WO2012014206A2

WO2012014206A2 - Capacitive touch digitizer sensor

Info

Publication number: WO2012014206A2
Application number: PCT/IL2011/000605
Authority: WO
Inventors: Eytan Mann; Gadi Garfinkel; Itamar Ben-Shalom
Original assignee: N-Trig Ltd.
Priority date: 2010-07-28
Filing date: 2011-07-27
Publication date: 2012-02-02
Also published as: WO2012014206A3

Abstract

A capacitive touch sensor (100) comprises a row array of conductive strips (22) and a column array of conductive strips (24) arranged in a grid with a plurality of junction areas (28) formed therebetween, wherein at least one of the row or column conductive strips includes at least one electrically isolated region (235) positioned between two contiguous junction areas of the plurality of junction areas formed by the grid.

Description

CAPACITIVE TOUCH DIGITIZER SENSOR

RELATED APPLICATION

The present application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/368,319 filed on July 28, 2010 which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention, in some embodiments thereof, relates to a capacitive touch sensor and, more particularly, but not exclusively, to a grid based capacitive touch sensor for a digitizer system.

BACKGROUND OF THE INVENTION

Capacitive touch sensors are used for position and proximity detection in many Human Interface Devices (HID) that include a digitizer system such as laptop, touchpads, tablet computers, MP3 players, computer monitors, and cell phones. The capacitive touch sensor senses positioning and proximity of a conductive object such as a conductive stylus or finger touch used to interact with the HID. Typically, the capacitive touch sensor is sensitive both to the size and the proximity of the interacting object.

Capacitive touch sensors include electrodes that can be constructed from different media, such as copper, Indium Tin Oxide (ITO) and printed ink. ITO is typically used to achieve transparency. Some capacitive touch sensors are grid based and are operated to detect mutual capacitance between the electrodes at different points in the grid.

U.S. Patent No. 7,372,455 entitled "Touch Detection for a Digitizer" assigned to N-Trig Ltd., the contents of which is incorporated by reference, describes a detector for detecting touches by fingers or like body parts on a capacitive sensitive sensor. Typically the detector includes a grid of sensing conductors, extending into the sensing surface, a source of electrical energy oscillating at a predetermined frequency, and detection circuitry for detecting capacitive influence on sensing conductors when an oscillating electrical energy is applied. International Publication WO2011/058562 entitled "Capacitive touch sensor for a digitizer system" assigned to N-Trig Ltd., the contents of which is incorporated by reference, describes a capacitive touch sensor structured to enhance capacitive coupling between electrodes of the capacitive touch sensor and conductive objects interacting with the sensor. The capacitive touch sensor disclosed includes a plurality of sensing electrodes electrically connected to circuitry as well as a plurality of auxiliary conductive areas spread over a sensing surface. The auxiliary conductive areas are electrically isolated from electrodes connected to the circuitry.

European Patent Application EP 1298803 entitled "Multiple input proximity detector and touch pad system," the contents of which is incorporated by reference, describes a touchpad including a first and second series of spaced apart conductors arranged in a grid with no electrical contact between the first and second series of conductors. It is disclosed that when using lower conductivity material, e.g. indium oxide, high sensitivity to changes in capacitance can be achieved by opening a "window" area at a junction formed by a second conductor crossing a first conductor. It is suggested that the window area need not be completely open and that an area of conductor material electrically isolated from the second conductor element can be left within the window.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention there is provided a capacitive touch sensor with enhanced sensitivity and resolution. According to some embodiments of the present invention, sensitivity and resolution is enhanced by constructing the capacitive touch sensor with conductive strips and/or antennas that are patterned with non-conductive areas. According to some embodiments of the present invention, the geometry of the non-conductive areas patterned on the conductive strips is defined to increase resistance of the strip to a desired level without adversely affecting capacitive coupling between an object interacting with the capacitive touch sensor and the conductive strips.

According to an aspect of some embodiments of the present invention there is provided a capacitive touch sensor comprising a row array of conductive strips and a column array of conductive strips arranged in a grid with a plurality of junction areas formed therebetween, wherein at least one of the row or column conductive strips includes at least one electrically isolated region positioned between two contiguous junction areas of the plurality of junction areas formed by the grid.

Optionally, the electrically isolated region includes at least one segment that extends along a direction of current flow.

Optionally, the electrically isolated region includes at least one segment that extends across a direction of current flow.

Optionally, the electrically isolated region is composed of one or more elongated regions, wherein each of the one or more elongated regions occupy a width of less than 15% of a width of the conductive strip on which it is positioned.

Optionally, the electrically isolated region is composed of one or more elongated regions, wherein each of the one or more elongated regions occupy a width of less than 5% of a width of the conductive strip on which it is positioned.

