Formation Mechanism of Metal Images by the Peel Apart System

Abstract

An imaging system based upon the peel apart procedure has been investigated. The imaging structure consists of a photochemically active layer comprising a polymer and a photosensitive material, a thin metal layer deposited on a substrate and a cover film laminated on the photosensitive layer. After imagewise exposure, following heating and peeling of the cover film off the base forms metal patterns on both the base and cover films.
In this paper, a possible imaging mechanism was proposed to explain the previous experimental results. In the positive working system, the adhesive strength between the photosensitive layer and metal interface was assumed to be increased by the formation of hydrogen bonds that are caused by light irradiation and heating. This result is the case in which poly(vinyl chloride) and 2, 6-bis(4-azidobenzylidene)-4-methyl-l-cyclohexanone were used for the photosensitive layer. In the negative working system of 1, 4-naphthoquinone and vinyl chloride-vinyl acetate-maleic acid terpolymer, the experimental results indicate the reduction of adhesion at the same interface by some photolyzed products.
In order to confirm the above mechanism, the photodecomposed products were separated by a liquid chromatographic procedure and the separated species were coated with the polymer onto the metal layer. It was found that adhesion between the polymer and matel interface was increased with increasing the amount and the polarity of added photoproducts. The proposed mechanism was demonstrated only for the positive working layer.
To clarify the negative working mechanism, electron spin resonance spectra of the photosensitive layer was measured after light exposure. A radical signal (g=2.0054) observed was decayed almost in the same manner as the dark change of imaging characteristics after illumination. The results suggest that the photoinduced radical in the photosensitive layer corresponds directly to the component which breaks hydrogen bonds at the interface.