FR2731537A1 - Integrated circuit smart card with display device - Google Patents

Abstract

The integrated circuit card (10) carries an electronic display panel (12) on one face. The display can show information stored in the memory (11) in the card. The display is erased by signals emitted from the card reader (20). Erasure is by electrical signals acting on the ferroelectric layer of the display. The ferroelectric material can be formed from a variety of bistable materials, including liquid crystals dispersed in polymer, bistable ceramic crystals, an electro-chromatic material or a thermo-chromatic material. Alternatively the ferroelectric material can be formed of a layer of monostable liquid crystals or an electro-chromatic material without memory effect, with the card supplied by a battery and a switching circuit that maintains the display.

Description

CHIP CARD WITH DISPLAY DEVICE
The invention relates to an integrated circuit card comprising a display device. A reader will read and / or write data in a memory of the chip and makes it possible to display, directly on the surface of the chip card, information taken by the reader in a memory of the chip.

 Such a device can validly be applied to electronic wallet systems.

 Indeed, currently it is only possible to access the information contained in the memory of a chip, such as for example the amount remaining in a wallet, only during a reading operation by the reader. Knowledge of the information is therefore only short-lived.

 Applications of smart cards, with or without contacts, are more and more developed these days. So that a user can have access to information contained in a memory of the chip when he wishes, there are pocket readers equipped with a liquid crystal display. These readers can also read the credit of a calling card, interrogate a bank card, or program an electronic wallet. However, these pocket readers have drawbacks for the user: they are in particular more bulky than a card and must be recharged periodically. In addition, there is a risk of loss, by forgetting the reader in a place for example, and the loss of such a reader results in the loss of knowledge of the information.

 This solution does not solve the problem of displaying information satisfactorily for a card user.

 An object of the present invention is to make it possible to display, on the very surface of the chip card, information contained in a memory of the chip.

 Thus, an electronic wallet user knows the remaining amount of money by a simple glance at the smart card, and he does not need to use another device to access the information.

 The present invention more particularly relates to a chip card comprising a display of information contained in the chip, the erasure of which is obtained only by the reception of signals transmitted during the uses of the card.

Other features and advantages of the invention will appear on reading the description given by way of illustrative and nonlimiting example, with reference to the appended figures which represent
FIG. 1, a perspective diagram of a smart card according to the invention, inserted into the slot of a reader,
FIG. 2, a block diagram of an embodiment of a display system according to the invention,
FIG. 3, a sectional view of a smart card according to the invention,
FIG. 4, a sectional view of another smart card according to the invention,
FIG. S, a sectional view of another smart card according to the invention,
- Figure 6, a perspective view of another smart card according to the invention.

 A preferred embodiment of a display system according to the invention will be better understood with reference to FIG. 1, which represents a smart card 10 partly inserted in the slot of a reader / writer 20. The reader 20 comes to read and / or write data in a memory of the chip 11. The chip card 10 comprises, in addition to the chip 11, a display 12 on which the reader 20 writes information taken from a memory of the chip 11.

 Throughout this description, there is talk of a smart card, however this card can be in any other geometric form, such as in the form of a key.

 Figure 2 illustrates in more detail a block diagram of an embodiment of a display system according to the invention.

 The reader 20 comprises a signal generator capable of controlling a display placed on a smart card. In the example shown, the reader 20 comprises a management block 21, a read / write head 22 and a write head 23.

 The read / write head 22 is connected, by means of a bus for example, to the management block 21. It makes it possible to read and / or write information in a memory of the chip 11. The management block 21 analyzes the information read by the read / write head 22 or transmits to the latter the information to be written in a memory of the chip 11.

 The management block 21 then transmits, for example via a data bus, to the write head 23, the information to be written on the display 12 of the card 10. The write head 23, controlled by the management block 21, emits signals capable of changing certain characteristics on the display 12, so as to carry out an entry.

