Liquid crystal display
View Patent ↗A liquid crystal display includes a back substrate, a front substrate, and an optical filter layer interposed therebetween. The optical filter layer contains a liquid crystal material which forms a bend configuration when a voltage is applied between electrodes of the back and front substrates. The electrodes of the back and front substrates are covered with alignment layers which include corrugated surfaces at positions of the electrodes. Each corrugated surface includes upslopes and downslopes steeper than the upslopes or vertical surfaces which are alternately joined.
1. A liquid crystal display comprising:
a back substrate which comprises a first substrate, a first electrode disposed on a main surface of the first substrate, and a first alignment layer covering the first electrode and including a first corrugated surface at a position of the first electrode, wherein the first corrugated surface includes first upslopes and first downslopes steeper than the first upslopes or first vertical surfaces which are alternately joined in an in-plane direction parallel to the main surface of the first substrate, and wherein a period of the first upslope in the in-plane direction is 1 μm or less;
a front substrate which comprises a second substrate facing the first alignment layer, a second electrode disposed on a main surface of the second substrate facing the first alignment layer, and a second alignment layer covering the second electrode and including a second corrugated surface at a position of the second electrode, wherein the second corrugated surface includes second upslopes and second downslopes steeper than the second upslopes or second vertical surfaces which are alternately joined in the in-plane direction, and wherein a period of the second upslope in the in-plane direction is 1 μm or less; and
an optical filter layer interposed between the back and front substrates and containing a liquid crystal material which forms a bend configuration when a voltage is applied between the first and second electrodes.
2. The display according to claim 1 , wherein the display is configured to display a first image when a first voltage is applied between the first and second electrodes, and display a second image darker than the first image when a second voltage whose absolute value is larger than an absolute value of the first voltage is applied between the first and second electrodes, and
wherein, when the second image is displayed, a difference ΔR ON between a maximum optical retardation and a minimum optical retardation in a region of the optical filter layer interposed between the first and second electrodes is 5 nm or less.
3. The display according to claim 1 , wherein the display is configured to display a first image when a first voltage is applied between the first and second electrodes, and display a second image darker than the first image when a second voltage whose absolute value is larger than an absolute value of the first voltage is applied between the first and second electrodes, and
wherein a maximum thickness D max of the optical filter layer at a position interposed between the first and second electrodes, a minimum thickness D min of the optical filter layer at the position interposed between the first and second electrodes, a maximum relative dielectric constant ∈ mjr of the liquid crystal material, a relative dielectric constant ∈ AL of the first and second alignment layers, and a maximum optical retardation R ON−max in nanometer in a region of the optical filter layer interposed between the first and second electrodes when the second image is displayed satisfy relationships represented by inequalities (1) and (2) or relationships represented by inequalities (3) and (4)
D
max
-
D
min
D
max
<
5
R
ON
-
max
(
1
)
ɛ
AL
≥
0.5
(
5
R
ON
-
max
)
⨯
D
max
-
D
min
D
max
⨯
ɛ
mjr
(
2
)
D
max
-
D
min
D
max
≥
5
R
ON
-
max
(
3
)
ɛ
AL
≥
0.5
⨯
ɛ
mjr
.
(
4
)
4. The display according to claim 1 , wherein the display is configured to display a first image when a first voltage is applied between the first and second electrodes, and display a second image darker than the first image when a second voltage whose absolute value is larger than an absolute value of the first voltage is applied between the first and second electrodes, and
wherein a difference Δ(R OFF −R ON ) between a maximum difference (R OFF −R ON ) max and a minimum difference (R OFF −R ON ) min is 5 nm or less in a region of the optical filter layer interposed between the first and second electrodes, the maximum difference (R OFF −R ON ) max and the minimum difference (R OFF −R ON ) min being a maximum value and a minimum value of difference between an optical retardation R OFF when the first image is displayed and an optical retardation R ON when the second image is displayed, respectively.
