Patent Publication Number: US-6221554-B1

Title: Self developing-film unit

Description:
This invention relates to photography and, more particularly, to novel photographic film units for forming images by diffusion transfer. 
     BACKGROUND OF THE INVENTION 
     Diffusion transfer film units of the self-developing or instant type are well known in the art. Such film units which generally include a photosensitive element, an image receiving element and a photographic processing composition, can be provided in black and white or multicolor formats. Further, such diffusion transfer film units may be of the type wherein the image-receiving element is designed to be separated from the photosensitive element after photoexposure and photographic processing are carried out, commonly referred to as “peel-apart” film units or they may be of the type wherein the photosensitive and image-receiving elements are designed to be maintained together after image formation is completed, commonly referred to as “integral” film units. 
     Typically, the images formed with diffusion transfer film units are stored in photo albums or placed in picture frames for viewing. However, as the state of the art advances and new uses are proposed for such images it would be desirable to have diffusion transfer film units where the images formed could be adhered to any convenient surface for viewing. 
     SUMMARY OF THE INVENTION 
     These and other objects and advantages are obtained in accordance with the invention by providing a self-developing film unit which includes a photosensitive element, an image-receiving element and wherein one outermost surface of the film unit comprises a support layer carrying a layer of a releasable material and a layer of an adhesive material. After an image is formed in the film unit by photoexposure of the photosensitive element and photographic processing of the exposed photosensitive element, the releasable material layer can be removed and the image-receiving element or the film unit, as the case may be, adhered to a surface for viewing the image. 
     The diffusion transfer film units of the invention may be adapted to provide black and white images or multicolor images. Further, the film units may be of the integral type or the peel apart type. In a preferred embodiment there is provided according to the invention an integral, multi color diffusion transfer photographic film unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following detailed description of various preferred embodiments thereof taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a partially schematic cross-sectional view of a preferred embodiment of a film unit according to the invention, wherein photoexposure of the photosensitive element and viewing of the image formed are through the same surface of the film unit; 
     FIG. 2 is a partially schematic, cross-sectional view of a preferred embodiment of a film unit according to the invention wherein photoexposure of the photosensitive element and viewing of the image formed are through opposing surfaces of the film unit; and 
     FIG. 3 is a partially schematic perspective view of a preferred embodiment of a film assemblage according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The diffusion transfer photographic film units of the invention include those wherein the image-receiving element is designed to be separated from the photosensitive element after exposure and photographic processing are carried out. 
     Various embodiments of peel-apart diffusion transfer film units are known and include those wherein images are formed in black and white (reduced silver) and color (image dyes) as described in E. H. Land, H. G. Rogers and V. K. Walworth in Neblettes Handbook of Photography and Reprography, 7th Edition, J. M. Sturge, editor, Van Nostrand Reinhold, New York 1977, pp 258-330; and V. K. Walworth and S. H. Mervis in Imaging Processes and Materials, Neblettes Eighth Edition, J. Sturge, V. Walworth and A. Shepp, editors, Van Nostrand Reinhold, New York, 1989, pp 181-225. Additional examples of peel-apart film units are described in U.S. Pat. Nos, 2,983,606, 3,345,163, 3,362,819, 3,594,164, 3,594,165, and 5,593,809. Black and white film units according to the invention can be provided in both the peel-apart and integral formats as described, for example, in U.S. Pat. Nos. 2,543,181, 4,489,152 and 5,858,608. All the foregoing references are incorporated by reference herein. 
     A particularly preferred embodiment according to the invention comprises an integral film unit such as is described in U.S. Pat. No. 3,415,644 which is incorporated by reference herein. In commercial embodiments of this type of film unit e.g., SX-70 film from Polaroid Corporation, the support for the photosensitive element is opaque, the support for the image-receiving element is transparent and a light-reflecting layer against which the image formed in the image-receiving element is viewed is formed by distributing a layer of processing composition containing a light-reflecting pigment such as, for example, titanium dioxide, between the super posed elements. By also incorporating suitable pH-sensitive optical filter agents, preferably pH-sensitive pathalein dyes, in the processing composition as described in U.S. Pat. No. 3,646,347 which is incorporated by reference herein, the film unit may be ejected from the camera immediately after the processing composition has been applied such that the development process is completed in ambient light while the photographer watches the transfer image energy. 
     Referring now to FIG. 1 there is seen a photographic film unit  10  according to the invention wherein the film unit is exposed, and the image formed in the film unit is viewed, through the support of the image-receiving element. The film unit  10  includes photo sensitive element  12 , which includes an opaque support and image-receiving element  14 , which includes a transparent support, arranged in superposed relationship with a rupturable pod  16  releasably holding a processing confirmation arranged between the photosensitive and image-receiving elements. 
