CA2190113A1 - Image-transfer process - Google Patents

Abstract

Decorative and/or security media particles, in liquid or solid form, are transferred without the use of heat or high pressures to a substrate by first printing a plurality of discrete raised semi-rigidized sharp-edged adhesive images onto thesurface of the substrate, using some form of radiation to render the adhesive tacky, and then bringing particles of the media into contact with the surface of the tacky images whereby the media particles are permanently retained by the images on thesubstrate. Alternatively, the media particles may be part of the adhesive composition.

Description

~ a ~ 13 `.
COLD IMAGE TRANSFER PROCESS
This invention relates to a unique image transfer method based upon the deposition of adhesive images onto substrates followed by the subsequent transfer 5 and adhesion of decorative and/or security media to these images. There are many novel A~ of this process, several of which are described in this application.
BACKGROUND OF THE INVENTION
A number of attempts bave been made over the last decade to devise a method of ~ `fi-, ;1.~ various media to substrates without having to resort to a transfer process involving heat, high application pressures and expensive tooling.
The use of heat to facilitate the transfer and bonding of materials carried by auxiliary webs has become a significant problem in recent years due to the 15 introduction of many new polymeric substrate materials. Because of the limitations of existing transfer methods, the applicant has worked for a number of years on developing a novel cold transfer process. In one early development, discrete adhesive images were first printed onto a substrate, and the substrate was then nipped to a foil web carrying a deposition of decorative metallic particles. This was 20 followed by the exposure of the substrate/adhesive/foil sandwich to UV radiation, and finally by the removal of the foil carrier web from the substrate. The goal of this development was to cure the adhesive images trapped between the foil and substrate webs, with the metallic particles only adhering to those areas of the substrate covered by the adhesive images. This version of the process had limited 25 success, the main drawbacks being the loss of detail and edge definition during wet (pre-cured) lamination, ?nd the lack of complete adhesive curing through the foil substrate sandwich.
Another alternative transfer method was developed by Kensol/Olsenmark 3 o Inc. of Melville, N.Y. In this system an adhesive is printed onto a web substrate, U.V. cured, and then wound into a rewind roll. The printed roll is then post processed on a second machine that unwinds the substrate and brings it into contact with a metalli~ed foil at a heated nip point. The nip point consists of a steel anvil and a heated smooth surfaced rubber applicator roll which is loaded against the steel 35 anvil. The substrate/foil is nipped between the heated applicator roll and the steel anvil. The heat at the nip reactivates the adhesive properties of the previously U.V.
cured adhesive and the foil adheres to those portions of the subs~rate carrying the activa~ed adhesive. After exiting the nip area the foil carrier (waste~ is stripped away from the substrate and rewound on a spindle. The image substrate is then rewound into a finished roll. Limitations of this system include: off-line handling of the printed web is required, poor edge definition results upon reheat of the printed 5 adhesiYe, and m~-ct ~ y, the lf ~ on the use of a heated nip roll, which greatly restricts the number of substrate materials that can be processed.
A significant illl~llU~ was realized with the adoption of the ,.. ~,.llodolo~y of pre-lamination curing, used in ( .. " j, .,, l .. with certain types of 10 custom U.V. curable adhesives. This invention is called the Cold Image Transfer Process and has enabled the applicant to devise a number of novel transfer applications.
A common exarnple of current technology that will be at least partially 1~ superseded by this new method is the hot transfer of metallized foil onto a substrate.
An overview of the existing hot foil transfer process will be used as a means for, a) illllUdU~.illg the new process, and b) explaining the benefits of the new prûcess relative to existing processes.

