US 12,351,730 B2
Hard coat film for foldable display and use thereof
Yohei Yamaguchi, Otsu (JP); Kokichi Tokuo, Otsu (JP); Shotaro Nishio, Tsuruga (JP); and Kiwamu Kawai, Tsuruga (JP)
Assigned to TOYOBO CO., LTD., Osaka (JP)
Appl. No. 17/625,291
Filed by TOYOBO CO., LTD., Osaka (JP)
PCT Filed Jun. 30, 2020, PCT No. PCT/JP2020/025671
§ 371(c)(1), (2) Date Jan. 6, 2022,
PCT Pub. No. WO2021/010158, PCT Pub. Date Jan. 21, 2021.
Claims priority of application No. 2019-130036 (JP), filed on Jul. 12, 2019.
Prior Publication US 2022/0389269 A1, Dec. 8, 2022
Int. Cl. C09D 167/02 (2006.01); C09D 7/61 (2018.01); C09D 7/63 (2018.01); G02B 1/14 (2015.01); C08K 3/22 (2006.01)
CPC C09D 167/02 (2013.01) [C09D 7/61 (2018.01); C09D 7/63 (2018.01); G02B 1/14 (2015.01); C08K 2003/2241 (2013.01); C08K 2003/2244 (2013.01)] 7 Claims
 
1. A hard coating film for a foldable display, the hard coating film comprising
a polyester film being a polyethylene terephthalate film and having a thickness of 10 to 80 μm and a draw ratio of 1.2-fold to 2.0-fold in the longitudinal direction,
an easy-to-adhere resin layer, and
a hard coating layer, the easy-to-adhere resin layer and the hard coating layer being stacked in this order on at least one surface of the polyester film,
wherein
the easy-to-adhere resin layer is a cured product of a composition containing
at least one compound selected from the group consisting of titanium compounds and zirconium compounds, and
a polyester resin, which is formed from a dicarboxylic acid component and a diol component, containing a naphthalene dicarboxylic acid component as at least part of the dicarboxylic acid component, and
the polyester film having the easy-to-adhere resin layer stacked thereon but not yet having the hard coating layer stacked thereon satisfies the following conditions (1) to (4):
(1) the polyester film has a refractive index in the bending direction of 1.590 to 1.620,
(2) the polyester film has a refractive index in the direction of a folding portion of 1.670 to 1.700,
(3) the polyester film has a refractive index in the thickness direction of 1.520 or less, and
(4) the polyester film has a density of 1.380 g/cm3 or more,
wherein the bending direction refers to a direction orthogonal to the folding portion of the polyester film to be folded.