Ultrathin glass is a promising substrate material for web processing (also called roll-to-roll processing) of flexible electronics, but is highly susceptible to breaking and cracking due to the almost inevitable presence of substrate-edge defects. Recently, a novel technique for removing the micro cracks on the edges of ultrathin glass substrates was devised at ITRI. It amounts to shining a CO2 laser on one edge of a substrate, which induces spontaneous peeling of a thin layer containing preexisting cracks on the edge from the substrate, resulting in an essentially crack-free new substrate edge. Exploiting the thinness of ultrathin glass substrates, here we propose a simplified two-dimensional thermal model for the laser peeling process, and obtain an analytic expression for the transient temperature variation in a substrate being peeled. This enables us to locate the "thermally affected zone" in the substrate, which turns out to be impressively similar in size and shape to the substrate-edge peels observed in experiments. Moreover, a quantitative criterion for the minimum cooling rate required for the progression of the peeling process is obtained. The results here thus provide useful insights into the laser peeling mechanism, and can be used to expedite the optimization of process parameters. Some preliminary purely numerical results using a finite element method (FEM) based software also are briefly discussed here.

Laser peeling is a surface defect removal process involving irradiating laser pulses on edges of ultra-thin glasses. Mechanical- or laser-cutting induced edge defects on glass edges are removed by peeling off a thin layer containing the cutting defects. The new edge-surfaces of the glasses are defect-free and much less prone to cracking failure. In this paper the mechanism of this material removal process is investigated. From experimental observations and theoretical calculations, it is shown that the laser glass peeling is a brittle fracture process driven by residual stress associated to glass surface phase change phenomenon, as opposed to the typical laser ablation material removal. A quantitative fracture mechanics model that simulates the laser induced glass peeling process is also presented. (C) 2016 Elsevier Ltd. All rights reserved.

Micromachining of Mg-based bulk metallic glasses (BMGs) is performed using two kinds of pulsed nanosecond lasers: a 355nm ultraviolet (UV) laser and a 1064nm infrared (IR) laser. Precision machining on the micrometer scale and the preservation of amorphous or short-range order characteristics are important for the application of BMGs in micro-electro-mechanical systems. A higher micromachining rate is achieved using the UV laser than using the IR laser due to a better absorption rate of the former by Mg-based BMGs and a higher photon energy. The cutting depth of Mg-based BMGs ranges from 1 to 80μm depending on the laser parameters. By appropriate adjustment of the laser power and scan speed, successful machining of the Mg-based BMG with preservation of the amorphous phase is achieved after the laser irradiation process. Short-pulse laser cutting represents a suitable alternative for machining of micro components.

An ultraviolet wavelength laser is used to manufacture the metal electrode of a cholesteric liquid crystal display (Ch-LCD) without a shadow mask. The proposed method effectively ablates the metal layer without damaging the liquid crystal layer and underlying indium tin oxide electrode. The width and morphology of the laser ablated sections were investigated as a function of laser power as well as scan speed. The minimum ablated line is around 43μm and the laser system operates at 1.5W at a scan speed of 200mm/s. The characteristics of a Ch-LCD prepared using laser patterning under the optimum ablation process conditions are similar to those of a Ch-LCD prepared using the screen printing method.