Driving method for a liquid crystal panel

• US 5,119,085 A
• Filed: 02/05/1991
• Issued: 06/02/1992
• Est. Priority Date: 08/13/1987
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Yamazaki, Katsunori
• Primary Examiner(s): Brier, Jeffery A.
• Application Number:
  US07/650,841
• Time in Patent Office: 483 Days
• Field of Search: 340/784, 340/765, 340/805, 340/793, 340/767, 359/55
• US Class Current: 345/96
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3681 suitable for passive matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

A liquid crystal display device for producing a substantially uniform tone pattern by placing in the same display state all display dots producing the tone pattern which are associated with the same scanning electrode during each frame of a cycle. The method further includes adjusting the scanning waveform applied to each scanning electrode during each frame based on the tone pattern. Alternatively, the liquid crystal display device places all display dots which produce the tone pattern in the lit state for the same duration of time during the cycle and concurrently adjusts the scanning waveform applied to each scanning electrode during the cycle based on the tone pattern. Different groups of display dots which produce the tone pattern are placed in the non-lit display state at different portions of the cycle. Voltage disturbances giving rise to spikes and rounding of the voltage pulses occuring on the scanning and signal electrodes are substantially eliminated.

Claims

1. A method for driving a liquid crystal display device for producing a tone pattern, said display device including a plurality of signal electrodes overlapping a plurality of scanning electrodes and a plurality of display dots arranged in a matrix of rows and columns in which each display dot corresponds to the overlapping of one of the plurality of signal electrodes with one of the plurality of scanning electrodes, said method including driving each display dot into a lit or non-lit display state during each frame of an at least two frame cycle based on a scanning waveform and signal waveform being applied to the associated scanning electrode and signal electrode, respectively, and further comprising the steps of:

placing in the same display state all display dots producing the tone pattern which are associated with the same scanning electrode during one frame of the cycle; and

concurrently adjusting the scanning waveform applied to each scanning electrode during said one frame based on the tone pattern.

2. The method of claim 1, wherein the steps of claim 1 are repeated for each frame of the cycle.

3. The method of claim 1, wherein the scanning waveform includes a first voltage group and a second voltage group which are alternately applied during each cycle.

4. The method of claim 3, wherein the cycle includes a first frame and a second frame and further including applying the first voltage group to the scanning electrodes during a first portion of the first frame and a last portion of the second frame and the second voltage group during the last portion of the first frame and the first portion of the second frame.

5. The method of claim 4, further including applying the scanning waveform during an additional cycle which includes a third frame and a fourth frame wherein the second voltage group is applied to the scanning electrodes during the first portion of the third frame and the last portion of the fourth frame and th first voltage group is applied to the scanning electrodes during the last portion of the third frame and the first portion of the fourth frame.

6. The method of claim 5, wherein the cycle and additional cycles are alternately repeated.

7. The method of claim 1, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

8. The method of claim 3, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

9. The method of claim 8, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

10. The method of claim 1, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">I=Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

11. The method of claim 10, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

12. The method of claim 11, wherein the scanning waveform includes a first voltage group and a second voltage group which are alternately applied during each cycle and which are polarity inversions of each other and wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

13. The method of claim 2, wherein the scanning waveform includes a first voltage group and a second voltage group which are alternately applied during each cycle.

14. The method of claim 13, wherein the cycle includes a first frame and a second frame and further including applying the first voltage group to the scanning electrodes during the first portion of the first frame and the last portion of the second frame and the second voltage group during the last portion of the first frame and the first portion of the second frame.

15. The method of claim 14, further including applying the scanning waveform during an additional cycle which includes a third frame and a fourth frame wherein the second voltage group is applied to the scanning electrodes during the first portion of the third frame and the last portion of the fourth frame and the first voltage group is applied to the scanning electrodes during the last portion of the third frame and the first portion of the fourth frame.

16. The method of claim 15, wherein the cycle and additional cycles are alternately repeated.

17. The method of claim 2, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

18. The method of claim 4, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

19. The method of claim 18, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

20. The method of claim 5, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

21. The method of claim 20, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

22. The method of claim 6, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

23. The method of claim 22, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

24. The method of claim 3, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">I=Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

25. The method of claim 24, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

26. The method of claim 25, wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

27. The method of claim 4, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">I=Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

28. The method of claim 27, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

29. The method of claim 28, wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

30. The method of claim 5, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">F=(Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

