Folding-type display and portable terminal device
Provided is a foldable display that is excellent in mass production applicability, and that is resistant to image distortion that can appear in the folding portion after the display is repeatedly folded, and also a mobile device equipped with such a foldable display. The foldable display includes a hard coating film on at least part of the front surface thereof, the hard coating film including a polyester film having an intrinsic viscosity of 0.65 to 1.0 dl/g as a substrate film; a hardened layer formed from a polyimide-based resin, the hardened layer having a thickness of 0.5 to 3.0 μm; and a hard coating layer, wherein the hardened layer and the hard coating layer are present in this order at least on the front surface side of the substrate film.
1. A foldable display comprising a hard coating film on at least part of the front surface thereof, the hard coating film comprising
a polyester film having an intrinsic viscosity of 0.65 to 1.0 dL/g as a substrate film,
a hardened layer formed from a polyimide-based resin, the hardened layer having a thickness of 0.5 to 3.0 μm, and
a hard coating layer, wherein
the hardened layer and the hard coating layer are present in this order at least on the front surface side of the substrate film,
the intrinsic viscosity is calculated based on the flow time of a solution with a concentration of 0.4 (g/dL) at 30° C. measured with an Ubbelohde viscometer, wherein the solution is obtained by pulverizing, drying, and then dissolving the polyester film in a solvent mixture of phenol and tetrachloroethane in a mass ratio of 60:40 phenol:tetrachloroethane followed by a centrifugation to remove inorganic particles,
the polyimide-based resin comprises a polyimide resin or a polyamide-imide resin,
the polyester film has a thickness of 10 to 75 μm,
an easy-to-adhere layer for improving adhesion with the hardened layer of polyimide-based resin is stacked on the polyester film, and
the easy-to-adhere layer comprises an acrylic resin, a polyester resin, a polyurethane resin, or a polyether resin.
2. The foldable display according to claim 1 , wherein the hard coating layer has a thickness of 1 to 40 μm.
3. The foldable display according to claim 1 , wherein the hard coating film is placed through the folding portion of the foldable display in a single continuous manner.
4. The foldable display according to claim 1 , wherein the polyester film is a biaxially oriented polyethylene terephthalate film.
5. The foldable display according to claim 1 , wherein the hard coating layer has a pencil hardness of 2H or higher as measured under a load of 750 g in accordance with JIS K5600-5-4:1999.
6. The foldable display according to claim 1 , which has a bend radius of 5 mm or less when folded.
7. A mobile device comprising the foldable display of claim 1 .
8. The foldable display according to claim 1 , wherein the hard coating film has a total light transmittance of 85% or more and a haze of 3% or less.
9. The foldable display according to claim 8 , wherein the hard coating layer is formed from a urethane-acrylate-based resin.
10. The foldable display according to claim 2 , wherein the hard coating film has a total light transmittance of 85% or more and a haze of 3% or less.
11. The foldable display according to claim 10 , wherein the hard coating layer is formed from a urethane-acrylate-based resin.
12. The foldable display according to claim 1 , wherein the hard coating layer is formed from a urethane-acrylate-based resin.
13. The foldable display according to claim 2 , wherein the hard coating layer is formed from a urethane-acrylate-based resin.
14. The foldable display according to claim 1 , wherein the foldable display (a) rises at a maximum height of less than 5 mm or (b) is not deformed when placed horizontally on a flat surface with the inner side of the foldable display facing downward after completion of the bending treatment, in which the foldable display is bent 50,000 times at a rate of 1 time/second using a tension-free folding clamshell jig, with the bend radius set to 3 mm and the hard coating layer facing outward.
15. The foldable display according to claim 6 , wherein the foldable display (a) rises at a maximum height of less than 5 mm or (b) is not deformed when placed horizontally on a flat surface with the inner side of the foldable display facing downward after completion of the bending treatment, in which the foldable display is bent 50,000 times at a rate of 1 time/second using a tension-free folding clamshell jig, with the bend radius set to 3 mm and the hard coating layer facing outward.
16. A mobile device comprising the foldable display of claim 15 .
17. A mobile device comprising the foldable display of claim 2 .
18. A mobile device comprising the foldable display of claim 4 .
19. A mobile device comprising the foldable display of claim 6 .
20. A mobile device comprising the foldable display of claim 9 .