JPH04134642A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To allow high-speed rewriting of information by extremely thinly forming a material which cannot attain a stable amorphous state at room temp. on a substrate. CONSTITUTION:Stabilizing layers 2 and recording layers 3 are repetitively laminated on a resin substrate 1 having a smooth surface and the uppermost layer is formed as the stabilizing layer. The stabilizing layers are preferably dielectric thin films from the reasons that these films are optically transparent and have a sufficiently high m. p. The recording layers are constituted of materials which hardly attain the amorphous state usually at room temp. The relations between the thicknesses of such stabilizing layers and the thicknesses of the recording thin-film layers are so determined as to hold the relations 3>=d1/d2>=1/3, 10nm>=d1>=1nm, 30nm>=d2>=1nm when the thickness of the recording layer is designated as d1 and the thickness of the stabilizing layer as d2. The recording medium which is excellent in all of stability, recording sensitivity, erasing sensitivity and rewriting times is formed in this way.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to optical information recording media that are capable of recording and rewriting information signals at high speed and high density using means such as laser beams. Although research is actively being conducted on large-capacity rewritable recording media that can record large amounts of information at high speed, reproduce it at high speed when necessary, rewrite it, and store it again. A lot of research has been done on phase change recording media, which is a promising candidate for recording information by causing a reversible structural change (phase change) at high speed by laser irradiation and using the accompanying change in optical properties. The typical recording thin film material that has been used is chalcogenide thin films, which are known to easily change their structure between an amorphous state and a crystalline state depending on the laser beam irradiation conditions. What was attempted was Te
A low melting point system mainly composed of, for example, Tea+Ge+s
S best (Special Publication No. 47-26897), T
e*sG esS n+5Auas (Unexamined Japanese Patent Publication No. 1986-1
12420), etc. In recent years, systems with high melting points near the compound composition have attracted attention, and GeTe
, (GeTe)ssSnIs (JP-A-62-40648
Publication), GeTe-5b*Te Spring (Proc, o
InS
b, AgZn, etc. are known, but when applying these thin films to the recording layer, in most cases the recording thin film is generally sandwiched between dielectric layers. For example, the above-mentioned GeTe, Sb2Te*
It has been shown that a ZnS thin film is used in the case of Z,
, Zn5M plays the role of efficiently dissipating the heat generated in the recording layer to the surroundings, and improves the recording and erasing characteristics.
Although it is obvious to use nitrides such as AIN, it is also known that a metal reflective layer is added to create a four-layer structure to increase light absorption efficiency. For the purpose of increasing the performance, a structure has been proposed in which a metal film with a thickness of 2 to 20 nm and an Sl oxide film with a thickness of 1 to 40 nm are repeatedly stacked (Japanese Patent Application Laid-Open No. 6O-187950). Here, examples of materials used as the recording layer include Sb*Te*, Co,
Pt, Te, and other metals have been mentioned, but there are no compositional proposals or limitations for performing rewrite recording. In the case of phase change materials, the materials that can be used are severely limited by the stability of the amorphous state. Furthermore, even if a thin film in a crystalline state is irradiated with a laser, it will not become amorphous. This means that the crystallization transition temperature of the material is much lower than room temperature. , or because the crystallization rate is too high and the critical cooling rate required for amorphous formation is not satisfied.
The composition of a compound containing Ge has been limited to a composition in which the amorphous phase is sufficiently stable for a recording thin film alone. However, the important characteristics for an optical recording medium are not only the stability of the amorphous state, but also the crystallization rate. There are many things that need to be satisfied, such as being large and having a long life after repeated recording and erasing.However, it cannot be said that a material that is stable in an amorphous state is necessarily superior in other properties, and can actually be used as a recording medium. The scope of the present invention was extremely narrow.The present invention was created in view of the above problems, and by making improvements to the structure of the recording medium and using a thin film of a material that could not be used as a phase change material in the past, information can be transmitted at high speed. In order to solve the above-mentioned problems, an amorphous state which is stable at room temperature has conventionally been realized. The material that could not be produced is made extremely thin from 1 nm to 10 nm and formed on the substrate, and at least a dielectric layer with a melting point higher than that of the material of the recording layer is laminated on the surface. By becoming thinner, the internal electronic state becomes different from the bulk state, suppressing rapid structural changes, stabilizing the amorphous state at room temperature, and reducing the amount of heat generated in the recording layer during laser irradiation. By reducing the heat dissipation effect and increasing the heat dissipation effect with the above structure, it becomes easier to realize a more stable amorphous state with lower order.

