JP2006294219A - Phase change type optical information recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase change type optical information recording medium having satisfactory information recording medium characteristics capable of corresponding to high linear speed/high sensitivity and excellent shelf stability and its manufacturing method and especially provide the optical information recording medium free from corrosion of a reflection layer made of an Ag based material, having satisfactory production efficiency and capable of maintaining recording signal characteristics and its manufacturing method. <P>SOLUTION: The phase change type optical recording medium includes at least a bottom protection layer, a recording layer, a top protection layer, and the reflection layer formed on a substrate having a guide groove in a concentric or spiral shape on one after another. A phase of the recordation layer can be changed by irradiation with a semiconductor laser light when information is to be recorded or rewritten. The reflection layer is made of Ag or a material mainly including Ag and the top protection layer is made of a material including an oxide as a main component and containing a nitride or a carbide. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical information recording medium for recording and reproducing information at high speed and high density using optical means such as a laser beam. Specifically, when high-thermal-conductivity material containing Ag or Ag as a main component is used for the reflective layer for high-speed recording, it is avoided that the reflective layer and components of the dielectric protective layer react and deteriorate. Therefore, the present invention relates to an optical information recording medium using a material composed of an element that does not have a high reactive activity with Ag as a material for a dielectric protective layer.

Among the recording type optical information recording media, the phase change type optical information recording medium is generally based on a functionally four-layer film structure such as substrate / protective layer / recording layer / protective layer / reflective layer. In each case, materials such as transparent plastic / dielectric material / chalcogen phase change recording material / dielectric material / Al, Ag type pure metal or alloy are used. The chalcogen phase change recording material used here has a crystalline and non-crystalline structure due to thermal history, and the recorded information can be identified by the difference in reflectance.
In recent years, phase change recording type optical information recording media have been frequently used, and higher density and higher writing speed have been increasingly demanded.
Various proposals have been made for higher density, and one example of this is to use a semiconductor laser with a short wavelength, and to increase the NA (Numerical Aperture) of the optical pickup and increase the recording laser beam. There is an attempt to narrow down the above and aim for high-density recording (see, for example, Patent Document 1).

For higher linear velocity, the reflective layer plays an important role, and it is required to be a reflective layer that can ensure high reflectivity and has a high cooling rate. , Au, Cu, and the like are selected, and Ag is particularly frequently used.
However, since Ag as a reflective layer material is chemically active against non-metallic elements such as chlorine and sulfur or ions thereof, it is sufficient in the environment or atmosphere in which the recording medium is used. There is a problem in that it does not have a good weather resistance.
As a technique for solving this problem, a proposal to introduce a metal element as an impurity into Ag, specifically, 0.1% to 5.0% of Au, and another specific metal element as an impurity is also proposed. (See, for example, Patent Document 2).

On the other hand, when at least an Ag-based material is used as the reflective layer material, there is a basic problem that occurs with other layers. That is, as a material used for the dielectric layer, thermal characteristics, optical characteristics, and productivity (speed of film formation speed) are emphasized, and ZnS · SiO ₂ (80: 20 mol%) satisfies these points. It is often used to do this. However, if a metal having high reflectivity and high thermal conductivity (including the case of only Ag) containing Ag as a main component is used as the reflective layer, there is a problem that corrosion occurs due to sulfur contained in the dielectric layer.
As a countermeasure, an intermediate layer made of a metal or semiconductor oxide, nitride, carbide, or amorphous carbon is provided between a dielectric layer containing sulfur atoms and a reflective layer containing Ag as a main component, and Ag reflection is performed. A method of preventing corrosion of the layer has been proposed (see, for example, Patent Document 3).
Further, for the purpose of preventing sulfuration of the reflective layer material, the element α (α is Sn, In, Zr, Si, Cr, Al, Ta, V, Nb) between the dielectric layer and the reflective layer as in Patent Document 3. , Mo, W, Ti, Mg and Ge have been proposed to provide a barrier layer containing a nitride, oxide, carbide or nitride oxide of at least one element (for example, see Patent Document 4).
Furthermore, as a better method than the intermediate layer or barrier layer proposed in Patent Document 3 and Patent Document 4, at least one metal selected from Ti, Zr, V, Nb, Ta, Cr, Mo and W is used. There has been proposed a method of providing a barrier layer formed of a material composed of a mixture of a carbide and an oxide containing (for example, see Patent Document 5).

However, both of these methods are methods in which another layer is inserted between the ZnS · SiO ₂ dielectric layer and the reflective layer mainly composed of Ag so as not to be in direct contact. When the layer located at is not formed, or when the layer is remarkably deteriorated and does not perform its function, corrosion of the reflective layer occurs.
Therefore, rather than forming an intermediate layer or a barrier layer, the dielectric layer is made of a material that does not contain chlorine or sulfur, which has high reactivity with Ag, and is in direct contact with the reflective layer mainly composed of Ag. However, it is more desirable to adopt a configuration in which Ag corrosion does not occur.
Therefore, as a dielectric layer material not containing sulfur, each of oxides of Ta, Ti, Zr, Al, Si, Ge, or a mixed material thereof, or each of Ta, Zr, Al, Si, Ge Nitride, ZnO simple substance, mixed oxide of ZnO and Al ₂ O ₃ , or a mixed material arbitrarily selected from these nitrides, ZnO simple substance, mixed oxide (for example, Patent Document 6), ZnO-based material (for example, Patent Document 7), mixed material of SiC and at least one of Zr, Ti, Ta, Nb (for example, Patent Document 8), Te oxide, or Te and others A material mainly composed of a metal oxide or a mixture of an oxide and a nitride (for example, Patent Document 9), cerium oxide and other oxides (chromium oxide, iron oxide, manganese oxide, niobium oxide, magnesium oxide) , Zinc oxide, aluminum oxide, titanium oxide, yttrium oxide, tantalum oxide, antimony oxide, zirconium oxide, mixed material of a bismuth oxide) (e.g., Patent Document _10), and _{ZrO 2, SiO 2, TiO 2} , Y 2 O ₃ , CeO, Al ₂ O ₃ , MgO, CaO, Nb ₂ O _5, and mixed materials with at least one of rare earth oxides (for example, Patent Document 11) have been proposed.

