Instant camera

An instant camera is used with a photo film pack, which includes plural photo film units of a self-processing type. Each of the photo film units includes a processing solution pod for containing processing solution. There is an exposure surface which is exposed by photographic subject light and on which the processing solution is spread for processing. A case contains a stack of the plural photo film units. A photo film outlet causes the photo film units to exit. The instant camera has a pack chamber loaded with the photo film pack. An exposure aperture is formed to open in one face of the pack chamber, and sets the exposure surface of the photo film units inside the photo film pack. A set of first and second spreader rollers press and convey an exposed one of the photo film units advanced from the pack chamber, and squeeze the solution pod to spread the processing solution on the exposure surface. A spread control wall is disposed between the photo film outlet and the spreader roller set, pushes the photo film unit advanced from the photo film outlet, and controls distribution of the processing solution on the exposure surface.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an instant camera. More particularly, the
 present invention relates to an instant camera capable of spreading
 processing solution in each photo film unit in a stably controlled manner.
 2. Description Related to the Prior Art
 A widely available instant camera is used with a photo film pack, which
 includes plural photo film units of a self-processing type. Each of the
 photo film units has an exposure surface, and a processing solution pod
 disposed on one edge of the exposure surface. The solution pod contains
 processing solution. The photo film pack has a case of a box shape, which
 encloses the photo film units light-tightly to be sold as a product. When
 the instant camera is loaded with the photo film pack, it is possible to
 take photographs without handling each of the photo film units
 individually.
 When an exposure is taken in an instant camera on the exposure surface of
 the photo film unit with light from a photographic subject, the camera
 causes the photo film unit being exposed to moved to the outside. In the
 course of this exiting movement, a pair of spreader rollers nip and
 squeeze the solution pod, and causes the processing solution to flow from
 the solution pod to the exposure surface, to develop the exposure surface.
 There are various ways conceivable for improving the quality of a printed
 image on the photo film unit in the instant camera. Among them, JP-B
 3-72975 (corresponding to U.S. Pat. No. 4,226,519) suggests spreading of
 the processing solution to the exposure surface in a uniform manner. A
 spread control surface is formed with the photo film outlet in the case to
 contact the exposure surface in the photo film unit. When the processing
 solution flows from the solution pod, the spread control surface spreads
 the processing solution on the exposure surface before the spreader
 rollers spreads the processing solution. Thus the spread control surface
 causes the processing solution to extend to lateral portions arranged in
 the film unit width direction, which would be impossible if the spread
 control surface were not added to the spreader rollers. According to this
 prior art, the quality of the printed image can be heightened. Also the
 cost of the photo film unit can be reduced by optimizing the amount of the
 processing solution as contained.
 To stabilize the effect of the spread control surface controlling the
 spread of the processing solution, it is necessary to regularize a
 contacting position, contacting pressure, and other contacting states
 between the spreader rollers and the spread control surface. The case of
 the photo film pack consists of a combination of plural parts formed from
 plastic material with a small thickness, and is likely to be deformed due
 to irregularities in the size occurring at the molding time or assembly
 time, and twisting or distortion in the shape according to temperature or
 the like. A problem lies in that a relative position between the spread
 control surface with the spreader rollers is likely to change, so as to
 change the control of spreading the processing solution.
 SUMMARY OF THE INVENTION
 In view of the foregoing problems, an object of the present invention is to
 provide an instant camera capable of spreading processing solution in each
 photo film unit in a stably controlled manner.
 In order to achieve the above and other objects and advantages of this
 invention, an instant camera has a pack chamber loadable with a photo film
 pack, wherein the photo film pack has a stack of plural photo film units
 of a self-processing type, a case contains the stack of the photo film
 units, each of the photo film units includes a solution pod and an
 exposure surface, the exposure surface is processed by spreading of
 processing solution from the solution pod after being exposed by
 photographic subject light, and the photo film units are respectively
 ejected through a photo film outlet in the case. In the instant camera, a
 spreader roller set is constituted by first and second spreader rollers,
 for pressing and conveying an exposed one of the photo film units advanced
 from the pack chamber, the spreader roller set squeezing the solution pod
 to spread the processing solution on the exposure surface. A spread
 control member is disposed between the photo film outlet and the spreader
 roller set, for pushing the one photo film unit in a first direction
 substantially perpendicular to an advance thereof during the advance, to
 control distribution of the processing solution on the exposure surface.
