JP2006035618A - Optical information recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a phase change type recording material with recording characteristics excellent especially in blue wavelength (the range of 380-430 nm) and, at the same time, provide a recording material, which is not only useful as a single layer phase change recording material but also proper for constituting a recording layer (hereinafter referred as a half-transmission recording layer), which is especially arranged on the laser irradiating front surface side of a multilayered optical information recording medium, laser beam transmissive and in which recording is performed with laser beam. <P>SOLUTION: In the phase change type optical information recording medium having at least one recording layer, in which phase transition is possible by the irradiation of light, on at least a transparent board, the recording layer material used for the recording layer consists of SbTe having a composition near eutectic system with GeTe and this optical information recording medium exists in a region surrounded by the respective compositional points: A(Ge<SB>29</SB>, Sb<SB>36</SB>and Te<SB>35</SB>), B(Ge<SB>25</SB>, Sb<SB>36</SB>and Te<SB>39</SB>), C(Ge<SB>5</SB>, Sb<SB>64.8</SB>and Te<SB>30.2</SB>) and D(Ge<SB>5</SB>, Sb<SB>76.5</SB>and Te<SB>18.5</SB>) in the compositional diagram having Ge, Sb and Te as its apices. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  An object of the present invention is to provide a phase change type multilayer optical information recording medium having excellent recording characteristics particularly in a blue wavelength (range of 380 to 430 nm). Specifically, it is arranged on the laser irradiation front side of a multilayer medium. The present invention relates to a recording material for a transparent recording layer.

  Conventionally, optical discs such as CD-R and CD-RW record sound, text, or image signals along a circumferential direction on a plastic circular substrate such as polycarbonate or a recording layer provided thereon. The reflective layer is formed by depositing or sputtering a metal such as aluminum, gold or silver on the surface. In this case, laser light is incident from the substrate surface side of the optical disc, and signal recording and reproduction are performed.

  In recent years, the amount of information handled by computer memory, memory for image and sound files, optical cards, etc. has increased significantly, so that the signal recording capacity and signal information of optical disks such as DVD + RW, DVD-RW, and DVD-RAM have increased. Densification is progressing. Currently, the recording capacity of a CD is about 650 MB, and the capacity of a DVD is about 4.7 GB. However, a higher recording density is required. As a method for increasing the recording density, in the optical system, it has been studied to shorten the wavelength of the semiconductor laser light source used and increase the numerical aperture NA (Numerical Aparture) of the objective lens. Furthermore, not only the improvement of the recording density in the two-dimensional direction but also a method for accumulating information recording by multilayering the recording layer in the thickness direction of the recording medium has been studied.

On the other hand, from the material point of view, there are two major flows of material development. That is, GeTe which is a write-once recording layer material, Sb ₂ Te ₃ which is an alloy of Sb and Te capable of reversibly phase change, and a ternary alloy of GeSbTe from the solid solution or eutectic composition of these two materials. The recording layer material is one flow. Furthermore, another flow is an alloy of Sb and Te, but a recording layer in which a trace element is added to SbTe whose eutectic composition of Sb and Sb ₂ Te ₃ is about 70%. The material is known. The former ternary alloy material is necessary for recording by stabilizing Te amorphous phase by adding Ge with Te as the main component and capable of reversible phase change, and mixing with Sb ₂ Te _3. Patent Documents 1 and 4 describe that information can be recorded, erased, and rewritten at high speed by reducing light energy and setting the mixing ratio to an optimum range. There are many disclosures of this composition, and Patent Documents 2, 3, and 5 are known as having a multilayer recording layer. However, the recording material alone is not sufficient in rewriting speed, and in order to improve the linear velocity above and below the recording layer, Patent Document 6 having a structure in which a crystallization auxiliary layer made of a metal alloy is laminated, or an interface such as GeN A structure provided with layers is generally used. Patent Document 7 and Non-Patent Document 1 disclose an interface layer such as GeN.

  Regarding the alloy of Sb and Te, which is another flow of the phase change material, as disclosed in Patent Document 8, the first information recording portion has Sb and Te as main components and its atoms. A phase change recording material having a ratio of 2.3 <Sb / Te ≦ 4.0 is disclosed. This phase change recording material has a high crystallization rate. For this reason, it is described that stable recording / reproduction and rewriting at a high transfer rate are possible.

On the other hand, as a means for obtaining a large-capacity recording medium, there are the following problems when a multilayer recording layer is provided in the light incident direction and the laser to be used is used for blue wavelength.
For example, when the recording layer is multi-layered as in a two-layer configuration, the first recording layer on the light incident side is improved in order to improve the light irradiation to the second recording layer on the light incident back side and to improve the transmission of irradiation return light. It is necessary to ensure light transmission of the recording layer. For this reason, when the recording layer is made very thin, the light transmittance increases, but the laser power absorbed by the first recording layer is reduced by the amount of light transmitted, and the recording signal difference sufficient for signal reading is reduced. There arises a problem that it becomes difficult to obtain a multi-layer structure, and there is a technically difficult problem to realize a multilayer structure. Patent Documents 2, 3, and 5 are known examples of multilayer optical information media. In this known example, a composition on a line connecting GeTe and Sb ₂ Te ₃ is shown. However, in this recording material system, the melting point is high and the crystallization temperature is high, so the rewriting speed is not sufficient. In order to improve the linear velocity above and below the recording layer, a configuration in which a crystallization auxiliary layer made of a metal alloy is laminated and a configuration in which an interface layer such as GeN is provided are generally used. Patent Document 7 and Non-Patent Document 1 disclose an interface layer such as GeN. Here, since the layer used for improving the linear velocity has a little light absorption, it can be said that it is a negative factor for the first recording layer that requires light transmission. Therefore, a material that can be recorded without requiring high power and can be formed with a simple layer structure is desired for the first recording layer.
Furthermore, in the case of the composition on the line connecting GeTe and Sb ₂ Te ₃ , a C / N ratio (Carrier to Noise Ratio) is as small as 30 dB, and a rewritable optical disk system which is said to be required to be at least 45 dB or more is constructed. It is difficult to build a stable system.
On the other hand, as a problem with respect to the blue wavelength, many phase change materials change the value of the optical constant at the blue wavelength, but the refractive index n decreases and the value of the extinction system number k increases. The extinction coefficient k is related to the light absorption, that is, the transmittance of the material, so that it is advantageous for the first recording layer to be small. In order to obtain a signal amplitude difference after laser recording, that is, a dynamic range, a crystal is used. A material having a large optical constant difference between the phase and the amorphous phase is good.

