Abstract: A transparent protective cover for the play side of an optical disc is made of poly-carbon film. The protective cover is annular in shape and is appropriately sized to fit the various disc formats. There is provided an inner crevice or groove that fits the inner molding of a disc allowing for greater structural integrity and which assists in the placement of the protector on the disc. The device is attached to the disc using several clips that are located around the perimeter.

Abstract: A composition suitable for forming an optical information recording layer for carrying out recording and readout with laser beams, which comprises at least one cyanine dye, and at least one leuco compound of formulae (VII) or (VIII); and optionally, at least one aminium compound of formulae (IV) or (V).

Abstract: A process for authenticating a medium which can be solid or liquid in which particles of an organic composition capable of absorbing or reflecting infrared or near-infrared radiation are incorporated in the medium. The transparent or opaque state can be irreversibly selected upon heating to a temperature greater than ambient temperature or to ultraviolet radiation and, whether or not particles are opaque can then be determined.

Abstract: A master disk used in the manufacturing of optical disks and having a substrate and a photoresist layer coated on the substrate. The method for manufacturing the master disk includes the steps of: coating a first photoresist layer on a substrate; exposing the first photoresist layer according to patterns of a groove formation recess and a land formation protrusion corresponding to a groove and a land, respectively; etching the exposed substrate and the first photoresist layer, to thereby form the groove formation recess and the land formation protrusion on the substrate; coating a second photoresist layer on the substrate, to thereby form the groove and the land at positions corresponding to the groove formation recess and the pit formation protrusion, respectively; exposing the second photoresist layer according to a pattern of a pit where predetermined information is recorded; and etching the second photoresist layer, to thereby form the pit on the groove and the land.

Abstract: An optical recording medium of phase change type which exhibits an increased number of overwritable operations is provided. The optical recording medium comprises a substrate, and a first dielectric layer, a recording layer, a second dielectric layer, and a metal reflective layer disposed on the substrate in this order, and the first dielectric layer comprises a dielectric layer 1a on the side of the substrate and a dielectric layer 1b in contact with the recording layer. The dielectric layer 1a comprises ZnS--SiO.sub.2, and the dielectric layer 1b comprises Si.sub.3 N.sub.4 and/or Ge.sub.3 N.sub.4. The second dielectric layer may comprise a single layer of ZnS--SiO.sub.2, SiO.sub.2 or oxide of a rare earth metal. The second dielectric layer may also comprise a laminate of a dielectric layer 2a comprising ZnS--SiO.sub.2 on the side of the substrate and a dielectric layer 2b comprising SiO.sub.2 or oxide of a rare earth metal on the side of the reflective layer. The dielectric layer 1b has a thickness of 0.

Abstract: A molded thermoplastic resin disc substrate specially adapted for use with floating head type recording/reproduction apparatus is provided. The molded disc substrate has surface smoothness characteristics which are the same or better than are provided with mirror polished aluminum discs. The molded disc substrates include a floating head scanning surface wherein the maximum projection height or maximum surface irregularity is less than about 50 nm to reduce or eliminate damage to either the disc or floating head caused by unwanted collisions between them. In a preferred embodiment, the molded disc substrates are molded from a thermoplastic resin composition containing 10000 particles/gram or less of particles having a particle diameter of 0.5 .mu.m or more. In a preferred embodiment, control of particle size and content is achieved by subjecting the resin molding composition to a sequence of filtering steps using filters of decreasing mesh size.

Abstract: A write-once-read-many type optical disk and a method for fabricating the same. The write-once optical disk includes a thin Fe--Zr--H recording layer formed on a substrate.

Abstract: A triple substrate optical disk comprises a center substrate layer, a top substrate layer, a bottom substrate layer, a top adhesion layer bonding the top substrate layer to the center substrate layer and a bottom adhesion layer bonding the center substrate layer to the bottom substrate layer. The center substrate layer has a center substrate containing a top surface and a bottom surface thereof, a first recording layer deposited on the top surface of the center substrate and a second recording layer deposited on the bottom surface of the center substrate. The top substrate layer includes a top substrate and a third recording layer, wherein the top substrate has a top surface and a bottom surface thereof and the third recording layer is deposited on the bottom surface of the top substrate.

