EP1754208A1

EP1754208A1 - Touch screen device

Info

Publication number: EP1754208A1
Application number: EP05781249A
Authority: EP
Inventors: Moustapha Hafez; Mohamed Benali-Khoudja; Nikola Vujic; Fadila Khelfaoui
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2004-06-07
Filing date: 2005-06-03
Publication date: 2007-02-21
Also published as: JP2008502017A; US20080182228A1; WO2006016077A1; FR2871270B1; FR2871270A1

Abstract

The invention relates to a touch screen device, comprising a touch plate (10) with a touch surface (10a), a network of taxels (25) formed within the touch plate or within a sub-plate (11) forming part of the touch plate (10), each taxel (25) comprising a sheet (23) capable of adopting at least two states, the passage from one state to the other, directly or indirectly providing a modification of the tactile sensation, means (23, 31, 4), for selectively modifying the state of the sheets (23) of the taxels (25), said means comprising addressing means (4) and means (23), for modification of the tactile sensation of the taxels (25), whereby each taxel sheet (23) has a spiral form, bounded on both sides by a spiral gap (14).

Description

TOUCH DISPLAY DEVICE DESCRIPTION

TECHNICAL AREA

The invention lies in the field of devices for transmitting tactile information to a user. It relates more particularly to a tactile display device comprising:

- a touch pad having a touch surface,

a network of taxels each consisting of a blade capable of at least two states, the passage from one of the states to the other constituting the modification of the tactile sensation, means for selectively actuating taxicles' slides , these means comprising addressing means and means for modifying the state of a taxonomy plate,

The deformation of the relief of the touch area or putting into vibration or its temperature change produces a change in condition of the blade and therefore a variation of the tactile sensation a user ^es' t can detect . The addressing means make it possible to select the micro-actuators that should be activated at a given instant to produce at this moment the desired tactile sensation. STATE OF THE PRIOR ART

US Patent 6,159,013 discloses a portable optical sensor for the blind. The device includes an electromagnetic unit. The electromagnetic unit has a key plate. This plate has holes. Movable rods centered on each of the holes may, depending on their axial position, cause a deformation of a surface of keys of the key plate. A coil placed behind the keypad surrounds each of the rods. Each coil moves one of the rods in its axial direction. Depending on the value of a current flowing in the coil, one end of the rod passes or not through the corresponding hole, thus changing the shape of the surface of keys. In this way, a particular touch sensation of the touch plate can be controlled at any time. For a device that can reach several hundred actuators, the method described in this patent can no longer be applied because of the complexity of assembly and wiring, especially when systems are miniaturized.

SUMMARY OF THE INVENTION

The present invention relates to a touch plate whose taxels are each constituted by a single blade cut in a solid part of a plate. The blades and the plate thus form an assembly in one piece. Each of the slices constituting a taxel can be formed in the single plate by employing collective techniques of manufacturing, in particular techniques for forming multilayer components in microelectronics.

The present invention aims with respect to this state of the art to increase the number of taxels per unit area. It aims to create a sensation of continuous during the tactile exploration of the touch surface. Ideally the distance between adjacent taxels of the touch surface should be of the order of 1 mm, which represents substantially the value of the mechanical resolution that can be felt by a human finger. The assembly complexity of the touch interface increases with the number of taxels per unit area, that is to say with the density of the taxels. This complexity increases especially as each taxel must be operated individually in a very small working volume whose base area is of the order of mm ² . According to the invention the blade cut from the surface of the plate has the shape of a spiral. Provisions relating to the vocabulary used will, for all purposes, be given below.

The term "taxel" is not used so ^running outside the professional environment of the tactile sensation. By analogy with the pixel, it is the surface of an element of modification of the sensation of tactile sensation. The overall tactile sensation is a function of the value of each taxel. The tactile sensation of a taxel can be modified by modifying its state with respect to the plane of the plate. The state can be constituted by the relative position of the taxel with respect to the rest of the plate or still its state of immobility or movement, for example vibratory, or its temperature.

