Patent Application
20130140073
The present invention relates to a structure and method for connecting touch-panel sensor electrodes to related electronic control subsystems for use in devices featuring touch-screen control.
Many of today's electronic devices, portable devices in particular, feature touch-panel control where a user touches a particular area of a glass screen, or an icon displayed below such a screen, and a subsystem detects that touch and performs a related control function. Touch-panel equipped glass screens are an alternative, for example, to having push-button or keyboard type input devices. In addition to sensing the location of a finger touch, such touch-panel screen controls can also be used to sense motion of the finger touch from one point to another and can respond by, for example, moving the position of an image, drawing a line segment, or increasing or decreasing the magnification of an image. These touch-panels and their control functions are well known in the art.
There are a variety of technologies used in touch-panel equipped systems to determine the position, relative to the screen, of the finger touch. One of the more current and popular technologies uses a mutual-capacitance sensing approach. For mutual-capacitance sensing, using a variety of materials and methods, an array of sensor electrodes are placed onto a transparent glass screen consisting of so-called transmitter and receiver electrodes in close proximity to one another. A voltage is applied to the transmitter electrode and the detector integrates the current at the receiver which is proportional to the mutual capacitance between the transmitter and receiver electrodes. The transmitter and receiver electrodes must remain isolated from one another, that is, the impedance measured between any two electrodes must be very high. The presence of a finger touch will add capacitance to ground lowering the effective mutual capacitance, and indicate where in the spatial array of transmitter and receiver electrodes the lowered mutual capacitance has occurred. That will coincide with where the finger has touched the glass panel. This is prior art and well known to someone practiced in the art.
Because the point where the finger will touch the screen is typically underscored by a displayed image on a display below it, the touch-panel screen and its sensor electrode array must be transparent. Special materials known as transparent conductive oxides (TCOs) are used to make those transparent electrodes, and these are well known in the art.
Some prior art touch sensing systems use multiple glass plates which enables keeping receiver and transmitter electrodes on separate planes and electrically isolated. But today's handheld devices are particularly sensitive to cost, weight and thickness. For all of these reasons, there is most interest in single-glass-plate touch-sensing systems. Ultimately, a single-glass-plate system requires that the sensor electrodes must be routed to a touch controller subsystem and this involves attaching and routing each electrode in such a way that they remain isolated from one another (e.g. a cross-over). Typically, the routing takes place on the periphery of the panel in an area that is opaque so as to hide the metallic routing traces from user view.
Because of the large difference in thickness of the transparent electrodes and the periphery artwork, and the fact that the artwork is laid down before the transparent electrodes, there is a point along the edge of the artwork where the transparent TCO electrodes have to extend up from the glass surface to the surface of the artwork. Indium-Tin-Oxide (ITO) is commonly used as the TCO material. As the ITO transparent electrode material is both very thin and brittle, this region where the transparent electrode extends up to the artwork surface is an area of significant vulnerability and accounts for either a low yield rate or complex process features that add difficulty, time and cost to the touch-panel manufacturing process.
Therefore, a way of routing the transparent electrodes to the touch-panel controller subsystem that would reduce vulnerability, increase yield, and lower overall manufacturing cost would be of great benefit and interest to those practiced in the art.
It is, therefore, an object of the present invention to reduce the vulnerability to failures of the prior art single-glass approach by using a different method for routing the TCO electrodes that does not expose them to extending above the glass surface thus increasing the likelihood of breaks and manufacturing failures.
In accordance with the disclosed exemplary embodiment, the transparent electrodes are laid down on the glass surface, first, and so remain flat to the glass surface from end to end.
The insulating artwork along the border area of the glass is laid down afterward, and using a system of conducting “vias,” provides the means for routing the electrodes with the requisite cross-over insulating properties (to preserve the electrode isolation), but without subjecting the transparent electrodes to the extension to the artwork surface that is characteristic of the prior art.
With the transparent electrodes, artwork and vias applied to the bottom side of the touch-screen glass, and by using the same artwork color for the conducting via plugs as is used for the insulating artwork, the routing remains hidden from view of the user, as before.
The exemplary embodiment disclosed in this application describes the structure of the insulating artwork, the metallic routing traces, and the vias. It also describes a method for applying the structures and routing the electrodes for connection by the touch-panel controller subsystem.
The following description covers the structure and methods used for routing the TCO electrodes of a touch screen sensor array, including the requisite cross-over electrode isolation required for proper operation, without extending the TCO electrodes off the glass surface in order to route them to the surface of a non-conducting artwork layer that is thousands of times thicker than the thickness of the TCO electrodes. By so doing, this invention avoids the vulnerability of the extended TCO electrodes leading to higher yields, lower costs, and simpler manufacturing.
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Without requiring any special implementation equipment, this invention accomplishes the cross-over routing required by the touch screen sensor and touch controller, and does so without the extension TCO vulnerability associated with the prior art. There are a variety of methods for laying down the TCO electrodes, a variety of methods for laying down the non-conducting artwork layer, and a variety of methods for laying down the metalized routing traces. There are a variety of methods for patterning the vias in the non-conductive artwork layer. There are a variety of methods for depositing the conductive via plugs in the non-conductive artwork layer. The preferred method uses laser patterning of the TCO electrodes, screen printing of conductive silver, screen printing or inkjet printing of the black conductive via inserts. Alternative methods could use laser patterning of multiple layers of material such as insulator-on-TCO; silver-on-TCO; silver-on-insulator-on-TCO, insulator-on-silver-on-TCO.
The method and structure could consist of a layer of TCO electrodes, a layer of non-conductive artwork in the border area, and a layer of metalized routing traces. It could also use laser patterning of multiple of layers of insulator-conductor-TCO material stacks allowing a narrower border region while accommodating all electrical cross-over routing.
A preferred structure would use a single-glass sensor with all touch-sensor structures on one surface and all cross-over routing done on a narrow border area. An alternative would be to allow cross over structure to be built on extensions of the touch-panel glass assembly, for example, on the surface of extension of panels in the scaffolding area of some touch-module structures.