EXAMPLES Hereinafter, the present invention will be described in detail with examples. FIG. 1 is a sectional view showing the structure of an optical information recording medium of the present invention. On top of the recording layer is Z, which promotes amorphousization of the recording layer and stabilizes the state by separating it from other recording layers.
It has a structure in which the nS stabilizing layer 2.5nTe recording layer 3 is repeatedly laminated in 5 layers, with the top layer being the stabilizing layer.The light absorption per recording layer is small, and the amount of change before and after recording cannot be too large. Therefore, even if the overall light absorption change is increased by repeatedly stacking recording layers, the thickness of each layer is 3 m. It has a structure in which it is laminated with an adhesive layer 4 in between (a) Of course, it may be a single-plate structure (t) It is also possible to laminate only a resin plate without a recording film or stabilizing layer on one side. Although the 5nTe thin film that forms the recording layer is conventionally known as a crystalline material, it cannot be processed by vapor deposition or sputtering.
When a recording film is formed using a conventional film formation method, a film in a crystalline state is formed. However, it has been confirmed optically and by X-ray diffraction that an amorphous state is indeed achieved in the structure of the present invention. It was confirmed that a stable amorphous state was formed without any sudden changes even when left for a long time.9 This recording medium was irradiated with a laser beam with a wavelength of 830 nm focused on a light spot of 0.9 μm in diameter. The laser irradiation was performed using the device shown in Figure 2. This has already been reported as a "static tester" (Proc.
f 5PIE V.

1, 695 P79), Strong irradiation storm of irradiation light It is possible to set the irradiation time arbitrarily, and even if the system detects changes in the irradiated area as changes in the reflectance of the recording medium, as shown in Figure 2 below, The recording and erasing method and recording and erasing characteristics of the optical information recording medium of the present invention will be explained with reference to the following.A laser beam 6 emitted from a semiconductor laser 5, which is a light source, becomes a parallel beam at a collimating lens 7 and a beam splitter 8.
, passes through the λ/4 plate 9, is focused by the objective lens 10, and is irradiated onto the recording medium 11, causing changes in the recording medium.The light source is directly driven by the pulse generator 12, and the pulse width (irradiation time), pulse Even if you can set a high (irradiation intensity), the state after irradiation is 】) Reduce the intensity of the irradiation light to the extent that it does not change the irradiation area. 2) Convert the reflected light from the irradiation area to the λ/4 plate 9, -8, guided to the photodetector 14 through the lens 13, 3) can be detected in the process of reading the output of the detector, but in the case of the recording medium using the above 5nTe, for example, 8mW
, laser irradiation for 200 ns causes crystallization and the reflectance increases.9 Furthermore, when a recording medium that has been pre-crystallized in an oven is irradiated with a laser at 15 mW for 200 ns, the irradiated area becomes amorphous and the reflectance decreases. 9. Section plate The substrate 1 constituting the above-mentioned recording medium in which information has been rewritten using a 5nTe thin film, which could not be applied as a conventional rewritable phase change recording thin film, is a resin substrate other than polycarbonate resin. For example, PMMA, vinyl chloride amorphous polyolefin, etc. are preferable.Also, a glass plate can also be used, but when a glass plate is used, a stabilizing layer on the substrate side of the recording film is not necessarily required.
, % If the recording medium has a structure that prevents the laser beam from entering from the substrate side,
Metal plates are also effective when forming recording layers on both sides of a single substrate. Copper plates Stainless steel plates, titanium plates, etc. are used as stabilizing layers, but they must be optically transparent and have a sufficient melting point. Dielectric thin films are preferable due to their high cost, etc.
Materials conventionally used in optical discs, such as Sio
z, Ge0t, T i Oa, Z rot
.

``f'at○5 etc. oxide thin wL ZnS, Zn5e etc. chalcogenide thin 111L TiN, SiN,
A.I.N.

Nitride thin trap such as ZrN Ca F 2. L a F
It is effective to use fluorides such as -, or an amorphous carbon film.The recording layer is usually made of a substance that is difficult to achieve an amorphous state at room temperature.For example, it is difficult to achieve an amorphous state when solidifying from a melt. The reason for this is that by making the recording layer extremely thin, the present invention realizes amorphousization of a substance that has conventionally been considered difficult to achieve an amorphous state, and uses this as a phase change recording thin film. This is because the amorphous layer is stabilized too much when a substance that has been conventionally used as a stable amorphous substance is used, which causes negative effects such as a decrease in crystallization sensitivity. A As a specific composition (for example, as a stoichiometric compound composition, in addition to the above 5nTe, SnSb2T
ea (SnTe-3b2Tes), Pb2Sb@
Te++ (2PbTe 3Sb2Te=) and the composition around these showed favorable effects.
