The present invention relates to touch screens having micro-wire electrodes, an unpatterned transparent conductor layer, and electrically isolated dummy structures.
Transparent conductors are widely used in the flat-panel display industry to form electrodes that are used to electrically switch light-emitting or light-transmitting properties of a display pixel, for example in liquid crystal or organic light-emitting diode displays. Transparent conductive electrodes are also used in touch screens in conjunction with displays. In such applications, the transparency and conductivity of the transparent electrodes are important attributes. In general, it is desired that transparent conductors have a high transparency (for example, greater than 90% in the visible spectrum) and a low electrical resistivity (for example, less than 10 ohms/square).
Transparent conductive metal oxides are well known in the display and touch-screen industries and have a number of disadvantages, including limited transparency and conductivity and a tendency to crack under mechanical or environmental stress. Typical prior-art conductive electrode materials include conductive metal oxides such as indium tin oxide (ITO) or very thin layers of metal, for example silver or aluminum or metal alloys including silver or aluminum. These materials are coated, for example, by sputtering or vapor deposition, and are patterned on display or touch-screen substrates, such as glass. For example, the use of transparent conductive oxides to form arrays of touch senses on one side of a substrate is taught in U.S. Patent Application Publication No. 2011/0099805 entitled “Method of Fabricating Capacitive Touch-Screen Panel”.
Transparent conductive metal oxides are increasingly expensive and relatively costly to deposit and pattern. Moreover, the substrate materials are limited by the electrode material deposition process (such as sputtering) and the current-carrying capacity of such electrodes is limited, thereby limiting the amount of power that is supplied to the pixel elements and the size of touch screens that employ such electrodes. Although thicker layers of metal oxides or metals increase conductivity, they also reduce the transparency of the electrodes.
Apparently transparent electrodes including very fine patterns of conductive elements, such as metal wires or conductive traces are known. For example, U.S. Patent Application Publication No. 2011/0007011 teaches a capacitive touch screen with a mesh electrode, as do U.S. Patent Application Publication No. 2010/0026664, U.S. Patent Application Publication No. 2010/0328248, and U.S. Pat. No. 8,179,381, which are hereby incorporated in their entirety by reference. As disclosed in U.S. Pat. No. 8,179,381, fine conductor patterns are made by one of several processes, including laser-cured masking, inkjet printing, gravure printing, micro-replication, and micro-contact printing. In particular, micro-replication is used to form micro-conductors formed in micro-replicated channels. The apparently transparent micro-wire electrodes include micro-wires between 0.5μ and 4μ wide and a transparency of between approximately 86% and 96%.
Conductive micro-wires are formed in micro-channels embossed in a substrate, for example as taught in CN102063951, which is hereby incorporated by reference in its entirety. As discussed in CN102063951, a pattern of micro-channels are formed in a substrate using an embossing technique. Embossing methods are generally known in the prior art and typically include coating a curable liquid, such as a polymer, onto a rigid substrate. A pattern of micro-channels is embossed (impressed or imprinted) onto the polymer layer by a master having an inverted pattern of structures formed on its surface. The polymer is then cured. A conductive ink is coated over the substrate and into the micro-channels, the excess conductive ink between micro-channels is removed, for example by mechanical buffing, patterned chemical electrolysis, or patterned chemical corrosion. The conductive ink in the micro-channels is cured, for example by heating. In an alternative method described in CN102063951, a photosensitive layer, chemical plating, or sputtering is used to pattern conductors, for example using patterned radiation exposure or physical masks. Unwanted material (such as photosensitive resist) is removed, followed by electro-deposition of metallic ions in a bath.
Capacitive touch screen devices are constructed by locating drive electrodes near sense electrodes to form an electric field. In one prior-art design, the drive and sense electrodes are located on a common substrate with bridge electrical connections to prevent electrical shorts between the drive and sense electrodes where the drive electrodes cross over or under the sense electrodes. In another prior-art design, the drive and sense electrodes are located on either side of a dielectric layer. Referring to
A display controller 142 connected through electrical buss connections 136 controls the display 110 in cooperation with a touch-screen controller 140. The touch-screen controller 140 is connected through electrical buss connections 136 and wires 134 and controls the touch screen 120. The touch-screen controller 140 detects touches on the touch screen 120 by sequentially electrically energizing and testing the x-dimension first and y-dimension second transparent electrodes 130, 132.
Referring to
As is known in the prior art, electromagnetic interference from the display 110 can interfere with the operation of the touch-screen 120. This problem can be ameliorated by providing a ground plane between the touch screen 120 and display 110. However, such a structure undesirably increases the thickness and decreases the transparency of the display and touch screen apparatus 100.
Alternatively, it has been recognized that shielding can be achieved by controlling the relative width of the drive and sense electrodes. For example U.S. Pat. No. 7,920,129 discloses a multi-touch capacitive touch-sense panel created using a substrate with column and row traces formed on either side of the substrate. To shield the column (sense) traces from the effects of capacitive coupling from a modulated Vcom layer in an adjacent liquid crystal display (LCD) or any source of capacitive coupling, the row traces were widened to shield the column traces, and the row (drive) traces were placed closer to the LCD. In particular, the rows can be widened so that there is spacing of about 30 microns between adjacent row traces. In this manner, the row traces can serve the dual functions of driving the touch sense panel, and also the function of shielding the more sensitive column (sense) traces from the effects of capacitive coupling.
Shielding has also been achieved by using metal micro-wire sense electrodes in combination with transparent conductive drive electrodes. For example U.S. Pat. No. 8,279,187 discloses a multi-layer touch panel having an upper electrode layer having a plurality of composite electrodes including a plurality of metal or metal alloy micro-wire conductors with a cross-sectional dimension of less than 10 microns, a lower electrode layer having a plurality of (patterned) indium oxide-based electrodes, the upper electrodes and lower electrodes defining an electrode matrix having nodes where the upper and lower electrodes cross over. The upper electrode layer is disposed between the first layer and the lower electrode layer and a dielectric layer is disposed between the upper electrode layer and the lower electrode layer. As noted above, it is difficult, expensive, or impossible to meet conductivity requirements for larger touch-screens using patterned indium tin oxide electrodes.