     In a preferred embodiment the multicolor photosensitive element  12  is of the type described in U.S. Pat. No. 4,740,448, which is incorporated by reference herein, although any of the known types of multicolor diffusion transfer photosensitive elements may be utilized. Image-receiving element  14  may be any of those known for use in diffusion transfer photographic film units. In a preferred embodiment the image-receiving element comprises a transparent support carrying an image receiving layer. 
     Film unit  10  also includes a layer of an adhesive material  18 , a layer of a release material  20 , a support layer  22  and an optional layer of a release material  24 . 
     In operation, film unit  10  is exposed through the image receiving element  14  and after photographic processing which is initiated by spreading the photographic processing composition between the photosensitive and image-receiving elements, such as by passing the film unit through a pair of rollers as is well known in the art, the image formed in the image-receiving element  14  is viewed through the support for that element. The support layer  22  can then be stripped away from the film unit, together with the release layer  20  thus leaving the adhesive layer as the outermost layer of the processed film unit and allowing the film unit to be affixed to any surface for viewing the image. 
     The adhesive layer  18  may comprise any suitable adhesive material and may be of any suitable thickness. Typically, adhesive layer is from about 0.4 mil (10 μm) to about 1 mil (25.4 μm) in thickness and preferably from about 0.6 mil (15 μm) to about 0.8 mil (20 μm). Preferred adhesives for layer  18  are photographically-compatible, water-based thermoplastic acrylic adhesives and in a particularly preferred embodiment layer  18  comprises a mixture of two water-based thermoplastic acrylic adhesives. Support layer  22  may comprise any suitable material and may be transparent or opaque. A typical suitable material is an approximately 0.92 mil (24 μm) thick polyester sheet material. Support layer  22  may be of any thickness; however it is preferred to have the layer be from about 20-25 μm for various reasons such as the considerations involved in passing the film unit through a pair of rollers to spread the processing composition. 
     As is well known in the art the processing composition is applied to the film unit typically by passing the film unit through a pair of opposed spread rollers which cause the rupturable container  16  to rupture in the desired predetermined edge whereby the processing composition is spread uniformly throughout the picture area of the film unit. The film unit typically includes a mask sheet which has a rectangular aperture formed therein which ultimately will frame the resulting picture formed in the image-receiving element because of the parallel side rails on each side of the film unit in the processing composition spreading direction and the opposed leading and trailing edge masking areas. For a detailed description of a mask layer structure see, for example, U.S. Pat. No. 4,824,761 which is hereby incorporated by reference herein. The processing composition flows into a chamber formed by the side rails and the layers or elements of the film unit between which it is desired to deposit the processing composition. The thickness of the side rails determines the spacing between the layers or elements of the film unit where the processing composition is spread such that a predetermined thickness of a coating of the processing composition is applied. Thus, to facilitate the maintaining of a substantially uniform thickness of a coating of the processing composition the adhesive layer preferably extends, in the processing composition spreading direction, beyond the picture area. In the direction perpendicular to the processing composition spreading direction the adhesive layer extends beyond at least a substantial portion of the width of the rails, e.g., overlaps preferably about one-half to three quarters of the rail width. 
     Release layer  20  may comprise any suitable release material which adheres more strongly to support layer  22  than to adhesive layer  18  so release layer  20  will be stripped away from the film unit along with support layer  22  when it is desired to make the adhesive layer available for adhering the developed film unit to a surface for viewing. A preferred release layer  20  comprises an approximately 1 μm thick cross-linked silicone acrylic polymeric material. 
     In a preferred embodiment the film unit includes optional release layer  24 . In a preferred method for manufacturing the film unit a discrete element comprising layers  18 ,  20 ,  22  and  24  is brought into contact with the support of the photosensitive element. This discrete element is typically provided in the form of a roll and therefore, in this instance, release layer  24  is present to prevent the adhesive layer  18  from adhering to another layer when the element is formed into a roll. Where release layer  24  is present in addition to release layer  20 , there should be a differential in the release characteristics of the two release layers, that is release layer  24  should release at about one-half the force required to cause release layer  20  to separate from adhesive layer  18 . Typically, release layer  24  should be separable at a force of from about 15 to about 25 grams/inch and release layer  20  at a force of about 60 to about 120 grams/inch. Release layer  24  preferably is an approximately 1 μm thick layer of a cross-linked silicone acrylic copolymer. Release layer  24  may also be formulated with silica particles, silicone beads or any like particles or beads to maintain a desired coefficient of friction on the surface of the film elements described in FIGS. 1 and 2. 
