Abstract:
A method for making a medium for transferring a univocal pattern, comprising the steps of preparing a transfer medium ( 1 ) provided with a transfer surface ( 2 ), preparing an amount of encapsulated microdrops ( 3 ) of color, applying a layer of adhesive material ( 4 ) or other material or technique adapted to stably withhold said micro droplets at least on said transfer surface, randomly distributing an amount of encapsulated microdrops of color at least on said surface. Apparatus for implementing the method and medium thereby obtained.

Description:
TECHNICAL SECTOR OF THE INVENTION 
       [0001]    The invention relates to a method and an apparatus for making a transfer medium, e.g. a ribbon or a film, coated with a layer of encapsulated microdrops of color anchored to the medium. 
         [0002]    In different preferred applications, the invention relates to the complete or partial coating with microdrops of a continuous ribbon woundable on a spool or to a medium for graphic printing lines, or again to media in form of individual sheets. 
         [0003]    The invention further relates to a method and apparatus for printing a univocal pattern by means of the medium thus obtained, e.g. by transferring the color from the transfer medium to a different medium, either on or off the graphic printing line, thus making the pattern directly on the transfer medium. 
       PRIOR ART 
       [0004]    The idea of micro encapsulating colors to be printed to create univocal, differentiated patterns is known in the sector of graphic printing in general. 
         [0005]    This solution is described in International Application publications WO2008059552 and WO2010001203 by this inventor. In this an innovative printing system, different color micro capsules are mixed with a paint and randomly and indiscriminately distributed on a basic medium, and then crushed by pressure to obtain univocal printed signs, different from one another. 
         [0006]    The systems described in WO2008059552 and WO2010001203, which are quoted herein as a whole, are a major innovation in the graphic printing sector, but the inventor has found that the industrial application of the system can be further improved. 
         [0007]    A limitation of the prior art is indeed the relative rigidity of the procedure for making univocal patterns, in particular if it is necessary or preferable to apply the encapsulated microdrops of color off the printing line in various product sectors. 
       OBJECT OF THE INVENTION 
       [0008]    It is the object of the present invention to suggest a method and an apparatus for making a medium for transferring univocal patterns with one side coated with encapsulated microdrops of color, which, by means of dry crushing in contact with a printing medium, breaks the microdrops thus creating and printing a pattern which is different each time. 
         [0009]    A further object of the invention is to suggest a method and an apparatus for making a univocal pattern during graphic printing. 
       SUMMARY OF THE INVENTION 
       [0010]    These objects are reached by a method and an apparatus according to at least one of the appended claims. 
         [0011]    A first advantage is in that the method and the apparatus for making the transfer medium are extremely simple to apply and use, and can be implemented either on or off the graphic printing process line. 
         [0012]    A second advantage is in that the colored univocal pattern thus obtained may be used to customize each single print and be adopted as anti-counterfeiting system. 
     
    
     
       LIST OF DRAWINGS 
         [0013]    These and further advantages will be better understood by a person skilled in the art from the description that follows and the accompanying drawings, provided by way of non-limitative example, in which: 
           [0014]      FIG. 1  diagrammatically shows the sequence of steps of a method for making a transfer medium according to the invention; 
           [0015]      FIG. 2  diagrammatically shows an apparatus according to the invention for transferring a univocal pattern onto a printing medium; 
           [0016]      FIG. 3  diagrammatically shows some possible techniques for applying encapsulated microdrops of color onto a transfer medium; 
           [0017]      FIG. 4  shows a possible diagram of an apparatus for making a transfer medium according to the invention; 
           [0018]      FIG. 5  shows a possible diagram of an apparatus for making a transfer medium according to the invention on-line with a univocal pattern printing device; 
           [0019]      FIG. 6  shows a diagram of a preferred embodiment of an apparatus according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The figures show a method for making a univocal pattern during graphic printing by crushing encapsulated microdrops of color. 
         [0021]    The method includes making a transfer medium  1  of the univocal pattern, e.g. a thin polyester film, with one side completely coated with a compact layer of encapsulated microdrops  3  of color, anchored to the paper medium by means of an adhesive  4 , preferably a transparent high-adhesion, fast-drying varnish, or by means of glues, resins, inks or any other system adapted to make the microdrops adhere to the material of the medium. 
         [0022]    Preferably, in an embodiment of the method, reflecting glitter or phosphorite or other micro particles which allow better visibility of the printed pattern but which cannot be replicated by photocopying or scanning, may be mixed to the encapsulated microdrops. 
