarbonate, etc. are used for the substrate. These substrates are preferably colorless and transparent.

The protective layer 6 protects the recording layer 1 from scratches caused by contact with external equipment and protects the recording layer 1 from dust adhering to it, and is made of oxides such as SiO ₂ glass and alumina. . Its thickness is tens of
It is preferably nm to 2 mm.

The information recording medium of the present invention can record, reproduce, or erase information by inputting energy to the side where the interference layer and absorption layer are provided, and further performs reproduction from the side opposite to the side where the interference layer and absorption layer are provided. be able to.
For reproduction on the opposite side, the substrate may be the colorless and transparent substrate described above. When using light for reproduction on the side opposite to the recording side, a colorless and transparent substrate, protective film, or other film with high light transmittance should be selected for the recording layer.

(Recording layer) The recording layer of the present invention 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), A metal or an alloy having a crystal structure (first crystal) that is in an equilibrium phase at room temperature and a crystal structure (second crystal) different from the first crystal is preferable.

The alloy according to the present invention has at least two types of spectral reflectance at the same temperature due to rapid cooling from a high-temperature solid state, and due to a phase change between a first crystal and a second crystal different from the first crystal. Therefore, 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 standard non-quenched 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.

The principle of the reversible change in reflectance according to the present invention will be explained using FIG. 4. The figure is a phase diagram of an X-Y binary alloy, in which an α solid solution and β, γ intermetallic compounds exist. Taking an alloy with composition A as an example, this alloy has a β single phase, a (β+γ) phase, and an (α+γ) phase in a solid state. The crystal structure is different in the single phase state of α, β, and γ, and the optical properties, such as spectral reflectance, are different in each of these single phases and mixed phases. Such alloys have a stable (α+γ) phase at T ₁ temperature, generally room temperature.
When this is heated and rapidly cooled to _T4 temperature, the β phase is rapidly cooled to _T1 temperature. Since this state is different from the (α+γ) phase, the spectral reflectance is also different. This rapid cooling β
When the phase alloy is heated and cooled to T ₂ temperature, which is lower than T _e temperature, the β phase transforms into the (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 layer of the present invention are as follows.

Alloy containing silver as the main component, zinc 30-46wt%, aluminum 6-10wt%, copper as the main component, aluminum 10-20wt%, indium 20
~40wt%, tin 16~35wt%, alloys containing gold as a main component and aluminum 2.5~5wt%, or these alloys with small amounts of b, b,
It can contain one or more of group b, b, b, a, and a group elements. Its content is preferably
It is 10wt% or less.

The recording density is 0.01 to 0.2 μm for producing information in a micro area with a recording density of 20 megabits/cm ² or more.
It is preferable to set the film thickness to . It is effective to form the recording layer into a predetermined shape by directly rapidly cooling and solidifying it from the gas phase or liquid phase. These methods include PVD method (vapor deposition, sputtering method, etc.), CVD method, high thermal conductivity material that rotates molten metal at high speed,
Particularly, there are a molten metal quenching method in which molten metal is poured onto the circumferential surface of a metal roll and rapidly solidified, an electric plating method, a chemical plating method, and the like. When using a powdered material, it is effective to apply it onto a substrate 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 sprayed together with a gaseous or liquid refrigerant and then poured into water to be rapidly cooled. The particle size is preferably 0.1 mm or less, and ultrafine powder with a particle size of 1 μm or less is particularly preferable.

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

(Applications) The information recording medium of the present invention has physical or electrical properties such as spectral reflectance of electromagnetic waves, electrical resistivity, refractive index, polarization index, transmittance, etc. due to a change in the crystal structure partially or entirely by heating and quenching. It can be used for recording, display, sensor, etc. elements by changing the physical characteristics and utilizing the changes in these characteristics.

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, laser beams such as semiconductor lasers, heat, etc.) can be used, and in particular optical disks that utilize changes in spectral reflectance due to irradiation. It is preferable to use it for Optical disks include digital audio disks (DAD or compact disks), video disks, memory disks, 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.

Record while erasing, erase the entire thing with erasing only,
There is a way to partially erase a wide area.

