JPH0636342A - Information recording medium - Google Patents

Abstract

(57) [Summary] [Structure] An information recording medium absorbs laser light, which is a recording layer made of an inorganic substance whose optical constants change due to changes in atomic arrangement without shape change upon irradiation with laser light. It includes an absorption layer, an interference layer that causes multiple interference of laser light, and a reflective layer that reflects laser light, and the medium reflectance with respect to the laser light from the substrate side is 65% or more in the unrecorded portion and 45% in the recorded portion.
It is the following. [Effect] It is possible to provide an information recording medium which has excellent recording / reproducing characteristics, a high medium reflectance with respect to laser light of 65% or more, and an excellent data holding life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to FM modulation of analog signals such as images and sounds by laser light, data of electronic computers and digital information such as facsimile signals and digital audio signals.
The present invention relates to a thin film for recording information that can be recorded in real time.

[0002]

2. Description of the Related Art Although there are various recording principles for recording on a thin film by laser light, a phase transition (also called a phase change) of a recording layer material made of an inorganic substance, diffusion of atoms between layers of a constituted thin film, and photodarkening Recording due to changes in the atomic arrangement, such as the one described above, has the advantage that a double-sided disc in which two discs are directly bonded together can be formed, because the deformation of the formed thin film is hardly accompanied. Many inventions relating to this type of recording have been filed, and the earliest one relating to the phase transition of the recording layer material is disclosed in Japanese Examined Patent Publication No. 47-26897. Here, Te-Ge system, As-Te-
Many thin films such as Ge-based and Te-O-based have been described. In Japanese Patent Laid-Open No. 54-41902, Ge ₂₀ T ₁₅ Sb ₅ S is also disclosed.
Various compositions such as e ₇₀ have been described. In addition,
No. 57-24039 also discloses Sb ₂₅ Te _12.5 Se _62.5 , Cd.
₁₄ Te ₁₄ Se ₇₂ , Bi ₂ Se ₃ , Sb ₂ Se ₃ , In ₂₀ Te
₂₀ Se ₆₀ , Bi ₂₅ Te _12.5 Se _62.5 , CuSe, and T
A thin film of e ₃₃ Se ₆₇ is described. Regarding the diffusion of atoms in a thin film material, Japanese Patent Application Laid-Open No. 61-188752 discloses a two-layer film of Sb ₂ Se ₃ / Bi.

Now, compact disc (CD), CD
-In read-only optical discs such as ROM, CD-I, and laser discs, concave or convex prepits having information in advance are transferred to a polycarbonate substrate, an acrylic substrate, or the like by a transfer technique such as an injection method or a photopolymerization method. A metal reflective layer having a high reflectance of 70% or more with respect to a reproducing laser beam such as Al or Au is directly formed on the above, and an organic protective layer for preventing scratches and the like is further formed thereon. It has a formed structure. Therefore, the reflectance of the reproduction laser beam on the flat portion of the reproduction-only optical disc is as high as 70% or more.

On the other hand, regarding an optical information recording medium in which the reflectance is 70% or more in an unrecorded portion in which recording is performed by changing the reflectance due to irradiation of a recording laser beam, an organic material is used as the recording layer, and the recording layer and An optical information recording medium of the type in which recording is performed by changing the shape of a substrate is disclosed in JP-A-2-873.
39, JP-A-2-87340 and JP-A-2-87342.

[0005]

Among the information recording media shown in the above-mentioned prior art, in the information recording medium of the type which records by changing the atomic arrangement of the recording layer material made of an inorganic material,
Since the recording layer material and layer structure for achieving high reflectance have not been optimized, if the medium reflectance for the unrecorded portion of the laser beam is set to 65% or more, the reproduced signal strength at the recording portion will be insufficient. In order to obtain a sufficient reproduction signal intensity, the medium reflectivity of the unrecorded portion with respect to the laser light needs to be less than 65%. Therefore, in an information recording medium of the type that records by changing the atomic arrangement of the recording layer material made of such an inorganic material, the medium reflectance of the unrecorded portion with respect to the laser beam is as low as less than 65%, and information is recorded on this information recording medium. Even if it is recorded, it is a read-only CD that is already widely used,
A device such as a laser disk has a drawback that information cannot be read directly.

On the other hand, among the information recording media shown in the prior art, in an information recording medium of a type in which an organic material is used as the recording layer and recording is performed by changing the shape of the recording layer and the substrate, the reflectance at the unrecorded portion is 70. A sufficient reproduction signal strength can be obtained even with a medium of not less than%. However, in an information recording medium of a type that uses such an organic recording layer and performs recording by changing the shape of the recording layer and the substrate, since a dye is used as the organic material of the recording layer, the retention life of recorded data is short. , Environmental resistance is poor. In particular, there is a drawback in that when the sun rays are directly applied, the dye fades and recording becomes impossible.

An object of the present invention is to provide an information recording medium of a type which records by changing the atomic arrangement of a recording layer material made of an inorganic material, has a long retention life of recorded data, is excellent in environmental resistance, and has excellent recording / reproducing characteristics. Moreover, the medium reflectivity of the unrecorded portion with respect to the laser beam is as high as 65% or more, and the recorded information is read by a device such as a read-only CD or a laser disc which is already widely used. It is to provide an information recording medium that can be used.

[0008]

In order to achieve the above object, the information recording medium of the present invention is formed directly on a substrate or through a protective layer composed of at least one of an inorganic substance and an organic substance, A recording layer made of an inorganic material, which is irradiated with a laser beam to change its atomic constant without causing a shape change and changes its atomic arrangement, an absorption layer which absorbs the laser beam,
The medium reflectivity for the laser beam from the substrate side is 65% or more in the unrecorded portion, including a reflective layer that reflects the laser beam, and an intermediate layer located between the absorbing layer and the reflective layer. , And 45% or less in the recording unit.

Here, the laser beam is absorbed by the laser beam irradiation, and the recording layer material undergoes a phase transition (phase change) between amorphous and crystalline or between crystalline and crystalline due to heat from the absorbing layer which has generated heat. Or photodarkening occurs, or atomic diffusion occurs between the absorption layer and the recording layer.
As a result of the change in the atomic arrangement of the recording layer, the optical constant of the recording layer changes and the medium reflectance with respect to the laser light changes.

The recording layer, the absorption layer, the intermediate layer, and the reflection layer are
It is assumed that the stacking order is the recording layer, the absorbing layer, the intermediate layer, and the reflecting layer in order from the side closer to the substrate. The recording layer, the absorbing layer, the intermediate layer, and the reflecting layer are adjacent to each other.

The recording layer in which the optical constant is changed by the change of the atomic arrangement without the change of the shape upon the irradiation of the laser beam made of the inorganic substance in the information recording medium of the present invention with respect to the laser beam in the unrecorded state It is assumed that the extinction coefficient, which is the imaginary part of the complex refractive index, is 0.2 or less. The recording layer is made of chalcogenide containing at least one element of Se and S.

