JP4216178B2 - Multi-layer phase change information recording medium and recording / reproducing method thereof - Google Patents

Description

  The present invention relates to a multilayer phase change information recording medium capable of recording and reproducing information by light such as a laser, and a recording and reproducing method thereof.

A phase change type optical disc (phase change type information recording medium) such as a CD-RW is generally provided with a recording layer made of a phase change type material on a plastic substrate, on which a light absorption rate of the recording layer is improved. In addition, a structure in which a reflective layer having a thermal diffusion effect is formed is a basic configuration, and laser light is incident from the substrate surface side to record and reproduce information.
Phase change materials change between a crystalline state and an amorphous state by heating with laser light irradiation and subsequent cooling, become amorphous when rapidly cooled after rapid heating, and crystallize when slowly cooled. The phase change type information recording medium applies this property to information recording / reproduction.
Further, for the purpose of preventing oxidation, transpiration, or deformation of the recording layer caused by heating due to light irradiation, a lower protective layer (also referred to as a lower dielectric layer) and a recording layer and a reflective layer are usually provided between the substrate and the recording layer. An upper protective layer (also referred to as an upper dielectric layer) is provided therebetween. Furthermore, these protective layers have a function of adjusting the optical characteristics of the recording medium by adjusting the thickness thereof, and the lower protective layer softens the substrate by heat during recording on the recording layer. It also has a function to prevent this.

In recent years, as the amount of information handled by computers and the like has increased, the signal recording capacity of optical discs such as DVD-RAM and DVD + RW has increased, and the density of signal information has been increasing. The current CD recording capacity is about 650 MB and the DVD is about 4.7 GB, but it is expected that the demand for higher recording density will increase in the future.
As a method for increasing the recording density of such a phase change information recording medium, for example, the laser wavelength used is shortened to the blue light region, or the numerical aperture NA of an objective lens used for a pickup for recording / reproducing is set. It has been proposed to increase the size of the laser beam so that the spot size of the laser beam applied to the optical recording medium is reduced.
As a method for improving the recording capacity by improving the recording medium itself, two layers having a structure in which at least two information layers including a recording layer and a reflective layer are stacked on one side of a substrate and these information layers are bonded with an ultraviolet curable resin or the like. Phase change information recording media have been proposed in, for example, Patent Documents 1 to 4.

The separation layer (referred to as an intermediate layer in the present invention), which is an adhesion portion between the information layers, has a function of optically separating the two information layers, and the information layer on the back side has as much recording / reproducing laser light as possible. Therefore, it is made of a material that does not absorb laser light as much as possible.
Each of these two-layer phase change information recording media is characterized by the first information layer, and the first protective layer and the second protective layer are provided as in the case of the single-layer phase change information recording medium. It is what was done.
The two-layer phase change information recording medium has been announced at academic societies as disclosed in Non-Patent Document 1, for example, but still has many problems.
For example, if the laser beam is not sufficiently transmitted through the information layer (first information layer) on the near side when viewed from the laser beam irradiation side, information is recorded on the recording layer of the information layer (second information layer) on the back side. Since recording and reproduction cannot be performed, it is conceivable that the reflective layer constituting the first information layer is eliminated or made extremely thin, or the recording layer constituting the first information layer is made extremely thin.

Recording with a phase change information recording medium is performed by irradiating a laser beam to the phase change material of the recording layer and quenching it to change the crystal to amorphous to form a mark. If it is very thin, such as about 10 nm, the thermal diffusion effect is reduced and it becomes difficult to form an amorphous mark.
In particular, the Sb—Te eutectic recording material, which is one of the materials widely used for phase change information recording media such as CD-RW, has an excellent erasure ratio compared to the Ge—Sb—Te compound recording material. Also, because of the high sensitivity, this is excellent in that the outline of the amorphous portion of the recording mark is clear.
However, since the Sb—Te eutectic recording material has a higher crystallization speed than the Ge—Sb—Te compound recording material, it needs to be rapidly cooled in a single hour to become amorphous. In other words, it is a material that needs to have a rapid cooling structure, and it is difficult to form a mark if the reflection layer is thin.

  A method of providing a layer (referred to as a thermal diffusion layer) for assisting the thermal diffusion function that the reflective layer has further provided on the reflective layer using nitride or carbide having a relatively high thermal conductivity and a small light absorption rate. The single-layer phase change information recording medium is disclosed in Patent Document 5, and the two-layer phase change information recording medium is disclosed in Patent Document 3, and this method is used when the reflective layer constituting the first information layer is thinned. This is considered to be an effective method for solving the above-mentioned drawbacks.

  However, these materials such as nitrides and carbides have large stresses, so that the formed thermal diffusion layer is likely to crack, and as a result, sufficient overwrite characteristics of the optical disc itself provided with the thermal diffusion layer cannot be obtained. There is a problem. Further, the carbide material has a particularly large absorption on the short wavelength side, and the next-generation optical disc such as a blue-ray disk system using a blue-violet laser cannot increase the light transmittance of the first information layer. Arise.

Japanese Patent No. 2702905 (Claims) JP 2000-215516 A (Claims) JP 2000-222777 A (Claims) JP 2001-243655 A (Claims) JP-A-8-50739 (Claims) ODS2001 Technical Digest P22-24 (P24, FIG. 5)

Accordingly, an object of the present invention is to provide a multilayer phase change information recording medium having excellent overwrite characteristics and a method for recording and reproducing information using the same even when the reflective layer of the information layer is thin.
In addition, the present invention can maintain a high transmittance even in a short wavelength region, can provide three or more recording layers, has excellent overwrite characteristics, and enables single-sided multilayer recording even when using a blue-violet laser. An object of the present invention is to provide a large-capacity multilayer phase change information recording medium and a recording / reproducing method thereof.
Thus, the present inventors first propose a multilayer phase change information recording medium using In, Zn and O as preferred materials for the thermal diffusion layer. A multilayer phase change information recording medium using this material is excellent in overwrite characteristics. Secondly, a multilayer phase change type information recording medium is proposed in which the absorption does not become so great as the wavelength becomes shorter, and therefore three or more recording layers can be provided even at the blue-violet wavelength.

As a result of intensive studies to solve the problems of the prior art, the present inventors have found the first group of inventions and the second group of inventions as solving means as follows.
That is, the above-described problems further include the inventions of the following first group inventions (1) to (3), the invention of the second group inventions (4) to (9), and more preferred embodiments of these inventions The present invention is solved by the inventions (10) to (20) (hereinafter referred to as the present invention 1 to 20).

[Invention of Group 1]
(1) In an optical information recording medium in which an information layer having a recording layer capable of recording information by phase change between a crystalline state and an amorphous state is provided by light incidence. When each information layer is a first information layer, a second information layer,... An Nth information layer as viewed from the light incident side, at least one information layer other than the Nth information layer is A multilayer phase change information recording medium comprising a lower protective layer, a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer, wherein the heat diffusion layer is mainly composed of indium, zinc and oxygen;
(2) The multilayer phase change information recording medium according to (1), wherein the atomic ratio of In to Zn is in the range of 0.05 ≦ Zn / (In + Zn) ≦ 0.5;
(3) The multilayer phase change information recording medium according to (1) or (2), wherein the thermal diffusion layer has a thickness of 20 to 200 nm.

[Invention of Group 2]
(4) An information layer having a recording layer capable of recording information by causing a phase change between a crystalline state and an amorphous state by the incidence of light is provided in N layers (N: an integer of 2 or more). In the optical information recording medium, when each information layer is a first information layer, a second information layer,... An Nth information layer as viewed from the light incident side, at least one information layer other than the Nth information layer. Has a layer structure in which a lower protective layer, a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer are stacked in this order, and the heat diffusion layer includes indium (In), zinc (Zn), oxygen (O), and A multilayer phase change information recording medium comprising at least one halogen as a main component;
(5) In addition to indium (In), zinc (Zn), oxygen (O), and at least one halogen, the thermal diffusion layer includes at least one third metal element having a valence of positive trivalent or higher. It is an essential constituent element, and the atomic ratio of the total amount of the third metal element to the entire metal element satisfies (total third metal element) / (In + Zn + total third metal element) ≦ 0.2. The multilayer phase change information recording medium according to (4);
(6) The atomic ratio of In and Zn in the thermal diffusion layer is in a range satisfying 0.55 ≦ In / (In + Zn) ≦ 0.9, as described in (4) or (5) above Multi-layer phase change information recording medium of
(7) The atomic ratio of the total amount of halogen in the thermal diffusion layer to the entire metal element satisfies 0.01 ≦ (total halogen) / (In + Zn + total third metal element) ≦ 0.3. (4) The multilayer phase change information recording medium according to any one of (6).
(8) The multilayer phase change information recording medium according to any one of (4) to (7), wherein the halogen of the heat diffusion layer is fluorine (F);
(9) The multilayer phase change information recording medium as described in any one of (4) to (8) above, wherein the thickness of the thermal diffusion layer is 10 to 200 nm.

