Methods for laser cutting articles from ion exchanged glass substrates

1. A method of cutting an article from a chemically strengthened glass substrate comprising:

generating a pulsed laser beam from a laser source, the pulsed laser beam having a pulse duration less than about 1000 fs and an output wavelength such that the chemically strengthened glass substrate is substantially transparent to the pulsed laser beam;

focusing the pulsed laser beam to form a beam waist;

positioning the beam waist of the pulsed laser beam such that the beam waist is located in the same horizontal plane as an inner tensile region of the chemically strengthened glass substrate;

translating the beam waist in a first pass along a cut line, thereby forming a molten defect line within the inner tensile region of the chemically strengthened glass substrate, wherein the beam waist traverses an edge of the chemically strengthened glass substrate; and

translating the beam waist in a second pass along the cut line that retraces the first pass, wherein the beam waist traverses the edge of the chemically strengthened glass substrate and travels along at least a portion of the molten defect line formed by the first pass such that a crack propagates from the edge of the chemically strengthened glass substrate along the cut line ahead of the translated beam waist during the second pass.

2. The method of claim 1 wherein

a size of the molten defect line is such that the crack controllably propagates along the defect line during the second pass.

3. The method of claim 1 wherein the pulse duration is about 50 fs.

4. The method of claim 3 wherein a duty cycle of the pulsed laser beam is about 1 kH and a power of the pulsed laser beam is about 850 mW.

5. The method of claim 1 wherein translating the beam waist in the first and second passes comprises translating the chemically strengthened glass substrate.

6. The method of claim 1 wherein the cut line comprises a curve.

7. The method of claim 1 wherein the cut line begins and terminates along a single edge of the chemically strengthened glass substrate.

8. A method of separating an article from a substrate having an inner tensile region positioned between a first and second surface compression layer, the method comprising:

forming an internal compression region within the inner tensile region of the substrate along a cut line, wherein the cut line begins at an edge of the substrate and the formation of the internal compression region generates a first and a second internal tension layer positioned above and below the internal compression region, respectively; and

heating the generated internal compression region such that a tensile stress of the first and second internal tension layers is increased and a crack initiates from the edge of the substrate and propagates along the inner tensile region.

9. The method of claim 8 wherein forming the internal compression region within the inner tensile region of the substrate further comprises:

generating a pulsed laser beam from a laser source;

focusing the pulsed laser beam to form a beam waist;

positioning the beam waist of the pulsed laser beam such that the beam waist is located in the same horizontal plane as the inner tensile region of the substrate; and

translating the beam waist in a first pass along the cut line, thereby forming a molten defect line within the inner tensile region of the substrate, wherein the beam waist traverses the edge of the substrate.

10. The method of claim 9 wherein heating the generated internal compression region further comprises translating the beam waist in a second pass along the cut line that retraces the first pass, wherein the beam waist traverses the edge of the substrate and travels along at least a portion of the molten defect line formed by the first pass such that the crack propagates from the edge of the substrate along the cut line ahead of the translated beam waist during the second pass.

11. The method of claim 10 wherein translating the beam waist in the first and second passes comprises translating the laser source.

12. The method of claim 10 wherein translating the beam waist in the first and second passes comprises translating the substrate.

13. The method of claim 10 wherein:

the cut line comprises a curve; and

a speed of the translated beam waist in the first and second passes is within the range of about 0.1 mm to about 5 mm per second.

14. The method of claim 10 wherein the pulsed laser beam has a pulse duration less than about 1000 fs and an output wavelength such that the substrate is substantially transparent to the pulsed laser beam.

15. The method of claim 14 wherein the pulse duration is about 50 fs.

16. The method of claim 15 wherein a duty cycle of the pulsed laser beam is about 1 kH and a power of the pulsed laser beam is about 850 mW.

17. The method of claim 8 wherein the cut line begins and terminates along a single edge of the substrate.

18. A method of cutting an article from a chemically strengthened glass substrate comprising:

generating a pulsed laser beam from a laser source, the pulsed laser beam having an output wavelength such that the chemically strengthened glass substrate is substantially transparent to the pulsed laser beam;

focusing the pulsed laser beam to form a beam waist;

positioning the beam waist of the pulsed laser beam such that the beam waist is located in the same horizontal plane as an inner tensile region of the chemically strengthened glass substrate;

translating the beam waist in a first pass along a cut line comprising a curve, thereby forming a molten defect line within the inner tensile region of the substrate, wherein the beam waist traverses an edge of the chemically strengthened glass substrate and a speed of the translated beam waist during the first pass is within the range of about 0.1 mm to about 5 mm per second; and

translating the beam waist in a second pass along the cut line that retraces the first pass, wherein the beam waist traverses the edge of the chemically strengthened glass substrate, the beam waist travels along at least a portion of the molten defect line formed by the first pass, and the speed of the translated beam waist during the second pass is within the range of about 0.1 mm to about 5 mm per second such that a crack propagates from the edge of the chemically strengthened glass substrate along the cut line trailing the translated beam waist during the second pass.

19. The method of claim 18 wherein the pulsed laser beam has a pulse duration less than about 1000 fs.

20. The method of claim 19 wherein the pulse duration is about 50 fs and the pulsed laser beam operates at a frequency of about 1 kHz.