The absorption layer that absorbs laser light in the information recording medium of the present invention is a metal, a semimetal, if the extinction coefficient, which is the imaginary part of the complex refractive index with respect to the laser light, is 2.0 or more.
Semiconductors and their alloys can be used.

The intermediate layer located between the absorbing layer and the reflecting layer of the present invention is an oxide, a fluoride, if the extinction coefficient, which is the imaginary part of the complex refractive index with respect to the laser beam, is 0.2 or less. Inorganic substances such as nitrides, sulfides, and selenides, mixtures thereof, or organic compounds, and mixtures of inorganic substances and organic substances can be used.

The reflective layer for reflecting laser light in the information recording medium of the present invention can be made of metal, semi-metal, semiconductor, and alloys thereof as long as the reflectance for the laser light is sufficient at 70% or more. Is.

If the complex refractive index and reflectance of the recording layer, the absorbing layer, the intermediate layer and the reflecting layer in the information recording medium of the present invention are within the above ranges, the composition may change in the film thickness direction. . However, it is more preferable that the change in composition is not discontinuous.

In the case where a large number of information recording mediums, some of which have the same information, are manufactured in the information recording medium of the present invention, read-only information is recorded in a portion of the information recording medium of the present invention.
It is preferable to form (ROM) in advance in the form of concave or convex prepits and mix them together.

[0017]

The information recording medium of the present invention is formed on the substrate directly or through the protective layer composed of at least one of an inorganic material and an organic material, and the atomic arrangement without being changed by the irradiation of the laser beam. A recording layer made of an inorganic material that undergoes changes to change optical constants, an absorption layer that absorbs the laser light,
At least a reflective layer that reflects laser light and an intermediate layer located between the absorbing layer and the reflective layer are formed.

In the recording layer of the information recording medium of the present invention, phase transition (transition from one amorphous or crystalline phase to another crystalline phase), photodarkening, and diffusion of atoms occur as an atomic arrangement change of an inorganic substance. (Diffusion of atoms between the recording layer and the absorption layer) may occur. Information is recorded by laser light having an irradiation time and power that can cause the above-mentioned atomic arrangement change and does not cause a large deformation in the recording layer, and information reproduction does not cause the atomic arrangement change. Irradiation time and power of laser light are used. Further, in the present invention, the initial crystallization of the recording layer by irradiation of Ar laser light, irradiation of semiconductor laser light, flash annealing, etc. before recording is not necessary at all. Even without such initialization
It is possible to obtain good recording / reproducing characteristics with good recording sensitivity, in which the initial reflectance of the unrecorded portion is 65% or more and the reflectance of the recorded portion is 45% or less. Further, among the information recording media of the present invention, those having an initial reflectance of 70% or more in the unrecorded portion and 28% or less in the recording portion are CD-WO (write-once type CD)
It is preferable because it can fully comply with the standard Orange Book.

In the information recording medium of the present invention, the recording layer in which the optical constant is changed by the change of the atomic arrangement without the change of the shape under the irradiation of the recording laser beam made of the above-mentioned inorganic substance is reproduced in the unrecorded state. It is assumed that the extinction coefficient, which is the imaginary part of the complex index of refraction for laser light, is 0.2 or less. The extinction coefficient is preferably 0.1 or less in that the medium reflectance of the unrecorded portion can be further increased. Further, the recording layer is assumed to be chalcogenide containing at least one element of Se or S because it has the value of the above extinction coefficient. The content of Se or S in the recording layer is 40 atomic% in that the extinction coefficient of the recording layer can be reduced and the oxidation resistance can be improved.
The above is preferable, and 55 atomic% or more is particularly preferable. The recording layer contains at least one element of Se or S and Sb, Sn, In, Tl, Te, Bi, Si and G.
It is preferable to contain at least one element of e, Pb, and Ga. The recording layers are Co, Pd, Ti, V, C
It is preferable to add a small amount of a transition metal such as r, Mn, Fe, Co, Ni, Cu, Ag, and Au in an amount of 10 atomic% or less because the stability of the amorphous state is improved. Among the above, in the alloy system containing Se and Sb as the main components, crystallization at the time of recording can be performed at high speed while maintaining the stability of the amorphous state, and the oxidation resistance of the recording layer is remarkably high. further,
By adding a Group 4b element such as Sn, Si, Ge, or Pb, the stability of the amorphous state can be further increased, and crystallization at the time of recording can be performed at a higher speed. Suitable as a medium. In the alloy system containing Se and In as the main components, the layer transition between the crystalline state and the amorphous state can be repeated many times. Furthermore, by adding an element such as Tl or Co, the crystallization speed is further improved, and thus it is suitable as a rewritable medium.

When the recording layer in the information recording medium of the present invention is produced by a sputtering method, argon gas is usually used, but sputtering may be performed using a gas in which nitrogen gas is mixed in argon gas. . This allows
The extinction coefficient can be reduced even in the case of a composition having a small content of Se or S. Here, the concentration of nitrogen gas is preferably 3 mol% or more and 30 mol% or less.

The absorption layer for absorbing laser light in the information recording medium of the present invention has the extinction coefficient of 2.0 or more, which is the imaginary part of the complex refractive index with respect to laser light, if it is metal, semimetal, semiconductor, and These alloys can be used. When the absorption layer is made of a material having a low thermal conductivity of 0.3 W / cm · deg or less, such as an alloy containing at least one element of Sb, Te and Bi, the recording layer It has the effect of suppressing extra heat conduction to other parts and ensuring recording even when irradiated with low power laser light. As a low thermal conductivity material, Sb alloy, Te alloy, Bi alloy, S
An alloy containing at least one of b-Te alloy, Sb-Bi alloy, Ti alloy alloy, manganin, constantan, stainless steel, nichrome, inconel, monel and the like is preferable.

The intermediate layer located between the absorbing layer and the reflecting layer in the information recording medium of the present invention is an oxide if the extinction coefficient, which is the imaginary part of the complex refractive index for laser light, is 0.2 or less. , Fluoride, nitride, sulfide, selenide and other inorganic substances,
A mixture of these, or an organic compound, and a mixture of an inorganic substance and an organic substance can be used. The extinction coefficient is preferably 0.1 or less in that the medium reflectance of the unrecorded portion can be further increased.

As the inorganic substance, Ce, La, Si, I
n, Al, Ge, Pb, Sn, Bi, Te, Ta, S
oxides of at least one element selected from the group consisting of c, Y, Ti, Zr, V, Nb, Cr and W, Mg, Ce,
Fluoride such as Ca, nitride such as Si, Al, Ta, B, Cd, Zn, Ga, In, Sb, Ge, Sn, P
a sulfide of at least one element selected from the group consisting of b and Bi, Cd, Zn, Ga, In, Sb, Ge, Sn, P
It is possible to use a selenide of at least one element selected from the group consisting of b and Bi, and a mixture thereof.