[Invention further comprising a more preferred embodiment]
(10) The recording layer of the information layer having the thermal diffusion layer is mainly composed of Sb and Te, Ag, In, Ge, Se, Sn, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Any one of the above (1) to (3), which includes at least one of Zn, Ga, Bi, Si, Dy, Pd, Pt, Au, S, B, C, and P, or ( 4) The multilayer phase change information recording medium according to any one of (9);
(11) The multilayer phase change information recording medium according to any one of (1) to (10), wherein the recording layer has a thickness of 3 to 15 nm;
(12) The reflective layer of the information layer having the thermal diffusion layer is described in any one of (1) to (11), in which at least one of Au, Ag, Cu, W, Al, and Ta is a main component. Multi-layer phase change information recording medium of
(13) The multilayer phase change information recording medium according to any one of (1) to (12), wherein the reflective layer has a thickness of 3 to 20 nm;
(14) Two-layer phase change information capable of recording / reproducing information, having two information layers between the first substrate and the second substrate, and having an intermediate layer between the information layers. The first information layer includes a first lower protective layer, a first recording layer, a first upper protective layer, a first reflective layer, and a first heat diffusion layer, and the second information layer includes a second lower layer Including a protective layer, a second recording layer, a second upper protective layer, and a second reflective layer, from the side on which light for recording and reproduction is incident, the first substrate, the first lower protective layer, the first recording layer, The first upper protective layer, the first reflective layer, the first thermal diffusion layer, the intermediate layer, the second lower protective layer, the second recording layer, the second upper protective layer, the second reflective layer, and the second substrate are arranged in this order. The two-layer phase change information recording medium according to any one of (1) to (13), wherein:
(15) The two-layer phase change information recording medium according to (14), wherein the light transmittance of the first information layer is 40 to 70% with respect to light having a wavelength of 350 to 700 nm;
(16) The two-layer phase change information recording medium according to (14) or (15), wherein a transparent layer is provided between the first substrate and the first lower protective layer;
(17) The method according to (14), further comprising a barrier layer between the first upper protective layer and the first reflective layer and / or between the second upper protective layer and the second reflective layer. Thru | or the two-layer phase change information recording medium in any one of (16);
(18) The two-layer phase change information recording medium according to any one of (14) to (17), wherein the thickness of the first substrate is 10 μm to 600 μm;
(19) A light beam having a wavelength of 350 to 450 nm is incident on each information layer of the multilayer phase change information recording medium according to any one of (1) to (3) from the first information layer side to store information. A recording / reproducing method of a multi-layer phase change information recording medium, wherein recording / reproducing is performed;
(20) A light beam having a wavelength of 350 to 700 nm is incident on each information layer of the multilayer phase change information recording medium according to any one of (4) to (9) from the first information layer side to store information. A recording / reproducing method for a multilayer phase change information recording medium, characterized in that recording / reproducing is performed.

  As will be apparent from the following detailed and specific description, according to the first group of the present invention, it is possible to provide a multi-layer phase change information recording medium having excellent overwrite characteristics, and the overwrite characteristics are excellent. It is possible to provide a multi-layer phase change information recording medium having excellent storage reliability and recording and reproducing the reflectance, recording sensitivity, and transmittance (excluding the Nth layer) of each layer. It is possible to provide a multilayer phase change type information recording medium that can be optimized according to conditions and has excellent recording / reproducing characteristics for all information layers.

  In addition, according to the second group of the present invention, it is possible to provide a multilayer phase change information recording medium having excellent overwrite characteristics and excellent sensitivity even when a laser having a wavelength of 350 to 700 nm is used. The layer's reflectivity, recording sensitivity, and transmittance (except for the Nth layer) can be optimized according to the recording and reproducing conditions, and the multilayer phase change has excellent recording and reproducing characteristics for all information layers. A type information recording medium can be provided.

  According to another aspect of the invention having a more preferable aspect of the present invention as a further feature, the first information layer and the second information layer can be optically separated by the intermediate layer, and the first information is further separated. A two-layer phase change type information recording medium having good sensitivity and good recording / reproducing characteristics for both the layer and the second information layer can be provided, and can be easily manufactured even when the thickness of the first substrate is thin When a changeable information recording medium can be provided, and a two-layer phase change information recording medium having excellent storage reliability with reduced corrosion of the reflective layer can be provided, and the numerical aperture NA of the objective lens changes. However, it is possible to provide a two-layer phase change information recording medium that can be recorded and reproduced satisfactorily, and a large capacity recording and reproduction can be performed using the multilayer phase change information recording medium of the present invention.

Hereinafter, the present invention will be described in detail.
[Invention of Group 1]
The multilayer phase change information recording medium of the first group of the present invention has N layers (N: an integer of 2 or more) of information layers on a substrate, and the information layers are in a crystalline state and an amorphous state by light irradiation. A recording / reproducing multilayer phase change type information recording medium having a recording layer made of a material that changes in phase with each other and having an intermediate layer between each information layer, from the side on which recording / reproducing light is incident At least one information layer other than the information layer formed on the farthest side is composed of a lower protective layer, a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer, which are sequentially laminated, and the heat diffusion layer is indium, It is characterized by containing zinc and oxygen. Here, the main component means that the total amount of indium, zinc and oxygen occupies 80 atomic% or more, preferably 90 atomic% or more of the entire thermal diffusion layer material.

[Invention of Group 2]
The multilayer phase change information recording medium of the second group of the present invention has N layers (N: integer of 2 or more) of information layers on a substrate, and the information layers are in a crystalline state and an amorphous state by light irradiation. A recording / reproducing multilayer phase change type information recording medium having a recording layer made of a material that changes in phase with each other and having an intermediate layer between each information layer, from the side on which recording / reproducing light is incident At least one information layer other than the information layer formed on the farthest side is composed of a lower protective layer, a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer, which are sequentially laminated, and the heat diffusion layer is indium, It contains zinc, oxygen and at least one halogen. Here, the main component means that the total amount of indium, zinc, oxygen, and at least one halogen occupies 80 atomic% or more, preferably 90 atomic% or more of the entire thermal diffusion layer material.

  In both groups of inventions, conventionally known techniques can be applied to the lower protective layer, the recording layer made of a phase change material, the upper protective layer, and the reflective layer, but specific materials should be used for the thermal diffusion layer. Therefore, it has a basic feature in that the above-mentioned problems are solved.

  Here, among the plurality of information layers, the information layer formed at the innermost side when viewed from the light incident side does not need to transmit light, and therefore the reflective layer can be thickened, so there is no need to provide a heat diffusion layer. . Further, if a thermal diffusion layer is provided in the innermost recording layer, the material constituting the thermal diffusion layer is a material containing indium, zinc, oxygen and at least one halogen as essential constituent elements as described above. There is no need.

  In addition, as described in, for example, ISOM 2001 Technical Digest P202, the Ag-based material has a refractive index n as small as 0.5 or less even in the blue wavelength region, and can suppress light absorption. Conventionally known as a preferable material for a reflective layer of a recording medium.

Hereinafter, embodiments of the optical recording medium of the present invention will be described in detail.
FIG. 1 is a schematic cross-sectional view showing an example of a two-layer phase change information recording medium of the present invention of a first group and a second group, and the first information layer (1) is formed on the first substrate (3). The intermediate layer (4), the second information layer (2), and the second substrate (5) are sequentially accumulated.
The first information layer (1) includes a first lower protective layer (11), a first recording layer (12), a first upper protective layer (13), a first reflective layer (14), and a first heat diffusion layer (15). The second information layer (2) includes a second lower protective layer (21), a second recording layer (22), a second upper protective layer (23), and a second reflective layer (24). A barrier layer (not shown) is provided between the first upper protective layer (13) and the first reflective layer (14) and / or between the second upper protective layer (23) and the second reflective layer (24). It may be provided. In addition, the 1st information layer (1) and 2nd information layer (2) of this invention are not limited to the said layer structure.

  FIG. 2 is a schematic cross-sectional view showing another example of the two-layer phase change information recording medium of the present invention of the first group and the second group, and shows a first substrate (3) and a first lower protective layer (11). ) With a transparent layer (6). Such a transparent layer is provided when a thin sheet is used for the first substrate and the manufacturing method is different from that of the recording medium of FIG.

The first substrate (3) needs to be made of a material that can sufficiently transmit the recording / reproducing light, but a material conventionally known in the technical field may be used.
As the material, glass, ceramics, resin and the like are usually used, and the resin is particularly preferable in terms of moldability and cost.
Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Acrylic resins such as polycarbonate resin and polymethyl methacrylate (PMMA), which are excellent in terms of moldability, optical characteristics, and cost, are preferable.

The surface on which the information layers (1) and (2) of the first substrate (3) are formed is a spiral or concentric groove for tracking laser light, if necessary, and is usually a groove or land. A concavo-convex pattern called a portion may be formed, and this is usually molded by an injection molding method or a photopolymer method.
Further, the thickness of the first substrate (3) is preferably about 10 to 600 μm.

As the material of the second substrate (5), the same material as that of the first substrate (3) can be used, but a material opaque to the recording / reproducing light may be used. The material and groove shape may be different.
The thickness of the second substrate (5) is not particularly limited, but it is preferable to select the thickness of the second substrate (5) so that the total thickness with the first substrate (3) is 1.2 mm. .
Similar to the first substrate (3), the second substrate (5) may be provided with an uneven pattern such as a groove and a guide groove formed by injection molding or a photopolymer method.