Optionally, the electrically isolated region includes at least one first segment and at least one second segment, wherein the at least one first segment is longer than the at least one second segment, and each of the at least one first segments are orthogonal to at least one of the at least one the second segment.

Optionally, the electrically isolated region includes at least one first segment and at least one second segment, wherein the at least one first segment is parallel to a current flow direction along the conductive strip and the at least one second segment is substantially perpendicular to the current flow direction along that conductive strip, and wherein the at least one first segment is longer than the at least one second segment,

Optionally, the electrically isolated region has a shape of an Ή.'

Optionally, only one of the row array of conductive strips and the column array of conductive strips includes electrically isolated regions positioned between contiguous junction areas.

Optionally, at least one of the row array of conductive strips and the column array of conductive strips includes a narrow portion in the vicinity of the junction areas and a wide portion between the junction areas.

Optionally, the electrically isolated region is positioned in the wide portion between the junction areas. Optionally, the array of row conductive strips and the column array of conductive strips are patterned on a single layer.

Optionally, the at least one of the row conductive strips and column conductive strips are formed by a plurality of discrete sections that are electrically connected in series at the junction areas by a bridge structure.

Optionally, the electrically isolated areas are formed on the discrete sections.

Optionally, the at least one electrically isolated region is etched on a conductive strip.

According to an aspect of some embodiments of the present invention there is provided a digitizer system including the capacitive touch sensor described hereinabove, a signal generator configured for providing a signal to at least one conductive strip, and a controller configured for sampling an output signal from at least one other conductive strip that crosses the at least one conductive strip.

According to an aspect of some embodiments of the present invention there is provided method for constructing a capacitive touch sensor, the method comprising defining dimensions of the capacitive touch sensor, wherein the capacitive touch sensor includes a row array of conductive strips and a column array of conductive strips arranged in a grid with a plurality of junction areas formed therebetween, determining material for constructing the capacitive touch sensor, determining a desired property of the capacitive sensor, determining geometry of an electrically isolated region to be formed on conductive strips of the capacitive touch sensor, wherein the at least one electrically isolated region is positioned between two contiguous junctions areas of the plurality of junction areas formed by the grid, and constructing the capacitive touch sensor with conductive strips including at least one electrically isolated region.

Optionally, the desired property is selected from the group consisting of: capacity, resistance, impedance, and cross talk between conductors.

Optionally, the electrically isolated region includes at least one segment that extends across a direction of current flow. W

5

Optionally, the electrically isolated region includes at least one first segment and at least one second segment, wherein the at least one first segment is longer than the at least one second segment, and wherein each of the at least one first segment is parallel to a current flow direction along the conductive strip on which the electrically isolated region positioned and each of the at least one second segment is substantially perpendicular to the current flow direction along that conductive strip.

Optionally, the electrically isolated region has a shape of an Ή.'

Optionally, the at least one electrically isolated region is etched onto the conductive strip.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIGs. 1A and IB are simplified schematic illustrations of a top and side view of a grid based capacitive touch sensor formed over two layers in accordance with some embodiments of the present invention;

FIG. 2 is a simplified schematic illustration of grid based capacitive touch sensor with cut-outs in conductive strips along one of the two axis of the sensor in accordance with some embodiments of the present invention;

FIG. 3 is a simplified schematic illustration of two crossing conductive strips of a capacitive touch sensor each of which are narrowed at a junction between the strips in accordance with some embodiments of the present invention;

FIG. 4 is a simplified schematic illustration of two crossing conductive strips of a capacitive touch sensor including separate cut-outs in and between junction areas in accordance with some embodiments of the present invention;

FIG. 5 is a simplified schematic illustration of a grid based capacitive touch sensor formed over a single layer in accordance with some embodiments of the present invention;

FIGs. 6A and 6B are simplified schematic illustrations of a top and cross- sectional view of an exemplary row conductive strip and top and cross-sectional view of an exemplary column conductive strip respectively in accordance with some embodiments of the present invention;

FIGs. 7A, 7B, 7C and 7D are simplified schematic illustrations of exemplary non-conductive region patterned on a conductive strip of a capacitive touch sensor in accordance with some embodiments of the present invention; and

FIG. 8 is a flow chart describing an exemplary method for defining construction of a capacitive touch sensor in accordance with some embodiments of the present invention;

FIG. 9 is a simplified block diagram of a digitizer system including a capacitive touch sensor in accordance with some embodiments of the present invention; and FIG. 10 is a schematic diagram describing a capacitive touch detection method used with a capacitive touch sensor in accordance with some embodiments of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

As used herein, the term digitizer system includes various types of digitizer systems including touch screens.

