Polarizing plate and liquid crystal display device

• US 20080158485A1
• Filed: 12/27/2007
• Published: 07/03/2008
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Wada, Minoru
• Granted Patent: US 7,767,286 B2
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: C09K 2323/031 Polarizer or dye
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 7/00 Mountings, adjusting means, or light-tight connections, for optical elements
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 2202/28 Adhesive materials or arrangements
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2203/60 Temperature independent
• CPC Class Codes: Y10T 428/24273 including aperture

Abstract

A novel polarizing plate is disclosed. The polarizing plate comprises at least a polarizing film, a pressure-sensitive adhesive layer, and an optical compensation sheet, having an absolute value of Y, defined by the following equation, equal to or smaller than 6.0×10⁻⁴:

Y=−7.0×10⁵×Cn+4.3×10⁻¹³×E−1.34×10⁻³

• • where Cn (1/Pa) is photoelastic modulus of said pressure-sensitive adhesive layer and E (Pa) is modulus of elasticity of said optical compensation sheet.

Claims

1. A polarizing plate comprising at least a polarizing film, a pressure-sensitive adhesive layer, and an optical compensation sheet;

and having an absolute value of Y, defined by the following equation, equal to or smaller than 6.0×

10<sup>−

4</sup>;

Y=−

7.0×

10⁵×

Cn+4.3×

10<sup>−

13</sup>×

E−

1.34×

10<sup>−

3</sup>

where Cn (1/Pa) is photoelastic modulus of said pressure-sensitive adhesive layer and E (Pa) is modulus of elasticity of said optical compensation sheet.

2. The polarizing plate of claim 1, wherein said pressure-sensitive adhesive layer comprises an acrylic pressure-sensitive adhesive.

3. The polarizing plate of claim 2, wherein said acrylic pressure-sensitive adhesive comprises at least one species of polymer comprising a repeating unit derived from a monomer of which homopolymer has a positive photoelastic coefficient.

4. The polarizing plate of claim 2, wherein said acrylic pressure-sensitive adhesive comprises at least one species of polymer comprising a repeating unit derived from a monomer represented by formula (1) below:

5. The polarizing plate of claim 1, wherein said optical compensation sheet has a photoelastic coefficient equal to or smaller than 50×

10<sup>−

12</sup> (1/Pa).

6. A liquid crystal display device comprising at least a liquid crystal cell and the polarizing plate as set forth in claim 1.

7. The liquid crystal display device of claim 6, wherein said polarizing plate is disposed so that a surface of the pressure-sensitive adhesive layer contacts a surface of said liquid crystal cell.

9. The polarizing plate of claim 2, wherein said acrylic pressure-sensitive adhesive comprises at least one species of copolymer comprising at least one repeating unit derived from a monomer of which homopolymer has a positive photoelastic coefficient.

10. The polarizing plate of claim 9, wherein said copolymer comprises at least one repeating unit derived from one selected from the group consists of aromatic acrylate monomers and aromatic methacrylate monomers.

11. The polarizing plate of claim 9, wherein said copolymer comprises at least one repeating unit derived from a compound represented by formula (1) below:

12. The polarizing plate of claim 9, wherein said optical compensation sheet has a photoelastic coefficient equal to or smaller than 50×

10<sup>−

12</sup> (1/Pa).

13. A liquid crystal display device comprising at least a liquid crystal cell and the polarizing plate as set forth in claim 9.

14. The liquid crystal display device of claim 13, wherein said polarizing plate is disposed so that a surface of the pressure-sensitive adhesive layer contacts a surface of said liquid crystal cell.

8. An acrylic pressure-sensitive adhesive to be used for polarizing plate, comprising at least one species of polymer comprising a repeating unit derived from a monomer represented by formula (1) below:

15. An acrylic pressure-sensitive adhesive to be used for polarizing plate, comprising at least one species of copolymer comprising at least one repeating unit derived from a monomer represented by formula (1) below: