DISPLAY DEVICE AND LIQUID CRYSTAL DISPLAY PANEL

• US 20070040780A1
• Filed: 07/06/2006
• Published: 02/22/2007
• Est. Priority Date: 07/08/2005
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Smith, Nathan, Evans, Allan, Wynne-Powell, Thomas, GASS, Paul, Kean, Diana, Broughton, Benjamin
• Granted Patent: US 7,965,268 B2
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/134381 Hybrid switching mode, i.e. for applying an electric field with components parallel and orthogonal to the substrates
• CPC Class Codes: G09G 2300/0434 Flat panel display in which a field is applied parallel to the display plane
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/068 for control of viewing angle adjustment
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A display device is provided that comprises a liquid crystal display panel for displaying an image by spatial light modulation, and circuitry for switching liquid crystal in the panel between having a first configuration in a first mode to cause an image displayed using the panel to be discernible from a wide range of viewing angles, and having a second configuration in a second mode to cause an image displayed using the panel to be discernible substantially only from within a narrow range of viewing angles. Several types of display panel to achieve such in-panel switching between public and private viewing modes are disclosed.

Claims

1. A display device comprising a liquid crystal display panel for displaying an image by spatial light modulation, and circuitry for switching liquid crystal in the panel between having a first configuration in a first mode to cause an image displayed using the panel to be discernible from a wide range of viewing angles, and having a second configuration in a second mode to cause an image displayed using the panel to be discernible substantially only from within a narrow range of viewing angles.

2. A display device as claimed in claim 1, wherein the second configuration of liquid crystal causes an image-confusing pattern to be visible in the image discerned by a viewer outside the narrow range of angles.

3. A display device as claimed in claim 1, wherein the liquid crystal in the first configuration comprises a single arrangement of liquid crystal across the display device.

4. A display device as claimed in claim 1, wherein the liquid crystal in the first configuration comprises a plurality of lateral regions each having one of at least two different arrangements of liquid crystal.

5. A display device as claimed in claim 4, wherein the first configuration regions are sized so as not to be resolvable by a viewer.

6. A display device as claimed in claim 1, wherein the liquid crystal in the second configuration comprises a plurality of lateral regions each having one of at least two different arrangements of liquid crystal.

7. A display device as claimed in claim 6, wherein the second configuration regions are sized so as to be resolvable by a viewer.

8. A display device as claimed in claim 6, wherein the second configuration regions have a lateral dimension at least two times greater than a lateral dimension of a picture element of the panel.

9. A display device as claimed in claim 8, wherein the second configuration regions have a lateral dimension at least five times greater than a lateral dimension of a picture element of the panel.

10. A display device as claimed in claim 9, wherein the second configuration regions have a lateral dimension at least ten times greater than a lateral dimension of a picture element of the panel.

11. A display device as claimed in claim 6, wherein the second configuration regions having the same or similar liquid crystal arrangement are arranged spatially in a predetermined manner.

12. A display device as claimed in claim 11, wherein the second configuration regions of the same or similar liquid crystal arrangement are arranged spatially in a chequerboard pattern or a pattern of text or a logo.

13. A display device as claimed in claim 6, wherein the circuitry comprises a plurality of in-plane electrodes for switching the liquid crystal to the second configuration.

14. A display device as claimed in claim 13, comprising in-plane electrodes disposed at least to each side of each second configuration region.

15. A display device as claimed in claim 13, comprising three or more in-plane electrodes disposed within each second configuration region.

16. A display device as claimed in claim 13, wherein the liquid crystal in the first configuration comprises a plurality of lateral regions each having one of at least two different arrangements of liquid crystal, and wherein the in-plane electrodes are patterned in at least two different orientations to produce the at least two different arrangements.

17. A display device as claimed in claim 13, wherein the electrodes are disposed on the same side of the liquid crystal display panel as electrodes used for switching picture elements of the panel.

18. A display device as claimed in claim 4, wherein neighbouring regions are arranged to have different arrangements of liquid crystal.

19. A display device as claimed in claim 4, wherein the at least two arrangements comprise liquid crystal having different respective substantially uniform orientations of liquid crystal.

