Neutral polarizer and liquid crystal display

• US 6,683,717 B1
• Filed: 04/26/2000
• Issued: 01/27/2004
• Est. Priority Date: 04/26/1999
• Status: Expired due to Term

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Miyatake, Minoru, Sakuramoto, Takafumi
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US09/558,324
• Time in Patent Office: 1,371 Days
• Field of Search: 359/487, 359/490, 359/491, 359/492, 359/494, 359/495, 359/500, 359/599, 349/96, 349/112, 349/183, 349/186, 349/61, 349/64, 349/65, 349/69, 349/70, 362/19, 362/31, 362/558, 362/661
• US Class Current: 359/487.06
• CPC Class Codes: C09K 19/3852 Poly(meth)acrylate derivatives
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133531 characterised by the arrangement of polariser or analyser axes
• CPC Class Codes: G02F 1/133567 on the back side

Abstract

A neutral polarizer has a dichroic polarizing sheet and a polarizing and scattering sheet laminated on the dichroic polarizing sheet. The polarizing and scattering sheet has anisotropy in light scattering properties depending on a direction of polarization, and has an optical axis showing intense scattering properties. Scattering intensity of linearly polarized light having a polarization direction of the optical axis is greatly dependent on wavelength. An absorption axis of the dichroic polarizing sheet and the optical axis of the polarizing and scattering sheet are in parallel to each other. A liquid crystal display is provided so that this neutral polarizer is disposed on a light source side of a liquid crystal panel.

Claims

1. A neutral polarizer comprising:

a dichroic polarizing sheet; and

a polarizing and scattering sheet which has anisotropy in light scattering properties dependent on a direction of polarization, said polarizing and scattering sheet having an optical axis with scattering properties, a scattering intensity of linearly polarized light having a polarization direction of said optical axis being dependent on wavelength, said polarizing and scattering sheet being laminated on said dichroic polarizing sheet,

wherein an absorption axis of said dichroic polarizing sheet and said optical axis of said polarizing and scattering sheet are in parallel to each other.

2. A neutral polarizer according to claim 1, wherein transmittance for linearly polarized light having a wavelength of 430 nm, and a polarization direction coincident with that of said optical axis of said polarizing and scattering sheet with scattering properties, is 90% or less of that for linearly polarized light having a wavelength of 610 nm and said polarization direction.

3. A neutral polarizer according to claim 1, wherein said polarizing and scattering sheet shows transmission spectral characteristics with little wavelength dependence for linearly polarized light having a polarization direction perpendicular to said optical axis of said polarizing and scattering sheet with scattering properties.

4. A neutral polarizer according to claim 1, wherein difference between transmittance for linearly polarized light having a wavelength of 430 nm and that for linearly polarized light having a wavelength of 610 nm, in a direction perpendicular to said optical axis of said polarizing and scattering sheet with scattering properties, is 5% or less.

5. A neutral polarizer according to claim 1, wherein said dichroic polarizing sheet and said polarizing and scattering sheet are joined via an adhesive layer.

6. A neutral polarizer according to claim 1, wherein said polarizing and scattering sheet also serves as a transparent protective layer on at least one side of said dichroic polarizing sheet.

7. A neutral polarizer according to claim 1, wherein said polarizing and scattering sheet has a total light transmittance of 90% or more for linearly polarized light having a polarization direction perpendicular to said optical axis of said polarizing and scattering sheet with scattering properties.

8. A neutral polarizer according to claim 1, wherein said polarizing and scattering sheet comprises a transparent polymer film having dispersed therein fine domains with birefringence characteristics different than that of a remaining portion of said polarizing and scattering sheet,

wherein a difference in refractive index between said fine domains and said remaining portion is 0.03 to 0.5 in the direction of said optical axis, in which said linearly polarized light is scattered most intensely, and is less than 0.03 in a direction of a second optical axis that is perpendicular to said optical axis and in which said linearly polarized light is scattered most weakly, and

said fine domains comprise a liquid crystal polymer which has a glass transition temperature of 50° C. or higher and exhibits a nematic liquid crystal phase in a temperature range lower than a glass transition temperature of polymer forming said remaining portion.

9. A neutral polarizer according to claim 8, wherein said fine domains have an average length of 0.1 to 10 μ

m in the direction of said optical axis, in which said linearly polarized light is scattered most intensely.

10. A neutral polarizer according to claim 8, wherein said polymer forming said remaining portion has a heat distortion temperature of 80°

C. or higher and a glass transition temperature of 110°

C. or higher.

11. A liquid crystal display having the neutral polarizer according to any one of claims 1 to 10 as a polarizer on a light source side of a liquid crystal panel.