For example, the main components are CeO ₂ , La ₂ O ₃ and S.
iO, SiO ₂ , In ₂ O ₃ , Al ₂ O ₃ , GeO, Ge
O ₂ , PbO, SnO, SnO ₂ , Bi ₂ O ₃ , TeO ₂ ,
Ta ₂ O ₅ , Sc ₂ O ₃ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , V ₂
O ₅ , Nb ₂ O ₅ , Cr ₂ O ₃ , WO ₂ , WO ₃ , MgF ₂ , C
eF ₃ , CaF ₂ , TaN, Si ₃ N ₄ , AlN, BN, C
_{dS, ZnS, In 2 S 3} , Sb 2 S 3, Ga 2 S 3, Ge
S, SnS, SnS ₂ , PbS, Bi ₂ S ₃ , CdSe, Z
nSe, In ₂ Se ₃ , Sb ₂ Se ₃ , Ga ₂ Se ₃ , GeS
e, SnSe, SnSe ₂ , PbSe, Bi ₂ Se ₃ , and a mixture thereof having a composition close to one of e, SnSe ₂ , SnSe ₂ , PbSe, and Bi ₂ Se ₃ .

Of these, the oxide is preferably Y ₂
O ₃ , Sc ₂ O ₃ , CeO ₂ , TiO ₂ , ZrO ₂ , SiO,
Ta ₂ O ₅ , In ₂ O ₃ , Al ₂ O ₃ , SnO ₂ or SiO
_It has a composition close to ₂ . For nitrides, Si ₃ N ₄ , A
It is preferable that the composition is close to 1N (aluminum nitride) or TaN. Among sulfides, those close to ZnS are preferable. Furthermore, a composition having exactly the same composition as the recording layer can be used, which is preferable in that the cost can be reduced.

Organic substances include acrylic resin, polycarbonate, polyolefin, epoxy resin, polyimide, polyamide, polystyrene, polyethylene, polyethylene terephthalate, fluororesin such as polytetrafluoroethylene (Teflon), ethylene-vinyl acetate copolymer, and ultraviolet rays. Cured resins and mixtures thereof can be used.
The intermediate layer is an inorganic layer and an inorganic layer, an inorganic layer and an organic layer,
You may make it a multilayered structure, such as an organic material layer and an organic material layer. In the case of this multi-layer structure, it is preferable to form a layer having a low thermal conductivity at the interface with the absorbing layer in terms of improving recording sensitivity.

The reflective layer that reflects the laser light in the information recording medium of the present invention has a reflectance of 70% with respect to the reproducing laser light.
Metals, semi-metals, semiconductors and alloys thereof can be used as long as the above is sufficient. As the reflective layer, Al, Au,
When a material mainly composed of a high-reflectance material having a reflectance of 80% or more, such as Ag and Cu and alloys containing these, is used, the reflectance of the information recording medium is increased to 70% or more,
This has the effect of increasing the reproduction signal strength when reproducing the recorded signal. That is, as the high reflectance material, Al, Au,
A material containing at least one of Ag, Cu and the like and alloys containing these is preferable.

If the complex refractive index and reflectance of the recording layer, the absorbing layer, the intermediate layer and the reflecting layer in the information recording medium of the present invention are within the above ranges, the composition may change in the film thickness direction. . However, it is more preferable that the change in composition is not discontinuous.

In the case where a large number of information recording mediums, some of which have the same information, are manufactured in the information recording medium of the present invention, read-only type information (Read Only Memory; ROM) is provided in a part of the information recording medium of the present invention. It is preferable to previously form () in the form of concave or convex pre-pits and to mix them.

When the recording layer, the absorption layer, the intermediate layer, and the reflective layer are combined to form an information recording medium layer, at least one surface of the information recording medium layer of the present invention is protected by closely contacting it with a protective layer made of another substance. If so, the environment resistance of the information recording medium is improved. Of course, if both sides are protected, the environment resistance of the information recording medium is further improved, and the number of rewritable times when used as a reversible type is improved ten times or more.

These protective layers are made of, for example, acrylic resin, polycarbonate, polyolefin, epoxy resin, polyimide, polyamide, polystyrene, polyethylene, polyethylene terephthalate, fluororesin such as polytetrafluoroethylene (Teflon), and ultraviolet curable resin. It may be formed of an organic substance, and these may be substrates. It may be formed of an oxide, a fluoride, a nitride, a sulfide, a carbide, a boride, boron, carbon, or an inorganic substance containing a metal as a main component. Also, a composite material of these may be used. A substrate containing glass, quartz, sapphire, iron, titanium, or aluminum as a main component can also serve as the inorganic protective layer.

Of the organic substances and the inorganic substances, it is preferable that they are 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, so the inorganic layer should be thin and opposite to the information recording medium layer of the inorganic layer. It is preferable that a thick organic layer is in close contact with the side of in order to increase the mechanical strength. This organic layer may be the substrate. This makes deformation less likely to occur.

Examples of organic substances include polystyrene,
Polytetrafluoroethylene (Teflon), Polyimide, Acrylic resin, Polyolefin, Polyethylene terephthalate, Polycarbonate, Epoxy resin, Ethylene-vinyl acetate copolymer known as hot melt adhesive, Adhesive, UV curing resin, etc. Is used.

In the case of the protective layer made of an inorganic substance, it may be formed as it is by electron beam evaporation, sputtering, etc., but reactive sputtering, or a layer made of at least one element of metal, semimetal and semiconductor is formed. After that, it may be reacted with at least one of oxygen, sulfur, and nitrogen.

Examples of the inorganic protective layer include Ce, L
a, Si, In, Al, Ge, Pb, Sn, Bi, T
an oxide of at least one element selected from the group consisting of e, Ta, Sc, Y, Ti, Zr, V, Nb, Cr and W,
Cd, Zn, Ga, In, Sb, Ge, Sn, Pb, B
a sulfide of at least one element selected from the group consisting of i,
Fluoride such as Mg, Ce, Ca, Si, Al, Ta, B
Etc., nitrides such as B, Si, etc., borides such as Ti, boron, carbon, and the like, whose main components are CeO ₂ , La ₂ O ₃ , SiO, SiO ₂ , In.
₂ O ₃ , Al ₂ O ₃ , GeO, GeO ₂ , PbO, SnO, S
nO ₂ , Bi ₂ O ₃ , TeO ₂ , Ta ₂ O ₅ , Sc ₂ O ₃ , Y ₂ O
₃ , TiO ₂ , ZrO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Cr ₂ O ₃ ,
WO ₂ , WO ₃ , CdS, ZnS, In ₂ S ₃ , Sb ₂ S ₃ ,
Ga ₂ S ₃ , GeS, SnS, SnS ₂ , PbS, Bi ₂ S
₃ , MgF ₂ , CeF ₃ , CaF ₂ , TaN, Si ₃ N ₄ , A
1N, BN, Si, TiB ₂ , B ₄ C, SiC, B, C, and mixtures thereof.