 In a preferred embodiment, the pack chamber includes a photo film
 passageway for passing the one photo film unit advanced from the photo
 film outlet toward the spreader roller set. The spread control member is
 one of two walls defined in the photo film passageway, and at least
 partially covers the photo film outlet.
 The spread control member includes an inclined face, disposed on an end
 thereof, opposed to the photo film outlet, for guiding a front end of the
 one photo film unit being advanced toward the spreader roller set.
 The spread control member is so disposed as to bend the one photo film unit
 convexly in the first direction between the photo film outlet and the
 spreader roller set.
 Furthermore a camera outlet is disposed outside the spreader roller set,
 for ejecting the photo film unit externally from the instant camera, the
 camera outlet being positioned offset from a position between the first
 and second spreader rollers, to push the one photo film unit in the first
 direction.
 The first spreader roller is movable in the first direction, is biased by a
 spring, and applies regular force of pressurization to the one photo film
 unit in cooperation with the second spreader roller. The spread control
 member is disposed on a side of the first spreader roller with respect to
 the photo film outlet.
 A camera outlet ejects the one photo film unit externally from the instant
 camera after having passed the spreader roller set, wherein the one photo
 film unit is bent substantially in an S-shape by the camera outlet, the
 spreader roller set, the photo film passageway and the photo film outlet
 while advanced.
 In a further preferred embodiment, the photo film units have a size equal
 to a size of an ID-1 type card defined by JIS X6301 or ISO 7810.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION
 In FIG. 1, an instant camera 2 of the present invention has a generally
 rectangular shape as viewed in the front. The instant camera 2 is loaded
 with a photo film pack 4 which contains a plurality of photo film units 3.
 See FIG. 2. A front of the center of the instant camera 2 has a lens
 barrel 6 incorporating a taking lens 5. The instant camera 2 has an
 auto-focus (AF) device of an infrared active type. The front of the lens
 barrel 6 has the taking lens 5, a light projector window 7, a light
 receiver window 8, a photometric window 9 and a flash measuring window 10.
 The light projector window 7 and the light receiver window 8 constitute a
 rangefinding device. The photometric window 9 is included in a photometric
 device. There are light projector elements or light receiver elements
 contained in inside positions of those windows.
 A grip 12 is formed on one lateral face of the instant camera 2. A power
 switch 13 and a shutter release button 14 are disposed on the top of the
 grip 12. The shutter release button 14 is depressible in two steps, and
 when depressed halfway, causes operation of rangefinding and photometry,
 and when depressed fully, releases a shutter device.
 A viewfinder 16 is disposed in an upper portion of the instant camera 2,
 and used to observe a region to be photographed. When the shutter release
 button 14 is halfway depressed, rangefinding and photometry are effected
 through the light projector window 7, the light receiver window 8 and the
 photometric window 9. Upon full depression of the shutter release button
 14, the shutter device inside the lens barrel 6 is released according to
 rangefinding and photometric values as obtained. If brightness of a
 photographic subject is very low, then a flash emitter 17 above the lens
 barrel 6 is automatically operated to emit flash light toward the
 photographic subject. After taking an exposure, the photo film unit 3 in
 the course of development is ejected from a camera outlet 18 in the top of
 the instant camera 2.
 In FIG. 2, the instant camera 2 has a body 21, a front cover 22 and a rear
 cover 23. The body 21 incorporates mechanisms for taking an exposure. A
 pack chamber 20 is disposed on the rear of the body 21 and loaded with the
 photo film pack 4. A door 24 of a plate shape is secured to the rear cover
 23 with a hinge 25 for opening and closing the pack chamber 20.
 A light-shielding tunnel 27 is formed in the front of the body 21, and
 shields ambient light from an optical path defined from the taking lens 5
 to the photo film units 3. An exposure aperture 28 is formed between the
 pack chamber 20 and the light-shielding tunnel 27 to determine a region to
 be exposed on the photo film units 3 in the photo film pack 4.