The intermediate layer (4) and the transparent layer (6) preferably have smaller light absorption at the wavelength of the recording / reproducing light, and the material is an ultraviolet curable resin or a slow-acting resin that is suitable in terms of moldability and cost. A thermoplastic resin or the like can be used.
In the intermediate layer (4), as in the case of the first substrate (3), concave and convex patterns such as grooves and guide grooves formed by injection molding or a photopolymer method may be formed.
The intermediate layer (4) is used to allow the pickup to discriminate between the first information layer (1) and the second information layer (2) and perform optical separation when recording and reproduction are performed. Is preferably 10 to 70 μm. If the thickness is less than 10 μm, interlayer crosstalk occurs. If the thickness is more than 70 μm, spherical aberration occurs when recording / reproducing the second recording layer (22), and recording / reproduction tends to be difficult.
The thickness of the transparent layer (6) is not particularly limited, but the optimum thickness of the first substrate (3) of the optical information recording medium manufactured by the manufacturing method without providing the transparent layer as shown in FIG. The thicknesses of the first substrate (3) and the transparent layer (6) are adjusted so that the total thickness of the first substrate (3) and the transparent layer (6) of the optical information recording media of different manufacturing methods is approximately the same. There is a need to. For example, if NA = 0.85, and the thickness of the first substrate (3) of the optical information medium of FIG. 1 is 100 μm and good recording and erasing performance is obtained, the optical information medium of FIG. If the thickness of the first substrate (3) is 50 μm, the thickness of the transparent layer (6) is preferably 50 μm.

The material of the first recording layer (12) and the second recording layer (22) is not particularly limited as long as it is a material that changes phase between crystal and amorphous by heating and cooling by light irradiation. What is conventionally known in the field is applied.
Examples thereof include thin films mainly composed of chalcogen alloys such as Ge—Te, Ge—Te—Sb, and Ge—Sn—Te, and Sb—Te eutectic materials. Crystallization) Sb—Te eutectic materials are particularly preferred in terms of sensitivity, speed, and erase ratio. Here, the main component means that it accounts for 90 atomic% or more of the entire thin film material.
These recording layer materials have Ag, In, Ge, Se, Sn, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Bi for the purpose of further improving performance and reliability. , Si, Dy, Pd, Pt, Au, S, B, C, P, and other elements and impurities can be added.

These recording layers (12) and (22) can be formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition, etc. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the first recording layer (12) is not particularly limited, but is preferably 3 to 15 nm. If it is less than 3 nm, it tends to be difficult to form a uniform film, and if it exceeds 15 nm, the transmittance tends to decrease.
The thickness of the second recording layer (22) is not particularly limited, but is preferably 3 to 25 nm. If it is less than 3 nm, it tends to be difficult to form a uniform film, and if it exceeds 25 nm, the recording sensitivity tends to decrease, such being undesirable.

The first reflective layer (14) and the second reflective layer (24) have functions such as making efficient use of incident light, improving the cooling rate and facilitating amorphization. A metal having high conductivity is used, and for example, Au, Ag, Cu, W, Al, Ta, or an alloy thereof can be used. Alternatively, a material containing at least one of these elements as a main component and at least one element selected from Cr, Ti, Si, Pd, Ta, Nd, Zn and the like may be used. Here, the main component means that it accounts for 90 atomic% or more, preferably 95 atomic% or more of the entire reflective layer material.
In particular, Ag-based materials have a low refractive index even in the blue wavelength region, n is 0.5 or less, and light absorption can be suppressed to a low level. Therefore, in the multilayer information recording medium as in the present invention, particularly the first information layer. It is preferable as a material used for the reflective layer.
Such reflective layers (14) and (24) can be formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, and electron beam deposition. Among these, the sputtering method is excellent in mass productivity and film quality.

Since the first information layer (1) requires high transmittance, it is preferable to use Ag having a low refractive index and high thermal conductivity or an alloy thereof as the material of the first reflective layer (14). Moreover, it is preferable that the thickness is about 3-20 nm. If the thickness is less than 3 nm, it becomes difficult to form a dense film having a uniform thickness. If it is thicker than 20 nm, the transmittance is reduced, and recording / reproduction of the second information layer becomes difficult.
The thickness of the second reflective layer (24) constituting the second information layer (2) is 50 to 200 nm, preferably 80 to 150 nm. If it is less than 50 nm, the repetitive recording characteristics are deteriorated, and if it is more than 200 nm, the sensitivity tends to be lowered.

The functions and materials of the first lower protective layer (11), the second lower protective layer (21), the first upper protective layer (13), and the second upper protective layer (23) are the same as those of the single-layer phase change information recording medium. This is the same as the case, and has effects such as preventing deterioration and deterioration of the first recording layer (12) and the second recording layer (22), increasing the adhesive strength, and improving the recording characteristics. Specific examples of the material include metal oxides such as SiO, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, and ZrO ₂ ; Si ₃ N ₄ , AlN, TiN, and ZrN. Nitrides such as ZnS, sulfides such as In ₂ S ₃ and TaS ₄ ; carbides such as SiC, TaC, B ₄ C, WC, TiC and ZrC; diamond-like carbons; or a mixture thereof.
These materials can be used alone as a protective layer, but may also be a mixture of each other. Moreover, you may contain an impurity as needed. The melting points of the protective layers (11), (13), (21), and (23) must be higher than those of the recording layers (12) and (22). Most preferred is a mixture of ZnS and SiO ₂ .

Such protective layers (11), (13), (21), (23) can be formed by various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, and electrons. It can be formed by a beam evaporation method or the like. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the first lower protective layer (11) and the second lower protective layer (21) is preferably 30 to 200 nm. If the thickness is less than 30 nm, the first substrate (3) or the intermediate layer (4) may be deformed by heat at the time of recording, and if it is thicker than 200 nm, there is a tendency to cause a problem in mass productivity. Therefore, the film thickness is designed so as to obtain an optimum reflectance within the above range.
Moreover, it is preferable that the thickness of a 1st upper protective layer (13) and a 2nd upper protective layer (23) is 3-40 nm. When the thickness is less than 3 nm, the recording sensitivity is lowered, and when it is thicker than 40 nm, the heat dissipation effect tends to be not obtained.

In the multilayer phase change information recording medium of the present invention, a barrier layer may be provided between the upper protective layers (13) and (23) and the reflective layers (14) and (24). As described above, the reflective layer (14), as the (24), Ag alloy, as the protective layer, a mixture of ZnS and SiO ₂ is most preferred, if the two layers are adjacent, the sulfur in the protective layer There is a possibility that Ag of the reflective layer may be corroded, and the storage reliability may be lowered. In order to eliminate this problem, it is preferable to provide a barrier layer when an Ag-based material is used for the reflective layer. The barrier layer does not contain sulfur and needs to have a higher melting point than the recording layer, specifically, SiO, ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, ZrO _2, etc. Metal oxides of the above; nitrides such as Si ₃ N ₄ , AlN, TiN, ZrN; carbides such as SiC, TaC, B ₄ C, WC, TiC, ZrC; or a mixture thereof. Of these, SiC is preferable. In addition, these barrier layers desirably have a low absorptance at the laser wavelength.
The barrier layer can be formed by various vapor phase growth methods such as vacuum vapor deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam vapor deposition and the like. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the barrier layer is preferably 2 to 10 nm. When the thickness is less than 2 nm, the effect of preventing Ag corrosion cannot be obtained, and the storage reliability is lowered. If it is thicker than 10 nm, the heat dissipation effect cannot be obtained, or the transmittance tends to decrease.

  Both the first thermal diffusion layer (15) in the present invention of the first group and the second group are desired to have a high thermal conductivity in order to quench the recording layer irradiated with the laser. It is also desirable that the absorption rate at the recording / reproducing laser light wavelength is small so that the information layer (2) on the back side can be recorded / reproduced. The extinction coefficient is preferably 0.5 or less, more preferably 0.3 or less, at the wavelength of the information recording / reproducing laser beam. If it is greater than 0.5, the absorptance in the first information layer (1) increases, and recording / reproduction of the second information layer (2) becomes difficult.

The thermal diffusion layer (15) is a feature of the present invention. In the first group of the present invention, by using a material having indium (In), zinc (Zn) and oxygen (O) as essential constituent elements, the above function as the thermal diffusion layer (15) is exhibited, Overwrite characteristics can be improved. Specifically, a mixture of indium oxide and zinc oxide is preferable. The atomic ratio of In and Zn is preferably in the range of 0.05 ≦ Zn / (In + Zn) ≦ 0.5. More preferably, the range is 0.05 ≦ Zn / (In + Zn) ≦ 0.3. When it is less than 0.05, the storage reliability is lowered, and when it is more than 0.5, the thermal conductivity is lowered and the overwrite characteristic is deteriorated. Further, other elements and compounds can be added for the purpose of further improving characteristics and reliability. Halides and oxides are considered preferable.
The extinction coefficient is preferably 1.0 or less at the wavelength of the laser beam used for recording / reproducing information. Furthermore, it is preferably 0.5 or less. If it is greater than 1.0, the absorptance in the first information layer increases, and recording / reproduction of the second information layer becomes difficult.
The thermal diffusion layer can be formed by various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, and electron beam deposition. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the first thermal diffusion layer (15) is preferably 20 to 200 nm. If it is thinner than 20 nm, the heat dissipation effect cannot be obtained. If it is thicker than 200 nm, the stress increases, and not only the repeated recording characteristics deteriorate, but also a problem arises in mass productivity.