Abstract: An improved optical recording medium is provided, and includes a surface of the optical recording medium having at least pits and grooves formed therein, a recording layer formed adjacent the surface of said optical recording medium, and a light transmissive layer formed adjacent the recording layer. Information is recorded and/or reproduced by irradiation of light from an optical pickup employing an objective lens having a numerical aperture of 0.7 or larger through the light transmission layer. At least a surface layer of said light transmissive layer is formed of a material having a Young's modulus of 70 GPa or larger thereby greatly reducing or eliminating scratches from the surface of the optical recording medium while allowing for an increase in the storage capacity of the optical storage medium.

Abstract: An optical recording medium including a substrate which transmits light, which has a main surface, and which has a groove defined in the main surface; a recording layer formed on the main surface; and a metal reflection layer formed on the recording layer, wherein the recording layer is a thin film comprised of organic dye, contains at least one cyanine dye represented by general formula (I) as a main constituent, and is capable of corresponding to short-wavelength laser beam: ##STR1## where X- represents an iodide ion, a bromide ion, a perchlorate ion, a borofluoride ion, a tetrafluorophosphate ion, a tetrafluoroantimonate ion, a methylsulfate ion or a methylbenzenesulfonate ion; one of R.sub.1 or R.sub.2 represents a C.sub.3-18 substituent having an unsaturated bond, and another one of R.sub.1 and R.sub.2 represents a C.sub.3-18 substituent having one of an unsaturated bond, an alkyl group, an aryl group or an alkoxy group; Y.sub.1 and Y.sub.

Abstract: An optical information carrier is in the form of a composite laminate having a carrier foil. The underside and the top side of the carrier foil are provided with optically effective structures. The carrier foil is approximately transparent for light in a predetermined spectral range. The structures allow light impinging on the top side to penetrate at least partially into the composite laminate. The structures on the underside are microscopically fine relief structures which are covered with a base layer whose refractive index differs from the refractive index of the carrier foil in at least a portion of the electromagnetic spectrum so that the structures on the underside at least partially reflect and diffract the light which has penetrated into the composite laminate. The structures on the top side in turn modify the diffracted light. The interplay of the two structures provides manifold characteristic optical effects such as moire effects and light guide effects.

Abstract: An optical recording medium has a substrate and a recording layer which is formed on the substrate and contains an azo metal chelate compound including an azo moiety of formula (I) and a bivalent or trivalent metal; ##STR1## wherein X is OH group, CooH group or CONH.sub.2 group; Y is a residual group forming a heterocyclic ring in combination with nitrogen atoms bonded thereto; and Z is a residual group forming an aromatic ring in combination with carbon atoms bonded thereto. In addition, there is provided a method of recording information and reproducing the information using the above-mentioned optical recording medium.

Abstract: A high density optical recording medium having wide-width grooves capable of reliable tracking is provided. The optical recording medium is formed with the wide-width grooves 12 in which a width g of the groove 12 is larger than a width L of a land between the grooves. The lands 11 and the grooves 12 are formed so that a track pitch Tp is less than 1 .mu.m, and a land height h from a groove bottom surface 13 satisfies [(.lambda./(8n)).multidot.Ltan.theta.]/[Ltan.theta.-(.lambda./(8n))].ltore q.h.ltoreq.[(.lambda./(5n)).multidot.Ltan.theta.]/[Ltan.theta.-(.lambda./(5 n))] with respect to a wavelength .lambda. of a reproducing light beam and a refractive index n of a substrate. An angle of inclination of a groove side wall is represented by .theta., and the refractive index of the substrate is represented by n.