2 o In the hot transfer process a metallized foil and a substrate (such as paper or polymer film), are laminated together under the ~ lf ~ application of heat and pressure. The laminating process may take place in either flat or rotary ,,.. . 1. .,;~",~
The rotary form, because of its higher operating speed, is the more common of the two for web fed applications. In the rotary format, a heated die roll with an integral 25 series of images formed on its surface is mated against a smooth-surfaced rubber coated backup anvil or 'support roll'. The foil web is nipped together with a web substrate at the contact ("nip") line between the anvil roll and the heated die roll. As a result of the heat and pressure existing at the nip point, the adhesive layer of the foil laminate is activated and in turn causes the metallic layer to adhere to the 3 o substrate. As the ~ Iwi~l~cl webs exit from the nip point, the non-adhered portion of the metallic layer is released (pulled away) &om the foil carrier. What is left on the substrate is a metallic image matching the raised image on the surface of the die roll. The remnant carrier web leaving the nip point is rewound onto a spindle and later discarded. The substrate image is typically embossed, that is, the image has an 3 5 indentcd relief pattern matching the profile of the die image(s).
There are many significant limitations to the conventional hot foil transfer 2~9~1~3 process, including:
Cost of the heated bronze die. The dies used are expensive to lu~lurhcLulc and each is dedicated to a specific job (image). Die cost is a sigluficant component of total job cost, and often limits this process to long run ,~ where the cost can be spread over many images.
Turna}ound time for die lllal.urh.Lu,c is significant, again limiting0 . usage to jobs that can be planned well in advance of running. This is a major problem given the current market trends towards shorter runs and just-in-time delivery. In addition, foil is often used for special effects in high-end product packaging, an area where the desire for product lirrclcllli~iu~ often results in frequent art work changes.
~he expense of a die often limits the freedQm of the packaging designer to change existing metallized images.
Running speeds of rotary hot stamping systems are typically lirnited to 150 ftlmin. This imposes a severe restraint on press operating 2 o : speeds (which are usually in the 200 to 400 ft/min range) and can jeopardize the overall economics of the foil Arrlir~lir,n The rotary die is typically installed on a press die station. This not only ties up one die station that mighL have been otherwise employed, 2 5 _ but more Si~llir~ ly, requires that the embossed foil images be registered with the printed ink images produced ahead of the rotary die section of the press. This IC4UilCIII~,.II can result in additional equipment costs for presses not equipped with rotary die lc~ io systems.
The process cannot be used in . .~ ". ~ . with polymer substrates that would be distorted by the heated nip point (typically 140-170 degrees Celsius). One of the major labelling trends today is the use of clear film labels, that is labels that are printed on a transparent substrate so that the image doesn't appear to be part of a pressure sensitive label. Such labels have much higher value if they can be decorated with metallized images.
-2~9~1 13 With the hot die process, image fd is also a problem. The reason for this is the elongation, or stretch, that occurs in the substrate when it is processed through a printing press. When the substrate is in its relaxed state (~ero tension after printing), the printed ink images end up being shorter than the length at which they were printed. This decrease in length is variable since tension in the press is, more often than not, variable. This, combined with the fact that a mechanical die has a fixed image length, means that even if the hot foil image is in 0 . register with the print, it will have a different length than any 'same- sized' printed images adjacent to it.
To overcome the above-listed limitations of the hot foil transfer process, a number of alternative processes have been attempted; however, none of the previous 'cold' processes has been successful in ~ l .Ig the image edge definition required in the market place.
GENERAL DES~RIPTION OF THIS INVENTION . :
2 o The proposed Cold Image Transfer Process presents a novel method of u ~ ,vlllillg many of the constraints of currently used media transfer methods . The basic process can be described as follows;
Liquid adhesive, such as the type cured by exposure to U.V. radiation, is "printed" by one of the conventional processes in current use within the printing industry. Adhesive images matching those carried by the mechanical image carrying element of the print mechanism are transferred to a substrate, in the same manner that inked images are transferred to a substrate, ie. instead of printing "ink" images, "adhesive" images are being printed. As mentioned, the adhesive images can be 3 0 printed by any of the UUll~ .llLiul al printing processes, including; letterpress, flexography (including P~ lu~la,ully), screen (rotary and flat), liLl~ù~la~lly, and gravure, plus all of the offset variants of these processes. Of particular interest are two processes that use the "raised-image" printing method. In accordance with general terminology utilized in the printing industry, the term "raised-image"
printing refers to a printing procedure in which the locations on the printing plate where ink is to be deposited are raised with respect to areas where ink is not to be deposited. Two .l;~ le forms of this process can be identif ~d; letterpress ~ 21~ 13 s and flexography. The first typically utilizes a relativeiy stiff printing plate working in uulljull~Liull with an impressiûn rûll having a compliant coating. In nc,~ y,the opposite is the case, ie. a relatively low stiffness printing plate is used, along with a relatively more stiff impression roll (frequently soeel). Primography, a hybrid 5 of the twû basic raised-image printing methods, uses the higher viscosity and thixotropy of the one process, and the plate/impression roll stiffness ICI~l~iUll~ U of the other.
The process, in its cold foil transfer ~ .;rr~ , and as employed with a10 raised-image printing method, results in the deposition of adhesive images onto the surface of the substrate. These printed images are themselves "raised-images" ofadhesive (not to be confused with the 'raised-image' relief pattern images on the printing plate) and possess highiy defined sharp edges in ~-"j",.. l;l,., with consistent uniform thickness (1i~rihlltion throughout the solid areas of the printed image. The 15 substrate, replete with printed adhesive images, then passes through a curing". such as a U.V. system, which initiates the curing process of the adhesive images. When utilizing an adhesive such as that supplied by 3M Canada Inc. under the ~ n~fil)n LC 7280 Cold Foil l.Am:n~ n Adhesive, the adhesive images after passing through the curing mechanism exhibit several unique 20 .l~,~,.t.li~iic~, including; a) semi~ of the raised images, b) tackiness for a short ~,cJ~,i ' length of time. In essence, a window of tackiness is created after curing has been initiated, with the delay in the initial onset of tackiness being controllable through the forr.A~ ti.~n of the adhesive. It is during this window ûf adhesion that it becomes possible to perform many new and nûvel transfers of 25 vario.us decorative and/or security media to the discrete, sharp-edged raised-images on the substrate.
In the cold foil lamination process, after the printed adhesive raised-images become tacky, they are then processed tbrough a foil laminator. The laminator 3 o consists of unwind and rewind .". ~ as is typically used in a hot transfer process. The foil is unwound and nipped to the substrate at the point of contactbetween a smooth base roll and a smooth nip roll. It is along the nip line between these two rolls that the metallized layer of particles is released from the carrier film and transferred to the tacky printed images. Because the adhesive images are still in 3 5 a semi-rigid state, the contact pressure at the nip line must be finely controlled in order to achieve optimum transfer of the metal particles without distorting the definition of the edges of the images. Exiting from the nip point, the remainder of 219al 13 6 .
the foil carrier web (missing the separated images) is separated from the substrate and a~ ' ' by the laminator rewind system. The substrate, replete with laminated images, then exits the laminator section and proceeds duwl~Ll~dlll to the next print head, where another printed image, either of ink, Yarnish or adhesive, is 5 transferred to the substrate.
The cold foil transfer process is used for illustrative purposes only. The essence of the proposed new process is the capability to produce a plurality of discrete, sharp-edged, raised images that exhibit strong adhesive ~lldld~L.,lio~ for a 10 controllable length of time. In general, these images have the following properties:
(a) composed of printable adhesive material having properties of adl.~,Oi~ ,OO and curability, (b) post-cured printed adhesive images have sharp semi-rigidized edge definition prior to subsequent coating/laminate transfers, (c) a time window of a~ Oi~ ,Os, the opening and closing of which is controllable &ough the r.,.. ~ ;.. ,. of the adhesive, (d) thickness, i.e. a raised surface of uull~;JI,l~lc thickness which when desired, can be produced to yield a "thick layer printing" effect, and (e) the ability to serve as a matrix for a wide variety of additives and/or 2 5 surface coatings of various media.
The images that are produced serve as receptors having properties that facilitate a number of novel media transfer processes. In some cases, the transfer processes replace analogous existing processes (eg. hot foil transfer), while in oLher 3 Q cases, entirely new transfer me~hods that did not exist before are possible. Some of these new d~liu~Liùllo are;
1. Cold Bronzing/Gold Dusting: In this case, the substrate is passed through a chamber in which fine metal particles, powder or platelettes are blown onto the 35 activated adhesive images and in turn become fused to the tacky surfaces of the images A nipping laminator may or may not be used in culljull~.Liùl~ with this process. This process permits many types of decorative and/or security particles to 2 ~ 9~ 1 1 3 .

