JPH08318679A - Phase change recording medium - Google Patents

Abstract

PURPOSE: To obtain a phase change recording medium for data recording good in recording/reproduction characteristics, high in sensitivity and good in stability by providing a reflecting layer on a data recording membrane of a specific compsn. through an intermediate layer. CONSTITUTION: A phase change recording medium is constituted by providing a reflecting layer on a data recording membrane of a specific compsn. through an intermediate layer. The average compsn. in the thickness direction of the data recording membrane is represented by formula CzGeαTeβ [wherein z, αand β are atomic % and z is 5<=z<=65 and α and β are not equal (α≠β) and a ratio α/β of α and β is set to 1/4<=α/β<=1 and C is at least one element among Sb and Sn] and the thickness of the data recording membrane is set to 15-50nm and the thickness of the intermediate layer is set to 3-400nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal obtained by FM-modulating an analog signal such as an image or a sound by a recording beam such as a laser beam or an electron beam, data of a computer, a facsimile signal or a digital audio signal. The present invention relates to a thin film for recording information capable of recording digital information such as in real time, particularly a phase change recording medium.

[0002]

2. Description of the Related Art There are various recording principles for recording on a thin film by laser light, but recording by changing the atomic arrangement such as phase transition (also called phase change) of the film material, photodarkening, etc. almost always involves deformation of the film. Since it does not touch, it has the advantage that a double-sided disc can be created by directly bonding two discs together. Further, if the composition is properly selected, the recording can be rewritten. Many inventions relating to this type of recording have been filed, and the earliest one is Japanese Patent Publication No. 47-
It is disclosed in Japanese Patent No. 26897. Here, Te-
Many thin films such as Ge-based, As-Te-Ge-based, and Te-O-based are described. In addition, JP-A-54-419
No. 02 also discloses Ge ₂₀ Tl ₅ Sb ₅ Se ₇₀ , Ge ₂₀ Bi ₁₀
Various compositions such as Se ₇₀ have been described. Further, in JP _{57-24039, Sb 25 Te 12.5, Se} 62.5, C
d ₁₄ Te ₁₄ Se ₇₂ , Bi ₂ Se ₃ , Sb ₂ Se ₃ , In ₂₀ T
_{e 20 Se 60, Bi 25 Te} 12.5 Se 62.5, CuSe, and a thin film of Te ₃₃ Se ₆₇ is described.

[0003]

The thin films disclosed in the above prior art have a low crystallization speed and a low absorption of semiconductor laser light when used as a once-writable or rewritable phase change recording film. It has drawbacks such as poor sensitivity, insufficient reproduction signal strength, poor stability of the amorphous state, and insufficient oxidation resistance, and is difficult to put into practical use.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a phase change recording medium for information recording having good recording / reproducing characteristics, high sensitivity and good stability.

[0005]

In order to solve the above problems, the phase change recording medium of the present invention has the following features.

(1) A substrate and an information recording thin film that is irradiated with a recording beam formed directly on the substrate or through a protective layer to cause an atomic arrangement change with almost no deformation of the film. The phase change recording medium has a structure in which a reflective layer is provided on the information recording thin film via an intermediate layer, and the information recording thin film has an average composition in the thickness direction of the general formula: CzGeαTeβ (however, , Z, α, and β
Are atomic percentages of 5 ≦ z ≦ 65 and α ≠ β, and the ratio α / β of α to β is 1/4 ≦ α / β <1, and C is at least one element of Sb and Sn). A phase change recording medium characterized in that the information recording thin film has a film thickness of 15 nm or more and 50 nm or less and the intermediate layer has a film thickness of 3 nm or more and 400 nm or less.

The process of selecting the configuration of the present invention will be described below. The average composition in the thickness direction of the information recording thin film is represented by the general formula AxByCzGeαTeβ.

