Abstract:
A self-developing type of instant camera is equipped with a processing liquid spreading device comprising a pair of pressure-applying processing rollers which ruptures a processing liquid containing pod and distributes a processing liquid in a film unit, a spread controller operative to press and rubs the film unit from one side of the film unit coming out from a film pack so as to spread the processing liquid distributed in the film unit and a guide member, disposed between the spread controller and the film pack, operative to force the film unit from another side of the film unit so as to direct the film unit toward the bite of pressure-applying processing rollers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a self-developing camera with an improved processing liquid spreading device for processing a self-developing film unit. 
     2. Description of the Prior Art 
     A mono-sheet type of self-developing or instant film unit or otherwise called an integrated or non-peel apart type of self-developing or instant film unit (which is hereinafter referred to as an instant film unit for simplicity in the specification) and a variety of self-developing or instant cameras and printers for use with this type of instant film unit have been on the market. The mono-sheet type of instant film unit includes a transparent front cover sheet through which an exposure is made, a rear cover sheet disposed at the back of the front cover sheet, and a photosensitive and an image receiving layer formed between the front cover sheet and the rear cover sheet. The instant film unit further includes a pod containing a processing liquid therein which is placed at the leading end of the instant film unit and a trap operative to catch an excess of processing liquid therein which is placed at the trailing end of the instant film unit. The mono-sheet type of instant film unit is classified into two basic types, namely a reflective type and a transmissive type. In the reflective type, an latent image formed on the photosensitive layer is transferred as a positive image onto the image-receiving layer and after development the positive image is viewed from the side on which the exposure is made. In the transmissive type, on the contrary, a positive image formed on the image receiving layer after development is viewed through the transparent rear cover sheet. The mono-sheet type of instant film unit is otherwise classified into two types in terms of peripheral structures of the instant film unit, namely a spacer type of instant film unit and an outer-frame type of instant film unit. The spacer type of instant film unit has a spacer between the front cover sheet and the rear cover sheet along both sides of the film unit. The spacer has a thickness which governs a distributed thickness of processing liquid by the processing rollers while preventing the processing liquid from leaking or escaping out of the instant film unit during processing. The outer-frame type of instant film unit has a binder frame for binding around the periphery of the instant film unit to securely couple the front cover sheet and the rear cover sheet together so as to prevent the processing liquid from leaking out of the instant film unit during processing. A significant feature of the outer-frame type of instant film unit is that the difference with respect to the front cover or a space over the front cover which is provided by the outer binder frame cooperates with the processing rollers to govern a distributed thickness of processing liquid between a photosensitive and an image receiving layer during processing. 
     Such instant film units are used together with an instant camera or a printer in the form of a film pack. An instant film unit pack holds a number of instant film units received in a stack therein. The instant camera or the printer for use with the instant film unit is equipped with a processing liquid spreading device operative to spread a processing liquid between the front cover sheet and the rear cover sheet and, more specifically, between the photosensitive layer and the image-receiving layer. The processing liquid spreading device includes a pair of pressure-applying members, such as a pair of processing rollers, by which an exposed instant film unit is processed and advanced to come out of the instant camera or the printer. Some instant cameras have a spread controller which controls a uniform spread and distribution of the processing liquid by rubbing the surface of the instant film unit with pressure while the instant film unit is advanced. 
     However, in the instant camera equipped with the spread controller, a top of the spread controller projects beyond the natural path of the instant film unit which is directed to a contact line of the pair of processing rollers so as to force the instant film unit to advance in an S-shaped path with an effect of increasing the effect of spread controller. This structure causes from time to time the film unit at the leading end to fail to enter between the processing rollers, as a result of which the instant film unit is crimped or folded. Further ejection of the instant film unit by the processing rollers is completed by a specified time of rotation of a motor. If the instant film unit at its leading end abuts one of the processing rollers and is thereafter bit between and by the processing rollers, an error occurs between an advancing distance of a claw mechanism for advancing the instant film unit and an advanced distance by which the instant film unit is advanced forwarded by the claw mechanism, which results in causing the instant film unit to fail to be fully ejected out of the instant camera even after the processing roller have come to a full stop. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an instant camera which ejects an instant film unit out therefrom without crimping, folding or leaving it in the inside thereof while the spread control of processing liquid is made sufficiently to obtain a thin uniform distribution of processing liquid. 
