Touch panel

Abstract

A projected capacitance touch panel is described. The touch panel comprises an electrode sensing layer comprising at least one sensing electrode, a layer of photo- capacitive material disposed over or under the electrode sensing layer, wherein the layer of photo-capacitive material is patterned according to an area fraction and disposed such that capacitances measured using the at least one sensing electrode are modulated by the dielectric constant of the photo-capacitive material.

Description

[0001] Touch panel

[0002] Field of the invention

[0003] The present invention relates to a projected capacitance touch panel comprising a layer of photo-capacitive material. The present invention also relates to a method of operating the projected capacitance touch panel.

[0004] Background

[0005] Some materials exhibit the photo-capacitive effect. This effect occurs when the materials are illuminated with light within a range of wavelengths and, in response, the spatial charge distribution of the materials change. These materials are referred to as photo-capacitive materials.

[0006] Some projected capacitance touch panels utilise the photo-capacitive effect by incorporating one or more layers of photo-capacitive material into the stack-up of the touch panel. In this way, the touch panels can perform both projected-capacitance measurements and photo-capacitance measurements. Photo-capacitance measurements can be used to study the pattern of reflected light from an object proximate to or in contact with the touch panel (e.g. for fingerprint sensing).

[0007] WO 2022 / 043661 A2 describes a photo-capacitance sensor which includes an input surface and one or more light sources arranged to illuminate a portion of the input surface. The photo- capacitance sensor also includes an array of photo-capacitors arranged to receive light from the one or more light sources which is reflected from an object in contact with, or proximate to, the illuminated portion of the input surface. The array of photo-capacitors is configured for detecting a reflective pattern of the object.

[0008] Summary

[0009] According to a first aspect of the present invention, there is provided a projected capacitance touch panel comprising an electrode sensing layer comprising at least one sensing electrode, and a layer of photo-capacitive material disposed over or under the electrode sensing layer. The layer of photo-capacitive material is patterned according to an area fraction and disposed such that capacitances measured using the at least one sensing electrode are modulated by the dielectric constant of the photo-capacitive material. The term “area fraction” has its usual meaning, namely that the layer of photo- capacitive material is patterned such that the area fraction corresponds to dividing the actual area of photo-capacitive material by the total area spanned by the layer of photo- capacitive material. The total area spanned by the layer of photo-capacitive material may be calculated as the convex hull surrounding all regions of photo-capacitive material forming the layer of photo-capacitive material. The area fraction would be equal to one for a uniform layer of photo-capacitive material. The area fraction of a patterned layer of photo-capacitive material is less than one. The projected capacitance touch panel may further comprise a ground plate for selfcapacitance sensing.

[0010] The ground plate may be patterned with photo-capacitive material. The electrode sensing layer may comprise a plurality of sensing electrodes comprising a plurality of first sensing electrodes extending in a first direction and spaced apart in a second direction, and a plurality of second sensing electrodes extending in the second direction and spaced apart in the first direction. The plurality of first sensing electrodes and the plurality of second sensing electrodes may be co-planar. The plurality of first sensing electrodes and the plurality of second sensing electrodes may be in a layered arrangement, such that one plurality of sensing electrodes is above the other. The photo-capacitive material may be disposed above or below the plurality of first sensing electrodes. The photo-capacitive material may be disposed above or below the plurality of second sensing electrodes.

[0011] The at least one sensing electrode may comprise alternating wide and narrow portions.

[0012] Each wide portion may be diamond-shaped. Each wide portion may be circle-shaped.

[0013] The layer of photo-capacitive material may comprise a strip of photo-capacitive material disposed above and formed about the periphery of at least one wide portion. The strip of the photo-capacitive material may have a surface area no more than 30% of the total area of the at least one wide portion.

[0014] The layer of photo-capacitive material may comprise a first region of photo-capacitive material disposed above and overlapping a non-peripheral region of at least one wide portion, each first region of photo-capacitive material having a smaller area than the respective wide portion.

[0015] Each first region may overlap the centre of the at least one wide portion.

[0016] Each first region may be circular.

[0017] The first regions may be patterned periodically across the layer of photo-capacitive material.

[0018] The first regions may be patterned to be evenly spaced apart across the layer of photo- capacitive material and / or the first regions may patterned to be spaced apart in multiple(s) of a pitch value. The first region of the photo-capacitive material may have a surface area of no more than 30% of the surface area of the at least one wide portion.

[0019] Wherein the electrode sensing layer comprises the plurality of sensing electrodes comprising the plurality of first sensing electrodes extending in the first direction and spaced apart in the second direction, and the plurality of second sensing electrodes extending in the second direction and spaced apart in the first direction, the projected capacitance touch panel may further comprise at least one second region of photo- capacitive material disposed between a junction of the first and second sensing electrodes.

[0020] The layer of photo-capacitive material may comprise at least one third region of photo- capacitive material disposed over a junction of the first and second sensing electrodes or a plurality of mutually adjacent junctions of the first and second sensing electrodes. The layer of photo-capacitive material may comprise a plurality of the third regions of photo-capacitive material. Wherein the layer of photo-capacitive material comprises a plurality of the third regions of photo-capacitive material, each third region may be disposed over a single junction. Wherein the third region is disposed over a single junction, the third region may be centrally located over the junction. The third region may completely or partially cover the junction.

[0021] The spacing between neighbouring third regions may be between 3 pm and 5 pm.

[0022] The plurality of third regions may be patterned periodically across the layer of photo- capacitive material.

