US3756824A - Rocessing liquid photographic self developing film unit with rupturable container of p - Google Patents

Abstract

A SELF-DEVELOPING FILM UNIT INCLUDING PHOTOSENSITIVE AND SECOND SHEETS SECURED IN FACE-TO-FACE RELATION AND ADAPTED TO BE PROCESSED BY A LIQUID PROCESSING COMPOSITION DISTRIBUTED BETWEEN SAID SHEETS FROM A RUPTURABLE CONTAINER SECURED TO THE SHEETS EXTERNALLY THEREOF ADJACENT A TRANSVERSE EDGE OF ONE OF THE SHEETS. THE CONTAINER IS FORMED OF A RECTANGULAR BLANK OF SHEET MATERIAL FOLDED UPON ITSELF TO FORM WALLS SEALED TO ONE ANOTHER ALONG THREE SIDES TO FORM A LIQUID-FILLED CAVITY. EDGE PORTIONS OF THE CONTAINER ARE ADAPTED TO BECOME UNSEALED IN RESPONSE TO THE APPLICATION OF COMPRESSIVE PRESSURE TO THE LIQUIDFILLED CONTAINER. THE CONTAINER IS ATTACHED TO ONE OF THE SHEETS BY A FIRST RETAINING SHEET SECURED TO AN EDGE POR-

TION OF THE CONTAINER AND A TRANSVERSE EDGE PORTION OF THE ONE SHEET. ANOTHER RETAINING SHEET IS SECURED TO THE OTHER SHEET AND TO THE CONTAINER SO AS TO PREVENT MOVEMENT OF AT LEAST A PORTION OF THE CONTAINER RELATIVE TO THE OTHER SHEET. THE FIRST RETAINING SHEET COOPERATES TO FORM A PASSAGE FOR CONDCUTING THE LIQUID CONTENTS OF THE CONTAINER BETWEEN THE PHOTOSENSITIVE AND SECOND SHEETS. THE CONTAINER IS ELONGATED IN THE DIRECTION OF LIQUID DISTRIBUTION AS IT IS FLATTENED BY COMPRESSIVE PRESSURE AND A SPACE IS PROVIDED BETWEEN THE EDGE PORTIONS OF THE CONTAINER AND THE TRANSVERSE EDGE OF THE ONE SHEET TO ACCOMMODATE THE CONTAINER ELONGATION.

Description

Spt, 4, 1973 CHEN PHOTOGRAPHIC SELF-DEVELOPING FILM UNIT WITH RUPTURABLE CONTAINER 0F PROCESSING LIQUID 3 Sheets-Sheet 1 Filed March 15, 1971 INVENTOR. RICHARD J. CHEN Wm MM cf? Catfi- ATTORNEYS R. J. CHEN Sept. 4, 1973 PHOTOGRAPHIC SELF'DEVELOPING FILM UNIT WITH RUPTURABLE CONTAINER OF PROCESSING LIQUID 3 Sheets-Sheet 2 Filed March 15, 1971 INVENTOR. RICHARD J. CHEN fiwmmm I ATTORNEYS Sept. 4, 1973 J CHEN 3,756,824

PHOTOGRAPHIC SELF-DEVELOPING FILM UNIT WITH RUPTURABLE CONTAINER OF PROCESSING LIQUID Filed March 15, 1971 5 Sheets-Sheet 5 INVENTOR. RICHARD J. CHEN meal/02mm and W fiawv ATTORNEYS United' States Patent 3,756,824 PHQTGGRAPHHQ SELF-DEVELOPING FILM UNIT WllTH RUPTURABLE CONTAINER 6F PROCESS- llNG LKQUID Richard J. Chen, Winchester, Masa, assignor to Polaroid Corporation, Cambridge, Mass. Continuation-impart of abandoned application Ser. No. 851,213, Aug. 9, 1969. This application Mar. 15, 1971, Ser. No. 124,273

