JP2011065731A - Optical information recording medium and sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium including a recording layer with high durability, and a sputtering target useful for forming the recording layer. <P>SOLUTION: The optical information recording medium includes a recording layer on which data is recorded by irradiation with a laser beam, and a dielectric layer formed adjacent to the recording layer. The recording layer contains oxide of a metal (hereinafter referred to as X metal) where an absolute value of standard generation free energy of the oxide with respect to oxygen 1 mol is larger than that of Pd, and Pd oxide. The Pd oxide includes Pd monoxide and Pd dioxide, and a ratio of Pd atoms in the total amount of X metal atoms and Pd atoms contained in the recording layer is 4 to 85 atom%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical information recording medium and a sputtering target useful for forming a recording layer of the optical information recording medium.

  Optical information recording media (optical discs) are typified by optical discs such as CDs, DVDs, and BDs, and are roughly classified into three types according to recording and playback methods: read-only type, write-once type, and rewritable type. Of these, the write-once type optical disc recording method mainly includes a phase change method for changing the phase of the recording layer, an interlayer reaction method for reacting a plurality of recording layers, a method for decomposing a compound constituting the recording layer, and a hole in the recording layer. It is roughly classified into a drilling method in which recording marks such as pits are locally formed.

  In the phase change method, a material using a change in optical characteristics due to crystallization of the recording layer has been proposed as a material for the recording layer. For example, Patent Document 1 proposes a recording layer containing Te-OM (where M is at least one element selected from a metal element, a metalloid element, and a semiconductor element), and Patent Document 2 discloses a recording layer containing Sb and Te. Layers have been proposed.

  As the recording layer of the interlayer reaction type optical information recording medium, for example, in Patent Document 3, the first recording layer is made of an alloy containing In—O— (Ni, Mn, Mo), and the second recording layer is used. Has been proposed that is made of an alloy containing Se and / or Te element, O (oxygen), and one element selected from Ti, Pd, and Zr. In Patent Document 4, a first recording layer: a metal containing In as a main component, and a second recording layer: a metal other than an oxide or a nonmetal containing at least one element belonging to Group 5B or Group 6B is laminated. It has been proposed to record by reaction by heating or alloying.

  As a recording layer of a method for decomposing a compound constituting the recording layer, for example, Patent Document 5 shows a recording layer mainly composed of nitride, and recording can be performed by decomposing the nitride by heating. Materials to be performed and organic pigment materials are being studied.

  As the perforated recording layer, a recording layer made of a low melting point metal material has been studied. For example, Patent Document 6 proposes an alloy made of an alloy obtained by adding a 3B group, 4B group, or 5B group element to a Sn alloy. Patent Document 7 proposes a recording layer made of a Sn-based alloy containing Ni and / or Co in the range of 1 to 50 atomic%. Further, Patent Document 8 discloses a recording layer made of an In alloy containing 20 to 65 atomic percent of Co, and further containing an In alloy containing 19 atomic percent or less of one or more elements selected from Sn, Bi, Ge, and Si. It is shown.

JP 2005-135568 A JP 2003-331461 A JP 2003-326848 A Japanese Patent No. 3499724 International Publication No. 2003/101750 Pamphlet JP 2002-225433 A JP 2007-196683 A Japanese Patent No. 4110194

  The required characteristics required for optical information recording media are mainly that it has sufficient reflectivity for reproduction, recording with practical recording laser power (high recording sensitivity), and reproduction of recorded signals. And a sufficient signal amplitude (high modulation degree), high signal strength (high C / N ratio), and the like.

However, it is difficult for the recording material disclosed as the prior art to satisfy these required characteristics with the recording material alone. In the phase change method, the reflectance of the recording layer alone is low. In order to increase the recording layer, and to increase the degree of modulation, it is necessary to provide dielectric layers such as ZnS—SiO ₂ above and below the recording layer, so that the number of layers constituting the optical disk increases. In addition, since the interlayer reaction method also requires a plurality of recording layers, the number of layers constituting the optical disk increases. For this reason, there is a problem that the number of film layers increases and productivity decreases. On the other hand, the perforation method has a high reflectivity of the recording layer itself and can secure a large degree of modulation, so that the number of layers constituting the optical disk can be reduced, but in achieving higher recording sensitivity, Further study is needed. Further, durability of the recording layer (particularly durability against high temperature and high humidity) is also required.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical information recording medium excellent in durability of the recording layer (particularly, durability against high temperature and high humidity), and the recording layer. It is to provide a sputtering target useful for formation.

