EP1565806A2 - Proximity detection-display device and method of using said device - Google Patents

Proximity detection-display device and method of using said device

Info

Publication number
EP1565806A2
EP1565806A2 EP03796061A EP03796061A EP1565806A2 EP 1565806 A2 EP1565806 A2 EP 1565806A2 EP 03796061 A EP03796061 A EP 03796061A EP 03796061 A EP03796061 A EP 03796061A EP 1565806 A2 EP1565806 A2 EP 1565806A2
Authority
EP
European Patent Office
Prior art keywords
electrode
high frequency
frequency signal
generating
control signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03796061A
Other languages
German (de)
French (fr)
Inventor
Pierre Thales Intellectual Property FAGARD
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
InterDigital CE Patent Holdings SAS
Original Assignee
Thales SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thales SA filed Critical Thales SA
Publication of EP1565806A2 publication Critical patent/EP1565806A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0412—Digitisers structurally integrated in a display
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/13338—Input devices, e.g. touch panels
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
    • G06F3/0443—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a single layer of sensing electrodes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/96—Touch switches
    • H03K17/962—Capacitive touch switches

Definitions

  • Proximity detection display device and method of using this device
  • the invention relates to a display device comprising proximity detection means and to a method of using this device.
  • Such devices are used in particular for producing communication terminals of the type enabling an operator to transmit and receive information within the framework of a user-friendly exchange with a processor.
  • the invention finds a particular application for the screens of interactive terminals comprising screens with liquid crystals, with plasma, with light-emitting diodes or with emission by field effect.
  • Known screens have two plates, at least one of which is transparent. Between these plates are liquid crystal molecules. To excite the liquid crystal molecules and change the polarity of a light ray passing through them, the screen includes transparent electrodes located on the internal faces of the two plates. One of these electrodes is commonly called a counter electrode.
  • a control signal generally low frequency, is applied between the electrodes to excite the liquid crystal molecules and thus obtain the desired display.
  • European patent EP 0 340 096 proposes to use the surface of the counter-electrode of a liquid crystal screen to replace added tactile layers.
  • This counter electrode has a large surface in relation to the surface of the operator's finger, which is well suited to the detection of a finger by capacitive effect.
  • such a screen allows the display of numeric characters each composed of seven segments which can be either on or off.
  • a counter electrode of this type of screen generally covers one or more predefined locations of characters.
  • Patent EP 0 340 096 describes the application of a high frequency signal to the counter-electrode.
  • the high frequency signal is attenuated by the presence of a user's finger near the screen and facing the counter-electrode. The detection of the attenuation of the high frequency signal makes it possible to detect the presence of the finger.
  • Patent EP 0 340 096 describes the independent application of the control signal and the high frequency signal so as not to disturb each other; this independent application requires interrupting one of the signals to apply the other. This does not allow the display to be changed and the presence of the finger to be detected simultaneously.
  • the invention aims to overcome this problem by proposing means making it possible to simultaneously apply the control signal and the high frequency signal.
  • the subject of the invention is an electronic display device comprising means for detecting the proximity of a conductive element located near a display area of the device, the device comprising two insulating plates, a layer of material having electro-optical properties capable of making all or part of its surface visible under the effect of an electrical control signal, the layer being disposed between the two plates, at least one first electrode disposed on one face of one of the insulating plates, a second electrode disposed on one face of the other insulating plate opposite at least one first electrode, means for generating an electrode control signal as a function of an image to be displayed on the area d display, means for generating a high frequency signal applied to the second electrode, means for detecting a possible modification of the high frequency signal, characterized é in that the device further comprises means for mixing the high frequency signal and the control signal arranged so as to allow the operation of the proximity detection means independently of the operation of the means for generating a control signal.
  • the invention also relates to a method of using the device described above, characterized in that the means for generating a control signal provide a periodic signal comprising positive and negative alternations, in that the means for generating a high frequency signal inject a high frequency signal in substantially equal quantity during as many positive alternations as negative alternations of the signal ordered.
  • the invention is particularly suitable for static display devices of the dedicated type or weakly multiplexed. Indeed, these types of displays do not include an electronic switch made directly on the electrodes allowing the display. In the presence of such a switch on an electrode, its opening makes it possible to raise the impedance of this electrode and to apply the high frequency signal to the counter-electrode situated opposite.
  • the invention overcomes this problem by controlling the mixing of the high frequency signal of the control signal which allows the operation of the proximity detection means independently of the operation of the means for generating a control signal.
  • FIG. 1 shows in section a dedicated display device
  • FIG. 2a and 2b show an example of electrodes of a display device according to the invention
  • FIG. 3 shows a schematic modeling of the operation of a display device comprising a liquid crystal screen
  • FIG. 4 schematically shows a display device according to the invention
  • FIG. 5 shows an advantageous alternative embodiment of one of the electrodes of a dedicated display device
  • FIG. 6 represents a schematic modeling of the operation of a display device comprising the electrode shown in FIG. 5.
  • the display device shown in Figure 1 comprises two insulating plates 1 and 2 arranged one above the other. At least one of the two plates 1 or 2 is transparent.
  • the device also comprises a layer 3 made of a material having electro-optical properties capable of transmitting or not light radiation under the effect of an electrical excitation. This material comprises for example liquid crystal.
  • the device comprises two first electrodes 4 and 5 having for example the shape of a pictogram. These first two electrodes are arranged on one side 6 of the insulating plate 2.
  • the device further comprises a second electrode 7, also called counter electrode 7, disposed on one side 8 of the other insulating plate 1.
  • the layer 3 is disposed between the faces 6 and 8 of the two insulating plates 1 and 2. The faces 6 and 8 are the faces of the plates closest to the layer 3.
  • the second electrode 7 is arranged opposite the first two electrodes 4 and 5 so that a control signal applied between one of the first electrodes and the second electrode 7 modifies the state of the liquid crystal between the electrodes.
  • FIG. 2a represents an example of a pictogram produced using electrodes 4 and 5.
  • the pictogram of electrode 4 represents three concurrent arrows and the pictogram of electrode 5 represents a seated human silhouette. These two pictograms can represent, for example, the state of ventilation in a motor vehicle.
  • the electrode 4 is electrically connected by a pad 9 to a connection pad 10.
  • the same is true for the electrode 5 which is connected by a pad 11 to a connection pad 12.
  • the pads 10 and 12 make it possible to apply the control signal of the device to electrodes 4 and 5.
  • the pads 10 and 12 are located on an edge 16 of the device.
  • FIG. 2b represents the electrode 7 and its electrical connection range 14. The range 14 makes it possible to supply the electrode 7 by a stud 15 located on the edge 16 of the device.
  • an outer contour 17 of the electrode 7 is substantially oval.
  • the electrode 7 When the electrode 7 is placed opposite the electrodes 4 and 5, the latter are situated inside the contour 17. In other words, the electrode 7 completely covers the electrodes 4 and 5. Thus the surface of the electrode 7 is greater than or equal to the sum of the surfaces of the electrodes 4 and 5.
  • the electrode 7 To ensure correct operation of the proximity detection by capacitive effect, the electrode 7 must have an area of at least 9 mm 2 . The capacitive effect is obtained by placing a user's finger on the device opposite the electrode 7. A capacitor is then created between the electrode 7 and the finger.
  • a high frequency electrical signal for example 2 MHz
  • the electrode 7 is clipped opposite the areas 9 and 10. More specifically, the change in state of the liquid crystal is obtained by applying a low frequency control signal, for example at 100 Hz, on the one hand l 'electrode 7 and on the other hand at least one of the electrodes 4 or 5.
  • the areas 9 and 11 are partly opposite the electrode 7 or more precisely inside the contour 17 of the electrode 7. If l electrode 7 completely occupies the surface located inside the contour 17, the parts of areas 9 and 11 opposite electrode 7 are then visible at the same time as the pictograms formed by electrodes 4 and 5. To overcome this fault and only show the pictograms, electrode 7 is deflected opposite the ranges. A clipping 18 is clearly visible in FIG. 2b.