The present inventors have found that increasing resistance of conductive strips of a capacitive touch sensor enhances both sensitivity and resolution of detection. For example, the present inventors have found that by increasing resistance of a conductive strip forming a junction in the sensor, voltage drop at the junction due to touch and/or hover of a finger is more pronounced. In addition to increasing voltage drop at a junction where touch occurs, the increased resistance also reduces voltage drop due to the touch in other junctions distanced from the touch, so that the resolution of touch detection and/or localization of the voltage drop due to touch is improved. Although, increased resistance can increase sensitivity and resolution of the capacitive touch sensor, if resistance is increased over a certain level, undesired signal decay can occur along the conductive strip and in particular at an end of the conductive strips opposite the end at which a trigger signal is induced. This signal decay may reduce sensitivity of the sensor at an end of the conductive strips opposite the end of that is triggered. Exemplary properties of conductive strips that can affect resistance include material, size and geometry of the conductive strips. Optionally, other properties, e.g. capacity, impedance, and cross talk between conductors are altered and sensor performance, e.g. sensitivity and resolution of detection is enhanced.

Although the resistance of the conductive strips can be increased by using narrow strips in the capacitive touch sensor, wide conductive strips have the advantage of enhancing capacitive coupling between an interacting finger and the conductive strips. Placing a finger on the sensor at the junction changes capacitance and resistance between conductive strips that form the junction, and ground. By increasing the coupling area between an interacting finger and a conductive strip, the capacitive coupling is enhanced. The changed capacitance changes the impedance driven by the junction, which in turn increases the driven current and the voltage drop across the junction.

According to some embodiments of the present invention, there is provided a grid based capacitive touch sensor including wide conductive strips patterned with cutouts, non-conductive areas and/or breaks within the conductive areas. According to some embodiments of the present invention, the pattern of cut-outs is shaped and sized to increase and/or adjust the resistance of the conductive strips to a desired level. The present inventors have found that by constructing the conductive strips as wide strips where portions of the strip are blocked with cut-outs and/or non-conductive material, the resistance of the conductive strips can be increased without significantly reducing the enhanced capacitive coupling between a finger and the strips. In some exemplary embodiments, the cut-outs are generally patterned along a length of the conductive strip with portions cutting across a width of the conductive strip. Typically, the cut-outs are patterned to narrow a conductive path and/or lengthen a conductive path through which current can flow from one end of the conductive strip to an opposite end. Optionally the cut-outs are not wide enough to significantly reduce capacitive coupling between the interacting finger and the conductive strip. The present inventors have found that non- conductive patterns on the conductive strips of the capacitive touch sensor can increase the resistance of the conductive strips by up to 4-10 times.

In some exemplary embodiments, the cut-outs are etched on the conductive strip. Optionally, the cut-out portion is shaped as an "H" shape with the two vertical strips of the "H" extending parallel to a longitudinal axis of the conductive strip and/or generally parallel to a flow direction of the current along the conductive strip. According to some embodiments of the present invention, the cut-outs are patterned along the conductive strips and between junction areas. Optionally, at least a portion of the strips is shaped to be narrowed around a junction area, e.g. narrower around a junction and wider between junctions.

According to some embodiments of the present invention, the geometry and/or size of the cut-out areas on the conductive strips are tailored for a particular capacitive touch sensor, e.g. based on size and design requirements of the particular capacitive sensor. According to some embodiments of the present invention, the resistance of the conductive strips is tailored to conform to design requirements of the capacitive touch sensor, e.g. size and material making up the capacitive touch sensor. Other parameters such as shape of the conductive strips, their width, and distance between neighboring conductive strips are also selected based on the design requirements.

It will be appreciated by a person skilled in the art that different shapes of cutouts can be used to adjust properties of the conductive strip, e.g. resistance, capacity, finger effect and cross talk between conductors.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Reference is now made to FIGS. 1A and IB showing simplified schematic illustrations of a top and side view of a grid based capacitive touch sensor formed over two layers in accordance with some embodiments of the present invention. According to some embodiments of the present invention, a capacitive touch sensor 100 is a grid based sensor including an array of row conductive strips 22 and an array of column conductive strips 24. According to some embodiments of the present invention, array of row conductive strips 22 and array of column conductive strips 24 are separated by a non-conductive layer 30 so that the conductive strips in the different arrays are isolated from each other but capacitively coupled with each other. Optionally, non-conductive layer 30 includes a substrate of glass, transparent foil, polyethylene-terephthalate (PET) substrate and/or non-conductive and transparent substrate on which conductive strips 22 and 24 are patterned.