  The optical information recording medium according to the present invention is an optical information recording medium comprising a recording layer on which recording is performed by laser light irradiation, and a dielectric layer formed adjacent to the recording layer, The recording layer includes an oxide of a metal (hereinafter referred to as X metal) whose absolute value of the standard free energy of formation of oxide relative to 1 mol of oxygen is greater than Pd, and oxidized Pd. The oxidized Pd is oxidized Pd and oxidized. It is characterized in that it contains Pd and the ratio of Pd atoms to the total of X metal atoms and Pd atoms contained in the recording layer is 4 to 85 atomic%.

  The X metal contained in the recording layer is preferably at least one selected from the group consisting of Sn, Zn, Bi, Ge, Co, W, Cu and Al.

  The ratio of Pd dioxide to the total of Pd monoxide and Pd contained in the recording layer is preferably 5 to 70 mol%.

  The dielectric layer may be an oxide (more preferably selected from the group consisting of In, Zn, Sn, Al, Si, Ge, Ti, Ga, Ta, Nb, Hf, Zr, Cr, Bi and Mg. Oxides of the above elements), nitrides (more preferably nitrides of one or more elements selected from the group consisting of Si, Ge and Ti), sulfides (more preferably Zn sulfides), carbides (more Preferably, a carbide of one or more elements selected from the group consisting of Si, Ti and W), or a mixture thereof.

  The thickness of the dielectric layer is preferably 2 to 40 nm.

  The recording layer preferably has a thickness of 5 to 100 nm.

  The optical information recording medium of the present invention is suitable for an optical information recording medium of a recording system in which recording is performed by generating bubbles in the portion of the recording layer irradiated with laser light and changing the volume.

  Furthermore, the present invention provides a sputtering target for forming a recording layer of the optical information recording medium, comprising an oxide of X metal and Pd, and Pd atoms relative to the sum of X metal atoms and Pd atoms contained in the sputtering target. Also included is a sputtering target characterized in that the ratio of is 4 to 85 atomic%. The present invention also relates to another sputtering target for forming the recording layer, which is based on an X metal containing 4 to 85 atomic% of Pd in a ratio of Pd atoms to the total of X metal atoms and Pd atoms. Also included are sputtering targets characterized by being made of an alloy.

  In the sputtering target, the X metal is preferably at least one selected from the group consisting of Sn, Zn, Bi, Ge, Co, W, Cu, and Al.

  ADVANTAGE OF THE INVENTION According to this invention, the optical information recording medium (especially write-once type optical information recording medium) excellent in the durability of a recording layer can be provided. Moreover, according to the present invention, a sputtering target useful for forming the recording layer can be provided.

  The inventors of the present invention have intensively studied to realize an optical information recording medium that is superior in durability of the recording layer as compared with the conventional recording layer. As a result, the recording layer in the optical information recording medium is different from the conventional recording layer in that the oxide of the metal (X metal) whose absolute value of the standard free energy of formation of oxide relative to 1 mol of oxygen is greater than Pd, and oxidized Pd. And the oxidized Pd is a recording layer containing Pd monoxide and Pd dioxide, and when the recording layer is irradiated with laser, the oxidized Pd is heated by the laser irradiation and decomposes to release oxygen. In addition, it is possible to perform irreversible recording by generating bubbles in the portion irradiated with the laser, and this recording method can greatly increase the recording sensitivity as compared with the conventional method, and the dielectric layer It has been found that the durability of the recording layer can be remarkably enhanced if is formed adjacent to the recording layer.

  The recording method using the recording layer is different from the phase change method using the fact that the structure of the recording layer before the laser irradiation is amorphous and is amorphous after the laser irradiation. .

