JP2713908B2 - Information storage medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a signal obtained by FM-modulating an analog signal such as a video or audio signal by a recording energy beam such as a laser beam or an electron beam, or an electronic computer. The present invention relates to an information storage medium capable of recording digital information such as data and digital audio signals in real time. [Prior Art] There are various recording principles of recording on a thin film by an energy beam such as a laser beam, but recording by a change in the atomic arrangement such as a phase change of a thin film material and photodarkening hardly involves a deformation of the film. Therefore, there is an advantage that a double-sided disc in which two discs are directly bonded can be formed. 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, As-Te-Ge, Te-
Many thin films such as O-based are described. JP-A-54-41902 also discloses Ge ₂₀ Tl ₅ Sb ₅ Se ₇₀ , Ge ₂₀ Bi ₁₀ Se ₇₀
Various compositions are described. Also, Japanese Patent Laid-Open No. 57-24
039 contains Sb ₂₅ Te _12.5 Se _62.5 , Cd ₁₄ Te ₁₄ Se ₇₂ , Bi ₂ Se ₃ , Sb ₂ S
e ₃ , In ₂₀ Te ₂₀ Se ₆₀ , Bi ₂₅ Te _12.5 Se _62.5 , CeSe, and Te ₃₃ Se
₆₇ thin films have been described. [Problems to be Solved by the Invention] When any of the thin films shown in the above-mentioned prior art is used as a once-writable or rewritable phase-change optical recording film, the crystallization speed is slow. Poor absorption, poor sensitivity, insufficient reproduction signal intensity, poor stability of the amorphous state, or insufficient oxidation resistance, has at least one of the following disadvantages:
Practical application is difficult. An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art and to record and
(Erasing)-Good reproduction characteristics, even if rewriting is repeated
An object of the present invention is to provide a thin film for information recording which has a small SN ratio, a high sensitivity and a good stability. [Means for Solving the Problems] The object of the present invention is to express the average composition in the film thickness direction of an information recording thin film used for an information recording member by a general formula A _X B _Y C _Z Dα. This is achieved by: Here, X, Y, Z and α are atomic percentages and 0X <30,50Y + Z100, The value is in the range of 0α <40. D is at least one element of Te, Se, and S, and B and C are Ga, In, Tl, Ge,
Any two or more elements selected from Sn, Pb, Sb, Bi, Au, Ag, Cu, Cd, and Zn, and A is at least one of all elements other than the elements represented by B, C, and D is there. The composition of the recording thin film of the present invention may change in the thickness direction as long as the average composition in the thickness direction is within the above range.
However, it is more preferable that the composition change is not discontinuous. The information recording thin film of the present invention having the above composition range has excellent recording / (erasing) / reproducing characteristics, a small decrease in the SN ratio even after repeated recording / erasing, and a laser used for recording and erasing. Light power may be low. Among the combinations of elements represented by B and C, those having Au as an essential element are most preferred, and then Ag or
Preferably, Cu is used as an essential element, and then, Sn is used as an essential element. Preferred combinations of the elements represented by B and C include Au and Sn, Au and Sb, Au and Ge, Au.
And Ga, Au and Pb, In and Sn, In and Bi, In and Pb, Sn and Pb, Sn and Bi, Sn
And Sb, Sb and Ga, Sb and Ge, and among them, Au and Sn, Au and Sb, Au and Ga, Au and Pb, Sn
And Sb and one of Sb and Ge. The role of at least one element of Te, Se, and S represented by D improves the stability of the amorphous state,
This is to facilitate amorphization by laser beam irradiation.
Of these three elements, at least one of Te and Se is particularly preferred. A is an element other than the elements represented by D, C, and B, for example, Si, As, Cu, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Ru, Co, Rh,
Ni, Pb, Hf, Ta, W, Ir, Pt, Hg, B, C, N, P, O, lanthanide,
It is at least one of an actinide element, an alkali metal element, an alkaline earth metal element, a halogen element, an inert gas element and the like. A more preferable composition range of the information recording thin film of the present invention is as follows. Further, it is particularly preferable that 5α <20. In the present invention, one or more of the elements represented by B, C, and D can be considered to be elements of Group A when another element in each group is already used. For example, when the content of S is less than 30 atomic% in the Au-Sn-Se system, the sum of the S content and the Se content is 40% of the upper limit of the D group element content.
