Radio frequency tag electromagnetic shielding device, assembly comprising an electromagnetic shielding device and a radio frequency tag and radio frequency tag electromagnetic shielding method

Abstract

Electromagnetic shielding device for a radio frequency tag, assembly comprising an electromagnetic shielding device and a radio frequency tag and method for electromagnetic shielding of a radio frequency tag Electromagnetic shielding device 8 for an HF radio frequency tag, forming a low-pass filter for frequencies below 100 MHz, frequencies between 2 and 4 GHz being filtered at more than 50%, preferably at more than 90%, comprising a protective layer 9 against mechanical and chemical attacks comprising a first surface for cooperating with the tag and a second surface opposite the first surface, and a metallic conductive pattern 10 with a thickness of less than 20 microns, in contact with the first or second surface and protected by the protective layer 9, the conductive pattern 10 being periodic, the conductive pattern 10 having a line width of less than 2 mm,the conductive pattern 10 having a minimum convex radius of at least 0.30 mm.,

Description

Title of the invention: Radio frequency tag electromagnetic shielding device, assembly comprising an electromagnetic shielding device and a radio frequency tag and method of electromagnetic shielding of a radio frequency tag

[0001] The invention relates to the field of tableware or kitchenware made of durable material. Tableware includes plates, dishes, hollow containers such as soup tureens or vegetable bowls, glasses, carafes, pitchers, ramekins, etc. Kitchenware partly overlaps tableware. Kitchenware includes containers in which food is prepared, in particular cut, ground or cooked.

[0002] Disposable tableware made from materials derived from the petrochemical industry has been used until recently. The high consumption of energy and raw materials, and the generation of polluting waste, are leading to a reconsideration, or even a ban, of disposable tableware.

[0003] There is a need to efficiently manage a fleet of dishes in a professional catering establishment, particularly a collective one. From another point of view, contactless payment without cashier staff is developing.

[0004] The emergence of automatic canteens with a need for dishes connected to contactless payment tills has given rise to numerous proposals for reusable glass containers (dishes, plates, ramekins, etc.) that can be digitally located or traced with contactless solutions such as RFID.

[0005] However, the connected tableware item could be damaged when put in a dishwasher or microwave oven.

[0006] Furthermore, the price of a tableware item requires the use of a standard RFID tag produced in large quantities. However, the applicant has observed that a standard RFID tag does not withstand being placed in a microwave oven due to the occurrence of short circuits or thermal destruction likely to cause a fire.

[0007] FR3125149 describes an RFID tag device equipped on one side with a layer of a silicone material and having a dielectric permittivity greater than at least three times the dielectric permittivity of air and a thickness of at least 6 millimeters. A waveguide is formed by 3D stacking. The RFID tag is provided on one side with a layer of plate copper with a thickness of at least 3 times, or even 10 times, the penetration depth of microwaves at 2.45 GHz. The RFID tag has an operating frequency of 868 MHz. However, the figures show an antenna unsuitable for this frequency. The total thickness is very high.

[0008] The Applicant also noticed that certain devices of the prior art boasting resistance to microwaves were in reality content with preserving the external appearance of the RFID tag after having been subjected to microwaves but did not offer multiple uses with a succession of a large number of cycles of heating the tableware item in microwaves and washing.

[0009] The applicant sought to offer real benefits to consumers with the reuse of containers made of durable material allowing repeated use, the durability of the communication function of said containers, and the quality of remote transmission.

[0010] The invention improves the situation.

[0011] The invention proposes an electromagnetic shielding device for an HF radio frequency tag, forming a low-pass filter for frequencies below 100 MHz, frequencies between 2 and 4 GHz being filtered at more than 50%, preferably at more than 90%, comprising a protective layer against mechanical and chemical attacks comprising a first surface for cooperating with the tag and a second surface opposite the first surface, and a metallic conductive pattern with a thickness of less than 20 microns, in contact with the first or second surface and protected by the protective layer. The conductive pattern is periodic. The conductive pattern has a line width of less than 2 mm. The conductive pattern has a minimum convex radius of at least 0.30 mm. The electromagnetic shielding is dishwasher-resistant, microwave-resistant, generates little heat under the effect of microwaves and is durable.Thus, the functions offered at the first use are retained for subsequent uses.

