Protected touch sensor and associated touch screen

Abstract

The present invention relates to a touch sensor (10) comprising: - a capacitive detector (11) comprising: a protective layer (12), a first insulating layer (13) arranged below said protective layer (12), a first electrode (14) arranged below said first insulating layer (13), a second insulating layer (15) arranged below said first electrode (14), and a second electrode (16) arranged below said second insulating layer (15); and - a resistive detector (21) formed by a deformable upper layer (22) associated with a detector (24) arranged below said deformable upper layer (22) by a frame (25); said detector (24) being fixed to a base plate (17); said capacitive detector (11) being joined to said resistive detector (21) by an adhesive layer (26) having a thickness less than 0.5 mm; said touch sensor (10) having a surface area less than 1500 cm 2 ; and said protective layer (12) having a thickness in the range 0.15 to 0.35 mm.

Description

TECHNICAL FIELD

[0001] The present invention relates to a protected touch sensor, i.e. a touch sensor measuring the detected touch by two different sources in a way limiting the risk of false signals. The touch sensor is preferably used to form a human-machine interface configured to detect a touch of a user, for example a button of a machine or a touch screen.

[0002] The present invention also relates to a touch screen formed by a screen on which a touch sensor is mounted.

[0003] The present invention has a particularly advantageous application for high-strength touch sensors.

[0004] The present invention can be applied to many technical fields requiring high security for commands sent via a human-machine interface, for example the railway or nuclear field. BACKGROUND

[0005] A high-strength touch sensor is a sensor configured to withstand particularly harsh environmental conditions. As an example, some standards adopt an impact strength of 0.7 to 1 joule, resistance to a humidity level in the range of 90% to 95%, resistance to temperatures varying between -40°C and +70°C, resistance to salt water spray for a period in the range of 48 to 96 hours, or indeed immunity to stray fields of 10 to 20 V / m.

[0006] In addition, there are a large number of different touch sensors, in particular capacitive and resistive sensors.

[0007] As can be seen in Figure 1 From the prior art, it is known that a capacitive detector 100 conventionally comprises a protective layer 12, usually made of glass, under which two electrodes 14 and 16 are arranged. The first electrode 14 is fixed under the protective layer 12 by a first adhesive layer 18. This first electrode 14 is conventionally mounted on a first insulating layer 13.

[0008] Under the first insulating layer 13, a second adhesive layer 18 is also used in order to attach a second insulating electrode 16 also mounted on a second insulating layer 15. The second electrode 16 can be fixed to a substrate of the screen or any support, for example, or fixed on the second insulating layer 15.

[0009] In order to obtain a black border around the touch sensor 100, it is also known to incorporate a shading 19 into the first adhesive layer 18 connecting the protective layer 12 and the first insulating layer 13, in particular in order to form a capacitive touch sensor mounted on a screen. To this end, the protective layer 12, the insulating layers 13, 15, the adhesive layer 18 and the electrodes 14, 16 are translucent and the second electrode 16 is deposited on the screen in a way forming a touch screen, for example using capacitive technology.

[0010] This type of capacitive touch sensor is often used to form high-intensity touch sensors because the size of the protective layer 12 can be adjusted to meet different requirements regarding intensity.

[0011] In a variation, based on existing technology, resistive technology can also be used to form a touch sensor, such as... Figure 2 For example, the resistance sensor 101 includes a resistance detector 21 formed by a deformable upper layer 22 connected via a frame 25 to a detector 24 mounted on a substrate 17. The detector 24 also has a resistive conductor 23 that enables the detection and transmission of deformation of the upper layer 22.

[0012] These types of resistance or capacitance sensors are commonly used to form touchscreens when they are mounted on a screen.

[0013] For certain security applications, it is desirable to be able to detect touches on the human-machine interface in order to prevent these sensors from detecting unwanted touches caused by, for example, water droplets falling onto the upper layer 12 or 22 or strong electromagnetic interference.

[0014] Therefore, solutions exist that combine capacitive or resistive detectors with observation devices to check whether the detection of touch on the human-machine interface of the detector actually originates from intentional contact by the user.

[0015] The observation device is designed to disable a touch detected on a human-machine interface, such as the presence of a water droplet.

[0016] However, the observation device may not work under certain lighting conditions or because the components are positioned between the upper surface of the sensor and the camera of the observation device.

[0017] To overcome this problem, it is desirable to couple the capacitive detector to the resistive detector by arranging the capacitive detector on top of the resistive detector, so as to use the protective layer 12 and obtain a high-strength sensor.

