Liquid crystal display device

• US 7,935,396 B2
• Filed: 01/09/2007
• Issued: 05/03/2011
• Est. Priority Date: 01/10/2006
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated)
• Inventors: Kunimatsu, Noboru, Matsumori, Masaki, Tomioka, Yasushi
• Primary Examiner(s): HON, SOW FUN
• Application Number:
  US11/621,218
• Publication Number:
  US 20070160778A1
• Time in Patent Office: 1,575 Days
• Field of Search: 428/1.2, 428/1.26, 428/1.28, 428/1.3, 428/1.31, 349/97, 349/106, 349123-124, 349/138
• US Class Current: 428/1.2
• CPC Class Codes: C08G 73/10 Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: C09K 19/02 characterised by optical, electrical or physical properties of the components, in general
• CPC Class Codes: C09K 2323/02 Alignment layer characterised by chemical composition
• CPC Class Codes: C09K 2323/031 Polarizer or dye
• CPC Class Codes: G02F 1/133723 Polyimide, polyamide-imide
• CPC Class Codes: G02F 1/133738 for homogeneous alignment
• CPC Class Codes: G02F 1/133788 by light irradiation, e.g. linearly polarised light photo-polymerisation
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]

Abstract

An object of the present invention is to provide a liquid crystal display device that has an excellent mass-productivity and gives an image improved by the reduction of the chromaticity difference between white display and black display, the reduction of coloring and luminance in black display, and the improvement of the contrast ratio. In the present invention, of a pair of alignment films 131 and 132 formed on a pair of substrates 101 and 102, respectively, the alignment film 132 formed on the glass substrate 102 on the observer side is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has anisotropic absorption all over the visible light wavelength region (approximately 400 nm to 750 nm).

Claims

1. A liquid crystal display device comprising:

a pair of substrates,

a polarizing plate located on at least one of the pair of said substrates,

a liquid crystal layer located between the pair of said substrates,

a group of electrodes formed on at least one of the pair of said substrates and used for applying an electric field to said liquid crystal layer,

a pair of alignment films formed on the pair of said substrates, respectively, and

a light source located outside the pair of said substrates,

wherein an alignment film formed on a substrate on an observer side is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has an anisotropic absorption all over a visible light wavelength region,

wherein an axis of absorption of the alignment film formed on the substrate on the observer side is substantially parallel to an axis of absorption of the polarizing plate located on the substrate on the observer side, and

wherein the photosensitive polymer and the photoisomerized compound are endowed with an orientation-controlling ability by irradiation with a polarized light.

2. A liquid crystal display device according to claim 1, wherein an alignment film formed on a substrate on a light source side is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has an anisotropic absorption all over the visible light wavelength region.

3. A liquid crystal display device according to claim 1, wherein at least one organic insulating film is formed on the substrate on the observer side between the pair of said substrates, and at least one of said organic insulating film is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has an anisotropic absorption all over the visible light wavelength region.

4. A liquid crystal display device according to claim 3, wherein an axis of absorption of the alignment film formed on the substrate on the observer side is parallel to an axis of absorption of the organic insulating film formed on the substrate on the observer side.

5. A liquid crystal display device according to claim 1, wherein at least one organic insulating film is formed on the substrate on the light source side between the pair of said substrates, and at least one of said organic insulating film is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has an anisotropic absorption all over the visible light wavelength region.

6. A liquid crystal display device according to claim 5, wherein an axis of absorption of the alignment film formed on the substrate on the observer side is parallel to an axis of absorption of the organic insulating film formed on the substrate on the light source side.

7. A liquid crystal display device according to claim 1, wherein an axis of absorption of the alignment film formed on substrate on the observer side is parallel to an axis of absorption of the alignment film formed on the substrate on the light source side.

8. A liquid crystal display device according to claim 1, wherein the photosensitive polymer is a photosensitive polyimide and/or a photosensitive poly (amic acid), including cyclobutane rings.

9. A liquid crystal display device according to claim 1, wherein the anisotropic absorption of said alignment films and an organic insulating layer formed on the substrate on the observer side are imparted by irradiation with a substantially linearly polarized light.

10. A liquid crystal display device according to claim 1, wherein the electric field to be applied to said liquid crystal layer has a component substantially parallel to the pair of the substrates.

11. A liquid crystal display device according to claim 1, wherein the degree of the anisotropic absorption in the wavelength range of 400 nm to 500 nm is higher than the degree of the anisotropic absorption in the wavelength range of 500 nm to 750 nm.

12. A liquid crystal display device according to claim 1, wherein the photoisomerized compound is composed of an azobenzene derivative and/or a stilbene derivative.

13. A liquid crystal display device according to claim 1, further comprising a color filter which includes the photoisomerized compound.

14. A liquid crystal display device comprising:

a pair of substrates,

a polarizing plate located on at least one of the pair of said substrates,

a liquid crystal layer located between the pair of said substrates,

a group of electrodes formed on at least one of the pair of said substrates and used for applying an electric field to said liquid crystal layer,

a pair of alignment films formed on the pair of said substrates, respectively, and

a light source located outside the pair of said substrates,

wherein an alignment film formed on a substrate on a light source side is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has an anisotropic absorption all over a visible light wavelength region,

wherein an axis of absorption of the alignment film formed on the substrate on the light source side is substantially parallel to an axis of absorption of the polarizing plate located on the substrate on the light source side, and

wherein the photosensitive polymer and the photoisomerized compound are endowed with an orientation-controlling ability by irradiation with a polarized light.

15. A liquid crystal display device according to claim 14, wherein at least one organic insulating film is formed on a substrate on an observer side between the pair of said substrates, and at least one of said organic insulating film is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer, and has an anisotropic absorption all over the visible light wavelength region.

16. A liquid crystal display device according to claim 15, wherein an axis of absorption of the alignment film formed on the substrate on the light source side is parallel to an axis of absorption of the organic insulating film formed on the substrate on the observer side.

17. A liquid crystal display device according to claim 14, wherein at least one organic insulating film is formed on a substrate on the light source side between the pair of said substrates, and at least one of said organic insulating film is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has an anisotropic absorption all over the visible light wavelength region.

18. A liquid crystal display device according to claim 17, wherein an axis of absorption of the alignment film formed on the substrate on the observer side is parallel to an axis of absorption of the alignment film formed on the substrate on the light source side.

19. A liquid crystal display device according to claim 14, wherein the alignment film formed on the substrate on the observer side is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer, and wherein an axis of absorption of the alignment film formed on the substrate on the observer side is parallel to an axis of absorption of the alignment film formed on the substrate on the light source side.

20. A liquid crystal display device according to claim 14, wherein the alignment film contains a resin and the photoisomerized compound is contained in an amount of 20% by weight or less based on the resin.