US 3768906 A
A film printer and processor transfers images from a master film onto an unexposed thermal or "vesicular" film. The two film strips overlap as they pass through a housing where they are exposed to ultravoilet light which irradiates the vesicular film to decompose nitrogen compounds in the film and release gaseous nitrogen. As the two film strips pass through the housing, a vacuum is produced along a pair of narrow slotted openings extending lengthwise adjacent to the longitudinal edges of the films to prevent air from seeping in between them, which maintains the films in intimate contact during exposure. The exposed vesicular film is developed by passing it over a heating drum which causes the released nitrogen to nucleate into microscopic vesicules in the areas of irradiation. The developed film is fixed by irradiating it with ultraviolet light while maintaining the film in intimate contact with a cooling drum, which decomposes the remaining nitrogen compounds in the film thus desensitizing the film to further irradiation. The simultaneous cooling and fixing insures a relatively low exit temperature of the film leaving the fixing station which allows a powerful light source to be used for fixing which enables the film to be printed at high speeds. The fixing lamp is movable away from the cooling drum so that the lamp will not have to be shut off each time the film is threaded through the fixing station.
Claims available in
Description (OCR text may contain errors)
United States Patent 1 Michelson et a1.
[ METHOD AND APPARATUS FOR PRINTING AND PROCESSING THERMAL FILM  Inventors: Gunnar P. Michelson, Santa Barbara; Gajus Michelson, Sherman Oaks; Wolf Michelson, Van Nuys; William W. Valliant, Los Angeles, all of Calif.
 Assignee: Producers Service Corporation,
22 Filed: Dec. 27, 1971 211 Appl. No.: 212,236
Primary Examiner--Fred L. Braun Attorney-Walter G. Maxwell et al.
[ Oct. 30, 1973  ABSTRACT A film printer and processor transfers images from a master film onto an unexposed thermal or vesicular" film. The two film strips overlap as they pass through a housing where they are exposed to ultravoilet light which irradiates the vesicular film to decompose nitrogen compounds in the film and release gaseous nitrogen. As the two film strips pass through the housing, a vacuum is produced along a pair of narrow slotted openings extending lengthwise adjacent to the longitudinal edges of the films to prevent air from seeping in between them, which maintains the films in intimate contact during exposure. The exposed vesicular film is developed by passing it over a heating drum which causes the released nitrogen to nucleate into microscopic vesicules in the areas of irradiation. The developed film is fixed by irradiating it with ultraviolet light while maintaining the film in intimate contact with a cooling drum, which decomposes the remaining nitrogen compounds in the film thus desensitizing the film to further irradiation. The simultaneous cooling and fixing insures a relatively low exit temperature of the film leaving the fixing station which allows a powerful light source to be used for fixing which enables the film to be printed at high speeds. The fixing lamp is movable away from the cooling drum so that the lamp will not have to be shut off each time the film is threaded through the fixing station.
9 Claims, 6 Drawing Figures Patented Oct. 30, 1973 5 Sheets-Sheet 1 Patented Oct. 30, 1973 3,768,906
5 Sheets-Sheet 2 Patented Oct. 30, 1973 3,768,905
5 Sheets-Sheet :3
Patented Oct. 30, 1973 3,768,906
5 Sheets-Sheet 4 fiiml mwr Patented Oct. 30, 1973 5 Sheets-Sheet 5 BACKGROUND OF THE INVENTION This invention relates to printing and processing of film, and more particularly to transferring images from a master film onto a radiation-sensitive film, such as thermal or vesicular" film.
This invention is particularly adapted to the printing and processing of a type of film known in the art as vesicular film, although the invention may be adapted for use with other types of film without departing from the sciope of the invention.
Vesicular film is developed by heat alone, which avoids processing by liquid developing solutions or the like. At the present time, the primary use of vesicular film is in microfilm reproduction and in information storage and retrieval systems. The dry process to develop vesicular film makes the film particularly suitable for use in high speed recording and rapid display systems.
Generally speaking, vesicular film has a transparent resin which includes an ultraviolet sensitive diazonium salt uniformly dispersed within the resin. The salt decomposes upon exposure to ultraviolet radiation, releasing nitrogen which collects in small nucleating centers. Upon subsequent heating, the thermoplastic resin is softened and the released nitrogen nucleates to form microscopic vesicules. The vesicules produced in the irradiated portions of the film will scatter light incident upon them and form an image.
