Method of driving organic EL device and display device
According to one aspect of the present invention, it is possible to sufficiently perform the discharging of charge without lowering the light emitting efficiency of an organic EL device and hence, the device can exhibit the light emitting efficiency higher than a conventional organic EL device and, at the same time, can prevent the degradation of the device. As an organic EL device to which the present invention is applied, on a glass transparent substrate, a transparent electrode, a hole injection layer and a hole transport layer which function as a hole transport function layer, a light emitting layer, an electron transport function layer, and a metal electrode are formed sequentially, and a drive power sources are connected to the transparent electrode and the metal electrode. Further, from the drive power source, as an applying voltage, a voltage which is obtained by overlapping any one of a sine wave, a pulse wave, a triangle wave and a sawtooth wave having two cycles or more to a drive signal or a voltage which is obtained by overlapping a sine wave having two cycles or more to the drive signal is supplied.
1. A display device which includes a drive power source for supplying a drive signal to organic EL devices which are arranged in a matrix array on respective intersecting portions of a plurality of scanning lines and a plurality of data lines, wherein
the drive power source supplies a positive and negative voltage in turn which is smaller than an absolute value of a light emitting start voltage of the organic EL device during an off period of the organic EL device,
wherein a number of pulses of the positive and negative voltage which is smaller than the absolute value of the light emitting start voltage is greater than a number of pulses of a voltage which is bigger than the absolute value of the light emitting start voltage.
2. A method of driving an organic EL device according to claim 1 , wherein the pulses of the positive and negative voltage which is smaller than the absolute value of the light emitting start voltage are in a sine wave form.
3. A method of driving an organic EL device according to claim 1 , wherein the pulses of the positive and negative voltage which is smaller than the absolute value of the light emitting start voltage are in a triangle wave form.
4. A method of driving an organic EL device according to claim 1 , wherein the pulses of the positive and negative voltage which is smaller than the absolute value of the light emitting start voltage are in an alternative DC wave form.
5. A method of driving an organic EL device according to claim 1 , wherein the pulses of the positive and negative voltage which is smaller than the absolute value of the light emitting start voltage are in a sawtooth wave form.
6. A method of driving an organic EL device according to claim 2 , wherein a peak of the sine wave form is limited.
7. A method of driving an organic EL device according to claim 6 , wherein both peaks of the sine wave form are limited.
8. A method of driving an organic EL device according to claim 6 , wherein the limited peak is a positive value.
9. A method of driving an organic EL device according to claim 6 , wherein the limited peak is a negative value.
10. A display device which includes a drive power source for supplying a drive signal to organic EL devices which are arranged in a matrix array on respective intersecting portions of a plurality of scanning lines and a plurality of data lines, wherein
the drive power source supplies a high and low voltage in turn which is smaller than a value of a light emitting start voltage of the organic EL device during an off period of the organic EL device,
wherein a number of pulses of the high and low voltage which is smaller than the value of the light emitting start voltage is bigger than the number of pulses of the voltage which is bigger than the value of the light emitting start voltage.
11. A method of driving an organic EL device according to claim 10 , wherein the pulses of the high and low voltage which is smaller than the value of the light emitting start voltage are in a sine wave form.
12. A method of driving an organic EL device according to claim 10 , wherein the pulses of the high and low voltage which is smaller than the value of the light emitting start voltage are in a triangle wave form.
13. A method of driving an organic EL device according to claim 10 , wherein the pulses of the high and low voltage which is smaller than the value of the light emitting start voltage are in an alternative DC wave form.
14. A method of driving an organic EL device according to claim 10 , wherein the pulses of the high and low voltage which is smaller than the value of the light emitting start voltage are in a sawtooth wave form.
15. A method of driving an organic EL device according to claim 11 , wherein a peak of the sine wave form is limited.
16. A method of driving an organic EL device according to claim 15 , wherein both peaks of the sine wave form are limited.
17. A method of driving an organic EL device according to claim 15 , wherein the limited peak is high value.
18. A method of driving an organic EL device according to claim 15 , wherein the limited peak is low value.