Abstract: Molds for injection molding a light guide plate in which a plurality of pin gates and/or film gates for injecting a melted resin material for molding into the cavity portion are formed at portions corresponding to the side portions of the product, a room for balancing flow having an ear shaped portion to which the material is supplied is disposed between each gate and a sprue or a runner, and the area of each gate is set so that the temperature of the material introduced into the cavity is higher than that supplied to each room by at least 5° C. due to heat generated from shearing when the material passes through the gate; and a process for producing a light guide plate using the molds. Formation of weld lines, sink marks, flow marks and warp is suppressed, and a product exhibiting excellent quality without the necessity of steps of gate cutting and finishing can be obtained.

Abstract: An optical system of an optical recording apparatus forms a main spot and sub-spots preceding and succeeding the main spot on a signal recording medium. The optical system is set such that the sub-spot is shifted from the main spot in the direction orthogonal to a signal track by a distance expressed by an expression (2k?1)P/4(k=natural number), in which P denotes a distance between adjacent signal tracks on the signal recording medium. Thus, the sub-spot succeeding the main spot can be used to effectively read the state of a signal recorded on the signal recording medium by the main spot.

Abstract: An optical system of an optical recording apparatus forms a main spot and sub-spots preceding and succeeding the main spot on a signal recording medium. The optical system is set such that the sub-spot is shifted from the main spot in the direction orthogonal to a signal track by a distance expressed by an expression (2k−1) P/4 (k=natural number), in which P denotes a distance between adjacent signal tracks on the signal recording medium. Thus, the sub-spot succeeding the main spot can be used to effectively read the state of a signal recorded on the signal recording medium by the main spot.

Abstract: There is provided a plastisol for use in a electrically conductive molded article comprising non-conductive high polymer particles having surfaces coated with an electrically conductive high polymer or non-conductive high polymer particles having surfaces coated with filler of electrically conductive fine particles, and a plastisizer compatible with the said non-conductive high polymer. The plastisol is excellent in fluidity and good in processability. Said plastisol can provide a molded article having excellent electrical conductivity and is suited for, e.g., production of floor materials or sealing materials having low static properties and formation of an electrically conductive path.

Abstract: An electron beam-crosslinkable plastisol is provided comprising, as requisite components, (A) a particulate epoxy group-containing paste resin for plastisol processing having an epoxy group concentration on the particle surface of 1.times.10.sup.-5 to 1.times.10.sup.-3 g equivalent/g and an average particle size of 0.05 to 5 .mu.m, (B.sub.1) an unsaturated acid having a pKa less than 4, (B.sub.2) an amino group-containing unsaturated compound, and (C) a plasticizer. This plastisol can effectively be crosslinked by application of an electron beam of low-speed energy to give moldings having suitable properties.

Abstract: A polyvinyl chloride plastisol composition is provided, which contains as essential components (A) polyvinyl chloride resin particles prepared by microsuspension polymerization of vinyl chloride in the presence of a polymethyl methacrylate resin soluble in vinyl chloride and having polymethyl methacrylate resin localized on the surfaces of the resin particles, and (B) a plasticizer, and which has excellent thermal stability and stability with time of viscosity. The composition can be used advantageously as a material for use in processing procedures in which heat accumulates in plastisol being retained, for example, in slush processing, dip processing, etc. or for use in coating processing in which adhesiveness is required.

Abstract: Foamed articles of polyvinyl chloride resins are prepared by mixing an organic foaming agent having a temperature of foaming by decomposition of 100.degree. C. or above and a plasticizer with a polyvinyl chloride resin containing epoxy group which is formed into particles having an average diameter in the range from 0.05 to 5 .mu.m and has a concentration of the epoxy group at the surface of the particle of 1.times.10.sup.-2 weight % or more and a concentration of the total epoxy group in the particles of the said resin of 10 weight % or less at a temperature where the organic foaming agent does not decompose and coating or molding the mixed compound with foaming by heating.Foamed articles of polyvinyl chloride resins having excellent physical properties and high expansion ratios can be prepared without utilizing a crosslinking agent at the ambient pressure.