US 7,460,198 B2
IPS LCD device having a wider viewing angle
Hiroshi Nagai, Kanagawa (Japan); and Hidenori Ikeno, Kanagawa (Japan)
Assigned to NEC LCD Technologies, Ltd., (Japan)
Filed on Dec. 08, 2004, as Appl. No. 11/7,425.
Claims priority of application No. 2003-415183 (JP), filed on Dec. 12, 2003; and application No. 2004-354292 (JP), filed on Dec. 07, 2004.
Prior Publication US 2005/0128411 A1, Jun. 16, 2005
Int. Cl. G02F 1/1335 (2006.01)
U.S. Cl. 349—117  [349/118; 349/96; 349/141] 6 Claims
OG exemplary drawing
 
1. An in-plane-switching-mode liquid crystal display (IPS LCD) device comprising:
a liquid crystal (LC) layer having a first optical axis;
first and second substrates sandwiching therebetween said LC layer, said first and second substrates being disposed on a light-emitting side and a light-incident side, respectively, of said LCD device;
first and second polarizing films sandwiching therebetween said first and second substrates and said LC layer, said first and second polarizing films having polarization axes extending normal to each other and being disposed on the light-emitting side and the light-incident side, respectively, of said LCD device, each of said first and second polarizing films including a first protective layer, a polarization layer and a second protective layer, which are disposed consecutively as viewed from the light-incident side, each of said first and second protective layers having a retardation in a thickness direction thereof; and
an optical compensation layer disposed between said first polarizing film and said first substrate, wherein:
said optical compensation layer has a birefringence satisfying the relationship 0.0≤(ns−nz)/(ns−nf)≤0.5, where ns, nf and nz are a refractive index along an in-plane slow axis, a refractive index along an in-plane fast axis, and a refractive index along a thickness direction, respectively, of said optical compensation layer;
an angle between said in-plane slow axis of said optical compensation layer and said first optical axis is within ±2 degrees; and
said optical compensation layer has an in-plane retardation N1 (nm), and said second protective layer of said second polarizing film has a retardation Rt2:

OG Complex Work Unit Drawing
in the thickness direction thereof, where npx2, npy2, npz2 and d2 are a refractive index along an in-plane slow axis, a refractive index along an in-plane fast axis, a refractive index along an orthogonal axis and a thickness, respectively, of said second protective layer of said second polarizing film; and
said N1 and Rt2 satisfy therebetween the following relationship:
83.050−1.18Rt2≤N1≤228.090−1.08Rt2
in a range of 0≤=Rt2≤55 nm.