# US 11,306,183 B2 · Polyimide film and method for producing same

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- Number: US 11,306,183 B2
- Document ID: US11306183B2
- Status: Granted
- Kind: B2
- Application number: 16/480,822
- Filed: 2018-02-05
- Published: 2019-12-26
- Granted: 2022-04-19
- Earliest claimed: 2017-02-08
- Assignees: Skc Co., Ltd.
- Applicants: Skc Co., Ltd.
- Inventors: Sunhwan Kim; Jin Woo Lee; Dae Seong Oh; Dawoo Jeong; Kyu-Hun Kim
- Web page: https://patentgrep.com/patent/US11306183B2

## CPC

- C08G 73/14: Polyamide-imides
- C08G 73/1039: {comprising halogen-containing substituents}
- C08G 73/1067: {Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound}
- C08J 5/18: Manufacture of films or sheets
- C08L 77/00: Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain (of polyhydrazides C08L79/06; of polyamideimides or polyamide acids C08L79/08); Compositions of derivatives of such polymers
- C08J 2379/00: Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
- C08J 2379/08: Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08L 2203/16: used for films
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

One embodiment may provide a method for producing a polyimide film, the method comprising the steps of: polishing the surface of a casting body; producing a gel sheet by casting a precursor on the polished surface of the casting body, and drying same; and producing a polyimide film by heat-treating the gel sheet, wherein the roughness of the polished surface of the casting body is 0.1 nm to 160 nm, and when the area of the casting body onto which the precursor is casted is partitioned by 1 cm×1 cm, the area corresponding to a defect reduction region is at least 90%, and the polyimide film has a yellowness of at most 3, a haze of at most 1%, a permeability of at least 88%, a modulus of at least 5.0 GPa and a surface hardness of at least HB.

## Claims

### Claim 1

A polyimide film, which has a yellow index of 3 or less, a haze of 1% or less, a transmittance of 88% or more, a modulus of 5.0 GPa or more, and a surface hardness of HB or higher, and which comprises a first surface having a surface roughness of 0.1 nm to 150 nm and a second surface opposite to the first surface and having a surface roughness of 0.1 nm to 40 nm,
wherein when the first surface is divided into 1 cm×1 cm, the area falling under a defect free region is 90% or more, the defect free region referring to a region that satisfies the conditions that the numbers of a first protrusion, a second protrusion, a third protrusion, and a fourth protrusion, which have a width of 0.3 μm to 3 μm, a height of 0.5 μm to 5 μm, and a length of 2 μm to less than 3 μm, 3 μm to less than 5 μm, 5 μm to less than 10 μm, and 10 μm or more, respectively, are 10 or less, 5 or less, 3 or less, and 0, respectively, in the divided area of 1 cm×1 cm, and
wherein the polyimide film is prepared from a polyamide-imide polymer formed by polymerizing an aromatic diamine compound, an aromatic dianhydride compound, and a dicarbonyl compound, wherein the aromatic diamine compound comprises 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFDB), the aromatic dianhydride compound comprises 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA), and the dicarbonyl compound comprises terephthaloyl chloride (TPC), 1,1′-biphenyl-4,4′-dicarbonyl dichloride (BPDC), or a combination thereof.

### Claim 2 (depends on 1)

A cover window, which comprises the polyimide film of claim 1.

### Claim 3 (depends on 2)

The cover window of claim 2, which further comprises a hard coating layer formed on the first surface.

### Claim 4 (depends on 2)

A display device comprising:
a display panel; and
the cover window of claim 2 disposed on the display panel.