JP2776847B2 - Information recording thin film and information recording / reproducing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention uses a recording beam such as a laser beam or an electron beam to FM-modulate, for example, an analog signal such as video or audio, or digital data such as computer data, facsimile signal or digital audio signal in real time. The present invention relates to a thin film for recording information that can be recorded by the above method.

[Prior art]

There are various recording principles of recording on a thin film by laser light. However, recording by a phase transition (also called phase change) of a film material or an atomic arrangement change such as photodarkening hardly involves deformation of the film. It has the advantage that a double-sided disc can be created by directly attaching two discs. If the composition is appropriately selected, the recording can be rewritten. Many inventions relating to this type of recording have been filed, and the earliest one is disclosed in Japanese Patent Publication No. 47-26897. Here, Te-Ge system, As-Te-Ge system, Te-O
Many thin films, such as systems, are described. Further, various compositions are set forth, such as Ge ₂₀ Tl ₅ Sb ₅ Se ₇₀ in JP-A-54-41902. Japanese Patent Application Laid-Open No. 57-24039 discloses Sb ₂₅ T
e _12.5 Se _62.5 , Cd ₁₄ Te ₁₄ Se ₇₂ , Bi ₂ Se ₃ , Sb ₂ Se ₃ , In ₂₀ Te
Thin films of ₂₀ Se ₆₀ , Bi ₂₅ Te _12.5 Se _62.5 , CuSe, and Te ₃₃ Se ₆₇ have been described.

[Problems to be solved by the invention]

When any of the above prior art thin films is used as a once-writable or rewritable phase change recording film, the crystallization speed is low, the semiconductor laser light absorption is low and the sensitivity is low, the reproduction signal intensity is not sufficient, There are drawbacks such as large waveform distortion, poor stability of the amorphous state, insufficient oxidation resistance, and a large disappearance.
Practical application is difficult. Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages of the prior art and to provide an information recording thin film having good recording / reproducing characteristics, high sensitivity and good stability.

[Means for Solving the Problems]

In order to achieve the above object, in the information recording thin film of the present invention, the average composition in the thickness direction of the information recording thin film is represented by the general formula SbxTeyAzBαCβDγ. Here, x, y, z, α, β, and γ are 5 ≦ x ≦ 70, 10 ≦ y ≦ 85, 3 ≦ z ≦ 50, 0 ≦ α ≦ 20, 0 ≦ β in atomic percent, respectively.
≦ 30, 0 ≦ γ ≦ 30, where A is Sn, Bi, Pb, Ga, Au
B is at least one element of a halogen element such as Tl and I and an alkali metal such as Na. These elements are found in materials containing Te and Se
It has the effect of cutting the chain atom arrangement of Te and Se, thereby increasing the crystallization rate. However, since the crystallization temperature is lowered, the stability of the amorphous is impaired unless it is added to a material having a high crystallization temperature. C is Ag, Cu, Pd, Ta, W, Ir, Sc, Y, Ti, Zr, V, N
b, Cr, Mo, Mn, Fe, Ru, Co, Rh and at least one element of Ni, D is an element other than the element represented by Sb, Te, A, B, C, for example, Hg, Se, S, As, Al, B, C, Si, N, P, O, a lanthanide element, an actinide element, an alkaline earth metal element, an inert gas element and the like are at least one element. However, one or more of the elements represented by A, B and C are also
If another element of each group is already in use, it can be considered a group D element. For example, a case is considered in which Ni is added to an Sb-Te-Sn-Co system in a range in which the total of the Ni content and the Co content is less than 30 atomic% and the upper limit of the content of the C group element is 30 atomic% or less. Was done. Of these, Al, Hg, alkaline earth metal elements, and inert gas elements are preferably less than 10 atomic%. The composition of the recording thin film of the present invention may vary in the film thickness direction as long as the average composition in the film thickness direction is within the above range. However, the change in the composition is more preferably not discontinuous. Recording is performed with an energy beam of irradiation time and power that can cause an atomic arrangement change (for example, change from one phase to another phase) and does not cause large deformation of the recording film.