It is specified that the term spiral is not limited to for example a logarithmic spiral. Thus for example each turn of the spiral may for example have a substantially square or elliptical shape or circle. These examples are given for illustrative and not limiting.

The term "touch plate" does not necessarily mean a flat plate. The plate can be formed by a stack of layers. The plate may be flat or curved, in particular to better fit the shape of a part of a body to which the tactile sensation is to be applied. In the remainder of the discussion, it will be considered that with respect to a taxel the plate is locally flat.

According to the invention the deformable parts of taxel or spikes are spiral-shaped, which deform out of plane or vibrate. This geometric shape maximizes the length of the active beam of the pin. It therefore allows a significant deflection out of plane, while remaining in the zone of elasticity, or super elasticity in the case of a shape memory alloy, the material constituting the plate in which the spiral blade is cut.

In summary, the invention relates to a tactile display device comprising:

- a touchpad having a touch surface, - a network of taxels formed in a touchpad or in a sub-plate forming a part of the touch-plate, each taxel having a blade capable of at least two states, the passage from one of the states to the other causing directly or indirectly the modification of the tactile sensation, - means for selectively modifying the state of taxel blades, these means comprising addressing means and means for modifying the tactile sensation of taxels, characterized in that each taxel plate has a spiral shape, bordered on either side by a recess spiral shaped.

In one embodiment each taxel blade has a double spiral shape. In one embodiment, the plate or a sub plate constituting with at least one other sub plate the key plate, and the blades are made of a shape memory material, each blade being a function of its temperature capable of two states, a first state in which the blade is in the local plane of the plate, and a second state in which the blade is deformed out of plane, thereby causing a tactile sensation of relief.

In one embodiment, the plate or an under-plate which together with at least one other sub-plate constitutes the touch plate, and the blades are made of a two-way shape memory material.

In one re ^'realization is the touch plate consists of two parallel plates in them under a plate-shaped memory material comprising the network of taxels and an underplate of elastic material, the underplate of elastic material comprising in correspondence with each taxel of the underplate of shape memory material, a leaf spring separated from the solid parts of the subplate by one or several recesses and connected to it by one or more arms, each leaf spring of the under plate of elastic material having a rigid mechanical connection with the spiral blade of the taxel corresponding thereto so as to exert on this blade taxel a force of reminder, when this taxel blade is in its off-plan state.

In one embodiment, the key plate is formed of two mutually parallel sub-plates, a sub-plate of shape memory material comprising the network of taxels and a sub-base plate also made of shape memory material, the sub plate. reminder comprising in correspondence with each taxel of the sub-plate of shape memory material comprising the network of taxels, a blade separated from the solid parts of the return plate under one or more recesses and connected to it by one or more arms , each plate of the return plate under depending on its temperature in a rest position or in a memorized position, each plate of the return plate. having a rigid mechanical connection with the spiral blade of the taxel corresponding thereto, so that in a memorized position, the plate of the return plate underlies on the blade of the taxel which corresponds to it a restoring force tending to bring back said taxel blade of his out-of-plane state to its rest state. Optionally, a thermally insulating layer separates the sub-plates of shape memory material from each other, the rigid mechanical connection between a plate of the return plate and the corresponding taxel plate comprising an element. thermally insulating rigidly mechanically connected to a portion of the taxel blade and a portion of the blade of the return plate under. Preferably, grooves are present on the solid portions of the plate or subplates of shape memory material together forming the touch plate, in spaces between two taxal blades adjacent to each other. These grooves slow down the propagation of heat between a heated plate of a taxel and the adjacent taxel blade.

In one embodiment the key plate has a bilayer material having a layer of a flexible material and a layer of piezoelectric material.

Thus, when an electric field is applied at a blade, it generates a deformation of the blade bending, which causes an out-of-plane deflection of the blade. The layer of flexible material, when present, makes it possible to increase the robustness of the layer of piezoelectric material, for example a ceramic, which is very brittle by nature.

