Pixel circuit with a writing period and a driving period, and driving method thereof
First Claim
1. A pixel circuit comprising:
- a light-emitting element; and
a drive thin film transistor (TFT) that supplies to the light-emitting element a first current controlling a gray scale according to luminance-current characteristics of the light-emitting element,wherein the drive TFT includes a semiconductor layer constituted by a channel region, a source region and a drain region, a gate electrode located at a top side or a bottom side of the semiconductor layer, and a back gate electrode disposed in an opposite side of the semiconductor layer to the gate electrode,wherein the drive TFT operates in a writing period so that a voltage is written between the gate electrode and the source region of the drive TFT by a second current flowing in the drive TFT and in a driving period so that the first current is supplied to the light-emitting element according to the voltage between the gate electrode and the source region of the drive TFT, andwherein different voltage levels are applied to the back gate electrode in the writing period and in the driving period so that a threshold voltage of the drive TFT in the driving period is higher than in the writing period, and thereby the second current is larger than the first current.
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Accused Products
Abstract
A pixel circuit including at least a light emitting element, and a thin film transistor that supplies to the light emitting element a first current controlling a gray scale according to luminance-current characteristics of the light emitting element, wherein the thin film transistor has a back gate electrode, at least a driving period in which the thin film transistor supplies the first current to the light emitting element, and a writing period in which a second current is written to the thin film transistor before the driving period in order to pass the first current to the thin film transistor during the driving period are included, and by changing voltages which are applied to the back gate electrode in the driving period and the writing period, current capability to a gate voltage of the thin film transistor is made to differ.
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Citations
11 Claims
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1. A pixel circuit comprising:
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a light-emitting element; and a drive thin film transistor (TFT) that supplies to the light-emitting element a first current controlling a gray scale according to luminance-current characteristics of the light-emitting element, wherein the drive TFT includes a semiconductor layer constituted by a channel region, a source region and a drain region, a gate electrode located at a top side or a bottom side of the semiconductor layer, and a back gate electrode disposed in an opposite side of the semiconductor layer to the gate electrode, wherein the drive TFT operates in a writing period so that a voltage is written between the gate electrode and the source region of the drive TFT by a second current flowing in the drive TFT and in a driving period so that the first current is supplied to the light-emitting element according to the voltage between the gate electrode and the source region of the drive TFT, and wherein different voltage levels are applied to the back gate electrode in the writing period and in the driving period so that a threshold voltage of the drive TFT in the driving period is higher than in the writing period, and thereby the second current is larger than the first current. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A driving method of a pixel circuit that includes a light-emitting element and a drive thin film transistor (TFT) that supplies to the light-emitting element a first current controlling a gray scale according to luminance-current characteristics of the light-emitting element, wherein the drive TFT includes a semiconductor layer constituted by a channel region, a source region, and a drain region, a gate electrode located at a top side or a bottom side of the semiconductor layer, and a back gate electrode disposed in an opposite side of the semiconductor layer to the gate electrode, the method comprising:
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writing a voltage between the gate electrode and the source region of the drive TFT by flowing a second current to the drive TFT during a writing period, the drive TFT supplying the first current to the light-emitting element according to the voltage between the gate electrode and the source region of the drive TFT during a driving period, and applying different voltage levels to the back gate electrode during the writing period and during the driving period so that a threshold voltage of the drive TFT in the driving period is higher than that in the writing period, and thereby the second current is larger than the first current. - View Dependent Claims (9, 10, 11)
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Specification