ITO pattern for capacitive touchscreen applications

A capacitive sensing structure is formed from first electrically conductive sensor structures electrically coupled to each other in a first direction, and second electrically conductive sensor structures electrically coupled to each other in a second direction. Each first electrically conductive sensor structure includes a first diamond-shaped central region with electrically coupled first finger structures extending away therefrom. Each second electrically conductive sensor structure includes a second diamond-shaped central region with electrically conducting second finger structures extending away therefrom. Each second finger structure extends between two adjacent ones of the first finger structures. Floating structures may be included within an opening formed in the first diamond shaped central region. Floating structures may further be included between the first and second finger structures.

TECHNICAL FIELD

The present invention relates to capacitive sensing input devices, and in particular to a single layer indium tin oxide (ITO) pattern for use in a capacitive touchscreen sensor.

BACKGROUND

Reference is now made toFIG. 1which illustrates a prior art two-layer indium tin oxide (ITO) pattern for a capacitive touchscreen sensor. A diamond-shaped electrode pattern is commonly used. A first set of diamond-shaped sensors12, often referred to in the art as the “Yforce” structure, are provided in a first material layer. The sensors12are arranged in a matrix. The sensors12in each column are connected to each other by a connecting member14. The sensors12in adjacent columns are isolated from each other. The sensors12and connecting members14are made of a first patterned ITO layer. A second set of diamond-shaped sensors22, often referred to in the art as the “Xsense” structure, are provided in a second material layer isolated from the first material layer. The sensors22are arranged in a matrix. The sensors22in each row are connected to each other by a connecting member24. The sensors22in adjacent rows are isolated from each other. The sensors22and connecting members24are made of a second patterned ITO layer.

The matrix of the sensors12is interleaved with the matrix of sensors22in a manner where the space between a group of four diamond-shaped sensors12is occupied by one of the diamond-shaped sensors22, and the space between a group of four diamond-shaped sensors22is occupied by one of the diamond-shaped sensors12.

The first patterned ITO material layer including sensors12and connecting members14may be the lower layer of the capacitive sensor and the second patterned ITO material layer including sensors22and connecting members24may be the upper layer (as shown inFIG. 1), or vice versa. The first and second patterned ITO material layers are isolated from each other by an interposed insulating layer. The insulating layer, first patterned ITO material layer and second patterned ITO material layer are supported by a transparent substrate layer.

Reference is now made toFIG. 2which illustrates a prior art single layer indium tin oxide (ITO) pattern for a capacitive touchscreen sensor. Again, a diamond-shaped electrode pattern is commonly used. A first set of diamond-shaped sensors32, often referred to in the art as the “Yforce” structure, are provided in a first material layer. The sensors32are arranged in a matrix. A second set of diamond-shaped sensors42, often referred to in the art as the “Xsense” structure, are also provided in the same first material layer. The sensors42are arranged in a matrix. The sensors42in each row are connected to each other by a connecting member44. The sensors42in adjacent rows are isolated from each other. The sensors32, sensors42and connecting members44are made of a first patterned ITO layer. The sensors32in each column are connected to each other by conductive bridges34provided in a second material layer isolated from the first material layer. The conductive bridges44may be made of a second patterned ITO layer, or made from any other patterned conductive material layer. The sensors32in adjacent columns are isolated from each other.

The matrix of the sensors32is interleaved with the matrix of sensors42in a manner where the space between a group of four diamond-shaped sensors32is occupied by one of the diamond-shaped sensors42, and the space between a group of four diamond-shaped sensors42is occupied by one of the diamond-shaped sensors32.

The first patterned ITO material layer including sensors32, sensors42and connecting members44may be the lower layer of the capacitive sensor and the second patterned ITO material layer including conductive bridges34may be the upper layer (as shown inFIG. 2), or vice versa. The first and second patterned ITO material layers are isolated from each other by an interposed insulating layer. The insulating layer, first patterned ITO material layer and second patterned ITO material layer are supported by a transparent substrate layer.

The prior art indium tin oxide patterns described above typically overlay a display screen in a stacked configuration. Commonly, that display screen is a liquid crystal display (LCD) although other display technologies may also be used. In operation, these prior art indium tin oxide patterns can suffer from an unacceptable amount of noise captured from the underlying LCD display screen. Additionally, there is room for improvement with respect to sensitivity of the prior art indium tin oxide patterns to capacitive touches (or proximity detections).

A need accordingly exists in the art for an improved ITO pattern for capacitive touchscreen applications.