However, x, y and z are atomic percentages of 0 ≦ x <40, 0 ≦ y ≦ 30 and 0 ≦ z ≦ 65,0, respectively.
≦ α ≦ 65, 10 <z + α <65, 35 ≦ β ≦ 60, where C is Sb, Sn, As, Pb, Bi, Z
At least one of n, Cd, Si, Al, Ga and In, which has the effect of increasing the stability of the amorphous state. B is at least one of a halogen element such as Tl and I and an alkali metal element such as Na. These elements have the effect of cutting the chain atomic arrangement of Te in a material containing Te, thereby increasing the crystallization rate. However, since the crystallization temperature is lowered, the stability of the amorphous state is impaired unless it is added to a material having a high crystallization temperature. A is an element other than the elements represented by Te, Ge and C, and B, for example, Cu, Ag, Au, Sc, Y,
Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, R
u, Co, Rh, Ni, Pd, Hf, Ta, W, Ir,
At least one element of Pt, Hg, B, C, N, P, O, S, Se, a lanthanide element, an actinide element, an alkaline earth metal element, an inert gas element and the like. However, one or more of the elements represented by Ge, Te and B and C can also be considered as elements of group A when another element of each group is already used. For example, when As is added to the Tl-Sb-Ge-Te system in a range of less than 40 atomic% and the sum of the As content and the Sb content being 70 atomic% or less, which is the upper limit of the C group element content, Conceivable. Of these, the content of Hg, alkaline earth metal element and inert gas element is preferably less than 10 atomic%.

The recording thin film of the present invention may have a composition varying in the film thickness direction as long as the average composition in the film thickness direction is within the range of the above (1). However, the change in the composition is more preferably not discontinuous. By the way, among the elements represented by A, transition metal elements such as Co facilitate the absorption of long-wavelength light such as semiconductor laser light to increase the recording sensitivity, and increase the crystallization temperature, that is, the amorphous state. It has the effect of increasing the stability of and has a high melting point or a compound with a high melting point of 600 ° C. or higher. Is possible.

The information recording thin film of the present invention having the above composition range (1) has excellent recording / reproducing characteristics, and the power of the laser beam used for recording and erasing may be low. Also,
Excellent stability.

The preferred ranges for x, y, z, α and β are as follows.

(A) 0 ≦ x <20, 0 ≦ y ≦ 10, 0 ≦
z ≦ 20, 0.85 ≦ α / β <1 and (b) 0 ≦ x <
20, 0 ≦ y ≦ 10, 0 ≦ z ≦ 20, 1 <α / β ≦ 1.
15 (c) 0 ≦ x <30, 0 ≦ y ≦ 25, 5 ≦ z ≦ 6
5,40 <z + α ≦ 65, 35 ≦ β <55 and (d)
1 ≦ x <30, 0 ≦ y ≦ 25, 40 <z + α ≦ 60,3
5 ≦ β <60 and (e) β / α ≠ 1, 1 ≦ x ≦ 20,
The range of 1 ≦ y ≦ 10, 40 <z + α ≦ 60, and 35 ≦ β ≦ 85 is more preferable.

Further, in (a) or (b), x = y
= Z = 0, x = y = 0 in (c), 40 <α ≦ 60 in (d) and (e), (d) and (e)
At 0.85 ≦ α / β <1 or 1 <α / β ≦ 1.1
5 and 5 ≦ z ≦ 20 in (d) and (e), and 2 ≦ y ≦ 10 in (e) are particularly preferable ranges.

The present invention is particularly applicable to AxByCzGeαTeβ
Where x = y = 0 and the ratio of α to β is considered,
C element is at least 1 selected from Sb and Sn
It is a seed.

Of the elements represented by B, Tl is most preferable, and Na is then preferable.

The change in the content of each element in the film thickness direction is usually small, but any change in the pattern may be present. It is preferable that Se and S increase in the vicinity of one of the interfaces of the recording thin film (may be the interface with another layer) than in the inside thereof. This improves the oxidation resistance.

The elements such as Sb represented by Ge and C and Te coexist in an appropriate ratio so that the amorphous state can be stably maintained. For example, Ge and T
The atomic ratio of the content of e is preferably in the range of 1: 0.5 to 1: 2. A is Co, Ni, Ti, V, Cr, M
n, Cu, Pd, Rh, Ru, Zr, Nb, Mo, A
g, Pt, Os, Ir, Hf, Ta, W, Re, and Au.
It is particularly preferable that the atomic ratio of the Ge and Te contents is in the range of 1: 0.85 to 1: 1.2 when x ≦ 25 and 1 ≦ y ≦ 20. G
When the content ratio of e and Te is around 1: 1, segregation occurs by repeating recording / erasing, and the number of rewritable times is small. By adding an element represented by A such as Co and Ti to this, segregation is less likely to occur, and the number of rewritable times increases. Among the elements represented by A, Co is particularly preferable, and Ti and Ni are next preferable.
Next preferred is V, Cr, then preferred is P
d, Zr, Nb, and Mn. Sb or Bi and Te
Is in the range of 1: 0.4 to 1: 1.4.
The atomic ratio of the contents of n and Si and Te is 1: 1.2 to
In the range of 1: 2.5, the atomic ratio of As and Te contents is 1: 0.9 to 1: 4, and the atomic ratio of In and Te contents is 1: 0.5 to 1: 1. A range of 2 is preferred. In addition, Se and S are preferable from the viewpoint of improving oxidation resistance. The content is preferably less than 30%.

