Structural changes of and the interactions between organic materials in liquid crystal display panel after UV exposure were systematically investigated using FT-IR, XPS, AFM, and LC-ESI-MS. When the photo-curing of the sealant was imperfect during the assembly of LCD panel, both the components in the sealant such as UV-initiator contaminated the LC's and the stray UV light oxidized the benzene rings and other chemical bonds in the polymer backbone of the alignment layer. This resulting contamination of LC's and degradation of the alignment layer could disturb the pretilt angle of the VA-mode LC's and cause the display defects on the LCD panel. In this regard, careful control of the photo-curing of the sealant will be required for precise alignment of the LCD panel and better performance of the display.