Global Oled Technology LLC

Eastman-kodak Company

Kazuyoshi Kawabe

Seiichi Mizukoshi

Makoto Kohno

Kouichi Onomura

Nobuyki Mori

An EL light-emitting element is driven digitally to reduce power consumption using a pixel having three transistors and two capacitors. A reset transistor for diode connection writes the threshold voltage of the drive transistor onto a coupling capacitor. The data voltage plus threshold voltage is then written onto the gate of the drive transistor. This reduces the amplitude of the data voltage required, further reducing power consumption.

Display panel

To alleviate an afterimage phenomenon caused by a hysteresis characteristic of a drive transistor. Current driven type light emitting elementsare provided for each of pixelsthat are arranged in a matrix shape, and current of the light emitting elementsis controlled using drive TFTsthat operate by receiving data voltage on a gate. At least two power supply voltages (PVDDa, PVDDb) for supply to each pixel are provided, one being set to a voltage such that current corresponding to a data voltage flows in the drive TFT, the other being set to a voltage beyond a variation range of data voltage and that reverse biases the drive TFT, and the two power supply voltages are switched and supplied to each pixel

Display device

Electroluminescent display panel with reduced power consumption

To reduce the number of sub-frames and perform high resolution display with low power consumption, each of the pixels has a digital emission period Td and an analog emission period Ta, and is driven in a time-divided fashion in a digital manner or in an analog manner. Each of the pixels performs high resolution display when being driven in an analog manner, and performs display with low power consumption when being driven in a digital manner.

Electroluminescent display device with combined analog and digital driving

[Problem to be solved] Obtain a constitution for a data driver which does not easily affected by transistor characteristics. [Solution] A plurality of coupling capacitancesis connected to data enable lines which is equipped to at least two set potentials. A plurality of bit transistorswhich is turned on and off in accordance with the display data of a plurality of bits controls the relation of connection between a plurality of coupling capacitances and data enable lines to control the total capacitance of the said plurality of coupling capacitances. Display element operates in accordance with the voltage accumulated to the total capacitance of the said coupling capacitance according to the difference between the two set potentials equipped to the data enable line. By the operations above, a display is controlled by multi-bit display data per each pixel.

Pixel circuit and display device

A display device which effectively reduces the occurrences of a false contour is provided. A driver digitally drives each pixel by obtaining a plurality of bit data from pixel data for one pixel to assign the plurality of bit data to a corresponding subframe; configuring one frame with a predetermined number of unit frames; and supplying corresponding bit data in each unit frame to each pixel. Specifically, an analyzing circuit-predicts a probability of occurrence of a false contour in one screen of the video signal based on the presence or absence of a true contour. A display method based on the video signal is set in accordance with an analysis result.

In order to efficiently execute threshold value compensation for a driving transistor, a coupling capacitor has one end connected to a data line. Another end of the coupling capacitor is connected to a selection transistor and one end of a reset transistor. A control terminal of a driving transistor is connected to the other end of the selection transistor, and an organic EL element is connected to this driving transistor via a light emission control transistor. A data voltage, corresponding to a gradation signal supplied to the data line, is written to a storage capacitor via the coupling capacitor, and with the selection transistor and the light emission control transistor in an off state and the reset transistor turned on, a compensation voltage corresponding to a degree of mobility of the driving transistor is written to the coupling capacitor.

Display device with compensation for variations in pixel transistors mobility

In order to efficiently execute threshold value compensation for a driving transistor, a coupling capacitor () has one end connected to a data line (). Another end of the coupling capacitor () is connected to a selection transistor () and one end of a reset transistor (). A control terminal of a driving transistor () is connected to the other end of the selection transistor (), and an organic EL element () is connected to this driving transistor via a light emission control transistor (). A data voltage, corresponding to a gradation signal supplied to the data line (), is written to a storage capacitor () via the coupling capacitor (), and with the selection transistor () and the light emission control transistor () in an off state and the reset transistor () turned on, a compensation voltage corresponding to a degree of mobility of the driving transistor () is written to the coupling capacitor ().

Display device using capacitor coupled light emission control transistors for mobility correction

A pixel circuit for an electroluminescent element with a first storage capacitor formed overlapping a data line and which comprises a section where a semiconductor thin film constituting the switching transistor or the reset transistor extends, an insulating film, and a metal layer which is connected to the data line as a first terminal. A first terminal of a switching transistor and a first terminal of a reset transistor are connected to the second terminal of the first storage capacitor. The second terminal of the switching transistor is connected to a driving transistor. A second storage capacitor connects the control terminal and the first terminal of the switching transistor. The electroluminescent element is connected to the second terminal of the driving transistor through a light emission controlling transistor.

Pixel circuit

A display device, includes an active matrix display array including pixel circuits arranged in a matrix of columns and rows, each pixel circuit having a current-driven diode emissive element, and a plurality of thin film transistors for controlling the diode emissive element; a data line provided corresponding to each column of the matrix for supplying a data signal to a pixel circuit in the corresponding column; a data driver for controlling supply of the data signal to the data line; a select line provided corresponding to each row of the matrix for supplying a select signal to the pixel circuit in the corresponding row; and a gate driver for supplying the select signal to the select line; wherein the data signal is a digital signal indicating '1' or '0' as to whether or not to supply ON or drive current to the diode emissive element.

Emissive display device driven in subfield mode and having precharge circuit

An organic EL display device capable of preventing generation of pseudo contours is provided. Digital data of pixels in one frame is stored in a frame memory, and display is performed according to the stored digital data. One frame is divided into a plurality of unit frames, each of which is divided into a plurality of sub-frames. In each of the sub-frames, display is performed for a bit corresponding to the digital data.

EL display device for reducing pseudo contour

A pixel circuit includes an organic EL element includes a storage capacitor charged with a data voltage; a first driving transistor responsive to charged voltage of the storage capacitor to supply drive current to the organic EL element; and a second driving transistor connected the storage capacitor and a predetermined power supply responsive to potential corresponding to a voltage drop in the organic EL element, and supplies charge current to the storage capacitor, circuitry for causing the second driving transistor to supply charge current to the storage capacitor from a time when the storage capacitor is charged with data voltage and the drive current from first driving transistor flows through the organic EL element. When drive current from the first driving transistor is stopped by changes in the charged voltage of storage capacitor, the drive current supplied to the organic EL element for a period corresponding to the data voltage.

Pixel drive circuit for organic EL display

An active matrix type display device includes array having pixel circuits arranged in rows and columns matrix form, each pixel circuit includes a current-driven diode type light-emitting element and a plurality of thin-film transistor for controlling the diode type light-emitting element; a data line provided for each column of the matrix for supplying a data signal to the pixel circuits on the corresponding column; data driver for controlling the supply of the data signal to the data line; a gate line provided for each row of the matrix for supplying a selection signal to pixel circuits on the corresponding row; a gate driver for supplying a selection signal to the gate line; and a control circuit for controlling the data driver and gate driver, wherein the data driver switches a plurality of sets of video signals alternately and supplies the video signals to the data line.

During image display, pixel current measurement for brightness irregularity correction is carried out. Display is carried out by sequentially writing pixel data in a horizontal direction to pixel sections that are arranged in a matrix shape. Horizontal power supply lines PVDD are arranged for each horizontal line, and power is supplied from these power supply lines to corresponding pixel sections. When carrying out measurement of pixel current by lighting pixel sections one at a time, a horizontal power supply line PVDD of a horizontal line to which the lit pixel belongs is connected to a power supply PVDDb by a switch, and other horizontal power supply lines PVDD are connected to PVDDa.

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Yokohama, Japan

Kazuyoshi Kawabe