US 7,071,911 B2 · Light emitting device, driving method thereof and electric equipment using the light emitting device

Abstract

A light emitting device is provided which is capable of displaying a high gradation image while preventing the drive frequency of a source signal line driving circuit from increasing. One pixel has a plurality of sub-pixels each having the same area of effective light emission. Sub-frame periods in each of the sub-pixels are all used to control the gradation of the corresponding pixel. The present light emitting device can operate as follows when, for example, adopting time gradation according to binary code. A sub-frame period for a specific bit is divided into a plurality of sub-frame periods, and a sub-frame period for another bit or a period in which no image is displayed (non-display period) is interspersed between the divided sub-frame periods, not successively starting the divided sub-frame periods. In a non-display period, light emitting, elements in all of the pixels in the pixel portion do not emit light.

Claims56

Dependent claims

A light emitting device comprising:

a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a thin film transistor, an erasing gate signal line and a power supply line,
wherein each of the plurality of sub-pixels having a same area of effective light emission;
wherein the light emitting element does not emit the light when the thin film transistor is on;
wherein a gate electrode of the thin film transistor is electrically connected to the erasing gate signal line;
and
wherein one of a source region and a drain region of the thin film transistor is electrically connected to the power supply line.

6 more elements

A method of operating a light emitting device,

said light emitting device comprising:
a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, a writing gate signal line, an erasing gate signal line, and a power supply line,
wherein a gate electrode of the first thin film transistor is electrically connected to the writing gate signal line;
wherein one of a source region and a drain region of the first thin film transistor is electrically connected to the source signal line while the other thereof is electrically connected to a gate electrode of the second thin film transistor;
wherein a source region of the second thin film transistor is electrically connected to the power supply line and a drain region of the second thin film transistor is electrically connected to a pixel electrode of the light emitting element;
wherein a gate electrode of the third thin film transistor is electrically connected to the erasing gate signal line;
and
wherein one of a source region and a drain region of the third thin film transistor is electrically connected to the power supply line and the other thereof is electrically connected to the gate electrode of the second thin film transistor,
said method comprising the steps of:
selecting writing gate signal lines of the plurality of pixels in a same period;
and
controlling a period of time in which the light emitting element emits a light in each of the plurality of sub-pixels by a digital video signal inputted to the source signal line to thereby control a gradation of each of the plurality of pixels,
wherein each of the plurality of sub-pixels has a same area of effective light emission.

13 more elements

A method of operating a light emitting device,

said light emitting device comprising:
a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, an erasing gate signal line, and a power supply line,
wherein the plurality of sub-pixels in a same pixel have commonly a writing gate signal line;
wherein a gate electrode of the first thin film transistor is electrically connected to the writing gate signal line;
wherein one of a source region and a drain region of the first thin film transistor is electrically connected to the source signal line and the other thereof is electrically connected to a gate electrode of the second thin film transistor;
wherein a source region of the second thin film transistor is electrically connected to the power supply line and a drain region of the second thin film transistor is electrically connected to a pixel electrode of the light emitting element;
wherein a gate electrode of the third thin film transistor is electrically connected to the erasing gate signal line;
and
wherein one of a source region and a drain region of the third thin film transistor is electrically connected to the power supply line and the other thereof is electrically connected to the gate electrode of the second thin film transistor,
said method comprising the steps of:
selecting writing gate signal lines of the plurality of pixels in a same period;
and
controlling a period of time in which the light emitting element emits a light in each of the plurality of sub-pixels by a digital video signal inputted to the source signal line to thereby control a gradation of each of the plurality of pixels,
wherein each of the plurality of sub-pixels has a same area of effective light emission.

14 more elements

A method of operating a light emitting device,

said light emitting device comprising:
a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, a writing gate signal line, and an erasing gate signal line,
wherein the plurality of sub-pixels in a same pixel have commonly a power supply line;
wherein a gate electrode of the first thin film transistor is electrically connected to the writing gate signal line;
wherein one of a source region and a drain region of the first thin film transistor is electrically connected to the source signal line and the other thereof is electrically connected to a gate electrode of the second thin film transistor;
wherein a source region of the second thin film transistor is electrically connected to the power supply line and a drain region of the second thin film transistor is electrically connected to a pixel electrode of the light emitting element;
wherein a gate electrode of the third thin film transistor is electrically connected to the erasing gate signal line;
and
wherein one of a source region and a drain region of the third thin film transistor is electrically connected to the power supply line and the other thereof is electrically connected to the gate electrode of the second thin film transistor,
said method comprising the steps of:
selecting writing gate signal lines of the plurality of pixels in a same period;
and
controlling a period of time in which the light emitting element emits a light in each of the plurality of sub-pixels by a digital video signal inputted to the source signal line to thereby control a gradation of each of the plurality of pixels,
wherein each of the plurality of sub-pixels has a same area of effective light emission.

