Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
2001-02-19
2003-05-06
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C178S018050, C178S019010, C345S156000
Reexamination Certificate
active
06559835
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an improved touch screen or contact input system, and more particularly to a touch screen having an improved superimposed electrode configuration for supplying power to the screen. The electrode configuration comprises multiple superimposed conductive layers disposed directly or indirectly upon a substrate with the substrate having a resistive film over its entire surface. One of the electrode layers is best characterized as being resistive, while it comprises a network or array of conductive segments which collectively have a configuration or layout with an edge linearization component for enhancing the accuracy of the X-Y input signals as detected. Another one of the electrode layers comprises an array of conductive buses through which an electrical potential is delivered from a power source to selected locations on the array of conductive segments. The arrangement of the present invention provides for stacking of the individual electrodes, thereby increasing the useful area of the screen by substantially reducing the perimeter size requirements. The present invention is an improvement particularly adapted for use with that particular touch system disclosed and claimed in U.S. Pat. No. 5,736,688, Barrett et al., assigned to the assignee of the present invention, the disclosure of which is incorporated fully by reference herein. It should be noted that the present invention may be adapted for use with other touch screen systems, as well.
In the past, contact input systems have been available including screens having conductive segments made of conductive ink or the like and laid out in a configuration or pattern to best linearize electrical fields created in the resistive surface. While the segments are indicated as being “conductive”, it will be recognized that only the segments per se are conductive, with the overall array being resistive. Thus, these segments create a network with a resistive property, with the description in this specification being intended to simply define the network of well known segments in the conventional fashion. One highly useful array network or arrangement of conductive segments is disclosed in detail in U.S. Pat. No. 5,736,688. Among the preferred arrays are those utilizing a pattern wherein there is a progressive inward displacement of the conductive segments to linearize the electric fields in the active or useful area of the surface. In other words, the network pattern of each array of segments is such that they collectively are generally inwardly directed or bowed, and may be parabolically configured between opposed spaced-apart corner segments, with each array having a mid-point segment located mid-way between the corners. The corner segments are rectangular in configuration defining a corner apex and includes a contact pad for electrical coupling to the buses. In one particularly desirable configuration, the mid-point segment of each array has a generally “T”-shaped and those conductive segments to the left of the mid-point have a generally “Z”-shaped configuration, with those to the right of the mid-point having a generally inverted “Z”-shape configuration. In order to create the field necessary for touch screen operation, and to enhance the accuracy of these screens, it is essential that the potential or signal applied to each of the opposed corner segments be accurate and consistent. In most applications, the potential applied to each of the spaced-apart contact pads must be equal. The arrangement of the present invention enhances the overall linearity, uniformity, and accuracy of the applied potentials to render the electrical fields created across the surface of the touch screen more uniform as well.
In the past, it has been the practice to arrange the edge arrays of conductive segments and the conductive buses which deliver the electrical energy to the arrays along generally parallel but spaced-apart lanes or paths. In such devices, the conductive buses are spaced laterally apart from the individual arrays of conductive segments. The disadvantage of this arrangement is that a substantial amount of additional perimeter area is required, thus increasing the overall size of the screen. The present arrangement reduces the overall size requirements by careful delineation of the superimposed lanes or paths, as more fully set forth below. Suffice it to say that the superimposed electrode arrangement of the present invention increases the useful area of the screen, thus reducing the overall size requirements.
In other known touch screen systems, the bus is isolated from the resistor network by means of an etch pattern which removes portions of the resistive layer lying between the bus and the resistor network. Still other systems utilize an arrangement wherein the elongated conductive bus is positioned over a dielectric layer, with the dielectric not extending over the resistor network. Such arrangements require greater areas, and for that reason, are less desirable. Certain other known screens employ arrays of conductive segments consisting of spaced-apart linear traces which are positioned along spaced-apart axes. These also require greater perimeter area.
The utilization of the superimposed electrodes is particularly well adapted for use in combination with the bowed electrode configuration, inasmuch as the configuration contributes to a reduction in the power requirements. This reduction taken together with the novel cross-over arrangement results in greater accuracy for the resulting screen system.
In one typical and widely utilized pattern arrangement, the conductive segments are formed generally along two laterally spaced rows of staggered, interspersed or interleaved “T”-shaped segments, with the buses being spaced laterally away from the segments. As indicated above, when the electrodes are laterally spaced apart, additional perimeter area is required, thus reducing the useful area of the finished screen.
In order to enhance accuracy while at the same time reducing the size requirements, highly conductive buses are formed in stacked or superimposed relationship above the surface of the screen. These buses are superimposed upon and electrically isolated from the arrays of conductive segments so as to simultaneously and reliably apply a given or known potential at respective opposed or adjacent corners of the arrays. Given the bowed or inwardly directed parabolic configuration of the conductive segments, and given the objective to minimize the overall size of the screen by maximizing the useful surface, the objective is facilitated by superimposing the buses so that they pass over and intersect the lane or path of the underlying pattern of conductive segments comprising the array. In accordance with the present invention, it has been further determined that the electrical potential applied to the corner segments is accurately delivered when the axes of the intersecting elongated buses and that of conductive segments are angularly arranged at the cross-over points, and with the actual intersection point being located along the main or solid body portion of the conductive segments.
SUMMARY OF THE INVENTION
In accordance with the present invention, therefore, the touch screen assembly providing the contact input to the system comprises an assembly with a substrate, preferably glass, with the substrate surface having an adherent electrically resistive film or coating thereon, normally consisting of indium-tin oxide (ITO). The conductive segments arranged in their inwardly directed parabolic pattern or array, are applied directly over the surface of the resistive film in a conventional fashion, such as by silk-screen, and preferably configured generally in the parabolic configuration disclosed in U.S. Pat. No. 5,736,688. A dielectric layer is applied over the conductive segments and adjacent the edge surfaces of the substrate, with the dielectric layer extending inwardly a distance sufficient to overlie all or a substantial portion of the pattern of the already appli
Haugen Law Firm LLP
Said Mansour M.
Shankar Vijay
The Bergquist Company
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