WO2015122881A1

WO2015122881A1 - Substrates of a touch sensing device

Info

Publication number: WO2015122881A1
Application number: PCT/US2014/015988
Authority: WO
Inventors: Kuan-Ting Wu; Wei Jen Chen; Ching-Yang Chang
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2014-02-12
Filing date: 2014-02-12
Publication date: 2015-08-20
Anticipated expiration: 2016-08-12

Abstract

A substrate for touch sensing device is provided. The substrate comprises a continuous surface formed by connecting a sapphire portion and a second portion.

Description

SUBSTRATES OF A TOUCH SENSING DEVICE

Background

[1 ] Devices such as mobile phones, tablets and portable (laptop or palm) computers are generally provided with touch sensor technologies.

Brief Description of Drawings

[2] By way of non-limiting examples, touch sensing devices and processes of manufacturing such devices according to the present disclosure will be described with reference to the following drawings in which

[3] Figure 1 (a) is a perspective view of a portable computer with an example touch sensing device.

[4] Figure 1(b) is a perspective view of the example touch sensing device of Figure 1 (a) in modular form. [5] Figure 1(c) is a sectional side v iew of a substrate of a touch sensing device of Figure 1(b).

[6] Figures 2(a) and 2(b) are top views of example substrates for a touching sensing device.

[7] Figure 2(c) is a sectional side view of an example substrate for a touch sensing device.

[8] Figures 3(a) and 3(b) are top views of further example substrates for a touching sensing device.

[9] Figures 3(c) and 3(d) are a sectional side view of example substrates for a touch sensing device of Figures 3(a) and 3(b) respectively. [10] Figure 4 is an illustration of the process to the touch sensing device.

[1 1 ] Figure 5 is a flow diagram illustrating an example method of man facturing a touch sensing device.

Detailed Description

[1 2] The present disclosure describes a substrate for a touch sensing device. The substrate of this example comprises a continuous surface having a first portion of sapphire and a second portion. The sapphire and second portion are connected to form the continuous surface of the substrate.

[1 3] Touch sensing technologies are used in electronic devices, particularly consumer electronics. A touch sensor is sensitive to touch, force or pressure and have found applications extending to robotics, computer hardware and security systems. In use, a substrate of a touch sensing device is incorporated into a touch sensing device such as a touch pad that forms part of the surface of an electronic device reserved for sensing touch. In other examples the surface reserved for sensing touches forms part or all of a surface of a. display of the electronic device, [14] An example of security and computer related application is fingerprint identification.

[15] While glass, plastic or metal materials are used as the substrate for sensing touch, due to their relatively low value of hardness (4.5 to 6.5 Mohs for glass and plastic, and 1.5 to 6 Mohs for metal), they are extremely susceptible to scratches and even breakages when sufficient pressure has been applied.

[16] In contrast, sapphire wafer has a high level of hardness (9 Mohs) and therefore offers good scratch resistance. Further, sapphire is optically transparent between 150 nm (UV) to 5500 nm (IR. Sapphire includes synthetic sapphire that can be mass produced. [17] By joining a substrate layer comprising a first material being sapphire and a second materi l such as glass, plastics or metal to form an integrated substrate tayer, where the surface of the integrated substrate layer includes a surface of the sapphire and a surface of she second material, the amount of sapphire used in fabricating the substrate layer can be reduced, leading to cost reductions.

[18] Further, the attractive optical and mechanical properties of sapphire can be exploited in a touch sensing device. In an example application, fingerprints can be identified with higher accuracy than glass while the physical hardness of sapphire ensures durability of the touch sensing device, [19] The integrated substrate layer can be manufactured with a transparent conductor, such as an indium tin oxide (TTO), to form a touch sensor. Since the sapphire portion and the second portion are connected, the process of fabricating the touch sensor can be simplified as it only needs to be performed once, rather than separately on the sapphire and then the second portion. This simplified fabrication process results in a reduced labour cost and a shorter production cycle time.

[20] Figure 3 (a) illustrates an example where a touch sensing device 120 is embedded in an electronic device 100. In this example the touch sensing device 120 is a touch pad and the electronic device 100 is a portable computer. The touching sensing device 120 includes a sapphire portion 140.

[21] The perspective view of the touch sensing device 120 in modular form, being before it is incorporated into a device, is shown in Figure 1(b). The touch sensing device 120 is comprised of a substrate 170, a touch sensor 150 such as an ΠΌ sensor and electrical interconnects 160.

