Koninklijke Philips Corporation N.v.

Tpo Hong Kong Holding Limited

Tpo Displays Corporation

Jason Roderick Hector

David Andrew Fish

Mark Johnathan Childs

Nigel David Young

Neil C Bird

Steven Charles Deane

Ian D French

Mark Jonathan Childs

Martin John Edwards

Alan G Knapp

John R Hughes

Mark Thomas Johnson

John M Shannon

Hidetoshi Watanabe

Martinus Petrus Creusen

Davud Andrew Fish

Takashi Ohmoto

An active matrix LED display has a light-dependent device for detecting the brightness of the display element and threshold voltage measurement circuitry for measuring a threshold voltage of a pixel the drive transistor. Compensation for ageing of the display element is thus provided by an optical feedback path, and compensation for drive transistor threshold variations is provided by measurement of the threshold voltage. This provides a reliable compensation scheme for the threshold voltage variations, while also providing ageing compensation.

Active matrix display device compensating for ageing of the display element and variations in drive transistor threshold voltage

An active matrix electroluminescent display device has pixels using an amorphous silicon or microcrystalline silicon drive NMOS transistor () connected between the anode of the display element () and a power supply line (). A storage capacitor () is connected between the anode of the display element and the gate of the drive transistor (). An amorphous silicon or microcrystalline silicon second drive NMOS transistor () supplies a holding voltage to the anode of the display element (). This arrangement enables the voltage across the display element to be held while the transistor gate drive voltage is stored on the storage capacitor. This enables an accurate current source pixel circuit to be implemented using NMOS transistors.

Electroluminescent display device having pixels with NMOS transistors

A method of manufacturing a color active matrix display device comprises forming islands over a rigid carrier substrate, forming a plastic substrate over the rigid carrier substrate, forming an array of pixel circuits over the plastic substrate and forming a display layer over the array of pixel circuits. The rigid carrier substrate is then released from the plastic substrate and the plastic substrate then has channels defined by the islands. These are filled to define color filter portions. The formation of a plastic substrate on a rigid carrier, with the use of a subsequent lift off process, enables the circuit arrays to be made on very thin plastic sheets. The color filters can then be made on the outside of the LC cell. Depressions are formed in the plastic substrate registered to the circuit array, and these are filled in with color filter material, for example by ink jet printing.

Colour active matrix displays

Physical barriers () are present between neighbouring pixels () on a circuit substrate () of an active-matrix electroluminescent display device, particularly with LEDs () of organic semiconductor materials. The invention forms these barriers () with metal or other electrically-conductive material () that serves as an interconnection between a first circuit element (, T, T, Tm, Tg, Ch) of the circuit substrate and a second circuit element (), for example, a sensor () of a sensor array supported over the pixel array. The conductive barrier material () is insulated () at the sides of the barriers adjacent to the LEDs and has an un-insulated top connection area () at which the second circuit element is connected to the conductive barrier material ().

Active matrix electroluminescent display devices, and their manufacture

A display device comprising an array of pixels, with gates of thin film transistors of the pixels in a row connected to a row conductor. Row driver circuitry provides row address signals for controlling the switching of the transistors of the pixels of the row including an ON gate voltage and an OFF gate voltage. Control circuitry shifts the ON gate voltage and the OFF gate voltage in dependence on drive and/or environmental conditions such as temperature and/or refresh rate. The control circuitry maintains a constant difference between the ON gate voltage and the OFF gate voltage. This allows the gap between the on and off voltages to be reduced, which results in power savings. The kickback voltage is kept constant so that kickback compensation is kept simple.

Active matrix display device

An addressing scheme is provided for a display having an array of current driven pixels. An input voltage is used for generating a desired source-drain current using a transistor operated with low duty cycle. This source-drain current is then passed through a drive transistor and the resulting gate-source voltage is stored on a capacitor for subsequent driving of the display element.

An active matrix display device uses an amorphous silicon drive transistor for driving a current through an LED display element. First and second capacitors are connected in series between the gate and source of the drive transistor, with a data input to the pixel provided to the junction between the first and second capacitors. The second capacitor is charged to a pixel data voltage, and a drive transistor threshold voltage is stored on the first capacitor. This pixel arrangement enables a threshold voltage to be stored on the first capacitor, and this can be done each time the pixel is addressed, thereby compensating for age-related changes in the threshold voltage.