One requirement of obtaining good resolution and sharpness is to maintain the vesicular film and master film in close contact during. exposure. This is usually done by running the two films over a common transparent drum, with the ultraviolet light source being inside the drum.
The exposed vesicular film is developed by heating it to a temperature sufficient to cause the nitrogen liberated during exposure to coalesce into vesicules. Immediately after the film is heated, it is cooled to prevent excessive growth of the vesicules. This is usually done by passing the vesicular film around an air-cooled drum.
After development and cooling, the unexposed areas in the film still contain unexposed nitrogen compounds which can cause fogging at subsequent exposure to light and heat, which would reduce the image quality of the film. Fixing is generally done by irradiating the previously developed and cooled film with ultraviolet light to liberate the residual nitrogen in the emulsion of the film. The liberated nitrogen slowly diffuses into the atmosphere without creating vesicules, and thereby produces a film which is insensitive to further exposure to light. Those portions of the film which have been exposed to ultraviolet light during printing are now opaque and thus give a replica of the original master film.
Deterioration of resolution and clarity are avoided if the film leaving the fixing station is at a relatively low temperature, i.e., belowabout lF. If the film is in a heated condition after fixing, the thermoplastic layer may be softened, which may give rise to the formation of unwanted vesciules.
SUMMARY OF THE INVENTION This invention provides a film printer and processor for transferring images of high clarity and resolution from a master film onto a radiation-sensitive and heatdevelopable film.
In a preferred embodiment of the invention, the two films are moved in overlapping relation along a fixed path where they are exposed to a light source which irradiates the radiation-sensitive film. To obtain high resolution and sharpness of the film formed on the radiation-sensitive film, the overlapping films are held in intimate contact during exposure. Preferably, a set of pinch rollers squeeze air out from between the films to achieve intimate contact between the films as they enter the exposure path. To maintain the intimate c0npolyester base coated with a layer of thermoplastic tact, suction is produced along both edges of the overlapping films during exposure to the light source to sub- I stantially prevent air from seeping in between the films.
In a preferred form of the invention, both films are wrapped around a common roller as they exit the exposure path. The uppermost film is wrapped around the exit roller a sufficient amount to prevent air from seeping in between the films as they exit the exposure path.
After leaving the exposure path the radiationsensitive film passes around a heating drum which causes the liberated nitrogen to form vesicules.
In another preferred embodiment of the invention, the radiation-sensitive film passes from the heating drum into intimate physical contact with an elongated surface for cooling the film. The cooling of the film prevents excessive growth of the vesicules produced during heating. The film is fixed by exposing it to radiation from a light source located adjacent to the film while it remains in intimate contact with the cooling surface. This decomposes the remaining nitrogen compounds. The liberated nitrogen thereby slowly diffuses into the atmosphere without producing vesicules in the film, and thereby produces a film which is insensitive to further exposure to light.
Since the film is cooled while it isbeing fixed the film leaving the fixing station is substantially cooler than in prior art printer-processors. Moreover, the simultaneous cooling and fixing substantially prevents overheating of the film in the event the machine should slow down or stop during fixing. A preferred form of the invention includes means for moving the fixing lamp away from the cooling surface to facilitate the threading of the film through the fixing station thus preventing the fixing lamp from overheating or melting the film.
As an added advantage, the good heat dissipation while the film is inintimate contact with the cooling surface during fixing permits a powerful fixing lamp to be used without damaging the film. For example, a fixing lamp having 1,200 watts of power may be used for a four inch wide film which substantially increases the speed at which the film is printed and processed.
BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be more fully understood by referring to the following detailed description and the accompanying drawings, in which:
FIGS. 1A and 1B are a plan elevation view, partly in section and partly broken away, showing a machine for printing and processing vesicular film;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 5 Referring to FIGS. 1A and 13, a film printer and processor' mounted on a flat base 12 is shown in use printing, developing, and fixing a moving strip of radiation-sensitive and heat-developable film 14, preferably vesicular film, which is threaded through the printerprocessor in a manner described "in detail below.
A supply roll 16 of raw stock vesicular film 14 is mounted-on a spindle 18, mounted on base 12 adjacent to the left edge of the base as viewed in FIG. 1. Vesicular film-14 moves through theprinter-processor and accumulates in a take up roll 20 mounted on a motordriven spindle22 located adjacent to the right edge of base 12 when viewed in FIG. 1.
A supply roll 24 of master film 26 is mounted on a spindle 27 located below supply roll 16. Master film 26 contains information to be printed on vesicular film 14. The master film is threaded through a portion of the printer-processor to a take-up roll 28 mounted on a motor-driven spindle 30 adjacent take-up roll20.
