Sheet exhibiting dielectric or magneto-dielectric properties

Abstract

Sheet comprising a flexible support and a coating at least partially covering at least one face of the support, the support being made of a support material exhibiting dielectric properties, the coating being made of a coating material different from the support material and exhibiting magneto-dielectric properties or dielectric properties.

Claims

1. A composite structure comprising a sheet comprising a flexible support and a coating at least partially covering at least one face of the support, the support being made of a support material being dielectric, the coating being made of a coating material different from the support material and being magneto-dielectric exhibiting both a relative permittivity and a relative permeability that are each greater than 1.0, the sheet being wound on itself around a winding axis or folded on itself.

2. The composite structure according to claim 1, the sheet being wound along a winding path defining a spiral at right angles to the winding axis.

3. The composite structure according to claim 2, having a generally tubular form extending along the winding axis.

4. A device for emitting or picking up an electromagnetic wave, the device comprising an electromagnetic antenna comprising the composite structure according to claim 3.

5. The composite structure according to claim 1, the support material being a thermoplastic or thermosetting polymer, selected from the group consisting of a polyimide, polyvinyl siloxane, polyethylene, polypropylene, polystyrene, acrylonitrile butadiene styrene and the mixtures thereof, or being a glass fiber-based composite.

6. The composite structure according to claim 1, wherein the coating entirely covers at least one face of the support.

7. The composite structure according to claim 1, wherein the coating partially covers one face of the support.

8. The composite structure according to claim 7, having elementary patterns defining a regular arrangement according to at least one direction.

9. The composite structure according to claim 7, the coating covering less than 90% of the area of a face of the support.

10. The composite structure according to claim 1, comprising a metallic layer at least partially covering one face of the support.

11. A method comprising: manufacturing a sheet comprising a flexible support and a coating at least partially covering at least one face of the support, the support being made of a support material being dielectric, the coating being made of a coating material different from the support material and being magneto-dielectric exhibiting both a relative permittivity and a relative permeability that are each greater than 1.0, depositing an ink comprising the coating material on at least one face of the support, to form the coating, and forming the sheet, comprising the winding of the sheet on itself around a winding axis, or folding the sheet on itself.

12. The method according to claim 11, wherein, during the manufacturing of the sheet, the ink is deposited by a technique selected from the group consisting of screen printing, spin coating, blade coating, ultrasonic spray coating, slot-die coating, inkjet printing, flexography and photogravure.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will be able to be better understood on reading the following detailed description, of nonlimiting exemplary embodiments thereof, and on studying the attached drawing in which:

(2) FIG. 1 represents, in cross section, an example of sheet according to the invention,

(3) FIG. 2 represents, in cross section, another example of sheet according to the invention,

(4) FIG. 3 represents, in cross section, yet another example of sheet according to the invention,

(5) FIG. 4 represents a top view of the example illustrated in FIG. 3,

(6) FIG. 5a) to f) represent other examples of sheet,

(7) FIG. 6a) to c) represent other examples of sheet,

(8) FIG. 7 is a top view of a sheet illustrating an example of particular arrangement of the coating on the support,

(9) FIG. 8 illustrates an example of implementation of the method for manufacturing a sheet according to the invention,

(10) FIG. 9 represents, according to a perspective view, a composite structure obtained by winding of the sheet illustrated in FIGS. 3 and 4,

(11) FIG. 10 represents, according to a respectively axial view, a composite structure obtained by winding of the sheet illustrated in FIGS. 3 and 4,

(12) FIG. 11 represents, according to a perspective view, a composite structure obtained by winding of the sheet illustrated in FIG. 7,

(13) FIG. 12 represents, according to a perspective view, a composite structure obtained by winding of the sheet illustrated in FIG. 5,

(14) FIG. 13 illustrates an example of implementation of the forming method according to the invention,

(15) FIG. 14 represents an example of composite structure, and

(16) FIG. 15 represents an example of composite structure.

DETAILED DESCRIPTION

(17) In the interests of clarity, the relative proportions of the constituent elements of the sheet and of the composite structure have not necessarily been respected in the figures.

(18) The sheet 5 illustrated in FIG. 1 comprises a support 10 and a coating 15. The coating is in contact with one face 20 of the support.

(19) The support is for example made of Kapton® marketed by the company Dupont or of PET. In FIG. 1, the coating partially covers the face 20. As a variant, as will be observed hereinbelow, the coating can cover all of the face 20.

(20) The sheet illustrated comprises an adhesive layer 25, disposed in contact with the face 30 of the support opposite the face 20 on which the coating is disposed. Such an adhesive layer is however optional.