In the second group of the present invention, by using a material having indium (In), zinc (Zn), oxygen (O), and at least one halogen as essential constituent elements, the above-mentioned thermal diffusion layer (15) is used. The function can be exhibited and the overwrite characteristics can be improved. In particular, a sufficient light transmittance in a short wavelength region can be secured.
In / Zn atomic ratio In / (In + Zn) in the thermal diffusion layer (15) is in the range of 0.55 to 0.9, that is, 0.55 ≦ In / (In + Zn) ≦ 0.9. It is preferable that it is in the range which satisfies. More preferably, it is 0.6-0.9, Most preferably, it is 0.7-0.9. If it is less than 0.55, the overwrite property is deteriorated due to a decrease in thermal conductivity, and if it is more than 0.9, the heat resistance is deteriorated to deteriorate the overwrite property. The atomic ratio between Zn and In is preferably in the range of 0.05 ≦ Zn / (In + Zn) ≦ 0.5. More preferably, the range is 0.05 ≦ Zn / (In + Zn) ≦ 0.3. When it is less than 0.05, the storage reliability is lowered, and when it is more than 0.5, the thermal conductivity is lowered and the overwrite characteristic is deteriorated.

In the second group of the present invention, the thermal diffusion layer (15) includes, in addition to In, Zn, O, and at least one halogen, at least one third metal element having a valence of positive trivalent or higher. May be contained as a constituent element. Specific examples of the third metal element include tin (Sn), aluminum (Al), antimony (Sb), gallium (Ga), titanium (Ti), silicon (Si), zirconium (Zr), and germanium (Ge). , Vanadium (V), tungsten (W), lanthanum (La), and ruthenium (Ru). Among these third metal elements, tin (Sn) is particularly preferable from the viewpoint of improving thermal conductivity.
The atomic ratio of the total amount of the third metal element to the entire metal element is preferably 0.2 or less, that is, (total third metal element) / (In + Zn + total third metal element) ≦ 0.2, More preferably, it is 0.1 or less. When the atomic ratio exceeds 0.2, the thermal conductivity is lowered.

On the other hand, the atomic ratio of the total amount of halogen, which is an essential constituent element in the thermal diffusion layer of the second group of the present invention, to the entire metal element is 0.01 to 0.3, that is, 0.01 ≦ (total halogen). / (In + Zn + all third metal elements) ≦ 0.3 is preferably satisfied. If it is less than 0.01, the thermal conductivity and light transmission in the short wavelength region due to the addition of halogen are not substantially improved, and if it exceeds 0.3, the thermal conductivity decreases. The atomic ratio is more preferably 0.2 or less. Further, since the thermal conductivity tends to decrease when it is 0.1 or more, in such a case, the thickness of the thermal diffusion layer is preferably 80 nm or more. In determining the atomic ratio, when the thermal diffusion layer does not have the third metal element as a constituent element, the values of all the third metal elements are calculated as 0 in the above formula.
Specific examples of the halogen include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). However, heat having higher thermal conductivity than the case where other halogen is used as a constituent element. From the viewpoint of obtaining a diffusion layer, fluorine is particularly preferable.

The thermal diffusion layers in the present invention of the first group and the second group are formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method, electron beam deposition method, etc. it can. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the thermal diffusion layer is preferably 20 to 200 nm in the first group of the present invention, and 10 to 200 nm in the second group of the present invention. If it is thinner than these minimum film thicknesses, the heat dissipation effect cannot be obtained. If it is thicker than 200 nm, the stress increases, and not only the repeated recording characteristics deteriorate, but also a problem arises in mass productivity.
In both the first and second groups of the present invention, there is no problem even if a thermal diffusion layer is provided between the first lower protective layer and the first substrate to further improve the thermal diffusion effect. Absent.
In the first and second groups of the present invention, the first information layer preferably has a light transmittance of 40 to 70% at a recording / reproducing laser beam wavelength of 350 to 700 nm, more preferably 40 ~ 60%.
In the two-layer phase change information recording medium on which recording is performed after initialization, the area where the recording layer is in the amorphous state is smaller than the area where the recording layer is in the crystalline state, so the light transmittance in the amorphous state is light transmission in the crystalline state. It may be smaller than the rate. In the case of the first group of the present invention, a laser beam having a wavelength of 350 to 450 nm can be preferably used as the light beam incident from the first information layer side.

Next, a method for producing the multilayer phase change information recording medium of the present invention will be described.
One of the methods for producing a two-layer phase change information recording medium of the present invention includes a film forming process, an initialization process, and an adhesion process, and each process is basically performed in this order. FIG. 3 is a schematic cross-sectional view of a two-layer phase change information recording medium manufactured by this method. Grooves are formed on the first substrate and the second substrate.
As the film forming process, a first substrate on which the first information layer is formed on the surface of the first substrate and a second substrate on which the second information layer is formed on the surface of the second substrate are separately formed. .
Each layer constituting each of the first information layer (1) and the second information layer (2) is formed by various vapor phase growth methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method, It is formed by an electron beam evaporation method or the like. Among these, the sputtering method is excellent in mass productivity and film quality. In the sputtering method, film formation is generally performed while flowing an inert gas such as argon. At this time, reactive sputtering may be performed while oxygen, nitrogen, or the like is mixed.

As an initialization process, the entire recording layer is initialized (crystallized) by emitting energy light such as laser light to the first information layer (1) and the second information layer (2).
If there is a possibility that the film may float due to laser light energy during the initialization process, the UV resin is placed on the first information layer (1) and the second information layer (2) before the initialization process. Etc. may be spin-coated and cured by irradiating with ultraviolet rays to give an overcoat. Moreover, after performing the next contact | adherence process previously, you may initialize a 1st information layer (1) and a 2nd information layer (2) from the 1st board | substrate (3) side.
Next, the first information layer (1) formed on the surface of the first substrate (3) initialized as described above, and the second information layer (2) on the surface of the second substrate (5) are initialized. The first information layer (1) and the second information layer (2) are bonded to each other through the intermediate layer (4).
For example, one of the film surfaces is spin-coated with an ultraviolet curable resin as an intermediate layer, the film surfaces face each other, both substrates are pressed and adhered, and then the resin is cured by irradiating with ultraviolet rays. .

Further, another method for producing the two-layer phase change information recording medium according to the present invention as shown in FIG. 2 will be described. This method includes a first film forming process, an intermediate layer forming process, a second film forming process, a substrate bonding process, and an initialization process, and each process is basically performed in this order. FIG. 4 is a schematic sectional view of a two-layer phase change type information recording medium manufactured by this method. Grooves are formed on the intermediate layer (4) and the second substrate (5).
As the first film formation step, the second information layer (2) is formed on the surface of the second substrate (5) where the guide groove is provided. The film forming method is as described above.
As the intermediate layer forming step, an intermediate layer (4) having a guide groove is formed on the second information layer (2). For example, an ultraviolet curable resin is applied to the entire surface of the second information layer (2) and cured by irradiating with ultraviolet rays while pressing a stamper made of a material capable of transmitting ultraviolet rays to form grooves. can do.
As the second film forming step, the first information layer (1) is formed on the intermediate layer (4). The film forming method is as described above.

As a board | substrate bonding process, a 1st information layer (1) and a 1st board | substrate (3) are bonded together through a transparent layer (4). For example, on the first information layer (1) or the first substrate (3), an ultraviolet curable resin that is a material of the transparent layer (4) is spin-coated, and the first information layer (1) and the first substrate ( 3) and then cured by irradiation with ultraviolet rays. Alternatively, the first substrate (3) may be formed by applying a resin, which is a material of the first substrate, on the first information layer (1) and curing without forming the transparent layer (4). Good.
As an initialization process, the entire recording layer is initialized (crystallized) by emitting energy light such as laser light from the first substrate side to the first information layer (1) and the second information layer (2). ) For the second information layer (2), there is no problem even if initialization is performed immediately after the intermediate layer forming step.

Furthermore, the manufacture of the phase change information recording medium having three information layers as shown in FIG. 5 is performed in the following process sequence.
First film forming step (forming the first information layer on the first substrate and forming the third information layer on the second substrate) → intermediate layer forming step (forming the second intermediate layer on the third information layer of the second substrate) → second film formation step (deposition of the second information layer on the second intermediate layer of the second substrate) → adhesion step (first substrate and second substrate of the first information layer and second information layer) Bonding via the first intermediate layer while facing each other) → Initialization process The initialization process may be performed immediately after each information layer is formed.
Next, the manufacture of a phase change information recording medium having three information layers as shown in FIG. 6 is performed in the following process sequence.
First film formation step (deposition of the third information layer) → First intermediate layer formation step (formation of the second intermediate layer) → Second film formation step (deposition of second information layer) → Formation of the second intermediate layer Step (formation of first intermediate layer) → Third film formation step (formation of first information layer) → First substrate bonding step (bonding via a transparent layer) → Initialization step The third information layer is after the first film formation step or immediately after the first intermediate layer formation, the second information layer is after the second film formation step or immediately after the second intermediate layer formation, and the first information layer is the third film formation step. It may be later.