Vesicular film 14 and master film 26 are fed together to a printing station, or exposure station, shown generally at 32. Master film 26 passes around a pair of idler rollers 34 and 36 and then to exposure station 32. Vesicular film 14 passes around a separate idler roller 38 to exposure station 32 where it overlaps master film 26 during printing.
Exposure station 32 includes an upright, elongated, substantially light-tight and box-like housing 40 having a hollow interior. The overlapping films l4 and 26 pass through an upper portion of housing 40 where they are exposed to irradiation from a vertically disposed utlraviolet lamp 42 (see FIG. 1B) mounted in the lower interior portion of the housing. Lamp 42 has an elongated lower end seal 44 disposed in a socket 46 for holding the lamp in its vertical position shown in FIG. 1B. A bulb 48 and electrode 50 of the lamp are located at the bottom central portion of an upwardly opening reflector 52 shaped as a tilted or rotated ellipsoid; The lamp also has an elongated upper end seal 54 disposed in the central portion of a horizontally extending copper spider 56 which is X-shaped when viewed from a plane normal to the plane of FIG. 1B. The ends of spider 56 are connected to a ring-shaped casting 58 which is rigidly held in place below housing 40. The spider is electrically coupled to an electrical power source (not shown) for conducting electricity to electrode 50 of lamp 42. The spider also provides structural rigidity for the lamp and conducts away thermal energy developed at upper end seal 54 of the lamp.
At exposure station 32, vesicular film 14 and master film 26 are brought into close contact as they pass through an upper portion of housing 40 where they are exposed to ultraviolet radiation from lamp 42. A lid 60 covers the upper portion of housing 40. As shown best in FIG. 4, the lid pivots open about a transverse axis through a pivot pin 62 releasably seated in an opening 64 formed in a post 66 on base 12 adjacent one side of the lid.
On the opposite side of the lid, a release lever assembly 67 releasably locks the lid in a fixed position above housing 40. The lever assembly includes a locking arm 68 rotatably mounted to a cylindrically shaped eccentric 70 which in turn is pivotally secured at a point eccentric of its central axis to an elongated link 72 which pivots on a lug at an edge of the lid.
When locking arm 68 is in the position shown in FIG. 1A, eccentric 70 toggles under a post 74 to hold the lid in a fixed position above the top of the housing. The lid pivots open by rotating the locking arm upwardly in the direction of an arrow 76 in FIG. 1A, which releases eccentric 70 from contact with post 74 andpermits the lid to pivot open about pin 62. The lid is held open by a' torsion spring 78 which exerts an upward force on the bottom lip of the lid.
The lid is held in its fixed position on housing 40 during printing by a latch assembly 79 which includes a vertically extending, fixed dowel pin 80 secured to a lip on the rear side of the lid, and a horizontally disposed pin 82 which makes a sliding releasable fit in a block 84 on base 12. Sliding pin 82'is fitted through one side of the block 84 to extend outwardly through the opposite side where it makes a tight friction hold against the dowel pin to securely fix the lid in place on top of the housing. Thus, when required, the lid can be quickly removed from the top of housing 40 simply-by sliding pin 82 out of contact with dowel pin 80, releasing lever arm 67 from engagement with post 74, and pulling the lid away from the plane of base 12 to release pivot pin 62 from contact with post 66.
The lid pivots open to allow threading of the vesicular film'and master film between the top of housing 40 and the underside of lid 60. For the purposes of printing, the master film and vesicular film overlap each other, with the vesicular film being uppermost as shown in FIG. 1A. The two films are initially brought into close contact by passing them between a cooperating pair of vertically aligned pinch rollers 86 and 88 at the entrance to housing 40. As shown best in FIGS. 2 and 4, pinch roller 86 is rotatably secured to front and rear sidewalls at the top of housing 40, and pinch roller 88 is secured to front and rear sidewalls of lid 60. When the lid is in its closed postion, the pinch rollers are squeezed tightly against each other, which squeezes air out from between the overlapping master film and vesicular film as they pass between the pinch rollers.
As the films exit housing 40, they pass over an exit roller 92 which extends between the front and rear sidewalls at the top of housing 40. The uppermost film engaging-surface of the exit roller is in the same horizontal plane as pinch roller 86.