In general, touch screens are intended to be invisible to a user. It is important, therefore, that any conductive structures in a touch screen be visually imperceptible. In prior-art designs, relatively transparent conductive electrodes made of transparent conductive oxides reduce electrode visibility. Nonetheless, such electrodes do absorb some light, having a transparency for example of 88% in the visible range and a slightly yellow appearance. Thus, electrode structures in a touch screen having transparent conductive oxides are visible to perceptive users. In particular, regular gaps between electrodes are visible as areas with increased transparency.
To reduce the visibility of gaps between electrodes in a touch screen, dummy structures are provided in the gaps. These dummy structures typically include conductive materials and structures similar to those found in the electrodes but are not electrically connected to the electrodes. Thus, the dummy structures provide optical uniformity in the touch screen by providing structures with an appearance similar to the electrodes but without any electrical function. Gaps between the dummy structures and the electrodes are typically so small (for example, a few microns) that the gaps are imperceptible to viewers. Referring to
U.S. Patent Application Publication No. 2011/0248953 entitled “Touch Screen Panel” describes conductive dummy patterns between adjacent sensing cells in a touch screen panel. U.S. Patent Application Publication No. 2011/0289771 entitled “Method for Producing Conductive Sheet and Method for Producing Touch Panel” describes unconnected dummy patterns formed near each side of a sensing region. U.S. Pat. No. 7,663,607 entitled “Multi-Point Touch Screen” describes dummy features disposed between driving lines and sensing lines to optically improve the visual appearance of the touch screen. The dummy features provide the touch screen with a more uniform appearance and are electrically isolated and positioned in the gaps between each of the lines. Although they can be patterned separately, the dummy features are typically patterned along with the lines and formed with the same conductive materials. The dummy features still produce some gaps but the gaps are much smaller than the gaps found between the lines.
There remains a need for further improvements in the structure of a multi-electrode structure that reduces susceptibility to electromagnetic interference, reduces thickness and cost, improves sensitivity and efficiency, and provides optical uniformity.
In accordance with the present invention, a micro-wire multi-electrode structure having an area of substantially uniform optical density comprises:
The present invention provides a micro-wire multi-electrode structure useful in capacitive touch screens having improved sensitivity, efficiency, consistency, optical uniformity, and reduced susceptibility to electromagnetic interference and reduced thickness and cost. The presence of an unpatterned conductive layer electrically connected to drive electrodes and drive micro-wires provides electromagnetic shielding to sense electrodes, thereby reducing electromagnetic interference. The integrated unpatterned conductive layer reduces device thickness by reducing the number of insulating layers, reducing conductive layer thickness, and improving transparency in comparison to a conventional shielding system. The presence of dummy structures improves optical uniformity without compromising the function of the unpatterned conductive layer.
The presence of the unpatterned conductive layer also increases capacitance between drive and sense electrodes, thereby reducing the voltage needed to sense changes in the capacitive field, for example due to touches, and improving efficiency.
The above and other features and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used to designate identical features that are common to the figures, and wherein:
The Figures are not drawn to scale since the variation in size of various elements in the Figures is too great to permit depiction to scale.
The present invention provides a micro-wire multi-electrode structure useful, for example, in touch-screen devices in combination with a display. The micro-wire multi-electrode structure reduces the effects of electromagnetic interference and improves touch-response sensitivity, efficiency, consistency, and optical uniformity over the extent of the touch screen.
Referring to
The area of the unpatterned conductive layer 30 is equal to or greater than the area 31 of uniform optical density and the unpatterned conductive layer 30 is not necessarily distinguished from the area 31 in the Figures. Generally, the unpatterned conductive layer 30 is illustrated in cross sections and the area 31 is indicated in the plan views.
The unpatterned conductive layer 30 in the area 31 can refer to the touch-sensitive portion of a layer of conductive material located over a substrate 10. The unpatterned conductive layer 30 is a layer of electrically conductive material that can extend beyond the area 31 and can be patterned outside of the area 31, for example around the periphery of a touch screen (such as in the bezel or buss areas of a touch screen), but is unpatterned within the area 31. The electrodes 22 can extend beyond the area 31 or the unpatterned conductive layer 30.
In an embodiment, the electrode micro-wires 24 form a mesh and typically have a width less than 10 microns and a pitch of hundreds or even more than a thousand microns. Since such relative sizes and spacing are difficult to illustrate in the Figures, the micro-structures (such as the electrode micro-wires 24) are typically shown much larger and closer together than is the case in a practical implementation. In an embodiment of the present invention, the micro-structures of the present invention, including the electrode micro-wires 24 and dummy micro-wires 90 are too small to be resolved by, or visible to, the unaided human visual system.
Optical uniformity, as used herein refers to optical uniformity as easily perceived by the unaided human visual system without special effort under typical display viewing conditions and is averaged over areas much larger than the individual micro-structures in the optically uniform area 31, for example areas of several square millimeters. Substantially uniform means that the area 31 appears uniform to the unaided human visual system. The area 31 can have less than 20%, 10%, 5%, 2%, or 1% variation over the area 31. The spatial distribution of the electrode micro-wires 22 and dummy micro-wires 90 in the area 31 can affect the optical uniformity of the area 31 so that, in an embodiment of the present invention, the area 31 has a substantially uniform spatial distribution of electrode micro-wires 22 and dummy micro-wires 90 in the area 31.
Although the present invention discloses an optically uniform area 31, such uniformity is not readily illustrated in the Figures and the optically uniform area 31 in the Figures is not necessarily illustrated as optically uniform. Furthermore, optical uniformity is taken over a two-dimensional area. Cross-sectional Figures represent only one dimension of the area 31 and are not, therefore, illustrative of optical uniformity.
The electrode micro-wires 24 are electrically connected within each electrode 22 but are not electrically connected to electrode micro-wires 24 of other electrodes 22. Thus, each electrode 22 is electrically isolated from any other electrode 22. Furthermore, the dummy micro-wires 90 are not electrically connected to any electrode micro-wires 24. In an embodiment, the dummy micro-wires 90 are formed in a common layer with the electrode micro-wires 24 or include one or more common materials with the electrode micro-wires 24. In another embodiment, the dummy micro-wires 90 and the electrode micro-wires 24 are formed from the same materials. In an embodiment, the dummy micro-wires 90 and the electrode micro-wires 24 are formed in a common step with common materials in a common layer and have a common thickness. In another embodiment, the dummy micro-wires 90 have a thickness that is less than the thickness of the electrode micro-wires 24.
