Technique and Theory of Vibration Assistant Scribing Process on LCD Glass Substrate

A technique of vibration assisted scribing of LCD glass substrate is developed in this thesis. An additional piezoelectric actuator is implemented on the servo controlled loading mechanism of the scribing machine, and a periodically varying load superposed on the constant load is provided to the standard scribing wheel. It is found that under a proper vibration frequency condition the median crack depth is significantly increased to about twice of that without vibration assisted scribing. As a result, automatic separation of the glass without the need of breaking process similar to the case with the use of toothed wheel (penett) can take place. On the other hand, while the bending strength of the glass panel after scribing by toothed wheel is merely about half of that resulting from scribing by standard wheel, it remains almost unchanged by the developed technique. Hence the cost of wheels and scribing machine can be reduced since toothed wheels can be replaced and the proposed technique can be applied by any commercially available machine. fundamental theory of vibration assisted scribing process is also manifested. It is proposed that the rapidly varying periodical scribing load does not lead to as much an increase of the plastic deformation as that due to the servo controlled constant scribing load. Instead it mainly results in an increase of elastic deformation. The increase of median crack depth through elastic deformation can avoid the lateral and radial cracks induced by large plastic deformation which are usually observed under an increasing constant load condition. The noticeable elastic component of the increased median crack depth was confirmed by experiments, and the proposed theory is verified.