However, the dielectric layer using these materials has low adhesion to the recording layer and the reflective layer mainly composed of Ag, and the film is peeled off or has a low sputtering rate during film formation by the sputtering method. Therefore, it takes time to form a film, and the temperature rise of the substrate increases, causing the substrate to be deformed, the crystallization promotion effect to lower the amorphous stability of the recording layer, causing deterioration of the recording characteristics, and the thermal conductivity. However, there are various problems such as higher recording quality than ZnS · SiO ₂ dielectric layer and poor recording sensitivity. Therefore, a dielectric material in which those problems are solved is required.
Furthermore, Example 2 of Patent Document 6 shows an example in which the second dielectric layer has a laminated structure of a ZnS · SiO ₂ layer and a TaNx · AlNx · SiNx layer. It is not preferable in terms of production cost. Further, when it is difficult to form the TaNx / AlNx / SiNx layer due to some inconvenience such as a manufacturing error, or when the film thickness becomes thinner than the assumed film thickness, the ZnS / SiO ₂ layer is formed as a lower layer. Therefore, there is a possibility of causing corrosion deterioration of Ag or a reflective layer mainly composed of Ag due to sulfur. On the other hand, according to the present invention, since the upper protective layer is a single layer and no sulfide is used as the material of the upper protective layer, the above-described problems do not occur.

WO99 / 00794 pamphlet JP 2002-129260 A JP-A-11-238253 JP 2002-74746 A JP 2004-185794 A Japanese Patent Laid-Open No. 2002-100076 Japanese Patent Laid-Open No. 2002-237095 JP 2002-269824 A JP 2002-298436 A JP 2003-166052 A Japanese Patent Laid-Open No. 2004-5767

  An object of the present invention is to provide a phase change type optical information recording medium having good information recording medium characteristics that can cope with high linear velocity and high sensitivity, and excellent storage stability, and a method for producing the same. In particular, it is an object of the present invention to provide an optical information recording medium that does not cause corrosion of a reflective layer made of an Ag-based material, has high production efficiency, and can maintain recording signal characteristics, and a manufacturing method thereof.

As a result of intensive studies to achieve the above object, a phase change optical information recording medium and a method for producing the same were found. That is, the above-described problems are solved by the following inventions (1) to (20).
(1) On a substrate having a concentric or spiral guide groove, at least a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are sequentially formed. In a phase-change optical information recording medium that causes change and records and / or rewrites information, the reflective layer is made of Ag or a material containing Ag as a main component, and the upper protective layer is mainly made of an oxide. A phase change optical information recording medium comprising a material containing nitride or carbide.
(2) The phase change light according to (1), wherein the oxide as a main component of the upper protective layer is an oxide of an element having an element-oxygen bond energy of 90 kJ / mol or less. Information recording medium.
(3) The phase change optical information recording medium according to (2), wherein the oxide is any one of ZnO, In ₂ O ₃ , and TeO ₂ .
(4) The phase change optical information recording medium according to any one of (1) to (3), wherein the content of the oxide as the main component of the upper protective layer is 50 mol% or more.
(5) At least a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are sequentially formed on a substrate having concentric or spiral guide grooves, and the recording layer is irradiated with semiconductor laser light. In a phase change optical information recording medium that causes change and records and / or rewrites information, the reflective layer is made of Ag or a material containing Ag as a main component, and the upper protective layer is made of two or more kinds of oxides A phase change type optical information recording medium comprising a material containing as a main component a nitride or a carbide.
(6) Two or more kinds of oxides which are main components of the upper protective layer are oxides of elements having an element-oxygen bond energy of 90 kJ / mol or less. Phase change type optical information recording medium.
(7) The phase change type according to (6), wherein the two or more kinds of oxides which are the main components of the upper protective layer are oxides selected from ZnO, In ₂ O ₃ and TeO ₂ Optical information recording medium.
(8) The phase change type light as described in any one of (5) to (7), wherein the total content of two or more kinds of oxides as a main component of the upper protective layer is 50 mol% or more Information recording medium.
(9) The nitride constituting the upper protective layer is a nitride of an element having an element-nitrogen bond energy of 100 kJ / mol or more, according to any one of (1) to (8), Phase change type optical information recording medium.
(10) The phase change optical information recording medium according to (9), wherein the nitride is any one of Si ₃ N ₄ , TiN, and ZrN.

(11) The phase according to any one of (1) to (8), wherein the carbide constituting the upper protective layer is a carbide of an element having an element-carbon bond energy of 100 kJ / mol or more. Changeable optical information recording medium.
(12) The phase change optical information recording medium according to (11), wherein the carbide is any one of SiC, TiC, and ZrC.
(13) The defect rate after being left for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is less than 1.0 × 10 ⁻⁴ (1) to (12) The phase change optical information recording medium according to any one of the above.
(14) Any one of (1) to (13), wherein the increase ratio of the defect rate after being allowed to stand for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is 3 times or less A phase change optical information recording medium according to claim 1.
(15) The increase ratio of defects in the reflective layer made of Ag or a material containing Ag as a main component after being left for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is 3 times or less. The phase change optical information recording medium according to any one of (1) to (14), wherein:
(16) The increase ratio of the data reproduction error after being left for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is 3 times or less. Any one of the phase change type optical information recording media.
(17) The phase according to any one of (1) to (16), wherein the information stored in the optical information recording medium includes information indicating that the maximum recording linear velocity is 12 m / s or more. Changeable optical information recording medium.
(18) The phase change optical information recording medium according to any one of (1) to (17), wherein the thickness of the upper protective layer is in the range of 5 to 40 nm.
(19) The phase according to any one of (1) to (17), wherein the upper protective layer is formed by a sputtering method using a target having the same material ratio as the material constituting the upper protective layer. A method of manufacturing a variable optical information recording medium.
(20) The method for producing a phase change optical information recording medium as described in (19), wherein the sputtering rate is in the range of 1 to 6.25 nm / sec.

Hereinafter, the present invention will be described in detail.
An example of the layer structure of the phase change optical information recording medium of the present invention is shown in FIG.
In the case of a rewritable phase change type optical information recording medium, basically, a lower protective layer 2, a recording layer 3 made of a phase change material, an upper protective layer 4, and a reflective layer 5 are formed on a transparent substrate 1 having guide grooves. The overcoat layer 6 is provided, but a print layer 7 may be provided on the overcoat layer, and a hard coat layer 8 may be provided on the mirror surface side of the substrate.
Further, a structure in which the above-described single plate disk and a transparent substrate or another similar single plate disk are bonded together through an adhesive layer 9 may be employed. Further, the single layer disc may be bonded without forming a print layer, and the print layer 7 ′ may be formed on the opposite side after the bonding.

  The material of the substrate is usually one of glass, ceramics, and resin, and the 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, and urethane resin. Polycarbonate resins and acrylic resins that are excellent in terms of moldability, optical characteristics, and cost are preferred.

