Electric device

• US 20010002703A1
• Filed: 11/29/2000
• Published: 06/07/2001
• Est. Priority Date: 11/30/1999
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Granted Patent: US 6,730,966 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• 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 2320/0233 Improving the luminance or brightness uniformity across the screen
• 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 3/3275 Details of drivers for data 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: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H10K 50/826 Multilayers, e.g. opaque multilayers
• CPC Class Codes: H10K 50/844 Encapsulations
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/873 Encapsulations

Abstract

There is provided an electric device which can prevent a deterioration in a frequency characteristic due to a large electric power external switch connected to an opposite electrode and can prevent a decrease in the number of gradations. The electric device includes a plurality of source signal lines, a plurality of gate signal lines, a plurality of power source supply lines, a plurality of power source control lines, and a plurality of pixels. Each of the plurality of pixels includes a switching TFT, an EL driving TFT, a power source controlling TFT, and an EL element, and the power source controlling TFT controls a potential difference between a cathode and an anode of the EL element.

Claims

1. An electric device comprising:

a plurality of source signal lines;

a plurality of gate signal lines;

a plurality of power source supply lines;

a plurality of power source control lines; and

a plurality of pixels,

each of the plurality of pixels including;

a switching thin film transistor,

an EL driving thin film transistor,

a power source controlling thin film transistor, and

an EL element, and

wherein the power source controlling thin film transistor controls a potential difference between a cathode and an anode of the EL element.

4. A device according to

claim 1

,

wherein one of a source region and a drain region of the switching thin film transistor is connected to one of the plurality of source signal lines, and the other is connected to a gate electrode of the EL driving thin film transistor,

wherein one of a source region and a drain region of the EL driving thin film transistor is connected to one of the plurality of power source supply tines, and the other is connected to one of a source region and a drain region of the power source controlling thin film transistor,

wherein the other of the source region and the drain region of the power source controlling thin film transistor is connected to one of a cathode and an anode of the EL element, and

wherein a gate electrode of the power source controlling thin film transistor is connected to one of the plurality of power source control lines.

5. A device according to

claim 1

,

wherein one of a source region and a drain region of the switching thin film transistor is connected to one of the plurality of source signal lines, and the other is connected to a gate electrode of the EL driving thin film transistor,

wherein one of a source region and a drain region of the EL driving thin film transistor is connected to one of a source region and a drain region of the power source controlling thin film transistor, and the other is connected to one of a cathode and an anode of the EL element,

wherein the other of the source region and the drain region of the power source controlling thin film transistor is connected to one of the plurality of power source supply lines, and

wherein a gate electrode of the power source controlling thin film transistor is connected to one of the plurality of power source control lines.

6. A device according to

claim 1

, further comprising a capacitor between a gate electrode of the EL driving thin film transistor and one of the plurality of power source supply lines.

7. A device according to

claim 1

,

wherein each of the plurality of EL elements includes an EL layer between the anode and the cathode, and

wherein the EL layer includes one selected from group consisting of a low molecular organic material and a polymer organic material.

8. A device according to

claim 7

,

wherein the low molecular organic material is one selected from the group consisting of Alq₃ (tris-8-quinolilite-aluminum) and TPD (triphenyl amine derivative).

9. A device according to

claim 7

,

wherein the polymer organic material is one selected from the group consisting of PPV (polyphenylenevinylene), PVK (polyvinylcarbazole), and polycarbonate.

10. A device according to

claim 1

,

wherein one frame period is {fraction (1/60)}s or less.

11. A computer using the electric device of

claim 1

.

12. A video camera using the electric device of

claim 1

.

13. A DVD player using the electric device of

claim 1

.

2. An electric device comprising:

a plurality of source signal lines;

a plurality of gate signal lines;

a plurality of power source supply lines;

a plurality of power source control lines; and

a plurality of pixels,

each of the plurality of pixels including;

a switching thin film transistor,

an EL driving thin film transistor,

a power source controlling thin film transistor, and

an EL element,

wherein a light emitting period in one frame period is controlled by a digital data signal, said light emitting period being defined as a period in which the EL element emits a light and

wherein the power source controlling thin film transistor controls a potential difference between a cathode and an anode of the El element.

14. A device according to

claim 2

,

wherein one of a source region and a drain region of the switching thin film transistor is connected to one of the plurality of source signal lines, and the other is connected to a gate electrode of the EL driving thin film transistor,

wherein one of a source region and a drain region of the EL driving thin film transistor is connected to one of the plurality of power source supply lines, and the other is connected to one of a source region and a drain region of the power source controlling thin film transistor,

wherein the other of the source region and the drain region of the power source controlling thin film transistor is connected to one of a cathode and an anode of the EL element, and

wherein a gate electrode of the power source controlling thin film transistor is connected to one of the plurality of power source control lines.

