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US 7,030,847 B2Granted
Light emitting device and electronic device
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorHajime Kimura
Life of this patent
Estimating the term…
Abstract
A TFT for controlling the amount of current flowing into a power supply line when an EL element does not emit light (electric discharge TFT) is provided in each pixel. When an EL driving TFT is turned ON to make an EL element emit light, the electric discharge TFT is turned OFF. On the other hand, the electric discharge TFT is turned ON when the EL driving TFT is turned OFF and no EL element emit light. Therefore variation of the difference in electric potential over the length of a power supply line depending on an image to be displayed is contained. Thus reduced is the difference in amount of current flowing into EL elements in adjacent pixels while the EL elements emit light, thereby avoiding crosstalk.
Claims99
A light emitting device comprising a plurality of pixels electrically connected to a power supply line, each of the plurality of pixels comprising:
- an EL driving TFT;
- an electric discharge TFT;
- an EL element;
- a reference power supply line;
- a switching TFT;
- a source signal line,
- wherein a source region of the EL driving TFT is electrically connected to the power supply line and a drain region of the EL driving TFT is electrically connected to a pixel electrode of the EL element, and
- wherein a drain region of the electric discharge TFT is electrically connected to the power supply line and a source region of the electric discharge TFT is electrically connected to the reference power supply line, and
- wherein a gate electrode of the electric discharge TFT is electrically connected to a gate electrode of the EL driving TFT, and
- wherein a gate electrode of the EL driving TFT is electrically connectable to the source signal line through the switching TFT.
7 more elements
A light emitting device comprising a plurality of pixels electrically connected to a power supply line, each of the plurality of pixels comprising:
- an EL driving TFT;
- an electric discharge TFT;
- an EL element;
- a reference power supply line;
- and
- a source signal line,
- wherein a source region of the EL driving TFT is electrically connected to the power supply line and a drain region of the EL driving TFT is electrically connected to a pixel electrode of the EL element,
- wherein a drain region of the electric discharge TFT is electrically connected to the power supply line and a source region of the electric discharge TFT is electrically connected to the reference power supply line,
- wherein a gate electrode of the EL driving TFT is electrically connected to a gate electrode of the electric discharge TFT, and
- wherein the polarity of the EL driving TFT is different from the polarity of the electric discharge TFT, and
- wherein a signal can be applied to the gate electrode of the EL driving TFT from the source signal line.
8 more elements
A light emitting device comprising a plurality of pixels electrically connected to a power supply line, each of the plurality of pixels comprising:
- an EL driving TFT;
- an electric discharge TFT;
- an EL element;
- and
- a reference power supply line,
- wherein the EL driving TFT controls the amount of a current supplied from the power supply line the to the EL element, and
- wherein the electric discharge TFT controls the amount of a current supplied from the power supply line to the reference power supply line when the EL driving TFT is turned OFF.
4 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- a plurality of switching TFTs;
- a source signal line,
- wherein a source region, of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a gate electrode of each of the plurality of electric discharge TFTs are electrically connected to a gate electrode of each of the plurality of EL driving TFTs,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein each of the plurality of electric discharge TFTs is turned OFF when each the plurality of EL elements emits light, and
- wherein a gate electrode of one of the EL driving TFTs is electrically connectable to the source signal line through one of the switching TFTs.
10 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- a plurality of switching TFTs;
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a gate electrode of each of the plurality of electric discharge TFTs are electrically connected to a gate electrode of each of the plurality of EL driving TFTs,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs when each of the plurality of EL elements emits light,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein each of the plurality of electric discharge TFTs is turned OFF when each the plurality of EL elements emits light, and
- wherein a gate electrode of one of the EL driving TFTs is electrically connectable to the source signal line through one of the switching TFTs.
11 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- and
- a power supply line;
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light, and
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the drain region to the source region if a current flow direction through the plurality of EL driving TFTs is from the source region to the drain region, and a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the source region to the drain region if a current flow direction through the plurality of EL driving TFTs is from the drain region to the source region.