[0012] In one embodiment, the conductive pattern is made from silver or copper and the protective layer comprises a vitreous enamel. The conduction is high. The heating is low. The protection against chemical agents is effective.

[0013] In one embodiment, the conductive pattern has a thickness of less than 15 microns, the protective layer has a thickness of less than 20 microns. The electromagnetic shielding is permeable to HF radio waves and effective against waves above 1 GHz. Thus, the electromagnetic shielding is sufficiently permeable in NFC mode and sufficiently impermeable in UHF mode. Said permeability allows communication with an electronic tag. Said impermeability allows the electronic tag to withstand heating microwaves.

[0014] In one embodiment, the conductive pattern has a line width of less than 0.5 mm and a width between lines of less than 4 mm, preferably less than 1 mm. Heating is low.

[0015] In one embodiment, the conductive pattern is single-layer and the shielding layer is single-layer. The electromagnetic shielding is very thin and low- bulky. The thickness of the electromagnetic shielding is less than 40 microns.

[0016] In one embodiment, the conductive pattern is continuous in the form of closed meshes or open patterns, in particular spirals. The risk of short circuit is low.

[0017] In one embodiment, the electromagnetic shield is attached to a microwave oven tray, on the upper face. The electromagnetic shield is thus positioned to protect an electronic tag attached to the lower face of a piece of crockery that is placed on the tray for the purpose of heating food placed on or in the piece of crockery.

[0018] In one embodiment, the electromagnetic shielding has rounded closed meshes in the shape of a tetrasceles.

[0019] In one embodiment, the electromagnetic shielding has rounded closed meshes in the shape of a triscele, pentascele or hexascele.

[0020] In one embodiment, an assembly comprises an HF radio frequency tag electromagnetic shielding device and an HF radio frequency tag, the maximum dimension of the conductive pattern being at least equal to the maximum dimension of the tag, preferably at least equal to 1.2 times the maximum dimension of the tag. The assembly may be attached to a small tableware item, for example a cup or drinking glass.

[0021] In one embodiment, a piece of tableware for household or professional use comprises an assembly as above. The electromagnetic shielding device and the radio frequency label are arranged in a concavity provided in the piece of tableware. The assembly may be affixed to a piece of tableware, for example to a hollow existing on the lower face of said piece of tableware.

[0022] In one embodiment, a dinnerware item includes a body made of ceramic, soda-lime glass, borosilicate glass, crystalline, stoneware, earthenware, porcelain, wood, or plastic. The dinnerware item is durable. The dinnerware item is returnable.

[0023] In one embodiment, a method for electromagnetically shielding an HF radio frequency tag is provided, comprising providing a piece of tableware, affixing an electromagnetic shielding device to the piece of tableware, and attaching an HF radio frequency tag to said device. The electromagnetic shielding may be formed at elevated temperature, for example at least 600° and the RFID tag may be disposed after cooling.

[0024] In one embodiment, the electromagnetic shielding may be formed at low temperature, in particular less than 100°, for example at room temperature. The electromagnetic shielding may comprise a pattern affixed to a plastic wall, in particular food-grade plastic. The electromagnetic shielding may comprise a pattern affixed to a plastic film.

[0025] In one embodiment, the electromagnetic shielding device is deposited by pad printing, screen printing, inkjet or metal film deposition. The yield is high for articles having non-planar surfaces.

[0026] In one embodiment, the conductive pattern is provided in the form of a metallized ink. The metallized ink is suitable for pad printing and for flat or non-flat surfaces.

[0027] In one embodiment, a method for electromagnetically shielding an HF radio frequency tag is provided, comprising providing an HF radio frequency tag, affixing an electromagnetic shielding device to the HF radio frequency tag, and affixing a protective varnish. The method is simple to implement.

[0028] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0029] [Fig.l]. is a top view of radio frequency tags according to one aspect of the invention.

