Method and a device for heating at least two elements by means of laser beams of high energy density

Abstract

A process and a device for joining or separating various workpieces, in particular made of plastic or plastic and other materials, by means of curtain-like laser beams. To join workpieces in a particular joining area of the contact surface, a mask, made of a laser-impermeable material, is arranged between the laser source and the workpieces to be joined. The laser beam and the mask are moved relative to each other. To generate high energy density in the joining area, laser beams of at least two diode lasers are brought together, and subsequently, differing laser line lengths are generated by means of a zoom optics arrangement. Via a beam splitter, a first laser beam aligned perpendicularly to the surface of the mask, is joined by at least one secondary laser beam arranged perpendicularly to the first laser beam, and the resulting laser beam is directed onto the mask. Laser beams either of different wavelengths or of the same wavelength but of different polarisation are used. In another arrangement, several laser beams are focussed parallel to each other onto the joining area by means of a lens. The method and the device not only provide adequate energy density in spite of the output of the individual lasers being insufficient per se, but also makes possible flexible adjustment of the line length.

What is claimed is:  
     
         1 . A method which comprises: selective heating of at least two materials by means of laser beams, with a mask made of a material impermeable to radiation arranged between a radiation source and the materials; removing regions from said mask, with the laser radiation being admitted through said regions to selected heating regions of the materials arranged below the mask; wherein all heating regions are heated by irradiation, thus leading to joining or separation of the materials, with a relative movement between one or several laser beams and the materials being carried out, and wherein for generating a high energy density, laser beams from at least two diode lasers are brought together into the heating region and with different laser line lengths being subsequently generated by means of zoom optics.  
     
     
         2 . A method according to    claim 1   , wherein a first laser beam is aligned perpendicularly to the surface of the mask, is joined by at least one secondary laser beam arranged perpendicularly to the first laser beam, with such joining or admixing taking place via a beam splitter for each secondary laser beam, and with a resulting laser beam being directed onto the joining area.  
     
     
         3 . A method according to    claim 2   , wherein laser beams either of different wavelengths or of the same wavelength but of different polarisation are used.  
     
     
         4 . A method according to    claim 1   , wherein several laser beams are focussed parallel to each other onto the joining area by means of a lens.  
     
     
         5 . A method which comprises: joining various workpieces made of one of (1) plastic and (2) plastic and other materials, with an upper workpiece facing a laser source for a laser beam; wherein said upper workpiece is a material which is transparent to the laser beam, and a second workpiece comprises a material which is absorbent to the laser beam so that the adjoining contact surfaces of the two workpieces melt and connect during subsequent cooling under pressure; arranging a mask made of a laser impermeable material between the laser source and the workpieces to be connected so as to connect the workpieces in a particular joining area of the contact surface; wherein the structures of said mask are larger than the wavelength of the laser beam applied; and wherein the laser source is set to the contact surface in such a way that a curtain-like laser beam is formed and that a line results at the contact surface, and that the laser beam and the mask are moved relative to each other; and wherein for generating high energy density in the joining area, laser beams of at least two diode lasers are brought together, and that subsequently, different laser line lengths are generated by means of zoom optics.  
     
     
         6 . A method according to    claim 5   , wherein a first laser beam is aligned perpendicularly to the surface of the mask, is joined by at least one secondary laser beam arranged perpendicularly to the first laser beam, with such joining or admixing taking place via a beam splitter for each secondary laser beam, and with a resulting laser beam being directed onto the joining area.  
     
     
         7 . A method according to    claim 6   , wherein laser beams either of different wavelengths or of the same wavelength but of different polarisation are used.  
     
     
         8 . A method according to    claim 5   , wherein several laser beams are focussed parallel to each other onto the joining area by means of a lens.  
     
     
         9 . A device for selective heating of at least two materials which comprises: laser beams, with a mask made of a material impermeable to radiation arranged between a radiation source and the materials, with regions having been removed from said mask, with the laser radiation passing through said regions to selected heating regions of the materials arranged below the mask, with all heating regions being heated by irradiation, thus leading to the joining or separation of the materials, and with relative movement between one or several laser beams and the materials taking place; including at least two diode lasers for generating high energy density at the contact surface of a laser beam concentration device for bringing together the laser beams, as well as an adjacent zoom optics arrangement for generating different laser line lengths.  
     
     
         10 . A device according to    claim 9   , including a first diode laser which generates a laser beam perpendicularly to the surface of the mask, at least a further diode laser perpendicular to the first diode laser which generates a laser beam impinging perpendicularly on the first laser beam, and a beam splitter as a laser beam concentration device.  
     
     
         11 . A device according to    claim 10   , wherein the diode lasers emit laser beams either of different wavelengths or of the same wavelength but of different polarization.  
     
     
         12 . A device according to    claim 9   , including several diode lasers which are arranged parallel to each other and arranging a convergent lens in the beam path as a laser beam concentration device and at the same time a zoom optics arrangement, said convergent lens focussing the laser beams onto the contact surface.