Light emitting device, driving method for the same and electronic apparatus

• US 6,661,180 B2
• Filed: 03/21/2002
• Issued: 12/09/2003
• Est. Priority Date: 03/22/2001
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Dinh, Trinh Vo
• Application Number:
  US10/101,628
• Publication Number:
  US 20020135312A1
• Time in Patent Office: 628 Days
• Field of Search: G09/G.310, G09/G.332, 315/169.3, 315/169.1, 315/169.4, 315/169.2, 345/76, 345/39, 345/46, 345/82, 345/92, 313/500, 313/504
• US Class Current: 315/169.3
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2300/0895 having more than one selection line for a two-terminal active matrix LCD, e.g. Lechner and D2R circuits
• 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 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0266 Reduction of sub-frame artefacts
• 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 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• 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: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• 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: H01L 27/1255 : integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 29/4908 : for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H10K 59/12 : Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/131 : Interconnections, e.g. wiring lines or terminals

Abstract

It is a problem to provide a light-emitting device capable of obtaining a constant brightness without being affected by deterioration in an organic light-emitting layer or temperature change, and of making desired color display. The towering in OLED brightness due to deterioration is reduced by causing the OLED to emit light while keeping constant the current flowing through the OLED instead of causing the OLED to emit light while keeping constant the OLED drive voltage. Namely, OLED brightness is controlled not by voltage but by current thereby preventing against the change in OLED brightness due to deterioration of OLED. Specifically, the drain current Id of a transistor for supplying a current to the OLED is controlled in a signal line drive circuit thereby keeping constant the drain current Id without relying upon the value of a load resistance.

Claims

1. A light-emitting device comprising:

a first transistor;

a second transistor,

a third transistor;

a fourth transistor;

an OLED;

a power line;

a signal line; and

a scanning line,

wherein gate electrodes of said third and fourth transistors are both connected to said scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line, and

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED.

2. A light-emitting device according to claim 1, wherein said third and fourth transistors being reverse in polarity to said second transistor.

3. A light-emitting device according to claim 1, wherein said third and fourth transistors are same in polarity.

4. A light-emitting device according to claim 1, wherein said first and second transistors are same in polarity.

5. An electronic device comprising the light emitting device according to claim 1, wherein said electronic device is selected from the group consisting of an organic light emitting display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and mobile telephone.

6. A light-emitting device comprising:

a first transistor;

a second transistor;

a third transistor;

a fourth transistor;

an OLED;

a power line;

a signal line;

a first scanning line; and

a second scanning line,

wherein gate electrodes of said third and fourth transistors are both connected to said first scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED, and

wherein a gate electrode of said second transistor is connected to said second scanning line.

7. A light-emitting device according to claim 6, wherein said third and fourth transistors being reverse in polarity to said second transistor.

8. A light-emitting device according to claim 6, wherein said third and fourth transistors are same in polarity.

9. A light-emitting device according to claim 6, wherein said first and second transistors are same in polarity.

10. An electronic device comprising the light emitting device according to claim 6, wherein said electronic device is selected from the group consisting of an organic light emitting display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and mobile telephone.

11. A light-emitting device comprising:

a first transistor;

a second transistor;

a third transistor;

a fourth transistor;

an OLED;

a power line;

a signal line; and

a scanning line,

wherein gate electrodes of said second, third and fourth transistors are all connected to said scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line, and

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED.

12. A light-emitting device according to claim 11, wherein said third and fourth transistors being reverse in polarity to said second transistor.

13. A light-emitting device according to claim 11, wherein said third and fourth transistors are same in polarity.

14. A light-emitting device according to claim 11, wherein said first and second transistors are same in polarity.

15. An electronic device comprising the light emitting device according to claim 11, wherein said electronic device is selected from the group consisting of an organic light emitting display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and mobile telephone.

16. A light-emitting device comprising:

a first transistor;

a second transistor;

a third transistor;

a fourth transistor;

a fifth transistor;

an OLED;

a power line;

a signal line;

a first scanning line; and

a second scanning line,

wherein gate electrodes of said second, third and fourth transistors are all connected to said first scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED,

wherein a gate electrode of said fifth transistor is connected to said second scanning line, and

wherein one of source and drain region of said fifth transistor is connected to said power line and the other to the gate electrode of said first transistor.

17. A light-emitting device according to claim 16, wherein said third and fourth transistors being reverse in polarity to said second transistor.

18. A light-emitting device according to claim 16, wherein said third and fourth transistors are same in polarity.

19. A light-emitting device according to claim 16, wherein said first and second transistors are same in polarity.

20. An electronic device comprising the light emitting device according to claim 16, wherein said electronic device is selected from the group consisting of an organic light emitting display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and mobile telephone.

21. A method for driving a light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, an OLED, a power line, a signal line and a scanning line,

wherein gate electrodes of said third and fourth transistors are both connected to said scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED, the method for driving said light emitting device comprising:

providing a first period in which said third and fourth transistors are on and a second period in which said third and fourth transistors are off in one frame period, wherein said second transistor is off in the first period and on in the second period; and

controlling a drain current of said first transistor in magnitude in the first period by an analog video signal in order to control a brightness of said OLED.