  The reason why the recording layer according to the present invention is excellent in recording sensitivity is that the transmittance is increased (that is, the reflectance is decreased) in the portion where bubbles are generated by laser irradiation compared to the portion where bubbles are not generated. Thus, it is considered that the degree of modulation could be increased.

  Further, by containing oxidized Pd as described above, the refractive index can be increased as compared with the case where oxidized Pd is not included, and a high reflectance can be obtained. Further, since the light absorption rate of the film can be increased, the energy of the laser for signal recording can be efficiently changed to heat, and as a result, the decomposition of the oxidized Pd can be performed with a practical recording laser power. Is promoted, and the recording sensitivity can be sufficiently improved.

  In order to fully express these effects, the ratio of Pd atoms to the total of metal atoms and Pd atoms whose absolute value of the standard free energy of formation of oxides relative to 1 mol of oxygen contained in the recording layer is larger than Pd (hereinafter referred to as “Pd atoms”). The “Pd amount” may be 4 atomic% or more. If the amount of Pd is less than 4 atomic%, the amount of released oxygen is not sufficient because the amount of oxidized Pd that decomposes during laser irradiation is small, resulting in fewer bubbles, resulting in a lower signal intensity. Further, since the light absorption rate of the recording layer is also reduced, the laser power required for recording is increased, which is not preferable. The amount of Pd is preferably 8 atomic% or more, more preferably 10 atomic% or more. On the other hand, if the amount of Pd exceeds 85 atomic%, the degree of modulation becomes small. Therefore, in the present invention, the upper limit of the amount of Pd is set to 85 atomic%. The upper limit of the amount of Pd is preferably 50 atomic%, more preferably 45 atomic%.

  By the way, in a multilayer optical disc having two or more recording layers, the transmittance is required except for the recording layer farthest from the laser incident surface. This transmittance can be increased by reducing the amount of Pd. Therefore, it is preferable that the recording layer that requires a certain degree of transmittance has a Pd content in the range of 4 to 30 atomic%. On the other hand, the lowermost layer (recording layer farthest from the laser incident surface) of a single-layer disk or multilayer disk needs a certain degree of reflectivity, so that the Pd content is preferably 30 to 85 atomic%. .

  If the oxidized Pd contains Pd monoxide and Pd in particular, the recording sensitivity can be improved sufficiently. The reason is that Pd dioxide, which is more unstable than monoxide Pd, is easily decomposed by laser irradiation to release oxygen, and Pd dioxide is present in the monoxide Pd that is more stable than Pd dioxide. Thus, it is conceivable that the natural decomposition of Pd dioxide is suppressed and a stable recording layer can be obtained.

  In order to improve the recording sensitivity by increasing the amount of oxygen released by the decomposition of Pd dioxide, the ratio of Pd dioxide to the total of Pd monoxide and Pd is preferably 5 mol% or more. On the other hand, if there is too much Pd dioxide relative to Pd monoxide, Pd dioxide cannot exist stably and it becomes difficult to produce a recording layer. Therefore, Pd dioxide with respect to the sum of Pd and Pd. The ratio is preferably 70 mol% or less. More preferably, it is 60 mol% or less.

  The recording layer in the optical information recording medium of the present invention contains an oxide of a metal (X metal) whose absolute value of the standard free energy of formation of oxide relative to 1 mol of oxygen is larger than Pd, together with the above-mentioned Pd. Thus, by including a metal oxide that is more stable than the oxidized Pd together with the oxidized Pd, it is possible to clearly and greatly increase the form change due to oxygen release when the oxidized Pd is decomposed, and to improve the recording sensitivity. be able to.