 In the example shown, the smart card 10 is of the contact card type: the contact zones, to which the chip is connected, are flush with the surface of the card. Consequently, in order to allow information to be exchanged between the chip 11 and the reader 20, the read / write head 22 includes metal contacts 24 capable of being positioned on flush contact areas of the chip card.

 However, according to an alternative embodiment, it is entirely possible to have a smart card 10 of the contactless type. For example, the chip can be connected to an antenna. In this case, a transmitter / receiver 22, placed in the reader 20, transmits radio frequency waves to the antenna associated with the chip, to read and / or write in a memory of this chip.

 In the case where the display is controlled only by the management block 21 of the reader 20, it is not necessary for the chip 11 to include a microprocessor, it may just be a memory chip. However, if it includes a microprocessor, it makes it possible to perform other applications, completely independent of the display operation.

 The display 12, via which the writing head 23 of the reader 20 writes information, is preferably placed on the central part of the card 10. It is nevertheless quite possible to place it elsewhere on the card .

 Preferably, the writing head 23 also makes it possible to erase the preexisting information in order to be able to write new information.

 A first exemplary embodiment, illustrated in FIG. 3, consists in making a smart card 10, into which a display 12 is inserted capable of receiving the signals transmitted by the reader / recorder 20. In this example, the writing head 23 of the reader 20 emits electrical signals making it possible to locally apply an alternating voltage.

 The display 12, embedded in the surface of the card 10 preferably comprises a layer of ferroelectric material, a few microns (10-6 meters) thick, enclosed between two glass plates 13.

Transparent electrodes 14, of ITO type, ie based on Indium and Tin oxide, are placed under the upper glass plate and other electrodes based on Vanadium oxide (V6013) 18 are placed on the lower glass plate. These electrodes are placed so as to draw numbers and / or letters for example.

 To be able to create an electric field between two electrodes 14 and 18, each of them is connected to a wire. The wires, connected to the electrodes, can be electrically connected to the chip 11, via contact areas of the smart card; or additional contacts can be provided on the card 10. The reader transmits electrical signals to these contacts or contact areas, to control the display.

 The ferroelectric material advantageously comprises bi-stable liquid crystals comprising small dispersed inorganic particles. These particles constitute nematic domains and have the particularity of being oriented differently according to the frequency of the voltage applied to the terminals of the electrodes 14-18. This change in orientation of the nematic domains causes a change in the optical properties and in particular a change in color of the birefringent liquid. In fact, the particles redirected inside the liquid crystal layer rotate the plane of polarization of the incident light.

 A first stable state (SS), scattering light, comprises a large quantity of nematic domains aligned in a random manner: A second stable state (TS), transparent, comprises nematic domains all aligned parallel to each other and in the direction of the electric field created between the electrodes 14 and 18. These two stable states thus make it possible to obtain a permanent display of the information contained in a memory of the chip 11, even in the absence of applied voltage, it is to even say when the card 10 is disconnected from the reader 20.

 The transition from the TS state to the SS state for example is obtained for a frequency of 20 kHz, while the transition from the SS state to the TS state is obtained for a lower frequency, of the order of 400 Hz. The transition time is very short, of the order of a few milliseconds and its maximum value is approximately 20 ms.

 To be able to erase the existing inscription and rewrite new information on the display 12, the writing head 23 emits electrical signals making it possible to apply, at the terminals of all the electrodes 14-18, an alternating voltage of a frequency particular corresponding to obtaining a stable state. Thus, the particles defining the nematic domains are all oriented in the same way: either they are randomly aligned and the display 12 has a uniform color corresponding to the stable state SS; either they are all aligned parallel to each other and the display 12 has a uniform color corresponding to the stable state TS.

 The writing head 23 can then again send signals to write information on the display 12 of the card 10. This new recording is carried out in the same manner as above, that is to say by applying an alternating voltage of particular frequency, at the terminals of certain electrodes 14-18, to activate them and to obtain another stable state in the zones situated under these activated electrodes. FIG. 3 thus diagrams the two stable states of the liquid crystals 15.

The display occurs for example in black on a transparent background, but it can also occur in transparent on a black background.

