Photosensitive resin and process for producing microlens

A positive resist composition comprising:

• an alkali-soluble polymer (A) containing a unit structure having an aromatic fused ring or a derivative thereof;
• a compound (B) having an organic group which undergoes photodecomposition to yield an alkali-soluble group;
• and
• a crosslinkable compound (D), wherein:
• the polymer (A) is a polymer containing:
• a unit structure represented by Formula (2):
• where:
• R1 represents a halogen atom, an alkyl group, an alkoxy group, a thiol group, a cyano group, an amino group, an amide group, an alkylcarbonyl group, or a thioalkyl group;
• R3 represents a hydrogen atom or a methyl group;
• m3 represents an integer of 1 or 2;
• when m3=1, m1 represents an integer of 0 to 7;
• and
• when m3=2, m1 represents an integer of 0 to 9;
• and
• a unit structure represented by Formula (3):
• where:
• R4 and R5 individually represents a hydrogen atom, a methyl group, a carboxyl group, or an alkylenecarboxyl group having 1 to 3 carbon atoms, and
• Q represents a single bond, an alkylene group having 1 to 3 carbon atoms, or an aromatic group having 6 to 10 carbon atoms;
• when a total number of all unit structures constituting the polymer (A) is 1.0, a ratio of a number n2 of unit structures represented by Formula (2) and a ratio of a number n3 of unit structures represented by Formula (3) satisfy 0.2≦n2≦0.8, 0.1≦n3≦0.7, and 0.3≦n2+n3≦1.0;
• and
• the compound (B) has a structure represented by Formula (7):
• where:
• R11 represents a hydrogen atom, a 1,2-quinonediazide group, or a derivative thereof;
• R12 represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, a halogen atom, or an alkoxy group having 1 to 10 carbon atoms;
• R13 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms;
• m5 represents an integer of 1 to 5;
• m6 represents an integer satisfying 0≦m6≦(5-m5);
• m10 represents an integer satisfying 0≦m10≦(5-m8-m9);
• m7 represents an integer of 0 to 10;
• m8 represents an integer of 0 or 1;
• m9 represents an integer of 0 to 5;
• and
• in all —OR11 groups existing in the compound (B), R11 is a 1,2-quinonediazide group or a derivative thereof in an amount of 10 to 98 mol%,
• wherein the positive resist composition is formulated so that upon curing a film of the positive resist composition, the cured film has a transmittance of 80% or more at wavelengths of 400 to 730 nm.