Driving method for liquid crystal device which is not affected by a threshold characteristic change

• US 5,469,281 A
• Filed: 08/24/1993
• Issued: 11/21/1995
• Est. Priority Date: 08/24/1992
• 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): Gross, Anita Pellman
• Assistant Examiner(s): MILLER, CHARLES LELAND
• Application Number:
  US08/111,509
• Time in Patent Office: 819 Days
• Field of Search: 359/56, 345/97, 345/101
• 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 2310/065 Waveforms comprising zero voltage phase or pause
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/207 by domain size control G09G3/3637 takes precedence
• CPC Class Codes: G09G 3/2074 using sub-pixels
• 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
• CPC Class Codes: G09G 3/364 with use of subpixels

Abstract

A liquid crystal device of the type including pixels, comprises a liquid crystal having a first and a second stable state, and which is stably driven for gradation display regardless of a change in threshold characteristic due to a temperature change, etc. The driving method includes the steps of: providing a pixel showing a transmittance (Ts) smaller than a prescribed transmittance (Tm), resetting the pixel to the first stable state and then applying at least two signals of alternating polarities to the pixel to obtain the transmittance (Ts); and providing a pixel showing a transmittance (T1) larger than the prescribed transmittance (Tm), resetting the pixel to the second stable state and then applying at least two signals of alternating polarities to the pixel to obtain the transmittance (T1).

Claims

1. A driving method for a liquid crystal device of the type including pixels comprising a liquid crystal having a first and a second stable state, comprising the steps of:

(A) providing a pixel having a transmittance (Ts) smaller than a prescribed transmittance (Tm), and sequentially applying to the pixel;

a first signal for resetting the pixel to the first stable state,

a second signal for inverting a portion of the reset pixel to the second stable state,

a third signal for partially inverting the invented portion of the pixel to the first stable state, and

a fourth signal for substantially not causing. inversion, and

(B) providing a pixel showing a transmittance (T₁) larger than the prescribed transmittance (Tm), and sequentially applying to the pixel;

a first signal for resetting the pixel to the first stable state,

a second signal for a resetting the pixel to the second stable state,

a third signal for inverting a portion of the pixel to the first stable state, and

a fourth signal for partially inverting the inverted portion of the pixel to the second stable state.

2. A method according to claim 1, wherein said prescribed transmittance is set to 50%.

3. A method according to claim 1, wherein the first to fourth signals are applied continuously.

4. A method according to claim 1, wherein the first to fourth signals are applied non-continuously.

5. A method according to claim 4, wherein the signals are applied with a time interval of at least 100 μ

s.

6. A method according to claim 1, wherein said pixels each have a distribution of inversion thresholds.

7. A method according to claim 1, wherein at least two of said pixels of equal areas are used as sub-pixels constituting one larger pixel.

8. A method according to claim 1, wherein at least two of said pixels of mutually different areas are used as sub-pixels constituting one larger pixel.

9. A method according to claim 1, wherein said liquid crystal comprises a ferroelectric liquid crystal.

10. A driving method for a liquid crystal device of the type including pixels comprising a liquid crystal having a first and a second stable state, comprising the steps of:

(A) providing a pixel having a transmittance (Ts) smaller than a prescribed transmittance (Tm), and sequentially applying to the pixel;

a first signal for resetting the pixel to the first stable state,

a second signal for inverting a p+β

% of the reset pixel to the second stable state,

a third signal for inverting a p% of the inverted pixel to the first stable state, and

a fourth signal for substantially not causing inversion, and

(B) providing a pixel having a transmittance (T₁), and sequentially applying to the pixel;

a first signal for resetting the pixel to the first stable state,

a second signal for resetting the pixel to the second stable state,

a third signal for inverting a p+α

% of the pixel to the first stable state, and

a fourth signal for inverting a p% of the pixel to the second stable state;

wherein p% represents a maximum inversion (%) below which a linear applied voltage-transmittance characteristic of a pixel is not attained, β

% represents an inversion of a pixel corresponding to the transmittance (Ts), and α

% represents an inversion of a pixel corresponding to the transmittance (T₁).

11. A driving method for a liquid crystal device of the type including pixels comprising a liquid crystal having a first and a second stable state, comprising the steps of:

(A) providing a pixel showing a transmittance (Ts) smaller than a prescribed transmittance (Tm), and sequentially applying to the pixel;

a first signal of a first polarity for resetting to the first stable state,

a second signal of a second polarity for inverting to the second stable state,

a third signal of the first polarity for inverting to the first stable state, and

a fourth signal of the second polarity not causing inversion, and

(B) providing a pixel showing a transmittance (T1) larger than the prescribed transmittance (Tm), and sequentially applying to the pixel;

a first signal of the first polarity for resetting to the first stable state,

a second signal of the second polarity for resetting to the first stable state,

a third signal of the first polarity for inverting to the first stable state, and

a fourth signal of the second polarity for inverting to the second stable state.