Abstract: An optical recording medium includes: a substrate having a first principal surface and a second principal surface; one or plural information signal layers formed on the first principal surface of the substrate for undergoing recording or reproduction of information signals upon irradiation with light; and a barrier layer formed on the second principal surface of the substrate for suppressing the gas release from the second principal surface of the substrate, wherein an area of a region exposing from the barrier layer of the second principal surface of the substrate is not more than 688 mm2.

Abstract: Disclosed herein is an optical recording medium, including: a substrate; and an information recording layer formed on the substrate, an information signal being recorded and reproduced in and from the information recording layer by radiation of a light; wherein the information recording layer includes a reflecting layer, a dielectric layer formed on the reflecting layer, and a recording layer formed on the dielectric layer, the dielectric layer includes a first dielectric layer and a second dielectric layer, and a thermal conductivity of the second dielectric layer located on the reflecting layer side is higher than that of the first dielectric layer located on the recording layer side.

Abstract: An optical recording medium includes: a substrate having a first principal surface and a second principal surface; one or plural information signal layers formed on the first principal surface of the substrate for undergoing recording or reproduction of information signals upon irradiation with light; and a barrier layer formed on the second principal surface of the substrate for suppressing the gas release from the second principal surface of the substrate, wherein an area of a region exposing from the barrier layer of the second principal surface of the substrate is not more than 688 mm2.

Abstract: Disclosed herein is an optical recording medium, including: a substrate; and an information recording layer formed on the substrate, an information signal being recorded and reproduced in and from the information recording layer by radiation of a light; wherein the information recording layer includes a reflecting layer, a dielectric layer formed on the reflecting layer, and a recording layer formed on the dielectric layer, the dielectric layer includes a first dielectric layer and a second dielectric layer, and a thermal conductivity of the second dielectric layer located on the reflecting layer side is higher than that of the first dielectric layer located on the recording layer side.

Abstract: An optical recording and reproducing method is able to record and reproduce information by using an optical system using recording and reproducing light with a wavelength selected in a range of from 780 nm±10 nm and an objective lens with a numerical aperture NA selected in a range of from 0.45±0.01 and records and reproduces first and second optical recording mediums having different recording capacities. The first optical recording medium is constructed by using a substrate with a track pitch Tp1 being selected in a range of from 1.5 ?m to 1.7 ?m and a groove depth d1 being selected in a range of from 70 nm to 90 nm, and the second optical recording medium is constructed by using a substrate 11 with a track pitch Tp2 being selected in a range of from 1.2 ?m to 1.3 ?m and a groove depth d2 of the groove 12 being selected in a range of from 150 nm to 180 nm. This, the optical recording medium has compatibility with existing optical discs and has a recording density high enough to record a moving picture.

Abstract: A magneto-optical disk having a small-sized diameter and a large capacity and able to record and reproduce disk discrimination information, and a recording method and a reproducing method of the same, wherein a recording layer including a main recording region in which a first information is recorded, a sub recording region in which a second information including the disk discrimination information is recorded, and a buffer region formed between the main recording region and the sub recording region and in which a third information is recorded is provided on a substrate, the second information is recorded by a mark array formed in stripe shapes in the sub recording region and the buffer region, a plurality of marks constituting the mark array are obtained by changing the magnetization state of the recording layer, and the third information is reproduced by a modulation signal of a reflection ratio along a circumferential direction of the disk.

Abstract: An optical recording and reproducing method is able to record and reproduce information by using an optical system using recording and reproducing light with a wavelength selected in a range of from 780 nm±10 nm and an objective lens with a numerical aperture NA selected in a range of from 0.45±0.01 and records and reproduces first and second optical recording mediums having different recording capacities. The first optical recording medium is constructed by using a substrate with a track pitch Tp1 being selected in a range of from 1.5 ?m to 1.7 ?m and a groove depth d1 being selected in a range of from 70 nm to 90 nm, and the second optical recording medium is constructed by using a substrate 11 with a track pitch Tp2 being selected in a range of from 1.2 ?m to 1.3 ?m and a groove depth d2 of the groove 12 being selected in a range of from 150 nm to 180 nm. This, the optical recording medium has compatibility with existing optical discs and has a recording density high enough to record a moving picture.