20. A display device as claimed in claim 19, wherein the at least two arrangements comprise one or more pairs of orientations, the orientations in the or each pair being disposed substantially symmetrically about a predetermined axis.

21. A display device as claimed in claim 20, wherein the predetermined axis lies in the narrow range of viewing angles.

22. A display device as claimed in claim 4, wherein the at least two different arrangements of liquid crystal have different respective angular transmission functions.

23. A display device as claimed in claim 22, wherein the respective angular transmission functions are asymmetric about an axis lying within the narrow range of viewing angles.

24. A display device as claimed in claim 22, wherein the liquid crystal in the second configuration comprises a plurality of lateral regions each having one of at least two different arrangements of liquid crystal, and wherein the respective angular transmission functions for the second configuration are substantially equal for viewing angles within the narrow range, and different for viewing angles outside the narrow range.

25. A display device as claimed in claim 22, wherein the first configuration regions are sized so as not to be resolvable by a viewer, and wherein the respective angular transmission functions for the first configuration are spatially averaged by a viewer in the first mode to provide a smoothly-varying average transmission function across at least part of the wide range of viewing angles.

26. A display device as claimed in claim 1, wherein the first and second configurations are vertically aligned nematic configurations.

27. A display device as claimed in claim 1, wherein the first and second configurations are bi- or multi-stable liquid crystal states, and wherein the circuitry is adapted to switch the liquid crystal between these states.

28. A display device as claimed in claim 27, comprising an alignment layer for producing the bi- or multi-stable states.

29. A display device as claimed in claim 1, wherein the first configuration is a continuous pinwheel aligned configuration.

30. A display device as claimed in claim 1, wherein an image is represented by a plurality of image elements, and comprising means for modifying the respective data values of at least some of the image elements such that when the modified image is displayed in a first scenario using a display panel having a first data value-to-luminance response to a viewer, the image perceived by the viewer through spatial averaging is substantially the same as the original image, and such that when the modified image is displayed in a second scenario using a display panel having a second data value-to-luminance response to a viewer, different to the first data value-to-luminance response, the image perceived by the viewer through spatial averaging is different to the original image, and wherein the first and second configurations of liquid crystal are arranged to provide the display panel with substantially the first and second data value-to-luminance responses respectively for viewing angles outside the narrow range, and are both arranged to provide substantially the first data value-to-luminance response for viewing angles inside the narrow range.

31. A display device as claimed in claim 30, wherein the second data value-to-luminance response is a substantially non-linear data value-to-luminance response.

32. A display device as claimed in claim 30, wherein the first data value-to-luminance response is a substantially linear data value-to-luminance response.

33. A display device as claimed in claim 30, wherein the liquid crystal in the first configuration comprises a plurality of lateral regions each having one of at least two different arrangements of liquid crystal, and wherein the first configuration regions are adapted such that light travelling at an angle outside the narrow range of angles passes through at least two regions having different arrangements of liquid crystal so as to have the first data value-to-luminance response.

34. A display device as claimed in claim 30, wherein the liquid crystal in the second configuration comprises a plurality of lateral regions each having one of at least two different arrangements of liquid crystal, and wherein the second configuration regions are adapted such that light travelling at an angle outside the narrow range of angles has the second data value-to-luminance response.

35. A display device as claimed in claim 30, wherein the first and second configurations are twisted nematic configurations.

36. A display device as claimed in claim 30, comprising at least one patterned alignment layer for producing the first and second configurations.

37. A display device as claimed in claim 36, wherein the circuitry is operable to apply an electric field to change the alignment properties of the at least one alignment layer to switch the liquid crystal between the first and second configurations.

38. A display device as claimed in claim 30, wherein the circuitry is operable to apply an electric field across and/or in the plane of the liquid crystal to switch the liquid crystal between the first and second configurations.

39. A display device as claimed in claim 38, wherein the circuitry is operable to apply fringe electric fields.

40. A display device as claimed in claim 30, wherein the original image is substantially hidden in the image perceived in the second scenario.

41. A display device as claimed in claim 30, wherein at least some of the data values are modified in dependence upon a masking image.

42. A display device as claimed in claim 41, wherein each data value is modified in dependence upon the data value at a corresponding position of the masking image.

43. A display device as claimed in claim 41, wherein the image perceived in the second scenario resembles at least to some extent the masking image.