be applied to a substrate, not just the metallic type. Only a few of the many particle types available can currently be transferred from a foil carrier. A beneflt of this approach is that only the material deposited on the substrate images is consumed.
Excess material is recirculated in the application chamber. In ~ .J~. the foil 5 transfer process is a one pass system and requires that the nipped foil carrier be rewound and discarded, most of en with only a small portion of its decorative medium having been consumed. This represents a significant economic waste. As corollaries of this application it is possible:
a) to deposit particles of a material that are too large to lend themselves to any of the printing processes, such as a number of pho~ olc~ L
materials, or b) to deposit particles of an irregular shape, the goal being to give an irregular relief pattern to the surface of the substrate, or c) to deposit particles or media that are too abrasive or corrosive to be = printed by standard means, or d) to deposit particles or media having physical properties (such as low surface tension) that prevent successful application with standard printing processes.
20 2. Post-Printing: This alterrlative deals with the ability to sequentially print an image of U.V. curable adhesive followed by the subsequent in-line and in-register printing of the same image. In essence, this process would produce a multi-layerimagc, the final properties of which would be determined by the . .~ of the adhesive(s) and ink(s) bemg used. The prime purpose of the initial adhesive layer 2 5 would be to increase the surface tension present on that portion of the substrate that would ~l.l,,~.~... ;ly be receiving depositions of ink. In addition, the final image would be of greater thickness, a property often desirable from a commercial point of view.
3 o 3. Blister Cards: This involves the application of a UV curable adhesive, specifically, one having the properties exhibited by the product supplied by 3M
under the ~h~ n~ n given earlier, whereby an image of adhesive would be printed,cured and then ~ y overprinted by an identical image of a second heat-activated adhesive. Alternatively, the heat-activated coating could be in powder35 form and be applied to the adhesive image using methods such as, but not limited to;
spraying, roller coating, pressure coating and/or dipping. One important use for this process would be the production of 'blister card' products. App~ication of the blister ~ 2',901 13 would be ;~ c-~ by bringing the blister into contact with the top coated heat-activated a&esive image under pressure and t~ Llllc. If desired, the app!icationof adhesives would be done on a substrate that had already been printed and/or flood coated.