To obtain high resolution of the film printed at exposure station 32, the two films 14, 26 are kept in intim ate contact during exposure to lamp 42. This is achieved by preventing air from seeping in between the films as they pass through housing 40. As described above, the first step in this procedure is accomplished by pinch rollers 86, 88 which squeeze air out from between the films as they enter housing 40. The films pass along a linear path through housing 40, and intimate contact between the films is maintained along this path by a vacuum produced along each longitudinal edge of the overlapping films, which prevents air from seeping in between the films as they pass through the housing. Thus, the films are kept in a flat condition tightly held against each other in the exposure area.
As shown best in FIGS. 2 and 3, the vacuum preferably is produced by a vacuum pump (not shown) located on the reverse side of base 12 and coupled to a tubular fitting 94 which opens into a bore 96 in the base. Housing 40 is secured to the base sothat a port 98 on the rear face of the housing opens into bore 96 and allows gas communication from the vacuum pump-to an interior portion of the housing. The upper portion of the housing has a hollow front wall portion 100 and a hollow rear wall portion 102 for supporting pinch roller 86 and exitroller 92. Front and rear wall portions 100, 102 have respective elongated front and rear passages 104 and 106 extending lengthwise through their interior. Port 98 opens into the passage in rear wallportion 102. Rear passage 106 communicates with front passage 104 through a pair of horizontally spaced apart metal cross-tubes 108 which connect the front and rear wall portions 100, 102. The cross-tubes allow gas flow communication from one side of the housing to the other, and also provide structural rigidity for the housing. 1
The inner top edge of each wall'portion 100, 102 has an elongated relief section 110 extending approximately from center-to-center between pinch roller 86 and exit roller 92. The relief sections define respective slotted openings 112 (see FIG. 3) adjacent to the longitudinal edges of the overlapping films, the slotted openings extending substantially the entire length of the travel of the film through housing 40. The vacuum drawn by the pump removes air from the housing through openings 112, passages 104, 106, cross-tubes 108, and out port 98 to produce a strong suction along the edges of the films. The suction prevents pair from seeping in between the films during exposure. Since the overlapping edges of the films are not restrained against relative movement in the exposure area, the edges of the two films can part slightly and allow the vacuum to suck out any air present between the films. This maintains the films in intimate contact during printing and produces high resolution of the printed film.
As vesicular film l4 exits housing 40, it passes around a guide roller 113 adjacent the exit side of the housing to deviate the path of the film from the path followed through the housing. A large deviation in the path of the master film is produced as it passes directly from exit roller 92 to 'takeup roll 28. The common angular deviations of films 14, 26 causes the films to continue their overlapping relationship on exit roller 92 past the extreme upper surface of the exit roller. This wrap angle" is small (a few degrees only is sufficient), and is for the purpose of preventing air from seeping in between the films as they exit the exposure housing, while keeping relative slippage between the films to a minimum.
Thus, printing takes place in an environment in which air is continuously prevented from seeping in between the films through their entire length of travel through the exposure area. As a result, the films are held in intimate contact as they are exposed to radiation, which produces high resolution and sharpness of the images formed on. the vesicular film.
Lamp 42 is a point light source which provides substantially collimated light when used in conjunction with reflector 52, so as to spread ultraviolet light over the entire width of the films. A flat light shield 114 disposed in an intermediate portion of the housing interior pivots on a pin 116 so as to adjust light exposure when rotated by a handle 118 outside the housing.
The exposure of the vesicular film to radiation decomposes nitrogen compounds in the light-sensitive coating of the vesicular film to liberate gaseous nitrogen. The nitrogen compounds decompose in areas of the film corresponding to the information present on the master film.
After vesicular film 14 leaves housing 40 it is developed by heating it to about 260-270F. on a heating drum 120 which receives the film as it passes away from guide roller 1 13. The heating softens the emulsion layer of the film and causes the nitrogen released at exposure station 32 to form microscopic vesicules.
Vesicular film 14 passes around a guide roller 122 prior to its contact with heating drum 120. Guide roller 122 is movable in an arcuate path adjacent the outer periphery of heating drum 120. The position of the guide roller is adjusted by moving a lever arm 124. Movement of guide roller 122 adjusts the length of contact between film l4 and the heating surface of heating drum 120. Thus, as lever arm 124 is rotated in a counterclockwise direction shown in FIG. 1A, guide roller 122 also rotates in a counterclockwise direction to reduce the length of contact from that shown in FIG. 1A. The minimum length of contact with the heating drum is illustrated in phantom line in FIG. 1A. Lever arm 124 is held in a predetermined fixed position relative to base 12 by a pin (not shown) fitted into one ofa plurality of arcuately aligned holes 128 in plate 12. An arcuate scale 130 and adjacent holes 128 provide means for determining which position of the lever arm and guide roller will produce a given temperature increase of the film for controlling its development.