Of these, sulfides close to ZnS are preferable in that the refractive index is appropriate and the layer is stable. In the case of nitride, the surface reflectance is not very high, and the layer is stable and strong, so TaN, Si ₃ N ₄ or A is used.
A composition close to 1N (aluminum nitride) is preferable. Preferred oxides are Y ₂ O ₃ , Sc ₂ O ₃ , CeO ₂ ,
TiO ₂ , ZrO ₂ , SiO, Ta ₂ O ₅ , In ₂ O ₃ , Al
_It has a composition close to that of ₂ O ₃ , SnO ₂ or SiO ₂ . Amorphous Si containing hydrogen is also preferred. If the protective layer is multilayered, the protective effect is further enhanced. For example, the thickness is 30 nm
A thin film having a composition close to that of SiO ₂ and having a thickness of 300 nm or less is formed on the side far from the information recording medium layer and has a thickness of 30 nm or more to 3
If a thin film having a composition close to that of ZnS and having a thickness of 00 nm or less is formed on the side closer to the information recording medium layer, environmental resistance and recording / erasing characteristics are greatly improved, and the number of rewritable times is also greatly improved.

The preferable range of the film thickness of each portion is, of the following, that the reflectance of the unrecorded portion with respect to the laser beam from the substrate is 6:
The combination is 5% or more.

Recording layer film thickness: 10 nm or more and 600 nm or less Absorption layer film thickness: 2 nm or more and 100 nm or less Intermediate layer film thickness: 10 nm or more and 600 nm or less Reflective layer film thickness: 10 nm or more and 300 nm or less Inorganic material protective layer: 20 nm or more and 1 μm or less Organic material protective layer : 500 nm or more and 10 mm or less Moreover, the particularly preferable range of the film thickness of each part is as follows.
The reflectance of the unrecorded area for the laser light from the substrate is 65%
It is the above combination.

Recording layer film thickness: 20 nm or more and 400 nm or less Absorption layer film thickness: 5 nm or more and 50 nm or less Intermediate layer film thickness: 20 nm or more and 400 nm or less Reflective layer film thickness: 20 nm or more and 150 nm or less Inorganic material protective layer: 40 nm or more and 600 nm or less Organic material protective layer : 2 μm or more and 1 mm or less The materials and film thicknesses of the layers other than the recording layer are not limited to those of the recording layer of the present invention, and other phase transition recording layers, mutual diffusion type recording layers,
It is also effective for a magneto-optical recording layer and the like.

As a method for forming each of the layers described above, any one of vacuum vapor deposition, vapor deposition in gas, sputtering, ion beam vapor deposition, ion plating, electron beam vapor deposition, injection molding, casting, spin coating, plasma polymerization and the like can be appropriately used. To choose. It is preferable that the recording layer, the reflective layer and the inorganic protective layer are all formed by sputtering because the composition and the film thickness can be easily controlled and the manufacturing cost can be reduced.

The recording layer of the present invention may be changed in its optical properties by some kind of atomic arrangement change which hardly accompanies a change in shape. In addition to the change between the amorphous state and the crystalline state, for example, the change in the crystal grain size or the crystal form, the change between the crystal and the metastable state, and the like may be used. Even if the amorphous state and the crystalline state change, the amorphous portion is not completely amorphous and may have a mixed crystal portion. Further, even if recording is performed between the recording layer and the reflective layer, some of the atoms constituting these layers move (due to diffusion, chemical reaction, etc.) or both due to movement and phase transition. Good.

The recording member of the present invention can be used not only in the form of a disk, but also in other forms such as a tape or a card.

[0043]

【Example】

<Embodiment 1> FIG. 1 shows a sectional view of a disk A according to an embodiment of the present invention.

A high frequency magnetron sputtering device was used on a replica substrate 1 having a spiral groove with a pitch of 1.5 μm for tracking formed on the surface of a disk-shaped polycarbonate plate having a diameter of 120 mm and a thickness of 1.2 mm by an injection molding method. First, the recording layer 2 having a composition of Sn ₁₇ Sb ₁₇ Se _{66 in} atomic% was formed to have a film thickness of 130 nm. Then, the absorption layer 3 having a composition of Sb ₈₀ Bi ₂₀ in atomic% was formed in the same sputtering apparatus to have a film thickness of 20 nm. Subsequently, in the same sputtering apparatus, an intermediate layer 4 having a composition of (ZnS) ₈₀ (SiO ₂ ) ₂₀ in atomic% was formed to have a film thickness of 150 nm. Then, the Au reflective layer 5 was formed in a film thickness of 60 nm in the same sputtering apparatus. Further, the ultraviolet curable resin spin-coated on the reflective layer 5 was cured to form the organic layer 6 having a thickness of 50 μm. Similarly, on another similar substrate 1 ', S
recording layer 2 of the composition of n ₁₇ Sb ₁₇ Se ₆₆ ', the absorption layer 3 having the composition of _{Sb 80 Bi 20', (ZnS} ) 80 (SiO 2) 20 intermediate layer 4 of the composition of the 'Au reflective layer 5', organics Layer 6'was formed sequentially. The two discs thus produced were bonded together with the adhesive layers 7 with the organic layers 6 and 6'side facing inward to produce a disc A.

As a comparative example of the present invention, FIG. 2 shows a Ge-S type in which the recording layer itself absorbs laser light and there is no absorbing layer.
FIG. 3 shows a sectional view of a prior art disc B having a b-Te based recording layer. This disk B was manufactured as follows.

That is, as with the disk A, the diameter 12
On a replica substrate 8 in which a spiral groove having a pitch of 1.5 μm for tracking is formed on the surface of a disk-shaped polycarbonate plate having a thickness of 0 mm and a thickness of 1.2 mm by an injection molding method,
First, a protective layer 9 having a composition of (ZnS) ₄₀ (SiO ₂ ) ₆₀ at 100% by atomic% was formed using a high frequency magnetron sputtering device.
It was formed to a film thickness of m. Subsequently, two recording layers 10 having a composition of Ge ₂₁ Sb ₂₆ Te ₅₃ in atomic% are formed in the same sputtering apparatus.
It was formed to a film thickness of 0 nm. Then, the intermediate layer 11 having a composition of (ZnS) ₄₀ (SiO ₂ ) ₆₀ in atomic% was formed in the same sputtering apparatus to have a film thickness of 132 nm. Then, the Au reflective layer 12 was formed to a film thickness of 60 nm in the same sputtering apparatus. Further, the ultraviolet curable resin spin-coated on the reflective layer 12 is cured to form an organic layer 1 having a thickness of 50 μm.
Formed 3. Similarly, another (ZnS) ₄₀ (SiO ₂ ) ₆₀ protective layer 9 ', Ge ₂₁ Sb ₂₆ T is formed on another similar substrate 8'.
recording layer 10 of the composition of the e ₅₃ ', (ZnS) ₄₀ intermediate layer 11 of the composition (SiO _{2) 60',} Au reflective layer 12 ', the organic layer 1
3'was formed sequentially. The two discs thus produced were bonded together with the adhesive layers 14 with the organic layers 13 and 13 'side facing inward to produce disc B.

