Polarizing plate with optical compensation layer and image display apparatus using the same

• US 7,548,290 B1
• Filed: 11/24/2006
• Issued: 06/16/2009
• Est. Priority Date: 11/28/2005
• Status: Expired due to Fees

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Takada, Katsunori, Kitamura, Yoshitsugu
• Primary Examiner(s): Kim; Richard H
• Application Number:
  US11/994,448
• Publication Number:
  US 20090135343A1
• Time in Patent Office: 935 Days
• Field of Search: None
• US Class Current: 349/96
• CPC Class Codes: C09K 2323/035 Ester polymer, e.g. polycarbonate, polyacrylate or polyester
• 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
• CPC Class Codes: G02F 1/133634 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 Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2201/50 Protective arrangements
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2413/03 Number of plates being 3
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation
• CPC Class Codes: G02F 2413/12 Biaxial compensators
• CPC Class Codes: G02F 2413/13 Positive birefingence

Abstract

The polarizing plate with an optical compensation layer of the present invention includes: a hardcoat layer; a polarizer; a first optical compensation layer placed so that a slow axis thereof intersects with an absorption axis of the polarizer; and a second optical compensation layer placed so that a slow axis thereof intersects with the absorption axis of the polarizer in the stated order, wherein: the first optical compensation layer provides a substantially ½ retardation with respect to a wavelength of monochromatic light; the second optical compensation layer provides a substantially ¼ retardation with respect to a wavelength of monochromatic light; and the hardcoat layer contains urethaneacrylate, polyol (meth)acrylate, and (meth) acrylic polymer having an alkyl group containing at least two hydroxyl groups. The polarizing plate with an optical compensation layer of the present invention may suitably be used for various image display apparatuses (such as a liquid crystal display apparatus and a self-luminous display apparatus).

Claims

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

a hardcoat layer;

a polarizer;

a first optical compensation layer placed so that a slow axis thereof intersects with an absorption axis of the polarizer; and

a second optical compensation layer placed so that a slow axis thereof intersects with the absorption axis of the polarizer in the stated order, wherein;

the first optical compensation layer provides a substantially ½

retardation with respect to a wavelength of monochromatic light;

the second optical compensation layer provides a substantially ¼

retardation with respect to a wavelength of monochromatic light; and

the hardcoat layer contains urethaneacrylate, polyol(meth)acrylate, and (meth)acrylic polymer having an alkyl group containing at least two hydroxyl groups.

2. The polarizing plate with an optical compensation layer according to claim 1, wherein the polyol(meth)acrylate contained in the hardcoat layer contains pentaerythritol triacrylate and pentaerythritol tetraacrylate.

3. The polarizing plate with an optical compensation layer according to claim 1, wherein the hardcoat layer has a thickness of 15 μ

m to 50 μ

m.

4. The polarizing plate with an optical compensation layer according to claim 1, wherein the first optical compensation layer contains a resin with an absolute value of a photoelastic coefficient of 2.0×

10<sup>−

11</sup> m²/N or less and has a relationship of nx₁>

ny₁=nz₁ and an in-plane retardation Re₁ of 200 to 300 nm.

5. polarizing plate with an optical compensation layer according to claim 1, wherein the second optical compensation layer contains a resin with an absolute value of a photoelastic coefficient of 2.0×

10<sup>−

11</sup> m²/N or less and has a relationship of nx₂>

ny₂=nz₂ and an in-plane retardation Re₂ of 90 to 160 nm.

6. The polarizing plate with an optical compensation layer according to claim 1, wherein each of the first optical compensation layer and the second optical compensation layer comprises a stretched film obtained by uniaxially stretching a polymer film containing a norbornene-based resin.

7. The polarizing plate with an optical compensation layer according to claim 1, further comprising a protective layer on at least one side of the polarizer.

8. The polarizing plate with an optical compensation layer according to claim 1, wherein the polarizer, the first optical compensation layer, and the second optical compensation layer are placed via a pressure-sensitive adhesive layer.

9. The liquid crystal panel, comprising the polarizing plate with an optical compensation layer according to claim 1, and a liquid crystal cell.

10. The liquid crystal panel according to claim 9, wherein the liquid crystal cell employs a TN mode, an ECB mode, or a VA mode.

11. A liquid crystal display apparatus comprising the liquid crystal panel according to claim 9.

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

13. A liquid crystal display apparatus comprising the liquid crystal panel according to claim 10.