  The guide groove formed on the substrate may be wobbled (wobbled), and the preformat information may be encoded by utilizing the modulation of the walling. In particular, the phase modulation wobbling encoding method used in DVD + RW is described in detail in Japanese Patent Laid-Open No. 10-69646, etc., for detailed explanation. Since it is not necessary to form a special ROM pit as in the method, it is excellent in productivity and suitable. In addition, the use of a high frequency wobbling frequency around 820 MHz as used in DVD + RW is more preferable because the accuracy of the address position can be increased. At this time, as the preformat information, the type of the recording medium, the name of the recording medium manufacturer, the recording conditions for the recording medium, and the like are input. In particular, information on the recordable linear velocity range, information on the optimum laser beam pulse pattern at the time of recording at each linear velocity, optimum recording power, test conditions for deriving optimum recording power, etc. Since the information about the recording condition is useful for recording with good characteristics, it is desirable that the information is encoded as preformat information.

As a material of a phase change recording layer used for a rewritable phase change optical information recording medium, Sb and Te that cause a phase change between a crystal and an amorphous phase and can take a stabilized or metastable state, respectively. The phase change type recording material to be included is suitable because the recording (amorphization) sensitivity / speed, the erasure (crystallization) sensitivity / speed, and the erasure ratio are good. By adding elements such as Ga, Ge, Ag, In, Bi, C, N, O, Si, and S to the SbTe material, recording / erasing sensitivity, signal characteristics, reliability, and the like can be improved. .
Therefore, the composition ratio of the elements and materials to be added is adjusted according to the target recording linear velocity and linear velocity region to control the optimum recording linear velocity, and at the same time, the reproduction stability of the recorded signal and the life of the signal (reliability) It is desirable to ensure

The phase change optical information recording medium of the present invention contains Ag and / or Ge, Ga and / or In, Sb, and Te as constituent elements as a recording layer material that can satisfy these characteristics comprehensively. When the composition formula is (Ag and / or Ge) α (Ga and / or In) βSbγTeδ (α, β, γ, and δ are atomic%, α + β + γ + δ = 100), a material that satisfies the following relationship: The signal reproduction stability and the signal life are excellent, which is preferable.
0 <α ≦ 6
2 ≦ β ≦ 10
60 ≦ γ ≦ 85
15 ≦ δ ≦ 27
The film thickness of the phase change recording layer is preferably 5 to 40 nm. Furthermore, considering initial characteristics such as jitter, overwrite characteristics, and mass production efficiency, the thickness is preferably 10 to 25 nm. If it is thinner than 5 nm, the light absorption ability is remarkably lowered, and the role as a recording layer cannot be achieved. On the other hand, if it is thicker than 40 nm, uniform phase change is difficult to occur at high speed.
Such a phase change recording layer can be formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition, and the like. Among these, the sputtering method is preferable because it is excellent in mass productivity and film quality.

A protective layer is formed on the lower and upper layers of the phase change recording layer, and a reflective layer is further formed on the upper layer.
As the reflective layer, a metal material such as Al, Au, Ag, Cu, Ta, Ti, W or an alloy containing these elements is generally used. In addition, in order to improve the corrosion resistance and the thermal conductivity, elements such as Cr, Ti, Si, Cu, Ag, Pd, and Ta may be added to the above materials. Such a reflective layer 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, Ag-based and Au-based materials having higher thermal conductivity than other metals are preferable because they can be cooled more quickly after the temperature of the recording layer is raised and are suitable for high-speed recording. In particular, phase-change optical information recording that requires recording in a high linear velocity region, such as a CD-ROM equivalent to 10 × speed (12 m / s) or a DVD-ROM equivalent to 4 × speed (14 m / s) or more. Suitable for the medium. Au is expensive, and considering production cost, it can be said that Ag or an Ag-based alloy containing Ag as a main component is more preferable.

However, when an Ag-based material is used, even if there is no problem in corrosion resistance, the flow of Ag cannot be suppressed by the adjacent upper protective layer or overcoat layer due to the fluidity of Ag. If the optical information recording medium is left in a high-humidity environment or the like, film defects may occur in the Ag-based alloy reflective layer containing Ag or Ag as a main component. In order to use the optical information recording medium without causing a reproduction error even after being left under a high temperature and high humidity condition, it is desirable that the defect rate is suppressed to less than 1.0 × 10 ⁻⁴ .
In addition, if the defect rate and the increase rate of the reproduction error are high under high temperature and high humidity conditions, there is a concern that a problem may occur when the optical information recording medium is used without causing a reproduction error after long-term storage. For this reason, it is better that the defect rate increase ratio and the reproduction error increase ratio are lower. However, it is desirable that the defect rate increase ratio and the reproduction error increase ratio do not exceed three times even when left at a temperature of 80 ° C. and a relative humidity of 85% RH for 300 hours.
The thickness of the reflective layer made of the metal or alloy is 50 to 200 nm, preferably 70 to 160 nm. In addition, the metal or alloy layer can be multi-layered. The film thickness of each layer in the case of multilayering is required to be at least 10 nm, and the total film thickness of the multilayered film is preferably 50 to 160 nm.

As a material for the protective layer, generally, a nitride such as Si ₃ N ₄ , AlN, TiN, BN, or ZrN; a sulfide such as ZnS, In ₂ S ₃ , or TaS ₄ ; or a mixture thereof, or the nitride Oxides such as SiO, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , TeO ₂ , In ₂ O ₃ , MgO, ZrO ₂ ; SiC, TaC, BC, WC, TiC And carbides such as ZrC; a mixture with diamond-like carbon, and may contain impurities as necessary. Further, not a single layer but a structure in which two or more layers are stacked may be employed. However, the melting point of the protective layer needs to be higher than that of the phase change recording layer.
Such a protective layer 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 preferable because it is excellent in mass productivity and film quality.
The film thickness of the protective layer greatly affects the reflectivity, modulation degree, and recording sensitivity. In order to satisfy these characteristics, the thickness of the lower protective layer needs to be 30 to 200 nm. In order to obtain better signal characteristics, the thickness is preferably 40 to 100 nm.

In the phase change optical information recording medium of the present invention, a material containing an oxide as a main component and containing nitride or carbide is used for the upper protective layer. The reason why the oxide is a main component is to ensure adhesion with a reflective layer made of Ag or an Ag-based material containing Ag as a main component. In general, an oxide is more excellent in adhesion to a reflective layer of an Ag-based material than a material having high hardness such as a nitride such as Si ₃ N ₄ and AlN, and a carbide such as SiC and ZrC. . The oxide used here may be a single compound or a mixture of two or more kinds of oxides as a mixture or compound, but in order to ensure adhesion, the oxides are added together. It is necessary to contain 50 mol% or more. More preferably, it is desirable to contain 70 mol% or more. When the content of nitride or carbide increases, the adhesion with the reflective layer composed of Ag or Ag-based material containing Ag as a main component decreases, and the film is peeled off in a high temperature environment or a high humidity environment. May occur. At this time, the sulfide is not desirable as a material included in the upper protective layer because Ag corrosion occurs as described above.

