Electrically-conductive articles having silver patterns or grids and methods for making and using them to make display devices
Publication Date: 2016-Feb-18
The IP.com Prior Art Database
Electrically-conductive articles can be prepared and assembled into various electronic devices and used for example as touch screen displays. The electrically conductive articles are prepared from silver halide emulsions coated onto suitable transparent polymeric substrates. The silver halide emulsions are imagewise exposed through masks having predetermined patterns to provide latent exposed patterns of lines or grids. Upon development and fixing using known silver halide processing chemistries, the latent patterns are changed into silver lines or grids of electrically-conductive patterns that correspond to the predetermined patterns in the masks.
Touch screen displays typically use Indium Tin Oxide (ITO) coatings to create arrays of capacitive areas used to distinguish multiple point contacts. ITO conductivity is relatively low and requires short line lengths to achieve adequate response rates. Touch screens for large displays are broken up into smaller segments to reduce the conductive line length to an acceptable resistance. These smaller segments require additional driving and sensing electronics. In addition ITO is a ceramic material, is not readily bent or flexed, and requires vacuum deposition with high processing temperatures to prepare the conductive layers.
Silver is an ideal conductor having conductivity 50 to 100 times greater than ITO. Unlike most metal oxides, silver oxide is still reasonably conductive and this reduces the problem of making reliable electrical connections. It would be desirable to make conductive film elements using silver as the source of conductivity.
U.S. Patent Application Publication 2011/0308846 (Ichiki) describes the preparation of conductive films formed by reducing a silver halide image in conductive networks with silver wire sizes less than 10 µm, which conductive films can be used to form touch panels in displays. In addition, U.S. Patent 3,464,822 (Blake) describes the use of a silver halide emulsion in a photographic element to form a conductive silver surface image by development and one or more treatment baths after development. Conductive patterns using photosensitive silver halide emulsions are described in U.S. Patent 8,012,676 (Yoshiki et al.). U.S. Patent Application Publication 2015/0316848 describes duplex silver halide conductive film element precursors containing an immobilized UV radiation absorber in the outermost hydrophilic overcoat.
A “black-and-white silver halide conductive film element precursor” (or “precursor”) refers to an article or element that can be used to provide a conductive film element (or “conductive article”). Such precursors therefore comprise a photosensitive precursor to the silver metal nuclei (particles), such as a silver halide as described below that is suitably converted (for example by reduction) to silver metal.
The term “duplex” is used in reference to black-and-white silver halide conductive film element precursors and conductive film elements having the described layers on both supporting sides of a transparent substrate. Unless otherwise indicated herein, the relationships and compositions of the various layers can be the same or different on both supporting sides of the transparent substrate. But in...