Manufacturing system for a flexible coil construction

Description

[0001] The invention relates to a manufacturing system for a flexible coil construction which can form part of an electronic circuit as an electromagnetic antenna. Such a circuit may for instance be fully integrated in a card-shaped object, for instance a value document, such as an identity card or a smart card. The coil construction, which is mostly substantially flat in the case of a card-shaped object, should not appreciably, if at all, curtail the normal practical uses of the object or the card and should therefore have substantially no effect on, for instance, the flexibility and/or the flatness thereof.

[0002] The invention further relates to a method for manufacturing a device comprising a flexible coil construction, as well as to a flexible coil construction and a device comprising a flexible coil construction obtained by the method.

[0003] Applicant's Dutch patent application 92.00835 discloses a card construction comprising a flat coil, yielding a product in which the coil is eventually present in the card with its turns not adhering to each other, so that when the card is bent, sufficient flexibility remains present in the coil not to cause any permanent deformation.

[0004] It is sometimes experienced as a drawback of this construction that several operations on different constituent parts are necessary to arrive at the desired end product.

[0005] The present invention provides a solution to this problem and makes it possible to arrive at a comparable end result with a minimum of parts and using simple manufacturing techniques. This is achieved by the use of a special adhesive system, as will be described in the following. According to the state of the art, it is known to wind coils of insulated wire, for instance copper wire, provided with a special coating which ensures that upon an increase of the temperature to approx. 60° C, for instance, the adjoining turns of the coil are stuck to each other.

[0006] Such a technique is disclosed, for instance, in US-A-4,048,713. The required temperature increase can be advantageously realised by passing an electrical current through the coil by way of contact clips on the terminal portions of the coil, so that the coil is heated to the desired temperature. Coils manufactured in this manner will not fall apart upon being removed from the winding tool, but will retain the shape imparted by the winding former. Thus these coils can be processed in the further production process in a mechanically stable manner. In order to impart sufficient flexibility to an identity card or chip card, whether contactless or not, which must for instance meet the requirements prescribed by the international standardisation organisation ISO, the bond between the turns of the coil must preferably be removed completely in the eventual product.

[0007] According to the invention, for that purpose a bond system in the form of a coating is applied to the wire to be wound into a coil, this adhesive system preferably satisfying the following properties:

• no adhesion at normal ambient temperatures, so that the wire can be normally processed on a winding machine;
• upon increase of the temperature to a first temperature range of, for instance, approx. 40 to 60° C the adjoining turns of the coil glue together, so that the coil, upon cooling and removal from the winding former, retains a stable form suitable for further processing;
• upon increase of the temperature to a second, higher temperature range of, for instance, approx. 100 to 120° C, a permanent modification occurs in the structure and/or chemical composition of the adhesive, whereby this adhesive loses its adhesive property, so that the wires in the turns of the coil end up in substantially loose arrangement relative to each other and, also after cooling, no longer stick together, or in any case are no longer rigidly bonded to each other.

[0008] Since in the lamination of contactless identity cards or chip cards, where the various plastic parts of these cards are adhered to each other, temperatures of 100 to 120° C are used, the bond between the turns of the coil arranged within this card can advantageously be removed at the same time during this production step. However, the required heating can also be effected in a different manner, for instance by passing an electrical current through the turns. Coating material suitable for use in a method according to the invention may for instance be adhesives of the acrylic type, for instance cyanoacrylate glue, or of the polyester, epoxy or urethane type, optionally modified according to requirements, as is known to the skilled worker. It is also possible, for instance, to use glues based on gum or protein. Preferably, use is made of a coating which does not lead to the formation of gas upon heating, because the removal of these gasses during the lamination process is difficult and may cause bubble formation.

[0009] The invention can be used not only in the manufacture of card-shaped responders, whether or not provided with contacts, but also for other products comprising a coil, whether or not connected with an electronic circuit, where a certain minimum degree of flexibility is required. As an example a flexible ear mark for identifying animals can be mentioned.

[0010] The invention is particularly suitable for use in a substantially flat coil, but may in principle be also used for other coil forms. The invention can also be also used in situations where the coil with mutually adhered turns has been manufactured elsewhere, for instance at a supplier's, so that the only necessary further step is to assemble the end product or, in fact, to merely render the bond between the coil turns ineffective.

[0011] These and similar modifications are understood to fall within the framework of the invention.

Claims

1. A method for manufacturing a flexible coil construction with insulated wire,
characterised in that a coil whose turns are substantially rigidly bonded to each other is used, the turns having been bonded to each other using a special coating of which at least the rigid bond can be substantially undone by increasing the temperature to within a predetermined temperature range; and that the coil after being brought into the desired eventual position of use is heated to the predetermined temperature range.

2. A method according to claim 1, characterised in that the special coating is selected such that upon a heating to a first, relatively low temperature range a bonding action is produced and that upon heating to a second, relatively high temperature range the bonding properties disappear substantially and substantially do not return upon cooling.

3. A method according to claim 1 or 2, characterised in that the first, relatively low temperature range is higher than room temperature and that a bond which develops upon heating to a temperature within the first temperature range is substantially retained upon cooling.

4. A method according to claim 2 or 3, characterised in that the heating to the first, relatively low temperature range and/or to the second temperature range is obtained by passing an electrical current through the coil.

5. A method according to any one of claims 2-4, characterised in that the first, relatively low temperature range is between approx. 40° C and approx. 60° C.

6. A method according to any one of the preceding claims, characterised in that the relatively high temperature range is above approx. 100° C.

7. A method according to any one of the preceding claims, characterised in that the coating contains a bonding agent of the acrylic, epoxy, polyester or urethane type.

8. A method according to any one of claims 1-6, characterised in that the coating contains a glue based on gum or protein.

9. A flexible coil construction manufactured according to any one of claims 1-8.

10. A method for manufacturing a device comprising a coil construction, characterised in that a coil construction is used which comprises a flexible coil manufactured according to one or more of claims 1-8.

11. A method according to claim 10, characterised in that the relatively high temperature range is selected such that it corresponds with an increased temperature required for the manufacture of the device for different reasons.

12. A device comprising a flexible coil construction, characterised in that the device is manufactured according to any one of claims 10 or 11.

13. A card-shaped object manufactured according to claim 10 or 11, characterised in that the second, relatively high temperature range is achieved during a laminating process in the manufacture of the card-shaped object.