Light emitting device and electronic equipment using the same

• US 20020105279A1
• Filed: 02/07/2002
• Published: 08/08/2002
• Est. Priority Date: 02/08/2001
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime
• Granted Patent: US 6,710,548 B2
• Time in Patent Office: Days
• US Class Current: 315/169.3
• 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 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 3/14 Semiconductor devices, e.g. diodes
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/122 Pixel-defining structures or layers, e.g. banks

Abstract

A light emitting device is provided which is capable of displaying in desired colors stably by controlling a change in luminance of OLED when an organic light emitting layer is degraded or there is a change in temperature of the surroundings. A reference value for the amount of current flowing into a pixel portion is calculated from data of a video signal. Then, the pixel portion displays an image in accordance with the data of the video signal and the drive current at the time is measured for all of OLEDs in the pixel portion. The two voltage values supplied from a variable power supply to the pixel portion are corrected such that the measured drive current approaches the reference value. With the above structure, lowering of luminance which accompanies degradation of an organic light emitting layer is prevented and a clear image can be displayed as a result.

Claims

1. A light emitting device with an OLED, comprising:

means for measuring the current flowing between a first electrode and a second electrode of the OLED;

means for calculating, using a video signal, a reference value for the current flowing between the first electrode and the second electrode of the OLED; and

means for correcting the voltage between the first electrode and the second electrode of the OLED such that the measured current value approaches the reference current value.

2. A device according to claim 1 wherein each time the deviation of the measured current value from the reference current value changes to a certain extent, the measured current value is changed to a certain extent.

3. A device according to claim 1 wherein said means for calculating the reference value is included in a current value calculating circuit.

4. A device according to claim 1 wherein said means for calculating the reference value comprises a multiplication circuit.

5. Electronic equipment comprising a light emitting device according to claim 1 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

6. A light emitting device with an OLED, comprising:

means for measuring the current flowing between a first electrode and a second electrode of the OLED;

means for calculating, using a video signal, a reference value for the current flowing between the first electrode and the second electrode of the OLED;

means for calculating the deviation of the measured current value from the reference current value;

means for calculating from the deviation such a voltage value between the first electrode and the second electrode of the OLED that makes the current flowing between the first electrode and the second electrode of the OLED approach the reference current value; and

means for correcting the voltage between the first electrode and the second electrode of the OLED so as to approach the calculated voltage value.

7. A device according to claim 6 wherein each time the deviation changes to a certain extent, the calculated voltage value is changed to a certain extent.

8. A device according to claim 6 wherein said means for calculating the reference value is included in a current value calculating circuit.

9. A device according to claim 6 wherein said means for calculating the reference value comprises a multiplication circuit.

10. A device according to claim 6 wherein said means for calculating the deviation of the measured current value comprises at least a subtraction circuit.

11. Electronic equipment comprising a light emitting device according to claim 6 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium and a DVD player.

13. A device according to claim 12 wherein each time the deviation of the measured total current value from the reference total current value changes to a certain extent, the measured total current value is changed to a certain extent.

14. A device according to claim 12 wherein said means for calculating the reference value is included in a current value calculating circuit.

15. A device according to claim 12 wherein said means for calculating the reference value comprises a multiplication circuit.

16. Electronic equipment comprising a light emitting device according to claim 12 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

18. A device according to claim 17 wherein each time the deviation changes to a certain extent, the calculated voltage value is changed to a certain extent.

19. A device according to claim 17 wherein said means for calculating the reference value is included in a current value calculating circuit.

20. A device according to claim 17 wherein said means for calculating the reference value comprises a multiplication circuit.

21. A device according to claim 17 wherein said means for calculating the deviation of the measured current value comprises at least a subtraction circuit.

22. Electronic equipment comprising a light emitting device according to claim 17 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

24. A device according to claim 23 wherein each time the deviation of the measured current value of each emitting OLED from the reference current value changes to a certain extent, the measured current value of each emitting OLED is changed to a certain extent.

25. A device according to claim 23 wherein said means for calculating the number of emitting OLEDs comprises at least a counter circuit.

26. A device according to claim 23 wherein said means for calculating the measured current value of each emitting OLED is at least a division circuit.

27. Electronic equipment comprising a light emitting device according to claim 23 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

29. A device according to claim 28 wherein each time the deviation changes to a certain extent, the calculated voltage value is changed to a certain extent.