In one embodiment, the touch plate is constituted by a three-layer material comprising a layer of a flexible material between two layers of piezoelectric material. In one embodiment the key plate is made of a bilayer material having two layers of piezoelectric material.

In one embodiment the touch plate has a layer of a magnetostrictive material. This makes it possible to directly produce high torque high speed actuators without the need to go through a gearbox, for tactile vibratory rendering. In one embodiment, the touch plate comprises a layer of an electrostrictive material.

In one embodiment the taxel blade is a motor element of a rod which constitutes at the level of the touch plate a modification of the tactile sensation.

In one embodiment the blades are mechanically linked to a rod itself mechanically connected to a magnet. In alternative embodiments of the latter two modes, the device according to the invention further comprises an intermediate plate of deformable material having passages for the rods. The rods are provided with bulged portions and narrow portions, these bulged and narrow portions cooperating with internal shapes of the passages to maintain the rod in one or more predefined positions. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with the aid of the accompanying drawings, in which: - Figure 1 shows a view of a touch plate of a display device according to the invention in the presence of a finger,

FIGS. 2a and 2b respectively show the detail of a taxel in the rest position and in the out-of-plane position,

FIGS. 3a and 3b respectively show the detail of a taxel in the rest position and in the out-of-plane position in the case where the blade is a double spiral, FIG. 4 represents a sectional view in perspective of a taxel. with the presence of an elastic return means in the rest position, the taxels appearing in a solid part of a first under plate of shape-memory material, or piezoelectric or electro-magnetic or magnetostrictive and the return means contained in a part full of a second under plate elastic material mechanically secured to the first under plate. FIG. 5 represents a perspective section of a taxel made in a solid part of a plate with presence of a return means towards a rest position consisting of a shape memory material having a memory shape that is antagonistic to the form stored in the plane. FIG. 6 represents a set of 4 taxels intended to show modes of thermal separation between adjacent taxels of a monolithic key plate. FIG. 7 represents a perspective view of another embodiment with the presence of an elastic return means, applicable in particular to the case where the tactile sensation is obtained in vibratory mode by a piezoelectric material; FIG. 8a is an exemplary embodiment in which the taxel blade indirectly causes the tactile sensation to change, The blade being used only as a driving element of another element, FIG. 8b is an exemplary embodiment in which the taxel blade is a guiding element of a rod itself actuated by a coil magnet assembly,

FIGS. 8c and 8d show implementation details for producing bistable or multi stable taxels respectively. FIG. 9 represents an exploded perspective view of an example of a tactile display device in the form of two layers or of two plates superimposed on each other, a touch plate and a plate carrying an addressing circuit. ,

FIG. 10 represents an exploded view of an exemplary embodiment in the form of several superimposed layers or plates, a touch plate comprising magnetic field sensitive blades, a coil layer or plate, and a circuit addressing the coils in the form of one or more layers.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 1 represents a plate 10 having an upper surface 10a comprising a set of taxels 25. The taxels 25 are constituted in a network, for example regular matrix, in rows and columns as shown in FIG. 1. The distance separating a center 24 a taxave of the center 24 of an adjacent taxel is typically of the order of mm. This resolution substantially represents the mechanical resolution in humans at the fingertips. According to the invention each of the taxels 25 is formed by a spiral-shaped blade 23, that is to say a blade whose central longitudinal line rotates from a peripheral portion to a center 24. Each point of intersection between this central longitudinal line and a radius coming from the center 24 is closer to the center 24 than the intersection point of the previous round. In Figure 1 each taxel blade has a circular spiral shape. This form is not mandatory. The spiral could have any other form of spiral, for example square, oval or other. In Figs. 2a and 2b which show an enlarged perspective view of an isolated taxel in the idle state and in the working state respectively, the blade 23 has a circular spiral shape. The rest form of a taxel blade 25, for example made of shape memory alloy (AMF), is the shape in which the blade 23 is in the plane of the plate 10. The form of work is the stored form in which the blade 23 is out of plane. Each of the blades 23 is formed by cutting an event 14, itself in the form of a spiral. A non-central end 26 of the blade 23 is connected to a solid part of the plate 10 by a junction 26 constituting an anchoring arm of the blade 23. In the rest position, the blade 23 is as shown in FIG. 2a in FIG. local plane of the plate 10. In the working position, the blade 23 is as shown in Figure 2b outside the local plane of the plate 10. It thus has a relief that is used to give a tactile sensation.