[Action]

The role of each of the above group elements is as follows. With elements such as Sn represented by Sb, Te and B, the amorphous state is stably maintained by coexisting at an appropriate ratio,
In addition, crystallization at the time of recording / erasing can be performed at high speed. Elements such as Co represented by C have the effect of facilitating the absorption of long-wavelength light such as semiconductor laser light to increase the recording sensitivity, and also enable high-speed crystallization. Elements such as Tl represented by B have the effect of improving the crystallization rate and also improving the stability of the amorphous state. When the group B element and the group C element coexist, high-speed crystallization is possible, the stability of the amorphous state is high, and the recording sensitivity is high. When one of the group B element and the group C element is added, it is preferable to add the group B element in terms of easiness of film formation, but the oxidation resistance is reduced. Elements such as Ar represented by D do not have a particularly remarkable effect when added, but there is no significant adverse effect if the added amount is small. Of these, rare earth elements and the like, when added in an amount of 1 to 20%, can play roles such as increasing the reproduction signal intensity and increasing the crystallization temperature. Se and S have an effect of improving oxidation resistance by adding 1 to 20% while keeping the ratio of other elements constant. However, the heat resistance is slightly reduced. From the viewpoint of erasing characteristics, the Se content is preferably 1 to 3%. The information recording thin film of the present invention having the above composition range has excellent recording / reproducing characteristics, and the power of the laser beam used for recording and erasing may be low. Also, the stability is excellent. More preferred ranges of x, y, z, α, β and γ are as follows. 10 ≦ x ≦ 45 35 ≦ y ≦ 80 5 ≦ z ≦ 300 0 ≦ α ≦ 15 0 ≦ β ≦ 200 0 ≦ γ ≦ 20. Particularly preferred ranges of x, y, z, α, β and γ are as follows. 13 ≦ x ≦ 40 47 ≦ y ≦ 70 7 ≦ z ≦ 23 0 ≦ α ≦ 10 0 ≦ β ≦ 10 0 ≦ γ ≦ 10. However, when the element represented by A is Au,
Since the recording sensitivity is low when the content is small, it is particularly preferable to satisfy 60 ≦ y ≦ 70. In each of the above ranges, if γ ≒ 0, film production is easy. If 1 ≦ α + β ≦ 20, the erasure remaining is further reduced, and the recording retention time is prolonged. 1 ≦ α ≦ 10 and 1 ≦
If β ≦ 10, the signal modulation is further increased. Among the elements represented by B, particularly preferred is Tl, then preferred is I, and then another halogen element such as Cl. Of the elements represented by D, rare earth elements are preferred. Of the elements represented by A, Pb, Ga, and In slightly reduce oxidation resistance. However, In has excellent recording / erasing characteristics.
Au improves the oxidation resistance which lowers the recording sensitivity. The change in the content of each element in the film thickness direction is usually small,
Any pattern change may be present. Sb, S
As for e and S, it is preferable that there are more near the interface of one of the recording thin films (there may be an interface with another layer) than the inside thereof. It is preferable that at least one surface of the recording film of the present invention is tightly protected by another substance. More preferably, both sides are protected. These protective layers may be formed of an organic material such as a fluororesin such as acrylic resin, polycarbonate, polyolefin, epoxy resin, polyimide, polyamide, polystyrene, polyethylene, polyethylene terephthalate, and polytetrafluoroethylene (Teflon). Often, these may be substrates. Further, it may be formed by an ultraviolet curing method. Oxides, fluorides, nitrides, sulfides, selenides, carbides,
It may be formed of an inorganic substance mainly composed of boride, boron, carbon, metal or the like. Further, these composite materials may be used. A substrate mainly composed of glass, quartz, sapphire, iron, titanium, or aluminum can also serve as one inorganic protective layer. Of the organic and inorganic substances, those that are in close contact with the inorganic substance are preferable in terms of heat resistance. However, increasing the thickness of the inorganic layer (excluding the case of the substrate) is likely to cause at least one of crack generation, transmittance reduction, and sensitivity reduction. It is preferable that a thick organic material layer adheres to the side to increase the mechanical strength. This organic layer may be a substrate. This makes deformation less likely to occur. Examples of the organic substance include polystyrene, polytetrafluoroethylene (Teflon), polyimide, acrylic resin, polyolefin, polyethylene terephthalate,
A polycarbonate, an epoxy resin, an ethylene-vinyl acetate copolymer known as a hot melt adhesive, an adhesive, and the like are used. UV curable resin may be used. In the case of a protective layer made of an inorganic material, it may be formed as it is by electron beam evaporation, sputtering, or the like, but after reactive sputtering, a metal, a metalloid, and a film made of at least one element of a semiconductor, Production is facilitated by reacting with at least one of oxygen, sulfur and nitrogen. To give an example of the inorganic protective layer,