[0023] The plurality of third regions may be patterned to be evenly spaced apart across the layer of photo-capacitive material and / or the third regions may be patterned to be spaced apart in multiple(s) of a pitch value.

[0024] A projected capacitance touch panel, in which the at least one third region is disposed over a plurality of adjacent junctions of the first and second electrodes, may be for use in low-light environments. This touch panel may also be for use in applications in which the spectrum of light incident on the photo-capacitive material is close to the edge of the photo-capacitive material’s responsive range.

[0025] The layer of photo-capacitive material may comprise at least one fourth region of photo-capacitive material disposed over a space defined by the first and second sensing electrodes.

[0026] Each of the sensing electrodes may comprise alternating wide and narrow portions. Each of the sensing electrodes may be rectangular.

[0027] The photo-capacitive material may be amorphous silicon.

[0028] The photo-capacitive material may be an organic material, such as poly(3- hexylthiophene) :phenyl-C6i-butyric acid methyl ester, or 2,7-dipentyl-benzothieno3,2- b [ i]benzothiophene. The photo-capacitive material may be a transparent oxide, such as indium tin oxide or indium gallium zinc oxide. The photo-capacitive material may have an optical absorption co-efficient of between approximately loom1at ipm and io8m1at 370nm.

[0029] The photo-capacitive material may be an organic material which is typically used in photodiodes and / or phototransistors.

[0030] The photo-capacitive material may be a transparent oxide which is typically used in a thin film transistor (TFT) backplane of an organic light-emitting diode (OLED) or liquid crystal display. The photo-capacitive material may be a nanomaterial (or “nanocomposite”) . Suitable nanomaterials are typically organic in nature but include inorganic nanostructures (e.g. nanoparticles, nanotubes, etc.).

[0031] The strip, first region(s), third region(s), and / or fourth region(s) of photo-capacitive material may be formed by vacuum deposition or solution processing. The strip, first region(s), and / or third region(s) of photo-capacitive material may be formed by other method(s) such that the photo-capacitive material is directly disposed on the at least one sensing electrode. The electrode sensing layer may comprise a plurality of sensing electrodes, wherein at least a subset of the plurality of sensing electrodes are configured for measurement of a fingerprint.

[0032] The subset of the plurality of sensing electrodes may be configured for measurement of a fingerprint by having spacings between sensing electrodes of the subset which are less than a spacing of ridges in a human fingerprint. Spacings between sensing electrodes of the subset may be less than 200 pm. Spacings between sensing electrodes of the subset may be less than too pm. At least a subset of the plurality of sensing electrodes may be configured for measurement of at least a portion of a palm print. Measuring at least a portion of a palm print may involve identifying the pattern of principle lines of a palm print. According to a second aspect of the present invention, there is provided a projected capacitance touch panel comprising a plurality of sensing electrodes arranged for projected capacitance measurements, and a layer of photo-capacitive material patterned to correspond to positions which will correspond, in use, to electric field concentrations generated by the sensing electrodes.

[0033] The projected capacitance touch panel according to the second aspect may include features corresponding to any features of the projected capacitance touch panel according to the first aspect, and / or a system including the projected capacitance touch panel according to the first aspect.

[0034] According to a third aspect of the present invention, there is provided a system comprising the projected capacitance touch panel according to the first or second aspect, one or more light sources arranged to irradiate the layer of photo-capacitive material, and a controller configured to measure signals from the one or more sensing electrodes indicative of a projected capacitance and / or a photo-capacitance.

[0035] The one or more light sources may comprise an infrared source arranged to irradiate the layer of photo-capacitive material. The infrared source may be arranged to irradiate a position corresponding to a subset of the plurality of sensing electrodes configured for measurement of a fingerprint.

[0036] The infrared source may be configured to apply infrared radiation having a wavelength of between 750 nm and 10 um.

[0037] The one or more light sources may be configured to apply radiation having a wavelength of between 400 nm and 750 nm.

[0038] The system may further comprise a display underlying the projected capacitance touch panel. According to a fourth aspect of the present invention, there is provided a method comprising use of the projected capacitance touch panel according to the first or second aspect or the system according to the third aspect to perform measurements of projected capacitance measurements and to perform measurements of photo- capacitance.

[0039] Measurements of projected capacitance and photo-capacitance may be performed alternately according to a predetermined or dynamically determined sequence. Measurements of projected capacitance and photo-capacitance may be performed concurrently.

[0040] The method may include features corresponding to any features of the projected capacitance touch panel of the first and / or second aspects, or a system including the projected capacitance touch panel of the first and / or second aspects.

[0041] Brief Description of Drawings

[0042] Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

[0043] Figure i schematically illustrates a sub-region of a sensing electrode; Figure 2 schematically illustrates a sub-region of a sensing electrode;

[0044] Figure 3a is a schematic plan view of a first electrode arrangement;

[0045] Figure 3b illustrates cross-sections of the arrangement shown in Figure 3a;

[0046] Figure 4 schematically illustrates a sub-region of a sensing electrode;

[0047] Figure 5 schematically illustrates a sub-region of a sensing electrode; Figure 6 schematically illustrates a sub-region of a sensing electrode;

[0048] Figure 7a is a schematic plan view of a second electrode arrangement;

[0049] Figure 7b illustrates cross-sections of the arrangement shown in Figure 7a;

[0050] Figure 8 schematically illustrates a sub-region of a sensing electrode;

[0051] Figure 9a is a schematic plan view of a third electrode arrangement; Figure 9b illustrates cross-sections of the arrangement shown in Figure 9a;