At least one surface of the recording film of the present invention is preferably protected by closely adhering to another substance. More preferably, both sides are protected. These protective layers are
Substrate such as acrylic resin plate, polycarbonate plate, epoxy resin plate, or, for example, acrylic resin,
It may be made of an organic material such as epoxy resin, polyimide, polyamide, polystyrene, or polyethylene, and contains oxides, fluorides, nitrides, sulfides, carbides, borides, boron, carbon, or metals as main components. It may be formed from an inorganic substance. Also, a composite material of these may be used. At least one of the protective layers adjacent to the recording film is preferably made of an inorganic material. A substrate mainly composed of glass, quartz, sapphire, iron, or aluminum can also serve as one inorganic protective layer. Among organic substances and inorganic substances, it is preferable that they are in close contact with the inorganic substances in terms of heat resistance. However, increasing the thickness of the inorganic layer (excluding the case of the substrate) is liable to cause at least one of crack generation, transmittance decrease, and sensitivity decrease. In order to increase the mechanical strength, it is preferable that the thick organic material layer is in close contact. This organic layer may be the 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 material, it may be formed as it is by electron beam evaporation, sputter link, or the like, but after reactive sputtering, or after forming a film made of at least one element of a metal, semimetal, or semiconductor, The reaction is facilitated by reacting with at least one of oxygen, sulfur and nitrogen. Examples of the inorganic protective layer include Ce, La, Si, In and A.
l, Ge, Pb, Sn, Bi, Te, Ta, Sc, Y,
Oxides of at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, and W; Cd, Zn, G
a, a sulfide or selenide of at least one element selected from the group consisting of In, Sb, Ge, Sn, and Pb;
g, Ce, fluorides such as Ca, Si, Al, Ta, nitrides such as B, borides such as Ti, carbides such as boron, boron, be comprised of carbon, for example principal component is CeO _2, La ₂ O ₃ , SiO, SiO ₂ , In ₂ O ₃ ,
Al ₂ O ₃ , GeO, GeO ₂ , PbO, SnO, Sn
O ₂ , Bi ₂ O ₃ , TeO ₂ , WO ₂ , WO ₃ , Ta ₂ O ₂ , S
c ₂ O ₃ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , CdS, ZnS, CdSe, ZnS
e, 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, S
i ₃ N ₄ , AlN, Si, TiB ₂ , B ₄ C, B, C has a composition close to one of them.

Of these, nitrides are not so high in surface reflectivity, and the film is stable and strong.
A composition close to N, Si ₃ N ₄ or AlN is preferable. Preferred oxides are Y ₂ O ₃ , Sc ₂ O ₃ and Ce.
_{O 2, TiO 2, ZrO 2} , In 2 O 3, Al 2 O 3, SnO 2
Alternatively, it has a composition close to SiO ₂ . 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 substance is used for the substrate, the substrate cannot be raised, so that crystallizing by another method is not possible. Need to be converted. In that case, it is preferable to perform irradiation with ultraviolet rays and heating, irradiation with light from a flash lamp, irradiation with light from a high-power gas laser, or combination of heating and irradiation with laser light. In the case of irradiation with light from a gas laser, the light spot diameter (half-value width) is 5 μm or more and 5 mm.
The efficiency is good when set to the following. The crystallization may be performed only on the recording tracks, and the tracks may remain amorphous.
Of course, it is possible to record on a recording thin film in an amorphous state by crystallization.

Generally, when light is applied to a thin film, the reflected light is superimposed on the light reflected from the front surface of the thin film and the light reflected from the back surface of the thin film, causing interference. When a signal is read by a change in reflectance, a light reflection (absorption) layer is provided close to the recording film to increase the effect of interference and increase the read signal. 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 an effect of preventing mutual diffusion between the recording film and the reflective layer at the time of rewriting recording. The intermediate layer is preferably made of a material 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 either side thereof. A particularly preferable thickness range of the intermediate layer is 5 nm or more and 40 nm or more.
It is in the range of nm or less. 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.

