LCD device having relationship between spontaneous polarization and capacitance
First Claim
1. A liquid crystal display device comprising:
- a first substrate having one major surface;
pixel electrodes arranged in matrix fashion on the major surface of the first substrate;
storage capacitors connected to the pixel electrodes;
switching elements connected to the pixel electrodes;
a liquid crystal layer provided close to the pixel electrodes arranged in matrix fashion, the liquid crystal having an inherent spontaneous polarization or a spontaneous polarization induced by application of an electric field;
a common electrode formed on the liquid crystal layer; and
a second substrate formed on the common electrode;
wherein an electrostatic capacitance of one pixel in a saturation alignment state of the liquid crystal is CLC (F), a spontaneous polarization of the liquid crystal per unit area is Ps (C/m2), a voltage applied between the pixel electrode and the common electrode is E (V), a pixel electrode area of one pixel is A (m2), and a storage capacitance for one pixel is Cs (F), they satisfy the following equation;
space="preserve" listing-type="equation">P.sub.s ×
A≦
5×
(C.sub.s +C.sub.LC)×
E(1).
1 Assignment
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Accused Products
Abstract
A liquid crystal display device is constituted so that liquid crystal having an inherent spontaneous polarization or a spontaneous polarization induced by applying an electric field is interposed between a pixel electrode disposed in matrix and a counter electrode, and a display signal is applied to the pixel electrode through a switching element. In the liquid crystal display device constituted mentioned above, when an electrostatic capacitance of one pixel is CLC (F), a spontaneous polarization per unit electrode area of the liquid crystal is Ps (C/m2), a voltage applied between the pixel electrode and the counter electrode is E (V), a pixel electrode area of one pixel is A (m2), and a storage capacitance for one pixel is Cs (F), they satisfy the following equation;
P.sub.s ×A≦5×(C.sub.s +C.sub.LC)×E(1)
Thereby, a display of high contrast and high response speed can be obtained. Further, a display of low power consumption and excellent display uniformity, that is, excellent image quality can be obtained.
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Citations
20 Claims
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1. A liquid crystal display device comprising:
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a first substrate having one major surface; pixel electrodes arranged in matrix fashion on the major surface of the first substrate; storage capacitors connected to the pixel electrodes; switching elements connected to the pixel electrodes; a liquid crystal layer provided close to the pixel electrodes arranged in matrix fashion, the liquid crystal having an inherent spontaneous polarization or a spontaneous polarization induced by application of an electric field; a common electrode formed on the liquid crystal layer; and a second substrate formed on the common electrode; wherein an electrostatic capacitance of one pixel in a saturation alignment state of the liquid crystal is CLC (F), a spontaneous polarization of the liquid crystal per unit area is Ps (C/m2), a voltage applied between the pixel electrode and the common electrode is E (V), a pixel electrode area of one pixel is A (m2), and a storage capacitance for one pixel is Cs (F), they satisfy the following equation;
space="preserve" listing-type="equation">P.sub.s ×
A≦
5×
(C.sub.s +C.sub.LC)×
E(1). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- 4. The liquid crystal display device as set forth in claim 1,
wherein the following equations are further satisfied, - space="preserve" listing-type="equation">E≧
V.sub.sat (
4)
and
space="preserve" listing-type="equation">F≦
1 (4'"'"')where Vsat (V) denotes a saturation voltage of a liquid crystal display device and the following equation is satisfied;
F=Ps ×
A×
exp (-(Tgon ×
loge 10/τ
))/((Cs +CLC)×
(E-Vsat))where Tgon (s) is a time period during which the switching element is selected for addressing a display signal to the pixel electrode; and
τ
(s) is a response time of a liquid crystal cell when a voltage E (V) is applied between the pixel electrode and the common electrode. - space="preserve" listing-type="equation">E≧
-
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5. The liquid crystal display device as set forth in claim 4,
wherein, when P1 =5× - 10-6 (C/m2), the following equation is further satisfied,
space="preserve" listing-type="equation">P.sub.s ≧
P.sub.1 (
5).