  • the two figures 2a and 2b are shown on the same scale and by superimposing them, the clipping 18 covers the part of the pads 9 and 11 located inside the contour 17. This superposition prefigures the arrangement of the electrodes 4, 5 and 7 in the device.
  • FIG. 2b there is also another clipping 19 made in the electrode 7, allowing, once the electrodes 4, 5 and 7 superimposed visually the body 19 of the head 20 in the representation of the human silhouette produced using the electrode 5.
  • the device comprises several counter-electrodes 7.
  • each is supplied separately. More specifically, each has its own range 14 each leading to a separate pad 15.
  • FIG. 3 explains the operation of an elementary display cell formed by a first electrode, for example the electrode 4 and a second electrode 7 located opposite. Liquid crystal molecules are placed between the two electrodes 4 and 7 and form an insulating material a few ⁇ m thick. The two electrodes then form a capacitance Cpsb also called capacitance of the elementary cell LCD.
  • the electrical connection of the first electrode 4 is provided by the range 9 forming a resistance Rlss whose value is advantageously adapted by etching the supply range 9 of the first electrode 4. More specifically, the value of the resistance Rlss is adapted by modifying the length and / or the width and / or the thickness of the supply area 9.
  • Capacitive losses in the electrical connection of the electrode 4 can be modeled by a capacitor Cp2 connected between a terminal of the resistor Rscs not connected to the pad 9 and the electrical ground.
  • the electrical connection of the second electrode 7 is provided by the pad 14 forming a resistance Rlsb. Capacitive losses in the electrical connection of the electrode 7 can be modeled by a capacity Cp1 connected between the end of the range 14 not connected to the electrode 7 and the ground 25. A capacity Cinj connected to the common point of the capacity Cp1 and range 14 makes it possible to inject a high frequency signal on the second electrode 7.
  • Figure 4 complements the elements described in Figure 3 by describing how a control signal and a high frequency signal are applied to the electrodes 4 and 5. More specifically, the device comprises means for generating the control signal 30 formed by an alternating source of low frequency voltage and connected between on the one hand the terminal of the resistor Rscs not connected to the resistor Rlss and on the other hand, the common point of range 14 and the Cinj injection capacity.
  • the means for generating the control signal 30 are, at their common points with the resistor Rscs, connected to ground 25 by means of a load impedance formed for example of a resistor R and a capacitor C connected in parallel. This impedance is an example of modeling the generator output impedance.
  • the device also comprises means for generating a high frequency signal 31 connected between earth 25 and the terminal of the injection capacity Cinj not connected to the pad 14.
  • Means 32 for detecting a possible modification of the high frequency signal are connected to the second electrode 7 via the resistor Rlsb and more precisely to the common point of the injection capacity Cinj and the resistor Rlsb.
  • the device comprises means for mixing the high frequency signal and the control signal.
  • These means include a resistor Rscb connected in series with the low frequency voltage source 30.
  • the value of the resistor Rscb is for example between 1 kilo-ohms and 100 kilo-ohms.
  • the value of the resistance Rscb is at least of the order of magnitude of the impedance of the injection capacitor Cinj at the frequency of the high frequency signal.
  • the value retained for the resistance Rscb will not be less than about 5 kilo-ohms.
  • the resistance value Rlsb of the supply range 14 of the electrode 7 is less than 5 k ohms in order to limit the attenuation of the signals received by the electrode 7.
  • the value of the resistance Rlss is adapted so that a time constant ⁇ formed by the capacitance Cpsb and the resistance Rlss is at least an order of magnitude smaller than a control signal period.
  • a control signal period We mean by an order of magnitude smaller, about ten times smaller.
  • the control signal will have a much higher voltage across the terminals of the capacitor Cpsb than across the terminals of the resistor Rlss.
  • the resistance Rlss can be supplemented by the additional resistance Rscs. In this case, account should be taken of the two resistances Rlss and Rscs for the calculation of the time constant ⁇ .
  • the value of the time constant is greater than or equal to a period of the high frequency signal.
  • the high frequency signal will have a much higher voltage at the terminals of the resistor Rlss, possibly supplemented by the additional resistor Rscs, than at the terminals of the capacitor Cpsb.
  • the LCD cell will be little disturbed by the application of the high frequency voltage.
  • the device comprises at least two electrodes 4 and 5 of different surface arranged opposite a second electrode 7, the value of the resistance Rlss, possibly supplemented by the additional resistance Rscs, of each electrode 4 or 5 increases with l inverse of the surface of the electrode 4 or 5 considered.
  • the invention also relates to a method of using a device described above, method in which the means for generating a control signal 30 provide a periodic signal comprising positive and negative alternations.
  • the means for generating a high frequency signal 31 inject a high frequency signal at a substantially equal amount during as many positive and negative alternations of the control signal 30 This makes it possible to avoid possible asymmetries in the application of the signal high frequency to the LCD cell. Indeed, such a cell can be damaged if a DC voltage component is applied across its electrodes, a DC component resulting from the asymmetrical application of a signal.
  • the high frequency signal is interrupted during the switching between the positive and negative half-waves of the control signal 30.
  • the duration and / or the amplitude of the high frequency signal delivered by the means for generating a high frequency signal 31 is such that the effective value of the high frequency signal is less than a threshold voltage of layer 3.
  • the threshold voltage of layer 3 as a voltage capable of changing the state of the liquid crystal, of passing it from a transparent state to an opaque state or vice versa. More precisely, the threshold voltage depends on the components of the cell itself and also on the cell multiplexing rate. In the case of a device comprising several cells, the smallest threshold voltage will be that of the cell having the smallest time constant ⁇ .
  • the amplitude of the high frequency signal acts directly on the effective value of the high frequency signal and the duration of the high frequency signal is understood to mean the duration within an alternation of the control signal as well as the number of alternation of the control signal where the high frequency signal appears.
  • FIG. 5 represents an advantageous alternative embodiment of one of the electrodes of a dedicated display device.
  • the resistor Rscb connected in series with the low-frequency voltage source 30, is advantageously produced by taking advantage of the natural resistance of an additional area 51 for connection of the electrode 7.
  • the area 51 is distinct from the pad 14 and connects the electrode 7 to the low frequency voltage source 30 via a pad 52 located on the edge of the device.
  • the pad 52 is distinct from the pad 15.
  • the value of the resistance Rscb is advantageously adapted by etching the area 51 of the electrode 7.
  • FIG. 6 represents a schematic modeling of the operation of a display device comprising the electrode 7 represented in FIG. 5.
  • the variant embodiment represented with the aid of FIGS. 5 and 6 makes it possible to dispense with mixing means made outside of the display and use the design of the electrode 7 to produce these mixing means.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Human Computer Interaction (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Liquid Crystal (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Position Input By Displaying (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

The invention relates to a display device comprising proximity-detection means and to the method of using said device. The inventive device consists of: a liquid crystal layer (3); at least two electrodes (4, 5 and 7) which can be used to excite the liquid crystal; means of generating an electrode-control signal (30); means of generating a high-frequency signal (31) which is applied to the second electrode; and means of detecting any alteration in the high-frequency signal (32). The device also comprises means of mixing (Rscb) the high-frequency signal and the control signal. According to the inventive method, the control signal (30)-generating means supply a periodic signal comprising positive and negative half-waves and the high-frequency signal (31)-generating means inject an essentially equal quantity of a high-frequency signal during as many positive half-waves and negative half-waves of the control signal (30).

