Touch-sensitive input device

Abstract

A method of fabricating a touch-sensitive input device is disclosed. The method comprises forming a first set of electrodes (2; Fig. 1), a first set of conductive tracks (3; Fig. 1) and a first set of contact pads (4; Fig. 1) on a first face (6) of a first substrate (8), wherein a conductive track in the first set of conductive tracks connects a respective line (13; Fig. 1) of electrodes in the first set of electrodes and a respective contact pad in the first set of electrodes. The method further comprises forming a first laminate (15) comprising overlaying a second substrate (16) which is self-adhesive onto the first face of the first substrate so that electrodes in the first set of electrodes are covered but contact pads in the first set of contact pads are uncovered by the second substrate. The method further comprises after forming the first laminate, forming a second set of electrodes (22; Fig. 1), a second set of conductive tracks (23; Fig. 1) and a second set of contact pads (24; Fig. 1) on a first face (17) of a second substrate (16), wherein a conductive track in the second set of conductive tracks connects a respective line of electrodes in the second set of electrodes and a respective contact pad in the second set of contact pads. The method further comprises forming a second laminate (26) comprising overlaying a third substrate (27) which is self-adhesive onto the first face of the second substrate so that electrodes in the first and second set of electrodes are covered but contact pads in the first and second set of contact pads are uncovered by the third substrate.

Description

[0001] Touch-sensitive input device

[0002] Field of the invention

[0003] The present invention relates to a touch-sensitive input device.

[0004] Background

[0005] Touch-sensitive input devices can be fabricated using flexographic printing. For example, WO 2017 / 037414 Al describes a method of fabricating a touch-sensitive input device in which electrodes are printed onto a first substrate. After the electrodes are dried or cured, a second substrate is laid onto the first substrate to form a laminate, and further electrodes are printed onto the second substrate in register with the first set of electrodes, and the electrodes are dried or cured.

[0006] Summary

[0007] According to a first aspect of the present invention there is provided a method of fabricating a touch-sensitive input device. The method comprises forming a first set of electrodes, a first set of conductive tracks and a first set of contact pads on a first face of a first substrate, wherein a conductive track in the first set of conductive tracks connects a respective line of electrodes in the first set of electrodes and a respective contact pad in the first set of electrodes, comprising printing a first conductive ink on the first face of the first substrate using a first printing process and allowing or causing the first conductive ink to dry or to be cured. The method comprises forming a first laminate comprising overlaying a second substrate which is self-adhesive onto the first face of the first substrate so that electrodes in the first set of electrodes are covered but contact pads in the first set of contact pads are uncovered by the second substrate. The method comprises, after forming the first laminate, forming a second set of electrodes, a second set of conductive tracks and a second set of contact pads on a first face of a second substrate, wherein a conductive track in the second set of conductive tracks connects a respective line of electrodes in the second set of electrodes and a respective contact pad in the second set of contact pads, comprising printing a second conductive ink on the first face of the second substrate in register with the first set of electrodes using a second printing process and allowing or causing the second conductive ink to dry or to be cured. The method comprises forming a second laminate comprising overlaying a third substrate which is self-adhesive onto the first face of the second substrate so that electrodes in the first and second set of electrodes are covered but contact pads in the first and second set of contact pads are uncovered by the third substrate.

[0008] The first and second printing processes may be screen printing. The first and second printing processes may be sheet-by-sheet fed printing processes or continuous reel fed printing processes.

[0009] The first substrate may comprise a plastic material, such as PET. The first substrate may consist of or may consist predominantly of a plastic material. The first substrate may be transparent. The first conductive ink may be a silver-based conductive ink or a carbon-based conductive ink.

[0010] The second substrate may comprise a plastic material, such as PET. The second substrate may consist of or may consist predominantly of a plastic material. The second substrate may be transparent. The second conductive ink may be a silverbased conductive ink or a carbon-based conductive ink. The third substrate may comprise a plastic material, such as PET. The third substrate may consist of or may consist predominantly of a plastic material. The third substrate may be transparent.

[0011] The first substrate may have a first width wl and a first length 11 and the second substrate may have a second width w2 and a second length 12, and the first width may be greater than the second width. The third substrate may have a third width w3 and a third length 13, and the second width may be greater than the third width.

