Polarization plate with optical compensation layer and image display device

• US 20050117217A1
• Filed: 06/17/2003
• Published: 06/02/2005
• Est. Priority Date: 06/18/2002
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Yamaoka, Takashi, Yoshimi, Hiroyuki, Murakami, Nao, Yano, Shuuji, Kawai, Masayuki, Adachi, Junichi, Wasai, Kanako
• Granted Patent: US 7,126,754 B2
• Time in Patent Office: Days
• US Class Current: 359/483
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/3083 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 Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation

Abstract

A polarizing plate with an optical compensation layer is provided, which has an excellent peelability and is easy to reattach after mounted on an image display apparatus. A pressure-sensitive adhesive layer satisfying the condition (I) below is formed on both surfaces of an optical compensation layer, and one of the pressure-sensitive adhesive layers is further laminated with a polarizing plate. condition (I): in the case where a pressure-sensitive adhesive layer causing the optical compensation layer and the polarizing plate to adhere to each other is expressed by a pressure-sensitive adhesive layer (A) and the other pressure-sensitive adhesive layer is expressed by a pressure-sensitive adhesive layer (B) and attached to a glass substrate, the pressure-sensitive adhesive layer (A) causing the optical compensation layer and the polarizing plate to adhere to each other has an adhesive strength exceeding 12 N/25 mm, and the pressure-sensitive adhesive layer (B) causing the optical compensation layer and the glass substrate to adhere to each other has an adhesive strength of 1 to 10 N/25 mm.

Claims

1. A polarizing plate with an optical compensation layer, comprising:

an optical compensation layer;

pressure-sensitive adhesive layers disposed on respective surfaces of the optical compensation layer; and

a polarizing plate attached via one of the pressure-sensitive adhesive layers;

wherein each of the pressure-sensitive adhesive layers satisfies condition (I) below;

a pressure-sensitive adhesive layer (A) causing the optical compensation layer and the polarizing plate to adhere to each other has an adhesive strength exceeding 12 N/25 mm, and when the other pressure-sensitive adhesive layer (B) is attached to a glass substrate, the pressure-sensitive adhesive layer (B) causing the optical compensation layer and the glass substrate to adhere to each other has an adhesive strength of 1 to 10 N/25 mm.

2. The polarizing plate with an optical compensation layer according to claim 1, wherein the pressure-sensitive adhesive layers (A) and (B) are formed of an acrylic pressure-sensitive adhesive containing an acrylic polymer.

3. The polarizing plate with an optical compensation layer according to claim 2, wherein the acrylic polymer has a glass transition temperature of equal to or lower than 0°

C.

4. The polarizing plate with an optical compensation layer according to claim 2, wherein the acrylic polymer in the pressure-sensitive adhesive layer (A) is a copolymer of butyl acrylate and an acrylic acid and that in the pressure-sensitive adhesive layer (B) is a copolymer of 2-ethylhexyl acrylate and an acrylic acid.

5. The polarizing plate with an optical compensation layer according to claim 4, wherein a weight ratio (a:

b) between the butyl acrylate (a) and the acrylic acid (b) in the copolymer is 100;

5 and a weight ratio (c;

d) between the 2-ethylhexyl acrylate (c) and the acrylic acid (d) in the copolymer is 100;

5.

6. The polarizing plate with an optical compensation layer according to claim 2, wherein the acrylic polymer in the pressure-sensitive adhesive layer (A) and that in the pressure-sensitive adhesive layer (B) are each a copolymer of butyl acrylate and an acrylic acid, a weight ratio (a:

b) between the butyl acrylate (a) and the acrylic acid (b) of the acrylic polymer in the pressure-sensitive adhesive layer (A) is 100;

5 and a weight ratio (a′

;

b′

) between the butyl acrylate (a′

) and the acrylic acid (b′

) of the acrylic polymer in the pressure-sensitive adhesive layer (B) is 100;

3.

7. The polarizing plate with an optical compensation layer according to claim 1, wherein the polarizing plate is subjected to a heating treatment in advance.

8. The polarizing plate with an optical compensation layer according to claim 7, wherein the polarizing plate that has been subjected to the heating treatment shows a physical property such that a ratio of dimensional change in an absorption axis direction ranges from −

0.3% to +0.3% after the polarizing plate that has been subjected to the heating treatment is further treated at 50°

C. for 60 minutes.

9. The polarizing plate with an optical compensation layer according to claim 1, wherein the optical compensation layer has a thickness ranging from 0.1 to 20 μ

m.

10. The polarizing plate with an optical compensation layer according to claim 1, wherein the optical compensation layer is a cholesteric layer whose constituent molecules are aligned while having a cholesteric structure.

11. The polarizing plate with an optical compensation layer according to claim 10, wherein the constituent molecules of the cholesteric layer are a liquid crystal monomer, the liquid crystal monomer is aligned while having the cholesteric structure, and the liquid crystal monomer is polymerized or cross-linked.

12. The polarizing plate with an optical compensation layer according to claim 11, wherein the cholesteric layer has a helical pitch of equal to or smaller than 0.25 μ

m.

13. The polarizing plate with an optical compensation layer according to claim 10, wherein the constituent molecules of the cholesteric layer are a liquid crystal polymer, and the liquid crystal polymer is aligned while having the cholesteric structure.

14. The polarizing plate with an optical compensation layer according to claim 1, wherein the polarizing plate comprises a polarizer and a transparent protective layer, and at least one surface of the polarizer is laminated with the transparent protective layer.

15. The polarizing plate with an optical compensation layer according to claim 1, wherein a surface of the pressure-sensitive adhesive layer (B) is provided with a release film.

16. A liquid crystal panel comprising:

a liquid crystal cell; and

the polarizing plate with an optical compensation layer according to claim 1.

17. A liquid crystal display comprising:

the liquid crystal panel according to claim 16.

18. An image display apparatus the polarizing plate with an optical compensation layer according to claim 1.

19. The self-light-emitting display apparatus of claim 18, which is an electroluminescence (EL) display.

20. The self-light-emitting display apparatus of claim 18, which is a plasma display (PD).

21. The self-light-emitting display apparatus of claim 18, which is a field emission display (FED).

22. The polarizing plate of claim 1, wherein the adhesive strength of pressure-adhesive layer (A) is equal to or larger than 15 N/25 mm.

23. The polarizing plate of claim 1, wherein the adhesive strength of pressure-adhesive layer (A) is equal to or larger than 15 N/25 mm.

24. The polarizing plate of claim 1, wherein the adhesive strength of pressure-adhesive layer (B) is from 1.5 to 9.5 N/25 mm.

25. A polarizing plate with an optical compensation layer, comprising:

an optical compensation layer;

pressure-sensitive adhesive layers disposed on respective surfaces of the optical compensation layer; and

a polarizing plate attached via one of the pressure-sensitive adhesive layers;

wherein one (A) of the pressure-sensitive layers causes the optical compensation layer and the polarizing plate to adhere to each other, and the other (B) of the pressure-sensitive adhesive layers causes the optical compensation layer and the glass substrate to adhere to each other, and

the adhesive strength of the pressure-sensitive adhesive layer (A) is larger than that of the pressure-sensitive adhesive layer (B).

26. The polarizing plate of claim 25, wherein the adhesive strength of pressure-sensitive adhesive layer (A) exceeds 12 N/25 mm.

27. The polarizing plate of claim 26, wherein the adhesive strength of pressure-sensitive adhesive layer (B) is from 1 to 12 N/25 mm.