According to some embodiments of the present invention, the row conductive strips, e.g. row conductive strips 22 and column conductive strips 24 include one or more non-conductive areas 235 that obstruct continuity of conductive areas 230 and/or obstruct the current flow along a length of the conductive strips. Optionally, non- conductive portions 235 are generally centered with respect to a longitudinal axis 99 of the conductive strips. According to some embodiments of the present invention, non- conductive areas 235 are elongated areas that extend along a length of conductive strips 22 and 24. Typically, non-conductive portions 235 extend along the conductive strips over a portion of the strip between junction areas 28. Optionally, non-conductive portions 235 partially or fully extend into junction region 28 and/or an area of overlapping between row and column conductive strips. Optionally, a single non- conductive portion 235 is patterned on conductive strips 22 and/or 24 that extend substantially over an entire length of the strip.

Typically, resistance of a rectangular shaped conductive strip segment (with constant thickness) may be defined by:

R = p₀— (Equation 1)

Where:

R is a resistance of the strip in ohms;

P_o is a constant defined by the material of the strip;

L is the length of the conductive path provided by the strip; and

W is the width of a conductive path provided by the strip.

By reducing a width of the conductive path provided by the conductive strip, the resistance of the strip can be increased by an amount that is generally proportional to the reduction of the width. Although, it is clear that the resistance of the strip can be increased by narrowing the strip, the present inventors have found that the width of the strip can be maintained while increasing the resistance by providing obstructions in the current path to reduce the width of the current path through which current can flow along the strip. Since mutual capacity depends on the overlapping area of the conductors, increasing the resistance by providing relatively narrow obstructions in the current path strip provides for constructing a sensor with wider strips with enhanced resistance without adversely affecting capacitive coupling between an interacting finger and the capacitive touch sensor.

Typically, for transparent sensors, conductive strips are formed with materials such as ITO, Indium-doped Zinc Oxide (IZO), a conductive polymer, carbon nano-tube, metal nano-particles such as Ag or Cu, Antimony Tin Oxide (ATO), or other conductive transparent materials. These conductive materials are typically associated with low resistance properties. For example ITO may typically have a resistance of about 40-60 ohm/mm². In some exemplary embodiments, non-conductive areas 235 are cut-out of and/or etched on the conductive strips.

It is noted that although all the conductive strips are shown to include non- conductive portions 235 between all junctions, optionally only a portion of one or more of the conductive strips include non-conductive portions 235, and/or non-conductive portions 235 are only included between a portion of the junctions 28. Optionally, only one array, e.g. either row or column array of conductive strips are patterned with non- conductive portions 235. Optionally, only the array of conductive strips, e.g. either row or column conductive strips that are closest to an interacting surface is patterned with non-conductive portions 235.

Reference is now made to FIG. 2 showing simplified schematic illustration of grid based capacitive touch sensor with cut-outs in conductive strips along one of the two axis of the sensor, in accordance with some embodiments of the present invention. According to some embodiments of the present invention, a grid based capacitive touch sensor 110 includes an array of narrow conductive strips 34 and an array of wide conductive strips 32 including non-conductive areas 245. Typically the narrow conductive strips are continuous, e.g. do not include non-conductive areas 245. Optionally, sensor 110 additionally includes one or more auxiliary conductive areas 50 that are electrically isolated from conductive strips 32 and 34. It is noted that although the row conductive strips are shown as the wide strips and the column conductive strips are shown as the narrow strips, the opposite may be applied. Typically, in a two layer sensor, the wide conductive strips are included on a layer that is closest to an interaction surface of the sensor.

According to some embodiments of the present invention, non-conductive areas 245 are patterned in an Ή' shape with extensions 316 and 320 generally parallel to a longitudinal axis 99 of conductive strip 32 and extension 324 generally perpendicular to longitudinal axis 99 of conductive strip 32. Typically, a width of each of extensions 316, 320 and 324 covers only 0.5 %-10% of a width of conductive strip 32, e.g. covers 2% of the width of conductive strip 32 so that the capacitive coupling that can be formed between an interacting finger and the conductive strip is not significantly reduced. Typically, a length of each of segments 316 and 320 covers 30-80% of a length of conductive strip 32 between two junction areas 28. Optionally, a width of non- conductive area 245 extends over 15% - 90% of the width of the conductive strip. The present inventors have found that an Ή' shaped non-conductive area 245 oriented with respect to conductive strip 32 as shown in FIG. 2 is one exemplary pattern that can significantly increase the resistance of the conductive strip 32 without significantly reducing the capacitive coupling between an interacting finger (or other object) and conductive strips 32. Optional dimensions and sizes of non-conductive portions 245 are discussed in more detail herein below.