However, when an oxide is used, there is a problem that a film formation rate at the time of sputtering is lower than that of nitride or carbide, and it takes a long time to form a film. If this film formation time is long, the production tact time is slowed, the production efficiency is lowered, and the cost is increased. Further, if the film formation time is too long, the substrate is deformed due to the temperature rise during the film formation. Therefore, as the oxide, it is preferable to use a material that is easily broken and has a relatively high sputtering rate, such as an oxide of an element having a low bond energy between element and oxygen. Preferably, a material having a binding energy of 90 kJ / mol or less is used. Examples of such a material include ZnO (65 kJ / mol), In ₂ O ₃ (77 kJ / mol), TeO ₂ (90 kJ / mol), and the like. There is no particular lower limit as long as the binding energy is low.

This oxide is stable as a main component and is the main component, such as a nitride of an element having a high element-nitrogen bond energy or a carbide of an element having a high element-carbon bond energy. By adding a material that is difficult to form a compound compatible with the oxide, a mixture of the oxide and the nitride or carbide is formed. By using such a mixture, the thermal conductivity can be significantly lowered. Since the nitride or carbide to be added is more stable and it is difficult to form a compound compatible with the oxide as the main material, the nitride of an element having a higher bond energy between element-nitrogen or element-carbon Or it is more preferable that it is a carbide | carbonized_material. In the case of a nitride or carbide having a low bond energy between element-nitrogen or element-carbon, the bond easily breaks and becomes compatible with the mixed oxide. Make a compound. In this case, since it is in a state like one compound, the thermal conductivity is relatively higher than the case where two or more compounds are mixed without being compatible, and there is a problem that the recording sensitivity is deteriorated. Arise. Therefore, at least a nitride or a carbide having a higher bond energy between element-nitrogen or element-carbon than the mixed oxide is required.
Preferably, a material having a binding energy of 100 kJ / mol or more is used. Such materials include Si ₃ N ₄ (105 kJ / mol), TiN (114 kJ / mol), ZrN (135 kJ / mol), SiC (108 kJ / mol), TiC (101 kJ / mol), ZrC (134 kJ / mol). ) And the like.

Also for the upper protective layer, a sputtering method is preferable as a method for forming a thin film because it is excellent in mass productivity, film quality, and the like. In particular, when forming a layer made of a material in which several compounds are mixed as in the present invention, a metal target or a metal carbide target is used, and sputtering is performed in an atmosphere into which oxygen gas or nitrogen gas is introduced. Thus, a protective layer is formed rather than forming a film by a so-called reactive sputtering method to obtain a metal oxide or nitride, or a mixture of metal carbide and oxide, or a mixture of carbide and nitride. It is preferable to form a film by sputtering using a target having the same material ratio as the material because a protective layer having a desired material ratio can be formed more stably.
The film thickness of the upper protective layer is 5 to 40 nm, preferably 10 to 25 nm. If the thickness is less than 5 nm, the function as a heat-resistant protective layer is not achieved, and the recording sensitivity is lowered. On the other hand, if it is thicker than 40 nm, interfacial delamination tends to occur, and the repeated recording performance also deteriorates.
In addition, if the film formation time is long during sputtering, problems of production cost and substrate deformation occur as described above. On the other hand, if the film formation time is too short, it becomes difficult to control the film thickness, resulting in variations in film thickness between individuals. Since it tends to occur, it becomes difficult to perform stable production. Therefore, the film formation time is preferably 2 to 15 seconds, but more preferably 4 to 10 seconds. Accordingly, the sputtering rate is preferably 0.33 to 20 nm / sec, but more preferably 1 to 6.25 nm / sec.

An overcoat layer is formed on the reflective layer to prevent corrosion. As the overcoat layer, an ultraviolet curable resin produced by spin coating is generally used. The thickness is suitably 3 to 15 μm. If the thickness is less than 3 μm, an increase in errors 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 disk.
As the hard coat layer, an ultraviolet curable resin produced by spin coating is generally used. The thickness is suitably 2 to 6 μm. If it is thinner than 2 μm, sufficient scratch resistance cannot be obtained. If it is thicker than 6 μm, the internal stress increases, which greatly affects the mechanical properties of the disk. The hardness must be H or higher, which is a pencil hardness that does not cause large scratches even when rubbed with a cloth. If necessary, it is also effective to mix a conductive material to prevent electrification and prevent adhesion of dust and the like.
The printed layer is used for the purpose of ensuring scratch resistance, label printing such as a brand name, and forming an ink receiving layer for an ink jet printer, and an ultraviolet curable resin is generally formed by a screen printing method. The thickness is suitably 3 to 50 μm. If it is thinner than 3 μm, unevenness will occur during layer formation. If it is thicker than 50 μm, the internal stress increases, which greatly affects the mechanical properties of the disk.

As the adhesive layer, an adhesive such as an ultraviolet curable resin, a hot melt adhesive, or a silicone resin can be used. The material of such an adhesive layer is applied on the overcoat layer or the print layer by a method such as spin coating, roll coating, or screen printing, depending on the material, and subjected to treatment such as ultraviolet irradiation, heating, and pressurization. Line up and paste the disc on the opposite side. The disk on the opposite surface may be a single-plate disk similar to the above-described layers or a transparent substrate alone, and the adhesive layer material may or may not be applied to the bonding surface of the disk on the opposite surface. Moreover, as an adhesive layer, an adhesive sheet can also be used.
The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 100 μm in view of the effects of material applicability, curability, and disk mechanical properties. The range of the adhesive surface is not particularly limited, but when applied to an optical information recording medium capable of DVD and / or CD compatibility, the position of the inner peripheral edge is 15 to 40 mm in diameter to ensure adhesive strength. The diameter is preferably 15 to 30 mm.

  According to the present invention, by providing an upper protective layer composed of a material obtained by adding nitride or carbide to an oxide, problems relating to corrosion when Ag or a material mainly composed of Ag is used as a reflective layer. Thus, it is possible to provide a phase change optical information recording medium having excellent medium characteristics that can cope with high linear velocity and high sensitivity, and excellent storage stability.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited by these Examples.

