GB568782A - Improvements in or relating to photographic materials - Google Patents

Abstract

Photographic printing paper comprises paper carrying surface coatings of hydrophobic polyvinyl acetal resin and carrying at least one emulsion layer, which may be separated from the resin layer by a colloid layer strongly adherent to both. The resin may be obtained from polyvinyl acetate by partial or complete hydrolysis with simultaneous or subsequent reaction with formaldehyde, or a higher aldehyde. A solvent of the resin in a preferably volatile organic solvent or solvent mixture is applied to one or both sides of paper base. A subbing layer containing cellulose nitrate and gelatin, or successive layers of cellulose nitrate and gelatin, is then applied. The first subbing solution should preferably contain a substance having a slight solvent action on the resin. In an example, paper base is successively coated on opposite sides with a solution comprising "Formvar" (Registered Trade Mark) 15-95, benzene, and ethyl alcohol, then on one side with a layer of nitrocellulose, with a gelatin layer, and finally with a gelatin silver halide emulsion layer. The resin solvent may alternatively be a chlorinated hydrocarbon; dioxane; acetic acid mixtures of ethyl alcohol with toluene, xylene, monochlorobenzene, or carbon tetrachloride; or a mixture of ethylene dichloride and methyl alcohol. A plasticizer such as benzyl benzoate, tricresyl phosphate, p-tert.-amylphenol, dibutyl phthalate, or tributyl phosphate or mixtures thereof may be added. The paper base may carry a baryta coating immediately adherent thereto.