An example of the principle of recording and reproduction when the present invention is used in an optical disk recording medium 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 to record the specified information locally based on the high temperature phase. Information can be reproduced by heating and recording locally in a low-temperature phase during a high-temperature phase, and by irradiating the recorded portion with light and detecting the difference in optical characteristics between the heated portion and the non-heated portion. Furthermore, the recorded information can be erased by heating the portion recorded as information at a temperature lower or higher than the heating temperature at the time of recording. The light is preferably a laser beam, particularly a short wavelength laser. Since the reflectance of the heated portion and non-heated portion of the present invention is greatest at a wavelength around 500 nm or 800 nm, it is preferable to use a laser beam having such a wavelength for reproduction. 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.

Furthermore, a disk using the recording medium of the present invention has a great advantage in that it can be visually determined whether information is recorded or not. Recording and erasing are performed using continuous beam or pulsed beam. The erasing beam heats the beam to a width greater than the width of the recorded information.

As a display, it is possible to partially change the spectral reflectance of visible light, so characters, figures, symbols, etc. can be recorded without using paint, and these displays can be visually identified. I can do it. 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. Can be used for display devices.

[Embodiments of the invention]

(Example 1) An Ag-40 wt % Zn alloy was melted in a carbon boat in an N ₂ gas atmosphere to prepare a target for sputter deposition of approximately 100 mmφ×10 t. Using this target, a recording medium having a film structure as shown in FIG. 5a was prepared. Sputter power 140-200W, substrate heating temperature 200W on glass substrate 10 of 25mmφ x 1.2t.
An Ag-40% by weight Zn film 8 was sputter-deposited to a thickness of about 100 nm under the conditions of .degree. After the inside of the container was evacuated to about 10 ^-7 Torr, Ar gas was introduced at 5 to 30 mTorr, and a DC magnetron type sputtering method was used. Further, on this alloy film, a laser beam interference layer 9 with a thickness of approximately
500 nm of Ta ₂ O ₅ was sputter deposited. This Ta ₂ O ₅
Approximately 5% O ₂ was introduced into the sputter deposition, and an RF type sputter method was used.

The surface of the 25 mmφ recording medium produced as described above had a silvery white color. When this recording medium was heated to approximately 350°C in an electric furnace and then rapidly cooled (water-cooled), it was found that the alloy film turned silvery white to a slightly pink color. This is because the β phase of Ag-40 wt % Zn was changed to the β' phase by rapid cooling. Furthermore, this rapidly cooled recording medium is heated in an electric furnace for approximately 200 minutes.
When heated to ℃ and slowly cooled (air cooled), the color changes from pink to the original silvery white color, which is due to the change from β' to phase. Incidentally, the recording and erasing characteristics of laser light also correspond to this. For example, the recording state is when the recording medium is irradiated with an Ar laser with a power of 10 to 50 mW and a beam diameter of 1 to 5 μm. At this time, the recording area changes from silvery white to pink. In addition, this recording section is 50~
When irradiated with a defocused beam of low power density at a power of 100 nW, the pink color returned to its original silvery white color, confirming erasure. In this way, as a method for evaluating recording and erasing characteristics of a recording medium, in addition to using laser light, a simple method using heat treatment as described above is also effective.

FIGS. 11a and 11b show the spectral reflection characteristics of a recording medium produced by the heat treatment method described above.
b in FIG. 11 is the interference film 9 (Ta ₂ O ₅ ,
This is the spectral reflection characteristics of a film structure with a thickness of 500 nm), and it can be seen that significant interference occurs. A in FIG. 11 shows Ag− on the glass substrate 10.
Only the 40% by weight Zn alloy film 8 was sputter-deposited, and the reflectance was high in both the recorded and unrecorded areas. On the other hand, diagram b uses the interference valley, but it is not possible to use an Ar laser (λ _Ar = 488 nm) and a semiconductor laser (λ _L = 488 nm).
It can be seen that the reflectance decreases significantly at each wavelength (830 nm). That is, compared to the case without the interference layer shown in Fig. a, the energy of the laser beam is absorbed into the recording medium more efficiently, and recording and erasing can be achieved with less power. Here, the interference layer 9 is made of Ta ₂ O ₅ with a high refractive index and has a thickness of 500 nm. Similarly, other examples using such light interference are shown in b to d of FIG. It is desirable that the interference layer 9 has a high refractive index and is transparent. b shows the case where Al ₂ O ₃ is used as an interference layer, and if the film thickness is adjusted to the interference conditions, the reflectance will similarly decrease. c and d are Cu-14 weight% recording alloy film.
This is the case where Al-4% by weight Ni12 is substituted, and in FIG. 12, a shows the spectral reflection characteristics in a film structure without the interference film 9, and b in the film structure with an interference film (Ta ₂ O ₅ , 500 nm thick) added. In this case as well, in Figure 10
As with the Ag-40% by weight Zn alloy film 8, it can be seen that the reflectance significantly decreases at each wavelength of Ar laser and semiconductor laser. Digital and analog recording with a width of 1 μm or less using a semiconductor laser,
It has been confirmed that playback is possible.