Japanese Patent No. 2692654 (Claim 5) Japanese Patent No. 02167944 (Claims 3 to 8, page 5, column 9, line 45 [0017]) JP-A-10-116441 (Claims 10 and 11) Japanese Patent Publication No. 8-032482 (Claims 1 and 3) JP 2001-143322 A (Claim 3) JP 2002-123977 A (Claim 6) JP 2002-293025 A (Claim 1) JP 2002-288876 A ([Summary], [0006], Claim 8) Proceedings of the 10th Phase Change Symposium, pp. 85-90 (1998)

Accordingly, the object of the present invention is to develop a phase change type recording material having excellent recording characteristics particularly in a blue wavelength (range of 380 to 430 nm) and to be useful as a phase change recording material for a single layer. In particular, a recording layer (hereinafter referred to as a semi-transmissive recording layer) which is disposed on the laser irradiation front side of the multilayer optical information recording medium and which is laser light transmissive and performs recording with laser light. It is in providing a suitable recording material.

In order to solve the above problems, the present inventors have studied various compositions in the phase change recording material, and as a result, returned to the phase diagram of the binary alloy of Sb and Te. The phase diagram is shown in FIG. The numbers on the lower side of the horizontal axis indicate Te concentration in atomic%. In the graph, the liquid phase line convex portion of Te atom 60% is the composition of the alloy-based composition Sb ₂ Te ₃ , and the numeral 622 indicates the melting point. Moreover, the liquid phase line recess of Te ₃₀ atomic% is a eutectic composition of Sb and Sb ₂ Te ₃ , and the numeral 540 indicates the melting point thereof. It can be seen that the eutectic composition of Sb and Sb ₂ Te ₃ has a lower melting point than the alloy composition Sb ₂ Te ₃ . It can be seen that the change of the liquidus line is gentle in the vicinity of the alloy composition and the eutectic composition, and both compositions are stable in the vicinity of the composition. In the case of the eutectic composition of Sb and Sb ₂ Te ₃ , it is superior to the alloy composition Sb ₂ Te ₃ in that it has a low melting point and is sufficiently melted by a semiconductor laser beam, resulting in a C / N ratio of about 50 dB. It can be said that.

  However, on the other hand, when the crystal constants at the blue wavelength and the optical constants in the amorphous state were checked, the result of FIG. 5 was obtained. At 405 nm, the optical constant differences near the eutectic composition are Δn 1.40 and Δk 0.26. In the amorphous state, n is about 2.5 and k is about 3.0. Compared to the values at 660 nm, which is the wavelength of DVD media (Δn 1.40, Δk 2.7, n in the amorphous state is 4.2, k is 2.5), the change in the optical constant is taken as the signal difference. As a result, it becomes difficult to capture the signal amplitude. Further, since the value of k is relatively large for use as a semi-transmissive layer, a material having a smaller k is desired for the semi-transmissive recording layer. Therefore, we thought that it was necessary to select or combine materials with large differences in optical constant values.

On the other hand, when attention is paid to GeTe, changes in the optical constants in the crystalline state and the amorphous state are shown in FIG. At 405 nm, the optical constant difference of GeTe is Δn 1.60, Δk 0.76. In the amorphous state, n is 3.1 and k is about 1.6. Since GeTe can obtain an optical constant difference between crystal and amorphous in the blue wavelength region, a wide dynamic range and modulation in the blue wavelength region can be obtained. Furthermore, since Ge in GeTe has a function of maintaining the stability of the amorphous state of the material, it is possible to prevent repetitive light degradation of the laser. For this reason, the light intensity of the reproducible light can be increased, and it is easy to obtain a wide dynamic range and modulation from that point.
However, GeTe alone has a high melting point and crystallization temperature, and the amorphous state is very stable. Therefore, it cannot be reversibly changed with the power of a semiconductor laser currently on the market.

From the above, the present inventor obtained GeTe that can easily take dynamic range and modulation at blue wavelength and can increase the reproducible light intensity and a large C / N ratio, and has a melting point lower than Sb ₂ Te ₃ and Sb and Sb _2. The inventors have come up with a material system that combines SbTe near the eutectic composition of Te ₃ . Furthermore, the advantage of this material system is that since the crystallization speed of SbTe near the eutectic composition of Sb and Sb ₂ Te ₃ is high, there is no need to use a crystallization promoting layer in contact with the recording layer, and a small layer structure Thus, a semi-transmissive recording layer can be configured.