[0012] According to a second aspect of the present invention there is provided a touch- sensitive input device fabricated by the method of the first aspect.

[0013] According to a third aspect of the present invention there is provided apparatus for fabricating a touch-sensitive input device. The apparatus comprises a first station for forming a first set of electrodes, a first set of conductive tracks, and a first set of contact pads on a first face of a first substrate, wherein a conductive track in the first set of conductive tracks connects a respective line of electrodes in the first set of electrodes and a respective contact pad in the first set of electrodes, comprising a first printer arranged to print a first conductive ink on the first face of the first substrate using a first printing process and a first drying / curing section for allowing or causing the first conductive ink to dry or to be cured. The apparatus comprises a second section for forming a first laminate comprising a laminator arranged to overlay a second substrate which is self-adhesive onto the first face of the first substrate so that electrodes in the first set of electrodes are covered but contact pads in the first set of contact pads are uncovered by the second substrate. The apparatus comprises a third station disposed after the second section, for forming a second set of electrodes, a second set of conductive tracks and a second set of contact pads on a first face of a second substrate, wherein a conductive track in the second set of conductive tracks connects a respective line of electrodes in the second set of electrodes and a respective contact pad in the second set of contact pads, comprising a second printer arranged to print a second conductive ink on the first face of the second substrate in register with the first set of electrodes using a second printing process; and a second drying / curing section allowing or causing the second conductive ink to dry or to be cured. The apparatus comprises a third section for forming a second laminate comprising a laminator arranged to overlay a third substrate which is self-adhesive onto the first face of the second substrate so that electrodes in the first and second set of electrodes are covered but contact pads in the first and second set of contact pads are uncovered by the third substrate.

[0014] The first printer may be a screen printer and second printer may be a screen printer.

[0015] Brief Description of the Drawings

[0016] Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of a touch-sensitive input device;

[0017] Figure 2 is a schematic cross-section of the touch-sensitive input device shown in Figure 1 taken along the line A-A';

[0018] Figure 3 is a process flow diagram of a method of fabricating a touch-sensitive input device;

[0019] Figures 4A to 4D illustrate, in plan, a touch-sensitive input device at different stages during fabrication;

[0020] Figure 5 illustrates, in plan, a touch-sensitive input device at different stages during fabrication using a continuous reel fed process;

[0021] Figure 6 is a schematic diagram of a screen printing-based process for fabricating a touch-sensitive input device; and

[0022] Figure 7 is a schematic diagram of a flexographic-based process for fabricating a touch-sensitive input device.

[0023] Detailed Description of Certain Embodiments

[0024] Referring to Figures 1 and 2, a touch-sensitive input device 1 is shown.

[0025] The device 1 includes a first set of electrodes 2, a first set of conductive tracks 3, a first set of contact pads 4 and a set of registration marks 5 disposed on a first face 6 (or "upper face") of a first substrate 8 (or "base layer") which is flexible, formed by printing a layer of conductive ink 9 on the substrate 8. The contact pads 4 generally run in two rows parallel and proximate to a first edge 10 of the substrate 8. The first set of electrodes 2 are interposed between the contact pads 4 and a second edge 11 on the substrate 8, which lies opposite to the first edge 10. The electrodes 2 are generally lozenge-shaped and are arranged in sub-sets 12 (or "lines") running in a first direction, in other words, in this case, in rows running parallel to the first and second edges 10, 11. The array of electrodes 2 form interstitial spaces 13, which in this case are also lozenge-shaped. There are 21 rows of electrodes, although there may be more or fewer rows. Electrodes in the row 12 closest to the first edge 10 are triangular (i.e., half lozenges). The electrodes 2 in the same row are electrically connected together, and a conductive track 3 connects a row 12 of electrodes to a respective contact pad 4. The conductive tracks 3 generally run across the substrate 8 perpendicular to the first and second edges 10, 11. The first substrate 8 has a first width wi between the first and second edges 10, 11. A first laminate 15 is formed by the first substrate 8 and a second substrate 16 which is also flexible and having first and second faces 17, 18 ("upper and lower faces") and first and second edges 19, 20. The second substrate 16 is self-adhesive. In particular, the second substrate 16 has a layer of adhesive (not shown) on its lower face 18. The second substrate 16 has a second width W2 between the first and second edges 19, 20. The first width wi is greater than second width W2. The second edge 11 of the first substrate 8 and the second edge 20 of the second substrate 16 coincide and so the first edge 19 of the second substrate 16 is offset from the first edge 10 of the first substrate 8 by a distance 02, where wi = W2 + 02, leaving an uncovered strip 21 of tracks 3, contact pads 4 and substrate 8 along the first edge 10. Thus, the electrodes 2, the contact pads 4 and the second substrate 21 are arranged such that the electrodes 2 are covered, but the contact pads 4 are left uncovered by the second substrate 16.