In a second embodiment, the blade 23 of each of the taxels 25 has a double spiral shape. A taxel 25 according to this embodiment is shown in Figure 3a in the rest position and Figure 3b in the working position. The spiral formed by the blade

23 is said to be double because a path along a central longitudinal line of the blade, from a first connecting arm 26 between a peripheral portion of the blade and a solid portion of the plate, is directed towards the center 24 of the blade, present at the center

24 a cusp and returns to a second connecting arm 27 between a peripheral portion of the blade and a solid portion of the plate.

The arms 26, 27 which are on peripheral portions of the blade keep a fixed position in the plane of the plate 10, whatever the state in the plane or out of plane of the blade 23. As a result, electrical connections between the first and second arms 26 and an addressing circuit, respectively, are fixed.

In the forms represented in FIGS. 2a, 2b or 3a, 3b, the taxels 25 may be formed in a touch plate 10 made of single or double-sided shape memory material, in a piezoelectric material, for example a piezoelectric ceramic, an electrostrictive material for example an electrostrictive ceramic or in a magnetostrictive material.

When the plate 10 or one of the sub plates or layers constituting it is in shape memory material, the transition from the rest form to the working form is provided by heating. This is done, for example, by passing a current directly through the shape memory material blade 23 or by using a nearby thermistor or heating resistor heated by conduction or radiation, or by any other heat source. and in particular a laser beam.

When the plate 10 or one of the sub-plates or layers constituting it is made of piezoelectric material, for example a piezoelectric ceramic, or an electrostrictive material, for example an electrostrictive ceramic, a relief deformation can be applied by applying a voltage between an upper part and a lower part of the layer of this material.

The form of rest is a form in which the blade 23 receives a low or zero voltage. The form of work is a form in which the blade 23 receives a variable voltage, for example alternative, causing a vibratory effect that can be felt tactilely.

Magnetostriction allows direct actuators "high torque high speed" without going through a gearbox. Alloys such as iron-cobalt can be deposited on a substrate as in the previous piezoelectric case. A magnetic field is necessary to reorient the magnetic dipoles and generate deformations. These individual magnetic fields must be close to each magnetostrictive tax. An exemplary embodiment of such fields will be explained later.

In the embodiments applicable to display devices comprising taxels comprising blades 23 made of single-sided shape memory material, or piezoelectric material, or electrostrictive material or magnetostrictive materials such as those represented for example in FIGS. 2a, 2b or 3a, 3b, a return means of the blade 23 of a taxel 25 from its off-plan position to its position in the plane is necessary. It is not when the material is two-way shape memory.

In a first embodiment, with the presence of a return means, the return means results from the fact that the shape memory material is a two-way material. The return to the flat position, low temperature position in this case, is achieved by a heat treatment performed beforehand which generates what is defined by the two-way effect in shape memory alloys. So the modes embodiment shown in one of FIGS. 2a, 2b; 3a, 3b, correspond to embodiments with return which can be realized with plates 10 of shape memory material in two directions. In a second variant embodiment, with the presence of a return means, the return to the plane position is accelerated by the presence of an elastic return means 28. This means with elastic return is applicable to cases where the material constituting the one of the plates of the plate of the plate 10 is a shape memory or piezoelectric or electrostrictive or magnetostrictive material.

In one embodiment of this variant with the presence of an elastic return means 28, shown in FIG. 4, the elastic means is a spring 28 which has the same dimensions as the active blade 23. In this case, the key plate 10 is in the form of a bilayer plate, a first under plate 11 of shape memory material, or piezoelectric or electrostrictive or magnetostrictive, and a second under plate 12 of mechanically secured elastic material the first under plate 11. In the example shown in Figures 4 the spring 28 is cut in the same way as the blade 23. In particular, the centers 20 of the spring 28 on the plate 12 and 24 of the blade 23 of the first under plate 11 are located one below the other and are mechanically secured to one another.