4. Security: The adhesive may be used as a matrix within which security micro taggants may be suspended prior to printing and curing, or alternatively, the taggants may be applied to the adhesive in its tacky state by any of the methodspreviously described. If the former, then the adhesive would contain the security 0 taggant and would likely be printed so as to leave a covert, completely invisible mark which could then be either over-printed by an ink, or laminated by any of anumber of available media. The net result would be the provision of a security image that was, a) not visible to the naked eye, and b) protected from wear and/or tampering by a protective/decorative material layer. This type of protection from ~.J~ could be applied to a label, or if desired, directly to a product.
Returning to the cnmp~icl~n with the traditional hot stamp foil process, the present mvention addresses the ~rul~lll.,.lLiollCI ~IIUIL- , of hot processes asfollows:
1. There is rlo die in the system; only a relatively ill~ IlUL~ I~
printing plate. Therefore, tooling cosOE are only a fraction of traditional tooling costs. As well, because of the light weight of a ~rinting cylinder/plateassembly, physical handling of the image-carrying element is much easier.
2. A printing plate can be made locally or m-house in a matter of hours as opposed to a typical turnaround time of at least one week for a rotary die.
3. The adhesive can be printed at higher press operating speeds, so no 3 o ~ UUI~IUIUI.~;l in optimum production speed are necessary, as is the case with the hot transfer process. This, combined with the lower tooling costs, malces the proposed cold process more economical tham its hot process equivalent.
4. Implicit is the absence of image registration problems, ie. the printed adhesive 3 5 becomes the foil image. R~iaLIcLiull with a subsequent die is not required.

5. Since the a&esive images are printed at the same time (and therefore, at the 2~901 13 same substrate tension) as the ink images, there are no image fit problems, ie.
the printed images, both ink and a&esive, are the correct length relative to each other.
5 6. Being prirlted in a normal print station allows for the printed adhesive to be registered using the print registration system on the press, should it have one.A die station position is not taken. The 'loss' of one print station (the one used by the adhesive printer) is usually not significant since the foil is often replacing an existing colour used in the job.