 In addition, according to an alternative embodiment, an erasing head controlled by the management block 21 of the reader 20 makes it possible to erase the preexisting inscriptions. In this case, the erasing head applies, at the terminals of all the electrodes 14-18, an alternating voltage of suitable frequency, corresponding to a stable state. For example, it applies a voltage with a frequency of 400 Hz to obtain the TS state. The writing head 23 then performs only the information writing operation, so that it applies a voltage with another suitable frequency, corresponding to the other stable state, such as 20 kHz for example. 'SS state.

 Another variant consists in dispersing such bi-stable liquid crystals in a polymer. This polymer is advantageously fixed to the card 10.

However, according to another variant, it is possible to disperse the bi-stable liquid crystals in a polymer of composition of the card 10. This embodiment facilitates the manufacture of the card 10. In addition, such a card is much less fragile than a card comprising a layer of liquid crystals enclosed between two glass plates. Transparent electrodes advantageously cover these dispersed liquid crystals in order to be able to apply a potential difference, and thus cause a change in orientation of the molecules. Preferably, the liquid crystals are dispersed so as to form numbers and / or letters.

 According to another variant, the ferroelectric material of the display 12 comprises a layer of bi-stable ceramic crystals. Two conductive electrode systems are placed above and below this layer of ceramic crystals. In fact, a single electrode is placed above the layer but, according to a variant, it is possible to place several.

These crystals are in particular PLZT crystals based on lead oxide, lantanum, zirconium and
Titanium. They are birefringent and have a single optical axis capable of being oriented, under the effect of an electric field, in two different directions characterizing two stable states. By applying, at the terminals of the electrodes, an electric field sufficiently intense to overcome the coercive field of the ceramic crystals, the optical axis is oriented either perpendicularly (state T) or parallel (state
L) to the layer of ceramic crystals.

 The upper electrode (or electrodes) is necessarily transparent so that an incident light beam can pass through both this (or these) electrode and the layer of ceramic crystals, and then be reflected by a reflecting surface placed under this layer . This (or these) electrode is for example of ITO type, that is to say based on indium and tin oxide. The lower electrodes are also transparent and a reflecting surface is advantageously placed under them in order to reflect the incident light beam.

 However, a variant consists in metallizing the lower electrodes. In this case, the metal electrodes themselves reflect the light beam and the use of a reflecting surface is no longer necessary.

 To be able to orient the electric field, and consequently the optical axis, parallel to the surface of the layer of ceramic crystals, electrodes are provided on the edges of this layer. Preferably, these lateral electrodes are produced by metallization of the edges of the ceramic layer.

 However, a variant consists in placing a system of interdigital electrodes under the layer of ceramic crystals. Thus, according to the desired orientation of the optical axis, these electrodes replace either, when they are connected in parallel, the lower electrodes; or the side electrodes, when a potential difference is applied across the two interdigital networks. This variant makes it possible to significantly reduce the potential difference necessary for the tilting of the optical axis in a direction parallel to the layer. In addition, these electrodes are placed so as to draw numbers and / or letters for example.

 An electrical addressing device makes it possible to place the interdigital electrodes in parallel and to apply to them a potential difference with respect to the upper transparent electrode (or electrodes), in order to orient the optical axis of all the crystallites constituting the ceramic layer parallel to this layer. Writing and erasing of information takes place in two different possible modes: writing in T mode and erasing in L mode or vice versa.

 During the writing operation, the mode which advantageously requires the lowest voltage across the electrodes is advantageously chosen, ie writing in the T mode for example. The erasing operation, which then requires a higher voltage, will be carried out by means of a suitable device, such as an erasing head controlled by the management block 21 of the reader / writer 20 for example. During a writing operation, the electronic addressing device makes it possible to create an electric field only between a fraction of interdigital electrodes so as to draw numbers and / or letters. During the erasing operation, the interdigital electrodes are connected in parallel and polarized with respect to the electrode, or to the upper transparent electrodes.

