Method of improving viewing angle and contrast of liquid crystal displays

• US 5,969,700 A
• Filed: 07/07/1997
• Issued: 10/19/1999
• Est. Priority Date: 07/07/1997
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Fitzgibbons, Thomas J., Dunn, Patrick M.
• Primary Examiner(s): Saras, Steven J.
• Assistant Examiner(s): Alphonse, Fritz
• Application Number:
  US08/888,796
• Time in Patent Office: 834 Days
• Field of Search: 345/87, 349/33, 349/34, 349/35, 349/36, 349/37
• US Class Current: 345/87
• CPC Class Codes: G09G 2320/028 by changing the viewing angle properties, e.g. widening the viewing angle, adapting the viewing angle to the view direction
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A novel method of driving an LCD simultaneously provides improved viewing angle and improved contrast. Multiple driving voltages are applied to the LC cell to optimize both the viewing angle and the contrast. A first voltage that is optimized for wide viewing angle is applied to the LCD. A second voltage that is greater than the first voltage is selected to provide maximum contrast in the LCD. The first and second voltages are alternately applied to In the LCD, resulting in a display that has high contrast and a wide viewing angle.

Claims

1. A method of driving an LCD to simultaneously provide improved viewing angle and improved contrast, comprising:

applying a first voltage optimized for wide angle viewing to the LCD;

applying a second voltage optimized for maximum contrast to the LCD, the second voltage being greater than the first voltage; and

alternating between the first and second voltages.

2. The method as described in claim 1, wherein the LCD is a twisted nematic.

3. The method as described in claim 1, wherein the step of alternating is performed in a display driver.

4. The method as described in claim 1, wherein the step of alternating is performed upstream of a display driver.

5. The method as described in claim 1, wherein the step of alternating is synchronized with an integer multiple of a frame rate of the LCD.

6. The method as described in claim 5, wherein the step of alternating is synchronized to the beginning of the frame.

7. The method as described in claim 1, wherein the step of alternating is performed at a rate less than the response time of the LCD.

8. The method as described in claim 1, wherein the first and second voltages are alternated at a rate greater than 30 Hz.

9. The method as described in claim 1, wherein the step of alternating is performed at a rate between 1 Hz and 1,000,000 Hz.

10. The method as described in claim 1, wherein the step of alternating is performed at a rate that is perceivable to a human eye.