[0018] However, mounting a conventional capacitance detector on a resistance detector means that the deformation of the upper layer 22 cannot be measured because the elasticity of the components forming the capacitance detector 11 is insufficient for its deformation to be captured by the resistance detector 21 while responding to normal intensity loads.

[0019] In practice, the protective layer 12 of a capacitive detector typically has a thickness ranging from 1 to 15 millimeters, and this protective layer 12 has very low elasticity. This is especially true when looking for sensors with high strength.

[0020] To overcome this problem, reference TWI654555 proposes combining the capacitance detector 11 with the resistance detector 21, such as...Figure 3 The deformable upper layer 22 of the resistance detector 21 is integrated into the layer forming the second electrode 16 of the capacitance detector 11. To this end, the electrodes 14 and 16 are mounted under the insulating layers 13, 15, contrary to a conventional capacitance detector in which the electrodes 14 and 16 are mounted on the insulating layers 13, 15. The number of layers forming this hybrid sensor 102 is therefore limited compared to a combination of a capacitance detector 11 and a resistance detector 21 produced independently.

[0021] However, the manufacture of this hybrid layer forming part of the capacitance detector 11 and of the resistance detector 21 is particularly complex due to the phenomenon of the various patterns that must be inserted without causing electromagnetic coupling or short circuits between these various patterns. Furthermore, the inversion of the electrodes 14 and 16 with respect to the insulating layers 13, 15, due to the separation of the electrodes 14 and 16 of the protective layer 12, can lead to a decrease in the sensitivity of the sensor.

[0022] The technical problem of the invention is therefore to find an alternative to obtain a hybrid touch sensor that integrates a capacitance detector and a resistance detector while meeting the requirements of mechanical strength, moisture strength and stray field immunity. SUMMARY

[0023] The invention stems from a discovery according to which, by associating a capacitance detector with a resistance detector, if the frame of the resistance detector is sufficiently small and if the bonding layer between the two detectors is sufficiently thin, the impact undergone by the protective layer is transmitted through all the layers and dissipated in the substrate.

[0024] According to this discovery, it is therefore possible to reduce the thickness of the protective layer of the capacitance detector to far below the thickness conventionally employed in order to facilitate its deformation and to improve the detection of a touch on the protective layer of the capacitance detector by the resistance detector arranged below the capacitance detector while meeting the requirements for a high-strength touch sensor.

[0025] To this end, according to a first aspect, the invention relates to a touch sensor comprising:

[0026] - a capacitance detector comprising: a protective layer, a first electrode arranged under the protective layer, a first insulating layer arranged under the first electrode, a second electrode arranged under the first insulating layer and a second insulating layer arranged under the second electrode; and

[0027] - a resistance detector formed of a deformable upper layer associated with a detector arranged under the deformable upper layer by a frame; the detector being fixed to a substrate.

[0028] The invention is characterized in that the capacitive detector is bonded to the resistive detector by means of an adhesive layer having a thickness less than 0.5 mm; and the surface area of the touch sensor is less than 1500 cm 2 ; and the thickness of the protective layer is in the range 0.15 to 0.35 mm.

[0029] The invention thus makes it possible to obtain a hybrid touch sensor, i.e. a touch sensor that integrates capacitive detection and resistive detection in order to obtain redundant information when detection is performed by the touch sensor.

[0030] Although the upper layer is particularly thin compared with known touch sensors, the transmission of the forces applied on this upper layer means that it can meet the requirements for a high-strength sensor. Generally, for a frame having a surface area less than 1500 cm 2 (i.e. a surface area such that the screen can be formed with a size smaller than that of a 22-inch screen), it is possible to meet the requirements for impact strength in an industrial environment, while using a protective layer having a thickness in the range 0.15 to 0.35 mm.

[0031] To do this, the adhesive layer that connects the capacitive detector and the resistive detector must have a thickness less than 0.5 mm, so that the deformation undergone by the capacitive detector can be transmitted to the substrate via the resistive detector.

[0032] Preferably, the thickness of the adhesive layer is less than 0.2 mm, for example in the range 0.04 to 0.1 mm. Indeed, if the adhesive layer is too thin, there is a risk of delamination of the touch sensor between the capacitive detector and the resistive detector. On the other hand, if the adhesive layer is too thick, the deformation of the capacitive detector cannot be transmitted to the substrate via the resistive detector.