Further, it is preferable to form an antireflection layer on the light incident side of the recording film to reduce the reflectance of at least one of the recording light, the erasing light and the 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. Regarding the antireflection layer and the protective layer, it is preferable that the thermal expansion coefficient is sequentially changed in the order of recording layer-protective layer-antireflection layer-substrate or adhesive or gas, and one of the protective layer antireflection layer is not formed. In the case or in the case where each layer is composed of two or more layers, it is preferable that the coefficient of thermal expansion is sequentially changed.

The recording film of the present invention may be in a form of being dispersed in an oxide, a fluoride, a nitride, an organic substance or the like which can be used as a protective film by co-evaporation, co-sputtering or the like. By doing so, it may be possible to adjust the light absorption coefficient and increase the reproduction signal strength. The mixing ratio is preferably such that oxygen, fluorine, nitrogen, and carbon account for 40% or less of the entire film. When such a composite film is formed, the crystallization speed is lowered and the sensitivity is usually lowered. However, by forming a composite film with an organic substance, the sensitivity is improved.

The preferred range of the film thickness of each part is as follows.

A. Recording film (a) Single layer film (without reflective film): 60 nm to 350 nm. A range of 180 nm or more and 300 nm or less is particularly preferable from the viewpoint of reproduction signal intensity and recording sensitivity.

(B) In the case of a structure having a reflective layer and two or more layers:
5 nm or more and 50 nm or less.

B. Inorganic protective layer: 5 nm or more and 200 nm
Less than. However, when protecting with the inorganic substrate itself, 0.1 to 0.1
20 mm.

C. Organic protective film: 10 nm or more, 10 m
m or less.

D. Intermediate layer: 3 nm or more and 400 nm or less.

E. Light reflection layer: 5 nm or more and 300 nm or less.

The method of forming each of the above-mentioned layers includes 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. Either one is appropriately selected.

In the recording film of the present invention, it is not always necessary to use the change between the amorphous state and the crystalline state for recording, and it is sufficient that the optical property is changed by some kind of atomic change. The recording member of the present invention can be used not only in the form of a disc, but also in other forms such as a tape and a card.

Incidentally, the applicant previously disclosed in Japanese Patent Application Laid-Open No. 60-4209.
No. 5 has been filed. These are As, Sb, Bi, S,
Si, Ge, Sn, Pb, Al, Ga, In, Tl, Z
n, Cd, Au, Ag, Cu, Ni, Pd, Rh, C
r, Mo, W, Ta is 2 atomic% or more and 40 atomic% or less, T
The composition is such that e is 30 atomic% to 95 atomic%, Se is 3 atomic% to 45 atomic%, and O is 0 atomic% to 20 atomic%.

The applicant has previously disclosed in Japanese Patent Application Laid-Open No. 61-8628.
I am applying for No. 7. This is a recording material having a quaternary composition in which Te and Se are essential. Also, JP-A-62-478
No. 39 is a recording material of a quaternary composition containing Te and Se,
The composition range of Te is 30 atomic% or less. Other prior applications include Japanese Patent Application Nos. 59-123001 to 123004. These relate to the improvement of oxide-based materials containing oxygen as an essential element.

[0034]

The phase change recording medium of the present invention has a high crystallization rate, a high stability in an amorphous state, a large absorption of semiconductor laser light, a high reproduction signal intensity and a good oxidation resistance.
Therefore, the recording / erasing characteristics are good, the sensitivity is high, and the recording state is stable.

The element C (Sb, Sn, As,
By adding a predetermined amount of Pb, Bi, Zn, Cd, Si, Al, Ga, and In),
Since the amorphous state can be maintained stably (high crystallization temperature),
The retention life of recorded data can be extended. This is presumably because the addition of the trivalent to pentavalent covalent bond typical element strengthens the amorphous network structure. In addition, since the activation energy of crystallization increases, while maintaining the stability of the amorphous state at room temperature,
The crystallization of the laser-irradiated portion becomes faster, rewriting (overwriting) by overwriting information becomes easy, and the erasing characteristics are improved. From the above viewpoint, among the elements represented by C, the particularly preferable element is Sb, the next preferable element is Sn, and the next preferable element is As, In,
Si, and secondly preferred are Pb, Bi and Ga.

[0036]

The present invention will be described below in detail with reference to examples.

