Driving method for liquid crystal device

• US 5,471,229 A
• Filed: 02/09/1994
• Issued: 11/28/1995
• Est. Priority Date: 02/10/1993
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Okada, Shinjiro, Inaba, Yutaka, Katakura, Kazunori
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US08/193,740
• Time in Patent Office: 657 Days
• Field of Search: 345/12, 345/63, 345/77, 345/89, 345/94, 345/95, 345/97, 345/101, 345/208, 345/210
• US Class Current: 345/89
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/207 by domain size control G09G3/3637 takes precedence
• CPC Class Codes: G09G 3/3637 with intermediate tones displayed by domain size control domain size control in flat matrix panels other than liquid crystal displays having memory effects G09G3/207

Abstract

A driving method is used for a liquid crystal device of the type comprising a pair of oppositely disposed electrode plates having thereon a group of scanning lines and a group of data lines, respectively, and a liquid crystal disposed between the pair of electrode plates so as to form a pixel at each intersection of the scanning lines and data lines. In the driving method, for displaying a halftone, a data line is supplied with a halftone signal selected from plural halftone signals determined according to a first relationship between applied voltage and transmittance of a pixel. On the other hand, for displaying a minimum or a maximum transmittance, a data line is supplied with an extreme signal determined according to a second relationship, different from the first one, between applied voltage and transmittance of a pixel. The extreme signal is applied for displaying a minimum or maximum transmittance state. As a result, a gradational display is performed at a high contrast ratio even when a temperature change occurs.

Claims

1. A driving method for a liquid crystal device of the type comprising a pair of oppositely disposed electrode plates having thereon a group of scanning lines and a group of data lines, respectively, and a liquid crystal disposed between the pair of electrode plates so as to form a pixel at each intersection of the Scanning lines and data lines, said driving method comprising:

for displaying a halftone, applying to a data line a halftone signal selected from plural halftone signals determined according to a first relationship between applied voltage and transmittance of a pixel; and

for displaying a minimum or a maximum transmittance, applying to a data line an extreme signal determined according to a second relationship between applied voltage and transmittance of a pixel, said second relationship being different from said first relationship,

wherein a scanning line is supplied with a reset signal for resetting pixels thereon and then a selection signal for writing, and said halftone signal or extreme signal is selectively applied to a data line for an associated pixel in synchronism with the selection signal.

2. A method according to claim 1, wherein the associated pixel is supplied with a compensation signal after application of the halftone signal or extreme signal to the data line.

3. A method according to claim 1, wherein said first relationship represents a higher threshold characteristic compared with said second relationship.

4. A method according to claim 1, wherein said first relationship represents a relationship for a pixel placed at a certain temperature, and said second relationship represents a relationship for the pixel placed at a temperature which is higher than said certain temperature.

5. A method according to claim 1, wherein said pixel has a threshold distribution such that a portion of the liquid crystal assumes a first orientation state and the remaining portion of the liquid crystal assumes a second orientation state in response to the halftone signal.

6. A method according to claim 1, wherein said reset signal and said selection signal have polarities which alternate for an adjacent scanning line.

7. A method according to claim 1, wherein said liquid crystal is placed in chiral smectic phase.

8. A method according to claim 1, wherein said liquid crystal is a ferroelectric liquid crystal.

9. A method according to claim 7, wherein the chiral smectic liquid crystal in a pixel assumes a state of mixture including a domain of a first orientation state and a domain of a second orientation state in response to a halftone signal applied thereto.