In another embodiment of this variant embodiment with the presence of a resilient biasing means 28, the passive spring 28 has, for reasons of rigidity and return force, a spiral geometry different from that of the active blade 23. In this case the two sub plates 11 and 12 are not fully mechanically secured to each other and only a point welding, for example, provides a mechanical connection between the center 24 of the blade 23 of shape memory material or piezoelectric or electrostrictive or magnetostrictive and the center 20 of the spring 28 cut in the sub plate 12. This other embodiment this second variant has not been shown.

The spring 28 is made of a passive material having interesting elastic characteristics, for example a spring steel. In another embodiment with the presence of a biasing means, the return is provided by a shape memory material having a memorized shape antagonistic to that of the blade 23. Such an embodiment is shown in FIG. case, the key plate 10 is in the form of a bilayer plate, a first under plate 11 of shape memory material and a second under plate 13 of shape memory material also mechanically secured to the first sub plate 11 In the example shown in FIGS. 5, a return spiral blade 29 is cut in the second sub-plate 13, in the same way as the blade 23 in the first sub-plate 11.

Preferably in this embodiment with return to the rest position by a blade 29 of shape memory material, of memorized form antagonistic to that of the active blade 23, the two sub plates 11, 13 are separated from one another by a thermal insulator. In this way, it is possible to independently heat the active blade 23 and the return blade 29. This embodiment is particularly well suited to the case shown in FIGS. 3a, 3b where the spiral is double, since an addressing circuit then comprises a common track. feeding one of the ends of one of the heating means of one of the blades 23 or 29 of the same taxel 25, and tracks independent of each other for the other end of each of the heating means of said taxel 25. The heating means of the blades 23 and 29 respectively can thus be powered independently of one another.

In a first mode of thermal separation of the blades 23 and 29 of the same taxel 25 shown in FIG. 5, a heat-insulating layer 30, for example made of polymer, is introduced between the two sub-plates 11 and 13. through the insulating layer 30 allow a common power supply of an electrically common end, a heating means of both blades 23, 29.

In a second mode of thermal separation not shown, the sub plates 11, 13 are thermally insulated from one another by a set of thermally insulating balls arranged between the centers of each blade 23 and each blade 29 of a single taxel 25. Optionally for all modes in which the keyplate taxels 10 respond to a thermal effect the key surface 10a is covered by a thermally insulating layer 50, shown in FIG. 3a, so as not to directly heat the fingertip.

It is advantageous when a blade 23 is heated to its transformation temperature from the martensite state to the austenite state to go from the in-plane position to the out-of-plane position, than the heat flow of a blade feed. 23 is not transmitted to the slides 23 of the neighboring taxels 25, so as not to trigger an undesirable movement of the slides 23 of these taxels. It is therefore interesting to increase the thermal resistance between neighboring taxels. Figure 6 shows an illustration of this concept for four taxels 25 neighbors a monolithic plate 10 whose total number of taxels is not limited to the number of four shown in Figure 6. In order to increase the thermal path between taxels 25 consecutive neighbors one or preferably several grooves 21 are arranged between two consecutive taxels. The grooves 21 are arranged between consecutive taxels 25 so as to increase the thermal path between two blades 23 of consecutive taxels 25. Due to the presence of the grooves 21, the key plate 10 becomes more mechanically flexible which is sometimes an advantage when the finger comes to rest on the plate. The plate 10 deforms locally and conforms to the profile of the finger or any other body zone of contact and this will result in better tactile performance.

Another embodiment with the presence of an elastic return means 28, applicable in particular to the case where the tactile sensation is obtained by a piezoelectric material is shown in FIG.