Hereinafter, the method for producing the phase change information recording medium of the present invention will be described.
One of the methods for producing a two-layer phase change information recording medium of the present invention includes a film forming process, an initialization process, and an adhesion process, and each process is basically performed in this order. FIG. 3 is a schematic sectional view of a two-layer phase change information recording medium manufactured by this method. Grooves are formed on the first substrate (3) and the second substrate (5).

In the film forming process, the first information layer (1) is formed on the surface of the first substrate (3) provided with the groove, and the second information is provided on the surface of the second substrate (5) provided with the groove. A layer having the layer (2) is separately prepared.
Each layer constituting each of the first information layer (1) and the second information layer (2) is formed by various vapor deposition methods such as a vacuum deposition method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, It is formed by an electron beam evaporation method or the like.
Among these, the sputtering method is excellent in mass productivity and film quality. In the sputtering method, film formation is generally performed while flowing an inert gas such as argon. At this time, reactive sputtering may be performed while oxygen, nitrogen, or the like is mixed.

As an initialization step, the entire surface is initialized, that is, the recording layer is crystallized by emitting energy light such as laser light to the first information layer (1) and the second information layer (2).
If there is a possibility that the film may float due to laser light energy during the initialization process, a UV resin or the like is spin-coated on the first information layer and the second information layer before the initialization process. It may be cured by irradiating with ultraviolet rays, and an overcoat may be applied.

  Moreover, after performing the next contact | adherence process previously, you may initialize a 1st information layer and a 2nd information layer from the 1st board | substrate side.

Next, the first information layer (1) formed on the surface of the first substrate (3) initialized as described above, and the second information layer on the surface of the second substrate (5) are initialized. The layer formed with (2) is bonded via the intermediate layer (4) while the first information layer (1) and the second information layer (2) face each other.
For example, one of the film surfaces is spin-coated with an ultraviolet curable resin as an intermediate layer, the film surfaces face each other, both substrates are pressed and adhered, and then the resin is cured by irradiating with ultraviolet rays. be able to.

  Further, another method for producing the two-layer phase change information recording medium according to the present invention as shown in FIG. 2 will be described. This method includes a first film forming process, an intermediate layer forming process, a second film forming process, a substrate bonding process, and an initialization process, and each process is basically performed in this order. FIG. 4 is a schematic sectional view of a two-layer phase change type information recording medium manufactured by this method. Grooves are formed on the intermediate layer (4) and the second substrate (5).

As the first film forming step, the second information layer (2) is formed on the surface of the second substrate (5) where the guide groove is provided. The film forming method is as described above.
As an intermediate layer forming step, an intermediate layer (4) having guide grooves is formed on the second information layer (2). For example, an ultraviolet curable resin is applied on the entire surface of the second information layer (2), and a groove made by irradiating ultraviolet rays while pressing a stamper made of a material capable of transmitting ultraviolet rays. Can be formed.

As the second film forming step, the first information layer (1) is formed on the intermediate layer (4). The film forming method is as described above.
As a board | substrate bonding process, a 1st information layer (1) and a 1st board | substrate (3) are bonded together through a transparent layer (6). For example, the first information layer (1) and the first substrate are spin-coated on the first information layer (1) or the first substrate (3) with an ultraviolet curable resin that is a material of the transparent layer (6). (3) can be bonded together and then cured by irradiation with ultraviolet rays. Also, without forming the transparent layer (6), the first substrate (3) is formed by applying and curing a resin, which is a material of the first substrate (3), on the first information layer (1). May be.

  As an initialization process, the entire surface is initialized by emitting energy light such as laser light from the first substrate (3) side to the first information layer (1) and the second information layer (2), that is, Crystallize the recording layer. For the second information layer (2), there is no problem even if initialization is performed immediately after the intermediate layer (4) formation step.

Furthermore, the manufacture of the phase change information recording medium having three information layers as shown in FIG. 5 is performed in the following process sequence.
First film forming step (forming the first information layer on the first substrate and forming the third information layer on the second substrate) → intermediate layer forming step (forming the second intermediate layer on the third information layer of the second substrate) → second film formation step (deposition of the second information layer on the second intermediate layer of the second substrate) → adhesion step (first substrate and second substrate of the first information layer and second information layer) Bonding via the first intermediate layer while facing each other) → initialization step.
The initialization process may be performed immediately after each information layer is formed.

Next, the manufacture of the phase change information recording medium having three information layers as shown in FIG. 6 is performed in the following process sequence.
First film formation step (deposition of the third information layer) → First intermediate layer formation step (formation of the second intermediate layer) → Second film formation step (deposition of second information layer) → Formation of the second intermediate layer Process (formation of first intermediate layer) → third film formation process (film formation of first information layer) → first substrate bonding process (bonding via a transparent layer) → initialization process.
The initialization process includes the third information layer after the first film formation process or immediately after the formation of the second intermediate layer, the second information layer after the second film formation process or immediately after the formation of the first intermediate layer, It may be after the third film formation step.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited at all by these Examples.
[Invention of Group 1]
[Example 1]
As a preliminary experiment, a target mainly composed of indium, zinc and oxygen (Zn / (In + Zn) = 0.1) used for a thermal diffusion layer on a glass substrate was sputtered using a single wafer sputtering apparatus manufactured by Balzers. A film of about 200 nm was provided. At that time, as the sputtering gas, a mixed gas of Ar and O _2, performs sputtering while changing the flow rate of O ₂ gas while the Ar gas flow rate constant, the electrical resistivity of the thin film was determined lowest consisting of O ₂ gas flow rate . The electrical resistivity was measured using the four probe method.
A first lower protective layer 120 nm made of ZnS · SiO ₂ and Ge ₅ Ag ₁ In ₂ Sb ₇₀ on a first substrate made of polycarbonate resin having a diameter of 12 cm and a thickness of 0.6 mm and having tracking guide irregularities formed by continuous grooves on the surface. Ar gas in the order of a first recording layer 6 nm made of Te _{22, a} first upper protective layer 15 nm made of ZnS · SiO _{2, a} first reflective layer 10 nm made of Ag—Zn—Al, and a first thermal diffusion layer 120 nm shown in Table 1. A film was formed by sputtering in an atmosphere. For the thermal diffusion layer of the present invention, a mixed gas of Ar and O ₂ (Ar: 10 sccm, O ₂ : 0.2 sccm) having a flow rate obtained in a preliminary experiment was used. Further, the same substrate as the second substrate, 120 nm of the second reflective layer of Al-Ti on the second substrate, the second upper protective layer 20nm made of _{ZnS · SiO 2, Ge 4 Ag} 1 In 3 Sb 70 Te _A second recording layer 12 nm made of ₂₂ and a second lower protective layer 130 nm made of ZnS · SiO ₂ were formed in this order by sputtering in an Ar gas atmosphere. Here, the light transmittance at a wavelength of 405 nm of the first information layer was measured from the first substrate side using a spectrophotometer manufactured by SHIMADZU. Next, the first information layer and the second information layer were irradiated with laser light from the first substrate side and the second information layer film surface side, respectively, and an initialization process was performed. Here, the transmittance of the first information layer at a wavelength of 405 nm was also measured. Next, an ultraviolet curable resin is applied on the film surface of the first information layer, the second information layer surface side of the second substrate is bonded and spin-coated, and the ultraviolet curable resin is irradiated with ultraviolet light from the first substrate side. Was cured as an intermediate layer to prepare a two-layer phase change type information recording medium having two information layers. The thickness of the intermediate layer was 35 μm. Sample 1-1 is an example, and samples 1-2 to 1-4 are comparative examples.

Each produced disc was recorded under the following conditions.
Laser wavelength: 405 nm
NA = 0.65
Line speed: 6.0 m / s
Track pitch: 0.43 μm
The jitter of the first information layer and the second information layer at a linear density of 0.18 μm / bit, and the jitter of the first information layer and the second information layer after overwriting 1000 times were measured.
Table 1 shows the measurement results for each sample. In Sample 1-1, which is a two-layer phase change information recording medium according to the present invention, the thermal diffusion layer is mainly composed of indium, zinc and oxygen (Zn / (In + Zn) = 0.1), and the light transmittance is The jitter value after recording once exceeding 40% was 9% or less for both the first information layer and the second information layer, which proved to be excellent as an optical disc. In Sample 1-2, aluminum nitride was used for the thermal diffusion layer. However, when the film was formed with a thickness of 120 nm, visible cracks frequently occurred, and recording / reproduction could not be performed. In Samples 1-3 and 1-4, silicon carbide and titanium oxide were used for the thermal diffusion layer, respectively. However, the light transmittance of the first information layer was 40% or less, the sensitivity of the second information layer was poor, and the jitter value was low. It was too large to be rewritten 1000 times. From the above results, it is preferable to use a material mainly composed of indium, zinc and oxygen for the heat diffusion layer of the first information layer.