Int Cl. G036 /54 US. Cl. 96-76 R 15 Claims ABSTRACT OF DISCLOSURE A self-developing film unit including photosensitive and second sheets secured in face-to-face relation and adapted to be processed by a liquid processing composition distributed between said sheets from a rupturable container secured to the sheets externally thereof adjacent a transverse edge of one of the sheets. The container is formed of a rectangular blank of sheet material folded upn itself to form walls sealed to one another along three sides to form a liquid-filled cavity. Edge portions of the container are adapted to become unsealed in response to the application of compressive pressure to the liquidfilled container. The container is attached to one of the sheets by a first retaining sheet secured to an edge portion of the container and a transverse edge portion of the one sheet. Another retaining sheet is secured to the other sheet and to the container so as to prevent movement of at least a portion of the container relative to the other sheet. The first retaining sheet cooperates to form a passage for conducting the liquid contents of the container between the photosensitive and second sheets. The container is elongated in the direction of liquid distribution as it is flattened by compressive pressure and a space is provided between the edge portions of the container and the transverse edge of the one sheet to accommodate the container elongation.

This application is a continuation-in-part of my application Ser. No. 851,213 filed Aug. 9, 1969, now abandoned.

This application is concerned with a self-developing, photographic film unit of thetype including photosensitive and second sheets arranged in superposed relation and a rupturable container of processing liquid adapted to be distributed between the photosensitive and second sheets by the progressive application of compressive pressure to the film unit commencing in the region of the container. The application is particularly concerned with a film unit of this type incorporating a well-known type of rupturable container formed by folding a rectangular blank of sheet material medially upon itself to form two walls and sealing the walls together at their margins to form a cavity for the processing liquid.

A number of United States patents including for example, Pats. Nos. 3,053,659 and 3,415,644, disclose selfdeveloping film units comprising a photosensitive sheet, a second or image-receiving sheet which is preferably transparent and is secured in face-to-face relation with the photosensitive sheet and a rupturable container of processing liquid secured to the sheets externally thereof in position to eject its liquid contents between the sheets in response to the application of compressive pressure to the container. In film units of this type, the photosensitive and second sheets are superposed and remain superposed prior to, during and subsequent to exposure and processing. Processing is accomplished by advancing the film unit, container foremost, relative to and between a pair of pressure-applying members which first eject the liquid contents of the container between the sheets at ice the leading end thereof and then spread the liquid as a thin layer between the sheets toward the opposite (trailing) end of the film unit. The two sheets include transverse leading edges which may be aligned with one another or the leading end of one sheet, preferably the second sheet, may extend beyond the leading edge of the photosensitive sheet.

A well known rupturable container of the type employed, for many years in this film unit, is disclosed, for example, in U.S. Pat. No. 2,543,181, and comprises a rectangular blank of a multilayer, fluid impermeable sheet material folded medially upon itself to form two walls sealed to one another along three sides to form an elongated cavity filled with the processing liquid. The container usually includes elongated lateral marginal sections and end marginal sections, the seal between the lateral marginal sections being weaker than the seal between the end marginal sections so as to become unsealed and form a liquid discharge passage in response to hydraulic pressure generated within the liquid contents of the container as a result of the application of compressive pressure to the Walls of the container. The liquid-filled cavity is formed by medial sections of the container walls that are bellied outwardly so that when the container is flattened by progressively applying compressive pressure to eject its liquid contents, the dimensions of the container are increased.

In film units of the type embodying the present invention-particular reference being made to application Ser. No. 5,799 filed Jan. 26', 1970, as a continuation-inpart of application Ser. No. 622,286 filed Mar. 10, 1967- the photosensitive and second sheets are retained together at their margins by a binding sheet secured to one of the sheets, usually the second sheet, which is preferably transparent. The binding sheet is secured to at least the leading end and lateral margins of the second sheet and is folded around the lateral edges thereof and secured to the lateral margins of the other (preferably photosensitive) sheet to retain the photosensitive and second sheet together at least at their lateral edges. The binding sheet is also secured to the container at the end margins thereof and/or at a transverse edge of the container so that at least portions of the walls of the container are fixed against movement relative to one of the sheets in the direction of spreading of the processing liquid. A binding strip is secured to the end margin of the other sheet, e.g. photosensitive sheet, and an elongated marginal section of one wall of the container defining one side of the liquid discharge passage. The binding sheet and binding strip cooperate to confine the processing liquid within the film unit so that it is forced to flow between the photosensitive and second sheet as it is ejected from the container through the discharge passage.

