Detection device with thermal protection arrangement

Abstract

Detection device with thermal protection arrangement The present invention relates to a detection device (10) comprising: - a substrate (14), comprising a first and a second face; - a force sensor (16), fixed to the first face of the substrate, so as to cover a first area (40); and - a conductive track (18), extending on the first face from the force sensor. The detection device further comprises: - a layer (22) of a first rigid adhesive, fixed to the second face (36) of the substrate, so as to cover a second area (46); the first and second areas being arranged opposite each other; and - two through slots (50) arranged in the substrate, surrounding the second area, the conductive track being arranged between the two slots. Figure for abstract: Figure 1

Description

Title of the invention: Detection device with thermal protection arrangement

[0001] The present invention relates to a detection device, of the type comprising: a substrate, comprising a first and a second opposite face; a force sensor, fixed to the first face of the substrate, so as to cover a first area of ​​said first face; and at least a first conductive track, extending on said first face from the force sensor.

[0002] The invention applies particularly to devices used in the manufacture of touch screens or touchpads, as described for example in document US9430099.

[0003] The use of force sensors in such sensing devices involves a strong mechanical connection between the sensor and the surface of the touchscreen, on which a user exerts pressure with their finger. It is therefore advantageous to connect said sensor and said surface using a rigid adhesive.

[0004] However, the various elements of the detection device, in particular the substrate and the rigid adhesive, have different coefficients of thermal expansion. During heating linked to the use of the device, the latter is therefore likely to deform, which can lead to a break in the conductive track. The device is then put out of use.

[0005] It is therefore advantageous to provide thermal protection to the detection device, in order to avoid deformation of said device under the effect of heat, near the areas comprising layers of rigid adhesive.

[0006] To this end, the invention relates to a detection device of the aforementioned type, further comprising: a layer of a first rigid adhesive, fixed to the second face of the substrate, so as to cover a second zone of said second face, the first and second zones being arranged opposite one another, a projection of the second zone on the first face containing the first zone; and at least two through slots formed in the substrate, said at least two slots being arranged on a closed-shaped contour surrounding the second zone, the first conductive track being arranged between two of said at least two slots.

[0007] According to other advantageous aspects of the invention, the detection device comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0008] - the detection device further comprises a second conductive track, extending on the first face from the force sensor; and the substrate comprises at least at least two bridges, each of said bridges being disposed between two of the at least two slots, each of the first and second conductive tracks extending over one of said bridges;

[0009] - a width of each of the at least two through slots is between 0.2 mm and 5 mm;

[0010] - a distance between an inner edge of at least one of the at least two slots tra slopes and an edge of the second zone is less than 5 mm;

[0011] - a thickness of the substrate is less than 250 pm;

[0012] - the detection device further comprises: a layer of a second adhesive flexible, attached to the second face of the substrate, so as to cover a third area of ​​said second face; and a capacitive electrode, attached to one of the first and second faces, so as to cover a fourth area of ​​said first or second face, the third area containing the fourth area or containing a projection of said fourth area on the second face.

[0013] The invention further relates to a control panel comprising: a support; an outer plate, comprising a contact surface and a bonding surface opposite each other; and a sensing device as described above, the substrate being arranged on the support such that the force sensor is in contact with said support; and the bonding surface of the outer plate is attached to the layer of first rigid adhesive.

[0014] Preferably, the control panel further comprises an electronic control module, connected to the first conductive track.

[0015] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0016] [Fig.l] [Fig.l] is a detailed view of a detection device according to a first embodiment of the invention;

[0017] [Fig.2] [Fig.2] is a detailed view, in section, of a control panel comprising the detection device of [Fig.l]; and

[0018] [Fig.3] [Fig.3] is a detailed view of a detection device according to a second embodiment of the invention.

[0019] Figures 1 and 3 show detection devices 10, 110, respectively according to a first and according to a second embodiment of the invention. The devices 10 and 110 are in particular intended for the production of a control panel 12, shown schematically in [Fig.2].

[0020] In the following description, the devices 10 and 110 will be described simultaneously, the common elements being designated by the same reference numbers.

[0021] The detection device 10, 110 comprises: a substrate 14; a sensor 16, 116 of force; and at least one conductive track 18, 20, 118, 120.

[0022] The detection device 10, 110 further comprises: a layer 22 of a first adhesive; and a thermal protection arrangement 24, 26, 126.

[0023] In the embodiments shown, the detection device 10, 110 further comprises: at least one layer 30 of a second adhesive; and at least one capacitive electrode 32.

[0024] The substrate 14 comprises a first 34 and a second 36 faces, opposite and substantially parallel to each other. In the embodiments shown, the substrate has the shape of a strip extending in a main direction X.