     Adhesive layer  18  should bind more strongly to photosensitive element  12  than either release layer binds to its adjacent layers, that is, the force required to separate adhesive layer  18  from photosensitive element  12  should be greater than the force (s) required to separate the release layer(s) from the next adjacent layer. The force required to separate adhesive layer  18  from photosensitive element  12  can vary. For example, where it is desired to provide a picture which can be adhered to a surface and subsequently removed and/or repositioned the force preferably is in the range of from about 400 to about 1000 grams/inch and where it is desired to affix the picture permanently the force preferably is in the range of from about 1000 to about 2000 grams/inch. 
     FIG. 2 illustrates a preferred embodiment of a film unit according to the invention, which is exposed and viewed through opposing outer surfaces. Diffusion transfer photographic film units of the type where exposure is made through one transparent outer surface and the image formed is viewed through the opposing outer surface are well known in the art and are described in detail for example in U.S. Pat. Nos. 3,594,165 and 3,689,262 which are incorporated by reference herein. In this type of film unit there are coated on one transparent support both the image-receiving and photosensitive elements and a transparent sheet element is arranged on the photosensitive element so as to form the other of the outer surface of the film unit. 
     Referring now to FIG. 2 there is seen a diffusion transfer film unit  30  according to the invention wherein transparent support layer  32  carries image-receiving element  34  and photosensitive element  36  and a transparent sheet element  38  is present. In this preferred embodiment, since the film unit is exposed through transparent sheet element  38  and the image is viewed through transparent support  32 , adhesive layer  40  is arranged adjacent to transparent sheet element  38  and thus must be optically transparent. Release layer  42 , support layer  44  and optional release layer  46  also must be optically transparent. Preferably, layers  40 ,  42 ,  44  and optional layer  46 , where present, have a combined optical density less than about 0.3. 
     A particularly preferred film assemblage according to the invention comprises the type described and claimed in U.S. Pat. No. 5,888,693 which is incorporated by reference herein. Referring now to FIG. 3 there is seen a perspective view of a film assemblage  50  according to the invention comprising self-developing film units  52  secured end to end to connection strips  54  in alternating arrangement to form a longitudinal strip. The film assemblage  50  is conveniently subdivided into image units, or frames,  55  extending lengthwise from a weakened section  56  on one connection strip  54  to the equivalent location  56  on the adjacent connection strip  54 . The weakened sections  56  preferably represent structurally weakened sections intended to permit easy separation of successive image units  55 . 
     Each image unit  55  comprises the film unit  52 , a rupturable container, or pod,  58  containing photographic processing composition, and adjacent the leading edge of the film unit  52 , a trap  60  adjacent the trailing edge of the film unit  52  adapted to receive excess processing conformation not consumed during processing of the film unit  52  in a cooperating exposure device such as a camera (not shown). Both the rupturable container  58  and the trap  60  are attached to the connection strip  54  by, for example, adhesives. 
     A liquid-tight fluid passageway is provided between the rupturable container  58  and the leading edge of the film unit  52  and between the trailing edge of the film unit  52  and the trap  60 . In one embodiment a comer strip  62 , generally coextensive in width with connection strip  54  is disposed on top of connection strip  54  and secured at its respective ends to the leading and trailing edges, respectively, of the film unit  52  by, for example, an adhesive. Furthermore, the connection strip  54  is secured and sealed fluid-tight along the side marginal portions proximate to the rupturable container  58  and along the side marginal portions proximate to the trap  60 . In the region between rupturable container  58  and the trap  60  the connection strip  54  and the cover strip  62  are affixed such as by adhesives or by heat-sealing to each other so as to seal, in a liquid-tight manner, the rupturable container  58  and the trap  60  from the environment. The film assemblage  50  and the manner in which it cooperates with an exposure device such as a camera to form an image in each film unit are described in detail in U.S. Pat. No.  5 , 888 , 693  and therefore such description is not required here. 
     Film units  52  may be any of those previously described herein. In a preferred embodiment film units  52  comprise the type illustrated in FIG. 1 wherein exposure is effected, and the image formed in the image-receiving element is viewed, through the transparent support of the image-receiving element  14 . In the preferred embodiment the film unit  52  is preferably disposed with the image receiving element remote from the connection strip  54  although it is apparent that, if so desired, the film unit could be disposed with the image-receiving element adjacent the connection strip. 
     In another preferred embodiment film units  52  comprise the type illustrated in FIG. 2 wherein exposure is effected through transparent sheet element  38  and the image is viewed through transparent support  32 . In this embodiment it is preferred to arrange the image unit with the image-receiving layer  38  and the adhesive layer  40 , the release layer(s) and the support layer  44  remote from the connection strip  54 . 
     Although the invention has been described in detail with respect to various preferred embodiments thereof, those skilled in the art will recognize that the invention is not limited thereto but rather that variations and modifications can be made which are within the spirit of the invention and the scope of the amended claims.