Each dummy micro-wire 90 extends along an equi-potential line. When adjacent electrodes 22 are energized at different voltages, an electrical field exists between the electrodes 22. For example, two opposing, parallel conductors will create an electrical field having field lines that extend orthogonally from one conductor to the other (ignoring edge effects). Each point along each field line has an electrical potential. The dummy micro-wires 90 extend from field line to field line at positions of equal electrical potential. In the case of two opposing, parallel conductors and orthogonal field lines, the equi-potential lines will be lines parallel to the conductors. Thus, an equi-potential line is a set of connected points forming at least a portion of a line, curved or straight, that have a common potential when the micro-wires 24 of adjacent electrodes 22 are controlled to have different voltage potentials. Each dummy micro-wire 90 extends along an equi-potential line. Different dummy micro-wires 90 can extend along different equi-potential lines so that the different dummy micro-wires 90 can have different electrical potentials. Moreover, the dummy micro-wires 90 can extend over only a portion of an equi-potential line. Multiple, electrically isolated dummy micro-wires 90 can extend along a common, same equi-potential line (for example as a sequence of dashed lines). Electrically isolated dummy micro-wires 90 are micro-wires that are not electrically connected to any electrode micro-wires 24.
By substantially equi-potential is meant that the conductivity of the unpatterned conductive layer 30 is not changed so much that the electrodes 22 cannot effectively maintain different voltages when driven by a drive circuit or that the conductivity of the unpatterned conductive layer 30 is not changed so much that electrical fields generated by the electrodes 22 cannot be distinguished with a sense circuit (e.g. drive and sense circuits in touch-screen controller 140). Thus, the dummy micro-wires 90 provide optical density in the gap 26 without compromising the conductivity of the unpatterned conductive layer 30 by increasing the conductivity to an unacceptable level.
In a further embodiment of a micro-wire multi-electrode structure 5, the electrodes 22 are drive electrodes 22, the electrode layer 20 is a drive layer 20, the electrode micro-wires 24 are drive micro-wires 24, gaps 26 separating the drive electrodes 22 are drive gaps 26, and the area 31 is a touch-sensitive area 31.
In this embodiment, a plurality of spatially separated patterned sense electrodes 52 is located in a sense layer 50 in the touch-sensitive area 31. Each sense electrode 52 includes a plurality of patterned conductive electrically connected sense micro-wires 54. The sense electrodes 52 are separated by sense gaps 56 and a dielectric layer 40 is located between the drive electrodes 22 and the sense electrodes 52. Areas in which the drive electrodes 22 and the sense electrodes 52 overlap form touch-pad areas 128. The touch-pad areas 128 form capacitors whose capacitance changes can be measured to detect a touch.
In one embodiment, the dielectric layer 40 is a separate layer (e.g. as shown in
Although illustrated in
Referring to
Referring to
Furthermore, the patterns of electrode micro-wires 24 can vary. Referring to
Referring to
Referring next to
In an embodiment of the present invention, a touch-screen device having a substantially uniform optical density in a touch-sensitive area 31 includes a plurality of spatially separated patterned drive electrodes 22 located in a drive layer 20 in the touch-sensitive area 31. Each drive electrode 22 includes a plurality of patterned conductive electrically connected drive micro-wires 24. A plurality of spatially separated patterned sense electrodes 52 in the sense layer 50 is located in the touch-sensitive area 31. Each sense electrode 52 includes a plurality of patterned conductive electrically connected sense micro-wires 54. A dielectric layer 40 is located between the drive electrodes 22 and the sense electrodes 52. One or more patterned electrically isolated equi-potential dummy micro-wires 90 are located in the touch-sensitive area 31 substantially along equi-potential lines between adjacent drive electrodes 22 and electrically disconnected from the adjacent drive electrodes 22, so that the touch-sensitive area 31 has a substantially uniform optical density. An unpatterned conductive layer 30 that is unpatterned in the touch-sensitive area 31 is in electrical contact with the drive micro-wires 24 and the dummy micro-wires 90. A controller is electrically connected to the drive and sense electrodes 22, 52 to control the drive and sense electrodes 22, 52.
Referring to the flow-diagram of
Referring to
Although the dummy micro-dots 92 have a negligible conductivity in any given direction, they do absorb or reflect light and can therefore provide a substantially uniform optical density in the area 31. A negligible conductivity in any given direction is a conductivity that is small enough that conductivity of the unpatterned conductive layer 30 is not changed so much that the electrodes 22 cannot effectively maintain different voltages when driven by a drive circuit or that the conductivity of the unpatterned conductive layer 30 is not changed so much that electrical fields generated by the electrodes 22 cannot be distinguished with a sense circuit (e.g. drive and sense circuits in touch-screen controller 140). Thus, the dummy micro-dots 92 provide optical density in the gap 26 without compromising the conductivity of the unpatterned conductive layer 30 by increasing the conductivity to an unacceptable level.
As shown in
In various embodiments, the dummy micro-dots 92 are in a common layer with the electrode 22 or electrode micro-wires 24, are formed in a common step with the electrode micro-wires 24, include similar materials or are made of the same materials as the electrode micro-wires 24, or have a similar depth as the electrode micro-wires 24.
In a further embodiment of a micro-wire multi-electrode structure 5, the electrodes 22 are drive electrodes 22, the electrode layer 20 is a drive layer 20, the electrode micro-wires 24 are drive micro-wires 24, gaps 26 separating the drive electrodes 22 are drive gaps 26, and the area 31 is a touch-sensitive area 31. In an embodiment, the dummy micro-dots 92 are in the same drive layer 20 as the drive micro-wires 24.
In this embodiment, a plurality of spatially separated patterned sense electrodes 52 is located in the sense layer 50 in the touch-sensitive area 31. Each sense electrode 52 includes a plurality of patterned conductive electrically connected sense micro-wires 54. The sense electrodes 52 are separated by sense gaps 56 and a dielectric layer 40 is located between the drive electrodes 22 and the sense electrodes 52. Areas in which the drive electrodes 22 and the sense electrodes 52 overlap form touch-pad areas 128. The touch-pad areas 128 form capacitors whose capacitance changes can be measured to detect a touch.
