`(12) Patent Application Publication (10) Pub. No.: US 2011/0007011 A1
`Mozdzyn
`(43) Pub. Date:
`Jan. 13, 2011
`
`US 2011 0007011A1
`
`(54) CAPACITIVE TOUCH SCREEN WITH A
`MESHELECTRODE
`
`(75) Inventor:
`
`Larry Stephen Mozdzyn, Garland,
`TX (US)
`
`MARTIN & ASSOCIATES, LLC
`
`Correspondence Address:
`PO BOX 548
`CARTHAGE, MO 64836-0548 (US)
`
`(73) Assignee:
`
`OCULAR LCD INC., Dallas, TX
`(US)
`
`(21) Appl. No.:
`
`12/824,167
`
`(22) Filed:
`
`Jun. 26, 2010
`
`Oa -
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`- - -
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`Related U.S. Application Data
`(60) Provisional application No. 61/224.999, filed on Jul.
`13, 2009, now abandoned.
`Publication Classification
`
`345/173
`
`(51) Int. Cl.
`(2006.01)
`(52) section
`ABSTRACT
`(57)
`An improved touch screen provides enhanced electrical per
`formance and optical quality. The electrodes on the touch
`screen are made of a mesh of conductors to reduce the overall
`electrode resistance thereby increasing the electrical perfor
`mance without sacrificing optical quality. The mesh elec
`trodes comprise a mesh pattern of conductive material with
`each conductor comprising the mesh having a very Small
`width such that the conductors are essentially invisible to the
`user of the touch screen.
`
`120 122 , 210 (3 Places)
`212
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`1. 2OO
`
`
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`224
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`||||||
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`|| || ||
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`130
`
`LCD DisplayLayers
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`110 Top Glass
`118 Column
`Electrodes
`114 Adhesive
`112 BOttom
`Glass
`
`126
`128 Light
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`Patent Application Publication
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`Jan. 13, 2011 Sheet 1 of 3
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`US 2011/0007011 A1
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`132
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`122
`12O
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`124
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`116
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`116
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`130
`.
`
`.
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`.
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`LCD Display Layers
`.
`.
`.
`.
`FIG.1
`(Prior Art)
`
`1. 1OO
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`110 Top Glass
`
`118 Column
`Electrodes
`114 Adhesive
`112 Bottom
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`112 Glass
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`A
`
`N
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`- 126 Back Light
`128 LiOht
`I9
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`120 122 , 210 (3 Places)
`212
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`- 200
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`
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`224 Imlil
`|||||||
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`||||||||
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`130
`
`LCD DisplayLayers
`
`FIG. 2
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`110 Top Glass
`118 Column
`Electrodes
`114 Adhesive
`U 112 Bottom
`
`Glass
`
`126
`128 Light
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`Patent Application Publication
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`Jan. 13, 2011 Sheet 2 of 3
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`US 2011/0007011 A1
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`210 (3 Places) 312
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`
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`
`
`
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`
`
`FIG. 3
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`Conductor wah-
`Mesh thickness || || || ||
`
`
`
`
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`210
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`
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`210
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`312
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`Patent Application Publication
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`Jan. 13, 2011 Sheet 3 of 3
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`US 2011/0007011 A1
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`310
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`712 ;I,
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`CAPACTIVE TOUCH SCREEN WITH A
`MESHELECTRODE
`
`BACKGROUND
`1. Technical Field
`0001
`0002 The disclosure and claims herein generally relate to
`touch screens, and more specifically relate to a touch screen
`having low resistance mesh electrodes to improve the electri
`cal characteristics of the touch screen without compromising
`the optical characteristics.
`0003 2. Background Art
`0004 Touch screens have become an increasingly impor
`tant input device. Touch screens use a variety of different
`touch detection mechanisms. One important type of touch
`screen is the capacitive touch screen. Capacitive touch
`screens are manufactured via a multi-step process. In a typical
`touch screen process, a transparent conductive coating. Such
`as indium tin oxide (ITO) is formed into conductive traces or
`electrodes on two Surfaces of glass. The conductive traces on
`the two Surfaces of glass typically form a grid that can sense
`the change in capacitance when a user's finger or a pointer
`touches the screen near an intersection of the grid. Thus the
`capacitive touch screen consists of an array of capacitors,
`where a capacitor is created at each crossing of the X and y
`conductive traces or electrodes which are separated by a
`dielectric. These capacitors are charged and discharged by
`scanning electronics. The scanning frequency of the touch
`screen is limited by a resistance/capacitive (RC) time con
`stant that is characteristic of the capacitors. As the resistance
`of the trace becomes larger and larger, Scanning times become
`proportionately longer and longer. Longer scan times are
`even more problematic as the panel sizes get larger. The larger
`the panel size the longer the traces and the higher the resis
`tance gets.
