Image display device having a drive transistor with a channel length longer than a channel length of individual switching transistors

• US 9,984,621 B2
• Filed: 01/08/2016
• Issued: 05/29/2018
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamashita, Junichi, Mitomi, Yutaka, Minami, Tetsuo, Tanikame, Takao
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): LAM, NELSON C
• Application Number:
  US14/991,573
• Publication Number:
  US 20160125805A1
• Time in Patent Office: 872 Days
• Field of Search: 345 76- 83, 3151693
• 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 2300/0861 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 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: H01L 29/78678 with inverted-type structure, e.g. with bottom gate
• CPC Class Codes: H01L 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/1216 the pixel elements being capacitors
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals

Abstract

An image display device includes: a pixel array part formed of first to fourth scanning lines arranged in rows, signal lines arranged in columns, pixel circuits in a matrix connected to the scanning lines and signal lines, and a plurality of power source lines which supplies first to third potentials necessary for the operations of pixel circuit; a signal part which supplies a video signal to the signal lines; and a scanner part which supplies a control signal to the first to fourth scanning lines, and in turn scans the pixel circuit for every row, wherein the pixel circuits include a sampling transistor, a drive transistor, first to third switching transistors, a pixel capacitance, and a light emitting device, and a channel length of the drive transistor is made longer than a channel length of the switching transistors to suppress fluctuations in threshold voltage.

Claims

1. An image display device comprising:

a pixel array part;

a scanner part; and

a signal part,

wherein

the pixel array part includes a first scanning line, a second scanning line, a third scanning line, and a fourth scanning line arranged in rows, signal lines arranged in columns, pixel circuits in a matrix connected to the scanning lines and signal lines, and a plurality of power source lines which supplies a first potential, a second potential, and a third potential necessary for operations of the pixel circuits,

the signal part supplies a video signal to the signal lines,

the scanner part supplies a control signal to the first scanning line, the second scanning line, the third scanning line, and the fourth scanning line,

each of the pixel circuits includes a sampling transistor, a drive transistor, a first switching transistor, a second switching transistor, a third switching transistor, a pixel capacitance, and a light emitting device,

the sampling transistor conducts in response to the control signal supplied from the first scanning line in a predetermined sampling period, and samples the signal potential of the video signal supplied from the corresponding signal line to the pixel capacitance,

the pixel capacitance applies an input voltage to a gate of the drive transistor in accordance with the signal potential of the video signal,

the drive transistor supplies an output current in accordance with the input voltage to the light emitting device,

the light emitting device emits light at a brightness in accordance with the signal potential of the video signal with the output current supplied from the drive transistor for a predetermined light emission period,

the first switching transistor conducts in response to the control signal supplied from the second scanning line prior to the sampling period, and sets a source of the drive transistor to the first potential, and

the second switching transistor conducts in response to the control signal supplied from the third scanning line prior to the sampling period, and connects the drive transistor to the second potential, whereby a voltage corresponding to the threshold voltage of the drive transistor is held in the pixel capacitance to correct the influence of the threshold voltage, and

the third switching transistor conducts in response to the control signal supplied from the fourth scanning line in the light emission period, and connects the drive transistor to the third potential to carry the output current through the light emitting device, in which a channel length of the drive transistor is made longer than a channel length of the first switching transistor, a channel length of the second switching transistor, and a channel length of the third switching transistor.

2. The image display device according to claim 1, wherein the scanner part is formed on a same substrate on which the pixel array part is formed.

3. The image display device according to claim 1, wherein the channel length of the drive transistor is 10 microns or greater.

4. An electronic appliance including the image display device according to claim 1.

5. The image display device according to claim 1, wherein the scanner part includes a scanner transistor, and a channel length of the drive transistor is made longer than a channel length of the scanner transistor.

6. The image display device according to claim 1, wherein the channel length of the drive transistor is from 15 micron to 20 micron.

7. The image display device according to claim 1, wherein the drive transistor includes a polycrystalline silicon film.

8. The image display device according to claim 7, wherein the channel length of the drive transistor is 10 microns or greater.

9. The image display device according to claim 7, wherein the channel length of the drive transistor is from 15 micron to 20 micron.

