CPC G02B 5/045 (2013.01) [B29C 55/02 (2013.01); C08J 7/046 (2020.01); G02B 1/14 (2015.01); G02B 5/04 (2013.01); G02B 5/3033 (2013.01); G02B 5/3083 (2013.01); G02F 1/133536 (2013.01); G02F 1/133711 (2013.01); B29C 55/12 (2013.01); C09K 2323/03 (2020.08); C09K 2323/031 (2020.08); C09K 2323/035 (2020.08)] | 6 Claims |
1. An optical polyester film, which is a uniaxially or biaxially stretched polyester film and has an in-plane retardation of 7,000 nm to 30,000 nm, a tensile strength in the transverse direction (TD) of 25 to 35 kgf/mm2, a tensile strength in the longitudinal direction (MD) of 8.0 to 19 kgf/mm2, a ratio of the tensile strength in the longitudinal direction to the tensile strength in the transverse direction of 0.25 to 0.7, an elastic modulus in the transverse direction of 450 to 560 kgf/mm2, and an elastic modulus in the longitudinal direction of 220 to 380 kgf/mm2,
wherein a stretching ratio of the polyester film is 1.2 times to 1.7 times in the longitudinal direction,
wherein a stretching ratio of the polyester film is 4.1 times to 6.0 times in the transverse direction, and
wherein the optical polyester film has a deviation in the retardation of 500 nm/m or less along a single axis, a shrinkage in the longitudinal direction of 0.05 to 0.6% and a shrinkage in the transverse direction of 0.05 to 0.6%, when measured under the conditions of 24 hours at 85° C., an elongation at breakage of 7% to 20% in the longitudinal direction, and an elongation at breakage of 75% to 100% in the transverse direction.
|