Example 1 A method for manufacturing a phase change recording medium using a Tl-Ge-Te recording film as an example will be described below.
A specific example of the evaluation method will be described. The evaluation method itself such as a manufacturing method, recording, and reproduction is a general method. As an example of the present invention, the composition of the recording film may be only the general formula CzGeαTeβ described in the above-mentioned condition (1), and the manufacturing method and the evaluation method will be described below with respect to Tl-Ge-Te.
This may be the same as in the case of the system recording film.

On the surface of a disk-shaped chemically strengthened glass plate having a diameter of 13 cm and a thickness of 1.2 mm, a replica of a tracking groove which also serves as a protective layer is formed by an ultraviolet curable resin.
Divide one round into 32 sectors, and at the beginning of each sector,
A track address, a sector address, and the like are formed in the form of uneven pits in the middle of a groove between grooves (this portion is referred to as a header portion). About 10
A 0 nm Si ₃ N ₄ layer was formed. Next, this substrate was placed in a vacuum evaporation apparatus having an internal structure as shown in FIG. Four evaporation sources 1, 2, 3, and 4 are arranged in the evaporation apparatus. Three of these are resistance heating evaporation boats, one of which is an electron beam evaporation source. These boats and electron beam evaporation sources
4 is located substantially below a portion where information is to be recorded, on a circle having the same center as the center axis 5 of substrate rotation. Ge and Te were put in two vapor deposition boats, respectively, and Tl was put in an 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. The substrate 14 was rotated at 120 rpm, a current was applied to each boat, and an electron beam was applied to deposit a deposition material.

The amount of evaporation from each evaporation source was detected by the crystal oscillator type film thickness monitors 15, 16, 17, and 18, and the current was controlled so that the evaporation rate was constant.

As shown in FIG. 1, Si ₃ on the substrate 19
A recording film 21 having a composition of Tl ₅ Ge ₄₅ Te ₅₀ was vapor-deposited on the N ₄ layer 20 to have a film thickness of about 250 nm. Since the refractive index of the Si ₃ N ₄ layer is higher than that of the substrate, the Si ₃ N ₄ layer also serves as an anti-reflection layer for semiconductor laser light by being appropriately formed. 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 protective layer 22 having a composition close to Si ₃ N ₄ was formed by magnetron sputtering again for about 100 hours.
nm. In the same way, another similar substrate 1
9 'protective layer 20 having a composition close to the Si ₃ N ₄ on', Tl ₅ G
A recording film 21 'having a composition of e ₄₅ Te ₅₀ and a protective layer 22' having a composition close to that of SiO ₂ were deposited. The UV-curable resin protective layers 23 and 23 'are applied and formed to a thickness of about 50 .mu.m on the respective film depositions of the two substrates 19 and 19' thus obtained. A disc was prepared by bonding together with the organic adhesive layer 24 with the 23 and 23 'sides inside.

The disk produced as described above was at 150 ° C.
After heating for about 1 hour, rotate the disc and
Aperture ratio from both sides while moving to (Numerical Aperture)
Argon ion laser beam focused with a lens of 0.05
(Wavelength 488 nm) to irradiate the recording films 21 and 21 ′ sufficiently.
Partially crystallized. Recording was performed as follows. Di
The disk is rotated at 1200 rpm and a semiconductor laser (wavelength
820 nm) at a level at which recording is not performed.
And converge with the lens in the recording head
By irradiating the recording film of the
The center of the light spot is always between the racking grooves
The head was driven to match. By doing this
The effect of noise generated from the groove can be avoided
It While performing tracking in this way,
Automatic focusing is performed so that the focus is on the recording film.
User power according to the information signal, or to the original level
Recording was done by returning. Also required
The recording was performed by jumping to another groove according to. above
According to the fact that the recording film changed to amorphous by recording
Probable reflectance changes occurred. With this recording film, the power
Recording light spot or track direction length
Is longer than the recording light spot, and
Laser beam is irradiated at the same level as the recording light spot.
By doing so, the record can be erased. address
The distance between the pits closest to the pits
Length of 1/2 to 2 times the length of the pot in the track direction
Then, even if the erasing light spot
You can read the address of the monitor. Pit length indicating address
The length of the erasing light spot in the track direction is 以 or less.
It is preferably above. Others provided on the header
The same goes for the pits. 3x10 for recording / erasing^FiveMore than once
It was repeatable. Si formed above and below the recording film₃N _Four
If the layer is omitted, a slight increase in noise occurs after several recording / erasing operations.
Addition has occurred.

