Method of making a curved electrode plate

The disclosure is of a cathode ray tube having a face plate for displaying information and carrying an electrode assembly which is curved to couple intimately to the face plate. The electrode assembly includes a shield against radio frequency interference and an insulating support sheet having an inner surface and an outer surface, on each of which an array of rows and columns of conductive areas is formed. On the inner surface, the rows of conductive areas are electrically connected together to output contact pads at a side edge of the sheet, and, on the outer surface, the columns of conductive areas are electrically connected together to output contact pads along the lower edge of the sheet. Each outer conductive area overlies and is capacitively coupled to an inner conductive area. A column conductor which extends from a contact pad at an edge of the outer surface of the sheet is capacitively coupled to each column of outer conductive areas. The method of the invention comprises forming the desired conductive areas of indium-tin-oxide on a flat glass sheet and then sagging the glass sheet to the desired curvature.

BACKGROUND OF THE INVENTION 
Touch-controlled display devices and systems are known in the art, and U.S. 
Pat. Nos. 3,757,322; 3,482,241; and 3,696,409 are examples of such devices 
and systems. However, in such devices in the past where the structure was 
shaped to conform to the curved face plate of a cathode ray tube (CRT), it 
was necessary to first curve a support sheet and then form the electrode 
arrays therein. Such a method produces imperfect electrode arrays. 
According to the present invention, the electrode arrays can be formed on 
a flat sheet, and this assembly is then curved or shaped as desired.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Apparatus 10 made according to the invention comprises a cathode ray tube 
20 having a phosphor-coated face plate 30, with an electronic assembly 40 
made according to the invention secured to, or removably coupled to, the 
face plate but shaped to match the curvature of the face plate. The 
assembly 40 includes a sheet of glass 32 having, on its inner surface, a 
transparent conductive layer 36 of tin oxide or the like which acts as a 
shield against radio frequency interference. The assembly 40 also includes 
a sheet 50 of insulating material, for example, glass, which carries on 
its inner surface 52 an array of transparent conductive film areas or 
electrodes 60 disposed in rows and columns. Each row of electrodes 60 is 
electrically connected by a conductor 70 (FIG. 2) to a contact pad 80 at 
an edge of the glass plate. The outer surface 54 of the glass plate is 
similarly provided with an array of rows and columns of transparent 
conductive film areas or electrodes 90, each area 90 overlying and aligned 
with one of the areas 60 on the inner surface. A column conductor 100 is 
provided for each column of conductive film areas and is capacitively 
coupled by means of conductive fingers 102 which are interleaved with 
conductive fingers 104 which extend from each of the outer areas. Each 
column conductor 100 extends to a conductive contact pad 110 at the lower 
edge of the glass plate. 
The interleaving of the conductive fingers 102 and 104 provides efficient 
coupling between the column conductors 100 and the electrodes 90. A layer 
42 of a clear dielectric is provided over the outer surface of plate 50 
for insulating purposes. 
According to the invention, the assembly 40 is prepared by coating both 
surfaces of a flat glass plate with a layer of indium-tin-oxide, screening 
patterns of etchant-resistant material on the inner and outer surfaces, 
and then etching to provide the electrodes 60 and 90 described above. The 
layer 42 is provided, and the flat plate thus treated is placed in a 
suitably shaped mold, and it is heated sufficiently to cause it to sag to 
conform to the shape of the cathode ray tube face plate 30 which comprises 
a support for the assembly 40. In the past, such curved assemblies had to 
be formed by first curving the glass plate and then forming electrodes 
thereon; the art did not permit forming the electrodes on a flat plate and 
then curving the plate. 
If desired, an anti-reflection coating 44 may be provided on the outer 
surface of the assembly 40. 
The operation of the assembly made by the invention is described in detail 
and claimed in application Ser. No. 928,958 filed on July 28, 1978 of 
George E. Holz entitled Touch Panel and Operating System, and incorporated 
herein by reference. For a brief description of the operation of the 
invention, positive pulses are applied to each of the column conductors 
100 in turn and thus to each of the outer conductive areas 90. The pulses 
couple through to the rear conductors and are sensed as being present on 
sense lines 70 by appropriate electronics including a computer. When the 
operator desires to display a unit of information, he touches his finger 
to the proper outer conductive area 90, and this decouples the applied 
pulse from the underlying inner area 60 and provides a zero output at the 
associated row and column contact pad 80 and 110, respectively. This 
output or switch closure is coupled through the associated circuitry, 
where the closure is computer-analyzed and activates a pertinent response 
which may be to display information on the CRT or activate an electronic 
circuit.