The recording / reproducing evaluation of the discs A and B produced in this way is performed by an optical disc drive (recording / reproducing apparatus).
Was carried out as follows. The disk is rotated at a constant rotation speed, and continuous light from a semiconductor laser with a wavelength of 780 nm is kept at a low power level where recording is not performed at an arbitrary radial position, and the numerical aperture (Numerical Aperture) in the optical head
By focusing with a 0.55 objective lens and irradiating the recording layer 2 through the substrate 1 and detecting the reflected light, the head is adjusted so that the center of the light spot is always aligned with the tracking groove and the middle of the groove. Driven. The influence of noise generated from the groove can be avoided by setting the recording track in the middle of the groove. While tracking is performed in this manner, recording is performed by further performing automatic focusing so that the focus is on the recording layer. When recording is performed on this recording track by crystallization, the range of laser power suitable for crystallization is a range that is high enough to cause crystallization and lower than a range where amorphous is generated. In addition, when recording by amorphization, the range of laser power suitable for amorphization is:
The range is higher than the crystallization power and lower than that which causes strong deformation or has holes.

Disks A and B were used as a write-once medium, and the disk linear velocity was 1.2 m / s (rotation speed 270r.
pm, radial position 43 mm), the reproducing light level is 1.0 mW (on the disk surface), the laser power is the reproducing light level, and the recording power level by crystallization (on the disk surface) 6.
Information was recorded by changing as shown in FIG. 3 between 5 mW. On the track recorded in this way, the disk surface of the reproduction light level 1.0 where recording and erasing are not performed while performing tracking and automatic focusing.
Information was reproduced by irradiating continuous light of mW and detecting the intensity of the reflected light. First, 1 at 8-14 modulation (EMF)
1T repetitive signal (0.17MHz, duty 50
%) Was recorded without initializing, the reflectance of the recording laser beam irradiation portion changed from 80% in the disk A to 18%, but was not recorded in the disk B because no change was observed. Therefore, when only the disk B was initialized after the entire surface was initialized with a laser beam of 15 mW, it was changed from 67% to 49%. Here, based on the medium reflectance (Ro) of the unrecorded portion and the medium reflectance (Rw) of the information recording portion, the reproduction signal modulation degree (Mod) in the information recording portion is defined as shown in the following Equation 1. Then,

[0049]

[Equation 1] Mod (%) = | Ro-Rw | / Ro * 100 ... Equation 1 In the disk A, the reproduction signal modulation degree is 78% and the measurement band is 10 k.
A reproduction signal output with a carrier-to-noise ratio of 61 dB can be obtained at Hz, and a reproduction signal modulation degree of 27% for the disk B and a measurement band of 1
A reproduced signal output with a carrier-to-noise ratio of 51 dB was obtained at 0 kHz. Next, a 3T repetitive signal (0.72
When the disk A is recorded at a recording power of 6.5 mW without being initialized, the reproduction signal modulation degree is 38%, the carrier band to noise ratio is 56 at a measurement band of 10 kHz.
The reproduced signal output of dB is obtained, and the reproduced signal modulation degree is 13% in the disk B and the carrier-to-noise ratio is 4 in the measurement band of 10 kHz.
A reproduction signal output of 6 dB was obtained.

Disks A and B were set at a disk linear velocity of 8 m /
At s (rotation speed 1800 rpm, radial position 43 mm), the reproduction light level is 1.0 mW (on the disk surface), the laser power is the reproduction light level and the recording power level by crystallization,
Information was recorded by changing it between 17.0 mW (on the disc surface) in the same manner as in FIG. 3, and the information was reproduced by detecting the intensity of reflected light at the recording portion. 2MHz,
When a signal with a duty of 50% is recorded, a reproduction signal output of a reproduction signal modulation degree of 78% and a carrier-to-noise ratio of 62 dB is obtained at a measurement band of 30 kHz in the disk A,
In the case of a reproduction signal modulation degree of 27% and a measurement band of 30 kHz, a reproduction signal output of a carrier-to-noise ratio of 52 dB was obtained. next,
Recording power 1 for a signal of 4.5 MHz and 50% duty
When recorded at 7.5 mW, the reproduction signal modulation degree is 38% in the disk A, and the carrier-to-noise ratio is 57 at the measurement band of 30 kHz.
A reproduction signal output of dB is obtained, and the reproduction signal modulation degree is 13% in the disk B and the carrier-to-noise ratio is 4 in the measurement band of 30 kHz.
A reproduction signal output of 7 dB was obtained.

As described above, in the prior art disc B, when the reflectance of the unrecorded portion is increased to 67% and 65% or more, the reflectance of the recording portion becomes 49% and 45% or more, and a very large reproduction signal output is produced. Although not obtained, the disk A of the present invention
However, even if the reflectance of the recording portion was increased to 80% and 65% or more, the reflectance of the recording portion was 18% and 45% or more, and a sufficiently large reproduced signal output was obtained.

In the disk B which is a comparative example (prior art) of the present invention, the film thickness of the other layers was kept constant (ZnS).
The intermediate layer 11 having a composition of ₄₀ (SiO ₂ ) ₆₀ is formed from 20 nm to 32
When changed to 00 nm, the medium reflectivity in the re-unrecorded portion after the initialization and the above-mentioned 2 MHz, duty 50
The medium reflectance at the recording portion where the signal of% was recorded changed as shown in FIG. There is no place where the medium reflectance in the unrecorded area is 65% or more and the medium reflectance in the recorded area is 45% or less.

On the other hand, in the disk A of the present invention, when the film thickness of the recording layer 2 having the composition of Sn ₁₇ Sb ₁₇ Se ₆₆ was changed from 10 nm to 160 nm while keeping the film thickness of the other layers constant, it was not reproduced. The medium reflectance at the recording unit and 2MH as described above
The medium reflectivity in the recording portion which recorded a signal with z and a duty of 50% changed as shown in FIG. 5, and the reproduction signal modulation degree changed as shown in FIG. Recording layer thickness is 23 nm or more 2
With a wide range of recording layer thicknesses of 9 nm or less, 67 nm or more and 149 nm or less, the medium reflectance in the unrecorded portion is 65% or more and the medium reflectance in the recording portion is 45% or less. Particularly, when the recording layer thickness is 114 nm or more and 145 nm or less, the medium reflectance in the unrecorded portion is 70% or more, the medium reflectance in the recording portion is 28% or less, and the reproduction signal modulation degree is 60% or more. The CD-WO standard was satisfied.

