International Business Machines Corporation

David H Martin

Donald J Barclay

Colin Leonard Bird

Anthony Cyril Lowe

William M Morgan

Thor A Larsen

Michael H Hallett

Frank T Moth

Raymond A Spanner

Completion of potentiostatic erasure of an electrochromic display is detected by monitoring the erase current supplied to addressed display electrodes by potentiostatic erase drive means. The occurrence of a fall in erase current, corresponding to completion of the erasure of the addressed display electrodes, is detected, preferably by a threshold detector, and an erase completion indication produced. This indication effects disconnection of the erase current path.

Electrochromic display employing potentiostatic erasure

An electrochromic matrix display of the kind in which the display electrodes are supported on a substrate above a corresponding matrix of transistor switches employs constant current writing and potentiostatic erasure. The transistors are switchable by signals applied on respective gate lines to pass electric current on the respective drive lines to their display electrodes. Gate and drive selection means define the active gate and drive lines During erasure, the potentiostatic erase voltage is applied to both ends of the selected drive lines simultaneously to speed up the current limited asynchronous erase operation. Optionally, the display may be driven alternately from opposite ends of the drive lines during a line-by-line writing operation.

Electrochromic matrix display

Electrolytic apparatus employing a reference electrode, e.g. an electrochromic display of the type employing potentiostatic control of write or erase operations, has at least one reference electrode on which a predetermined coating thickness of electrochromic or other electrodepositable material is maintained or replenished by intermittent connection of the electrode to a source of write current. Such a coated reference electrode has a stable potential with respect to the solution which is necessary for potentiostatic control. Two such reference electrodes may be used alternately such that one is being erased and rewritten while the other is connected as a reference.

Electrolytic apparatus having a stable reference electrode and method of

An electrochromic display device comprises a single counter electrode and a plurality of display electrodes. The counter electrode is charged and is maintained at a given potential by a donor electrode which transfers charge to the counter electrode in response to the action of a reference electrode. A potentiostat operates to supply current to the donor electrode in accordance with the potential of the counter electrode as sensed by the reference electrode. Both the donor electrode and the counter electrode are preferably of platinum black. The donor electrode is preferably arranged in the manner of a frame about the display area. The counter electrode is preferably grid-shaped.

Counter electrode arrangement of an electrochromic display device

An electrochromic display device, preferably employing an organic electrochromic material such as heptyl viologen, has display electrodes with a rough surface in contact with the electrochromic material. The device is operated at a sufficiently high current density so that the diffusion depth of the material conforms to the contours of the electrodes.

Electrochromic display device

According to the disclosure, electrochromic display apparatus is provided, comprising, an electrolyte containing an electrochromic material, a plurality of display electrodes in the electrolyte, the display electrodes being connected in at least one group to enable selection of display electrodes, means for selecting at least some display electrodes, means to effect deposition of a visible coating of colored species derived from the electrochromic material onto the selected display electrodes, and means to effect deposition of an invisible coating of the colored species onto all unselected display electrodes, whereby the potentials of selected and unselected display electrodes are equalized.

An electrochromic display device adapted to be accurately erased has an opaque counter electrode in the shape of a pattern of lines, preferably reticulate, on the underside of the face of the display device through which the display is viewed. The counter electrode is brought to a predetermined potential either by trapping a suitable material capable of a reversible redox reaction at the counter electrode or by initially charging the counter electrode with heptyl vilogen cation radical. This enables voltage erase to be used.

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Eastleigh, United Kingdom

David H Martin