7. The proposed process, being cold, can be used in c--njlln~ n with a wide range of substrate materials. Substrate distortion/destruction due to heat is not a concern.
15 8. The nip point in the laminator is lightly loaded compared to a hot die process.
The presence of a heavily nipped hot die tends to cause registration problems in the rest of the press.
9. Cold foil transfer has the ability to transfer flner details due to the fact that the 2 o detail of the printed adhesive image is fmer than the detail achievable with the hot transfer process. As well, image edge definition achievable with the Cold Image Transfer Process is superior to that of the hot transfer process.
10. Since the anvil and die used in this process both have smooth surfaces, theimages produced are coplanar with the substrate. Unlike the hot transfer process, there is no permanent distortion/.l;~ 1 of the substrate material due to the action of the relief pattern of a hot die.
More ~ uLIlly, this invention provides a method for l~ `F 1;1-~ particles 3 o ~ of a liquid or solid medium to a substrate, comprising the steps:
a) prmting a plurality of discrete, sharp edged, raised images on the substrate, the said images mcluding ultra-violet-polymerizable adhesive, ~5 b) using ultra-violet radiation to begin to polymerize the adhesive in said images so that the adhesive becomes serni-rigid and tacky, and remains tacky for a ~l~' ' length of time, and c) within said ~lr.~ length of time, bringing the said particles together with the substrate at a common transfer point, . such that said particles are adhesively retained by said semi-rigid raused irnages on the substrate.
Further, this invention provides, am apparatus for ~ `f' ~ discrete portions of foil from a continuous foil web to a substrate, ~
0 a) printmg means for printing, on the substrate, a plurality of discrete,sharp-edged, raised images which include an adhesive which, when subjected to ultra-violet radiation, is at least partly poly~ li~d so as to become tacky and semi-rigid, and remain tacky for a ~ lrd length of time, b) ultra-violet radiation means dVWll:~i of the printing means for at least partly pol, ~ the adhesive in said images, c) roll means duwll~L~ ll of the ultra-violet radiation means, said roll means including a drive roll and a web nip roll, at least one of said rolls having a resilient surface, said rolls defining a nip through which said substrate and said foil web can pass together, such that when passage through said nip takes place within said ~lr.l~" .III;Ilr~l length of time, said discrete portions of foil are adhesively retained by said images on the substrate, d) separation means at a location dO~ LI~ I of said nip, for separating 2 5 the remamder of the foil web from the substrate, and e) rewind means for separately rewmding the remainder of the foil web.
Also useful in the Cold Image Transfer Process are particular methods and techniques consisting of: optimal engraving geometry of form rolls; foil transfer 30 techniques in lamination processes; ultra-violet adhesive curing techniques; nip roll interface techniques; ink and adhesive metering and transfer techniques; and webhandlmg techniques.
GENERAL DESCRIPTION OF THE DRAWINGS

~1 9Q1 1 3 One rll,l,.J.I;.~....1 of this invention is illustrated in the â~,ulllyallyill~; drawings, m which like numerals denote like parts throughout the several views, and in which:
Figure 1 is a schematic side elevational view of a previous prototype process 5 developed by the applicant;
Figure 2 is a schematic side elevational view of a process ("rotary hot foil transfer") belonging to the prior art;
Figure 3 is a schematic side elevational view of a specific application ("cold foil transfer") of the proposed new Cold ~nage Transfer Process;
Figure 4 is a schematic side elevational view of a specific application ( particle dusting ) of the proposed new Cold Image Transfer Proces~; and Figure 5 is a cross-sectiorlal view through a typical foil laminate.
DET.'~ILED DESCRIPTION OF THE DRAWINGS ~ =
Figure 1 shows a schematic cross section thrQugh one of the earlier cold Iamination systems developed by the applicant. The printing method shown in Figure 1 is fl~ a~lly, however, it will be understood by those skilled in the art that other print methods, such as screen, letterpress, gravure, etc. can be used. This particular application shown is for foil transfer. In the case illustrated, a web-fed substrate I is 2 5 drawn through a print head 2 which consists of an impression roll 3, a printing plate 4, a plate cylinder 5, an irlk (adhesive) fountain 6 and a form (anilox) roll 7. The substrate 1 is first drawn around the driven impression roll 3, the function of which is to serve as a rigid backup for the substrate during the adhesive printing step. A U.V.
curable liquid adhesive is contained within the reservoir ("fountain") 6. The adhesive 3 o is accurately metered to the surface of the form roll from the fountain 6 by a doctor blade system located at the rnterface between the fountain 6 and the form roll 7 (for example, an engraved anilox roll). The adhesive is carried in engraved pockets on the surface of the form roll 7. A precisely controlled rolling contact is maintamed between the form roll 7 and the printing plate 4 thus enabling a uniform layer of adhesive to be 3 5 deposited onto the raised-imag~ surface of the printing plate 4. The printing plate 4 is : .. .. ... .. .. .... ... . .. .. .... . .. .. . ... .. ...... .. . _ . . .... ... .. . ..