Examples of the metal (X metal) whose absolute value of the standard free energy of formation of oxide relative to 1 mol of oxygen is larger than Pd include Sn, Zn, Bi, Ge, Co, W, Cu, and Al (oxygen at room temperature). The standard free energy of formation of oxide for 1 mol is about −150 kJ / mol for Pd, whereas −520, −640, and −330 for Sn, Zn, Bi, Ge, Co, W, Cu, and Al, respectively. , -420, -420, -500, -270, -1050 kJ / mol). Here, the standard free energy of formation of oxide with respect to 1 mol of oxygen is
For example, in the case of Al,
4 / 3Al + O ₂ = 2 / 3Al ₂ O ₃
In the case of Zn,
2Zn + O ₂ = 2ZnO
It is a value in the reaction represented by.

  The recording layer according to the present invention contains an X metal oxide as described above, and preferably contains 50 mol% or more of an X metal oxide. The recording layer according to the present invention may contain inevitable impurities that are inevitably mixed during production, in addition to the X metal oxide and the oxidized Pd. Furthermore, Sn, Al, Bi, Cu, Nb, Ti, Si, and Ta are included within a total of about 30 atomic% or less in the state of oxide or metal for the purpose of improving the absorption rate and controlling the refractive index. You may go out.

  The film thickness of the recording layer depends on the structure of the optical information recording medium, such as inserting other layers such as a metal compound layer and a metal layer above and below the recording layer, but is preferably 5 to 100 nm, for example. This is because if the thickness of the recording layer is smaller than 5 nm, it is difficult to obtain a sufficient reflectance change due to recording. More preferably, it is 10 nm or more, More preferably, it is 20 nm or more, Most preferably, it is 25 nm or more. On the other hand, if the thickness of the recording layer is larger than 100 nm, it takes time to form the film, the productivity is lowered, and the laser power required for recording is increased. More preferably, it is 70 nm or less, More preferably, it is 60 nm or less.

As described above, the recording layer according to the present invention contains oxidized Pd (for example, PdO, PdO ₂ , PdO _X, etc.). In order to obtain such a recording layer, the recording layer is formed by sputtering. It is preferable to do. The sputtering method is preferable because the film thickness distribution uniformity within the disk surface can be secured.

In order to form the recording layer containing the oxidized Pd by sputtering, it is preferable that the ratio of the oxygen flow rate to the Ar (argon) flow rate is 0.5 to 10.0 as the sputtering condition. Other conditions in the sputtering method are not particularly limited, and a widely used method can be adopted. The gas pressure is in the range of 0.1 to 1.0 Pa, for example, and the sputtering power is in the range of 0.5 to ²⁰ W / cm ² , for example. What is necessary is just to control to a range.

As a sputtering target (hereinafter, simply referred to as “target”) used in the sputtering method,
(A) an oxide of X metal (preferably one or more selected from the group consisting of Sn, Zn, Bi, Ge, Co, W, Cu and Al) (specifically, for example, an oxide of X metal) And Pd (for example, oxidized Pd and / or metal Pd), and the ratio of Pd atoms to the total of X metal atoms and Pd atoms contained in the sputtering target is 4 to 85 atom% A sputtering target characterized in that
(B) X metal (preferably one or more selected from the group consisting of Sn, Zn, Bi, Ge, Co, W, Cu, and Al) 4 to 85 in terms of the ratio of Pd atoms to the total of atoms and Pd atoms A sputtering target having a feature in that it is made of an alloy based on X metal containing atomic% of Pd (for example, metal Pd) may be used. Also,
(C) It is mentioned to perform multi-source sputtering by using an X metal target (pure X metal target) and a metal Pd target (pure Pd metal target) and simultaneously discharging them.

  As the sputtering target (A) above, it is particularly preferable to use an X metal oxide and a metal Pd powder mixed and sintered so that the productivity and the composition of the formed thin film are uniform in the plane. From the viewpoint of property and thickness control. In the production of the sputtering target, impurities may be mixed in the sputtering target as impurities in a small amount. However, the component composition of the sputtering target of the present invention does not prescribe even the trace components that are inevitably mixed, and the trace amounts of these unavoidable impurities are allowed as long as the above characteristics of the present invention are not impaired.

  The optical information recording medium of the present invention is characterized in that it includes the above-mentioned recording layer and the following dielectric layer formed adjacent to the recording layer.