[0025] The substrate 14 is formed from a thin film. Preferably, a thickness 38 of the substrate 14 is less than 250 μm. More preferably, the thickness of the substrate 14 is between 50 μm and 250 μm.

[0026] The substrate 14 is formed from a plastic material, preferably a thermoplastic material. The material of the substrate 14 is for example chosen from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polymethyl methacrylate (PMMA) and mixtures thereof.

[0027] The force sensor 16, 116 is fixed to the first face 34 of the substrate, so as to cover a first zone 40 of said first face.

[0028] In the embodiments shown, the force sensor 16, 116 is in the form of a pellet of a first functional material, deposited on the first face 34. The first functional material is for example a piezoelectric material. Alternatively, the force sensor is for example of resistive, capacitive or inductive technology.

[0029] In the embodiments shown, the pad forming the sensor 16, 116 has a round shape. Alternatively, said pad has, for example, an oval or polygonal shape.

[0030] The force sensor 16, 116 is for example produced by printing one or more functional inks on the first face 34 of the substrate.

[0031] According to one embodiment, such as that shown in [Fig. 3], the detection device 10, 110 comprises several force sensors 16, 116 arranged on the first face 34 of the substrate 14. Said several sensors 16, 116 are preferably distributed along the main direction X.

[0032] The at least one conductive track 18, 20, 118, 120 extends on the first face 34 of the substrate 14. The at least one conductive track 18, 20, 118, 120 has the shape of a strip deployed from the force sensor 16, 116.

[0033] The at least one conductive track 18, 20, 118, 120 is capable of conducting an electric current from the force sensor 16, 116. In the embodiments shown, the detection device 10, 110 comprises a first 18, 118 and a second 20, 120 conductive tracks associated with the or each force sensor 16, 116.

[0034] In the embodiments shown, each conductive track 18, 20, 118, 120 comprises: a main portion 42, extending parallel to the direction X; and a connecting portion 44, 144, connecting said main portion to the force sensor 16, 116. Preferably, the connecting portion 44, 144 is substantially rectilinear and forms a non-zero angle with the direction X.

[0035] The layer 22 of first adhesive is fixed to the second face 36 of the substrate, so as to cover a second zone 46 of said second face.

[0036] The first 40 and second 46 zones are arranged opposite each other. As can be seen in [Fig. 1], a projection 48 of the second zone 46 on the first face contains the first zone 40. In other words, the first zone 40, in contact with the force sensor 16, 116, is included in said projection 48 of the second zone 46.

[0037] Preferably, the second zone 46 has a shape similar to that of the first zone 40. In the embodiments shown, the second zone 46 has the shape of a disc with a diameter greater than that of the first zone 40.

[0038] The first adhesive forming the layer 22 is a rigid adhesive. The term “rigid adhesive” is understood in particular as an adhesive whose Young’s modulus is greater than 500 MPa.

[0039] Preferably, the layer 22 of first adhesive has a thickness of between 15 μm and 200 μm, more preferably of the order of 50 μm.

[0040] In the embodiments shown, the detection device 10, 110 comprises a thermal protection arrangement 24, 26, 126 associated with the or each force sensor 16, 116.

[0041] The thermal protection arrangement 24, 26, 126 comprises through slots 50, 150, arranged in the substrate 14. By "through" is meant that the slots 50, 150 connect the first 34 and second 36 faces of the substrate.

[0042] The slots 50, 150 of an arrangement 24, 26, 126 are arranged on a contour 52 of closed shape, surrounding the first zone 40 in contact with the corresponding force sensor 16, 116. More precisely, the contour 52 surrounds the second zone 46 in contact with the layer 22 of first adhesive, associated with said force sensor 16, 116.

[0043] In the embodiments shown, the contour 52 has the shape of a circle with a diameter greater than that of the second zone 46.

[0044] Preferably, a distance 54 between an internal edge of a slot 50, 150 and an edge of the corresponding second zone 46 is less than 5 mm.

[0045] Preferably, a width 56 of each slot 50, 150 is between 0.2 mm and 5 mm.

[0046] The arrangement 24, 26, 126 comprises at least two slots 50, 150. More specifically, the substrate 14 comprises at least two bridges 58, 158, each of said bridges being arranged on the contour 52, between two of the at least two slots 50, 150. The bridges 58, 158 mechanically connect the second zone 40 to the rest of the substrate 14.

[0047] According to one embodiment, the arrangement 24, 26 comprises two slots 50 and two bridges 58, alternating on the contour 52. According to another embodiment, the arrangement 126 comprises a number of slots 150 and bridges 158 greater than two, for example equal to three or four.