 The photo film pack 4 is constituted of a case 30 of plastic material in a
 box shape and a stack of the photo film units 3 contained in the case 30.
 The photo film units 3 include an exposure surface 3a, a processing
 solution pod 3b and a trap member 3c. The exposure surface 3a exists on
 the front of layers including emulsion layers and a light receiving layer.
 The solution pod 3b contains processing solution. The trap member 3c traps
 the surplus of the processing solution having flowed from the solution pod
 3b to the exposure surface 3a, and hardens the surplus. The photo film
 units 3 have a rectangular shape, and is a mono-sheet type, which can be
 handled as a single sheet.
 An exposure opening 30a is formed in the front wall of the case 30 to
 uncover the exposure surface 3a of the one of the photo film units 3. A
 photo film outlet 32 in a slit shape is formed in the top of the case 30
 for ejecting an exposed one of the photo film units 3 from inside the case
 30. A light-shielding sticker 33 with flexibility (See FIG. 3) is attached
 to close the photo film outlet 32 when the photo film pack 4 is unused.
 A light-shielding cover sheet 35 of a plate shape is contained in the photo
 film pack 4 with the photo film units 3 when the photo film pack 4 is
 unused, and protects the inside of the case 30 from ambient light. When
 the shutter is released for the first time after loading the pack chamber
 20 with the photo film pack 4, the cover sheet 35 is automatically ejected
 from the camera outlet 18 in the top of the instant camera 2. In the
 course of this ejection, a weakly attached portion of the sticker 33 over
 the photo film outlet 32 is peeled to open the photo film outlet 32.
 A recess (not shown) is formed in a portion under the exposure opening 30a
 in the case 30 for receiving a claw mechanism known in the art. The claw
 of the claw mechanism is driven in response to shutter releasing, and is
 moved upwards, enters the recess in the case 30 and contacts a bottom end
 of a foremost one of the photo film units 3. The claw moves further in the
 upward direction to lift the foremost photo film unit 3 in the case 30,
 until a top end of the foremost photo film unit 3 is moved out of the
 photo film outlet 32 in the case 30.
 A push ridge 37 is formed on the center of the rear inside wall of the case
 30. Light-shielding sheets 38 and 39 are disposed behind the photo film
 units 3. The push ridge 37 pushes the photo film units 3 to the front
 indirectly with the light-shielding sheets 38 and 39, to flatten the
 foremost one of the photo film units 3. Holes 40 and 41 are formed in the
 rear of the case 30, between which the push ridge 37 is located. Press pad
 mechanisms 42 and 43 are arranged on the inside of the door 24, and when
 the door 24 is closed with the photo film pack 4 inside the pack chamber
 20, enter the holes 40 and 41.
 The press pad mechanisms 42 and 43 have press pads 42a and 43a, which are
 disclosed in U.S. Pat. No. 5,541,683 (corresponding to JP-A 7-244336). The
 press pads 42a and 43a are movable in a direction of the thickness of the
 photo film units 3, and biased by springs to push the photo film units 3,
 the foremost one of which is kept flat. The holes 40 and 41 to be entered
 by the press pad mechanisms 42 and 43 are closed by the light-shielding
 sheets 38 and 39 light-tightly before the photo film pack 4 is used.
 In FIG. 3, a photo film passageway 45 of a slit shape is formed in the top
 of the pack chamber 20 to cause the photo film unit 3 to exit from the
 pack chamber 20 after each exposure. The photo film passageway 45 is in a
 position offset forwards from the photo film outlet 32 formed in the photo
 film pack 4. A spread control wall 46 constitutes one of the two edges of
 the photo film passageway 45, and contacts the back surface of the photo
 film unit 3 to control the spread state of the processing solution flowing
 from the solution pod 3b to the exposure surface 3a.
 An end of the spread control wall 46 has such a rounded shape as to protect
 the back surface of the photo film unit 3 from being damaged. A guiding
 inclined surface is formed on the end of the spread control wall 46 to
 guide the photo film unit 3 toward the photo film passageway 45.