  The optical information recording medium of the present invention has a recording layer exhibiting the above excellent characteristics, but it is also necessary to maintain the above excellent characteristics even in a high temperature and high humidity environment, that is, to ensure excellent durability. It is. Therefore, in the present invention, a dielectric layer is formed adjacent to the recording layer. Under the above environment, the oxidized Pd in the portion not irradiated with laser (that is, recording is not performed) is gradually reduced to release oxygen, resulting in a change in optical characteristics and a decrease in reflectance. Appearance is considered as a cause of the decrease in durability. However, it seems that by forming the dielectric layer adjacent to the recording layer, unnecessary decomposition of oxidized Pd (particularly Pd dioxide) in the recording layer can be suppressed and stably held.

  The above-mentioned “formation of the dielectric layer adjacent to the recording layer” includes, for example, the case where the dielectric layer is formed between the substrate and the recording layer and adjacent to the recording layer, and / or the recording layer and will be described later. A case where it is formed between the light transmission layer and adjacent to the recording layer can be mentioned.

  The dielectric layer also improves durability by acting as an oxygen barrier layer. By preventing the escape of oxygen in the recording layer, a change in reflectance (particularly, a decrease in reflectance) can be prevented, and the reflectance necessary for the recording layer can be ensured.

  Furthermore, recording characteristics can be improved by forming a dielectric layer. This is because the thermal diffusion of the laser incident by the dielectric layer is optimally controlled to prevent the bubbles in the recording portion from becoming too large or the decomposition of the oxidized Pd from proceeding too much to collapse the bubbles. This is considered to be possible to optimize.

Examples of the material for the dielectric layer include oxides, nitrides, sulfides, carbides, fluorides, and mixtures thereof. Examples of the oxides include In, Zn, Sn, Al, Si, Ge, Ti, and Ga. An oxide of one or more elements selected from the group consisting of Ta, Nb, Hf, Zr, Cr, Bi, and Mg. The nitride includes a nitride of one or more elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Nb, Mo, Ti, W, Ta, and Zn (preferably Si, Ge And nitrides of one or more elements selected from the group consisting of Ti) and the sulfides include Zn sulfides. The carbide is a carbide of one or more elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Ti, Zr, Ta and W (preferably from the group consisting of Si, Ti and W). The carbide of one or more elements selected) and the fluoride include a fluoride of one or more elements selected from the group consisting of Si, Al, Mg, Ca, and La. Examples of these mixtures include ZnS—SiO _{2 and the} like. Of these, more preferable is the above compound (oxide or the like) containing at least one of In, Zn, Sn, Al, Si, Ti, and Mg, or a mixture thereof, and more preferable is In, Zn, Sn, The above compound containing any one or more of Al or a mixture thereof.

  The thickness of the dielectric layer is preferably 2 to 40 nm. This is because if the thickness is less than 2 nm, the effect of the dielectric layer (particularly, the effect as an oxygen barrier) is hardly exhibited. More preferably, it is 3 nm or more. On the other hand, if the film thickness of the dielectric layer is too large, it is difficult to cause a change in the recording layer (generation of bubbles) due to laser irradiation, resulting in a decrease in recording characteristics. Therefore, the thickness of the dielectric layer is preferably 40 nm or less, more preferably 35 nm or less.

  Although the present invention does not prescribe the method for forming the dielectric layer, it is preferably formed by the sputtering method in the same manner as the recording layer.

In forming the dielectric layer by a sputtering method, as a sputtering condition, an Ar flow rate is set in a range of, for example, 10 to 100 sccm. When a metal target is used as described below, an oxygen flow rate at the time of forming an oxide layer is set as follows: For example, the range of 5 to 60 sccm and the nitrogen flow rate when forming the nitride layer may be set to a range of 5 to 80 sccm, for example. Further, for example, the gas pressure is in the range of 0.1 to 1.0 Pa, and the sputtering power is in the range of 0.5 to 50 W / cm ² , for example.

  As a sputtering target used for forming the dielectric layer, in addition to a target made of the above compound (oxide, nitride, sulfide, carbide, fluoride), other than oxygen, nitrogen, sulfur, carbon, fluorine in the compound A metal target containing a constituent element (a target made of a pure metal or an alloy) can be used.