The effect was also confirmed with Tea, Ag2Te, and their surrounding compositions.Also, by adding a small amount of Ge to the above composition, or by replacing a part of Sn or Pb in these systems, the concentration of which is higher than the concentration of Sn or Pb. G without exceeding
In addition, systems in which the polar portion of Te in these systems is replaced with Se have a particularly large effect on the number of rewrites.What is important here is the thickness of these stabilizing layers and the recording thin film. The thickness of the stabilizing layer is related to the thickness of the layer.
It is determined from three points: the mechanical strength that separates each recording layer, and the light absorption efficiency.The thicker the stabilizing layer, the greater the heat diffusion efficiency. The volume ratio of the light-absorbing substance in the medium decreases, and the light absorption rate decreases, resulting in a decrease in both recording and erasing sensitivity.
On the other hand, if the thickness of the recording film is made thinner than that of the recording film, the overkill and the volume change of the recording thin film caused by the heat process of erasing records will destroy the stabilizing layer. Put it away. Based on the configuration shown in Figure 1, various film thicknesses and film thickness ratios of 5nTe and ZnS were selected and laser irradiation was repeated, and when the 5nTe recording layer was thinner than 10 nm, it was possible to make it amorphous by laser irradiation. As the thickness of the recording film was further reduced, the amorphization sensitivity increased, and the laser irradiation power required for near-amorphization gradually decreased.On the other hand, when the recording film was made thinner than 1 nm or 1 m, amorphization became extremely easy, but crystallization occurred. 9. When the recording layer becomes thinner, the electronic state is significantly different from the bulk state. In other words, the degree of freedom of the electrons decreases, so it is thought that the speed of structural change and the stability of the structure change. In a region where the layer is thinner than 1 nm, the characteristics change significantly from the bulk state, and it is thought that the unique characteristics disappear.When the recording layer is 1 nm or more, the thickness of the stabilizing layer is determined regardless of the thickness of the recording layer. It is necessary that the film be thicker than 1 nm; if it becomes thinner than this, the preservation of the structure will deteriorate.
The most favorable characteristics were obtained between the nine-section plate and a stable amorphous state, which simultaneously achieved a high crystallization rate. The thickness of the stabilizing layer is d
When set to 2, 3≧ d 1/d 2 ≧ 1/3 (1) 10n
m ≧ dl ≧ 1 nm (2) 30 nm
≧ d2 ≧ Inm Stabilization method when the three relational expressions (3) hold. It has been found that a recording medium with excellent recording sensitivity, erasing sensitivity, and number of rewrites can be formed. The structure of the recording medium is the above repetition method. Of course, it is also possible to consider the multilayer structure as one recording layer and configure it as a conventional three-layer structure or four-layer structure.In this case, as shown in FIG. 3, an enhancement layer 14 on both sides of the recording layer, a reflective layer The thickness of each film in No. 15 is determined so that the light absorption rate in the recording layer becomes large.The water is applied so that the optical change becomes large.As the material of the enhancement layer, the same substance as the above-mentioned stabilizing layer is used.

In addition, the reflective layer includes Au, AI, Ti,
Metals such as CuNi, Cr, Pd, and Pt, or associations between them, such as Au-Al, Ni-Cr,
AlTi, Al-Cr, Au-Pd, etc. can be used.

The optical information recording medium of the present invention can be formed in the same manner as the process for manufacturing ordinary thin films. In the case of the embodiment shown in Fig. 1, a sputtering device having two targets of 5nTe and ZnS in a vacuum chamber is used to form a film using Ar gas as the sputtering gas, and the two targets can be opened and closed independently by shutters. It was formed by depositing films of a specified thickness alternately on a substrate.The vacuum evaporation method using electron beam heating could also be used for the formation method.