`0005. As mentioned above, in typical capacitive touch
`screens, the conductive traces or electrodes are formed with a
`layer of indium tin oxide (ITO). ITO is used because of its
`conductive and transparent qualities. However, the ITO traces
`are not completely transparent. The visibility of the electrode
`traces is distracting to the user. It is desirable for the touch
`screen to have the sense electrodes and other traces on the
`touch screen to be substantially invisible to the user, but it is
`also desirable to reduce the resistance of the traces to reduce
`the scan times and the performance of the touch screen.
`Increasing the thickness of the ITO layer can reduce the
`electrode trace resistance. However, increasing the thickness
`of the ITO layer sufficiently to decrease the electrode trace
`resistance results in reduced optical performance because the
`thicker ITO layer becomes more visible.
`
`BRIEF SUMMARY
`0006. The application and claims herein are directed to an
`improved touch screen with enhanced electrical performance
`and optical quality. The electrodes on the touch screen are
`made of a mesh of conductors to reduce the overall electrode
`resistance thereby increasing the electrical performance with
`out sacrificing optical quality. The mesh electrodes comprise
`a mesh pattern of conductive material with each conductor
`comprising the mesh having a very Small width Such that the
`conductors are essentially invisible to the user of the touch
`SCC.
`0007. The description and examples herein are directed to
`capacitive touch screens with two Substrates for the conduc
`
`tive sense electrodes, but the claims herein expressly extend
`to other arrangements including a single glass or plastic Sub
`Strate.
`0008. The foregoing and other features and advantages
`will be apparent from the following more particular descrip
`tion, and as illustrated in the accompanying drawings.
`
`BRIEF DESCRIPTION OF DRAWINGS
`0009. The disclosure will be described in conjunction with
`the appended drawings, where like designations denote like
`elements, and:
`0010 FIG. 1 is a cross-sectional side view of a capacitive
`touch screen according to the prior art;
`0011
`FIG. 2 is a cross-sectional side view of a capacitive
`touch screen as described and claimed herein;
`0012 FIG. 3 shows a top view of mesh electrodes on a
`portion of the bottom glass of the touch screen shown in FIG.
`2:
`0013 FIG. 4 shows an enlarged view of the cross section
`of the mesh electrode taken on the lines 4-4 of the touch
`screen shown in FIG. 3;
`0014 FIG. 5 shows an enlarged top view of the mesh
`conductors of the electrode shown in FIGS. 3 and 4:
`0015 FIG. 6 shows an example of mesh electrodes with a
`diamond shape pattern; and
`0016 FIG. 7 shows an example of mesh electrodes with
`stacked layers.
`
`DETAILED DESCRIPTION
`0017. As claimed herein, the electrodes on a touch screen
`are made of a mesh of conductors to reduce the overall elec
`trode resistance thereby increasing the electrical performance
`without sacrificing optical quality. The mesh electrodes com
`prise a mesh pattern of conductive material with each con
`ductor comprising the mesh having a very small width such
`that the conductors are essentially invisible to the user of the
`touch screen.
`0018 Touch Panel Transparency
`0019. The optical quality of a touch screen panel can be
`described in terms of transparency, where 100% transparent
`means 100% of the light transfers through the panel. A typical
`single layer of glass used in a touch screen panel has a trans
`parency of about 97%. A typical optical adhesive has a trans
`parency of about 99.5%. For a touch panel constructed out of
`two sheets of glass and a single layer of optical adhesive (No
`electrodes on the glass at all), the overall transparency of the
`panel can be calculated as follows:
`Total Panel transparency=0.97*0.97*0.995=93.6%
`0020. As described in the background, a typical touch
`screen panel has a layer of ITO on the glass to form electrodes
`for sensing the location where the screen is touched. The
`transparency of ITO coated glass with 100 ohm/square ITO is
`~92%. A touch panel constructed out of 100 ohm ITO glass
`with the optical adhesive is therefore about 0.92*0.92*0.
`995-85%. Thinner layers of ITO can give a higher transpar
`ency, but as discussed above, it is advantageous to reduce the
`electrode resistance for better performance. Thus there is a
`tradeoff between transparency for better optical performance
`and resistance of the electrode for better touch performance.