As disclosed in the aforementioned patents, it has been the practice to locate the edges of the container walls as close as possible to the leading transverse edge of one or both of the photosensitive and second sheets. However, it has been discovered that the progressive application of compressive pressure to the container walls results in motion of the edge of at least one of the walls relative to the photosensitive and second sheets in the direction of spreading of the processing liquid and if an edge or edges of the container and an edge or edges of one or both sheets are closely abutted or are in contact, the edge of the container wall may be forced against an edge of one of the photosensitive or second sheets causing the sheet to bend or buckle and/ or the container wall to be forced between the photosensitive and second sheets. Inasmuch as an image is formed between the sheets which are retained in face-to-face relation subsequent to completion of image formation, anything that interferes with the formation of a uniform layer of processing liquid between the sheets is likely to impair the visible image formed therebetween. Thus, if one of the sheets is caused to buckle during spreading of the processing liquid, a separation may occur between the sheets as the buckling force is removed subsequent to spreading resulting in either too much or too little processing liquid in regions near the leading edge of the image area and/or separation of the sheets in this region. Of course, the interjection of the leading edge of a container wall between the sheets will also result in separation of the sheets in the region of the edge of the image resulting in impairment thereof.

Another result of too close proximity between the edge of the container and the leading edge of one or both sheets may be the fact that there is no place provided for the liquid to flow as it is ejected from the container through the discharge passage. This may result from the fact that the edge portion of one of the sheets is aligned with the seal between the margins of the container so that the discharge liquid first strikes the edge of one of the sheets. This may result in the liquid flowing between one of the sheets and the binding strip and/or binding sheet causing separation and permitting escape of the processing liquid from the film unit.

An object of the present invention is to provide a novel and improved film unit structure of the foregoing type in which a gap or space is provided between the edge of the container and the leading edge of one or both sheets to accommodate the elongation of the container resulting from compressive flattening thereof and to provide a space into which the processing liquid may first flow prior to entry between the sheets.

These features are particularly important in a film unit of the type described in the aforementioned patents in which the photosensitive and second sheets are laminated to one another so that the hydraulic pressure of the processing liquid effects the delamination of the sheets as the liquid is distributed therebetween.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and the relation of components which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view, partially in section, showing a self-developing, photographic film unit embodying the invention;

FIG. 2 is an exploded perspective view showing components of the film unit of FIG. 1;

FIG. 3 is an elevational, sectional view taken substantially along the line 3-3 of FIG. 1 illustrating details of the construction of the film unit, the method of spread ing the processing liquid between the sheets and the advantages of this construction;

FIG. 4 is a perspective view, partially in section, of another embodiment of a film unit incorporating the invention;

FIG. 5 is an elevational sectional view of the film unit taken substantially along the line 5-5 of FIG. 4; and

FIG. 6 is a view similar to FIG. 3 also taken along the line 55 of FIG. 4.

Reference is now made to FIGS. 1 through 3 of the drawings wherein there is illustrated a photographic film unit 10 embodying the invention, the thicknesses of the materials being exaggerated for purposes of clarity of illustration. Film unit 10 comprises a photosensitive or image-recording sheet 12, a second or image-receiving sheet 14 and rupturable container 16 holding a quantity of processing liquid 18, Sheets 12 and 14 are preferably rectangular and of equal width with sheet 14 being slightly longer than sheet 12. The sheets are arranged in superposed face-to-face contact with the leading edge of each sheet aligned with the leading edge of the other and the trailing end section of second sheet 14 extending beyond the trailing edge of photosensitive sheet 12.

The film unit may be adapted to produce a photographic image by a variety of photographic processes depending upon the nature and composition of the photosensitive and second sheets and the processing liquid. In the preferred form of film unit 10 shown, the structures and compositions are designed to produce a full color image on the second sheet by a diffusion transfer process in which a photographic, image-recording medium including a photosensitive material such as silver halide, is exposed to form an image and is treated by wetting with an aqueous alkaline liquid processing agent to develop the image in the image-recording medium, form an imagewise distribution of transferable image-forming substances and transfer the image-forming substances by difi'usion to an image receptive stratum in which they are immobilized to form a positive image. The photosensitive and image-receiving layers may be supported on the same sheets, e.g. sheet 12, with the second sheet merely functioning to aid in the distribution of the processing liquid or the imagereceiving stratum may be formed in the layer of processing liquid or in a layer carried by second sheet 14. Materials, compositions, and processes for producing visible transfer images in monochrome or in full color, are wellknown in the art, are described in the aforementioned patents and are considered to require no further description herein.