In this case, three sources of Sn, Te, and ZnS were prepared in a vacuum chamber. The three sources can be opened and closed independently by shutters, and when the recording film is deposited, Sn and T
The ZnS source was co-deposited on the substrate with the two sources of e open, and when the stabilizing layer was deposited, the ZnS source was turned on and deposited alternately on the substrate, and the thickness of each layer was determined by measuring the sputtering rate or evaporation rate in advance. However, for more accuracy, it is possible to calculate the change in optical reflectance with respect to film thickness in advance from the relationship between optical constants and film thickness, and then monitor the reflectance. However, when using multiple targets and deposition sources, rotating the substrate and passing it over each target and source has an effect on composition uniformity.When using a reflective layer, the number of targets can be However, it was important to configure each layer in-line without breaking the vacuum.For example, if the vacuum was broken between each layer, There was a tendency that the number of repetitions decreased due to the formation of an oxide layer and the unevenness of the interface.The present invention will be explained below based on more specific examples.Example 1 5 by sputtering on a glass substrate
nTe thin film or PbTe thin film, respectively. 5nm,
In@Znm, 3nm, 4nrrb5n
m, 6n@7nm, 8nm, 9nm,
For samples in which a 10n film was formed to a thickness of 15nm or 20nm and a 10nm 5iOa film was formed thereon, a (recording layer formation and stabilization layer formation were formed in-line), b (recording layer formation and stabilization layer formation) Two types of thin films were prepared (those exposed to the atmosphere once during layer formation) and their structures were examined by X-ray diffraction immediately after forming these thin films71.
The following results are commonly obtained for both PbTe and 5nTe.
A slightly crystalline diffraction peak was observed in the 0 nm sample915
, the 20 nm sample is completely crystalline.
No crystalline diffraction peaks were observed in the thinner samples.9 In the sample b, in addition to the 15 nm and 20 nm samples, the 10 nm sample was already crystallized, and the 9n melon 8
A broad and low crystalline diffraction peak was detected at nm? , :,, No crystalline peak was observed in samples with a diameter of 7 nm or less. When each of the above samples was irradiated with a laser beam under various conditions using the apparatus shown in Figure 2, in both cases a and b. For samples with a thickness of Znm or more, the pulse width is 200n.
Due to laser irradiation of s, the reflectance changes and crystallization occurs.91
A longer laser irradiation was required for a 0.5 nm sample.In addition, no crystallization due to laser irradiation was observed for a 0.5 nm sample.Subsequently, the crystallized sample was irradiated under different irradiation conditions, resulting in a 10 nm laser irradiation. Example 2 It was found that the following samples were made amorphous, and samples with a thickness of 1 nm to 5 nm had higher sensitivity than thicker samples and were relatively easily made amorphous. In Example 1, the recording thin film was made of SnSbiTe4 or P.
The bus beT e++ and the stabilizing layer film is ZnS.
A film was formed using the vapor deposition method, and a similar experiment was carried out.In this case, the following results were obtained for two types of recording film compositions. 20
The 15 nm sample was completely crystallized, and the 15 nm sample had a diffraction peak with slightly advanced crystallization.
No crystalline diffraction peak was observed in the thinner samples. When each of the above samples was irradiated with a laser beam under various conditions using the apparatus shown in Figure 2, the thickness was Znm in both cases a and b. Pulse width 200n for the above samples
Due to laser irradiation of s, the reflectance changes and crystallization occurs.9
For samples with a thickness of 1 nm, longer laser irradiation was required.9 Also, for samples with a diameter of 0.5 nm, crystallization due to laser irradiation could not be confirmed. It was found that the following samples were made amorphous, and that samples with a thickness of Inm to 5 nm had higher sensitivity than thicker samples and were relatively easily made amorphous.9 Example 3 Substrate 1. A 2mm thick PMMA or polycarbonate plate with 10nm thick ZnS on each surface! ! L
5nTe or PbTe recording trap 10nm thick Z
9. Form three layers of nS film by in-line sputtering without breaking the vacuum. 9. Glue the same plate as the substrate on top of it using ultraviolet curing resin. 9. Adjust the thickness of the recording layer from 0.5 nm to 0.5 nm.
The same experiment as in the example was carried out for each sample, varying up to 20 nm in m increments.The results showed that an amorphous state was achieved for all recording films with a film thickness of 10 nm or less in the analysis by X-ray diffraction. 0.5 according to laser irradiation
It was confirmed that it was difficult to crystallize a sample with a diameter of 130 mm and a thickness of 1.2 mm.
mm, depth 0. 7μa 1. 6μm pitch)
A ZnS-5ide mixed film (S
i Os: 20mo 1%), 5n4eQe+
5Tess films are repeatedly stacked, and the top layer is ZnS.
