Method for bonding using adhesive layers with the aid of a laser

Abstract

The invention relates to a method and a device for bonding two substrates, wherein an adhesive is applied to a first substrate and a second film-type substrate consisting of a thermoplastic material is converted into a plasticized state by heating before being bonded to the first substrate.

Claims

1. A method for bonding two substrates, wherein an adhesive is applied to a first substrate, a second film substrate consisting of a thermoplastic material is transported in a feed direction and a surface of the second film substrate is converted into a plasticized state by heating with electromagnetic radiation in the form of a laser beam, wherein the laser beam is guided over the second substrate at an angle of 120 degrees to 60 degrees with regard to the feed direction, and wherein the side of the first substrate which is coated with adhesive is disposed onto the side of the second substrate which has been irradiated by the laser beam.

2. The method according to claim 1, wherein the laser beam is parallel to and spaced from the feed direction and is deflected by means of a polygonal mirror which is rotatably mounted about an axis of rotation, and the laser beam is guided along a line over the second substrate.

3. The method according to claim 1, wherein the two substrates are bonded continuously, wherein the laser beam is guided over the second substrate and matched to a feed speed in so that the time between impingement of the laser beam and the subsequent bonding is substantially the same for each point of the surface of the second substrate to be bonded.

4. The method according to claim 1, wherein the laser beam is guided over the second substrate substantially orthogonally to the feed direction.

5. The method according to claim 1, wherein the laser beam is a laser beam with IR radiation in the wavelength range from 0.8 to 25 m.

6. The method according to claim 1, wherein the adhesive is not a hot melt adhesive.

7. The method according to claim 1, wherein the second substrate is irradiated prior being bonded to the first substrate.

8. The method according to claim 1, wherein the entire surface of the second film substrate is converted into a plasticized state.

9. A method for bonding substrates, comprising: providing a first material having a first planar surface; applying adhesive to the first material first surface to provide a first material adhesive coated first surface; moving the first material in a feed direction; providing a second material having a first planar surface, the second material being a flexible thermoplastic film material having a plasticizing temperature; moving the second material in the feed direction; providing a laser beam parallel to and spaced from the feed direction; deflecting the laser beam toward the moving material first surface; irradiating only the moving second material first surface with the laser beam at an angle of 120 degrees to 60 degrees with regard to the feed direction to heat at least a portion of the second material first surface to about the plasticizing temperature to form a second material plasticized first surface; and contacting the adhesive coated first surface and the plasticized first surface to bond the first material to the second material.

10. The method of claim 9, wherein the step of applying adhesive to the first material first surface to provide an adhesive coated first surface occurs while moving the first material in the feed direction.

11. The method of claim 9, wherein the steps of irradiating the second material first surface with a laser beam and contacting the adhesive coated first surface and the plasticized first surface both occur while both the first material and the second material are each moving in the feed direction.

12. The method of claim 9, wherein the step of irradiating the second material first surface with a laser beam heats at least a portion of the second material first surface to a temperature in the range of 40 C. below the plasticizing temperature to 40 C. above the plasticizing temperature.

13. The method of claim 9, wherein the step of contacting the adhesive coated first surface and the plasticized first surface to bond the first material to the second material further comprises pressing the adhesive coated first surface and the plasticized first surface into contact with each other.

14. The method according to claim 9, wherein only the surface of the second film substrate is converted into a plasticized state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic view of a device according to the invention.

(2) FIG. 2 shows a snapshot of a sectional view through the section line A-A of the device from FIG. 1.

(3) FIG. 3 shows the sectional view from FIG. 2 after the expiry of a time t.

(4) FIG. 4 shows the sectional view from FIG. 2 after the expiry of a time t2.

(5) FIG. 1 shows a schematic view of the device 1 according to the invention for continuously bonding a first substrate 2 in the form of a laminated film to a second film-type substrate 10 consisting of a thermoplastic material. Here, the first film-type substrate 2 is located on a storage roller 3 and is guided by means of a feed device, which is not shown in detail here and which, in particular can include a drive and a plurality of deflector and/or guide rollers, to an adhesive unit 4, in which an adhesive 6 is applied to one side of the first substrate in a planar manner by roller coating. The adhesive 6 is dispensed via an applicator nozzle 5 and accumulates in the intermediate space between an applicator roller 9 and a dosing roller 8. An adhesive film 7 is applied to the first substrate 2 by means of the applicator roller 9, wherein the amount of adhesive 6 to be applied can be adjusted by means of the dosing roller 8. In the exemplary embodiment shown, an adhesive film with a layer weight in the range from 0.05 g/m.sup.2 to 0.9 g/m.sup.2 is applied. Further, the adhesive unit 4 can include a storage container (not shown) for the adhesive in a cold state and a heating device (not shown) for heating and melting the adhesive.

(6) The same components are known to the person skilled in the art. It is, of course, also possible to provide the said and further components decentrally, that is to say not to provide them as part of the adhesive unit 4. The first substrate 2 coated with the adhesive film 7 is subsequently fed to a pressing unit 13 for pressing the side of the first substrate 2 coated with the adhesive film 7 onto the second substrate 10 in a planar manner.