Description

Dispositif d'affichage à détection de proximité et procédé d'utilisation de ce dispositif Proximity detection display device and method of using this device
L'invention se rapporte à un dispositif d'affichage comportant des moyens de détection de proximité et à un procédé d'utilisation de ce dispositif. On utilise de tels dispositifs notamment pour la réalisation de terminaux de communication du type permettant à un opérateur de transmettre et de recevoir des informations dans le cadre d'un échange convivial avec un processeur. L'invention trouve une application particulière pour les écrans des terminaux interactifs comportant des écrans à cristaux liquides, à plasma, à diodes électroluminescentes ou à émission par effet de champ. Des écrans connus comportent deux plaques dont l'une au moins est transparente. Entre ces plaques on dispose des molécules de cristal liquide. Pour exciter les molécules de cristal liquide et modifier la polarité d'un rayon lumineux qui les traverse, l'écran comporte des électrodes transparentes situées sur des faces internes des deux plaques. L'une de ces électrodes est communément appelée contre-électrode. On applique un signal de commande, en général basse fréquence, entre les électrodes pour exciter les molécules de cristal liquide et ainsi obtenir l'affichage souhaité.The invention relates to a display device comprising proximity detection means and to a method of using this device. Such devices are used in particular for producing communication terminals of the type enabling an operator to transmit and receive information within the framework of a user-friendly exchange with a processor. The invention finds a particular application for the screens of interactive terminals comprising screens with liquid crystals, with plasma, with light-emitting diodes or with emission by field effect. Known screens have two plates, at least one of which is transparent. Between these plates are liquid crystal molecules. To excite the liquid crystal molecules and change the polarity of a light ray passing through them, the screen includes transparent electrodes located on the internal faces of the two plates. One of these electrodes is commonly called a counter electrode. A control signal, generally low frequency, is applied between the electrodes to excite the liquid crystal molecules and thus obtain the desired display.
Il est connu de réaliser des terminaux de communication interactifs en disposant sur le dispositif une ou plusieurs couches tactiles transparentes à contact ou à effet capacitif, inductif ou équivalent. Le dispositif peut alors servir à délimiter des zones d'appuis de cette plage selon une composition désirée. L'appui sur la couche se fait habituellement par un doigt d'un opérateur. Les inconvénients associés à ces procédés connus sont relatifs au coût du composant sensible ajouté sur l'écran et au fait que les informations visuelles fournies par le dispositif sont inévitablement altérées par les plages tactiles rapportées.It is known to produce interactive communication terminals by placing on the device one or more transparent tactile layers with contact or with capacitive, inductive or equivalent effect. The device can then be used to delimit support zones of this range according to a desired composition. The support on the layer is usually done by an operator's finger. The drawbacks associated with these known methods relate to the cost of the sensitive component added to the screen and to the fact that the visual information provided by the device is inevitably altered by the reported tactile areas.
Pour remédier à ce problème le brevet européen EP 0 340 096 propose d'utiliser la surface de la contre-électrode d'un écran à cristaux liquides en remplacement de couches tactiles rapportées. Cette contre- électrode a une surface importante en rapport avec la surface du doigt de l'opérateur, ce qui convient bien à la détection d'un doigt par effet capacitif. A titre d'exemple, un tel écran permet l'affichage de caractères numériques composés chacun de sept segments qui peuvent être soit allumés ou éteints. Une contre-électrode de ce type d'écran recouvre en général un ou plusieurs emplacements prédéfinis de caractères.To remedy this problem, European patent EP 0 340 096 proposes to use the surface of the counter-electrode of a liquid crystal screen to replace added tactile layers. This counter electrode has a large surface in relation to the surface of the operator's finger, which is well suited to the detection of a finger by capacitive effect. By way of example, such a screen allows the display of numeric characters each composed of seven segments which can be either on or off. A counter electrode of this type of screen generally covers one or more predefined locations of characters.
Le brevet EP 0 340 096 décrit l'application d'un signal haute fréquence à la contre-électrode. Le signal haute fréquence est atténué par la présence du doigt d'un utilisateur à proximité de l'écran et en regard de la contre-électrode. La détection de l'atténuation du signal haute fréquence permet de détecter la présence du doigt.Patent EP 0 340 096 describes the application of a high frequency signal to the counter-electrode. The high frequency signal is attenuated by the presence of a user's finger near the screen and facing the counter-electrode. The detection of the attenuation of the high frequency signal makes it possible to detect the presence of the finger.
Le brevet EP 0 340 096 décrit l'application indépendante du signal de commande et du signal haute fréquence afin de ne pas se perturber l'un l'autre ; cette application indépendante nécessite d'interrompre un des signaux pour appliquer l'autre. Ceci ne permet pas de modifier l'affichage et de détecter la présence du doigt simultanément.Patent EP 0 340 096 describes the independent application of the control signal and the high frequency signal so as not to disturb each other; this independent application requires interrupting one of the signals to apply the other. This does not allow the display to be changed and the presence of the finger to be detected simultaneously.
L'invention vise à pallier ce problème en proposant des moyens permettant d'appliquer simultanément le signal de commande et le signal haute fréquence.The invention aims to overcome this problem by proposing means making it possible to simultaneously apply the control signal and the high frequency signal.
A cet effet, l'invention a pour objet un dispositif d'affichage électronique comprenant des moyens de détection de proximité d'un élément conducteur situé à proximité d'une zone d'affichage du dispositif, le dispositif comportant deux plaques isolantes, une couche de matériau présentant des propriétés électro-optique aptes à rendre visible tout ou partie de sa surface sous l'effet d'un signal de commande électrique, la couche étant disposée entre les deux plaques, au moins une première électrode disposée sur une face d'une des plaques isolantes, une seconde électrode disposée sur une face de l'autre plaque isolante en regard d'au moins une première électrode, des moyens pour générer un signal de commande des électrodes en fonction d'une image à afficher sur la zone d'affichage, des moyens pour générer un signal haute fréquence appliqué à la seconde électrode, des moyens pour détecter une éventuelle modification du signal haute fréquence, caractérisé en ce que le dispositif comporte en outre des moyens de mixage du signal haute fréquence et du signal de commande disposés de telle sorte à permettre le fonctionnement des moyens de détection de proximité indépendamment du fonctionnement des moyens pour générer un signal de commande.To this end, the subject of the invention is an electronic display device comprising means for detecting the proximity of a conductive element located near a display area of the device, the device comprising two insulating plates, a layer of material having electro-optical properties capable of making all or part of its surface visible under the effect of an electrical control signal, the layer being disposed between the two plates, at least one first electrode disposed on one face of one of the insulating plates, a second electrode disposed on one face of the other insulating plate opposite at least one first electrode, means for generating an electrode control signal as a function of an image to be displayed on the area d display, means for generating a high frequency signal applied to the second electrode, means for detecting a possible modification of the high frequency signal, characterized é in that the device further comprises means for mixing the high frequency signal and the control signal arranged so as to allow the operation of the proximity detection means independently of the operation of the means for generating a control signal.
L'invention a également pour objet un procédé d'utilisation du dispositif décrit précédemment, caractérisé en ce que les moyens pour générer un signal de commande fournissent un signal périodique comportant des alternances positives et négatives, en ce que les moyens pour générer un signal haute fréquence injectent un signal haute fréquence à quantité sensiblement égale pendant autant d'alternances positives que d'alternances négatives du signal de commande.The invention also relates to a method of using the device described above, characterized in that the means for generating a control signal provide a periodic signal comprising positive and negative alternations, in that the means for generating a high frequency signal inject a high frequency signal in substantially equal quantity during as many positive alternations as negative alternations of the signal ordered.
L'invention est particulièrement adaptée à des dispositifs d'affichage statiques de type dédié ou faiblement multiplexes. En effet, ces types d'afficheurs ne comportent pas d'interrupteur électronique réalisés directement sur les électrodes permettant l'affichage. En présence d'un tel interrupteur sur une électrode son ouverture permet d'élever l'impédance de cette électrode et d'appliquer le signal haute fréquence à la contre-électrode située en regard.The invention is particularly suitable for static display devices of the dedicated type or weakly multiplexed. Indeed, these types of displays do not include an electronic switch made directly on the electrodes allowing the display. In the presence of such a switch on an electrode, its opening makes it possible to raise the impedance of this electrode and to apply the high frequency signal to the counter-electrode situated opposite.