Reference is now made to FIG. 3 showing a simplified schematic illustration of two crossing conductive strips of a capacitive touch sensor, each of which is narrowed at a junction between the strips in accordance with some embodiments of the present invention. According to some embodiments of the present invention, a column conductive strip 42 and a row conductive strip 44 are shaped have a narrower dimension 13 near a junction 28 and a wide dimension 14 between junctions 28 and/or distanced from junction 28. In some exemplary embodiments, narrowing the conductive strips near junction points reduces the capacitive coupling between the row and column conductive line and thereby increases the capacitive coupling that can be formed between an interacting finger and the conductive strips. According to some embodiments of the present invention, non-conductive portions 245 are included in the portion of the conductive strips with wide dimension 14. Although non-conductive portions 245 is shown as an Ή shaped area near junction 28 for convenience in illustration, non-conductive portions 245 typically fully extend between two junction areas as shown for example in FIG. 2.

Reference is now made to FIG. 4 showing a simplified schematic illustration of two crossing conductive strips of a capacitive touch sensor including separate cut-outs in and between junction areas in accordance with some embodiments of the present invention. According to some embodiments of the present invention, column conductive strips 43 and row conductive strip 46 maintain full width 14, but the capacitive coupling between row and column conductive strips is reduced by including a non-conductive portion 211 in junction region 28. Typically, non-conductive portion 211 is sized to provide overlap between the row and conductive line so that a capacitive link between the strips is maintained. Optionally, non-conductive portion 211 encompasses an isolated conductive area 222. Reference is now made to FIG. 5 showing a simplified schematic illustration of a grid based capacitive touch sensor formed over a single layer in accordance with some embodiments of the present invention. Reference is additionally made to FIGS. 6 A and 6B showing simplified schematic illustrations of a top and cross-sectional view of an exemplary row conductive strip and top and cross-sectional view of an exemplary column conductive strip, respectively, in accordance with some embodiments of the present invention. According to some embodiments of the present invention, a capacitive touch sensor 200 is patterned on a single layer and each of the row conductive strips 54 and the column conductive strips 52 are composed of sections 544 and 522 respectively extending between junction areas 28 of sensor 200. Typically, each of segments 522 and 544 are narrowed toward junction area 28 and so that a narrow gap 306 is formed between segments 522 and 544 at the junction. According to some embodiments of the present invention, each of segments 522 and 544 includes a non-conductive pattern 245 that obstructs current flow, e.g. block current flow across a portion of the segments width.

According to some embodiments of the present invention, arrays of segments 522 are electrically connected to each other in series to form column conductive strips 52 and arrays of segments 544 are electrically connected in series by conductive bridge structures 80 to form row conductive strips 54. Typically, bridge structures 80 are electrically isolated from segments 522 in the column direction so that electrical connection can be made between segments 544 without making contact with segments 522 in the row direction. Typically, each of conductive strips 52 is a continuous strips and sections 522 of strip 52 are not separated sections. Alternatively, column segments 544 are connected by bride structures 80, and row segments 522 are directly and/or continuously connected.

Reference is now made to FIGS. 7 A, 7B, 7C and 7D, showing simplified schematic illustrations of exemplary non-conductive region patterned on a conductive strip of a capacitive touch sensor in accordance with some embodiments of the present invention. Typically, the cut-out patterns are composed from narrow slits so that the conductive path can be obstructed without significantly reducing capacitive coupling between an interacting finger (and/or other object) and the capacitive strips. Referring now to FIG. 7A, in some exemplary embodiments a conductive strip segment 544 includes an Ή shaped non-conductive pattern 245 that blocks current flow through a central region of the strip so that current flow along a length of the strip is limited to the peripheral regions of the segment on either side of the Ή' shaped pattern. Optionally, conductive strip segment 544 is one of a column or row segment and is approximately 1.4 mm wide and 4.7 mm long. In some exemplary embodiments, non-conductive portions 316, 320, 324 and 328 are narrow relatively to the dimensions of the segment, e.g. having a width of 0.03 mm so that the capacity to the finger is negligibly reduced and therefore the finger touch effect is negligibly affected. Optionally, the Ή' shaped non-conductive pattern 245 can increase the resistance of segment 544 about 2.5 times, e.g. may increase resistance from 150 ohm per segment without etching a shape thereon, to into 400 to 1000 ohms per segment once the shape is applied and the relevant areas are made non-conductive.

Referring now to Fig. IB, in some exemplary embodiment, a conductive strip segment 544 includes two non-conductive portions 420 and 424 which are substantially parallel to the direction of the current flow along segment 544, and two non-conductive portions 428 and 432 which are substantially perpendicular to the direction of current flow and/or perpendicular to a longitudinal axis of conductive strip segment 544. Optionally, in conductive strip segment 544, current flow along a length of the strip is limited to a narrow path in a central region of the strip between portions 420 and 424 and the current flow along a peripheral path of the strip is blocked. Typically, the segments parallel to the current flow direction are longer than the segments perpendicular to the current flow direction.