 A spreader roller set 48 is disposed above the photo film passageway 45,
 and nips an advancing end of the one of the photo film units 3 advancing
 from the pack chamber 20, and conveys it toward the camera outlet 18. Also
 the camera outlet 18 squeezes the solution pod 3b and causes the
 processing solution to flow to the exposure surface 3a, and spreads the
 solution to the whole of the exposure surface 3a. The spreader roller set
 48 is constituted of first and second spreader rollers 49 and 50. The
 first spreader roller 49 as a driving roller is rotated by a motor in the
 clockwise direction. The second spreader roller 50 as a driven roller is
 rotated in the counterclockwise direction by rotation of the first
 spreader roller 49 via the contact with pressure.
 The spreader rollers 49 and 50 are respectively formed from hard steel
 material to reduce errors in the diameter in relation to the axial
 direction. The second spreader roller 50 is movable in the thickness
 direction of the photo film unit 3 to spread the processing solution on
 the exposure surface 3a in a uniform manner, and is biased by a spring 51
 to push the first spreader roller 49. In the present embodiment, the first
 spreader roller 49 is kept from shifting in its width direction, as the
 first spreader roller 49 is disposed to cause the photo film unit 3 to be
 pushed on the spread control wall 46. This is effective in stabilizing a
 contacting position, contacting pressure, and other contacting states
 between the photo film unit 3 and the spread control wall 46. Note that,
 if a driven roller is disposed on the side of pressing the photo film unit
 3 to the spread control wall 46, then the driven roller can be kept from
 shifting, and a driving roller can be set movable in the thickness
 direction of the photo film unit 3.
 The spreader roller set 48 is so disposed that a position of the contact
 between the spreader rollers 49 and 50 is located directly over the end of
 the spread control wall 46. As the photo film unit 3 is caused to contact
 the spreader roller set 48, the spread control wall 46 and an edge of the
 photo film outlet 32 in the case 30, the photo film unit 3 is curved in an
 S-shape loosely. A contacting state of the photo film unit 3 with the
 spread control wall 46 is ensured to make the operation of the spread
 control wall 46 effective for spreading the processing solution. Note
 that, in spite of the present embodiment, the position of the contact
 between the spreader rollers 49 and 50 may be slightly offset from a
 position directly over the end of the spread control wall 46. The spreader
 roller set 48 may be positioned in any suitable manner such that the photo
 film unit 3 is curved loosely to keep the back surface in tight contact
 with the spread control wall 46. It is preferable that the end of the
 spread control wall 46 is 0.1 mm offset in the rearward direction from the
 position where the first spreader roller 49 contacts the photo film unit
 3.
 A camera outlet passageway 53 is formed with an inclination toward the
 front, and guides the photo film unit 3 toward the camera outlet 18 after
 passage in the spreader roller set 48. Thus an area of contact of the
 first spreader roller 49 with the solution pod 3b of the photo film unit 3
 is enlarged. An effect of the first spreader roller 49 for spreading the
 solution is raised.
 The operation of the above construction is described now. To take an
 exposure with the instant camera 2 in FIG. 1, the power switch 13 is
 depressed to power the instant camera 2. A photographic field is observed
 through the viewfinder 16. The shutter release button 14 is depressed
 halfway, to effect the rangefinding and photometry by use of the light
 projector window 7, the light receiver window 8 and the photometric window
 9 located in the front of the lens barrel 6. When the shutter release
 button 14 is depressed fully, the shutter device in the lens barrel 6 is
 released in accordance with the values obtained by the rangefinding and
 the photometry. If the brightness of the photographic subject is very low,
 the flash emitter 17 automatically emits flash light toward the
 photographic subject. The subject light passes through the taking lens 5,
 and exposes the exposure surface 3a of the foremost one of the photo film
 units 3 through the light-shielding tunnel 27, the exposure aperture 28
 and the exposure opening 30a.
 When an operation of releasing of the shutter device is finished, a motor
 causes the claw of the claw mechanism to move upwards, for the claw to
 enter the recess communicating with the exposure opening 30a of the case
 30. The claw comes in contact with the bottom of the foremost one of the
 photo film units 3, and then moves up to raise the foremost one of the
 photo film units 3 inside the case 30.