That is, the subject of the present invention is the following (1) “Recording layer used for a recording layer in a phase change optical information recording medium having at least one recording layer capable of phase transition by light irradiation on a transparent substrate” The material is composed of SbTe having a composition close to eutectic system with GeTe. In the composition diagram having Ge, Sb, and Te as vertices, A (Ge ₂₉ , Sb ₃₆ , Te ₃₅ ), B (Ge ₂₅ , Sb ₃₆ , Te ₃₉ ), C (Ge ₅ , Sb _64.8 , Te _30.2 ), D (Ge ₅ , Sb _76.5 , Te _18.5 ), and a region surrounded by each composition point Optical information recording medium characterized by ",
(2) “A phase in which at least one laser beam transmitting recording layer is provided on a transparent substrate, and each of the recording layers is laminated in the same light incident direction with optically separable intervals. In a changeable optical information recording medium, a recording layer material used for a laser light-transmitting recording layer is composed of SbTe having a composition close to that of GeTe and a eutectic system, and has Ge, Sb, and Te as vertices. In the figure, A (Ge ₂₉ , Sb ₃₆ , Te ₃₅ ), B (Ge ₂₅ , Sb ₃₆ , Te ₃₉ ), C (Ge ₅ , Sb _64.8 , Te _30.2 ), D (Ge ₅ , Sb _{76). .5,} the optical information recording medium, characterized in that present in a region surrounded by the composition points of Te _18.5) ",
(3) “The recording material used for the recording layer is composed of a composition on a line connecting GeTe and Sb ₈₀ Te ₂₀ in a composition diagram having each of Ge, Sb, and Te as vertices. The optical information recording medium according to item (1) or (2) ",
(4) “In the composition diagram in which the recording material used for the recording layer has each of Ge, Sb, and Te as vertices, D (Ge ₅ , Sb _76.5 , Te _18.5 ), E (Ge _7.5 , Sb _72.2 , Te _20.3 ), F (Ge ₅ , Sb _72.2 , Te _22.8 ) are present in the region surrounded by the composition points of (1) to (1) above The optical information recording medium according to any one of (3) ",
(5) "The optical information recording medium according to any one of (1) to (4) above, wherein the recording layer has a thickness of 4 nm or more and less than 20 nm";
(6) “Having a layer configuration in which a lower dielectric layer, a recording layer having a laser beam transparency, an upper dielectric layer, an intermediate layer, a reflective layer, and a transparent conductive layer film are sequentially laminated on a transparent substrate. The optical information recording medium according to any one of (1) to (5),
(7) "The optical information recording medium according to any one of (1) to (5) above, wherein a wavelength range of a laser beam to be used is 380 to 430 nm";
(8) "The optical information recording medium according to any one of (1) to (7) above, wherein the optical information recording medium is multi-level recording",
Further, the above-mentioned problem is described in any one of (1) to (8) above, wherein the recording layer forming method is a direct current sputtering forming method having a pulse waveform. Of the optical information recording medium.

  According to the present invention, even in a highly transmissive recording layer among a plurality of recording layers, a sufficient recording signal difference can be obtained even in a blue wavelength range of 380 to 430 nm, and data can be recorded and read out. In addition, because of the high transmittance, it is possible to provide a phase change type optical information recording medium capable of sufficiently recording / reproducing data signals from the further laminated recording layer.

The present invention is described in detail below.
That is, the optical information recording medium of the present invention has at least one recording layer on a transparent substrate. In addition, in the case where a plurality of recording layers are provided on a transparent substrate, the respective recording layers are laminated in the same light incident direction with optically separable intervals to transmit laser light. And a recording layer (semi-transmissive recording layer) for recording. In the present invention, the material constituting these recording layers is composed of SbTe having a composition near the eutectic system with GeTe, and in FIG. 3, which is a composition diagram having Ge, Sb, and Te as vertices. (Ge ₂₉ , Sb ₃₆ , Te ₃₅ ), B (Ge ₂₅ , Sb ₃₆ , Te ₃₉ ), C (Ge ₅ , Sb _64.8 , Te _30.2 ), D (Ge ₅ , Sb _76.5 , Te _18.5 ) having a composition existing in a region surrounded by each composition point.

As a composition ratio of SbTe, one point of mixing Sb ₇₂ Te _{28 in} which the Sb amount capable of securing a crystallization transition linear velocity of 6 m / s, which is usually used for blue recording in a mixed system of SbTe + metal atoms, is 72 atomic% or more. It is preferable that the amount of Sb is larger than that of the line connected to GeTe. Further, as the upper limit, Sb is less than the line connected to GeTe as one point for mixing Sb ₈₅ Te ₁₅ which is the upper limit of recording rewriting because the linear velocity is too high. Is preferred. Further, since the composition has a large amount of Sb, 5 atomic% or more is required as Ge alone from the viewpoint of maintaining the storage characteristics. The ratio of GeTe to SbTe in the vicinity of the eutectic composition is preferably in the range where the abundance of Sb ₇₂ Te ₂₈ is 50% or more from the viewpoint of ensuring rewriting characteristics. In the same composition, the rewriting speed is determined by the amount of Sb in the entire system, so that the region can be divided by the Sb equivalence line.
Furthermore, in the composition diagram having the respective elements of Ge, Sb, and Te as vertices, the composition is preferably composed of a composition on a line connecting GeTe and Sb ₈₀ Te ₂₀ , and more preferably, the composition of Ge, Sb, and Te. In the composition diagram having each element as the apex, D (Ge ₅ , Sb _76.5 , Te _18.5 ), E (Ge _7.5 , Sb _72.2 , Te _20.3 ), F (Ge ₅ , Sb _72.2 and Te _22.8 ).
The film thickness of the semi-transmissive recording layer for recording by transmitting the laser beam is preferably 4 nm to 20 nm, more preferably 6 nm to 14 nm, and the wavelength range of the laser beam used is preferably 380 to 430 nm. is there.
In the optical information recording medium of the present invention, at least one recording layer made of a material capable of phase transition by light irradiation is provided on at least a transparent substrate. In this recording layer, the recording material having the above-described Ge, Sb, and Te composition is used.

