EP2521964A2 - Multi-contact, tactile sensor with a high electrical contact resistance - Google Patents

Abstract

The invention relates to a multi-contact, tactile sensor (1) comprising an upper layer (2) provided with strip conductors (3) arranged in lines, a lower layer (4) provided with strip conductors (5) arranged in columns, and spacer means (8) positioned between the upper layer (2) and the lower layer (4) in such a way as to insulate said upper layer (2) and lower layer (4). Said sensor comprises electromechanical means (10) arranged between the upper (2) and lower (4) layers such as to increase the electrical contact resistance during contact between at least one strip conductor (3) of the upper layer (2) and at least one strip conductor (5) of the lower layer (4).

Description

 MULTICONTACT CONTACT TOUCH SENSOR WITH CONTACT RESISTANCE

 HIGH ELECTRICITY

The present invention relates to a multicontact touch sensor.

It relates more particularly to a multicontact tactile sensor comprising:

 an upper layer provided with conductive tracks organized in lines,

 a lower layer provided with conducting tracks organized in columns,

 spacing means positioned between the upper layer and the lower layer so as to isolate these upper and lower layers.

 Such a sensor is described for example in patent document EP 1 719 047. As illustrated by FIGS. 1 and 2, this sensor 1 operates so as to perform a sequential scanning of the rows 3 and the columns 5 of conductive tracks, which allows simultaneous detection of several contact zones during the same scanning phase.

 More specifically, when a user presses on this sensor, the upper layer 2 comes into contact with the lower layer 4 in the parts located between the spacing spacers 8. The two layers being provided with conductive tracks 3 and 5, a signal electrical is sequentially injected into the conductive tracks 3 of the upper layer 2 and the detection takes place at the level of the conductive tracks 5 of the lower layer 4. The detection of a signal at some of these tracks allows from then on to locate the position of the points of contact.

The upper and lower layers are for example made of a translucent conductive material, for example transparent metal oxides such as ΓΙΤΟ (indium tin oxide), solutions based on metal nanoparticles or conductive micro-wires. The upper layer can be positioned under a layer 6 of polyethylene terephthalate (PET) and the lower layer on a layer of glass 7. When the user presses the sensor, the conductive lines 3 come into contact with the conductive columns 5 between the spacers 8.

 However, the transparent conductive materials have a significant linear resistance along the rows and columns, but a much lower vertical resistance at the contact areas between the two layers.

 For the following, the conductive tracks that are fed will be called lines and those on which an electrical characteristic is measured will be called columns.

As illustrated by FIGS. 3 and 4, each column has a column resistance and each line a line resistor. Specifically, each column portion has a column resistor Rc and each line portion a line resistor R _L. Moreover, when a line approaches a column, a contact resistance R _T appears between this line and this column.

 When feeding a line and measuring the impedance on a column in order to know if there is a contact or not, one measures the resistance induced by the resistive path along the lines and columns.

 In Figure 3 there is a contact at point 9a. The supply of the corresponding line makes it possible to measure on the corresponding column a resistive path equal to RL + 3 Rc + RT, corresponding to the shortest resistive path between the end of the line which feeds and the end of the column which measures .

 In Figure 4, there is no contact at point 9a, but there are three simultaneous contacts at points 9b, 9c and 9d near 9a. When the line corresponding to 9a is supplied and measured on the column corresponding to 9a, the shortest resistive path is no longer measured (as in FIG. 3), but a resistive path is measured between the line and the column of point 9a, via contact points 9b, 9c and 9d. We thus measure a resistive path equal to 3 RL + 3 Rc + 3Rj.

Thus, because of the low contact resistance R _T (ie the resistance vertical) produced by ΓΙΤΟ, it is possible to measure resistive paths at contactless points, whose values may be substantially equal to those that would provide the same point if it were a point of contact. This can lead to actually detect a contact where there is none.

 In particular, when several contact points are activated, and notably orthogonally on the lines and columns, the electrical characteristics appearing at the intersection of a line and a column are disturbed by the other contact points located on the line and the column. these same lines and columns.