(7) Here, the second substrate 10 is in turn located on a storage roller 11 and is fed in a feed direction 12 to the pressing unit 13 by means of a feed device which is likewise not shown in detail. Immediately before reaching the pressing unit 13, the surface of the second substrate 10 which is to come into planar contact with the adhesive film 7 is heated by means of a heating device. In the exemplary embodiment shown, the energy for heating the second substrate 10 is introduced by means of a laser beam 17 in a wavelength range between 9 to 11 m, which is emitted by a laser unit 16. In the exemplary embodiment shown, the laser unit 16 comprises a CO.sub.2 laser, wherein the CO.sub.2 laser has a power in the range between 500 and 1500 W. In addition, the CO.sub.2 laser is operated continuously or quasi-continuously. A deflector unit 18, which in particular comprises a rotatably mounted polygonal mirror 19, is provided to guide the laser beam 17 over the surface of the second substrate 10. The polygonal mirror 19 has a drive in the form of a servomotor in order to drive the polygonal mirror 19 at a required rotational speed. The deflector unit can also comprise a focusing device (not shown). Particularly in conjunction with the rotatably mounted polygonal mirror 19, the deflector unit 18 provides a facility for deflecting the laser beam 17 and guiding it over the surface of the second substrate 10 so that its projection is moved in a relative movement with regard to the surface in a projection movement direction over the surface of the second substrate 10 to enable heating of the second substrate 10 and to convert the same into a plasticized state. At the same time, the deflector unit 18 is designed in such a way that it guides the laser beam 17 at least temporarily in such a way that the projection movement direction runs at an angle to the feed direction 12 over the surface of the second substrate 10 in order to enable heating of the surface in a planar manner when the second substrate 10 moves in the feed direction 12. In order to maintain the required temperature of the surface of the second substrate 10, a temperature sensor 22, which, after the guiding of the laser beam 17 over the surface and the accompanying heating of the same, measures the temperature of the surface immediately before reaching the pressing unit 13, is also provided. Further, a beam trap 20 is also provided in order to be able to block laser radiation possibly passing through the second substrate 10 in a controlled manner. To control the device 1, the feed devices, the adhesive unit 4, the laser unit 16, the deflector unit 18 and the temperature sensor 22 are connected to a control unit 21. Said control unit can in particular match feed speeds of the substrates 2, 10 and the guiding speed of the laser beam 17 over the surface of the second substrate 10 to one another so that the required temperature of the surface of the second substrate 10 is present.

(8) In the further course of events, the surface of the second substrate 10, which has been converted by means of the laser beam 17 into the plasticized state, is brought into contact in the pressing unit with the side of the first substrate 2 which has been coated with the adhesive film 7. For this purpose, the two substrates 2, 10 pass through the pressing unit 13, wherein the two substrates 2, 10 are pressed together by means of a pressure roller 14 and a corresponding bearing roller 15.

(9) FIG. 2 shows a side view through the section line A-A of the device from FIG. 1, wherein the section extends through the pressure roller 14 and the section surface runs parallel to the surface of the second substrate 10. Here, the device 1 is shown in a photographic snapshot to illustrate the irradiation of the second substrate 10 by the laser unit 16 described above and the deflector unit 18. The laser beam 17 impinges on the surface of the second substrate 10 in a projection 25, wherein the energy introduced results in a heating of the surface. For further heating of the surface, the laser beam 17 is deflected by means of the deflector unit 18 in such a way that its projection 25 moves over the surface in a projection movement direction 23. At the same time, this active projection movement relative to the surface is independent of the movement of the substrate in the feed direction 12. In the exemplary embodiment shown, the projection movement direction 23 runs substantially orthogonally to the feed direction 12.

(10) FIG. 3 shows the section view from FIG. 2 after the expiry of a time t1 at which, on the one hand, the laser beam 17 has been guided over the second substrate 10 in such a way that the projection 25 shown in FIG. 2 has been moved from the first side of the substrate 10 to the opposite second side relative to the surface by means of the active projection movement described above. On the other hand, the second substrate 10 has been moved in the feed direction 12 during the irradiation such that a projection line in the form of a parallelogram extends over the surface even though the projection movement direction 23 has run substantially orthogonally to the feed direction 12. The movement of the second substrate 10 in the feed direction 12 has therefore led to a passive projection movement over the surface. The width of the projection line 27 has been set by the focusing device described above to a projection width 26 of approximately 8 mm.

(11) FIG. 4 shows the section view from FIG. 2 after the expiry of a time t2 which corresponds to a multiple of the time t1 from FIG. 3, at which, as described above, the laser beam 17 has been guided over the second substrate 10 in such a way that the projection 25 shown in FIG. 2 has been moved from the first side of the substrate 10 to the opposite second side relative to the surface by means of the active projection movement described above. As a result of using the rotatably mounted polygonal mirror 19, after reaching the second side of the substrate 10, the laser beam 17 is again deflected to the starting point on the first side of the substrate 10 from where it is once again guided over the surface. Here too, the projection movement direction 23 runs substantially orthogonally to the feed direction 12. At the same time, the projection width 26, the time between reaching two adjacent starting points on the first side of the substrate 10, and the movement speed of the second substrate in the feed direction 12 are chosen such that no point on the surface is irradiated twice, wherein the projection lines 27, 27, 27, 27 resulting from the projection 23 which is moved over the surface in the time t2 constitute parallelograms on the surface of the substrate 10 which abut one another. Further, said parameters are chosen such that the second substrate has the same temperature at all points on a line orthogonal to the feed direction after irradiation by the laser beam 17.

(12) TABLE-US-00001 List of references: 1 Device 2 First substrate 3 Storage coil 4 Adhesive unit 5 Applicator nozzle 6 Adhesive 7 Adhesive film 8 Dosing roller 9 Applicator roller 10 Second substrate 11 Storage coil 12 Feed direction 13 Pressing unit 14 Pressure roller 15 Bearing roller 16 Laser unit 17 Laser beam 18 Deflector unit 19 Polygonal mirror 20 Beam trap 21 Control unit 22 Temperature sensor 23 Projection movement direction 24 Angle 25 Projection 26 Projection width 27 Projection line