[0026] The device 1 includes a second set of electrodes 22, a second set of conductive tracks 23, a second set of contact pads 24 disposed on the upper face 17 of the second substrate 17, formed by printing a layer of conductive ink 25 on the substrate 16. The contact pads 24 generally run in a row parallel and proximate to the first edge 19 of the second substrate 16. The second set of electrodes 22 are interposed between the contact pads 24 and a second edge 21 of the substrate 16. The electrodes 22 are generally lozenge-shaped and are arranged in lines 25 running in a second direction perpendicular to the first direction, in other words, in this case, in columns. The second set of electrodes 22 sit over the interstitial spaces 13 between electrodes 2 in the first set. In this case, there are 12 columns of electrodes. The electrodes 22 in the outermost columns 25 are triangular. Triangular electrodes 2, 22 can be used to form a rectangular touch-sensitive active area.

[0027] A third laminate 26 is formed by the first laminate 16 and a third substrate 27 which is flexible and which is self-adhesive. The third substrate 27 has first and second faces 28, 29, and first and second edges 30, 31. The third substrate 16 is self-adhesive.

[0028] The substrates 8, 16 27 may comprise a plastic material, such as polyethylene terephthalate (PET). However, other types of plastic material can be used. The same plastic material need not be used for all the substrates.

[0029] The electrodes 2, 22, tracks 3, 23 and contact terminals 4, 24 may be configured (e.g., have geometries, dimensions and / or materials) which are the same as or similar to those described in WO 2013 / 128208 Al or WO 2013 / 128209 Al. The conductive inks 9, 25 may be a carbon-based conductive ink, silver-based conductive ink or other suitable conductive ink.

[0030] As will now be explained, the touch-sensitive input device 1 can made using screen printing. An individual sheet fed screen printing process (using planar screen) or a continuous reel fed screen printing process (using a rotary screen) can be used. Using screen printing, a layer of conductive ink having a thickness of at least 10 pm, for example between 20 pm and 50 pm, can be printed which is generally thicker than a layer formed by flexographic printing, which typically prints a layer having a thickness less than 10 pm. A thicker conductive layer can have benefits, such as reducing resistance of printed regions which can improve the sensitivity of the device and also increase robustness of the device.

[0031] Referring also to Figure 3 and to Figures 4A, 4B, 4A and 4B, a method of fabricating the touch-sensitive input device 1 will now be described. In this case, printing on individual sheets is shown.

[0032] Referring in particular to Figure 3 and 4A, a first set of electrodes 2, a set of conductive tracks 3, a set of contact pads 4 and a set of registration marks 5 are formed by printing conductive ink 9 on the first face 6 of the first substrate 7 for example formed of PET or other suitable plastic and which has a width wi between first and second edges 10, 11 (step SI). Interstitial sites 13 (or "gaps") are left between electrodes 2. The conductive ink 5 is allowed or caused to dry or to be cured (step S2).

[0033] Drying the conductive ink may comprise allowing the ink to dry in air sufficiently long for water or other solvent to evaporate. Drying may be promoted using heat lamps. Curing the conductive ink may comprise irradiating the ink, e.g., using ultraviolet lamps, so as to cause polymer cross-linking.

[0034] Referring in particular to Figure 3 and 4B, a self-adhesive substrate 16 is attached to the printed substrate 8 over the first set of electrodes 2 to form a first laminate 15 (step S3). The width wi of the first substrate 8 is greater than the width W2 of the second substrate 16. The second edge 11 of the first substrate 8 and the second edge 20 of the second substrate 16 coincide and so the first edge 19 of the second substrate 16 is offset from the first edge 10 of the first substrate 8 by a distance 02, where wi = W2 + 02, leaving an uncovered strip 21 of tracks 3, contact pads 4 and substrate 8 along the first edge 10. Thus, the electrodes 2 are covered, but the contact pads 4 are left uncovered by the second substrate 16.