44. A display device as claimed in claim 41, wherein the original image is substantially hidden in the image perceived in the second scenario, and wherein the masking image is such as to provide a high degree of visually confusing information in the second scenario.

45. A display device as claimed in claim 44, wherein the masking image comprises a chequerboard pattern or a pattern of text or a logo.

46. A display device as claimed in claim 41, different masking images are used in different time frames.

47. A display device as claimed in claim 30, wherein at least some of the data values are modified in dependence upon a masking parameter.

48. A display device as claimed in claim 47, wherein the degree of modification is determined at least in part by the masking parameter.

49. A display device as claimed in claim 30, wherein the data values are modified such that localised groups of displayed image elements are perceived in the first scenario through spatial averaging to have substantially the same overall luminance as those image elements would have done without such modification.

50. A display device as claimed in claim 49, wherein at least some of the data values are modified in dependence upon a masking image, and wherein the degree of modification for each image element in a group is determined in dependence upon the data value at a position in the masking image corresponding to the image element.

51. A display device as claimed in claim 49, wherein, if any modification is to be performed for a group, the data value of at least one image element in the group is increased while the data value of at least one other image element in the group is decreased.

52. A display device as claimed in claim 51, wherein the amount of increase is substantially the same as the decrease.

53. A display device as claimed in claim 51, wherein the amount of increase relative to the amount of decrease is determined in dependence upon the first data value-to-luminance response.

54. A display device as claimed in claim 51, wherein the image elements designated for increase and decrease are swapped in different time frames.

55. A display device as claimed in claim 51, wherein at least some of the data values are modified in dependence upon a masking image, and wherein the degree of modification for each image element in a group is determined in dependence upon the data value at a position in the masking image corresponding to the image element, and wherein for each of the at least one image element an amount related to the corresponding respective masking image data value is added to the image element data value, and for each of the at least other one image element an amount related to the corresponding respective masking image data value is subtracted from the image element data value.

56. A display device as claimed in claim 55, wherein the amount is equal to the corresponding masking image data value.

57. A display device as claimed in claim 55, wherein the amount is determined in dependence upon the difference between the image data value and the maximum or minimum data value, whichever is closer.

58. A display device as claimed in claim 57, wherein the amount is proportional to the difference multiplied by the corresponding masking image data value.

59. A display device as claimed in claim 49, wherein each group comprises two image elements.

60. A display device as claimed in claim 49, wherein the data values of at least some of the image elements are averaged in a group.

61. A display device as claimed in claim 49, wherein the data values of at least some of the masking image elements are averaged in a group.

62. A display device as claimed in claim 49, wherein image elements having corresponding modifications performed on them are arranged in lines of the image.

63. A display device as claimed in claim 49, wherein image elements having corresponding modifications performed on them are arranged in columns of the image.

64. A display device as claimed in claim 49, wherein image elements having corresponding modifications performed on them are arranged in a chequerboard pattern or a pattern of text or a logo.

65. A display device as claimed in claim 30, wherein it is ensured that a modified data value does not fall outside the normal range of data values allowed.

66. A display device as claimed in claim 65, wherein at least some of the data values are modified in dependence upon a masking image, and wherein the degree of modification for each image element in a group is determined in dependence upon the data value at a position in the masking image corresponding to the image element, and wherein the data value range of the image is compressed before modification.

67. A display device as claimed in claim 65, wherein the data value range of the masking image is compressed before modification.

68. A display device as claimed in claim 30, wherein only the data values of the image elements in a sub-portion of the image are so modified.

69. A display device as claimed in claim 30, wherein each image element relates to a plurality of colour components corresponding to a pixel of the display device.

70. A display device as claimed in claim 30, wherein each image element relates to a single colour component corresponding to a sub-pixel of the display device.

71. A display device as claimed in claim 30, wherein the viewer is at least a predetermined distance away from the display device.

72. A display device as claimed in claim 1, wherein the circuitry is adapted to operate the display panel to apply an electric field in first and second different ways in the first and second modes respectively to achieve the first and second liquid crystal configurations.

73. A display device as claimed in claim 72, wherein the circuitry is adapted to operate the display panel using different respective ranges of applied electric field strengths in the first and second modes.

