Abstract
The demand of liquid crystal display panels for handy type personal computers etc. have been remarkably increased. Liquid crystal display panels were generally formed on glass substrates. In these production process, precise arid fine cutting of glass plates is very important because of the final manufacturing process. Hard and brittle materials like glass plates are conventionally cut by growing vertical cracks. They are generated by scribing with a diamond point or a rotating chisel under optimum load and grown by applying mechanical force onto the scribed trace successively. In the laser braking method, vertical cracks formed on glass plates are grown by tensile stress due to thermal expansion which arises from temperature rise by a CO2 laser beam irradiation onto the scribed trace. High quality and high speed breaking can be achieved without applying mechanical force. In this breaking process, formation of fine vertical cracks by scribing is indispensable. This paper deals with the effect of scribing conditions on features of scribed trace and the vertical crack length experimentally and theoretically. Generation and growing process of vertical cracks were observed. Close agreement of vertical cracks length grown between observed and calculated values was obtained.