22. A method for driving a light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, an OLED, a power line, a signal line, a first scanning line and a second scanning line,

wherein gate electrodes of said third and fourth transistors are both connected to said first scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED, and

wherein a gate electrode of said second transistor is connected to said second scanning line, the method for driving said light emitting device comprising:

providing a first period in which said third and fourth transistors are on and a second period in which said third and fourth transistors are off in one frame period, wherein said second transistor is off in the first period and on in the second period; and

controlling a drain current of said first transistor in magnitude in the first period by an analog video signal in order to control a brightness of said OLED.

23. A method for driving a light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, an OLED, a power line, a signal line and a scanning line,

wherein gate electrodes of said second, third and fourth transistors are all connected to said scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor being connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED, the method for driving a light emitting device comprising:

providing a first period in which said third and fourth transistors are on and a second period in which said third and fourth transistors are off in one frame period, wherein said second transistor is off in the first period and on in the second period; and

controlling a drain current of said first transistor in magnitude in the first period by an analog video signal in order to control a brightness of said OLED.

24. A method for driving light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, an OLED, a power line, a signal line, a first scanning line and a second scanning line,

wherein gate electrodes of said second, third and fourth transistors are all connected to said first scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED,

wherein a gate electrode of said fifth transistor is connected to said second scanning line, and

wherein one of source and drain regions of said fifth transistor is connected to said power line and the other to the gate electrode of said first transistor, the method for driving said light emitting device comprising:

providing a first period in which said third and fourth transistors are on and said fifth transistor is off, a second period in which said third and fourth transistors are off and said fifth transistor is off, and a third period in which said third and fourth transistors are off and said fifth transistor is on, wherein said second transistor is off in the first period, on in the second period and on in the third period; and

controlling a drain current of said first transistor in magnitude in the first period by an analog video signal in order to control a brightness of said OLED.

25. A method for driving a light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, an OLED, a power line, a signal line and a scanning line,

wherein gate electrodes of said third and fourth transistors are both connected to said scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED, the method for driving said light emitting device comprising:

providing a first period and a second period corresponding to respective bits of a digital video signal in one frame period, wherein in the first period, said third and fourth transistors are on and said second transistor is off and in the second period, said third and fourth transistors are off and said second transistor is on; and

controlling said OLED in a presence or an absence of light emission in the first period on the basis of information possessed by each bit of a corresponding one of the digital video signal.

26. A method for driving a light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, an OLED, a power line, a signal line, a first scanning line and a second scanning line,

wherein gate electrodes of said third and fourth transistors are both connected to said first scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED,

wherein a gate electrode of said second transistor is connected to said second scanning line, the method for driving said light emitting device comprising:

providing a first period and a second period corresponding to respective bits of a digital video signal in one frame period, wherein in the first period, said third and fourth transistors are on and said second transistor off and in the second period, said third and fourth transistors are off and said second transistor is on; and

controlling said OLED in a presence or an absence of light emission in the first period on the basis of information possessed by each bit of a corresponding one of the digital video signal.

27. A method for driving a light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, an OLED, a power line, a signal line and a scanning line,

wherein gate electrodes of said second, third and fourth transistors are all connected to said scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line, and

wherein one of source and drain regions of said second transistor is connected to the drain region of said first transistor and the other to a pixel electrode of said OLED, the method for driving a light emitting device comprising:

providing a first period and a second period corresponding to respective bits of a digital video signal in one frame period, wherein in the first period, said third and fourth transistors are on and said second transistor is off and in the second period, said third and fourth transistors are off and said second transistor is on; and

controlling said OLED in a presence or an absence of light emission in the first period on the basis of information possessed by each bit of a corresponding one of the digital video signal.

28. A method for driving light-emitting device comprising a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, an OLED, a power line, a signal line, a first scanning line and a second scanning line,

wherein gate electrodes of said second, third and fourth transistors are all connected to said first scanning line,

wherein one of source and drain regions of said third transistor is connected to said signal line and the other to a gate electrode of said first transistor,

wherein one of source and drain regions of said fourth transistor is connected to said signal line and the other to a drain region of said first transistor,

wherein a source region of said first transistor is connected to said power line,

wherein one of source and drain regions of said second transistor being connected to the drain region of said first transistor and the other to a pixel electrode of said OLED,

wherein a gate electrode of said fifth transistor is connected to said second scanning line, and

wherein one of source and drain region of said fifth transistor is connected to said power line and the other to the gate electrode of said first transistor, the method for driving said light emitting device comprising:

providing a first period, a second period and a third period corresponding to respective bits of a digital video signal in one frame period, wherein in the first period, said third and fourth transistors are on and said second and fifth transistors are off, in the second period, said third and fourth transistors are off, said second transistor is on, and said fifth transistor is off, and in the third period, said third and fourth transistors are off, said second transistor is on, and said fifth transistor is on; and

controlling said OLED in a presence or an absence of light emission in the first period on the basis of information possessed by each bit of a corresponding one of the digital video signal.