Liquid crystal display apparatus

• US 5,734,365 A
• Filed: 01/22/1997
• Issued: 03/31/1998
• Est. Priority Date: 01/25/1996
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ohno, Tomoyuki, Iwasaki, Manabu, Katakura, Kazunori
• Primary Examiner(s): CHOW, DOON Y
• Application Number:
  US08/786,287
• Time in Patent Office: 433 Days
• Field of Search: 345/97, 345/99, 345/103, 345/94, 345/87, 345/96, 345/208, 345/209, 345/55, 345/50, 345/51, 345/60, 349/33, 349/37, 348/790, 348/792
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A liquid crystal display apparatus for presenting a high-quality image at a reduced power consumption comprises a liquid crystal display panel having scanning-signal electrodes and information-signal electrodes arranged in a matrix configuration, liquid crystals interposed between the scanning-signal electrodes and the information-signal electrodes, information electrode driving means for applying an information-signal voltage waveform to the information-signal electrodes, and scanning electrode driving means for applying a scanning-signal voltage waveform to the scanning-signal electrodes. The frequency of information-signal voltage waveform is lowered without changing the frame frequency of the apparatus by allowing two lines of scanning-signal electrodes to scan during a write pulse having a pulse length of ΔT within one scanning period to select presentations of two pixels for each information-signal electrode.

Claims

1. A liquid crystal display apparatus comprising:

a liquid crystal display panel having scanning-signal electrodes, information-signal electrodes and a liquid crystal, information electrode driving means for applying an information-signal voltage waveform to the information-signal electrodes, and scanning electrode driving means for applying a scanning-signal voltage waveform to the scanning-signal electrodes, wherein;

said scanning electrode driving means generates a first scanning-signal voltage waveform comprising a first write pulse having a pulse length of Δ

T and a first erase pulse just prior to the first write pulse, and a second scanning-signal voltage waveform, phase-shifted from the first scanning-signal voltage waveform by Δ

T, comprising a second write pulse having a pulse length of Δ

T and a second erase pulse just prior to the second write pulse, so that two lines of scanning-signal electrodes are scanned and selected sequentially within the same scanning period according to the first and second scanning-signal voltage waveforms; and

said information electrode driving means selectively applies a first information-signal voltage waveform comprising a first information pulse having a pulse length of Δ

T, and a second information pulse following the first information pulse, having a polarity opposite the polarity of the first information pulse and having a pulse length of Δ

T, and a second information-signal voltage waveform comprising a third information pulse having a pulse length of 2Δ

T.

2. A liquid crystal display apparatus according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal.

3. A liquid crystal display apparatus according to claim 1, wherein the liquid crystal is an anti-ferroelectric liquid crystal.

4. A multiplex driving method for driving a liquid crystal display apparatus having a plurality of first and second scanning electrodes each having pixels thereon, and a plurality of information electrodes, said method comprising the steps of:

applying a write pulse having a pulse length of Δ

T to the first scanning electrodes during a first duration and applying a write pulse having a pulse length of Δ

T to the second scanning electrodes during a second duration that is in succession to the first duration; and

applying an information signal to the information electrodes during the first and second durations to determine the presentation statuses of the pixels on the first and second scanning electrodes within one horizontal scanning period,

wherein one of four types of signals is selected as the information signal in accordance with the presentation statuses of the pixels and is applied to one of the information electrodes, and the four types of signals comprise first and second voltage waveforms being different in phase to each other, each of the first and second voltage waveforms having opposite polarities from the first duration to the second duration, and the third and fourth voltage waveforms being opposite in polarity to each other and each of the third and fourth voltage waveforms having the same polarity over the first duration and the second duration.

5. A method according to claim 4, wherein the write pulses are applied to two different scanning electrodes within an immediately subsequent horizontal scanning period.

6. A method according to claim 4, wherein erase pulses are applied to two different scanning electrodes within the one horizontal scanning period.

7. A method according to claim 4, wherein scanning electrodes that are not mutually adjacent are concurrently selected within the one horizontal scanning period.

8. A method according to claim 4 or 7, wherein a pair of scanning electrodes that are not mutually adjacent are sequentially selected within two consecutive horizontal scanning periods.

9. A method according to claim 4, wherein erase pulses are concurrently applied to two selected scanning electrodes within the one horizontal scanning period.