posttreatment. The present invention relates to a method and an apparatus for applying a perforation in an initially flat laminated substrate having a thickness of at least 0.2 mm by irradiating the substrate by laser.

The last years increasing use of laser has been made to personalize identification documents like passports and driving licences. This personalization may relate to the application of a personalised number into the identification document or the application of a perforation pattern representing the passport photograph of the bearer, hence making the falsification of these documents more difficult. This improves the safety and reliability of these documents. EP-A-0 936 975 discloses documents provided with such features and the apparatuses and methods for personalising these documents.

Often the perforations are applied in a card of laminated material, having a thickness of at least 0.2 mm. This card is also provided with other personalized features like the name, address, date and place of birth and a passport photograph of the bearer. This card may form the personalized document on itself, but it may also form part of a bigger document, like a passport booklet comprising several pages of which the personalized card is one of the pages. It is noted that such a laminated card can be protected against falsification and forgery by applying personalized features in the card in the form of perforations. When a perforation is applied by laser to a card, the cards are often warped, leading to handling problems in the next processing steps of the card. Also, a deformed warped card is not considered to be a high quality product which conflicts with the very nature of identification documents.

The aim of the invention is to provide a method and an apparatus to avoid these problems.

This aim is reached by a method for applying a perforation in an initially flat laminated substrate having a thickness of at least 0.2 mm by irradiating the substrate by laser, wherein after the irradiation and a possible post treatment the substrate is flat. A corresponding apparatus for applying a perforation in an initially flat laminated substrate having a thickness of at least 0.2 mm, comprises an irradiation support member for supporting the substrate during irradiation, a laser unit for irradiating the substrate to apply the perforation in the substrate, wherein the apparatus is adapted to deliver a flat perforated substrate.

Often a substrate forms a part of a booklet. In such a situation it is preferred when the that the remaining pages of the booklet are folded such that the substrate is accessible from at least one side.

Accordingly the apparatus is adapted to perforate a substrate which forms part of the booklet and that the apparatus comprises holding means to maintain the remaining pages of the booklet folded over when the substrate is on the substrate carrier such that the substrate is accessible from at least one side.

A first possibility for reaching this aim is by application of a laser irradiation process wherein the properties of the laser are chosen such that the substrate is flat after the irradiation and by a corresponding apparatus.

Hence the same embodiment provides an apparatus of the kind referred to above wherein the laser has a wavelength of substantially 9.3 μιη when the substrate is polycarbonate.

A more specialized embodiment provides the feature that the wavelength of the laser is substantially 9.3 μιη when the substrate is polycarbonate.

An alternative possibility is to use a method wherein the substrate is flattened after the irradiating by laser.

According to a preferred embodiment the substrate is flattened by heating the substrate. The embodiment also provides an apparatus wherein the heating station comprises at least one heated temperature controlled plate, which is moveable between an inactive position and a heating position in which it is adapted to be contacted to a substrate on the heating support member.

The substrate is preferably heated by bringing at least one side of the substrate into contact with a heated temperature controlled body, however, it may also be possible that the substrate is heated by bringing both sides of the substrate into contact with a heated temperature controlled body.

Accordingly the same embodiment provides an apparatus wherein the heating station comprises at least one heated temperature controlled plate, which is moveable between an inactive position and a heating position in which it is adapted to be contacted to a substrate on the heating support member., or, as an alternative wherein the heating station comprises two heated temperature controlled plates, which are each moveable between an inactive position and an active position wherein a substrate on the heating support member is clamped between both plates.

As an alternative to the heating by the heated plates, its is possible that the substrate is heated by IR irradiation.

This leads to an wherein the heating station comprises an IR-source adapted to irradiate a substrate on the heating support. It is not excluded that the heating takes place on the same location as the irradiation by laser, but to increase throughput, it is preferred if the substrate is transported between the irradiation by laser and the heating.

Another preferred embodiment provides the feature that the heating member comprises two flat, temperature controlled plates, which are moveable between an inactive position and a heating position and in which a substrate is clamped between both plates

Yet another preferred embodiment provides the feature that transport means are adapted for transporting the substrate from the support to the heating location and that the holding means are adapted to maintain the pages of the booklet not being the substrate folded over when the substrate is in the heating location such that the substrate is accessible for the heating plates from both sides. Subsequently the present invention will be elucidated with the help of the following drawings wherein:

Figure 1 : shows a cross-sectional view of a laser perforating apparatus according to the prior art;

Figure 2: shows an elevated view of a laser perforating apparatus is depicted in figure 1, to which a heating apparatus according to the invention is added;

Figure 3: shows a side view of the apparatus depicted in figure 2; and

Figure 4: shows a cross sectional view of the apparatus depicted in figures 2 and 3.

