Mechanically inspired laser scribing of thin flexible glass

Abstract

Laser cutting of thin glass (<100 μm) has proven problematic. We describe an alternative laser scribing method that utilizes surface stress raisers. An ultrashort laser source is used to precisely pattern a plurality of aligned elliptical recesses on the glass. The apex of an ellipse concentrates applied tensile stresses. Depending on the elliptical dimensions, the stress concentration factor can be several tens of magnitude. The orientation of the ellipses defines a preferred scribing path. Tensile stress is applied orthogonally to the path and causes mode I fracture. The resulting scribe is of higher quality and strength than are possible with a full body laser cut. The optical setup is simple, low in cost, and compatible with future roll-to-roll manufacturing. The stress field around a stress raiser was analyzed using finite element method analysis. Consequently, the stress raiser process offers an alternative to other processes which employ high numerical aperture optics for thin glass scribing.