Light emitting device
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsHajime Kimura, Shunpei Yamazaki
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Abstract
In order to suppress the influence of deterioration of a light emitting element resulting from a change over time, the present invention provides a light emitting device in which an electrical circuit for flowing a constant charge between both electrodes of the light emitting element is provided in each pixel. In addition, the present invention provides a light emitting device in which a transistor provided in each pixel is operated in a linear region and used as only a switch, so that the light emitting device is not influenced by a variation in characteristic of the transistor.
Claims24
A light emitting device comprising a plurality of pixels, each having a capacitor element and a light emitting element, comprising:
- means for supplying a charge to the capacitor element until a potential difference of the capacitor element becomes equal to a power source potential Vdd;
- and
- means for supplying a charge to the light emitting element until the potential difference of the capacitor element becomes equal to a light emission start voltage Vth of the light emitting element.
A light emitting device comprising a plurality of pixels, each having a capacitor element and a light emitting element, comprising:
- means for supplying a charge to the capacitor element until a potential difference of the capacitor element becomes equal to a power source potential Vdd;
- and
- means for supplying a charge to the light emitting element until the potential difference of the capacitor element becomes equal to a light emission start voltage Vth of the light emitting element,
- wherein a proportional coefficient C of the capacitor element and a charge A flowing between both electrodes of the light emitting element satisfy A=C×(Vdd−Vth).
A light emitting device comprising a plurality of pixels, each having a capacitor element and a light emitting element, comprising:
- means for supplying a charge to a first capacitor element until a potential difference of the first capacitor element becomes equal to a power source potential Vdd;
- means for transferring a charge stored in the first capacitor element to the second capacitor element until a potential difference of the second capacitor element becomes equal to a sum of the power source potential Vdd and a light emission start voltage Vth of the light emitting element;
- and
- means for supplying a charge to the light emitting element until the potential difference of the second capacitor element becomes equal to the light emission start voltage Vth of the light emitting element.
A light emitting device comprising a plurality of pixels, each having a capacitor element and a light emitting element, comprising:
- means for supplying a charge to the first capacitor element until a potential difference of the first capacitor element becomes equal to a power source potential Vdd;
- means for transferring a charge stored in the first capacitor element to the second capacitor element until a potential difference of the second capacitor element becomes equal to a sum of the power source potential Vdd and a light emission start voltage Vth of the light emitting element;
- and
- means for supplying a charge to the light emitting element until the potential difference of the second capacitor element becomes equal to the light emission start voltage Vth of the light emitting element,
- wherein a proportional coefficient C1 and a potential difference V1 of the first capacitor element, a proportional coefficient C2 and a potential difference V2 of the second capacitor element, and a charge A flowing between both electrodes of the light emitting element satisfy A=C2×{(2×C1×Vdd)/(C1+C2)−(C1×Vth)/(C1+C2)}.
A light emitting device comprising:
- a plurality of pixels, each comprising:
- a capacitor element;
- a light emitting element;
- and
- a first switch and a second switch,
- wherein the light emitting element, the first switch and the second switch are electrically connected in series, and
- wherein an electrode of the capacitor element is disposed between the first switch and the second switch.
A light emitting device comprising:
- a plurality of pixels, each comprising:
- a first capacitor element and a second capacitor element;
- a light emitting element;
- and
- a first switch, a second switch and a third switch,
- wherein the light emitting element, the first switch, the second switch, and the third switch are electrically connected in series,
- wherein an electrode of the first capacitor element is disposed between the first switch and the second switch, and
- wherein an electrode of the second capacitor element is disposed between the second switch and the third switch.
Dependencies are inferred from the claim text.