[0030] [Fig.2]. is a side elevational view of a piece of crockery equipped with a radio frequency tag assembly and electromagnetic shielding device according to one aspect of the invention.

[0031] [Fig.3] is a bottom elevation view of a piece of crockery fitted with a radio frequency tag assembly and electromagnetic shielding device according to another aspect of the invention.

[0032] [Fig.4]. is a bottom elevation view of a piece of crockery equipped with a radio frequency tag assembly and electromagnetic shielding device according to another aspect of the invention.

[0033] [Fig.5] is a detail view of [Fig.4].

[0034] The attached drawings may not only serve to complete the invention, but also contribute to its definition, where appropriate.

[0035] The Applicant realized that there was a need to produce a durable, traceable and reusable piece of tableware. The resistance of the radio frequency label to washing and to microwaves used for heating or cooking presents major difficulties. Microwaves generate overvoltages in the radio frequency label leading to breakdown by short circuit or destruction by heating.

[0036] The Applicant has carried out tests of electromagnetic shielding against microwaves of common frequency, i.e. 2.45 GHz. The electromagnetic shielding intercepts part of the useful signal of the radio frequency tag, both in transmission and in reception.

[0037] Affixing the electromagnetic shielding on one side and the radio frequency label on the other side of the piece of crockery can lead to the destruction of the radio frequency label depending on the wall thickness between the faces of the tableware piece and other parameters. It is desirable that the electromagnetic shielding and the radio frequency label are arranged on the same face of the tableware piece.

[0038] In one embodiment, the electromagnetic shielding is affixed to an upper face of a microwave oven tray. The microwave oven tray may be made of glass.

[0039] As illustrated in [Fig.l], radio frequency tags 1 are available by being provided on a support strip 2. The support strip 2 is common to several radio frequency tags. The radio frequency tags 1 are HF, i.e. in the band from 3 to 30 MHz. The radio frequency tags 1 are flexible and can be planar. The radio frequency tags 1 comprise an antenna 3 and an electronic chip 4. In the embodiment shown, the antenna 3 is wound around the electronic chip 4. The antenna 3 comprises a plurality of turns, with an inner turn connected to the electronic chip 4 directly, and an outer turn connected to the electronic chip 4 by an electrical bridge passing over the other turns and electrically insulated from the other turns. Alternatively, the antenna has a rectangular shape. Alternatively, the antenna has a square shape.

[0040] In [Fig. 2], a piece of tableware 5 is shown. Here, the piece of tableware 5 is a cup with a handle. The piece of tableware 5 can be made of earthenware, glass, in particular soda-lime, borosilicate, fluosilicate, crystalline, stoneware, earthenware, porcelain, wood or plastic.

[0041] . The piece of crockery 5 has a cylindrical wall 6 having a surface ex exterior. The piece of crockery 5 carries a shielded radio frequency tag assembly 7. The shielded radio frequency tag assembly 7 is arranged on the outer surface of the cylindrical wall 6. The shielded radio frequency tag assembly 7 is thus supported by a convex surface.

[0042] In another embodiment, the shielded radio frequency tag assembly 7 is supported by a concave surface of a piece of crockery, for example a plate bottom, see [Fig.3].

[0043] The shielded radio frequency tag assembly 7 comprises a radio frequency tag 1 and an electromagnetic shielding device 8. The electromagnetic shielding device 8 is affixed to the outer surface of the cylindrical wall 6. The electromagnetic shielding device 8 is fixed by adhesion. Here, the electromagnetic shielding device 8 is circular. Here, the electromagnetic shielding device 8 has a diameter of between 30 mm and 120 mm. The electromagnetic shielding device 8 has a thickness of between 0.03 mm and 0.1 mm.

[0044] The radio frequency label 1 is affixed to the surface of the electrical shielding device electromagnetic 8. The radio frequency label 1 is fixed by adhesion. The radio frequency label 1 has a surface area smaller than the surface area of ​​the electromagnetic shielding device 8. The radio frequency label 1 is centered on the electromagnetic shielding device 8. Alternatively, the radio frequency label 1 is off-center relative to the electromagnetic shielding device 8. The radio frequency label 1 is circular, in particular with a diameter of between 9 mm and 40 mm. The radio frequency label 1 has a thickness of between 0.075 mm and 0.200 mm.

