Passive-matrix type liquid crystal display apparatus and drive circuit thereof with single analog switch/adjusted scanning voltage based operation

• US 6,177,919 B1
• Filed: 03/04/1997
• Issued: 01/23/2001
• Est. Priority Date: 06/07/1996
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: Numao, Takaji
• Primary Examiner(s): NGUYEN, CHANH DUY
• Application Number:
  US08/810,549
• Time in Patent Office: 1,421 Days
• Field of Search: 345/89, 345/95, 345/94, 345/96, 345/97, 345/100, 345/101, 345/210, 345/147, 345/208, 349/149, 349/169, 349/179
• US Class Current: 345/94
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/364 with use of subpixels
• CPC Class Codes: G09G 3/3681 suitable for passive matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 3/3692 suitable for passive matrices only

Abstract

A segmented electrode drive circuit of a passive-matrix type liquid crystal display apparatus includes one analog switch in each of segmented electrodes, supplies “0” as a control signal in the first slot of a three-slot selecting period so as to make the electrical potential of a segmented electrode zero. “1” is supplied as a control signal in the second slot so as to bring the output terminal of an analog switch selected by the data signal into a high-impedance state. As a result, the electric potential of the segmented electrode in the high-impedance state becomes an average electric potential of scanning electrodes capacitive-coupled with the segmented electrode.

Claims

1. A passive-matrix type liquid crystal display apparatus having a pixel formed by a liquid crystal lying at each intersection of scanning electrodes and segmented electrodes, characterized in that:

said liquid crystal is a ferroelectric liquid crystal; and

a DC voltage varying according to a measured change in temperature of said liquid crystal is superimposed over a drive voltage applied to said scanning electrodes,

wherein a blanking voltage is applied to said scanning electrodes before a selecting period, and a voltage for cancelling a superimposed DC component is applied to said scanning electrodes after said blanking voltage and before said selecting period.

2. The passive-matrix type liquid crystal display apparatus according to claim 1,

wherein said ferroelectric liquid crystal has negative dielectric anisotropy.