Patent ID: 7390571

Claim:
A varnish for laminate or prepreg, said varnish comprising: an epoxy resin as component (a); dicyandiamide as component (b); a compound having an imidazole ring as component (c), said compound being present in an amount of 0.001 to 0.03% by weight, based on the weight of component (a); and an inorganic filler as component (d); wherein said varnish is produced by a process comprising the steps of: (1) forming a mixture of components (a), (b), and (c), wherein component (c) is present in an amount of 0.001 to 0.03% by weight, based on the weight of component (a); (2) forming a solution by dissolving said mixture in a solvent; (3) heating said solution to a temperature of 70° C. to less than 140° C., thereby causing pre-reaction of components (a) and (b); and (4) adding component (d); wherein the pre-reaction product of components (a) and (b) enhances compatibility between components (a) and (b), yielding a varnish in which: components (a), (b), and (c) are all compatible with each other in the absence of a solvent; and component (d) remains uniformly dispersed therein.