PLASTIC LAYER FOR A SMART CARD

Abstract

A plastic sheet for manufacturing of a plurality of smart cards which respectively include a plurality of electronic units, includes a first sheet formed of a first material having a first hardness or a first Vicat softening temperature, the first sheet including a plurality of apertures and/or cavities. The plastic sheet includes a second material having, when the first material has the first hardness, a second hardness lower than the first hardness, and when the first material has the first Vicat softening temperature, a second Vicat softening temperature lower than the first Vicat softening temperature, the second material being located inside the apertures and/or cavities in the first sheet. The apertures and/or cavities with the second material located inside the apertures and/or cavities are configured to respectively receive said electronic units via an at least partial penetration from the electronic units into the second material.

Claims

1. A plastic sheet for manufacturing of a plurality of smart cards which respectively include a plurality of electronic units, comprising: a first sheet formed of a first material having a first hardness or a first Vicat softening temperature, the first sheet including a plurality of apertures and/or cavities; and a second material having, when the first material has the first hardness, a second hardness lower than the first hardness, and when the first material has the first Vicat softening temperature, a second Vicat softening temperature lower than the first Vicat softening temperature, the second material being located inside the plurality of apertures and/or cavities in the first sheet, wherein the plurality of apertures and/or cavities with the second material located inside the plurality of apertures and/or cavities are configured to respectively receive said plurality of electronic units via an at least partial penetration from the plurality of electronic units into the second material.

2. The plastic sheet according to claim 1, wherein said second Vicat softening temperature under a load of 10 N is lower than fifty degrees.

3. The plastic sheet according to claim 1, wherein said second hardness is less than 96 Shore A.

4. The plastic sheet according claim 1, wherein said first Vicat softening temperature under a load of 10 N is lower than sixty-five degrees.

5. The plastic sheet according to claim 1, wherein said first hardness is more than 60 Shore D.

6. The plastic sheet according to claim 1, wherein said second material is formed by a thermoplastic polyurethane elastomer.

7. The plastic sheet according to claim 1, wherein said first material forms the first sheet having the plurality of apertures at least partially filled by said second material.

8. The plastic sheet according to claim 1, wherein said first material forms the first sheet having the plurality of cavities at least partially filled by said second material.

9. The plastic sheet according to claim 1, wherein the second material that is located inside the plurality of apertures and/or cavities is substantially flush with a face of the plastic sheet in which the plurality of apertures and/or cavities are formed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention will be described below with reference to the annexed drawings, given by way of non-limiting example, and in which:

[0009] FIG. 1 is a schematic view of a step of the method of the invention for fabricating a bimaterial plastic sheet.

[0010] FIGS. 2 to 3 are schematic cross-sections of a next step of the fabrication method according to the invention.

[0011] FIG. 4 shows a schematic cross-section of a first embodiment of a bimaterial plastic sheet according to the invention.

[0012] FIG. 5 is a schematic view of a second embodiment of a bimaterial plastic sheet according to the invention.

[0013] FIG. 6 is a schematic view of a third embodiment of a bimaterial plastic sheet according to the invention.

[0014] FIG. 7 is a schematic top view of a fourth embodiment of a bimaterial plastic sheet according to the invention.

[0015] FIG. 8 is a schematic view of one use of a bimaterial sheet according to the invention in a first smart card fabrication method.

[0016] FIG. 9 shows an intermediate product occurring in the first smart card fabrication method and resulting from the step described in FIG. 8.

[0017] FIG. 10 is a schematic view of one use of a bimaterial sheet according to the invention in a second smart card fabrication method.

[0018] FIG. 11 shows an intermediate product occurring in the second smart card fabrication method and resulting from the step described in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Firstly, a method will be described for fabricating a plastic sheet involved in the formation of a plurality of smart cards which respectively include a plurality of electronic units. This plastic sheet is intended to at least partially receive the plurality of electronic units by penetrating the material forming the units, as will be explained below.