Following heating, vesicular film 14 passes over a rotating cooling drum 136. While the film is on the cooling drum it is irradiated to liberate the residual nitrogen in the coating of the vesicular film. During fixing, the film is prevented from reaching such a temperature as to initiate the formation of vesicules of nitrogen. Thus, the nitrogen liberated during fixing slowly diffuses into the environment without creating vesicules. The film leaving the fixing station is thus in a stable condition unaffected by further exposure to ultraviolet radiation.
A fixing station 137 preferably slides away from cooling drum 136. Film 14 passes from heating drum 120 around cooling drum 136 for exposure to an ultraviolet fixing lamp 138, preferably a tubular mercuryarc lamp.
Fixing station 137 includes a housing which opens above cooling drum 136. The housing has a rounded, generally C-shaped outer periphery remote from the cooling drum, and spaced apart, arcuate, front and rear marginal edges which are closely spaced from the cooling drum 136 and match the rounded outer periphery of the drum. Lamp 138 is mounted within the interior of housing 140 in a position spaced above the film on the cooling drum and extending ina direction which traverses the width of the film. An arcuate reflector 142 in the housing above lamp 138 spreads light rays from the lamp to irradiate the entire surface of the film while it is in contact with the cooling drum. As best shown in FIG. 5, the front and rear end seals of lamp 138 are held in place in housing 140 by respective lamp holders 144 and 146.
Cooling of the housing is provided by a vacuum pump (not shown) on the rear side of base 12 which includes a pair of parallel guide rails 152 rigidly se-- cured to opposite sides of the housing, each guide rail being adapted to'slide in a separate pair of longitudinally aligned front and rear bearing blocks 154. Each front bearing block is rigidly secured to base 12, and each rear bearing block is ridigly secured to the rear side of an elongated fixed cross piece 156' extending substantially parallel to the reverse face of base 12. Cross piece 156 is held in a fixed position behind base 12 by apair of rearwardly extending and parallel elongated support posts 158 spaced outwardly from guide rails 152. Each guide rail 152 is seated on an arcuate bearing surface 159 provided by the adjacent front and rear bearing blocks. A handle 160 of the upper front face of housing 140 provides means for gripping the housing during its sliding movement. The housing slides away from cooling drum 136 to a position substantially behind the face of base 12. During sliding movement, the rear portions of guide rails 152 pass through holes 162 in the cross piece. A pair of front and rear O-rings 164 fitted around each guide bar provide bumpers to limit sliding movement of the housing and reduce shock transmitted to the fixing lamp.
During fixing, film 14 is held in intimate contact with terior of the cooling drum. By simultaneously cooling the film as it is fixed, the film exits the fixing station at a sufficiently low temperature, say ll0F. It has been found that film heated immediately after fixing can become fogged. Prior art film printer-processors generally fix the film after it is cooled, which can raise the temperature of the film. This problem is overcome by the present invention, because the film is held in intimate contact with the cooling surface of cooling drum 136 duringfixing; The film which exits fixing station 137 is at a relatively low temperature as a result of its contact with cooling drum 136, and this substantially eliminates the possibility that exposure to heat after fixing may cause fogging. Thus, the film exiting fixing station 137 has a permanent image with a high degree of clarity and resolution.
The fixing method of this invention also permits fixing at high speed. Generally speaking, the rate at which film is fixed is proportional to the intensity of the light produced bythe fixing lamp. The power of the fixing lamp generally is limited by the fact that otherwise unwanted vesicules may be formed. A powerful fixing lamp, sa 1,200 watts for a 4 inch wide film, may be used for fixing film 14, because the film is in intimate physical contact with the'cooling drum 136 as it is being exposed to fixing lamp 138. As a result, printing, developing, and fixing may be achieved at substantially higher speeds .than when fixing and cooling are done separately.
When it is necessary to slow down or stop the machine, fixing station 137 may be moved away from its position over the cooling drum so as toprevent overheating of the film. The fixing station also is moved away from the cooling drum to facilitate threading of the film. Thus, by moving the fixing lamp out of the way when the film is threaded, the lamp does not have to be switched off, which saves restarting timeof the lamp and increases lamp life.
After film 14 is fixed it passes around a series of guide rollers 168, 170, and 172 for guiding the film around the fixing station to take-up roll 20.
