Display device

• US 20050012731A1
• Filed: 08/18/2004
• Published: 01/20/2005
• Est. Priority Date: 04/18/2000
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Osame, Mitsuaki, Koyama, Jun, Yamazaki, Shunpei, Osada, Mai
• Granted Patent: US 7,623,098 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0281 Arrangement of scan or data electrode driver circuits at the periphery of a panel not inherent to a split matrix structure
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H10K 59/00 Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays

Abstract

The present invention is intended to suppress power consumption of an EL display. In accordance with the brightness of an image to be displayed in a pixel portion, the contrast of the image is determined whether to be inverted or not, and the number of bits of the digital video signal to be input into the pixel portion is reduced, and the magnitude of a current to flow through the EL element is allowed to be maintained at a constant level even when a temperature of an EL layer changes by providing the EL display with another EL element to be used for monitoring a temperature.

Claims

1-45. -45. (canceled)

46. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

47. A display device according to claim 46, wherein the monitoring light emitting element is provided independently of the pixel portion.

48. A display device according to claim 46, wherein the monitoring light emitting element is included in the pixel portion.

49. A display device according to claim 46, wherein the light emitting material comprises an organic compound.

50. A display device according to claim 46, wherein the display device is an EL display device.

51. A display device according to claim 46, wherein the display device is incorporated in at least one selected from the group consisting of a portable telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

52. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

53. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

54. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

55. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

56. A display device according to claim 55, wherein the constant current source comprises an amplifier, a variable resistor and a bipolar transistor.

57. A display device according to claim 55, wherein the constant current source is formed over an IC chip.

58. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

59. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

60. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

61. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element, and

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

62. A display device according to claim 61, wherein the buffer amplifier is formed over an IC chip.

63. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element, and

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

64. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element, and

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

65. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element, and

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

66. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line, and

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

67. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line, and

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

68. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line, and

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element.

69. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line, and

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element.

70. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

71. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

72. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

73. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line,

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

74. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

75. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

76. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

77. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween;

a monitoring light emitting element electrically connected to the at least one light emitting element through a power source line; and

a constant current source electrically connected to the monitoring light emitting element,

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

78. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element,

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

79. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element,

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

80. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element,

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

81. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element,

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

82. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line,

wherein a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

83. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line,

wherein a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

84. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line,

wherein a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

85. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a buffer amplifier, a monitoring light emitting element, and a constant current source,

wherein the monitoring light emitting element and the constant current source are electrically connected to an input of the buffer amplifier,

wherein an output of the buffer amplifier is electrically connected to the at least one light emitting element through a power source line,

wherein a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material is suppressed by using the monitoring light emitting element, and

wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the at least one light emitting element.

86. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material.

87. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material.

88. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material.

89. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material.

90. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness change of the at least one light emitting element caused by a deterioration of the light emitting material, the means electrically connected to the at least one light emitting element through a power source line.

91. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness change of the at least one light emitting element caused by a temperature change of the light emitting material, the means electrically connected to the at least one light emitting element through a power source line.

92. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness decrease of the at least one light emitting element caused by a deterioration of the light emitting material, the means electrically connected to the at least one light emitting element through a power source line.

93. A display device comprising:

a pixel portion formed over a substrate, the pixel portion having at least one light emitting element, wherein the at least one light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and

a means for suppressing a brightness increase of the at least one light emitting element caused by a temperature change of the light emitting material, the means electrically connected to the at least one light emitting element through a power source line.