IPS LCD device having a wider viewing angle
View Patent ↗An in-plane-switching-mode (IPS) LCD device includes a TFT substrate and a CF substrate sandwiching therebetween an LC layer, and a pair of polarizing films sandwiching therebetween the substrates and the LC layer. Each polarizing film has a polarization layer and a protective layer An optical compensation layer having a birefringence is disposed between the light-emitting-side polarizing film and the CF substrate. The optical compensation layer has an in-plane retardation of N 1 satisfying the following relationship: 83.050−0.810× D 1 ≦N 1 ≦−228.090−0.74 D 1 in the range of 0<D 1 ≦80 μm, wherein D 1 is the thickness of the protective layer of the light-incident-side polarizing film.
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 N 1 (nm), and said second protective layer of said second polarizing film has a retardation R t2 :
R
t2
=
(
npx
2
+
npy
2
2
-
npz
2
)
×
d
2
in the thickness direction thereof, where npx 2 , npy 2 , npz 2 and d 2 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 N 1 and R t2 satisfy therebetween the following relationship:
83.050−1.18 R t2 ≦N 1 ≦228.090−1.08 R t2
in a range of 0 ≦=R t2 ≦55 nm.
2. The IPS LCD device according to claim 1 , wherein:
said birefringence of said optical compensation layer satisfies the relationship 0.0≦(ns−nz)/(ns−nf)<0.2;
said first protective layer of said first polarizing film has a retardation R t3 :
R
t3
=
(
npx
3
+
npy
3
2
-
npz
3
)
)
×
d
3
in the thickness direction thereof, where npx 3 , npy 3 , npz 3 and d 3 are a refractive index along an in-plane slow axis, a refractive index along an in-plane fast axis, a refractive index along a thickness direction and a thickness, respectively, of said first protective layer of said first polarizing film; and
said R t2 and R t3 satisfy therebetween the following relationship:
48.3−1.05 R t2 +0.00952 R t2 2 ≦R t3 ≦111.0−0.529 R t2 −0.00472 R t2 2
in a range of 0.0≦R t2 <37.5; and
342.0−16.9 R t2 −0.222 R t2 2 ≦R t3 111.0−0.529 R t2 −0.00472 R t2 2
in a range of 37.5≦Rt 2 ≦55.0.
3. The IPS LCD device according to claim 1 , wherein:
said birefringence of said optical compensation layer satisfies the relationship 0.2≦(ns−nz)/(ns−nf)≦0.4;
said first protective layer of said first polarizing film has a retardation R t3 :
R
t3
=
(
npx
3
+
npy
3
2
-
npz
3
)
×
d
3
in the thickness direction thereof, where npx 3 , npy 3 , npz 3 and d 3 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 first protective layer of said first polarizing film; and
said R t2 and R t3 satisfy the following relationship:
8.75−0.957 R t2 +0.0093 R t2 2 ≦R t3 ≦90.3−0.368 R t2 −0.00832 R t2 2
in a range of 0.0≦R t2 <10.0;
0≦ R t3 <90.3−0.368 R t2 −0.00832 R t2 2
in a range of 10.0≦R t2 <38: and
431.0−22.8 R t2 +0.302 R t2 2 ≦R t3 ≦90.3−0.368 R t2 −0.00832 R t2 2
in a range of 38.0≦R t2 ≦55.0.
4. The IPS LCD device according to claim 1 , wherein:
said birefringence of said optical compensation layer satisfies the relationship 0.4≦(ns−nz)/(ns−nf)<0.5;
said first protective layer of said first polarizing film has a retardation R t3 :
R
t3
=
(
npx
3
+
npy
3
2
-
npz
3
)
)
×
d
3
in the thickness direction thereof, where npx 3 , npy 3 , npz 3 and d 3 are a refractive index along an in-plane slow axis, a refractive index along an in-plane fast axis, a refractive index along a thickness direction and a thickness, respectively, of said first protective layer of said first polarizing film; and
said R t2 and R t3 satisfy the following relationship:
0 ≦R t3 ≦65.2−0.805 R t2
in a range of 0.0≦R t2 ≦55.0.
5. The IPS LCD device according to claim 1 , wherein 0≦R t2 ≦25.
6. The IPS LCD device according to claim 1 , wherein:
( npx 2 −npy 2 )× d 2 <10; and
( npx 3 −npy 3 )× d 3 ≦10.