Abstract: An optical recording and reproducing method is able to record and reproduce information by using an optical system using recording and reproducing light with a wavelength selected in a range of from 780 nm±10 nm and an objective lens with a numerical aperture NA selected in a range of from 0.45±0.01 and records and reproduces first and second optical recording mediums having different recording capacities. The first optical recording medium is constructed by using a substrate with a track pitch Tp1 being selected in a range of from 1.5 ?m to 1.7 ?m and a groove depth d1 being selected in a range of from 70 nm to 90 nm, and the second optical recording medium is constructed by using a substrate 11 with a track pitch Tp2 being selected in a range of from 1.2 ?m to 1.3 ?m and a groove depth d2 of the groove 12 being selected in a range of from 150 nm to 180 nm. This, the optical recording medium has compatibility with existing optical discs and has a recording density high enough to record a moving picture.

Abstract: A magneto-optical recording medium includes a first magnetic layer (reproduction layer), a second magnetic layer (control layer), a third magnetic layer (blocking layer), and a fourth magnetic layer (recording layer) having respective Curie temperatures TC1, TC2, TC3 and TC4. The Curie temperatures of the layers satisfy the relationships TC1>TC3>TC2 and TC4>TC3. In addition, the magnetic anisotropy of the third magnetic layer Ku3 is greater than that of the second magnetic layer Ku2. A magnetic domain wall in the first magnetic layer in front of the spot irradiated by the reproduction light in the direction of travel is displaced toward the peak temperature portion so that a recorded domain is expanded. Displacement in the spot direction of a domain wall in the first magnetic layer behind the reproduction light spot in the direction of travel is suppressed. The second and third magnetic layers control the magnetic exchange coupling between the first and fourth magnetic layers.

Abstract: An optical recording and reproducing method is able to record and reproduce information by using an optical system using recording and reproducing light with a wavelength selected in a range of from 780 nm±10 nm and an objective lens with a numerical aperture NA selected in a range of from 0.45±0.01 and records and reproduces first and second optical recording mediums having different recording capacities. The first optical recording medium is constructed by using a substrate with a track pitch Tp1 being selected in a range of from 1.5 ?m to 1.7 ?m and a groove depth d1 being selected in a range of from 70 nm to 90 nm, and the second optical recording medium is constructed by using a substrate 11 with a track pitch Tp2 being selected in a range of from 1.2 ?m to 1.3 ?m and a groove depth d2 of the groove 12 being selected in a range of from 150 nm to 180 nm. This, the optical recording medium has compatibility with existing optical discs and has a recording density high enough to record a moving picture.

Abstract: A magneto-optical disk having a small-sized diameter and a large capacity and able to record and reproduce disk discrimination information, and a recording method and a reproducing method of the same, wherein a recording layer including a main recording region in which a first information is recorded, a sub recording region in which a second information including the disk discrimination information is recorded, and a buffer region formed between the main recording region and the sub recording region and in which a third information is recorded is provided on a substrate, the second information is recorded by a mark array formed in stripe shapes in the sub recording region and the buffer region, a plurality of marks constituting the mark array are obtained by changing the magnetization state of the recording layer, and the third information is reproduced by a modulation signal of a reflection ratio along a circumferential direction of the disk.

Abstract: In reproduction from a magneto-optical recording medium by the domain wall displacement detection method, it is possible to avoid occurrence of ghost signals and to improve dropout, and moreover design of magnetic layers is made easy. A configuration is adopted having at least, in order from the side of incidence of laser light for reproduction, a first magnetic layer 11 constituting a reproduction layer, a second magnetic layer 12 constituting a control layer, a third magnetic layer 13 constituting a blocking layer, and a fourth magnetic layer 14 constituting a recording layer, which if the respective Curie temperatures thereof are TC1, TC2, TC3 and TC4, satisfy the relations TC1>TC3>TC2 and TC4>TC3. At the same time, if the magnetic anisotropy of the second magnetic layer is Ku2 and the magnetic anisotropy of the third magnetic layer is Ku3, the relation Ku3>Ku2 is satisfied.