The apparatus depicted in figure 1 shows a longitudinal support 1 over which

documents 2 to be provided with a laser perforation are transported in the longitudinal direction of the support 1. To drive these documents 2, a pair of driving belts 3 is provided over the longitudinal support 2. These driving belts 3 are each wrapped around two pulleys 4, of which at least one is driveable by an electric motor not depicted in the drawings. By driving the belts 3, the documents 2 are driven along the longitudinal support. The apparatus further comprises a laser unit 5, which is depicted by a rectangle. It will be clear to a skilled man that the laser unit 5 comprises both a laser source and means for deflecting and control of a laser beam 6 emerging from the laser source 5. Further the apparatus comprises a control unit not depicted in the drawings, but which is adapted to control the movement of the belts 3 and hence of the document 2 and the laser unit 5.

The apparatus so far belongs to the prior art. Hence the problem arises that the document 2 after being perforated by laser is not completely flat anymore. Expressed otherwise it may be forced to a flat shape, but it may incorporate internal stresses which make the document return to a warped shape when the document 2 is not submitted to external forces. These stresses are generated by the thermal energy supplied by the laser to the document during the perforation by the laser. According to a first embodiment, the properties and the control of the laser are amended such that the transfer of heat to the document is minimised, so that only the energy needed to make the actual perforation is transferred to the document. This may be implied by using a laser with a wavelength which is optimally absorbed by the material to be processed. For instance, when using a polycarbonate substrate the wavelength of 9.3 μιη is far better absorbed than the more common wavelength of 10.6 μιη. As a result the 9.3 μιη wavelength does not warp the substrate whereas the 10.6 μιη does.

Further the document can be a single card, for instance a driving licence, but it may also be formed by a card being part of a booklet, like a passport. In such a case the transport means, comprising the longitudinal support, and the belts must be adapted to the transport of the document of the booklet type. In particular the pages of the booklet different from the card, will be folded over to allow the laser to reach the card for perforation, so that the transport means must be adapted to transport such a document.

Yet another solution for the problem of the warped card, resides in the application of heat to the card to release the stresses in the card. Therefore a second embodiment of the invention comprises a heating member to heat the card to smooth out the stresses caused by the local application of heat of the perforating laser.

A corresponding embodiment is shown in figure 2. Herein the support 1 appears to consist of three support rails la, lb and lc, over which the document 2 can be transported. Herein the outer rails have a substantial L-shape to allow a proper guiding of the document 2. Further the document 2 is composed of the actual document 2a, which is to be provided with a personalized perforation and pages 2b, which are folded over to allow the card 2a to be reached by the laser beam 6. Further three belts 3a, 3b , 3 c are located over the rails 2 to transport the documents in the longitudinal direction of the support. Herein the location of the belts 3a, 3b, 3c in the width of the support is chosen to make the card 2 accessible for the laser beam 6. After the laser perforation has taken place the folded document 2 is further transported along the support 1 in its longitudinal direction. Although it is possible to stop the document during the laser perforation, it is also possible to execute the laser treatment during movement of the document 2. Subsequently to the laser perforation the document is moved to a heating member, comprising two heating plates 10, of which only the upper heating plate 10a is visible in figure 2. In figure 3 both heating plates 10a 10b are visible, together with a document 2 located between the two heating plates 10a, 10b.

As visible from figure 4, the lower heating plate 10b is fixed relative to the support 1, but the upper heating plate 10a is swivably connected to the support 1. This swivable connection allows the upper heating plate 10a to swivel between its inactive position wherein movement of the document 2 is possible and a an active, heating position wherein the document 2 is enclosed between the two heating plates 10a, 10b to allow intimate contact between the document 2 and each of the heating plates 10a, 10b. As stated before the laser perforated document 2 is transported to the location in between the two heating plates, when the heating plate 10a is in its upper, inactive position. When the document has arrived in this position, the upper heating plate 10a is moved to its lower position and the document is clamped between the heating plates 10a, 10b The heating plates are constantly kept at a certain adjustable temperature which is controlled by a control loop consisting of a temperature sensor, a heating element and control electronics. The heating and subsequent cooling of the document 2 leads to a release of the internal mechanical stresses in the material of the document 2, so that it retakes its flat shape. After the heating of the document, the upper heating plate is raised to its upper, inactive position and the document 2 is transported further for further processing. During this further transport it is cooled down.

You attention is drawn to the fact that the heating takes place by contact between heated bodies 10 and the document 2. It is conceivable that the same effect can be achieved by other means of transfer of heat, for instance by radiation or by convection. However an advantage of the method using contact heat, is the fact that the application of heat coincides with the pressing of the document 2 in the required flat shape, so that flattening of the document is promoted.