In one embodiment, the dielectric layer 40 is a separate layer (e.g. as shown in
Although illustrated in
In an embodiment, the dummy micro-dots 92 are arranged in lines, arrays, or other regular arrangements. As shown in
Referring to
Referring to
Drive or sense electrodes 22, 52 can be formed in a variety of patterns. Electrodes can be rectangular and arranged in regular arrays. Drive electrodes 22 and sense electrodes 52 can be arranged orthogonally to each other. Alternatively, electrodes can be arranged using polar coordinates, in circles, or in other curvilinear patterns. Electrodes can have uniform spacing or widths. Alternatively, electrodes can have non-uniform spacing and variable widths.
Referring to
Referring next to
In an embodiment of the present invention, a touch-screen device having a substantially uniform optical density in a touch-sensitive area 31 includes a plurality of spatially separated patterned drive electrodes 22 located in a drive layer 20 in the touch-sensitive area 31. Each drive electrode 22 includes a plurality of patterned conductive electrically connected drive micro-wires 24. A plurality of spatially separated patterned sense electrodes 52 in the sense layer 50 is located in the touch-sensitive area 31. Each sense electrode 52 includes a plurality of patterned conductive electrically connected sense micro-wires 54. The dielectric layer 40 is located between the drive electrodes 22 and the sense electrodes 52. One or more patterned electrically isolated dummy micro-dots 92 are located in the touch-sensitive area 31 and electrically disconnected from the adjacent drive electrodes 22, so that the touch-sensitive area 31 has a substantially uniform optical density. The unpatterned conductive layer 30 that is unpatterned in the touch-sensitive area 31 is in electrical contact with the drive micro-wires 24 and the dummy micro-wires 90. The touch screen controller 140 is electrically connected to the drive and sense electrodes 22, 52 to control the drive and sense electrodes 22, 52.
In a method of the present invention, referring again to
In various embodiments, the unpatterned conductive layer 30 is provided in various configurations with respect to the drive layer 20, the sense layer 50 and the substrate 10. In these embodiments, the dummy micro-wires 90 or dummy micro-dots 92 are formed in the same layer as the drive micro-wires 24 and are not shown separately.
Referring to
As is illustrated further in the embodiment of
According to various embodiments of the present invention,
In the embodiment of
In various embodiments of the present invention, the drive electrodes 22 are adjacent to the substrate 10, as shown in
In an embodiment illustrated in
In the embodiment of
Not all possible combinations and arrangements of layers are illustrated herein. Other arrangements that provide patterned micro-wire drive electrodes 22 electrically connected to an unpatterned conductive layer 30 on a side of the dielectric layer 40 opposite patterned micro-wire sense electrodes 52 are included within the present invention. In particular: either the drive electrodes 22 or the sense electrodes 52 can be independently arranged adjacent to the substrate 10; the unpatterned conductive layer 30 is located between the drive electrodes 22 and the dielectric layer 40, the drive electrodes 22 are located between the conductive layer and the dielectric layer 40, or the drive electrodes 22 are located at least partially in the unpatterned conductive layer 30; the drive micro-wires 24, dummy micro-wires 90, or dummy micro-dots 92 are formed in the separate drive layer 20, in the dielectric layer 40, in the unpatterned conductive layer 30, or in the substrate 10; or the sense electrodes 52 are located in a separate sense layer 50 or in the dielectric layer 40. Various arrangements of each of these layers can be combined with other layer arrangements. In general, the touch surface of the touch-screen device is adjacent to the sense electrode 52. For example, in
There are at least three methods of providing the drive micro-wires 24, dummy micro-wires 90, dummy micro-dots 92, and sense micro-wires 54. In one method, the drive layer 20 or sense layer 50 is first formed and then the drive or sense micro-wires 24, 54, respectively, dummy micro-wires 90, or dummy micro-dots 92 are formed in micro-channels imprinted in the drive layer 20 or sense layer 50 to embed the drive or sense micro-wires 24, 54, dummy micro-wires 90, or dummy micro-dots 92 in the provided layer. In the Figures, the drive or sense micro-wires 24, 54, dummy micro-wires 90, or dummy micro-dots 92 are formed in micro-channels and are illustrated as filling the micro-channels. Thus, the micro-channels are not distinguished from the micro-wires in the illustrations. In a second method, the drive or sense micro-wires 24, 54, dummy micro-wires 90, or dummy micro-dots 92 are first formed, for example by printing or transfer onto the surface of substrate 10, and then any subsequent drive layer 20 or sense layer 50 is coated, deposited, or otherwise provided over the drive or sense micro-wires 24, 54, dummy micro-wires 90, or dummy micro-dots 92 to embed the drive or sense micro-wires 24, 54, dummy micro-wires 90, or dummy micro-dots 92 in the provided layer. In a third method, a pre-made layer (for example using either of the first or second method) is laminated onto an underlying layer, for example the surface of substrate 10. The pre-made layer can be, for example, either of the sense layer 50 with sense micro-wires 54 or the drive layer 20 with drive micro-wires 24, dummy micro-wires 90, or dummy micro-dots 92.
As shown in
Referring to
In the second method of first forming micro-wires and then coating over the micro-wires and as shown in the example of
In all these various embodiments, the various layers can alternatively be pre-made and laminated together. Optically clear adhesives can be used as can conductive adhesives, if desired, for example to electrically connect the unpatterned conductive layer 30 to the drive micro-wires 24. In such an embodiment, the conductive adhesive is considered to be part of the unpatterned conductive layer 30.
In an embodiment of the present invention, the electrical resistance of the unpatterned conductive layer 30 is greater than the resistance of each of the drive electrodes 22. The resistance of the unpatterned conductive layer 30 was measured as the sheet resistance of the unpatterned conductive layer 30 independently of the drive micro-wires 24. The resistance of the drive electrodes 22 is the resistance measured along the length of the drive electrode 22.
In an embodiment, the unpatterned conductive layer 30 has a sheet resistance greater than 1 kΩ per square, greater than 10 kΩ per square, greater than 100 kΩ per square, greater than 1 MΩ per square, greater than 10 MΩ per square, greater than 100 MΩ per square, greater than 1 GΩ per square, greater than 10 GΩ per square, or greater than 100 GΩ per square. This lower limit in resistivity of the unpatterned conductive layer 30 is dependent in part on the frequency at which the drive electrodes 22 are driven and on the drive current and voltage characteristics and on the conductivity of the drive electrodes 22.
