# US 12,180,382 B2 · Window cover film and flexible display panel including the same

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- Number: US 12,180,382 B2
- Document ID: US12180382B2
- Status: Granted
- Kind: B2
- Application number: 17/229,095
- Filed: 2021-04-13
- Published: 2021-10-14
- Granted: 2024-12-31
- Earliest claimed: 2020-04-14
- Assignees: SK Innovation Co., Ltd.; SK ie technology Co., Ltd.
- Applicants: SK Innovation Co., Ltd.; SK IE Technology Co., Ltd.
- Inventors: Jong Nam Ahn
- Web page: https://patentgrep.com/patent/US12180382B2

## CPC

- C09D 133/08: Homopolymers or copolymers of acrylic acid esters
- C08F 283/122: {on to saturated polysiloxanes containing hydrolysable groups, e.g. alkoxy-, thio-, hydroxy-}
- C08G 73/1042: {Copolyimides derived from at least two different tetracarboxylic compounds or two different diamino compounds}
- C08G 73/1075: {Partially aromatic polyimides}
- C08G 73/14: Polyamide-imides
- C09D 4/06: {Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond} in combination with a macromolecular compound other than an unsaturated polymer of groups C09D159/00 - C09D187/00
- C09D 183/04: Polysiloxanes
- H05K 5/03: Covers
- C08G 77/20: containing silicon bound to unsaturated aliphatic groups
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS

## Abstract

Provided is a window cover film and a flexible display panel including the same. More particularly, a window cover film including a substrate layer and a hard coating layer and a flexible display panel including the same are provided.

## Claims

### Claim 1

A window cover film comprising a substrate layer made up of a polyamideimide-based resin and a hard coating layer formed directly on at least one surface of the substrate layer,
wherein a kinetic friction coefficient is less than 0.15, the kinetic friction coefficient being measured at a speed of 100 mm/min with a force of 5 N under a load of 200 g using parchment paper as an object to be frictionized on the hard coating layer, and a ratio of a static friction coefficient a to the kinetic friction coefficient b satisfies the following Equation 1:
1≤a/b≤1.2, [Equation 1]
wherein the substrate layer is made up of a polyamideimide (PAI)-based resin including a fluorine atom and an aliphatic cyclic structure and the hard coating layer is formed of a composition for forming a hard coating layer including a (meth) acryl-based siloxane resin and a polyfunctional (meth) acrylate-based compound, and
wherein the polyamideimide (PAI)-based resin is prepared by preparing an amine-terminated polyamide oligomer from a first fluorine-based aromatic diamine and an aromatic diacid dichloride, and polymerizing the amine-terminated polyamide oligomer with a monomer derived from a second fluorine-based aromatic diamine, an aromatic dianhydride, and a cycloaliphatic dianhydride.

### Claim 2 (depends on 1)

The window cover film of claim 1, wherein the static friction coefficient is 0.2 or less.

### Claim 3 (depends on 1)

The window cover film of claim 1, wherein the kinetic friction coefficient is 0.1 or less.

### Claim 4 (depends on 1)

The window cover film of claim 1, wherein the substrate layer has a modulus in accordance with ASTM D882 of 3 GPa or more, an elongation at break of 8% or more, a light transmittance of 5% or more as measured at 388 nm in accordance with ASTM D1746, a total light transmittance of 87% or more as measured at 400 to 700 nm, a haze of 2.0% or less, a yellow index of 5.0 or less, and a b* value of 2.0 or less.

### Claim 5 (depends on 1)

The window cover film of claim 1, wherein the substrate layer has a thickness of 10 to 500 μm and the hard coating layer has a thickness of 1 to 50 μm.

### Claim 6 (depends on 1)

The window cover film of claim 1, wherein the hard coating layer has a pencil hardness of 4H or more and a water contact angle of 80° or more.

### Claim 7 (depends on 1)

The window cover film of claim 1, wherein the window cover film has a curl amount of 5 mm or less, the curl amount being measured at each vertex of a square sample having a side length of 10 cm each which has been cut to be inclined at an angle of 45° to an MD direction of the film.

### Claim 8 (depends on 1)

The window cover film of claim 1, wherein the window cover film has no crack occurrence at 30,000 to 200,000 times in evaluation of dynamic bending properties.

### Claim 9 (depends on 1)

A flexible display panel comprising the window cover film of claim 1.