The photosensitive and second sheets 12 and 14 are retained in superposed relation by a binding element 20 in the form of a rectangular sheet larger than either of the photosensitive or image-receiving sheets, folded (along the broken line shown in FIG. 2) around three sides of the sheets and secured to the two sheets at the margins thereof. Binding element 20 is in the general form of a frame having a large rectangular opening 22 defining the extent of the image produced in the film unit, surrounded by lateral marginal portions 24 and end marginal portions 26 and 28. Sheet 14 includes lateral marginal portions 30, a leading end marginal portion 32 and a trailing end section 34. The lateral marginal portions 24 of the binding sheet 20 are adhered to the lateral marginal portions 30 of sheet 14 and are folded (along the broken lines) around the edges of sheets 14 and 12 and adhered to the lateral margins of sheet 12 for retaining the sheets in face-to-face relation at their lateral edges. End portion 26 of binding element 26 is adhered to lead ing end portion 32 of sheet 14 and extends beyond the leading edge of sheet 14 as will be described in greater detail hereinafter. Trailing end portion 28 of the binding element is adhered to trailing end section 34 of sheet 14 and folded around the trailing edges of the two sheets and secured to the trailing edge portion of sheet 12. In this construction, binding sheet 20 functions to retain sheets 12 and 14 in face-to-face relation at their lateral and trailing end edges and in the preferred form of the film unit, provides a border surrounding the image and for this purpose it is preferably formed of an opaque white material providing a more aesthetically pleasing print.

Container 16 is of the type shown in U.S. Pat. No. 2,543,181 and includes a rectangular blank of a fluidimpervious sheet material folded medially to form two walls which are secured to one another along three sides to form a cavity for containing processing liquid 18. The seal between longitudinal marginal sections 38 and 40 of the container is weaker than the seal between the end sections 42 at opposite ends of the container so that upon the application of compressive pressure to the walls of the container in the region of the liquid-filled cavity, there Will be generated within the liquid hydraulic pressure sufficient to separate longitudinal marginal sections 38 and 40 throughout the major portion of their length to form a discharge passage. This passage is at least equal in length to the length of the liquid-filled cavity which in turn, is preferably at least equal in length to the Width of opening 22. Container 16 is formed of a multilayer laminate including paper, lead foil and an innerlayer of a thermoplastic material such as a polyvinyl chloridevinyl acetate copolymer which not only functions as a liquid barrier, but enables sealing of the container by the application of heat and compressive pressure to the marginal sections thereof. The thickness of this laminated sheet material is on the order of 3.5 to 4 mils so that the total thickness of the container when compressed and the marginal sections 38 and 40 will be of the order of 7.5 mils.

Container 16 is attached to sheets 12 and 14 at the leading edges thereof with the discharge mouth defined by marginal sections 38 and 40 facing the leading edges of sheets 12 and 14. The retaining means for attaching the container to the sheets include leading end portion 26 of binding element which is adhered to the longitudinal marginal section 38 of the container and defines at least one side of a cavity or passage between the container and the leading edges of sheets 12 and 14, for conducting the processing liquid from the container between the sheets. The retaining means also include a binding element or strip 44 adhered to the leading edge portion of sheet 12 and to longitudinal marginal section 40 of container 16. Binding element 44 also cooperates to provide a conduit for conducting the liquid from the container between the leading end of sheets 12 and 14.

In order to insure rupture of the longitudinal seal between sections 38 and 40 throughout substantially the full length of the liquid-filled cavity, the processing liquid is preferably quite viscous and for this purpose, contains a polymeric film-forming material in quantities suflicient to impart a viscosity in excess of 1,000 centipoises at a temperature of 20 C. and preferably of the order of 1,000 to 200,000 centipoises at said temperature. The preferred method of discharging the liquid contents of the container and spreading them between sheets 12 and 14 is to advance the film unit, container foremost, relative to and between a pair of pressure-applying members shown in the form of juxtaposed rollers 48 and 50 which first, progressively apply compressive pressure to the container to separate the longitudinal marginal sections 38 and 40; discharge the processing liquid from the container as a mass extending across the film unit; and then advance the mass between the photosensitive and second sheets toward the trailing ends thereof.

