Anti-ferroelectric liquid crystal display and method of driving the same

• US 6,509,887 B1
• Filed: 02/19/1999
• Issued: 01/21/2003
• Est. Priority Date: 06/20/1997
• Status: Expired due to Fees

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Kondoh, Shinya, Takahashi, Shigekazu
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): ZAMANI, ALI A
• Application Number:
  US09/242,491
• Time in Patent Office: 1,432 Days
• Field of Search: 345/97, 345/100, 345/102, 345/98, 345/87, 345/95, 345/88, 345/89, 345/94, 345/96, 345/208, 349/174
• US Class Current: 345/87
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 3/3633 with transmission/voltage characteristic comprising multiple loops, e.g. antiferroelectric liquid crystals

Abstract

An antiferroelectric liquid crystal display comprises: an antiferroelectric liquid crystal display element which includes an antiferroelectric liquid crystal that is sandwiched between a pair of substrates having a plurality of scanning electrodes and signal electrodes deposited respectively on the opposing surfaces thereof; and a light source which successively emits a plurality of different colors of light. In the thus constructed antiferroelectric liquid crystal display, a scanning period (TS) during which the light source emits light of one of the plurality of colors is divided into two periods, of which the first period (SC1) includes a selection period for determining a display state and a non-selection period for holding therethrough the display state selected during the selection period, and the second period (SC2), constituting the remainder of the scanning period, includes a selection period for forcing the display state into a black display state and a non-selection period for holding therethrough the black display state selected during the selection period.

Claims

1. An antiferroelectric liquid crystal display comprising:

an antiferroelectric liquid crystal display element which includes an antiferroelectric liquid crystal that is sandwiched between a pair of substrates having at least one electrode deposited on an opposing surface thereof; and

a light source which sequentially emits Red, Green, and Blue colors of light, wherein

a scanning period during which said light source emits light of one of said Red, Green, and Blue colors is divided into two periods, of which the first period includes a selection period for determining a display state and a non-selection period for holding therethrough the display state selected during said selection period, and

the second period, constituting the remainder of said scanning period, includes a selection period for forcing said display state into a black display state and a non-selection period for holding therethrough the black display state selected during said selection period.

2. An antiferroelectric liquid crystal display as claimed in claim 1, wherein said antiferroelectric liquid crystal is capable of exhibiting a first ferroelectric state, a second ferroelectric state that is entered when a voltage opposite in polarity to that for said first ferroelectric state is applied, and an antiferroelectric state, and wherein a voltage value of a composite voltage waveform produced by compositing a scanning voltage waveform and a signal voltage waveform applied during said selection period in said second period is less than a threshold voltage value at which said antiferroeletric liquid crystal makes a transition to said first or said second ferroelectric state.

3. An antiferroelectric liquid crystal display as claimed in claim 1, wherein the signal voltage waveform applied during said second period is always set as a black display producing signal voltage waveform.

4. An antiferroelectric liquid crystal display as claimed in any one of claims 1 to 3, wherein said first period and said second period are substantially equal in length.

5. An antiferroelectric liquid crystal display as claimed in any one of claims 1 to 3, wherein said first period is located somewhere near the middle of said scanning period.

6. An antiferroelectric liquid crystal display comprising:

an antiferroelectric liquid crystal display element which includes an antiferroelectric liquid crystal that is sandwiched between a pair of substrates having N scanning electrodes and M signal electrodes deposited respectively on the opposing surfaces thereof; and

a light source which sequentially emits Red, Green, and Blue colors of light,

wherein a period during which said light source emits light of one of said Red, Green, and Blue colors is divided into an even number of scanning periods, wherein, in an odd-numbered scanning period, one of forward scanning and backward scanning is performed, and in an even-numbered scanning period, the other of the forward scanning and the backward scanning is performed, and

wherein the forward scanning is performed by scanning said scanning electrodes forward, starting at the first scanning electrode and progressing toward the N-th scanning electrode and the backward scanning is performed by scanning said scanning electrodes backward, starting at the N-th scanning electrode and progressing toward the first scanning electrode.

7. An antiferroelectric liquid crystal display as claimed in claim 6, wherein in said odd-numbered scanning period, the forward scanning is performed and, in said even-numbered scanning period, the backward scanning is performed.