[Example 2]
The target of the thermal diffusion layer used in Example 2 is mainly composed of indium, zinc and oxygen, and the atomic ratio of Zn is as shown in Table 2. A two-layer phase change information recording medium was produced in the same manner as in Example 1 except that this target was used for the thermal diffusion layer.
Each prepared sample was recorded under the same conditions as in Example 1, and the jitter of the first information layer and the second information layer and the jitter of the first information layer and the second information layer after overwriting 1000 times were measured.
It was found that by adding Zn at an atomic ratio in the range of 0.05 to 0.5, the jitter after 1000 rewrites was reduced and the overwrite characteristics were improved. Sample 2-1, which is a comparative example, has no overwrite added Zn and has good overwrite characteristics, but measures the jitter of the 3T reproduction signal of the initial recording mark after storage for 300 hours at 80 ° C. and 85% RH. As a result, it became 9% or more, and it turned out that storage reliability fell. In contrast, Samples 2-5 and 2-6 had Zn addition amounts of 0.8 and 1.0, respectively, and the overwrite characteristics of the first information layer were deteriorated. However, since the transmittance was larger than that of Samples 1-2 to 1-4 as comparative examples and the jitter value after 1000 times of repeated recording was large, measurement was possible, so indium, zinc and oxygen were mainly used in the thermal diffusion layer. It is considered that the effect of the present invention by using the material as the component is obtained. From the above results, it is understood that the Zn ratio is preferably 0.05 ≦ Zn / (In + Zn) ≦ 0.5.
Also, from other prototype experiments, the first information layer, the second information layer, the second information layer, and the thermal diffusion layer are in the range of 3 to 15 nm, the reflective layer is 3 to 20 nm, and the thermal diffusion layer is 20 to 200 nm. It was confirmed that the information layer can be recorded and reproduced satisfactorily, and the transmittance of the first information layer is required to be 40% or more in order to record and reproduce the second information layer satisfactorily.

[Example 3]
As Example 3, Ag was used for the first reflective layer, and Sample 1-1 of Example 1 except that SiC with a film thickness of 3 nm was provided as a barrier layer between the first upper protective layer and the first reflective layer. Similarly, a two-layer phase change information recording medium of Sample 3-1 as an example was produced.
Sample 3-2 was produced in the same manner as Sample 3-1, except that no barrier layer was provided.
Each prepared sample was recorded under the same conditions as in Example 1, and the jitter of the first information layer and the second information layer was measured. Further, in order to examine the storage reliability, the jitter of the 3T reproduction signal of the initial recording mark after each initially recorded medium was stored at 80 ° C. and 85% RH for 300 hours was measured. The results are shown in Table 3. When Ag was used for the first reflective layer, it was found that the sample provided with the barrier layer had good jitter after storage and was excellent as an optical disk.

[Example 4]
As Example 4, a second reflective layer made of Al—Ti is formed to 120 nm on a second substrate made of polycarbonate resin having a diameter of 12 cm and a thickness of 1.1 mm, and the surface of which has a tracking groove by a continuous groove, and ZnS · SiO _2. A second upper protective layer 20 nm made of Ge, a second recording layer 12 nm made of Ge ₅ Ag ₁ In ₂ Sb ₇₀ Te ₂₂ , and a second lower protective film 130 nm made of ZnS · SiO ₂ , produced in this order by sputtering in an Ar gas atmosphere. A second information layer was formed. On the second information layer thus formed, a resin was applied, and an intermediate layer having irregularities of tracking guides by continuous grooves was formed by a 2P (photopolymerization) method. The thickness of the intermediate layer is 30 μm. Furthermore, a first thermal diffusion layer 120 nm is provided using the same target as that of Sample 1-1, a first reflective layer 10 nm made of Ag—Pd—Cu, a first upper protective layer 15 nm made of ZnS · SiO ₂ , A first information layer is formed by sputtering in an Ar gas atmosphere in the order of a first recording layer 6 nm made of Ge ₄ Ag ₁ In ₃ Sb ₇₀ Te ₂₂ and a first lower protective layer 120 nm made of ZnS · SiO _2. Formed. Regarding the thermal diffusion layer, a mixed gas of Ar and O ₂ is used as a sputtering gas, and the film is formed at a ratio of Ar gas to O ₂ gas (Ar: 10 sccm, O ₂ : 0.2 sccm) that increases electrical conductivity and transmittance. Was done. Further, a first substrate made of a polycarbonate film having a diameter of 12 cm and a thickness of 50 μm is bonded on the first information layer film surface through a transparent layer made of a double-sided adhesive sheet having a thickness of 45 μm, thereby providing a two-layer phase change type information. A recording medium was created. Separately from this, for the transmittance measurement, the first information layer, the transparent layer, and the first substrate were similarly provided on the substrate having a thickness of 1.1 mm, and the light transmittance from the first substrate side was measured.
The transmittance of the first information layer of this example at a wavelength of 405 nm before initialization was 44%, and the transmittance after initialization was 50%.

The created media was recorded under the following conditions.
Laser wavelength: 405 nm
NA = 0.85
Line speed: 6.5m / s
Track pitch: 0.32 μm
The jitter of the first information layer and the second information layer at a linear density of 0.16 μm / bit, and the jitter of the first information layer and the second information layer after overwriting 1000 times were measured. Both the two information layers could be recorded and reproduced satisfactorily.
Also, from other prototype experiments, the transmittance of the first information layer is required to be 40% or more in order to record / reproduce the second information layer satisfactorily even when recording / reproduction with NA = 0.85 pickup. It was confirmed that there was.
From the above, the optical disks of the first group of the present invention are good by adjusting the thickness of the first substrate in the range of 10 μm to 600 μm even when the numerical aperture NA of the objective lens for recording / reproducing changes. Recording and playback can be performed.

[Invention of Group 2]
[Example 5]
As a preliminary experiment, on a polycarbonate substrate, a target obtained by sintering the ZnF2, ZnO and _In 2 _{O 3} used in the thermal diffusion layer, and sputtering using a Balzers Ltd. leaf sputtering apparatus provided with a 200nm about film . Ar gas was used as the film forming gas.
In this thin film, the atomic ratio of In to Zn, In / (In + Zn), and the atomic ratio of the total amount of halogen to the whole metal element, (total halogen) / (In + Zn + total third metal element) were obtained (however, in this example) Then, all the third metal elements = 0). As a method, the composition of the thin film was determined by XPS (X-ray photoelectron spectroscopic analysis), and the result was calculated using the above formula.
The results are shown in Table 4.
Separately from the preliminary experiment, a first substrate made of (ZnS) ₇₀ · (SiO ₂ ) _{30 is formed} on a first substrate made of a polycarbonate resin having a diameter of 12 cm and a thickness of 0.6 mm and having irregularities for tracking guides by continuous grooves on the surface. Lower protective layer (thickness 120 nm), first recording layer (thickness 6 nm) made of Ge ₅ Ag ₁ In ₂ Sb ₇₀ Te _22, first upper protective layer (thickness) made of (ZnS) ₇₀ · (SiO ₂ ) ₃₀ 15 nm), a first reflective layer (thickness 10 nm) made of Ag ₉₆ -Zn ₃ -Al ₁ and a first thermal diffusion layer (thickness 120 nm) in this order in a Ar gas atmosphere using a single wafer sputtering apparatus manufactured by Balzers. The film was formed by the sputtering method. The target used in the preliminary experiment was used for the first thermal diffusion layer.
Next, on the second substrate having the same configuration as the first substrate, a second reflective layer (thickness 120 nm) made of Al ₉₈ -Ti ₂ and a second upper protective layer (ZnS) ₇₀ · (SiO ₂ ) ₃₀ ( A second recording layer (thickness 12 nm) made of Ge ₄ Ag ₁ In ₃ Sb ₇₀ Te _{22, a} second lower protective layer (thickness 130 nm) made of (ZnS) ₇₀ · (SiO ₂ ) ₃₀ . Films were formed in this order by sputtering in an Ar gas atmosphere. Here, the light transmittance at a wavelength of 407 nm of the first information layer was measured from the first substrate side using a spectrophotometer manufactured by SHIMADZU.
Next, the first information layer and the second information layer were irradiated with laser light from the first substrate side and the second information layer film surface side, respectively, and an initialization process was performed. Here, the transmittance of the first information layer at a wavelength of 407 nm was also measured.
Next, an ultraviolet curable resin is applied onto the film surface of the first information layer, and is bonded to the second information layer surface side of the second substrate and spin-coated, and the ultraviolet curable resin is irradiated by irradiating ultraviolet rays from the first substrate side. A two-layer phase change type information recording medium having two information layers was prepared by curing. The thickness of the intermediate layer was 35 μm.

[Example 6]
As a thermal diffusion layer, a target obtained by sintering ZnO and In ₂ O ₃ was used, and a mixed gas of Ar gas, fluorine gas and oxygen gas [Ar: O ₂ : F ₂ = 10: 0.2: 0.2 ( A two-layer phase change information recording medium was prepared in the same manner as in Example 5 except that the film forming gas was used as the volume ratio. Table 4 shows the atomic ratio of In and Zn calculated in the same manner as in the preliminary experiment of Example 5 and the atomic ratio of the total amount of halogen to the entire metal element (halogen atomic ratio).