In order to insure more uniform distribution of the processing liquid within container 16 and throughout the mass of liquid discharged therefrom, the container is divided into three liquid-filled cavities designated 52 by sealing transverse sections 54 of the container to one another. The liquid-filled cavities 52 are formed by portions of the walls of the container which bulge or are bellied outwardly from the marginal and transverse sections 54 of the container walls. A more secure seal between end marginal sections 42 and transverse sections 54 as well as shortening of the dimensions of the container in these sections is obtained by forming ribs or corrugations in these regions which extend in the direction of discharge and spreading of the processing liquid.

It will be apparent from the drawings that as compressive pressure is progressively applied to the walls of the container in the region of liquid-filled cavities 52 tending to flatten the container and compress the walls against one another, the container will be elongated slightly in the direction of movement of the pressure-applying members relative to the container. Longitudinal marginal section 38 of one wall of the container is adhered to binding sheet 20 so that at least this section of the container is fixed insofar as lengthwise motion in the direction of liquid spreading is concerned due to the inherent rigidity of the binding element. However, longitudinal marginal section 40 is attached to binding strip 44- whieh, because it is not folded around the lateral margins of the photosensitive and second sheets, is less rigid and permits movement of marginal section 40 in the direction of movement of the processing liquid. Thus, as the container is progressively compressed the wall of the container of which marginal section 40 is a part will be elongated moving the edge of the marginal section in the direction of spreading relative to the leading edges of sheets 12 and 14 by virtue of the fact that marginal section 38 of the other wall of the container is essentially fixed with respect to the leading edges of sheets 12 and 14.

It has been found that if the edges of marginal sections 38 and 40 are butted against the edges of sheets 12 and 14 or are located sufficiently close thereto, the edge of marginal section 40 will be moved, due to the elongation of the container, against the edge of sheet 12 causing marginal section 40 and/or the leading edge portion of sheet 12 to buckle. In the alternative, such a construction has also been found to result in marginal section 40 extending between the leading edges of sheets 12 and 14 and/or causing a rupture in the seal between strip 44 and sheet 12 through which the processing liquid may escape.

As previously noted, the film unit of the invention is of the type in which the photosensitive and second sheets are retained in superposition following formation of a visible image in a layer between the sheets. To accomplish image formation and a permanent lamination of the sheets, the processing liquid is required to be spread in a continuous layer of uniform thickness throughout at least the image area defined by opening 22 and binding element 20. However, buckling of either a marginal section of the container or sheet 12 adjacent its leading edge will result in regions of excess processing liquid and/or insutlicient processing liquid which may extend into the image area and thereby result in excess or insufiicient processing liquid as well as delamination of the photosensitive and second sheets in the region of their leading ends after the pressure-applying members have passed by. Extension of marginal section it) between the leading edge portions of sheets 12 and 14 will also result in separation of the sheets in these regions causing nonuniform distribution of the processing liquid and result in voids which occur as the liquid is absorbed between various layers comprising the photosensitive and second sheets. Also, the combined sheet thickness will be altered thus interfering with uniform distribution of the liquid. Such voids and/ or regions of excess or insufiicient processing liquid will also extend into the area of the visible image causing visible impairment of the image.

In accordance with the invention this problem is solved as shown in detail in FIG. 3, by providing a gap between the edges of longitudinal marginal sections 38 and 40 and the leading edges of sheets 12 and 14. This gap should be in excess of the maximum elongation of either or both marginal sections 38 and 40' relative to sheets 12 and 14 and is on the order of 0.020 to 0.030 inch. This spacing is on the order of 3 to 5 times the combined thickness of marginal sections 38 and 40 or 2 to 3 times the combined thickness of the photosensitive sheet which has a thickness of the order of 0.0041 inch and the second sheet which has a thickness of the order of 0.0053 inch. This construction permits the edge of marginal section 40 to move, as shown in FIG. 3, in the direction of spreading the processing liquid beyond the edge of section 38 toward the leading edge of sheet 12 without coming into contact with the edge of sheet 12 or extending between the latter and sheet 14.