5. The display according to claim 1 , wherein the display is configured to display a first image when a first voltage is applied between the first and second electrodes, and display a second image darker than the first image when a second voltage whose absolute value is larger than an absolute value of the first voltage is applied between the first and second electrodes, and
wherein the period P of the first or second upslope and a value P lim calculated from a following equation (5) satisfy a relationship represented by following inequality (6), or the period P, the value P lim , a maximum relative dielectric constant ∈ mjr of the liquid crystal material, and a relative dielectric constant ∈ AL of the first and second alignment layers satisfy relationships represented by following inequalities (7) and (8), D max being a maximum thickness of the optical filter layer at a position interposed between the first and second electrodes, α being a slope angle of the first or second upslopes, and (R OFF −R ON ) max being a maximum difference between an optical retardation R OFF when the first image is displayed and an optical retardation R ON when the second image is displayed in a region of the optical filter layer interposed between the first and second electrodes
P
lim
=
D
max
2
⨯
tan
α
⨯
5
(
R
OFF
-
R
ON
)
max
(
5
)
P
≤
0.6
⨯
P
lim
(
6
)
P
>
0.6
⨯
P
lim
(
7
)
ɛ
AL
≥
[
9
4
⨯
(
P
P
lim
-
0.6
)
+
0.1
]
⨯
ɛ
mjr
.
(
8
)
6. The display according to claim 1 , wherein the periods of the first and second upslopes are 0.04 μm or more.
7. The display according to claim 1 , wherein the liquid crystal material forms the bend configuration before energizing the display.
8. The display according to claim 1 , further comprising a optically compensation film disposed on the back and/or front substrates.
9. The display according to claim 1 , wherein each of the first and second alignment layers is subjected to a rubbing process in which the alignment layer is rubbed in the in-plane direction.
10. The display according to claim 1 , wherein the back or front substrate further comprises a color filter.
11. The display according to claim 1 , wherein the display is an active matrix display.
12. The display according to claim 11 , wherein the back substrate is an array substrate and further comprises a color filter between the first substrate and the first electrode.
13. The display according to claim 1 , wherein the display is a passive matrix display.
14. The display according to claim 13 , wherein the front substrate further comprises a color filter between the second substrate and the second electrode.
15. A liquid crystal display comprising:
a back substrate which comprises a first substrate, a first electrode disposed on a main surface of the first substrate, and a first alignment layer covering the first electrode and including a first corrugated surface at a position of the first electrode, wherein the first corrugated surface includes first upslopes and first downslopes steeper than the first upslopes or first vertical surfaces which are alternately joined in an in-plane direction parallel to the main surface of the first substrate;
a front substrate which comprises a second substrate facing the first alignment layer, a second electrode disposed on a main surface of the second substrate facing the first alignment layer, and a second alignment layer covering the second electrode and including a second corrugated surface at a position of the second electrode, wherein the second corrugated surface includes second upslopes and second downslopes steeper than the second upslopes or second vertical surfaces which are alternately joined in the in-plane direction; and
an optical filter layer interposed between the back and front substrates and containing a liquid crystal material which forms a bend configuration when a voltage is applied between the first and second electrodes.
16. The display according to claim 15 , wherein the liquid crystal material forms the bend configuration before energizing the display.
17. The display according to claim 15 , wherein each of the first and second alignment layers is subjected to a rubbing process in which the alignment layer is rubbed in the in-plane direction.
18. A liquid crystal display comprising:
a back substrate which comprises a first substrate, a first electrode disposed on a main surface of the first substrate, and a first alignment layer covering the first electrode and including a first corrugated surface at a position of the first electrode, wherein the first corrugated surface includes first upslopes and first downslopes steeper than the first upslopes or first vertical surfaces which are alternately joined;
a front substrate which comprises a second substrate facing the first alignment layer, a second electrode disposed on a main surface of the second substrate facing the first alignment layer, and a second alignment layer covering the second electrode and including a second corrugated surface at a position of the second electrode, wherein the second corrugated surface includes second upslopes and second downslopes steeper than the second upslopes or second vertical surfaces which are alternately joined; and
an optical filter layer interposed between the back and front substrates and containing a liquid crystal material which forms a bend configuration when a voltage is applied between the first and second electrodes.
19. The display according to claim 18 , wherein the liquid crystal material forms the bend configuration before energizing the display.
20. The display according to claim 18 , wherein each of the first and second alignment layers is subjected to a rubbing process.