We have studied the thermal stability of optical film composed of transparent acrylic resin and the diimmonium dye, which is capable of absorbing intense near infrared (NIR) light from Plasma Display Panels (PDPs). After thermal aging, the color of optical film was changed and the efficiency of NIR absorption was decreased due to the deterioration of the dye. These phenomena were found to be sensitive to variations in characteristics of polymers and dyes. First of all, it was determined when the polymer resin possessed hydroxyl or carboxylic functional groups, although dyes's durability was slightly improved for the film with higher Tg polymer. These observations imply that the destructive mechanism of dye molecules is related to the effect of dye mobility and unpredictable chemical reactions between the dye and the reactive group of polymer. Additionally, we investigated the effect of solvent polarity as well as dye's rigidity on the thermal stability of the film in order to support these results.