[0052] Figure 10a is a schematic plan view of a fourth electrode arrangement;

[0053] Figure 10b illustrates cross-sections of the arrangement shown in Figure 10a;

[0054] Figure 11 schematically illustrates a first system including a first touch panel;

[0055] Figure 12 schematically illustrates a second system including the first touch panel; Figure 13a schematically illustrates a second touch panel;

[0056] Figure 13b schematically illustrates a third touch panel;

[0057] Figure 14a schematically illustrates a fourth touch panel;

[0058] Figure 14b schematically illustrates a fifth touch panel;

[0059] Figure 15a schematically illustrates a sixth touch panel; Figure 15b schematically illustrates a seventh touch panel;

[0060] Figure 16 is a schematic plan view of a fifth electrode arrangement;

[0061] Figure 17 is a schematic plan view of a sixth electrode arrangement;

[0062] Figure 18 is a schematic plan view of a seventh electrode arrangement; and

[0063] Figure 19 is a schematic plan view of an eighth electrode arrangement.

[0064] Detailed Description of Certain Embodiments

[0065] In the following, like parts are denoted by like references.

[0066] The present invention is concerned with a projected-capacitance touch panel (herein simply referred to as “touch panel”') which performs, in addition to projected- capacitance measurements, photo-capacitance measurements by way of photo- capacitive material disposed above or below the sensing electrodes of the panel.

[0067] The present invention provides an improvement over the integrated touch and photo- capacitance sensor disclosed in International patent application no.

[0068] PCT / GB2021 / 052144. In particular, the present invention provides an improvement by way of the arrangement of the photo-capacitive material disposed above or below the sensing electrodes. Referring to Figure 1, a sub-region of a sensing electrode 1 is shown. The sensing electrode 1 may be incorporated into a touch panel (not shown), along with additional sensing electrodes, as will be hereinafter explained.

[0069] The sub-region includes two narrow portions 2 and a wide portion 3 of the sending electrode 1. The wide portion 3 is position between each narrow portion 2. As will be hereinafter shown and described for some examples, the sensing electrode 1 includes alternating narrow and wide portions 2, 3. The sensing electrode 1 extends in a first direction x. The wide portion 3 has a width, di, in a second direction y which is greater than a width, d2, of the narrow portion 1 in the second direction.

[0070] The wide portion 3 may be diamond-shaped and the narrow portion 2 may be rectangular-shaped (as shown in Figure 1). However, the narrow and wide portions 2,3 may take any shape. Referring also to Figure 2, an alternative example of the sensing electrode 1 is shown in which the wide portion 3 is circle-shaped.

[0071] A strip of photo-capacitive material 4 (herein simply referred to as “strip” 4) is supported on the wide portion 3 such that the strip 4 capacitively couples to the sensing electrode 1. In one example, the strip 4 directly contacts the sensing electrode. In another example, the strip 4 does not directly contact the sensing electrode 1 and instead may be formed, for example, in or on a laminated layer (not shown) separate to the sensing electrode 1. In yet another example, the strip 4 is separated from the sensing electrode 1 by an interleaving layer (not shown), for example a dielectric layer, onto which the strip 4 is provided. The strip 4 is formed about the periphery of the wide portion 3. In other words, the strip 4 overlays the peripheiy of the wide portion 3 so that a path traced by the strip 4 aligns with the path defined by the periphery of the wide portion 3. Thus, in an example where the wide portion 3 is diamond-shaped (as shown in Figure 1), the path of the strip 4 is in the shape of a diamond. In an example where the wide portion 3 is circleshaped, the path of the strip 4 is in the shape of a circle.

[0072] As will be hereinafter explained, at least one, some, or all of the wide portions 3 of the sensing electrode 1 may have a strip 4 formed about their periphery.

[0073] As will also be hereinafter described, the strip 4 may help to enhance the mutual capacitance between interleaving sensing electrodes 1.

[0074] The strip of the photo-capacitive material 4 has a surface area, a,, no more than 30% of the total area, a2, of the wide portion 3. The surface area of the strip 4 depends on the optical absorption co-efficient of the photo-capacitive material. Preferably, the surface area ai is at the upper bound of the surface area the strip 4 can take before the optical transparency of the touch panel (not shown) is insufficient for proper functioning of a display (not shown) of the touch panel.

[0075] Preferably, the photo-capacitive material has an optical absorption co-efficient of between approximately loom1at 1 urn and io8m1at 370nm. Preferably, the photo- capacitive material is amorphous silicon, a-Si. The material selected for the photo- capacitive material is selected according to the intended purpose of the touch panel. Any photo-capacitive material may be used provided that the material has a tail state density of at least to20eV’W.

[0076] In one example, the photo-capacitive material is an organic material, for example P3HT (poly(3-hexylthiophene)):PCBM (phenyl-C6i-butyric acid methyl ester), C5-BTBT (2,7- dipentyl-benzothieno3,2-b[i]benzothiophene), or suitable composition variations thereof. Organic materials which are typically used in photodiodes and / or phototransistors may be selected as the photo-capacitive material.

[0077] In another example, the photo-capacitive material is a transparent oxide, for example indium zinc oxide (IZO), or indium gallium zinc oxide (IGZO), or composition variations thereof. Transparent oxides which are typically used in a thin film transistor (TFT) backplane of an organic light-emitting diode (OLED) or liquid crystal display may be selected as the photo-capacitive material. In another example, the photo-capacitive material is a nanomaterial (or “nanocomposite”). Suitable nanomaterials are typically organic in nature but include inorganic nanostructures (e.g. nanoparticles, nanotubes, etc.). The proportion of nanostructures included in a suitable nanomaterial will depend on the desired optical properties and trap state densities for photo-capacitive behaviour.

