OPTIMIZATION OF THE ACTIVATION OF ADHESIVE AGENTS BY LASER RADIATION

Abstract

The present invention relates to devices with which, for example, narrow surfaces of preferably plate-like workpieces can be provided with a coating material. The device includes a laser for outputting a laser beam to a laser beam emitter, wherein the laser beam is directed onto the coating material or onto the workpiece in such a manner that the laser beam forms a plane of reference with solder on the surface of the coating material or the workpiece.

Claims

1. A method for activating an adhesive agent provided on a coating material of a workpiece, comprising using a movement device to move the coating material or workpiece; outputting a laser beam from a laser to a laser beam emitter, directing the laser beam to the coating material or the workpiece such that the laser beam forms a plane of reference perpendicular to a surface of the coating material or the workpiece, utilizing more p-polarized light than s-polarized light in the plane of reference within the laser beam; activating the adhesive agent provided on the coating material with the laser beam, and pressing the coating material with a pressure roller onto the workpiece after activation of the adhesive agent.

2. The method according to claim 1, characterized in that more than 75% of p-polarized light is present in the plane of reference.

3. The method according to claim 1, characterized in that almost exclusively p-polarized light is present in the plane of reference.

4. The method according to claim 1, wherein the method further comprises using a deflection mirror or prism to deflect the laser beam.

5. The method according to claim 1, characterized in that the light of the laser beam comprises direct radiation.

6. The method according to claim 1, wherein the laser beam is directed to activate the adhesive agent of the coating material or the workpiece such that the laser beam forms an angle of 15-35° with a plane of the coating material or a plane of the workpiece.

7. The method according to claim 1, characterized in that the laser emits a laser beam with only a particular polarization and wherein the laser is selected from the group consisting of a diode laser, a fiber laser, a CO.sub.2 laser and a solid state laser.

8. The method according to claim 1, further comprising a movement device for moving the workpiece.

9. The method according to claim 6, wherein the laser beam forms an angle from 20-30°.

10. The method according to claim 6, wherein the laser beam forms an angle from 20-27°.

11. The method according to claim 1, wherein the coating material with the adhesive agent comprises a coextruded material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a schematic plan view showing a portion of a coating device

[0020] FIG. 2 is a schematic perspective view illustrating the incidence angle of the laser beam on an edge band

[0021] FIG. 3 is a view illustrating the polarization direction of the laser light

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] FIG. 1 shows a schematic view of a preferred embodiment of the present invention. The shown elements are highly simplified in order to be able to illustrate the core of the present invention more clearly.

[0023] In particular, a workpiece 1 is illustrated that moves in a traveling direction through the coating device (see arrow in FIG. 1). A coating material 2 is pressed onto the workpiece 1 by means of a pressure roller 4, said coating material 2 being provided with an adhesive agent on the side facing the workpiece 1.

[0024] Furthermore, a diode laser 5 is provided in the present embodiment, which emits a laser beam L and deflects said laser beam via a schematically illustrated mirror or prism 6 into the area of the reaction zone. Alternatively, fiber lasers or CO.sub.2 lasers are also suited for this use. In this regard, it is preferably provided that the laser beam L impacts the plane of the coating material at an angle α of 20-30°. This preferred angle results from the refractive index of air (approximately 1) and the value of 1.5 typical of plastics such as the adhesive agent.

[0025] According to the invention it is provided that the laser 5 oriented such that p-polarization is predominant in the plane of reference of the adhesive agent 3. The assessment that laser light with p-polarization is “predominant” is associated with the use of a diode laser having a particular polarization. This polarization particular to the diode laser is not lost since mirrors and prisms are used to deflect the laser light to the adhesive agent. If a glass fiber cable were to be used alternatively, the polarization of the laser light emitted by the diode laser would be lost owing to refraction/scattering. However, it may be that despite said procedure a certain refraction/scattering or polarization shift of the laser light cannot be avoided.

[0026] The conversion of laser power into heat energy depends not only on the incidence angle of the laser radiation, but also on the optical penetration depth into the adhesive agent to be activated. To achieve a fast and, at the same time, uniform activation it has been shown that an optimum penetration depth of approximately 0.4 mm is to be chosen.

[0027] Since the laser beam is oriented such that p-polarization is predominant in the plane of reference and the path of the laser beam through the adhesive means is maximized by the choice of the incidence angle, an optimal coupling of the energy of the laser beam into the adhesive agent can be used for the activation thereof.

[0028] In FIG. 2, a coating material 2 is shown schematically, onto which is applied an adhesive agent 3 to be activated. Furthermore, a laser beam L is shown which forms a plane of reference E perpendicular to the plane of the coating material.

[0029] In FIG. 3, the preferred polarization of the laser light is illustrated clearly in a schematic side view: the amplitude of the laser light beam L oscillates in the above-defined plane of reference and impacts the coating material 2 at an incidence angle α.

[0030] The tests carried out within the framework of this invention have shown that the maximum converted power of the laser with the here preferred p-polarization of the laser light is approximately 20-30° maximum. In this angle range, there is firstly a low refraction of the laser light at the adhesive agent. Secondly, an even heat penetration of the adhesive agent is achieved.

[0031] The characteristic values for laser light with mixed polarization, which is usually used, moreover exhibit a lower converted laser power as compared to laser light with p-polarization. This applies in particular with regard to the angle range, in which a low refraction of the laser light can be expected.