Abstract: A high density optical disc having an optical disc protective structure for enabling a high density information recording and retrieval optical disc. The optical disc includes: a first protective film coated by a few tens of microns, on the reading surface of the optical disc, the first protective film having good transmissivity and high hardness against abrasion; and a second protective film coated by a few microns and having a lower surface energy and a minute molecular structure, providing protection against fingerprints on the surface of the first protective film.

Abstract: An optical disc in which a desired exchange reciprocal action is displayed between two sorts of the rare earth-transition metal alloy films to realize optimum recording/reproducing characteristics, and a manufacturing method for the optical disc. To this end, an optical disc 1 includes a first rare earth-transition metal alloy film containing rare earth elements and transition elements and a second rare earth-transition metal alloy film layered on the first rare earth-transition metal alloy film. The second rare earth-transition metal alloy film has a composition different from that of the first rare earth-transition metal alloy film and contains rare earth elements and transition elements. An oxidized area defined between the first rare earth-transition metal alloy film and the second rare earth-transition metal alloy film has an oxygen content not higher than 2.5 atom % and a thickness not larger than 7 nm.

Abstract: A recording medium is for recording information by varying optical characteristic thereof by application of an external energy thereto, and includes a first substance and a second substance. When the external energy is applied to the recording medium, the first and second substances react with each other to form a third substance having a tungsten-bronze crystalline structure, thereby varying the optical characteristic. The third substance absorbs the external energy and varies the reflectivity of the external energy. Thus, the recording medium records information thereon. The recording medium is good in environmental resistance and information retention, because the third substance is stable energetically.

Abstract: An optical memory material includes a two-photon storage component which can be written from a first to a second state in response to WRITE light, mixed with a signal component which fluoresces by one-photon absorption only at the written locations in response to READ light. The storage material may be a fulgide. The memory material may also include a frequency upconversion material to aid writing. Writing is performed by a spatial light modulator (SLM) with a dynamic focussing system, for concentrating sufficient power at WRITE locations for nonlinear two-photon absorption. Crosstalk is avoided during simultaneous writing in some embodiments, by spacing the individual WRITE beams apart by an integer number of inter-beam spacings, so that non-adjacent datels are written simultaneously in a "paragraph," and the non-written areas are written at a different time with different paragraphs.

Abstract: An improved optical data storage medium and a method of forming and utilizing such a medium. One such optical data storage medium has a substrate having an upper surface including a series of physical deformations which encode data. A reflective film stack carried by the upper surface of the substrate includes both a reflective layer and an overlayer. The reflective layer is formed of a reflective metal and is able to generate a readable data stream from a reflected data reading light. The overlayer is formed of a material which has a higher Young's modulus and/or a higher modulus of compression than the reflective metal and is less reflective of the reading light than is the reflective metal at the same thickness. A protective layer is carried behind the reflective film stack and may serve to protect the reflective film stack against physical damage and environmental attack.

Abstract: The invention provides a phase charge type optical recording medium comprising on both sides of a recording layer dielectric layers, each containing zinc sulfide and silicon oxide as main components. The medium comprises on a substrate 2 a first dielectric layer 31, a recording layer 4, a second dielectric layer 32 and a reflective layer 5 made up of a metal. The first dielectric layer 32 comprises a dielectric lamina 1a on a substrate 2 side thereof and a dielectric lamina 1b on a recording layer 4 side thereof. The dielectric lamina 1a has a silicon oxide content of 2 to less than 40 mol %, the dielectric lamina 1b has a silicon oxide content of 40 to 100 mol %, and the second dielectric layer 32 has a silicon oxide content of 2 to 50 mol % and a thickness of 10 to 35 nm. The number of overwritable cycles can be increased.

Abstract: Copolycarbonates comprise structural units derived from a bisphenol such as bisphenol A, a spiro(bis)indane bisphenol such as 6,6'-dihdyroxy-3,3,3',3'-tetramethyl-1,1'-spiro(bis)indane and a polyoxyalkylene glycol such as polyethylene glycol. These copolycarbonates have high processability and are expected to have low birefringence. They are useful for the fabrication of optical disks.