<Example 1>
A polycarbonate substrate having a wobbling guide groove, diameter 120 mm, thickness 0.6 mm is manufactured by injection molding, and a lower protective layer, a phase change recording layer, an upper protective layer, and a reflective layer are sequentially sputtered on this substrate. Were laminated. (ZnS) ₈₀ (SiO ₂ ) _{20 for} the lower protective layer, phase change recording material Ag ₁ Ge ₃ In ₄ Sb ₇₂ Te _{20 for} the recording layer, and (ZnO) ₇₀ (Si ₃ N ₄ ) _{30 for the} upper protective layer. Sputtering was performed using an Ag target for the reflective layer, and the film thicknesses were set to 60 nm, 15 nm, 15 nm, and 140 nm in this order from the substrate side. At this time, the film formation time of the upper protective layer was 8.0 sec, and the sputtering rate was 15/8 = 1.9 nm / sec.
Further, an overcoat layer of an ultraviolet curable resin material (SD-318, manufactured by Dainippon Ink & Chemicals, Inc.) having an average film thickness of 6 μm is formed on the reflective layer by a spin coating method, and has a DVD-ROM reproduction compatibility. A single disc of a changeable optical information recording medium was produced.
Next, on the overcoat layer, a 0.6 mm-thickness is formed through an adhesive layer formed of an ultraviolet curable resin material (KAYARAD DVD-003 manufactured by Nippon Kayaku Co., Ltd.) having an average film thickness of 50 μm formed by spin coating. A polycarbonate substrate was bonded to obtain a bonded disc of 1.2 mm.
Then, using an initialization apparatus having a large aperture LD (beam diameter 75 × 1 μm), CLV (Constant Linear Velocity), linear speed 11 m / s, feed amount 36 μm / rotation, initialization laser power 1300 mW Under the conditions, the entire recording layer was crystallized.

The optical information recording device (Ricoh Co., Ltd. MP5240A) for DVD-ROM compatible optical discs obtained in this way was used at a linear velocity equivalent to four times the DVD-ROM (14 m / s). The content data was recorded.
As a result of evaluating the characteristics of this recording unit using a DVD reproduction evaluation apparatus (CATS SA300 manufactured by Audio Development), as shown in Table 1, the jitter (data-to-clock jitter) characteristic is 7.0% (DVD -ROM standard: 8% or less), modulation degree is 0.67 (DVD-ROM standard: 0.6 or more), and reflectance is 20.4% (two-layer DVD-ROM standard: 18-30%). The average value of PI error was 2.3 and the maximum value was 8 (DVD-ROM standard: 280 or less), and recording was possible with good characteristics.
With respect to this optical disk, content data recorded by a DVD-ROM playback device (MP9120A manufactured by Ricoh Co., Ltd.) was read, and the data was successfully read without causing a reading error.
Further, when the optical disk manufactured under the same conditions was measured with a defect rate measuring device, the defect rate was 4.5 × 10 ⁻⁵ , and there was light transmission in the visual inspection of the transmitted light with white light. There were six spots on the entire disk surface. The defect rate is described in detail in Japanese Patent Laid-Open No. 2002-260224. The defect rate is defined as the existence ratio of the section outside the predetermined threshold with respect to the average reflected light intensity. In the examples and comparative examples of the invention, the measurement is performed with a threshold value of ± 20%.
When these optical discs were stored in a high-temperature and high-humidity environment at 80 ° C. and 85% RH for 300 hours, they were visually observed. As a result, film floating, peeling of the film, and black spots considered to be corrosion of the Ag reflection layer were observed. Was not. In the visual inspection of the transmitted light by the white light, the number of spots where light was transmitted was 14 on the entire disk surface, and the defect rate was 5.3 × 10 ⁻⁵ .
Further, the result of the characteristic evaluation again as before storage is as shown in Table 1. The jitter (data to clock jitter) characteristic is 7.5%, the modulation factor is 0.66, and the reflection is performed. The rate was 18.9%, the average value of PI error was 2.5, and the maximum value was 10, and there was no significant deterioration, and good characteristics could be maintained. Further, reading of recorded content data by a DVD-ROM playback device (MP9120A manufactured by Ricoh Co., Ltd.) succeeded in reading the data without causing a reading error.

<Example 2>
A polycarbonate substrate having a wobbling guide groove, diameter 120 mm, thickness 0.6 mm is manufactured by injection molding, and a lower protective layer, a phase change recording layer, an upper protective layer, and a reflective layer are sequentially sputtered on this substrate. Were laminated. (ZnS) ₈₀ (SiO ₂ ) _{20 for} the lower protective layer, phase change recording material Ag ₁ Ge ₂ In ₅ Sb ₆₇ Te _{25 for} the recording layer, (ZnO) ₇₅ (ZrC) _{25 for} the upper protective layer, reflective layer Was sputtered using a target of Ag ₉₈ Pt ₁ Pd ₁ , and the film thicknesses were set to 80 nm, 20 nm, 20 nm, and 140 nm in this order from the substrate side. At this time, the film formation time of the upper protective layer was 9.5 sec, and the sputtering rate was 20 / 9.5 = 2.1 nm / sec.
Further, an overcoat layer of an ultraviolet curable resin material (SD-318, manufactured by Dainippon Ink & Chemicals, Inc.) having an average film thickness of 6 μm is formed on the reflective layer by a spin coating method, and has a DVD-ROM reproduction compatibility. A single disc of a changeable optical information recording medium was produced.
Next, on the overcoat layer, a 0.6 mm-thickness is formed through an adhesive layer formed of an ultraviolet curable resin material (KAYARAD DVD-003 manufactured by Nippon Kayaku Co., Ltd.) having an average film thickness of 50 μm formed by spin coating. A polycarbonate substrate was bonded to obtain a bonded disc of 1.2 mm.
Thereafter, using an initialization device having a large aperture LD (beam diameter 100 × 1 μm), CLV (Constant Linear Velocity) rotation control, linear velocity 3 m / s, feed amount 50 μm / rotation, initialization laser power 750 The recording layer was crystallized on the entire surface under the condition of ˜800 mW.

