DISPLAY DEVICE AND ELECTRONIC DEVICE PROVIDED WITH THE SAME

• US 20090166638A1
• Filed: 12/23/2008
• Published: 07/02/2009
• Est. Priority Date: 12/27/2007
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: HONDA, Tatsuya
• Granted Patent: US 7,863,627 B2
• Time in Patent Office: Days
• US Class Current: 257/71
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0823 used to establish symmetry in driving, e.g. with polarity inversion
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

An object is to suppress decrease in luminance and appearance of flicker of a still image and to control a threshold voltage of a transistor for driving an EL element even in a state where the EL element continues to emit light for a certain period. An n-channel transistor and a p-channel transistor are provided as driving transistors for driving a light-emitting element, and a polarity of a potential which is supplied from a data line is reversed every given period and supplied to gates of the driving transistors in each pixel, whereby the threshold voltages of the driving transistors are controlled and change of luminance of the light-emitting element due to the threshold voltage shifts of the driving transistors can be reduced.

Claims

1. A display device comprising:

an n-channel transistor including at least a first terminal and a second terminal, wherein the first terminal of the n-channel transistor is electrically connected to a power supply line and the second terminal of the n-channel transistor is electrically connected to a light-emitting element;

a p-channel transistor including at least a first terminal and a second terminal, wherein the first terminal of the p-channel transistor is electrically connected to the power supply line and the second terminal of the p-channel transistor is electrically connected to the light-emitting element; and

a switching element including at least a first terminal and a second terminal, wherein the first terminal of the switching element is electrically connected to a data line and the second terminal of the switching element is electrically connected to a gate electrode of the n-channel transistor and a gate electrode of the p-channel transistor.

5. A display device according to claims 1 and 2,

wherein the switching element is formed using a thin film transistor.

7. A display device according to claims 1 to 4,

wherein the light-emitting element includes a first electrode, a second electrode, and a light-emitting layer interposed between the first electrode and the second electrode.

8. A display device according to claims 1 to 4,

wherein the n-channel transistor and the p-channel transistor are enhancement-type transistors.

9. A display device according to claims 1 to 4,

wherein the n-channel transistor and the p-channel transistor are separately turned on and off alternately while the light-emitting element is emitting light.

10. A display device according to claims 1 to 4,

wherein the gate electrode of the n-channel transistor and the gate electrode of the p-channel transistor are supplied with a positive potential and a negative potential alternately while the light-emitting element is emitting light.

11. An electronic device having the display device according to claims 1 to 4, the electronic device is one selected from a portable game machine, a digital camera, a television set, a computer and a mobile phone.

2. A display device comprising:

an n-channel transistor including at least a first terminal and a second terminal, wherein the first terminal of the n-channel transistor is electrically connected to a power supply line and the second terminal of the n-channel transistor is electrically connected to a light-emitting element;

a p-channel transistor including at least a first terminal and a second terminal, wherein the first terminal of the p-channel transistor is electrically connected to the power supply line and the second terminal of the p-channel transistor is electrically connected to the light-emitting element;

a capacitor element including a first terminal and a second terminal, wherein the first terminal of the capacitor element is electrically connected to a gate electrode of the n-channel transistor and a gate electrode of the p-channel transistor and the second terminal of the capacitor element is electrically connected to the power supply line; and

a switching element including at least a first terminal and a second terminal, wherein the first terminal of the switching element is electrically connected to a data line and the second terminal of the switching element is electrically connected to the gate electrode of the n-channel transistor and the gate electrode of the p-channel transistor.

3. A display device comprising,

an n-channel transistor including at least a first terminal and a second terminal, wherein the first terminal of the n-channel transistor is electrically connected to a first power supply line and the second terminal of the n-channel transistor is electrically connected to a light-emitting element;

a p-channel transistor including at least a first terminal and a second terminal, wherein the first terminal of the p-channel transistor is electrically connected to the first power supply line and the second terminal of the p-channel transistor is electrically connected to the light-emitting element;

a first switching element including at least a first terminal and a second terminal, wherein the first terminal of the first switching element is electrically connected to a data line and the second terminal of the first switching element is electrically connected to a gate electrode of the n-channel transistor and a gate electrode of the p-channel transistor; and

a second switching element including at least a first terminal and a second terminal, wherein the first terminal of the second switching element is electrically connected to a second power supply line and the second terminal of the second switching element is electrically connected to the gate electrode of the n-channel transistor and the gate electrode of the p-channel transistor

6. A display device according to claims 3 and 4,

wherein the first switching element and the second switching element are formed using a thin film transistor.

4. A display device comprising:

an n-channel transistor including at least a first terminal and a second terminal, wherein the first terminal of the n-channel transistor is electrically connected to a first power supply line and the second terminal of the n-channel transistor is electrically connected to a light-emitting element;

a p-channel transistor including at lest a first terminal and a second terminal, wherein the first terminal of the p-channel transistor is electrically connected to the first power supply line and the second terminal of the p-channel transistor is electrically connected to the light-emitting element;

a capacitor element including a first terminal and a second terminal, wherein the first terminal of the capacitor element is electrically connected to a gate electrode of the n-channel transistor and a gate electrode of the p-channel transistor and the second terminal of the capacitor element is electrically connected to the first power supply line;

a first switching element including at least a first terminal and a second terminal, wherein the first terminal of the first switching element is electrically connected to a data line and the second terminal of the first switching element is electrically connected to the gate electrode of the n-channel transistor and the gate electrode of the p-channel transistor; and

a second switching element including at least a first terminal and a second terminal, wherein the first terminal of the second switching element is electrically connected to a second power supply line and the second terminal of the second switching element is electrically connected to the gate electrode of the n-channel transistor and the gate electrode of the p-channel transistor.