In another embodiment, the resistance of the unpatterned conductive layer 30 between any two drive electrodes 22 is at least five times greater, at least ten times greater, at least twenty times greater, at least fifty times greater, at least 100 times greater, at least 500 times greater, at least 1,000 times greater, at least 10,000, at least 100,000, or at least 1,000,000 times greater than the resistance of either of the two drive electrodes 22. For example, as illustrated in
In various embodiments of the present invention, the resistance of the unpatterned conductive layer 30 can be adjusted to compensate for any unwanted conductivity between adjacent drive electrodes 22. Although the dummy micro-wires 90 extend along equi-potential lines or the dummy micro-dots have a limited extent and an aspect ratio of approximately one, the dummy micro-wires 90 and dummy micro-dots 92 do have a physical width and therefore they do have some conductivity. If the dummy micro-wires 90 and dummy micro-dots 92 are made with common materials and in a common step with the driver micro-wires 24, the physical width of the dummy micro-wires 90 and dummy micro-dots 92 will slightly decrease the resistance between adjacent driver electrodes 22. This slight decrease can be compensated by a corresponding slight reduction in the conductivity of the unpatterned conductive layer 30, for example by changing the material composition of the unpatterned conductive layer 30 or by reducing the thickness of the unpatterned conductive layer 30.
In a further embodiment of the present invention, a driver, for example an integrated circuit, for driving the drive electrodes 22 provides voltage and current to the drive electrodes 22 in a desired drive waveform having a period and frequency. The frequency of the drive waveform limits the rate at which the capacitance between the drive and sense electrodes 22, 52 can be measured. Because the unpatterned conductive layer 30 is electrically connected to the drive electrode 22 and has a limited conductivity, the rate at which the drive electrode 22 and the unpatterned conductive layer 30 can be charged is likewise limited. A micro-wire electrode, such as the drive electrode 22, has gaps 26 between the micro-wires in the micro-wire electrode that, according to the present invention, are bridged with conductive material in the unpatterned conductive layer 30. Thus, the conductivity of the unpatterned conductive layer 30 will define, in combination with the open area defined by the geometry of the drive micro-wires 24 in the drive electrode 22, the rate at which the drive electrode 22 and the unpatterned conductive layer 30 can be charged or discharged. Therefore, the conductivity of the unpatterned conductive layer 30 and the open area define the time constant for charging or discharging the drive electrode 22 and the center of the open area in response to a voltage change as provided by the drive waveform. Therefore, according to the further embodiment of the present invention, the sheet resistance of the unpatterned conductive layer 30, including the dummy micro-wires 90 or dummy micro-dots 92, is sufficiently low that the time constant for charging the center of the open area between drive micro-wires 24 in the drive electrode 22 is less than the period of a drive waveform. In another embodiment, the time constant is substantially less than the period. By substantially less is meant at least 5% less, at least 10% less, at least 20% less, or at least 50% less.
In operation, a touch-screen controller (for example touch-screen controller 140 of
In comparison to other prior-art solutions using a separate ground plane beneath drive electrodes to reduce the effect of electro-magnetic radiation, for example from a display located beneath the touch screen, the present invention provides a thinner touch-screen and display structure. Moreover, the use of dummy micro-wires 90 or dummy micro-dots 92 provides optical uniformity over the touch-screen area 31.
If prior-art dummy micro-wires 152, for example those illustrated in
Referring again to
A variety of techniques are usable to construct a touch screen device of the present invention. In various embodiments, the patterned drive electrodes 22 are formed in a layer, such as drive layer 20, unpatterned conductive layer 30, or dielectric layer 40, printed or transferred onto a layer, such as the substrate 10, unpatterned conductive layer 30, or dielectric layer 40, or laminated on the substrate 10 or other layer on the substrate 10. In other embodiments, the unpatterned conductive layer 30 is laminated, coated, formed by evaporation, sputtering, or chemical vapor deposition, or formed by atomic layer deposition on the drive electrodes 22 or drive layer 20. The dielectric layer 40 is laminated, coated, formed by evaporation, sputtering, or chemical vapor deposition, or formed by atomic layer deposition on the unpatterned conductive layer 30. The patterned sense electrodes 52 are formed in a layer, such as sense layer 50 or dielectric layer 40, printed or transferred onto a layer, such as the substrate 10 or dielectric layer 40, or laminated on the substrate 10 or other layer on the substrate 10.
In an embodiment, unpatterned conductive layer 30 or dielectric layer 40 is deposited by sputtering or deposition and patterned outside the touch-sensitive area 31 either with masks or by photolithographic processes. In an embodiment, conductive material is only deposited in the touch-sensitive area 31. Alternatively, conductive material is deposited over the entire substrate 10 and removed as needed, for example in peripheral regions of the touch screen outside the touch-sensitive area 31. In another embodiment, atomic layer deposition methods are used to form a transparent conductive layer, for example a patterned aluminum zinc oxide layer using methods known in the art. Patterning outside the touch-sensitive area 31 is accomplished, for example, by masking the deposition, using patterned deposition inhibitors, or by photolithographic processes.
Alternatively or in addition, referring to
In other embodiments, imprinting methods are used to imprint drive micro-channels in the dielectric layer 40 (as shown in
Printing methods are usable in other embodiments of the present invention. A conductive ink is printable, for example with a flexographic plate, on a substrate 10 or other layer and cured to form micro-wires. Alternatively, a pattern of micro-wires is transferrable to the substrate 10 or other layer. For example, in
In an alternative embodiment, micro-wires are formed by coating a flexographic substrate having a raised pattern corresponding to a desired micro-wire pattern with a conductive ink. The flexographic substrate is brought into contact with a layer surface to print the conductive ink onto the layer surface. In an optional step, the conductive ink is dried. Flexographic substrates are known in the flexographic printing arts.
In yet another embodiment, layer structures are laminated to another layer. Referring to
In various embodiments, the unpatterned conductive layer 30 is laminated, coated, or deposited on the drive electrodes 22. In an embodiment, atomic layer deposition is used to form the unpatterned conductive layer 30. In other embodiments, the dielectric layer 40 is laminated, coated, or deposited on the drive electrodes 22 or sense electrodes 52.
Dielectric layer 40 can be any of many known dielectric materials included polymers or oxides and are deposited or formed in any of a variety of known ways, including pattern-wise inkjet deposition, sputter or coating through a mask or blanket coated and patterned using known photo-lithographic methods. Such known photo-lithographic technology can include a photo-sensitive material that is optically patterned through a mask to cure the photo-sensitive material and removal of uncured material.