It is conceivable that it is added in a range of not more than atomic%. 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 acrylic resin plate, a polycarbonate plate, an epoxy resin plate, or the like, which is also a substrate, or an organic material such as an acrylic resin, an epoxy resin, polyimide, polyamide, polystyrene, or polyethylene. It may be formed of an inorganic substance mainly containing a substance, fluoride, nitride, sulfide, carbide, boride, boron, carbon, or a metal. Further, these composite materials may be used. At least one of the protective layers adjacent to the recording film is preferably made of an inorganic material. Substrates mainly composed of glass, quartz, sapphire, iron, or aluminum
It can work as one inorganic protective layer. Among organic and inorganic substances, it is preferable that the substance is in close contact with the inorganic substance in terms of heat resistance. However, increasing the thickness of the inorganic layer (excluding the case of the substrate) tends to cause at least one of crack generation, transmittance reduction, and sensitivity reduction. It is preferable that a thick organic material layer is in close contact to increase the mechanical strength. This organic layer may be a substrate. This makes deformation less likely to occur.
As the organic substance, for example, polystyrene, acrylic resin, polycarbonate, epoxy resin, polyimide, polyamide, ethylene-vinyl acetate copolymer known as a hot melt adhesive, and an adhesive are used. UV curable resin may be used. In the case of a protective layer made of an inorganic substance, it may be formed as it is by electron beam evaporation, sputtering, or the like. However, after forming a film made of at least one element of reactive sputtering, metal, metalloid, and semiconductor, Production is facilitated by reacting with at least one of oxygen, sulfur and nitrogen. Examples of the inorganic protective layer include Ce, La, Si, In, Al, Ge, Pb, Sn, and B.
an oxide of at least one element selected from the group consisting of i, Te, Ta, Sc, Y, Ti, Zr, V, Nb, Cr, and W; Cd, Zn, Ga, In, Sb, G
e, Sn, sulfide of at least one element selected from the group consisting of Pb, or selenide, fluoride such as Mg, Ce, Ca, Si, A
It is composed of nitrides such as l, Ta, B, etc., borides such as Ti, carbides such as boron, boron, and carbon. For example, the main components are CeO ₂ , La ₂ O ₃ , SiO, SiO ₂ , In ₂ O ₃ , Al ₂ O ₃ , GeO, GeO ₂ , P
bO, 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 , Ti
O 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, MgF 2, CeF 2, CeF 3, CaF 2, GeS, GeSe, GeSe 2,
SnS, SnSe, PbS, PbSe, Bi ₂ Se ₃ , Bi ₂ S ₂ , TaN, Si ₃ N ₄ , AlN, Si, Ti
It has a composition close to one of B ₂ , B ₄ C, B, and C. Of these, not high surface reflectance is too a nitride, film is stable, TaN in that they are strong, Si ₃ N ₄ or A
A composition close to 1N is preferred. The preferred oxide is
Y ₂ O ₃ , Sc ₂ O ₃ , CeO ₂ , TiO ₂ , ZrO ₂ , In ₂ O ₃ , Al ₂ O ₃ , SnO ₂ or Si
It has a composition close to O ₂ . An amorphous material containing hydrogen of Si or C is also preferable. When performing recording by phase transition, it is preferable to crystallize the entire surface of the recording film in advance, but if an organic material is used for the substrate, the substrate cannot be heated to a high temperature. Need to be done. In this case, it is preferable to perform ultraviolet irradiation and heating, irradiation of light from a flash lamp, irradiation of light from a high-power gas laser, or a combination of heating and laser light irradiation. In the case of irradiation with light from a gas laser, efficiency is good if the light spot diameter (half width) is 5 μm or more and 5 mm or less. Of course, it is also possible to record by crystallization on a recording thin film in an amorphous state. 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, causing interference. When a signal is read by a change in reflectance, the effect of interference can be increased by providing a light reflection (absorption) layer close to the recording film. The reflective layer also has the effect of preventing an increase in noise due to film deformation during recording / rewriting.