 This phenomenon gives rise to problems of masking and orthogonality, which make it difficult to accurately detect contact zones, since orthogonalities tend to limit the detection to rectangular zones, even in the case of contact with more complex shapes.

 In the state of the art, these problems can be solved through electronic processing and different correction algorithms.

 An object of the invention is to reduce the problems of masking and orthogonality at the contact points on the sensor without necessarily implementing additional electronic processing.

 This problem is solved according to the invention by a multicontact tactile sensor as described above, comprising electromechanical means arranged between the upper and lower layers adapted to reduce the contact surface during a contact between at least one conductive track of this layer. upper and at least one conductive track of this lower layer.

 Thanks to these additional electromechanical means, when a user presses on the sensor, an additional contact resistance is added between the upper layer and the lower layer.

Therefore, when measuring the impedance on a column after feeding a line, we obtain different results between an area where there is contact and an area where there is none. Indeed, where there is contact, one measures the portions of resistance of line and column as well as the resistance higher contact. Where there is no contact, one measures line and column resistance portions, to which are added several contact resistances or none. Therefore, at a contact area, an impedance of an order of magnitude different from the impedance measured at a non-contact area is measured.

 This significant increase in electrical contact resistance makes it possible to reduce masking and orthogonality problems, which initially originated in the low vertical resistance of the conductive tracks at the contact areas between the upper and lower layers. The simultaneous detection of a plurality of contact points is then possible without using additional electronic processing means.

 In an arbitrary manner, we consider that the spacing means are arranged on the lower layer. Those skilled in the art will note, however, that these spacers may be arranged on the upper layer, and therefore the arrangement of the electromechanical means with respect to the upper and lower layers will have to be reversed with respect to follows.

 Similarly, it will be possible to invert the lower and upper layers, so that the fed tracks are arranged in columns and those on which an electrical characteristic is measured are arranged in lines. A predominant criterion remains that the conductive tracks respectively of the upper layer and the lower layer are organized so as to be orthogonal to each other.

 According to a first variant of implementation, the electromechanical means comprise intermediate dielectric layers arranged between the lower layer and the spacing means

In the latter case, the intermediate dielectric layers are preferably in the form of a dielectric layer perforated at at least one potential point of contact between a conductive track of the upper layer and a conducting track of the lower layer. These perforations have a surface in the plane of the intermediate layer smaller than that of the potential contact area between rows and columns. The contact area between the rows and the columns is therefore reduced, and the electrical contact resistance increased.

 In the latter case, the dielectric layer is advantageously perforated at all the potential contacts between a conductive track of the upper layer and a conductive track of the lower layer.

 Still in the latter case, the dielectric layer advantageously has several perforations at a single point of potential contact between a conductive track of the upper layer and a conductive track of the lower layer. These multiple perforations at the same potential contact (2x2 or 3x3 matrix) can modulate the perforated surface. As a result, during manufacture, the tolerance is improved and therefore the realization of these perforations is better controlled.

 According to a second variant of implementation, the electromechanical means comprise conductive pads disposed on one of the upper and lower layers, at at least one potential point of contact between a conducting track of the upper layer and a track. conductive of the lower layer. The electrical contact is then operated at these conductive pads. Due to their small surface, the electrical contact between the lines and the columns is on a reduced surface, which increases the electrical contact resistance. The electrical resistance of the conductive pads can be adjusted either by the geometric shape of the pads, or by the composition of the material constituting the pads which can be more or less conductive.

 In the latter case, the conductive pads are advantageously arranged at all the potential contacts between a conductive track of the upper layer and a conductive track of the lower layer.

According to a third variant of implementation, the electromechanical means comprise at least a part of spacing means arranged to limit the electrical contact surface during a contact between at least one conductive track of the upper layer and at least one track conductive of the lower layer. This variant presents the advantage of not requiring additional means, by directly using the spacing means, for a result obtained equivalent.

 In this case, the arrangement of the spacing means advantageously consists of occupying a large area, except at the potential contact points between a conductive track of the upper layer and a conductive track of the lower layer.

 In order to further reduce the electrical contact area, the three implementation variants above can advantageously be combined.

