Insulating film, metal-clad laminate member, and rewiring layer

1. An insulating film comprising a semi-cured product of a resin composition,

the resin composition containing: at least one of a component (A1) or a component (A2); a component (B); a component (C1); and a component (C2),

the component (A1) including an epoxy resin having at least one of a naphthalene skeleton or a biphenyl skeleton,

the component (A2) including a phenolic resin having at least one of the naphthalene skeleton or the biphenyl skeleton,

the component (B) including a high molecular weight substance having structures expressed by at least the following formulae (b2) and (b3) out of the following formulae (b1), (b2), and (b3) and having a weight average molecular weight equal to or greater than 200,000 and equal to or less than 850,000,

the component (C1) including a first filler obtained by subjecting a first inorganic filler to surface treatment using a first silane coupling agent expressed by the following formula (c1),

the component (C2) including a second filler obtained by subjecting a second inorganic filler to surface treatment using a second silane coupling agent expressed by the following formula (c2),

the insulating film containing an inorganic filler having a maximum particle size equal to or less than 5 μm,

the insulating film having a thickness equal to or greater than 0.1 μm and equal to or less than 10 μm,

(R6)Si(R5) 3   (c1)

(R8)Si(R7) 3   (c2)

where x in the formula (b1), y in the formula (b2), and z in the formula (b3) satisfy the following relational expression: x:y:z (in mole fractions)=0:0.95:0.05 to 0.2:0.6:0.2 (where x+y+z≤1, 0≤x≤0.2, 0.6≤y≤0.95, and 0.05≤z≤0.2); in the formula (b2), R1 is either a hydrogen atom or a methyl group, R2 is selected from the group consisting of a hydrogen atom, an alkyl group, a glycidyl group, and an epoxidized alkyl group and at least includes either the glycidyl group or the epoxidized alkyl group; in the formula (b3), R3 is either a hydrogen atom or a methyl group and R4 is Ph (phenyl group), —COOCH 2 Ph, or —COO(CH 2 ) 2 Ph; in the formula (c1), R5 is either a methoxy group or an ethoxy group and R6 has an isocyanate group, a glycidyl group, or an amino group at an end of an aliphatic alkyl group having a carbon number equal to or greater than 3 and equal to or less than 18; and in the formula (c2), R7 is either a methoxy group or an ethoxy group and R8 has either a methacryloyl group or a vinyl group at an end of an aliphatic alkyl group having a carbon number equal to or greater than 3 and equal to or less than 18.

2. The insulating film of claim 1 , wherein

either the component (C1) or the component (C2) is a nanofiller having a mean particle size equal to or less than 500 nm.

3. The insulating film of claim 2 , wherein

content of the nanofiller falls within a range from 1 part by mass to 30 parts by mass with respect to 100 parts by mass in total of the components (A1), (A2), and (B).

4. The insulating film of claim 1 , wherein

a ratio by mass of a sum of the components (A1) and (A2) to the component (B) is 90:10 to 50:50.

5. The insulating film of claim 1 , wherein

combined content of the components (C1) and (C2) is equal to or less than 80% by mass with respect to an entire mass of the resin composition.

6. The insulating film of claim 1 , wherein

a ratio by mass of the component (C1) to the component (C2) is 100:0 to 60:40.

7. The insulating film of claim 1 , wherein

the components (A1) and (A2) and the component (B) are in a phase separation state without exhibiting compatibility.

8. The insulating film of claim 1 , wherein

the component (B) has an epoxy value falling within a range from 0.01 eq/kg to 0.80 eq/kg.

9. The insulating film of claim 1 , wherein

the component (B) has no unsaturated bonds between any pair of adjacent carbon atoms.

10. The insulating film of claim 1 , wherein

the resin composition further contains a phosphorus-based flame retardant.

11. The insulating film of claim 1 , wherein

the insulating film in a cured state has a loss modulus to storage modulus ratio equal to or greater than 0.05 in a temperature range equal to or lower than 100° C. and in a temperature range equal to or higher than 200° C.

12. A metal-clad laminate member comprising:

a semi-cured product of the insulating film of claim 1 ; and

a sheet of metal foil bonded to the semi-cured product.

13. A rewiring layer comprising:

a cured product of the insulating film of claim 1 ; and

a conductor pattern provided for the cured product.