(Example 2) Similarly to Example 1, a in FIG. 6 is the glass substrate 1.
An Ag-40 wt % Zn alloy film 8 (film thickness 100 nm) was provided on top of 0 by sputter deposition, and further on top of that
Cr.Ox (chromium oxide) 13 was deposited to a thickness of 5 to 10 nm by vacuum evaporation. As described above, this Cr.Ox is added as a heat absorption layer on the metal information recording layer with high reflectance. The above-mentioned crystal-crystal phase change alloy film itself has a high reflectance, so the heat input efficiency of laser light is poor. To cover this, Cr.Ox 13 is provided on the recording layer. FIG. 13 compares the spectral reflection characteristics with and without a heat absorption layer. As you can see from this figure, about 300 ~
It can be seen that in the wavelength range of 1000 nm, the reflectance of the film structure with a heat absorption layer decreases. Furthermore,
In FIG. 6b, the recording layer is made of Cu-14% by weight Al-4% by weight Ni, and Cr.Ox is similarly added thereto. It was found that this case also had the effect of lowering the reflectance. Further, C and d are cases where the heat absorption layer 13 is replaced with Cu ₂ O 14 or Fe ₃ O ₄ 15, but the same effect of lowering the reflectance can be seen.

(Example 3) As in Example 1, FIG. 7 shows that an Ag-40 wt % Zn alloy gold film 8 of about 100 nm is provided on a glass substrate 10 by sputter deposition, and further 100 nm of Cr.Ox is added on top of it.
~20nm was provided by vacuum evaporation method. In addition to giving this Cr.Ox the properties of a heat absorption layer shown in FIG. 13, the thickness is further increased, and at the same time, the aim is to reduce the reflectance due to interference. Since this CrOx has transparency and a high refractive index, a large interference effect was obtained with a small film thickness. 14th
The figure shows the spectral reflection characteristics in the case of the above structure aiming at both heat absorption and interference effects and in the case of only the recording layer 8. As can be seen from this figure, in the wavelength range of 500 to 1000 nm, the reflectance significantly decreases due to interference effects, and at the same time absorption effects are also observed, indicating that the overall reflectance decreases. In this respect,
Like Ta ₂ O ₅ , CrOx is also suitable for lowering the reflectance and increasing the heat input efficiency of laser light, and the film structure shown in Figure 7 is considered to be very practical. I can say it.

(Example 4) As in Example 1, a in FIG. 8 is the glass substrate 2.
An Ag-40 wt% Zn alloy film 8 of approximately 100 nm is provided on the 0 by sputter deposition, and further Cr/Ox 1 is deposited on top of it.
3 was deposited to a thickness of about 5 nm by vacuum evaporation, and then a 50 μm layer of SiO ₂ 1
0 was set. In this case, CrOx corresponds to the heat absorption layer in Example 2, but the thickly formed SiO ₂ is a transparent protective layer, which has a certain size effect in addition to the effect of protecting the recording medium. Since the laser beam possessed by the laser beam is rapidly focused on the recording film, during playback, dirt or dust of less than a certain size may cause damage.
It has the effect of preventing SN reduction. As another structure of this transparent protective layer, as shown in figure b, the recording film 8
There is also a method of further adhering a glass substrate 10 on top of the interference layer 9. That is, the glass substrate 10 (thickness: 1.2 mm) itself can act as the transparent protective layer to prevent a decrease in the SN ratio.