8. A method of driving an antiferroelectric liquid crystal display that comprises:

an antiferroelectric liquid crystal display element which includes an antiferroelectric liquid crystal that is sandwiched between a pair of substrates having at least one electrode deposited on an opposing surface thereof; and

a light source which sequentially emits Red, Green, and Blue colors of light, wherein

a scanning period during which said light source emits light of one of said Red, Green, and Blue colors is divided into two periods, in the first period of which a display state is determined, said first period having a selection period and a non-selection period for holding therethrough the display state selected during said selection period, and in the second period, constituting the remainder of said scanning period, said display state is forced into a black display state.

9. A method of driving the antiferroelectric liquid crystal display as claimed in claim 8, wherein said antiferroelectric liquid crystal is capable of exhibiting a first ferroelectric state, a second ferroelectric state that is entered when a voltage opposite in polarity to that for said first ferroelectric state is applied, and an antiferroelectric state, and wherein a voltage value of a composite voltage waveform produced by compositing a scanning voltage waveform and a signal voltage waveform applied during a selection period in said second period is less than a threshold voltage value at which said antiferroelectric liquid crystal makes a transition to said first or said second ferroelectric state.

10. A method of driving the antiferroelectric liquid crystal display as claimed in claim 8, wherein the signal voltage waveform applied during said second period is always set as a black display producing signal voltage waveform.

11. A method of driving the antiferroelectric liquid crystal display as claimed in any one of claims 8 to 10, wherein said first period and said second period are substantially equal in length.

12. A method of driving an antiferroelectric liquid crystal display, the antiferroelectic liquid crystal display comprising an antiferroelectric liquid crystal antiferroelectric liquid crystal that is sandwiched between a pair of substrates having N scanning electrodes and M signal electrodes deposited respectively on the opposing surfaces thereof, the method comprising the steps of:

dividing a period during which said light source emits light of one of said Red, Green, and Blue colors into even number of scanning periods; and

in an odd-numbered scanning period, performing one of forward scanning and backward scanning; and

in an even-numbered scanning period, performing the other of the forward scanning and the backward scanning,

wherein the forward scanning is performed by scanning said scanning electrodes forward, starting at the first scanning electrode and progressing toward the N-th scanning electrode and the backward scanning is performed by scanning said scanning electrodes backward, starting at the N-th scanning electrode and progressing toward the first scanning electrode.

13. A method of driving the antiferroelectric liquid crystal display as claimed in claim 12, wherein in said odd-numbered scanning period, the forward scanning is performed and, in said even-numbered scanning period, the backward scanning is performed.

14. An antiferroelectric liquid crystal display comprising:

an antiferroelectric liquid crystal display element which includes an antiferroelectric liquid crystal that is sandwiched between a pair of substrates having at least one scanning electrode and at least one signal electrode deposited respectively on the opposing surfaces thereof;

a control circuit operatively connected to said scanning electrode and said signal electrode; and

a light source which successively emits a plurality of different colors of light, wherein

a scanning period during which said light source emits light of one of said plurality of colors is divided into two periods, of which the first period includes a selection period for determining a display state and a non-selection period for holding therethrough the display state selected during said selection period, wherein the second period, constituting the remainder of said scanning period, includes a selection period for forcing said display state into a black display state and a non-selection period for holding therethrough the black display state selected during said selection period, and wherein said first period is located somewhere near the middle of said scanning period.

15. A method for driving an antiferroelectric liquid crystal display having an antiferroelectric liquid crystal display element which includes an antiferroelectric liquid crystal that is sandwiched between a pair of substrates have at least one scanning electrode and at least one signal electrode deposited respectively on the opposing surfaces thereof;

a control circuit operatively connected to said scanning electrode and said signal electrode; and

a light source which successively emits a plurality of different colors of light, the method comprising the steps of;

providing a scanning period during which said light source emits light of one of said plurality of colors is divided into two periods, wherein the first period includes a selection period for determining a display state and a non-selection period for holding therethrough the display state selected during said selection period, and wherein

the second period, constituting the remainder of said scanning period, includes a selection period for forcing said display state into a black display state and a non-selection period for holding therethrough the black display state selected during said selection period, and

locating said first period somewhere near the middle of said scanning period.