Electro-optical display with circuitry for applying predetermined potentials to all display segments to effect activation of a selected segment only

Abstract

A horological instrument includes a liquid crystal electro-optical display which simulates the movement of hands about a center by activating circumferentially spaced radial conductive segments. Generally, for the liquid crystal material between two corresponding segments to be activated an electrical potential must be applied between the segments which is, typically to achieve full brightness, substantially greater than the activation voltage of the liquid crystal material. The present invention effects activation of a selected segment-hand by applying an electrical potential, predetermined greater than the activation voltage, between the selected segment-hand and a corresponding segment or electrode. However, the deleterious effects of leakage currents and/or unwanted activation of a segment-hand not selected for activation is reduced by applying an electrical potential between all unselected segment-hands and their corresponding segment or electrode, which electrical potential is predetermined to be less than the activation voltage of the liquid crystal material.

What is claimed is: 
     
       1. An electro-optical display .Iadd.for a timepiece .Iaddend.comprising: a first and a second plate each having on one side thereof a pattern formed by segments, said segments being layers of conductive material, .[.at least some of said segments being electrically connected together;.]. .Iadd.said second plate segment pattern comprising a plurality of radial segments and said first plate segment pattern comprising a plurality of common segments, each common segment being aligned with a predetermined number of said radial segments, each radial segment, aligned with one common segment, being electrically connected to only one radial segment from said number of radial segments aligned with another common segment, .Iaddend.said plates being spaced from each other and with the segments on each plate aligned; a thin layer of liquid crystal material sandwiched between said plates, said liquid crystal material characterized by a threshold voltage of V t  ;   a driver circuit connected to said segments and a voltage source of V s  connected to said driver circuit, said driver circuit having first voltage supply means .Iadd.adapted .Iaddend.to provide .[.a.]. .Iadd.to .Iaddend.first .[.selectable.]. segments of the first plate to voltage V 1  which is a fraction of V s  and less than V 2 , second voltage supply means .Iadd.adapted .Iaddend.to provide to first .[.selectable.]. .Iadd.predetermined .Iaddend.segments of said second plate .[.with.]. a voltage V 2  greater than V 1  and a fraction of V s  wherein V 1  +V 2  =V s  and V 2  >V t  >V 1 , third voltage supply means .Iadd.adapted .Iaddend.to supply voltage V s  .[.,.]. to second .[.selectable.]. .Iadd.predetermined .Iaddend.segments of the first plate and fourth means .Iadd.adapted .Iaddend.to switch second  .[.selectable.]. .Iadd.predetermined .Iaddend.segments of the second plate to zero voltage, whereby the liquid crystal material between the first segments is not activated and the liquid crystal material between the second segments is activated.   
     
     
       2. An electro-optical display as in claim 1 wherein said first plate and the segments thereon are transparent. 
     
     
       3. An electro-optical display as in claim 1 wherein .[.the.]. .Iadd.both .Iaddend.said third .[.voltage supply means.]. and fourth voltage supply means .Iadd.and both said first and second voltage supply means .Iaddend.rapidly .[.inter.]. change .Iadd.in a predetermined relationship .Iaddend.to provide alternating .[.current.]. .Iadd.voltages .Iaddend.to the segments on both plates. 
     
     
       4. An electro-optical display as in claim 1 wherein V 1  is about one-third of V s  and V 2  is about two-thirds of V s . 
     
     
       5. An electro-optical display .Iadd.for a timepiece .Iaddend.comprising: a first and second plate each having on one side thereof a pattern formed by segments, said segments being layers of conductive material, .[.at least some of said segments being electrically connected together;.]. .Iadd.said second plate segment pattern comprising a plurality of radial segments and said first plate segment pattern comprising a plurality of common segments, each common segment being aligned with a predetermined number of said radial segments, each radial segment, aligned with one common segment, being electrically connected to only one radial segment from said number of radial segments aligned with another common segment, .Iaddend.said plates being spaced from each other and with the segments on each plate aligned; a thin layer of liquid crystal material sandwiched between said plates; said liquid crystal material characterized by threshold voltage of V t  ;   a driver circuit connected to said segments and a voltage source of V s  connected to said driver circuit, said driver circuit having first voltage supply means .Iadd.adapted .Iaddend.to provide .[.a.]. .Iadd.to .Iaddend.first .[.selectable.]. .Iadd.predetermined .Iaddend.segments of the first plate a voltage V 1  which is a fraction of V s  and less than V 2 , second voltage supply means .Iadd.adapted .Iaddend.to supply voltage V s  to second .[.selectable.]. .Iadd.predetermined .Iaddend.segments of the first plate .[.voltage V s  .]., and third means .Iadd.adapted .Iaddend.to switch second .[.selectable.]. .Iadd.predetermined .Iaddend.segments of the second plate to zero voltage, whereby the liquid crystal material between the first segments is not activated and the liquid crystal material between the second segments is activated.   
     
     
       6. An electro-optical display as in claim 5 wherein said first plate and the segments thereon are transparent. 
     
     
       7. An electro-optical display as in claim 5 wherein the said second and third means rapidly interchange to provide alternating current to the segments on both plates. 
     
     
       8. An electro-optical display as in claim 5 wherein V 1  is about one-half of V s . 
     
     
       9. In a wrist watch, the combination comprising: an electrical optical display comprising first and second plates parallel to each other, each having on the facing sides thereof a pattern formed of segments, said segments being layers of a conductive material, said first plate having a multiplicity of relatively large segments and a plurality of terminals, each plate being connected to a terminal, said second plate having a multiplicity of smaller .Iadd.radial .Iaddend.segments arranged in groups, one group each facing one segment of said first plate, .[.corresponding segements in each of said groups being electrically connected together and to a terminal thereby forming a matrix of elements.]. .Iadd.each radial segment in one group electrically connected to only one radial segment in another group.Iaddend., a thin layer of liquid crystal material of threshold voltage V t  sealed between said plates,   driver circuit means connected to said segments and to a voltage source V s , said driver circuits having first voltage supply means .Iadd.adapted .Iaddend.to selectively provide voltage V s  or zero to one desired selectable segment of said first plate, second voltage supply means .Iadd.adapted .Iaddend.to supply alternately zero voltage or V s  to desired selectable electrically connected together .[.corresponding.]. segments on said second plate, third voltage supply means .Iadd.adapted .Iaddend.to supply .[.aternately V s  13.]. .Iadd.Vs/3 .Iaddend.to all other segments of said first plate and fourth voltage supply means .Iadd.adapted .Iaddend.to supply alternatively 2V/3 to all other segments of said second plate .Iadd.in predetermined relationship with alternately supplied zero voltage and Vs .Iaddend.thereby ensuring that the maximum voltage between any undesired segments of first and second plates is V s  /3<V t .   
     
     
       10. A wrist watch in accordance with claim 9 wherein: the segment pattern on the first and second plates each comprise a series of radial segments circularly arranged about a common center to provide an analog watch display.   
     
     
       11. A wrist watch in accordance with claim 10 wherein: 24 segments are provided in an inner ring to indicate half hours and 60 segments are provided on an outer ring to indicate minutes on one of said plates, wherein said 24 half-hour segments are arranged in a suitable matrix arrangement and said minute segments are arranged in an 8×8 matrix with four unused matrix positions.