In this embodiment, the key plate 10 is in the form of a three-layer material in which a layer 28 made of a material which has interesting elastic properties, for example steel, copper or Beryllium, is sandwiched between two layers. , 33 of piezoelectric material. This three-layer material can be produced in particular by deposition of a piezoelectric ceramic for example by sol-gel deposition technologies. When an electric field is applied to the two piezoelectric layers, it generates a bending deformation which causes an out-of-plane deflection. An exemplary embodiment will now be described in connection with Figure 8a in which the blade 23 indirectly causes the modification of the tactile sensation. The blade 23 is only used as a driving element of another element, for example a rod 22 mechanically connected to the blade, this other element 22 flush with or protruding from the touchpad 10 according to the state of the blade 23. In the case of indirect modification, it is this other element which constitutes the modification of the tactile sensation. The blade directly modifies the tactile sensation when it is the blade itself, possibly via a protection, which is in contact with the finger of a user.

In the embodiments which have just been described and in their variant embodiments, each blade 23 directly constitutes the modification of the tactile sensation.

In the example represented in FIG. 8a, the tactile display device according to the invention comprises a touch plate 10 formed of two sub-plates or layers 16, 17. The sub-plate 16 comprises, according to the invention, for each taxel 25, a spiral blade 23 separated from a solid portion of the sub plate 16 by a recess 14. The rod 22 is fixed to the center 24 of the blade 23. The rod 22 is perpendicular to the local plane of the sub plate 16. The sub-plate 17 is superposed and mechanically secured to the sub-plate 16. The sub-plate 17 comprises, facing each taxel of the sub-plate 16, a cavity 18 of sufficient size to accommodate the blade 23 when it is in its off position. plan. In the preferred embodiment, the cavity 1-8 has a substantially frustoconical shape. A through hole 19 occupies the narrow bottom of the cavity 18, allowing the passage and guiding of the rod 22. The upper surface 15a of the key plate 15, formed by the upper surface of the sub plate 17 is the touch surface .

This embodiment with the addition of a rod 22 to the center 24 of each blade 23 is compatible with each of the embodiments which have been described above. The operation is as follows: When no bias is applied to the blade 23, the rod 22 is housed entirely in the hole 19, or partially in the hole 19 and partially in the cavity 18, so that the rod does not exceed of the upper surface 17a of the key plate 10.

When the blade 23 is deformed by applying a heater if the material forming the sub plate 16 is a shape memory material, or by applying an electric field if it is a piezoelectric or electrostrictive material or by application of a magnetic field if it is a magnetostrictive material, the rod 22 is pushed upwards so as to constantly or periodically exceed the surface 17a of the sub plate 17, thus modifying the tactile sensation at level of this surface.

In the examples just described, the blade 23 has an active role as it is the blade that is deformed under the action of a physical phenomenon. It eventually leads to a pin 22. It will be described below in connection with Figure 8b cases in which the blade 23 serves as a guide element to a rod or pin 22 which serves as a tactile pin. In this case the blade is cut as previously described in a solid part of a plate 10 forming the touch plate. In this case the material constituting said plate is of elastic material, for example spring steel or beryllium copper. A pin 22 which constitutes a pusher has a first end 22a mechanically linked to the center 24 of a blade 23. The flexible guide allows large displacements without exceeding the elastic zones of the material constituting the blade. The pin 22 has a second end mechanically connected to a magnet 57 whose movement towards the key plate 10 or away from it is provided by the direction of a current flowing in a coil 31 associated with each pin 22. An intermediate guide plate 52 is preferably inserted between the key plate and a plate 3 carrying the coils 31. The pin does not necessarily as shown in Figure 8b, the shape of a rod. It may have as shown in Figure 8c, and 8d, a shape having cross sectional dimensional variations, narrower sections forming lock position stops. Thus, FIG. 8c, the rod 22 have two bulges 53, 54 separated from each other by a narrow portion 55. In the locked position of the elastic blades 51 formed around a passage of the rod 22 through the plate 52 abut on the narrow portion 55. In Figure 8d the rod 22 has a bulge 54 and the intermediate plate 52 has in its thickness notches 56. Each notch 56 is in connection with the bulge 54 a locking position of the rod 22.