  In the optical information recording medium of the present invention, the configuration other than the recording layer and the dielectric layer is not particularly limited, and a configuration known in the field of optical information recording media can be adopted.

  Examples of the optical information recording medium (optical disk) include a structure in which a recording layer and a dielectric layer are laminated on a substrate on which a laser guide groove is engraved, and a light transmission layer is further laminated thereon. .

  For example, examples of the material for the substrate include polycarbonate resin, norbornene resin, cyclic olefin copolymer, and amorphous polyolefin. Further, as the light transmission layer, polycarbonate or ultraviolet curable resin can be used. As a material for the light transmission layer, it is preferable that the light transmission layer has a high transmittance with respect to a laser for recording and reproduction, and has a small light absorption rate. The thickness of the substrate is, for example, 0.5 to 1.2 mm. The thickness of the light transmission layer is, for example, 0.1 to 1.2 mm.

  The recording layer of the present invention exhibits excellent recording characteristics by itself, but if necessary, an optical adjustment layer is provided between the substrate and the recording layer in order to further increase the reflectivity as an optical disk. Also good. Examples of the material of the optical adjustment layer include Ag, Au, Cu, Al, Ni, Cr, Ti, and alloys thereof.

  In the above, a single-layer optical disc in which one recording layer and one light transmission layer are formed is shown. However, the present invention is not limited to this, and two or more optical discs in which a plurality of recording layers and light transmission layers are stacked are shown. It may be.

  In the case of the optical disc having two or more layers, it is made of, for example, an ultraviolet curable resin between the recording layer group composed of the recording layer and the optical adjustment layer or the dielectric layer laminated as necessary, and another recording layer group. You may have a transparent intermediate | middle layer.

  The feature of the present invention is that the recording layer described above is adopted and a dielectric layer is formed adjacent to the recording layer. The recording layer, the substrate other than the dielectric layer, the light transmission layer, and the optical layer A method for forming the adjustment layer, the transparent intermediate layer, and the like is not particularly limited, and an optical information recording medium may be manufactured by a method that is usually performed.

  Examples of the optical information recording medium include CD, DVD, and BD. For example, a BD capable of recording and reproducing data by irradiating a recording layer with blue laser light having a wavelength of about 380 nm to 450 nm, preferably about 405 nm. -R is given as a specific example.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the following examples are not intended to limit the present invention, and may be implemented with appropriate modifications without departing from the spirit of the preceding and following descriptions. And are within the scope of the present invention.

(1) Production of optical disk A polycarbonate substrate (thickness: 1.1 mm, diameter: 120 mm, track pitch: 0.32 μm, groove depth: 25 nm) was used as a disk substrate. And No. About 4-10, the dielectric material layer (lower) of the component and film thickness shown in Table 1 was formed by the DC magnetron sputtering method using the oxide target or the pure metal target. The sputtering conditions for forming this dielectric layer (lower) are: Ar flow rate: 10-30 sccm, oxygen flow rate (when using a pure metal target as a target): 0-10 sccm, gas pressure: 0.2-0.4 Pa, DC sputtering power: 100 to 400 W, substrate temperature: room temperature.

  Next, a recording layer was formed. Specifically, on the substrate [No. For 4 to 10, recording layers were formed on the dielectric layer (lower) by DC magnetron sputtering. The film thickness of the recording layer was 40 nm. Sputtering was performed by multi-source sputtering by simultaneous discharge of two targets, a pure X element metal (Zn, W, Sn, Cu) target and a pure Pd metal target. The sputtering conditions for forming the recording layer were Ar flow rate: 10 sccm, oxygen flow rate: 15 sccm, gas pressure: 0.4 Pa, DC sputtering power: 100 to 200 W, and substrate temperature: room temperature.

  Next, no. About 3, 5-13, the oxide layer or the pure metal target was used and the dielectric material layer (upper) of the component and film thickness shown in Table 1 was formed like the said dielectric material layer (lower).