     It is another object of the invention to provide an instant camera which gives a way that the instant film unit is reliably bit between a pair of processing rollers. 
     It is still another object of the invention to provide an improved processing liquid spreading device such as a pair of pressure-applying processing rollers particularly suitable for processing an outer-frame type film unit. 
     According to an embodiment of the invention, the instant camera is provided with a guide member which is disposed facing a spread controller in order to bring the leading end of an instant film unit into a bite of a pair of processing rollers by applying a processing pressure the instant film unit from one side opposite to the side of the instant film unit on which the spread controller rubs. 
     According to another embodiment of the invention, the processing liquid spreading device facing which an instant film unit egress slot of a film pack is located comprises a pair of pressure-applying processing rollers operative to rupture a pod containing a processing liquid therein and spread and distribute the processing liquid over a photosensitive layer while advancing the instant film unit, and a spread controller which is disposed between the instant film unit egress slot and the pressure-applying processing rollers and controls uniform distribution of the processing liquid between a front cover sheet and a rear cover sheet by giving the instant film unit an S-shaped film path. Either one of the pressure-applying processing rollers has smaller diameter portions at its both ends so as to apply a proper processing pressure on an exposed area of the instant film unit without causing a harmful influence on the uniform layer of processing liquid distribution due to a somewhat thick outer-frame of the instant film unit. The smaller diameter portion of the pressure-applying processing roller is divided into two sections adjacent to each other, namely a first small diameter section and a second small diameter section. The second smaller diameter section which is axially closer to the end of the pressure-applying processing roller is larger in diameter than the first smaller diameter section closer to the central portion of the pressure-applying processing roller. This roller configuration produces some gaps between the pair of pressure-applying processing rollers at their opposite end through which the instant film unit at the outer-framed opposite sides advances while it is processed. 
     Furthermore the spread controller is adjusted in its width so as not to contact the outer-frame to improve the spread control. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and features of the invention will be understood more clearly from the following description when read in conjunction with the accompanying drawings, in which the same reference numerals have been used to denote same or similar parts or mechanisms throughout the drawings and wherein: 
     FIG. 1 is a perspective view showing an outer appearance of an instant camera according to an embodiment of the invention; 
     FIG. 2 is a fragmentary cross-sectional view of an overall structure of a pair of pressure-applying processing device and its associated elements of the instant camera; 
     FIG. 3 is a fragmentary cross-sectional view of the instant camera illustrating essential internal structure thereof; 
     FIG. 4 is an explanatory illustration of an instant film unit advancing mechanism and a processing liquid spreading device of the instant camera; 
     FIG. 5 is a fragmentary cross-sectional view of an essential internal structure of an instant camera according to another embodiment of the invention; 
     FIGS. 6A and 6B are perspective views showing an appearance of a transmissive outer-frame type of instant film unit used in the instant camera shown in FIG. 5; 
     FIG. 7 is a cross-sectional view of the instant film unit taken along line VII—VII of FIG. 6A; 
     FIG. 8 is a cross-sectional view of the instant film unit taken along line VIII—VIII of FIG. 6A; 
     FIG. 9A is an explanatory view of a processing liquid spreading device of the instant camera in which a processing liquid containing pod is ruptured; 
     FIG. 9B is an explanatory view of a processing liquid spreading device of the instant camera in which a processing liquid is spread and distributed between front and rear cover sheets of the instant film unit; 
     FIG. 10 is an illustration showing a dimensional configuration of a pair of pressure-applying processing rollers used in an instant camera according to still another embodiment of the invention; and 
     FIG. 11 is an explanatory illustration partly showing the pressure-applying processing rollers between which an instant film unit is bit. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in detail and in particular to FIG. 1 which is a perspective view of an instant camera equipped with a processing liquid spreading device according to an embodiment of the present invention, an instant camera  2  has an approximately rectangular box-shaped camera body  5  into which an instant film unit pack holding a stuck of a number of instant film units  17 A is loaded from the back of the camera body  5 . A lens barrel  4  in which a taking lens  3  is incorporated is installed to the central area of a front wall of the camera body  5 . The lens barrel  4  is of a telescopic type which is extendable from the camera body  5  when the instant camera  2  is used and retractable into the camera body  5  when the instant camera  2  is not used for a good portability. The camera body  5  is equipped with an infrared active distance-measuring type of automatic focussing device which includes a beam projection window  7  through which an infrared beam emanating from an light emitting element is projected toward a subject to be photographed and a reflected beam receiving window  8  through which a beam reflected from the subject enters and impinges a photoelectric element, and an window  9  through which ambient light is received and impinges a photoelectric element for reading scene brightness. Those windows are formed in a front wall of the lens barrel  4 . 
