Resin composition, copper foil with resin, dielectric layer, copper-clad laminate, capacitor element, and printed wiring board with built-in capacitor

A method of producing a resin-coated copper foil, comprising:

• coating a copper foil with a resin composition comprising a resin component comprising an epoxy resin, a diamine compound, and a polyimide resin;
• and a dielectric filler composed of a complex metal oxide comprising at least two elements selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, and Bi, the content of the dielectric filler being 60 to 85 parts by weight on the basis of 100 parts by weight of solid content in the resin composition;
• and
• drying the resin composition,
• wherein the content of the polyimide resin is 20 to 40 parts by weight on the basis of 100 parts by weight of the resin component,
• wherein the content of the epoxy resin in the resin composition is 45 to 60 parts by weight on the basis of 100 parts by weight of resin component,
• wherein the content of the diamine compound is determined such that when the number of epoxy groups in the epoxy resin is set to 1, the number of active hydrogen groups in the diamine compound is 0.5 to 1.5, and
• the polyimide resin has at least one functional moiety selected from the group consisting of carboxyl, sulfonic acid, thiol, and phenolic hydroxyl moieties, at its ends or in its side chains, provided that when the functional moiety is carboxyl moiety, the polyimide resin has carboxyl moiety at terminal ends of the polyimide.

A resin composition comprising:

• a resin component comprising an epoxy resin, a diamine compound, and a polyimide resin;
• and
• a dielectric filler composed of a complex metal oxide comprising at least two elements selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, and Bi, the content of the dielectric filler being 70 to 85 parts by weight on the basis of 100 parts by weight of solid content in the resin composition,
• wherein the content of the polyimide resin is 20 to 40 parts by weight on the basis of 100 parts by weight of the resin component,
• wherein the content of the epoxy resin in the resin composition is 45 to 60 parts by weight on the basis of 100 parts by weight of resin component,
• wherein the content of the diamine compound is determined such that when the number of epoxy groups in the epoxy resin is set to 1, the number of active hydrogen groups in the diamine compound is 0.5 to 1.5, and
• the polyimide resin has at least one functional moiety selected from the group consisting of sulfonic acid, thiol, and phenolic hydroxyl moieties, at its ends or in its side chains.