[0033] In order to prevent delamination between the capacitive detector and the resistive detector, it is possible to use a very strong glue to form the adhesive layer. As an example, by arranging the adhesive layer only at the periphery of the touch sensor, it is possible to use an opaque glue.

[0034] The adhesive layer can correspond to a double-sided adhesive produced from a flexible acrylic core, for example to the number H7004, H7008 or H7012 from the Hyperjoint series from the company Nitto, Japan.

[0035] The limited size of the surface area of the touch sensor can ensure the transmission of the forces applied on this upper layer to the substrate. To do this, the forces must be transmitted by a frame arranged only at the periphery of the touch sensor; if the touch sensor has too large a surface area, the transmission of these forces is limited.

[0036] In order to ensure the transmission of the forces and obtain a high-strength touch sensor, the surface area of the frame is preferably less than 700 cm 2i.e. such that the screen can form a surface area of a size smaller than the size of a 15 inch screen. In order to further increase the strength of the touch sensor, the surface area of the frame can be smaller than 280 cm 2 i.e. such that a screen of a size smaller than a 10 inch screen can be formed.

[0037] The flexibility of the capacitive detector is also regulated by the overall size of the capacitive detector.

[0038] By using an insulating layer and a thin electrode, for example an electrode with a thickness of approximately 70 μm and an insulating layer with a thickness of approximately 50 μm, a capacitive detector with an overall thickness of less than 0.5 mm can be obtained.

[0039] To this end, the protective layer preferably has a thickness in the range of 0.20 to 0.22 mm.

[0040] Preferably, the overall thickness of the capacitive detector is in the range of 0.8 to 1 mm, while the overall thickness of the resistive detector is in the range of 1 to 3 mm.

[0041] According to a second aspect, the application relates to a touch screen comprising a screen on which a touch sensor according to the first aspect of the application is mounted. BRIEF DESCRIPTION OF DRAWINGS

[0042] The manner in which the application is implemented and its advantages will become apparent from the following description, given by way of non-limiting indication and by way of non-limiting indication and with the aid of the accompanying drawings in which: Figure 1 to the accompanying drawings in which: Figure 4 The manner in which the application is implemented and its advantages will become apparent from the following description, given by way of non-limiting indication and by way of non-limiting indication and with the aid of the accompanying drawings in which:

[0043] Figure 1 a schematic cross-sectional view of a capacitive detector of the prior art is shown;

[0044] Figure 2 a schematic cross-sectional view of a resistive detector of the prior art is shown;

[0045] Figure 3 a schematic cross-sectional view of a hybrid touch sensor of the prior art is shown; and

[0046] Figure 4 a schematic cross-sectional view of a touch sensor according to an embodiment of the application is shown. DETAILED DESCRIPTION

[0047] Figure 4 A touch sensor 10 mounted on a substrate 17 is illustrated. In the case where the touch sensor 10 forms a simple switch, for example a touch-sensitive button of a machine tool, the substrate 17 can correspond to a flat inert surface.

[0048] Preferably, the substrate 17 corresponds to a layer of strong translucent material, for example tempered glass, having a thickness greater than 1 mm, so that a touch screen can be formed by arranging a screen under the touch sensor 10.

[0049] The touch sensor 10 comprises a capacitive detector 11 fixed to a resistive detector 21 by an adhesive layer 26, which is in turn mounted on the substrate 17.

[0050] The capacitive detector 11 comprises a protective layer 12, for example made of glass of the Gorilla Glass type, under which two electrodes 14 and 16 are arranged. The first electrode 14 is fixed under the protective layer 12 by a first adhesive layer 18 and a first insulating layer 13. Under the first electrode 14, a second adhesive layer 18 is also used in order to attach a second insulating layer 15 separating the two electrodes 14 and 16.

[0051] The two electrodes 14 and 16 can be made using silver nanowires, while the insulating layers 13 and 15 can be made of Polyethylene Terephthalate (PET). The assembly formed by the electrodes 14 and 16 and the insulating layers 13 and 15 can have a thickness in the range of 100 to 150 pm, for example a thickness of 125 pm.

[0052] The thickness of the adhesive layer 18 can be in the range of 50 to 120 pm, for example a thickness of 100 pm. In order to obtain a black border around the touch sensor 10, a masking 19 can be integrated into the first adhesive layer 18 connecting the protective layer 12 and the first insulating layer 13.