     The camera body  5  is integrally formed with a grip  11  at one of opposite sides. A shutter release button  12  is on the top of the grip  11 . The distance-metering and brightness-reading are made when a shutter release button  12  is depressed halfway and shutter-releasing is made when the shutter release button  12  is fully depressed. After framing the subject through a view finder  14  installed in an upper part of the camera body  5 , the shutter release button  12  is depressed halfway to fix focussing and an exposure condition, and then fully depressed down to release a shutter incorporated in the lens barrel  4 . A built-in electronic flash  15  mounted above the lens barrel  4  flashes automatically when the subject brightness is low. 
     As shown in FIG. 3,  9 A and  9 B, image carrying light rays from the subject through the taking lens  3  are directed through a dark chamber  27  to a photographic layer  37  of a foremost instant film unit  17 A whose bound of a generally square or rectangular image-foaming area is defined by an aperture  28  of the camera body  5 , a picture framing aperture  32  of an instant film unit pack housing  30  of an instant film unit pack  19  and an peripheral frame  47  of the instant film unit  17 A. As shown in detail in FIG. 2 and 3 which are fragmentary cross-sectional views of the instant camera  2 , the camera body  5  includes an instant film unit pack receiving chamber  20  formed in the rear section thereof, a base  21  on which a variety of picture taking functional elements (not shown) are mounted, a front cover  22  covering the front of the base  21  and a rear cover  23  covering the back of the camera body  5 . The rear cover  23  has a back lid  24  which is pivotally connected thereto with a hinge  25  and is opened and closed when the instant film unit pack  19  is loaded into and unloaded from the pack receiving chamber  20 . The dark chamber  27  is formed on the base  21  to keep a light path between the taking lens  3  and the instant film unit pack  19  light-shielded. One open end of the dark chamber  27  forms the aperture  28 . 
     As shown in FIG. 3, the instant film unit pack  19  holds a stuck of a number of instant film units  17 A in its open-ended, box-shaped plastic housing  30 . Each instant film unit  17 A includes a front cover sheet functioning as a transparent window through which an exposure is made, a rear cover sheet disposed opposite to the front cover sheet, a photosensitive layer and an image-receiving layer disposed between the front cover sheet and the rear cover sheet and a rupturable pod  17   b  containing processing liquid at the leading end of the instant film unit  17 A and a trap  17   c  for catching excess processing liquid and solidified at the trailing end of the instant film unit  17 A. The user of this type of instant film unit can view and keep the picture without removing any part of the original instant film unit assembly. The instant film pack housing  30  has a picture framing aperture  32  through which the instant film unit  17 A is exposed. An instant film unit egress slot  33  is formed in a leading end wall (upper end as seen in FIGS. 2 and 3) of the instant film unit pack housing  30 . A virgin instant film unit pack  19  includes a plate-like cover sheet  34  on top of the foremost instant film unit  17 A and a flexible light seal  35  across over the instant film unit egress slot  33 . These elements are incorporated in the instant film unit pack housing  30  for the purpose of the instant film units  17 A from being exposed to light before it is loaded in the camera body  5 . First operation of the shutter release button  12  after the instant film unit pack  19  has been loaded causes the plate-like film cover  34  to break the flexible light seal  35  along its weakly adhered part to the leading end wall around the film unit egress slot  33  and come out of the camera body  5  through the instant film unit egress slot  33 . On an inner side of a rear wall of the instant film unit pack housing  30  there is provided a main instant film unit raising projection  38  at its central portion. The main instant film unit raising projection  38  raises the stack of instant film units  17 A through a light shielding sheet  39  adjacent to the rearmost instant film unit  17 A to give a better flatness to the foremost instant film unit  17 A. The instant film unit pack housing  30  at the inner side of the rear wall is further provided with two holes  40  and  41  between which the raising projection  38  locates. Those holes  40  and  41  receive other two supplementary instant film unit raising projections  42  and  43  which extend from the back lid  24  to raise the stack of instant film units  17 A while the back lid  24  is closed after the instant film unit pack  19  has been loaded in the camera body  5 . Each of the supplementary raising projections  42  and  43  is spring-loaded and has a slidably movable top-half portion which is similar to that disclosed in, for example, Japanese Unexamined Patent Publication No. 7-244336. The slidably movable top-half portions push forwardly the stack of the instant film units  17 A at the peripheral region to give a better flatness to the foremost instant film unit  17 A in cooperation with the main raising projection  138 . The holes  40  and  41  are light-shielded by light shielding sheets  45  and  39  before the instant film unit pack  19  is loaded in the camera body  5 . 
