Abstract:
A process for forming a light-reflecting bar code on an end disc of photographic film spool is performed by the steps of placing on the end disc of photographic film spool a hot-stamp film comprising, in order, an adhesive layer, a light-reflecting metal layer, a transparent protective layer, a releasing layer, a support film, and a stain-shielding layer formed of material inhibiting migration of a compound having a low molecular weight from the support film (e.g., compound having a siloxane bonding or deposited inorganic oxide) in such manner that the adhesive layer is brought into contact with the end disc, and pressing for 0.1 to 2.0 seconds a stamper having a heated bar code-stamping die, so as to transfer the light-reflecting metal layer onto the end disc in the form of the bar code.

Description:
FIELD OF THE INVENTION 
     This invention relates to a process for forming a light-reflecting bar code on end disc of photographic film spool. 
     BACKGROUND OF THE INVENTION 
     In a known photographic film patrone of APS (i.e., Advanced Photo System), a light-reflecting bar code is generally provided on an end disc (or flange) which is attached to an end of the spool. The light-reflecting bar code gives encoded film data such as film sensitivity and the number of exposed frames, and thereby the film data can be photoelectrically recognized. The light-reflecting bar code can be formed, for example, by the process disclosed in Japanese Patent Provisional Publication No. 8-254794. In the disclosed process, a hot-stamp film having a light-reflecting metal layer such as aluminum foil is pressed onto an end disc of spool by a stamping die having the bar code on its surface, so as to transfer the light-reflecting metal layer onto the end disc in the pattern of the bar code. 
     Japanese Patent Provisional Publication Nos. 9-14622 and 11-133552 disclose a hot-stamping process and a hot-stamping apparatus for industrially and advantageously forming light-reflecting bar codes on an end disc of spool. The hot-stamping apparatus disclosed in Japanese Patent Provisional Publication No. 9-14622 is shown in the attached FIG.  2 . In FIG. 2, the hot-stamping apparatus  20  comprises a fixed holder  21 , a movable holder  24  which can move along the direction of arrow, and a stamper (i.e., bar code pattern transfer die)  27  by which a hot-stamp film  10  is pressed onto an end disc of spool. In the apparatus  20 , the spool  28  is made to stand in the fixed holder  21  with a tenon  22  and a supporting wall  23  so that the end disc  29  may be placed on the top. The spool  28  standing in the fixed holder  21  is then passed to a fork claw  25  provided on the movable holder  24 . The fork claw  25  has an independent cushion member  26 , and the cushion member  26  gives constant even force with which the stamper  27  presses the hot-stamp film  10  onto the end disc  29  of the spool  28 . (Hereinafter, this force is referred to as “stamping force”.) Thus, by means of the hot-stamping apparatus, a light-reflecting bar code can be formed on the end disc. In the process with the hot-stamping apparatus described above, bar code pattern-transferring troubles such as missing foil or forming fins at the foil edge can be avoided. Further, the disclosed bar code pattern-transferring process is also described to give plural light-reflecting bar codes in a relatively short time. 
     SUMMARY OF THE INVENTION 
     The applicants have noticed that transferring troubles often occurs when plural light-reflecting bar codes are successively formed on end discs of spools by means of the aforementioned apparatus. In fact, if one stamper is used in the transferring process to form 3,000 to 4,000 light-reflecting bar code patterns on end discs of the corresponding number, transferring troubles remarkably increase (troubles arise twice or more as frequently as those at the beginning). The applicants have studied this problem, and found that stains deposited on the stamper make the stamper surface uneven to cause the troubles. When a light-reflecting bar code is formed in the transferring process (i.e., when the stamper presses a hot-stamp film onto an end disc), the die surface of the stamper is stained. Accordingly, after 3,000 to 4,000 light-reflecting bar codes are formed on end discs (i.e., after the transferring process is repeated 3,000 to 4,000 times), accumulated stains make the die surface uneven and hence make stamping force so uneven as to cause the troubles. 
     Although the stains on the die surface of the stamper can be removed by washing, the process must be discontinued when the die surface is washed or exchanged. Consequently, the efficiency for producing light-reflecting bar code patterns is considerably impaired. 
     Accordingly; it is an object of the present invention to provide a process for efficiently forming light-reflecting bar code patterns on end discs of photographic film spools. In the process of the invention, the surface of die surface of the stamper is hardly stained. 
     The applicants have studied to achieve the object, and finally found that the stains on the-die surface of stamper can be avoided by a hot-stamp film having a stain-shielding layer provided on the face to be brought into contact with the die surface. 
     The present invention resides in a process for forming a light-reflecting bar code on an end disc of photographic film spool, comprising the steps of: 
     placing on the end disc of photographic film spool a hot-stamp film comprising, in order, an adhesive layer, a light-reflecting metal layer, a transparent protective layer, a releasing layer, a support film, and a stain-shielding layer formed of material inhibiting migration of a compound having a low molecular weight from the support film in such manner that the adhesive layer is brought into contact with the end disc and 
