El display panel, its driving method, and el display apparatus

• US 20050041002A1
• Filed: 09/06/2002
• Published: 02/24/2005
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: JDI Design and Development GK
• Original Assignee: JOLED Inc.
• Inventors: Takahara, Hiroshi, Tsuge, Hitoshi
• Granted Patent: US 8,823,606 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0404 Matrix technologies
• CPC Class Codes: G09G 2300/0413 Details of dummy pixels or dummy lines in flat panels
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• 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 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/0218 with collection of electrodes in groups for n-dimensional addressing
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• 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 2320/06 : Adjustment of display parameters
• CPC Class Codes: G09G 2320/0606 : Manual adjustment
• CPC Class Codes: G09G 2320/0626 : for control of overall brightness
• CPC Class Codes: G09G 2320/0646 : Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 : Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 3/2003 : Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2007 : Display of intermediate tones
• CPC Class Codes: G09G 3/32 : semiconductive, e.g. using light-emitting diodes [LED]
• 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
• CPC Class Codes: G09G 3/325 : the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: G09G 3/3258 : with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3266 : Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3275 : Details of drivers for data electrodes
• CPC Class Codes: G09G 5/02 : characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H01L 27/124 : with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• 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 27/127 : with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement
• CPC Class Codes: H01L 27/156 : two-dimensional arrays
• CPC Class Codes: H01L 29/78645 : with multiple gate
• CPC Class Codes: H01L 29/78672 : Polycrystalline or microcrystalline silicon transistor
• CPC Class Codes: H01L 33/56 : Materials, e.g. epoxy or silicone resin
• CPC Class Codes: H01L 33/58 : Optical field-shaping elements
• CPC Class Codes: H05K 999/99 : dummy group
• CPC Class Codes: H10K 50/8428 : Vertical spacers, e.g. arranged between the sealing arrangement and the OLED
• CPC Class Codes: H10K 50/844 : Encapsulations
• CPC Class Codes: H10K 50/846 : comprising getter material or desiccants
• CPC Class Codes: H10K 50/86 : Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/12 : Active-matrix OLED [AMOLED] displays
• 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 59/126 : Shielding, e.g. light-blocking means over the TFTs
• CPC Class Codes: H10K 59/35 : comprising red-green-blue [RGB] subpixels
• CPC Class Codes: H10K 59/352 : the areas of the RGB subpixels being different

Abstract

An EL display apparatus according to the present invention includes EL device (15) adapted to emit light at a luminance corresponding to a current fed thereto. A source driver (14) outputs a current higher than a current corresponding to an image signal to the EL device (16) through a source signal line (18). This operation charges/discharges a parasitic capacitance present in the source signal line (18). A transistor (11d) formed between the EL device (15) and the source driver (14) operates so that the EL device (15) is fed with the current for only a part of a one-frame period. As a result, the El device (15) emits light for only the part of the period.

Claims

1. An EL display apparatus comprising:

a plurality of gate signal lines and a plurality of source signal lines, which are arranged to intersect each other;

EL devices arranged in a matrix pattern, each of the EL devices being operative to emit light at a luminance corresponding to a current fed thereto;

a gate driver operative to output a gate signal to each of the gate signal lines;

a source driver operative to output to each of the source signal lines a current having a predetermined value for realizing a gray scale display corresponding to an image signal inputted from outside;

a transistor provided for each of the EL devices for outputting the current outputted from the source driver to the EL device; and

a first switching device capable of feeding the current outputted from the source driver to the EL device by switching to bring the EL device and the transistor into and out of conduction thereacross in accordance with the gate signal fed thereto through the gate signal line,

wherein the gate driver is configured to output a current about N times as high as the predetermined value, where N is an integer not less than 2, and

the gate driver is configured to output the gate signal to the gate signal line in a manner to bring the EL device and the transistor into and out of conduction thereacross at least once in a one-frame period, whereby the EL device is fed with the current outputted from the source driver for about 1/N of the one-frame period.

2. The EL display apparatus according to claim 1, wherein the gate driver is configured to output the gate signal to the gate signal line in a manner to bring the EL device and the transistor into and out of conduction thereacross plural times periodically in the one-frame period.

3. The EL display apparatus according to claim 1, further comprising a second switching device capable of feeding the current outputted from the source driver to the transistor by switching to bring the source driver and the transistor into and out of conduction thereacross in accordance with the gate signal fed thereto through the gate signal line,

wherein the gate driver is configured to bring the source driver and the transistor into conduction thereacross to program the transistor with the current outputted from the source driver while bringing the EL device and the transistor out of conduction thereacross and then output the gate signal to the gate signal line in a manner to bring the EL device and the transistor into and out of conduction thereacross at least once in the one-frame period.

4. The EL display apparatus according to claim 1, wherein the gate driver and the transistor are formed in a same process.

5. The EL display apparatus according to claim 1, wherein the source driver comprises a semiconductor chip.

10. An electronic apparatus comprising:

an EL display apparatus as recited in claim 1, and an arrangement for outputting an image signal to the EL display apparatus.