In an embodiment, unpatterned conductive layer 30 is transparent and includes one or more of a variety of transparent conductive materials, for example organic conductive polymers such as Poly(3,4-ethylenedioxythiophene) (PEDOT), Poly(3,4-ethylenedioxythiophene) PEDOT: poly(styrene sulfonate) PSS, Poly(4,4-dioctylcyclopentadithiophene), and Polypyrrole (PPy), long-chain aliphatic amines (optionally ethoxylated) and amides, quaternary ammonium salts (such as, behentrimonium chloride or cocamidopropyl betaine), esters of phosphoric acid, polyethylene glycol esters, or polyols, polyaniline nanofibers, carbon nanotubes, graphene, metals such as silver nanowires, and inorganic conductive oxides such as ITO, SnO2, In2O3, ZnO, Aluminum-doped zinc oxide (AZO), CdO, Ga2O3, V2O5. Deposition methods for conductive materials can include solvent or aqueous coating, printing by for example inkjet, gravure, offset litho, flexographic, or electro-photographic, lamination, evaporation, chemical vapor deposition (CVD), sputtering, atomic-layer deposition (ALD) or spatial-atomic-layer deposition (SALD).
In another embodiment, unpatterned conductive layer 30 is an ionic conductor, a solid ionic conductor, an electrolyte, a solid electrolyte, or a conductive gel, as are known in the art.
In an embodiment, the unpatterned conductive layer 30 has a thickness less than or equal to 50 nm, 100 nm, 200 nm, 500 nm, or 1 micron. In other embodiments, the unpatterned conductive layer 30 has a thickness less than or equal to 10 microns, 100 microns, 200 microns, 500 microns, or 1 mm.
According to various embodiments of the present invention, the substrate 10 is any material on which a layer is formed. The substrate 10 is a rigid or a flexible substrate made of, for example, a glass, metal, plastic, or polymer material, can be transparent, and can have opposing substantially parallel and extensive surfaces. Substrates 10 can include a dielectric material useful for capacitive touch screens and can have a wide variety of thicknesses, for example 10 microns, 50 microns, 100 microns, 1 mm, or more. In various embodiments of the present invention, substrates 10 are provided as a separate structure or are coated on another underlying substrate, for example by coating a polymer substrate layer on an underlying glass substrate.
In various embodiments substrate 10 is an element of other devices, for example the cover or substrate of a display or a substrate, cover, or dielectric layer of a touch screen. In an embodiment, the substrate 10 of the present invention is large enough for a user to directly interact therewith, for example using an implement such as a stylus or using a finger or hand. Methods are known in the art for providing suitable surfaces on which to coat or otherwise form layers. In a useful embodiment, the substrate 10 is substantially transparent, for example having a transparency of greater than 90%, 80% 70% or 50% in the visible range of electromagnetic radiation.
Electrically conductive micro-wires and methods of the present invention are useful for making electrical conductors and busses for transparent micro-wire electrodes, dummy micro-wires 90, or dummy micro-dots 92 and electrical conductors in general, for example as used in electrical busses. A variety of micro-wire patterns are used and the present invention is not limited to any one pattern. Micro-wires can be spaced apart, form separate electrical conductors, or intersect to form a mesh electrical conductor on, in, or above the substrate 10. Micro-channels can be identical or have different sizes, aspect ratios, or shapes. Similarly, micro-wires can be identical or have different sizes, aspect ratios, or shapes. Micro-wires can be straight or curved.
A micro-channel is a groove, trench, or channel formed on or in a layer extending from the surface of the layer and having a cross-sectional width for example less than 20 microns, 10 microns, 5 microns, 4 microns, 3 microns, 2 microns, 1 micron, or 0.5 microns, or less. In an embodiment, the cross-sectional depth of a micro-channel is comparable to its width. Micro-channels can have a rectangular cross section. Other cross-sectional shapes, for example trapezoids, are known and are included in the present invention. The width or depth of a layer is measured in cross section. Micro-channels are not distinguished in the Figures from the micro-wires.
Imprinted layers useful in the present invention can include a cured polymer material with cross-linking agents that are sensitive to heat or radiation, for example infra-red, visible light, or ultra-violet radiation. The polymer material is a curable material applied in a liquid form that hardens when the cross-linking agents are activated. When a molding device, such as an imprinting stamp having an inverse micro-channel structure is applied to liquid curable material and the cross-linking agents in the curable material are activated, the liquid curable material in the curable layer is hardened into a cured layer. The liquid curable materials can include a surfactant to assist in controlling coating. Materials, tools, and methods are known for embossing coated liquid curable materials to form cured layers.
A cured layer is a layer of curable material that has been cured. For example, a cured layer is formed of a curable material coated or otherwise deposited on a layer surface to form a curable layer and then cured to form the cured layer. The coated curable material is considered herein to be a curable layer before it is cured and cured layer after it is cured. Similarly, a cured electrical conductor is an electrical conductor formed by locating a curable material in micro-channel and curing the curable material to form a micro-wire in a micro-channel. As used herein, curing refers to changing the properties of a material by processing the material in some fashion, for example by heating, drying, irradiating the material, or exposing the material to a chemical, energetic particles, gases, or liquids.
The curable layer is deposited as a single layer in a single step using coating methods known in the art, such as curtain coating. In an alternative embodiment, the curable layer is deposited as multiple sub-layers using multi-layer deposition methods known in the art, such as multi-layer slot coating, repeated curtain coatings, or multi-layer extrusion coating. In yet another embodiment, the curable layer includes multiple sub-layers formed in different, separate steps, for example with a multi-layer extrusion, curtain coating, or slot coating machine as is known in the coating arts.
Curable inks useful in the present invention are known and can include conductive inks having electrically conductive nano-particles, such as silver nano-particles. In an embodiment, the electrically conductive nano-particles are metallic or have an electrically conductive shell. The electrically conductive nano-particles can be silver, can be a silver alloy, or can include silver. In various embodiments, cured inks can include metal particles, for example nano-particles. The metal particles are sintered to form a metallic electrical conductor. The metal nano-particles are silver or a silver alloy or other metals, such as tin, tantalum, titanium, gold, copper, or aluminum, or alloys thereof. Cured inks can include light-absorbing materials such as carbon black, a dye, or a pigment.