10. An image display device comprising:

a first scanning line extending along a row;

a second scanning line extending along the row;

a third scanning line extending along the row;

a fourth scanning line extending along the row;

a signal line configured to supply a video signal and extending along a column;

a first voltage line;

a second voltage line;

a third voltage line;

a pixel circuit connected to the first scanning line, the second scanning line, the third scanning line, the fourth scanning line, the signal line, the first voltage line, the second voltage line, and the third voltage line; and

a scanner part configured to supply a first control signal to the first scanning line, a second control signal to the second scanning line, a third control signal to the third scanning line, and a fourth control signal to the fourth scanning line, wherein

the pixel circuit includes a sampling transistor, a drive transistor, a first switching transistor, a second switching transistor, a third switching transistor, a pixel capacitance, and a light emitting device,

the sampling transistor is configured to conduct in response to the first control signal supplied in a predetermined sampling period, and supply a signal potential of the video signal to the pixel capacitance,

the drive transistor is configured to supply an output current in accordance with the signal potential to the light emitting device,

the light emitting device is configured to emit light at a brightness in accordance with the output current for a predetermined light emission period,

the first switching transistor is configured to conduct in response to the second control signal prior to the sampling period, and supply a first potential from the first voltage line to an anode of the light emitting device,

the second switching transistor is configured to conduct in response to the third control signal prior to the sampling period, and supply a second potential from the second voltage line to the pixel capacitance, whereby a voltage related to the threshold voltage of the drive transistor is held in the pixel capacitance to correct the influence of the threshold voltage,

the third switching transistor is configured to conduct in response to the fourth control signal in the light emission period, and supply a third potential from the third voltage line to the drive transistor, and

a channel length of the drive transistor is longer than a channel length of the first switching transistor, a channel length of the second switching transistor, and a channel length of the third switching transistor.

11. The image display device according to claim 10, wherein the scanner part is formed on a same substrate on which the pixel array part is formed.

12. The image display device according to claim 10, wherein the channel length of the drive transistor is 10 microns or greater.

13. An electronic appliance including the image display device according to claim 10.

14. The image display device according to claim 10, wherein the scanner part includes a scanner transistor, and a channel length of the drive transistor is longer than a channel length of the scanner transistor.

15. The image display device according to claim 10, wherein the channel length of the drive transistor is from 15 micron to 20 micron.

16. The image display device according to claim 10, wherein the drive transistor includes a polycrystalline silicon film.

17. The image display device according to claim 16, wherein the channel length of the drive transistor is 10 microns or greater.

18. The image display device according to claim 16, wherein the channel length of the drive transistor is from 15 micron to 20 micron.

19. An image display device comprising:

a first scanning line extending along a row;

a second scanning line extending along the row;

a third scanning line extending along the row;

a fourth scanning line extending along the row;

a signal line configured to supply a video signal and extending along a column;

a first voltage line;

a second voltage line;

a third voltage line;

a pixel circuit connected to the first scanning line, the second scanning line, the third scanning line, the fourth scanning line, the signal line, the first voltage line, the second voltage line, and the third voltage line; and

a scanner part configured to supply a first control signal to the first scanning line, a second control signal to the second scanning line, a third control signal to the third scanning line, and a fourth control signal to the fourth scanning line, wherein

the pixel circuit includes a sampling transistor, a drive transistor, a first switching transistor, a second switching transistor, a third switching transistor, a pixel capacitance, and a light emitting device,

the sampling transistor is configured to conduct in response to the first control signal supplied in a non-emission period, and supply a signal potential of the video signal to the pixel capacitance,

the drive transistor is configured to supply an output current in accordance with the signal potential to the light emitting device,

the light emitting device is configured to emit light at a brightness in accordance with the output current for a predetermined light emission period,

the first switching transistor is configured to conduct in response to the second control signal in the non-emission period, and supply a first potential from the first voltage line to an anode of the light emitting device,

the second switching transistor is configured to conduct in response to the third control signal in the non-emission period, and supply a second potential from the second voltage line to the pixel capacitance, whereby a voltage related to the threshold voltage of the drive transistor is held in the pixel capacitance to correct the influence of the threshold voltage,

the third switching transistor is configured to conduct in response to the fourth control signal in the light emission period, and supply a third potential from the third voltage line to the drive transistor, and

a channel length of the drive transistor is longer than a channel length of the first switching transistor, a channel length of the second switching transistor, and a channel length of the third switching transistor.

20. The image display device according to claim 19, wherein the scanner part is formed on a same substrate on which the pixel array part is formed.

21. The image display device according to claim 19, wherein the channel length of the drive transistor is 10 microns or greater.

22. An electronic appliance including the image display device according to claim 19.

23. The image display device according to claim 19, wherein the scanner part includes a scanner transistor, and a channel length of the drive transistor is longer than a channel length of the scanner transistor.

24. The image display device according to claim 19, wherein the channel length of the drive transistor is from 15 micron to 20 micron.

25. The image display device according to claim 19, wherein the drive transistor includes a polycrystalline silicon film.

26. The image display device according to claim 25, wherein the channel length of the drive transistor is 10 microns or greater.

27. The image display device according to claim 25, wherein the channel length of the drive transistor is from 15 micron to 20 micron.