[0045] The electromagnetic shielding device 8 comprises a conductive pattern 10. The conductive pattern 10 may have a thickness of less than 15 microns, for example between 5 and 13 microns. The conductive pattern 10 is made from a conductive metal, in particular from silver or copper. The conductive pattern 10 may be single-layer. The conductive pattern 10 may be deposited by pad printing, screen printing or metal film deposition. The conductive pattern 10 may be provided in the form of conductive metallized ink by an industrial inkjet printer. In contrast to a continuous conductive layer which would filter the microwaves and radio frequency waves of the radio frequency label, the conductive pattern 10 aims to allow the radio frequency waves of the radio frequency label to pass through and to filter the microwaves. For this purpose, the conductive pattern 10 has conductive zones and non-conductive zones according to a chosen design.The conductive pattern 10 is resistant to a temperature of more than 600°C in order to be able to undergo a ceramization step. The ceramization ensures that the conductive pattern 10 lasts over time and is resistant to washing and common rubbing when using a piece of tableware.

[0046] In a variant, the conductive pattern 10 is produced by low-temperature polymerization of an organic metallized ink. The polymerization ensures that the conductive pattern 10 lasts over time and is resistant to washing and common friction when using a piece of tableware. The electromagnetic shielding device 8 comprises a protective layer 9. The protective layer 9 is provided against mechanical and chemical attack. The protective layer 9 comprises an enamel, in particular a vitreous enamel. The protective layer 9 may be single-layer. The protective layer has a thickness of less than 20 microns, in particular between 5 and 15 microns. The protective layer 9 may be wider than the conductive pattern 10. The protective layer 9 is electrically insulating. The conductive pattern 10 is entirely covered by the protective layer 9.

[0047] The conductive pattern 10 may be formed by a conductive track. The conductive pattern 10 may have a contour shape of tetrasceles neighboring each other, see [Fig.2] for a cup and [Fig.3] for a plate. Said contour is continuous. The contour of the tetrasceles is conductive. The tetrasceles are distant from each other. of others. The conductive pattern 10 is closed mesh while each tetrasceles is insulating. The conductive pattern 10 is continuous. Said conductive track surrounds each tetrasceles. A space of constant width, formed by the conductive track, is provided between two neighboring tetrasceles. In other words, the tetrasceles are insulating, due to the absence of conductive material. Said conductive track has a constant width or line width. The width is less than 2 mm, preferably less than 0.50 mm.

[0048] Said conductive track has a minimum convex radius of at least 0.35 mm, preferably at least 0.40 mm, in a local plane of the conductive track in [Fig.2], in a plane of the conductive pattern 10 in [Fig.3]. Thus, convex sharp angles of the conductive track are absent to reduce the risks of short-circuiting while concave sharp angles of the conductive track are permitted.

[0049] Each tetrasceles is inscribed in a square with a side length between 3 mm and 8 mm. The tetrasceles have four branches extending over an angle between 30 and less than 60°. Said angle is defined between the hypotenuse and the adjacent small side of a right triangle in which one branch of the tetrasceles is inscribed. The tetrasceles are arranged in a diamond shape.

[0050] The electromagnetic shielding device 8 has a diameter between 1.5 and 3 times the diameter of the radio frequency tag 1.

[0051] The tetrasceles conductive pattern 10 of [Fig.2] filters more than 85% of the microwaves at 2.45 GHz with a track width of 0.42 mm and allows more than 40% of the signal from the radio frequency tag 1 to pass at 13.56 MHz.

[0052] In the embodiment of Figures 3 and 4, the piece of tableware 5 is a plate or dish. The piece of tableware 5 has an upper face for receiving food and a lower face 15. The lower face 15 includes a peripheral rim 16 on which the piece of tableware 5 rests during use and a hollow 17. The peripheral rim 16 surrounds the hollow 17. The shielded radio frequency tag assembly 7 is affixed in the hollow 17. Alternatively, the hollow is partially or completely filled with resin having a refractive index or color similar to that of the structural material of the piece of tableware 5. Alternatively, the shielded radio frequency tag assembly 7 is affixed to a flat lower face.

