Image display device and electronic appliance

• US 9,818,340 B2
• Filed: 03/10/2011
• Issued: 11/14/2017
• 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:
  US13/064,195
• Publication Number:
  US 20110163943A1
• Time in Patent Office: 2,441 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:

scanning lines arranged in rows;

signal lines arranged in columns;

a scanner part configured to supply a control signal to the scanning lines; and

pixel circuits in a matrix connected to the scanning lines and the signal lines,

wherein at least one of the pixel circuits includes a sampling transistor, a drive transistor, a pixel capacitor, a light emitting device, a first switching transistor directly connected between a first voltage line and the pixel capacitor, a second switching transistor directly connected between a second voltage line and the light emitting device, and a third switching transistor directly connected between a third voltage line and the drive transistor,

the sampling transistor is configured to supply a signal potential from the signal line to the pixel capacitor,

the pixel capacitor connected between a current terminal and a control terminal of the drive transistor, and

a channel length of the drive transistor is made longer than a channel length of each of the three switching transistors and transistors in the scanner part.

2. The image display device according to claim 1, wherein the channel length of the drive transistor is set to at least 10 μ

m.

3. The image display device according to claim 1, wherein in at least one of the pixel circuits, the channel length of the drive transistor is set so that during a light emission period, a source potential and a gate potential of the drive transistor rise together, wherein a voltage difference between the gate potential and the source potential stays constant throughout the light emission period.

4. The image display device according to claim 1, wherein a current is configured to be applied to the pixel capacitor via the drive transistor while the signal potential is being sampled.

5. The image display device according to claim 1, wherein the drive transistor is formed by a low temperature poly-silicon process.

6. An electronic appliance having the image display device according to claim 1.

7. An image display device comprising:

scanning lines arranged in rows;

signal lines arranged in columns;

a scanner part configured to supply a control signal to the scanning lines; and

pixel circuits in a matrix connected to the scanning lines and the signal lines,

wherein at least one of the pixel circuits includes a sampling transistor, a drive transistor, a pixel capacitor, a light emitting device, a first switching transistor directly connected between a first voltage line and the pixel capacitor, a second switching transistor directly connected between a second voltage line and the light emitting device, and a third switching transistor directly connected between a third voltage line and the drive transistor,

the sampling transistor is configured to supply a signal potential from the signal line to the pixel capacitor,

the pixel capacitor connected between a current terminal and a control terminal of the drive transistor, and

a channel length of the drive transistor is made longer than a channel length of each of the three switching transistors and transistors in the scanner part.

8. The image display device according to claim 7, wherein the channel length of the drive transistor is set to at least 10 μ

m.

9. The image display device according to claim 7, wherein in at least one of the pixel circuits, the channel length of the drive transistor is set so that during a light emission period, a source potential and a gate potential of the drive transistor rise together, wherein a voltage difference between the gate potential and the source potential stays constant throughout the light emission period.

10. The image display device according to claim 7, wherein a current is configured to be applied to the pixel capacitor via the drive transistor while the signal potential is being sampled.

11. The image display device according to claim 7, wherein the drive transistor is formed by a low temperature poly-silicon process.

12. An electronic appliance having the image display device according to claim 7.

13. An image display device comprising:

scanning lines arranged in rows;

signal lines arranged in columns;

a scanner part configured to supply a control signal to the scanning lines; and

pixel circuits in a matrix connected to the scanning lines and the signal lines,

wherein at least one of the pixel circuits includes a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a drive transistor, a pixel capacitor, and a light emitting device;

the first switching transistor is configured to supply a signal potential to the pixel capacitor, a gate of the first switching transistor is connected to a first scanning line;

the second switching transistor is directly connected between a first voltage line and the pixel capacitor and is configured to supply a first predetermined potential to the pixel capacitor, a gate of the second switching transistor is connected to a second scanning line;

the third switching transistor is directly connected between a second voltage line and the light emitting device and is configured to supply a second predetermined potential to an anode of the light emitting device, a gate of the third switching transistor is connected to a third scanning line;

the fourth switching transistor is directly connected between a third voltage line and the drive transistor and is configured to supply a third predetermined potential to the drive transistor, a gate of the fourth switching transistor is connected to a fourth scanning line; and

a channel length of the drive transistor is longer than a channel length of each of the first, second, third, fourth switching transistor, and transistors in the scanner part.

14. The image display device according to claim 13, wherein, while the signal potential is sampled, the drive transistor is configured to apply a negative feedback of an output current of the drive transistor to a first terminal of the pixel capacitor.

15. The image display device according to claim 14, wherein a potential of the first terminal of the pixel capacitor is increased towards a potential of a second terminal of the pixel capacitor by the negative feedback.

16. The image display device according to claim 13, wherein the channel length of the drive transistor is at least 10μ

m.

17. The image display device according to claim 13, wherein the channel length of the drive transistor is set so that during a light emission period, a source potential of the drive transistor and a gate potential of the drive transistor rise together, wherein a voltage difference between the gate potential and the source potential stays constant throughout the light emission period.

18. The image display device according to claim 13, wherein a current is configured to be applied to the pixel capacitor via the drive transistor while the signal potential is being sampled.

19. The image display device according to claim 13, wherein the drive transistor is formed by a low temperature poly-silicon process.

20. The image display device according to claim 13, wherein the second predetermined potential is lower than a threshold voltage of the light emitting device.

21. An electronic appliance having the image display device according to claim 13.