 Preferably, the upper and lower layers are transparent, so that the sensor is itself transparent.

 Preferably, the conductive tracks of the upper layer and the conductive tracks of the lower layer form a matrix of rectangular cells.

 The conductive tracks of the upper layer advantageously consist of transparent conductive oxide (for example indium tin oxide ITO). Similarly, those of the lower layer are also advantageously constituted by transparent conductive oxide (for example indium tin oxide ITO).

 Finally, preferably, the upper layer is located below a flexible layer (for example polyethylene terephthalate PET) and the lower layer is located above a rigid layer (for example glass).

 Other advantageous features of the invention are described below with reference to the appended figures in which:

 FIG. 1 represents a view from above of the arrangement of the rows and columns of conductive tracks of a multicontact tactile sensor of the prior art;

 FIG. 2 represents a sectional view of a multicontact tactile sensor of the prior art;

FIGS. 3 and 4 show an illustrative diagram in the art previous possible resistive paths when feeding a line and measurement on a column;

 FIG. 5 represents a view from above of the arrangement of the electromechanical means according to a first embodiment;

 FIG. 6 represents a sectional view of a multicontact tactile sensor according to this first embodiment;

 FIGS. 7A and 7B show enlarged sectional views of this sensor according to this first embodiment;

 FIG. 8 represents a view from above of the arrangement of the electromechanical means according to a second embodiment;

 FIG. 9 represents a sectional view of a multicontact tactile sensor according to this second embodiment;

 FIGS. 10A and 10B show enlarged sectional views of this sensor according to this second embodiment;

 - Figure 1 1 shows a top view of the arrangement of the electromechanical means according to a third embodiment;

 FIG. 12 represents a sectional view of a multicontact tactile sensor according to this third embodiment;

 FIGS. 13A and 13B show enlarged sectional views of this sensor according to this third embodiment; and

 FIG. 14 represents a view of a display equipped with a two-dimensional tactile sensor multicontact according to the invention.

 For better legibility, in these figures, identical reference numerals refer to similar technical elements.

 For each of the embodiments described below, the spacing means are arranged on the lower layer. This provision is however arbitrary and the skilled person will adapt the invention to a provision other than that described below.

 FIGS. 5, 6, 7A and 7B show a multicontact tactile sensor according to a first embodiment of the invention.

The multicontact touch sensor 1 described here is preferably transparent, but it is understood that the invention is also applicable to a sensor 1 not transparent, thus comprising at least one non-transparent layer.

 In FIGS. 5 and 6, the sensor 1 comprises an upper layer 2 provided with conductive tracks 3 organized in lines, as well as a lower layer 4 provided with conductive tracks 5 organized in columns. The arrangement of these tracks in rows and columns makes it possible to have a matrix of cells, each cell being formed by the intersection of a conductive track 3 of the upper layer 2 and of a conductive track 5 of the lower layer. 4. These conductive tracks consist of ITO (indium tin oxide), which is a translucent conductive material.

 When one wants to know if a line has been put in contact with a column, determining a contact point on the sensor 1, the electrical characteristics - voltage, intensity or resistance - are measured at the terminals of each line / column intersection of the matrix.

 The sensor 1 also comprises, in its upper part, a layer of PET (polyethylene terephthalate) 6. Under this layer of PET 6, is the top layer 2. The top layer 2 of ITO thus forms a structuring of the PET 6 and corresponds to lines 3 of the sensor 1.

 The sensor 1 further comprises, in its lower part, a glass layer 7. Above this layer, is the lower layer 4. The lower layer 4 of ITO thus forms a structuring of the glass layer 7 and corresponds to columns 5 of the sensor 1.

 It is understood that the notions of lines and columns are relative and arbitrary notions, and that they can therefore be interchanged according to the orientation of the sensor. By convention only, it will be considered that the top layer of ITO 2 forms the lines of a matrix sensor, but it is clear to those skilled in the art that it could also form the columns. In this case, the lower layer of ITO 4 would form the lines of this matrix sensor. In both cases, the direction of the ITO tracks 3 forming the upper layer 2 is perpendicular to the direction of the ITO tracks 5 forming the lower layer 4.

