Abstract:
A die and a method for forming a die to produce optically varying effects in a light reflective surface. A design generally formed as a plurality of parallel grooves of varying widths and depths are engraved in a soft metal foil adhered to a substrate. A hard metal coating is formed on the engraved soft metal foil in a metal plating bath. The hard metal coating, removed from the soft metal foil provides a die formed as a mirror image of the grooves engraved in the soft metal foil. The die is used to deform a reflective surface such that the surface produces optically varying effects. A die formed in the same manner with further processing is used to both deform a reflective surface and hot stamp it to a substrate.

Description:
This application claims the benefit of Provisional Application No. 60/073,008 filed Jan. 29, 1998 
     This application is a division of copending U.S. application Ser. No. 09/238,846, filed Jan. 28, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the production of interesting optical effects by grooves formed in a light reflecting surface, and more specifically, this invention relates to a method and apparatus for mass producing light reflecting surfaces having grooved surfaces. 
     2. Description of the Prior Art 
     It is known that various interesting and pleasing optical effects can be achieved by placing grooves or lines in a reflecting surface, such as a metallic foil. An example of a use of these optical effects may be found in certain handmade greeting cards. 
     While the effects achieved with such reticulated prior art arrangements can be quite impressive, they have been limited in applicability because of the inability to mass produce such grooves surfaces. Previous attempts to hot stamp metallic foil or other light reflecting surfaces in web printing have not been very successful. 
     Since there are many uses for the optical effects that may be achieved with lined surfaces of this type, a process by which such items could be mass produced, such as by using a web type press, would be most beneficial. The limited number of such items which can be hand or individually produced is economically unfeasible for many applications which would be feasible with a web type press production method. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of mass producing reticulated devices that have desirable optical effects. In accordance with this invention, a hand or computer generated engraving is first made in a relatively soft deformable metal foil which is secured to a more rigid substrate, with an intervening deformable material therebetween, which together form a laminated structure. Using suitable hand engraving tools, having engraving edges of varying sizes and shapes, a hand engraved design is formed in the metal foil. An engraved design may also be generated by a computer and engraved by computer controlled engraving tools. The design is typically formed by making a plurality of parallel depressions in the foil. The parallel depressions are made of varying depths and widths by the use of various tools, and by manipulating each of the tools, such as by rotating and by applying variable pressures to the tools. In forming the parallel depressions of varying widths and depths, the metal foil is depressed into the deformable material, which retains the shape of the parallel depressions formed in the metal foil, and provides backup support to the deformed foil. 
     The laminated structure, with an engraved design formed therein, is placed in a metal plating bath, in a plating tank, to form a relatively hard metal coating over the engraved soft deformable metal foil. The laminated structure is maintained in the metal plating bath for a sufficient length of time to form a hard metal coating on the soft metal foil, which coating is of sufficient strength to be used as a die which is in the form of a mirror image of the grooves first formed in the soft deformable metal foil. The die may then be used to form grooves, corresponding to those first engraved in the soft deformable metal foil, in a metal foil, a metallized Mylar foil, or similar material which is capable of being deformed to the shape of the hand or computer controlled engraved grooves. 
     Upon being removed from the metal plating bath, the laminated structure, and more particularly the soft metal foil, is separated from the hard metal coating. The hard metal coating thus forms a hard metal plate having a mirror image of the engraved design therein. While the metal plate is hard in the sense of retaining the engraved surface thereon, it is also, in its entirety, somewhat flexible. That is, while it is generally formed as a flat surface, it can be resiliently bend into a curved form. One side of a substrate, which has an adhesive on both sides, is secured to the back side of the hard metal plate which was separated from the soft metal foil. The hard metal plate is then secured to the drum of a web type printer by the adhesive on the second side of the substrate. With the hard metal plate secured to the web printer drum, the web printer may be used to apply the originally hand or computer formed engraving, to a material engaged by the hard metal plate on the drum, as it is passed through the web type printer. 