[0078] Referring also to Figure 3a, a plurality of sensing electrodes 1, as hereinbefore described, is provided in a first electrode arrangement 5, 51. The first electrode arrangement 51 is an example arrangement of sensing electrodes 1 which may be incorporated into the touch panel.

[0079] The first electrode arrangement 51 includes sensing electrodes 1 consisting of a number, e.g. N, of first sensing electrodes 1, ii and a number, e.g. M, of second sensing electrodes 1, i2. The first sensing electrodes ii extend in the first direction x and are spaced apart in the second direction y. The second sensing electrodes i2extending in the second direction y and are spaced apart in the first direction x. Preferably, the first and second electrodes are arranged in an interleaving structure, as shown in Figure 3a. The first and second electrodes 11, 12 are separated by a distance, d3, in a third direction z, which is mutually perpendicular to the first and second directions.

[0080] At least one of the sensing electrodes 1 has at least one wide portion 3 for which a strip 4, as hereinbefore described, is formed about its periphery. Thus, photo-capacitive material does not need to be provided for all of the sensing electrodes 1. Preferably, at least one first sensing electrode ii and at least one second sensing electrode i2are provided with strips 4.

[0081] Defining an x-y plane region in which all sensing electrodes 1 of the electrode arrangement 5 are found as an electrode region, the strips 4 may be found in the entirety of the electrode region, or one or more sub-regions of the electrode region. In one example, a first sub-region is defined by a single first sensing electrode ii and a single second sensing electrode 12which cross over. In that example, each wide portion 3 of each sensing electrode 1 within the first sub-region is provided with a strip 4 formed about its peripheiy, and strips 4 are not present for any other sub-region of the electrode region. Other electrodes arrangements 5 according to the present invention are possible. In one example, the electrode arrangement 5 includes first and second sensing electrodes 1, ii, 12having circular-shaped wide portions (see Figure 5). In another example, the first and second sensing electrodes ii, i2are co-planar.

[0082] Referring also to Figure 3b, a cross-section a-a and a cross-section b-b taken of the first electrode arrangement 51 is shown.

[0083] The cross-section a-a is taken along one of the first sensing electrodes ii for which each wide portion 3 of the electrode ii has a strip 4 formed about its periphery. The crosssection b-b is taken along one of the second sensing electrodes i2for each wide portion 3 of the electrode i2has a strip 4 formed about its peripheiy. In the example shown in Figure 3b, each strip 4 is directly provided on the wide portion 3. Referring also to Figure 4, a sub-region of the sensing electrode 1 as hereinbefore described is shown. However, in place of the strip of photo-capacitive material 4, a first region of photo-capacitive material 6 (herein also referred to as a “first region”) overlaps a non-peripheral region of the wide portion 3. In the example shown in Figure 4, the first region 6 overlaps the centre of the wide portion 3. However, the first region 6 may overlap an off-centre region of the wide portion 3 only.

[0084] The first region 6 may be circular-shaped. Thus, the first region 6 may take the form of a dot of photo-capacitive material, preferably at the centre of the wide portion 3.

[0085] Referring also to Figure 5, the first region 6 may be diamond-shaped. However, the first region 6 may be any shape provided that the first region 6 does not extend to the periphery of the wide portion 3. Referring also to Figure 6, another example of the first sensing electrode 1 and first region 6 is shown in which both the electrode 1 and first region 6 are circular-shaped.

[0086] The first region 6 may be directly provided on the wide portion 3. In another example, the first region 6 does not contact the wide portion 3, in a similar way as hereinbefore described for the strip 4. The first region 6 has a surface area, a3, of no more than 30% of the total area, a2, of the wide portion 3. The surface area a3depends on the optical absorption co-efficient of the photo-capacitive material selected. As will be described hereinafter, the first region 6 and the strip 4 may be provided on or overlapping the same wide portion 3. In which case, the combined surface area of the first region 6 and the strip 4 is no more than

[0087] 30% of the total area, a2, of the wide portion 3.

[0088] The first region 6 is formed of the same or similar photo-capacitive material as hereinbefore specified for the strip 4.

[0089] The self-capacitance of a sensing electrode 1 may be measured relative to a ground plate (not shown), which may help to enhance the self-capacitance of the sensing electrode 1.

[0090] Referring also to Figure 7a, a second electrode arrangement 5, 52is shown. The second electrode arrangement 52is the same as the first electrode arrangement 51. However, the second electrode arrangement 52is provided with at least one first region 6 in place of the strips 4.

[0091] In a similar way to hereinbefore described for the strip 4, the first region(s) 6 may be found in the entirety of the electrode region, or one or more sub-regions of the electrode region of the second electrode arrangement 52. Preferably, at least one first sensing electrode ii and at least one second sensing electrode i2are provided with first regions 6. Preferably, wherein more than one wide portion 3 is overlapped by a respective first region 6, each first region 6 overlaps the same region of the wide portion 3 such that the first regions 6 form a regular arrangement with each other (as shown in Figure 7a). This may help to enhance self-capacitance of the sensing electrodes 1 relative to a ground plate (not shown).

[0092] Referring to Figure 7b, a cross-section c-c and a cross-section d-d taken of the second electrode arrangement 52is shown.