     FIG. 4 shows an instant film unit pack  19  and an instant film unit advancing and processing mechanism. The instant film unit pack housing  30  has a pickup slot or opening  48  in the lower end portion or trailing end portion through which an instant film unit ejecting claw  47  is received. The instant film unit ejecting claw  47  is reciprocally operated by a claw driving mechanism  51  including a motor  50  and a reduction gear train  49  to pick up the foremost exposed instant film unit  17 A or the plate-like film cover  34  by engaging the trailing edge of the instant film unit  17 A or the plate-like film cover  34  and advance it from the instant film unit pack housing  30  through the instant film unit egress slot  33  until it is bite between the pair of pressure-applying processing rollers  55  and  56  which forms a processing liquid spreading device  53  mounted in a housing  57 . A slot-shaped deflected gate  52  is formed between the instant film unit egress slot  33  and the pair of pressure-applying processing rollers  55  and  56  such that it is deviated a little forwardly from the instant film unit egress slot  33  of the instant film unit pack housing  30  as shown in FIG. 2. A spread controller  60  is one of members to form the slot-shaped deflected gate  52  which controls uniform distribution of the processing liquid spread and distributed between the front cover sheet  36  and the rear cover sheet  38  by rubbing the surface of the instant film unit  17 A with a certain pressure while the instant film unit  17 A is advanced. 
     Referring to FIGS. 4,  9 A and  9 B, a tip of the spread controller  60  is formed round to prevent a surface of the instant film unit  17 A from being scratched. The top portion of the spread controller  60  at a side facing the instant film unit egress slot  33  is tapered so as to easily guide the leading edge of the instant film unit  17 A into the slot-shaped deflected gate  52 . One of the pair of pressure-applying processing rollers, namely the processing roller  55 , is provided with a drive gear  55   a  at one of its opposite ends. The drive gear is driven clockwise by the motor  50 . Another one of the pair of pressure-applying processing rollers, namely the processing roller  56 , is provided with a driven gear  56   a  at one of opposite ends. The driven gear  56 a is in mesh with the drive gear  55   a  to drive the processing roller  56  counterclockwise. The reduction gear train  49  is arranged between the motor  50  and the drive roller  55   a  and transmits rotation of the motor  50  to the drive gear  55   a  at a reduced-speed. These processing rollers  55  and  56  are made of hard steel to minimize a manufacturing error of diameter along the axis of rotation. The driven processing roller  56  is movable in a direction perpendicular to a plane in which the instant film unit  17 A is placed and is biased by a spring  58  (see FIG. 2) toward the drive processing roller  55  so as to apply a suitable processing pressure to the instant film unit  17 A for uniform spread and distribution of the processing fluid equally on the photographic layer. The motor  50 , which drives the pair of pressure-applying processing rollers  55  and  56  in opposite directions and the claw drive mechanism  51 , is started in response to exposure of the foremost instant film unit  17 A to automatically advance the exposed instant film unit  17 A for processing and ejecting it. The pair of pressure-applying rollers  55  and  56  are disposed so that the contact line or bite line between the drive roller  55  and the driven roller  56  is disposed directly above the tip of the spread controller  60 . Such disposition forces the instant film unit  17 A to advance along a gentle S-shaped passage between the bite line of the pair of pressure-applying rollers  55  and  56  and the instant film unit egress slot  33 . This curvature brings a better spread because the spread controller  60  increases its compressive force onto the instant film unit  17 A when stroking the instant film unit  17 A while it advancing. The position of the bite line is obviously not limited to the aforementioned position, directly above the tip, as long as an S-shaped curve is formed. Furthermore the camera body  5  is formed with a slant passage  62  extending from the vicinity of the bite line to an instant film unit egress slot  16  (see FIG. 1) is slanted forwardly with an effect of increasing a contact area between the processing liquid containing pod  17   b  of the instant film unit  17 A and the drive processing roller  55  and of providing a reliable spread and distribution of the processing liquid. 
