Abstract: A process for producing a curable resin comprises reacting (a) at least one cyanate ester compound selected from the group consisting of polyfunctional cyanate esters having 2 or more cyanato groups per one molecule, prepolymers of the cyanate esters or mixtures thereof with (b) at least one compound having 1,2-epoxy group(s) and radical-polymerizable unsaturated double bond(s) in its molecule, the cyanate ester compound (a) and the compound (b) being used so that the ratio of the cyanato group to the 1,2-epoxy group is in the range of about 1:0.25 to about 1:2, in the presence of (c) a radical polymerization inhibitor at a temperature of about 90.degree.--about 140.degree. C.The curable resin produced according to the present invention is capable of giving cured products having excellent heat resistance and electrical properties.

Abstract: A method for delaying curing rate of a curable resin composition comprising a polyfunctional cyanate ester compound or mixture of a polyfunctional cyanate ester compound and a polyfunctional maleimide compound, characterized in that a specific benzene sulfonic acid is added to said composition is disclosed.

Abstract: A curable resin composition comprising a mixture and/or a preliminary reaction product of (a) polyfunctional cyanate ester, prepolymer of the cyanate ester, or coprepolymer of the cyanate ester and an amine, and (b) acrylic epoxy esters, methacrylic epoxy esters, prepolymers of acrylic epoxy esters, prepolymers methacrylic epoxy esters, coprepolymers of acrylic epoxy esters and methacrylic epoxy esters and mixtures thereof, and a curable resin composition comprising a mixture or a preliminary reaction product of above component (a), above component (b) and (c) a polyfunctional maleimide, prepolymer of the maleimide or coprepolymer of the maleimide and an amine are disclosed. Cured resin having excellent impact-resistance, adhesive power, heat-resistance and chemical resistance can be prepared from the compositions.

Abstract: A photo-curable resin composition is disclosed comprising (i) a mixture and/or a preliminary reaction product of (a) at least one cyanate compound selected from the group consisting of polyfunctional cyanate esters, prepolymers of the cyanate esters, coprepolymers of the cyanate esters and an amine and mixtures thereof, (b) at least one compound selected from the group consisting of monomers having at least one olefinically double bond prepolymers of the monomers, liquid rubbers having one or more acryloyl or methacryloyl groups and mixtures thereof and optionally (c) at least one maleimide compound selected from the group consisting of polyfunctional maleimides, prepolymers of the maleimides, coprepolymers of the maleimides and an amine and mixtures thereof and (ii) a photo polymerization initiator or a photo sensitizer.