# US 8,570,458 B2 · Liquid crystal display device and polarizing plate

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- Number: US 8,570,458 B2
- Document ID: US8570458B2
- Status: Granted
- Kind: B2
- Application number: 13/123,333
- Filed: 2009-10-09
- Published: 2011-08-11
- Granted: 2013-10-29
- Earliest claimed: 2008-10-31
- Assignees: Nitto Denko Corporation
- Applicants: Akinori Izaki; Seiji Umemoto; Shouji Yamamoto; Kentarou Takeda; Mitsuru Suzuki
- Inventors: Akinori Izaki; Seiji Umemoto; Shouji Yamamoto; Kentarou Takeda; Mitsuru Suzuki
- Web page: https://patentgrep.com/patent/US8570458B2

## Abstract

Provided is a liquid crystal display in which occurrence of iridescent unevenness is suppressed, even when a film with high level of mechanical properties, chemical resistance and water-barrier properties is used as a polarizer-protective-film. Also, disclosed is a polarizing plate to be used in the liquid crystal display. The liquid crystal display includes a liquid crystal cell, a light source, a first polarizing plate placed between the liquid crystal cell and the light source, and a second polarizing plate placed on a viewer side of the liquid crystal cell. The first polarizing plate includes a polarizer and a first protective film placed on a light source side principal surface of the first protective film, and the first protective film satisfies following relations: (i) 0 nm≦Re1≦3000 nm; (ii) Nz1≧5; and (iii) Rth1>2500 nm.

## Claims

### Claim 1

A liquid crystal display, comprising:
a liquid crystal cell;
a light source;
a first polarizing plate placed between the liquid crystal cell and the light source; and
a second polarizing plate placed on a viewer side of the liquid crystal cell,
wherein the first polarizing plate comprises a polarizer and a first protective film placed on a light source side principal surface thereof,
wherein, among protective films included in first polarizing plate and the second polarizing plate, only the first protective film satisfies following relations:
(i) 0 nm≦Re1≦3000 nm;
(ii) Nz1≧5; and
(iii) Rth1>2500 nm,
wherein Re1, Rth1 and Nz1 are defined by following equations:
Re1=(nx1−ny1)d1;
Rth1=(nx1−nz1)d1; and
Nz1=Rth1/Re1,
wherein
d1 represents a thickness of the first protective film,
nx1 represents a refractive index in a direction of an in-plane slow axis of the protective film,
ny1 represents a refractive index in a direction of an in-plane fast axis of the protective film, and
nz1 represents a refractive index in a direction of the thickness of the protective film, and
each refractive index being measured at 23° C. at a measurement wavelength of 590 nm;
wherein light emitted from the light source is incident on the first polarizing plate in the form of substantially natural light with an Im/Ix ratio of 0.90 or more,
wherein Ix and Im represents maximum and minimum, respectively, of light intensity measured by rotating analyzer method, in which analyzer is rotated by 360°.

### Claim 2 (depends on 1)

The liquid crystal display according to claim 1, wherein the first protective film comprises aromatic polyester as a main component.

### Claim 3 (depends on 2)

The liquid crystal display according to claim 2, wherein the aromatic polyester is polyethylene terephthalate or polyethylene naphthalate.

### Claim 4 (depends on 1)

The liquid crystal display according to claim 1, wherein neither reflective polarizing film nor absorptive polarizing film is provided between the light source and the first polarizing plate.

### Claim 5 (depends on 1)

The liquid crystal display according to claim 1, wherein the first polarizing plate has no protective film on a liquid crystal cell side principal surface of the polarizer.

### Claim 6 (depends on 1)

The liquid crystal display according to claim 1, wherein the first polarizing plate further comprises a second protective film on a liquid crystal cell side principal surface of the polarizer.

### Claim 7 (depends on 1)

The liquid crystal display according to claim 1, wherein the first protective film has a haze of less than 10%.