Assessment of surface damage characteristics of polymeric optical sheets of LCD backlight unit

The backlight unit of a liquid crystal display (LCD) consists of a set of vertically stacked polymeric optical sheets that may experience sliding motion when subjected to vibration. In this work, the surface damage characteristics of the optical sheets were assessed by conducting sliding tests between specimens sampled from the sheets. Surface morphology and hardness of the sheets were also measured using surface characterization tools. It was found that friction coefficient between the polarization film of the LCD panel and dual brightness enhanced film (DBEF) was the highest with a value of ∼0.35. Also, DBEF and diffusion plate suffered the most amount of surface damage. Based on the results of the wear tests, wear maps were constructed from which the relative degree of surface damage could be identified. It was determined that the friction and wear behavior of the polymeric sheets were influenced significantly by their surface morphology and hardness.