Reading was performed as follows. The disk was rotated at 1200 rpm, and tracking and automatic focusing were performed in the same manner as during recording, while the intensity of reflected light was detected with a low-power semiconductor laser light that does not perform recording or erasing, and information was reproduced. In this embodiment, about 1
A signal output of 00 mV was obtained. The recording film of this example was excellent in oxidation resistance and was hardly oxidized even when a film without a Si ₃ N ₄ protective film was placed under the conditions of 60 ° C. and 95% relative humidity.

In the above Tl-Ge-Te system recording film, when the Tl content was changed while keeping the relative ratio of the Ge and Te contents constant, the crystallization temperature and the irradiation time required for erasing. Changed as follows.

Irradiation time required for erasing Crystallization temperature y = 0 1.0 μs 200 ° C. y = 0.5 0.8 μs 190 ° C. y = 10.5 μs 180 ° C. y = 2 0.4 μs 175 ° C. y = 50. 3 μs 170 ° C. y = 10 0.2 μs 160 ° C. y = 15 0.2 μs 155 ° C. y = 25 0.1 μs 150 ° C. y = 30 0.1 μs 130 ° C. y = 35 0.1 μs 100 ° C y = 50 0.1 μs 80 C. Also, the deterioration due to oxidation over time before the upper protective film was applied became remarkable when the Tl content was 30 atomic% or more. When y is too small, there is a disadvantage that the irradiation time required for erasure is long, and when y is too large, there is a disadvantage that the crystallization temperature is low.

Here, similar characteristics can be obtained by substituting a part or all of Tl and adding at least one of a halogen element and an alkali metal element. Among the halogen elements F, Cl, Br, and I, I is particularly preferable. On the other hand, Cl, an alkali metal element, Li, Na, K, Rb, C
Of s, Na is particularly preferable, and K is more preferable.

Next, in the above Tl-Ge-Te system recording film, the content of Tl was kept constant at 5 atom%, and Ge and T were maintained.
When the content of e was changed, the required irradiation time for erasing and the number of rewritable times changed as follows.

The erase rewritable alpha beta required irradiation time allowable number 10 85 10 [mu] s 10 ⁶ times 20 75 5 .mu.s 10 ⁶ times 41 54 1 [mu] s 10 ⁶ times 43 52 0.8 .mu.s 10 ⁶ times 44 51 0.3μs 10 ⁶ times 46 49 0 .2 μs 3 × 10 ⁵ times 47.5 47.5 0.1 μs 10 ² times 49 46 0.2 μs 3 × 10 ⁵ times 51 44 0.5 μs 10 ⁵ times 55 40 0.8 μs 3 × 10 ⁵ times 60 35 1 μs 10 ⁴ times 65 30 10 μs 10 ³ times When α is less than 10, the crystallization temperature is low (the stability of the amorphous state is poor). When α exceeds 65, recording is difficult. If α and β are too large or too small, In either case, there is a drawback that the irradiation time required for erasing is long and the number of rewritable times is small. However, when the composition is α = β, the number of rewritable times becomes extremely small.

Here, Sb, Sn, As, Pb, Bi, which is an element represented by C by substituting a part or all of Ge,
Similar characteristics can be obtained by adding at least one element of Zn, Cd, Si, Al, Ga and In. Of these, Sb is particularly preferred, then Sn, then As, In, Si, and then Pb, Bi, Ga. However, when the addition amount of Sn is increased, the crystallization temperature is significantly lowered. When the addition amount of the element such as Sb is set to 5 atomic percent or more, there are effects such as improvement in recording sensitivity. When the recording sensitivity is also taken into consideration, the particularly preferred range of the ratio of the number of atoms of Sb or Bi to Te is 1: 0.4 to 1: 1.6, Sn
And in the case of Si and Te, 1: 1.2 to 1: 2.5, As
In the case of In and Te, the ratio is 1: 0.9 to 1: 4, and in the case of In and Te, the ratio is 1: 0.5 to 1: 2.

As a method of evaluating the recording medium, for example, there is a method of measuring the power of the laser beam and the reproduction signal intensity necessary for recording. It is possible to evaluate the drawback that the power of the laser light required for recording is high and the drawback that the reproduction signal intensity becomes small.

The thickness of the recording film is preferably in the range of 80 nm or more and 150 nm or less and the range of 180 nm or more and 300 nm or less because the effect of light interference causes a large change in reflectance due to recording. The recording sensitivity is high in the range from 180 nm to 300 nm. However, recording / reproduction is possible within the range of 15 nm to 350 nm.