         [0023]    This solution consequently allows to preliminarily check authenticity of the patterns as anti-counterfeiting function by checking whether the added micro particles are present in the pattern or not. 
         [0024]    Advantageously, if the transfer medium is in the form of continuous ribbon, the medium  1  with the encapsulated microdrops of color may then be wound on a spool  10  ( FIG. 4 ) to be inserted in a complete apparatus for making the transfer medium and printing on a printing base medium  24  ( FIG. 2 ). 
         [0025]    By way of example, such an apparatus comprises a first unwinder/winder W 1  which moves the transfer medium  1  and a second unwinder/winder W 2  which moves the printing medium  24 . 
         [0026]    A printing assembly  20 , comprising for example a roll  20  with plate  26  and counter roll  27 , is provided between the two unwinders. 
         [0027]    In operation, the medium  1  with the encapsulated microdrops of color is mated and inserted together with the medium to be printed  24  between the plate roll and the counter roll. The microdrops of color are broken by the pressure exerted by the plate roll and by the counter roll, thus creating the printing of a differentiated, univocal pattern on the medium  24 . 
         [0028]    With reference to  FIG. 1 , the transfer medium is obtained by means of a series of opposite rolls, thus providing a compact, uniform layer  4  of adhesive, preferably a high-viscosity, quick-drying varnish which is reactive to UV lamps or IR infrared lamp, air ovens or any other system for drying the color and making it strong and constant over time, on one side of the medium  1  only (step f 1 ). 
         [0029]    The glued medium  1  advances and passes under a container  8  filled with encapsulated microdrops  3  of color, e.g. of the size of 30-60 micron, which by means of a sieve (step f 2 ) distributes them indiscriminately on the entire surface underneath, previously treated with high-adhesion varnish. 
         [0030]    Finally, the medium carrying the varnish and the encapsulated microdrops of color passes under a UV lamp or an IR infrared lamp, in air ovens or any system for drying the color and making it strong and constant over time (step f 3 ), which dries it immediately and anchors the encapsulated microdrops of color onto the surface of the same. 
         [0031]    Advantageously, in the case of continuous ribbon-like medium  1 , the medium thus obtained is packed and wound on a spool  10  ( FIG. 2 ) to then be used in a later printing process, e.g. by means of dry transferring of the microdrops, which when crushed during graphic printing, impress a univocal, multicolor drawing onto a printing medium  24  coupled thereto. 
         [0032]    In a preferred embodiment of the method, the medium carrying the microdrops, before being wound on the spool  10 , may be subjected to crushing and subsequent application of a layer of transparent varnish. 
         [0033]    Advantageously, a transfer medium carrying the univocal patterns to be transferred which may be used in particular for heat transfer techniques, is obtained with this solution. 
         [0034]      FIG. 3  diagrammatically shows various procedures (provided by way of non-limitative examples) for applying the encapsulated microdrops  3  of color onto the transfer medium. In particular, the figures show a technique by means of immersion in a chemical reaction container ( 8   a ), by roller printing ( 8   b ), indiscriminate or regulated dispersion ( 8   c ), silk-screen printing and spreading ( 8   d ) or vertical immersion in a tank. 
         [0035]    We will now briefly illustrate the printing apparatus in  FIG. 2 , which inserted on normal graphic printing lines allows to provide a differentiated, univocal pattern on a printing support  24 . 
         [0036]    The spool  10  with the encapsulated microdrops of color is inserted in a winder-unwinder W 1  with the side of the ribbon  25  with the encapsulated microdrops of color facing the inside of the spool. 
         [0037]    A winder-unwinder w 2  underneath conveys a printing medium  24 , e.g. paper, onto which the univocal pattern will be printed, by dry transfer in this illustrated case, on the line. 
         [0038]    Both the medium  1  with the layer of encapsulated microdrops of color and the paper to be printed pass between a roll  26  with plate  20  and a counter roll  27  in contact with the coupled media  1 ,  24  which break the microdrops of color by pressure. 
         [0039]    With this solution, the microdrops, by breaking in direct contact with the paper underneath, create each time univocal patterns which is are differentiated for the color and the random positioning of the microdrops. 
         [0040]    Advantageously, the method and apparatus thereof described above is simple to apply and manage, and may be inserted either on or off a graphic printing process line in which the univocal color pattern obtained customizes each single print allowing use as anti-counterfeiting system on any printing line in general, and on various printing media, such as paper, ceramic, glass, metal, plastic which require the printing of a univocal pattern. 
