Light emitting device

• US 20020044140A1
• Filed: 04/13/2001
• Published: 04/18/2002
• Est. Priority Date: 04/18/2000
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Inukai, Kazutaka
• Granted Patent: US 6,903,731 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• 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 3/3291 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 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 85/341 Transition metal complexes, e.g. Ru(II)polypyridine complexes H10K85/331 takes precedence
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/649 Aromatic compounds comprising a hetero atom

Abstract

The present invention provides an active-matrix electro-optical device allowing clear multi-gray-scale color display. In the electro-optical display according to the present invention, a plurality of pixels included in a pixel portion have a first and a second source signal lines, a first and a second gate signal lines, and a power source supply line. Each of the pixels has a first TFT for switching, a second TFT for switching, a TFT for driving and a light emitting element.

Claims

1. A light emitting device comprising:

a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion;

wherein said pixel portion has a plurality of pixels;

wherein each of said plurality of pixels includes a light emitting element, a TFT for current control for controlling light emission from said light emitting element, a first TFT for switching and a second TFT for switching for controlling driving of said TFT for current control;

wherein driving of said first TFT for switching is controlled by said first source signal line driver circuit and said first gate signal line driver circuit;

wherein driving of said second TFT for switching is controlled by said second source signal line driver circuit and said second gate signal line driver circuit; and

wherein gray-scale display is performed by controlling a length of a time period during which said light emitting element emits light.

20. A light emitting device according to claim 1, wherein said first TFTs for switching and said second TFTs for switching have the same polarity.

25. A light emitting device according to claim 1, wherein a display time period that is the last to appear is the longest black display time period within the one frame time period.

32. A light emitting device according to claim 1 wherein said light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a sound reproduction apparatus, a notebook type personal computer, a game apparatus, a portable information terminal, and an image playback device.

2. A light emitting device comprising:

a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion;

a plurality of first source signal lines connected to said first source signal line driver circuit, a plurality of second source signal lines connected to said second source signal line driver circuit, a plurality of first gate signal lines connected to said first gate signal line driver circuit, a plurality of second gate signal lines connected to said second gate signal line driver circuit, and a plurality of power source supply lines,

wherein said pixel portion has a plurality of pixels including a plurality of light emitting elements, a plurality of TFTs for current control, a plurality of first TFTs for switching, and a plurality of second TFTs for switching;

wherein gate electrodes included in said plurality of first TFTs for switching are connected to said plurality of first gate signal lines;

wherein gate electrodes included in said plurality of second TFTs for switching are connected to said plurality of second gate signal lines;

wherein one of source regions and drain regions included in said plurality of first TFTs for switching are connected to said plurality of first source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control;

wherein one of source regions and drain regions included in said plurality of second TFTs for switching are connected to said plurality of second source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control; and

wherein one of source regions and drain regions included in said plurality of TFTs for current control are connected to said plurality of power source supply lines, and the other are connected to said plurality of light emitting elements.

21. A light emitting device according to claim 2, wherein said first TFTs for switching and said second TFTs for switching have the same polarity.

26. A light emitting device according to claim 2, wherein a display time period that is the last to appear is the longest black display time period within the one frame time period.

33. A light emitting device according to claim 2 wherein said light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a sound reproduction apparatus, a notebook type personal computer, a game apparatus, a portable information terminal, and an image playback device.

3. A light emitting device comprising:

a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion,

a plurality of first source signal lines connected to said first source signal line driver circuit, a plurality of second source signal lines connected to said second source signal line driver circuit, a plurality of first gate signal lines connected to said first gate signal line driver circuit, a plurality of second gate signal lines connected to said second gate signal line driver circuit, and a plurality of power supply line held at a constant electric potential,

wherein said pixel portion has a plurality of pixels including a plurality of light emitting elements, a plurality of TFTs for current control, a plurality of first TFTs for switching, and a plurality of second TFTs for switching;

wherein each of said plurality of light emitting elements has a pixel electrode, a counter electrode held at a constant electric potential, and an organic compound layer provided between said pixel electrode and said counter electrode;

wherein gate electrodes included in said plurality of first TFTs for switching are connected to said plurality of first gate signal lines;

wherein gate electrodes included in said plurality of second TFTs for switching are connected to said plurality of second gate signal lines;

wherein one of source regions and drain regions included in said plurality of first TFTs for switching are connected to said plurality of first source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control;

wherein one of source regions and drain regions included in said plurality of second TFTs for switching are connected to said plurality of second source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control; and

wherein one of source regions and drain regions included in said plurality of TFTs for current control are connected to said plurality of power source supply lines, and the other are connected to said plurality of pixel electrodes.

4. A light emitting device according to claim 3, wherein said organic compound layer is formed of a low-molecular organic material or a polymer organic material.

5. A light emitting device according to claim 4, wherein said low-molecular organic material is made of Alq₃ (tris-8-quinolilite-aluminium) or TPD (triphenylamine derivative).