     One of the preferred metals for use in the metal plating bath to form the hard metal coating is a compound containing a significant amount of nickel and also iron. However, other metals having similar desirable characteristics may also be used. Typically, of the materials to which the engraving may be imparted are metal foils, metallized Mylar, and other highly reflective materials. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a laminated structure in accordance with the present invention having a surface suitable for engraving; 
     FIG. 2 shows the laminated structure of FIG. 1 being hand engraved; 
     FIG. 3 shows the engraved laminated structure of FIG. 2 being metal plated in a metal plating bath; 
     FIG. 4 shows the laminated structure being separated from the metal plating applied in the metal plating bath as shown in FIG. 3; 
     FIG. 5 shows the metal plate with a substrate secured thereto, which substrate is provide with an adhesive on each side; and 
     FIG. 6 shows the metal plate applied to the drum of a web type printer. 
     FIG. 7 shows a cross-section of a portion of an engraved soft deformable metal foil, and a metal plate formed therefrom in accordance with a second embodiment of this invention. 
     FIG. 8 shows the metal plate of FIG. 7 used to hot stamp foil to a paper board. 
     FIG. 9 shows a partial cross-sectional view of foil hot stamped to a paper board in accordance with the second embodiment of this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, in accordance with the method of this invention, a hand or computer generated engraving is first made in a soft aluminum foil which is secured by a pressure sensitive material to a plastic substrate, forming a laminated structure  10  suitable for engraving. A soft deformable metal foil  12 , such as aluminum foil, is secured to a deformable substrate  14 , such as a plastic substrate, by a layer of pressure sensitive material  16 , which has the desired adhesive properties to adhere to the soft deformable metal foil  12  and the deformable substrate  14 . In a preferred embodiment of this invention, the soft deformable metal foil  12  is an aluminum foil approximately 0.0003″ thick, the pressure sensitive adhesive material  16  is preferably at least as thick as the aluminum foil  12 , and the deformable substrate is formed of a plastic sufficiently strong to provide a somewhat rigid backing for the aluminum foil  12  and pressure sensitive material  16 . A plastic substrate approximately ⅛″ thick has been found to provide the desired backing for a suitable laminated structure upon which engraving may be undertaken. 
     Referring to FIG. 2, using suitable hand engraving tools, one of which is shown as  18 , an engraved design  20  is formed in the aluminum foil  12 . The hand engraved design is typically formed by making a plurality of parallel depressions in the foil, typically 100 per inch. The parallel depressions are made of varying depths and widths by the use of various tools, and by manipulating, such as by rotating and applying variable pressure to the tools. In forming the parallel depressions of varying widths and depths, the aluminum foil  12  is depressed into the pressure sensitive material  16 , which is formed of a material which will retain the shape of the parallel depressions formed in the aluminum foil. The depressions may be as deep as the thickness of the aluminum foil  12 . 
     Referring to FIG. 3, the laminated structure  10 , with an engraved design  20  formed therein is placed in a nickel or other suitable metal plating bath  22  in a plating tank  24  to form a hard metal coating  26  on the engraved soft deformable metal foil. The laminated structure  10  is maintained in the bath  22  for a sufficient length of time to form a hard metal coating, which is approximately 0.010 inches thick, on the aluminum foil  12 . 
     Referring to FIG. 4, upon being removed from the bath  22 , the laminated structure  10  is separated from the hard metal coating  26 . That is, the aluminum foil  12  is separated from the hard metal coating  26 . The hard metal coating  26  thus forms a hard metal plate  28  having the mirror image of the engraved design formed therein. 
     Referring to FIG. 5, one side of a substrate  30 , which has an adhesive on both sides, is applied to the side of the hard metal plate  28  opposite that which was separated from the soft deformable metal foil  12 . Referring to FIG. 6, the hard metal plate  28  is then secured to a drum  32  by the adhesive of the second side of the substrate  30 . With the flexible hard metal plate completely encircling and secured to the drum  32 , it may be used in a web printer for applying engraving to a material  34  engaged by the hard metal plate on the drum. Typically, of the materials to which the engraving is imparted are metal foils, metallized Mylar, and other highly reflective materials. 
     While in the preferred embodiment, the thickness of the soft aluminum foil is 0.0003″ thick, it has also been found that foil up to approximately 0.0007″ may be used in accordance with this invention. It has also been found, depending up various variable characteristics of a web type printer, that the hard metal plate which is formed to be placed a web printer drum may be up to approximately 0.030″ thick. 