30. A device according to claim 28 wherein said means for calculating the number of emitting OLEDs comprises at least a counter circuit.

31. A device according to claim 28 wherein said means for calculating the measured current value of each emitting OLED is at least a division circuit.

32. A device according to claim 28 wherein said means for calculating the deviation of the measured current value comprises at least a subtraction circuit.

33. Electronic equipment comprising a light emitting device according to claim 28 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

35. A device according to claim 34 wherein each time the deviation of the measured total current value from the reference total current value changes to a certain extent, the measured total current value is changed to a certain extent.

36. A device according to claim 34 wherein the variable power supply, the ammeter, and the correction circuit in the OLED of one color are different from the variable power supply, the ammeter, and the correction circuit in the OLED of another color.

37. A device according to claim 34 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached to the top face of a first substrate with the OLED formed thereon.

38. A device according to claim 34 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by COG, to the top face of a first substrate with the OLED formed thereon.

39. A device according to claim 34 wherein am second substrate with the correction circuit or the ammeter formed thereon is attached, by wire bonding to the top face of a first substrate with the OLED formed thereon.

40. A device according to claim 34 wherein said circuit for calculating the reference value is included in a current value calculating circuit.

41. A device according to claim 34 wherein said circuit for calculating the reference value comprises a multiplication circuit.

42. Electronic equipment comprising a light emitting device according to claim 34 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

12. A light emitting device with an OLED provided in each of plural pixels, comprising:

means for measuring the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs;

means for calculating, using a video signal, a reference value for the total current between the first and second electrodes of all the OLEDs; and

means for correcting the voltage between the first electrode and the second electrode of every OLED such that the measured total current value approaches the reference total current value.

17. A light emitting device with an OLED provided in each of plural pixels, comprising:

means for measuring the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLED;

means for calculating, using a video signal, a reference value for the total current between the first and second electrodes of all the OLEDs;

means for calculating the deviation of the measured total current value from the reference total current value;

means for calculating from the deviation such a voltage value between the first electrode and the second electrode of every OLED that makes the total current between the first and second electrodes of all the OLEDs approach the reference total current value; and

means for correcting the voltage between the first electrode and the second electrode of every OLED so as to approach the calculated voltage value.

23. A light emitting device with an OLED provided in each of plural pixels, comprising:

means for measuring the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs;

means for calculating, using a video signal, the number of emitting OLEDs and for calculating a measured current value of each emitting OLED from the number of emitting OLEDs and from the measured total current value; and

means for correcting the voltage between the first electrode and the second electrode of every OLED such that the measured current value of each emitting OLED approaches a reference value for the current flowing between the first electrode and the second electrode of each emitting OLED.

28. A light emitting device with an OLED provided in each of plural pixels, comprising:

means for measuring the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs;

means for calculating, using a video signal, the number of emitting OLEDs and for calculating a measured current value of each emitting OLED from the number of emitting OLEDs and from the measured total current value;

means for calculating the deviation of the measured current value of each emitting OLED from a reference value for the current flowing between the first electrode and the second electrode of each emitting OLED;

means for calculating from the deviation such a voltage value between the first electrode and the second electrode of every OLED that makes the current between the first and second electrodes of each emitting OLED approach the reference current value; and

means for correcting the voltage between the first electrode and the second electrode of every OLED so as to approach the calculated voltage value.

34. A light emitting device having a pixel portion, a correction circuit, a variable power supply, and an ammeter,

wherein the pixel portion is provided with a plurality of pixels each having an OLED,

wherein the ammeter measures the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs,

wherein the correction circuit has:

at least one circuit for calculating, using a video signal, a reference value for the total current between the first and second electrodes of all the OLEDs; and

at least one circuit for correcting with the variable power supply the voltage between the first electrode and the second electrode of every OLED such that the measured total current value approaches the reference total current value.

43. A light emitting device having a pixel portion, a correction circuit, a variable power supply, and an ammeter.

wherein the pixel portion is provided with a plurality of pixels each having an OLED,

wherein the ammeter measures the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs,

wherein the correction circuit has:

at least one circuit for calculating, using a video signal, a reference value for the total current between the first and second electrodes of all the OLEDs;

at least one circuit for calculating the deviation of the measured total current value from the reference total current value;

at least one circuit for calculating from the deviation such a voltage value between the first electrode and the second electrode of every OLED that makes the total current between the first and second electrodes of all the OLEDs approach the reference total current value; and

at least one circuit for correcting with the variable power supply the voltage between the first electrode and the second electrode of every OLED so as to approach the calculated voltage value.

