Abstract:
An apparatus and method for applying a solution having a predetermined viscosity to a photosensitive material, such as a photographic print, involves the conveyance of the photosensitive material through a tank. A guide member mounted in the tank is effective to guide viscous solution to an area in the vicinity of a nip portion between first and second rollers. This arrangement creates at least one bead in a vicinity of the nip portion between the rollers so as to promote an even and consistent application of solution to the photosensitive material, and at the same time, permits an upper roller of the drive rollers to stay evenly wet.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the photoprocessing and/or photofinishing field. More particularly, the present invention relates to a method and apparatus for applying a solution of a predetermined viscosity to photosensitive material, preferably processed photosensitive material, to form a protective overcoat on at least one surface of the photosensitive material. 
     BACKGROUND OF THE INVENTION 
     In order to apply a protective coating to an emulsion surface of a photosensitive material, control over the thickness, uniformity and lay down amount of the coating being applied is needed in order to provide for adequate protection against moisture and scratches. The control is needed for several reasons: 1) the protective coating must be applied in a manner that insures that the surface is uniformly coated so that the coating can provide adequate protection to the entire surface; 2) that thickness of the coating must be controlled because if the coating is too thick, it could cause cracking, due to non-uniform drying; 3) a thick coating could dull the surface and the underlying image of photographic print; and 4) the coating solutions can be of different viscosities. 
     U.S. Pat. No. 5,318,804 discloses a coater for applying a liquid onto a surface of a moving object. In the coater of U.S. Pat. No. 5,318,804, a coating liquid is applied onto a coating roll which transports the coating liquid onto a supporter that is positioned on a backup roll. A drawback of the coater of U.S. Pat. No. 5,318,804 is that no provision is made for assuring that the coating liquid is guided to and kept at a nip portion between the rolls, so as to provide for an even application of coating liquid and to maintain the rolls in a wet state. 
     U.S. Pat. No. 5,690,999 discloses a coating device for the coating of a size-press roll, paper or board. This patent discloses a revolving coating bar which rests against a press roller. Like the arrangement shown in U.S. Pat. No. 5,318,804, the arrangement of U.S. Pat. No. 5,690,999 also does not provide for a mechanism for guiding and keeping coating liquid at a vicinity of a nip portion between rollers, so as to assure a uniform application of coating liquid and to maintain the rolls in a wet state. 
     SUMMARY OF THE INVENTION 
     The present invention provides for a novel method and apparatus which can apply a solution of a predetermined viscosity to the surface of photosensitive material, preferably processed photosensitive material, prior to the final drying of the material to form a protective overcoat. In the present invention, the solution is applied a manner that allows the solution to be uniformly applied to the surface of the photosensitive material at a specific thickness. 
     With the method and apparatus of the present invention, a solution of predetermined viscosity is guided to a vicinity of a nip portion between two drive rollers by a solution supply guide member. The arrangement of the present invention assures that at least an upper roller of the drive rollers is maintained wet with the solution, and also provides for the formation of a bead of solution in a vicinity of the nip portion, so as to promote a consistent and even application of solution to photosensitive material that is guided between the drive rollers. 
     The present invention relates to a method of applying at least one solution of a predetermined viscosity to photosensitive material. The method comprises the steps of providing a solution supply guide member at a position relative to first and second rollers, such that one end of the guide member extends toward a nip portion between the first and second rollers; supplying a solution of a predetermined viscosity onto the guide member so that the solution flows along the guide member and is guided toward the nip portion between the first and second rollers, so as to form at least one bead of the solution; and conveying a photosensitive material toward the nip portion, such that the solution is applied to the surface of a photosensitive material. 
     The present invention also relates to an apparatus for applying at least one solution of a predetermined viscosity to photosensitive material. The apparatus comprises first and second rollers rotatably mounted in a tank so as to define a nip portion therebetween; a solution supply guide member positioned relative to the first and second rollers such that one end of the guide member extends toward the nip portion; and a solution supply port for introducing a solution of a predetermined viscosity onto the guide member, such that the solution flows along the guide member and is guided toward the nip portion to form at least one bead of the solution. 
