The shelf life of over coating layer (OCL) materials for TFT-LCD panels prepared by mixing methacrylate copolymer and epoxy compound was improved compared with other materials consisting of a single component. However, a rough surface was formed on the OCL during the post-baking process. Previously, we reported that fatty acids with longer alkyl chains were very effective in preventing the roughing of the OCL surface [1]. In this study, the reaction of carboxy and epoxy groups was studied by using near infrared (NIR) spectroscopy. It was confirmed that the fatty acids do not accelerate the reaction, but compatibilize each component of the OCL material.