Ce, La, Si, In, Al, Ge, Pb, Sn, Bi, Te, Ta, Sc, Y, Ti, Zr, V, Nb, C
oxide of at least one element selected from the group consisting of r and W, Cd, Zn, Ga, In, Sb, Ge, Sn, sulfide of at least one element selected from the group consisting of Pb, or selenide, Mg, C
e, Fluoride such as Ca, nitride such as Si, Al, Ta, B, boron,
Composed of carbon, for example, whose main components are CeO ₂ and La ₂
O ₃ , SiO, SiO ₂ , In ₂ O ₃ , Al ₂ O ₃ , GeO, GeO ₂ , PbO, SnO, SnO ₂ , Bi ₂ O
_{3, TeO 2, WO 2,} WO 3, Ta 2 O 5, Sc 2 O 3, Y 2 O 3, TiO 2, ZrO 2, CdS, ZnS,
CdSe, ZnSe, In ₂ S ₃ , In ₂ Se ₃ , Sb ₂ S ₃ , Sb ₂ Se ₃ , Ga ₂ S ₃ , Ga ₂ Se ₃ , M
_{gF 2, CeF 3, CaF 2} , GeS, GeSe, GaSe 2, SnS, SnS 2, SnSe, SnSe 2, P
bS, PbSe, Bi ₂ Se ₃ , Bi ₂ S ₃ , TaN, Si ₃ N ₄ , AlN, Si, TiB ₂ , B ₄ C, Si
One having a composition close to one of C, B, and C, and a mixture thereof. Among these, sulfides that are close to ZnS are preferable because the refractive index is appropriate and the film is stable. A nitride having a composition close to TaN, Si ₃ N ₄ or AlN (aluminum nitride) is preferable in that the surface reflectance is not so high and the film is stable and strong. Preferred oxides are Y ₂ O ₃ , Sc ₂ O ₃ , CeO ₂ , TiO ₂ , ZrO ₂ , SiO, Ta ₂ O ₅ ,
It has a composition close to In ₂ O ₃ , Al ₂ O ₃ , SnO ₂ or SiO ₂ .
Amorphous containing hydrogen of Si is also preferable. If the protective film is made into a multilayer, the protective effect is further enhanced. For example, 100-500nm thick Si
The film having a composition close to the O ₂ to form a recording layer farther, 80 thickness
A film having a composition close to ZnS of about 130 nm is formed on the side close to the recording film, and the recording / erasing characteristics and the multi-time rewriting characteristics are excellent. By forming the protective film as described above, it is possible to prevent an increase in noise due to deformation of the recording film at the time of recording / rewriting. When performing recording by phase transition (change), it is preferable to crystallize the entire surface of the recording film in advance, but if an organic substance is used for the substrate, the substrate cannot be heated to a high temperature. Need to be crystallized. In that case, the laser beam is irradiated by focusing to a spot diameter of 2 μm or less, ultraviolet irradiation and heating of a xenon lamp, a mercury lamp, etc., irradiation of light from a flash lamp, irradiation of light by a large light spot from a high-power gas laser, Alternatively, it is preferable to perform a combination of heating and laser beam irradiation. In the case of irradiation with light from a gas laser, efficiency is good when the light spot diameter (half width) is 5 μm or more and 5 mm or less. Crystallization may occur only on the recording tracks, and the space between the tracks may remain amorphous. There is also a method of crystallizing only between recording tracks. On the other hand, for example, when a thin film containing Sn, Sb and Te as main components is formed by rotary evaporation from a plurality of evaporation sources, Sn, Sb and Te are often hardly bonded immediately after the evaporation. Also, when formed by sputtering, the atomic arrangement is extremely disturbed. In such a case, it is preferable to first irradiate the recording track with a laser beam having a high power density to melt the film in some cases. Further, when the recording track is irradiated with a laser beam having a low power density to be crystallized, the reflectance over the track circumference tends to be uniform. It is possible to record with a laser beam whose power has been modulated between the power level at which it crystallizes and the power level at which it approaches an amorphous state, regardless of the state after initialization as described above. is there. Generally, when light is applied to a thin film, the reflected light is superimposed on the reflected light from the front surface of the thin film and the reflected light from the back surface of the thin film, and causes interference. When a signal is read by a change in reflectance, a light reflection (absorption) layer is provided close to the recording film, so that the effect of interference can be increased and the read signal can be increased. In order to further increase the effect of interference, it is preferable to provide an intermediate layer between the recording film and the reflection (absorption) layer. The intermediate layer also has the effect of preventing the interdiffusion between the recording film and the reflective layer from occurring during recording rewriting. However, depending on how the material of the intermediate layer is selected, for example, when the intermediate layer is made of selenide, at least a part of the element of the recording film is diffused into the intermediate layer, or at least a part of the element of the intermediate layer is transferred to the recording film or