Optical film, polarizing plate comprising the same, and optical display apparatus comprising the same

1 . An optical film comprising: a first layer; and a second layer stacked on a lower surface of the first layer via a first primer layer, the first primer layer being formed of a first composition comprising a first urethane-based polymer and a first isocyanate-based curing agent,

wherein the first urethane-based polymer comprises a repeat unit derived from a first alicyclic isocyanate-based compound, and the first isocyanate-based curing agent comprises a first isocyanate-based trimer.

2 . The optical film according to claim 1 , wherein the first alicyclic isocyanate-based compound comprises at least one selected from among methylene bis(cyclohexyl isocyanate), cyclohexylene diisocyanate, cyclopentylene diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(diisocyanatomethyl)cyclohexane, 3,5,5-trimethyl-3-isocyanatomethyl cyclohexane, and isophorone diisocyanate.

3 . The optical film according to claim 1 , wherein the first isocyanate-based trimer comprises a compound represented by the following Formula 3:

where R 1 , R 2 , and R 3 are each independently a substituted or unsubstituted C 1 to C 10 alkylene group, a substituted or unsubstituted C 3 to C 10 cycloalkylene group, or a substituted or unsubstituted C 6 to C 10 arylene group.

4 . The optical film according to claim 1 , wherein the first isocyanate-based trimer comprises at least one selected from among a hexamethylene diisocyanate trimer and an isophorone diisocyanate trimer.

5 . The optical film according to claim 1 , wherein the first isocyanate-based curing agent is present in an amount of 20 parts by weight to 160 parts by weight relative to 100 parts by weight of the first urethane-based polymer.

6 . The optical film according to claim 1 , wherein the first primer layer has a glass transition temperature of higher than 60° C.

7 . The optical film according to claim 1 , wherein the first layer and the second layer are formed of different materials and exhibit different birefringence.

8 . The optical film according to claim 1 , wherein each of the first layer and the second layer is a hydrophobic layer.

9 . The optical film according to claim 1 , wherein the first layer comprises at least one selected from among a cyclic olefin polymer (COP) resin and a cyclic olefin copolymer (COC), and the second layer comprises a halogen-containing polystyrene-based polymer.

10 . The optical film according to claim 9 , wherein a halogen of the halogen-containing polystyrene-based polymer is fluorine.

11 . The optical film according to claim 9 , wherein the halogen-containing polystyrene-based polymer comprises a repeat unit represented by the following Formula 1:

where is a linking site;

R 1 , R 2 , and R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen;

each R is independently an alkyl group, a substituted alkyl group, a halogen, a hydroxyl group, a carboxyl group, a nitro group, an alkoxy group, an amino group, a sulfonate group, a phosphate group, an acyl group, an acyloxy group, a phenyl group, an alkoxy carbonyl group, or a cyano group,

at least one of R 1 , R 2 , and R 3 being a halogen and/or at least one R being a halogen; and

n is an integer of 0 to 5.

12 . The optical film according to claim 1 , wherein the first layer has an in-plane retardation of 180 nm to 240 nm at a wavelength of 550 nm, and the second layer has an in-plane retardation of 70 nm to 120 nm at a wavelength of 550 nm.

13 . The optical film according to claim 1 , further comprising a third layer stacked on an upper surface of the first layer via a second primer layer.

14 . The optical film according to claim 13 , wherein the first layer and the third layer are formed of different materials and exhibit different birefringence.

15 . The optical film according to claim 13 , wherein the first layer comprises at least one selected from among a cyclic olefin polymer (COP) resin and a cyclic olefin copolymer (COC), and the third layer comprises a halogen-containing polystyrene-based polymer.

16 . The optical film according to claim 15 , wherein the halogen-containing polystyrene-based polymer comprises a repeat unit represented by the following Formula 1:

where is a linking site;

R 1 , R 2 , and R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen;

each R is independently an alkyl group, a substituted alkyl group, a halogen, a hydroxyl group, a carboxyl group, a nitro group, an alkoxy group, an amino group, a sulfonate group, a phosphate group, an acyl group, an acyloxy group, a phenyl group, an alkoxy carbonyl group, or a cyano group,

at least one of R 1 , R 2 , and R 3 being a halogen and/or at least one R being a halogen; and

n is an integer of 0 to 5.

17 . The optical film according to claim 13 , wherein the second primer layer is formed of a second composition comprising a second urethane-based polymer and a second isocyanate-based curing agent,

the second urethane-based polymer comprising a repeat unit derived from a second alicyclic isocyanate-based compound,

the second isocyanate-based curing agent comprising a second isocyanate-based trimer.

18 . The optical film according to claim 17 , wherein the second isocyanate-based trimer comprises at least one selected from among a hexamethylene diisocyanate trimer and an isophorone diisocyanate trimer, and the second alicyclic isocyanate-based compound comprises at least one selected from among methylene bis(cyclohexyl isocyanate), cyclohexylene diisocyanate, cyclopentylene diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(diisocyanatomethyl)cyclohexane, 3,5,5-trimethyl-3-isocyanatomethyl cyclohexane, and isophorone diisocyanate.

19 . A polarizing plate comprising: a polarizer and the optical film according to claim 1 on at least one surface of the polarizer.

20 . An optical display apparatus comprising the polarizing plate according to claim 19 .