Changes in the Composition of the Dried Asian Lacquer (Korean Lacquer) Film Irradiated with Ultraviolet Light

다국어 초록 (Multilingual Abstract)

Asian lacquer is a material that has been used in Asia from ancient times to coat the surfaceof objects. It is a durable material, but is known to be weak to ultraviolet light (UV). Here, to understandthe deterioration characteristics of Asian lacquer due to UV, the changes were analyzed using ultravioletphotometry, IR, and pyrolysis/GC/MS (pyrolysis/GC/MS), after exposing the lacquer coating film toUV (λ= 340 nm). In the ultraviolet photometry, the surface exposed to UV showed fluorescence. InIR analysis, the powder sample showed little change after exposure to UV, but on the surface, C =O groups increased, while C―H groups decreased significantly. Analysis with pyrolysis/GC/MSrevealed that the composition of organic acid increased significantly. Carboxylic acids having 9 or lesscarbon atoms and dicarboxylic acids were significantly increased compared to carboxylic acid having16 carbon atoms. In addition, urushiol with the oxidized side chain was also increased. This showsthat the penetration depth of UV is the limiting factor for deterioration, and that the deterioration oflacquer due to UV proceeds with the destruction of carbon–carbon single and double bonds and thesubsequent formation of carboxylic acid.