Active matrix display devices

In an active matrix display, each pixel has a storage capacitor for storing a voltage to be used for addressing a drive transistor. A discharge transistor is provided for discharging the storage capacitor thereby to switch off the drive transistor. The timing of this is controlled by a light-dependent device which is illuminated by the display element. The drive transistor is controlled to provide a constant light output from the display element, and the duration is controlled in dependence on the data voltage. Optical feedback is used to alter further the timing of operation of the discharge transistor to provide ageing compensation of the display element and compensation for changes in the drive transistor.

Light emissive active matrix display devices with optical feedback effective on the timing, to counteract ageing

A display has circuitry () which generates all possible pixel drive signal levels on separate signal level lines. A buffer () is associated with each signal level line. The outputs of the buffers are selectably switchable onto the columns. The signal levels for each column are stored in a memory () and the buffers are controlled in dependence on the stored signal levels. The response of the buffers is heavily dependent on the output load, and there is a very large variation in the output load of the buffers (), as a function of the number of columns to which the buffer output is to be provided. The buffers are controlled in dependence on stored signal levels to ensure stability of the buffers for any output load.

A display device has a plurality of pixels, each having a current-driven display element coupled between a first conductive layer and a second conductive layer, the second conductive layer being coupled to a current supply via a switchable device having a thin film component on a first area of a substrate. Each pixel has a first capacitive device having a first capacitor plate on a second area of the substrate, the first capacitor plate conductively coupled to the thin film component, a second capacitor plate and a first insulating layer between the first capacitor plate and the second capacitor plate. On top of the first capacitive device is a second capacitive device sharing the second capacitor plate, the second capacitive device including a third capacitor plate sharing the second conductive layer, and a second insulating layer between the second capacitor plate and the third capacitor plate.

Active matrix pixel drive circuit for oled display

Physical barriers () are present between neighboring pixels () on a circuit substrate () of an active-matrix display device, such as an electroluminescent display formed with LEDs () of organic semiconductor materials. The invention forms at least parts of the barriers () with metal or other electrically-conductive material () that is insulated () from the LEDs but connected to the circuitry (, T, T, Tm, Tg, Ch etc.) within the substrate (). This conductive barrier material () may back up or replace, for example, matrix addressing lines () and/or form an additional component either within the pixel array or outside. The additional component comprising the conductive barrier material () is advantageously a capacitor (Ch), or an inductor (L) or transformer (W), or even an aerial.

Active matrix display devices, and their manufacture

Physical barriers () are present between neighbouring pixels () on a circuit substrate () of an active-matrix electroluminescent display device, particularly with LEDs () of organic semiconductor materials. In order to reduce parasitic capacitance in the circuit substrate, the invention forms these barriers () with metal or other electrically conductive material () that provides at least part of the signal lines () at a higher level than the circuit substrate (). This conductive barrier material () is connected to the matrix circuitry within the substrate () but is insulated () at least at the sides adjacent to the LEDs (). Preferably, an inter-capacitance guard line () is included in the circuit substrate () between the signal lines () and the circuitry in the substrate ().

Physical barriers () are present between neighbouring pixels () on a circuit substrate () of an active-matrix electroluminescent display device, particularly with LEDs () of organic semi conductor materials. The invention forms these barriers () with metal or other electrically-conductive material (), that is insulated () from the LEDs but connected to the circuitry within the substrate (). This conductive barrier material () backs-up or replaces at least a part of the drive supply line () to which the LEDs are connected by a drive element T. This transfers the problem of line resistance and associated voltage drop from within the circuit substrate (), where it is severely constrained, to the much freer environment of the pixel barriers () on the substrate () where the conductive barrier material () can provide much lower resistance. Very large displays can be made with low voltage drops along this composite drive supply line (). Furthermore, the structure can be optimised to form a smoothing capacitor (Cs) between this drive supply line () with its conductive barrier material () and the further supply line () of the LED upper electrodes () extending on an insulating coating () over the top of the conductive barrier material ().

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Redhill, United Kingdom

Jason Roderick Hector