     A guide member  64 , which is formed as an integral part of the camera base  21  and, more specifically, as an integral part of the instant film unit pack receiving chamber  20 , is disposed facing the spread controller  60  in the vicinity of the slot-shaped deflected gate  52 . The guide member  64  is designed wide enough to contact the instant film unit  17 A along an entire width and applies a pressure to the instant film unit  17 A in the direction toward the spread controller  60  with an effect of bending the instant film unit  17 A so as to guide the leading edge of the instant film unit  17 A into the bite of the pair of pressure-applying processing rollers  55  and  56 . A tip of the guide member  64  is also formed round to prevent the instant film unit  17 A from scratches. 
     To summarize a series of operation to have a viewable image on the instant film unit  17 A, first of all the instant film unit pack  19  is loaded into the instant film unit pack receiving chamber  20  of the camera body  5  and the instant camera is powered on. Then the shutter release button  12  is depressed once to eject the film cover  34 . Ejection may be automatically done in response to closing the back lid  24  of the camera body  5 . After ejecting the film cover  34 , the photographer frames a subject to be photographed through the finder  14  and depresses halfway the shutter release button  12  to automatically adjust the camera condition of focussing and exposure. Distance to the subject for focussing is measured by the infrared active type of automatic focussing device which includes the infrared emitting element behind the beam projection window  7  and the infrared photoelectric element behind the reflected beam receiving window  8 . Light-reading for determining an exposure condition is done through the metering window  9  by a well-known technique. These windows  7  and  8  are disposed on the front of the lens barrel  4  as well as the taking lens  3 . Then the shutter incorporated in the lens barrel  4  is released according to the camera condition already set upon fully depressing the shutter release button  12 . The electronic flash  15  above the lens barrel  4  flashes automatically when the subject brightness is low. Image carrying light rays from the subject through the taking lens are directed through the dark chamber  27 , the aperture  28  of the camera body  5 , the picture framing aperture  32  of the instant film unit pack housing  30  and the exposure plane  17   a  (see FIG. 3) of the front cover sheet  36  onto the photographic layer of the foremost instant film unit  17 A. 
     The motor  50 , which drives both pressure-applying processing rollers  55  and  56  and claw drive mechanism  51 , is actuated in response to the shutter releasing, so as to cause the claw drive mechanism  51  to move the claw  47  upward in the pickup slot  48  in the trailing end (lower end) portion of the instant film unit pack housing  30 . The claw  47  engages the trailing end of the plate-like film cover  34  or the foremost instant film unit  17 A and advances it from the instant film unit pack housing  30  through the instant film unit egress slot  33 . The leading edge of the instant film unit  17 A advances through the instant film unit egress slot  33  with breaking the flexible light seal  35  toward the tapered surface of the top portion of the spread controller  60  and reaches the slot-shaped deflected gate  52  with being guided by the tapered surface. Then the guide members  64 , which is disposed opposed to the spread controller  60 , guides the leading end into the bite of the pair of pressure-applying processing rollers  55  and  56 . As the guide member  64  certainly feeds the leading end of the instant film unit  17 A into the bite of the pair of pressure-applying processing rollers  55  and  56 , the instant film unit  17 A will be never crimped or folded, or be left in the camera body  5  without being ejected from the camera body  5  in the specified time in which the pair of processing rollers  55  and  56  rotate. The processing liquid containing pod  17   b  at the leading end of the instant film unit  17 A is ruptured by the pair of pressure-applying processing rollers  55  and  56  while the leading end of the instant film unit  17 A advances toward the instant film unit egress slot  33 . The processing liquid discharged from the pod  17   b  is spread out and distributed between the front cover sheet  36  and the rear cover sheet  38  of the instant film unit  17 A. The instant film unit  17 A is finally fed into the slant passage  62  and ejected outside of the camera body  5  through the instant film unit egress slot  33 . This increases a contact area between the processing liquid containing pod  17   b  of the instant film unit  17 A and the drive processing roller  55 , which also serves to provide a better spread of processing liquid. 