Further, in the disk A, when the film thickness of the absorption layer 3 having the composition of Sb ₈₀ Bi ₂₀ was changed from 2 nm to 40 nm while keeping the film thickness of the other layers constant, the medium reflectance of the unrecorded part The medium reflectance at the information recording portion changed as shown in FIG. 7, and the reproduction signal modulation degree changed as shown in FIG. Where the absorption layer thickness is 2 nm or more and 29 nm or less,
The medium reflectance in the unrecorded area was 65% or more, and the medium reflectance in the recorded area was 45% or less. Particularly, when the film thickness of the absorption layer is 2 nm or more and 25.5 nm or less, the medium reflectance in the unrecorded portion is 70% or more, and the medium reflectance in the recorded portion is 28% or more.
%, The reproduction signal modulation degree becomes 60% or more, and CD-
The WO standard was satisfied. However, when the film thickness of the absorption layer was 2 nm or more and less than 8 nm, the recording sensitivity was low because the light absorption rate in the absorption layer was small.

In the disk A, a recording layer 2 having a composition of Sn ₁₇ Sb ₁₇ Se ₆₆ 2, an absorbing layer 3 having a composition of Sb ₈₀ Bi ₂₀ 3, (Zn
S) ₈₀ (SiO ₂ ) ₂₀ composition intermediate layer 4 and Au reflective layer 5
Have excellent oxidation resistance, and each test piece with each layer alone formed on glass was tested at 60 ° C and 95% relative humidity.
%, There was no change in the medium reflectance or transmittance with respect to the laser beam even after being left for 3,000 hours, and it was hardly oxidized. Further, even if the disk A on which a signal having a linear velocity of 8 m / s and a frequency of 2 MHz and a duty of 50% is recorded is left to stand for 3000 hours under the condition of 60 ° C. and 95% relative humidity, the reproduction signal output is 78%. No change was observed at the carrier-to-noise ratio of 62 dB.

The optical constant (complex refractive index) of the Sn ₁₇ Sb ₁₇ Se ₆₆ thin film, which is the composition of the recording layer 2 in the disk A, at the laser light wavelength of 780 nm was measured, and the refractive index (the real part of the complex refractive index) n) was 3.19, and the extinction coefficient (k), which is the imaginary part of the complex refractive index, was 0.01. In the Sn-Sb-Se recording layer 2, when Te is added while keeping the relative ratio of other elements constant and the Te content is changed, the recording layer 2 is erased at a laser light wavelength of 780 nm. The extinction coefficient and the medium reflectance from the substrate side when the film thickness of the recording layer 2 in the disk A is 120 nm and the film thickness of the absorbing layer 3 is 10 nm change as follows.

Te content (at%) Extinction coefficient Medium reflectance (%) 0 0.01 92 2 0.05 5 85 4 0.1 78 6 0.15 71 7 8 0.2 65 65 10 0.25 60 12 0.3 55 14 0.35 51 In the disk A, the composition of the recording layer 2 was Sn ₁₇ Sb.
Similar results were obtained by using Sn—Sb—Se system having other composition ratio instead of ₁₇ Se ₆₆ . However, when the content of Se is less than 55 atom%, the reproduction signal modulation degree is reduced by 10% or more, and when it is less than 40 atom%, the reproduction signal modulation degree is 20%.
It decreased more than that.

In the disk A, as the composition of the recording layer 2, in place of Sn—Sb—Se system, instead of Sn of Sn—Sb—Se system, at least one element of other Si, Ge and Pb was used. Similar results were obtained using a system consisting of Sb and Se. Further, instead of Sn-Sb-Se system, instead of Sn and Sb of Sn-Sb-Se system,
Other Sn, Sb, Si, Ge, Pb, In, Ga, Bi
Similar results were obtained using a system consisting of Se and at least one of the elements. However, the recording layer having a composition containing no Sb may have poor oxidation resistance.

The optical constant (complex refractive index) of the Sb ₈₀ Bi ₂₀ thin film, which is the composition of the absorption layer 3 in the disk A, at a laser light wavelength of 780 nm was measured, and the refractive index (n) which is the real part of the complex refractive index was measured. Was 3.67, and the extinction coefficient (k), which is the imaginary part of the complex refractive index, was 5.23. This Sb ₈₀
In the Bi ₂₀ absorption layer 3, Se is further added while keeping the relative ratio of other elements constant, and the newly added Se is added.
When the content is changed, the laser light wavelength of the absorption layer 3 is 78
Extinction coefficient at 0 nm and disk linear velocity of 1.2 m / s
The recording power when recording a signal of 0.17 MHz at a duty of 50% changed as follows.

Se content (at%) Extinction coefficient Recording power (mW) 0 5.23 6.5 5 5 5 7.0 7.0 10 4.5 7.5 15 4 4 8.0 20 20 3.5 9.0 25 3 11.0 30 2.5 14.0 35 2 18.0 40 1.5 Not recordable, as the absorption layer 3 in the disk A, instead of the Sb-Bi system, the same thermal conductivity was 0.3 mW / cm. At least one of Sb alloy system, Te alloy system, Bi alloy system, Sb-Te alloy system, Sb-Bi alloy system, manganin, Constantan, stainless steel, Nichrome, Inconel, Monel, etc. having a thermal conductivity of deg or less The same recording / reproducing characteristics as those of the disk A were obtained by using the alloy containing the same.

The optical constant (complex refractive index) of (ZnS) ₈₀ (SiO ₂ ) ₂₀ , which is the composition of the intermediate layer 4 in the disk A, was measured at a laser light wavelength of 780 nm. The index (n) was 2.17, and the extinction coefficient (k), which is the imaginary part of the complex refractive index, was 0.00. In this (ZnS) ₈₀ (SiO ₂ ) ₂₀ intermediate layer 4, when Si is further added while keeping the relative ratio of other elements constant and the content of the newly added Si is changed, the intermediate layer 4 Extinction coefficient at a laser light wavelength of 780 nm and disk A
When the film thickness of the recording layer 2 was 110 nm and the film thickness of the absorbing layer 3 was 25 nm, the medium reflectance from the substrate side changed as follows.

