Retardation film, manufacturing method thereof, and liquid crystal display device including the same

Patent metadata

Field	Value
Publication number	US-9690138-B2
Application number	US-201214130874-A
Country	US
Kind code	B2
Filing date	Jul 2, 2012
Priority date	Jul 6, 2011
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

There are provided a retardation film, a manufacturing method thereof, and a liquid crystal display device including the same. The retardation film includes 1) an acrylic film, 2) a coating layer of a negative C-type material, and 3) a primer layer including a copolymer containing an aromatic vinyl-based unit and a maleic acid-based unit, provided between the acrylic film and the coating layer of the negative C-type material. The retardation film may be used in an in-plane switching mode liquid crystal display device.

First claim

The invention claimed is:

1. A retardation film comprising:
1) an acrylic film comprising a resin blend of an acrylic resin and a copolymer resin containing an aromatic vinyl-based unit, wherein the copolymer resin containing an aromatic vinyl-based unit is a styrene-maleic anhydride copolymer (SMA), a styrene-acrylonitrile copolymer (SAN), or an α-methyl styrene-acrylonitrile copolymer (AMSAN), and the content of the aromatic vinyl-based unit is in a range of 10 to 25 wt % of the entire composition of the resin blend,
2) a coating layer of a negative C-type material, wherein the C-type layer comprises a cellulose derivative having a weight average molecular weight of 100,000 to 300,000, and
3) a primer layer including a copolymer containing an aromatic vinyl-based unit and a maleic acid-based unit, provided between, and in contact with, the acrylic film and the coating layer of the negative C-type material, wherein the copolymer has a weight average molecular weight of 50,000 to 1,000,000,
wherein a retardation value R in of 1 the acrylic film in an in-plane direction thereof, represented by the following equation 1, is 50 to 200 nm, and a retardation value R th of 1) the acrylic film in a thickness direction thereof, represented by the following equation 2, is 50 to 250 nm:
R in =( n x −n y )× d   Equation 1

R th =( n z −n y )× d   Equation 2

where n x refers to the highest refractive index among refractive indexes in the in-plane direction of the film, n y refers to a refractive index in a direction perpendicular to the n x direction among refractive indexes in the in-plane direction of the film, n z refers to a refractive index in the thickness direction of the film, and d refers to a thickness of the film, and
wherein 3) the primer layer has a thickness of 0.1 to 5 μm.

2. The retardation film of claim 1 , wherein 1) the acrylic film has a thickness of 30 to 100 μm.

3. The retardation film of claim 1 , wherein 2) the coating layer of the negative C-type material includes a compound comprising an aromatic ring or cyclo-olefin in a polymer main chain.

4. The retardation film of claim 1 , wherein 2) the coating layer of the negative C-type material includes an ethyl cellulose resin.

5. The retardation film of claim 1 , wherein 2) the coating layer of the negative C-type material has a retardation value R in of −5 to 5 nm in an in-plane direction thereof, represented by the following equation 1 and has a retardation value of −30 to −200 nm in a thickness direction thereof, represented by the following equation 2:
R in =( n x −n y )× d   Equation 1

R th =( n z −n y )× d   Equation 2

where n x refers to the highest refractive index among refractive indexes in the in-plane direction of the film, n y refers to a refractive index in a direction perpendicular to the n x direction among refractive indexes in the in-plane direction of the film, n z refers to a refractive index in the thickness direction of the film, and d refers to a thickness of the film.

6. The retardation film of claim 1 , wherein 2) the coating layer of the negative C-type material has a thickness of 3 to 20 μm.

7. The retardation film of claim 1 , wherein 3) the primer layer includes the aromatic vinyl-based unit in a content thereof ranging from 50 to 80 mol % and the maleic acid-based unit in a content thereof ranging from 20 to 50 mol %.

8. The retardation film of claim 1 , wherein 3) the copolymer containing the aromatic vinyl-based unit and the maleic acid-based unit in the primer layer is a styrene-maleic anhydride copolymer (SMA).

9. A liquid crystal display device comprising the retardation film of claim 1 .

10. The liquid crystal display device of claim 9 , wherein the liquid crystal display device is an in-plane switching (IPS) mode liquid crystal display device.

11. An integrated polarizing plate comprising a polarizer and the retardation film of claim 1 , provided as a protective film, on a single surface or both surfaces of the polarizer.

12. A liquid crystal display device comprising the integrated polarizing plate of claim 11 .

13. The retardation film of claim 1 , wherein the cellulose derivative is ethyl cellulose resin.

14. The retardation film of claim 13 , wherein ethyl cellulose resin has an ethoxyl content of 40% to 50%.

15. A method of manufacturing a retardation film comprising:
a) preparing an acrylic film comprising a resin blend of an acrylic resin and a copolymer resin containing an aromatic vinyl-based unit,
wherein the copolymer resin containing an aromatic vinyl-based unit is a styrene-maleic anhydride copolymer (SMA), a styrene-acrylonitrile copolymer (SAN), or an α-methyl styrene-acrylonitrile copolymer (AMSAN), and the content of the aromatic vinyl-based unit is in a range of 10 to 25 wt % of the entire composition of the resin blend,
b) forming a primer layer by coating at least one surface of the acrylic film with a composition including a copolymer containing an aromatic vinyl-based unit and a maleic acid-based unit and having a weight average molecular weight of 50,000 to 1,000,000, and
c) coating an upper part of the primer layer with a negative C-type material, wherein the C-type material comprises a cellulose derivative having a weight average molecular weight of 100,000 to 300,000,
wherein a) a retardation value R in of the acrylic film in an in-plane direction thereof, represented by the following equation 1, is 50 to 200 nm, and a retardation value R th of the acrylic film in a thickness direction thereof, represented by the following equation 2, is 50 to 250 nm:
R in =( n x −n y )× d   Equation 1

R th =( n z −n y )× d   Equation 2

where n x refers to the highest refractive index among refractive indexes in the in-plane direction of the film, n y refers to a refractive index in a direction perpendicular to the n x direction among refractive indexes in the in-plane direction of the film, n z refers to a refractive index in the thickness direction of the film, and d refers to a thickness of the film, and
wherein b) the primer layer has a thickness of 0.1 to 5 μm.

Assignees

• Park Jun-Wuk
• Choi Jeong-Min
• Lee Nam-Jeong
• Lg Chemical Ltd

Inventors

• Park Jun-Wuk
• Choi Jeong-Min
• Lee Nam-Jeong

Classifications

• G02B5/3083 Primary

  Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001) · CPC title

• G02F1/133634

  the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis · CPC title

• Y10T428/1036

  Cross-Sectional Technologies · mapped topic

• G02B5/32

  Holograms used as optical elements · CPC title

• Y10T428/105

  Cross-Sectional Technologies · mapped topic