As a protective film, SiO ₃ instead of Si ₃ N ₄ ,
Oxides such as SiO ₂ , Y ₂ O ₃ , CeO ₂ , ZrO ₂ , T
nitrides such as aN and AlN, sulfides such as Sb ₂ S ₃ and ZnS, fluorides such as CeF ₃ , or amorphous Si and Ti
A composition close to B ₂ , B ₄ C, B, C or the like may be used.

Example 2 In the same manner as in Example 1, a Ge ₄₈ Te ₅₂ recording film having a film thickness of 100 nm was formed, and the disc shown in FIG. 2 was produced. In the above Ge-Te recording film, the required erasing time for erasing and the number of rewritable times when the contents of Ge and Te were changed changed as follows.

[0053] alpha beta required irradiation time of erasing rewritable count 20 80 20 .mu.s 10 ⁶ times 42 58 4 .mu.s 10 ⁶ times 46 54 1 [mu] s 10 ⁶ times 49 51 0.5μs 3 × 10 ⁵ times 50 50 0.2 .mu.s 10 ² times 51 49 0.5 μs 3 × 10 ⁵ times 54 46 1 μs 10 ⁵ times 58 42 5 μs 5 × 10 ⁴ times 80 20 Recording is not possible Irrespective of whether α and β are too large or too small, irradiation required for erasing It has a drawback that the time is long and the number of rewritable times is small. However, when the composition is α = β, the number of rewritable times becomes extremely small. Α and β of this thin film
At least one of the elements represented by A less than 30 atomic%, at least one of the elements represented by B not more than 25 atomic%, and the element represented by C not more than 65 atomic% Good characteristics can be obtained by adding at least one of them. As an example of the present invention, AxByC
In the general formula of zGeαTeβ, A and B are not added, but at least one selected from Sb and Sn is added as C, and the composition of CzGeαTeβ is 5
≦ z ≦ 65, α ≠ β, and the ratio α / β of α to β is 1
/ 4 ≦ α / β <1 is set.

As a reference example, a recording film made of CzTe having a film thickness of 100 nm was formed in the same manner as in Example 1.
C is Sb, Sn, As, Pb, Bi, Zn, Cd, S
One element of i, Al, Ga and In. A plurality of these elements may be included.

As the effect of the C element, among these, Sb is particularly preferable in that the crystallization temperature is high, then Sn, then As, In, Si, then Pb, Bi,
Ga is preferred. Considering the recording sensitivity as well, the preferable range of the atomic number ratio of Sb or Bi and Te is 1: 0.4 to.
1: 1.4, in case of Sn and Si and Te, 1: 1.2
~ 1: 2.5, As and Te: 1: 0.9-1: 4,
In the case of In and Te, the ratio is 1: 0.5 to 1: 2.

(Embodiment 3) Next, a manufacturing method and an evaluation method of another embodiment will be described. Here, the recording film is Tl-Ge-Te.
Although the system material is used, in the embodiment of the present invention, the recording film material is only the CzGeαTeβ material of the present invention, and there is no other change.

As shown in FIG. 2, using a substrate 25 having a groove for tracking formed on the surface of a polycarbonate plate by an injection molding method, a protective film 26 having a composition close to that of SiO and having a thickness of 40 nm is formed by sputtering. Formed. Next, a film having a composition of Tl ₁₀ Ge ₄₇ Te ₄₃ and a film thickness of 3
A 0 nm recording film 27 was formed. Subsequently, an intermediate layer 28 having a composition close to that of SiO and having a thickness of 20 nm is formed.
A reflective layer 29 having a Bi ₇ Sb ₃ composition of 0 nm and a protective layer 30 having a composition close to that of SiO and having a thickness of 40 nm were formed. Another substrate was prepared in the same manner, and the uppermost SiO 2 of both substrates was
After a polyimide 31 was sputtered on the layer 30 to a thickness of about 0.5 μm, both substrates were bonded together with the polyimide layer side inside by a hot melt adhesive 32 mixed with a black pigment to prepare a disk. If a polyimide layer is formed on the surface of the polycarbonate plate by the sputtering method, a more stable disk can be obtained. The crystallization method, recording method, erasing method, and reading method are almost the same as in the first embodiment.