Hereinafter, this layer structure will be exemplified.
For example, as shown in FIG. 1, the layer structure of an optical information recording medium having a single-layer recording layer according to the present invention includes a lower dielectric layer (2), a recording layer (3) on a first transparent substrate (1). ), An upper dielectric layer (4), an intermediate layer (5), a reflective layer (6), an environmental protection layer (7), an adhesive layer (8) and a second transparent substrate (9) are sequentially laminated.

In the multilayer optical information recording medium of the present invention, the case where two recording layers are provided is shown. For example, as shown in FIG. 2, the first lower dielectric layer (2) is formed on the transparent substrate (1). , Recording layer (3), first upper dielectric layer (4), intermediate layer (5), reflective layer (6), transparent conductive film layer (61), environmental protection layer (7), adhesive layer (8), Environmental protection layer (77), second lower dielectric layer (22), second recording layer (33), second upper dielectric layer (44), second intermediate layer (55), second reflective layer (66) The second transparent substrate (9) is sequentially laminated.
Such a structure has a first lower dielectric layer (2), a recording layer (3), a first upper dielectric layer (4), an intermediate layer (5), a reflective layer (6) on a transparent substrate (1). ), A transparent conductive film layer (61), an environmental protection layer (7), and a first information recording substrate, and a second reflective layer, a second intermediate layer, and a second upper portion on the second transparent substrate (9). A second information recording substrate on which a dielectric layer (44), a second recording layer (33), a second lower dielectric layer (22), and an environmental protection layer (77) are sequentially laminated is bonded to each other through an adhesive layer. Can be created.
However, the intermediate layer can be omitted if the upper dielectric layer does not contain sulfur.

The constituent materials of each layer constituting the optical information recording medium of the present invention will be described below except for the recording layer already described.
Examples of the transparent substrate include glass, ceramics, and resin. A resin substrate is 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, urethane resin, etc. Polycarbonate resins and acrylic resins that are excellent in terms of moldability, optical characteristics, and cost are preferred. In general, a transparent substrate made of polycarbonate resin in which predetermined grooves are formed by an injection molding method is frequently used as a substrate for CD and DVD.

Examples of materials used for the first or second dielectric layer include 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 Nitrides such as AlN, TiN, BN, and ZrN; sulfides such as ZnS and TaS ₄ ; carbides such as SiC, TaC, B ₄ C, WC, TiC, and ZrC; diamond-like carbon; or a mixture thereof . Among them, substances containing ZnS and SiO ₂ such as ZnS—SiO ₂ (15 mol%), ZnS—SiO ₂ (20 mol%), ZnS—SiO ₂ (25 mol%) (all are mol% of SiO _{2 in} the whole). In particular, the first dielectric layer positioned between the recording layer and the substrate with thermal expansion change, thermal damage due to high temperature / room temperature change, and ZnS with optimized optical constant, thermal expansion coefficient, and elastic modulus are preferable. —SiO ₂ (20 mol%) is frequently used because thermal characteristics, optical characteristics, and productivity (speed of film formation speed) are important.

  In addition, since the film thickness of the first dielectric layer greatly affects the reflectivity, the degree of modulation, and the recording sensitivity, the film thickness is such that the medium reflectivity is near the minimum value with respect to the film thickness of the first dielectric layer. It is desirable to do. In this film thickness region, the recording sensitivity is good, recording is possible with a power with less heat damage, and the overwriting performance is improved.

  The reflective layer material may be usually composed of a single metal or semimetal such as Al, Au, Ag, Pt, Cu, Ni, Cr, Ti, Si, or a metal deposit including one or more of these. In order to form a recording mark, a rapid cooling structure is preferable. Therefore, it is preferable that the reflective layer is made of a material having high thermal conductivity. As the material having high thermal conductivity, Ag or an Ag alloy is preferable.

As a transparent conductive film layer material, In ₂ O ₃ , SnO ₂ , ITO (mixed composition of In ₂ O ₃ and SnO ₂ ), ZnO, a mixture thereof, or a mixture of 20 mol% or less generally used as a transparent conductive film is used. A material to which a trace additive such as a metal or an oxide is added can be used.

  As the environmental protection layer or adhesive layer material, an ultraviolet curable resin or a thermosetting resin can be used. Since the use of a thermosetting resin may affect the tilt of the substrate, an ultraviolet curable resin produced by a spin coating method is generally preferable.

  In the case of an optical information recording medium having a single recording layer, the film thickness is suitably 3 to 15 μm. If the thickness is less than 3 μm, an increase in error may be observed when a printed layer is provided on the overcoat layer. On the other hand, if it is thicker than 15 μm, the internal stress increases, which greatly affects the mechanical properties of the medium. On the other hand, in the case of an optical information recording medium having two recording layers, a distance capable of optically separating the first recording layer and the second recording layer is necessary, and in the case of a blue wavelength of 405 nm, about 35 μm ± 5 μm. It is preferable to do this.