`0021. In capacitive touchpanels there area different meth
`odologies to measure the capacitive coupling effect when the
`panel is touched. Some methods use a separate sense line to
`sense the change incapacitance while the electrodes are being
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`driven by the controller. In other methods, the electrodes are
`constantly being Switched such that one electrode is driven
`and another electrode is used as the “sense' line. The touch
`panel described above does not show separate sense line.
`However, the mesh electrodes described hereincan be used to
`reduce the resistance of touch panel structures, including
`sense lines and electrodes. The claims herein extend to any of
`these touch panel technologies whether using a separate sense
`line, or using electrodes that are doing double duty as elec
`trodes and sense lines.
`0022 FIG. 1 shows a simplified side view of a capacitive
`touch screen 100 according to the prior art. The touch screen
`100 has a top glass 110 and a bottom glass 112. The top glass
`110 is bonded to the bottom glass 112 with a bonding layer or
`adhesive 114. Between the top glass and bottom glass there
`are row electrodes 116 and column electrodes 118. Only a
`single column electrode 118 is visible in this side view but
`there are multiple column electrodes such that the column
`electrode and the row electrodes form a grid in the manner
`known in the art. The column electrodes 118 are typically
`formed on the bottom surface 120 of the top glass 110 and the
`row electrodes 116 are formed on the top surface 122 of the
`bottom glass 112. The top glass 110 and bottom glass 112
`attached by the adhesive layer 114 form a touch panel 124.
`Below the touch panel 124 is a back light 126 that provides
`light 128 to an LCD 130 that projects an image to the user
`through the touch panel 124. There may be a space (not
`shown) between the backlight 126 and the LCD 130. Sense
`electronics (not shown) connected to the row and column
`electrodes are able to determine the location of touch by a
`user's finger 132 in the manner known in the prior art.
`0023 FIG. 2 illustrates a cross sectional side view of a
`capacitive touch screen 200 as claimed herein. The touch
`screen panel 200 is similar to that shown in FIG. 1 with
`corresponding structures having the same number as
`described above. Instead of electrodes formed in an ITO layer
`as described above, the touch screen panel 224 has mesh
`electrodes 210 formed of low resistance conductors 212 to
`reduce the trace resistance of the electrode traces. As used
`herein, the term “mesh' means a light-transmissive layer of
`connected Strands of opaque material. The mesh Strands
`appears woven together similar to a web or net but are pref
`erably formed in a layer of material rather than actually
`woven strands. The mesh electrodes 210 are thus an open
`pattern of low resistance conductors 212 that are electrically
`connected together to form an essentially transparent elec
`trode. The mesh electrodes 210 are preferably formed directly
`on the bottom glass layer 112. The mesh electrodes 210 could
`be made from any Suitable low resistance, opaque material
`Such as nickel, copper, gold, silver, tin, aluminum and alloys
`and combinations of these metals. The mesh conductors 210
`forming the mesh electrode could also be formed with a
`pattern to reduce visibility as described further below. The
`mesh conductors may be formed using methods such as pat
`tern electrode plating, pattern electroless plating, plating fol
`lowed by an etching process, thin film deposition followed by
`photo etching, or an other Suitable method to produce the
`structures described herein whether known or developed in
`the future.
`0024 FIG. 3 shows a top view of mesh electrodes 210 on
`a portion of the bottom glass 112 of the touch screen 200
`shown in FIG. 2. The mesh electrodes 210 each have a bond
`ing pad 310 on one side of the electrode in the manner known
`in the prior art. FIG. 3 shows only a small number of elec
`
`trodes of a touch panel as an example. A typical touch panel
`would have many such electrodes on the bottom glass 112.
`Similarly, a typical touch panel would have many column
`electrodes on the top glass orthogonal to the row electrodes in
`the manner known in the art. The column electrodes (shown
`in FIG.2) are preferably also formed as mesh electrodes in the
`same manner as shown for row electrodes in FIG. 3. In this
`example, the mesh electrodes 210 have a mesh of metal
`conductors formed as a pattern of rectangles 312.
`0025 FIG. 4 shows an enlarged view of a cross section of
`the mesh electrode 210 on the bottom glass 112 taken on the
`lines 4-4 of touch screen 200 shown in FIG. 3. FIG. 5 shows
`an enlarged top view of the mesh conductors of the electrode
`shown in FIGS. 3 and 4. In FIG. 5, the mesh conductors 312
`are more readily apparent as a pattern of rectangles 312.
