Glass cutting in LCD manufacturing by using tungsten carbide wheel

Abstract

Glass cutting is one of the key processes in Liquid Crystal Display (LCD) manufacturing whereby the large sheet of glass laminate containing many LC cells is cut into individual cell according to required specification. In order to be competitive and to maintain profitability, the required production yield rate has to be maximized. There are various emerging cutting technologies and various cutting techniques are available. A discussion on laser cutting technology applied on LCD glass cutting is included, highlighting the advantages and disadvantages for its application. However, almost all LCD manufacturers are still applying mechanical scribe/break technique that uses tungsten carbide wheel as a cutting tool. In this work, studies on crack creation and propagation in glass using point indentation method were conducted to examine the applicability of the method in scribe/break mechanism for LCD glass cutting. It is found that analytical method for point indentation is potentially applicable to the analysis of crack propagation. Fracture analysis has been adapted to cut glass samples collected from actual manufacturing plant to find out the causes of the faulty cutting. It is observed that four deterioration modes presence on the cut surface are attributed mainly to the scribe wheel edge features. It has been concluded that clear-cutting strongly depends on wheel tip features. The influence of scribe wheel dimensions on the scribability and breakability has been evaluated. An equation with wheel dimensional factors and material properties has been used to predict median crack depth as a function of scribing depth. The influence of the wheel geometry to the breakability is studied, and it is found that the influence of tip angle on the lateral crack creation is larger than that of the wheel radius. The influence of the residual stress on the breaking force reduction has been also analyzed. It has been finally evaluated that through in-depth study and understanding of the various influencing factors of glass cutting, it is possible to control the quality and cost of LCD manufacturing by using scribe/break method.