Prepare an optical disc with two recording layers laminated on the inside of Si0g films formed by sputtering.
The thickness of the recording layer is 3 nm, and the thickness of the stabilizing layer is 0.
5nm, ln@3nm, 5nm.

Each recording layer is formed in an amorphous state, and each recording layer is formed in an amorphous state.The optical disc has a wavelength of 830n and one semiconductor laser with a maximum output of 40mW. A laser recording erasure experiment was conducted on an experimental deck that rotated at 180 rpm.The experimental deck has a common configuration among people engaged in this technical field, and has a mechanical disk servo (rotation) and tracking. , a laser drive circuit (power servo), an optical recording head (the numerical aperture of the objective lens is 0.5), etc. Even if the irradiation is performed while selecting the irradiation power for each optical disk, it will not work on any optical disk. It was confirmed that crystallization occurs at a certain power P1 depending on each optical disc, and that amorphization occurs at a power P2 greater than P1, that is, it is possible to record and erase information.9 At this time, the stabilizing layer It has been observed that the sensitivity decreases as the thickness increases, and in the case of a stabilizing layer of 1 nm, the area that can become amorphous decreases. The reflectance from the disk was measured each time the stabilization layer was measured, and the thickness of the stabilizing layer was Q.
For a 51m disk, the reflectance shifted significantly after several irradiations, and the L structure was destroyed.When the thickness of the stabilizing layer was 1 nm or more, no change was observed even after irradiation was repeated 1000 times.Example 5 M-Te- Ge (M is Sn or Pb) ternary system with 5n
The following experiments were performed using compositions around Te or PbTe.7', 2 nm thick ZnS was deposited on a PMMA resin substrate
A thin film and a 2 nm thick M-Te-Ge thin film of various compositions were repeatedly laminated in 10 layers, and a ZnS film was formed on the top layer.
A recording medium was constructed by pasting the same plate as the substrate on top of this. Using the above-mentioned static tester, crystallization was performed with a pulse width of 200 ns (8 8 ns on the sample surface).
As a result of repeated experiments of m W ) and amorphization (20 mW at the sample surface), the compositional gradient plate shown in Figure 4 was obtained.
tax MxGeyTez (25<x<60゜Q<
y<25. 37. 5<z<60), the following conditions are satisfied: 1) an amorphous film is formed, 2) crystallization is achieved, 3) repetition is possible over 1000 times, and 4) there is no shift in reflectance during that time. Experiments were also conducted with different pulse widths (
Example 6 It was found that recording and erasing was possible in a short time of 100 ns or less, especially on the MTe-GeTe composition line.Experiment similar to Example 5 around the ternary compositions of SnSb*Te4 and pbtSb*Te++ performed
In this case, for each central composition, the content of each of the first constituent elements will be increased.Example 7 where the above conditions are satisfied for a change of -5 at%.In the composition range obtained in Example 6, Sn or Pb When an attempt was made to replace part with Ge, the addition of Ge improved the sensitivity of amorphization.9 When the Ge concentration exceeded the concentration of Sn or Pb, the crystallization sensitivity decreased.Also, recording and erasing was repeated over 5,000 times. Example 8 A ZnS 5ift layer with a thickness of 1100 nm was formed on a glass disk substrate with the same grooves as in Example 4, and 2
．． 5nm thick SnaGesTesa film and 5nm thick
15 thick ZnS-5ide films were alternately stacked, and then a 1100nm ZnS-5ide layer was added on top of that.
, 50 layers of Al-Cr (Cr: 5at%) film
Two laminated discs were prepared and pasted together with the recording surface inward.The disk was rotated at 1800 rpm and a recording experiment was conducted at the outermost periphery (linear velocity 15 m/s).First, the irradiation power was set to lomW on the recording surface. continuous irradiation as
One track was crystallized Next When the laser power was modulated at 5 Hz between a peak level of 20 mW and a bias level of 10 mW and the crystallized track was irradiated, the area irradiated with the peak power became amorphous and no recording was made. 9 When the laser power was lowered to 1 mW and the information was reproduced while being continuously irradiated, a CN ratio of 50 dB was obtained for the 5 MHz component.9 Next, the laser power was modulated at 2 MHz. When irradiation was performed, the 50MHz component was 35% before irradiation.
dB decrease, and the 2MHz component has changed to 50dB CN.