(21) In the example of FIG. 2, the coating is disposed in contact with each of the opposite faces 20, 30 of the support.

(22) In FIG. 3, the coating covers all of the face 20 of the support with which it is in contact. Moreover, the sheet comprises a metallic layer 35, which partially covers the coating and extends over all the length of the sheet. The sheet has a parallelepipedal strip form of length L, of width l and of thickness e. The metallic layer 35, as appears in FIG. 4, is of width l.sub.c smaller than the width l of the sheet.

(23) FIGS. 5a to 5f illustrate other examples of sheets according to the invention seen according to a direction normal to one face of the sheet. The support 10 of each of the sheets of FIGS. 5a to 5f is partially covered by the coating 15. The coating is defined by the regular repetition along the length and the width of the sheet of a square elementary pattern 45. The elementary pattern can be rectangular, or of rhomboid or of circular form.

(24) The sheets of FIGS. 5a and 5d both have the same ratio of area covered by the coating to area of the face of the support on which the coating is disposed. In this particular case, the ratio is equal to 0.25. They differ in that they comprise a different number of elementary patterns according to the width of the sheet (5 and 10 for the examples of FIGS. 6a and 6d respectively).

(25) For one and the same number of elementary patterns according to the width of the sheet, the examples of FIGS. 5b-c and 5e-f respectively illustrate a variation of the ratio of area occupied by the coating to area of the face of the support on which the coating is disposed, in this particular case equal to 0.5 and 0.75.

(26) According to another example illustrated in FIGS. 6a to 6c, the elementary patterns 45 are disposed staggered relative to one another along the length of the sheet. For each of the sheets illustrated, the number of elementary patterns according to the width of the sheet is identical and equal to 5, and the ratio of area covered by the elementary patterns to the area of the face on which they are disposed is 0.25, 0.50 and 0.75 for the examples of FIGS. 6a to 6c respectively.

(27) FIG. 7 illustrates another example of implementation of the invention. The coating 15 extends progressively from one long edge 50a to the opposite long edge 50b moving lengthwise along the length L of the sheet. The area coated by the coating changes linearly between the two long edges of the sheet.

(28) To manufacture the sheets of the examples illustrated in FIGS. 1 to 7, it is possible to proceed as illustrated in FIG. 8 and as detailed hereinbelow.

(29) A screen printing device 60 is fed by means of the flexible support 10 made of a support material with the dielectric properties as described previously, for example made of Kapton®. The support 10 is disposed on a printing table 65.

(30) To perform a screen printing, it is possible to use the X-nano magnetic ink marketed by the company DNC Materials, or the Nanum Ink ink marketed by the company Nanum, or one of the inks H400, H270, P2189 and WL330 marketed by the company Mulann.

(31) The ink 70 comprising the coating material, for example a magneto-dielectric material, is deposited on one face 75 of the support 20. In the variant in which the aim is to partially cover the face of the support, the ink is deposited through a mask 80 and a blade 85 made of polyethylene is applied to scrape the ink on the surface of the mask so as to ensure a uniform deposition thickness.

(32) The mask is disposed on a screen 90 formed by a fabric 92 stretched on a frame 95, for example made of steel. The fabric is formed by metal or polyester wires. The wires define meshes through which the ink can flow. The ink is then deposited only in zones where there is no superposition with the mask.

(33) The ink is then dried, by evaporation of the solvent that it contains. The drying can be done at ambient temperature, or during a bake carried out at a temperature of between 100° C. and 135° C., for example for a duration of 30 minutes. The bake can be implemented by irradiating the ink by means of a laser. It can be photonic, that is to say that it is implemented by means of a light source, for example a flash UV lamp. Advantageously, the photonic bake heats up the solvent to evaporation and sinters the particles of the ink to one another without damaging the support. The photonic bake can be performed by means of the PulseForge 3200 lamp marketed by the company NovaCentrix.

(34) There is thus obtained a flat sheet formed by the support on which the coating 15 is deposited.

(35) Optionally, the sheet is then cut so as to have a determined width and length.

(36) The sheet can be formed to form all or part of a composite structure.

(37) FIGS. 9 and 10 illustrate an example of composite structure 100 comprising a wound sheet 100 formed by the spiral-winding on itself, around a winding axis X, of the sheet represented in FIGS. 3 and 4.

(38) The wound sheet has a generally tubular and hollow form of axis X.

(39) For example, it has:

(40) a width l, measured along the winding axis, of between 1 mm and 1 m, for example equal to to 10 mm,

(41) an outer diameter De, measured according to a radial direction, of between 2 mm and 40 mm, for example equal to 5 mm, and

(42) an inner diameter Di, measured according to a radial direction, of between 1 mm and 40 mm, for example equal to 4.5 mm.