     pressing for a period of 0.1 to 2.0 seconds a stamper which has a bar code-stamping die heated to 150 to 200° C. so as to transfer the light-reflecting metal layer onto the end disc in the form of the bar code. 
     The support film of the hot-stamp film is preferably made of polyester resin, and the material inhibiting migration of a compound having a low molecular weight from the support film preferably is a compound having a siloxane bonding or deposited inorganic oxide. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 shows a schematic sectional view of an example of the hot-stamp film used in the process of the invention. 
     FIG. 2 shows a schematic view of the hot-stamping apparatus disclosed in Japanese Patent Provisional Publication No. 9-14622. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a schematic sectional view of an example of the hot-stamp film used in the process of the invention. In FIG. 1, a hot-stamp film  10  comprises a stain-shielding layer  11 , a support film  12 , a releasing layer  13 , a transparent protective layer  14 , a light-reflecting metal layer  15 , and an adhesive layer  16 . The releasing layer  13 , the transparent-protective layer  14 , the light-reflecting metal layer  15  and the adhesive layer  16  are formed in order on one face of the support film  12  (i.e., base film), and the stain-shielding layer  11  is formed on the other face of the support film  12  to prepare the hot-stamp film  10 . Each layer and film of the hot-stamp film is described below. 
     The stain-inhibiting layer  11  does not melt or decompose when it is pressed for a period of 0.1 to 2.0 seconds by the die surface heated at 150 to 200° C. The stain-shielding layer  11  can be formed by various processes such as applying and drying a coating liquid dissolving an appropriate material, ion beam irradiation process, chemical reaction deposition process and physical deposition process. From the viewpoint of production cost, the layer  11  is preferably formed by applying and drying the coating liquid. As the coating process for applying the liquid, various known processes such as gravure roll coating can be used. After drying the liquid, it may be hardened by heating or by irradiating with rays of far infrared, infrared or ultraviolet. The stain-shielding layer preferably has a thickness of 0.05 to 5.0 μm, more preferably 0.1 to 1.0 μm, if it is formed by applying and drying the coating liquid or by ion beam irradiation process. If the layer is formed by chemical reaction deposition process or by physical deposition process, the thickness preferably is 5 to 100 nm, more preferably 20 to 70 nm. 
     The stain-shielding layer is preferably formed, for example, by chemical reaction deposition or physical deposition of an inorganic compound such as silicon oxide, aluminum oxide or silicon nitride. It is also preferred to form the layer by applying and drying a coating liquid dissolving a siloxane bond-having compound such as silicone resin or a organic polysiloxane derivative. 
     Typical examples of the organic polysiloxane derivatives are those having the following formulas (1) to (3): 
     Organic polysiloxane derivative (1)                           
     [n is an integer of 2 to 10] 
     Organic polysiloxane derivative (2)                           
     [m is an integer of 2 to 10] 
     Organic polysiloxane derivative (3)                           
     [p is an integer of 2 to 10] 
     The organic polysiloxane derivatives (1) to (3) may be used singly or in combination. 
     The support film  12  may be a conventional film used as a base film for known hot-stamp films. Examples of the film employable as the support film include polyester films such as films of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and copolymer of polyethylene terephthalate and isophthalate; polyamide film; synthetic resin films such as cellulose acetate film; and films of machine-made paper (e.g., cellophane, glassine paper), Japanese paper and composites thereof. A polyester film, particularly a polyethylene terephthalate film, is preferred in consideration of thermal stability and dimension stability. The support film preferably has a thickness of 10 to 30 μm. 
     The releasing layer  13  can be formed by the steps of coating the support film with a coating liquid in which a material such as synthetic resin, wax and a surface active agent is dissolved in a solvent according to known coating processes such as gravure roll coating, and drying (and, if needed, hardening by heating or by irradiating with rays of far infrared, infrared or ultraviolet). Examples of the synthetic resins include acrylic resins, urethane resins, urethane-acryl copolymers, melamine resins, urea resins, urea-melamine resins, silicone resins, cellulose resins and benzoguanamine resins. Examples of the waxes include paraffin wax and ester wax. The releasing layer preferably has a thickness of 0.01 to 0.15 μm. 
     The transparent protective layer  14  can be formed by the steps of coating the releasing layer with a coating liquid in which synthetic resins (such as acrylic resins, urethane resins, urethane-acryl copolymers, melamine resins, urea resins, urea-melamine resins, silicone resins, cellulose resins, rosin modified maleic acid resins, benzoguanamine resins and mixture thereof) are dissolved in a solvent according to known coating processes such as gravure roll coating, and drying (and, if needed, hardening by heating or by irradiating with rays of far infrared, infrared or ultraviolet). The protective layer preferably has a thickness of 1 to 5 μm. 