6. A light emitting device according to claim 4, wherein said polymer organic material is made of PPV (polyphenylene vinylene), PVK (polyvinylcarbazole) or polycarbonate.

22. A light emitting device according to claim 3, wherein said first TFTs for switching and said second TFTs for switching have the same polarity.

27. A light emitting device according to claim 3, wherein a display time period that is the last to appear is the longest black display time period within the one frame time period.

34. A light emitting device according to claim 3 wherein said light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a sound reproduction apparatus, a notebook type personal computer, a game apparatus, a portable information terminal, and an image playback device.

7. A light emitting device comprising:

a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion,

a plurality of first source signal lines connected to said first source signal line driver circuit, a plurality of second source signal lines connected to said second source signal line driver circuit, a plurality of first gate signal lines connected to said first gate signal line driver circuit, a plurality of second gate signal lines connected to said second gate signal line driver circuit, and a plurality of power source supply lines,

wherein said pixel portion has a plurality of pixels including a plurality of light emitting elements, a plurality of TFTs for current control, a plurality of first TFTs for switching, and a plurality of second TFTs for switching;

wherein gate electrodes included in said plurality of first TFTs for switching are connected to said plurality of first gate signal lines;

wherein gate electrodes included in said plurality of second TFTs for switching are connected to said plurality of second gate signal lines;

wherein one of source regions and drain regions included in said plurality of first TFTs for switching are connected to said plurality of first source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control;

wherein one of source regions and drain regions included in said plurality of second TFTs for switching are connected to said plurality of second source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control;

wherein one of source regions and drain regions included in said plurality of TFTs for current control are connected to said plurality of power source supply lines, and the other are connected to said plurality of light emitting elements;

wherein n writing time periods Ta1, Ta2, . . . , Tan sequentially appear within one frame time period;

wherein a writing time period that follows the last writing time period Tan among the n writing time periods Ta1, Ta2, . . . , Tan is a first writing time period Ta1 among the n writing time periods Ta1, Ta2, . . . , Tan,

wherein time periods from apparition of the respective n writing time periods Ta1, Ta2, . . . , Tan until apparition of writing time periods following the respective n writing time periods Ta1, Ta2, . . . , Tan are n display time periods Td1, Td2, . . . , Tdn;

wherein during the n writing time periods Ta1, Ta2, . . . , Tan, a digital signal is input to said plurality of pixels through said plurality of first source signal lines from said first source signal line driver circuit or through said plurality of second source signal lines from said second source signal line driver circuit;

wherein among the n writing time periods Ta1, Ta2, . . . , Tan, some adjacent writing time periods partially overlap with each other; and

wherein said plurality of light emitting elements are selected to be brought into a light emitting state or a non-light emitting state during the n display time periods Td1, Td2, . . . , Tdn by the digital signal.

12. A light emitting device according to 7, wherein said digital signal is input to said plurality of pixels through said plurality of first source signal lines from said first source signal line driver circuit during one writing time period of the partially overlapping adjacent writing time periods, and said digital signal is input to said plurality of pixels through said plurality of second source signal lines from the second source signal line driver circuit during the other writing time period.

14. A light emitting device according to claim 7, wherein j display time periods (j is an integer equal to or more than 0 and equal to or less than n) among the n display time periods Td1, Td2, . . . , Tdn are black display time periods during which all said plurality of light emitting elements are brought into a non-light emitting state.

16. A light emitting device according to claim 7, wherein the lengths of the n writing time periods Ta1, Ta2, . . . , Tan are equal to each other.

18. A light emitting device according to claim 7, wherein a ratio of lengths of (n−

j) display time periods among the n display time periods Td1, Td2, . . . , Tdn excluding black display time periods when arranged in order of short length is 2⁰;

2¹;

. . . ;

2<sup>(n−

j−

1)</sup>.

23. A light emitting device according to claim 7, wherein said first TFTs for switching and said second TFTs for switching have the same polarity.

28. A light emitting device according to claim 7, wherein a display time period that is the last to appear is the longest black display time period within the one frame time period.

35. A light emitting device according to claim 7 wherein said light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a sound reproduction apparatus, a notebook type personal computer, a game apparatus, a portable information terminal, and an image playback device.