15. A device according to

claim 2

,

wherein one of a source region and a drain region of the switching thin film transistor is connected to one of the plurality of source signal lines, and the other is connected to a gate electrode of the EL driving thin film transistor,

wherein one of a source region and a drain region of the EL driving thin film transistor is connected to one of a source region and a drain region of the power source controlling thin film transistor, and the other is connected to one of a cathode and an anode of the EL element,

wherein the other of the source region and the drain region of the power source controlling thin film transistor is connected to one of the plurality of power source supply lines, and

wherein a gate electrode of the power source controlling thin film transistor is connected to one of the plurality of power source control lines.

16. A device according to

claim 2

, further comprising a capacitor between a gate electrode of the EL driving thin film transistor and one of the plurality of power source supply lines.

17. A device according to

claim 2

,

wherein each of the plurality of EL elements includes an EL layer between the anode and the cathode, and

wherein the EL layer includes one selected from group consisting of a low molecular organic material and a polymer organic material.

18. A device according to

claim 17

,

wherein the low molecular organic material is one selected from the group consisting of Alq₃ (tris-8-quinolilite-aluminum) and TPD (triphenyl amine derivative).

19. A device according to

claim 17

,

wherein the polymer organic material is one selected from the group consisting of PPV (polyphenylenevinylene), PVK (polyvinylcarbazole), and polycarbonate.

20. A device according to

claim 2

,

wherein one frame period is {fraction (1/60)}s or less.

21. A computer using the electric device of

claim 2

.

22. A video camera using the electric device of

claim 2

.

23. A DVD player using the electric device of

claim 2

.

3. An electric device comprising:

a plurality of source signal lines;

a plurality of gate signal lines;

a plurality of power source supply lines;

a plurality of power source control lines, and

a plurality of pixels,

each of the plurality of pixels including;

a switching thin film transistor,

an EL driving thin film transistor,

a power source controlling thin film transistor, and

an EL element,

wherein one frame period includes n subframe periods SF₁, SF₂, . . . , SF_n,

wherein the n subframe periods include write-in periods Ta₁, Ta₂, . . . , Ta_n and display periods Ts₁, Ts₂, . . . , Ts_n,

wherein a plurality of digital data signals are inputted to all of the plurality of pixels in the write-in periods Ta₁, Ta₂, . . . , Ta_n,

whether or not the plurality of EL elements emit a light in the display periods Ts₁, Ts₂, . . . , Ts_n is selected by the digital data signals,

wherein lengths of the write-in periods Ta₁, Ta₂, . . . , Ta_n are all identical,

wherein a ratio of lengths of the display periods Ts₁, Ts₂, . . . , Ts_n is expressed by 2⁰;

2<sup>−

1</sup>;

. . . ;

2<sup>−

(n-1)</sup>, and

wherein the power source controlling thin film transistor controls a potential difference between a cathode and an anode of the EL element.

24. A device according to

claim 3

,

wherein one of a source region and a drain region of the switching thin film transistor is connected to one of the plurality of source signal lines, and the other is connected to a gate electrode of the EL driving thin film transistor, p1 wherein one of a source region and a drain region of the EL driving thin film transistor is connected to one of the plurality of power source supply lines, and the other is connected to one of a source region and a drain region of the power source controlling thin film transistor,

wherein the other of the source region and the drain region of the power source controlling thin film transistor is connected to one of a cathode and an anode of the EL element, and

wherein a gate electrode of the power source controlling thin film transistor is connected to one of the plurality of power source control lines.

25. A device according to

claim 3

,

wherein one of a source region and a drain region of the switching thin film transistor is connected to one of the plurality of source signal lines, and the other is connected to a gate electrode of the EL driving thin film transistor,

wherein one of a source region and a drain region of the EL driving thin film transistor is connected to one of a source region and a drain region of the power source controlling thin film transistor, and the other is connected to one of a cathode and an anode of the EL element,

wherein the other of the source region and the drain region of the power source controlling thin film transistor is connected to one of the plurality of power source supply lines, and

wherein a gate electrode of the power source controlling thin film transistor is connected to one of the plurality of power source control lines.

26. A device according to

claim 3

, further comprising a capacitor between a gate electrode of the EL driving thin film transistor and one of the plurality of power source supply lines.

27. A device according to

claim 3

,

wherein each of the plurality of EL elements includes an EL layer between the anode and the cathode, and

wherein the EL layer includes one selected from group consisting of a low molecular organic material and a polymer organic material.

28. A device according to

claim 27

,

wherein the low molecular organic material is one selected from the group consisting of Alq₃ (tris-8-quinolilite-aluminum) and TPD (triphenyl amine derivative).

29. A device according to

claim 27

,

wherein the polymer organic material is one selected from the group consisting of PPV (polyphenylenevinylene), PVK (polyvinylcarbazole), and polycarbonate.

30. A device according to

claim 3

,

wherein one frame period is {fraction (1/60)}s or less.

31. A computer using the electric device of

claim 3

.

32. A video camera using the electric device of

claim 3

.

33. A DVD player using the electric device of

claim 3

.