Application of the Taguchi approach to improve performance of the alignment-layer printing process in liquid crystal displays

摘要

The uniformity of the alignment-layer thickness on indium tin oxide glass plays an important role in producing liquid crystal display panels of quality images. However, thickness non-uniformity results in producing liquid crystal display panel of poor color image, which increases rework cost and scrap. The Taguchi method is utilized in the define-measureanalyze-improve-control approach to improve the capability of this process. In the define phase, process mapping and quality characteristic definition are discussed. The x and R control charts and process capability analysis are employed in the measure phase. The L_(18) array and signal-to-noise ratio, followed by analysis of variance, are utilized in the analyze phase. In the improve phase, two-step optimization is conducted to reduce thickness variations and adjust process mean on target. The control charts for the thickness are regularly constructed in the control phase. Initially, the estimates of the capability indices for the alignment-layer printing process are 0.731 and 0.69, respectively, which indicate that this process is incapable. Utilizing the Taguchi method, confirmation experiments showed that the potential and actual capability indices are respectively improved to 3.48 and 3.47. Hence, the process becomes highly capable. This proves the effectiveness of the Taguchi method in improving the performance of the alignment-layer printing process.