 To visualize the orientation of the optical axis and therefore to read the information displayed, it is advantageous to use the ability of birefringent crystals to rotate the plane of polarization of light, by an angle proportional to their thickness, when the incident light beam is parallel to their optical axis. For this, the layer of ceramic crystals is advantageously placed between two light polarizers and the assembly is placed on a mirror having a non-depolarizing diffuse surface.

 These ferroelectric crystals operate with electric fields of a few kV / cm. The transition time between the two stable states, T and L, is however longer than in the case of a bi-stable liquid crystal display: it varies from a few seconds to about a minute. In addition, according to a variant and just as in the case of a bi-stable liquid crystal display, the reader 20 comprises an erasing head controlled by the management block 21.

 A second exemplary embodiment, illustrated in FIG. 4, consists in making a smart card 10, in which is embedded a display 12 comprising a layer of electro-chrome material. The write head 23 of the reader 20 emits electrical signals. The electro-chromium material chosen has, advantageously, a memory effect. In particular, tungsten oxide W03 constitutes a good electrochromic material.

 The display 12 therefore advantageously comprises a layer of an electrolyte 17 on the surface of which is placed a layer 16 of WO3. These two layers are enclosed between two glass plates 13. Transparent electrodes 14 of ITO type for example, that is to say based on oxide and Indium and Tin, are placed under the upper glass plate, while other electrodes 18, based on Vanadium oxide V6013 for example, are placed on the lower glass plate. The electrolyte layer 17 makes it possible to conduct the electric current created between the electrodes 14 and 18.

The electrolyte consists for example of a polymer.

The electrodes are advantageously placed so as to draw numbers and / or letters.

 The application of a voltage of a few volts at the terminals of certain electrodes 14-18, in order to activate them, causes a change in the structure of the tungsten oxide found in the zones situated under these activated electrodes. Indeed, the tungsten oxide 16 contained in the display 12 is not perfectly stoichiometric and, by the application of a voltage, of the order of 5 Volts for example, the electrochromic material oxidizes more or less. This phenomenon causes a change in the optical properties of tungsten oxide. In addition, the application of a reverse voltage, of the order of -5 Volts for example, causes a second color change. The two colors obtained correspond to two stable states and the display produced is therefore permanent, even in the absence of voltage applied to the terminals of the electrodes.

 It is however necessary to produce a very waterproof display 12 in order to avoid any possible entry of oxygen which would considerably disturb the display.

 To be able to erase the existing inscription and rewrite new information on the display 12, the writing head 23 emits electrical signals making it possible to apply, at the terminals of all the electrodes, a particular voltage corresponding to the obtaining of a specific color. The display thus has a uniform color.

 The writing head 23 can then again send signals to write information on the display 12 of the card 10. This new recording is carried out in the same manner as above, that is to say by applying an inverse voltage corresponding to another color, at the terminals of certain electrodes. The display occurs for example in yellow on a black background, but it can also occur in black on a yellow background depending on the voltages applied to the terminals of the electrodes.

 In addition, according to an alternative embodiment, an erasing head controlled by the management block 21 of the reader 20 makes it possible to erase the preexisting inscriptions. In this case, the erasing head applies, at the terminals of all the electrodes, a determined voltage, corresponding to a color such as black for example. The writing head 23 then performs only the information writing operation so that it applies, at the terminals of certain electrodes, the voltage opposite to that applied by the erasing head and corresponding to another color, such as yellow for example.

 According to a third exemplary embodiment, illustrated in FIG. 5, the display 12 of the card 10 comprises a layer of thermochromic material and the writing head 23 emits electrical signals. The thermochromic material advantageously comprises bi-stable mineral materials 15 whose color changes under the effect of a rise in temperature. In addition, these materials are advantageously dispersed in a polymer and are placed so as to draw numbers and / or letters for example. The card 10 also includes resistors 19 placed under these materials so as to heat them.

 The write head 23 of the reader 20 emits signals making it possible to apply a current and a voltage across the terminals of certain resistors in order to activate them. These resistors heat to a relatively high temperature, for example greater than 100 OC.