`Preferably, the conductors of the mesh electrodes 210 have a
`Small line geometry or trace width Such that they are unde
`tectable with the naked eye. The line geometries of the mesh
`conductors are preferably less than 0.025 millimeters (mm) in
`width and most preferably about 0.010 mm or less. Further,
`the overall percentage of area of the mesh electrodes conduc
`tors is substantially small compared to the total area of the
`mesh electrode to enhance the overall transparency of the
`electrodes such that the mesh electrode is essentially invisible
`to the naked eye. Preferably the percentage of the electrode
`area that comprises the mesh electrode conductors is less than
`15% and more preferably 5% or less of the total area covered
`by the mesh electrode. This means that the surface area of the
`mesh electrode conductors 312, as seen from the top as shown
`in FIG. 3, covers 15% or less of the total area of the mesh
`electrode 210, also as seen from the top. The thickness of the
`conductors is not critical. A thicker mesh conductor material
`will lower the resistance of the electrode and improve perfor
`mance as described above so a thicker mesh conductor is
`preferable depending on the geometries.
`0026. We will now consider how the mesh electrodes
`affect the resistance and optical clarity of a panel with mesh
`electrodes as shown in FIG. 4. In this example, we assume the
`mesh conductors 210 are 0.025 mm wide by 200 mm long by
`0.001 mm thick nickel conductors. The equivalent transpar
`ency of the glass sheet with the mesh electrodes is a ratio of
`the open glass area to the mesh conductor area. The opaque
`mesh conductors cover about 4.0% of the electrode area, thus
`reducing the transparency of the area of the glass with mesh
`electrodes by about 4.0% (from 0.97 to about 0.93). In the
`non-trace area of the panel the transparency would remain at
`the glass transparency value of 97%. We assume the mesh
`electrodes cover about 30% of the overall glass area leaving
`about 70% of the area not covered by electrodes. Thus, the
`overall effective transparency to the single sheet of glass with
`mesh electrodes would be 0.970.7+0.930.3=96%. This
`would result in an overall panel transparency of 0.96*0.960.
`995=91% (two sheets of glass with mesh electrodes and adhe
`sive). Thus our example panel of mesh electrodes would have
`about the same effective optical transparency of a panel made
`with 100 ohm ITO glass but the effective trace resistance
`would be many times lower that the typical 100 ohm ITO
`glass, which will significantly increase performance of the
`touch screen panel.
`0027 FIG. 6 illustrates another example of mesh elec
`trodes. In this example, the mesh electrodes 210 have an
`outline that is a repeating pattern of diamond shapes 610.
`Other geometric shapes or irregular shapes could also be used
`together to forman electrode depending on the application. In
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`this example, the diamond shapes 610 are connected with a
`narrow neck or bridge 612 and the diamonds shapes are
`connected together in a line to form an electrode 210. The
`diamond shaped mesh electrodes 210 comprise a mesh of
`conductors similar to that described above with reference to
`FIG.3. This means that the lines of the diamond shape and the
`mesh of lines within the diamond shape in the drawing rep
`resent conductors and the white spaces in the drawings are
`open space to the glass 112 below in the manner described
`above. The mesh of conductors inside the diamond shape may
`be a pattern of squares as shown in the top three electrodes
`310. Many other geometric shapes could be used to pattern
`the mesh of conductors inside the outline of the electrodes to
`reduce the visibility of the electrodes. For example, the last
`electrode 210a is shown with a mesh of conductors with a
`circle pattern 614. Similarly, other regular or irregular shapes
`with electrically connected conductors could be used for the
`mesh electrodes.
`0028 FIG. 7 illustrates a side view of a stacked layer mesh
`electrode 700 as described and claimed herein. In this
`example, a stacked layer mesh electrode 700 comprises an
`electrode with a base layer 710 and a stacked layer 712. The
`stacked layer mesh electrode 700 may comprise different
`layers for different reasons. For example, the base layer 710
`may be a copper, nickel, or aluminum with a gold or silver
`stacked layer 712 to achieve a lower resistance. Alternatively,
`the stacked layer 712 may consist of a layer of low reflectivity
`material to reduce visibility of the conductive trace. The low
`reflectivity material would be placed on the side of the stacked
`electrode 700 facing the user of the touch panel. The low
`reflectivity material may include materials such as magne
`sium fluoride.
`0029. In the examples described above, the mesh elec
`trodes were formed on a transparent layer of glass as the
`Substrate. Touch panels substrates may also be constructed of
`other transparent materials such as plastic, polyester, poly
`carbonate and acrylic. The disclosure and claims herein
`expressly extend to any suitable substrate material, whether
`currently known or developed in the future.