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. The intermediate layer is preferably made of a substance that does not absorb much light used for reading. It is preferable that the thickness of the intermediate layer be 3 nm or more and 400 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 reflective layer may be formed between the recording film and the substrate and on any of the opposite sides. A particularly preferred thickness range of the intermediate layer is in the range of 5 nm to 40 nm. It is preferable to form a protective layer made of the above organic material on the side of the reflective layer opposite to the intermediate layer. It is preferable to form an anti-reflection layer on the light incident side of the recording film to reduce the reflectance of at least one of recording light, erasing light, and reading light. The antireflection layer may also serve as a protective layer for the recording film, or a protective layer may be formed between the antireflection layer and the recording film. The anti-reflection layer and the protective layer preferably have a sequentially changing thermal expansion coefficient in the order of recording layer-protective layer-anti-reflective layer-substrate or adhesive or gas, and one of the protective layer and the anti-reflective layer is not formed. It is preferable that the coefficient of thermal expansion changes sequentially also in the case and when each of the layers includes two or more layers. These reflective layers, intermediate layers, antireflection layers, and the like are not limited to the recording film of the present invention, but are also effective when other recording films are used. The recording film of the present invention may be in the form of being dispersed in an oxide, a fluoride, a nitride, an organic material or the like, which can be used as a protective film, by co-evaporation or co-sputtering. By doing so, there are cases where the light absorption coefficient can be adjusted and the intensity of the reproduced signal can be increased. The mixing ratio is the ratio of oxygen, fluorine, nitrogen, and carbon in the entire film.
40% or less is preferable. By forming such a composite film, the crystallization speed is usually decreased, and the sensitivity is usually decreased. However, the sensitivity is improved by forming a composite film with an organic substance. The preferred range of the thickness of each part is as follows. Recording film 30 nm or more and 300 nm or less for a single layer film. 50 nm or more 1
The range of 50 nm or less is particularly preferable in view of the reproduction signal intensity and the recording sensitivity. In the case of a structure having two or more layers with a reflective layer, 15 nm or more and 50 nm or less. However, when protecting with the inorganic substrate itself, 0.1 to 20 mm Organic protective film: 10 nm or more and 10 mm or less Intermediate layer: 3 nm or more and 400 nm or less Light reflective layer: 5 nm or more and 5000 nm or less m ・ K or more 100W / m
When using, for example, stainless steel (Fe _85.9 Cr _13.7 Ni _0.4 , iron alloy containing Cr or V), nichrome, Ni alloy containing Cr, etc. in the range of K or less, recording by heat conduction of this layer This is preferable because there is almost no decrease in sensitivity, and on the other hand, there is an effect of increasing the cooling rate of the recording layer after light irradiation and ensuring the phase transition. The range of the above thermal conductivity is more preferably 10 W / m · K or more and 50 W / m · K or less. In this case, the thermal conductivity of the intermediate layer is 0.1W / m · K or more
It is particularly preferable if it is 3 W / m · K or less. Both the light reflection layer and the intermediate layer have a melting point of 600 to prevent melting during recording / erasing.