The operation is as follows: Each rod or pin 22 is suspended from a blade 23 of the key plate. According to the direction of a current flowing in the coil 31 the rod has a high position pushing the blade 23 out of plane or a low position bringing it back into the plane.

Embodiments of the addressing circuit for selectively applying heating currents or voltages or magnetic fields to the pixels of the touch pad 10 will now be described in connection with FIGS. 9 and 10.

For a simple spiral like that shown in FIGS. 2a, 2b, for delivering a current to a blade 23 of shape-memory material or a thermistor or a heating resistor deposited on the blade 23, a mobile power supply connection for example in the form of a conductive wire is fixed, for example at the center 24 of the blade 23. This connection electrically connects a first end 26 of the blade shape memory material or the thermistor or the heating resistor in the opposite case to an end 45 of a track 41, 44 of an addressing circuit 4 which will be briefly described below.

As shown in FIG. 9, the addressing circuit 4 can be made in the form of a printed circuit 4, comprising tracks 41-44 each connecting an outer edge of the circuit to a position corresponding to a center 24 of a taxel 25. The tactile display device is then in the form of two layers or two plates 4, 10 superimposed on one another as shown in exploded perspective FIG. 9. The operation is as follows. A controller not shown, connects edge ends of the tracks 41-44, according to patterns to be represented on the key plate 10 to a power source not shown. A current then flows from the selected track to the heating element blade 23 which corresponds to each of the selected tracks. The return of the current is ensured by a common mass. When the selected blades 23 have reached their transformation temperature, said blades recover their out-of-plane shapes stored together, thus constituting together the pattern to achieve.

An addressing circuit 4 such as that shown in FIG. 9 can also be used to address voltages if the blades 23 are cut from a plate of piezoelectric material, or electrostrictive. In this case the connections 45 are connected to a control electrode applied to the material of the blade 23. Another electrode is connected to a constant potential.

In the case where the material constituting the plate is a magnetostrictive material, it is necessary to apply a selective magnetic field to each taxel. In order to create this variable magnetic field, a circuit 3 of coils 31 is interposed between the addressing circuit 4 and the touch pad 10.

In the case where the material constituting the plate is a magnetic material and where the blades 23 are cut in this material, a tactile effect vibration is obtained by applying an alternating current to the coils 31.

Figure 10 shows an exploded view of an exemplary embodiment of this embodiment. This figure shows a layer 3 of flat coils 31 and three layers 46-48 together forming a multilayer addressing printed circuit 4. In the representation of FIG. 10, the layer 3 of coils 31 has a purpose of simplification. of the representation, only eight columns of eight lines of coils 31. The addressing takes place through tracks 41-44 of the multilayer circuit 4 which come into contact with the center of the coils. Each of the coils 31 can therefore be addressed independently. This configuration of the addressing circuit 4 is of great interest when the number of coils 31 and corresponding taxels 25 is very high.

Claims

1) A tactile display device comprising: a key plate (10) having a key surface (10a),

a network of taxels (25) formed in solid portions of the touchpad or in solid portions of a sub-plate (11) forming part of the touchpad (10), each taxel (25) having a blade (23) capable of at least two states, the passage from one of the states to the other directly or indirectly causing the modification of the tactile sensation,

means (23, 31, 4) for selectively modifying the state of slats (23) of taxels (25), said means comprising addressing means (4) and means (23) for modifying the tactile sensation of taxels (25), characterized in that each taxel blade (23) has a spiral shape, bordered on both sides by a spiral-shaped recess (14).

2) A touch display device according to claim 1 characterized in that each blade (23) taxel (25) has a double spiral shape

3) A tactile display device according to one of claims 1 or 2 characterized in that the plate (10) or a sub plate (11) constituting with at least another sub plate the key plate (10) and the slats (23) of taxels (25) are made of a shape memory material, each slat (23) being a function of its temperature capable of two states, a first state in which the slat is in the local plane of the plate (10) or subplate (11), and a second state in which the blade is deformed out of plane, thereby causing a tactile sensation of relief.

