Lighting system

• US 20070085070A1
• Filed: 10/12/2006
• Published: 04/19/2007
• 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
• Granted Patent: US 8,154,192 B2
• Time in Patent Office: Days
• US Class Current: 257/13
• 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;

a second light emitting element;

a first control circuit which controls light emission of the first light emitting element; and

a second control circuit which controls light emission of the second light emitting element,

wherein the first light emitting element emits light having a first emission color at a start of light emission and light having a second emission color after change over time, and

wherein the second light emitting element emits light having a complementary color of the second emission color.

7. A lighting system according to claim 1, wherein the second light emitting element comprises one light emitting unit.

13. A lighting system according to claim 1, wherein the second light emitting element comprises a plurality of light emitting units.

19. A lighting system according to claim 1, wherein the first light emitting element and the second light emitting element are adjacent to each other.

2. A lighting system comprising:

a first light emitting element including a plurality of light emitting units;

a second light emitting element;

a first control circuit which controls light emission of the first light emitting element; and

a second control circuit which controls light emission of the second light emitting element,

wherein the second light emitting element comprises a light emitting unit formed of the same material as that of a light emitting unit having short life among the plurality of light emitting units of the first light emitting element.

8. A lighting system according to claim 2, wherein the second light emitting element comprises one light emitting unit.

14. A lighting system according to claim 2, wherein the second light emitting element comprises a plurality of light emitting units.

20. A lighting system according to claim 2, wherein the first light emitting element and the second light emitting element are adjacent to each other.

3. A lighting system comprising:

a first light emitting element including a plurality of light emitting units;

a second light emitting element; and

a control circuit which controls light emission of the second light emitting element in accordance with a change in emission color of the first light emitting element,

wherein the first light emitting element emits light having a first emission color at a start of light emission and light having a second emission color after change over time, and

wherein the second light emitting element emits light having a complementary color of the second emission color.

9. A lighting system according to claim 3, wherein the second light emitting element comprises one light emitting unit.

15. A lighting system according to claim 3, wherein the second light emitting element comprises a plurality of light emitting units.

21. A lighting system according to claim 3, wherein the first light emitting element and the second light emitting element are adjacent to each other.

4. A lighting system comprising:

a first light emitting element including a plurality of light emitting units;

a second light emitting element; and

a control circuit which controls light emission of the second light emitting element in accordance with a change in emission color of the first light emitting element,

wherein the second light emitting element comprises a light emitting unit formed of the same material as that of a light emitting unit having short life among the plurality of light emitting units of the first light emitting element.

10. A lighting system according to claim 4, wherein the second light emitting element comprises one light emitting unit.

16. A lighting system according to claim 4, wherein the second light emitting element comprises a plurality of light emitting units.

22. A lighting system according to claim 4, wherein the first light emitting element and the second light emitting element are adjacent to each other.

5. A lighting system comprising:

a first light emitting element including a plurality of light emitting units;

a second light emitting element; and

a control circuit,

wherein the control circuit suppresses 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 from a first luminance at a start of light emission to a second luminance after change over time.

11. A lighting system according to claim 5, wherein the second light emitting element comprises one light emitting unit.

17. A lighting system according to claim 5, wherein the second light emitting element comprises a plurality of light emitting units.

23. A lighting system according to claim 5, wherein the first light emitting element and the second light emitting element are adjacent to each other.

6. A lighting system comprising:

a first light emitting element including a plurality of light emitting units;

a second light emitting element; and

a control circuit,

wherein the control circuit adjusts a luminance of the second light emitting element after t hours so as to satisfy Formula (1) when a luminance of the first light emitting element at a start of light emission is denoted by L_total(0), a luminance of the first light emitting element after t hours by L_total(t), an amount of change in luminance of a monitor element between at a start of light emission and after t hours by Δ

L_mon, and the luminance of the second light emitting element after t hours by Δ

L₂,

Δ

L₂=L_total(0)−

L_total(t)−

α

·

Δ

L_mon(1)

where α

is a factor with respect to luminance of the monitor element.

12. A lighting system according to claim 6, wherein the second light emitting element comprises one light emitting unit.

18. A lighting system according to claim 6, wherein the second light emitting element comprises a plurality of light emitting units.

24. A lighting system according to claim 6, wherein the first light emitting element and the second light emitting element are adjacent to each other.

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

emitting light having a first emission color from a first light emitting element including a plurality of light emitting units at a start of light emission;

emitting light having a second emission color from the first light emitting element after change over time; and

emitting light having a complementary color of the second emission color from a second light emitting element,

wherein a control circuit controls light emission of the second light emitting element in accordance with a change in the first emission color and the second emission color of the first light emitting element.

27. A driving method of a lighting system according to claim 25, wherein the second light emitting element comprises one light emitting unit.

29. A driving method of a lighting system according to claim 25, wherein the second light emitting element comprises a plurality of light emitting units.

31. A driving method of a lighting system according to claim 25, wherein the first light emitting element and the second light emitting element are adjacent to each other.

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

emitting light having a first emission color from a first light emitting element including a plurality of light emitting units at a start of light emission;

emitting light having a second emission color from the first light emitting element after change over time; and

emitting light having a complementary color of the second emission color from a second light emitting element,

wherein a control circuit suppresses a change in total luminance of the first light emitting element and the second light emitting element by intensifying the light of the second light emitting element in accordance with a change in luminance of the first light emitting element from a first luminance at the start of light emission to a second luminance after the change over time.

28. A driving method of a lighting system according to claim 26, wherein the second light emitting element comprises one light emitting unit.

30. A driving method of a lighting system according to claim 26, wherein the second light emitting element comprises a plurality of light emitting units.

32. A driving method of a lighting system according to claim 26, wherein the first light emitting element and the second light emitting element are adjacent to each other.