SUMMARY

In an embodiment, a capacitive sensing structure comprises: a plurality of first electrically conductive sensor structures electrically coupled to each other in a first direction, and a plurality of second electrically conductive sensor structures electrically coupled to each other in a second direction intersecting (preferably, but not limited to, orthogonal to) the first direction. Each of the first electrically conductive sensor structures comprises: a central diamond-shaped region having a peripheral edge; and a plurality of first finger structures electrically coupled to the central diamond-shaped region and extending away from the peripheral edge towards the second direction.

In an embodiment, a capacitive sensing structure comprises: a plurality of first electrically conductive sensor structures electrically coupled to each other in a first direction, and a plurality of second electrically conductive sensor structures electrically coupled to each other in a second direction intersecting (preferably, but not limited to, orthogonal to) the first direction. Each of the first electrically conductive sensor structures comprises: a first central region; and a plurality of first finger structures electrically coupled to the first central region and extending away from the first central region. Each of the second electrically conductive sensor structures comprises: a second central region; and a plurality of second finger structures electrically coupled to the second central region and extending away from the second central region. Each second finger structure extends between adjacent first finger structures.

In an embodiment, a capacitive sensing structure, comprises a plurality of electrically conductive sensor structures electrically coupled to each other in a first direction. Each electrically conductive sensor structure comprises: a diamond-shaped central region; and a plurality of finger structures electrically coupled to the diamond-shaped central region and extending away from the diamond-shaped central region either in the same direction as the first direction or towards a second direction intersecting (preferably, but not limited to, orthogonal to) the first direction.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is now made toFIG. 3which illustrates an embodiment for a diamond-shaped ITO pattern100for use in a capacitive touchscreen sensor. The diamond-shaped ITO pattern100is illustrated for use in connection with the “Xsense” structure and comprises central diamond-shaped region102with a reduced area (in comparison to the area of the conventional prior art diamond shaped regions as shown inFIGS. 1 and 2). The area of the central diamond-shaped region102is reduced by flattening the central diamond-shaped region102such that its vertical bisecting height (“h”) is a fraction of the horizontal bisecting width (“w”). The ratio of height to width (h:w) of the flattened central diamond-shaped region102may range from 1:3 to 3:4, with 1:2 being preferred.

The central diamond-shaped region102has a perimeter defined by four edges104. Extending from each of the four edges104are a plurality of projecting fingers106. In a preferred embodiment, the projecting fingers106extend from the edges104in a vertical direction (i.e., perpendicular to the horizontal width bisector, and parallel to the vertical height bisector) and terminate at a distal end. It will be understood that any suitable orientation angle for the projecting fingers106may be selected. For example, the projecting fingers106may alternatively extend in a direction that is generally towards the vertical direction, and in a specific implementation of this in a direction which is perpendicular to the edges104.

Adjacent diamond-shaped ITO patterns100are connected by a connecting member108.

The central diamond-shaped region102, the plurality of projecting fingers106and the connecting member108may be fabricated of a single patterned ITO layer for the capacitive touchscreen sensor. In a two-layer ITO capacitive touchscreen sensor pattern, the “Yforce” sensors for the vertical columns (see, for example, sensors12ofFIG. 1) would be formed in a separate patterned ITO layer insulated from the patterned ITO layer providing the central diamond-shaped region102, the plurality of projecting fingers106and the connecting member108. In a single layer ITO capacitive touchscreen sensor pattern, the “Yforce” sensors for the vertical columns (see, for example, sensors32ofFIG. 2) would be formed in the same patterned ITO layer providing the central diamond-shaped region102, the plurality of projecting fingers106and the connecting member108. A connecting bridge110formed on a separate second patterned ITO layer or made from any other patterned conductive material layer would then be provided for making the vertical electrical connections. Structures108and110would be electrically isolated from each other by an interposed insulating layer.

The central diamond-shaped region102, projecting fingers106and connecting member108are electrically connected to each other.

The diamond-shaped ITO pattern100is preferably used in connection with the horizontal sensing structure of the capacitive touchscreen sensor as the “Xsense” structure. Thus, the diamond-shaped ITO pattern100would replace, for example, the second set of diamond sensors22in a sensor as shown inFIG. 1, or replace the second set of diamond sensors42in a sensor as shown inFIG. 2.

Although the preferred implementation is for use of the diamond-shaped ITO pattern100in the horizontal sensor, it will be understood that the diamond-shaped ITO pattern100could alternatively be used in the vertical sensor as the “Yforce” structure.

The regions112between projecting fingers106are preferably occupied by projecting fingers114(illustrated with dashed lines) of “Yforce” sensors for the vertical columns which extend from a central region (see,FIG. 4Afor example) and terminate at a distal end near the edge104. Thus, it will be understood that the projecting fingers106and projecting fingers114are interdigitated. In a preferred single layer ITO implementation, the projecting fingers114for the vertical column “Yforce” sensors are formed by the same single patterned ITO layer used for the central diamond-shaped region102, the plurality of projecting fingers106and the connecting member108.

