Electro-optical device and driving device thereof

• US 7,274,345 B2
• Filed: 05/13/2004
• Issued: 09/25/2007
• Est. Priority Date: 05/19/2003
• Status: Active Grant

• Current Assignee: Element Capital Commercial Company Pte. Ltd.
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kasai, Toshiyuki, Imamura, Yoichi, Ozawa, Tokuro
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): LESPERANCE, JEAN E
• Application Number:
  US10/844,485
• Publication Number:
  US 20040257353A1
• Time in Patent Office: 1,230 Days
• Field of Search: 345/36, 345/45, 345/48, 345/76, 345/84, 345/204
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/043 Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than 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 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• 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
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror

Abstract

The invention provides an electro-optical device having circuits for driving electro-optical elements, such as organic EL elements, and a driving device, which can employ driving elements having low driving ability, such as α-TFTs. By providing a charge storage capacitor between the source electrode and the gate electrode of a driving transistor which is between power sources, the electro-optical device can allow the driving transistor to control a driving current, even when an electro-optical element is connected to the source side of the driving transistor. In addition, driving data can be stored in the charge storage capacitor by applying a predetermined voltage to the source electrode of the driving transistor.

Claims

1. An electro-optical device, comprising:

a plurality of scanning lines;

a plurality of data lines;

a plurality of pixels arranged correspondingly to intersections of the plurality of scanning lines and the plurality of data lines; and

a plurality of first power wiring lines,

each of the plurality of pixels further comprising;

a first switching transistor an electrical conduction of which is controlled based on a scan signal supplied through a corresponding scanning line of the plurality of scanning lines;

an electro-optical element having a pixel electrode, a common electrode, and an electro-optical material therebetween;

a driving transistor coupled to the electro-optical element; and

a capacitor which has a first electrode and a second electrode forming a capacitance and which is coupled to a gate of the driving transistor through the first electrode,

the capacitor holding, as electric charge, a data signal supplied through the first switching transistor and a corresponding data line of the plurality of data lines, an electrical conduction state of the driving transistor being set in accordance with a quantity of electric charge held in the capacitor, and the electro-optical element and the corresponding first power wiring line of the plurality of first power wiring lines being electrically coupled to each other through the driving transistor in accordance with an electrical conduction state thereof, and

the second electrode being coupled between the driving transistor and the pixel electrode.

2. The electro-optical device according to claim 1, the first predetermined potential being equal to the potential of the common electrode.

3. The electro-optical device according to claim 1, the driving transistor being an n-channel transistor or a p-channel transistor.

4. The electro-optical device according to claim 1, the driving transistor being an amorphous thin film transistor.

5. The electro-optical device according to claim 1, in each of the plurality of pixels, before the data signal is supplied through the corresponding data line of the plurality of data lines, an electrode of the first switching transistor at a side holding the data signal is set to a second predetermined potential.

6. The electro-optical device according to claim 5, each of the plurality of pixels further including a second switching transistor that controls a connection between the electrode of the first switching transistor at a side holding the data signal and the second predetermined potential, and

an electrical conduction state of the second switching transistor being controlled by a periodic signal supplied before a scan signal that controls an electrical conduction state of the first switching transistor is supplied.

7. The electro-optical device according to claim 6, the periodic signal that controls the electrical conduction state of the second switching transistor being supplied through one of the plurality of scanning lines before the scan signal that controls the electrical conduction state of the first switching transistor is supplied.

8. The electro-optical device according to claim 1, in each of the plurality of pixels, the second electrode being set to a first predetermined potential until the data signal supplied through the corresponding data line of the plurality of data lines is intercepted by the first switching transistor.

9. The electro-optical device according to claim 1, each of the plurality of pixels further including a plurality of second power wiring lines that supply the first predetermined potential to the second electrode included in each of the plurality of pixels.

10. The electro-optical device according to claim 9, the plurality of first power wiring lines and the plurality of second power wiring lines sharing a metal wiring layer portion, and being arranged to intersect each other.

11. The electro-optical device according to claims 1, the electro-optical element being an organic electroluminescent element.

12. An electro-optical device, comprising:

a plurality of scanning lines;

a plurality of data lines;

a plurality of pixels arranged correspondingly to intersections of the plurality of scanning lines and the plurality of data lines; and

a plurality of first power wiring lines,

each of the plurality of pixels further comprising;

a first switching transistor an electrical conduction of which is controlled based on a scan signal supplied through a corresponding scanning line of the plurality of scanning lines;

an electro-optical element having a pixel electrode, a common electrode, and an electro-optical material therebetween;

a driving transistor coupled to the electro-optical element; and

a capacitor which has a first electrode and a second electrode forming a capacitance and which is coupled to a gate of the driving transistor through the first electrode,

the capacitor holding, as electric charge, a data signal supplied through the first switching transistor and the corresponding data line of the plurality of data lines, an electrical conduction state of the driving transistor being set in accordance with a quantity of electric charge held in the capacitor, and the electro-optical element and the corresponding first power wiring line of the plurality of first power wiring lines being electrically coupled to each other through the driving transistor in accordance with the electrical conduction state thereof, and

the second electrode being coupled between the driving transistor and the pixel electrode, and the second electrode being set to a first predetermined potential by an electrically conducting switching device that controls an electrical connection between the second electrode and the first predetermined potential.