As illustrated by FIGS. 6, 7A and 7B, spacers 8 are arranged between the upper 2 and lower 4 layers so as to isolate these layers from one another. More specifically, the spacers 8 are arranged to be connected to the lower layer 4. They are positioned at the level of the areas where the tracks of the upper layer 2 and those of the lower layer 4 are not likely to form intersections defining detection cells.

 Those skilled in the art will understand that it is possible, however, to connect the spacer spacers 8 to the upper layer 2, or some spacers to the lower layer 4 and others to the upper layer 2, without departing from the scope of the present invention.

 According to this first embodiment, an intermediate layer 10 is disposed between the lower layer 4 and the spacers 8. This intermediate layer 10 is made of a high-strength material and is preferably a dielectric layer. It is perforated in zones 10 'included inside the intersection zones between the conductive tracks 3 and 5. As well illustrated in FIG. 5, the surface S of these perforations 10' in the plane of the intermediate layer 10 is less than that of the potential contact area between tracks 3 and 5, at the intersections defining the detection cells.

 In this way, as illustrated in FIGS. 7A and 7B, when a user 9 'presses the sensor 1, the contact 9 between the conductive tracks 3 and 5 can only be made at the level of the surface S defined by the perforations 10 'of the intermediate layer 10. The electrical contact surface between the tracks is reduced compared to the case where there is no intermediate layer 10, and the electrical resistance of contact is increased.

 Figures 8, 9, 10A and 10B show a second embodiment of the invention, wherein the perforated intermediate layer 10 is replaced by conductive pads 1 1.

The sensor 1 always comprises an upper layer 2 provided with conducting track lines 3, a lower layer 4 provided with conductive track columns 5 and spacing spacers 8 arranged in areas where these tracks 3 and 5 are not susceptible of to form an intersection during a contact.

 In this embodiment, conductive pads 1 1 are arranged on the conductive tracks 3 of the upper layer 2, at the level of areas likely to intersect with the conductive tracks 5 of the lower layer 4 during a contact by support on the sensor.

 These studs may be in a form identical to that of spacer spacers 8. These pads 1 1 are however conductive, insofar as their role is to allow the passage of an electric current between tracks 3 and 5 when a support on the sensor 1 by a user 9 '. They also have dimensions in the plane of the upper layer 2 smaller than the width of a conductive track 3.

 With these pads 1 1, when a user 9 'presses the sensor 1, the contact between the conductive tracks 3 and 5 is established at the surface defined by the conductive pads 1 1, and no longer at the level of the area defined by the intersection of the conductive tracks. The electrical contact surface between the tracks is therefore reduced compared to the case where there would not be these conductive pads, and the electrical resistance of contact is increased.

 Finally, FIGS. 11, 12, 13A and 13B show a third embodiment of the invention, in which the two previously described embodiments are combined with one another.

 More specifically, he is willing:

 between the lower layer 4 and the spacing spacers 8, an intermediate layer 10 having perforations 10 'at the potential contact areas between the conductive tracks 3 and 5, these perforations 10' having dimensions in the plane of the lower layer 4 less than the width of a track 5, and

 - On the conductive tracks 3 of the upper layer 2, conductive pads 1 1 at the potential contact areas between the conductive tracks 3 and 5, these pads 1 1 having dimensions in the plane of the upper layer 2 lower than the width of a track 3 and smaller than the dimensions of the perforations 10 'of the intermediate layer 10.

In this way, when pressing on the sensor 1, the electrical contact between the conductive tracks 3 and 5, respectively of the upper 2 and lower 4 layers, can be established only inside the perforations 10 'of the intermediate layer 10 and on a surface delimited by the surface of the conductive pads 1 1 . The contact surface is all the more reduced, and the electrical contact resistance thereby increased.

 According to a fourth embodiment not shown, the electromechanical means directly comprise a part of the spacing means 8 arranged to limit the electrical contact surface during a contact between at least one conductive track 3 of the upper layer 2 and at least a conductive track 5 of the lower layer 4.

