printed picture image for illuminated display on a light box wherein a treating liquid is applied on the non printed back side of the paper sheet to impregnate liquid paraffin into the sheet to increase its light transmittivity and the sharpness of the picture image application_number US 64047375 A description the term 34 paper sheet 34 as herein used includes 34 grade paper 34 34 art paper 34 34 coated paper 34 34 japanese paper 34 34 printing paper photographic 34 and 34 kent 34 with a sign or picture of desired motif printed on one surface thereof for illuminated display on a light box according to the invention applied on the back side of the printed paper sheet is a treating liquid comprising 60 0 to 80 0 by weight of liquid paraffin as a light transmittivity increasing agent 0 03 to 0 06 of butyl hydroxyanisole as antioxidant and a balance of diluent such as toluole xylol an ester of acetic acid butanol and methyl isobutyl ketone the treating liquid is applied with a brush uniformly over the back side of the printed paper sheet and dried artificially by means of an electric fan followed by natural drying over a period of about 12 to 24 hours it is preferable to apply the treating liquid at an ambient temperature within the range of 5 u00b0 c to 30 u00b0 c and at a humidity below 75 since with an ambient temperature below 5 u00b0 c the fluidity of the treating liquid will be lowered to delay its impregnation into the paper sheet considerably giving adverse effects on the working.