[0093] The cross-section c-c is taken along one of the first sensing electrodes ii for which each wide portion 3 of the electrode ii has a first region of photo-capacitive material 4. The cross-section d-d is taken along one of the second sensing electrodes i2for each wide portion 3 of the electrode i2has a first region of photo-capacitive material 6. In the example shown in Figure 7b, each first region 6 is directly provided on the wide portion 3- Referring also to Figure 8, a sub-region of the sensing electrode 1 as hereinbefore described is shown. In this example, both the strip of photo-capacitive material 4 and the first region of photo-capacitive material 6 are supported by the wide portion 3.

[0094] In this example, the first region 6 overlaps the centre of the wide portion 3 and the first region 6 is circular-shaped. However, any combination of first region 6 shape and position may be combined with the strip 4.

[0095] Referring also to Figure 9a, a third electrode arrangement 5, 53is shown. The third electrode arrangement 53 may be considered a combination of the first and second electrode arrangements 51, 52 because the third arrangement 53 includes both the strips 4 and the first regions 6 (collective referred to as “the photo-capacitive regions”).

[0096] The example in Figure 9a shows all wide portions 3 of each of the first and second sensing electrodes ii, 12having both strips 4 and first regions 6 (also as shown in Figure 8). However, the photo-capacitive regions 4, 6 may be found in the entirety of the electrode region, or one or more sub-regions of the electrode region of the second third arrangement 53. Preferably, at least one first sensing electrode ii and at least one second sensing electrode i2are provided with both of the photo-capacitive regions 4, 6. Referring also to Figure 9b, a cross-section e-e and a cross-section f-f taken of the third electrode arrangement 53is shown.

[0097] The cross-section e-e is taken along one of the first sensing electrodes ii for which each wide portion 3 of the electrode ii has both photo-capacitive regions 4, 6. The cross- section f-f is taken along one of the second sensing electrodes i2for each wide portion 3 of the electrode i2has both capacitive regions 4, 6. In the example shown in Figure 7b, both capacitive regions 4, 6 are directly provided on the wide portion 3.

[0098] Referring also to Figure 10a, a fourth electrode arrangement 54is shown. Referring also to Figure 10b, a cross-section g-g and a cross-section h-h taken of the fourth electrode arrangement 54is shown. The fourth electrode arrangement 54is the same as the third electrode arrangement 53. However, the fourth electrode arrangement 54includes at least one second region of the photo-capacitive material 7 (herein also referred to as a “second region”').

[0099] Each second region 7 is disposed between the first and second sensing electrodes i i2and at a junction 8 (or “intersection”) formed by the interleaving first and second sensing electrodes i 12. In the example shown in Figure 10b, the second region 7 is in direct contact with the underside of the second sensing electrode i2(wherein the second sensing electrode i2is provided above the first sensing electrode ii). In another example, the second region 7 is provided on or in a separate laminated layer (not shown) between the first and second electrodes i i2. The second region 7 does not directly contact both the first and second electrodes i i2, as this would cause shorting. Thus, according to the present invention, photo-capacitive material is supported on a plurality of first sensing electrodes i and optionally disposed between first and second sensing electrodes i i2.

[0100] The second region 7 may be formed of the same or similar photo-capacitive material as hereinbefore specified for the strip 4 and first region 6.

[0101] The example in Figure 10a shows the second region 7 provided at each junction 8.

[0102] However, the second region 7 may be provided at each, some, or one junction 8 of an electrode arrangement 5.

[0103] The second region 7 may influence the mutual capacitance between the first and second sensing electrodes i i2and / or influence the self-capacitance of the first and second sensing electrodes i i2. Projected capacitance touch panel and operation

[0104] As hereinbefore briefly explained, each of the electrode arrangements 5 may be incorporated into a projected-capacitance touch panel.

[0105] Referring also to Figure 11, a first system 9, 91 is shown. The system 91 includes a first touch panel 10, io a light source 11 arranged to irradiate the first touch panel io and a controller 12 coupled to the touch panel io The system 91 may further include a display (not shown) underlying the projected capacitance touch panel. The first touch panel tOi includes the first and second sensing electrodes ii, i2and photo-capacitive material layer 14 supported by the first sensing electrode ii. The photo capacitive material layer 14 consists of at least one strip 4 and / or at least one first region 6 as hereinbefore described. The electrodes 1 and photo-capacitive material layer 14 may take the form of the first or second electrode arrangements 51, 52 hereinbefore described. The second sensing electrode i2is a receiver electrode, Rx, and the first sensing electrodes ii is a transmitter electrode, Tx.

[0106] The first touch panel tOi further includes cover glass 13 arranged over the photo- capacitive material layer 14. The first touch panel tOi may further include a ground plate (not shown) for self-capacitance measurements.

[0107] When an object (such as a finger) is in contact with, or proximate to, the cover glass 13, light emitted by the light source 11 may be reflected by the object. In this scenario, at least a portion of the light reflected by the object irradiates the photo-capacitive material layer 14 to modify the spatial charge distribution of the photo-capacitive material (in other words, to modify the dielectric constant), which in turn modifies a distribution of electric field lines between the sensing electrodes 1. This will be explained hereinafter in reference to International application no. PCT / GB2021 / 052144.

[0108] In one example, the light sources 11 is an infrared light source. In one example, the infrared light source is configured to apply infrared radiation at a pulse frequency of between 20 Hz and 60 Hz, for example between 25 Hz and 35 Hz. Any suitable pulse frequency may be selected depending on the specific application.

