US 11,926,720 B2
Polyester film and application therefor
Shotaro Nishio, Tsuruga (JP); Kiwamu Kawai, Tsuruga (JP); and Akira Shimizu, Tsuruga (JP)
Assigned to TOYOBO CO., LTD., Osaka (JP)
Appl. No. 17/614,228
Filed by TOYOBO CO., LTD., Osaka (JP)
PCT Filed May 14, 2020, PCT No. PCT/JP2020/019266
§ 371(c)(1), (2) Date Nov. 24, 2021,
PCT Pub. No. WO2020/241280, PCT Pub. Date Dec. 3, 2020.
Claims priority of application No. 2019-099160 (JP), filed on May 28, 2019.
Prior Publication US 2022/0227950 A1, Jul. 21, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C08J 5/18 (2006.01); G02B 3/00 (2006.01); G06F 1/16 (2006.01); G06F 3/041 (2006.01)
CPC C08J 5/18 (2013.01) [G02B 3/0087 (2013.01); G06F 1/1652 (2013.01); G06F 3/0412 (2013.01); C08J 2367/00 (2013.01); G06F 2203/04102 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A polyester film for a touchscreen module substrate of a foldable display, the polyester film satisfying the following conditions:
(1) a refractive index in a bending direction is from 1.591 to 1.606;
(2) a refractive index in a folding portion direction is from 1.670 to 1.700;
(3) a refractive index in a thickness direction is 1.520 or less; and
(4) a density is 1.380 g/cm3 or more,
wherein the bending direction refers to a direction orthogonal to a folding portion of the polyester film at a time when the polyester film is folded,
wherein the polyester film is a biaxially stretched polyethylene terephthalate film, and
wherein the polyester film comprises an easy-to-adhere layer on at least one surface thereof and a hard coating layer having a thickness of from 1 μm to 50 μm.