Mixed composition

A mixed composition of

• a compound (A1) represented by the following formula (a1);
• an organosilicon compound (B) represented by the following formula (b1);
• and
• a solvent (E),
• wherein the solvent (E) comprises a compound (E1) satisfying a Hansen solubility parameter of 18 (J/cm3)1/2 or more and 23.5 (J/cm3)1/2 or less and a hydrogen bonding term (H) of the Hansen solubility parameter, of 5.5 (J/cm3)1/2 or more:
• wherein Aa1 represents a hydroxy group or a hydrolyzable group, and a plurality of Aa1s, when present, are optionally different from each other;
• Za1 represents a hydrocarbon group, a trialkylsilyl group-containing molecular chain, or a siloxane backbone-containing group, and a plurality of Za1s, when present, are optionally different from each other;
• r1 represents an integer of 1 to 3;
• and
• Ra1 represents a group represented by the following formula (a11);
• wherein Rs2s each independently represent an alkyl group having 1 to 4 carbon atoms;
• Ra11 represents a hydrocarbon group or a trialkylsilyloxy group, hydrogen atoms in the hydrocarbon group or the trialkylsilyloxy group are optionally replaced by fluorine atoms, and a plurality of Ran s, when present, are optionally different from each other;
• Aa11 represents a hydroxy group or a hydrolyzable group, and a plurality of Aa11s, when present, are optionally different from each other;
• Zs1 represents —O— or a divalent hydrocarbon group, and —CH2— in the divalent hydrocarbon group is optionally replaced by —O—;
• Ys1 represents a single bond or —Si(Rs2)2-Ls1-, Ls1 represents a divalent hydrocarbon group, and —CH2— in the divalent hydrocarbon group is optionally replaced by —O—;
• r2 represents an integer of 0 to 3;
• r10 represents an integer of 1 or more;
• and
• * represents a bond;
• Si(Rb1)b20(Xb1)4-b20 (b1)
• wherein Rb1 represents a hydrocarbon group having 1 to 5 carbon atoms;
• Xb1 represents a hydrolyzable group;
• and
• b20 is 0 or 1.