C. or higher, particularly preferably 1100.degree. C. or higher. Such a light reflecting layer and an intermediate layer are effective not only for the recording layer of the present invention but also for an optical recording member due to another phase change. The method for forming each of the above layers may be any of vacuum deposition, vapor deposition in gas, sputtering, ion beam sputtering, ion beam deposition, ion plating, electron beam deposition, injection molding, casting, spin coating, plasma polymerization, and the like. It is selected as appropriate. 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 use any change in the atomic arrangement (phase transition, change in crystal form, change in crystal grain size) or the like. What is necessary is just to cause a change in optical properties. 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. [Function] The information recording thin film of the present invention has a high crystallization speed, a high stability of an amorphous state, a large absorption of semiconductor laser light,
High reproduction signal strength and good oxidation resistance. Therefore,
Good recording / erasing characteristics, high sensitivity, and good recording state stability. In addition, even if rewriting is repeated, a decrease in the SN ratio is small. EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples. Example 1 A replica of a tracking groove serving also as a protective layer was formed on the surface of a disk-shaped chemically strengthened glass plate having a diameter of 13 cm and a thickness of 1.2 mm with an ultraviolet curable resin, and one circumference was divided into 32 sectors, and each sector was started. A track address and a sector address are provided in the form of a concave and convex pit in a mountain part in the middle of a groove between grooves (this part is called a header part). On the substrate 14, first, an anti-reflection layer and a protective layer are formed by magnetron sputtering. A 100 nm thick Si ₃ N ₄ layer was formed. Next, this substrate was placed in a vacuum deposition apparatus having an internal structure as shown in FIG. Four evaporation sources 1,2,
3,4 are arranged. Two of these are resistance heating evaporation boats, one of which is an electron beam evaporation source. These boats and the electron beam evaporation source are located substantially below a portion where information is to be recorded on the substrate 14 and on a circle having the same center as the central axis 5 of the substrate rotation. Two deposition boats were charged with Sn and Se, respectively, and Au was charged in the electron beam evaporation source. A mask with a fan slit between each boat and the board 6,
7,8,9 and shutters 10,11,12,13 are arranged and finished. Substrate 14
Was rotated at 120 rpm, a current was applied to each boat, and an electron beam was applied to evaporate the vapor deposition material. The amount of evaporation from each evaporation source is measured using a quartz crystal film thickness monitor 1
Detected at 5, 16, 17, and 18, the current was controlled so that the evaporation rate was constant. As shown in FIG. 1, a recording film 21 having a composition of Au ₃₀ Sn ₆₀ Se ₁₀ was deposited to a thickness of about 70 nm on a layer 20 having a composition close to Si ₃ N ₄ on a substrate 19. Since the Si ₃ N ₄ layer has a higher refractive index than the substrate,
An appropriate thickness also serves as an antireflection layer for semiconductor laser light. When the recording film is in an amorphous state or in a state of poor crystallinity, the reflectance is substantially minimized in the vicinity of the wavelength of the laser beam used for reading when the light reflected by the front surface and the back surface of the recording film interferes with each other. The film thickness is as follows. Subsequently, the thickness of the protective layer 22 having a composition close to that of Si ₃ N ₄ was reduced to about 100 nm by magnetron sputtering again. Similarly 'Si ₃ N ₄ protective layer 20 having a composition close to the above' another one similar substrate 19, the recording of the composition of the Au ₃₀ Sn ₆₀ Se ₁₀ film 21 ', a protective layer having a composition close to SiO ₂ 22 'Was deposited. After applying and forming the UV-curable resin protective layers 23 and 23 'to a thickness of about 50 .mu.m on each of the vapor-deposited films of the two substrates 19 and 19' thus obtained, the two are coated with the UV-curable resin layers 23 and 23 '. Then, the disc was prepared by bonding together with the organic adhesive layer 24 with the 23 'side inside. After heating the disk prepared as described above at 150 ° C. for about 1 hour, rotating the disk, and moving the disk in the radial direction, argon ion laser light (wavelength) collected from both sides by a lens having an aperture ratio (Numerical Aperture) of 0.05 488 nm) to sufficiently crystallize the recording films 21, 21 '. Recording was performed as follows. The disk is rotated at 1200 rpm, and the light of the semiconductor laser (wavelength 820 nm) is kept at a level where recording is not performed. The light is condensed by the lens in the recording head, irradiates one recording film 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 doing so, the effect of noise generated from the groove can be avoided. While performing tracking in this way, perform automatic focusing so that the focal point comes further on the recording film, and increase the laser power according to the information signal,
The recording was made by returning to the original level. Further, recording was performed by jumping to another groove as necessary. Due to the above recording, the recording film was changed in reflectivity, which is considered to be due to the change in the number and size of the crystal grains due to cooling once after melting. In this recording film, recording is erased by irradiating a recording light spot with reduced power or a laser beam whose length in the track direction is longer than the recording light spot and which is wider in the adjacent track direction than the recording light spot. You can also. Recording / erasing could be repeated 3 × 10 ⁵ times or more. When the Si ₃ N ₄ 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. 1200rp disc
While rotating at m, tracking and automatic focusing were performed in the same manner as during recording, and the intensity of the reflected light was detected with a low-power semiconductor laser beam on which recording and erasing were not performed, and information was reproduced. In this embodiment, a signal output of about 100 mV was obtained. The recording film of this example has excellent oxidation resistance, and the film without the Si ₃ N ₄ protective layer was treated at 60 ° C. and 95% relative humidity.