[0020] According to the invention, the method of fabricating a plastic sheet including the following steps:

[0021] A) Taking a first sheet 2 formed of a first material having a first hardness or a first Vicat softening temperature, said first sheet having a plurality of apertures 4 (see FIG. 1);

[0022] B) Respectively placing in said plurality of apertures 4 a plurality of discs 6 formed of a second material having a second hardness lower than the first hardness, respectively a second Vicat softening temperature lower than the first Vicat softening temperature (see FIGS. 1 and 2; it will be noted that, for the sake of clarity of the drawing, FIG. 1 only shows the discs provided for one row of apertures).

[0023] In a variant, the first sheet has a plurality of cavities (blind holes) and the discs are placed in said plurality of cavities. In another variant, the first sheet has apertures (which traverse the first sheet) and cavities which receive all the discs formed of a second material, these apertures and cavities being arranged to receive first and second electronic units respectively.

[0024] In the geometric plane parallel to general plane 10 of the first sheet 2, the plurality of discs 6, provided in the aforementioned step B), have smaller dimensions than those of the corresponding apertures 4 and/or cavities and a greater height H, along an axis perpendicular to said general plane, than that of the corresponding apertures and/or cavities, so that they rise above a face 8 of the first sheet. For circular discs, it is the diameter D of these circular discs which will be smaller than the diameter of the corresponding apertures 4 and/or cavities. For rectangular discs, the smaller dimensions are of course the width and length of the rectangular discs. Other disc geometries may be provided in general plane 10 in other variants.

[0025] Preferably, the first sheet 2 and discs 6 are placed on a support 12 having a top layer 14 which is non-adherent to the first sheet and the discs. The top layer 14 is for example formed of Teflon®. Support 12 for example forms part of a press 16 shown schematically in FIG. 2.

[0026] Following the insertion of each disc 6 in a corresponding aperture 4 or cavity, the following step is provided for the disc:

[0027] C) Exerting a pressure on disc 6 to reduce the height thereof so that the disc is substantially flush with face 8 of first sheet 2 and is at least partially in contact with lateral wall 20 of the corresponding aperture or cavity, disc 6 then being connected to the first sheet.

[0028] In a first implementation shown in FIG. 3, step C) is performed using laminating press 16. The bottom surface of the top part of the press is advantageously formed by a layer of Teflon® 18. It will be noted that layers 14 and 18 may be replaced by non-adherent sheets which are removable. In a preferred implementation, step C) consists of a hot lamination, the plurality of discs 6 being at least partially welded to the first sheet 2. Press 16 then includes a heating means. In this first implementation, the set of discs is placed in the corresponding apertures and then the aforementioned step C) is simultaneously performed for the plurality of discs. In a second implementation not shown in the Figures, steps B) and C) are performed cyclically for each disc or for subsets of discs among the plurality of discs. In a first variant, each disc is individually placed in the corresponding aperture using a tool. Next, a thermode is individually applied to the disc to perform step C); and these two steps are repeated with the following disc.

[0029] Preferably, the dimensions of the thermode are slightly larger than those of the apertures. The thermode thus covers the aperture and a peripheral area of the aperture when a disc inserted into the aperture is pushed in. This can thus be termed a localised lamination. In a particular variant, the first tool and the thermode form one and the same tool and step C) immediately follows step B) for each disc. In a second variant, a first subset of discs is placed in a first subset of corresponding apertures. Next, several thermodes are respectively placed on the subset of discs and step C) of the method is simultaneously performed for the subset of discs. The subset of apertures is, for example, a line or a column of apertures in a first sheet having a matrix of apertures.

[0030] A first embodiment of a bimaterial plastic sheet 22 according to the invention, obtained notably via the fabrication method described above, is shown in cross-section in FIG. 4. This plastic sheet is formed of a first sheet 2 formed of a first material, having a first hardness. This first sheet 2 has a plurality of apertures which are filled by discs 6 formed of a second material having a second hardness, lower than the aforementioned first hardness. The second material adheres to the lateral wall 20 of the holes. The plurality of apertures 4 defines a plurality of areas 5 of the plastic sheet 22 in which the second material is located. This plurality of areas of lower hardness is respectively intended to receive a plurality of electronic units via penetration of the second material, as will be explained below.