     The processing liquid spread between the front cover sheet  36  and the rear cover sheet  38  of the instant film unit  17 A is uniformly spread out by the aid of spread controller  60  before being compressed by the pair of pressure-applying processing rollers  55  and  56 . The spread controller  60  is integrally-formed with the camera base  21  and the drive processing roller  55  operative to urge the instant film unit  17 A toward the spread controller  60  is fixed onto the same camera base  21 , so as to give a mechanically very stable relationship between the instant film unit  17 A and the spread controller  60  while the instant film unit  17 A advances, which helps the spread controller function well without having fluctuation. The processing rollers can be mounted on the same members where the pair of pressure-applying pressure rollers  55  and  56  are mounted on with the same effects as described above. Thus after a certain period of time a viewable image is formed on the instant film unit  17 A with high quality because of uniform spread and distributed processing liquid. 
     In the embodiment described above, the guide member  64  is designed wide enough to cover contact with the instant film unit  17 A along its entire width. It is also possible to use a less wide single guide member which contacts only a central portion of an instant film unit  17 A or a plurality of narrow guides which contact across the instant film unit  17 A. 
     The instant camera of the aforementioned embodiment of the invention is adaptable to both spacer-type of instant film unit and outer-frame type of instant film unit. Hereinafter an instant camera according to another embodiment of the invention which is particularly suitable for the outer-frame type of instant film unit is described. 
     FIGS. 6A,  6 B,  7  and  8  show a transmissive outer-frame type of instant film unit  17 B. FIG. 6A shows the instant film unit  17 B which is viewed from the exposed side thereof and FIG. 6B shows the other side of the instant film unit  17 B from an image viewable side on which the positive image on the image receiving layer is viewed. The transmissive outer-frame type of instant film unit  17 B includes an exposure plane  31  through which the instant film unit  17 B is exposed, an image-forming plane  132  disposed opposite to the exposure plane  131 , a pod  17   b  containing processing liquid at the leading end and a trap  17   c  for trapping an excess of processing liquid at the trailing end. 
     Referring to FIGS. 7 and 8 which are longitudinal and transverse sectional views of the instant film unit  17 B taken along line VII—VII and line VIII—VIII of FIG. 6A, respectively, a photosensitive layer  137  is formed adjacent to a front cover sheet (an exposure side)  36  which is made of a transparent plastic film and an image receiving layer  139  including a reflective layer is formed on a rear cover sheet (an image viewable side)  38  which is made of a transparent plastic film. The processing liquid containing pod  17   b  comprises a bag-shaped pod cover  141  and a processing liquid  142  contained in the bag-shaped pod cover  141 . The bag-shaped pod cover  141  at transverse sides  141   a  interposed between the leading transverse ends of the front and rear cover sheets  36  and  38  is weakly adhered to each other. The bag-shaped pod cover  141  is ruptured along its weakly adhered part  141   a  to allow the processing liquid  142  to flow out thereof and spread out between the front and rear cover sheets  36  and  38 . The trap  17   c  comprises a liquid absorption pad  144  which is made of a material efficiently absorbing the processing liquid  142  and is disposed along the trailing transverse end of the instant film unit  17 B. The transmissive outer-frame type of film unit  17 B is one whose elements are bound and wrapped around along its peripheral margins by an outer-frame sheet  146  (see FIG. 6A) to secure the front cover sheet  36  and the rear cover sheet  38  together with the processing liquid containing pod  17   b  and the trap  17   c . The outer-frame sheet  146  forms an exposure frame  147  by which a generally square or rectangular image-forming area is defined on the front of the instant film unit  17 B and a picture viewing frame  148  by which a generally square or rectangular image-viewable area on the back of the instant film unit  17 B. 