Was hardly oxidized even under the conditions described above. In the above recording film, when the ratio between Sn and Au was kept constant and the sum of both was changed, the laser power required for recording changed as follows. 0%: Cannot record 70%: 11mW 40%: Cannot record 90%: 10mW 50%: 15mW 100%: 11mW 60%: 13mW The ratio was changed while keeping the sum of Sn and Au and their contents constant. When the value of Z / Y was changed with the content of Au being Y% and the content of Sn being Z% in atomic%, the shortest possible erasing time was changed as follows. 0: Cannot record 1: 0.05μs 2.5: 0.05μs 3: 0.1μs 4: 0.7μs 6: 1.0μs 9: 2.0 μs 10:20 μs 14: Irreversible Δ: Irreversible (that is, Y = 0) In the above recording film, when the content of Se was changed while keeping the relative ratio of other elements constant, the temperature rose. Speed 5 ℃ /
Start temperature of crystallization when heated in minutes (called crystallization temperature)
The shortest erasable time (called the erasing time) changed as follows. Crystallization temperature 0%: 60 ° C 20%: 150 ° C 3%: 80 ° C 30%: 175 ° C 5%: 100 ° C 40%: 200 ° C 10%: 130 ° C 50%: 150 ° C Minimum erasing time 0%: 0.03 μs 10%: 0.05 μs 20%: 0.1 μs 30%: 0.5 μs 40%: 2.0 μs 50%: 10 μs When Si is added while keeping the relative ratio of other elements constant, the crystallization temperature and The erasing ratio at the time of erasing (the ratio of the signal at the time of recording to the signal after erasing expressed in dB) changed as follows. Crystallization temperature 0%: 130 ° C 20%: 180 ° C 5%: 150 ° C 30%: 200 ° C 10%: 160 ° C 40%: 170 ° C Erasure ratio 0%:-35dB 20%:-30dB 5%:-32dB 30%: -27 dB 10%: -30 dB 40%: -10 dB A part or all of Au and Sn in the present embodiment are Ga, Tl, Ge, Pb, Sb, Bi, Sn, which are elements of the B and C groups. Similar results can be obtained by substituting one or more of Ag, Cu, Cd and Zn. Part or all of Se of the present embodiment is a group D element Te.
Substantially the same result can be obtained by replacing at least one of S and S. Part or all of Si of the present embodiment is an element of Group A.
Similar results can be obtained by replacing with at least one element other than the elements in the B, C, and D groups. Among these, the element having an interatomic distance of 3.0 ° or more, more preferably 3.5 ° or more, when contained by 1% or more, has an effect of facilitating phase change. Good characteristics were obtained when the thickness of the recording film of this example was 60 nm or more and 350 nm or less, and when the inorganic protective layer was 5 nm or more and 200 nm or less. Instead of Si ₃ N ₄ as a protective film, ZrO ₂ , SiO, SiO ₂ , Y ₂ O ₃ or T
It is possible to use nitrides such as aN and AlN, sulfides such as Sb ₂ S ₃ , fluorides such as CeF ₃ , or amorphous Si, TiB ₂ , B ₄ C, B, C, etc. Good. It is preferable that the protective film on the light incident side has a film thickness having an antireflection effect, because it has an effect of improving recording sensitivity and the like. Example 2 A disk shown in FIG. 1 was produced in the same manner as in Example 1. On the recording film 21, a recording film having a composition of In ₃₇ Sb ₄₈ Au ₁₅ was formed with a thickness of about 80 nm. In the above recording film, the ratio of In to Sb was kept constant to Au
When the content was changed, the time until the C / N decreased by 3 dB when the disk was left in a constant temperature and humidity of 80 ° C. and a relative temperature of 95% was changed as follows. Time until C / N decreases by 3dB 0%: 100 hours 5%: 300 hours 10%: 1000 hours 15%: 2000 hours 20%: 2000 hours In the above recording film, the relative values of In, Sb and An When adding Se while keeping the ratio constant, the linear velocity of the disk rotation
Bandwidth 30kH when recording 8m / s, recording frequency 4MHz signal
The carrier-to-noise ratio (C / N) at z and the erasure time changed as follows. C / N erase time 0%: 40dB 0.02μs 10%: 45dB 0.04μs 20%: 50dB 0.5μs 30%: 52dB 2.0μs 40%: 50dB 10μs Example 3 As shown in FIG. Using a polycarbonate plate 25 having tracking grooves formed on the surface of a polycarbonate plate, a 200 nm thick protective film 26 having a composition close to that of ZrO ₂ was formed by sputtering. Next, a recording film 27 having a composition of Au ₅₀ Sb _{50 and} a thickness of 30 nm was formed thereon.
