Abstract: A humidity sensor includes a pair of opposed electrodes disposed on an insulating substrate and defining a gap therebetween and a humidity sensitive thin film covering the gap. This thin film is formed by coating a polymer of specific structure having an ethylenically unsaturated reactive group and exposing the coating to ultraviolet radiation for crosslinking. The sensor is fully water resistant and produces accurate outputs over a wide humidity range and thus can detect and determine moisture in the surrounding atmosphere.

Abstract: An optical disk includes a pair of disk substrates and a recording layer on at least one substrate, the disk substrates being mated by bonding the substrates at their inside surfaces through an adhesive layer such that the recording layer is internally enclosed. In one form, a pair of self-adhesive layers are applied to the respective substrate inside surfaces and formed with a plurality of channels extending over the surface from the outer or inner circumferential edge to the outer circumferential edge. The self-adhesive layers are bonded together to integrate the pair of disk substrates in which the channels form passages for allowing air escape. In another form, a pair of adhesive layers are applied to the respective substrate inside surfaces. The pair of disk substrates are joined by bonding the adhesive layers together through a buffer foam sheet.

Abstract: An optical disk includes a resinous substrate and a recording layer thereon. A hard coat layer containing conductive particles is provided on a light incident side of the substrate for protecting the substrate from physical damages and rendering the disk antistatic for preventing dust deposition.

Abstract: A protective coating made of resin, preferably a radiation curable resin containing fluoroplastic fine particles having a low surface energy is provided in the form of the uppermost layer facing a magnetic head, thereby improving the frictional properties and durability of a magneto-optical disc that is used with a magnetic field modulation system in which the magnetic head comes in constant contact therewith.