The regions between projecting fingers106and the projecting fingers114may be occupied by floating separators120. The floating separators120are conductive linear segments which are not electrically connected to either the “Yforce” vertical sensor or the “Xsense” horizontal sensor In other words, the floating separators120have no electrical connection to either the projecting fingers106or108or102or the projecting fingers114. In a preferred single layer ITO implementation, the floating separators120are formed by the same single patterned ITO layer used for the central diamond-shaped region102, the plurality of projecting fingers106, the connecting member108and the projecting fingers114and vertical column sensors.

FIG. 3illustrates placement of floating separators120between the projecting fingers106and the projecting fingers114. It will be understood that the floating separators120could additionally, or alternatively, be placed between the ends of the projecting fingers114and the side edges of the central diamond-shaped region102. It will also be understood that the floating separators120could additionally be placed between the ends of the projecting fingers106and the structure of the vertical column sensors. Thus, it will be understood that the floating separators120comprise interposed structures.

Reference is now made toFIG. 4Awhich illustrates an alternative embodiment for a diamond-shaped ITO pattern100for exemplary use as an “Xsense” structure in a capacitive touchscreen sensor. Like reference numbers refer to like or similar parts.FIG. 4Aillustrates placement of floating separators120having a linear segment shape between the distal ends of the projecting fingers114and the side edges of the central diamond-shaped region102.FIG. 4Afurther illustrates placement of floating separators120having a curved segment (for example, horseshoe) shape between the distal ends of the projecting fingers106and the structure200of the “Yforce” vertical column sensors. The structures200for the vertical column sensors are connected in a column by the connecting bridge110(preferably provided on a separate patterned ITO/conductive material layer), with the columns of structures200separated from each other at the region202.

All of the structures illustrated inFIG. 4A, with the exception of the connecting bridge110, are preferably formed from a single patterned ITO layer.

The structure200of each “Yforce” vertical column sensor may accordingly be considered to be formed by a central region with projecting fingers114extending away from that central region. The central region for the structure200may be considered to comprise a diamond-shaped structure as shown by reference206. The projecting fingers114accordingly extend away from a peripheral edge of the central region206.

FIG. 4Billustrates dimensional relationships for the diamond-shaped ITO pattern100structure ofFIG. 4A. The following Table provides information concerning selection of the dimensional values for an exemplary implementation of the sensor.

Dimensions (suggestedSymbolDescriptionexemplary figures)vVertical diagonal of XSense50% of hhHorizontal diagonal of Xsensep′ − wpDistance between adjacent XsenseCalculated based onchannelsthe aspect ratio andp′Distance between adjacent Yforcenumber of channelschannelsgGap between adjacent Xsense channels0.1 mmfWidth of the finger projecting0.1 mm-0.2 mminto Yforce(depending on ITOresistivitycFloating Separation between the40% to 50% of theYForce and XSenseCover Lens thicknesssDistance between projecting fingers2*f or 3*fin the same XSenselLength of the XSense finger(p − v − 2*g)/2projecting into the YForcewLength of the bridge connecting two0.2 mm (depending onstructuresthe ITO resistivity)

Reference is now made toFIG. 5which illustrates an alternative embodiment for a diamond-shaped ITO pattern100for exemplary use as an “Xsense” structure in a capacitive touchscreen sensor. Like reference numbers refer to like or similar parts.FIG. 5illustrates a different structure for the central diamond-shaped region102. In this implementation, the central diamond-shaped region102is hollow formed by a diamond-shaped ring210encircling a diamond-shaped opening212. The diamond-shaped opening212may be empty. However, in a preferred embodiment, a floating separator220is provided in each opening210. The floating separators220are conductive segments which are not electrically connected to each other or to any other structure of the sensor. In a preferred single layer ITO implementation, the floating separators220are formed by the same single patterned ITO layer used for the diamond-shaped ring210(of the central diamond-shaped region102), the plurality of projecting fingers106, the connecting member108, the structures200of the column sensors (including projecting fingers114) and floating separators120.

Reference is now made toFIG. 6which illustrates an alternative embodiment for a diamond-shaped ITO pattern100for exemplary use as an “Xsense” structure in a capacitive touchscreen sensor. Like reference numbers refer to like or similar parts.FIG. 6illustrates a different structure for the floating separators120which are made from a plurality of individual tile segments arranged together (the number of tile segments being exemplary only).FIG. 6further illustrates a different structure for the floating separators220provided within the diamond-shaped opening212of the central diamond-shaped region102. In this implementation, rather than provide a single floating separator220structure within each opening212(as shown inFIG. 5), a plurality of floating separators230are providing within each opening212.FIG. 6illustrates a tiled arrangement for the plurality of floating separators230. It will be understood, however, that this arrangement is merely exemplary of one way to arrange the plurality of floating separators230within each opening212. Furthermore, the use of diamond-shaped tiles for the plurality of floating separators230is exemplary only, it being understood that other tile shapes, for example, round, triangular, hexagonal, rectangular, and the like, could instead be chosen. The floating separators230are conductive segments which are not electrically connected to each other or to any other structure of the sensor. In a preferred single layer ITO implementation, the floating separators230are formed by the same single patterned ITO layer used for the diamond-shaped ring210(of the central diamond-shaped region102), the plurality of projecting fingers106, the connecting member108, the structures200of the column sensors (including projecting fingers114) and floating separators120.

