|Número de publicación||WO1995012144 A1|
|Tipo de publicación||Solicitud|
|Número de solicitud||PCT/CA1993/000468|
|Fecha de publicación||4 May 1995|
|Fecha de presentación||29 Oct 1993|
|Fecha de prioridad||29 Oct 1993|
|Número de publicación||PCT/1993/468, PCT/CA/1993/000468, PCT/CA/1993/00468, PCT/CA/93/000468, PCT/CA/93/00468, PCT/CA1993/000468, PCT/CA1993/00468, PCT/CA1993000468, PCT/CA199300468, PCT/CA93/000468, PCT/CA93/00468, PCT/CA93000468, PCT/CA9300468, WO 1995/012144 A1, WO 1995012144 A1, WO 1995012144A1, WO 9512144 A1, WO 9512144A1, WO-A1-1995012144, WO-A1-9512144, WO1995/012144A1, WO1995012144 A1, WO1995012144A1, WO9512144 A1, WO9512144A1|
|Inventores||Nigel M. Coe|
|Solicitante||Litton Systems Canada Limited|
|Exportar cita||BiBTeX, EndNote, RefMan|
|Citas de patentes (5), Otras citas (3), Citada por (1), Clasificaciones (7), Eventos legales (2)|
|Enlaces externos: Patentscope, Espacenet|
REPAIRABLE BUS STRUCTURE FOR AMLCD ARRAY
Field of the Invention
This invention relates in general to Active Matrix Liquid Crystal Displays (AMLCDs) , and more particularly to a repairable bus structure for AMLCD arrays. Background of the Invention
Thin film transistor-based active matrix liquid crystal displays are now in production at a number of large electronics companies. These displays, used for high resolution applications such as avionics as well as low resolution applications such as in personal televisions and lap-top computer screens, present video information by modulating light intensity on a pixel-by- pixel basis. Source and gate buses are arranged to form a rectangular grid of pixels. Each pixel contains a Thin Film Transistor (TFT) switch which uses amorphous silicon or cadmium selenide as the semiconductor, and which has a drain electrode connected to a pixel output pad in the form of a transparent electrode. By scanning the gate bus, which functions as a select line, data may be written to a given pixel through the associated TFT onto the transparent electrode. The voltage appearing on the transparent electrode modulates light via the LCD effect. Since the metal gate and source buses are separated only by a gate insulator, gate-to-source electrical short circuits are possible if the gate insulator breaks down or is damaged at the intersection of the two buses. According to prior art techniques, in order to repair such a condition, one or the other of the metal buses must be cut on both sides of the short circuit, which leaves a discontinuous bus structure. In order to repair this bus structure, a wire or other circuit path must connect the two opposite ends of the bus together from outside of the array since the array is encapsulated. As such, only one repair can be effected per bus. Summary of The Invention
According to the present invention, a circuit bypass or shunt is provided at each bus intersection or crossover point in the pixel array of an AMLCD. Thus, according to the invention, an alternate circuit path is present at each crossover. More importantly, the bus shunts according to the present invention are accessible through the transparent rear side of the array, without obstruction caused by the black light shield layer or the colour filter of the AMLCD.
Brief Description of the Drawings
A detailed description of the preferred embodiment and of the prior art is provided herein below, with reference to the following drawings, in which: Figure 1 is a plan view showing a prior art TFT array for AMLCD;
Figure 2 is a plan view of a shunt repairable AMLCD array according to a preferred embodiment of the present invention; Figure 3 is a rear view of a repairable shunt TFT according to the preferred embodiment;
Figure 4 is a plan view of a shunt repairable AMLCD array according to an alternative embodiment of the present invention; and Figure 5 is a rear view of a repairable shunt TFT according to the alternative embodiment of Figure 4. Detailed Description of the Preferred Embodiment and Prior Art
Figure 1 shows the structure of an AMLCD incorporating a plurality of inverted TFTs 1 arranged on a transparent insulating substrate, such as glass, in the form of a matrix. Gate electrodes of each TFT 1 are commonly connected though gate buses 4 so as to form select lines of the array. Source electrodes of each TFT 1 are commonly connected to source buses 6 to form data lines of the array. A drain electrode of each TFT 1 is connected to an output pad comprising a transparent electrode 8 which is formed as a rectangular pixel output pad between the gate buses 4 and source buses 6 of the array. A layer of semiconductor material overlaps the source and drain electrodes and forms a thin-film semiconductor channel there between.