En l'absence d'interrupteur sur l'électrode, on peut moins facilement élever l'impédance de l'électrode et l'application du signal haute fréquence risque de modifier l'affichage.If there is no switch on the electrode, it is less easy to raise the electrode impedance and the application of the high frequency signal may change the display.
L'invention permet de pallier ce problème en maîtrisant le mixage du signal haute fréquence du signal de commande ce qui permet le fonctionnement des moyens de détection de proximité indépendamment du fonctionnement des moyens pour générer un signal de commande.The invention overcomes this problem by controlling the mixing of the high frequency signal of the control signal which allows the operation of the proximity detection means independently of the operation of the means for generating a control signal.
L'invention sera mieux comprise et d'autres avantages apparaîtront à la lecture de la description détaillée d'un mode de réalisation donnée à titre d'exemple, description illustrée par le dessin joint dans lequel :The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, description illustrated by the attached drawing in which:
- la figure 1 représente en coupe un dispositif d'affichage dédié ; - les figures 2a et 2b représentent un exemple d'électrodes d'un dispositif d'affichage conforme à l'invention ;- Figure 1 shows in section a dedicated display device; - Figures 2a and 2b show an example of electrodes of a display device according to the invention;
- la figure 3 représente une modélisation schématique du fonctionnement d'un dispositif d'affichage comportant un écran à cristaux liquides ; - la figure 4 représente schématiquement un dispositif d'affichage conforme à l'invention ;- Figure 3 shows a schematic modeling of the operation of a display device comprising a liquid crystal screen; - Figure 4 schematically shows a display device according to the invention;
- la figure 5 représente une variante avantageuse de réalisation d'une des électrodes d'un dispositif d'affichage dédié ; - la figure 6 représente une modélisation schématique du fonctionnement d'un dispositif d'affichage comportant l'électrode représentée sur la figure 5.- Figure 5 shows an advantageous alternative embodiment of one of the electrodes of a dedicated display device; FIG. 6 represents a schematic modeling of the operation of a display device comprising the electrode shown in FIG. 5.
Le dispositif d'affichage représenté sur la figure 1 comporte deux plaques isolantes 1 et 2 disposées l'une au-dessus de l'autre. Au moins l'une des deux plaques 1 ou 2 est transparente. Le dispositif comporte également une couche 3 réalisée dans un matériau présentant des propriétés électrooptiques aptes à transmettre ou non un rayonnement lumineux sous l'effet d'une excitation électrique. Ce matériau comporte par exemple du cristal liquide. Le dispositif comporte deux premières électrodes 4 et 5 ayant par exemple la forme d'un pictogramme. Ces deux premières électrodes sont disposées sur une face 6 de la plaque isolante 2. Le dispositif comporte en outre une seconde électrode 7, également appelée contre-électrode 7, disposée sur une face 8 de l'autre plaque isolante 1. La couche 3 est disposée entre les faces 6 et 8 des deux plaques isolantes 1 et 2. Les faces 6 et 8 sont les faces des plaques les plus proches de la couche 3. Ces faces sont encore appelées faces internes des plaques isolantes 1 et 2. La seconde électrode 7 est disposée en regard des deux premières électrodes 4 et 5 de telle sorte qu'un signal de commande appliqué entre l'une des premières électrodes et la seconde électrode 7 modifie l'état du cristal liquide entre les électrodes.The display device shown in Figure 1 comprises two insulating plates 1 and 2 arranged one above the other. At least one of the two plates 1 or 2 is transparent. The device also comprises a layer 3 made of a material having electro-optical properties capable of transmitting or not light radiation under the effect of an electrical excitation. This material comprises for example liquid crystal. The device comprises two first electrodes 4 and 5 having for example the shape of a pictogram. These first two electrodes are arranged on one side 6 of the insulating plate 2. The device further comprises a second electrode 7, also called counter electrode 7, disposed on one side 8 of the other insulating plate 1. The layer 3 is disposed between the faces 6 and 8 of the two insulating plates 1 and 2. The faces 6 and 8 are the faces of the plates closest to the layer 3. These faces are also called internal faces of the insulating plates 1 and 2. The second electrode 7 is arranged opposite the first two electrodes 4 and 5 so that a control signal applied between one of the first electrodes and the second electrode 7 modifies the state of the liquid crystal between the electrodes.
Sur la figure 1 seules trois électrodes 4, 5 et 7 ont été représentées à titre d'exemple. Il est bien entendu que l'invention peut être mise en oeuvre quel que soit le nombre d'électrodes.In Figure 1 only three electrodes 4, 5 and 7 have been shown by way of example. It is understood that the invention can be implemented regardless of the number of electrodes.
La figure 2a représente un exemple de pictogramme réalisé à l'aide des électrodes 4 et 5. Le pictogramme de l'électrode 4 représente trois flèches concourantes et le pictogramme de l'électrode 5 représente une silhouette humaine assise. Ces deux pictogrammes peuvent représenter par exemple l'état de la ventilation dans un véhicule automobile. L'électrode 4 est reliée électriquement par une plage 9 à un plot de connexion 10. Il en est de même pour l'électrode 5 qui est reliée par une plage 11 a un plot de connexion 12. Les plots 10 et 12 permettent d'appliquer aux électrodes 4 et 5 le signal de commande du dispositif. Les plots 10 et 12 sont situés sur un bord 16 du dispositif. La figure 2b représente l'électrode 7 et sa plage de raccordement électrique 14. La plage 14 permet d'alimenter l'électrode 7 par un plot 15 situé sur le bord 16 du dispositif. Dans l'exemple de réalisation représenté, un contour 17 extérieur de l'électrode 7 est sensiblement ovale. Lorsque l'électrode 7 est placée en regard des électrodes 4 et 5, ces dernières sont situées à l'intérieur du contour 17. Autrement dit, l'électrode 7 recouvre complètement les électrodes 4 et 5. Ainsi la surface de l'électrode 7 est supérieure ou égale à la somme des surfaces des électrodes 4 et 5. Pour assurer un fonctionnement correct de la détection de proximité par effet capacitif, l'électrode 7 doit avoir une surface d'au moins 9 mm2. L'effet capacitif est obtenu en posant un doigt d'un utilisateur sur le dispositif en regard de l'électrode 7. Une capacité est alors créée entre l'électrode 7 et le doigt. En injectant un signal électrique haute fréquence, par exemple 2MHz, sur l'électrode 7, on peut détecter la présence du doigt en analysant un éventuel affaiblissement du signal haute fréquence dû à l'existence de la capacité créée entre le doigt et l'électrode 7. Des essais ont montré que si la surface de l'électrode 7 est inférieure à 9 mm2, l'affaiblissement du signal haute fréquence est si faible qu'il est pratiquement impossible à détecter.FIG. 2a represents an example of a pictogram produced using electrodes 4 and 5. The pictogram of electrode 4 represents three concurrent arrows and the pictogram of electrode 5 represents a seated human silhouette. These two pictograms can represent, for example, the state of ventilation in a motor vehicle. The electrode 4 is electrically connected by a pad 9 to a connection pad 10. The same is true for the electrode 5 which is connected by a pad 11 to a connection pad 12. The pads 10 and 12 make it possible to apply the control signal of the device to electrodes 4 and 5. The pads 10 and 12 are located on an edge 16 of the device. FIG. 2b represents the electrode 7 and its electrical connection range 14. The range 14 makes it possible to supply the electrode 7 by a stud 15 located on the edge 16 of the device. In the embodiment shown, an outer contour 17 of the electrode 7 is substantially oval. When the electrode 7 is placed opposite the electrodes 4 and 5, the latter are situated inside the contour 17. In other words, the electrode 7 completely covers the electrodes 4 and 5. Thus the surface of the electrode 7 is greater than or equal to the sum of the surfaces of the electrodes 4 and 5. To ensure correct operation of the proximity detection by capacitive effect, the electrode 7 must have an area of at least 9 mm 2 . The capacitive effect is obtained by placing a user's finger on the device opposite the electrode 7. A capacitor is then created between the electrode 7 and the finger. By injecting a high frequency electrical signal, for example 2 MHz, on the electrode 7, one can detect the presence of the finger by analyzing a possible weakening of the high frequency signal due to the existence of the capacitance created between the finger and the electrode. 7. Tests have shown that if the surface of the electrode 7 is less than 9 mm 2 , the attenuation of the high frequency signal is so small that it is practically impossible to detect.