Si content (at%) Extinction coefficient Medium reflectivity (%) 0 0.00 78 2.5 0.05 0.05 73 5 0.1 70 70 7.5 0.15 67 15 0.2 65 65 12. 5 0.25 64 15 0.3 0.3 63 17.5 0.356 As the intermediate layer 4 in the disk A, (ZnS)-(Si
Instead of O ₂ ), Z which also causes multiple interference of laser beams
nS, SiO ₂ , SiO, CeO ₂ , Al ₂ O ₃ , Ta
₂ O ₅ , Y ₂ O ₃ , ZrO ₂ , V ₂ O ₅ , TaN, Si ₃ N ₄ ,
Even if AlN 3 or the like and a mixture thereof were used, the recording / reproducing characteristics similar to those of the disk A were obtained by controlling the film thickness according to each optical constant.

As the reflective layer 5 in the disk A, Al
Similarly, instead of the Au system, Al, Au, Ag, Cu or the like having a high reflectance of 80% or more and an Al alloy, an Au alloy, an Ag alloy, a Cu alloy or the like containing these are used. Recording / reproducing characteristics similar to those of the disk A were obtained.

<Embodiment 2> FIG. 9 shows a sectional structural view of a disk C of the present embodiment.

Spiral grooves with a pitch of 1.5 μm for tracking are formed on the surface of a disk-shaped polyolefin plate having a diameter of 300 mm and a thickness of 1.2 mm by injection molding, and one circumference is divided into 49 sectors. At the start of each sector. First, using a high-frequency magnetron sputtering apparatus, first, on a replica substrate 15 in which a track address, a sector address, etc. are provided in the form of concave and convex pits in the groove portion between the grooves and in the middle of the groove (this portion is called a header portion), ZnS) ₄₀ (SiO ₂ ) ₆₀
The protective layer 16 having the above composition was formed to a film thickness of 100 nm. Subsequently, the recording layer 17 having a composition of In ₄₉ Se ₄₉ Tl _{2 in} atomic% was formed to a film thickness of 70 nm. Then, the absorption layer 18 having a composition of Sb ₄₀ Te ₆₀ in atomic% is formed in the same sputtering device.
It was formed to a film thickness of 0 nm. Then, an intermediate layer 19 having a composition of (ZnS) ₄₀ (SiO ₂ ) ₆₀ in atomic% was formed in the same sputtering apparatus to have a film thickness of 160 nm. Then, the Al ₇₀ Au ₃₀ reflective layer 20 was formed in an atomic percentage of 6 in the same sputtering apparatus.
It was formed to a film thickness of 0 nm. Further, the ultraviolet curable resin spin-coated on the reflective layer 20 was cured to form an organic material layer 21 having a thickness of 50 μm.

Similarly, a protective layer 16 ', In having a composition of (ZnS) ₄₀ (SiO ₂ ) ₆₀ is formed on another similar substrate 15'.
A recording layer 17 'having a composition of ₄₉ Se ₄₉ Tl ₂ , an absorbing layer 18' having a composition of Sb ₄₀ Te ₆₀ , an intermediate layer 19 'having a composition of (ZnS) ₄₀ (SiO ₂ ) ₆₀ , an Al ₇₀ Au ₃₀ reflective layer 20'. , Organic layer 2
1'was formed sequentially. The two disks thus produced were bonded together with the adhesive layers 22 with the organic material layers 21 and 21 'side facing inward to produce a disk C.

Using the disk C thus produced as a reversible type, recording / erasing / reproducing evaluation was performed by the optical disk drive (recording / erasing / reproducing apparatus) as follows. The disk is rotated at a constant rotation speed, and continuous light from a semiconductor laser with a wavelength of 780 nm is maintained at an arbitrary radial position at a low power level where recording is not performed, and the numerical aperture (Numerical Aperture) of the optical head is set to 0.55. The head was driven so that the center of the light spot was always aligned with the tracking groove and the middle of the groove by detecting the reflected light by converging with the objective lens and irradiating the recording layer 2 through the substrate 1. The influence of noise generated from the groove can be avoided by setting the recording track in the middle of the groove. While tracking is performed in this manner, automatic focusing is performed so that the focus is on the recording layer, and recording and erasing are simultaneously performed by overwriting with one beam.

When recording is performed by crystallization on a track (tracking groove and groove middle), the range of laser power suitable for crystallization is high enough to cause crystallization, and amorphization occurs. It's the lower range that happens. In the case of erasing by amorphization, the range of laser power suitable for amorphization is higher than the power for crystallization and lower than the range where strong deformation occurs or holes are formed. Overwriting with one beam was performed by changing the laser power between an intermediate power level causing crystallization and a high power level causing amorphization. The power ratio between the high power level for amorphization and the intermediate power level for crystallization is particularly preferably in the range of 1: 0.4 to 1: 0.8.

After passing the portion to be recorded, the laser power was lowered to the reproduction light level which did not cause any change, and the tracking and the automatic focusing were continued. Note that tracking and automatic focusing are continued during recording. As a result, the recorded information is rewritten to the newly recorded information even if the already recorded portion is performed.
However, after erasing by irradiating continuous light with a power close to the higher power of the laser power modulation at the first rotation or multiple rotations at the time of recording / rewriting and then once erasing, a high power level is set according to the information signal according to the information signal. By irradiating and recording with laser light modulated to an intermediate power level, there is little unerased information previously written, and a high carrier-to-noise ratio can be obtained. In this case, the power of the continuous light that is emitted first is
When the high power level was set to 1, good rewriting could be performed in the range of 0.8 to 1.1.

At a linear velocity of the disk C of 1.2 m / s (rotation speed of 270 rpm, radial position of 43 mm), a reproducing light level of 1.0 mW, and a laser power of an intermediate power level (on the disk surface) due to crystallization and a non-power level. Information was recorded by changing between a high power level (on the disk surface) due to crystallization in the same manner as in FIG. On the track recorded in this way, while performing tracking and automatic focusing, continuous light of 1.0 mW of the disk surface at the reproduction light level where recording and erasing is not performed is irradiated, and the intensity of this reflected light is detected to obtain information. Replayed. Here, an 11T repetitive signal (0.17 MHz, duty 50%) and a 6T repetitive signal (0.36 MHz, duty 50%) in EMF are alternately used with a recording laser beam having a high power level of 10 mW and an intermediate power level of 6 mW. Was overwritten. First, 11T repetitive signal (0.17M in EMF)
Recording was performed without initializing (Hz, duty 50%), and the reflectance of the recording laser light irradiation portion was 74% to 21%.
Changes to, playback signal modulation degree 71%, measurement band 10 kHz
Thus, a reproduction signal output having a carrier-to-noise ratio of 60 dB was obtained.
On top of this, repeat signal of 6T in EMF (0.36MH
(z, duty 50%), a reproduction signal output was obtained with a reproduction signal modulation factor of 64%, a carrier-to-noise ratio of 58 dB, and a previous signal (repeated signal of 11T) erasing ratio of 28 dB in a measurement band of 10 kHz. Further, the rewritable number at this time was 10,000 times or more.