 The photo film unit 3 advanced through the photo film outlet 32 in the case
 30 forcibly peels the sticker 33 to exit from the case 30. The photo film
 unit 3 is guided by the lower inclined face of the spread control wall 46,
 and directed through the photo film passageway 45 in the pack chamber 20.
 Then the photo film unit 3 from the photo film passageway 45 is nipped by
 the spreader roller set 48 which has been rotating, and is conveyed toward
 the camera outlet 18.
 In the course of the movement, the solution pod 3b of the photo film unit 3
 is squeezed by the spreader roller set 48. The processing solution flows
 from the solution pod 3b, and is caused by the spreader roller set 48 to
 spread on the exposure surface 3a. The photo film unit 3 having passed the
 spreader roller set 48 is introduced to the outlet passageway 53 having
 the inclination toward the front of the instant camera 2. As the outlet
 passageway 53 enlarges the area of the contact between the solution pod 3b
 of the photo film unit 3 and the first spreader roller 49, the effect of
 the spreader roller set 46 spreading the solution is ensured.
 The processing solution having flowed to the exposure surface 3a is spread
 by the spreader roller set 48, and at the same time, caused to extend to
 the whole of the exposure surface 3a with a uniform thickness by an effect
 of the spread control wall 46 contacting the back surface of the photo
 film unit 3. The spread control wall 46 is formed with the body 21
 constituting the instant camera 2. As a position of the first spreader
 roller 49 is stationary in the body 21 on the side opposing to the spread
 control wall 46, the contacting state between the photo film unit 3 and
 the spread control wall 46 is kept unchanged, to stabilize the spread
 state of the processing solution.
 As the spread control wall 46 is included in walls of the pack chamber 20
 to constitute the photo film passageway 45, it is possible to use the
 spread control wall 46 without raising the size or cost of the camera.
 Furthermore the spread control wall 46 contacts the back surface of the
 photo film unit 3 in reverse to the exposure surface 3a, which can be
 prevented from being damaged or contaminated.
 The photo film unit 3 having passed the outlet passageway 53 is ejected
 through the camera outlet 18 from the instant camera 2. As the exposure
 surface 3a of the photo film unit 3 is processed by the processing
 solution spread by the spread control wall 46 and the spreader roller set
 48, a printed image appears on the exposure surface 3a when a
 predetermined time lapses. The quality of the printed image of the photo
 film unit 3 is heightened because the area of the contact between the
 solution pod 3b and the spreader roller set 48 is enlarged.
 In the above embodiment, the spread control wall is formed to constitute
 the photo film passageway 45. Alternatively a spread control wall may be
 formed with a different part associated with the spreader rollers, either
 inside the pack chamber 20 or outside the pack chamber 20. An end portion
 of the spread control wall can be shaped with modifications in its width
 direction so as to optimize the spreading effect of the processing
 solution.
 In a preferred embodiment, the photo film units 3 have a preferable size
 which is substantially equal to a size of the ID-1 type card being 85.60
 mm long and 53.98 mm wide, which is defined according to JIS X6301 or ISO
 7810. Furthermore a ratio of an area of a frame region of the photo film
 units 3 to an area of their margin region is equal to or more than 1.50.
 These features are hereinafter described with reference to FIGS. 4-7.
 In FIG. 6, the photo film unit 3 has a structure including a mask sheet 62,
 a photosensitive sheet 63, a pair of spacer rail members 64 and a cover
 sheet 65 connected sequentially with one another. A frame opening 62a is
 formed in the center of the mask sheet 62. The solution pod 3b and the
 trap member 3c are attached to outer portions which are on the periphery
 of the mask sheet 62 and defined by bend lines 60a and 60b. After the
 photosensitive sheet 63, the spacer rail members 64 and the cover sheet 65
 are attached to the mask sheet 62, the outer portions of the mask sheet 62
 are bent along the bend lines 60a and 60b and are attached to the cover
 sheet 65. The trap member 3c is attached to the mask sheet 62 with
 adhesive agent. An under member 69 or pad is connected with the
 photosensitive sheet 63 on the side of the solution pod 3b, and operates
 to adjusts the height of the solution pod 3b and the photosensitive sheet
 63 by receiving the solution pod 3b.