13. An electro-optical device, comprising:

a plurality of scanning lines;

a plurality of data lines;

a plurality of pixels arranged correspondingly to intersections of the plurality of scanning lines and the plurality of data lines; and

a plurality of first power wiring lines,

each of the plurality of pixels further comprising;

a first switching transistor an electrical conduction of which is controlled based on a scan signal supplied through the corresponding scanning line of the plurality of scanning lines;

an electro-optical element having a pixel electrode, a common electrode, and an electro-optical material therebetween;

a driving transistor coupled to the electro-optical element; and

a capacitor which has a first electrode and a second electrode forming a capacitance and which is coupled to a gate of the driving transistor through a first electrode,

the capacitor holding, as electric charge, a data signal supplied through the first switching transistor and the corresponding data line of the plurality of data lines, an electrical conduction state of the driving transistor being set in accordance with a quantity of electric charge held in the capacitor, and the electro-optical element and the corresponding first power wiring line of the plurality of first power wiring lines being electrically coupled to each other through the driving transistor in accordance with an electrical conduction state thereof, and

the electro-optical element being set to a non-activated state based on a scan signal supplied through one of the plurality of scanning lines, before the scan signal that controls an electrical conduction state of the first switching transistor is supplied.

14. A driving device for driving a plurality of electro-optical elements arranged in a matrix, the driving device comprising:

a plurality of scanning lines;

a plurality of data lines;

a plurality of first power wiring lines; and

a plurality of pixel circuits arranged correspondingly to intersections of the plurality of scanning lines and the plurality of data lines,

each of the plurality of pixel circuits further comprising;

a first switching transistor the electrical conduction of which is controlled based on a scan signal supplied through a corresponding scanning line of the plurality of scanning lines;

a driving transistor that controls current to be supplied to the electro-optical element in accordance with an electrical conduction state thereof; and

a capacitor which has a first electrode and a second electrode forming a capacitance and which is coupled to a gate of the driving transistor through a first electrode,

the capacitor holding, as electric charge, a data signal supplied through the first switching transistor and the corresponding data line of the plurality of data lines, the electrical conduction state of the driving transistor being set in accordance with the quantity of electric charge held in the capacitor, and current having a current level corresponding to an electrical conduction state that is supplied to the corresponding electro-optical element of the plurality of electro-optical elements through the driving transistor from the corresponding first power wiring line of the plurality of first power wiring lines, and

the second electrode being coupled to a source of the driving transistor, and for at least a period before the data signal is supplied to the capacitor, the source of the driving transistor being electrically coupled to a first predetermined potential through a switching device.

15. The driving device according to claim 14, the driving transistor being an n-channel transistor or a p-channel transistor.

16. The driving device according to claim 14, the driving transistor and the first switching transistor being amorphous thin film transistors.

17. The driving device according to claim 14, for at least a period before the data signal is supplied to the capacitor, an electrode of the first switching transistor at a side holding the data signal being set to a second predetermined potential.

18. The driving device according to claim 17, each of the plurality of pixel circuits further including a second switching transistor that controls a connection between the electrode of the first switching transistor at the side holding the data signal and the second predetermined potential, and

an electrical conduction state of the second switching transistor being controlled by a periodic signal supplied before a scan signal that controls an electrical conduction state of the first switching transistor is supplied.

19. The driving device according to claim 18, the periodic signal that controls the electrical conduction state of the second switching transistor being supplied through one of the plurality of scanning lines before the scan signal that controls the electrical conduction state of the first switching transistor is supplied.

20. The driving device according to claim 17, the second switching transistor and the switching device being controlled by a common signal.

21. The driving device according to claim 14, each of the plurality of pixel circuits further including a plurality of second power wiring lines that set a potential of the source of the driving transistor to the first predetermined potential through the switching device.

22. The driving device according to claim 21, the plurality of first power wiring lines and the plurality of second power wiring lines sharing a metal wiring layer portion, and being arranged to intersect each other.

23. The driving device according to claim 22, the first predetermined potential being equal or substantially equal to that of a potential of the plurality of first power wiring lines or a potential of the plurality of second power wiring lines which ever is lower.

24. A driving device for driving a plurality of electro-optical elements arranged in a matrix, the driving device comprising:

a plurality of scanning lines;

a plurality of data lines;

a plurality of first power wiring lines; and

a plurality of pixel circuits arranged correspondingly to intersections of the plurality of scanning lines and the plurality of data lines,

each of the plurality of pixel circuits including;

a first switching transistor an electrical conduction of which is controlled based on a scan signal supplied through the corresponding scanning line of the plurality of scanning lines;

a driving transistor that controls current to be supplied to the electro-optical element in accordance with an electrical conduction state thereof; and

a capacitor which has a first electrode and a second electrode forming a capacitance and which is coupled to a gate of the driving transistor through a first electrode,

the capacitor holding, as electric charge, a data signal supplied through the first switching transistor and the corresponding data line of the plurality of data lines, the electrical conduction state of the driving transistor being set in accordance with a quantity of electric charge held in the capacitor, and current having a current level corresponding to an electrical conduction state being supplied to the corresponding electro-optical element of the plurality of electro-optical elements through the driving transistor from the corresponding first power wiring line of the plurality of first power wiring lines,

the second electrode being connected to a source of the driving transistor, and

for at least a period when the capacitor holds the quantity of electric charge corresponding to the data signal, a device that keeps constant a potential difference between a source and a gate of the driving transistor being further provided.