Subsequently, an intermediate layer 28 having a composition close to ZrO _{2 and} having a thickness of 200 nm is formed, and a reflective layer 29 having a composition of 500 nm thick Fe ₇₄ Cr ₁₈ Ni ₈ and a ZrO 2
_A 200 nm thick protective layer 30 having a composition close to ₂ was formed. Prepare another substrate in the same way, and ZrO ₂ layer on top of both substrates
After sputtering the polyimide 31 on each of the layers 30 to a thickness of about 0.5 μm, both substrates were bonded together with the hot melt adhesive 32 mixed with a black pigment with the polyimide layer side inward to produce a disk. If a polyimide layer is also formed on the surface of the polycarbonate plate by a sputtering method, a more stable disk can be obtained. The crystallization method, recording method, erasing method, and reading method are almost the same as those in the first embodiment. In the disk A having the reflective layer 29 and the disk B without the reflective layer 29, the carrier-to-noise ratio (C / N) at a bandwidth of 30 kHz after repeated recording / erasing was changed as follows. Number of repetitions Disk A Disk B 1 time 53dB 53dB 10 times 53dB 48dB 10 ³ times 52dB 42dB 10 ⁵ times 50dB 35dB Instead of ZrO _{2 for} the intermediate layer, GeO ₂ , Al ₂ which can be used as a protective layer in Example 1 O ₃ , CeO ₂ , Y ₂ O ₃ , SiO, SiO ₂ , AlN, Ta
Another inorganic transparent substance such as N may be used, or an organic layer may be used. The thermal conductivity of these layers is particularly preferably from 10 W / m · K to 50 W / m · K. If the reflective layer also undergoes a change in the atomic arrangement during recording, the reproduced signal becomes slightly larger. A part or all of the elements of the groups B and C included in the recording film may be replaced with at least one of the other elements in the same group. In that case, Au as an essential element has the longest storage life and is most preferable. Next, it is preferable that Ag or Cu is an essential element, and then that Sn is an essential element. In addition, in the combination of the elements represented by B and C, Au and Sn, Au and Ge, Au in addition to Au and Sb.
And Ga, Au and Pb, In and Sn, In and Bi, In and Pb, Sn and Pb, Sn and Bi, Sn
And Sb, Sb and Ga, Sb and Ge, and particularly preferred are Au and Sn, Au and Sb, Au and Ga, Au and Pb, Sn and Sb, and Sb and Ge.