     In another or second embodiment of this invention, the hard metal plate or die  28  is further processed, such that it may be used to hot stamp a metal foil to a substrate such as a paper board in grooves corresponding to those first formed in the soft deformable metal foil. Machinery has recently been developed for providing a station, in a line on a web press, to hot stamp foil on continuous rolls of paper board. These web presses are primarily intended to print paper board used by the folding carton industry. The station is formed of two sets of two cylinders. Each set has an upper magnetic roller that holds a thin double level plate and a base roller that has a rubber compound cover with a hardness just softer than steel. As the web passes through the first set of cylinders, foil is applied with heat and pressure in a very smooth mirror like finish to the underlying continuous roll of paper board. The second set of cylinders engraves a computer generated hologram image to the foil. 
     In accordance with the second embodiment of this invention, the further processed hard metal plate or die  28  is affixed to the magnetic cylinder which applies the foil, such the foil is simultaneously applied and embossed on the paper board. Using the modify die  28  in this manner, the foil is only applied to the paper board in grooves corresponding to those first formed in the soft deformable metal foil. 
     Referring to FIG. 7, the further processing of the hard metal plate or die  28  in accordance with the second embodiment of this invention will be described. The soft originally engraved metal foil  12  is shown with grooves  20  formed therein. The hard metal plate  28  formed as a hard metal coating  26  on the engraved metal foil  12  in a plating tank is shown positioned above the engraved metal foil  12 . As originally formed in the plating tank  24 , the hard metal plate  28  is approximately 0.025 inches thick as represented by the dimension “A”. Since the electroform plating process does not usually result in a uniform thickness, the back of the plate  28  is machined or ground to provide a plate of uniform thickness of approximately 0.020 inches as represented by the dimension “B”. The projections  36  on the engraved side of the plate, which represent mirror images of the grooves first formed in the soft deformable metal foil are provided with a protective coating  38 , such that when the engraved side is exposed to an acid for etching, the projections  36  are not etched. The etching is continued until the hard metal plate  28  is etched to a depth of approximately 0.012 inches, as represented by the dimension “C”. Thus, the hard metal plate is left with a base thickness of 0.008 inches as represented by the dimension “D”. The projections  36  as formed in the plating tank  24  are approximately 0.0003 inches high as represented by the dimension “E”. 
     Referring to FIG. 8, the hard metal plate  28 , as formed in the second embodiment is secured to the upper roller  40  of a set of rollers  40  and  42  forming the set of roller in a station to hot stamp foil on a continuous roll of paper board. The upper roller  40  has a magnetic layer  44  which is used to secure the hard metal plate  28  to the roller. The lower  10  roller  42  has a rubber compound cover with a hardness just softer than steel for materials up to 0.010 inches thick. For thicker materials a steel cover may be used. As a continuous strip of paper board  46  is feed between the rollers  40  and  42 , a continuous strip of foil  48  is fed on top of the paper board  46  and under the hard metal plate  28 . The only portions of the hard metal plate  28  which contact the strip of foil  48  are the projections  36 . Thus, the only portions of the foil strip  48  which are hot bonded or stamped to the paper board  46 , are those pressed by the projections  36  into the paper board  46 . The remaining portions  50  of the foil strip are drawn away from the paper board  46 . As shown in FIG. 9, foil  52  is only bonded to the paper board in the depressions  54  formed by the projections  36 . Further, the areas  56  between the depressions  54  is forced upward, thereby embossing the paper board  46 . As previously set forth, a second set of cylinders may be employed to engrave a computer generated hologram image on the foil  52  bonded in the depressions  54 . 
     While only two embodiments of the invention have been shown and described, it should be apparent to those skilled in the art that what have been described are considered at present to be preferred embodiments of the device and method of this invention. In accordance with the Patent Statute, changes and modification, may be made in the methods and devices of this invention without actually departing from the true spirit and scope of this invention. The appended claims are intended to cover all such changes and modification which fall in the true spirit and scope of this invention.