A Study of Polyvinyl Alcohol Photoresists.

Polyvinyl alcohol (PVA) photoresists came into use in this country because of the need for a material that was usable with magnesium plates in the Dow etching process. The resist consists of a water solution of low viscosity PVA and a preservative. It is sensitized, in the usual way, with ammonium dichromate. The shelf life of the sensitized resist is short compared to that of cold-top enamels. After exposure the print is developed in water, or in a water solution of a dye which makes visual observation of the image more convenient. The print may or may not be further insolubilized by a fixing step, prior to drying and burning in. Only a moderate temperature is required for burning in and, hence, the resist may be used on Zinc or magnesium plates. This paper presents the results of an investigation of the stability of sensitized PVA solutions, the effect of dichromate-PVA ratio on photosensitivity, the mechanism of development and fixation of prints, the effect of film thickness on photosensitivity and on the integrity of the film in the Dow etching bath, and factors affecting the useful life of sensitized magnesium plates.