[0109] Furthermore, as will be hereinafter explained, the first and second sensing electrodes ii, i2of the touch panel 10 are used to perform both touch capacitance measurements and photo-capacitive measurements (herein also referred to as “combined readout”). Referring also to Figure 12, a second system 9, 92is shown. The second system 92is the same as the first system 91. However, this system 92includes a plurality of discrete (or separate) light sources n. This allows for targeted illumination of one or more subregions of the electrode regions hereinbefore described. Targeted illumination allows for one, some, or all of the strips 4, first regions 6, and / or second regions 7 to be illuminated at a particular time, and for different sub-regions to be illuminated at different times.

[0110] With respect to the operation of the first and second systems 9, reference is made to the A2 publication of International application no. PCT / GB2021 / 052144. Firstly, reference is made to page 39, line 35 to page 40, lines 5, and page 40, line 19 to page 41, line 24, and page 42, line 26 to page 44, line 15 and corresponding Figures 23 to 30B. These passages outline the method steps involved in performing combined readout including how to calculate the change in photo-capacitance for determining, for example, fingerprint identification.

[0111] Secondly, reference is made to page 44, line 26 to page 47, line 31, and corresponding figure 31; this passage describes a specific addressing scheme for the plurality of sensing electrodes 1 that allows the method steps in the previously cited passage to be performed.

[0112] Referring also to Figures 13a, 13b, 14a, 14b, 15a, and 15b, alternative stack-up structures will now be described for the touch panel 10.

[0113] Referring to Figure 13a, a second touch panel 10, io2is shown. The second touch panel 102 is the same as the first touch panel lOi, but further includes a dielectric layer 15 between the first and second electrodes ii, i2.

[0114] Referring to Figure 13b, a third touch panel to3is shown. The third touch panel to3is the same as the second touch panel io2but further includes a dielectric layer 15 between a first photo-capacitive layer 14, 141 and the plurality of second sensing electrodes i2. The first photo-capacitive layer 141 includes at least one strip 4 and / or at least one first region of photo-capacitive material 6 as hereinbefore described.

[0115] Referring to Figure 14a, a fourth touch panel to4is shown. The fourth touch panel to4is the same as the second touch panel io2but further includes a second photo-capacitive material layer 14, 142 between the first and second sensing layers i 12; this layer 14 includes at least one second region of photo-capacitive material 7 hereinbefore described.

[0116] Referring to Figure 14b, a fifth touch panel io5is shown. The fifth touch panel io5is the same as the fourth touch panel to4but further includes a dielectric layer 15 between the photo-capacitive material layer 14 and the plurality of second sensing electrodes i2.

[0117] Referring to Figures 15a and 15b, a co-planar arrangement of the first and second sensing electrodes ii, 12is shown for sixth (Figure 15a) and seventh (Figure isbg) touch panels 106, to7. Touch panels 106, to7include a dielectric layer 15 on which the first and second electrodes 11, 12 are supported and separated by. The seventh touch panel io7further includes a dielectric between the photo-capacitive material layer 14 and the coplanar sensing electrodes 1. Any one of the touch panels 10, 10i, io2, to3, to4, io5, 106, io7hereinbefore described may be used for combined readout, and may be incorporated into the first or second systems 9 hereinbefore described.

[0118] Additional example electrode arrangements Referring now to Figure 16, a fifth electrode arrangement 5, 55is shown.

[0119] The fifth electrode arrangement s5is similar to the other electrode arrangements 5 hereinbefore described. However, the sensing electrodes 1 of the fifth electrode arrangement 55are rectangular. In other words, they do not have alternating narrow and wide portions 2, 3. Furthermore, the fifth electrode arrangement s5does not include the strip(s) of photo-capacitive material 4, the first region(s) 5, nor the second region(s) 6 hereinbefore described.

[0120] The plurality of sensing electrodes 1 consists of a plurality of the second sensing electrodes i2and a plurality of the first sensing electrodes ii. The second sensing electrodes 12may be receiver electrodes Rxi, Rx2, Rx3, Rx4. The first sensing electrodes

[0121] 11 may be transmitter electrodes, Txt, Tx2, Tx3, Tx4. The first and second electrodes i

[0122] 12are in an interleaving arrangement, such that the first and second electrodes ii, i2form junctions 8 in the same way as hereinbefore described for other arrangements 5. The fifth electrode arrangement s5includes at least one third region of photo-capacitive material 16 (herein referred to as a “third region” 16) disposed over one of the junctions 8. Each third region 16 may completely or partially overlap a single junction 8. Figure 16 shows a plurality of third regions 16 each disposed over a single function 8.

[0123] However, the one or more third regions 16 may be found in one or more sub-regions of an electrode region. As for previously described arrangements 5, the electrode region is defined by an x-y plane region in which all sensing electrodes 1 of the electrode arrangement 55are found.

[0124] In one example, each third region 16 is in direct contact with the respective second sensing electrode 12. In another example, the third regions 16 do not directly contact the sensing electrodes 1 and instead may be formed, for example, in or on a laminated layer (not shown) separate to the sensing electrodes 1.

[0125] Although shown in Figure 16 as square-shaped, the third region 16 may take other shapes (e.g. circular) which result in generation of a suitable photo-capacitance signal profile. The third regions 16 may be patterned periodically across the x-y plane they occupy. For example, the third regions 16 may be patterned to be evenly spaced apart across the x-y plane, as shown in Figure 16, and / or the third regions 16 may be spaced apart in multiple(s) of a pitch value. This distribution may help to generate a predictable photo-capacitance signal profile.