[0031] In a first variant, the second hardness is less than 96 Shore A. In a second variant, the first hardness is more than 60 Shore D. In a particular embodiment, the first and second variants are advantageously combined. Preferably, the second material is formed by a thermoplastic polyurethane elastomer. For the definition of Shore A and Shore D, reference may be made to ISO standard 868 and DIN standard 53505 respectively. Thermoplastic polyurethane elastomers are sold, in particular, by BASF under the name Elastollan®.

[0032] In an alternative of the invention, the plastic sheet according to the invention is formed of a first material 2, having a first Vicat softening temperature, and of a second material 6 having a second Vicat softening temperature, which is lower than the first Vicat softening temperature. In a first variant, the second Vicat softening temperature under a load of 10 N is less than fifty degrees (50° C.). In a second variant, the first Vicat softening temperature under a load of 10 N is more than sixty-five degrees (65° C.). In a particular embodiment, the first and second variants are advantageously combined. Preferably, the second material is formed by a thermoplastic polyurethane elastomer. The Vicat softening temperature is the temperature measurement at which a pin with a section of 1 mm.sup.2 penetrates a thermoplastic material to a depth of 1 mm tested under a load of 10 N or 50 N (for further information, reference may be made to ISO 306). The various embodiments of the plastic sheet of the invention also apply to this alternative.

[0033] A second embodiment of a bimaterial plastic sheet 24 according to the invention is shown in cross-section in FIG. 5. This plastic sheet 24 differs from the first embodiment in that it is formed of a first sheet 2A formed of said first material and having a plurality of cavities 26 filled with discs 6A formed of said second material. The plurality of cavities 26 open out on the top face 8 of plastic sheet 24 and define a plurality of areas 5A in which the second material is located. This plurality of areas of lower hardness is respectively intended to receive a plurality of electronic units via penetration of the second material, as will be explained below. It will be noted that, in a variant embodiment, the first sheet 2A is formed by two layers 28 and 29, layer 28 having a plurality of holes whereas layer 29 is continuous and defines the bottom of cavities 26. Layers 28 and 29 may be welded or bonded in a preliminary step prior to the insertion of the plurality of discs 6A. Preferably, they are welded during step C) of the fabrication method described above, simultaneously as discs 6A are pushed in and welded to first sheet 2A.

[0034] It will be noted that, in a variant, discs 6 or 6A may be respectively bonded inside apertures 4 or cavities 26. In another variant, the second material is introduced into apertures 4 or cavities 26 by a technique of injecting or casting said second material.

[0035] A third embodiment of a bimaterial plastic sheet 32 according to the invention is shown in cross-section in FIG. 6. The third embodiment differs from the preceding embodiments in that the plurality of apertures 4B in first sheet 2B each has an annular shoulder 34 in the bottom part thereof. Discs 6B have an initial diameter such that they abut against the lateral walls 20B of the respective shoulders 34 during the pushing in which occurs in step C) of the fabrication method described above, without however filling the annular areas 35 located above the annular shoulders. Discs 6B define, on the top face 8 of plastic sheet 32, areas 5B of lower hardness having a smaller diameter than that of the respective apertures 4B. The space remaining in each annular area 35 is advantageous for the subsequent penetration of an electronic unit, in particular when the unit has relatively large dimensions and the second material forming discs 6B is not compressible. Finally, it will be noted that, as in the second embodiment, the first sheet 2B is formed in a preferred variant of two layers 36 and 37, respectively having a first plurality of holes and a second plurality of holes, the latter having smaller diameters than those of the first plurality of holes. These two layers 36 and 37 are preferably hot laminated in a preliminary step prior to the insertion of discs 6B into apertures 4B.