the reflective layer. By diffusing in, at least a portion of the recording can be carried. It is preferable that the thickness of the intermediate layer be 3 nm or more and 600 nm or less, and that the reflectance of the recording member be close to the minimum value near the wavelength of the reading light in the recording state or the erasing state. The reflection layer may be formed between the recording film and the substrate and on any of the reflection sides thereof. Particularly preferred thickness ranges of the intermediate layer are 60 / Nnm or more and 160 / Nnm or less and 470 / Nnm or more and 570 / Nnm when the refractive index of the intermediate layer is N. It is preferable to form a protective layer made of the above-mentioned inorganic substance on the side of the reflective layer opposite to the intermediate layer. These three layers (intermediate layer, reflective layer, and protective layer) form a stronger protective layer as a whole than a single protective layer. As the reflective layer, metals, metalloids and semiconductors can be used, but Au, Ag, Cu, Ni, Fe, Al, Co, Cr, Ti, Pd, Pt, W, Ta, Mo
Alternatively, a layer of these alloys or a composite layer of these with another substance such as an oxide is preferable. When a reflective layer made of a material having a high thermal conductivity of at least 2.0 W / cm-deg, such as Au, as the main component, is used, the thermal conductivity is increased, and even if a recording film that crystallizes at a high speed is used, the reflective layer becomes high. When irradiated with power laser light, it also has the effect of ensuring that the laser beam becomes amorphous. In this case, Al ₂ O ₃ , AlN, Si ₃ N ₄ , Zn
In particular, use a material with a composition close to that of S, or use a material with a medium thermal conductivity such as SiO ₂ (0.02 W / cm · deg or more and 0.1 W / cm · deg or less), and make the intermediate layer thin. preferable. The recording film of the present invention may be in the form of an oxide, a fluoride, a nitride, an organic material, or the like described as usable as a protective film, or dispersed in carbon or carbide by co-evaporation or co-sputtering. By doing so, there are cases where the light absorption coefficient can be adjusted and the reproduction signal intensity can be increased. The mixing ratio is oxygen, fluorine, nitrogen,
The proportion of carbon in the whole film is preferably 40% or less. The formation of such a composite film usually lowers the crystallization speed and lowers the sensitivity. However, the sensitivity is improved by forming a composite film with an organic substance. The preferred range of the film thickness of each component is as follows. Recording film In the case where the reflective layer is not used, the range of 15 nm or more and 500 nm or less and 25 nm or more and 300 nm or less is particularly preferable in view of the reproduction signal intensity and recording sensitivity. In the case of a structure with two or more layers with a reflective layer 15 nm or more and 150 nm or less Inorganic protective layer 5 nm or more and 500 nm or less However, when protecting with the inorganic substrate itself, 0.1 to 20 mm Organic protective layer 500 nm or more and 10 nm or less Intermediate layer 3 nm or more and 600 nm or less Layer 5 nm or more and 300 nm or less Inorganic protective layer adjacent to the light reflection layer 50 nm or more and 500 nm or less The material and film thickness of each layer other than the recording film as described above are not limited to the recording film of the present invention, and other phase change recording films, magneto-optical It is also effective for a recording film, a mutual diffusion type recording film and the like. The method of forming each of the above layers is a method of appropriately selecting any one of vacuum deposition, vapor deposition in gas, sputtering, ion beam deposition, ion plating, electron beam deposition, injection molding, casting, spin coating, plasma polymerization and the like. is there. Most preferably, the protective layer, the recording film, the intermediate layer, the reflective layer, and the protective layer adjacent to the reflective layer are all formed by sputtering. The recording film of the present invention does not necessarily need to utilize the change between the amorphous state and the crystalline state for recording, and may change the optical properties by any atomic arrangement change that hardly accompanies the change in the film shape. . For example, a change in crystal grain size or crystal form, a change between a crystal and a metastable state (π, γ, or the like) may be used. Even in the change between the amorphous state and the crystalline state,
The amorphous is not completely amorphous, and may have a mixture of crystal parts. In addition, some of the atoms constituting these layers move (diffusion, chemical reaction, etc.) between the recording layer and at least one of the protective layer and the intermediate layer, or It may be recorded by both phase changes. The recording member of the present invention can be used not only in a disk shape but also in other forms such as a tape shape and a card shape.

