Electro-optical device

• US 6,587,086 B1
• Filed: 10/19/2000
• Issued: 07/01/2003
• Est. Priority Date: 10/26/1999
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Primary Examiner(s): Shankar, Vijay
• Assistant Examiner(s): Shapiro, Leonid
• Application Number:
  US09/692,713
• Time in Patent Office: 985 Days
• Field of Search: 345/76, 345/77, 345/92, 345/84, 345/94, 345/100, 345/205, 315/169.3, 315/169.1, 257/71, 257/72, 257/88, 349/42, 349/44, 313/500-506, 313/512, 313/486-9, 428/69, 428/76, 428/317, 428/690
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• 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 2300/0809 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 2300/0847 being a dynamic memory without any storage capacitor, i.e. with use of parasitic capacitances as storage elements
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• 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 3/2077 by a combination of two or more gradation control methods
• CPC Class Codes: G09G 3/2081 with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• 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 3/3266 Details of drivers for scan electrodes
• 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 27/1248 : with a particular composition or shape of the interlayer dielectric specially adapted to the circuit arrangement
• CPC Class Codes: H01L 29/78672 : Polycrystalline or microcrystalline silicon transistor
• CPC Class Codes: H10K 50/11 : characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/8445 : multilayered coatings having a repetitive structure, e.g. having multiple organic-inorganic bilayers
• CPC Class Codes: H10K 59/122 : Pixel-defining structures or layers, e.g. banks
• CPC Class Codes: H10K 59/124 : Insulating layers formed between TFT elements and OLED elements
• CPC Class Codes: H10K 59/131 : Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/8731 : multilayered coatings having a repetitive structure, e.g. having multiple organic-inorganic bilayers
• CPC Class Codes: Y10S 428/917 : Electroluminescent

Abstract

An electro-optical device for performing time division gray scale display and which is capable of arbitrarily setting the amount of time during which light is emitted by EL elements is provided. From among n sustain periods Ts1, . . . , Tsn, the brightness of light emitted by the EL elements during at least one sustain period is set to be always lower than the brightness of light emitted by the EL elements during the other sustain periods, and the sustain periods are extended by the amount that the brightness has dropped. In accordance with the above structure, the sustain periods can be extended by lowering the setting of the brightness of light emitted by the EL elements.

Claims

1. An electro-optical device comprising:

a plurality of EL elements; and

a plurality of pixels having the plurality of EL elements;

wherein;

one frame period comprises n subframe periods, each subframe period comprising a sustain period having a length corresponding to each subframe, where n is a natural number greater than or equal to 1,

the plurality of EL elements are selected to emit light during each sustain period in accordance with the digital data signals, and

the brightness of the light emitted by the EL elements during at least one sustain period is 1/m of the brightness of the light emitted by the EL elements during the other sustain periods in order to extend said at least one sustain period by m times, where m is a positive number greater than 1.

3. An electro-optical device according to claim 1, wherein:

the plurality of EL elements each have a first electrode, a second electrode, and an EL layer formed between the first electrode and the second electrode; and

the EL layers contain a low molecular weight organic material or an organic polymer material.

7. An electro-optical device according to claim 3, wherein the low molecular weight organic material is made from Alq3 (tris-8-quinolinolate aluminum complex) or TPD (tri-phenylamine dielectric).

9. An electro-optical device according to claim 3, wherein the organic polymer material is made from PPV (poly-paraphenylene vinylene), PVK (poly-vinyl carbazole), or polycarbonate.

11. An electro-optical device according to any of claim 1, wherein one frame period is equal to or less than 1/60 second.

14. An electro-optical device according to any of claim 1, wherein:

the electro-optical device has a memory circuit for storing correction data in order to apply a correction to a display; and

the digital video signal corrected by the memory circuit is input to a source signal side driver circuit.

17. A electro-optical device according to claim 1, wherein said electro-optical device is selected from the group consisting of a computer, a video camera and a DVD.

21. A electro-optical device according to claim 1, wherein said at least one sustain period is the shortest sustain period among sustain periods of said n subframes.