     The present invention also relates to a method of applying at least one solution of a predetermined viscosity to photosensitive material which comprises the steps of providing a solution supply guide member at a position relative to first and second rollers so that one end of the guide member extends toward a nip portion between the first and second rollers; supplying a solution of a predetermined viscosity onto one of the first and second rollers, such that the solution flows along an outer peripheral surface of the one of the first and second rollers in a direction toward the one end of the guide member, and is guided by the guide member toward the nip portion, wherein the solution guided by the guide member toward the nip portion forms a bead in a vicinity of the nip portion; and conveying a photosensitive material toward the bead and into the nip portion, such that the solution is applied to the photosensitive material. 
     The present invention further relates to an apparatus for applying at least one solution of a predetermined viscosity to photosensitive material which comprises first and second rollers rotatably mounted in a tank so as to define a nip portion therebetween; a solution supply guide member positioned relative to the first and second rollers such that the one end of the guide member extends toward the nip portion; and a solution supply port for introducing solution of a predetermined viscosity onto one of the first and second rollers, such that the solution flows along an outer peripheral surface of the one of the first and second rollers in a direction toward the one end of the guide member, wherein the guide member guides the solution toward the nip portion and the solution forms a bead in a vicinity of the nip portion. 
     The present invention also relates to an apparatus for applying at least one solution of a predetermined viscosity to photosensitive material which comprises first and second rollers mounted in a tank so as to define a nip portion therebetween; a solution supply guide member positioned relative to the first and second rollers such that one end of the guide member extends toward the nip portion; and a solution supply port for introducing a solution of a predetermined viscosity into the tank, such that the guide member guides the solution toward the nip portion and the solution forms a bead in a vicinity of the nip portion. 
     The present invention also relates to a photoprocessing system which comprises a processor for processing photosensitive material; and a coating apparatus for applying at least one solution of a predetermined viscosity to the processed photosensitive material. The coating apparatus includes first and second rollers mounted in a tank so as to define a nip portion therebetween; a solution supply guide member positioned relative to the first and second rollers such that one end of the guide member extends toward the nip portion; and a solution supply port for introducing a solution of a predetermined viscosity into the tank, such that the guide member guides the solution toward the nip portion and the solution forms a bead in a vicinity of the nip portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a first example of the apparatus of the present invention; 
     FIG. 2 is an isolated view of a solution supply guide member and drive rollers of the apparatus of FIG. 1; 
     FIG. 3 is a schematic illustration of a further example of the apparatus of the present invention; and 
     FIG. 4 is an isolated view of a solution supply guide member and drive rollers applicable to the apparatus of FIGS.  1  and  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, wherein like references numerals represent identical or corresponding parts throughout the several views, FIG. 1 illustrates a coating apparatus  5  for applying a layer of solution  6  of a predetermined viscosity to photosensitive material  7  prior to the drying of photosensitive material  7 . Photosensitive material  7  can be a processed photosensitive material and can be in the form of a photographic print, a web, cut sheet or film. Viscous solution  6  when dried will form a protective coating on photosensitive material  7  which exhibits moisture-proof and scratch-proof properties. Coating apparatus  5  can be added to the end of an existing processing device as an accessory, can be built in as part of a new processor, or retrofit into an existing processor. 
     With respect to the properties of viscous solution  6 , reference is made to applications U.S. Ser. No. 08/965,560, now U.S. Pat. No. 5,984,539, U.S. Ser. No. 08/965,639, now U.S. Pat. No. 5,905,924, and U.S. Ser. No. 08/965,105, now U.S. Pat. No. 5,875,370, the subject matter of which is herein incorporated by reference. Since solution  6  is to be applied in a minilab or photographic processing center, water-based solutions that are substantially free of volatile organic compounds are preferred. It is recognized that numerous viscous solutions can be utilized and that the type of viscous solution applied is based on design considerations in view of the desired viscosity, water-proofing and scratch-proof properties of the applied coating. 
     Apparatus  5  comprises a tank  9  which can be in the form of a solution pan that includes a photosensitive material entry port  11  as well as a viscous solution entry port  14 . Mounted within tank  9  in a rotatable manner are first and second drive rollers  15 ,  17 . Roller  15  is preferably a metering roller and roller  17  is preferably a pinch roller. Rollers  15  and  17  are mounted within tank  9  so as to define a nip portion  19  therebetween for the passage of photosensitive material  7 . 