Referring now to FIG. 7C, in some exemplary embodiments, a conductive strip segment 544 includes a non-conductive pattern with one long portion 520 which is substantially parallel to the direction of the current flow along the segment and another short portion 524 which is substantially perpendicular to the longer segment. In this exemplary embodiment, the currently flow path is blocked along one side of segment 544, e.g. the left side and is limited to a narrower path on an opposite side of long portion 520.

Referring now to Fig. 7D, in some exemplary embodiment, a conductive strip segment 544 includes non-conductive portions 589 extending in a direction that crosses the direction of current flow and/or substantially perpendicular to a longitudinal axis of conductive strip segment 544. Optionally, non-conductive portions 589 extend from edges of segment 544. In some exemplary embodiments, non-conductive portions extend across a longitudinal axis of segment 544.

In some exemplary embodiments, each of the conductive strip segments 544 are electrically connected to additional segments in a conductive strip with a conductive bridge 80. Alternatively, the segments are directly connected to each other, e.g. are parts of a continuous conductive strip. Optionally, conductive strips are not divided into segments, and the non-conductive pattern is applied on the conductive strip between junctions of the capacitive touch sensor. Optionally, the non-conductive pattern overlaps a least a portion of the junction area.

Reference is now made to FIG. 8 showing a flow chart describing an exemplary method for defining construction of a capacitive touch sensor in accordance with some embodiments of the present invention. Typically, one or more properties of a capacitive touch sensor such as material of the row a column strips (block 810), length of the row and column strips (block 820) and geometry of row and column strips (block 830) is determined and/or noted. Other properties that may be considered include, material of the substrate on which the strips are to be patterned, number of layers that will be used to form the sensor, and thickness of a protective layer that will be positioned over the capacitive touch sensor.

Desired (and/or required) properties of the sensor and/or strips, such as but not limited to sensitivity and resolution of the sensor are defined (block 840). Based on the determined (or known) sensor properties, an adjustment in the shape of the conductors is determined, for example to achieve resistance needed to reach a desired sensitivity and resolution is defined (block 850). According to some embodiments of the present invention, a size and pattern for the non-conductive pattern that can provide the required adjustment to the resistance is determined (block 860). In some exemplary embodiments, the non-conductive patterns determined are etched onto existing conductive strips. Optionally, the conductive strips are constructed with the determined pattern and/or conductive strips with the determined pattern (block 870).

It will be appreciated by a person skilled in the art that although the exemplary patterns refer to adjusting the resistance of the conductors, etching or otherwise forming isolated areas of other patterns can be used for altering other properties or behaviors of the sensor, such as capacity, impedance, cross-talk between conductors, production yield or the like.

Reference is now made to FIG. 9 showing a simplified block diagram of a digitizer system including a capacitive touch sensor in accordance with some embodiments of the present invention. According to some embodiments of the present invention, digitizer system 500 includes a capacitive touch sensor 100 including a patterned arrangement of conductive strips, e.g. thin conductive lines or areas arranged in a grid. In some exemplary embodiments, capacitive touch sensor 10 is transparent and is optionally overlaid on a flat panel display (FPD). Typically, circuitry is provided on one or more printed circuit boards (PCBs) 40 positioned around capacitive touch sensor 10. One or more application specific integrated circuit (ASICs) 16 positioned on PCB 40 comprise circuitry to sample and process the sensor's output into a digital representation. Digital output is optionally forwarded to a digital unit 120, e.g. a digital ASIC unit also on PCB 40, for further digital processing. Typically, output from digital unit 120 is forwarded to a host 122 via an interface 124 for processing by the operating system or any current application.

Capacitive touch sensor 100 is a grid based sensor including row conductive strips 22 and column conductive strips 24, also referred to as antennas. In some exemplary embodiments, additional dummy conductive regions and/or areas, e.g. auxiliary conductive areas 50 (FIG. 2) are patterned between adjacent row and/or column conductive lines to enhance capacitive coupling between conductive strips of the sensor and conductive objects interacting with the sensor.

Typically, capacitive touch sensor 100 is transparent and the conductive strips of the sensor are formed with materials such as ITO, IZO, a conductive polymer, carbon nano-tube, metal nano-particles such as Ag or Cu, ATO, or other conductive transparent materials. The transparent conductive strips may be patterned on a substrate of glass, foil and/or other non-conductive substrate in one or more layers. Optionally, the conductive strips are not transparent but are thin enough so that they do not substantially interfere with viewing an electronic display placed behind the strips.

