US 12,466,926 B2
Polyester film and use thereof
Shotaro Nishio, Tsuruga (JP); Mei Matsumura, Tsuruga (JP); and Akira Shimizu, Tsuruga (JP)
Assigned to TOYOBO CO., LTD., Osaka (JP)
Appl. No. 17/996,249
Filed by TOYOBO CO., LTD., Osaka (JP)
PCT Filed Apr. 15, 2021, PCT No. PCT/JP2021/015609
§ 371(c)(1), (2) Date Oct. 14, 2022,
PCT Pub. No. WO2021/215349, PCT Pub. Date Oct. 28, 2021.
Claims priority of application No. 2020-075937 (JP), filed on Apr. 22, 2020.
Prior Publication US 2023/0192974 A1, Jun. 22, 2023
Int. Cl. C08J 5/18 (2006.01); C08J 7/04 (2020.01); C08J 7/043 (2020.01); C08L 67/02 (2006.01); G02B 1/14 (2015.01); G06F 1/16 (2006.01); G09F 9/30 (2006.01); H04M 1/02 (2006.01)
CPC C08J 5/18 (2013.01) [G02B 1/14 (2015.01); G06F 1/1652 (2013.01); C08J 7/0427 (2020.01); C08J 7/043 (2020.01); C08J 2367/03 (2013.01); C08L 67/02 (2013.01); G09F 9/301 (2013.01); H04M 1/0214 (2013.01); H04M 1/0268 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A polyester film for a foldable display, wherein the polyester film is a single-layer film comprising 95 weight % or more of a polyethylene-2,6-naphthalene dicarboxylate homopolymer satisfying the following conditions:
(1) having a refractive index in a bending direction of 1.644 to 1.730, and
(2) having a refractive index in a folding direction of 1.770 to 1.854, and
(3) having a thickness of 10 μm or more and 125 μm or less and a high-temperature hold angle in a bending direction of 70° or more, wherein the high-temperature hold angle refers to an angle of a crease formed after fixing the polyester film at a heating temperature of 85° C. for 18 hours in such a manner that a strain of 1.7% is applied to both surfaces of the polyester film at a bent portion, and the bending direction refers to a direction that is orthogonal to a folding portion.