 More specifically, these spacing means 8 occupy a large area, except at the potential contact points 9 between a conductive track 3 of the upper layer 2 and a conductive track 5 of the lower layer 4.

 Thus, in this embodiment, the electromechanical means consist of spacing means 8, already present in the touch sensor 1, but arranged judiciously. Therefore, it is no longer necessary to use additional electromechanical means to obtain an equivalent result.

 The embodiments described above can be combined depending on the specificities desired for the sensor.

 If the multicontact touch sensor above is intended to be positioned above a screen for displaying different objects, the various aforementioned layers are preferably transparent.

 In particular, ITO has the advantage of being a conductive and transparent material.

In use, a user presses on the top layer of PET 2, if necessary with several fingers at the same time, which has the effect that, in the embodiments described above, the ITO 2 top layer is in contact with the lower layer of ITO 4, either directly inside the perforations 10 'of an intermediate layer 10, or via conductive pads 1 1, or both. Preferably, a sequential scan of the matrix formed by the rows and columns of ITO can be performed. This scanning is for example as described in patent document EP 1 719 047.

 Finally, FIG. 14 shows a display 20 according to the invention. This display comprises in addition to a matrix two-dimensional multicontact tactile sensor 1, a display screen 22, a capture interface 23, a main processor 24 and a graphics processor 25.

 The first fundamental element of this tactile device is the multicontact tactile sensor 1, necessary for the acquisition - the multicontact manipulation - using a capture interface 23. This capture interface 23 contains the acquisition and processing circuits. 'analysis. The touch sensor 1 is of the matrix type. This sensor can be optionally divided into several parts to accelerate the capture, each part being scanned simultaneously.

 The data coming from the capture interface 23 is transmitted after filtering, to the main processor 24. This executes the local program making it possible to associate the data of the slab with graphical objects which are displayed on the screen 22 in order to example of being manipulated. The main processor 24 also transmits to the graphical interface 25 the data to be displayed on the display screen 22. This graphic interface can also be driven by a graphics processor.

 The touch sensor is controlled as follows: one feeds successively, during a first scanning phase, the conductive tracks of one of the networks and the response is detected on each of the conductive tracks of the other network. Contact zones corresponding to the nodes whose state is modified with respect to the idle state are determined as a function of these responses. One or more sets of adjacent nodes are determined whose state is changed. A set of such adjacent nodes defines a contact area. From this set of nodes, a position information referred to here as a cursor is calculated. In the case of several sets of nodes separated by non-active zones, several independent cursors will be determined during the same scanning phase.

This information is refreshed periodically during new scanning phases. Cursors are created, tracked or destroyed based on information obtained during successive scans. The cursor is for example calculated by a barycentre function of the contact zone. The general principle is to create as many sliders as there are zones detected on the touch sensor and to follow their evolution over time. When the user removes his fingers from the sensor, the associated sliders are destroyed. In this way, it is possible to capture the position and the evolution of several fingers on the touch sensor simultaneously.

 The matrix sensor 1 is here a resistive type sensor. It is composed of two transparent layers on which are arranged lines or columns corresponding to conductive tracks. These tracks consist of conductive wires. These two layers of conductive tracks thus form a matrix network of conducting wires.

 When one wants to know if a line has been put in contact with a column, determining a contact point on the sensor 1, the electrical characteristics - voltage, intensity or resistance - are measured at the terminals of each node of the matrix. The device makes it possible to acquire the data on the whole of the sensor 1 with a sampling frequency of the order of 100 Hz, by implementing the sensor 1 and the control circuit integrated in the main processor 24.

 The main processor 24 executes the program for associating the sensor data with graphic objects that are displayed on the display screen 22 for manipulation.

 The second element making it possible to produce the display is the display screen 22. This screen comprises a network of display pixels. These pixels are provided with three areas respectively red, green and blue, to achieve a display that is multicolored. A backlighting device also allows to illuminate the screen from below, passing through the sensor and its conductive tracks networks, to allow display.