14 more elements

A method of operating a light emitting device,

said light emitting device comprising:
a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, and an erasing gate signal line,
wherein the plurality of sub-pixels in a same pixel have commonly a writing gate signal line and a power supply line;
wherein a gate electrode of the first thin film transistor is electrically connected to the writing gate signal line;
wherein one of a source region and a drain region of the first thin film transistor is electrically connected to the source signal line and the other thereof is electrically connected to a gate electrode of the second thin film transistor;
wherein a source region of the second thin film transistor is electrically connected to the power supply line and a drain region of the second thin film transistor is electrically connected to a pixel electrode of the light emitting element;
wherein a gate electrode of the third thin film transistor is electrically connected to the erasing gate signal line;
and
wherein one of a source region and a drain region of the third thin film transistor is electrically connected to the power supply line and the other thereof is electrically connected to the gate electrode of the second thin film transistor,
said method comprising the steps of:
selecting writing gate signal lines of the plurality of pixels in a same period;
and
controlling a period of time in which the light emitting element emits a light in each of the plurality of sub-pixels by a digital video signal inputted to the source signal line to thereby control a gradation of the respective pixels,
wherein each of the plurality of sub-pixels has a same area of effective light emission.

14 more elements

A light emitting device comprising:

a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, an erasing gate signal line, and a power supply line,
wherein the plurality of sub-pixels in a same pixel have commonly a writing gate signal line;
wherein a gate electrode of the first thin film transistor is electrically connected to the writing gate signal line;
wherein one of a source region and a drain region of the first thin film transistor is electrically connected to the source signal line and the other thereof is electrically connected to a gate electrode of the second thin film transistor;
wherein a source region of the second thin film transistor is electrically connected to the power supply line and a drain region of the second thin film transistor is electrically connected to a pixel electrode of the light emitting element;
wherein a gate electrode of the third thin film transistor is electrically connected to the erasing gate signal line;
wherein one of a source region and a drain region of the third thin film transistor is electrically connected to the power supply line and the other thereof is electrically connected to the gate electrode of the second thin film transistor;
and
wherein each of the plurality of sub-pixels has a same area of effective light emission.

9 more elements

A light emitting device comprising:

a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, a writing gate signal line, and an erasing gate signal line,
wherein the plurality of sub-pixels in a same pixel have commonly a power supply line;
wherein a gate electrode of the first thin film transistor is electrically connected to the writing gate signal line;
wherein one of a source region and a drain region of the first thin film transistor is electrically connected to the source signal line and the other thereof is electrically connected to a gate electrode of the second thin film transistor;
wherein a source region of the second thin film transistor is electrically connected to the power supply line and a drain region of the second thin film transistor is electrically connected to a pixel electrode of the light emitting element;
wherein a gate electrode of the third thin film transistor is electrically connected to the erasing gate signal line;
wherein one of a source region and a drain region of the third thin film transistor is electrically connected to the power supply line and the other thereof is electrically connected to the gate electrode of the second thin film transistor;
and
wherein each of the plurality of sub-pixels has a same area of effective light emission.

9 more elements

A light emitting device comprising:

a plurality of pixels;
each of the plurality of pixels having a plurality of sub-pixels;
and
each of the plurality of sub-pixels having a light emitting element, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, and an erasing gate signal line,
wherein the plurality of sub-pixels in a same pixel have commonly a writing gate signal line and a power supply line;
wherein a gate electrode of the first thin film transistor is electrically connected to the writing gate signal line;
wherein one of a source region and a drain region of the first thin film transistor is electrically connected to the source signal line and the other thereof is electrically connected to a gate electrode of the second thin film transistor;
wherein a source region of the second thin film transistor is electrically connected to the power supply line and a drain region of the second thin film transistor is electrically connected to a pixel electrode of the light emitting element;
wherein a gate electrode of the third thin film transistor is electrically connected to the erasing gate signal line;
wherein one of a source region and a drain region of the third thin film transistor is electrically connected to the power supply line and the other thereof is electrically connected to the gate electrode of the second thin film transistor;
and
wherein each of the plurality of sub-pixels has a same area of effective light emission.

9 more elements

Dependencies are inferred from the claim text.

Light emitting device, driving method thereof and electric equipment using the light emitting device

Life of this patent

Light emitting device, driving method thereof and electric equipment using the light emitting device

Life of this patent

Abstract

Claims56