[0048] According to one embodiment, visible in [Fig. 3], the arrangement 26 further comprises at least two substantially rectilinear notches 60, each notch extending one of the slots 50 in the direction opposite to the second zone 46.

[0049] Each of the conductive tracks 18, 20, 118, 120, associated with a force sensor 16, 116, extends between two slots 50, 150 of the arrangement 24, 26, 126 corresponding to said force sensor.

[0050] More precisely, in the embodiments shown, the connecting portion 44, 144 of each conductive track 18, 20, 118, 120 extends over a bridge 58, 158 of the corresponding arrangement 24, 26, 126.

[0051] In the arrangement 26 visible in [Fig.3], each connecting portion 44 further extends along a notch 60.

[0052] The layer 30 of second adhesive is fixed to the second face 36 of the substrate 14. More precisely, the layer 30 covers a third zone 62 of the second face 36.

[0053] The second adhesive forming the layer 30 is a flexible adhesive. The term “flexible adhesive” is understood in particular as an adhesive whose Young’s modulus is less than 500 MPa. The second adhesive is for example an ASP type adhesive (pressure-sensitive adhesive).

[0054] The layer 30 of second adhesive has a thickness similar to that of the layer 22 of first adhesive.

[0055] The capacitive electrode 32 is fixed to one of the first 34 and second 36 faces, so as to cover a fourth zone 64 of said first or second face.

[0056] In the embodiments shown, the capacitive electrode 32 is fixed to the first face 34. The fourth zone 64 is located opposite the third zone 62, so that said third zone contains a projection 66 of said fourth zone 64 on the second face 36.

[0057] In an embodiment not shown, the capacitive electrode is attached to the second face of the substrate and the third area contains the fourth area. In such an embodiment, the layer 30 of second adhesive covers the capacitive electrode 32.

[0058] In the embodiments shown, the capacitive electrode 32 is in the form of a pellet of a second functional material, deposited on the substrate 14. The second functional material is for example a conductive ink. Said ink can be transparent or opaque. For example, it is a silver, carbon or Pedot type ink.

[0059] In the embodiments shown, the pad forming the capacitive electrode 32 has a round shape. Alternatively, said pad has, for example, an oval or polygonal shape.

[0060] Preferably, the detection device 10, 110 comprises several capacitive electrodes 32 arranged on the substrate 14. Said several capacitive electrodes 32 are preferably distributed along the main direction X.

[0061] According to one embodiment, the same layer 30 of second adhesive covers several capacitive electrodes 32 or the projections of several of said electrodes on the second face 36. According to a particular embodiment of the invention, a layer 30 of second adhesive continuously covers the second face 36 of the substrate 14, with the exception of the interior of the contour(s) 52.

[0062] In the embodiments shown, the detection device 10, 110 further comprises at least one third conductive track 68, having the shape of a strip deployed from the capacitive electrode 32. Said third conductive track 68 is arranged on the same face as said capacitive electrode. Preferably, the detection device 10, 110 comprises at least one third conductive track 68 associated with each capacitive electrode 32.

[0063] [Fig. 2] shows the aforementioned control panel 12. The panel 12 comprises the control device 10 as described above and shown in [Fig. 1]. Alternatively, not shown, the panel 12 comprises the control device 110 shown in [Fig. 3].

[0064] The control panel 12 further comprises: a support 72; an external plate 74; and an electronic control module 76.

[0065] The support 72 comprises an upper surface 78 on which the control device 10 is arranged. The first face 34 of said control device 10 is opposite the upper surface 78 of the support 72. More precisely, the force sensor(s) 16, 116 are in contact with said support.

[0066] In the embodiment shown, the upper surface 78 is substantially planar.

[0067] The outer plate 74 comprises a contact surface 80 and a bonding surface 82, opposite each other. The bonding surface 82 is oriented towards the control device 10 and attached to the layers 22, 30 of first and second adhesives.

[0068] More precisely, the or each layer 22 of the first adhesive is fixed to a fifth zone 84 of the bonding surface 82. Said fifth zone 84 corresponds to a projection 86 on the contact surface 80

[0069] Preferably, the external plate 74 is made of a plastic material. comprising compounds of the polypropylene, polycarbonate, acrylonitrile butadiene styrene type or their mixtures.

[0070] The electronic control module 76, shown schematically in [Fig.2], is connected to the ends of the conductive tracks 18, 20, 118, 120, 68, opposite the force sensors 16, 116 or the corresponding capacitive electrodes 32.

[0071] A method of operating the control panel 12 will now be described.