`0030. In the examples described above, mesh electrodes
`were used for both row electrodes 116 and column electrodes
`118 shown in FIG.1. In some application it may be advanta
`geous to only use one mesh electrode. The disclosure and
`claims hereinapply to touchpanels with a mixed construction
`of mesh electrodes and conventional electrodes. In a mixed
`construction, either the row electrode or the column electrode
`is a mesh electrode as described above, while the other elec
`trode is a conventional solid electrode.
`0031 One skilled in the art will appreciate that many
`variations are possible within the scope of the claims. Thus,
`while the disclosure has been particularly shown and
`described above, it will be understood by those skilled in the
`art that these and other changes in form and details may be
`made therein without departing from the spirit and scope of
`the claims. For example, the mesh electrode described herein
`could be used on a touchpanel configurations known in the art
`that use a single glass layer with patterned electrodes sepa
`rated by a dielectric or on opposing sides of the glass.
`1. A touch screen comprising:
`a mesh electrode with a total mesh electrode area formed
`on a transparent layer, wherein the mesh electrode com
`prises electrically connecting mesh conductors formed
`ofan opaque conductive material that covers less than 15
`percent of the total mesh electrode area.
`
`2. The touch screen of claim 1 wherein the opaque conduc
`tive material is a metal chosen from the following: nickel,
`copper, gold, silver, tin, aluminum and alloys and combina
`tions of these metals.
`3. The touch screen of claim 1 wherein the touch screen is
`a capacitive touch screen and the mesh electrodes are formed
`directly on a glass Surface.
`4. The touch screen of claim 1 wherein an outline of the
`mesh electrode is a repeating geometric shape.
`5. The touch screen of claim 1 wherein an outline of the
`mesh electrode is filled with a pattern of electrically connect
`ing mesh conductors.
`6. The touch screen of claim 1 wherein the electrically
`connecting mesh conductors are formed in a pattern chosen
`from the following: rectangles, squares, circles, and irregular
`shapes.
`7. The touch screen of claim 1 wherein the mesh conduc
`tors are formed of stacked layers of materials.
`8. The touch screen of claim 1 wherein the mesh conduc
`tors are less than 0.025 mm in width.
`9. The touch screen of claim 1 wherein the mesh conduc
`tors are less than 0.010 mm in width.
`10. The touchscreen of claim 1 wherein opaque conductive
`material covers less than 5 percent of the total mesh electrode
`aca.
`11. A touch screen comprising:
`a first plurality of mesh electrodes formed on a first trans
`parent layer,
`a second plurality of mesh electrodes formed on a second
`transparent layer,
`wherein the first and second plurality of mesh electrodes
`have a total electrode area; and
`wherein the first and second plurality of mesh electrodes
`comprises electrically connecting mesh conductors
`formed of an opaque conductive material that covers less
`than 15 percent of the total electrode area.
`12. The touch screen of claim 11 wherein the opaque con
`ductive material is a metal chosen from the following: nickel,
`copper, gold, silver, tin, aluminum and alloys and combina
`tions of these metals.
`13. The touch screen of claim 11 wherein the touch screen
`is a capacitive touch screen and the mesh electrodes and the
`first and second transparent layers comprise a material chosen
`from glass, plastic, polyester, polycarbonate and acrylic.
`14. The touch screen of claim 11 wherein an outline of the
`mesh electrode is a repeating geometric shape.
`15. The touch screen of claim 11 wherein an outline of the
`mesh electrode is filled with a pattern of electrically connect
`ing mesh conductors.
`16. The touch screen of claim 11 wherein the electrically
`connecting mesh conductors are formed in a pattern chosen
`from the following: rectangles, squares, circles, and irregular
`shapes.
`17. The touch screen of claim 11 wherein the mesh con
`ductors are formed of stacked layers of materials.
`18. The touch screen of claim 11 wherein the mesh con
`ductors are less than 0.025 mm in width.
`19. The touch screen of claim 11 wherein the mesh con
`ductors are less than 0.010 mm in width.
`20. A capacitive touch screen comprising:
`a mesh electrode with a total mesh electrode area formed
`on a transparent layer,
`wherein the mesh electrode comprises electrically con
`necting mesh conductors that are less than 0.01 mm in
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`width and formed of an opaque conductive material that
`covers less than 5 percent of the total mesh electrode
`area,
`wherein the opaque conductive material is a metal chosen
`from the following: nickel, copper, gold, silver, tin, alu
`minum and alloys and combinations of these metals; and
`
`wherein an outline of the mesh electrode is filled with a
`pattern of electrically connecting mesh conductors
`formed in a pattern chosen from the following: rect
`angles, squares, circles, and irregular shapes.
`
`ck
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