(Example 5) As in Example 1, a in FIG. 9 is the glass substrate 1.
An Ag-40 wt% Zn alloy film 8 of approximately 100 nm is provided on the 0 by sputter deposition, and a heat absorption layer is placed on top of it.
Cr.Ox 13 was vacuum-deposited to a thickness of 5 nm, and an interference layer of Ta ₂ O ₅ 9 was further formed to a thickness of about 500 nm on top by sputter deposition. According to this membrane configuration, the interference effect can be reduced.
By having Ta ₂ O ₅ share the heat absorption effect and then Cr.Ox share the heat absorption effect, it is possible to efficiently transmit the input energy of the laser beam to the recording layer 8. Similarly, in figure b, the heat absorption layer is made of Cu ₂ O14,
Furthermore, the interference layer is made of Al ₂ O ₃ 11, and as expected,
This film structure helps to share heat absorption and interference effects with each other and increases heat input efficiency by laser light.

(Example 6) Similar to Example 1, Fig. 10 shows SiO ₂ 10 deposited to a thickness of approximately 100 nm on a PMMA 17 substrate by sputter deposition.
On top of that, about 100 nm of Ag-40wt% Zn8 is placed, and on top of that, about Cr/Ox13 of a heat absorption layer is placed.
Place 5nm of SiO 2 10 on top of this and add about 100nm of SiO ₂ 10 again.
establish. That is, the film structure is such that the recording layer and the heat absorption layer are sandwiched with SiO ₂ 10, which has a high thermal insulation effect. This SiO ₂ 10 is intended to improve efficiency by narrowing the heat input distribution contributing to phase change without dispersing the energy generated within the heat absorption layer and the recording layer.

(Embodiment 7) FIG. 1 is a partial cross-sectional configuration diagram of an information recording medium of the present invention. This example is manufactured similarly to the method described in the previous example. A tracking groove 19 is formed on the silica glass substrate 7 by etching or the like, and then Ag-35
% Zn alloy is applied to a thickness of approximately 100 nm, on which an interference layer 9 of Ta ₂ O ₅ is applied to a thickness of approximately 500 nm, and then a transparent layer 4 of PMMA is applied. According to this embodiment, the optical energy of the laser beam 18 focused by the lens 20 can be effectively applied to the recording layer 1 by the interference layer 2, so that information can be recorded, reproduced, and erased with small energy. It becomes possible.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a film structure with high energy utilization efficiency, especially as an optical disk recording medium that utilizes the spectral reflectance difference due to phase change between crystals.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional perspective view of the information recording medium of the present invention, FIGS. 2 and 3 are cross-sectional configuration diagrams of the information recording medium of the present invention, and FIG. 4 is a binary alloy system related to the recording layer of the present invention. FIGS. 5 to 10 are cross-sectional configuration diagrams of information recording media shown in examples of the present invention, and FIGS. 11 to 14 are diagrams showing spectral reflectance characteristics. DESCRIPTION OF SYMBOLS 1... Recording layer, 2... Interference layer, 2'... Interference and suction layer, 3... Heat absorption layer, 4... Transparent layer, 5... Heat insulation layer,
6... Protective layer, 7... Media support layer, 8... Ag-40Zn,
9...Ta ₂ O ₅ , 10... SiO ₂ , 11... Al ₂ O ₃ , 12...
Cu-15%Al-4%Ni alloy, 13...Cr・Ox, 1
4... _Cu2O , ₁₅ ... _Fe3O4 , 16... _{Ta2O5 -x} , 17
...PMMA, 18...Laser light, 19...Tracking groove, 20...Lens.

Claims (1)

[Claims] 1. Information can be recorded by irradiating optical energy onto an optical recording medium having a recording layer made of an alloy and a layer that reduces the surface reflectance of the recording layer and heating the recording layer. In the recording/erasing method of recording or erasing information, the light energy is incident on the recording layer through a layer that reduces the surface reflectance of the recording layer, and is heated to a high phase temperature region and then rapidly cooled. A recording layer is reversibly formed between a first crystal to be formed and a second crystal, which is formed by heating and cooling in a low phase temperature region and is different from the first crystal and has an intermetallic compound. A method for recording and erasing information, characterized in that information is recorded or erased by changing the phase of the alloy forming the recording layer and changing the reflectance of the alloy forming the recording layer.