 The mask sheet 62 operates to define the periphery of each frame, and has a
 thickness of 50 .mu.m. The mask sheet 62 includes a support, which
 consists of lamination of first and second films, the first being a
 transparent polyethylene terephthalate (PET) film with a thickness of 12
 .mu.m, and the second being a polyethylene terephthalate (PET) film having
 a deposit of aluminum and with a thickness of 12 .mu.m. A first surface of
 the support is coated with an adhesive layer of an EVA-SBS type at a
 thickness of approximately 12 .mu.m. The second surface of the support is
 coated with a white-color layer and then coated with a logo-printing
 layer. The white-color layer includes titanium oxide and silica, and has a
 thickness of approximately 8 .mu.m. The logo-printing layer is gray.
 The spacer rail members 64 are produced from material for controlling the
 thickness with which the processing solution is spread, and for attaching
 the cover sheet 65 to the photosensitive sheet 63, and have an average
 thickness of 64 .mu.m. Transparent sheets of polyethylene terephthalate
 (PET) with a thickness of 38 .mu.m are used. A first surface of
 transparent sheets is coated with a light-shielding layer at a thickness
 of 10 .mu.m and then coated with an adhesive layer of an EVA-SBS type a t
 a thickness of 8 .mu.m. The second surface of the transparent sheets are
 coated with an adhesive layer of an EVA-SBS type at a thickness of 8
 .mu.m. It is to be noted that the thickness or formulation of the adhesive
 layers may be changed as required, in order to ensure the adhesion on the
 side of the photosensitive sheet. As the sum of the thickness of the two
 adhesive layers should be unchanged, one of the adhesive layers must have
 a decreased thickness if the other of the adhesive layers must have an
 increased thickness.
 The photosensitive sheet 63 includes a polyethylene terephthalate (PET)
 support which is 90 .mu.m thick and includes titanium oxide of a small
 amount. A first surface of the support is coated with a back layer of an
 acetyl cellulose type. The second surface of the support is coated
 sequentially with an image receiving layer, a white-color reflection
 layer, a light-shielding layer, a red-sensitive emulsion layer, a
 green-sensitive emulsion layer, a blue-sensitive emulsion layer, a
 ultraviolet ray absorbing layer, and then a protective layer. A color
 mixture preventing layer is disposed respectively between those sensitive
 emulsion layers. A thickness of the entirety of the photosensitive sheet
 63 is approximately 115 .mu.m.
 The cover sheet 65 includes a polyethylene terephthalate (PET) support
 which is 70 .mu.m thick and includes blue dye of a small amount. A first
 surface of the support is coated with a filter dye layer of an acetyl
 cellulose type. The second surface of the support is coated with a
 neutralizing layer, a neutralizing timing layer, and then a temperature
 compensating layer. The whole thickness of the cover sheet 65 is
 approximately 80 .mu.m.
 The solution pod 3b includes processing solution of 280 microliters (.mu.l)
 and a container member for containing the processing solution. The
 container member consists of a paper support and an aluminum foil attached
 thereto by adhesion, and coated with adhesive agent of an EVA type. In
 FIG. 7, the solution pod 3b is provided with middle sealed portions 81, 82
 and 83. Edges of the container member from which the processing solution
 exits are sealed with a weak sealed portion 84, which is indicated by the
 hatching in the drawing. The middle sealed portions 81-83 are disposed for
 uniforming the spreading of the processing solution when the solution pod
 3b flows out upon breakage of the weak sealed portion 84. The trap member
 3c has a width of 3.6 mm, a length of 45 mm, and a thickness of 0.75 mm.
 The under member 69 is a transparent polyethylene terephthalate (PET) film
 having a thickness of 100 .mu.m.