Avantageusement, l'électrode 7 est détourée en regard des plages 9 et 10. Plus précisément, la modification d'état du cristal liquide est obtenue en appliquant un signal de commande basse fréquence, par exemple à 100 Hz, entre d'une part l'électrode 7 et d'autre part au moins une des électrodes 4 ou 5. Les plages 9 et 11 sont en partie en regard de l'électrode 7 ou plus précisément à l'intérieur du contour 17 de l'électrode 7. Si l'électrode 7 occupe entièrement la surface située à l'intérieur du contour 17, les parties des plages 9 et 11 en regard de l'électrode 7 sont alors visibles en même temps que les pictogrammes formés par les électrodes 4 et 5. Pour pallier ce défaut et ne laisser apparaître que les pictogrammes, l'électrode 7 est détournée en regard des plages. Un détourage 18 est bien visible sur la figure 2b. Les deux figures 2a et 2b sont représentées à la même échelle et en les superposant, le détourage 18 recouvre la partie des plages 9 et 11 située à l'intérieur du contour 17. Cette superposition préfigure de la disposition des électrodes 4, 5 et 7 dans le dispositif. Sur la figure 2b, on distingue également un autre détourage 19 réalisé dans l'électrode 7, permettant, une fois les électrodes 4, 5 et 7 superposées de séparer visuellement le corps 19 de la tête 20 dans la représentation de la silhouette humaine réalisée à l'aide de l'électrode 5.Advantageously, the electrode 7 is clipped opposite the areas 9 and 10. More specifically, the change in state of the liquid crystal is obtained by applying a low frequency control signal, for example at 100 Hz, on the one hand l 'electrode 7 and on the other hand at least one of the electrodes 4 or 5. The areas 9 and 11 are partly opposite the electrode 7 or more precisely inside the contour 17 of the electrode 7. If l electrode 7 completely occupies the surface located inside the contour 17, the parts of areas 9 and 11 opposite electrode 7 are then visible at the same time as the pictograms formed by electrodes 4 and 5. To overcome this fault and only show the pictograms, electrode 7 is deflected opposite the ranges. A clipping 18 is clearly visible in FIG. 2b. The two figures 2a and 2b are shown on the same scale and by superimposing them, the clipping 18 covers the part of the pads 9 and 11 located inside the contour 17. This superposition prefigures the arrangement of the electrodes 4, 5 and 7 in the device. In FIG. 2b, there is also another clipping 19 made in the electrode 7, allowing, once the electrodes 4, 5 and 7 superimposed visually the body 19 of the head 20 in the representation of the human silhouette produced using the electrode 5.
Avantageusement, le dispositif comporte plusieurs contre- électrodes 7. Pour assurer la détection de présence d'un élément conducteur à proximité de chaque contre-électrode 7, chacune est alimentée séparément. Plus précisément, chacune possède sa propre plage 14 aboutissant chacune à un plot 15 distinct.Advantageously, the device comprises several counter-electrodes 7. To ensure the detection of the presence of a conductive element near each counter-electrode 7, each is supplied separately. More specifically, each has its own range 14 each leading to a separate pad 15.
La figure 3 permet d'expliquer le fonctionnement d'une cellule élémentaire d'affichage formée par une première électrode, par exemple l'électrode 4 et une seconde électrode 7 située en regard. Des molécules de cristal liquide sont placées entre les deux électrodes 4 et 7 et forment un matériau isolant de quelque μm d'épaisseur. Les deux électrodes forment alors une capacité Cpsb appelée également capacité de la cellule élémentaire LCD. Le raccordement électrique de la première électrode 4 est assuré par la plage 9 formant une résistance Rlss dont la valeur est avantageusement adaptée par gravure de la plage d'alimentation 9 de la première électrode 4. Plus précisément, la valeur de la résistance Rlss est adaptée en modifiant la longueur et/ou la largeur et/ou l'épaisseur de la plage d'alimentation 9.FIG. 3 explains the operation of an elementary display cell formed by a first electrode, for example the electrode 4 and a second electrode 7 located opposite. Liquid crystal molecules are placed between the two electrodes 4 and 7 and form an insulating material a few μm thick. The two electrodes then form a capacitance Cpsb also called capacitance of the elementary cell LCD. The electrical connection of the first electrode 4 is provided by the range 9 forming a resistance Rlss whose value is advantageously adapted by etching the supply range 9 of the first electrode 4. More specifically, the value of the resistance Rlss is adapted by modifying the length and / or the width and / or the thickness of the supply area 9.
Si la valeur de la résistance Rlss est insuffisante, on peut ajouter en série avec la plage 9 une résistance additionnelle Rscs par exemple sous forme de composant discret. Des pertes capacitives dans le raccordement électrique de l'électrode 4 peuvent être modélisées par une capacité Cp2 reliée entre une borne de la résistance Rscs non raccordée à la plage 9 et la masse 25 électrique.If the value of the resistance Rlss is insufficient, it is possible to add in series with the range 9 an additional resistance Rscs, for example in the form of a discrete component. Capacitive losses in the electrical connection of the electrode 4 can be modeled by a capacitor Cp2 connected between a terminal of the resistor Rscs not connected to the pad 9 and the electrical ground.
Le raccordement électrique de la seconde électrode 7 est assuré par la plage 14 formant une résistance Rlsb. Des pertes capacitives dans le raccordement électrique de l'électrode 7 peuvent être modélisées par une capacité Cp1 reliée entre l'extrémité de la plage 14 non raccordée à l'électrode 7 et la masse 25. Une capacité Cinj raccordée au point commun de la capacité Cp1 et de la plage 14 permet d'injecter sur la seconde électrode 7 un signal haute fréquence.The electrical connection of the second electrode 7 is provided by the pad 14 forming a resistance Rlsb. Capacitive losses in the electrical connection of the electrode 7 can be modeled by a capacity Cp1 connected between the end of the range 14 not connected to the electrode 7 and the ground 25. A capacity Cinj connected to the common point of the capacity Cp1 and range 14 makes it possible to inject a high frequency signal on the second electrode 7.
La figure 4 complète les éléments décrits sur la figure 3 en décrivant la façon dont un signal de commande et un signal haute fréquence sont appliqués aux électrodes 4 et 5. Plus précisément le dispositif comporte des moyens pour générer le signal de commande 30 formés par une source alternative de tension basse fréquence et raccordés entre d'une part la borne de la résistance Rscs non raccordée à la résistance Rlss et d'autre part le point commun de la plage 14 et de la capacité d'injection Cinj. Les moyens pour générer le signal de commande 30 sont, à leurs points communs avec la résistance Rscs, raccordés à la masse 25 par l'intermédiaire d'une impédance de charge formée par exemple d'une résistance R et d'une capacité C raccordés en parallèle. Cette impédance est un exemple de modélisation de l'impédance de sortie du générateur. Le dispositif comporte en outre des moyens pour générer un signal haute fréquence 31 raccordés entre la masse 25 et la borne de la capacité d'injection Cinj non raccordée à la plage 14. Des moyens 32 pour détecter une éventuelle modification du signal haute fréquence sont reliés à la seconde électrode 7 par l'intermédiaire de la résistance Rlsb et plus précisément au point commun de la capacité d'injection Cinj et de la résistance Rlsb.Figure 4 complements the elements described in Figure 3 by describing how a control signal and a high frequency signal are applied to the electrodes 4 and 5. More specifically, the device comprises means for generating the control signal 30 formed by an alternating source of low frequency voltage and connected between on the one hand the terminal of the resistor Rscs not connected to the resistor Rlss and on the other hand, the common point of range 14 and the Cinj injection capacity. The means for generating the control signal 30 are, at their common points with the resistor Rscs, connected to ground 25 by means of a load impedance formed for example of a resistor R and a capacitor C connected in parallel. This impedance is an example of modeling the generator output impedance. The device also comprises means for generating a high frequency signal 31 connected between earth 25 and the terminal of the injection capacity Cinj not connected to the pad 14. Means 32 for detecting a possible modification of the high frequency signal are connected to the second electrode 7 via the resistor Rlsb and more precisely to the common point of the injection capacity Cinj and the resistor Rlsb.