The previously described embodiments of the present invention are given by way of examples and are in no way limiting. It is understood that the skilled person is able to realize different variants of the invention without departing from the scope of the invention.

 In particular, those skilled in the art can add at least one resistive intermediate layer positioned between spacing spacers 8 on the one hand and at least one of the conductive upper layer 2 and the conductive lower layer 4 on the other hand. This intermediate layer may have a linear resistance greater than that of the upper 2 and lower 4 layers, for example a hundred times higher. It can also have an impedance much greater than the impedance of the conductive material (ITO) of the upper layers 2 and lower 4. An adequate value of vertical resistance for this intermediate layer may be between 50 and 200 kiloOhms. It can for this reason be made in semiconductor, for example silicone. Its thickness can be of the order of 300 micrometers and its resistivity of the order of 640 Ohm. m.

Claims

1. Multicontact touch sensor (1) comprising an upper layer (2) provided with conductive tracks (3) arranged in lines, a lower layer (4) provided with conductive tracks (5) arranged in columns, and spacing means (8). ) positioned between the upper (2) and lower (4) layers so as to isolate said upper (2) and lower (4) layers, characterized in that it comprises electromechanical means (10, 1 1) arranged between said layers upper (2) and lower (4) adapted to reduce the contact surface during a contact between at least one conductive track (3) of said upper layer (2) and at least one conductive track (5) of said lower layer (4).  2. multicontact touch sensor (1) according to the preceding claim, wherein the spacing means (8) are arranged on the lower layer (4) and the electromechanical means (10.1 1) comprise intermediate dielectric layers disposed between said lower layer (4) and said spacer means (8).  3. multicontact touch sensor (1) according to the preceding claim, wherein the intermediate dielectric layers are in the form of a dielectric layer (10) perforated at at least one potential point of contact (9) between a track conductor (3) of the upper layer (2) and a conductive track (5) of the lower layer (4).  4. multicontact touch sensor (1) according to the preceding claim, wherein the dielectric layer (10) is perforated at all potential contacts (9) between a conductive track (3) of the upper layer (2) and a track conductor (5) of the lower layer (4).  The multicontact touch sensor (1) according to claim 3 or 4, wherein the dielectric layer (10) has a plurality of perforations at a single potential point of contact (9) between a conductive track (3) of the upper layer (2) and a conductive track (5) of the lower layer (4). 6. multicontact touch sensor (1) according to one of the preceding claims, wherein the spacing means (8) are arranged on the lower layer (4) and the electromechanical means (10, 1 1) comprise conductive pads (1 1) arranged on one of the upper (2) and lower (4) layers, at at least one potential contact (9) between a conductive track (3) of the upper layer (2) and a conductive track (5) of the lower layer (4).  7. multicontact touch sensor (1) according to the preceding claim, wherein the conductive pads (1 1) are arranged at all potential contacts (9) between a conductive track (3) of the upper layer (2) and a conductive track (5) of the lower layer (4).  8. multicontact touch sensor (1) according to one of the preceding claims, wherein the spacing means (8) are arranged on the lower layer (4) and the electromechanical means (10.1 1) comprise at least a portion said spacing means (8) arranged to limit the electrical contact area upon contact between at least one conductive track (3) of the upper layer (2) and at least one conductive track (5) of the lower layer (4).  9. multicontact touch sensor (1) according to the preceding claim, wherein the arrangement of spacing means (8) is to make them occupy a large area, except at the potential points of contact (9) between a conductive track (3) of the upper layer (2) and a conductive track (5) of the lower layer (4).  10. multicontact touch sensor (1) according to one of the preceding claims, wherein the upper layers (2) and lower (4) are transparent.  1 1. Multicontact touch sensor (1) according to one of the preceding claims, wherein the conductive tracks (3) of the upper layer (2) and the conductive tracks (5) of the lower layer (4) form a matrix of rectangular cells.  12. multicontact touch sensor (1) according to one of the preceding claims, wherein the upper layer (2) is located below a layer (6) flexible. 13. Multicontact touch sensor (1) according to one of the claims previous, wherein the lower layer (4) is located above a layer (7) rigid.