 In FIG. 4, the photo film unit 3 on the side of the exposure surface 3a is
 illustrated. The frame opening 62a in which an image appears has a size of
 D20.times.D21. A pod section 71 (See FIG. 5) containing the solution pod
 3b is reverse to a blank margin space 72 of the mask sheet 62 which is
 used by users for filling in words or the like. A trap section 73 or
 T-section (See FIG. 5) containing the trap member 3c is reverse to a
 horizontal portion 74 or T-frame of the mask sheet 62. The spacer rail
 members 64 are behind lateral portions 75 of the mask sheet 62. The blank
 margin space 72 has a width of D22. The horizontal portion 74 has a width
 of D2. The lateral portions 75 have a width of D23.
 In FIG. 5A, let D1 be a distance between an end of the photosensitive sheet
 63 and an end of the mask sheet 62 before bending of the mask sheet 62. In
 FIG. 5B, let D3 be a distance between the end of the mask sheet 62 and an
 end 62c of the photo film unit 3. The distance D1 is determined longer
 than the distance D3 for facilitating bending of the mask sheet 62 with
 the surplus length. If the difference between D1 and D3 is too great, the
 mask sheet 62 will be so bent that the distance to the end of the mask
 sheet 62 will become over a distance D2 between the end 62c and an end of
 the frame opening 62a. Thus a value of D1-D3 should be within a range
 between upper and lower limits, and in the present embodiment, is
 determined 0.6 mm.
 Let D4 be a distance between the end 62c and an end of the trap member 3c.
 Let D5 be a distance between the trap member 3c and a position where the
 cover sheet 65 is connected with the end of the mask sheet 62 near to an
 air path 77 depicted in FIG. 5. The distances D4 and D5 depend upon a size
 of the trap member 3c and a position of attachment of the trap member 3c.
 The distance D4 is 1.0 mm for the purpose of preventing the solution from
 spreading laterally and from returning to the inside of the frame. The
 distance D5 is 1.30 mm for the purpose of sufficiently introducing air
 inside the photo film unit to the air path 77.
 In FIG. 5, the back surface of the photo film unit 3 is illustrated. The
 air path 77 is defined by keeping a central portion of the trap section 73
 without being sealed. The air path 77 is in a position D25 away from a
 lateral side of the photo film unit 3, and D25=24.5 mm. The air path 77
 has a width D26=5 mm. Let D6 be a sealed width of the trap section 73 on
 the photosensitive sheet side. Let D27 be a sealed width of the trap
 section 73 on each lateral side. D6=0.8 mm, and D27=2.2 mm. Let D29 be a
 sealed width at the corner of a first one of the lateral sides of the trap
 section 73. Let D28 be a sealed width at a corner 78 of the second one of
 the lateral sides of the trap section 73. D29=3 mm, but D28=4.0 mm,
 because the corner 7B is engageable with the claw mechanism of the instant
 camera. The spacer rail members 64 have a width D30=2.2 mm. Let D24 be a
 bend width of the pod section 71. Let D31 be a sealed width of the pod
 section 71 one each lateral side. Let D32 be a sealed width of the pod
 section 71 on the side of the photosensitive sheet. D24=15.4 mm, D31=1.8
 mm, and D32=0.8 mm.
 In FIG. 7, let D35 be a length of the solution pod 3b. Let D36 be a width
 of the solution pod 3b. Let D37 be a width of the weak sealed portion 84.
 Let D38 be a length of the middle sealed portion 81. Let D39 be an
 interval between the middle sealed portion 81 and an edge of the solution
 pod 3b. Let D40 be a length of the middle sealed portions 82 and 83. Let
 D41 be an interval between the middle sealed portions 82 and 83. Let D42
 be an interval between the edge of the solution pod 3b oriented away from
 the frame opening 62a and the middle sealed portions B2 and B3. Let D43 be
 a width of the middle sealed portions 82 and 83. Those sizes are
 determined as D35=48.6 mm, D36=12.5 mm, D37=1.5 mm, D38=7.5 mm, D39=0.55
 mm, D40=3.5 mm, D41=7.6 mm, D42=8.55 mm, and D43=1 mm.
 Examples 1-4 are indicated in the table below. The trap section 73, which
 is a thickest portion of the photo film unit 3 after the spreading, has a
 thickness of 0.9 mm.