Light emitting device using organic electroluminescent element

• US 20060290623A1
• Filed: 06/22/2006
• Published: 12/28/2006
• Est. Priority Date: 06/22/2005
• Status: Abandoned Application

• Current Assignee: Kabushiki Kaisha Toyota Jidoshokki
• Original Assignee: Kabushiki Kaisha Toyota Jidoshokki
• Inventors: Okabe, Takanori, Miura, Hiroyuki, Ito, Hironori, Iwata, Hiromu, Noritake, Kazuto
• Application Number:
  US11/473,841
• Publication Number:
  US 20060290623A1
• Time in Patent Office: Days
• US Class Current: 345/82
• 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: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light emitting device (10) may comprise a constant current source (12), a first organic electroluminescent element (16), switches (14, 20), and a second organic electroluminescent element (18). The first organic electroluminescent element (16) may be connected to the constant current source (12). The switches (14, 20) may switch the direction of a voltage applied from the constant current source (12) to the first electroluminescent element (16). The second organic electroluminescent element (18) may be connected in parallel with the first organic electroluminescent element (16). When reverse voltage is applied to the first organic electroluminescent element (16), electric current from the constant current source (12) flows to the second organic electroluminescent element (18) and the second organic electroluminescent element (18) generates an electric potential.

Claims

1. A light emitting device comprising:

a constant current source,

a first organic electroluminescent element connected to the constant current source,

switches that switch the direction of a voltage applied from the constant current source to the first electroluminescent element, and

an electric potential difference generating means connected in parallel with the first organic electroluminescent element, wherein when reverse voltage that extinguishes the first organic electroluminescent element is applied to the first organic electroluminescent element, electric current from the constant current source flows to the electric potential difference generating means and the electric potential difference generating means generates an electric potential difference.

2. A light emitting device according to claim 1, wherein the electric potential difference generating means comprises a second organic electroluminescent element, wherein an anode of the second organic electroluminescence element is connected to a cathode of the first organic electroluminescence element, and wherein a cathode of the second organic electroluminescence element is connected to an anode of the first organic electroluminescence element.

3. A light emitting device according to claim 1, wherein the electric potential difference generating means comprises a resistor.

4. A light emitting device according to claim 3, wherein the electric potential difference generating means further comprises a diode connected in series with the resistor, wherein an anode of the diode is connected to a cathode of the first organic electroluminescence element via the resistor, and wherein a cathode of the diode is connected to an anode of the first organic electroluminescence element.

5. A light emitting device according to claim 3, wherein the electric potential difference generating means further comprises a diode connected in series with the resistor, wherein an anode of the diode is connected to a cathode of the first organic electroluminescence element, and wherein a cathode of the diode is connected to an anode of the first organic electroluminescence element via the resistor.

6. A light emitting device comprising:

a plurality of organic electroluminescent elements,

a constant current source connected to each of the plurality of organic electroluminescent elements, the constant current source supplying electric current to each of the plurality of organic electroluminescent elements, and

a lighting control circuit for switching the lighting and extinguishing of each of the plurality of organic electroluminescent elements,

wherein each organic electroluminescent element is applied reverse voltage, during at least a portion of the time period in which each organic electroluminescent element is extinguished, by using forward voltage applied to another lit organic electroluminescent element.

7. A light emitting device according to claim 6, wherein two of the plurality of organic electroluminescent elements form a light emitting unit in which the two organic electroluminescent elements are connected in parallel,

wherein an anode of one of the organic electroluminescent elements of the light emitting unit is connected to a cathode of the other organic electroluminescent element, and a cathode of the one organic electroluminescent element is connected to an anode of the other organic electroluminescent element, and

wherein the lighting control circuit switches the direction of the voltage applied from the constant current source to the light emitting unit.

8. A display device comprising:

a liquid crystal panel comprising a plurality of pixels and an image signal output circuit that outputs image signals to each pixel on each main scanning line, and

a light emitting device arranged on the rear side of the liquid crystal panel in order to illuminate the liquid crystal panel, the light emitting device comprising a plurality of organic electroluminescent elements, a constant current source that supplies electric current to each of the plurality of organic electroluminescent elements, and a lighting control circuit that switches the lighting and extinguishing of the plurality of organic electroluminescent elements,

wherein each organic electroluminescent element is applied reverse voltage, during at least a portion of the time period in which each organic electroluminescent element is extinguished, by using forward voltage applied to another lit organic electroluminescent element, and

wherein the lighting control circuit (1) extinguishes the organic electroluminescent elements corresponding to one main scanning line of the liquid crystal panel to which the data is output while image signals are output to each pixel on the one main scanning line, and (2) lights the organic electroluminescent elements corresponding to the main scanning line at a predetermined timing after the output of the image signals to the main scanning line is completed.

9. A display device according to claim 8, wherein each organic electroluminescent element extends in a direction parallel to the main scanning line, and wherein the plurality of organic electroluminescent elements are aligned in a direction perpendicular to the main scanning line.

10. A display device comprising:

a plurality of organic electroluminescent elements,

a liquid crystal panel arranged on the front side of the plurality of electroluminescent elements, the liquid crystal panel comprising a plurality of pixels and an image signal output circuit that outputs image signals to each pixel on each main scanning line of the liquid crystal panel, wherein each pixel display an image via light from the plurality of organic electroluminescent elements,

a lighting control circuit that switches the lighting and extinguishing of the plurality of organic electroluminescent elements, and

a directional transparent member arranged on the front side of the liquid crystal panel, the directional transparent member directing the light from the organic electroluminescent elements through each pixel,

wherein each organic electroluminescent elements extends in a direction perpendicular to the main scanning line of the liquid crystal panel, wherein the plurality of organic electroluminescent elements are aligned in a direction parallel to the main scanning line of the liquid crystal panel, and

wherein the lighting control circuit (1) lights some of the plurality of the organic electroluminescent elements and extinguishes the remainder, and (2) applies reverse voltage to the extinguished organic electroluminescent elements, during at least a portion of the period in which the organic electroluminescent elements are extinguished, by using forward voltage applied to the other lit organic electroluminescent elements.