     Tank  9  further includes a solution supply guide member  21  which is mounted at an angle with respect to a horizontal line and includes an end  21  a that is approximately located in an area between first and second rollers  15 ,  17  and at a vicinity of nip portion  19 . 
     As illustrated in FIG. 1, rollers  15  and  17  are mounted in a slanted manner within tank  9 . More specifically, rollers  15  and  17  are mounted such that a center line  23  which connects a center of rotation  15   r  of roller  15  to a center of rotation  17   r  of roller  17  makes an approximately 30° angle α with a horizontal line  25 . Also, guide member  21  includes a longitudinal axis  21 L which makes an approximately 90° angle with center line  23 . With this specific arrangement, as solution  6  is introduced onto guide member  21  by way of entry port  14 , solution  6  will flow along guide member  21  in the manner illustrated in FIG.  1 . As shown in FIGS. 1 and 2, guide member  21  guides solution  6  onto drive roller  15  such that solution  6  forms a first bead  6   a  that extends above guide member  21  and between guide member  21  and an outer peripheral surface of roller  15 . Guide member  21  also causes solution  6  to form a second bead  6   b  in the vicinity of nip portion  19  which extends below guide member  21  and between guide member  21  and an outer peripheral surface of roller  17 . It is recognized that the present invention is not limited to the angles described above with respect to the positioning of rollers  15 ,  17  and guide member  21 . These angles could be varied depending on design considerations such as, for example, the type or viscosity of solution  6 . 
     The positioning of guide member  21  so that end  21   a  extends to a vicinity of nip portion  19  in the manner shown in FIG. 1, as well as the isolated view of FIG. 2, permits the formation of first and second beads  6   a,    6   b  as described above. With this arrangement, bead  6   a  deposited on the outer peripheral surface of roller  15  assures that roller  15  is maintained in a wet state by solution  6 ; while bead  6   b  formed in the vicinity of nip portion  19  assures that solution  6  is maintained at nip portion  19  and that photosensitive material introduced through entry port  11  will be evenly coated by solution which forms bead  6   b.  That is, the specific orientation of rollers  15 ,  17  and guide member  21  as illustrated in FIGS. 1 and 2, assures that solution  6  flowing along guide member  21  forms beads  6   a,    6   b,  and also assures the maintenance of solution at nip portion  19 . 
     Therefore, with the use of coating apparatus  5  as illustrated in FIG. 1, photosensitive material  7 , such as processed photosensitive material, exits the last station of a processing assembly  75  and is introduced into apparatus  5  by way of entry port  11 . Processing assembly  75  of a processing system could be a known arrangement which includes a series of tanks that include developer solution, bleach solution, fixer solution and washing solution; or a combination of bleach-fix solution and a wash/stabilizer solution. Each of the tanks would thereby represent steps in the developing process. After entering coating apparatus  5 , photosensitive material  7  is guided by the combination of the guide  30  and guide member  21  into nip portion  19  between rollers  15  and  17 . Viscous solution  6  is applied by way of entry port  14  onto guide member  21  and flows along guide member  21  so as to form first bead  6 a and second bead  6   b  as shown. First bead  6   a  extends along the outer peripheral surface of drive roller  15  so as to assure that drive roller  15  is maintained wet with solution  6 . Second bead  6   b  formed in the vicinity of nip portion  19  is located in front of nip portion  19  with respect to a conveying direction  100  of photosensitive material  7 . With this arrangement, photosensitive material  7  introduced into nip portion  19  will first flow into second bead  6   b  and be coated with viscous solution  6  as photosensitive material  7  passes nip portion  19 . 
     As described above, drive roller  15  can be a metering roller which meters viscous solution  6  applied to surface  7   a  of photosensitive material  7  as photosensitive material  7  passes through nip portion  19 . Metering roller  15  could be, for example, a known wire wrapped roller bar that can be set across photosensitive material  7  and applied against solution  6  coated on photosensitive material  7 . Metering roller  15  removes a desired amount of solution  6  in a controlled manner and leaves a desired thickness of solution  6  on photosensitive material  7 . Roller  17  which can be a pinch roller serves to remove excess solution from opposite surface  7   b  of photosensitive material  7 , and with roller  15  drives photosensitive material  7  through nip portion  19 . As photosensitive material  7  leaves nip portion  19 , a guide bar  22  positioned downstream of nip portion  19  serves to guide photosensitive material  7  to exit  35 , and if desired, can aid in scraping any further excess viscous solution from surface  7   b  of photosensitive material  7 . 