The effect of the invention is that it has been confirmed that information can be repeatedly rewritten by alternately irradiating at 92 frequencies. It has become possible to apply substances that have been developed for phase change recording media, and it has become possible to provide recording media using novel recording thin films.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional diagram showing the configuration of one embodiment of the optical information recording medium of the present invention. FIG. 2 is a schematic configuration of a stationary evaluation system for examining the characteristics of the optical information recording medium of the present invention against laser irradiation. Figure 3 is a cross-sectional view showing the structure of another embodiment of the optical information recording medium of the present invention.
is a diagram showing the composition range of the ternary thin film (Sn or Pb).
...Adhesive support 5...Semiconductor laser 6...Laser light fttL 7...Collimating train X 8...
Beam splitter 9...λ/4 plate, 10... Objective lens, C11... Recording medium 12... Pulse generator 13... Len X 13... Photodetector 14... Enhancement # 15... Repeated multi-layered wind 16... Enhancement [17... Name of reflective seed agent Patent attorney Akira Okaji and 2 others V Rido l Haji Ni) Fig. 1 ---D) Hensjn F date (number 4th figure e 7e (5n nu+sPb>

Claims (15)

[Claims] (1) A recording thin film that undergoes a reversible phase transition between a plurality of optically detectable states upon irradiation with a laser beam, and a recording thin film that is formed in close contact with at least an upper side of the recording thin film to promote phase change of the recording thin film. An optical information recording medium comprising at least two stabilizing layers stacked on a substrate, wherein the recording thin film contains a substance that does not form a non-equilibrium state that is stable at room temperature in a bulk state. 1. An optical information recording medium, characterized in that the stabilizing layer is a dielectric thin film having a melting point higher than that of the recording thin film, and the stabilizing layer is a thin film having a thickness of between 10 nm and 1 nm. (2) The optical information recording medium according to claim 1, characterized in that a reversible phase change between a crystalline state and an amorphous state is used. (3) The optical information recording medium according to claim 1, wherein the stabilizing layer is provided on both the upper and lower sides of the recording thin film, and comprises at least three laminated layers. (4) The optical information recording medium according to claim 1 or 3, characterized in that a plurality of recording thin film layers and stabilizing layers are alternately stacked. (5) The optical information recording medium according to claim 1 or 4, wherein 1/3≦d1/d2≦3 with respect to the thickness d1 of the recording thin film and the thickness d2 of the stabilizing layer in contact therewith. (6) The optical information recording medium according to claim 1, wherein the thickness of the recording thin film layer is between 5 nm and 2 nm. (7) The recording thin film is at least M (Sn or Pb),
It consists of three elements, Te and Ge, and the composition of each component is M.
xGeyTez(25≦x≦60, 0≦y<25, 37
．． 5≦z≦60) Claim 1
The optical information recording medium described above. (8) The composition of the recording thin film is M_5_0_-_aGe_aT
The optical information recording medium according to claim 1 or 7, wherein e_5_0 (0≦a<25). (9) The optical information recording medium according to claim 1, wherein the recording thin film is made of either SnTe or PbTe. (10) The recording thin film is composed of at least three elements of Sn, Sb, and Te, and its composition has a stoichiometric compound composition SnSb_2
Each component is plus or minus 5, centering on Te_4.
The optical information recording medium according to claim 1, wherein the optical information recording medium is within a range of at%. (11) The optical information recording medium according to claim 1 or 10, wherein the composition of the recording thin film is at least four elements of Sn, Sb, Te, and Ge, and the Ge concentration is lower than the Sn concentration. (12) The composition of the recording thin film is Sn_1_−_bGe_bSb_2Te_4 (0<b<
0.5) Claim 1 or 1 characterized in that
1. The optical information recording medium according to 1. (13) The recording thin film is composed of at least three elements, Pb, Sb, and Te, and its composition has a stoichiometric compound composition of Pb_2Sb.
2. The optical information recording medium according to claim 1, wherein each component is within a range of plus or minus 5 at% with respect to _3Te_1_1. (14) The optical information recording medium according to claim 1 or 13, wherein the composition of the recording thin film is composed of at least four elements of Pb, Sb, Te, and Ge, and the Ge concentration is lower than the Sb concentration. (15) The composition of the recording thin film is Pb_2_-_cGe_cS
The optical information recording medium according to claim 1 or 14, characterized in that it is expressed by b_6Te_1_1 (0<c<1).