Curable inks provided in a liquid form are deposited or located in drive or sense micro-channels and cured, for example by heating or exposure to radiation such as infra-red light, visible light, or ultra-violet radiation. The curable ink hardens to form the cured ink that makes up drive or sense micro-wires 24, 54, dummy micro-wires 90, or dummy micro-dots 92. For example, a curable conductive ink with conductive nano-particles are located within drive or sense micro-channels and cured by heating or sintering to agglomerate or weld the nano-particles together, thereby forming an electrically conductive drive or sense micro-wire 24, 54. Materials, tools, and methods are known for coating liquid curable inks to form micro-wires.
In an embodiment, a curable ink can include conductive nano-particles in a liquid carrier (for example an aqueous solution including surfactants that reduce flocculation of metal particles, humectants, thickeners, adhesives or other active chemicals). The liquid carrier is located in micro-channels and heated or dried to remove liquid carrier or treated with hydrochloric acid, leaving a porous assemblage of conductive particles that are agglomerated or sintered to form a porous electrical conductor in a layer. Thus, in an embodiment, curable inks are processed to change their material compositions, for example conductive particles in a liquid carrier are not electrically conductive but after processing form an assemblage that is electrically conductive.
Once deposited, the conductive inks are cured, for example by heating. The curing process drives out the liquid carrier and sinters the metal particles to form a metallic electrical conductor. Conductive inks are known in the art and are commercially available. In any of these cases, conductive inks or other conducting materials are conductive after they are cured and any needed processing completed. Deposited materials are not necessarily electrically conductive before patterning or before curing. As used herein, a conductive ink is a material that is electrically conductive after any final processing is completed and the conductive ink is not necessarily conductive at any other point in the micro-wire formation process.
In various embodiments of the present invention, micro-channels or micro-wires have a width less than or equal to 10 microns, 5 microns, 4 microns, 3 microns, 2 microns, or 1 micron. In an example and non-limiting embodiment of the present invention, each micro-wire is from 10 to 15 microns wide, from 5 to 10 microns wide, or from 5 microns to one micron wide. In some embodiments, micro-wires can fill micro-channels; in other embodiments micro-wires do not fill micro-channels. In an embodiment, the micro-wires are solid; in another embodiment, the micro-wires are porous.
Micro-wires can be metal, for example silver, gold, aluminum, nickel, tungsten, titanium, tin, or copper or various metal alloys including, for example silver, gold, aluminum, nickel, tungsten, titanium, tin, or copper. Micro-wires can include a thin metal layer composed of highly conductive metals such as gold, silver, copper, or aluminum. Other conductive metals or materials are usable. Alternatively, micro-wires can include cured or sintered metal particles such as nickel, tungsten, silver, gold, titanium, or tin or alloys such as nickel, tungsten, silver, gold, titanium, or tin. Conductive inks are used to form micro-wires with pattern-wise deposition or pattern-wise formation followed by curing steps. Other materials or methods for forming micro-wires, such as curable ink powders including metallic nano-particles, are employed and are included in the present invention.
Electrically conductive micro-wires of the present invention are operable by electrically connecting micro-wires through connection pads and electrical connectors to electrical circuits that provide electrical current to micro-wires and can control the electrical behavior of micro-wires. Electrically conductive micro-wires of the present invention are useful, for example in touch screens such as projected-capacitive touch screens that use transparent micro-wire electrodes and in displays. Electrically conductive micro-wires can be located in areas other than display areas, for example in the perimeter of the display area of a touch screen, where the display area is the area through which a user views a display.
Referring to
Drive electrodes 22 were prepared as were the sense electrodes 52, on a separate 4 mil PET support (substrate 10), and with the final addition of a transparent unpatterned conductive layer 30 formed on the lithographically patterned micro-wires 24 by spin coating a solution of PEDOT/PSS at 3000 rpm and drying on a hotplate for 2 minutes at 110° C. Sheet resistance of the dried PEDOT/PSS coating on a section of bare PET support using a four point probe was 8 MΩ/square. Drive electrode resistance was measured to be on the order of 450Ω from end-to-end with approximately 160 kΩ between nearest neighbor electrodes. Thus the ratio of shorting resistance to drive resistance in this inventive example was 356 to 1.
A functional touch-screen was fabricated from the prepared sense and drive electrodes 52, 22 by first, laminating a cover sheet of 4 mil PET (protective overcoat layer 70) on the exposed side of the sense electrodes 52 on dielectric layer 40 using optically clear adhesive (first optically clear adhesive layer 80), OCA (Adhesives Research, ARClear 8154 Optically Clear Unsupported Transfer Adhesive) to form a coversheet of the touch-screen example. Sense electrodes 52 were oriented 90 degrees with respect to drive electrodes 22 and offset such that the intersections of the diamonds were directly above the center of the diamonds of the drive electrodes 22. The uncoated side of the dielectric layer 40 was laminated to the exposed side of the unpatterned conductive layer 30 using the same optically clear adhesive as a second optically clear adhesive layer 82. The dielectric thus includes both the OCA (second optically clear adhesive layer 82) and the 4 mil PET dielectric layer 40.
For the purpose of comparison, a control touch-screen representing an example of the prior art was prepared exactly as described above except the coating of PEDOT/PSS forming the unpatterned conductive layer 30 was eliminated in the comparative example.
The measurement apparatus consisted of two translation stages which were used to move a mechanical, artificial finger incrementally across the sample. The weight of the finger was used to provide a constant touch force and the tip of the artificial finger consisted of a compliant, conductor loaded polymer foam mounted on the end of a conductive rod. All but one drive electrode 22 were held at ground while a voltage waveform consisting of a controlled burst of sine waves (either 100 kHz or 1 MHz) was applied to one of the drive electrodes 22. All of the sense electrodes 52 were held at ground and one was connected to a charge sensitive pre-amplifier (operational amplifier with capacitor feedback) which held the sense electrodes 52 at ground and output a voltage proportional to the input charge. The output voltage from the sensing amplifier was sampled periodically at 20 MHz. Digital processing was used to synchronously (with respect to the driven waveform) rectify the sampled signal and compute an average (in phase) voltage. By spatially stepping the artificial finger across the sample in a spatial matrix of locations, the sensed voltages are mapped as a function of the artificial finger location. By inference, the response of a single repetitive unit at a single location is the same as the response at any other location (except for boundaries). By measuring a known conventional capacitor with the same instrument, the voltage reading is converted to effective capacitance readings.