Since the recording layer made of the recording material having the above composition of the present invention has a large dynamic range, multi-value recording can be performed. The recording layer is preferably formed by a direct current sputtering method having a pulse waveform.
In addition, as described above, the optical information recording medium of the present invention is formed on a transparent substrate, and is a recording layer made of an alloy containing at least a mixed composition of a composition close to the eutectic system of GeTe, Sb, and Sb ₂ Te _3. Have Since the optical constant in the amorphous state of the recording layer has a large optical constant value in the blue wavelength region, a signal difference can be obtained even with a thin film thickness. Further, since the extinction coefficient k is small, it has a high transmittance and can be used as a semi-transmissive recording layer. Since this semi-transmissive recording layer can be reliably formed, it becomes easy to obtain an optical information recording medium having multiple recording layers.

Hereinafter, a specific configuration will be described in accordance with an embodiment, but the present invention is not necessarily limited to this embodiment.
Example 1
Example in which (Ge ₅₀ Te ₅₀ ) ₃₀ (Sb ₈₀ Te ₂₀ ) ₇₀ is used as a semi-transmissive recording layer First, a substrate of a semi-transmissive recording layer in front of the laser irradiation direction was manufactured by the following procedure.
A dielectric protective layer (50 nm), a recording layer (8 nm), a dielectric on a polycarbonate transparent substrate having a diameter of 12 cm, a thickness of 0.6 mm, and a continuous guide groove with a wobble on the surface and a pitch of 0.46 μm. A protective layer (10 nm), an intermediate layer (3 nm), a reflective layer (10 nm), and a transparent conductive film layer (30 nm) were sequentially formed. ZnS—SiO ₂ (20 mol%) is used for the dielectric protective layer, and GeTe and Sb ₈₀ Te ₂₀ are mixed in the ratio of 3: 7 for the recording layer (Ge ₅₀ Te ₅₀ ) ₃₀ (Sb ₈₀ Te ₂₀ ) ₇₀ A phase change recording material, a mixed dielectric layer of SiC—SiO ₂ (20 mol%) as an intermediate layer, an Ag alloy with Ag of 95 mol% or more as a reflective layer, and IZO (In ₂ O ₃ 90 mol% − as a heat dissipation layer). ZnO 10 mol%) was formed by sputtering using a Arzer as a sputtering gas in a single wafer sputtering apparatus manufactured by Balzers. When the transmittance of the entire laminated film including the substrate was measured at the end of sputtering, it was 46.4% at a wavelength of 405 nm. Further, an ultraviolet curable resin was applied thereon using a spin coater and then cured by ultraviolet irradiation, and a first environmental protection layer having a thickness of about 3 μm was provided to produce a first information recording substrate.

Next, using the same polycarbonate transparent substrate, a substrate for a recording layer (referred to as a second recording layer) on the back side in the laser irradiation direction was manufactured according to the following procedure.
As a second information substrate, a reflective layer (120 nm), an intermediate layer (2 nm), a dielectric protective layer (10 nm), an optical information recording layer (14 nm), and a dielectric protective layer (70 nm) are formed on a second transparent substrate. Sequentially formed. An Ag alloy having an Ag ratio of 95% or more is recorded in the reflective layer, a mixed dielectric layer of SiC-SiO ₂ (20 mol%) is recorded in the intermediate layer, and ZnS—SiO ₂ (20 mol%) is recorded in the dielectric protective layer. A material having the same composition as that of the first information layer was used for the layer, and sputtering was performed using Ar gas as a sputtering gas by a single wafer sputtering apparatus manufactured by Balzers. On top of that, an ultraviolet curable resin was applied using a spin coater and then cured by ultraviolet irradiation, and a second environmental protection layer having a thickness of about 3 μm was provided to produce a second information recording substrate.

Next, the first information substrate and the second information substrate were bonded together. An ultraviolet curable resin was spin-coated as an adhesive layer on the environmental protection layer film surface of the first information substrate, and the ultraviolet curable resin was cured by irradiating ultraviolet light from the first information substrate side. Here, the total thickness of the first environmental protection layer, the adhesive layer, and the second environmental protection layer was adjusted and formed so as to be within about 35 ± 5 μm. In this way, a two-layer phase change type information recording medium having two information layers was manufactured.
Add part number and conditions of UV curable resin.
Prior to the evaluation, laser initialization was performed in a processing time of about 100 seconds under the following conditions using a phase change optical disk initialization device (POP120-3Ra) manufactured by Hitachi Computer. For the semi-transmissive recording layer, the recording medium is rotated by CLV (Constant Linear Velocity), the linear velocity is 3.0 m / s, the feed amount is 36 μm / rotation, the initialization range is a radial position of 23 to 58 mm, and the laser power is 800 mW. The center emission wavelength of the LD of this apparatus is 810 ± 10 nm, and the spot size is about 1 μm × 96 ± 5 μm. Next, the focus position was shifted by 0.6 mm of the substrate thickness, the linear velocity was 2.6 m / s, the feed amount was 36 μm / s, the radial position was similarly 23 to 58 mm, and the laser power was 1000 mW.