2. An electro-optical device comprising:

a plurality of EL elements; and

a plurality of pixels having the plurality of EL elements;

wherein;

one frame period comprises n subframe periods SF1, SF2, . . . , SFn;

the n subframe periods SF1, SF2, . . . , SFn have address periods Ta1, Ta2, . . . , Tan and sustain periods Ts1, Ts2, . . . , Tsn, respectively;

digital data signals in the address periods Ta1, Ta2, . . . , Tan are input to the plurality of pixels;

the plurality of EL elements are selected to emit light or not to emit light during the sustain periods Ts1, Ts2, . . . , Tsn in accordance with the digital data signals;

the brightness of the light emitted by the EL elements during at least one sustain period Tsp (where p is a natural number greater than or equal to 1, and less than or equal to n), among the sustain periods Ts1, Ts2, . . . , Tsn, is 1/m (where m is a positive number) of the brightness of the light emitted by the EL elements during an arbitrary sustain period Tsq, excepting the sustain period Tsp, and (where q is an arbitrary natural number greater than or equal to 1, and less than or equal to n, excepting p);

the length of the sustain period Tsp is expressed as 2<sup>−

(p−

1)</sup>T×

m (where T is a positive constant); and

the length of the sustain period Tsq is expressed as 2<sup>−

(q−

1)</sup>T.

4. An electro-optical device according to claim 2, wherein:

the plurality of EL elements each have a first electrode, a second electrode, and an EL layer formed between the first electrode and the second electrode; and

the EL layers contain a low molecular weight organic material or an organic polymer material.

12. An electro-optical device according to any of claim 2, wherein one frame period is equal to or less than 1/60 second.

15. An electro-optical device according to any of claim 2, wherein:

the electro-optical device has a memory circuit for storing correction data in order to apply a correction to a display; and

the digital video signal corrected by the memory circuit is input to a source signal side driver circuit.

18. A electro-optical device according to claim 2, wherein said electro-optical device is selected from the group consisting of a computer, a video camera and a DVD.

22. A electro-optical device according to claim 2, wherein said at least one sustain period Tsp is shorter than said arbitrary sustain period Tsq.

5. An electro-optical device comprising:

a plurality of EL elements; and

a plurality of pixels having the plurality of EL elements;

wherein;

one frame period comprises n subframe periods SF1, SF2, . . . , SFn;

the n subframe periods SF1, SF2, . . . , SFn have address periods Ta1, Ta2, . . . , Tan and sustain periods Ts1, Ts2, . . . , Tsn, respectively;

digital data signals in the address periods Ta1, Ta2, . . . , Tan are input to the plurality of pixels;

the plurality of EL elements are selected to emit light or not to emit light during the sustain periods Ts1, Ts2, . . . , Tsn in accordance with the digital data signals;

the brightness of the light emitted by the EL elements during at least one sustain period Tsp (where p is a natural number greater than or equal to 1, and less than or equal to n), among the sustain periods Ts1, Ts2, . . . , Tsn, is 1/m (where m is a positive number) of the brightness of the light emitted by the EL elements during an arbitrary sustain period Tsq, excepting the sustain period Tsp, and (where q is an arbitrary natural number greater than or equal to 1, and less than or equal to n, excepting p);

the length of the sustain period Tsp is expressed as 2<sup>−

(p−

1)</sup>T×

m (where T is a positive constant);

the length of the sustain period Tsq is expressed as 2<sup>−

(q−

1)</sup>T;

the plurality of EL elements each have a first electrode, a second electrode, and an EL layer formed between the first electrode and the second electrode; and

the brightness of the light emitted by the EL elements is controlled by an on EL driver voltage applied between the first electrode and the second electrode.

6. An electro-optical device according to claim 5, wherein the EL layers contain a low molecular weight organic material or an organic polymer material.

8. An electro-optical device according to claim 6, wherein the low molecular weight organic material is made from Alq3 (tris-8-quinolinolate aluminum complex) or TPD (tri-phenylamine dielectric).

10. An electro-optical device according to claim 6, wherein the organic polymer material is made from PPV (poly-paraphenylene vinylene), PVK (poly-vinyl carbazole), or polycarbonate.

13. An electro-optical device according to any of claim 5, wherein one frame period is equal to or less than 1/60 second.

16. An electro-optical device according to any of claim 5, wherein:

the electro-optical device has a memory circuit for storing correction data in order to apply a correction to a display; and

the digital video signal corrected by the memory circuit is input to a source signal side driver circuit.

19. A electro-optical device according to claim 5, wherein said electro-optical device is selected from the group consisting of a computer, a video camera and a DVD.

23. A electro-optical device according to claim 5, wherein said at least one sustain period Tsp is shorter than said arbitrary sustain period Tsq.

20. A method of driving an electro-optical device comprising a plurality of EL elements provided at a plurality of pixels, said method wherein one frame comprises n subframes, a sustain period of at least one p-th subframe is T×

2<sup>p−

1</sup>×

m, a sustain periods of the other i-th subframes is T×

2<sup>i−

1</sup>, and an intensity of light emission of said EL elements during the sustain period of the at least one p-th subframe is 1/m of an intensity of light emission during the sustain periods of i-th subframes.

24. A electro-optical device according to claim 20, wherein said sustain period of said at least one p-th subframe is shorter than the sustain periods of i-th subframes.