Abstract: An optical recording medium which can produce a read signal free from waveform distortion during reproduction of information. The optical recording medium comprises groove information tracks on which information pits carrying information data is to be formed, and prepit tracks provided with a plurality of previously formed land prepits connected to the groove information tracks. The groove information tracks and the prepit tracks are arranged in alternation. The groove information track has a track width smaller in at least a part of each of sections in which the land prepit exists than in sections in which no land prepit exists.

Abstract: A stamper having a good cost performance, which can be easily separated (released) from a layer of photo-curing resin, is provided. A process for producing an optical multi-layer recording medium having a good productivity is also provided by using such a stamper. The process for producing an optical multi-layer recording medium includes the steps of: laminating a layer of non-cured photo-curing resin and a transparent stamper made of amorphous polyolefin resin in this sequence on a substrate; curing the non-cured photo-curing resin with light permeated through the transparent stamper; and removing the transparent stamper.

Abstract: An optical recording medium is designed to generate a read signal free from waveform distortion during reproduction of information. The optical recording medium is formed with information tracks on which data pits carrying information data is to be formed, and prepit tracks previously formed with a plurality of prepits. Each of the information tracks and each of the prepit tracks are positioned adjacent to each other, and each of the prepits is formed to be spaced apart from adjacent information tracks in at least its bottom part.

Abstract: An optical recording medium is provided which comprises: a substrate including concentrically or spirally formed grooves each having a V-shaped cross section; a first dielectric layer formed on the substrate; a phase-change recording layer formed on the first dielectric layer; a second dielectric layer formed on the phase-change recording layer; and a metallic reflecting layer formed on the second dielectric layer. In particular, the optical recording medium is so formed that an objective lens having an aperture number of 0.55-0.70 can be used and a laser beam having a wavelength of 600-700 nm and passing through the objective lens is passed through the substrate and then converged on the recording layer, thereby recording or reproducing information on the recording layer in areas corresponding to the grooves.

Abstract: A rewritable type optical disc includes recording tracks formed with break portions; and recording marks corresponding to predetermined data and formed on the recording tracks. The recording marks are formed over the break portions on the recording tracks. If the predetermined data, such as control data, recorded as the recording mark is illegally altered, the position of the recording marks are changed and some break portions are not covered by the recording marks. Since the return light level of the break portion, which is not covered by the recording mark, is different from the return light level of the break portion covered by the recording mark, such illegal alteration of the predetermined data such as the control data may be detected.

Abstract: An optical recording medium has a substrate having an annular grooves, a recording layer including an organic coloring matter and formed on the substrate, and a metallic reflection layer. The recording layer has a thickness so as to have an absorbance between 0.65 and 0.75. Information is recorded in the recording layer by a laser beam having a wavelength between 600 and 700 nm, using an objective lens having a numerical aperture between 0.55 and 0.70.

Abstract: A recordable optical disc on which information is recorded by applying a light beam on the surface thereof, includes: a first recording area on which information is recorded and reproduced while the disc is rotated at a first linear velocity; and a second recording area on which information is recorded and reproduced while the disc is rotated at a second linear velocity. The first recording area and the second recording area include guide grooves having wobble frequency lower than frequency band of EFM signal.

Abstract: An apparatus for recording information on a recordable optical disc by applying a light beam on the surface thereof, the disc includes a first recording area on which information is recorded and reproduced while the disc is rotated at a first linear velocity; and a second recording area on which information is recorded and reproduced while the disc is rotated at a second linear velocity. The first recording area includes a test recording area. The apparatus includes recording power determining unit for determining first optimum recording power for recording information on the first area by a test recording utilizing the test recording area, and for determining second optimum recording power for recording information on the second area by multiplying the first optimum recording power by a predetermined constant.

Abstract: An optical information recording medium recordable of the analogue NTSC color video signal under the conditions of a high S/N ratio and a low jitter, and capable of being played by a commercially available LD player. The medium comprises: a transparent substrate on which pre-grooves are formed with a depth of 1450-2050 angstroms; an optical absorbing layer with an absorbance of 0.7-0.

Abstract: An optical disk of the type including guide grooves is improved by regulating the width of the grooves, and thus the width of the adjacent land portion, in accordance with the type of information recorded at that part of the land.

Abstract: In an optical disk manufacturing method in which a first photo resist layer, an intermediate resin layer, and a second photo resist layer are formed on a substrate in the stated order, a resin solution which is unsoluble in organic solvent is applied to the first photo resist layer, heated, and hardened to form the intermediate resin layer. Thereby the use of a large, expensive device such as a vacuum deposition device or sputting device is eliminated.