Next, this manufactured optical information medium was evaluated using an optical disk evaluation apparatus (Pulstec DDU1000) having a NA (Numerical Aparture) 0.65 pickup equipped with a 405 nm semiconductor laser. The recording linear density was 0.184 μm / bit (evaluation clock frequency was 65.4 MHz), and a random pattern of 3T to 14T was recorded. The recording linear velocity is 6.0 m / s. Evaluation items are reflectivity, modulation of random pattern, random pattern jitter, minimum pattern 3T pattern C / N, rewrite recording, ie jitter change by DOW (Direct Over Wright) number, DOW power margin, storage reliability It was sex.
First, the semi-transmissive recording layer was evaluated. The evaluation power conditions were Pw = 10 to 14 mW, Pe = 6 mW, reading / reproducing laser power Pr = 0.9 mW, and an optimized pulse strategy. As a result, the reflectance was 7 to 8%. As other characteristics, the dynamic range was 155 mW, the modulation was 65%, the jitter when a random pattern was recorded was 9.5%, and no particular trouble occurred during writing and reproduction. At this time, the C / N ratio of the 3T pattern was 54 dB.
Further, the second recording layer was also evaluated by making the focus jump to the back recording layer. Recording / evaluation was performed using the same waveform pattern except that the recording power was increased to 12 to 15 W. The reflectivity was 7-9%. As other characteristics, the modulation was 60%, the jitter when a random pattern was recorded was 9.5%, and no trouble occurred during the writing and reproduction.
Next, overwrite recording was performed on each of the recording layers. The overwriting conditions were exactly the same as the initial recording conditions. The jitter for the first recording layer was 10% for the second recording, 9.7% for the tenth recording, 9.6% for the 100th recording, and 9.8% for the 1000th recording.

  Next, after the recording check, this optical information recording medium was stored in a high-temperature and high-humidity bath for 400 hours under conditions of 80 ° C. and 85% RH, and then jitter (or 3T C / N ratio) was evaluated again. The measured values of jitter (or 3T C / N ratio) were changes of 0.5% or less (about 2 dB), and were not problematic. In addition, the film was not lifted, the film was peeled off, or the appearance of spot-like discoloration considered to be abnormal was not observed.

(Example 2)
_{(Ge 50 Te 50) 45 (} Sb 72 Te 28) 55 a in place of the recording layer material of Example semitransparent recording layer only Example 1 when used as a semi-transmissive recording layer _{(Ge 50 Te 50) 45 (} Sb ₇₂ Te ₂₈ ) ₅₅ was used as a recording layer material, and an optical information recording medium having the same configuration was manufactured and evaluated in the same manner. However, the recording linear velocity was 3.5 m / s.
First, the semi-transmissive recording layer was evaluated. The evaluation power condition required a slightly higher recording power of Pw = 11 to 15 mW. Pe = 6 mW, reading / reproducing laser power Pr = 0.9 mW, and an optimized pulse strategy. As a result, the reflectance was 7 to 8%. Other characteristics were a dynamic range of 165 mW, a modulation of 70%, and a jitter of 9.3% when a random pattern was recorded, and no particular trouble occurred during writing and reproduction. At this time, the C / N ratio of the 3T pattern was 52 dB. As for the recording power, no deterioration in signal amplitude was observed even when the recording power was increased to 1.1 mW.
Next, the second recording layer was also evaluated by causing the pickup to jump the focus to the back recording layer. Since the recording layer material was not changed from that in Example 1, the results were exactly the same. That is, recording / evaluation was performed using the same waveform pattern except that the power was increased to 12 to 15 W. The reflectivity was 7-9%. As other characteristics, the modulation was 60%, the jitter when a random pattern was recorded was 9.5%, and no trouble occurred during the writing and reproduction.
Next, overwrite recording was performed on each of the recording layers. The overwriting conditions were exactly the same as the initial recording conditions. The jitter for the first recording layer was 12% for the second recording, 10% for the 10th recording, 10.5% for the 100th recording, and 11% for the 1000th recording. Although repeated jitter was high, overwriting was possible.
Next, after the recording check, this optical information recording medium was stored in a high-temperature and high-humidity bath for 400 hours under conditions of 80 ° C. and 85% RH, and then jitter (or 3T C / N ratio) was evaluated again. The measured values of jitter (or 3T C / N ratio) were changes of 0.3% or less (about 1.6 dB), respectively, and were not problematic. In addition, no film floating, film peeling, or the appearance of spot-like discoloration that seemed to be abnormal was observed.

Example 3
Composition within the range of DEF: (Ge ₅₀ Te ₅₀ ) ₁₂ (Sb _82.5 Te _17.5 ) ₈₈
An optical information recording medium having the same configuration is manufactured by using (Ge ₅₀ Te ₅₀ ) ₁₂ (Sb _82.5 Te _17.5 ) ₈₈ as the recording layer material instead of the recording layer material of Example 1 only for the semi-transmissive recording layer. Thereafter, evaluation was performed in the same manner. The evaluation linear velocity was 8 m / s.
First, the semi-transmissive recording layer was evaluated. The evaluation power condition required a slightly higher recording power of Pw = 10 to 14 mW. Pe = 6 mW, reading / reproducing laser power Pr = 0.9 mW, and an optimized pulse strategy. As a result, the reflectance was 7 to 8%. As other characteristics, the dynamic range was 140 mW, the modulation was 62%, the jitter when a random pattern was recorded was 9.5%, and no particular trouble occurred during writing and reproduction. At this time, the C / N ratio of the 3T pattern was 52 dB.
Next, the second recording layer was also evaluated by causing the pickup to jump the focus to the back recording layer. Since the recording layer material was not changed from that in Example 1, the results were exactly the same. That is, recording / evaluation was performed using the same waveform pattern except that the power was increased to 12 to 15 W. The reflectivity was 7-9%. As other characteristics, the modulation was 60%, the jitter when a random pattern was recorded was 9.5%, and no trouble occurred during the writing and reproduction.
Next, overwrite recording was performed on each of the recording layers. The overwriting conditions were exactly the same as the initial recording conditions. The jitter for the first recording layer was 10.2% for the second recording, 9.5% for the tenth recording, 9.6% for the 100th recording, and 9.8% for the 1000th recording.
Next, after the recording check, this optical information recording medium was stored in a high-temperature and high-humidity bath for 400 hours under conditions of 80 ° C. and 85% RH, and then jitter (or 3T C / N ratio) was evaluated again. The measured values of jitter (or 3T C / N ratio) were changes of 0.5% or less (about 2 dB), and were not problematic. In addition, no film floating, film peeling, or the appearance of spot-like discoloration that seemed to be abnormal was observed.