(43) The wound sheet is defined by the winding of the sheet according to a winding path characterized by the arrow E, around the winding axis X. As can be observed in FIG. 9, the winding path E according to which the sheet is wound defines a spiral of axis X.

(44) The coating 15 is sandwiched between two consecutive windings 110, 120 of the support, whatever the windings considered. It is in contact with each of the facing faces 125,130 of the two consecutive windings.

(45) The wound sheet thus exhibits uniform and anisotropic magneto-dielectric or dielectric properties, although each winding defines a set with heterogeneous magneto-dielectric or dielectric properties.

(46) Notably, the wound sheet can have a permittivity tensor ε and/or a permeability tensor μ, expressed within a cylindrical reference frame centered on the winding axis, equal respectively to:

(47) $\begin{array}{cc}\mathrm{.Math.}=\left(\begin{array}{ccc}{\mathrm{.Math.}}_0{\mathrm{.Math.}}_1& & \\ & {\mathrm{.Math.}}_0{\mathrm{.Math.}}_2& \\ & & {\mathrm{.Math.}}_0{\mathrm{.Math.}}_3\end{array}\right)\mathrm{and}& \left[\mathrm{Math}1\right]\\ \mu =\left(\begin{array}{ccc}{\mu }_0{\mu }_1& & \\ & {\mu }_0{\mu }_2& \\ & & {\mu }_0{\mu }_3\end{array}\right)& \left[\mathrm{Math}2\right]\end{array}$

(48) With ε.sub.0 and μ.sub.0 being the permeability and the permittivity of the vacuum and ε.sub.i and μ.sub.i with i=1 to 3 being the components according to the axial, radial and orthoradial directions of the permeability and of the permittivity of the wound sheet.

(49) Moreover, the metallic layer 35 is, for its part, also spiral-wound around the winding axis. In a preferred variant in which the composite structure forms all or part of an electromagnetic antenna, the currents which are induced in the metallic layer transform a guided wave into a propagated wave.

(50) The composite structure illustrated in FIG. 11 comprises the sheet illustrated in FIG. 7 spiral-wound around the winding axis X. Moreover, the sheet is wound around a mandrel 70, cylindrical-of-revolution, with which it is in contact.

(51) Because of the increasing area of the surface of the support covered by the coating when moving along the wound sheet around the winding path E, the composite structure illustrated in FIG. 10 exhibits an anisotropic and heterogeneous magneto-dielectric or dielectric behavior, dependent notably on the radial distance to the winding axis and on the position according to the winding axis.

(52) The composite structure illustrated in FIG. 12 is obtained by winding of a sheet as illustrated in FIG. 6. The sheet of FIG. 6 thus wound thus defines a composite material exhibiting a local ratio of relative permittivity to relative permeability that changes periodically both angularly around and along the winding axis X respectively.

(53) FIG. 13 illustrates an example of forming of a sheet according to the invention to produce a wound sheet as described above.

(54) A sheet according to the invention is placed in contact with a mandrel 140 of axis X and cylindrical-of-revolution, linked for example to a motor. The mandrel is rotated so as to wind the sheet on itself to form the wound sheet of a composite structure according to the invention.

(55) The forming method can comprise the cutting of a sheet according to the invention, for example according to the width of the sheet, so as to form a plurality of small plates 150.sub.1-4. The small plates are then stacked one on top of the other, as illustrated in FIG. 15, according to a stacking direction D.sub.E normal to one of respective faces 155.sub.1-4 so as to form the composite structure 100. In order to ensure the cohesion between the small plates within the composite structure, the sheet can comprise an adhesive layer disposed on the face 155.sub.2-4 covered by the coating or on the face 160.sub.1-3 which is opposite to it. As a variant, prior to the assembling of the small plates with one another, an adhesive can be coated between two consecutive small plates of the stack.

(56) The forming method can comprise the folding of the sheet on itself, for example so as to bring a face 165 of the sheet into contact with itself, as is illustrated in FIG. 14. In this example, the sheet comprises an adhesive layer 25 disposed on one face of the support 10 opposite to that covered by the coating 15. During the folding step, the adhesive layer 25 is brought into contact with itself, so as to bind together the parts 170.sub.1-2 of the sheet disposed on either side of the fold line 180.

(57) As emerges clearly from the present description, the invention makes it possible to manufacture, simply and in industrial quantities, a sheet and a composite structure, which exhibit anisotropic and/or heterogeneous dielectric or magneto-dielectric properties.

(58) Obviously, the invention is not limited to the embodiments and implementations presented above by way of illustration.