Typically, the parallel conductive areas are spaced at a distance of approximately 2-6.5 mm, e.g. 4 mm, depending on the size of the FPD and a desired resolution. Optionally, the ends of the lines remote from the amplifiers are not connected, so that the lines do not form loops.

According to some embodiments, digital unit 120 produces and sends a triggering pulse to at least one of the conductive lines.18 KHz or 20-40 KHz. In some exemplary embodiments, finger touch detection is facilitated when sending a triggering pulse to the conductive lines.

According to some embodiments of the subject matter, digital unit 120 produces and controls the timing and sending of a triggering pulse to be provided to an excitation coil 26 that surrounds the sensor arrangement and the display screen. The excitation coil provides a trigger pulse in the form of an electric or electromagnetic field that excites passive circuitry in stylus 144 or other object used for user interaction to produce a response from the stylus 144 that can subsequently be detected. In other exemplary embodiments, an excitation coil is not included.

ASICs 16 are connected to outputs of the conductive strips forming the grid. ASICs 16 optionally include one or more filters to remove frequencies that do not correspond to frequency ranges used for excitation and/or obtained from objects used for user interactions. The signal is then sampled by an A/D, optionally filtered by a digital filter and forwarded to digital unit 120, for further digital processing. Typically, digital unit 120 together with ASICs 16 serve as a controller of the digitizer system and/or has functionality of a controller and/or processor. Optionally, ASICs 16 and digital unit 120 are integrated into a single unit, e.g. a single ASIC.

Typically, digital unit 120 receives the sampled data from ASIC 16, reads the sampled data, processes it and determines and/or tracks the position of physical objects, such as a stylus 144, token 145 and/or a finger 146, and/or an electronic tag touching the digitizer sensor from the received and processed signals. Optionally, hovering of an object, e.g. stylus 144, finger 146 is also detected and processed by digital unit 120.

Typically, calculated position and/or tracking information are sent to a host computer

122 via interface 124.

Typically the triggering pulses and/or signals are analog pulses and/or signals. According to some embodiments of the present invention, the triggering pulse and/or signal implemented may be confined to one or more pre-defined frequencies. In some exemplary embodiments, finger touch detection is facilitated when sending a triggering pulse to one of the row and column conductive lines.

Reference is now made to FIG. 10 showing a schematic diagram describing a capacitive touch detection method used with a capacitive touch sensor in accordance with some embodiments of the present invention. According to some embodiments of the present invention, digital unit 120 and/or ASIC 16 (FIG. 9) produce and send an interrogation signal or pulse such as a triggering signal 60 to conductive strips along at least one axis, e.g. row or column axis of the sensor. Typically, the triggering signal is a pulse sinusoidal and/or AC signal. When a finger 146 touches capacitive touch sensor 10 at a position 41 where trigger signal 60 is induced, the capacitance between column conductive strip 22 and a row conductive strip 24 changes in the junctions proximal to the position 41, and triggering signal 60 crossing to row conductive strip 24 produces a lower amplitude signal 65, e.g. lower in reference to a base-line amplitude. Base-line amplitude is amplitude recorded when no user interaction is present. Typically, the presence of a finger decreases the amplitude of the coupled signal by 15-30%. Optionally, a finger hovering above the display, i.e. near touch, can also be detected, although the decrease of the signal is generally smaller.

More than one finger touch with a finger 146 and/or other capacitive object (e.g. token 145) can be detected at the same time (multi-touch). Typically, a triggering signal is transmitted to an array of conductive strips, row or column conductive strips in a sequential manner. Optionally, all or parts of the conductive areas are interrogated concurrently. Output may be simultaneously sampled from conductive strips crossing the triggered conductive strips in response to each transmission of a trigger signal. Digitizer systems used to detect stylus and/or finger touch location may be, for example, similar to digitizer systems described in U.S. Patent No. 6,690,156, U.S. Patent No. 7,292,229 or U.S. Patent No. 7,372,455, the full contents of which are incorporated herein by reference. The present disclosure may also be applicable to other capacitive touch sensors and touch screens known in the art, depending on their construction.

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to". The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Claims

WHAT IS CLAIMED IS:

1. A capacitive touch sensor comprising:

a row array of conductive strips and a column array of conductive strips arranged in a grid with a plurality of junction areas formed therebetween,

wherein at least one of the row or column conductive strips includes at least one electrically isolated region positioned between two contiguous junction areas of the plurality of junction areas formed by the grid.

2. The capacitive touch sensor according to claim 1, wherein the electrically isolated region includes at least one segment that extends along a direction of current flow.

3. The capacitive touch sensor according to claim 1 or claim 2, wherein the electrically isolated region includes at least one segment that extends across a direction of current flow.