[0053] Thus, between the protective layer 12 and the adhesive layer 26, the capacitive sensor 11 can have a thickness of 0.45 mm, with two adhesive layers 18 of 100 pm and the electrodes and insulating layers 13-16 together of 125 pm.

[0054] Compared to existing capacitive sensors, the thickness of the capacitive sensor 11 is mainly obtained by the protective layer 12. According to the invention, the protective layer 12 has a thickness in the range of 0.15 to 0.35 mm.

[0055] Preferably, the protective layer 12 has a thickness in the range of 0.20 to 0.22 mm, for example substantially 0.21 mm.

[0056] Thus, the capacitive sensor 11 can have a total thickness in the range of 0.6 to 0.9 mm, for example, assuming a protective layer 12 of 0.21 mm and a thickness between the protective layer 12 and the adhesive layer 26 of 0.45 mm, the total thickness is 0.66 mm.

[0057] According to another example, the total thickness of the capacitive sensor 11 can be 0.68 mm, wherein the protective layer 12 is 0.33 mm and the thickness between the protective layer 12 and the adhesive layer 26 is 0.35 mm. To this end, two adhesive layers 18 of 50 pm can be used and two electrode and insulation layers 13-16 of 125 pm.

[0058] The adhesive layer 26 can be deposited underneath the entire second electrode 16 of the capacitive detector 11. Preferably, the adhesive layer 26 is only deposited on the periphery of the second electrode 16. According to the present application, the adhesive layer 26 has a thickness of less than 0.5 mm. Preferably, the thickness of the adhesive layer 26 is less than 0.2 mm. More preferably, the thickness of the adhesive layer 26 is in the range of 0.04 to 0.1 mm, for example a thickness of 0.08 mm.

[0059] Below the adhesive layer 26, the touch sensor 10 comprises a resistive detector 21. The resistive detector 21 is formed by a deformable upper layer 22 connected via a frame 25 to a detector 24 mounted on the substrate 17. The detector 24 further has a resistive conductor 23 that can detect and transmit the deformation of the upper layer 22. Preferably, the resistive detector 21 has a total thickness in the range of 1 to 3 mm.

[0060] According to the present application, the touch sensor 10 has a surface area of less than 1500 cm 2 . As an example, the touch sensor 10 can have a surface area of less than 700 cm 2 or a surface area of less than 280 cm 2 .

[0061] Hence, the present application can be used to obtain a redundant touch sensor 10, i.e. having two different detection means generated by the capacitive detector 11 and the resistive detector 21.

[0062] Furthermore, the present application can also be used to form a high strength touch sensor 10.

Claims

1. A touch sensor (10) comprising: - a capacitive detector (11) comprising: a protective layer (12), a first electrode (14) arranged below said protective layer (12), a first insulating layer (13) arranged below said first electrode (14), a second electrode (16) arranged below said first insulating layer (13), and a second insulating layer (15) arranged below said second electrode (16); and - a resistive detector (21) formed by a deformable upper layer (22) associated with a detector (24) arranged below said deformable upper layer (22) by means of a frame (25); said detector (24) being fixed to a base plate (17); characterized in that said capacitive detector (11) is coupled to said resistive detector (21) by means of an adhesive layer (26) having a thickness less than 0.5 mm; and in that the surface area of said touch sensor (10) is less than 1500 cm 2 ; and in that the thickness of said protective layer (12) is in the range 0.15 to 0.35 mm.

2. The touch sensor of claim 1, wherein, said thickness of said adhesive layer (26) is less than 0.2 mm.

3. The touch sensor of claim 1 or 2, wherein, said thickness of said adhesive layer (26) is in the range 0.04 to 0.1 mm.

4. The touch sensor of claim 1 or 2, wherein, said adhesive layer (26) extends only on the periphery of said touch sensor (10).

5. The touch sensor of claim 1 or 2, wherein, The touch sensor (10) has a surface area of less than 700 cm 2 .

6. The touch sensor of claim 1 or 2, wherein, The touch sensor (10) has a surface area of less than 280 cm 2 .

7. The touch sensor of claim 1 or 2, wherein, said total thickness of said capacitive detector (11) is in the range 0.6 to 0.9 mm.

8. The touch sensor of claim 1 or 2, wherein, said total thickness of said resistive detector (21) is in the range 1 to 3 mm.

9. The touch sensor of claim 1 or 2, wherein, said thickness of said protective layer (12) is in the range 0.20 to 0.33 mm.

10. A touch screen comprising a screen on which a touch sensor (10) according to any one of claims 1 to 9 is mounted.

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