Resin varnish, prepreg, laminate, and printed wiring board

1. A resin varnish comprising:

(A) a maleimide compound,

(B) an epoxy resin,

(C) a copolymer resin having a structural unit derived from an aromatic vinyl compound and a structural unit derived from a maleic anhydride,

(D) a silica treated with an aminosilane coupling agent, and

(G) an organic solvent.

2. The resin varnish according to claim 1 , wherein the component (A) is a maleimide compound having an acidic substituent and an N-substituted maleimide group, which is obtained by reacting (a1) a maleimide compound having at least two N-substituted maleimide groups in one molecule, (a2) a monoamine compound having an acidic substituent, and (a3) a diamine compound.

3. The resin varnish according to claim 1 , wherein the component (A) is a maleimide compound having an acidic substituent and an N-substituted maleimide group, which is obtained by reacting (a1) a maleimide compound having at least two N-substituted maleimide groups in one molecule, (a2) a monoamine compound represented by the following general formula (a2-1), and (a3) a diamine compound represented by the following general formula (a3-1):

wherein R A4 represents an acidic substituent selected from a hydroxy group, a carboxy group and a sulfonic acid group, R A5 represents an alkyl group having 1 to 5 carbon atoms or a halogen atom, t represents an integer of 1 to 5, u represents an integer of 0 to 4, and t and u satisfy 1≤t+u≤5, provided that when t is an integer of 2 to 5, plural R A4 's may be the same or different, and when u is an integer of 2 to 4, plural R A5 's may be the same or different;

wherein X A2 represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or —O—, R A6 and R A7 each independently represent an alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy group, a carboxy group or a sulfonic acid group, and v and w each independently represent an integer of 0 to 4.

4. The resin varnish according to claim 1 , wherein the component (C) is a copolymer resin having a structural unit represented by the following general formula (C-i) and a structural unit represented by the following formula (C-ii):

wherein R C1 represents a hydrogen atom, or an alkyl group having 1 to 5 carbon atoms, R C2 represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 6 to 20 carbon atoms, a hydroxy group, or a (meth)acryloyl group, and x represents an integer of 0 to 3, provided that when x is 2 or 3, plural R C2 's may be the same or different.

5. The resin varnish according to claim 4 , wherein in the general formula (C-i), R C1 is a hydrogen atom and x is 0.

6. The resin varnish according to claim 1 , wherein in the component (C), the content ratio of the structural unit derived from an aromatic vinyl compound to the structural unit derived from a maleic anhydride [aromatic vinyl compound-derived structural unit/maleic anhydride-derived structural unit] (molar ratio) is from 2 to 9.

7. The resin varnish according to claim 1 , wherein in the component (C), the content ratio of the structural unit derived from an aromatic vinyl compound to the structural unit derived from a maleic anhydride [aromatic vinyl compound-derived structural unit/maleic anhydride-derived structural unit] (molar ratio) is from 3 to 7.

8. The resin varnish according to claim 1 , wherein the weight average molecular weight of the component (C) is from 4,500 to 18,000.

9. The resin varnish according to claim 1 , wherein the weight average molecular weight of the component (C) is from 9,000 to 13,000.

10. The resin varnish according to claim 1 , wherein the component (B) is a bisphenol F epoxy resin, a phenol-novolak epoxy resin, a cresol-novolak epoxy resin, a naphthalene epoxy resin, an anthracene epoxy resin, a biphenyl epoxy resin, a biphenylaralkyl epoxy resin or a dicyclopentadiene epoxy resin.

11. The resin varnish according to claim 1 , further comprising

(E) a curing agent.

12. The resin varnish according to claim 1 , further comprising

(F) a flame retardant.

13. The resin varnish according to claim 1 , wherein the organic solvent (G) is at least one selected from the group consisting of an alcohol solvent, a ketone solvent, an ether solvent, an aromatic solvent, a nitrogen atom-containing solvent, a sulfur atom-containing solvent and an ester solvent.

14. A prepreg comprising a resin varnish of claim 1 .

15. A laminate comprising a prepreg of claim 14 and a metal foil.

16. A printed wiring board provided with a laminate of claim 15 .