The DVD-ROM compatible optical disk thus obtained is equivalent to 2.4-times DVD-ROM (8.5 m / s) by a DVD-compatible optical information recording device (MP5240A manufactured by Ricoh Co., Ltd.). Content data was recorded at a linear velocity of.
As a result of evaluating the characteristics of this recording unit with a DVD reproduction evaluation apparatus (CATS SA300 manufactured by Audio Development), as shown in Table 2, the jitter (data to clock jitter) characteristics are 6.8%, The degree of modulation was 0.65, the reflectance was 21.2%, the average value of PI errors was 1.6, and the maximum value was 7, and recording was possible with good characteristics. Further, when the content data recorded on this optical information recording medium was read by a DVD-ROM reproducing device (MP9120A manufactured by Ricoh Co., Ltd.), the data was successfully read without causing a reading error.
Further, when the optical disk manufactured under the same conditions was measured with a defect rate measuring device, the defect rate was 3.9 × 10 ⁻⁵ , and there was light transmission in visual inspection of transmitted light with white light. There were 15 spots on the entire disk surface.
When these optical discs were stored in a high-temperature and high-humidity environment at 80 ° C. and 85% RH for 300 hours, they were visually observed. As a result, film floating, peeling of the film, and black spots considered to be corrosion of the Ag reflection layer were observed. Was not. In the visual inspection of the transmitted light by the white light, the number of spots where light was transmitted was 26 on the entire surface of the disk, and the defect rate was 4.7 × 10 ⁻⁵ .
Furthermore, the result of the characteristic evaluation again as before storage is as shown in Table 2. The jitter (data to clock jitter) characteristic is 7.1%, the modulation factor is 0.65, the reflection The rate was 19.4%, the average value of PI error was 1.8, the maximum value was 8, and there was no significant deterioration, and good characteristics could be maintained. Further, reading of recorded content data by a DVD-ROM playback device (MP9120A manufactured by Ricoh Co., Ltd.) succeeded in reading the data without causing a reading error.

<Example 3>
A polycarbonate substrate having a wobbling guide groove and having a diameter of 120 mm and a thickness of 1.2 mm is manufactured by injection molding. On this substrate, a lower protective layer, a phase change recording layer, an upper protective layer, and a reflective layer are sequentially sputtered. Were laminated. (ZnS) ₈₀ (SiO ₂ ) _{20 for} the lower protective layer, phase change recording material Ag ₂ In ₈ Sb ₆₅ Te _{25 for} the recording layer, and (In ₂ O ₃ ) ₄₀ (TeO ₂ ) ₄₀ (for the upper protective layer. (SiC) ₂₀ , and a target of Ag ₉₈ Cu ₁ Pd ₁ was used for the reflective layer, and the film thickness was 90 nm, 20 nm, 20 nm, and 140 nm in this order from the substrate side. At this time, the film formation time of the upper protective layer was 7.1 sec, and the sputtering rate was 20 / 7.1 = 2.8 nm / sec.
Furthermore, an overcoat layer of an ultraviolet curable resin material (Diabeam MH-7617N manufactured by Mitsubishi Rayon Co., Ltd.) having an average film thickness of 6 μm is formed on the reflective layer by a spin coating method, and a phase change having CD-ROM reproduction compatibility. Type optical information recording medium (CD-RW) disc was obtained.
Then, using an initialization apparatus having a large aperture LD (beam diameter 100 × 1 μm), linear speed 5 m / s, feed amount 50 μm / rotation, initialization laser power 750 by CLV (Constant Linear Velocity) rotation control. The recording layer was crystallized on the entire surface under the condition of ˜800 mW.

For the CD-ROM compatible optical disk obtained in this way, a CD-compatible optical information recording apparatus (MP7120A manufactured by Ricoh Co., Ltd.) is used at a linear velocity equivalent to 10 times the CD-ROM (12 m / s). The content data was recorded.
As a result of evaluating the characteristics of this recording unit using a CD reproduction evaluation apparatus (CD CATS SA-3 manufactured by Audio Development), as shown in Table 3, the 3T jitter characteristic is 30 ns (CD-RW standard: 35 ns or less). The degree of modulation is 0.64 (CD-RW standard: 0.55 or more), the reflectance is 18.5% (CD-RW standard: 15-25%), and the average value of C1 error (BLER) is 3. 2. The maximum value was 9 (CD-RW standard: 220 or less), and recording was possible with good characteristics. Further, when the content data recorded on this optical disc was read by a device (MP9120A manufactured by Ricoh Co., Ltd.) that supports playback of a CD-ROM, the data was successfully read without causing a reading error. .
Further, when the optical disk manufactured under the same conditions was measured with a defect rate measuring device, the defect rate was 8.2 × 10 ⁻⁶ , and light was transmitted in the visual inspection of the transmitted light with white light. There were three spots on the entire disk surface.
When these optical discs were stored in a high-temperature and high-humidity environment at 80 ° C. and 85% RH for 300 hours, they were visually observed. As a result, film floating, peeling of the film, and black spots considered to be corrosion of the Ag reflection layer were observed. Was not. In the visual inspection of the transmitted light with white light, the number of spots where light was transmitted was 6 on the entire disk surface, and the defect rate was 9.4 × 10 ⁻⁶ .
Further, the result of the characteristic evaluation again as before storage is as shown in Table 3. The 3T jitter characteristic is 35 ns, the modulation factor is 0.63, the reflectance is 18.0%, the C1 error (BLER). The average value of) was 3.8, the maximum value was 12, and there was no significant deterioration and good characteristics could be maintained. Further, reading of recorded content data by an apparatus (MP9120A manufactured by Ricoh Co., Ltd.) compatible with CD-ROM playback has succeeded in reading the data without causing a reading error.

<Example 4>
A polycarbonate substrate with a guide groove having a thickness of 1.1 mm was produced by injection molding, and a reflective layer, an upper protective layer, a phase change recording layer, and a lower protective layer were sequentially laminated on the substrate by a sputtering method. Ag for the reflective layer, (ZnO) ₇₀ (TiN) _{30 for} the upper protective layer, phase change recording material Ag _0.5 Ge ₄ In _0.5 Sb ₇₅ Te _{20 for} the recording layer, and (ZnS) for the lower protective layer. ) Sputtering was performed using a target of ₇₀ (SiO ₂ ) ₃₀ , and the film thicknesses were set to 140 nm, 10 nm, 10 nm, and 120 nm in order from the substrate side. At this time, the film formation time of the upper protective layer was 6.7 sec, and the sputtering rate was 10 / 6.7 = 1.5 nm / sec.
Further, after an overcoat layer of an ultraviolet curable resin material (Diabeam MH-7617N manufactured by Mitsubishi Rayon Co., Ltd.) having an average of 5 μm is formed on the reflective layer by spin coating, a 0.1 mm cover film is adhered. A phase change optical information recording medium (optical disk) having a thickness of 2 mm was obtained.
Thereafter, using an initialization apparatus having a large aperture LD (beam diameter 75 × 1 μm), the recording layer is controlled by CLV rotation control under the conditions of a linear velocity of 3 m / s, a feed amount of 36 μm / rotation, and an initialization laser power of 600 to 650 mW. Was crystallized entirely.