Thus, the film printer-processor of this invention prints and fixes thermal film at high speeds, while producing a high degree of clarity and resolution during printing and insuring that the clarity and'resolution are maintained after the film is fixed.
1. The method of transferring images onto a radiation-sensitive film from a separate master film, the method comprising moving the radiation-sensitive film and master film together for exposure to a light source capable of irradiating the radiation-sensitive film, developing the exposed radiation-sensitive film, and fixing the developed film to desensitize it to further irradiation, the fixing step including moving the developed film along a fixed path, maintaining the developed film in intimate physical contact with an elongated cooling surface as it moves along the fixed path, and simultaneously exposing the developed film to irradiationas it moves along the fixed path.
2. The method according to claim 1 in which the fixing. step includes maintaining the developed film in contact with a cooling drum, and disposing a light source adjacent to the portion of the developed film which contacts the cooling drum so the light source irradiates the portion of the developed film which is held in intimate contact with the cooling drum.
3. The method according to claim 1 including moving the two films in overlapping relation as they are exposed to said light source, and producing a suction along both longitudinal edges of the overlapping films as they are exposed to the light source to prevent air from seeping in between the films during exposure. 4. In a film printer and processor for transferring images onto a radiation-sensitive film from a separate master film, the combination comprising a first lightsource, means for moving the radiation-sensitive film and the master film together for exposure to the first light source, means for developing the exposed radiation-sensitive film, and means for fixing the developed film to desensitize it to further irradiation, the fixing means including means for moving the developed film along a fixed path in intimate physical contact with an elongated surface for cooling the film, and a second light source adjacent the fixed path for subjecting the developed film to radiation to fix the developed film as it is, cooled.
5. The combination according to claim 4 in which the surface for cooling the developed film comprises a cooling drum, and including means for holding the developed film in intimate contact with the cooling drum as the developed film moves along the fixed path,'the second light source being positioned adjacent to the portion of the developed film which contacts the cooling drum so as to subject said portion to irradiation.
6. The combination according to claim 4 in which the second light source is movable in and out of position for subjecting the developed film to radiation during fixing.
7. The combination according to claim 4 in which the radiation-sensitive film and master film are moved in overlapping relation along a fixed path for exposure to the first light source, and including means for producing a suction adjacent to both edges of the overlapping films as they pass along the path adjacent the first light source to prevent air from seeping in between the films during exposure.
8. A film printing and processing system for transferring images onto a radiation-sensitive film from a sepa rate master film, each ofthe two films having opposed longitudinal edges spaced apart by a known width, the system including a light source, support means disposed above the light source for maintaining the two films in a freely suspended overlapping relationship extending along an elongated fixed path for exposure to the light source,
the support means including a transverse entrance guide roller defining an entrance boundary of the exposure path, a transverse exit guide roller spaced longitudinally from the entrance guide roller and defining an exit boundary of the exposure path, the two guide rollers having a width substantially as wide as the two films, and means for moving the two films lengthwise along the exposure path in pressure contact with the entrance and exit guide rollers for exposure to the light source to irradiate the radiation-sensitive film, the two films being freely suspended between the guide rollers and being maintained in intimate overlapping contact continuously for their entire width along the exposure path, with the entire width of the two films being exposed to the light source,
a pinch roller at the entrance boundary for cooperating with the entrance guide roller to apply pressure to the two films as they pass over the entrance roller to squeeze air from between the two films prior to their movement along the fixed path,
a pair of hollow vacuum housings extending lengthwise along the opposite longitudinal edges of the two films and spaced apart by a distance slightly greater than the width of the two films, the housings having respective elongated slotted openings extending adjacent to the opposite longitudinal edges of the two films, each slotted opening extending continuously from the film point of pressure contact with the entrance guide roller to the film point of pressure contact with the exit guide roller, and
means applying a continuous uninterrupted suction to both overlapping longitudinal edges of the two films via the slotted openings for a distance extending continuously from the entrance boundary to the exit boundary of the exposure path to prevent air from seeping in between the two films during exposure to the light source,
the two films being in pressure contact only with the exit guide roller as they exit the exposure path, said pressure contact being arranged to prevent air from seeping back in between the films prior to when they exit the exposure path.
9. The system according to claim 8 in which said pressure contact at the exit guide roller is produced by means for guiding both films in the same general direction after they pass over the exit guide roller to produce an angular deviation of the films relative to the plane of the fixed path and thereby prevent air from seeping in between them as they exit said fixed path.