Is one set. However, those containing Sb have some problems in terms of toxicity. Further, when at least one element of Te, Se, and S in the D group is added in less than 30%, there is an effect that the stability of the recording state increases, the thermal conductivity decreases, and the recording sensitivity improves. Further, when at least one of the elements such as Co in Group A is added in an atomic number of less than 30%, the effect of improving the erasing speed and the recording sensitivity can be obtained. However, it is preferable that the amount of addition be 1% or more and 15% or less in terms of the SN ratio. When the thickness of the recording film is in the range of 15 nm or more and 50 nm or less, the reflectance when the recording film is in an amorphous state is reduced by interference, and a large reproduction signal is obtained. The thickness of the reflective layer is 5 nm or more and 5000 nm
The following range, more preferably in the range of 200 nm or more and 1000 nm or less, is preferred because the effect of preventing deformation during recording / erasing is large. By providing the reflective layer, a large reproduction signal can be obtained in a region where the film thickness of the recording film is thinner than in the case of a single layer, so that good characteristics can be obtained even in a composition region where the absorption coefficient of the recording film is larger than in the case of a single layer. Can be When the thicknesses of the recording film and the intermediate layer are changed, the wavelength at which the minimum occurs due to the interference of the read light reflectance changes. The minimum required reflectance for autofocusing and tracking is
Since it is 10 to 15%, when the minimum value of the reflectance is equal to or less than this value, it is necessary to set the minimum value on the long wavelength side or the short wavelength side with respect to the wavelength of the reading light. When the minimum value comes to the short wavelength side, the thickness of the recording film can be reduced, and energy loss due to heat conduction can be prevented. However, it is preferable that the minimum value comes to the longer wavelength side because the film thickness becomes thicker, in terms of the life of the recording film and the prevention of noise at the time of recording / rewriting. The reflective layer is made of stainless steel, nichrome, etc. and has a thermal conductivity of 5 W / m · K or more and 100 W / m · K at room temperature.
The following can be used: Thermal conductivity at room temperature
More preferably, it is 10 W / m · K or more and 50 W / m · K or less. If the thermal conductivity is too high, the recording sensitivity is lowered, and if it is too low, phase transition, particularly, amorphization becomes difficult. Further, in this case, it is particularly preferable that the thermal conductivity of the intermediate layer be 0.1 W / m · K or more and 3 W / m · K or less. The recording film of this embodiment is also excellent in oxidation resistance like the recording film of the first embodiment. For example, even if there is a pinhole in the protective film, oxidation does not progress around the pinhole. It goes without saying that the recording layer of this embodiment can obtain good characteristics even when the reflective layer is not formed. [Effects of the Invention] According to the present invention, it is learned to obtain an information storage medium having an information recording thin film that has a simple manufacturing process, good reproducibility, good recording / reproducing characteristics, and long-term stability. . Records can be rewritten many times.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are sectional views showing the structure of a recording member according to an embodiment of the present invention, and FIG. 3 is a plan view showing the structure of a vacuum deposition apparatus used in the embodiment. It is. 19,19 '... substrate, 20,20', 22,22 '... Si ₃ N ₄ layer, 21,2
1 ': Recording layer, 23, 23' UV curable resin layer, 24: Organic adhesive layer, 25, 25 ': Substrate, 26, 26', 28, 28 ', 30, 30'
... ZrO ₂ layer, 27, 27 ′: recording film, 29, 29 ′: stainless steel film, 31, 31 ′: polyimide resin layer, 32: hot melt adhesive layer.

Continuation of front page    (72) Inventor Keikichi Ando               1-280 Higashi Koigabo, Kokubunji-shi               Central Research Laboratory, Hitachi, Ltd. (72) Inventor Yasushi Miyauchi               1-280 Higashi Koigabo, Kokubunji-shi               Central Research Laboratory, Hitachi, Ltd. (72) Inventor Reiji Tamura               1-188 Usutora, Ibaraki               Inside Maxell Co., Ltd.                (56) References JP-A-60-179954 (JP, A)                 JP-A-59-218644 (JP, A)                 JP-A-60-177446 (JP, A)                 JP-A-63-155435 (JP, A)

Claims (1)

(57) [Claims] An information storage medium having a thin film formed directly on a substrate or through a protective layer made of at least one of an inorganic substance and an organic substance and undergoing an atomic arrangement change upon irradiation with an energy beam, wherein the thin film is the film The average composition in the thickness direction is represented by the general formula A _X B _Y C _Z D α (where X, Y, Z and α are respectively 0 ≦ X <30, 50 ≦ Y + Z ≦ 100, 1/9 ≦ Z / Y ≦
9,0 ≦ α <30, D is Se, B and C are Au
And Sn, Au and Ga, Au and Pb, A is an element represented by B, C, and D, and other than Au, Ge, Sb, In, Tl, Bi, Ag, Cu, Cd, and Zn. (At least one of the above). 2. 2. The information storage medium according to claim 1, wherein the elements represented by B and C in the general formula are Au and Sn.
An information storage medium characterized by the following.