         [0041]    A preferred embodiment for making a transfer medium in form of continuous ribbon is shown now in  FIG. 4 . 
         [0042]    A ribbon  1 , e.g. a transparent polyester ribbon, departs from a unwinding spool  9 , which passes into a gluing assembly  7  provided with rolls  11  which spread glue on the inner side  25  of the ribbon. 
         [0043]    The ribbon is then made to transit on a layer of encapsulated microdrops  3  of color distributed in a container  13 . 
         [0044]    The inner part  25  of the transparent polyester ribbon spread with glue, in contact with the microdrops make them adhere and create a compact, uniform surface coat. Finally, the ribbon is wound on a spool  10 . 
         [0045]    With reference to  FIG. 5 , the same procedure may be essentially adopted for printing a univocal sign either on or off a normal line during graphic printing. 
         [0046]    In such a case, by means of the rolls  11 , which may carry engraving of any shape or pattern, a portion of adhesive, e.g. high-adhesion varnish, having any pattern, is applied onto the medium  1 . 
         [0047]    The medium  1  carrying the adhesive portions with the pattern passes on the microdrops  3 , which are glued onto the adhesive portion and repeat the pattern thereon. 
         [0048]    Afterwards, by passing between the two rolls  26 ,  27 , the microdrops of color pressed by the rolls are broken and create a univocal drawing on the printed medium which may be wound on a spool  34 . 
         [0049]    In greater detail, in the described embodiment, a ribbon  1  departs from the unwinder spool  9  and then passes into the roll assembly, named glue spreader  11 , which either entirely or partially spread glue on the inner side  25  of the ribbon. 
         [0050]    In the following segment, the ribbon is conveyed downward and held taut by two conveyor rolls  12  which make the microdrops of color adhere totally to the inner part of the transparent polyester ribbon spread with glue. 
         [0051]    Preferably, an electrostatic or electromagnetic induction strain-relieving blow pressure or friction plate  14  may be used for a more complete, total coverage of the adhesive surface of the medium  1  with the encapsulated microdrops of color. 
         [0052]    Advantageously, if an electrostatic induction plate is used, it will be possible to attract colored, organic micro particles, e.g. salt or sugar, preferably of size from 100 to 600 micron, by way of non-limitative example, in addition to microdrops. 
         [0053]    Furthermore, if an electromagnetic induction plate is used it will be possible to attract variably colored ferrous micro particles, preferably of size from 100 to 600 micron, by way of non-limitative example, in addition to microdrops. 
         [0054]    Moreover, the upper part of the ribbon  1  may pass in an electrostatic load neutralizer, an air or suction barrier  15  which lets possible microdrops of color in excess or residual microdrops of color either fall into the tank  13  underneath or aspirates them. 
         [0055]    Finally, the ribbon  1  is then wound on a spool  10 , e.g. with a winder. 
         [0056]    Preferably, the bottom of the containment tank  13  of the microdrops is provided with an upward movement device  17  synchronized with the advancement of the ribbon  1  so as to keep the contact level constant on the surface of the encapsulated microdrops with the adhesive base of the ribbon. 
         [0057]    Preferably, in case of adhesion of the microdrops to the spool, by means of an electrostatic or electromagnetic system  14 , the feeding tank  13  may be positioned a given distance from the ribbon. 
         [0058]    As seen, the diagram in  FIG. 4  may also be adopted, with changes or appropriate accessories, to directly print a univocal sign on a transfer medium  1  on the printing line. 
         [0059]    In this case, the medium  1 , e.g. paper, from the unwinding spool  9  passes through the gluing assembly with the rolls  11  which print from the bottom ad adhesive portion of any pattern on the back underneath the medium. 
         [0060]    The medium is then conveyed downwards and held taut by the rolls  12  and by the possible plate  13 , so that the microdrops, in contact with the pattern printed with high-adhesion varnish, adhere to the glue and cover it completely, thus repeating the pattern, before passing in the electrostatic load neutralizer and between the two opposite rolls  26 ,  27  (smooth continuous rolls in such a case), which crush the microdrops of color glued onto the sign, thus forming a univocal pattern on the medium  1 . 
         [0061]    A scraping doctor  28  cleans possible crushed microdrop residues. Finally, the resulting univocal drawing passes under a UV lamp  30  for drying and final polymerization. 
