Abstract: Provided are an indicating material having excellent facility and high security and an indicating method for recording and indicating information on this indicating material. The indicating material has a structure that an ultraviolet light-screening layer having visible light-transmitting ability is laminated on a recording layer having visible light-transmitting ability and composed of a recording layer-forming material containing a color-developing component that becomes a color-developed state by the action of ultraviolet light. The indicating method is an indicating method for recording and indicating information on the above-described indicating material, comprising condensing a laser beam having a wavelength of a visible range or longer on the recording layer in the indicating material to irradiate the recording layer with the laser beam and recording and indicating the information by two-photon absorption.

Abstract: A photon mode reaction is caused in an optical recording medium by irradiating the optical recording medium susceptible to the photon mode reaction with light emitted from a light emitting device when driven by a pulsed current.

Abstract: An optical material contains a photochromic compound which is expressed in the following general formula (I): ##STR1## where A represents an oxygen atom, a nitrogen atom, or a substituted nitrogen atom, B represents a thiophene ring, benzothiophene ring, pyrrole ring or indole ring, R.sub.1 represents a methyl group, an alkoxy group or a perfluoroalkyl group, R.sub.2 to R.sub.7 represent a hydrogen atom, a halogen atom, a hydroxy group, an alkyl group and the like respectively. This photochromic compound may be bonded with a polymer as a side chain in the position of A.

Abstract: An optical recording medium is provided with a masking layer on a side of a recording layer for receiving a reproducing beam. The masking layer is prepared from that containing photochromic dye molecules having absorption at the wavelength of the reproducing beam and causing a photon mode reaction by absorbing the reproducing beam to be reduced in absorption.

Abstract: A technique for improving a number of reproducible times in reproduction of information from an optical recording medium having a recording layer which reacts in a photon mode. The power of a reproducing beam is set in proximity to P.sub.rep (W) appearing in the following expression (I) or within a range of P.sub.rep (W) appearing in the following expression (II): ##EQU1## In order to improve an S-N ratio, squeezed light having suppressed photon number fluctuation is employed as a reproducing beam at need. If improvement of the number of reproducible times is in preference to improvement of the S-N ratio, such squeezed light having suppressed photon number fluctuation is employed as a reproducing beam with power which is set within a range of P.sub.

Abstract: Disclosed herein is an optical recording medium comprising a recording layer containing a photochromic material and a polymer which are so combined with each other that a photostationary state attained upon irradiation with light of a specific wavelength is varied with temperatures, a reflective layer for reflecting light which is passed through the recording layer, and a substrate for supporting a laminate of the recording layer and the reflective layer.

Abstract: A recording medium comprises a recording layer, a birefringent layer, and a reflecting layer. The recording layer is formed of a material whose optical rotatory power is alterable such that in one state no optical rotatory power is present and, in a second state, optical rotatory power is present. Information is recorded in the recording layer by selectively altering the state of the recording layer. The birefringent layer is formed of a material having constant birefringence without regard to the state of the recording layer. The reflecting layer reflects a light beam transmitted through the recording layer and the birefringent layer to reintroduce the beam into the birefringent layer and the recording layer. A method of reproducing information from this recording medium applies a polarized light beam to the recording medium and detects change of the polarized state of the polarized light beam reflected from the recording medium, thereby reading the information recorded in the recording layer.

Abstract: Disclosed herein is a recording/reproducing method for an optical recording medium comprising a step of heating a recording layer containing a photochromic material and a polymer which are so combined with each other that a photostationary state attained upon irradiation with light of a specific wavelength is varied with temperatures, and a step of applying the light of a specific wavelength to the heated recording layer for bringing the same into a photostationary state and recording information. In order to reproduce the information, a portion of the recording layer which is in a photostationary state is selectively heated, and reproducing light is applied to reproduce recorded and unrecorded states.