【Example】

Hereinafter, the present invention will be described in detail with reference to Examples. A replica of a tracking groove that also serves as a protective layer is formed on the surface of a disk-shaped chemically strengthened glass plate 13 cm in diameter and 1.2 mm in thickness with an ultraviolet-curing resin, and one round is divided into 32 sectors. A substrate 1 having a track address, a sector address, and the like in the form of a concave / convex pit in a mountain portion between the grooves (referred to as a header portion).
First, an SiO ₂ layer 2 having a thickness of about 300 nm as a protective layer was formed by magnetron sputtering. Since the SiO ₂ layer has a small difference in refractive index from the substrate, the film thickness may have some unevenness or variation. Next, this disk has a plurality of targets and can be successively formed into a laminated film. The disk is transferred to a sputtering apparatus having good uniformity and reproducibility of the film thickness, and ZnS is sputtered to a thickness of about 110 nm to form a layer 3 with ZnS. did. Next, ZnS layer 3
A recording film 4 having a composition of Sn _14.3 Sb _28.6 Te _57.1 was formed to a thickness of about 30 nm on the same sputtering apparatus. Subsequently, a ZnS protective layer 5 was formed to a thickness of about 50 nm in the same sputtering apparatus. Further, an Au reflective layer 6 was formed thereon to a thickness of about 50 nm in the same sputtering apparatus, and then a ZnS protective layer 7 was formed to a thickness of 150 nm. In the same manner, another SiO ₂
A layer 2 ', a ZnS layer 3', a recording film 4 'having a composition of Sn _14.3 Sb _28.6 Te _57.1 , a ZnS layer 5', an Au reflective layer 6 'and a ZnS layer 7' were formed in this order. The two disks obtained in this way are layered 7 and 7 '.
Lamination was performed with the adhesive layer 8 with the side facing inward. At this time, if the entire surface was adhered, the number of rewritable times could be increased, and if no adhesive was applied to the recording area, the recording sensitivity was slightly increased. Recording, reproduction, and erasure were performed on the disk manufactured as described above as follows. The disk is rotated at 1800 rpm, the light of the semiconductor laser (wavelength 830 nm) is kept at a level where recording is not performed, the light is focused by the lens in the recording head, and one of the recording films is irradiated through the substrate and the reflected light is detected. By doing so, the head was driven such that the center of the light spot always coincided with the middle of the tracking groove.
By setting the middle of the groove as the recording track, the influence of noise generated from the groove can be avoided. While performing tracking in this manner, automatic focusing is performed so that the focus is further on the recording film.First, the recording film on the recording track is heated by continuously irradiating a laser beam having a high power density, Each element was reacted and crystallized. The range of laser power suitable for amorphization is higher than the power for crystallization, but lower than the one that causes strong deformation or has holes. The range of laser power suitable for crystallization is high enough to cause crystallization but lower than where amorphization occurs. Recording in an optical disk drive (recording / reproducing device) was performed as follows. The disk is rotated at 1800 rpm, and the light of the semiconductor laser (wavelength 830 nm) is kept at a level (about 1 mW) at which recording is not performed. The light is focused by the lens in the recording head and irradiated on one recording film through the substrate. By detecting the reflected light, the head was driven such that the center