[0126] The third regions 16 may be evenly space apart by between 3 pm and 5 pm (measured from region edge to region edge). The gaps between the third regions 16 may depend on the capability of the manufacturing techniques used and / or the desired photo- capacitive signal profile. The gaps between the third regions 16 may be set to help avoid image smearing. The minimum gap beyond which image smearing occurs depends on the circuitry / design of the touch panel 10 into which the fifth electrode arrangement s5may be incorporated.

[0127] Each third region 16 may have an area, a4, of between 3 pm2and 5 pm2. The lower bound of the area, a4, is limited by the capabilities of the manufacturing techniques used. The area, a4, may depend on the circuitry / design of the touch panel 10 into which the fifth electrode arrangement s5may be incorporated (for example to allow sufficient differentiation between different photo-capacitive signals). Each third region 16, in combination with the respective junction 8 over which the third region 16 is disposed, provides a touch sensing node 17. Each touch sensing node 17 defines a virtual pixel (not shown). Thus, the pattern of third regions 16 across the x-y plane provides an array of virtual pixels for photo-capacitance measurements or combined readout. In photo-capacitance measurements / combined readout, the greater the number of pixels, the greater the sensitivity of a touch panel 10 incorporating the fifth electrode arrangement s5. The material of the third region 16 may be formed of any photo-capacitive material hereinbefore outlined, for example. If opaque photo-capacitive material is used for the third region 16, then the gaps between the regions 16 may be widened to improve transparency of the fifth electrode arrangement 55. However, increasing gap distance decreases sensitivity (as there are fewer virtual pixels per surface area of the fifth electrode arrangement 55). Thus, there is a trade-off between sensitivity and transparency when opaque materials are used for the third regions 16. However, for transparent photo-cap materials, this trade off does not exist.

[0128] Referring also to Figure 17, a sixth electrode arrangement 5, 56 is shown.

[0129] The sixth electrode arrangement 56 is the same as the fifth electrode arrangement s5. However, the at least one third region 16 is disposed over more than one adjacent junction 8. In the example shown in Figure 17, a single third region 16 is disposed over four junctions 8 which are mutually adjacent. In that example, a single third region 16, in combination with the four junctions 8, provides four virtual pixels 18.

[0130] In comparison with the fifth electrode arrangement 55, the sixth electrode arrangement 56 includes photo-capacitive material occupying a greater area of the x-y plane but having the same or a similar density of virtual pixels. For this reason, the sixth electrode arrangement 56 may be particularly suited for operation in low-light environments or in applications in which the spectrum of light incident on the photo- capacitive material is close to the edge of the photo-capacitive material’s responsive range. In these scenarios, reduced transparency of the sixth electrode arrangement 56 can be used as a trade-off for higher sensitivity. Specific examples of scenarios include remote sensing (e.g. laser pointers on a screen), and finger hover sensing. Referring now to Figure 18, a seventh electrode arrangement 5, 57is shown.

[0131] The seventh electrode arrangement 57is the same as the fifth electrode arrangement s5hereinbefore described. However, the seventh electrode arrangement 57includes at least one fourth region of photo-capacitive material 19 (herein “fourth region” 19) instead of the third regions 16.

[0132] Each fourth region 19 is disposed over (or overlapping) a space defined by the interleaving first the second sensing electrodes 1, ii, 12. Each fourth region 19 may be shaped to conform to the outline of the space it overlaps. Each fourth region 19 may be a different shape to the space. Each fourth region 19 may be spaced apart from the other fourth regions 19 by 1 pixel pitch. Each fourth region 19 may have an area, a5, of between 3 pm2and 5 pm2. The area a5may depend on similar considerations as those described for the fifth electrode arrangement s5.

[0133] In the example shown in Figure 18, the first and second sensing electrodes ii, i2are rectangular and interleave to define a square space between each of the first and second electrodes ii, i2. Each fourth region 19 is square shaped. Furthermore, a fourth region 19 overlaps each space. However, in other examples, the fourth regions 19 may simply occupy a subregion of the electrode region, as hereinbefore described for the fifth electrode arrangement s5. The at least one fourth region 19 may be formed of the same photo-capacitive material hereinbefore described.

[0134] In the seventh electrode arrangement 57, each touch sensing node 17 is modulated by one or more fourth regions 19 adjacent to the respective touch sensing node 17. In the example shown in Figure 18, each touch sensing node 17 is modulated by four adjacent fourth regions 19.

[0135] Depending on touch panel design requirements and the detection algorithm(s) used, the seventh electrode arrangement 57may produce a projected capacitance signal profile which has a spatial profile such that differentiating between the projected capacitance and photo-capacitance signal profiles is less difficult. Other benefits of this arrangement 57may be appreciated by the person skilled in the art. The electrode arrangements 5 shown in each of Figures 16 to 18 include rectangular sensing electrodes 1. However, the fifth, sixth, and seventh electrode arrangements 55, 56, 5? hereinbefore described instead may include sensing electrodes i having alternating narrow and wide portions 2, 3, in a similar way as described for the first electrode arrangement 51. Figure 19 shows a seventh electrode arrangement 57having sensing electrodes 1 with alternating narrow and wide portions 2, 3. The layer of photo-capacitive material (not shown) in the seventh electrode arrangement 57may take the form of the third or fourth regions 16, 19 hereinbefore described. Each touch sensing node 17 is formed at the junction 8 (or intersection) of a narrow portion 2 of one of the first sensing electrodes ii and a narrow portion 2 of one of the second sensing electrodes t2. The photo-capacitive material (not shown) in combination with a touch sensing node 17 defines a respective virtual pixel 18. Each of the fifth, sixth, seventh, and eighth electrode arrangements 55, 56, 57, 5s may be incorporated into the touch panel 10 hereinbefore described. The system 9 including the fifth, sixth, seventh, and eighth electrode arrangements 55, 56, 57, 5s may be operated in the same way as hereinbefore described as for the other electrode arrangements 5.