     After photosensitive material  7  having side  7   a  coated with viscous solution  6  leaves apparatus  3  via exit  35 , it can thereafter enter a dryer  37  schematically illustrated in FIG.  1 . Dryer  37  can be a known dryer which dries photosensitive material  7  by way of, for example, air blowers as described in copending applications U.S. Ser. Nos. 08/965,560, 08/965,639 and 08/965,105. As an alternative feature and based on design considerations, photosensitive material  7  can be first lead to, for example, a curing mechanism and thereafter a dryer or visa versa. 
     Also, as shown in FIG. 1, tank  9  can include a trough  39  into which roller  17  is partially submerged. Trough  39  collects solution  6  as it flows downward and leads solution  6  to a recirculation assembly  40 . Recirculation assembly  40  can include a pump  40   b  positioned in a conduit  40   a  connected to trough  39 . Recirculation assembly  40  can further include a filter module  40   d  connected to pump  40   b  which can remove solid contaminates from solution  6 , as well a heat exchanger  40   e  which can rapidly regulate the temperature of solution  6 . Recirculation assembly  40  is effective to recirculate solution  6  to a recirculating supply means (not shown) which is associated with entry port  14 . 
     Thus, with the mechanism illustrated in FIG. 1, guide member  21  assures that solution  6  applied from solution entry port  14  is delivered into a vicinity of nip portion  19  and forms beads  6   a,    6   b.  The formation of bead  6   a  assures that metering roller  15  will be maintained in a wet state with solution  6 , while the formation of bead  6   b  in the vicinity of nip portion  19  assures that photosensitive material  7  delivered to nip portion  19  will be evenly and consistently coated with solution  6 . 
     FIG. 3 illustrates a second embodiment  5 ′ of the apparatus of the present invention. As illustrated in FIG. 3, in this embodiment viscous solution supply port  14  supplies solution  6  directly onto roller  15 , such that solution  6  flows along the outer periphery of roller  15  to a vicinity of nip portion  19  between rollers  15  and  17 . Guide member  21  is positioned such that it will guide and maintain solution  6  at nip portion  19  and form a bead  6   c  in a vicinity of nip portion  19 . Thus, with the arrangement of FIG. 3, roller  15  is maintained in a wet state due to the application of viscous solution  6  onto roller  15 , while bead  6   c  is positioned in a vicinity of and in front of nip portion  19  with respect to conveying direction  100  of photosensitive material  7 . This arrangement assures that photosensitive material  7  entering apparatus  5 ′ will be lead into bead  6   c  and thereafter to nip portion  19 . This provides for an even and consistent coating of photosensitive material  7  with solution  6 . 
     The remaining features and mode of operation of coating apparatus  5 ′ as illustrated in FIG. 3 with respect to, for example, metering, recirculating, drying, etc. is the same as described with reference to FIG.  1 . 
     In a further feature of guide member  21  as illustrated in FIGS. 1-4, end  21   a  defines a slanted flat surface. Slanted flat surface of end  21   a′  is spaced from an outer periphery of roller  15  by a distance which assures the formation of first bead  6   a  and second bead  6   b  as described with reference to FIG. 1; and bead  6   c  as described with reference to FIG.  3 . Furthermore, as shown in FIG. 4, slanted flat surface of end  21   a  extends along a line  21   a′  which is substantially parallel to a line  60  that is tangent to the outer peripheral surface of roller  15  and faces slanted flat surface of end  21   a.  This applies to the embodiments of FIGS. 1 and 3. In a preferred embodiment of the invention as illustrated in FIG. 4, a distance between slanted flat surface of end  21   a  and line  60  which is tangent to the outer peripheral surface of roller  15  is within the range of approximately 0.5 to 1.5 mm. This range as well as the placement of rollers  15 ,  17  and guide member  21  as shown in FIGS. 1 and 3 promotes the formation of beads  6   a,    6   b  of FIG.  1  and bead  6   c  of FIG. 3 as previously described. It is recognized that the present invention is not limited to the range described above, and that depending on design considerations, such as the type or viscosity of solution applied, the range could be varied. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.