- 10-6 (C/m2), the following equation is further satisfied,
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6. The liquid crystal display device as set forth in claim 1,
wherein the liquid crystal display device has a thin film transistor (TFT) as the switching element. -
7. The liquid crystal display device as set forth in claim 6,
wherein the thin film transistor has a polycrystalline silicon layer. -
8. The liquid crystal display device as set forth in claim 6,
wherein the thin film transistor has an amorphous silicon layer. -
9. The liquid crystal display device as set forth in claim 6,
wherein the following equation is satisfied; -
space="preserve" listing-type="equation">(P.sub.s ×
A+(C.sub.s +C.sub.LC)×
E)/(2×
T.sub.gon)≦
I.sub.on (
6)where Tgon (s) is in one frame time a time period during which the gate electrode of the thin film transistor is selected; and
Ion (A) is the maximum value of a current that flows between a source and drain electrodes of the thin film transistor while the gate electrode is selected.
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10. The liquid crystal display device as set forth in claim 9,
wherein the following equations hold; -
space="preserve" listing-type="equation">I.sub.on ≦
I.sub.max (
7)and
space="preserve" listing-type="equation">I.sub.max 3×
10.sup.-4 (A) (7'"'"')where Imax is the maximum value of an electric current that the thin film transistor can flow.
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11. The liquid crystal display device as set forth in claim 6, further comprising:
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a frame memory for memorizing a potential being applied to a signal line to apply a potential to the liquid crystal; wherein one frame time is consisting of a plurality of sub-frame times, and within the respective sub-frame times, a gate line is selected on-state once.
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12. A liquid crystal display device comprising:
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a first substrate having one major surface; pixel electrodes arranged in matrix fashion on the major surface of the first substrate; storage capacitors connected to the pixel electrodes; switching elements connected to the pixel electrodes; a liquid crystal layer provided close to the pixel electrodes arranged in matrix fashion, the liquid crystal having an inherent spontaneous polarization or a spontaneous polarization induced by application of an electric field; a common electrode formed on the liquid crystal layer; and a second substrate formed on the common electrode; and
wherein the following equations are satisfied;
space="preserve" listing-type="equation">E≧
V.sub.sat and F≦
1,where Vsat (V) is a saturation voltage of a liquid crystal display element;
CLC (F) is an electrostatic capacitance of one pixel in a saturation alignment of the liquid crystal;
Ps (C/m2) is a spontaneous polarization of the liquid crystal per unit area is;
E (V) is a voltage applied between the pixel electrode and the common electrode;
A (m2) is an pixel electrode area for one pixel;
Cs (F) is a storage capacitance for one pixel;
Tgon (s) is a time period during which the switching element is selected for addressing display signal to the pixel electrode; and
τ
(s) is a response time of a liquid crystal cell when a voltage E (V) is applied between the pixel electrode and the common electrode and the following relation is satisfied;
space="preserve" listing-type="equation">F=P.sub.s ×
A×
exp(-(T.sub.gon ×
log.sub.e 10/τ
))/((C.sub.s +C.sub.LC)×
(E-V.sub.sat)). - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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17. The liquid crystal display device as set forth in claim 14,
wherein the thin film transistor has an amorphous silicon layer. - 18. The liquid crystal display device as set forth in claim 17,
wherein the following equation is satisfied, - space="preserve" listing-type="equation">F≦
2/3 (9).
- space="preserve" listing-type="equation">F≦
-
- 19. The liquid crystal display device as set forth in claim 17,
wherein the following equation is satisfied, - space="preserve" listing-type="equation">F≦
1/3 (10).
- space="preserve" listing-type="equation">F≦
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20. A liquid crystal display device comprising:
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a first substrate having one major surface; pixel electrodes arranged in matrix fashion on the major surface of the first substrate; storage capacitors connected to the pixel electrodes; switching elements connected to the pixel electrodes; a liquid crystal layer provided close to the pixel electrodes arranged in matrix fashion, the liquid crystal having an inherent spontaneous polarization or a spontaneous polarization induced by application of an electric field; a common electrode formed on the liquid crystal layer; and a second substrate formed on the common electrode; wherein the following equation is satisfied;
space="preserve" listing-type="equation">5×
C.sub.gs ×
Δ
V.sub.g ≦
(C.sub.s +C.sub.cell)×
V.sub.sat (
11)where Ccell (F) is a combined capacitance for one pixel consisting of a ferroelectric capacitance due to the spontaneous polarization of the liquid crystal and a capacitance of an alignment film;
Cgs (F)is a parasitic capacitance for one pixel between the gate electrode of the thin film transistor and the pixel electrode;
Cs (F) is the storage capacitance for one pixel;
Δ
Vg (V) is a potential difference of the gate electrode upon on/off; and
Vsat (V) is a saturation voltage of a liquid crystal display element.
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Specification