  Then, No. For Nos. 1, 2, and 4, no. 3 and 5-13, after spin coating an ultraviolet curable resin (“BRD-864” manufactured by Nippon Kayaku Co., Ltd.) on the dielectric layer (top), the film was irradiated with ultraviolet rays to have a film thickness of about 0.1 mm. The optical transmission layer was formed to obtain an optical disk.

  It was separately confirmed that the recording layer contained oxide In and oxide Pd, and the oxide Pd contained monoxide Pd and dioxide Pd.

(2) Evaluation of optical disk The durability of the manufactured optical disk was evaluated as follows.

  With an optical disk evaluation device ("ODU-1000" manufactured by Pulstec Industrial Co., Ltd., recording laser wavelength: 405 nm, NA (numerical aperture): 0.85), the laser is irradiated onto the track, and the laser beam of the unrecorded portion of the optical disk The reflectance (initial reflectance) at a wavelength of 405 nm was determined in terms of the return light intensity.

  In addition, an accelerated environment test (constant temperature and humidity test) was held for 96 hours in an air atmosphere at a temperature of 80 ° C. and a relative humidity of 85%, and the reflectance after the test was measured in the same manner as described above. These results are also shown in Table 1.

  From Table 1, by forming the dielectric layer adjacent to the recording layer, the change in reflectance can be made sufficiently smaller than when the dielectric layer is not formed, and an optical information recording medium excellent in durability can be obtained. It can be seen that it can be realized.

Claims (11)

An optical information recording medium comprising a recording layer on which recording is performed by laser light irradiation, and a dielectric layer formed adjacent to the recording layer,
The recording layer includes an oxide of a metal (hereinafter referred to as X metal) whose absolute value of the standard free energy of formation of oxide relative to 1 mol of oxygen is greater than Pd, and oxidized Pd. An optical information recording medium containing Pd dioxide and having a Pd atom ratio of 4 to 85 atomic% with respect to a total of X metal atoms and Pd atoms contained in the recording layer.   2. The optical information recording medium according to claim 1, wherein the X metal contained in the recording layer is at least one selected from the group consisting of Sn, Zn, Bi, Ge, Co, W, Cu, and Al.   The optical information recording medium according to claim 1, wherein a ratio of Pd dioxide to a total of Pd monoxide and Pd contained in the recording layer is 5 to 70 mol%.   The optical information recording medium according to claim 1, wherein the dielectric layer is made of an oxide, nitride, sulfide, carbide, or a mixture thereof.   The oxide constituting the dielectric layer is one selected from the group consisting of In, Zn, Sn, Al, Si, Ge, Ti, Ga, Ta, Nb, Hf, Zr, Cr, Bi, and Mg. The oxide of the above elements, the nitride is a nitride of one or more elements selected from the group consisting of Si, Ge and Ti, the sulfide is Zn sulfide, and the carbide is Si The optical information recording medium according to claim 4, wherein the optical information recording medium is a carbide of one or more elements selected from the group consisting of Ti and W.   The optical information recording medium according to claim 1, wherein the dielectric layer has a thickness of 2 to 40 nm.   The optical information recording medium according to claim 1, wherein the recording layer has a thickness of 5 to 100 nm.   The optical information recording medium according to any one of claims 1 to 7, wherein recording is performed by generating bubbles and changing a volume in a portion of the recording layer irradiated with laser light. A sputtering target for forming a recording layer of an optical information recording medium according to any one of claims 1 to 8,
A sputtering target comprising an oxide of X metal and Pd, and the ratio of Pd atoms to the total of X metal atoms and Pd atoms contained in the sputtering target is 4 to 85 atomic%. A sputtering target for forming a recording layer of an optical information recording medium according to any one of claims 1 to 8,
A sputtering target comprising an alloy based on X metal containing 4 to 85 atomic% of Pd in a ratio of Pd atoms to the total of X metal atoms and Pd atoms.   The sputtering target according to claim 9 or 10, wherein the X metal is at least one selected from the group consisting of Sn, Zn, Bi, Ge, Co, W, Cu, and Al.