4. The capacitive touch sensor according to any of claims 1-3, wherein the electrically isolated region is composed of one or more elongated regions, wherein each of the one or more elongated regions occupy a width of less than 15% of a width of the conductive strip on which it is positioned.

5. The capacitive touch sensor according to any of claims 1-4, wherein the electrically isolated region is composed of one or more elongated regions, wherein each of the one or more elongated regions occupy a width of less than 5% of a width of the conductive strip on which it is positioned.

6. The capacitive touch sensor according to any of claims 1-5, wherein the electrically isolated region includes at least one first segment and at least one second segment, wherein the at least one first segment is longer than the at least one second segment, and each of the at least one first segments are orthogonal to at least one of the at least one the second segment.

7. The capacitive touch sensor according to any of claims 1-6, wherein the electrically isolated region includes at least one first segment and at least one second segment, wherein the at least one first segment is parallel to a current flow direction along the conductive strip and the at least one second segment is substantially perpendicular to the current flow direction along that conductive strip, and wherein the at least one first segment is longer than the at least one second segment.

8. The capacitive touch sensor according to any of claims 1-7, wherein the electrically isolated region has a shape of an Ή.'

9. The capacitive touch sensor according to any of claims 1-8, wherein only one of the row array of conductive strips and the column array of conductive strips includes electrically isolated regions positioned between contiguous junction areas.

10. The capacitive touch sensor according to any of claims 1-9, wherein at least one of the row array of conductive strips and the column array of conductive strips includes a narrow portion in the vicinity of the junction areas and a wide portion between the junction areas.

11. The capacitive sensor according to claim 10, wherein the electrically isolated region is positioned in the wide portion between the junction areas.

12. The capacitive touch sensor according to any of claims 1-11, wherein the array of row conductive strips and the column array of conductive strips are patterned on a single layer.

13. The capacitive touch sensor according to claim 12, wherein the at least one of the row conductive strips and column conductive strips are formed by a plurality of discrete sections that are electrically connected in series at the junction areas by a bridge structure.

14. The capacitive touch sensor according to claim 13, wherein the electrically isolated areas are formed on the discrete sections.

15. The capacitive touch sensor according to any of claims 1-14, wherein the at least one electrically isolated region is etched on a conductive strip.

16. A digitizer system comprising:

a capacitive touch sensor according to any of claims 1-15;

a signal generator configured for providing a signal to at least one conductive strip; and

a controller configured for sampling an output signal from at least one other conductive strip that crosses the at least one conductive strip.

17. A method for constructing a capacitive touch sensor, the method comprising:

defining dimensions of the capacitive touch sensor, wherein the capacitive touch sensor includes a row array of conductive strips and a column array of conductive strips arranged in a grid with a plurality of junction areas formed therebetween;

determining material for constructing the capacitive touch sensor;

determining a desired property of the capacitive sensor;

determining geometry of an electrically isolated region to be formed on conductive strips of the capacitive touch sensor, wherein the at least one electrically isolated region is positioned between two contiguous junctions areas of the plurality of junction areas formed by the grid; and

constructing the capacitive touch sensor with conductive strips including at least one electrically isolated region.

18. The method according to claim 17, wherein the desired property is selected from the group consisting of: capacity, resistance, impedance, and cross talk between conductors.

19. The method according to claim 17 or claim 18, wherein the electrically isolated region includes at least one segment that extends along a direction of current flow.

20. The method according to any of claims 17-19, wherein the electrically isolated region includes at least one segment that extends across a direction of current flow.

21. The method according to any of claims 17-20, wherein the electrically isolated region is composed of one or more elongated regions, wherein each of the one or more elongated regions occupy a width of less than 15% of a width of the conductive strip on which it is positioned.

22. The method according to any of claims 17-21, wherein the electrically isolated region is composed of one or more elongated regions, wherein each of the one or more elongated regions occupy a width of less than 5% of a width of the conductive strip on which it is positioned.

23. The method according to any of claims 17-22, wherein the electrically isolated region includes at least one first segment and at least one second segment, wherein the at least one first segment is longer than the at least one second segment, and each of the at least one first segments are orthogonal to at least one of the at least one the second segment.

24. The method according to any of claims 17-23, wherein the electrically isolated region includes at least one first segment and at least one second segment, wherein the at least one first segment is longer than the at least one second segment, and wherein each of the at least one first segment is parallel to a current flow direction along the conductive strip on which the electrically isolated region positioned and each of the at least one second segment is substantially perpendicular to the current flow direction along that conductive strip.

25. The method according to any of claims 17-24, wherein the electrically isolated region has a shape of an Ή.'

26. The method according to any of claims 17-25, wherein the at least one electrically isolated region is etched onto the conductive strip.