E Ink Corporation (Cambridge, MA) garnered U.S. Patent 7,667,886 for its nanochromic multi-layer film, useful as a front sub-assembly in electro-optic displays. The film is comprised of, in this order: a light-transmissive electrically-conductive layer; a light-transmissive first protective layer; a light-transmissive moisture barrier layer; and a light-transmissive second protective layer. This multi-layer film can be used in forming electro-optic displays, according to inventors Guy M. Danner and Sandra Rifai.
Such electro-optic displays typically contain an electro-optic medium used in "solid electro-optic displays", in the sense that the electro-optic medium has solid external surfaces, although the medium may, and often does, have internal liquid- or gas-filled spaces. The term "solid electro-optic displays" includes encapsulated electrophoretic displays, encapsulated liquid crystal displays, and other types of displays.
E Ink provides a multi-layer sheet for use as a front sub-assembly in electro-optic displays which are thin and rollable. The process also provides a lamination process which can be used to form the multi-layer sheet in a manner which allows each of the individual layers to be optimized to fulfill its function independently of the other layers. The layers can also be produced economically for their particular functions.
In the prior art, the front electrodes of electro-optic displays have typically been formed from a sputtered metal oxide ceramic, for example indium tin oxide (ITO). Such sputtered ceramic layers are expensive and can constitute a substantial fraction of the overall cost of the display.
E Ink process can replace the sputtered ceramic layer with a continuous or wet coated conducting layer which can reduce cost, but which may also reduce the barrier properties of the front sub-assembly since ITO does itself provide some useful barrier properties. The process allows for use of such a continuous or wet coated conducting layer while still maintaining good barrier properties. The ITO layer can be replaced by any sputtered or evaporated metal or ceramic layer or polymer having sufficient transparency and conductivity; examples of appropriate materials may include aluminum, a conductive polymer such as PEDOT (poly(3,4-ethylenedioxythiophene)), and carbon nanotubes.