Active matrix type liquid crystal display apparatus

• US 7,790,248 B2
• Filed: 02/21/2007
• Issued: 09/07/2010
• Est. Priority Date: 05/16/1997
• Status: Expired due to Fees

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Tomioka, Yasushi, Kondo, Katsumi, Yokokura, Hisao, Miwa, Takao
• Primary Examiner(s): HON, SOW FUN
• Application Number:
  US11/708,462
• Publication Number:
  US 20070178250A1
• Time in Patent Office: 1,294 Days
• Field of Search: 429 12- 13, 349123-124, 349/135, 349/96
• US Class Current: 428/1.26
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: C09K 2323/02 Alignment layer characterised by chemical composition
• CPC Class Codes: C09K 2323/025 Polyamide
• CPC Class Codes: C09K 2323/027 Polyimide
• CPC Class Codes: G02F 1/133397 for suppressing after-image or image-sticking
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/133784 by rubbing
• 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]
• CPC Class Codes: G02F 2202/023 curable

Abstract

An active matrix type liquid crystal display apparatus has a pair of substrates, at least one of the substrates being transparent; a liquid crystal layer arranged between the pair of substrates; and electrode structure for generating an electric field having a dominant component parallel to a surface of the substrate and passing through the liquid crystal layer, the electrode structure being formed on one of the pair of substrates; a pair of alignment layers formed on respective surfaces in contact with the liquid crystal layer of the pair of substrates; and a pair of polarizing plates arranged so as to sandwich the pair of substrates, wherein the glass transition temperature Tg of a boundary surface between said liquid crystal layer and the alignment layer is higher than the nematic-isotropic phase transition temperature T(N−I) of a liquid crystal composite forming the liquid crystal layer.

Claims

1. An active matrix type liquid crystal display apparatus having a plurality of thin film transistors, comprising:

a pair of substrates, at least one of which is transparent;

a pair of electrodes for applying an electric field nearly parallel to surfaces of the pair of substrates, comprising a pixel electrode and a common electrode provided on one substrate of the pair of substrates;

a liquid crystal layer arranged between the pair of substrates;

an alignment layer arranged between the liquid crystal layer and one of the pair of substrates; and

a pair of polarizing plates arranged on the opposite sides of the pair of substrates to the liquid crystal layer;

wherein

the alignment layer is photoreactive, provided with a liquid crystal alignment function produced by irradiation of ultraviolet rays to cause a photochemical reaction, and made of at least one of polyamic acid made from pyromellitic acid dianhydride, 1,2,3,4-cyclobutane-tetracarboxylic acid dianhydride and diamine, and polyimide obtained by dehydration ring closure of the polyamic acid; and

wherein

the active matrix type liquid crystal display apparatus has an after image intensity, defined as a magnitude of a brightness change Δ

B/B(10%) of a brightness B in an after image portion to a peripheral gray portion having a brightness 10% of a maximum brightness, that is below 3%.

2. An active matrix type liquid crystal display apparatus according to claim 1, wherein the relation 0.2 μ

m<

Δ

n·

d<

0.5 μ

m is satisfied, where Δ

n is an anisotropy of refractive index of the liquid crystal layer and d is a thickness of the liquid crystal layer.

3. An active matrix type liquid crystal display apparatus according to claim 1, wherein the alignment layer comprises an organic polyimide.

4. An active matrix type liquid crystal display apparatus according to claim 3, wherein a weight average molecular weight of the organic polyimide polymer is not smaller than 10,000 and not larger than 300,000.

5. An active matrix type liquid crystal display apparatus according to claim 3, wherein a ratio of weight average molecular weight/number average molecular weight of the organic polyimide polymer is not larger than 2.

6. An active matrix type liquid crystal display apparatus according to claim 3, wherein the organic polyimide polymer contains one of a polymer precursor and a polymer curable by being subjected to irradiation treatment of at least one of heat, light and radiation rays.

7. An active matrix type liquid crystal display apparatus according to claim 6, wherein the one of a polymer precursor and a polymer has any one of ethylene group, acetylene group, diacetylene group and maleimide group.

8. An active matrix type liquid crystal display apparatus according to claim 1, which further comprises a transparent organic polymer arranged between the alignment layer and the one of the substrates, the transparent organic polymer being thicker in thickness than the alignment layer.

9. An active matrix type liquid crystal display apparatus according to claim 1, wherein a glass transition temperature Tg of the alignment layer is not lower than 300°

C.

10. An active matrix type liquid crystal display apparatus according to claim 1, wherein the ultraviolet rays are linearly polarized ultraviolet rays.

11. An active matrix type liquid crystal display apparatus according to claim 1, wherein a pretilt angle of the liquid crystal layer is not larger than 5 degrees.