The intermediate layer was replaced with SiO in Example 1
GeO that can be used as a protective layer ₂, Al₂O₃, Ce
O₂, Y₂O₃, SiO₂, AlN, TaN and other inorganic transparent materials
A bright substance may be used, or an organic layer may be used. This
When the recording layer is rewritten, the thickness of the intermediate layer of 3 to 40 nm
Prevents the interdiffusion between the recording film and the reflective layer, but optically
It is almost the same as not existing. Therefore, due to the interference of light
The change in the reflectance due to wavelength is caused by two layers, a recording film and a reflective layer.
Similar to the structure case.

When the reflective layer also changes the atomic arrangement during recording, the reproduction signal becomes a little larger.

Part or all of the B and C elements contained in the recording film may be replaced with at least one of the other elements in the same group. Further, it is possible to add at least one element out of the elements such as Co in Group A in atomic percentage of 30% or less. However, it is preferable that the added amount be 20% 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 lowered by interference, and a large reproduced signal can be obtained. The thickness of the reflective layer is preferably 5 nm or more and 300 nm or less, more preferably 40 nm or more and 200 nm or less. By providing the reflective layer, a large reproduction signal can be obtained in a region where the thickness of the recording film is thinner than that in the case of a single layer as described above. Therefore, even in a composition region where the absorption coefficient of the recording film is larger than that in the case of a single layer. Good characteristics are obtained.

When the film thicknesses of the recording film and the intermediate layer are changed, the wavelength at which the minimum due to the interference of the reflectance of the read light is changed. Since the minimum reflectance required for automatic focusing and tracking is 10 to 15%, if the minimum reflectance is less than this value, it is minimized on the longer wavelength side or shorter wavelength side than the read light wavelength. The value needs to come. By making the minimum value on the short wavelength side, the thickness of the recording film can be made thinner and the energy loss due to heat conduction can be prevented. However, it is preferable that the local minimum value is on the long wavelength side because the film thickness becomes thicker, and it is preferable from the viewpoint of the life of the recording film and the prevention of noise generation during recording and rewriting.

The material of the reflective layer is Bi, Bi ₂ Te ₃ , Te, Sn, Sb, Al, A instead of Bi-Sb.
Many semiconductors such as u and Pb, semimetals, metals and mixtures and compounds thereof can be used.

The recording film of this example is also excellent in oxidation resistance like the recording film of Example 1, and even if the protective film has pinholes, the oxidation does not proceed to the periphery thereof.

[0065]

As described above, according to the present invention,
It is possible to obtain a phase change recording medium having a simple manufacturing process, good reproducibility, good recording / reproducing characteristics, and long-term stable information. Records can be rewritten many times.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a recording member according to an embodiment of the invention.

FIG. 2 is a cross-sectional view illustrating a structure of a recording member according to the embodiment of the present invention.

FIG. 3 is a side view showing the internal structure of a vacuum vapor deposition apparatus used for producing the recording member of the present invention.

[Explanation of symbols]

1,2,3 ... evaporation boat, 4 ... electron beam evaporation source, 6,
7, 8, 9 ... Mask with fan-shaped slit, 10, 1
1, 12, 13 ... shutter, 14 ... substrate, 15, 1
6,17,18 ... Crystal oscillator type film thickness monitor, 19,1
9 '... substrate, 20, 20', 22, 22 '... SiO
₂ layers, 21 and 21 ': recording film, 23, 23': ultraviolet curing resin layer, 24: organic adhesive layer, 25, 25 ': substrate,
26, 26 ', 28, 28', 30, 30 '... SiO ₂
Layer, 27, 27 '... Recording film, 29, 29' ... Bi-Sb
Film, 31, 31 ': polyimide resin layer, 32: hot melt adhesive layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinkichi Horigo 1-280, Higashi-Kengokubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (1)

[Claims] 1. A substrate, and an information recording thin film which is directly or via a protective layer formed on the substrate and undergoes an atomic arrangement change with almost no deformation of the film when irradiated with a recording beam. In the phase change recording medium, having a configuration in which a reflective layer is provided on the information recording thin film via an intermediate layer,
The above-mentioned information recording thin film has an average composition in the thickness direction of CzGeαTeβ (where z, α, and β are atomic percentages, and 5 ≦ z ≦ 65 and α ≠ β, respectively,
Further, the ratio α / β of α and β is set to 1/4 ≦ α / β <1, and C
Is at least one element of Sb or Sn),
A phase change recording medium characterized in that the thickness of the information recording thin film is 15 nm or more and 50 nm or less and the thickness of the intermediate layer is 3 nm or more and 400 nm or less.