LASER PROCESSING OF SLOTS AND HOLES
The present invention relates to a process for cutting and separating interior contours in thin substrates of transparent materials, in particular glass. The method involves the utilization of an ultra-short pulse laser to form perforation or holes in the substrate, that may be followed by use of a CO 2 laser beam to promote full separation about the perforated line.
1 . A method of laser drilling a material comprising:
focusing a pulsed laser beam into a laser beam focal line, viewed along the beam propagation direction;
directing the laser beam focal line into the material at a first location, the laser beam focal line generating an induced absorption within the material, the induced absorption producing a damage track along the laser beam focal line within the material;
translating the material and the pulsed laser beam relative to each other starting from the first location along a first closed contour, thereby laser drilling a plurality of holes along the first closed contour within the material; and
directing a focused carbon dioxide (CO2) laser into the material around a second closed contour contained within the first closed contour to facilitate removal of an inner plug of the material along the first closed contour.
2 . The method of claim 1 , further comprising:
directing the laser beam focal line into the material at a second location, the laser beam focal line generating an induced absorption within the material, the induced absorption producing a damage track along the laser beam focal line within the material; and
translating the material and the pulsed laser beam relative to each other starting from the second location along a third closed contour, thereby laser drilling a plurality of damage tracks along the third closed contour within the material, the third closed contour contained within the first closed contour.
3 . The method of claim 2 , wherein the second closed contour is offset from the first closed contour by less than 500 μm.
4 . The method of claim 2 , wherein the second closed contour and the third closed contour coincide.
5 . The method of claim 2 , wherein the second closed contour is contained between the first closed contour and third closed contour.
6 . The method of claim 2 , wherein the second closed contour is contained within the third closed contour at an offset of less than 500 μm.
7 . The method of claim 1 , further comprising directing an assist gas toward the material and collinear with the CO 2 laser beam.
8 . The method of claim 1 , wherein removal of the inner plug defines an opening in the material, the opening having a width between 0.5 mm and 100 mm.
9 . The method of claim 1 , wherein removal of the inner plug defines a slot in the material that has a width between 0.5 mm and 100 mm.
10 . The method of claim 1 , wherein the induced absorption produces subsurface damage at the first contour of up to a depth less than or equal to about 75 μm within the material.
11 . The method of claim 1 , wherein the induced absorption produces an Ra surface roughness at the first contour of less than or equal to about 0.5 μm.
12 . The method of claim 1 , wherein the material has a thickness in a range of between about 100 μm and about 8 mm.
13 . The method of claim 1 , wherein the material and pulsed laser beam are translated relative to each other at a speed in a range of between about 1 mm/sec and about 3400 mm/sec.
14 . The method of claim 1 , wherein the pulse duration is in a range of between greater than about 1 picosecond and less than about 100 picoseconds.
15 . The method of claim 14 , wherein the pulse duration is in a range of between greater than about 5 picoseconds and less than about 20 picoseconds.
16 . The method of claim 1 , wherein the repetition rate is in a range of between about 1 kHz and 2 MHz.
17 . The method of claim 16 , wherein the repetition rate is in a range of between about 10 kHz and 650 kHz.
18 . The method of claim 1 , wherein the pulsed laser beam has an energy per burst measured at the material greater than 40 μJ per mm thickness of material.
19 . The method of claim 1 , wherein the pulses are produced in pulse bursts of at least two pulses separated by a duration in a range of between about 1 nsec and about 50 nsec, and the burst repetition frequency is in a range of between about 1 kHz and about 650 kHz.
20 . The method of claim 19 , wherein the pulses are separated by a duration of about 10-50 nsec.
21 . The method of claim 1 , wherein the pulsed laser beam has a wavelength selected such that the material is substantially transparent at this wavelength.
22 . The method of claim 1 , wherein the laser beam focal line has a length in a range of between about 0.1 mm and about 100 mm.
23 . The method of claim 22 , wherein the laser beam focal line has a length in a range of between about 0.1 mm and about 10 mm.
24 . The method of claim 23 , wherein the laser beam focal line has a length in a range of between about 0.1 mm and about 1 mm.
25 . The method of claim 1 , wherein the laser beam focal line has an average spot diameter in a range of between about 0.1 μm and about 5 μm.
26 . The method of claim 1 , wherein the material comprises chemically strengthened glass.
27 . The method of claim 1 , wherein the material comprises non-strengthened glass.
28 . A glass article prepared by the method of claim 1 .
29 . A glass article having at least one inner contour edge having a plurality of defect lines extending perpendicular to the major face of the glass sheet at least 250 μm, the defect lines each having a diameter less than or equal to about 5 μm.
30 . A glass article according to claim 29 , wherein said major face of glass sheet is flat.
31 . The glass article of claim 29 where the smallest dimension or width of the inner contour defined by the inner contour edge is less than 5 mm.
32 . The glass article of claim 29 , wherein the glass article comprises post-ion exchange glass.
33 . The glass article of claim 29 , wherein the defect lines extend the full thickness of the at least one inner contour edge.
34 . The glass article of claim 29 , wherein the at least one inner contour edge has an Ra surface roughness less than about 0.5 μm.
35 . The glass article of claim 29 , wherein the at least one inner contour edge has subsurface damage up to a depth less than or equal to about 75 μm.
36 . The glass article of claim 29 , wherein the defect lines extend the full thickness of the edge.
37 . The glass article of claim 29 , wherein a distance between the defect lines is less than or equal to about 7 μm.
38 . The method of claim 1 , wherein the pulsed laser produces pulse bursts with at least 2 pulses per pulse burst.
39 . The method of claim 1 , wherein the pulsed laser has laser power of 10 W-150 W and produces pulse bursts with at least 2 pulses per pulse burst.
40 . The method of claim 39 , wherein the pulsed laser has laser power of 10 W-100 W and produces pulse bursts with at least 2-25 pulses per pulse burst.
41 . The method of claim 39 , wherein the pulsed laser has laser power of 25 W-60 W, and produces pulse bursts with at least 2-25 pulses per burst and the periodicity between the defect lines is 2-10 microns.
42 . The method of claim 39 , wherein the pulsed laser has laser power of 10 W-100 W and the workpiece or the laser beam is translated relative to one another at a rate of at least 0.25 m/sec.
43 . The method of claim 39 , wherein (i) the pulsed laser has laser power of 10 W-100 W; and (ii) the workpiece or the laser beam is translated relative to one another at a rate of at least 0.4 m/sec.