Characterization and Image-Based Performance Evaluation on the Longevity of LCDs Under High Temperature and Humid Environment

Quality inspection and long term reliability of liquid crystal displays (LCDs) are critical for product assurance. In this work, the degradation of LCDs under both high temperature (~90°C) and high humidity (~near 100%) are characterized as a reference for related product reliability test in accelerating manner. Traditionally, manually inspection is performed for finding display defects such as Mura. Such an approach could be biased easily by subjective opinions and a more objective evaluation should be sought. In this paper, a computer-based inspection approach is proposed for addressing this need through a systematic design of LCD durability test. By capturing standard LCD display images during operation and perform essential image processing, it is possible to evaluate defect quantitatively. After each heating period, the LCD images are taken and analyzed either by Otsu thresholding or by analyzing their statistical properties in the gray level histograms. The results indicate that these image-based methods are highly correlated and therefore can be adapted as the measures of display qualities. The mean time to failure is characterized as 1500 hours under the testing condition. Meanwhile, both the Young's modulus and warpage testing of the polarizer and the diffuser membranes of the LCDs, as well as the essential finite element deformation analyses, are performed for correlating the display performance of the LCDs. It is found that the resulted warpage and the reported Mura are also highly correlated. This provides a rational approach for improving device longevity based on fundamental mechanics.