[0053] The conductive pattern 10 with tetrasceles of [Fig.3] filters more than 90% of the microwaves at 2.45 GHz with a track width of 0.42 mm and allows more than 40% of the signal from the radio frequency tag 1 to pass at 13.56 MHz, or even more than 50%.

[0054] The electromagnetic shielding device 8 has a diameter between 4 and 8 times the diameter of the radio frequency tag 1 in the mode shown.

[0055] The conductive pattern 10 may have a shape of triskelions adjacent to each other, see figures 4 and 5. The conductive pattern 10 is discontinuous. The conductive pattern 10 is open mesh. Each triscel comprises three spirals 11 each formed of a wire. The wire or line has a width of less than 2 mm, for example between 0.2 mm and 1.6 mm. The spirals are nested two by two between neighboring triscels. Double spirals are thus formed. The wires of a double spiral are disjointed at the center of the spiral and diametrically opposed outside the spiral. At the center of the double spiral, each wire has a free end formed in an arc of a circle. The free end in an arc of a circle is opposite the free end in an arc of a circle of the other wire. Preferably, the salient angle between said arc of a circle and the chord of said arc of a circle is at most 90°. Depending on the graphic resolution of the manufacturing process, the free end in an arc of a circle may be left raw as shown or may be formed with a fillet.On the outside of the spiral, each wire is connected to the wires of two neighboring spirals forming a triscele. The connection between said wire and the wires of the two neighboring spirals in the center of the triscele is formed in a triangle with concave rounded sides. The two wires of a double spiral are 0.2 to 2 mm apart.

[0056] Each triskelion is electrically independent. Three neighboring triskelions leave an interior space free of conductive pattern 10. The interior space has a six-pointed star shape with a small diameter close to the diameter of a spiral. The triskelions have a minimum radius of at least 5 mm, preferably at least 6 mm. The triskelions are inscribed in a triangle with a side length between 13 mm and 17 mm, preferably 14.5 mm and 15.5 mm. The ratio of the side of the triangle to the minimum radius is of the order of 2.48. The conductive pattern 10 has the general shape of a hexagon. The spirals of the outer edges of the conductive pattern 10 are simple spirals, i.e. not nested with another spiral of another triskelion. A spiral is wound on two turns. [Fig.5] shows a detail of an outer edge spiral. The 10-conductor trisceles pattern provides inductive-capacitive coupling.The 10-conductor triskelion pattern of Figures 4 and 5 filters more than 70% of microwaves at 2.45 GHz, or even more than 80%.

[0057] In an embodiment not shown, each spiral is close to six spirals. Said six spirals are arranged in a hexagon around said spiral.

[0058] In an embodiment not shown, each spiral comprises six independent wires. The conductive pattern 10 with hexafilar trisceles filters more than 90% of microwaves at 2.45 GHz with a track width of 1 mm, in particular with a turn angle of between more than 215° and 230°. The conductive pattern 10 with hexafilar trisceles filters more than 90% of microwaves at 2.45 GHz with a track width of 0.5 mm, in particular with a turn angle of between more than 415° and less than 420°.

[0059] The tetrasceles motif is superior to the trisceles motif in terms of limiting warming.

[0060] In an embodiment not shown, the tetrasceles comprise spirals rolled at an angle between 180 and 540°.

[0061] The electromagnetic shielding device 8 has a diameter between 4 and 8 times the diameter of the radio frequency tag 1 in the mode shown. The electromagnetic shielding device 8 complies with standard EN 15284.

[0062] Tests were carried out on plates which had previously been exposed to the same household microwave oven set with the same cooking parameters in order to eliminate the case of defective plates whose structure or decoration may present overheating or electric arcing in a microwave oven.

