GB1265408A - - Google Patents

Abstract

1,265,408. Photographic film units. POLAROID CORP. Dec. 24, 1969 [Dec.30, 1968], No. 62790/69. Heading G2A. In a film unit comprising a photo-sensitive sheet 12 and a second sheet 14 which receives an image from sheet 12 by diffusion transfer, the two sheets are maintained in face-to-face relationship by a retaining sheet 20 which is secured to the margins of the two sheets, sheet 14 also being embossed at its trailing end to form a number of ribs 54 which abut sheet 12 to provide spaces in which excess processing liquid may be collected. The film unit is of the type in which the processing liquid is initially held in a rupturable container, Fig. 1 (not shown), at the leading edge of the sheets. The container is ruptured by drawing the sheets between rollers 46, after which continued movements of the sheets between the rollers causes the liquid to be spread between sheets 12 and 14. Sheets 12 and 14 are of the same width, but sheet 14 is longer than sheet 12 at the trailing end. The retaining or binding sheet 20 is in the form of a rectangular frame larger than sheets 12 and 14, and having a rectangular opening 22 which defines the size of the image produced. The lateral edge portions 24 of binding sheet 20 are secured around and to the outer marginal portions 30 and 32 of sheets 12 and 14. Similarly the trailing edge portion 28 of sheet 20 is secured to and folded round trailing edge 36 of sheet 14 and also secured to trailing edge 34 of sheet 12. Thus sheets 12 and 14 are effectively bound to each other along three sides, so that any escape of processing liquid is prevented. As shown, the trailing end 36 of sheet 14 is embossed to form a series of short longitudinal ribs 54 joined together by a transverse rib 52. Ribs 54 function to provide spaces in which excess processing liquid may be trapped and retained, as shown in Fig. 5, which represents the position after the sheets 12, 14 have been drawn almost completely through the rollers 46. Rib 52 has been bonded by pressure to the wet surface of folded-end 28 of sheet 20, which prevents flowback of liquid from the trapping space to the image area. Air trapped during the spreading of the processing liquid, and pushed along with it, is also collected between ribs 54. Means such as slits 60 or pinholes 62 may be provided to allow this air to escape.