US 5,296,870 AGranted

Matrix display devices

AssigneeU.S. Philips Corporation

InventorKeith H. Nicholas

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Abstract

A matrix display device, suitable for displaying TV pictures, has a plurality of display elements (20) arranged in a matrix array and defined by electrodes (33 and 41) on opposing substrates with, for example, liquid crystal material (32) therebetween and with the display elements being individually controllable via switching elements (40) such as thin film transistors. Each display element is sub-divided into a plurality of sub-elements using a plurality of sub-electrodes (55) on one substrate which are each connected via a series capacitor (C.sub.X) to a switching element, the ratio of capacitances of the sub-elements to their respective series capacitors differing from one another. As applied voltage is increased, progressively more sub-elements are caused to change state providing in effect various grey scale levels. Display materials having comparatively sharp switching characteristics can be used.

Claims20

Dependent claims

A matrix display device comprising a plurality of display elements arranged in a matrix and defined by respective electrodes carried on opposed substrates between which is disposed an electrically excitable display material which, together with the electrodes, exhibits inherent capacitance in operation, and in which the display elements are controlled by selectively applying voltages to the respective electrodes via respective switching means carried on one substrate,

characterized in that the display element electrodes on the one substrate each comprise a plurality of separate electrodes defining a plurality of sub-elements, which separate electrodes are each capacitively coupled to the respective switching means by means of a respective series capacitor, the series capacitors each comprising an extension of the respective sub-element electrode, the overlying portion of an extension of an output electrode of the switching means, and an intervening dielectric insulator layer, and in that the ratio of the inherent capacitance of each sub-element to the capacitance of its respective series capacitor differs from one sub-element to another;
and further characterized in that the capacitance value of each series capacitor is determined by the area of the overlying portions of the output electrode extension and the extension of the sub-element electrode.

A liquid crystal display device comprising:

a plurality of display elements arranged in a matrix and defined by respective electrodes carried on first and second opposed substrates between which is disposed an electrically excitable liquid crystal display material which, together with the electrodes, exhibit inherent capacitance, each of the display element electrodes on the first substrate comprising a plurality of separate electrodes defining a plurality of sub-elements,
a plurality of switching means on said first substrate for selectively applying DC voltages to respective ones of said separate electrodes on the first substrate in a sequential row-by-row process and in a manner whereby between row selection periods the switching means electrically isolate their respective sub-elements from any externally applied sustaining voltage, and
a plurality of capacitors each of which is serially connected with a respective one of said electrodes to a respective switching means to form with respective sub-elements a plurality of series connected capacitive voltage dividers in which the ratio of the inherent capacitance of each sub-element to the capacitance of its respective series capacitor differs from one sub-element to another thereby to establish different voltage operating thresholds for at least some of the sub-elements of each display element.

A matrix display device comprising:

a pair of spaced substrates sandwiching a layer of electrically excitable display material to produce a display effect, electrodes carried on opposing surfaces of the substrates which, together with respective portions of the layer of display material, define a plurality of display elements arranged in a matrix and which exhibit inherent capacitance in operation, the display elements being connected to respective switching means carried on one substrate and disposed laterally adjacent to respective display element electrodes on that substrate, and drive means connected to the switching means and operable to selectively control the switching means so as to apply voltage signals to the display elements thereby to produce a display effect, wherein the display element electrode on the one substrate each comprise a plurality of separate electrodes defining a plurality of display sub-elements , which separate electrodes are arranged in a planar array and are each capacitively coupled to the respective switching means via a respective series capacitor carried on that substrate, the series capacitors each comprising an extension of the respective sub-element electrode, the overlying portion of an extension of an output electrode of the switching means, and an intervening dielectric insulator layer, and in which the area of the overlying portions of the output electrode extension and the extension of the sub-element electrode for each of the series capacitors is selected in relation to the inherent capacitance of the respective sub-element such that the ratio of the inherent capacitance of each sub-element to the capacitance of its respective series capacitor differs from one sub-element to another whereby, in response to a voltage applied to a display element via the switching means, the voltage at the sub-elements differs from one sub-element to another with the number of sub-elements producing a display effect being determined in accordance with the amplitude of the applied voltage.

Dependencies are inferred from the claim text.

Facts

Application: 07/680,022Filed 28 Mar 1991 · continuation
Priority: GB 863041019 Dec 1986
Granted: 22 Mar 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H04N 3/127
By switched stationary formation of lamps, photocells or light relays: using liquid crystals
G02F 1/13624
Active matrix addressed cells: having more than one switching element per pixel
G02F 1/134345
Characterised by their geometrical arrangement: subdivided pixels, e.g. for grey scale or redundancy
G02F 1/136213
Active matrix addressed cells: storage capacitors associated with the pixel electrode