[0036] It will be noted that, where cavities are provided in the first plastic sheet, it is possible to provide discs with dimensions such that the discs do not come into contact with the lateral wall of the cavities, the connection between these discs and the first sheet being achieved via the bottom of the cavities. It is thus possible for a circular space (empty space) to remain inside the cavities around the discs.

[0037] A fourth embodiment of a bimaterial plastic sheet 40 according to the invention is shown in FIG. 7. The fourth embodiment differs in that the discs 6C inserted into apertures 4 of the first sheet 2 each have a profile in the general plane of the first sheet which is different from the contour of the corresponding aperture. In the fabrication method described above, the initial profile of disc 6C is selected such that, during step C) of the method, protruding portions of the disc come into contact with the lateral wall 20 of the corresponding aperture 4, while leaving empty areas 39 in the aperture. During the final pushing in of discs 6C, the protruding portions are slightly deformed due to the pressure exerted by lateral wall 20 on said protruding portions which eventually adhere to the first material forming first sheet 2. In a variant, only a small amount of heat is provided to deform the discs and ensure the connection thereof to the first sheet. It will be noted that it is also possible to provide at least one recess in the disc, particularly in the central area. Preferably, this recess is made in accordance with the electronic unit or units to be inserted into the corresponding aperture. For example, the recess will be positioned in an area provided for the thickest portion of the electronic unit or, in the case of several electronic units inserted into the same aperture in first sheet 2; the recess will be positioned in the area provided for the thickest electronic unit. In a variant, it is the most fragile portion of an electronic unit or the most fragile electronic unit of the electronic units used which is positioned in the area of the recess.

[0038] FIG. 8 shows a schematic view of one use of a plastic sheet 22A according to the invention in a first smart card fabrication method. The plastic sheet 22A is placed on a support 12A. The plastic sheet is similar to the plastic sheet 22 described above, with the addition of an electrical circuit arranged on top face 8. At the periphery of each area 5 defined by a disc 6 of low hardness, this electrical circuit includes contact pads 44 for electrical connection to an electronic unit 46. Electronic unit 46 and conductive segments 48 are moved above plastic sheet 22A using a gripping tool 50 so that the electronic unit is located above a disc 6. Next, the gripping tool lowers the assembly formed of the electronic unit and conductive segments towards disc 6 and inserts electronic unit 46 into the relatively soft material forming the disc. Thus, the electronic unit easily penetrates the plastic sheet according to the invention. In a variant, the material forming disc 6 is compressible. The intermediate product 52 shown in cross-section in FIG. 9 is then obtained. The material of disc 6 is either compressed or in a compressed state. In another variant, notably with an integrated circuit of small dimensions, the material forming disc 6 comes out of aperture 4 slightly when the electronic unit penetrates the aperture. This may permit the top surface of the integrated circuit to be partially covered and prevent any subsequent electrical problems between the integrated circuit and the conductive segments 48 which must only have electrical contact with one determined pad of the integrated circuit. In a variant implementation, disc 6 has a lower Vicat softening temperature and the penetration of electronic unit 46 into the disc is achieved by applying heat to soften the disc quickly without deforming first sheet 2 and without any risk of damaging the electronic unit.

[0039] FIG. 10 is a schematic view of one use of a plastic sheet 56 according to the invention in a second smart card fabrication method. Plastic sheet 56 is formed by a plastic sheet 32 described above and a continuous plastic film 58 closing apertures 4B on the rear face side of plastic sheet 32. It is noted that apertures 4B define a plurality of cavities in plastic sheet 56. A printed circuit 54 with electronic units 46A arranged on the top surface thereof is placed on a support 12. Plastic sheet 56 is placed opposite printed circuit 58 and deposited on the printed circuit so that the electronic units are located facing discs 6B. Next, using a press, the electronic units are inserted into cavities 4B penetrating the material forming discs 6B. During this penetration, discs 6B are deformed and at least substantially fill the annular areas 35 by displacing the material of the discs so as to substantially reduce the spaces initially remaining in cavities 4B. A smart card 60 shown in cross-section in FIG. 11 is thus obtained.