     The light-reflecting metal layer  15  is made of a light-reflecting metal. Examples of the light-reflecting metals include aluminum, chromium, nickel, titanium, gold, silver, platinum, zinc, silicon and an alloy thereof. The layer can be formed by known film-forming processes such as vacuum deposition process, spattering process and ion-plating process. Generally, aluminum foil formed by vacuum deposition process is used. The light-reflecting metal layer preferably has a thickness of 30 to 120 nm. 
     The adhesive layer  16  is made of an organic solvent-soluble adhesive agent, an emulsion adhesive agent or a water-soluble adhesive agent. The organic solvent-soluble adhesive agent mainly comprises resins such as acrylic resins, vinyl acetate resins, vinyl chloride resins, styrene-butadiene copolymers, acryl-styrene copolymers, vinyl chloride-vinyl acetate copolymers, polyester resins, chlorinated rubbers, chlorinated polypropylene, urethane resins or mixtures thereof. The layer can be formed by coating the light-reflecting metal layer with the adhesive agent according to known coating processes such as gravure roll coating, and drying. The adhesive layer preferably has a thickness of 0.5 to 5 μm. 
     A light-reflecting bar code is formed from the hot-stamp film onto an end disc of photographic film spool by the pattern-transferring process by means of a hot-stamping apparatus. In the process, the hot-stamping apparatus disclosed in Japanese Patent Provisional Publication Nos. 9-14622 and 11-133552 can be used. The stamper (or die surface) is heated to a temperature of 150 to 200° C., preferably 160 to 180° C. The period of time for which the hot-stamp film is pressed by the stamper (or die surface) is in the range of 0.1 to 2.0 seconds, preferably 0.2 to 0.6 second. There is no specific limitation with respect to the material of the stamping die. Examples of the material include metals (such as brass and copper alloy) and rubbers (such as silicone rubber and fluororubber). In consideration of hardness and thermal conductivity, brass is preferred. 
     EXAMPLE 1 
     (1) Preparation of Hot-stamp Film 
     Onto one face of a polyethylene terephthalate film (support film) of 12 μm thick, a coating liquid in which ester wax was dissolved was coated by the gravure roll coating process. The coated liquid was dried to form a releasing layer of 50 nm thick. The releasing layer was then coated with a solution in which rosin modified maleic acid resin, urea-melamine resin and polyisocyanate (hardening agent) were dissolved, according to the gravure roll coating process, and the coated solution was then dried to form a protective layer of 1.1 μm thick. On the protective layer, an aluminum layer (light-reflecting metal layer) of 50 nm thick was formed by vacuum deposition process. The aluminum layer was further coated with a coating solution in which acrylic resin, acrylstyrene resin and vinyl chloride-vinyl acetate copolymer resin were dissolved, according to the reverse roll coating process, and the coated solution was then dried to form an.adhesive layer. Onto the other face of the polyethylene terephthalate film (support layer), a coating solution in which the organic polysiloxane derivatives of the formulas (1) to (3) in a mixed solvent of isopropyl alcohol and n-butanol (content of the organic polysiloxane derivatives: 5 wt. %) was coated by the gravure roll coating process. The coated solution was dried with hot blow, and then further dried with far infrared rays to form a stain-shielding layer. Thus, a hot-stamp film was prepared. 
     (2) Process for Forming Light-Reflecting Bar Codes on End Discs of Photographic Film Spools 
     The above-prepared hot-stamp film was placed in the hot-stamp apparatus shown in FIG. 2, and then light-reflecting bar code pattern was successively formed on end discs of photographic film spools by the transferring process. The formed bar code patterns were observed, and the number of the stamped end discs were counted until the transferring troubles arose twice or more as frequently as those at the beginning. In the process, a brass stamper die was used and heated at 170° C., and the hot-stamp film is pressed by the stamper die for 0.4 second to form each bar code. The result is set forth in Table 1. 
     COMPARISON EXAMPLE 1 
     A hot-stamp film was prepared by the process of Example 1, except that no stain-shielding layer was formed. Using thus prepared hot-stamp film, the procedure of Example 1 was repeated to successively form the light-reflecting bar code pattern on end discs of photographic film spools by the transferring process. The formed bar codes were observed, and the number of the stamped end discs were counted until the transferring troubles arose twice or more as frequently as those at the beginning. The result is also set forth in Table 1. 
     
       
         
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 number of end discs 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Example 1 
                 60,000 
               
               
                   
                 Comparison Example 1 
                 3,000 
               
               
                   
                   
               
             
          
         
       
     
     The results given in Table 1 indicate that the stain-shielding layer on the hot-stamp film increases the number of the stamped end discs by about 20 times or more until the transferring troubles arise frequently. Accordingly, if the hot-stamp film having the stain-shielding is used in the process for forming light-reflecting bar codes, the frequency of washing the stamper die surface can be reduced by {fraction (1/20)} or less. 
     Consequently, the process of the invention enables one stamper die to stamp increased number of light-reflecting bar codes onto end discs of spools without increasing the transferring troubles. Further, since the frequency of washing the stamper die surface can be reduced, the production efficiency is improved and the stamper die surface hardly wears away.