[0072] The external plate 74 is for example used as a touchpad. More precisely, pressure from a user's finger on the contact surface 80 leads to the generation of an electrical signal by a force sensor 16, 116 or by a capacitive electrode 32. The signal is transmitted to the electronic module 76 by the corresponding conductive track(s) 18, 20, 118, 120, 68.

[0073] More specifically, due to the rigid nature of the first adhesive, the or each layer 22 of said first adhesive provides a strong mechanical bond between the outer plate 74 and the sensor 16, 116 corresponding to said layer. Pressure from the user's finger on the projection 86 of the fifth zone 84 is therefore efficiently transmitted to the corresponding force sensor 16, 116.

[0074] Due to the flexible nature of the second adhesive, the mechanical bond formed by the layer 30, between the external plate 74 and the capacitive electrode(s) 32, is less strong. Such a bond is nevertheless sufficient for pressure from the user's finger opposite a capacitive electrode 32 to generate the expected signal.

[0075] In particular, the mechanical link is associated with an absence of an air gap between the capacitive electrode and the facade 74. Indeed, the presence of such an air gap would lead to a loss of sensitivity of the capacitive electrode.

[0076] The substrate 14, the layer(s) 22 of first adhesive and the layer(s) 30 of second adhesive have different coefficients of thermal expansion. In particular, the first and second adhesives have different coefficients of thermal expansion.

[0077] During operation of the control panel 12, heating leads to expansion of the layers 22 and 30. Such expansions lead to shear forces on the surface of the substrate 14.

[0078] In the vicinity of the second zone(s) 46 in contact with the layer(s) 22 of first adhesive, the presence of the slots 50, 150 allows local elastic deformation of the substrate, preventing rupture of the first and second tracks 18, 20, 118, 120 by shearing. In addition, the presence of said slots makes it possible to reduce the temperature rise of the device 10, 110 in the vicinity of said second zones 46.

[0079] The implementation of a thermal protection arrangement 24, 26, 126 comprising the slots 50, 150 makes it possible to connect the substrate 14 and the external plate 74 by several layers 22, 30 of adhesive of different natures, each providing a suitable mechanical connection with the sensor 16, 116 or the corresponding capacitive electrode 32. The integrity of the device 10, 110 is preserved during its temperature rise, despite the different coefficients of thermal expansion of the adhesives.

Claims

Claims

1. A detection device (10, 110) comprising: - a substrate (14), comprising a first (34) and a second (36) opposite faces; - a force sensor (16, 116), fixed to the first face of the substrate, so as to cover a first zone (40) of said first face; and - at least one first conductive track (18, 118), extending on said first face from the force sensor; the detection device being characterized in that it further comprises: - a layer (22) of a first rigid adhesive, fixed to the second face (36) of the substrate, so as to cover a second zone (46) of said second face; the first (40) and second (46) zones being arranged opposite each other, a projection (48) of the second zone on the first face (34) containing the first zone;and - at least two through slots (50, 150) provided in the substrate, said at least two slots being arranged on a contour (52) of closed shape surrounding the second zone (46), the first conductive track (18, 118) being arranged between two of said at least two slots.;

2. A sensing device according to claim 1, further comprising a second conductive track (20, 120) extending across the first face (34) from the force sensor; and wherein the substrate comprises at least two bridges (58, 158), each of said bridges being disposed between two of the at least two slots (50, 150), each of the first (18, 118) and second conductive tracks (20, 120) extending across one of said bridges.

3. A detection device according to claim 1 or 2, wherein a width (56) of each of the at least two through slots is between 0.2 mm and 5 mm.

4. Detection device according to one of the preceding claims, wherein a distance (54) between an inner edge of at least one of the at least two through slots (50, 150) and an edge of the second zone (46) is less than 5 mm.

5. A detection device according to one of the preceding claims, wherein a thickness (38) of the substrate is less than 250 pm.

6. A detection device according to one of the preceding claims, further comprising: a layer (30) of a second flexible adhesive, attached to the second face (36) of the substrate, so as to cover a third area (62) of said second face; and a capacitive electrode (32), attached to one of the first and second faces, so as to cover a fourth area (64) of said first or second face, the third area containing the fourth area or containing a projection (66) of said fourth area on the second face.

7. Control panel (12), comprising: a support (72); an external plate (74), comprising a contact surface (80) and a bonding surface (82) opposite each other; and a detection device (10, 110) according to one of the preceding claims, the substrate (14) being arranged on the support so that the force sensor (16, 116) is in contact with said support; and the bonding surface of the external plate is fixed to the layer (22) of first rigid adhesive.

8. Control panel according to claim 7, further comprising an electronic control module (76), connected to the first conductive track (18, 118).

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