Abstract: Data is recorded in a phase-change optical storage medium having data layers. A first recording pulse sequence is generated for recording to a first data layer located most remote from a beam-incident surface. The first sequence has a recording pulse carrying an erasing power and a recording power rising from the erasing power, and a cooling pulse carrying a bottom power lower than the erasing power. A second recording pulse sequence is generated for recording to a second data layer. The second sequence has recording pulse carrying an erasing power and a recording power rising from the erasing power, a cooling puse carrying a bottom power lower than the erasing power, and an erasing top pulse carrying an erasing top power higher than the erasing power.

Abstract: A heat-storage agent which can store a large quantity of cold heat in the temperature range of 3-5° C., is highly effective in preventing supercooling, and can retain the supercooling-preventing effect even when hydrate solidification/melting is frequently repeated. Also provided are an aqueous solution which enables the formation of a clathrate hydrate serving as a major component of the heat-storage agent, and a process for producing the clathrate hydrate. The aqueous solution contains at least one of tetra-n-butylammonium bromide and tri-n-butyl-n-pentylammonium bromide as a solute and contains tetraisopentylammonium bromide as a supercooling inhibitor, the weight proportion of the tetraisopentylammonium bromide to the tetra-n-butylammonium bromide and/or tri-n-butyl-n-pentylammonium bromide being in a given range. This aqueous solution is cooled to or below a hydrate formation temperature to thereby produce a clathrate hydrate. The heat-storage agent contains this clathrate hydrate as a major component.

Abstract: An optical storage medium has a substrate having a first surface and an opposite second surface, light being incident via the first surface in recording or reproduction and at least two composite layers formed on the second surface of the substrate, each composite layer having at least a recording film.

Abstract: An optical storage medium has a substrate having a first surface and a second surface on both sides, the first surface allowing light to pass therethrough in recording or reproduction. The medium also has at least one composite layer having at least a first protective film, a second protective film and a recording film formed in order on the second surface, the first and second protective films exhibiting refractive indices n1 and n2, respectively, having the following relations therebetween, to the light having a specific wavelength ?: n1>n2, n1?n2?0.02 and 2.1?n1?2.5, 1.5?n2?2.1. The composite layer may have at least a first protective film, a second protective film, a third protective film and a recording film formed in order on the second surface, the first, second and third protective films exhibiting refractive indices n21, n22 and n23, respectively, having a relation n21>n22>n23 or n22>n21>n23 thereamong, to the light having a specific wavelength ?.

Abstract: Data is recorded in a phase-change optical storage medium having a beam-incident surface and a plurality of data layers provided over the surface, each data layer having at least a recording film. Data to be recorded is modulated to generate modulated data. Desired mark-length data is generated based on the modulated data. A recording beam is emitted onto each data layer based on the mark-length data, to form a recorded mark carrying the data to be recorded in each data layer. A first recording pulse sequence is generated when a recorded mark is formed in a first data layer located most remote from the beam-incident surface among the data layers. The first sequence has at least a first recording pulse carrying a first erasing power and a first recording power rising from the first erasing power, and a first cooling pulse carrying a first bottom power lower than the first erasing power. A recording beam is emitted onto the first data layer in accordance with the first sequence.