     FIGS. 5,  10  and  11  show a processing liquid spreading devices for spreading and distributing a processing liquid particularly suitable for the transmissive outer-frame type of instant film unit  17 B. As shown, the processing device is similar to that shown in FIGS. 2 and 3 excepting that the aforementioned guide member  64  is not provided. A processing liquid spreading device  53  comprises a first pressure-applying processing roller  55  which contacts the rear cover sheet  38  and a second pressure-applying processing roller  56  which contacts the front cover sheet  36 . Most of the constructions described before about the processing liquid spreading device including the processing rollers assembly and a spread controller  60  are applicable to this embodiment. As shown in FIG. 10, the second processing roller  56  is divided into two portions one of which is a central liquid spreading portion  82  and contacts and presses the rear cover sheet  38  and the other of which are opposite end portions  83  adjacent to the central liquid spreading portion  82  and have a smaller diameter than the central liquid spreading portion  82 . Each of the end portions consists  83  comprises a first smaller diameter portion  83   a  closer to the central liquid spreading portion  82  and a second smaller diameter portion  83   b  located outside the first one  83   a . Relation among the diameters “D”, “D 1 ” and “D 2 ” of the central liquid spreading portion  82  the first smaller diameter portion  83   a  and the second smaller diameter portion  83   b  is given by D&gt;D 2 &gt;D 1 . A gap indicated by “G 1 ”, which is defined as a difference between halves of the diameters “D” and “D 1 ” of the central liquid spreading portion  82  and the first smaller diameter portion  83   a , is approximately equal to the thickness “t” of the outer-frame sheet  146  of the instant film unit  17 B (see FIG.  7 ). Likewise a gap indicated by “G 2 ”, which is defined as a difference between halves of the diameters “D 1 ” and “D 2 ” of the first and second smaller diameter portions  83   a  and  83   b , is approximately equal to the thickness of a layer of properly spread and distributed processing liquid  142 . The length “H” of the first processing roller  55  and the second processing roller  56  is approximately equal to the width “J” of the instant film unit  17 B (see FIG.  6 B). The length “K” of the central liquid spreading portion  82  of the second processing roller  56  is a little less than the width “F” of the image-viewable area defined by the picture viewing frame  148  (see FIG.  6 B). The total length “L” of the lengths “L 1 ” and “L 2 ” of the first and second smaller portions  83   a  and  83   b  is approximately equal to the width “M” of the lateral side frame part of the outer-frame sheet  146  (see FIG.  6 B). The second processing roller  56  is formed with a tapered portion  84  between the central liquid spreading portion  82  and the first smaller diameter portion  83   a . The width of the spread controller  60  is a little less than the width F of the image-viewable area defined by the picture viewing frame  148  so that the transverse end portion of the spread controller  60  do not contact with the lateral side frame part of the outer-frame sheet  146 . 
     As shown in FIG. 11, the opposite side frame parts of the outer-frame sheet  146  are nipped between the second smaller diameter portion  83   b  of the second pressure roller  56  and the first processing roller  55 . This forms a proper gap for spreading processing liquid  142  between the central liquid spreading portion  82  of the second processing roller  56  and the first processing roller  55  without having a harmful effect from the existence of the outer-frame sheet  146  when the instant film unit  17  is nipped. Furthermore, as the diameter of the first smaller diameter portion  83   a  of the second processing roller  56  is smaller than that of the second smaller diameter portion  83   b , a space of which thickness equals to the height “t” of the outer-frame sheet  146  is formed between the first smaller diameter portion  83   a  and the first processing roller  55  while the instant film unit  17  is nipped. Therefore, the processing liquid  142  can easily flow into the edge area under the space so as to form a high quality of picture even at its marginal area. The tapered portion  84  can bend smoothly the rear cover sheet  38  and the image receiving layer  39 , which prevents the instant film unit  17 B from cracks caused by stress concentration on the rear cover sheet  38  and helps the processing liquid  142  expand to the marginal area of the picture viewing frame  148  and the exposure frame  147 . 
     The first and second processing rollers  55  and  56  are made of hard steel to minimize manufacturing errors of diameter and other dimensions along the axis of rotation. The length “K” of the central liquid spreading portion  82  of the second processing roller  56 , the width of the spread controller  60 , the distance “N” between the center of the second processing roller  56  and the tip of the spread controller  60  and other dimensions with respect to those elements relating to the processing liquid spreading device  53  are determined according to the size and other physical characteristics of the instant film unit  17 B. 
     Although the above described embodiment of the processing liquid spreading device is adapted suitably for the transmissive type of instant film unit as an example, obviously the processing liquid spreading device can be suitably used for the reflective of instant film unit as long as the instant film unit is of an outer-frame type. 
     It is to be understood that whereas the present invention has been described in detail with respect to preferred embodiments, nevertheless, various other embodiments and variants are possible which are within the spirit and scope of the invention, and such are intended to be covered by the following claims.