Light emitting device and drive method thereof
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsAya Anzai, Mitsuaki Osame, Yoshifumi Tanada, Keisuke Miyagawa, Satoshi Seo, Shunpei Yamazaki
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Abstract
The reliability of an EL element is enhanced while the increase of the electric power consumption is suppressed. It becomes possible that in a SES drive, the reverse bias is applied to the EL element driven at a constant electric current. Moreover, the application of the reverse bias is performed by varying only the counter electrode, and thus withstand voltage of TFT and the increase of the electric power consumption due to the increase of voltage of the gate signal line drive circuit, which becomes a problem when changing greatly the electric current supplying line, can be suppressed.
Claims10
A method of driving a light emitting device having a plurality of pixels in which light emitting elements have been provided and performing a gradation by controlling a difference between light emitting times of said light emitting elements, comprising:
- performing a writing of a picture signal in at least one of said plurality of pixels,
- making at least one of said light emitting elements provided in said at least one of said plurality of pixels in a light emitting state or in a non-light emitting state based on said written picture signal,
- subsequently forcibly making said at least one of said light emitting elements into a non-light emitting state, and
- applying reverse bias voltage V2 whose polarity is inversed between a first electrode and a second electrode of said at least one of said light emitting elements with respect to forward bias voltage V1 applied between the first electrode and the second electrode of said at least one of said light emitting elements when said at least one of said light emitting elements emits, wherein an expression of |V1|≧|V2| is held.
A method of driving a light emitting device having a plurality of pixels in which light emitting elements have been provided and performing a gradation by controlling the difference between light emitting times of said light emitting elements, wherein one frame period has n pieces (n is a natural number, 2<n) of subframe periods, each piece of said subframe periods has an address period in which a picture signal is written in at least one of said plurality of pixels and a sustain period in which display is performed by controlling the light emitting or non-light emitting state of at least one of said light emitting elements provided in said at least one of said plurality of pixels based on the picture signal written in said at least one of said plurality of pixels, respectively,
- m pieces (m is a natural number, 0<m≦n−1) of subframe periods selected from said n pieces of subframe periods have m pieces of reset periods in which writing of a reset signal is performed in a pixel after said sustain period has been completed and do not overlap with each other, and m pieces of blanking periods in which state of said at least one of said light emitting elements is forcibly made into a non-light emitting state in a line in which a reset signal is written and said blanking periods do not overlap with each other, respectively,
- k pieces (k is a natural number, 0<k≦m) of subframe periods selected from said m pieces of subframe periods have k pieces of reverse bias application periods in which reverse bias voltage V2 whose polarity is inversed is applied with respect to forward bias voltage V1 applied between a first electrode and a second electrode of said at least one of said light emitting elements when said at least one of said light emitting elements emits and said reverse bias application periods do not:
- overlap with each other, respectively,
- said address period, said sustain period, said reset period, said blanking period, and said reverse bias application period have a period whose one portion is overlapped with each other, respectively,
- wherein an expression of |V1|≧|V2| is held.
Dependencies are inferred from the claim text.