Example 4
Example in which (Ge ₅₀ Te ₅₀ ) ₂₅ (Sb ₈₅ Te ₁₅ ) ₇₅ is used as a semi-transmissive recording layer Only the semi-transmissive recording layer is replaced with the recording layer material of Example 1 (Ge ₅₀ Te ₅₀ ) ₁₂ (Sb _82.5 Te _17.5 ) ₈₈ was used as a recording layer material, and an optical information recording medium having the same structure was manufactured and evaluated in the same manner. The evaluation linear velocity was 6 m / s.
First, the semi-transmissive recording layer was evaluated. The evaluation power condition required a slightly higher recording power of Pw = 10 to 14 mW. Pe = 6 mW, reading / reproducing laser power Pr = 0.9 mW, and an optimized pulse strategy. As a result, the reflectance was 7 to 8%. As other characteristics, the dynamic range was 150 mW, the modulation was 62%, and the jitter when a random pattern was recorded was 9.5%, and no particular trouble occurred during writing and reproduction. At this time, the C / N ratio of the 3T pattern was 52 dB.
Next, the second recording layer was also evaluated by causing the pickup to jump the focus to the back recording layer. Since the recording layer material was not changed from that in Example 1, the results were exactly the same. That is, recording / evaluation was performed using the same waveform pattern except that the power was increased to 12 to 15 W. The reflectivity was 7-9%. As other characteristics, the modulation was 60%, the jitter when a random pattern was recorded was 9.5%, and no trouble occurred during the writing and reproduction.
Next, overwrite recording was performed on each of the recording layers. The overwriting conditions were exactly the same as the initial recording conditions. The jitter for the first recording layer was 10.2% for the second recording, 9.5% for the tenth recording, 9.6% for the 100th recording, and 9.8% for the 1000th recording.
Next, after the recording check, this optical information recording medium was stored in a high-temperature and high-humidity bath for 400 hours under conditions of 80 ° C. and 85% RH, and then jitter (or 3T C / N ratio) was evaluated again. The measured values of jitter (or 3T C / N ratio) were changes of 0.5% or less (about 2 dB), and were not problematic. In addition, no film floating, film peeling, or the appearance of spot-like discoloration that seemed to be abnormal was observed.

(Example 5) Example of multilevel recording The SDR is measured when recording is performed on the recording medium of Example 1 by controlling the amorphous area of less than 0.26 μm in seven steps in the laser beam scanning direction. did. The laser wavelength, NA, and recording linear velocity are the same as in Example 1. The reproduction power was 1.0 mW. By recording with controlling the amorphous area in 7 steps, it becomes an 8-value recording that combines the reflectance of the crystal, and even when the laser beam size is the same, compared with the binary EFM modulation recording, The recording capacity can be at least 1.5 times. Here, SDR (sigma to dynamic range) is a value obtained by dividing the standard deviation of the reflectivity at each stage by the difference between the maximum reflectivity level and the minimum reflectivity level, and when the SDR is approximately 3% or less. This is the error rate that can be corrected. The SDR of the recording medium of the example was 2.9% for the first information layer and 2.8% for the second information layer.
In the case of the recording material according to the present example, since reproduction light degradation is small with high transmittance at a blue wavelength, reproduction can be performed at high power, and the reflection signal amplitude of the non-crystal part and the crystal part when recording is obtained. It is considered that SDR can be reduced even when multi-level recording is performed.

(Comparative Example 1)
Comparative example Sb ₇₅ Te ₂₅ near the eutectic system
Using the recording layer material AgInSbTe (Ag _0.2 In _0.2 Sb _77.0 Te _18.6 Ge _4.0 ) containing the SbTe system having a composition close to the eutectic system, the same structure and the same film as in Example 1 A thick light information recording medium was manufactured. During the production of a single plate including a semi-transmissive recording layer, the transmittance was measured before forming the first environmental protection layer, and found to be 34%. Then, the 1st environmental protection layer was provided with the film thickness of about 3 micrometers. Then, the same 2nd recording layer board | substrate as Example 1 was bonded together on the same conditions, and the optical information recording medium which has the same shape was manufactured.
First, the semi-transmissive recording layer was evaluated. The evaluation power condition required a slightly higher recording power of Pw = 10 to 14 mW. Pe = 6 mW, reading / reproducing laser power Pr = 0.9 mW, and an optimized pulse strategy. As a result, the reflectance was 7 to 8%. As other characteristics, the modulation was 62%, the initial jitter when a random pattern was recorded was 9.5%, and no particular trouble occurred during writing and reproduction. However, the amplitude of the signal level was about 60% after about 40 seconds after continuing to irradiate the reproduction light, and the jitter was 13%. When the reproduction light power Pr was lowered by 0.1 mW, the change stopped at 0.6 mW. When the dynamic range was seen at 0.6 mW with no reproduction light deterioration, it was reduced to 60% of 0.9 mW. The jitter of the random pattern at Pr = 0.6 mW was 13%, and the C / N ratio of the 3T pattern at this time was 40 dB.
Next, overwrite recording was performed on the transflective recording layer. The overwriting conditions were exactly the same as the initial recording conditions. The jitter for the first recording layer was 15% for the second recording, 13.5% for the 10th recording, 14% for the 100th recording, and 14.6% for the 1000th recording.
Next, after the recording check, the optical information recording medium was stored in a high-temperature and high-humidity tank at 80 ° C. and 85% RH for 100 hours, and jitter (or 3T C / N ratio) was evaluated again. The recording mark disappeared and jitter could not be measured.