[0035] Referring in particular to Figure 3 and 4C, a second set of electrodes 22, a second set of conductive tracks 23, and a second set of contact pads 24 are formed by printing conductive ink 25 on the first face 17 of the second substrate 16 which may be from PET or another suitable plastic (step S4). The conductive ink 25 is allowed or caused to dry or to be cured (step S5). This results in a printed laminate 15'.

[0036] Referring in particular to Figure 3 and 4D, a self-adhesive substrate 27 is attached to the printed laminate 15' (Figure 4D) over the second set of electrodes 22 to form a second laminate 26 (step S6). The width W2 of the second substrate 16 is greater than the width W3 of the third substrate 27. The second edge 20 of the second substrate 16 and the second edge 31 of the third substrate 27 coincide and so the first edge 30 of the third substrate 27 is offset from the first edge 10 of the first substrate 8 by a distance 03, where wi = W3 + 03, leaving an uncovered strip 33 of tracks 3, 23, contact pads 4, 24, first substrate 8 and second substrate 16 along the first edge 10. Thus, the first and second sets of electrodes 2, 22 are covered, but the first and second sets of contact pads 4, 24 are left uncovered by the third substrate 27.

[0037] In this arrangement, a layer of conductive ink is printed on one substrate and so a conductive track (or other printed region) does not need to run over the edge of a substrate.

[0038] Referring to Figure 5, the touch-sensitive input device 1 can be fabricated using a continuous reel printing process in which three sheet-like substrates 8, 16, 27 are paid off respective unwind rollers (not shown), the first and second conductive inks 9, 25 are printed on the first and second substrates 8, 16 respectively, each conductive ink 9, 25 is dried or cured after printing before lamination, the substrates are laminated, and after the final lamination, the laminate 25 is wound onto a take-up roller (not shown). Figure 5 illustrates the same stages during fabrication shown in Figures 4A to 4D and so the description of the process will not be repeated again.

[0039] Referring to Figure 6, a screen printing apparatus 41 (or a "press") for manufacturing the touch-sensitive input device is shown. The press 41 can be a continuous reel printing process or a sheet-by-sheet printing process. The first substrate 8 is supplied by a first substrate feeder 42 (which may feed a sheet one-at-a-time or a continuous sheet) and passes through a series of sections including a first printing station 43, a first drying station 44, a first lamination station 46, a second printing station 47, a second drying section 48 and a second lamination station 50. The second substrate 16 is supplied by a second substrate feeder 45 and is fed into the first lamination station 46. The third substrate 27 is supplied by a third substrate feeder 49 and is fed into the second lamination station 50. The laminate 26 may be fed into a curing station 51 which may be in line or off line.

[0040] Referring to Figure 7, a flexographic printing apparatus 61 for manufacturing the touch-sensitive input device is shown.

[0041] The first substrate 8 is paid out from an unwind roller 62 and passes through a series of stations including a first printing station 63, a first drying station 64, a first lamination station 66, a second printing station 67, a second drying section 68 and a second lamination station 60. The second substrate 16 is supplied by a second substrate feeder 65 and is fed into the first lamination station 66. The third substrate 27 is supplied by a third substrate feeder 69 and is fed into the second lamination station 70. The laminate 26 may be fed into a curing station 71 which may be in line or off line.

[0042] It will be appreciated that many modifications may be made to the embodiments hereinbefore described.