6. An EL display apparatus comprising:

a plurality of gate signal lines and a plurality of source signal lines, which are arranged to intersect each other;

EL devices arranged in a matrix pattern, each of the EL devices being operative to emit light at a luminance corresponding to a current fed thereto;

a gate driver operative to output a gate signal to each of the gate signal lines;

a source driver operative to output to each of the source signal lines a current having a predetermined value for realizing a gray scale display corresponding to an image signal inputted from outside;

a first switching device provided for each of the EL devices and capable of feeding the EL device with a current fed through the source signal line by switching to bring the EL device and the source signal line into and out of conduction thereacross in accordance with the gate signal fed thereto through the gate signal line;

a plurality of dummy devices located in a region different from a region where the EL devices are formed, the dummy devices being of substantially no use in image display; and

a second switching device provided for each of the dummy devices and capable of feeding the dummy device with the current fed through the source signal line by switching to bring the dummy device and the source signal line into and out of conduction thereacross in accordance with the gate signal supplied thereto through the gate signal line,

wherein the source driver is configured to output a current about N times as high as the predetermined value, where N is an integer not less than 2, and

the gate driver is configured to output gate signals to the gate signal line associated with the EL device and the gate signal line associated with the dummy device at substantially the same timing so as to feed the EL device and the dummy device with the current fed through the source signal line dividedly therebetween, whereby the EL device is fed with a current having a value substantially equal to the predetermined value.

7. The EL display apparatus according to claim 6, wherein:

the gate signal line associated with the dummy device is formed to extend adjacent the gate signal line associated with EL devices in a first or final row; and

the gate driver is configured to output gate signals to gate signal lines associated with a series of adjacent rows at substantially the same timing series by series sequentially, whereby plural EL devices or the pair of the EL device and the dummy device are fed with the current fed through the source signal line dividedly therebetween.

8. A method of driving an EL display apparatus having an EL device which is operative to emit light at a luminance corresponding to a current fed thereto, and a source driver operative to output a current to the EL device through a source signal line,

the method comprising the steps of:

causing the source driver to output to the source signal line a current about N times as high as predetermined value, where N is an integer not less than 2, for realizing a gray scale display corresponding to an image signal inputted from outside; and

feeding the EL device with the current outputted to the source signal line for about 1/N of a one-frame period to cause the EL device to emit light at a luminance corresponding to the current outputted to the source signal line for about 1/N of the one-frame period.

9. The method according to claim 8, wherein the part of the one-frame period is divided into plural periods.

11. An EL display apparatus comprising:

EL devices arranged in a matrix pattern;

a driving transistor operative to feed a current to each of the EL devices;

a first switching device disposed between the EL device and the driving transistor; and

a gate driver operative to on-off control the first switching device,

wherein the gate driver is configured to control the first switching device in a manner to turn the first switching device off at least once within a one-frame period.

12. The EL display apparatus according to claim 11, wherein the first switching device is controlled in a manner to turn off plural times periodically within the one-frame period.

22. An electronic apparatus characterized by comprising:

an EL display apparatus as recited in claim 11;

a receiver; and

a speaker.

13. An EL display apparatus comprising:

a source driver circuit operative to output a programming current;

EL devices arranged in a matrix pattern;

a driving transistor operative to feed a current to each of the EL devices;

a first switching device disposed between the EL device and the driving transistor;

a second switching device forming a path for transmitting the programming current to the driving transistor; and

a gate driver circuit operative to on-off control the first and second switching devices,

wherein the gate driver is configured to control the first switching device in a manner to turn the first switching device on at least once and off at least once within a one-frame period.

14. The EL display apparatus according to claim 13, wherein the gate driver and the driving transistor are formed in a same process, while the source driver comprises a semiconductor chip.

15. An EL display apparatus comprising:

gate signal lines;

source signal lines;

a source driver operative to output a programming current;

a gate driver;

EL devices arranged in a matrix pattern;

a driving transistor operative to feed a current to each of the EL devices;

a first transistor disposed between the EL device and the driving transistor; and

a second transistor forming a path for transmitting the programming current to the driving transistor,

wherein;

the source driver is operative to output the programming current to each of the source signal lines;

the gate driver is connected to each of the gate signal lines;

the second transistor has a gate terminal connected to the gate signal line, a source terminal connected to the source signal line, and a drain terminal connected to the drain terminal of the driving transistor; and

the gate driver is configured to select plural ones of the gate signal lines to feed the programming current to the driving transistor of each of plural pixels and control the first transistor in a manner to turn the first transistor on at least once and off at least once within a one-frame period.

16. The EL display apparatus according to claim 15, wherein the gate driver and the driving transistor are formed in a same process, while the source driver comprises a semiconductor chip.

17. An EL display apparatus comprising:

a display region including I pixel rows (I is an integer not less than

     2) and J pixel columns (J is an integer not less than

     2);

a source driver operative to apply video signals to source signal lines in the display region;

a gate driver operative to apply on-voltage or off-voltage to gate signal lines in the display region; and

a dummy pixel row formed in a region other than the display region,

wherein the display region is formed with EL devices arranged in a matrix pattern, each of which is operative to emit light in accordance with the video signals from the source driver, while the dummy pixel row is configured such that the dummy pixel row fails to emit light or its light-emitting state is not recognized visually.

18. The EL display apparatus according to claim 17, wherein the gate driver is configured to select plural pixel rows at a time for the pixel rows selected to be applied with the video signals from the source driver in a manner that the dummy pixel row is selected when the first pixel row or the I^th pixel row is selected.

19. A method of driving an EL display apparatus characterized by:

feeding the EL device with a current that causes the EL device to emit light at a luminance higher than a predetermined luminance; and

causing the EL device to emit light for a 1/N part of a one-frame period (N is less than

     1).

20. The method according to claim 19, wherein the 1/N part of the one-frame period is divided into plural periods.

21. A method of driving an EL display apparatus adapted for programming of a current to pass through an EL device based on a current, characterized by:

causing the EL device to emit light at a luminance higher than a predetermined luminance to provide a display in a 1/N (N>

1) portion of a display region; and

sequentially shifting the 1/N portion of the display region to another thereby causing the whole display region to display.