[0063] The tests carried out with a radio frequency tag 1 of frequency 13.56 MHz, i.e. in the HF band, with the electromagnetic shielding device 8, in a household microwave oven have shown that the radio frequency tag 1 and its functionality are preserved. Thus, the radio frequency tag 1 is operational after several dozen passages in the household microwave oven of frequency 2.45 GHz.

[0064] In comparative tests, an identical radio frequency label 1, affixed to the same piece of crockery, but without the electromagnetic shielding device, is destroyed almost instantly with the appearance of electric arcs in the same household microwave oven set with the same cooking parameters. In other comparative tests, an identical radio frequency label 1, affixed to the same piece of crockery, and with an electromagnetic shielding device 8 affixed to the same piece of crockery but on an opposite face, i.e. 2-3 mm apart, is destroyed after a few seconds with the appearance of electric arcs in the same household microwave oven set with the same cooking parameters.

[0065] The tests were carried out with identical plates with the electromagnetic shielding device 8 and the radio frequency tag 1 in mutual contact and arranged in a hollow of the plate. The tests carried out on plates made of fluosilicate glass with a fluorine content of at least 1% by mass and on plates made of soda-lime glass comprising from 1 to 20% of Ca, from 5 to 20% of Na and from 50 to 80% of Si showed identical results in terms of filtering.

[0066] The electromagnetic shielding device 8 attached to the radio frequency label 1 forms a low-pass filter for frequencies below 100 MHz, in particular with high transmission for the frequency 13.56 MHz. The electromagnetic shielding device 8 attached to the radio frequency label 1 forms a filter for frequencies above 1 GHz, in particular for frequencies between 2 and 4 GHz being filtered at more than 50%. The patterns shown in FIGS. 2 to 5 provide filtering of the 2.45 GHz frequency at more than 90%.

[0067] The plates with tetrasceles patterns on the bottom of the plate withstood a 2-minute cycle in the same household microwave oven. The tests were carried out with 7 sets of shielded radio frequency tags with Ag conductive pattern of diameters 39 mm, 48 mm, 60 mm, 73.3 mm, 93.6 mm and 139.2 mm and a radio frequency tag 1 of 25 mm diameter without highlighting any difference in behavior. The temperatures of the plate at the outlet of the domestic microwave oven were between 32 and 48°C, increasing with the diameter of the sets 7 of shielded radio frequency tag. No electric arc occurred. The presence or absence of an ornamental decoration in the plate did not generate any difference in the test results.

[0068] Then the same plates with tetrasceles patterns withstood a long cycle according to the EN15284 standard of 12 minutes in the same household microwave oven. The temperatures of the plates at the outlet of the household microwave oven were 52°C regardless of the diameter of the sets 7 of shielded radio frequency label. No electric arc occurred.

[0069] Fatigue tests with 50 passages in a household microwave oven for 2 minutes showed satisfaction of the two criteria of absence of electric arc during passages in the household microwave oven and reading of the radio frequency label 1 at the end.

[0070] In one embodiment, the shielded communicating crockery piece is manufactured as follows. A commercially available crockery piece is supplied. An electromagnetic shielding device 8 is applied by pad printing to the underside of the crockery piece. The conductive pattern is provided in the form of a metallic ink, in particular silver-based. The protective layer is provided in the form of a vitreous mineral enamel. In another embodiment, the protective layer is provided in the form of an organic ink based on epoxy, silicone or polyurethane followed by polymerization. A ceramization step at at least 600°C may be provided. A radio frequency label 1 is applied to the electromagnetic shielding device 8. The radio frequency label 1 is fixed.

[0071] In another embodiment, the shielded communicating crockery piece is manufactured as follows. A commercial crockery piece is supplied. A radio frequency label 1 is affixed to the underside of the crockery piece. An electromagnetic shielding device 8 is affixed by pad printing to the same underside of the crockery piece, covering the radio frequency label 1. The conductive pattern is provided in the form of metallized ink, in particular silver-based. The protective layer is provided in the form of organic ink or organic protective varnish. The organic ink can be applied by screen printing or pad printing. The organic varnish can be applied by spraying. The electromagnetic shielding device 8 is applied to the radio frequency label 1. A polymerization step can be provided by heating to less than 250° or UV or drying.