8. A light emitting device comprising:

a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion,

a plurality of first source signal lines connected to said first source signal line driver circuit, a plurality of second source signal lines connected to said second source signal line driver circuit, a plurality of first gate signal lines connected to said first gate signal line driver circuit, a plurality of second gate signal lines connected to said second gate signal line driver circuit, and a plurality of power source supply lines held at a constant electric potential,

wherein said pixel portion has a plurality of pixels including a plurality of light emitting elements, a plurality of TFTs for current control, a plurality of first TFTs for switching, and a plurality of second TFTs for switching;

wherein each of said plurality of light emitting elements includes a pixel electrode, a counter electrode held at a constant electric potential, and an organic compound layer provided between said pixel electrode and said counter electrode;

wherein gate electrodes included in said plurality of first TFTs for switching are connected to said plurality of first gate signal lines;

wherein gate electrodes included in said plurality of second TFTs for switching are connected to said plurality of second gate signal lines;

wherein one of source regions and drain regions included in said plurality of first TFTs for switching are connected to said plurality of first source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control;

wherein one of source regions and drain regions included in said plurality of second TFTs for switching are connected to said plurality of second source signal lines, and the other are connected to gate electrodes included in said plurality of TFTs for current control;

wherein one of source regions and drain regions included in said plurality of TFTs for current control are connected to said plurality of power source supply lines, and the other are connected to said plurality of pixel electrodes;

wherein n writing time periods Ta1, Ta2, . . . , Tan sequentially appear within one frame time period;

wherein a writing time period that follows the last writing time period Tan among the n writing time periods Ta1, Ta2, . . . , Tan is a first writing time period Ta1 among the n writing time periods Ta1, Ta2, . . . , Tan,

wherein time periods from apparition of the respective n writing time periods Ta1, Ta2, . . . , Tan until apparition of writing time periods following the respective n writing time periods Ta1, Ta2, . . . , Tan are n display time periods Td1, Td2, . . . , Tdn;

wherein during the n writing time periods Ta1, Ta2, . . . , Tan, a digital signal is input to said plurality of pixels through said plurality of first source signal lines from said first source signal line driver circuit or through said plurality of second source signal lines from said second source signal line driver circuit;

wherein among the n writing time periods Ta1, Ta2, . . . , Tan, some adjacent writing time periods partially overlap with each other; and

wherein said plurality of light emitting elements are selected to be brought into a light emitting state or a non-light emitting state during the n display time periods Td1, Td2, . . . , Tdn by the digital signal.

9. A light emitting device according to claim 8, wherein said organic compound layer is formed of a low-molecular organic material or a polymer organic material.

10. A light emitting device according to claim 9, wherein said low-molecular organic material is made of Alq₃ (tris-8-quinolilite-aluminium) or TPD (triphenylamine derivative).

11. A light emitting device according to claim 9, wherein said polymer organic material is made of PPV (polyphenylene vinylene), PVK (polyvinylcarbazole) or polycarbonate.

13. A light emitting device according to 8, wherein said digital signal is input to said plurality of pixels through said plurality of first source signal lines from said first source signal line driver circuit during one writing time period of the partially overlapping adjacent writing time periods, and said digital signal is input to said plurality of pixels through said plurality of second source signal lines from the second source signal line driver circuit during the other writing time period.

15. A light emitting device according to claim 8, wherein j display time periods (j is an integer equal to or more than 0 and equal to or less than n) among the n display time periods Td1, Td2, . . . , Tdn are black display time periods during which all said plurality of light emitting elements are brought into a non-light emitting state.

17. A light emitting device according to claim 8, wherein the lengths of the n writing time periods Ta1, Ta2, . . . , Tan are equal to each other.

19. A light emitting device according to claim 8, wherein a ratio of lengths of (n−

j) display time periods among the n display time periods Td1, Td2, . . . , Tdn excluding black display time periods when arranged in order of short length is 2⁰;

2¹;

. . . ;

2<sup>(n−

i−

1)</sup>.

24. A light emitting device according to claim 8, wherein said first TFTs for switching and said second TFTs for switching have the same polarity.

29. A light emitting device according to claim 8, wherein a display time period that is the last to appear is the longest black display time period within the one frame time period.

36. A light emitting device according to claim 8 wherein said light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a sound reproduction apparatus, a notebook type personal computer, a game apparatus, a portable information termina1, and an image playback device.

30. A light emitting device comprising:

a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion,

wherein said pixel portion has a plurality of pixels;

wherein said plurality of pixels include a plurality of light emitting elements; and

wherein driving of said plurality of light emitting elements is controlled by a digital signal output from said first source signal line driver circuit and said second source signal line driver circuit and a selecting signal output from said first gate signal line driver circuit and said second gate signal line driver circuit.

37. A light emitting device according to claim 30 wherein said light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a sound reproduction apparatus, a notebook type personal computer, a game apparatus, a portable information terminal, and an image playback device.

31. A light emitting device comprising:

a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion,

wherein said pixel portion has a plurality of pixels;

wherein said plurality of pixels include a plurality of light emitting elements; and

wherein a time period during which the light emitting elements emit light is controlled by a digital signal output from said first source signal line driver circuit and said second source signal line driver circuit and a selecting signal output from said first gate signal line driver circuit and the second gate signal line driver circuit to perform gray-scale display.

38. A light emitting device according to claim 31 wherein said light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a sound reproduction apparatus, a notebook type personal computer, a game apparatus, a portable information terminal, and an image playback device.