A recording layer for an optical data recording medium according to one embodiment of the present invention makes it possible to record an information signal by irradiation with laser beam. The recording layer for an optical data recording medium comprises metal oxides including a Mn oxide, a W oxide, and a Sn oxide. The atomic ratio of Mn with respect to the total number of atoms of metal elements constituting the metal oxides is 3-40 atm %.

An information recording medium and a method for producing the same according to the present disclosure are configured to have an information layer in which a larger amount of light for reproduction can be obtained, so that the medium is suitable for recording information at high recording density and is useful for a multi-layer optical disc that records a large amount of contents.

An information recording medium according to the present disclosure is an information recording medium of a write-once-read-many type and records or reproduces information when irradiated with laser light. The information recording medium includes: a substrate; a plurality of information layers at least one information layer of which includes a recording film that is a W—O-based recording film comprising at least tungsten (W) and oxygen (O); and a dielectric film A in contact with the W—O-based recording film, the dielectric film A comprising at least 30 mol % tin oxide.

An optical disc recording medium includes: a substrate; at least one recording layer formed on at least one side of the substrate; and a cover layer formed on the substrate and the recording layer. The cover layer having a first thickness with reference to a surface of the substrate, in an inside of a circle having a first radius from a center of the substrate. The cover layer having a second thickness larger than the first thickness with reference to the surface of the substrate, on a circumference having a second radius longer than the first radius from the center of the substrate. The cover layer having a third thickness smaller than the first thickness with reference to the surface of the substrate, on a circumference having a third radius longer than the first radius and shorter than the second radius from the center of the substrate.

A thin film is provided that primarily comprises titanium oxide and includes Ti, Ag and O. The thin film contains 29.6 at % or more and 34.0 at % or less of Ti, 0.003 at % or more and 7.4 at % or less of Ag, and oxygen as the remainder thereof and has a ratio of oxygen to metals, O/(2Ti+0.5Ag), of 0.97 or more. The thin film has a high refractive index and a low extinction coefficient. In addition, the thin film has superior transmittance, minimally deteriorates in reflectance, and is useful as an interference film or a protective film for an optical information recording medium. The film may also be applied to a glass substrate to provide a heat reflective film, an antireflective film, or an interference filter. A method of producing the thin film is also disclosed.

A thin film is provided that primarily comprises titanium oxide and includes Ti, Ag and O. The thin film contains 29.6 at % or more and 34.0 at % or less of Ti, 0.003 at % or more and 7.4 at % or less of Ag, and oxygen as the remainder thereof and has a ratio of oxygen to metals, O/(2Ti+0.5Ag), of 0.97 or more. The thin film has a high refractive index and a low extinction coefficient. In addition, the thin film has superior transmittance, minimally deteriorates in reflectance, and is useful as an interference film or a protective film for an optical information recording medium. The film may also be applied to a glass substrate to provide a heat reflective film, an antireflective film, or an interference filter. A method of producing the thin film is also disclosed.

An information recording medium and a method for producing the same according to the present disclosure are configured to have an information layer in which a larger amount of light for reproduction can be obtained, so that the medium is suitable for recording information at high recording density and is useful for a multi-layer optical disc that records a large amount of contents.

An Sb—Te-based alloy sintered compact sputtering target having Sb and Te as main components and which contains 0.1 to 30 at % of carbon or boron and comprises a uniform mixed structure of Sb—Te-based alloy particles and fine carbon (C) or boron (B) particles is provided. An average grain size of the Sb—Te-based alloy particles is 3 μm or less and a standard deviation thereof is less than 1.00. An average grain size of the C or B particles is 0.5 μm or less and a standard deviation thereof is less than 0.20. When the average grain size of the Sb—Te-based alloy particles is X and the average grain size of the carbon or boron particles is Y, Y/X is within a range of 0.1 to 0.5. This provides an improved Sb—Te-based alloy sputtering target that inhibits generation of cracks in the sintered target and prevents generation of arcing during sputtering.

A dielectric layer is formed from an oxide containing Sn and at least one of Zn, Zr, Si and Ga. The molar percentages of Sn, Zn, Zr, Si, and Ga, relative to the total elements in the oxide, represented by a, b, c, d, and e, respectively, satisfy the conditions (1)-(7): (1) 0≤b/(a+b)≤0.6, (2) 0≤(c+d)/(a+b+c+d+e)≤0.5, (3) 0≤b≤50, (4) 0≤c≤40, (5) 0≤d≤45, (6) 0≤e≤40, and (7) 20≤b+c+d+e≤80. The dielectric layer enables favorable information recording in an oxide-based recording layer on which the dielectric layer is directly overlaid, does not require preventive measures for health hazard, and is superior in durability.

An optical recording medium includes a first disk, a second disk, and an adhesive layer for bonding the first disk to the second disk. The first disk and the second disk each include a substrate having a first surface and a second surface and having a gradient on an outer peripheral portion of the second surface, two or more information signal layers disposed on the first surface, an intermediate layer disposed between adjacent information signal layers, and a cover layer covering the two or more information signal layers and the intermediate layer. The second surface of the substrate included in the first disk faces the second surface of the substrate included in the second disk with the adhesive interposed therebetween.