[0136] Modifications

[0137] It will be appreciated that various modifications may be made to the embodiments hereinbefore described. Such modifications may involve equivalent and other features which are already known. Features of one embodiment may be replaced or supplemented by features of another embodiment.

[0138] Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combination of features disclosed herein either explicitly or implicitly or any generalization thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicant hereby gives notice that new claims may be formulated to such features and / or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

Claims1. A projected capacitance touch panel comprising: an electrode sensing layer comprising at least one sensing electrode; a layer of photo-capacitive material disposed over or under the electrode sensing layer, wherein: the layer of photo-capacitive material is patterned according to an area fraction and disposed such that capacitances measured using the at least one sensing electrode are modulated by the dielectric constant of the photo-capacitive material.

2. The projected capacitance touch panel of claim i, the projected capacitance touch panel further comprising a ground plate for self-capacitance sensing.

3. The projected capacitance touch panel of claims i or 2, wherein the electrode sensing layer comprises a plurality of sensing electrodes comprising: a plurality of first sensing electrodes extending in a first direction and spaced apart in a second direction; and a plurality of second sensing electrodes extending in the second direction and spaced apart in the first direction.

4. The projected capacitance touch panel of any preceding claim, wherein the at least one sensing electrode comprises alternating wide and narrow portions.

5. The projected capacitance touch panel of claim 4, wherein the layer of photo- capacitive material comprises a strip of photo-capacitive material disposed above and formed about the peripheiy of at least one wide portion.

6. The projected capacitance touch panel according to claim 5, wherein the strip of the photo-capacitive material has a surface area no more than 30% of the total area of the at least one wide portion.

7. The projected capacitance touch panel of any one of claims 4 to 6, wherein the layer of photo-capacitive material comprises a first region of photo-capacitive material disposed above and overlapping a non-peripheral region of at least one wide portion, each first region of photo-capacitive material having a smaller area than the respective wide portion.

8. The projected capacitance touch panel according to claim 7, wherein the first region of the photo-capacitive material has a surface area of no more than 30% of the surface area of the at least one wide portion.9 The projected capacitance touch panel of any one of claims 5 to 8, wherein the electrode sensing layer comprises the plurality of sensing electrodes comprising: the plurality of first sensing electrodes extending in the first direction and spaced apart in the second direction; and the plurality of second sensing electrodes extending in the second direction and spaced apart in the first direction, the projected capacitance touch panel further comprising at least one second region of photo-capacitive material disposed between a junction of the first and second sensing electrodes.

10. The projected capacitance touch panel of claim 3, wherein the layer of photo- capacitive material comprises at least one third region of photo-capacitive material disposed over: a junction of the first and second sensing electrodes, or a plurality of mutually adjacent junctions of the first and second sensing electrodes.

11. The projected capacitance touch panel of claim 10, wherein the layer of photo- capacitive material comprises a plurality of the third regions of photo-capacitive material.

12. The projected capacitance touch panel of claim 3, wherein the layer of photo- capacitive material comprises at least one fourth region of photo-capacitive material disposed over a space defined by the first and second sensing electrodes.

13. The projected capacitance touch panel of any one of claims 10 to 12, wherein each of the sensing electrodes comprise alternating wide and narrow portions.

14. The projected capacitance touch panel of any one of claims 10 to 12, wherein each of the sensing electrodes is rectangular.15- The projected capacitance touch panel of any preceding claim, wherein the photo-capacitive material is amorphous silicon.

16. The projected capacitance touch panel of any one of claims i to 14, wherein the photo-capacitive material is an organic material, such as poly(3- hexylthiophene):phenyl-C6i-butyric acid methyl ester, or 2,7-dipentyl-benzothieno3,2- b [ i]benzothiophene.

17. The projected capacitance touch panel of any one of claims 1 to 14, wherein the photo-capacitive material is a transparent oxide, such as indium tin oxide or indium gallium zinc oxide.

18. The projected capacitance touch panel of any preceding claim, the electrode sensing layer comprising a plurality of sensing electrodes, wherein at least a subset of the plurality of sensing electrodes are configured for measurement of a fingerprint.

19. A projected capacitance touch panel comprising: a plurality of sensing electrodes arranged for projected capacitance measurements; and a layer of photo-capacitive material patterned to correspond to positions which will correspond, in use, to electric field concentrations generated by the sensing electrodes.

20. A system comprising: the projected capacitance touch panel of any one of claims 1 to 19; one or more light sources arranged to irradiate the layer of photo-capacitive material; and a controller configured to measure signals from the one or more sensing electrodes indicative of a projected capacitance and / or a photo-capacitance.

21. The system of claim 20, wherein the one or more light sources comprise an infrared source arranged to irradiate the layer of photo-capacitive material.

22. The system of claim 21, wherein the infrared source is configured to apply infrared radiation having a wavelength of between 750 nm and 10 um.

23. The system of claim 20, wherein the one or more light sources are configured to apply radiation having a wavelength of between 400 nm and 750 nm.

24. The system of any one of claims 20 to 23, further comprising a display underlying the projected capacitance touch panel.

25. A method comprising use of the projected capacitance touch panel of any one of claims 1 to 19 or the system of any one of claims 20 to 24 to perform measurements of projected capacitance measurements and to perform measurements of photo- capacitance.

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