As discussed above, in the event of a short circuit between the gate bus 4 and source bus 6, one of the buses must be broken on both sides of the affected TFT 1, and a wire or other circuit path must be connected between opposite ends of the bus, outside of the array, in order to preserve functioning of the buses.
Turning to Figures 2 and 3, according to the present invention each source bus 6 incorporates a plurality of circuit shunts 12 extending around each TFT 1. As shown in Figure 3, the shunt 12 may be accessed from beneath the AMLCD array, from either side of the underlying gate bus 4. Thus, in the event of an accidental short circuit, the source bus 6 may be broken on both sides of the affected TFT, by directing a low power laser (eg. an excimer laser) through the transparent substrate and then focussing the light on the portions of the bus to be broken. The cross-sectional dimensions of the laser light may be adjusted using a suitable aperture in order to precisely illuminate the bus to be broken (eg. a 10 micron trace) , while not illuminating other parts of the circuit. Appropriate backlighting may be employed on the laser platform to which the circuit is mounted to ensure proper visibility of the circuit parts, in a well known manner. The laser light melts the metal bus where the light is focussed and the shunt 12 provides an automatic alternate circuit path around the TFT 1, without any requirement for additional wires, etc.
With reference to Figures 4 and 5, an alternative embodiment of the invention is shown in which the shunt 12' is collinear with the source bus 6, instead of traversing a D-shaped path as in the preferred embodiment of Figures 2 and 3. However, in the embodiment of Figures 4 and 5, the principal circuit path of source bus 6 to the TFT 1 is shown as being generally D-shaped, although any suitable shape of shunt may be utilized.
The shunt repairable AMLCD of the present invention may be fabricated using well known methodology. In fact the only departure from standard AMLCD fabrication techniques is that the masks for patterning the source bus 6 and transparent electrode 8 must be appropriately shaped to create the shunt 12 (Figure 2 and 3) or shunt 12*' (Figures 4 and 5) when deposited on the gate oxide. An AMLCD array constructed in accordance with the present invention may suffer more than one short circuit failure on any given bus, and still be able to function with the remaining TFTs, as contrasted with the prior art.
Other embodiments and variations of the invention are possible. For example, although the embodiments of Figures 2 - 5 show the shunt 12 as forming part of the source bus 6, it is contemplated that the shunt may advantageously incorporated into the gate bus instead of, or in the case of large displays in addition to, the shunt forming part of the source bus 6. This and all other such modifications and embodiments are believed to be within the sphere and scope of the claims appended hereto.
|Patente citada||Fecha de presentación||Fecha de publicación||Solicitante||Título|
|EP0200138A2 *||21 Abr 1986||5 Nov 1986||Asahi Glass Company Ltd.||Thin film transistor, method of repairing the thin film transistor and displaying apparatus having the thin film transistor|
|FR2649523A1 *||Título no disponible|
|JPH0496023A *||Título no disponible|
|JPS63221325A *||Título no disponible|
|US4853755 *||17 Mar 1988||1 Ago 1989||Alps Electric Co., Ltd.||Method for manufacturing a thin-film transistor array and a thin-film transistor array manufactured by the method|
|1||*||M. YAMANO ET AL.: "The 5-Inch Size Full Color Liquid Crystal Television Addressed by Amorphous Silicon Thin Film Transistors", IEEE TRANSACTIONS ON CONSUMER ELECTRONICS, vol. 31, no. 1, February 1985 (1985-02-01), NEW YORK, US, pages 39 - 46, XP011158360|
|2||*||PATENT ABSTRACTS OF JAPAN vol. 13, no. 17 (P - 813)<3365> 17 January 1989 (1989-01-17)|
|3||*||PATENT ABSTRACTS OF JAPAN vol. 16, no. 327 (P - 1387) 16 July 1992 (1992-07-16)|
|Patente citante||Fecha de presentación||Fecha de publicación||Solicitante||Título|
|EP1882978A1 *||24 Jul 2007||30 Ene 2008||Samsung Electronics Co., Ltd.||Liquid crystal display|
|Clasificación internacional||G02F1/1362, G02F1/13|
|Clasificación cooperativa||G02F2001/136268, G02F1/136259, G02F1/1309, G02F2001/13629|
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