About the phase change type optical disk thus obtained, a recording / reproduction evaluation apparatus (DDU-1000 manufactured by Pulstec Industrial Co., Ltd .; pickup laser light wavelength λ = 405 nm, condensing lens NA = 0.85) is used. The characteristics were evaluated.
First, the reflectance was evaluated. A conversion value when using a pure Ag sputtered film deposited on glass with a film thickness of 1400 mm and a 0.1 mm cover substrate as the evaluation disk as a reference for comparison of reflectance of 82.6% is 19 The reflectance was 8%.
Next, marks were recorded on this optical disk at a density of 0.130 μm / bit, and repeated recording / rewriting evaluation was performed.
The evaluation conditions were as follows: the clock frequency was 66 MHz, the recording linear velocity was 5.7 m / s, and the recording strategy was TSFP = 1.77 ns, TEFP = 2 ns, TMP = 0.230 ns, and TLE = 2.2 ns.
As a result of the evaluation, the repetitive jitter characteristics using the equalizer were stable up to 1000 times with an initial jitter of 5.9% and then about 7.8%. The modulation was 62% in the initial stage and 60% after 1000 recordings.
When this optical disc was visually inspected with white light, 22 spots were found on the entire surface of the disc.
When this optical disk was stored in an environment of high temperature and high humidity of 80 ° C. and 85% RH for 300 hours and jitter was measured again, each change was 1% or less, and this was not a problem characteristic. Further, as a result of visual observation, there was no observation of black spots or the like that seemed to be film floating / peeling or corrosion of the Ag reflection layer. In the visual inspection of the transmitted light with white light, there were 84 spots with light transmission over the entire surface of the disk.

<Comparative Example 1>
A polycarbonate substrate having a wobbling guide groove, diameter 120 mm, thickness 0.6 mm is manufactured by injection molding, and a lower protective layer, a phase change recording layer, an upper protective layer, and a reflective layer are sequentially sputtered on this substrate. Were laminated. (ZnS) ₈₀ (SiO ₂ ) _{20 for} the lower protective layer, phase change recording material Ag ₁ Ge ₃ In ₄ Sb ₇₂ Te _{20 for} the recording layer, (ZnS) ₈₀ (SiO ₂ ) _{20 for} the upper protective layer, reflection Sputtering was performed using an Ag target for the layer, and the film thicknesses were set to 60 nm, 15 nm, 13 nm, and 140 nm in this order from the substrate side. At this time, the film formation time of the upper protective layer was 4.3 sec, and the sputtering rate was 13 / 4.3 = 3.0 nm / sec. The bond energy between Zn—S in ZnS is 49 kJ / mol, and the bond energy between Si—O in SiO ₂ is 191 kJ / mol.
Further, an overcoat layer of an ultraviolet curable resin material (SD-318 manufactured by Dainippon Ink & Chemicals, Inc.) having an average of 6 μm is formed on the reflective layer by a spin coat method, and is a phase change type having DVD-ROM reproduction compatibility. A single disc of an optical information recording medium was produced.
Next, on the overcoat layer, a 0.6 mm-thickness is formed through an adhesive layer formed of an ultraviolet curable resin material (KAYARAD DVD-003 manufactured by Nippon Kayaku Co., Ltd.) having an average film thickness of 50 μm formed by spin coating. A polycarbonate substrate was bonded to obtain a bonded disc of 1.2 mm.
Then, using an initialization apparatus having a large aperture LD (beam diameter 75 × 1 μm), CLV (Constant Linear Velocity), linear speed 11 m / s, feed amount 36 μm / rotation, initialization laser power 1300 mW Under the conditions, the entire recording layer was crystallized.

The optical information recording device (Ricoh Co., Ltd. MP5240A) for DVD-ROM compatible optical discs obtained in this way was used at a linear velocity equivalent to four times the DVD-ROM (14 m / s). The content data was recorded.
As a result of evaluating the characteristics of this recording unit with a DVD reproduction evaluation apparatus (CATS SA300 manufactured by Audio Development), as shown in Table 4, the jitter (data to clock jitter) characteristic is 7.2%, The degree of modulation was 0.69, the reflectance was 20.1%, the average value of PI errors was 3.1, the maximum value was 11, and recording was possible with good characteristics. Further, when the content data recorded on this optical disk was read by a DVD-ROM playback device (MP9120A manufactured by Ricoh Co., Ltd.), the data was successfully read without causing a reading error.
Further, when the optical disk manufactured under the same conditions was measured with a defect rate measuring device, the defect rate was 1.0 × 10 ⁻⁵ , and there was light transmission in the visual inspection of the transmitted light with white light. There were seven spots on the entire disk surface.
When these optical disks were stored in a high-temperature and high-humidity environment of 80 ° C. and 85% RH for 300 hours and then visually observed, no film floating or film peeling was observed, but corrosion of the Ag reflection layer is considered. Black spots were generated. As for the visual inspection of the transmitted light with white light, there were 8 spots where the light was transmitted on the entire surface of the disk, but the defect rate was 2.7 × 10 ⁻⁴ .
Furthermore, the result of the characteristic evaluation again as before storage is as shown in Table 4. The jitter (data-to-clock jitter) characteristic is 8.6%, the modulation factor is 0.55, the reflection The rate was 18.2%, the average PI error value was 124.7, and the maximum value was 346. The characteristics were greatly degraded. In addition, when reading the recorded content data by the DVD-ROM playback device (MP9120A manufactured by Ricoh Co., Ltd.), a reading error occurred and the data reading failed.

<Comparative Example 2>
A polycarbonate substrate having a wobbling guide groove, diameter 120 mm, thickness 0.6 mm is manufactured by injection molding, and a lower protective layer, a phase change recording layer, an upper protective layer, and a reflective layer are sequentially sputtered on this substrate. Were laminated. (ZnS) ₈₀ (SiO ₂ ) _{20 for} the lower protective layer, phase change recording material Ag ₁ Ge ₂ In ₅ Sb ₆₇ Te _{25 for} the recording layer, Si ₃ N _{4 for} the upper protective layer, and Ag _{98 for the} reflective layer. Sputtering was performed using a Pt ₁ Pd ₁ target, and the film thicknesses were set to 80 nm, 20 nm, 25 nm, and 140 nm in this order from the substrate side. At this time, the film formation time of the upper protective layer was 9.5 sec, and the sputtering rate was 25 / 9.5 = 2.6 nm / sec.
Further, an overcoat layer of an ultraviolet curable resin material (SD-318, manufactured by Dainippon Ink & Chemicals, Inc.) having an average film thickness of 6 μm is formed on the reflective layer by a spin coating method, and has a DVD-ROM reproduction compatibility. A single disc of a changeable optical information recording medium was produced.
Next, on the overcoat layer, a 0.6 mm-thickness is formed through an adhesive layer formed of an ultraviolet curable resin material (KAYARAD DVD-003 manufactured by Nippon Kayaku Co., Ltd.) having an average film thickness of 50 μm formed by spin coating. A polycarbonate substrate was bonded to obtain a bonded disc of 1.2 mm.
Thereafter, using an initialization device having a large aperture LD (beam diameter 100 × 1 μm), CLV (Constant Linear Velocity) rotation control, linear velocity 3 m / s, feed amount 50 μm / rotation, initialization laser power 750 The recording layer was crystallized on the entire surface under the condition of ˜800 mW.

