Abstract: meso-Tetraphenyl-porphyrin (H₂TPP) was first used as an indicator of acid sensitive film composed of vinylidene chloridemethyl acrylate copolymer.The color of H₂TPP-acid sensitive film changes from purplish red to green upon exposure to 254 nm light due to the formation of HCl salt of H₂TTP. HCl is released from acid sensthive film up on UV irradiation. H₂TPP-acid sensitive film showed a better image stability than that with dimethyl yellow because a shang polar compound is formed from IR spectra results.

Key words: meso-tetraphenyl-porphyrin, acid sensitive film, vinylidene chloride-methyl acrylate, dimethyl yellow