 An alternative embodiment of the present invention, illustrated in FIG. 6, consists in producing a chip card 10 comprising a display 12 with mono-stable liquid crystals or with electrochromic material having no memory effect. In this case, it is necessary to power the display permanently to be able to keep the display.

For this, the card 10 also includes a battery
P and a switching circuit CC which makes it possible to artificially create a certain bistability. This switching circuit CC is controlled by the chip 11. In order to maintain the recording of the information, the switching circuit CC is turned on and the battery P delivers, at the terminals of the electrodes of the display, an alternating frequency voltage suitable in the case of a liquid crystal display; or a DC voltage determined in the case of an electrochromic display. The blocking of the switching circuit CC causes the erasing of the preexisting inscription since, in this case, the battery P can no longer deliver voltage across the terminals of the electrodes of the display.

 According to a variant, this battery P is advantageously replaced by a rechargeable battery. Thus, when the card 10 is inserted into the reader 20, the reader supplies the chip with a certain energy which is switched to the battery, by means of the switching circuit: this makes it possible to recharge the battery.

 According to another variant, the display 12 has a memory effect. In this case, the battery P delivers a voltage across the electrodes of the display only to cause writing or erasing. In this example, the chip 11 also includes a microprocessor intended to manage the display. A reader is therefore no longer necessary to write and erase information.

Claims (17)

 1. Chip card (10) comprising a display (12) of information contained in the chip (11), the erasure of which is obtained only by the reception of signals transmitted during the uses of the card.  2. Chip card according to claim 1, characterized in that the signals are transmitted by a reader / recorder (20).  3. Chip card according to one of claims 1 to 2, characterized in that the signals are electrical signals and in that the display (12) comprises a layer of ferroelectric material.  4. Chip card according to claim 3, characterized in that the ferroelectric material comprises bi-stable liquid crystals (15).  5. Chip card according to claim 3, characterized in that the ferroelectric material comprises bi-stable liquid crystals (15) dispersed in a polymer.  6. Chip card according to claim 3, characterized in that the ferroelectric material comprises bi-stable ceramic crystals.  7. Chip card according to claim 6, characterized in that the bistable ceramic crystals are PLZT crystals based on lead oxide, Lanthanum, Zirconium and Titanium.  8. Chip card according to one of claims 1 to 2, characterized in that the signals are electrical signals and in that the display (12) comprises a layer of electro-chrome material (16).  9. Chip card according to claim 8, characterized in that the electro-chromium material comprises tungsten oxide WO3.  10. Chip card according to one of claims 1 to 2, characterized in that the signals are electrical signals and in that the display (12) comprises a layer of thermochromic material.  11. Smart card according to claim 10, characterized in that the thermochromic material comprises bi-stable mineral materials.  12. Chip card according to one of claims 10 to 11, characterized in that small resistors (19), placed under the thermo-chrome material, make it possible to heat said thermo-chrome material.  13. Chip card according to one of claims 1 to 2, characterized in that the signals are electrical signals, the display (12) comprises a layer of mono-stable liquid crystals or a layer of electro-chrome material without memory effect, and in that the card (10) comprises a battery P and a switching circuit CC capable of maintaining the display permanently.  14. Chip card according to claim 1, characterized in that the chip (11) comprises a microprocessor and in that the signals are emitted by the chip.  15. Chip card according to one of claims 1 or 14, characterized in that the signals are electrical signals, the display (12) comprises a layer of bi-stable liquid crystals or a layer of electro-chromium material to memory effect, and in that the card (10) comprises a battery and a switching circuit in order to be able to cause a display.  16. Chip card according to one of claims 1 to 15, characterized in that the display (12) is placed in the center of the card (10).  17. Chip card according to one of claims 1 to 16, characterized in that an erasing head, controlled by the management block (21) of the reader / recorder (20), makes it possible to erase the preexisting inscriptions.  28. Reader / recorder (20), characterized in that it comprises a signal generator capable of controlling a display placed on a smart card.