Image Formation by Use of Poly(vinyl alcohol) Film Containing Copper(II) Chloridet

Abstract

Image formation by use of poly(vinyl alcohol) (PVA) film containing copper( II) chloride and its mechanism have been investigated. Brownblack image was obtained by exposing the PVA film to ultraviolet light and then heating it. Also relief image was formed by washingout with water, since PVA of the image area became insoluble in water. The PVA film had both the properties of photosensitivity and thermosensitivity. Copper(II) chloride in PVA was reduced to form copper(I) chloride by exposing to ultraviolet light, with the simultaneous oxidation of PVA. The same redox-reaction took place on heating the PVA film at 130°C for about 7 min. The rate of the thermal reaction increased in the presence of copper(I) chloride or copper. The results suggest that the image formation takes place via the following stages:
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2CuCl →hν Cu + CuCl₂
CuCl or Cu formed in this reaction acts as a catalyst for the subsequent thermal reaction. Therefore, the thermal reaction takes place preferentially in the area exposed to ultraviolet light to form Cu and oxidized PVA, that is, to form brownblack and insoluble image. Other products, such as CuO and Cu₂O may be formed as colored products for the image formation.