Selon l'invention, le dispositif comporte des moyens de mixage du signal haute fréquence et du signal de commande. Ces moyens comportent une résistance Rscb raccordée en série avec la source de tension basse fréquence 30. La valeur de la résistance Rscb est par exemple comprise entre 1 kilo-ohms et 100 kilo-ohms.According to the invention, the device comprises means for mixing the high frequency signal and the control signal. These means include a resistor Rscb connected in series with the low frequency voltage source 30. The value of the resistor Rscb is for example between 1 kilo-ohms and 100 kilo-ohms.
Avantageusement, la valeur de la résistance Rscb est au moins de l'ordre de grandeur de l'impédance du condensateur d'injection Cinj à la fréquence du signal haute fréquence. Ainsi le fait de mixer le signal de commande et le signal haute fréquence au moyen de la résistance Rscb n'atténue pas trop le signal haute fréquence. Par exemple, si le signal haute fréquence a une fréquence de 2 MHz, et si on choisit une capacité d'injection Cinj de 10 pF, la valeur retenue pour la résistance Rscb ne sera pas inférieure à environ 5 kilo-ohms. Avantageusement, la valeur de résistance Rlsb de la plage d'alimentation 14 de l'électrode 7 est inférieure à 5 k ohms afin de limiter l'atténuation des signaux reçus par l'électrode 7.Advantageously, the value of the resistance Rscb is at least of the order of magnitude of the impedance of the injection capacitor Cinj at the frequency of the high frequency signal. Thus mixing the control signal and the high frequency signal by means of the resistor Rscb does not attenuate the high frequency signal too much. For example, if the high frequency signal has a frequency of 2 MHz, and if a Cinj injection capacity of 10 pF is chosen, the value retained for the resistance Rscb will not be less than about 5 kilo-ohms. Advantageously, the resistance value Rlsb of the supply range 14 of the electrode 7 is less than 5 k ohms in order to limit the attenuation of the signals received by the electrode 7.
Avantageusement, la valeur de la résistance Rlss est adaptée de telle sorte qu'une constante de temps τ formée par la capacité Cpsb et la résistance Rlss soit au moins d'un ordre de grandeur plus petite qu'une période du signal de commande. On entend par un ordre de grandeur plus petite, environ dix fois plus petite. Ainsi le signal de commande aura une tension beaucoup plus importante aux bornes de la capacité Cpsb qu'aux bornes de la résistance Rlss. Comme on l'a vu précédemment, la résistance Rlss peut être complétée par la résistance additionnelle Rscs. Dans ce cas, on devra tenir compte des deux résistances Rlss et Rscs pour le calcul de la constante de temps τ.Advantageously, the value of the resistance Rlss is adapted so that a time constant τ formed by the capacitance Cpsb and the resistance Rlss is at least an order of magnitude smaller than a control signal period. We mean by an order of magnitude smaller, about ten times smaller. Thus the control signal will have a much higher voltage across the terminals of the capacitor Cpsb than across the terminals of the resistor Rlss. As we saw previously, the resistance Rlss can be supplemented by the additional resistance Rscs. In this case, account should be taken of the two resistances Rlss and Rscs for the calculation of the time constant τ.
Avantageusement, la valeur de la constante de temps est supérieure ou égale à une période du signal haute fréquence. Ainsi le signal haute fréquence aura une tension beaucoup plus importante aux bornes de la résistance Rlss, complétée éventuellement de la résistance additionnelle Rscs, qu'aux bornes de la capacité Cpsb. Ainsi La cellule LCD sera peu perturbée par l'application de la tension haute fréquence.Advantageously, the value of the time constant is greater than or equal to a period of the high frequency signal. Thus the high frequency signal will have a much higher voltage at the terminals of the resistor Rlss, possibly supplemented by the additional resistor Rscs, than at the terminals of the capacitor Cpsb. Thus the LCD cell will be little disturbed by the application of the high frequency voltage.
Avantageusement, lorsque le dispositif comporte au moins deux électrodes 4 et 5 de surface différente disposée en regard d'une seconde électrode 7, la valeur de la résistance Rlss, complétée éventuellement de la résistance additionnelle Rscs, de chaque électrode 4 ou 5 croit avec l'inverse de la surface de l'électrode 4 ou 5 considérée. Autrement dit, plus la surface d'une électrode 4 ou 5 est petite plus on augmentera la valeur de la résistance Rlss, complétée éventuellement de la résistance additionnelle Rscs, pour ainsi conserver une même constante de temps τ pour toutes les premières électrodes 4 et 5.Advantageously, when the device comprises at least two electrodes 4 and 5 of different surface arranged opposite a second electrode 7, the value of the resistance Rlss, possibly supplemented by the additional resistance Rscs, of each electrode 4 or 5 increases with l inverse of the surface of the electrode 4 or 5 considered. In other words, the smaller the area of an electrode 4 or 5, the more the value of the resistance Rlss will be increased, possibly supplemented by the additional resistance Rscs, so as to keep the same time constant τ for all the first electrodes 4 and 5 .
L'invention a également pour objet un procédé d'utilisation d'un dispositif précédemment décrit, procédé dans lequel les moyens pour générer un signal de commande 30 fournissent un signal périodique comportant des alternances positives et négatives. Les moyens pour générer un signal haute fréquence 31 injectent un signal haute fréquence à quantité sensiblement égale pendant autant d'alternances positives et que d'alternances négatives du signal de commande 30 Ceci permet d'éviter d'éventuelles dissymétries dans l'application du signal haute fréquence à la cellule LCD. En effet une telle cellule peut être endommagée en cas d'application d'une composante de tension continue aux bornes de ses électrodes, composante continue résultante d'application dissymétrique d'un signal. Avantageusement, le signal haute fréquence est interrompu lors des commutations entre les alternances positives et négatives du signal de commande 30. En effet lors de ces commutations, l'application du signal haute fréquence pourrait conduire, de la même façon que précédemment, à un déséquilibre de tension pouvant induire l'application d'une composante continue aux bornes des électrodes. Cette contrainte temporelle sur l'injection du signal haute fréquence est beaucoup moins pénalisante que celle existante dans une réalisation conforme à l'enseignement du brevet EP 0 340 096 dans laquelle il fallait interrompre le signal de commande pour injecter le signal haute fréquence.The invention also relates to a method of using a device described above, method in which the means for generating a control signal 30 provide a periodic signal comprising positive and negative alternations. The means for generating a high frequency signal 31 inject a high frequency signal at a substantially equal amount during as many positive and negative alternations of the control signal 30 This makes it possible to avoid possible asymmetries in the application of the signal high frequency to the LCD cell. Indeed, such a cell can be damaged if a DC voltage component is applied across its electrodes, a DC component resulting from the asymmetrical application of a signal. Advantageously, the high frequency signal is interrupted during the switching between the positive and negative half-waves of the control signal 30. In fact during these switching operations, the application of the high frequency signal could lead, in the same way as before, to an imbalance voltage which can induce the application of a DC component across the electrodes. This time constraint on the injection of the high frequency signal is much less penalizing than that existing in an embodiment in accordance with the teaching of patent EP 0 340 096 in which it was necessary to interrupt the control signal to inject the high frequency signal.