In a preferred form of the film unit the photosensitive and second sheets are laminated to one another throughout substantially the entire area of their facing surfaces and are forced apart or delaminated by the advancing mass of processing liquid. The provision of a gap between the edges of marginal sections 38 and 40 and the leading edges of the photosensitive and second sheets provides a chamher for receiving an initial, small quantity of processing liquid as the liquid is ejected from the container and helps to insure complete rupture of the container seal as well as initiation of separation of the sheets prior to any substantial advancement of the mass of processing liquid between the sheets. Initiation or rupture between the sheets is also facilitated by providing a very narrow region adjacent the leading edges of the photosensitive and second sheets in which the sheets are not laminated and into which the liquid can flow without being forced to delaminate the sheets. The provision of the gap or chamber between the edges of marginal sections 38 and 40 and the leading edges of sheets 12 and 14 also permits greater outward deformation or bulging or binding element 20 and binding strip 44 facilitating the separation of sheets 12 and 14 and helping to prevent the processing liquid from being forced from within the film unit between binding strip 44 and sheet 12 or binding element 20 and sheet 14.

In order to insure the presence of suificient processing liquid to provide a layer of predetermined area, extent and thickness, processing liquid in excess of the minimum required is provided in the container and the fihn unit includes means for collecting and retaining any excess processing liquid overrun. In the form shown in FIGS. 1 and 2, these means comprise sections of trailing end section 34 of sheet 14 embossed to form ribs 56 for spacing apart the facing surfaces of trailing end portion 34 and marginal portion 28 of binding element 20 to form spaces in which excess processing liquid is collected and retained as the trailing end of the film unit passes between the pressureapplying members.

Another embodiment of a film unit incorporating the invention is illustrated in FIGS. 4 through 6 of the drawings. This film unit, designated 60, is basically the same as film unit and may be identical insofar as the composition of the components is concerned. Film unit 60 includes a rectangular photosensitive sheet 62 located in superposed relation with a rectangular second or imagereceiving sheet 64, the latter having a length exceeding the length of sheet 62 by at least the shorter dimension of container 16. Sheet 64 includes a leading end portion 65 extending beyond the leading edge of photosensitive sheet 62, and container 16 is mounted on leading end portion 65 in position to discharge its liquid contents between the photosensitive and second sheets. A gap similar in dimension to that previously described is provided between the leading edge of photosensitive sheet 62 and the aligned edges of marginal sections 38 and 40 of container 16.

The photosensitive and image-receiving sheets 62 and 64 are secured to one another at their lateral and trailing end margins by a binding element 66 having lateral edge portions 70 secured around and to the lateral margins of elements 62 and 64 and an end edge portion 72 secured around and to the trailing end margins of the photosensitive and second sheets. Binding element 66 includes a leading end section 74 extending at least to the leading edge of receiving sheet 64 and secured to the outer surfaces of leading end section 65 of second sheet 64. Container 16 is preferably formed with a planar wall facing sheet 64 and a bulged or bellied wall facing away from sheet 64 and providing the liquid-filled cavities. Container 16 may be secured at its planar wall directly to leading end section 65 of sheet 64 or, as in the embodiment shown, the leading end section 74 of the binding element may be folded around the leading edge of sheet 64 and secured to an edge portion 76 of container 16 to retain the container against second sheet 64. A binding strip 78 is secured in overlapping relation to the leading edge section of photo sensitive sheet 62 and marginal section 40 of container 16 for conducting the procesisng liquid from the container between the photosensitive and second sheets,

As will be noted from FIG. 6, the wall of the container including marginal section 38 located against second sheet 14 is substantially planar so that there will be no elongation of this wall of movement of marginal section 38. However when the container is flattened, i.e., when the wall which is bellied to form the liquid-filled cavities is flattened as shown in FIG. 6, there will be a substantial elongation of the wall or movement of the edge of marginal section 40 toward the leading edge of sheet 62 in the direction of spreading of the processing liquid. This elongation or edge movement is from the position designated C to the position designated C a distance which is less than the gap between the edges of the container at position C and the leading edge of photosensitive sheet 62 which is originally located at the position designated S in FIG. 6. The dimension of the gap and the thicknesses of the various sheet materials incorporated in the embodiment of the film unit shown in FIGS. 4 through 6 are essentially the same as those of the film unit embodiment of FIGS. 1 through 3.

