Resin compositions which comprise the following components (A) to (E) are useful for interlayer insulation of a multilayer printed wiring board: (A) an
epoxy resin having 2 or more
epoxy group in one molecule and which exists in a
liquid state at a temperature of 20° C.; (B) an aromatic
epoxy resin having 3 or more epoxy groups in one molecule and an epoxy equivalent of 200 or less; (C) a
phenol type curing agent; (D) one or more resins selected from the group consisting of a phenoxy resin, a polyvinyl
acetal resin, a
polyamide resin, a polyamideimide resin, and mixtures thereof, and having a
glass transition temperature of 100° C. or more; and (E) an
inorganic filler, wherein: the
inorganic filler (E) is present in an amount of 35% by weight or more based on the total weight of the non-volatile components of the resin composition; the epoxy resin (A) and the aromatic epoxy resin (B) are present in a weight ration of from 1:0.3 to 1:2 by weight of epoxy resin (A) to aromatic epoxy resin (B); the epoxy resin (A), the aromatic epoxy resin (B), and the
phenol type curing agent (C) are present in relative amounts such that the weight ratio of epoxy groups in the resin composition and phenolic hydroxyl groups in the
phenol type curing agent (C) is from 1:0.5 to 1:1.5; and the resin (D) is present in an amount of from 2 to 20% by weight based on the total weight of the non-volatile components of the resin composition. Such resin compositions are useful for interlayer insulation of a multilayer printed wiring board and are capable of forming an insulating layer which has a low
thermal expansion coefficient and exhibits excellent peel strength for a conductor layer. Such resin compositions are also useful for preparing
adhesive films and prepregs for a multilayer printed wiring boards, as well as multilayer printed wiring boards having an insulating layer formed of a cured product of the resin composition or the prepreg.