Electro-optical device for the display of dark symbols composed of separately selectable display segments against a bright background and a means for addressing this device

Claim 1

An electro-optical indicating device for representing a plurality of numerical symbols consisting of seven separately controllable indicating elements arranged in the shape of a numeral 8, said indicating device comprising: a front electrode; a rear electrode; an electro-optical activatable medium located between said front and rear electrodes, said medium acting to absorb light in areas thereof where a potential difference of less than a transition voltage is imposed across said medium, said medium acting to transmit light in areas thereof where a potential difference at least equal to said transition voltage is imposed, siad transition voltage being specific to said medium; said front electrode being formed of a first portion (h) which can apply a voltage across said medium in regions outside the regions of said indicating elements and seven second portions (a-g), each of which can apply a voltage across said medium in the region of one of said indicating elements, said portions being isolated from each other by very thin recesses so that the front electrode is substantially covered by said first and second portions; said rear electrode being formed of a first portion (i) which forms the outer and inner boundaries for said indicating elements and for applying a voltage to the background region of said numeral 8 and a second portion (j) for simultaneously applying a voltage to all of said indicating elements, said first and second portions of said rear electrode being isolated from each other by very thin recesses so that the rear electrode is substantially covered by said first and second portions; each of said portions being connected to an electrical contact for receiving electrical signals from a control circuit; each of said second portions of said front electrode (a-g) consisting of a segment electrode for one of said indicating elements and a supply line; said second portion of said rear electrode (j) consisting of a first part in the shape of a numeral eight for applying a voltage to all of said indicating elements and a supply line; wherein the said first portion of the front electrode (h) overlays the supply line of said second portion of said rear electrode (j); wherein the said first portion of the rear electrode (i) overlays the supply lines of said plurality of second portions of said front electrode (a-g); wherein said portions of said front and rear electrodes are selectively supplied with electrical signals from said control circuit to form a specific one of said plurality of numerical symbols, the potential difference between said second portion of said rear electrode (j) and said second portions of said front electrode (a-g) being less than said transition voltage, the potential difference between the rear electrode and the first portion of said front electrode (h) being at least equal to said transition voltage, the potential difference between the said first portion of the rear electrode (i) and the supply lines of the plurality of second portions of said front electrode (a-g) being at least equal to said transition voltage; and whereby said specific numerical symbol appears as a dark symbol against a uniformly bright background.