It will be noted from the foregoing that the object of providing for a change in dimension of a section of the rupturable liquid-filled container is achieved with a simple and inexpensive structural modification of the film unit which provides the added advantages of more uniform container rupture and liquid distribution, while contributing to the assurance that the processing liquid does not escape from the film unit. This novel structure insures the formation of a high quality, visible image free from defects resulting from any of the aforementioned factors particularly, elongation of the container in the direction of liquid spreading.

Since certain changes may be made in the above product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in the limiting sense.

What is claimed is:

1. In a photographic film unit including a photosensitive sheet and a second sheet secured in face-to-face relation and including an area between said sheets adapted to be processed by a liquid processing composition introduced between said sheets at a transverse edge of one of said sheets and distributed between said sheets toward the opposite end thereof, a rupturable container of said liquid formed of a rectangular blank of sheet material folded upon itself and including end and side marginal portions sealed to one another to form a liquid filled cavity, the seal between said side marginal portions along one side of said cavity being weaker than the seal between end marginal portions at the ends of said cavity so as to become unsealed and form a discharge passage by and in response to the application of compressive pressure to said container in the region of said cavity, and means securing said sheets to one another and said container to said sheets externally thereof adjacent said transverse edge, the improvement comprising:

first retaining means secured to said sheets at least at their lateral margins and to said container for securing said sheets together at their lateral edges and securing said container to the other of said sheets;

said container being positioned with said edges of said marginal portions spaced from said transverse edge to provide a narrow gap between said container and said transverse edge;

second retaining means being secured to at least one of said side marginal portions and at least said one sheet adjacent said transverse edge and at the ends of said gap to bridge said gap and cooperate with said container and said sheets and said first retaining means to form a sealed chamber between said edges of said marginal portions and said transverse edge, said chamber being at least equal in length to the width of said area to be processed,

2. A photographic film unit as defined in claim 1 wherein said first retaining means include a retaining sheet adhered to the lateral margins of said other sheet, to the end marginal section of said other sheet in the region of said container and to said container to prevent movement of at least a portion of said container relative to said other sheet in the direction of distribution of said processing liquid.

3. A photographic film unit as defined in claim 2 wherein said retaining sheet is secured to said end marginal portions of said container.

4. A photographic film unit as defined in claim 1 wherein the depth of said chamber ranges from the combined thickness of said photosensitive and second sheets to the combined thickness of said side marginal portions and the width of said chamber is of the order of 3 to 5 times the depth thereof.

5. A photographic film unit as defined in claim 1 wherein the width of said gap is of the order of .020 to .030 inch.

6. A photographic film unit as defined in claim 1 wherein said photosensitive and second sheets are laminated to one another at their facing surfaces.

7. A photographic film unit as defined in claim 6 wherein said photosensitive and second sheets are laminated to one another over an area extending substantially to said transverse edge.

8. A photographic film unit as defined in claim 6 wherein said photosensitive and said second sheets are laminated over an area extending to a line substantially parallel with said transverse edge and spaced therefrom by a distance of the order of 1 to 3 times the width of said chamber.

9. A photographic film unit as defined in claim 1 wherein said container includes a plurality of said liquid filled cavities bounded by said marginal portions and separated by narrow transverse regions, the aggregate length of said cavities and transverse regions being approximately equal to the length of said chamber.

10. A photographic film unit as defined in claim 1 wherein the other of said sheets includes an end section extending beyond said transverse edge of said one sheet.

11. A photographic film unit as defined in claim 10 wherein said container is mounted on said end section of said other sheet.

12. A photographic film unit as defined in claim 10 wherein said second retaining means include a binding strip adhered to one of said side marginal portions and the margin of said one sheet adjacent said transverse edge thereof.

13. A photographic film unit as defined in claim 10 wherein said one sheet is said photosensitive sheet and said other sheet is said second sheet.

14. A photographic film unit as defined in claim 13 wherein said retaining means include a binding strip adhered to one of said side marginal portions and the margin of said photosensitive sheet adjacent said transverse edge thereof.

15. A photographic film unit as defined in claim 14 wherein said end section is substantially equal in length to the shorter dimension of said container.

References Cited UNITED STATES PATENTS 3,619,l93 11/1971 Knight 96-76R NORMAN G. TORCHIN, Primary Examiner I. L. GOODROW, Assistant Examiner

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