Abstract: A hologram recording medium includes a glass substrate and an information recording layer supported on the glass substrate. The information recording layer is formed of a photosensitive material having a dynamic storage elastic modulus of 1.0×105 Pa or more as measured at 80° C. and a measurement frequency of 1 Hz after interference exposure or post-curing. The photosensitive material is dissolvable or dispersible in an organic solvent, and the information recording layer has sufficient storage stability that allows recorded signals to be stably held for at least 100 hours or longer at 80° C.

Abstract: A method for forming an information recording layer including a multilayer stack of reflection hologram layers modulated in the depth direction of a hologram material layer is provided. The method includes: generating a first pair of polarized coherent laser beams and a second pair of polarized coherent laser beams that are incoherent with the first pair; directing the first pair of polarized coherent laser beams to the hologram material layer from opposite sides thereof, respectively, such that the incident angles of the first pair are symmetric with respect to the hologram material layer; directing the second pair of polarized coherent laser beams to the hologram material layer from the opposite sides thereof, respectively, at incident angles different from the incident angles of the first pair; and forming the multilayer stack of reflection hologram layers according to the interference pattern of the first and second pairs of polarized coherent laser beams.

Abstract: A recording and reading system for a multi-layered optical recording medium includes: a multi-layered optical recording medium including a plurality of recording layers and a single servo layer; and an optical head. The optical head includes a recording and reading objective lens of a signal recording and reading optical system and a servo objective lens of a servo signal detection optical system that are disposed on a common actuator. The recording and reading objective lens is mounted on the common actuator through a minute-drive apparatus so as to be minutely driven in a focusing direction relative to the servo objective lens. When the servo objective lens is focused on the servo layer, a reading light beam is quickly focused on a target one of the plurality of recording layers.

Abstract: An optical recording medium has a recording layer formed of a plurality of reflection hologram layers. A spacer layer is interposed between the respective reflection hologram layers. The reflection hologram layer is made of a material having a thermal threshold value which allows, when being irradiated with a recording laser beam, local absorbed heat to vary hologram diffraction conditions at a focal position, and allows the hologram to be retained at non-focal positions. The spacer layer is made of a material which is insensitive to a laser beam of a recording wavelength and which has a smaller extinction coefficient than that of the reflection hologram layer.

Abstract: An optical recording medium includes a support substrate and an information recording layer which is supported on the support substrate and made of a photosensitive material which is irradiated with light to be refractive index modulated and amplitude modulated, thereby recording information. The information recording layer has the shape of a coating which is formed by applying a photosensitive material reversibly dissolved or dispersed in an organic solvent onto the support substrate. The photosensitive material in the shape of a coating, as a photopolymer for hologram recording material, contains the cross-linked matrix to maintain the rigidity of the recording material. The optical recording medium is retained in shape with stability, and particularly prevented from being deformed due to shrinkage, thereby facilitating manufacturing of the optical recording medium.

Abstract: An optical recording medium comprises a laminate of at least two recording layers; each of the recording layers contains a metal complex dye and an organic dye in a predetermined concentration; when the recording layers comprise a first recording layer and a second recording layer in order from a light entrance side, the first recording layer contains 20 to 50 parts by weight of the metal complex dye where a total amount of the metal complex dye and the organic dye is 100 parts by weight, and the second recording layer contains 20 to 100 parts by weight of the metal complex dye where a total amount of the metal complex dye and the organic dye is 100 parts by weight. The optical recording medium is provided as one with a satisfactorily excellent initial error rate and a satisfactorily excellent error rate after a light resistance test, in each of the recording layers.

Abstract: At least two recording layers are laminated, a dye in each of the recording layers contains predetermined concentrations of a metal complex dye and an organic dye, the recording layers are referred to as first and second recording layers successively from the light entrance surface side, the first recording layer contains 60 to 100 parts by weight of a metal complex dye where the total amount of the metal complex dye and organic dye is 100 parts by weight, and the second recording layer contains 10 to 80 parts by weight of a metal complex dye where the total amount of the metal complex dye and organic dye is 100 parts by weight. A recording medium is provided, in which recording is possible in the first and second recording layers by recording powers equivalent to each other while the initial error rate after a high-temperature storage test is sufficiently low in each recording layer.

Abstract: An optical recording medium provided with a recording layer that comprises a cation represented by the following general formula (1) and a chelate compound of an azo compound represented by the following general formula (2) and a metal. In the formulas, R1-R4 each independently represent a monovalent group represented by Chemical Formula (10) below or other groups, R5 and R6 each independently represent an optionally substituted alkyl group or other groups, R7 represents a hydrogen atom or other groups, Q1 and Q2 each independently represent a group that forms an optionally substituted benzene ring or other groups, at least one from among R1-R4 is a monovalent group represented by Chemical Formula (10) below, [Chemical Formula 2] [CH2?CH—CH2???(10) and at least one of Ar1 and Ar2 is an aryl or other group having a substituent capable of coordinating with a metal atom.

Abstract: It is an object of the present invention to provide a multilevel optical recording medium in which influence of variation in characteristics of a recording layer in a plane of the recording layer on reproduced data can be corrected The multilevel optical recording medium according to the present invention includes at least a recording layer 12 and is constituted so that data can be recorded therein in a multilevel manner by controlling a state of the recording layer 12 among multiple stages and the multilevel optical recording medium according to the present invention is characterized in that a plurality of calibration signals are stored in the recording layer 12.

Abstract: A reproduction method for a multi-level optical recording medium according to the present invention rotates an optical recording medium, on which recording data has been recorded according to a multi-level recording method which sets several levels for light reflectivity of virtual recording cells, emits a reproduction laser beam towards the optical recording medium, and reproduces the recording data based on an electric signal generated in accordance with a received level of reflected light, the method setting the emission power of the reproduction laser beam in a range of 1.0 mW to 2.5 mW inclusive when the optical recording medium is rotated at a linear velocity in a range of 9 m/s to 25 m/s inclusive. By doing so, it is possible to improve the read accuracy for recording data while suppressing the reproduction deterioration of the optical recording medium to a level where deterioration effectively does not occur.

Abstract: It is an object of the present invention to provide a multilevel optical recording medium in which influence of variation in characteristics of a recording layer in a plane of the recording layer on reproduced data can be corrected. The multilevel optical recording medium according to the present invention includes at least a recording layer 12 and is constituted so that data can be recorded therein in a multilevel manner by controlling a state of the recording layer 12 among multiple stages and the multilevel optical recording medium according to the present invention is characterized in that a plurality of calibration signals are stored in the recording layer 12.

Abstract: A reproduction method for a multi-level optical recording medium according to the present invention rotates an optical recording medium, on which recording data has been recorded according to a multi-level recording method which sets several levels for light reflectivity of virtual recording cells, emits a reproduction laser beam towards the optical recording medium, and reproduces the recording data based on an electric signal generated in accordance with a received level of reflected light, the method setting the emission power of the reproduction laser beam in a range of 1.0 mW to 2.5 mW inclusive when the optical recording medium is rotated at a linear velocity in a range of 9 m/s to 25 m/s inclusive. By doing so, it is possible to improve the read accuracy for recording data while suppressing the reproduction deterioration of the optical recording medium to a level where deterioration effectively does not occur.