Polyimide film and method for producing same

Patent metadata

Field	Value
Publication number	US-2019390014-A1
Application number	US-201816480822-A
Country	US
Kind code	A1
Filing date	Feb 5, 2018
Priority date	Feb 8, 2017
Publication date	Dec 26, 2019
Grant date	—

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.

First claim

1 . A process for preparing a polyimide film, which comprises polishing a surface of a casting body;
casting a precursor on the polished surface of the casting body and drying the cast precursor to produce a gel sheet; and thermally treating the gel sheet to prepare a polyimide film, wherein the polished surface of the casting body has a roughness of 0.1 nm to 160 nm; when the area of the casting body on which the precursor is cast is divided into 1 cm×1 cm, the area falling under a defect reduced region is 90% or more, the defect reduced region referring to a region that satisfies the conditions that the numbers of a first groove, a second groove, a third groove, and a fourth groove, which have a width of 0.3 μm to 3 μm, a depth 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 the polyimide film 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 FIB or higher.

2 . The process for preparing a polyimide film of claim 1 , wherein the defect reduced region satisfies the conditions that the numbers of the first groove, the second groove, the third groove, and the fourth groove, which have a width of 0.2 μm to 3 μm, a depth of 0.3 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.

3 . The process for preparing a polyimide film of claim 2 , wherein the defect reduced region satisfies the conditions that the numbers of the first groove, the second groove, the third groove, and the fourth groove, which have a width of 0.15 μm to 3 μm, a depth of 0.2 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.

4 . The process for preparing a polyimide film of claim 3 , wherein the defect reduced region satisfies the conditions that the number of the first groove is 5 or less, the number of the second groove is 3 or less, and the number of the third groove is 1 or less in the divided area of 1 cm×1 cm.

5 . The process for preparing a polyimide film of claim 4 , wherein the defect reduced region satisfies the condition that the number of the third groove is 0.

6 . The process for preparing a polyimide film of claim 1 , wherein the defect reduced region satisfies the conditions that the numbers of the first groove, the second groove, and the third groove are 0 in the divided area of 1 cm×1 cm.

7 . The process for preparing a polyimide film of claim 1 , wherein the precursor comprises a polymer formed by polymerizing an aromatic diamine compound, an aromatic dianhydride compound, and a dicarbonyl compound.

8 . The process for preparing a polyimide film of claim 1 , wherein in the polishing step, the surface of the casting body is polished with a slurry that comprises abrasive particles having an average diameter of 30 mu to 100 mu and a polishing liquid.

9 . The process for preparing a polyimide film of claim 8 , wherein the polydispersity index (PDI) of the abrasive particles is 0.05 or less.

10 . The process for preparing a polyimide film of claim 8 , wherein the polishing liquid comprises an oxidizing agent.

11 . 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.

12 . The polyimide film of claim 11 , which comprises a 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.

13 . A cover window, which comprises a polyimide film that 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,
wherein the polyimide film 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; and 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.

14 . The cover window of claim 13 , which further comprises a hard coating layer formed on the first surface.

15 . A display device, which comprises a display panel; and the cover window of claim 13 disposed on the display panel.

Assignees

• Skc Co Ltd

Inventors

• Kim Sunhwan
• Lee Jin Woo
• Oh Dae Seong
• Jeong Dawoo
• Kim Kyu-Hun

Classifications

• C08L2203/16

  used for films · CPC title

• C08G73/1039

  comprising halogen-containing substituents · CPC title

• C08G73/1067

  Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound · CPC title

• C08G73/14 Primary

  Polyamide-imides · CPC title

• C08L77/00

  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 · CPC title