Sacrificial layers to enable laser cutting of textured substrates
A method of separating a transparent workpiece comprises depositing a sacrificial layer onto a textured surface of the transparent workpiece, the sacrificial layer comprising a refractive index that is less than or equal to a refractive index of the transparent workpiece and greater than or equal to a refractive index of air. A defect-forming laser beam is generated via an optical assembly and used to form a plurality of defects in the transparent workpiece through sacrificial layer. The defect forming laser beam either comprises a pulsed laser beam forming a laser beam focal line in the transparent workpiece or an optical power of greater than or equal a critical power level to induce Kerr effect self-focusing in the transparent workpiece. The transparent workpiece is separated along the contour.
1. A method of separating a transparent workpiece, the method comprising:
depositing a sacrificial layer onto a textured surface of the transparent workpiece, the transparent workpiece having a thickness between the textured surface and a second surface of the transparent workpiece, the sacrificial layer comprising a refractive index that is less than or equal to a refractive index of the transparent workpiece and greater than or equal to a refractive index of air, the textured surface having an Sa value of greater than or equal to 0.1 μm;
generating a defect-forming laser beam via an optical assembly;
forming a plurality of defects comprising an ablated region in the transparent workpiece by directing the defect-forming laser beam directly onto an impingement surface of the sacrificial layer from the optical assembly such that the laser beam propagates through the transparent workpiece via the sacrificial layer and translating the transparent workpiece and the laser beam relative to each other along a contour, wherein the defect forming laser beam comprises:
a pulsed laser beam forming a laser beam focal line at the textured surface or within the transparent workpiece, and
an optical power of greater than or equal to a critical power level to induce Kerr effect self-focusing throughout the entirety of the thickness; and
separating the transparent workpiece along the contour.
2. The method of claim 1 , wherein the defect-forming laser beam comprises the pulsed laser beam forming the laser beam focal line in the transparent workpiece, the laser beam focal line inducing absorption in the transparent workpiece, the induced absorption producing an individual defect of the plurality of defects in the transparent workpiece.
3. The method of claim 2 , wherein the laser beam focal line formed from the pulsed laser beam comprises:
a wavelength λ;
a spot size w o ; and
a Rayleigh range Z R that
F
D
π
w
o
2
λ
,
is greater than where F D is a dimensionless divergence factor comprising a value of 10 or greater.
4. The method of claim 3 , wherein the optical assembly includes a phase-altering optical element that generates a quasi-non-diffracting beam from the pulsed laser beam.
5. The method of claim 2 , wherein the pulsed laser beam comprises pulse bursts comprising two or more sub-pulses per pulse burst, wherein each pulse burst comprises an energy of greater than or equal to 25 μJ and less than or equal to 5000 μJ.
6. The method of claim 1 , wherein each of the plurality of defects comprise modified material of the transparent workpiece that is completely encapsulated within the transparent workpiece.
7. The method of claim 1 , wherein the plurality of defects comprise a defect length D l , a maximal defect diameter D dmax , and a defect aspect ratio comprising a ratio of D l to D dmax , wherein the aspect ratio is greater than or equal to 15:1.
8. The method of claim 1 , wherein:
the plurality of defects extend through a defect surface, the defect surface extending between the contour on the textured surface and end points of the plurality of defects at the second surface, and
at the defect surface, the plurality of defects extend from the textured surface by a distance that greater than or equal to 80% of the thickness of the transparent workpiece along the defect surface.
9. The method of claim 1 , wherein the textured surface has an Sa value of greater than or equal to 0.3 μm.
10. The method of claim 1 , wherein the thickness is greater than or equal to 500 μm in a direction perpendicular to the textured surface and the second surface.
11. The method of claim 10 , wherein the thickness is greater than or equal to 1 mm and less than or equal to 5 mm in a direction perpendicular to the textured surface and the second surface.
12. The method of claim 1 , wherein the separating the transparent workpiece along the contour results in a glass article having a cut edge conforming to the contour in an as-cut condition, wherein, over any given 100 μm length of the separated contour, a surface of the cut edge deviates from a fitted surface to the cut edge by less than or equal to 10 μm.
13. The method of claim 1 , wherein the sacrificial layer comprises a polymer-based material, wherein the depositing the sacrificial layer onto the textured surface comprises:
laminating the polymer-based material onto the textured surface; and
curing the polymer-based material by exposing the laminated polymer-based material to a radiation source.
14. The method of claim 13 , wherein the sacrificial layer has a thickness of greater than or equal to 10 μm and less than or equal to 20 μm.
15. A method of separating a transparent workpiece, the method comprising:
depositing a polymer-based sacrificial layer directly onto a textured surface of the transparent workpiece, the polymer-based sacrificial layer comprising a refractive index between that of the transparent workpiece and air;
generating a defect-forming laser beam via an optical assembly, wherein the defect forming laser beam comprises:
a pulsed laser beam forming a laser beam focal line at the textured surface or within the transparent workpiece, and
an optical power of greater than or equal to a critical power level to induce Kerr effect self-focusing throughout the entirety of the thickness;
forming a plurality of defects comprising an ablated region in the transparent workpiece by directing the defect-forming laser beam directly onto an impingement surface of the polymer-based sacrificial layer from the optical assembly such that the laser beam propagates through the transparent substrate via the polymer-based sacrificial layer and translating the transparent workpiece and the laser beam relative to each other along a contour line, wherein the plurality of defects extend along a contour and extend from the textured surface into the transparent workpiece by a distance that greater than or equal to 80% of the thickness of the transparent workpiece;
removing at least a portion of the polymer-based sacrificial layer from the transparent workpiece to expose at least a portion of the plurality of defects at the textured surface; and
separating the transparent workpiece along the contour.
16. The method of claim 15 , wherein the sacrificial layer has a thickness of greater than or equal to 10 μm and less than or equal to 20 μm.
17. The method of claim 15 , wherein the transparent workpiece comprises at least one of a rolled glass sheet and a glass-ceramic material.