The mutual no-touch capacitance for the inventive example was 1.8 times higher than the comparative example at either 100 kHz or 1 MHz. This increase illustrates the effective field-spreading characteristic of the unpatterned conductive layer 30 in the inventive example at practical measurement frequencies and is usable to reduce the relative power consumption of a touch-sense controller resulting in improved system efficiency.
To test touch sensitivity, the examples were scanned with a 10.4 mm diameter artificial finger in a matrix pattern centered at an intersection of the active sense and drive electrodes 52, 22. In each case, far from the intersection, the capacitance was equivalent to the no-touch condition, as expected. Centered on the intersection the capacitance was less than the no-touch condition and the relative difference between the near node touch and no-touch reading was taken as a measure of the touch sensitivity.
p Touch-Sensitivity=−(Ctouch−Cno
At 1 MHz the relative touch sensitivity was 42% for the inventive example and 50% for the comparative example. Thus, the touch signal in the inventive example was strong and differences between the inventive and comparative example small, demonstrating that the unpatterned conductive layer 30 has minimal effect on the touch sensitivity while increasing the capacitance. The observed difference in touch sensitivity can be due in part or entirely to imperfections of the alignment of sense and drive electrodes in each example.
To test the shielding properties, connections to the sense and drive electrodes 52, 22 were exchanged thus reversing the roles of the drive and sense electrodes 22, 52 and the artificial finger was scanned over the back-side of the examples. By symmetry this makes no difference for the comparative example but shows a reduction in touch sensitivity due to the shielding effects of the field-spreading unpatterned conductive layer 30 in the inventive example. Indeed, the results showed a factor of 3 reductions in touch sensitivity at 1 MHz and complete elimination of touch signal at 100 kHz for the inventive example. This reduction in frequency response is an illustration of the time constant for charging or discharging the open areas of the unpatterned conductive layer 30 in the drive electrode 22. Touch sensitivity of the comparative example was unaffected, as expected. Thus the field spreading unpatterned conductive layer 30 in the inventive example exhibited highly effective shielding at practical frequencies with no deleterious effects due to shorting between drive electrodes 22. Capacitance signal increased and little change in touch sensitivity was observed when driven and sensed in the intended configuration achieving a considerable improvement in overall system efficiency relative to the prior art example was demonstrated.
The optical uniformity of the dummy micro-wires 90 and dummy micro-dots 92 located between electrodes 20 were tested using image patterns displayed on a high-resolution monitor at standard viewing distances. Dummy micro-wires 90 arranged in lines along different equi-potential lines and dummy micro-wires 90 arranged in dashed lines along different equi-potential lines were both tested with electrode micro-wires arranged as shown in the drive layer 20 of
Methods and devices for forming and providing substrates and coating substrates are known in the photo-lithographic arts. Likewise, tools for laying out electrodes, conductive traces, and connectors are known in the electronics industry as are methods for manufacturing such electronic system elements. Hardware controllers for controlling touch screens and displays and software for managing display and touch screen systems are well known. These tools and methods are usefully employed to design, implement, construct, and operate the present invention. Methods, tools, and devices for operating capacitive touch screens are used with the present invention.
In addition to the inventive and comparative examples described, a touch-screen structure having a PEDOT/PSS unpatterned conductive layer 30 was constructed using the imprinting techniques described and, in a separate sample, an unpatterned conductive layer 30 of AZO on etched drive micro-wires 24 was formed using atomic-layer deposition methods.
The present invention is useful in a wide variety of electronic devices. Such devices can include, for example, photovoltaic devices, OLED displays and lighting, LCD displays, plasma displays, inorganic LED displays and lighting, electrophoretic displays, electrowetting displays, dimming mirrors, smart windows, transparent radio antennae, transparent heaters and other touch-screen devices such as capacitive touch screen devices.
The invention has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
B cross section line
C cross section line
5 micro-wire multi-electrode structure
10 substrate
11 touch surface
20 drive layer/electrode layer
22 drive electrode/electrode
23 edge electrode
24 drive micro-wire/micro-wire
26, 26A, 26B drive gap/gap
30 unpatterned conductive layer
31 area/touch-sensitive area
33 area edge 40 dielectric layer
50 sense layer
52 sense electrode
54 sense micro-wire
57 sense gap
60 gap
70 protective overcoat layer
80 first optically clear adhesive layer
92 second optically clear adhesive layer
90, 90A, 90B equi-potential dummy micro-wires
92, 92A, 92B dummy micro-dots
94 additional dummy micro-wires
95 additional dummy micro-dots
96 edge dummy micro-wires
98 edge dummy micro-dots
100 display and touch-screen apparatus
110 display
Parts List cont'd
120 touch screen
122 first transparent substrate
124 dielectric layer
126 second transparent substrate
128 touch pad area
130 first transparent electrode
132 second transparent electrode
134 wires
136 electrical buss connections
140 touch-screen controller
142 display controller
150 micro-wire
152 dummy micro-wire
156 micro-pattern
200 provide substrate step
205 provide stamps step
210 provide drive layer step
215 imprint drive micro-channels step
220 cure drive micro-channels step
230 provide conductive ink in drive micro-channels step
235 cure conductive ink in drive micro-channels step
300 coat conductive layer step
305 coat dielectric layer step
310 provide sense layer step
315 imprint sense micro-channels step
320 cure sense micro-channels step
330 provide conductive ink in sense micro-channels step
335 cure conductive ink in sense micro-channels step 400 optional coat overcoat step
Parts List cont'd
500 provide drive micro-wire electrode step
505 provide dummy micro-wire step
510 locate unpatterned conductive layer step
515 locate dielectric layer step
520 provide sense micro-wire electrode step
Reference is made to commonly-assigned, co-pending U.S. patent application Ser. No. ______ filed concurrently herewith, entitled “Micro-Wire Electrodes with Equi-Potential Dummy Micro-Wires” by Cok and to commonly-assigned, co-pending U.S. patent application Ser. No. 14/032,213 filed Sep. 20, 2013 entitled “Micro-Wire Touch-Screen with Unpatterned Conductive Layer” by Burberry et al, the disclosures of which are incorporated herein.