44. A device according to claim 43 wherein each time the deviation changes to a certain extent, the calculated voltage value is changed to a certain extent.

45. A device according to claim 43 wherein the variable power supply, the ammeter, and the correction circuit in the OLED of one color are different from the variable power supply, the ammeter, and the correction circuit in the OLED of another color.

46. A device according to claim 43 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached to the top face of a first substrate with the OLED formed thereon.

47. A device according to claim 43 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by COG, to the top face of a first substrate with the OLED formed thereon.

48. A device according to claim 43 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by wire bonding to the top face of a first substrate with the OLED formed thereon.

49. A device according to claim 43 wherein said circuit for calculating the reference value is included in a current value calculating circuit.

50. A device according to claim 43 wherein said circuit for calculating the reference value comprises a multiplication circuit.

51. A device according to claim 43 wherein said circuit for calculating the deviation of the measured current value comprises at least a subtraction circuit.

52. Electronic equipment comprising a light emitting device according to claim 43 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

53. A light emitting device having a pixel portion, a correction circuit, a variable power supply, and an ammeter,

wherein the pixel portion is provided with a plurality of pixels each having an OLED,

wherein the ammeter measures the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs,

wherein the correction circuit has:

at least a circuit for calculating, using a digital video signal, the number of emitting OLEDs and at least a circuit for calculating a measured current value of each emitting OLED from the number of emitting OLEDs and from the measured total current value; and

at least one circuit for correcting with the variable power supply the voltage between the first electrode and the second electrode of every OLED such that the measured current value of each emitting OLED approaches a reference value for the current flowing between the first electrode and the second electrode of each emitting OLED.

54. A device according to claim 53 wherein each time the deviation of the measured current value of each emitting OLED from the reference current value changes to a certain extent, the measured current value of each emitting OLED is changed to a certain extent.

55. A device according to claim 53 wherein each of pixels further has at least one TFT for controlling light emission of the OLED.

56. A device according to claim 53 wherein the variable power supply, the ammeter, and the correction circuit in the OLED of one color are different from the variable power supply, the ammeter, and the correction circuit in the OLED of another color.

57. A device according to claim 53 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached to the top face of a first substrate with the OLED formed thereon.

58. A device according to claim 53 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by COG, to the top face of a first substrate with the OLED formed thereon.

59. A device according to claim 53 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by wire bonding, to the top face of a first substrate with the OLED formed thereon.

60. A device according to claim 53 wherein said circuit for calculating the number of emitting OLEDs comprises at least a counter circuit.

61. A device according to claim 53 wherein said circuit for calculating the measured current value of each emitting OLED is at least a division circuit.

62. Electronic equipment comprising a light emitting device according to claim 53 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

63. A light emitting device having a pixel portion, a correction circuit, a variable power supply, and an ammeter.

wherein the pixel portion is provided with a plurality of pixels each having an OLED,

wherein the ammeter measures the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs.

wherein the correction circuit has:

at least one circuit for calculating, using a digital video signal, the number of emitting OLEDs and for calculating a measured current value of each emitting OLED from the number of emitting OLEDs and from the measured total current value;

at least one circuit for calculating the deviation of the measured current value of each emitting OLED from a reference value for the current flowing between the first electrode and the second electrode of each emitting OLED;

at least one circuit for calculating from the deviation such a voltage value between the first electrode and the second electrode of every OLED that makes the current between the first and second electrodes of each emitting OLED approach the reference current value; and

at least one circuit for correcting with the variable power supply the voltage between the first electrode and the second electrode of every OLED so as to approach the calculated voltage value.

64. A device according to claim 63 wherein each time the deviation changes to a certain extent, the calculated voltage value is changed to a certain extent.

65. A device according to claim 63 wherein each of pixels further has at least one TFT for controlling light emission of the OLED.

66. A device according to claim 63 wherein the variable power supply, the ammeter, and the correction circuit in the OLED of one color are different from the variable power supply, the ammeter, and the correction circuit in the OLED of another color.

