Abstract: A portable electronic device, such as a portable sound reproducing device, a portable sound recording/reproducing device, a portable radio receiver or a portable video tape recorder, comprising a case containing an electronic circuit assembly and having a front panel, a plurality of operating buttons for operating control switches for controlling the electronic circuit assembly, supported on the front panel is provided with a sliding cover assembly slidably provided on the front panel and capable of being shifted between a first position to cover the operating buttons and a second position to expose the operating buttons. The sliding cover assembly is retained at the first position by a retaining mechanism to prevent the accidental operation of the operating buttons.

Abstract: An oxygen permeable hard contact lens having an improved oxygen permeability and an improved fragility as well as excellent hardness and rigidity, made of a copolymer comprising an organosilane or organosiloxane having in one molecule at least one group of the general formula (I): ##STR1## wherein R.sup.1 is hydrogen atom or methyl group, k is 0 or 1, and l is 1 or 3,and having at most 16 silicon atoms, and a fluoroalkyl acrylate or methacrylate of the general formula (II): ##STR2## wherein R.sup.1 is as defined above, m is 0 or 1, n is 0 or an integer of 1 to 3, and R.sub.f is a straight or branched fluoroalkyl group having 2 to 21 fluorine atoms.

Abstract: A polymerization product suitable for contact lenses comprising (a) an organosiloxane monomer having the following general formula ##STR1## wherein n is an integer of 1 to 3, X is --(CH.sub.2).sub.p --O].sub.q in which p is an integer of 2 to 4 and q is 0 or an integer of 1 to 3, and Y.sup.1, Y.sup.2 and Y.sup.3 are methyl group or --O--Si--(CH.sub.3).sub.3, and (b) a hydrophobic methacrylic acid alkyl ester monomer. The polymerization product and cross-linked polymerization product have excellent oxygen permeability and proper hydrophilic property and are substantially water-nonabsorptive, and contact lenses made thereof can be comfortably worn continuously for a long period of time.

Abstract: A copolymer suitable for use as soft contact lenses, comprising a polymerization product of (a) at least one monomer selected from methyldi(trimethylsiloxy)sylylpropylglycerol methacrylate and methyldi(trimethylsiloxy)sylylpropylglycerolethyl methacrylate, (b) a hydrophilic monomer and (c) a cross-linking agent having at least two copolymerizable functional groups. Soft contact lens made of the above copolymer has excellent oxygen permeability in spite of low water content and can be comfortably worn continuously for a long term without a foreign body sensation and pain.

Abstract: A copolymer suitable for use as contact lenses, comprising a polymerization product of (a) at least one monomer selected from methyldi(trimethylsiloxy)sylylpropylglycerol methacrylate and methyldi(trimethylsiloxy)sylylpropylglycerolethyl methacrylate, (b) a hydrophilic monomer, (c) a methacrylic acid alkyl ester and (d) a cross-linking agent having at least two copolymerizable functional groups. Contact lenses made of the above copolymer has excellent oxygen permeability and can be comfortably worn continuously for a long term without a foreign body sensation and pain.

Abstract: A novel methacrylic acid ester derivative, methyldi(trimethylsiloxy)sylylpropylglycerol methacrylate which is availably employed as a main monomer for preparing copolymers useful as a material of contact lenses. The derivative has siloxane bond which contributes to increase of the oxygen permeability of its copolymers, and has hydrophilic hydroxyl group and ether bond by which the derivative is miscible with a hydrophilic monomer in all proportions and is easily copolymerizable therewith and colorless transparent copolymers are obtained.