[0072] In another embodiment, a self-adhesive assembly comprises an electromagnetic shielding device 8, a flexible plastic support supporting the device, and a radio frequency label 1. The electromagnetic shielding device 8 and the flexible plastic support are fixed together, for example by gluing. Said self-adhesive assembly is provided with an adhesive on an external face and a peelable film for protecting the adhesive. Preferably, the electromagnetic shielding device 8, the radio frequency label 1 and the flexible plastic support have similar dimensions, diameter or width and length. Thus the electromagnetic shielding device 8 has a diameter between 1 and 1.5 times the diameter of the radio frequency label 1.

[0073] Thus, a resonant system with respect to the blocking of microwaves is formed. This corresponds to a minimum impedance of the printed circuit forming the electromagnetic shielding at the microwave frequency. In the vicinity of the electromagnetic shielding, the electric field caused by the microwaves vanishes, giving rise to significant electric currents in the electromagnetic shielding which acts as a quasi-short circuit. The RFID tag attached to the electromagnetic shielding is then protected against the polarizing electrical effects which disappear with the disappearing electric field. The electromagnetic shielding behaves like a broadband resonant circuit. At the RFID frequency, the electromagnetic shielding has an impedance high enough not to absorb the entire RFID signal, so that a portion of it remains sufficient to operate with the RFID tag.

Claims

Claims

1. Electromagnetic shielding device (8) for an HF radio frequency tag, forming a low-pass filter for frequencies below 100 MHz, frequencies between 2 and 4 GHz being filtered at more than 50%, preferably at more than 90%, comprising a protective layer (9) against mechanical and chemical attacks comprising a first surface for cooperating with the tag and a second surface opposite the first surface, and a metallic conductive pattern (10) with a thickness of less than 20 microns, in contact with the first or second surface and protected by the protective layer (9), the conductive pattern (10) being periodic, the conductive pattern (10) having a line width of less than 2 mm, the conductive pattern (10) having a minimum convex radius of at least 0.30 mm.

2. Device according to claim 1, in which the conductive pattern (10) is made from silver or copper and the protective layer (9) comprises a vitreous enamel.

3. Device according to claim 1 or 2, in which the conductive pattern (10) has a thickness of less than 15 microns, the protective layer (9) has a thickness of less than 20 microns.

4. Device according to one of the preceding claims, in which the conductive pattern (10) has a line width of less than 0.5 mm and a width between lines of less than 4 mm, preferably less than 1 mm.

5. Device according to one of the preceding claims, in which the conductive pattern (10) is single-layer and the protective layer (9) is single-layer.

6. Device according to one of the preceding claims, in which the conductive pattern (10) is continuous in the form of closed meshes or open patterns, in particular spirals.

7. Assembly (7) comprising a device according to one of the preceding claims and a radio frequency tag (1) HF, the maximum dimension of the conductive pattern (10) being at least equal to the maximum dimension of the tag, preferably at least equal to 1.2 times the maximum dimension of the tag.

8. A piece of tableware (5) for household or professional use comprising an assembly (7) according to claim 7, the electromagnetic shielding device (8) and the radio frequency tag (1) being arranged in a

9.

10.

11.

12.

13. concavity provided in the piece of crockery (5). A piece of tableware according to claim 8, comprising a body made of ceramic, soda-lime glass, borosilicate glass, crystalline, stoneware, earthenware, porcelain, wood or plastic. A method of electromagnetic shielding of an HF radio frequency tag, comprising providing a piece of crockery (5), affixing an electromagnetic shielding device (8) according to one of claims 1 to 6 to the piece of crockery, and attaching an HF radio frequency tag (1) to said device. A method according to claim 10, wherein the electromagnetic shielding device (8) is deposited by pad printing, screen printing, inkjet or metal film deposition. A method according to claim 10 or 11, wherein the conductive pattern (10) is provided in the form of metallic ink. Method for electromagnetic shielding of an HF radio frequency tag, comprising providing an HF radio frequency tag, affixing a device according to one of claims 1 to 6 on the HF radio frequency tag and affixing a protective varnish.

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