In the disc C, the composition of the recording layer is In
For disk D with ₄₇ Se ₄₇ Tl ₆ , disk linear velocity 8 m / s (rotation speed 1800 rpm, radial position 43 m
m), the reproduction light level is 1.0 mW, 2 MHz,
50% duty signal and 3MHz, 50% duty
Signal, laser power is high power level (on disk surface) 25 mW, intermediate power level (on disk surface) 1
Modulation was performed between 5 mW, and the data was alternately overwritten by changing as shown in FIG. First, 2MHz,
When a signal with a duty of 50% was recorded without initial crystallization, the reflectance of the recording laser light irradiation portion was 72% to 22%.
%, Reproduced signal modulation degree 69%, measurement band 30 kHz
A reproduced signal output having a carrier-to-noise ratio of 59 dB was obtained at z. When a signal of 3 MHz and a duty of 50% is overwritten on this, the reproduction signal modulation degree is 62%, the carrier-to-noise ratio is 57 dB at the measurement band of 30 kHz, and the previous signal (11T
A reproduction signal output with an erasing ratio of 27 dB was obtained. The rewritable number at this time was 100,000 or more.

Each of the disks C and D had very excellent oxidation resistance, and there was no change in the medium reflectance or transmittance with respect to the laser beam even if the disks C and D were left under the condition of 60 ° C. and 95% relative humidity for 3000 hours. . Also, 2M at a linear velocity of 8m / s in advance.
Even if the disks C and D on which a signal of Hz and a duty of 50% is recorded are left under the condition of 60 ° C. and a relative humidity of 95% for 3,000 hours, the reproduced signal output shows no change in the reproduced signal modulation degree and the carrier-to-noise ratio. I couldn't do it.

In the disks C and D, instead of the (ZnS)-(SiO ₂ ) system used for the protective layer 9, the extinction coefficient, which is the imaginary part of the complex refractive index with respect to the laser light, is 0.
2 or less ZnS, SiO ₂ , SiO, CeO ₂ , A
l ₂ O ₃ , Ta ₂ O ₅ , Y ₂ O ₃ , ZrO ₂ , V ₂ O ₅ , Ta
Even when N, Si ₃ N ₄ , AlN or the like and a mixture thereof were used, the recording / erasing characteristics similar to those of the disks C and D were obtained by controlling the film thickness in accordance with the respective optical constants.

If the protective layer 9 is a laminated film of two or more layers, it is more effective to increase the protective strength. For example, a SiO ₂ layer having a thickness of 200 nm is provided on the side far from the information recording medium layer, and (ZnS)-(Si having a thickness of 100 nm is provided on the side closer to the information recording medium layer.
With the two-layer structure in which the O ₂ ) layer is arranged, rewriting is possible over 300,000 times, and the rewriting characteristics were good.

As the substrate of this embodiment, in addition to the polycarbonate substrate and the polyolefin substrate manufactured by the injection molding method, the surface of the chemically strengthened glass plate, the polycarbonate plate, the polyolefin plate, the epoxy plate, the acrylic resin plate, etc. is subjected to the photopolymerization method. As a result, similar results of recording / erasing / reproducing characteristics were obtained even when a replica formed with an ultraviolet curable resin layer having a groove for tracking was used.

[0076]

According to the present invention, in the information recording medium of the type in which recording is performed by changing the atomic arrangement of the recording layer material made of an inorganic material, the reflectance of the unrecorded portion with respect to the laser beam is 6
Even if it is as high as 5% or more, it is possible to obtain an information recording medium having good recording / erasing / reproducing characteristics, a long holding life of recorded data, and excellent environmental resistance. Further, the information recorded on the information recording medium of the present invention can be read by a reproducing apparatus such as a read-only compact disc or a laser disc which is already widely used.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an information recording medium of a disc A in an example.

FIG. 2 is a cross-sectional view showing the structure of the information recording medium of the disc B in the example.

FIG. 3 is a waveform diagram of a write-once recording laser according to an example.

FIG. 4 is a characteristic diagram showing the dependency of medium reflectance on the thickness of the intermediate layer in the disk B of the example.

FIG. 5 is a characteristic diagram showing the recording layer film thickness dependence of the medium reflectance in the disk A of the example.

FIG. 6 is a characteristic diagram showing the dependence of the degree of modulation of the reproduced signal on the recording layer thickness in the disk A of the example.

FIG. 7 is a characteristic diagram showing the dependence of the medium reflectance on the absorption layer film thickness of the disk A of the example.

FIG. 8 is a characteristic diagram showing the dependency of the reproduction signal modulation degree on the absorption layer film thickness in the disc A of the example.

FIG. 9 is a sectional view showing the structure of an information recording medium of disks C and D in the example.

FIG. 10 is a waveform diagram of a reversible recording laser for overwriting according to an example.

[Explanation of symbols]

1, 1 '... substrate, 2, 2' ... recording layer, 3, 3 '... absorption layer, 4, 4' ... intermediate layer, 5, 5 '... reflective layer, 6, 6' ...
Organic substance layer, 7 ... Adhesive layer.

Continuation of the front page (72) Inventor Shinkichi Horigo 1-280, Higashi Koigokubo, Kokubunji, Tokyo

Claims (8)

[Claims] 1. An optical arrangement, which is formed directly on a substrate or through a protective layer made of at least one of an inorganic material and an organic material and is irradiated with laser light to cause a change in atomic arrangement without a shape change. For information recording including a recording layer made of an inorganic material whose constant changes, an absorption layer that absorbs the laser light, a reflection layer that reflects the laser light, and an intermediate layer located between the absorption layer and the reflection layer In the medium, the medium reflectance with respect to the laser beam from the substrate side is 6 at the unrecorded portion.
An information recording medium, which is 5% or more and 45% or less in a recording portion. 2. The information recording medium according to claim 1, wherein the stacking order is the recording layer, the absorbing layer, the intermediate layer, and the reflecting layer in order from the side closer to the substrate. 3. The recording layer according to claim 1,
An information recording medium in which the absorbing layer, the intermediate layer, and the reflecting layer are adjacent to each other. 4. The information recording medium according to claim 1, 2, 3 or 4, wherein the extinction coefficient, which is an imaginary part of a complex refractive index of the recording layer in the unrecorded state, is 0.2 or less. . 5. The information recording medium according to claim 1, wherein the extinction coefficient, which is an imaginary part of a complex refractive index of the absorption layer with respect to a laser beam, is 2.0 or more. 6. The information recording medium according to claim 1, wherein an extinction coefficient, which is an imaginary part of a complex refractive index of the intermediate layer with respect to a laser beam, is 0.2 or less. 7. The information recording medium according to claim 1, wherein the reflectance of the reflection layer with respect to the laser light is 70% or more. 8. The information recording medium according to claim 1, 2, 3 or 4, wherein the recording layer contains at least one element of Se and S.