of the light spot always coincided with the middle of the tracking groove. By doing so, the effect of noise generated from the groove can be avoided. In this way, while performing tracking, automatic focusing is performed so that the focal point is further on the recording film, and in the recording portion, the laser power is switched between the intermediate power level of 11 mW and the high power level of 18 mW as shown in FIG. Recording was performed by changing as indicated. The power ratio between the high power level and the intermediate power level is particularly preferably in the range from 1: 0.4 to 1: 0.8. In addition, other power levels may be set for each short time. A portion near the amorphous portion of the recorded portion is considered as a recording point. Once past the part to be recorded, the laser power was reduced to 1 mW and tracking and autofocusing continued. Note that tracking and automatic focusing are continued during recording. Even if such a recording method is performed on a part that has already been recorded, the recorded information is rewritten with newly recorded information. That is, overwriting with a single circular light spot is possible. Such overwriting is a feature of the recording film material of the present invention described in the present embodiment. However, during the first or multiple rotations at the time of recording / rewriting, a continuous light of a power close to 18 mW, for example, 16 mW, which is the higher power of the above laser power modulation, is irradiated to erase once, and then the next one rotation By irradiating and recording a laser beam power-modulated according to the information signal between 11 mW and 18 mW, the previously written information is less likely to be erased,
A high carrier-to-noise ratio is obtained. In this case, as for the power of the continuous light to be irradiated first, good rewriting could be performed in the range of 0.8 to 1.1 when the above high power level was 1. This method is effective not only for the recording film of the present invention but also for other recording films. Recording and erasing was possible repeat in more than 10 ^five times. When the ZnS layers formed above and below the recording film were omitted, a slight increase in noise occurred after several recording / erasing operations. Reading was performed as follows. 1800 rp disc
While rotating at m, tracking and automatic focusing were performed in the same manner as during recording, and the intensity of reflected light was detected with a low-power semiconductor laser beam that was not recorded or erased, and information was reproduced. In this embodiment, a signal output of about 100 mV was obtained. The recording film of this example was excellent in oxidation resistance, and was hardly oxidized even when a ZnS protective film was not formed at 60 ° C. and 95% relative humidity. In the above Sn—Sb—Te type recording film, when the relative content of other elements was kept constant and the Te content was changed, the required irradiation time for erasing was changed as follows. Irradiation time required for erasure Sn ₃₁ Sb ₆₂ Te ₇ 5.0μsec Sn ₃₀ Sb ₆₀ Te ₁₀ 1.0μsec Sn _21.7 Sb _43.3 Te ₃₅ 0.5μsec Sn _17.7 Sb _35.3 Te ₄₇ 0.1μsec Sn ₁₀ Sb ₂₀ Te ₇₀ 0.1μsec Sn _6.7 Sb _13.3 Te ₈₀ 0.5 μsec Sn ₅ Sb ₁₀ Te ₈₅ 1.0 μsec Sn ₄ Sb ₈ Te ₈₈ 5.0 μsec When the Sb content is changed while keeping the relative ratio of other elements constant, the required irradiation time for erasure is as follows. Changed to Irradiation required irradiation time Sn _19.4 Sb ₃ Te _77.6 5.0μsec Sn ₁₉ Sb ₅ Te ₇₆ 1.0μsec Sn ₁₈ Sb ₁₀ Te ₇₂ 0.5μsec Sn _17.4 Sb ₁₃ Te _69.4 0.1μsec Sn ₁₂ Sb ₄₀ Te ₄₈ 0.1μsec Sn ₁₁ Sb ₄₅ Te ₄₄ 0.5μsec Sn ₆ Sb ₇₀ Te ₂₄ 1.0μsec Sn ₅ Sb ₇₅ Te ₂₀ 5.0μsec When the relative content of other elements is kept constant