[22] Referring to Figures i(b) and 1 (c), the perspective and sectional side views of the substrate 170 are shown respectively. The integrated substrate layer 170 is comprised of a first portion 140 of sapphire and a second portion 130 of different material. The second portion 130 is connected or joined to the sapphire portion 140 to form a continuous surface 190, that in turn, is also the continuous surface 190 of She integrated substrate layer 170 as a whole. This continuous surface 190 provides no tactile or clearly visible break in the surface and in turn provides a touch sensing device wish smooth tactile quality for a finger 395. [23] The second portion 130 can be, for example, glass, plastic and metal. Examples of glass materials include fused silica, sodium borosilicate, lead oxide glass, aluminosilicate and oxides. Suitable plastic materials that may be used include polyacrylate (e.g. polymethyl methacrylate), polycarbonate (PC), polyethylene terephthalate (PET), olefsn polymer, polyimide, optically transparent plastics, or the copoiymer thereof. Suitable metals include light metals that are characterised by low atomic weight such as lithium, beryllium, sodium, magnesium, aluminium, titanium, niobium, zinc or alloys Shereof.

[24] As can be seen from Figure 1(c) and the second portion 130 are connected to form the continuous surface 190. The sapphire portion 140 also extends to the full depth of the second portion 130.

[25] As will be shown by the examples below, the substrate 370 can be comprised of various configurations of sapphire portion 140 with the second portion 130,

[26] Figures 2(a) to 2(c) illustrate examples of the substrate 170 for a touch sensing device 120 that are formed to have a continuous surface 190. [27] In the top view of the substrate 220 in Figure 2(a), the first sapphire portion 340 has a rectangular shape 240 when viewed from the top and is surrounded by She second portion 230 that together form the continuous surface.

[28] in Figure 2(b), the substrate 222 includes sapphire portion 140 that is circular in shape 242 when viewed from the top. The circular sapphire portion 242 is also completely surrounded by the second portion 232. [29] Figure 2(c) sho ws a sectional side v iew of the substrate 220 of Figure 2(a) where the sapphire portion 2.40 extends partially into the depth of the second portion 230. It can also be seen that the sapphire portion 240 and the second portion 230 are connected to form the continuous surface 250 of the substrate 220. [30] Figures 3(a) to 3(d) further illustrate examples of the substrate 170 for a touch sensing device 120. In the top view of the substrate 300 shown in Figure 3(a), the sapphire portion 340 is partially surrounded by the second portion 330, in particular, a right hand corner of the second portion 330 is replaced by the sapphire portion 340. Alternatively, the sapphire portion 342 is joined adjacent to the second portion 332 of substrate 320 as shown in Figure 3(b). Figures 3(c) and 3(d) show respective sectional side views of Figures 3(a) and 3(b) where the sapphire portion extends completely 340 or partially 342 into the depth of the substrate 300 and 320 respectively. Like all the previous examples, the sapphire portion 340 and the second portion 330 are connected to form a continuous surface of the substrate 300. Again, the same applies for the surface of substrate 320.

[31 ] Following these examples, it is understood that any combination of shape, spatial positioning and thickness of sapphire can be manufactured with the second portion to form the substrate layer,

[32] Figures 4( a) to 4(j) show the sectional side view of the manufacturing the touching sensing device from the substrate 170.

[33] The process of manufacturing the substrate starts in the form of a planar glass, plastics or metal portion 130 shown in Figure 4(a). Using cutting away process or mo ukling process, a predefined area or shape on any spatial position through the depth of the portion 130 is made as shown in Figure 4(b), As shown in Figure 4(c), a piece of sapphire wafer 140 with identical physical dimension to the cut out is joined, such as bonded, to the glass, plastics or metal portion 130 in any suitable way that creates a continuous surface 190 on the substrate 170. Suitable techniques of joining include laser welding, glass inter-fusion, UV resin, hot melt resin or thermoplastic/thermosei adhesives.

[34] Following the substrate preparation process, a touch sensor is formed on the opposite surface to the continuous surface 190 of the substrate 170. Examples of the touch sensor 150 include an ITO sensor, a conductive polymer sensor, a metal mesh sensor, silver nanowire sensor, a carbon nanotube sensor or a graphene sensor.

[35] The photolithography process of forrniiig the touch sensor is started by applying a layer of touch sensing material 450 of less than 3 μιη, such as an ITO coating, on the opposise surface of the continuous surface 190 of the substrate 170 shown in Figure 4(d). in general, uniform thin film deposition techniques can be used including sputtering, ion beam, plating, screen printing, roller coating and air-knife/rod coating for flexible substrates.

[36] A layer of photoresist 460 of a thickness less man 3 μιη is men applied to the external surface of tire touch sensing material 450 by means of spin coating, roller coating, dip coating or spray coating as illustrated in Figure 4(e). The photoresist coated substrate is then baked to drive off excess photoresist solvent, typically at 90 to 120°C for less than three minutes on a hotplate.