4) A touch display device according to claim 3 characterized in that the shape memory material in which the plate (10) or the sub plate (11) and the blades (23) are made is two-way.

5) A tactile display device according to one of claims 3 or 4 characterized in that the plate (10) of key is formed of two sub plates (11, 12, 13), parallel to each other, a sub plate (11). ) of shape memory material comprising the network of taxels (25) and a sub-plate (12) of elastic material, the sub-plate (12) of elastic material corresponding to each taxel

(25) of the sub-plate (11) of shape memory material, a leaf spring (28) separated from a solid part of the sub-plate (12) by one or more recesses and connected to it by one or more arms each leaf spring (28) of the underplate (12) of elastic material having a rigid mechanical connection with the spiral blade (23) of the taxel (25) corresponding thereto so as to exert on this blade (23) of a taxel (25) a restoring force, when this taxel blade (23) is in its off plan state.

6) A tactile display device according to one of claims 3 or 4 characterized in that the plate (10) of key is formed of two sub plates (11, 13), parallel to each other, a sub plate (11) in shape memory material comprising the network of taxels (25) and a sub-plate (13) for return also made of shape memory material, the sub plate (13) for recall corresponding to each taxel (25) of the sub plate (11) of shape memory material comprising the taxels network (25), a blade (29) separated from a solid part of the plate under (13) for returning one or more recesses and ^one connected to it by one or more arms (26, 27), each blade (29) of the return plate (13) depending on its temperature in a rest position or in a memorized position, each blade (29) of the under plate (13) comprising a rigid mechanical connection with the spiral blade (23) of the taxel

(25) corresponding thereto, so that in a memorized position the blade (29) of the subplate (13) of return on the blade (23) of the taxel (25) which corresponds to it a restoring force tending returning said taxel blade (23) from its out-of-plane state to its rest state.

7) A touch display device according to claim 6 characterized in that a thermally insulating layer (30) separates from one another the under plates (11, 13) of shape memory material, the rigid mechanical connection between a blade (29) of the underplate (13) of return and the blade (23) of taxel

(25) corresponding thereto comprising a thermally insulating element rigidly mechanically connected to a portion (24) of the taxel blade (23) and to a portion of the blade (29) of the return plate (13) .

8) A tactile display device according to one of claims 3 to 7 characterized in that grooves (21) are present on the solid parts of the plate (10) or sub plates (11, 13) of memory material shape forming together the key plate (10) in spaces between two blades.

9) A touch display device according to one of claims 1 or 2 characterized in that the touch plate (10) comprises a bilayer material comprising a layer (12) of an elastic material a layer (11) of piezo material electric.

10) A tactile display device according to one of claims 1 or 2 characterized in that the key plate (10) is constituted by a three-layer material comprising a layer (12) of an elastic material between two layers (32, 33) of piezoelectric material. 11) A touch display device according to one of claims 1 or 2 characterized in that the touch plate (10) is constituted by a bilayer material comprising two layers of piezoelectric material.

12) A touch display device according to one of claims 1 or 2 characterized in that the touch plate (10) comprises a layer of a magnetostrictive material or an electrostrictive material.

13) A tactile display device according to one of claims 1 or 2 characterized in that the blade (23) taxel is a motor element of a rod (22) which constitutes at the level of the touch plate a modification of the tactile sensation.

14) A touch display device according to one of claims 1 or 2 characterized in that the blades (23) are mechanically connected to a rod (22) itself mechanically connected to a magnet (57).

15) A tactile display device according to one of claims 13 or 14 characterized in that it further comprises an intermediate plate (52) of deformable material having passages for the rods (22), in that the rods are with bulging parts (53, 54) and narrow parts (55), those bulging and narrow portions (53, 54, 55) co-operating with internal shapes of the passages for holding the rod in one or more predefined positions.