Claims

Claims1. A method of fabricating a touch-sensitive input device, the method comprising:■ forming a first set of electrodes (2), a first set of conductive tracks (3) and a first set of contact pads (4) on a first face (6) of a first substrate (8), wherein a conductive track in the first set of conductive tracks connects a respective line (13) of electrodes in the first set of electrodes and a respective contact pad in the first set of electrodes, comprising : printing a first conductive ink (9) on the first face of the first substrate using a first printing process; and allowing or causing the first conductive ink to dry or to be cured;■ forming a first laminate (15) comprising : overlaying a second substrate (16) which is self-adhesive onto the first face of the first substrate so that electrodes in the first set of electrodes are covered but contact pads in the first set of contact pads are uncovered by the second substrate;■ after forming the first laminate, forming a second set of electrodes (22), a second set of conductive tracks (23) and a second set of contact pads (24) on a first face (17) of a second substrate (16), wherein a conductive track in the second set of conductive tracks connects a respective line of electrodes in the second set of electrodes and a respective contact pad in the second set of contact pads, comprising: printing a second conductive ink (25) on the first face of the second substrate in register with the first set of electrodes using a second printing process; and allowing or causing the second conductive ink to dry or to be cured;■ forming a second laminate (26) comprising: overlaying a third substrate (27) which is self-adhesive onto the first face of the second substrate so that electrodes in the first and second set of electrodes are covered but contact padsin the first and second set of contact pads are uncovered by the third substrate.

2. The method of claim 1, wherein the first and second printing processes are screen printing.

3. The method of claim 1 or 2, wherein the first and second printing processes are sheet-by-sheet fed printing processes.

4. The method of claim 1 or 2, wherein the first and second printing processes are continuous reel fed printing processes.

5. The method of claim 1 or any one of claims 2 to 4, wherein the first substrate (8) comprises a plastic material.

6. The method of claim 1 or any one of claims 2 to 5, wherein the first substrate (8) is transparent.

7. The method claim 1 or any one of claims 2 to 6, wherein the first conductive ink (9) is a silver-based conductive ink.

8. The method claim 1 or any one of claims 2 to 6, wherein the first conductive ink (9) is a carbon-based conductive ink.

9. The method of claim 1 or any one of claims 2 to 8, wherein the second substrate (16) comprises a plastic material.

10. The method of claim 1 or any one of claims 2 to 6, wherein the first substrate (16) is transparent.

11. The method of claim 1 or any one of claims 2 to 10, wherein the second conductive ink (25) is a silver-based conductive ink.

12. The method of claim 1 or any one of claims 2 to 10, wherein the second conductive ink (25) is a carbon-based conductive ink.

13. The method of claim 1 or any one of claims 2 to 12, wherein the third substrate (27) comprises a plastic material.

14. The method of claim 1 or any one of claims 2 to 13, wherein the third substrate (27) is transparent.

15. The method of claim 1 or any one of claims 2 to 14, wherein the first substrate (8) has a first width wi and a first length li and the second substrate (16) has a second width W2 and a second length I2, wherein the first width is greater than the second width.

16. The method of claim 15, wherein the third substrate (27) has a third width W3 and a third length I3, wherein the second width is greater than the third width.

17. A touch-sensitive input device (1) fabricated by the method of any one of claims 1 to 16.

18. Apparatus for fabricating a touch-sensitive input device, the apparatus comprising:■ a first station for forming a first set of electrodes, a first set of conductive tracks, and a first set of contact pads on a first face of a first substrate, wherein a conductive track in the first set of conductive tracks connects a respective line of electrodes in the first set of electrodes and a respective contact pad in the first set of electrodes, comprising :- a first printer arranged to print a first conductive ink on the first face of the first substrate using a first printing process; and- a first drying / curing section for allowing or causing the first conductive ink to dry or to be cured;■ a second section for forming a first laminate comprising:- a first laminator arranged to overlay a second substrate which is self-adhesive onto the first face of the first substrate so that electrodes in the first set of electrodes are covered but contact pads in the first set of contact pads are uncovered by the second substrate;■ a third station disposed after the second section, for forming a second set of electrodes, a second set of conductive tracks and a second set of contact pads on a first face of a second substrate, wherein a conductive track in the second set of conductive tracks connects a respective line of electrodes in the second set of electrodes and a respective contact pad in the second set of contact pads, comprising:- a second printer arranged to print a second conductive ink on the first face of the second substrate in register with the first set of electrodes using a second printing process; and a second drying / curing section allowing or causing the second conductive ink to dry or to be cured;■ a third section for forming a second laminate comprising: a second laminator arranged to overlay a third substrate which is self-adhesive onto the first face of the second substrate so that electrodes in the first and second set of electrodes are covered but contact pads in the first and second set of contact pads are uncovered by the third substrate.

19. The apparatus of claim 1, wherein the first printer is a screen printer and second printer is a screen printer.

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