Lighting system

• US 8,154,192 B2
• Filed: 10/12/2006
• Issued: 04/10/2012
• Est. Priority Date: 10/17/2005
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Sakata, Junichiro
• Primary Examiner(s): Le, Tung X
• Application Number:
  US11/580,200
• Publication Number:
  US 20070085070A1
• Time in Patent Office: 2,007 Days
• Field of Search: 3151691-1693, 315/291, 345 60- 63, 345 76- 77, 345 82- 84, 345/89, 345694-695, 313/500, 313/504, 313/506, 257/13
• US Class Current: 313/504
• CPC Class Codes: G09G 2320/048 using evaluation of the usage time
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/35 comprising red-green-blue [RGB] subpixels
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An object of the present invention is to provide a lighting system which uses a stacked light emitting element provided with a plurality of light emitting units and causes little change in emission color even after being used for a long time. A lighting system is provided, which includes a first light emitting element including a plurality of light emitting units; a second light emitting element; a first control means which controls light emission of the first light emitting element; and a second control means which controls light emission of the second light emitting element, where the first light emitting element emits light of a first emission color that is an initial emission color and a second emission color that is an emission color after change over time, and the second light emitting element emits light of a complementary color of the second emission color. With the above structure, color shift due to change over time can be suppressed.

Claims

1. A lighting system comprising:

a first light emitting element including;

a plurality of light emitting units formed between a first pair of electrodes; and

a charge generation layer formed between the plurality of light emitting units, wherein the plurality of light emitting units have different emission colors from each other and are electrically connected in series through the charge generation layer;

a second light emitting element comprising a light emitting unit between a second pair of electrodes, wherein emission color of the second light emitting element is substantially the same as emission color of one of the plurality of light emitting units which has the shortest lifetime among the plurality of light emitting units; and

a control circuit,

wherein the control circuit is arranged to suppress a change in total luminance of the first light emitting element and the second light emitting element by intensifying a luminance of the second light emitting element in accordance with a change in luminance of the first light emitting element.

2. A lighting system according to claim 1,

wherein the number of the light emitting units in the second light emitting element is 1.

3. A lighting system according to claim 1,

wherein the number of the light emitting units in the second light emitting element is larger than 1.

4. A lighting system according to claim 1,

wherein the first light emitting element and the second light emitting element are adjacent to each other.

5. A lighting system according to claim 1,

wherein the second light emitting element has a light emitting material, and

wherein the light emitting material is included in one of the plurality of light emitting units which has the shortest lifetime among the plurality of light emitting units.

6. A lighting system according to claim 1,

wherein the first light emitting element is arranged to emit white light.

7. A lighting system according to claim 1,

wherein the second light emitting element emits blue light.

8. A driving method of a lighting system comprising the steps of:

emitting light having a first color from a first light emitting element including;

a plurality of light emitting units formed between a first pair of electrodes; and

a charge generation layer formed between the plurality of light emitting units and being capable of electrically connecting the plurality of light emitting units to each other;

emitting light having a second color from a second light emitting element comprising a light emitting unit between a second pair of electrodes, wherein the first color is different from the second color; and

intensifying the light of the second light emitting element by a control unit in accordance with a change in luminance of the first light emitting element, allowing total luminance of the first light emitting element and the second light emitting element to be constant,

wherein the plurality of light emitting units have different emission colors from each other, and

wherein emission color of one of the plurality of light emitting units, which has the shortest lifetime among the plurality of light emitting units, is substantially the same as the second color.

9. A driving method of a lighting system according to claim 8,

wherein the number of the light emitting units in the second light emitting element is 1.

10. A driving method of a lighting system according to claim 8,

wherein the number of the light emitting units in the second light emitting element is larger than 1.

11. A driving method of a lighting system according to claim 8,

wherein the first light emitting element and the second light emitting element are adjacent to each other.

12. A driving method of a lighting system according to claim 8,

wherein the second light emitting element has a light emitting material, and

wherein the light emitting material is included in one of the plurality of light emitting units which has the shortest lifetime among the plurality of light emitting units.

13. A driving method of a lighting system according to claim 8,

wherein the first light emitting element is arranged to emit white light.

14. A driving method of a lighting system according to claim 8,

wherein the second light emitting element emits blue light.

15. A lighting system comprising:

a first light emitting element including;

a plurality of light emitting units formed between a first pair of electrodes; and

a charge generation layer formed between the plurality of light emitting units, wherein the plurality of light emitting units have different emission colors from each other and are electrically connected in series through the charge generation layer; and

a second light emitting element comprising a light emitting unit between a second pair of electrodes, and

wherein emission color of the second light emitting element is substantially the same as emission color of one of the plurality of light emitting units which has the shortest lifetime among the plurality of light emitting units.

16. A lighting system according to claim 15,

wherein the first light emitting element and the second light emitting element are adjacent to each other.

17. A lighting system according to claim 15,

wherein the first light emitting element is arranged to emit white light.

18. A lighting system according to claim 15,

wherein the second light emitting element emits blue light.

19. A lighting system according to claim 15, comprising:

a light emitting region comprising a first region and a second region which are horizontally divided with respect to a substrate, the first light emitting element is provided in the first region, and the second light emitting element is provided in the second region.

20. A lighting system according to claim 15,

wherein the number of the light emitting units in the second light emitting element is 1.