Abstract: A polymer excellent in transparency, mechanical properties, moisture resistance suitable for optical use is obtained by copolymerizing a (meth)acrylate compound (I) and a (meth)acrylate compound (II).

Abstract: A method for producing an optical disk base to store, record, and retrieve sounds, images, and information. An improved method for producing an optical disk base includes the steps of injecting a photo-curable resin into a cavity, curing the photo-curable resin by irradiation with light, and demolding, where the photo-curable resin is injected from an injection nozzle having an outside diameter which is substantially equal to the diameter of the center hole of the optical disk base and also having a horn-shaped opening at the forward end. The injection nozzle is arranged at the center of the optical disk base. The forward end of the nozzle is closed after injection and the photo-curable resin is irradiated with light, with the injection nozzle projected into the cavity. A liquid resin is injected in the form of uniform flow without entrapped bubbles, so that the anamolous molecular orientation is avoided and the contamination with insufficiently cured or uncured resin is also avoided.

Abstract: In an optical recording disk wherein a resin layer cured with ultraviolet radiation is provided on a surface of a transparent substrate, the present invention consists in that a material having a heat distortion temperature of at least 65.degree. C. is employed for the ultraviolet-cured resin layer. The appearance of wrinkles on a UV-cured resin surface is suppressed, whereby an optical recording disk of high carrier-to-noise ratio and long lifetime can be provided.

Abstract: An optical disc wherein a transparent base plate is made from a special light-curable resin composition comprising at least one compound of the formula: ##STR1## wherein R.sub.1 =H or methyl and n=0-5, and a photopolymerization initiator, is excellent in heat resistance, mechanical strength, moisture resistance, etc.

Abstract: The invention discloses an optical disc base plate obtained by curing with irradiation of light a light- or radiation-curable resin composition in which a photopolymerization initiator is contained in an amount of 0.5 to 5 parts by weight per 100 parts by weight of a resin composition comprising the compounds (1), (2) and (3) mixed in amounts falling in the area defined by lines A-B-C-D-E-A in the triangular diagram of FIG.

Abstract: An optical disc obtained by placing in parallel two optical disc base plates comprising a transparent substrate, a primer layer formed thereon, and a recording film formed thereon, or the transparent substrate and the primer layer being integrated into one body, wherein the primer layer is made from a special resin composition, is excellent in properties, particularly in moisture resistance.

Abstract: Optical discs obtained by using as a primer layer formed on a transparent substrate and under a metal-made recording film a cured ultraviolet-curable resin composition comprising (a) a reaction product of isophorone diisocyanate or the like and an acrylate or methacrylate, (b) a diacrylate or dimethacrylate and (c) a photopolymerization initiator are excellent in recording sensitivity, moisture resistance, heat resistance, adhesive properties, reliability, etc.

Abstract: In a band compression method using an adaptive prediction system preferably applicable to facsimile transmission, a method of selecting picture elements to be referred (hereinafter defined as reference picture elements) for predicting an information value of a picture element wherein the reference picture elements are not selected uniformly and continuously from the neighborhood of the predicted picture element, but a group of picture elements (the first order picture elements) adjacent to the predicted picture element and further a group of picture elements of equal or higher order than the third order are selected as reference picture elements by excluding those shaded picture elements which lie on lines connecting the predicted picture element and the first order picture elements.

Abstract: This invention relates to a substrate for optical disc recording media which contains a UV-curable resin film between a transparent film and a thermally-decomposing high molecular film, the UV-curable resin film being formed with a UV-curable resin composition comprising given quantities of:(a) a polybutadiene having acrylic or methacrylic group at one or both ends of the molecule,(b) a hydroxyalkyl acrylate or methacrylate,(c) an acrylic- or methacrylic-group-containing diluent, and(d) a photo-polymerization initiator.