EL display device and electronic device

• US 7,358,531 B2
• Filed: 05/19/2004
• Issued: 04/15/2008
• Est. Priority Date: 06/23/1999
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Primary Examiner(s): Owens; Douglas W.
• Assistant Examiner(s): Tran; Chuc
• Application Number:
  US10/848,147
• Publication Number:
  US 20040207331A1
• Time in Patent Office: 1,427 Days
• Field of Search: 315/169.1, 314/169.3, 257/59, 257/347
• US Class Current: 257/59
• CPC Class Codes: G09G 2300/026 Video wall, i.e. juxtaposition of a plurality of screens to create a display screen of bigger dimensions
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• 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 2300/0885 Pixel comprising a non-linear two-terminal element alone in series with each display pixel element
• CPC Class Codes: G09G 2310/0221 with use of split matrices G09G3/3644 and G09G3/3666 take precedence
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal 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 2330/021 Power management, e.g. power saving
• 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 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• 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 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/1251 comprising TFTs having a different architecture, e.g. top- and bottom gate TFTs
• CPC Class Codes: H01L 27/1255 : integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 27/156 : two-dimensional arrays
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H10K 59/1213 : the pixel elements being TFTs
• CPC Class Codes: H10K 59/123 : Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/126 : Shielding, e.g. light-blocking means over the TFTs
• CPC Class Codes: H10K 59/131 : Interconnections, e.g. wiring lines or terminals

Abstract

An EL display device capable of producing a vivid multi-gradation color display, and an electronic device having the EL display device. An electric current supplied to an EL element 110 is controlled by providing a resistor 109 between a current control TFT 108 and the EL element 110 formed in a pixel 104, the resistor 109 having a resistance higher than the on-resistance of the current control TFT 108. The gradation display is executed by a time-division drive system which controls the emission and non-emission of light of the EL element 110 by time, preventing the effect caused by a dispersion in the characteristics of the current control TFT 108.

Claims

1. An electronic device comprising:

a substrate;

a TFT provided over said substrate;

an EL element provided over said substrate;

a resistor comprising a semiconductor provided between said EL element and a drain of said TFT; and

a light-shielding film provided over said semiconductor of said resistor,

wherein an amount of light emitted from said EL element varies depending on an amount of direct current flowing through said EL element.

2. A device according to claim 1 wherein said resistor has a resistance of 1 kΩ

to 50 MΩ

.

3. A device according to claim 1 wherein said light-sheilding film comprises the same material as a gate electrode of said TFT.

4. An EL display device comprising:

a substrate;

a TFT provided over said substrate;

an EL element provided over said substrate;

a resistor comprising a semiconductor provided between said EL element and a drain of said TFT; and

a light-shielding film provided over said semiconductor of said resistor,

wherein an amount of light emitted from said EL element varies depending on an amount of direct current flowing through said EL element.

5. A device according to claim 4 wherein said resistor has a resistance of 1 kΩ

to 50 MΩ

.

6. A device according to claim 4 wherein said light-shielding film comprises the same material as a gate electrode of said TFT.

7. A personal computer comprising:

a substrate;

a TFT provided over said substrate;

an EL element provided over said substrate;

a resistor comprising a semiconductor provided between said EL element and a drain of said TFT; and

a light-shielding film provided over said semiconductor of said resistor,

wherein an amount of light emitted from said EL element varies depending on an amount of direct current flowing through said EL element.

8. A personal computer according to claim 7 wherein said resistor has a resistance of 1 kΩ

to 50 MΩ

.

9. A personal computer according to claim 7 wherein said light-shielding film comprises the same material as a gate electrode of said TFT.

10. A video camera comprising:

a substrate;

a TFT provided over said substrate;

an EL element provided over said substrate;

a resistor comprising a semiconductor provided between said EL element and a drain of said TFT; and

a light-shielding film provided over said semiconductor of said resistor,

wherein an amount of light emitted from said EL element varies depending on an amount of direct current flowing through said EL element.

11. A video camera according to claim 10 wherein said resistor has a resistance of 1 kΩ

to 50 MΩ

.

12. A video camera according to claim 10 wherein said light-shielding film comprises the same material as a gate electrode of said TFT.

13. A head-mounted display comprising:

a substrate;

a TFT provided over said substrate;

an EL element provided over said substrate;

a resistor comprising a semiconductor provided between said EL element and a drain of said TFT; and

a light-shielding film provided over said semiconductor of said resistor,

wherein an amount of light emitted from said EL element varies depending on an amount of direct current flowing through said EL element.

14. A head-mounted display according to claim 13 wherein said resistor has a resistance of 1 kΩ

to 50 MΩ

.

15. A head-mounted display according to claim 13 wherein said light-shielding film comprises the same material as a gate electrode of said TFT.

16. A picture reproducing apparatus comprising:

a substrate;

a TFT provided over said substrate;

an EL element provided over said substrate;

a resistor comprising a semiconductor provided between said EL element and a drain of said TFT; and

a light-shielding film provided over said semiconductor of said resistor,

wherein an amount of light emitted from said EL element varies depending on an amount of direct current flowing through said EL element.

17. A picture reproducing apparatus according to claim 16 wherein said resistor has a resistance of 1 kΩ

to 50 MΩ

.

18. A picture reproducing apparatus according to claim 16 wherein said light-shielding film comprises the same material as a gate electrode of said TFT.

19. A mobile computer comprising:

a substrate;

a TFT provided over said substrate;

an EL element provided over said substrate;

a resistor comprising a semiconductor provided between said EL element and a drain of said current control TFT; and

a light-shielding film provided over said semiconductor of said resistor,

wherein an amount of light emitted from said EL element varies depending on an amount of direct current flowing through said EL element.

20. A mobile computer according to claim 19 wherein said resistor has a resistance of 1 kΩ

to 50 MΩ

.

21. A mobile computer according to claim 19 wherein said light-shielding film comprises the same material as a gate electrode of said TFT.

22. An electronic device comprising:

a plurality of pixels, each of the plurality of pixels comprising;

a thin film transistor formed over a substrate;

a first insulating layer formed over the thin film transistor;

a pixel electrode formed over the first insulating layer, the pixel electrode being connected to the thin film transistor;

a second insulating layer formed over the pixel electrode, the second insulating layer having an opening over the pixel electrode; and

a light emitting layer formed over the pixel electrode and the second insulating layer,

wherein an edge of the pixel electrode is covered with the second insulating layer,

wherein the second insulating layer includesa resin material, and

wherein the pixel electrode comprises indium oxide and zinc oxide.