[37] Similarly to a lithographic process used in display and semiconductor industries, a pre-fabricated photo-mask 470 featuring the inverse touch sensing pattern is provided. The touch sensing pattern can be applied by on-cell or tn-cell process with capacitive touch sensor. The photoresist coated substrate is exposed to UV radiation shown in Figure 4(f) to form the touch sensing pattern on the surface of photoresist 460. The UV exposed area of the photoresist will allow for easy removal during the developing process. The photo-mask 470 in general can be fabricated on a quartz substrate, where a layer of chromium is formed by sputtering that is subsequently coated by a thin layer of photoresist. Using an electron beam, mask pattern is written onto the photoresist layer to produce the inverse mask pattern. A developer is then applied to remove the exposed photoresist area where the exposed chromium layer is etched away to reveal the quartz by means of either dry or wet etching. The remaining photoresist can be stripped away by cleaning where the exposed area on the photomask allows for light transmission while chromium covered area is opaque.

[38] In Figure 4(g), the substrate is baked at a temperature of 90 to 120°C for less than three minutes to assist in the reduction of the standing wave phenomena caused by the UV interference patterns while further solidifying the remaining photoresist to make it more durable and protective over the embedded layer prior to subsequent processing such as chemical wet etching, ion implantation or plasma etching.

[39] The UV exposed photoresist area is then removed with the aid of a developer such sodium hydroxide or potassium hydroxide or tetramethylammonium hydroxide to produce the substrate structure shown in Figure 4(h).

[40] Using dry or chemically wet etching techniques, the touching sensing material 450 such as an ITO coating overlayed on the opposite surface to the continuous surface

190 of the substrate 170 is etched away to form a touch sensor pattern as shown in Figure 4(i).

[41 ] Finally, the remaining photoresist la er that has not been exposed to UV radiation is removed as shown in Figure 4(j) by immersion in a 'resist stripper' that chemically alters the photoresist such that the photoresist no longer adheres to the touch sensor. Alternatively, photoresist can be removed by wet chemistry or plasma induced oxidation.

[42] Figure 5 is a flow diagram illustrating an example method of manufacturing touch sensing device. The method involves forming a substrate by connecting a sapphire portion and a second portion such the substrate has a continuous surface 510. A layer of touch sensing material such as ITO is then applied to the substrate 520 so that a touch sensing pattern can be formed from the touch sensing material 530, [43] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in ail respects as illustrative and noi restrictive.

Claims

CLAIMS:

1. A substrate of a touch sensing de vice, comprising a continuous surface having: a first portion of sapphire; and

a second portion,

wherein the first portion and the second portion are connected to form the continuous surface of the substrate.

2. The substrate according to claim 1, wherein the second portion is glass, plastic or metal.

3. The substrate according to claim 1, further comprising a touch sensing material that is applied to an opposite surface of the continuous surface of the substrate.

4. The substrate according to claim 1 , wherein the first portion and the second portion are connected by laser welding, glass interfusion, UV resin, hot melt resin, thermoplastic adhesive or thermoset adhesive.

5. The substrate according to claim 1, wherein a surface of the first portion is surrounded by a surface of the second portion.

6. A device for sensing a touch, comprising:

an integrated substrate layer comprising a first material being sapphire and a second material, the first material and the second material being joined to form the integrated substrate layer, wherein a surface of the in tegrated subs trate layer includes a surface of the first material and a surface of the second material; an d

a touch sensor on the integrated substrate layer.

7. The device according to claim 6, wherein the touch sensor is an indium tin oxide (ITO) sensor, a conductive polymer sensor, a metal mesh sensor, silver nanowire sensor, a carbon nanotube sensor or a graphene sensor,

8. The device according to claim 6, wherein the first material extends a depth of the integrated substrate layer.

9. The device according to claim 6, wherein the touch sensor is on an opposite surface to the surface of the substrate layer.

10. The device according to claim 6, wherein the first material and the second material are joined by laser welding, glass interfusion, UV resin, hot melt resin, thermoplastic adhesive or thermoset adhesive.

11. The device according to claim 6, wherein the surface of the first material is surrounded by the surface of the second material

12. A method for manufacturing a touch sensing device, comprising:

forming a substrate comprising a continuous surface having:

a first portion of sapphire; and

a second portion,

wherein the first portion and the second portion are connected to form the continuous s urface of the substrate:

applying a layer of a touch sensing material to the substrate; and

forming a touch sensing pattern from the layer of the touch sensing material on the substrate.

13. The method according to claim 12, wherein

the layer of the touch sensing material is a lay er of indium tin oxide (ITO), and forming the touch sensing pattern comprises etching the layer of ITO through an etch process.

14. The method according to claim 12, wherein the second portion of the continuous surface of the substrate is glass, plastic or metal.

15. The method according to claim 12, wherein the first portion of the continuous surface of the substrate is surrounded by the second portion of the continuous surface of the substrate.