and the Sn content is changed, the power of laser light required for recording and The required irradiation time for erasing varied as follows. Recording laser power Sn ₁ Sb ₃₃ Te ₆₆ 16mW Sn ₃ Sb _32.3 Te _64.7 16mW Sn ₅ Sb _31.7 Te _63.3 16mW Sn ₇ Sb ₃₁ Te ₆₂ 16mW Sn ₂₃ Sb _25.7 Te _51.3 16mW Sn ₃₀ Sb _23.3 Te _46.7 18mW Sn ₅₀ Sb _16.7 Te _33.3 20mW Sn ₅₅ Sb ₁₅ Te ₃₀ Cannot record and required erase time Ir ₁ Sb ₃₃ Te ₆₆ 2.0μsec Sn ₃ Sb _32.3 Te _64.7 1.0μsec Sn ₅ Sb _31.7 Te _63.3 0.5μsec Sn ₇ Sb ₃₁ Te ₆₂ 0.1μsec Sn ₂₃ Sb _25.7 Te _51.3 0.1 μsec Sn ₃₀ Sb _23.3 Te _46.7 0.5 μsec Sn ₅₀ Sb _16.7 Te _33.3 0.5 μsec Sn ₅₅ Sb ₁₅ Te ₃₀ 0.5 μsec Sn-Sb-Te3 On the straight line connecting Sb ₂ Te ₃ and SnTe in the original phase diagram When the composition was changed, the required irradiation time for erasing and the crystallization temperature when the temperature was raised at a constant rate changed as follows. Irradiation required irradiation time Sn ₂ Sb _38.5 Te _59.6 2.0 μsec Sn ₃ Sb _37.6 Te _59.4 1.0 μsec Sn ₅ Sb ₃₆ Te ₅₉ 0.5 μsec Sn ₇ Sb _34.4 Te _58.6 0.1 μsec Sn ₂₃ Sb _21.6 Te _55.4 0.1 μsec Sn ₃₀ Sb ₁₆ Te ₅₄ 0.1μsec Sn _43.8 Sb ₅ Te _51.2 0.1μsec Sn ₄₅ Sb ₄ Te ₅₁ 0.1μsec Crystallization temperature Sn ₂ Sb _38.5 Te _59.6 220 ℃ Sn ₃ Sb _37.6 Te _59.4 220 ℃ Sn ₅ Sb ₃₆ Te ₅₉ 200 ℃ Sn ₇ Sb _34.4 Te _58.6 180 ° C Sn ₂₃ Sb _21.6 Te _55.4 180 ° C Sn ₃₀ Sb ₁₆ Te ₅₄ 160 ° C Sn _43.8 Sb ₅ Te _51.2 140 ° C Sn ₄₅ Sb ₄ Te ₅₁ 120 ° C Keeping the relative ratio of other elements constant, Tl When the content was changed, the required irradiation time for erasing changed as follows. Irradiation time required for erasure α = 0 0.1 μsec α = 1 0.05 μsec α = 10 0.05 μsec α = 15 0.05 μsec If Tl is more than the above content, the time until transmittance increases by 20% at 60 ° C 95% is short. . When the Co content was changed while keeping the relative proportions of the other elements constant, the crystallization temperature and the power of the laser beam required for recording when the temperature was raised at a constant rate changed as follows. Crystallization temperature β = 0 180 ° C β = 1 280 ° C β = 10 300 ° C β = 20 300 ° C β = 30 300 ° C β = 35 300 ° C Recording laser power β = 0 16mW β = 116mW β = 10 16mW β = 20 18 mW β = 30 20 mW β = 35 Cannot be recorded. By keeping the relative ratio of other elements constant and simultaneously adding Tl and Co, there is an effect of increasing the signal modulation degree. In addition, there is an effect that the crystallization temperature is increased by adding 30% or less of a rare earth element such as Gd while keeping the relative ratio of other elements constant. 20% or less is preferable. Particularly preferred is 10% or less. Addition of other elements represented by D also has effects such as a slight improvement in sensitivity and an improvement in oxidation resistance. The thickness of the intermediate layer is 60 / N when the refractive index of the intermediate layer is N.
The range of not less than nm and not more than 160 / Nnm is preferable in that the erase ratio is large. In a thinner region, the cooling rate after laser irradiation is higher in a region with a smaller thickness, so that the region can be surely made amorphous. However, recording / reproducing is possible even in the range of 3 nm or more and 600 nm or less. Bi, Pb, Ga, Au and In by substituting part or all of Sn
Similar characteristics can be obtained even if at least one element is added. Au _14.3 Sb _28.6 Te in which Sn was replaced with Au
_With respect to _57.1 , when the content of Te was changed while keeping the ratio of other elements constant, the laser power required for recording changed as follows. Recording laser power y = 47 20 mW y = 55 18 mW y = 60 16 mW y = 70 16 mW Part or all of Sn is replaced with Bi, and all ZnS layers are replaced with S.