74. A display device as claimed in claim 72, wherein the circuitry is adapted to operate the display panel using different respective directions of applied electric field in the first and second modes.

75. A display device as claimed in claim 74, wherein the circuitry is adapted to operate the display panel using in-plane switching in the first mode and electrically controlled birefringence switching in the second mode.

76. A display device as claimed in claim 75, wherein the circuitry comprises a first set of electrodes for performing the in-plane switching and a second set of electrodes for performing the electrically controlled birefringence switching.

77. A display device as claimed in claim 76, wherein the first set electrodes are disposed on the same side of the display panel to apply a field substantially in the plane of the panel.

78. A display device as claimed in claim 76, wherein the second set electrodes are disposed on opposite sides of the display panel to apply a field across the panel.

79. A display device as claimed in claim 72, wherein the display panel comprises first and second sets of regions, the circuitry being adapted to apply the electric field in the first and second ways in the first and second sets of regions respectively.

80. A display device as claimed in claim 79, wherein pixels of the display each comprise a region from the first set and a region from the second set.

81. A display device as claimed in claim 80, wherein the circuitry is operable in the second mode to operate some pixels in the first way and other pixels in the second way so as to cause an image confusing pattern to a viewer outside the narrow range of viewing angles.

82. A display device as claimed in claim 1, wherein pixels of the display each comprise first and second regions having liquid crystal respectively having the first and second configurations.

83. A display device as claimed in claim 82, wherein the circuitry is operable in the second mode to operate some pixels using the first regions and other pixels using the second regions so as to cause an image confusing pattern to a viewer outside the narrow range of viewing angles.

84. A display device as claimed in claim 6, wherein the circuitry is adapted to operate in the second mode to use different respective driving voltage ranges to produce the at least two different arrangements of liquid crystal, the liquid crystal arrangements being such as to have substantially the same transmission to viewers within the narrow range of angles for different respective voltages selected from each of the driving voltage ranges and different respective transmissions for those selected voltages to viewers outside the narrow range of angles.

85. A display device as claimed in claim 84, wherein a first one of the driving voltage ranges has a transmission-to-voltage function suitable for image display to viewers outside the narrow range of angles and a second one of the driving voltage ranges has a transmission-to-voltage function unsuitable for image display to viewers outside the narrow range of angles.

86. A display device as claimed in claim 85, wherein the second one of the driving voltage ranges has a substantially constant, low, transmission to viewers outside the narrow range of angles for voltages across at least most of the range.

87. A display device as claimed in claim 85, wherein the second one of the driving voltage ranges has a substantially constant, high, transmission to viewers outside the narrow range of angles for voltages across at least most of the range.

88. A display device as claimed in claim 85, wherein the circuitry is adapted to operate in the first mode to use only the first one of the driving voltage ranges for each of the lateral regions to produce a substantially uniform arrangement of liquid crystal across the panel.

89. A display device as claimed in claim 6, wherein the circuitry is adapted to operate in the second mode to use different respective ground electrode voltage arrangements to produce the at least two different arrangements of liquid crystal, the liquid crystal arrangements being such as to have substantially the same transmission to viewers within the narrow range of angles for different respective voltage arrangements and different respective transmissions for those voltages to viewers outside the narrow range of angles.

90. A display device as claimed in claim 89, wherein the circuitry is adapted to cause the first and second arrangements of liquid crystal to be skewed with respect to one another.

91. A display device as claimed in claim 90, wherein the circuitry comprises a patterned electrode.

93. An operating program which, when loaded into an apparatus, causes the apparatus to become apparatus as claimed in claim 1.

94. An operating program as claimed in claim 93, carried on a carrier medium.

95. An operating program as claimed in claim 94, wherein the carrier medium is a transmission medium.

96. An operating program as claimed in claim 94, wherein the carrier medium is a storage medium.

92. A liquid crystal display panel for use in a display device for displaying an image by spatial light modulation, the display panel being adapted to enable switching of liquid crystal in the panel between having a first configuration in a first mode to cause an image displayed using the panel to be discernible from a wide range of viewing angles, and having a second configuration in a second mode to cause an image displayed using the panel to be discernible substantially only from within a narrow range of viewing angles.