Patent Publication Number: US-2005126406-A1

Title: Die plate for a foil stamping machine

Description:
TECHNICAL FIELD  
      The present invention relates to the field of graphic arts and more particularly to die plates employed in stamping machines such as foil stamping machines.  
     BACKGROUND OF THE INVENTION  
      Described in International Patent Publication No. WO 00/67953 and U.S. Pat. No. 5,904,096 are methods and apparatus relating to foil stamping.  
      The above-discussed publications disclose a magnetic holding device to secure a steel-backed polymer die plate to a foil stamping heating element.  
      Conventionally, the die plates are rigid, except for silicon rubber dies. Typically, the image layer is provided by magnesium, brass, copper, steel, zinc or a photo-polymer. However, there is required within the process some compressibility to ensure a quality image is applied to the substrate. Conventionally, the compression takes place in the packing, that is, the material behind the substrate.  
      It is also the practice in foil stamping to correct low points in the die plate by inserting material behind the packing. Typically, this material is paper or plastics and is fastened in position by means of glue or tape. When the die plate is to be replaced or re-positioned the clean-up will generally require the use of a flammable solvent. Accordingly, the conventional mounting of die plates is time-consuming and requires the undesirable use of flammable solvents.  
     OBJECT OF THE INVENTION  
      It is the object of the present invention to overcome or substantially ameliorate the above disadvantage.  
     SUMMARY OF THE INVENTION  
      There is disclosed herein a die plate for a stamping machine, the die plate including: 
          a plate steel back to be secured to the machine;     a metal impression layer secured to the steel back and to engage a substrate to impart an image thereto upon pressure being applied to the die plate and substrate by the machine; and     a compressible adhesive securing the image layer to the steel back.        

      Preferably, the compressible adhesive is an acrylic polymer.  
      Preferably, the impression layer is formed of brass, steel, copper, zinc, magnesium, aluminium or photo-polymer.  
      Preferably, said die plate has iron embedded in the adhesive.  
      Preferably, the adhesive is an epoxy resin.  
      In one preferred form, the iron embedded in said adhesive is in a particle form.  
      In a further preferred form, the iron embedded in said adhesive is in the form of a mesh.  
      In a further preferred form, the iron embedded in said adhesive is in the form of a perforated plate. Preferably, the plate is 0.25 mm to 1 mm in thickness. Preferably, the thickness is about 0.25 mm or 0.6 mm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings wherein:  
       FIG. 1  is a schematic side elevation of a foil stamping machine within which there is located a die plate to apply an image to a substrate;  
       FIG. 2  is a schematic sectioned side elevation of the die plate employed in the machine of  FIG. 1 ;  
       FIG. 3  is a schematic side elevation of the foil stamping machine of  FIG. 1  with a modified die plate; and  
       FIG. 4  is a schematic side elevation of the foil stamping machine of  FIG. 1  with a further modified die plate. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      In  FIGS. 1 and 2  of the accompanying drawings there is schematically depicted a foil stamping machine  10 . The machine  10  includes a base  11  upon which there is pivotally mounted a platen  12 . Secured to the base  11  is a bed  13  which is electrically heated by means of heating elements  23 . Secured to the bed  13  is a magnetic holding device  16 . Typically, the device  16  would be the magnetic holding device described in either of the above-mentioned patent publications.  
      Secured to the device  16  by magnetic attraction are die plates  14  and  15 . To cooperate with the die plates  14  and  15  is a jacket member (packing)  17 , which is secured to the platen  12 , having image portions  18 . Preferably, the member  17  is a non-magnetic stainless steel or other non-magnetic metal. The image portions  18  are typically formed of fibreglass. If a foil image is to be applied to a substrate  19 , a foil layer ( 27 ,  FIGS. 3 and 4 ) is located between the substrate  19  and the die plate  14 . The platen  12  applies pressure to the substrate  19  and the foil layer, so that the image is applied to the substrate  19 . In addition, the bed  13  heats the die plate  14  to aid in transfer of the foil to the substrate  19 .  
      Each of the die plates  14  and  15  includes a plate steel back  20  to which there are secured image layers  21  and  24  respectively. The layer  21  is secured to the back  20  by means of a compressible adhesive  22 . Preferably, the adhesive  22  is an acrylic polymer. The image layer  21  is formed of metal, such as brass, steel, copper, zinc, aluminium, photo-polymer or magnesium, while the layer  24  is formed of a photo-polymer. The above-described preferred embodiments provide the advantage of eliminating the use of having to insert material to “make up” low spots. Accordingly, the above-described preferred embodiment is time-efficient and eliminates the use of flammable solvents.  
      The above-described preferred embodiment also offers the advantage of substantially ameliorating the crushing and distortion of the substrate, which is of particular interest in security and anti-counterfeiting applications. Preferably, in the case of the die plate  14 , the plate steel back  20  would have a thickness of about 0.25 mm and the image layer of a thickness of about 1.50 mm. In respect of the die plate  15 , preferably the plate steel back  20  would have a thickness of about 0.6 mm and the image layer (photo-polymer) a thickness of about 1.15 mm.  
      Accordingly, the die plates  14  and  15  would each have a total thickness of about 1.75 mm.  
      The above-described preferred embodiment lends itself to the processes of flat-foil stamping, embossing, de-bossing, die-cutting, perforating, top-slitting and a combination of foil stamp embossing and de-bossing.  
      In  FIGS. 3 and 4  of the accompanying drawings, a modified die plate  14  is being used with the machine  10 . More particularly, the adhesive layer  22  has embedded in it iron in various forms. The iron has been provided to aid in maintaining the die plates  14  and  15  generally planar. That is, to inhibit distortion due to different heat expansion rates.  
      In the embodiment of  FIG. 3 , the iron is in the form of iron particles  25 . More preferably, the adhesive  22  within which the iron particles  25  are embedded has a thickness of about 0.25 mm to 1 mm, preferably about 0.25 mm or about 0.6 mm.  
      In the embodiment of  FIG. 4 , the adhesive  22  has embedded in it iron in sheet form. For example the sheet form could be woven or non woven mesh or alternatively, perforated iron plate  26 . In respect of the plate  26 , it would have a thickness of 0.25 mm to 1 mm (preferably about 0.25 mm or about 0.6 mm), with the adhesive  22  extending through the perforations in the plate  26 .  
      In the embodiment of  FIGS. 3 and 4  preferably, the adhesive  22  is an epoxy resin. In that respect, it should be appreciated that the epoxy resin is slightly less compressible than the acrylic polymer used with the embodiment of  FIGS. 1 and 2 . An alternative adhesive is a phenolic based resin.