8 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- and
- a power supply line;
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the drain region to the source region if a current flow direction through the plurality of EL driving TFTs is from the source region to the drain region, and a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the source region to the drain region if a current flow direction through the plurality of EL driving TFTs is from the drain region to the source region, and
- wherein the amount of the current flowing through the channel formation region of each of the plurality of EL driving TFTs is the same as the amount of current flowing through the channel formation region of each of the plurality of electric discharge TFTs.
9 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein each of the plurality of electric discharge TFTs is turned OFF when each the plurality of EL elements emits light, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
10 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein the polarity of the plurality of EL driving TFTs is different from the polarity of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein each of the plurality of electric discharge TFTs is turned OFF when each the plurality of EL elements emits light, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
11 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light, and
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
10 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the drain region to the source region if a current flow direction through the plurality of EL driving TFTs is from the source region to the drain region, and a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the source region to the drain region if a current flow direction through the plurality of EL driving TFTs is from the drain region to the source region, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
11 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light,
- wherein a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the drain region to the source region if a current flow direction through the plurality of EL driving TFTs is from the source region to the drain region, and a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the source region to the drain region if a current flow direction through the plurality of EL driving TFTs is from the drain region to the source region, and
- wherein the amount of the current flowing through the channel formation region of each of the plurality of EL driving TFTs is the same as the amount of current flowing through the channel formation region of each of the plurality of electric discharge TFTs, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
12 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein the polarity of the plurality of EL driving TFTs is different from the polarity of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light, and
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
11 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein the polarity of the plurality of EL driving TFTs is different from the polarity of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light, and
- wherein a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the drain region to the source region if a current flow direction through the plurality of EL driving TFTs is from the source region to the drain region, and a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the source region to the drain region if a current flow direction through the plurality of EL driving TFTs is from the drain region to the source region, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
12 more elements
A light emitting device comprising:
- a plurality of EL driving TFTs;
- a plurality of electric discharge TFTs;
- a plurality of EL elements;
- a power supply line;
- and
- a source signal line,
- wherein a source region of each of the plurality of EL driving TFTs and a drain region of each of the plurality of electric discharge TFTs are electrically connected to the power supply line,
- wherein a pixel electrode of each of the plurality of EL elements is electrically connected to a drain region of each of the plurality of EL driving TFTs,
- wherein a predetermined electric potential is applied to a source region of each of the plurality of electric discharge TFTs,
- wherein a gate electrode of each of the plurality of EL driving TFTs is electrically connected to a gate electrode of each of the plurality of electric discharge TFTs,
- wherein the polarity of the plurality of EL driving TFTs is different from the polarity of the plurality of electric discharge TFTs,
- wherein a current flows through a channel formation region of each of the plurality of EL driving TFTs and each of the plurality of electric discharge TFTs is turned OFF when each of the plurality of EL elements emits light,
- wherein a current flows through a channel formation region of each of the plurality of electric discharge TFTs when each of the plurality of EL elements does not emit light,
- wherein a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the drain region to the source region if a current flow direction through the plurality of EL driving TFTs is from the source region to the drain region, and a current flow direction through the plurality of electric discharge TFTs in it's ON state is from the source region to the drain region if a current flow direction through the plurality of EL driving TFTs is from the drain region to the source region, and
- wherein the amount of the current flowing through the channel formation region of each of the plurality of EL driving TFTs is the same as the amount of current flowing through the channel formation region of each of the plurality of electric discharge TFTs, and
- wherein a signal can be applied to the gate electrode of each of the plurality of EL driving TFTs from the source signal line.
13 more elements
A light emitting device comprising a plurality of pixels electrically connected to a power supply line, each of the plurality of pixels comprising:
- an EL driving TFT;
- an electric discharge TFT;
- and
- an EL element,
- wherein a source region of the EL driving TFT is electrically connected to the power supply line and a drain region of the EL driving TFT is electrically connected to a pixel electrode of the EL element,
- wherein a drain region of the electric discharge TFT is electrically connected to the power supply line and a source region of the electric discharge TFT is electrically connected to a reference power supply line,
- wherein a gate electrode of the EL driving TFT is electrically connected to a gate electrode of the electric discharge TFT, and
- wherein the polarity of the EL driving TFT is different from the polarity of the electric discharge TFT.
5 more elements
Dependencies are inferred from the claim text.