Abstract: An optical disc comprises two facing disc units, at least one of which has a recording layer formed on its surface facing to the other disc unit. The disc units are bonded together by a layer of adhesive which may be a room-temperature curing thermosetting adhesive having a glass transition temperature higher than the upper limit of the range of temperatures of environments in which the disc may be used. Alternatively, the adhesive may be a room-temperature curing two-pack epoxy adhesive which comprises a bisphenol epoxy resin base agent and a modified aliphatic polyamine curing agent, and which has a viscosity of 100-1000 cps, a pot life of one hour or more, a cure shrinkage of 1.0% or less, a water absorption, after curing, of 0.2% or less, and a Shore hardness, after curing, of 80-90.

Abstract: An optical disc comprises two facing disc units, at least one of which has a recording layer formed on its surface facing to the other disc unit. The disc units are bonded together by a layer of adhesive which may be a room-temperature curing thermosetting adhesive having a glass transition temperature higher than the upper limit of the range of temperatures of environments in which the disc may be used. Alternatively, the adhesive may be a room-temperature curing two-pack epoxy adhesive which comprises a bisphenol epoxy resin base agent and a modified aliphatic polyamine curing agent, and which has a viscosity of 100-1000 cps, a pot life of one hour or more, a cure shrinkage of 1.0% or less, a water absorption, after curing, of 0.2% or less, and a Shore hardness, after curing, of 80-90.

Abstract: The present invention relates to a master disk used as a matrix for manufacturing a stamper by transferring, which is used for reproducing an optical disk, the master disk according to the present invention is provided with an appointed number of calibration tracks formed at an appointed pitch symmetrically relative to the center of guide tracks in the area including a position corresponding to an edge portion of a center hole of the stamper, whereby the center hole of the stamper can be easily formed concentrically with the guide tracks of the master disk and the tolerance of diameter of the center hole or the eccentricity between the center of the center hole and the center of the guide track can be easily measured.

Abstract: The apparatus inspects defects on tracks of an object to be inspected such as an optical disc or stamper. The apparatus has a defect detector, a controller for controlling the movement of the object, and a microscope for observing the tracks of the object. Position information on defects is obtained by the detector and, according to this position information, the object is moved so that the defects can be in the visual field of the microscope.

Abstract: A novel epoxy resin composition is comprised of a mixture of a cyclic epoxide type epoxy resin having an epoxy equivalent of 200 or below and a phenoxy resin having a molecular weight of approximately 30,000, a curing agent, and an inorganic filler. This resin composition is useful in the fabrication of cast insulators to be employed in electric machines.

Abstract: A novel epoxy resin composition is prepared by first mixing 100 parts by weight of an epoxy resin having an epoxy equivalent of no more than 200 with 0.5-10 parts by weight of a phenoxy resin to form a uniform mixture, then blending the mixture with a curing agent (i.e., a condensation product of a polybasic carboxylic acid and bisphenol A) and an inorganic filler. The epoxy resin composition has a suitable degree of rigidity and softness within the molecular chain without sacrificing its resistance to heat or thermal shock and will not cause precipitation of any portion of the filler in the resin composition. This resin composition is useful in the making of cast insulators employed in electric machines.

Abstract: An epoxy resin composition consisting essentially of an epoxy resin having an epoxy equivalent of 200 or lower, a mixture of polybasic carboxylic acid anhydride and aromatic ester as a curing agent, and inorganic powder as a filler.

Abstract: An epoxy resin composition which comprises:(a) an epoxy resin having an epoxy equivalent of at most 200;(b) a condensation mixture of 1 mol of a polybasic carboxylic acid anhydride, from 0.07 to 0.3 mol of a bisphenol A having the formula: ##STR1## and from 0.07 to 0.3 mol of a monohydric phenol having the formula: ##STR2## wherein R is an alkyl group, as a curing agent; and (c) an inorganic powder, as a filler.

Abstract: An epoxy resin composition which comprises an epoxy resin having an epoxy equivalent of at most 200; a condensation mixture (A) of a polybasic carboxylic acid anhydride, a bisphenol A having the formula: ##STR1## and a polyhydric alcohol, as a curing agent; and an inorganic powder, as a filler.

Abstract: An epoxy resin composition which comprises a mixture (a) obtained by mixing 100 parts by weight of a polybasic carboxylic acid anhydride with from 10 to 70 parts by weight of a compound having at least two phenol groups, an epoxy resin having at least two epoxy groups in the molecule, a catalyst, and an inorganic powder as a filler.