The DVD-ROM compatible optical disk thus obtained is equivalent to 2.4-times DVD-ROM (8.5 m / s) by a DVD-compatible optical information recording device (MP5240A manufactured by Ricoh Co., Ltd.). Content data was recorded at a linear velocity of.
As a result of evaluating the characteristics of this recording unit using a DVD reproduction evaluation apparatus (CATS SA300 manufactured by Audio Development), as shown in Table 5, the jitter (data to clock jitter) characteristic is 7.4%, The degree of modulation was 0.63, the reflectance was 20.1%, the average value of PI error was 2.4, and the maximum value was 13, and recording was possible with good characteristics. Further, when the content data recorded on this optical disk was read by a DVD-ROM playback device (MP9120A manufactured by Ricoh Co., Ltd.), the data was successfully read without causing a reading error.
Further, when the optical disk manufactured under the same conditions was measured with a defect rate measuring device, the defect rate was 6.7 × 10 ⁻⁶ , and there was light transmission in the visual inspection of the transmitted light with white light. There were 13 spots on the entire disk surface.
When these optical disks were stored in a high-temperature and high-humidity environment at 80 ° C. and 85% RH for 300 hours and visually observed, no black spots or the like that seemed to corrode the Ag reflection layer were observed, but the film floated.・ Peeling of the film was observed. In the visual inspection of the transmitted light with white light, there were innumerable spots with light transmission, and measurement was impossible. The defect rate was 3.8 × 10 ⁻³ .
Furthermore, the result of the characteristic evaluation again as before storage is as shown in Table 5. The jitter (data to clock jitter) characteristic is 8.9%, the modulation factor is 0.60, the reflection The rate was 18.5%, the average PI error value was 220.4, and the maximum value was 563. The characteristics were greatly degraded. In addition, when reading the recorded content data by the DVD-ROM playback device (MP9120A manufactured by Ricoh Co., Ltd.), a reading error occurred and the data reading failed.

The figure which shows an example of the layer structure of the phase change type | mold optical information recording medium of this invention.

Claims (20)

  At least a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are sequentially formed on a substrate having concentric or spiral guide grooves, and a phase change occurs in the recording layer when irradiated with semiconductor laser light. In the phase change type optical information recording medium for recording and / or rewriting information, the reflective layer is made of Ag or a material containing Ag as a main component, and the upper protective layer is made of an oxide as a main component, nitride or A phase change optical information recording medium comprising a material containing carbide.   2. The phase change optical information recording medium according to claim 1, wherein the oxide as a main component of the upper protective layer is an oxide of an element having an element-oxygen bond energy of 90 kJ / mol or less. . _3. The phase change optical information recording medium according to claim 2, wherein the oxide is any one of ZnO, In ₂ O ₃ , and TeO ₂ .   The phase change optical information recording medium according to any one of claims 1 to 3, wherein the content of an oxide as a main component of the upper protective layer is 50 mol% or more.   At least a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are sequentially formed on a substrate having concentric or spiral guide grooves, and a phase change occurs in the recording layer when irradiated with semiconductor laser light. In the phase change type optical information recording medium for recording and / or rewriting information, the reflective layer is made of Ag or a material mainly composed of Ag, and the upper protective layer is composed mainly of two or more kinds of oxides. And a phase change optical information recording medium comprising a material containing nitride or carbide.   6. The phase change according to claim 5, wherein the two or more kinds of oxides as a main component of the upper protective layer are oxides of elements having an element-oxygen bond energy of 90 kJ / mol or less. Type optical information recording medium. 7. The phase change optical information recording according to claim 6, wherein the two or more kinds of oxides as a main component of the upper protective layer are oxides selected from ZnO, In ₂ O ₃ and TeO _2. Medium.   The phase change type optical information recording medium according to any one of claims 5 to 7, wherein a total content of two or more kinds of oxides as a main component of the upper protective layer is 50 mol% or more.   The phase change light according to any one of claims 1 to 8, wherein the nitride constituting the upper protective layer is a nitride of an element having an element-nitrogen bond energy of 100 kJ / mol or more. Information recording medium. The phase change optical information recording medium according to claim 9, wherein the nitride is any one of Si ₃ N ₄ , TiN, and ZrN.   9. The phase change optical information recording according to claim 1, wherein the carbide constituting the upper protective layer is a carbide of an element having an element-carbon bond energy of 100 kJ / mol or more. Medium.   12. The phase change optical information recording medium according to claim 11, wherein the carbide is any one of SiC, TiC, and ZrC. 13. The defect rate after leaving for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is less than 1.0 × 10 ^−4. Phase change type optical information recording medium.   14. The phase according to claim 1, wherein an increase ratio of the defect rate after being left for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is 3 times or less. Changeable optical information recording medium.   The increase ratio of defects of the reflective layer made of Ag or a material containing Ag as a main component after being left for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is 3 times or less. The phase change optical information recording medium according to claim 1.   16. The increase ratio of data reproduction error after being left for 300 hours under conditions of a temperature of 80 ± 2 ° C. and a relative humidity of 85 ± 5% is 3 times or less. Phase change type optical information recording medium.   17. The phase change optical information recording according to claim 1, wherein the information stored in the optical information recording medium includes information indicating that the maximum recording linear velocity is 12 m / s or more. Medium.   18. The phase change optical information recording medium according to claim 1, wherein the thickness of the upper protective layer is in the range of 5 to 40 nm.   18. The phase change optical information recording according to claim 1, wherein the upper protective layer is formed by a sputtering method using a target having the same material ratio as the material constituting the upper protective layer. A method for manufacturing a medium. The method for producing a phase change optical information recording medium according to claim 19, wherein the sputtering rate is in the range of 1 to 6.25 nm / sec.

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