(Comparative Example 2)
In the case of Ge ₂ Sb ₂ Te ₅ without a buffer layer In Example 1, the recording layer was replaced with Ge ₂ Sb ₂ Te ₅ , and an optical information recording medium having the same layer configuration was manufactured and evaluated. The transition linear velocity was 3 m / s, and it was found that the transition linear velocity was low in the layer configuration without the crystallization promoting layer formed in contact with the recording layer.

(Comparative Example 3)
Comparative example outside the range When there is more Sb Using the (Ge ₅₀ Te ₅₀ ) ₁₀ (Sb ₉₀ Te ₁₀ ) ₉₀ having a high Sb composition in the recording layer, a semi-transmissive layer optical information recording medium is formed. did. The line speed was as fast as 15m / s. Recording was performed at a maximum setting power of 15 mW, and an initial jitter value of 10% was obtained, but when a high-temperature and high-humidity test was performed under conditions of 80 ° C. and 85% RH and taken out after 100 hours, the recording mark was It was completely gone.

(Comparative Example 4)
Comparative Example 2 out of range When GeTe is large: Comparative Example of Example 2 Optical information is obtained in the same manner as in Example 2 using (Ge ₅₀ Te ₅₀ ) ₅₅ (Sb ₇₂ Te ₂₈ ) ₄₅ with a large amount of GeTe. A recording medium was produced. When the linear velocity was measured, it was 1 m / s, which was the same as that of GeTe alone. Nevertheless, when the first recording was performed at 6 m / s, writing was possible, and random pattern recording could be performed by a single pulse strategy used in write-once recording. Jitter gained 9%. However, when repeated recording was performed, rewriting was not possible, and the amplitude gradually decreased when repeated recording was performed.

It is a figure showing the 1 layer medium in this invention. It is a figure showing the 2 layer medium in this invention. It is a figure showing the composition range of the material by this invention. It is a figure showing the phase diagram of SbTe. It is a figure showing the change of the optical constant with the wavelength of an amorphous phase of SbTe system, and a crystal phase. It is a figure showing the change of the optical constant by the wavelength of the amorphous phase and crystalline phase of GeTe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 1st lower dielectric layer 3 Transflective recording layer 4 1st upper dielectric layer 5 Intermediate layer 6 Reflective layer 7 Environmental protection layer 8 Adhesive layer 9 2nd transparent substrate (bonding substrate)
22 Second lower dielectric layer 33 Second recording layer 44 Second upper dielectric layer 55 Second intermediate layer 61 Transparent conductive layer 66 Second reflective layer 77 Environmental protection layer

Claims (9)

In a phase change optical information recording medium having at least one recording layer capable of phase transition by light irradiation on a transparent substrate, the recording layer material used for the recording layer is composed of SbTe having a composition close to that of GeTe and a eutectic system. In the composition diagram having Ge, Sb, and Te as vertices, A (Ge ₂₉ , Sb ₃₆ , Te ₃₅ ), B (Ge ₂₅ , Sb ₃₆ , Te ₃₉ ), C (Ge ₅ , Sb _64.8 , Te _30.2 ), D (Ge ₅ , Sb _76.5 , Te _18.5 ), an optical information recording medium characterized by being present in a region surrounded by composition points. Phase change type optical information having at least one laser beam transmitting recording layer on a transparent substrate, each recording layer being laminated in the same light incident direction with optically separable intervals In a recording medium, a recording layer material used for a recording layer having a laser beam transmission property is composed of SbTe having a composition near the eutectic system with GeTe, and in the composition diagram with Ge, Sb, and Te as vertices, A (Ge ₂₉ , Sb ₃₆ , Te ₃₅ ), B (Ge ₂₅ , Sb ₃₆ , Te ₃₉ ), C (Ge ₅ , Sb _64.8 , Te _30.2 ), D (Ge ₅ , Sb _76.5 , Te _The optical information recording medium is present in a region surrounded by each composition point of _18.5 ). The recording material used for the recording layer is composed of a composition on a line connecting GeTe and Sb ₈₀ Te ₂₀ in a composition diagram having Ge, Sb, and Te elements as apexes. Or the optical information recording medium of 2. In the composition diagram in which the recording material used for the recording layer has Ge, Sb, and Te elements as apexes, D (Ge ₅ , Sb _76.5 , Te _18.5 ), E (Ge _7.5 , Sb _72.2 , Te _20.3 ), F (Ge ₅ , Sb _72.2 , Te _22.8 ), which is present in a region surrounded by the composition points. Information recording medium. 5. The optical information recording medium according to claim 1, wherein the thickness of the recording layer is 4 nm or more and less than 20 nm. The invention has a layer structure in which a lower dielectric layer, a laser light-transmitting recording layer, an upper dielectric layer, an intermediate layer, a reflective layer, and a transparent conductive film layer are sequentially laminated on a transparent substrate. Item 6. The optical information recording medium according to any one of Items 1 to 5. 6. The optical information recording medium according to claim 1, wherein a wavelength range of a laser beam to be used is 380 to 430 nm. The optical information recording medium according to claim 1, wherein multi-value recording is performed. 9. The method of manufacturing an optical information recording medium according to claim 1, wherein the recording layer is formed by a direct current sputtering method having a pulse waveform.

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