31. The method of claim 30, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

32. The method of claim 31, wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

33. The method of claim 3, wherein the first voltage group is a polarity inversion of the second voltage group.

34. The method of claim 7, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

35. The method of claim 6, wherein the first voltage group is a polarity inversion of the second voltage group.

36. The method of claim 7, wherein the first voltage group is a polarity inversion of the second voltage group.

37. The method of claim 9, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

38. The method of claim 37, wherein the first voltage group is a polarity inversion of the second voltage group.

39. The method of claim 16, wherein the first voltage group is a polarity inversion of the second voltage group.

40. The method of claim 39, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

41. The method of claim 23, wherein the first voltage group is a polarity inversion of the second voltage group.

42. The method of claim 41, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

43. The method of claim 32, wherein the first voltage group is a polarity inversion of the second voltage group.

44. The method of claim 43, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

45. A method for driving a liquid crystal display device for producing a tone pattern, said display device including a plurality of signal electrodes overlapping a plurality of scanning electrodes and a plurality of display dots arranged in a matrix of rows and columns in which each display dot corresponds to the overlapping of one of the plurality of signal electrodes with one of the plurality of scanning electrodes, said method including driving each display dot into a lit or non-lit display state during each frame of an at least two frame cycle based on a scanning waveform and signal waveform being applied to the associated scanning electrode and signal electrode, respectively, and further comprising the steps of:

placing all display dots which produce the tone pattern in the lit state for the same duration of time during the cycle; and

concurrently adjusting the scanning waveform applied to each scanning electrode during the cycle based on the tone pattern;

wherein different groups of display dots which produce the tone pattern are placed in the non-lit display state at different portions of the cycle.

46. The method of claim 45, wherein the scanning waveform includes a first voltage group and a second voltage group which are alternately applied during each cycle.

47. The method of claim 46, wherein the cycle includes a first frame and a second frame and further including applying the first voltage group to the scanning electrodes during a first portion of the first frame and a last portion of the second frame and the second voltage group during the last portion of the first frame and the first portion of the second frame.

48. The method of claim 47, further including applying the scanning waveform during an additional cycle which includes a third frame and a fourth frame wherein the second voltage group is applied to the scanning electrodes during the first portion of the third frame and the last portion of the fourth frame and the first voltage group is applied to the scanning electrodes during the last portion of the third frame and the first portion o the fourth frame.

49. The method of claim 48, wherein the cycle and additional cycles ar alternately repeated.

50. The method of claim 45, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

51. The method of claim 50, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

52. The method of claim 45, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">I=Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

53. The method of claim 52, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

54. The method of claim 53, wherein the scanning waveform includes a first voltage group and a second voltage group which are alternately applied during each cycle and which are polarity inversions of each other and wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

55. The method of claim 47, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

56. The method of claim 55, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

57. The method of claim 48, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

58. The method of claim 57, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

59. The method of claim 49, wherein the step of adjusting occurs when the voltage of the signal waveform changes.

60. The method of claim 59, wherein the step of adjusting also occurs when the scanning waveform changes from one voltage group to another voltage group.

61. The method of claim 46, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">I=Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i+1 lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

62. The method of claim 61, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

63. The method of claim 62, wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

64. The method of claim 47, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">F=(Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

65. The method of claim 64, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

66. The method of claim 65, wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

67. The method of claim 48, wherein the step of adjusting is based on a value selected from a pair of parameters I and F, where:

space="preserve" listing-type="equation">I=Y.sub.i lit -Y.sub.i+1 lit

space="preserve" listing-type="equation">F=(Y.sub.i lit +Y.sub.i+1 lit)-X

where

Y_i lit is the number of display dots currently lit on a selected scanning electrode

Y_i+1 lit is the number of display dots to be lit on the next selected scanning electrode

X is the total number of signal electrodes.

68. The method of claim 67, wherein the step of adjusting includes adding compensating voltages to the scanning waveform, the compensating voltages being based on the magnitude and polarity of the value selected from the pair of parameters I and F.

69. The method of claim 68, wherein the value F is selected when the scanning waveform changes from one voltage group to another voltage group and the value of I is selected when the voltage of the signal waveform changes.

70. The method of claim 46, wherein the first voltage group is a polarity inversion of the second voltage group.

71. The method of claim 50, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

72. The method of claim 49, wherein the first voltage group is a polarity inversion of the second voltage group.

73. The method of claim 50, wherein the first voltage group is a polarity inversion of the second voltage group.

74. The method of claim 51, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

75. The method of claim 74, wherein the first voltage group is a polarity inversion of the second voltage group.

76. The method of claim 60, wherein the first voltage group is a polarity inversion of the second voltage group.

77. The method of claim 76, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

78. The method of claim 69, wherein the first voltage group is a polarity inversion of the second voltage group.

79. The method of claim 78, wherein the step of adjusting occurs when the voltage of the signal waveform changes from a lit to a non-lit level or from a non-lit to a lit level.

80. The method of claim 47, wherein the first portion and last portion of each frame are equal to half the frame.

81. The method of claim 48, wherein the first portion and last portion of each frame are equal to half the frame.