When the b ₂ Se ₃ layer was used, Bi diffused into the adjacent layer, resulting in high recording sensitivity and a sharp rising characteristic of the recording power vs. reproduction signal intensity curve. Has grown. Similar characteristics can be obtained by substituting at least one of a halogen element and an alkali metal element by substituting a part or all of Tl. Preferred halogen element after Tl
Among F, Cl, Br and I, I is particularly preferred, and then Cl is preferred. Among the alkali metal elements, Li, Na, K, Rb, and Cs, Na is particularly preferred, and K is more preferred. Substitute some or all of Co for Cu, Ag, Sc, Y, Zr, V, Nb, C
Similar characteristics can be obtained by adding at least one of r, Mo, Mn, Fe, Ru, Ti, Rh, Ta, W, Ir and Ni. Among them, at least one element of Ti, V, Cr, Mn, Zr and Ni is preferable in that the deposition is easy. Used for at least one of protective film and intermediate layer
SiO _2, SiO instead of ZnS, Y ₂ O ₃ and TaN, AlN, oxides and nitrides such as Si ₃ N _4, sulfides such as Sb ₂ S _3, a selenide such as SnSe _2, SbSe _2, CeF Fluoride such as ₃ , or amorphous Si, TiB ₂ ,
B ₄ C, BC, or the like, or a material having a composition close to each of all the above materials may be used. These laminated films (two or more layers) are also effective for increasing the protection strength. For example, a two-layer structure in which a SiO ₂ layer having a thickness of 300 nm is disposed farther from the recording film and a ZnS layer having a thickness of 110 nm is disposed closer to the recording film has little change in characteristics due to rewriting, and is excellent. As a reflective layer, Ag, Cu,
Similar characteristics were obtained using Ni, Fe, Al, Co, Cr, Ti, Pd, Pt, W, Ta, Mo, etc. As the substrate, instead of chemically strengthened glass having an ultraviolet-curable resin layer formed on the surface, polycarbonate, polyolefin, epoxy, acrylic resin, or the like having a surface directly formed with irregularities such as a tracking guide may be used.

【The invention's effect】

As described above, according to the present invention, it is possible to obtain an information recording member having good recording / reproducing characteristics and stable for a long period of time. Rewriting of the record is possible many times.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a recording member according to an embodiment of the present invention, and FIG. 2 is a diagram showing a recording laser waveform for overwriting in the embodiment of the present invention. 1,1 '... substrate, 2,2' ... SiO ₂ layer, 3,3 '... ZnS layer, 4,4' ... Recording film, 5,5 '... ZnS layer, 6,6' ... ... Au reflection layer, 7,7 '... ZnS layer, 8, ... Organic adhesive layer.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Miyauchi 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Keikichi Ando 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Hitachi Inside the Central Research Laboratory (72) Inventor Tetsuya Nishida 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-62-208442 (JP, A) JP-A-63-76120 ( JP, A) JP-A-62-208441 (JP, A) JP-A-63-187430 (JP, A) JP-A-63-263643 (JP, A) JP-A-63-237990 (JP, A) JP-A-63-251290 (JP, A) JP-A-63-261552 (JP, A) JP-A-1-100748 (JP, A) JP-A-1-220147 (JP, A) JP-A-1-277338 (JP) , A) JP-A-1-303364 (JP, A) JP-A-1-287834 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/26

Claims (3)

(57) [Claims] An information recording thin film, which is formed on a substrate directly or via a protective layer made of at least one of an inorganic substance and an organic substance and which undergoes an atomic arrangement change upon irradiation with a recording beam, wherein the information recording The average composition in the thickness direction of the thin film for use has the general formula SbxTeyAzBαCβDγ (however,
x, y, z, α, β, and γ are 13 ≦ x in atomic percent, respectively.
≦ 40,47 ≦ y ≦ 70,7 ≦ z ≦ 23,0 ≦ α ≦ 10,0 ≦ β ≦ 10,0 ≦
A value in the range of γ ≦ 10 and 1 ≦ α + β ≦ 20;
Is In, B is at least one of Tl, a halogen element and an alkali metal, C is Ag, Cu, Pd, Ta, W, Ir, Sc, Y, Ti, Zr,
V, Nb, Cr, Mo, Mn, Fe, Ru, Co, Rh, and at least one element of Ni, and D is an element other than the elements represented by Sb, Te, A, B, and C)
A thin film for information recording, characterized by being represented by: 2. The general formula SbxTeyAzBαCβDγ (where x, y, z, α, β, and γ are each expressed in atomic percent, formed directly on a substrate or via a protective layer made of at least one of an inorganic substance and an organic substance. 13 ≦ x ≦ 40,47 ≦ y ≦ 7
0,7 ≦ z ≦ 23,0 ≦ α ≦ 10,0 ≦ β ≦ 10,0 ≦ γ ≦ 10 and 1 ≦ α + β ≦ 20, A is In, B is Tl,
At least one of a halogen element and an alkali metal, C is Ag, Cu, Pd, Ta, W, Ir, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, Mn,
Fe, Ru, Co, Rh and at least one element of Ni, D is Sb, T
e) irradiating a recording beam onto the information recording thin film represented by elements other than the elements represented by e, A, B and C) to change the atomic arrangement of the irradiated portion of the thin film, A method for irradiating a beam and reading out the change in the atomic arrangement. 3. The information recording / reproducing method according to claim 2, wherein said recording beam is a laser beam.