Norbornene-based copolymer for photoresist, preparation method thereof, and photoresist composition comprising the same

A preparation method of a 5-norbornene-2-alkane-1,3-dione derivative including transketalization step of the 5-norbornene-2-alkane-1,3-dione having the structure which is represented by the following Formula 1a with a cyclic ketal or cyclic acetal compound under acid catalyst in organic solvent:

• 14
• wherein R1 is C1-12 linear, branched or cyclic alkyl group;
• R2 is hydrogen atom or C1-6 linear, branched or cyclic alkyl group;
• R3, R4 and R5 are independently hydrogen atom or C1-6 linear or branched alkyl group, or R1 and R5 are bonded with each other to form a cyclic diketone;
• p is an integer of 0 to 6;
• and
• l is 0 or 1.

A norbornene-based copolymer for photoresist, represented by the following Formula 3:

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• wherein R1 is C1-12 linear, branched or cyclic alkyl group;
• R2 is a hydrogen atom or C1-6 linear, branched or cyclic alkyl group;
• R3, R4 and R5 are independently hydrogen atom or C1-6 linear or branched alkyl group, or R1 and R5 are bonded with each other to form a cyclic diketone;
• R6 and R7 are independently C1-6 alkyl group, or R6 and R7 are bonded with each other to form a ring;
• p is an integer of 0 to 6;
• R8 and R9 are independently hydrogen atom, C1-10 linear or branched alkyl group, —(CH2)q—C(O)OR10, —(CH2)q—OR10, —(CH2)q—C(O)R10, —(CH2)q—OC(O)R10, —(CH2)q—OC(O)OR10 or —(CH2)q—C(O)OCH2OR10, in which R10 is a hydrogen atom or C1-10 linear, branched or cyclic alkyl group, q is an integer of 0 to 6, and R8 and R9 can be bonded with each other to form a ring;
• a, b and c independently satisfy 0.01≦a/(a+b+c)≦0.30, 0≦b/(a+b+c)≦0.50 and 0.20≦c/(a+b+c)≦0.99;
• and
• l, m and n is each independently 0 or 1.