Avantageusement, la durée et/ou l'amplitude du signal haute fréquence délivré par les moyens pour générer un signal haute fréquence 31 est telle que la valeur efficace du signal haute fréquence est inférieure à une tension de seuil de la couche 3. On définit la tension de seuil de la couche 3 comme une tension apte faire changer l'état du cristal liquide, à le faire passer d'un état transparent à un état opaque ou l'inverse. Plus précisément, la tension de seuil dépend des composants de la cellule elle-même et également du taux de multiplexage de la cellule. Dans le cas d'un dispositif comportant plusieurs cellules, la plus petite tension de seuil sera celle de la cellule ayant la plus petite constante de temps τ. Par ailleurs, l'amplitude du signal haute fréquence agit directement sur la valeur efficace du signal haute fréquence et on entend par durée du signal haute fréquence la durée à l'intérieur d'une alternance du signal de commande ainsi que le nombre d'alternance du signal de commande où le signal haute fréquence apparaît.Advantageously, the duration and / or the amplitude of the high frequency signal delivered by the means for generating a high frequency signal 31 is such that the effective value of the high frequency signal is less than a threshold voltage of layer 3. We define the threshold voltage of layer 3 as a voltage capable of changing the state of the liquid crystal, of passing it from a transparent state to an opaque state or vice versa. More precisely, the threshold voltage depends on the components of the cell itself and also on the cell multiplexing rate. In the case of a device comprising several cells, the smallest threshold voltage will be that of the cell having the smallest time constant τ. Furthermore, the amplitude of the high frequency signal acts directly on the effective value of the high frequency signal and the duration of the high frequency signal is understood to mean the duration within an alternation of the control signal as well as the number of alternation of the control signal where the high frequency signal appears.
la figure 5 représente une variante avantageuse de réalisation d'une des électrodes d'un dispositif d'affichage dédié. Dans cette variante, la résistance Rscb, raccordée en série avec la source de tension basse fréquence 30, est avantageusement réalisée en mettant à profit la résistance naturelle d'une plage supplémentaire 51 de raccordement de l'électrode 7. La plage 51 est distinct de la plage 14 et relie l'électrode 7 à la source de tension basse fréquence 30 par l'intermédiaire d'un plot 52 situé sur le bord du dispositif. Le plot 52 est distinct du plot 15. Comme pour la résistance Rlss, la valeur de la résistance Rscb est avantageusement adaptée par gravure de la plage 51 de l'électrode 7. La figure 6 représente une modélisation schématique du fonctionnement d'un dispositif d'affichage comportant l'électrode 7 représentée sur la figure 5. La variante de réalisation représentée à l'aide des figures 5 et 6 permet de s'affranchir de moyens de mixage réalisés à l'extérieur de l'afficheur et d'utiliser le dessin de l'électrode 7 pour réaliser ces moyens de mixage. FIG. 5 represents an advantageous alternative embodiment of one of the electrodes of a dedicated display device. In this variant, the resistor Rscb, connected in series with the low-frequency voltage source 30, is advantageously produced by taking advantage of the natural resistance of an additional area 51 for connection of the electrode 7. The area 51 is distinct from the pad 14 and connects the electrode 7 to the low frequency voltage source 30 via a pad 52 located on the edge of the device. The pad 52 is distinct from the pad 15. As for the resistance Rlss, the value of the resistance Rscb is advantageously adapted by etching the area 51 of the electrode 7. FIG. 6 represents a schematic modeling of the operation of a display device comprising the electrode 7 represented in FIG. 5. The variant embodiment represented with the aid of FIGS. 5 and 6 makes it possible to dispense with mixing means made outside of the display and use the design of the electrode 7 to produce these mixing means.

Claims

REVENDICATIONS
1. Dispositif d'affichage électronique comprenant des moyens de détection de proximité d'un élément conducteur situé à proximité d'une zone d'affichage du dispositif, le dispositif comportant deux plaques isolantes (1, 2), une couche (3) de matériau présentant des propriétés électro -optique aptes à rendre visible tout ou partie de sa surface sous l'effet d'un signal de commande électrique, la couche (3) étant disposée entre les deux plaques (1 , 2), au moins une première électrode (4, 5) disposée sur une face (6) d'une (2) des plaques isolantes, une seconde électrode (7) disposée sur une face (8) de l'autre (1) plaque isolante en regard d'au moins une première électrode (4, 5), des moyens pour générer un signal de commande (30) des électrodes (4, 5, 7) en fonction d'une image à afficher sur la zone d'affichage, des moyens pour générer un signal haute fréquence (31) appliqué à la seconde électrode (7), des moyens pour détecter une éventuelle modification du signal haute fréquence (32), caractérisé en ce que le dispositif comporte en outre des moyens de mixage (Rscb) du signal haute fréquence et du signal de commande disposés de telle sorte à permettre le fonctionnement des moyens de détection de proximité indépendamment du fonctionnement des moyens pour générer un signal de commande.1. Electronic display device comprising means for detecting the proximity of a conductive element located near a display area of the device, the device comprising two insulating plates (1, 2), a layer (3) of material having electro-optical properties capable of making all or part of its surface visible under the effect of an electrical control signal, the layer (3) being disposed between the two plates (1, 2), at least one first electrode (4, 5) disposed on one side (6) of one (2) of the insulating plates, a second electrode (7) disposed on one side (8) of the other (1) insulating plate facing at least at least a first electrode (4, 5), means for generating a control signal (30) of the electrodes (4, 5, 7) according to an image to be displayed on the display area, means for generating a high frequency signal (31) applied to the second electrode (7), means for detecting a possible modification tion of the high frequency signal (32), characterized in that the device further comprises means (Rscb) for mixing the high frequency signal and the control signal arranged so as to allow the operation of the proximity detection means independently of the operation of the means for generating a control signal.
2. Dispositif selon la revendication 1, caractérisé en ce que les moyens pour générer le signal de commande comportent une source de tension basse fréquence (30) dont la première borne est reliée à la première électrode (4,5) et dont une seconde borne est reliée à la seconde électrode (7), en ce que les moyens pour générer le signal haute fréquence (31) sont reliés à la seconde électrode (7), en ce que les moyens de mixage comportent une première résistance (Rscb) raccordée en série avec la source de tension basse fréquence.2. Device according to claim 1, characterized in that the means for generating the control signal comprise a low frequency voltage source (30) whose first terminal is connected to the first electrode (4,5) and whose second terminal is connected to the second electrode (7), in that the means for generating the high frequency signal (31) are connected to the second electrode (7), in that the mixing means comprise a first resistor (Rscb) connected in series with the low frequency voltage source.
3. Dispositif selon la revendication 2, caractérisé en ce que les moyens pour détecter une éventuelle modification du signal haute fréquence (32) sont reliés à la seconde électrode (7). 3. Device according to claim 2, characterized in that the means for detecting a possible modification of the high frequency signal (32) are connected to the second electrode (7).
4. Dispositif selon l'une quelconque des revendications 2 ou 3, caractérisé en ce que la valeur de la première résistance (Rscb) est comprise entre 1 kilo-ohms et 100 kilo-ohms.4. Device according to any one of claims 2 or 3, characterized in that the value of the first resistance (Rscb) is between 1 kilo-ohms and 100 kilo-ohms.
5. Dispositif selon l'une quelconque des revendications 2 à 4, caractérisé en ce que les moyens pour générer le signal haute fréquence (31) sont reliés à la seconde électrode (7) par l'intermédiaire d'un condensateur d'injection (Cinj), et en ce que la valeur de la première résistance (Rscb) est au moins de l'ordre de grandeur de l'impédance du condensateur d'injection (Cinj) à la fréquence du signal haute fréquence.5. Device according to any one of claims 2 to 4, characterized in that the means for generating the high frequency signal (31) are connected to the second electrode (7) via an injection capacitor ( Cinj), and in that the value of the first resistance (Rscb) is at least of the order of magnitude of the impedance of the injection capacitor (Cinj) at the frequency of the high frequency signal.