[Example 7]
A target obtained by sintering ZnO, In ₂ O ₃ and SnO ₂ was used as the thermal diffusion layer, and a mixed gas of Ar gas, fluorine gas and oxygen gas [Ar: O ₂ : F ₂ = 10: 0.2: 0 .4 (volume ratio)] was used in the same manner as in Example 5 except that the film forming gas was used, and a two-layer phase change information recording medium was prepared. Table 4 shows the atomic ratio of In and Zn, the atomic ratio of the total amount of the third metal element to the entire metal element (the atomic ratio of the third metal element), and the atomic ratio of halogen calculated in the same manner as in the preliminary experiment of Example 5. Shown in

[Example 8]
The two-layer phase change information recording is performed in the same manner as in Example 5 except that a target obtained by sintering ZnF ₂ , ZnO and In ₂ O ₃ having a composition ratio different from that in Example 5 is used as the thermal diffusion layer. Created media. Table 4 shows the atomic ratio of In and Zn and the atomic ratio of halogen calculated in the same manner as in the preliminary experiment of Example 5.

[Example 9]
As the thermal diffusion layer, a target obtained by sintering ZnO, In ₂ O ₃ and SnO ₂ having a composition ratio different from that in Example 7 was used, and a mixed gas of Ar gas, fluorine gas and oxygen gas [Ar: O ₂ : F ₂ = 10: 0.2: 0.3 (volume ratio)] was used in the same manner as in Example 7 except that the film forming gas was used, and a two-layer phase change information recording medium was prepared. Table 4 shows the atomic ratio of In and Zn, the atomic ratio of the third metal element, and the atomic ratio of halogen calculated in the same manner as in the preliminary experiment of Example 5.

Example 10
The two-layer phase change information recording is performed in the same manner as in Example 1 except that a target obtained by sintering ZnF ₂ , ZnO, and In ₂ O ₃ having a composition ratio different from that in Example 5 is used as the thermal diffusion layer. Created media. Table 4 shows the atomic ratio of In and Zn and the atomic ratio of halogen calculated in the same manner as in the preliminary experiment of Example 5.

Example 11
A target obtained by sintering ZnO, In ₂ O ₃ and Ge was used as a thermal diffusion layer, and a mixed gas of Ar gas, fluorine gas and oxygen gas [Ar: O ₂ : F ₂ = 10: 0.2: 0. 5 (volume ratio)] was used in the same manner as in Example 7 except that the film forming gas was used, and a two-layer phase change information recording medium was prepared. Table 4 shows the atomic ratio of In and Zn, the atomic ratio of the third metal element, and the atomic ratio of halogen calculated in the same manner as in the preliminary experiment of Example 5.

Comparative Example 1
A two-layer phase change information recording medium was prepared in the same manner as in Example 5 except that a target obtained by sintering ZnO and In ₂ O ₃ was used as the thermal diffusion layer. Table 4 shows the atomic ratio of In and Zn calculated in the same manner as in the preliminary experiment of Example 5.

Recording was performed on each recording medium prepared as described above under the following conditions.
・ Laser wavelength: 407 nm
・ NA = 0.65
・ Line speed: 6.0m / s
・ Track pitch 0.43μm
The jitter of the first information layer and the second information layer at a linear density of 0.18 μm / bit, and the jitter of the first information layer and the second information layer after 100 times overwriting were measured. The recording power (Pw) at which the jitter value of the second information layer was 9% or less was also measured. Table 4 shows the measurement results of each recording medium.

  The light transmittance in the crystalline state of the first information layer of the recording media of Examples 5 to 11 is 52% or more, and the jitter value after one recording is 9% or less for both the first information layer and the second information layer. It was found that it is excellent as a recording medium. On the other hand, the recording medium of Comparative Example 1 has a light transmittance of 50%, but the recording power of the second information layer is required to be 15 mW or more, which is inferior to Examples 5 to 11. . As a result of comparing Examples 10 and 11 with Example 5 and other prototype experiments, 0.55 ≦ In / (In + Zn) ≦ 0.9, (all third metal elements) / (In + Zn + all third metals) Element) ≦ 0.2, 0.01 ≦ (total halogen) / (In + Zn + all third metal elements) ≦ 0.3, both the first information layer and the second information layer can be recorded and reproduced satisfactorily. Also, it was confirmed that the transmittance of the first information layer is required to be 40% or more in order to record and reproduce the second information layer satisfactorily.

Example 12
Sample No. 5 was used in the same manner as in Example 5 except that Ag was used for the first reflective layer and SiC having a film thickness of 3 nm was provided as a barrier layer between the first upper protective layer and the first reflective layer. A two-layer phase change information recording medium of 8-1 was produced.
In addition, except that a barrier layer is not provided, In the same manner as in Sample 8-1, sample no. A two-layer phase change information recording medium of 8-2 was produced.
Recording was performed on the created samples under the same conditions as in Example 5, and jitters of the first information layer and the second information layer were measured. Further, in order to investigate the storage reliability, the jitter of the 3T reproduction signal of the initial recording mark after each initially recorded sample was stored at 80 ° C. and 85% RH for 300 hours was measured. The results are as shown in Table 5. Sample No. with a barrier layer was obtained. The increase in jitter after storage in 8-1 was about 0.5%, and it was found that the configuration was more preferable as an optical recording medium.

[Example 13]
A second reflective layer (thickness 120 nm) made of Al ₉₈ -Ti ₂ on a second substrate made of a polycarbonate resin having a diameter of 12 cm and a thickness of 1.1 mm and having irregularities for tracking guides by continuous grooves on the surface, (ZnS ) ₇₀ · (SiO ₂ ) ₃₀ second upper protective layer (thickness 20 nm), Ge ₅ Ag ₁ In ₂ Sb ₇₀ Te ₂₂ second recording layer (thickness 12 nm), (ZnS) ₇₀ · (SiO ₂₎ film was formed by sputtering in an Ar gas atmosphere in order of the second lower protective layer made of ₃₀ (thickness 130 nm), thereby forming a second information layer.
A resin was applied onto the second information layer, and an intermediate layer having irregularities for tracking guides by continuous grooves was formed by a 2P (photopolymerization, photopolymerization) method. The thickness of the intermediate layer is 30 μm.
Further thereon, a first thermal diffusion layer (thickness 120 nm) formed by using the same target as in Example _5, the first reflective layer made of Ag ₉₈ -Pd 1 -Cu ₁ (thickness 10 nm), (ZnS ) First upper protective layer (thickness 10 nm) made of ₇₀ · (SiO ₂ ) _30, first recording layer (thickness 6 nm) made of Ge ₄ Ag ₁ In ₃ Sb ₇₀ Te ₂₂ , (ZnS) ₇₀ · (SiO 2 ₂₎ film was formed by sputtering in an Ar gas atmosphere in order of the first lower protective layer made of ₃₀ (thickness 120 nm), thereby forming a first information layer.
Further, a first substrate made of a polycarbonate film having a diameter of 12 cm and a thickness of 40 μm is bonded onto the surface of the first information layer film through a transparent layer made of a double-sided adhesive sheet having a thickness of 45 μm. An information recording medium was created.
Separately from this, for the transmittance measurement, the first information layer, the transparent layer, and the first substrate were similarly provided on the substrate having a thickness of 1.1 mm, and the light transmittance from the first substrate side was measured.
In the first information layer of this example, the transmittance at a wavelength of 405 nm before initialization was 48%, and the transmittance after initialization was 55%.
Recording was performed on the recording medium prepared as described above under the following conditions.
・ Laser wavelength: 405 nm
・ NA = 0.85
・ Line speed: 5.7m / s
・ Track pitch 0.32μm
The jitter of the first information layer and the second information layer at a linear density of 0.13 μm / bit, and the jitter of the first information layer and the second information layer after overwriting 100 times were measured. Both the second information layer could be recorded and reproduced satisfactorily.

[Examples 14 to 21]
A two-layer phase change information recording medium was prepared in the same manner as in Example 13 except that the film thicknesses of the first heat diffusion layer, the first reflection layer, and the first recording layer were changed. (Each film thickness is as described in Table 6)
As a result of measuring the jitter of the first information layer and the second information layer and the jitter of the first information layer and the second information layer after 100 times overwriting under the same conditions as in Example 13 for each of the created recording media As shown in Table 6, the light transmittance of each recording medium is 47% or more, and the jitter after recording once and after overwriting 100 times is 9% or less, indicating that the recording medium is excellent as an optical recording medium. It was.

Also, from other prototype experiments, the transmittance of the first information layer is required to be 40% or more in order to record / reproduce the second information layer satisfactorily even when recording / reproduction is performed with a pickup with NA = 0.85. It was confirmed that.
From the above, the optical recording medium of the present invention can be recorded satisfactorily by adjusting the thickness of the first substrate in the range of 10 to 600 μm even when the numerical aperture NA of the objective lens for recording and reproduction is changed. Playback can be performed.
Also, from other prototype experiments, the first information layer, the second information layer, the second information layer, the recording layer thickness of 3 to 15 nm, the reflective layer 3 to 20 nm, and the thermal diffusion layer 10 to 200 nm. Both information layers were recorded and reproduced satisfactorily. In particular, if the recording layer thickness of the first information layer and the thickness of the reflective layer are greater than 15 nm and 20 nm, respectively, the light transmittance after initialization cannot be made 40% or more. Could not be recorded. Further, it has been found that if the thermal diffusion layer is thicker than 200 nm, it takes 60 seconds to produce a two-layer optical disc, which is difficult for mass production.