         [0062]      FIG. 6  diagrammatically shows a further embodiment of an apparatus for making media, and for directly printing univocal patterns according to the invention. 
         [0063]    In such a case, the apparatus comprises an assembly  7  of the type described above which applies glue, either partially in the case of direct painting of the univocal sign or totally in the case of making ribbon for transferring onto a medium  1  which is advancing horizontally. The medium  1  is diverted vertically by means of a vertical idle roll  35  to be immersed and then emerge from a hopper container  36  containing the microdrops  3 , which are made to adhere to the glue by contact in a lower collection cradle  38 , possibly with the assistance of a blow from the bottom  37 . 
         [0064]    At the outlet of the container  36 , the medium may pass through a crushing assembly of the microdrops  20  of the type described above or wound back on a spool in case of ribbon-shaped medium. 
         [0065]    According to the invention, the transfer medium  24  of the univocal pattern is additionally provided with a portion of adhesive layer  4 , with a further outer layer formed by transparent varnish, protective film, or resin arranged to protect or transfer univocal drawings generated by the crushed microdrops onto the medium. 
         [0066]    The outer film may be of the type adapted for heat transfer of the pattern. 
         [0067]    With this solution, transferring the univocal pattern from the medium  24  to another medium of any type may be obtained by means of techniques known in themselves, e.g. by heat transfer of the outer film carrying the pattern. 
         [0068]    The present invention is described herein according to preferred embodiments but equivalent variants may be devised without because of this departing from the provided scope of protection. 
         [0069]    It is further described a transfer medium of a univocal pattern, comprising a base  1  provided with at least one portion of an adhesive layer  4  on which an amount of compression-fragile encapsulated microdrops of color  3  is stably withheld is provided. 
         [0070]    The base may be a continuous ribbon wound on a spool or an individual sheet. 
         [0071]    It is also described a medium for transferring a univocal pattern, comprising a base  24  provided with at least one portion of an adhesive layer  4  on which at least one univocal pattern originated by crushing an amount of compression-fragile encapsulated microdrops of color  3  is applied, the medium comprising a further outer layer of transparent varnish or protective film, e.g. of the heat transfer type, arranged to either protect or transfer the univocal patterns generated on the medium by the crushed microdrops. 
         [0072]    The base may be a continuous ribbon wound on a spool or an individual sheet. 
         [0073]    Again it is described a printing method of a univocal pattern starting from a transfer medium above described, comprising a step of transferring a univocal pattern onto the transfer medium by means of hot or dry pressure, pad printing or other techniques adapted to determine the transfer of the pattern by means of crushing compression of said microdrops. 
         [0074]    The step of transferring may be implemented on a printing line and following a method of making a transfer medium as described above. 
         [0075]    In the printing method the formulation of the colors encapsulated the microdrops may be chosen according to the printing medium on which they must be transferred and crushed, and possibly mixed with magnetic responding metallic pigments adapted for detecting the printed datum. 
         [0076]    Moreover the colors encapsulated in the microdrops may be mixed with reflecting glitter, phosphorite or micro particles to increase visibility of printed sign. 
         [0077]    The printing method may comprise a preliminary step of selecting a printing medium  24  different from the transfer medium and a step of approaching the printing medium to a side  25  of the transfer medium carrying the encapsulated microdrops. 
         [0078]    It is further described a printing apparatus of a univocal pattern starting from a transfer medium referred above, comprising means  20  for transferring a univocal pattern by means of hot or dry pressure, pad printing or other techniques adapted to determine the transfer the pattern by means of crushing compression of said microdrops. 
         [0079]    The transfer medium may be in the form of a continuous ribbon and said transfer means  20  comprise a pair of opposite plate rolls and counter roll  26 ,  27  which crush at least one portion of the color microdrops glued onto the transfer medium thus forming a univocal pattern on the medium. 
         [0080]    The apparatus may comprise a scraping doctor ( 28 ) arranged downstream of said transfer means to clean possible residues of crushed microdrops. 
         [0081]    The apparatus may also comprise a UV lamp ( 30 ) arranged downstream of said transfer means for drying and polymerizing the color. 
         [0082]    It may also have means  31  for approaching a printing medium  24  on one side  25  of the transfer medium carrying the microdrops  3  operating downstream of said transfer means  20 . 
         [0083]    In the apparatus said printing medium may be a continuous ribbon and in may comprises means  32  for winding the printed ribbon  24  onto a spool. 
         [0084]    The printing medium may also consists of a sequence of individual sheets.