Organic Electroluminescent Device Allowing Adjustment of Chromaticity
An object of the invention is to provide an organic electroluminescent device emitting a light at an emission chromaticity properly adjusted while the luminescence brightness is kept constant. The organic electroluminescent device according to the invention, has an organic electroluminescence element having electrodes and an organic electroluminescent layer emitting white light at a chromaticity corresponding to the drive current density formed between the electrodes, and a drive unit driving the organic electroluminescence element while supplying current and controlling the drive current and the current-applying period per unit time in response to chromaticity adjustment input. And, the drive unit controls the drive current to be a first current and the current-applying period to be a first period respectively in response to a first chromaticity adjustment input, and controls the drive current to be a second current larger than the first current and the current-applying period to be a second period shorter than the first period respectively in response to a second chromaticity adjustment input, and adjusts the emission chromaticity of the light emitted while the luminescence brightness of the organic electroluminescence element is kept almost constant. In this way, in response to the chromaticity adjustment input for adjusting emission chromaticity, it is possible to adjust the emission chromaticity corresponding to the chromaticity adjustment input by controlling the drive current to the organic light-emitting element while keeping the luminescence brightness almost constant by adjusting the current-applying period per unit time according to the control of the drive current, thereby the light emission is adjusted to a desired emission chromaticity without change in luminescence brightness.
1 . An organic electroluminescent device, comprising:
an organic electroluminescence element having electrodes, and, formed between the electrodes, an organic electroluminescent layer emitting white light at a chromaticity corresponding to a drive current density; and
a drive unit driving the organic electroluminescence element by application of current and controlling the drive current and the current-applying period per unit of time according to a chromaticity adjustment input, wherein
in response to a first chromaticity adjustment input the drive unit controls, respectively, the drive current to be a first current and the current-applying period to be a first period, and in response to a second chromaticity adjustment input the drive unit controls, respectively, the drive current to be a second current larger than the first current and the current-applying period to be a second period shorter than the first period.
2 . An organic electroluminescent device, comprising:
an organic electroluminescence element having electrodes, and formed between the electrodes an organic electroluminescent layer emitting white light at a chromaticity corresponding to a drive current density; and
a drive unit driving the organic electroluminescence element at a particular drive voltage and controlling the drive voltage and the voltage-applying period per unit time in response to a chromaticity adjustment input, wherein
in response to a first chromaticity adjustment input the drive unit controls, respectively, the drive current to be a first current and the voltage-applying period to be a first period, and in response to a second chromaticity adjustment input controls, respectively, the drive current to be a second current larger than the first current and the voltage-applying period to be a second period shorter than the first period.
3 . The organic electroluminescent device according to claim 1 , wherein the organic electroluminescent layer emits light of multiple emission colors that enable white luminescence in combination.
4 . The organic electroluminescent device according to claim 3 , wherein the organic electroluminescent layer emits lights of red, blue, and green simultaneously.
5 . The organic electroluminescent device according to claim 3 , wherein the organic electroluminescent layer comprises red, blue, and green light-emitting layers.
6 . The organic electroluminescent device according to claim 3 , wherein the organic electroluminescent layer comprises a red light-emitting layer and a blue and green light-emitting layer.
7 . The organic electroluminescent device according to claim 3 , wherein the organic electroluminescent layer comprises a red and blue light-emitting layer and a green light-emitting layer.
8 . The organic electroluminescent device according to claim 3 , wherein the organic electroluminescent layer comprises a red and green light-emitting layer and a blue light-emitting layer.
9 . The organic electroluminescent device according to any one of claim 4 , wherein the organic electroluminescent layer comprises a hole-transporting layer and an electron-transporting layer, both layers being provided in contact with the electrodes.
10 . The organic electroluminescent device according to claim 1 , wherein the drive unit comprises a current source, a drive switch connecting the current source to the organic electroluminescence element, a current-controlling circuit controlling the current of the current source in response to the chromaticity adjustment input, and a driving time-controlling circuit controlling the connection period of the drive switch in response to the chromaticity adjustment input.
11 . The organic electroluminescent device according to claim 2 , wherein the drive unit comprises a voltage source, a drive switch connecting the voltage source to the organic electroluminescence element, a voltage-controlling circuit controlling the voltage of the voltage source in response to the chromaticity adjustment input, a driving time-controlling circuit controlling the connection period of the drive switch in response to the chromaticity adjustment input.
12 . A liquid crystal display device, comprising: the organic electroluminescent device of claim 1 , as a backlight unit; and a liquid crystal layer formed on the organic electroluminescent device.