Reference is now made toFIG. 7which illustrates an alternative embodiment for a diamond-shaped ITO pattern100for exemplary use as an “Xsense” structure in a capacitive touchscreen sensor. Like reference numbers refer to like or similar parts.FIG. 7illustrates a different structure for the floating separators120. In this implementation, rather than provide floating separators120in the form of linear segments (as shown inFIG. 4A), the regions112between projecting fingers106are filled with a plurality of floating separators240.FIG. 7illustrates a tiled arrangement for the plurality of floating separators240. It will be understood, however, that this arrangement is merely exemplary of one way to arrange the plurality of floating separators240within the regions112. Furthermore, the use of diamond-shaped tiles for the plurality of floating separators240is exemplary only, it being understood that other tile shapes, for example, round, triangular, hexagonal, rectangular, and the like, could instead be chosen. The floating separators240are conductive segments which are not electrically connected to each other or to any other structure of the sensor. In a preferred single layer ITO implementation, the floating separators240are formed by the same single patterned ITO layer used for the central diamond-shaped region102, the plurality of projecting fingers106, the connecting member108, and the structures200of the column sensors (including projecting fingers114). It will further be noted that the floating separators240substantially fill the regions112between projecting fingers106. In this implementation, the projecting fingers114(for the Yforce structure) are either shortened in length (as shown) or eliminated.

Reference is now made toFIG. 8which illustrates an alternative embodiment for a diamond-shaped ITO pattern100for exemplary use as an “Xsense” structure in a capacitive touchscreen sensor. Like reference numbers refer to like or similar parts.FIG. 8illustrates a different structure for the floating separators220provided within the diamond-shaped opening212of the central diamond-shaped region102. In this implementation, rather than provide a single floating separator220structure within each opening212(as shown inFIG. 5), a plurality of floating separators230are providing within each opening212.FIG. 8illustrates a tiled arrangement for the plurality of floating separators230. It will be understood, however, that this arrangement is merely exemplary of one way to arrange the plurality of floating separators230within each opening212. Furthermore, the use of diamond-shaped tiles for the plurality of floating separators230is exemplary only, it being understood that other tile shapes, for example, round, triangular, hexagonal, rectangular, and the like, could instead be chosen.

FIG. 8further illustrates a different structure for the floating separators120. In this implementation, rather than provide floating separators120in the form of linear segments (as shown inFIG. 4A), the regions112between projecting fingers106are filled with a plurality of floating separators240.FIG. 8illustrates a tiled arrangement for the plurality of floating separators240. It will be understood, however, that this arrangement is merely exemplary of one way to arrange the plurality of floating separators240within the regions112. Furthermore, the use of diamond-shaped tiles for the plurality of floating separators240is exemplary only, it being understood that other tile shapes, for example, round, triangular, hexagonal, rectangular, and the like, could instead be chosen.

The floating separators230and240are conductive segments which are not electrically connected to each other or to any other structure of the sensor. In a preferred single layer ITO implementation, the floating separators230and240are formed by the same single patterned ITO layer used for the diamond-shaped ring210(of the central diamond-shaped region102), the plurality of projecting fingers106, the connecting member108, and the structures200of the column sensors (including projecting fingers114).

The structures described herein provide a number of advantages in comparison to the prior art structures ofFIGS. 1 and 2.

The reduction in the Xsense diamond area reduces the noise captured from the LCD below the capacitive touchscreen panel.

The finger projections increase the perimeter of interaction between the Xsense and Yforce. The mutual capacitance is now focused in the Xsense fingers projecting into the Yforce structure. This improves the sensitivity of the touch panel by increasing the mutual coupling resulting in improved sensitivity in spite of reduced Xsense area.

The operating linearity profile for the sensor is improved as the coupling is more uniform moving across channels.

The floating separator aids in increasing the fringing fields which in turn increases the sensitivity of the capacitive touchscreen panel.

The structure in its preferred implementation uses only one layer of ITO for both the X and Y sensors, therefore providing a reduced thickness of the sensor and accordingly a reduced thickness of an LCD stack up including the sensor.