[Example 22]
A first lower protective layer (thickness) made of (ZnS) _80. (SiO ₂ ) ₂₀ on a first substrate made of polycarbonate resin having a diameter of 12 cm and a thickness of 0.6 mm and having irregularities for tracking guides by continuous grooves on the surface. 50 nm), a first recording layer (thickness 6 nm) made of Ge ₅ Ag ₁ In ₂ Sb ₇₀ Te _{22, a} first upper protective layer (thickness 15 nm) made of (ZnS) ₈₀ · (SiO ₂ ) ₂₀ , Ag ₉₆ A first reflective layer (thickness: 10 nm) made of —Zn ₃ —Al ₁ and a first thermal diffusion layer (thickness: 100 nm) are formed in this order by a sputtering method in an Ar gas atmosphere using a Balzers single wafer sputtering apparatus. did. The same target as in Example 1 was used for the first thermal diffusion layer.
Next, on the second substrate having the same configuration as the first substrate, a second reflective layer (thickness 80 nm) made of Al ₉₈ -Ti ₂ and a second upper protective layer (ZnS) _80. (SiO ₂ ) ₂₀ ( A second recording layer (thickness 12 nm) made of Ge ₄ Ag ₁ In ₃ Sb ₆₇ Te _25, and a second lower protective layer (thickness 80 nm) made of (ZnS) _80. (SiO ₂ ) ₂₀ . Films were formed in this order by sputtering in an Ar gas atmosphere. Here, the light transmittance at a wavelength of 660 nm of the first information layer was measured from the first substrate side using a spectrophotometer manufactured by SHIMADZU.
Next, the first information layer and the second information layer were irradiated with laser light from the first substrate side and the second information layer film surface side, respectively, and an initialization process was performed. Here, the transmittance of the first information layer at a wavelength of 660 nm was also measured.
Next, an ultraviolet curable resin is applied onto the film surface of the first information layer, the second information layer surface side of the second substrate is bonded and spin coated, and the ultraviolet curable resin is irradiated by irradiating ultraviolet rays from the first substrate side. A two-layer phase change type information recording medium having two information layers was prepared by curing. The thickness of the intermediate layer was 50 μm.
In the first information layer of this example, the transmittance at a wavelength of 660 nm before initialization was 56%, and the transmittance after initialization was 50%.
Recording was performed on the recording medium prepared as described above under the following conditions.
・ Laser wavelength: 660 nm
・ NA = 0.65
・ Line speed: 3.49m / s
・ Track pitch 0.74μm
The jitter of the first information layer and the second information layer at a linear density of 0.267 μm / bit, and the jitter of the first information layer and the second information layer after overwriting 100 times were measured. Both the two information layers could be recorded and reproduced satisfactorily.

1 is a schematic cross-sectional view showing an example of a two-layer information recording medium of the present invention. The schematic sectional drawing which shows the other example of the two-layer information recording medium of this invention. FIG. 2 is a schematic cross-sectional view of a two-layer phase change information recording medium in which grooves are provided on a first substrate and a second substrate. 1 is a schematic cross-sectional view of a two-layer phase change information recording medium in which grooves are provided on a first substrate and an intermediate layer. The figure which shows the phase-change-type information recording medium which has three information layers based on this invention. The figure which shows the phase change type information recording medium which has the other three information layers based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st information layer 2 2nd information layer 3 1st board | substrate 4 Intermediate layer 5 2nd board | substrate 6 Transparent layer 11 1st lower protective layer 12 1st recording layer 13 1st upper protective layer 14 1st reflection layer 15 1st heat | fever Diffusion layer 21 Second lower protective layer 22 Second recording layer 23 Second upper protective layer 24 Second reflective layer

Claims (20)

In an optical information recording medium provided with N information layers (N: an integer of 2 or more) having information recording layers capable of recording information by phase change between a crystalline state and an amorphous state by the incidence of light, When the information layer is the first information layer, the second information layer,... The Nth information layer as viewed from the light incident side, at least one information layer other than the Nth information layer is a lower protective layer. A multilayer phase change information recording medium comprising: a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer, wherein the heat diffusion layer is mainly composed of indium, zinc, and oxygen. 2. The multilayer phase change information recording medium according to claim 1, wherein an atomic ratio of In to Zn is in a range of 0.05 ≦ Zn / (In + Zn) ≦ 0.5. The multilayer phase change information recording medium according to claim 1 or 2, wherein the thermal diffusion layer has a thickness of 20 to 200 nm. Optical information recording in which an information layer having a recording layer capable of recording information by causing a phase change between a crystalline state and an amorphous state by the incidence of light is provided (N: an integer of 2 or more). In the medium, when each information layer is a first information layer, a second information layer,... An Nth information layer as viewed from the light incident side, at least one information layer other than the Nth information layer It has a layer structure in which a protective layer, a recording layer, an upper protective layer, a reflective layer, and a thermal diffusion layer are stacked in this order, and the thermal diffusion layer is indium (In), zinc (Zn), oxygen (O), and at least one kind A multilayer phase change information recording medium characterized by comprising as a main component halogen. In addition to indium (In), zinc (Zn), oxygen (O), and at least one halogen, the thermal diffusion layer includes at least one third metal element having a valence of at least positive trivalent as an essential constituent element. 5. The atomic ratio of the total amount of the third metal element to the whole metal element satisfies (total third metal element) / (In + Zn + total third metal element) ≦ 0.2. The multilayer phase change information recording medium described. 6. The multilayer phase change information according to claim 4, wherein an atomic ratio of In and Zn in the thermal diffusion layer is in a range satisfying 0.55 ≦ In / (In + Zn) ≦ 0.9. recoding media. The atomic ratio of the total amount of halogen in the thermal diffusion layer to the entire metal element satisfies 0.01 ≦ (total halogen) / (In + Zn + total third metal element) ≦ 0.3. The multilayer phase change information recording medium according to any one of 6. The multilayer phase change information recording medium according to any one of claims 4 to 7, wherein the halogen of the heat diffusion layer is fluorine (F). 9. The multilayer phase change information recording medium according to claim 4, wherein the thermal diffusion layer has a thickness of 10 to 200 nm. The recording layer of the information layer having the thermal diffusion layer is mainly composed of Sb and Te, Ag, In, Ge, Se, Sn, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga Any one of Claim 1 thru | or 3 or any one of Claim 4 thru | or 9 characterized by including at least 1 sort (s) of Bi, Si, Dy, Pd, Pt, Au, S, B, C, P A multilayer phase change information recording medium described in 1. The multilayer phase change information recording medium according to claim 1, wherein the recording layer has a thickness of 3 to 15 nm. The multilayer phase change information according to any one of claims 1 to 11, wherein the reflective layer of the information layer having the thermal diffusion layer is mainly composed of at least one of Au, Ag, Cu, W, Al, and Ta. recoding media. The multilayer phase change information recording medium according to claim 1, wherein the reflective layer has a thickness of 3 to 20 nm. A two-layer phase change information recording medium capable of recording / reproducing information, comprising two information layers between a first substrate and a second substrate and an intermediate layer between the information layers. The first information layer includes a first lower protective layer, a first recording layer, a first upper protective layer, a first reflective layer, and a first thermal diffusion layer, and the second information layer includes a second lower protective layer, The first substrate, the first lower protective layer, the first recording layer, and the first upper portion from the side on which the light for recording / reproducing is incident, including the second recording layer, the second upper protective layer, and the second reflective layer The protective layer, the first reflective layer, the first thermal diffusion layer, the intermediate layer, the second lower protective layer, the second recording layer, the second upper protective layer, the second reflective layer, and the second substrate are disposed in this order. The two-layer phase change information recording medium according to any one of claims 1 to 13. 15. The two-layer phase change information recording medium according to claim 14, wherein the light transmittance of the first information layer is 40 to 70% with respect to light having a wavelength of 350 to 700 nm. 16. The two-layer phase change information recording medium according to claim 14, further comprising a transparent layer between the first substrate and the first lower protective layer. 17. The barrier layer according to claim 14, further comprising a barrier layer between the first upper protective layer and the first reflective layer and / or between the second upper protective layer and the second reflective layer. A two-layer phase change information recording medium according to claim 1. 18. The two-layer phase change information recording medium according to claim 14, wherein a thickness of the first substrate is 10 μm to 600 μm. Information recording / reproduction is performed by making a light beam having a wavelength of 350 to 450 nm incident on each information layer of the multilayer phase change information recording medium according to any one of claims 1 to 3 from the first information layer side. A recording / reproducing method for a multilayer phase change information recording medium. Information recording / reproduction is performed by making a light beam having a wavelength of 350 to 700 nm incident on each information layer of the multilayer phase change information recording medium according to any one of claims 4 to 9 from the first information layer side. A recording / reproducing method for a multilayer phase change type information recording medium.

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