67. A device according to claim 63 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached to the top face of a first substrate with the OLED formed thereon.

68. A device according to claim 63 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by COG, to the top face of a first substrate with the OLED formed thereon.

69. A device according to claim 63 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by wire bonding, to the top face of a first substrate with the OLED formed thereon.

70. A device according to claim 63 wherein said circuit for calculating the number of emitting OLEDs comprises at least a counter circuit.

71. A device according to claim 63 wherein said circuit for calculating the measured current value of each emitting OLED is at least a division circuit.

72. A device according to claim 63 wherein said circuit for calculating the deviation of the measured current value comprises at least a subtraction circuit.

73. Electronic equipment comprising a light emitting device according to claim 63 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

74. A light emitting device having a pixel portion, a correction circuit, a variable power supply, and an ammeter, the correction circuit including a memory.

wherein the pixel portion is provided with a plurality of pixels each having an OLED,

wherein the ammeter measures the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs, and

wherein the correction circuit has:

at least one circuit for calculating, using a digital video signal, the number of emitting OLEDs in each line to store the calculated number in the memory;

at least one circuit for calculating the total number of emitting OLEDs from the number of emitting OLEDs in each line which has been stored in the memory;

at least one circuit for calculating a measured current value of each emitting OLED from the total number of emitting OLEDs and from the measured total current value;

at least one circuit for correcting with the variable power supply the voltage between the first electrode and the second electrode of every OLED so that the measured current value of each emitting OLED approaches the reference current value flowing between the first electrode and the second electrode of each emitting OLED.

75. A device according to claim 74 wherein the variable power supply, the ammeter, and the correction circuit in the OLED of one color are different from the variable power supply, the ammeter, and the correction circuit in the OLED of another color.

76. A device according to claim 74 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached to the top face of a first substrate with the OLED formed thereon.

77. A device according to claim 74 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by COG, to the top face of a first substrate with the OLED formed thereon.

78. A device according to claim 74 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by wire bonding, to the top face of a first substrate with the OLED formed thereon.

79. Electronic equipment comprising a light emitting device according to claim 74 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium, and a DVD player.

80. A light emitting device having a pixel portion, a correction circuit, a variable power supply, and an ammeter, the correction circuit including a memory,

wherein the pixel portion is provided with a plurality of pixels each having an OLED,

wherein the ammeter measures the current flowing between a first electrode and a second electrode of every OLED to obtain the total current between the first and second electrodes of all the OLEDs, and

wherein the correction circuit has:

at least one circuit for calculating, using a digital video signal, the number of emitting OLEDs in each line to store the calculated number in the memory;

at least one circuit for calculating the total number of emitting OLEDs from the number of emitting OLEDs in each line which has been stored in the memory;

at least one circuit for calculating a measured current value of each emitting OLED from the total number of emitting OLEDs and from the measured total current value;

at least one circuit for calculating the deviation of the measured current value of each emitting OLED from a reference value for the current flowing between the first electrode and the second electrode of each emitting OLED;

at least one circuit for calculating from the deviation such a voltage value between the first electrode and the second electrode of every OLED that makes the current between the first and second electrodes of each emitting OLED approach the reference current value; and

at least one circuit for correcting with the variable power supply the voltage between the first electrode and the second electrode of every OLED so as to approach the calculated voltage value.

81. A device according to claim 80 wherein the variable power supply, the ammeter, and the correction circuit in the OLED of one color are different from the variable power supply, the ammeter, and the correction circuit in the OLED of another color.

82. A device according to claim 80 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached to the top face of a first substrate with the OLED formed thereon.

83. A device according to claim 80 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached, by COG, to the top face of a first substrate with the OLED formed thereon.

84. A device according to claim 80 wherein a second substrate with the correction circuit or the ammeter formed thereon is attached by wire bonding, to the top face of a first substrate with the OLED formed thereon.

85. Electronic equipment comprising a light emitting device according to claim 80 wherein said electronic equipment is selected from the group consisting of include a video camera, a digital camera, a goggles-type display, a head mount display, a navigation system, a sound reproduction device (a car audio equipment and an audio set), note-size personal computer, a game machine, a portable information terminal, a mobile computer, a portable telephone, a portable game machine, an electronic book, an image reproduction apparatus including a recording medium and a DVD player.