Appeal No. 96-1249
Application 08/270,215
a top transparent layer disposed over a bottom
transparent layer, the top layer comprising a flexible sheet
having a layer of a semiconductive ceramic coated on a lower
face thereof, and the bottom transparent layer comprising a
substrate sheet having a thin layer of a semiconductive
ceramic coated on an upper face thereof;
a non-electrically conductive spacer interposed between
the top and bottom layers effective for spacing apart the
layers of semiconductive ceramic except when the top layer is
flexed by an external touch so that electrical contact occurs
between the semiconductive layers at a location where the
touch occurred;
a noncontinuous, electrically conductive metallic film
which in use does not form an appreciable amount of an
insulating oxide, the film covering at least one of the layers
of semiconductive ceramic so that the film is interposed
between the semiconductive layers during electrical contact
caused by a touch, the metallic film being of a thickness
effective to reduce the effects of repeated operation on
contact resistance over many operating cycles of the touch
screen without substantially varying the sheet resistance of
the underlying semiconductive ceramic layer; and
conductors connected to the transparent layers for
applying an electrical current to the semiconductive layers to
determine the horizontal and vertical position of the external
touch on the top layer.
The references
The examiner relies on the following references:
Kuhlman 4,786,767 Nov. 22, 1988
Olson 4,958,148 Sep. 18, 1990
Mikoshiba et al.
(Mikoshiba) 5,225,273 July 6, 1993
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