6. Dispositif selon l'une des revendications précédentes, caractérisé en ce que la seconde électrode (7) est reliée aux moyens pour générer le signal de commande (30) et aux moyens pour générer le signal haute fréquence (31) par une plage d'aliimentation (14) dont la valeur de résistance (Rlsb) est inférieure à 5 k ohms.6. Device according to one of the preceding claims, characterized in that the second electrode (7) is connected to the means for generating the control signal (30) and to the means for generating the high frequency signal (31) by a range d power supply (14) whose resistance value (Rlsb) is less than 5 k ohms.
7. Dispositif selon l'une des revendications précédentes, caractérisé en ce que la première électrode (4, 5) et la seconde électrode (7) forment une capacité (Cpsb), en ce que la première électrode (4, 5) est reliée aux moyens pour générer le signal de commande par l'intermédiaire d'une seconde résistance (Rlss + Rscs) dont la valeur est adaptée de telle sorte qu'une constante de temps (τ) formée par la capacité (Cpsb) et la seconde résistance (Rlss + Rscs) soit au moins d'un ordre de grandeur plus petite qu'une période du signal de commande.7. Device according to one of the preceding claims, characterized in that the first electrode (4, 5) and the second electrode (7) form a capacitor (Cpsb), in that the first electrode (4, 5) is connected to the means for generating the control signal via a second resistance (Rlss + Rscs) whose value is adapted so that a time constant (τ) formed by the capacitance (Cpsb) and the second resistance (Rlss + Rscs) is at least an order of magnitude smaller than a period of the control signal.
8. Dispositif selon la revendication 7, caractérisé en ce que la valeur de la constante de temps (τ) est supérieure ou égale à une période du signal haute fréquence.8. Device according to claim 7, characterized in that the value of the time constant (τ) is greater than or equal to a period of the high frequency signal.
9. Dispositif selon l'une quelconque des revendications 7 ou 8, caractérisé en ce que la valeur de la seconde résistance (Rlss + Rscs) est adaptée par gravure d'une plage d'alimentation (9, Rlss) de la première électrode (4, 5). 9. Device according to any one of claims 7 or 8, characterized in that the value of the second resistance (Rlss + Rscs) is adapted by etching a supply range (9, Rlss) of the first electrode ( 4, 5).
10. Dispositif selon la revendication 9, caractérisé en ce que la valeur de la seconde résistance (Rlss + Rscs) est adaptée en modifiant la longueur et/ou la largeur et/ou l'épaisseur de la plage d'alimentation (9, Rlss) de la première électrode (4, 5).10. Device according to claim 9, characterized in that the value of the second resistance (Rlss + Rscs) is adapted by modifying the length and / or the width and / or the thickness of the supply range (9, Rlss ) of the first electrode (4, 5).
11. Dispositif l'une quelconque des revendications 7 à 10, caractérisé en ce que la seconde résistance (Rlss + Rscs) comporte une résistance additionnelle (Rscs) connectée en série avec la plage d'alimentation (9, Rlss) de la première électrode (4, 5).11. Device any one of claims 7 to 10, characterized in that the second resistor (Rlss + Rscs) comprises an additional resistor (Rscs) connected in series with the supply range (9, Rlss) of the first electrode (4, 5).
12. Dispositif selon l'une quelconque des revendications 7 à 11, caractérisé en ce qu'il comporte au moins deux premières électrodes (4, 5) de surface différente disposées en regard d'une seconde électrode (7), en ce que la valeur de la seconde résistance (Rlss + Rscs) de chaque première électrode (4, 5) croit avec l'inverse de la surface de la première électrode (4, 5) considérée.12. Device according to any one of claims 7 to 11, characterized in that it comprises at least two first electrodes (4, 5) of different surface arranged opposite a second electrode (7), in that the value of the second resistance (Rlss + Rscs) of each first electrode (4, 5) increases with the inverse of the surface of the first electrode (4, 5) considered.
13. Dispositif selon l'une des revendications précédentes, caractérisé en ce que la seconde électrode (7) comporte deux plages (14, 51) de raccordement distinctes reliées chacune par des plots (15, 52) distincts.13. Device according to one of the preceding claims, characterized in that the second electrode (7) has two separate connecting pads (14, 51) each connected by separate pads (15, 52).
14. Dispositif selon la revendication 13, caractérisé en ce que le premier des plots (15) est relié aux moyens pour générer un signal haute fréquence (31), et en ce que le second des plots (52) est relié aux moyens pour générer un signal de commande (30).14. Device according to claim 13, characterized in that the first of the pads (15) is connected to the means for generating a high frequency signal (31), and in that the second of the pads (52) is connected to the means for generating a control signal (30).
15. Dispositif selon la revendication 14, caractérisé en ce qu'une valeur des moyens de mixage (Rscb) est adaptée par gravure de la plage (51) reliée au second des plots (52).15. Device according to claim 14, characterized in that a value of the mixing means (Rscb) is adapted by etching the pad (51) connected to the second of the pads (52).
16. Procédé d'utilisation d'un dispositif selon l'une des revendications précédentes, caractérisé en ce que les moyens pour générer un signal de commande (30) fournissent un signal périodique comportant des alternances positives et négatives, en ce que les moyens pour générer un signal haute fréquence (31) injectent un signal haute fréquence à quantité sensiblement égale pendant autant d'alternances positives que d'alternances négatives du signal de commande (30).16. Method of using a device according to one of the preceding claims, characterized in that the means for generating a control signal (30) provide a periodic signal comprising positive and negative alternations, in that the means for generate a high frequency signal (31) inject a high frequency signal in substantially equal quantity during as many positive alternations as negative alternations of the control signal (30).
17 Procédé selon la revendication 16, caractérisé en ce que le signal haute fréquence est interrompu lors des commutations entre les alternances positives et négatives du signal de commande (30).17 Method according to claim 16, characterized in that the high frequency signal is interrupted during the switching between the positive and negative half-waves of the control signal (30).
18. Procédé selon l'une quelconque des revendications 16 ou 17, caractérisé en ce que la durée et/ou l'amplitude du signal haute fréquence délivré par les moyens pour générer un signal haute fréquence (31) sont telles que la valeur efficace du signal haute fréquence est inférieure à une tension de seuil de la couche (3). 18. Method according to any one of claims 16 or 17, characterized in that the duration and / or the amplitude of the high frequency signal delivered by the means for generating a high frequency signal (31) are such that the rms value of the high frequency signal is less than a threshold voltage of the layer (3).
EP03796061A 2002-11-28 2003-11-26 Proximity detection-display device and method of using said device Withdrawn EP1565806A2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR0215071A FR2847997B1 (en) 2002-11-28 2002-11-28 PROXIMITY DETECTION DISPLAY DEVICE AND METHOD OF USING THE SAME
FR0215071 2002-11-28
PCT/EP2003/050900 WO2004049094A2 (en) 2002-11-28 2003-11-26 Proximity detection-display device and method of using said device

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EP1565806A2 true EP1565806A2 (en) 2005-08-24

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EP (1) EP1565806A2 (en)
JP (1) JP4293369B2 (en)
CN (1) CN100392575C (en)
AU (1) AU2003298327A1 (en)
FR (1) FR2847997B1 (en)
WO (1) WO2004049094A2 (en)

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FR2847997B1 (en) 2005-10-07
AU2003298327A8 (en) 2004-06-18
US20060125717A1 (en) 2006-06-15
WO2004049094A2 (en) 2004-06-10
AU2003298327A1 (en) 2004-06-18
FR2847997A1 (en) 2004-06-04
CN1754140A (en) 2006-03-29
CN100392575C (en) 2008-06-04
JP4293369B2 (en) 2009-07-08
JP2006508444A (en) 2006-03-09
US7663611B2 (en) 2010-02-16
WO2004049094A3 (en) 2004-11-18

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