~ 2190~ ~

a&ered to the periphery of the printing plate 5 by a special double-sided plate mounting. The plate cylinder 5 is driven, typically by a gear train from the impression roll 3. As the substrate travels over the impression roll, it comes into contact with the printing plate 4, the relief surface of which carries the adhesive image to be "printed".
5 The result of this transfer system is the deposition of adhesive images 8 onto the surface of the substrate 1. These printed images are themselves "raised-images" (not to be corlfused with the 'raised-image' relief pattern images on the printing plate 4) of adhesive and possess highly defmed sharp edges in rrnjllnrtil~n with consistent uniforrn thickness distribution throughout the solid areas of the printed image.o Subsequent to printing, the substrate l replete with printed images is passed through a driven I /".~ assembly 10. The laminator 10 consists of a roll of metallrzed foil 11, as typically used in current industry hot transfer processes, a controlled tension unwind system 14, a driven base roll 12, a nip roll 13, and a controlledtension rewind system 15. The foil 11 is unwound from the unwind system 14 and 15 brought into contact with and nipped to the substrate 1 at the point of contact between the base roll 12 and the nip roll 13. At this point, the still uncured adhesive image is ~Gl~dwi~lled between the substrate 1 and the foil 11. The laminated sandwich then passes through a U.V. Iamp 9 and the adhesive images are cured. This action binds the metallic particles of the foil carrier to the substrate 1 on those areas of the 20 substrate that have received the printed a&esive images. Subsequent to curing, the remainder of the foil carrier web (rnissing the transferred images) is separated from the substrate 1 and: ' ' by the tension-controlled rewind system 15. The substrate 1, replete with laminated images 16, then exits the lamirlator 10 and proceeds d~,WII~ l to the next print head 17.

Figure 2 is a schematic side elevational view of a typical "rotary hot foil transfer" process. In this process, a foil layer is married to a substrate 18 by nipping a foil 19 to the substrate at a nip between an internally heated roller die 21 and a resilient back-up anvil roller 20. The pattern of the transferred image is machmed in 3 o relief onto the periphery of the roller die. The roller die is heated in order to melt the release layer, causing the decorative layers to part from the carrier. S~ y, the heat from the die activates the heat-sensitive a&esive, causing the decorative coatings to a&ere to the substrate (see Figure ~) . Pressure is applied to the nip point by overbearer pressure device 22 acting on top of the roller die. Foil unwind and 3 5 rewind systems are similar to those described in Figure 1.

21 q~l ~ 3 The Cold Image Transfer Process, in its cold foil transfer l"~.,;f. -/.lil~.~ and as employed with a raised-image printing method a`~ printing process shown), is depicted in Figure 3. The initial printing section of this process is very 5 similar to that used in the process illustrated in Figure 1, with the exception that a special liquid adhesive, such as is available from 3M Canada Inc., is used. In the case illustrated, a web-fed substrate 1 is drawn through a print head 2 which consists of an impression roll 3, a printing plate 4, a plate cylinder 5, an ink (adhesive~ fountain 6 and a form (anilox) roll 7. As the substrate 1 as drawn around the driven impression 10 roll 3, the substrate is brought into contact with the printing plate 4, the relief surface of which carries the adhesive image to be ''printed". The transfer of the finely metered layer of adhesive from the fountain 6 through to the surface of the substrate 1 is via a print head identical to that described in Figure 1. The result of this transfer system is the deposition of adhesive images 8 onto the surface of the substrate 1. Again, these 15 printed images are themselves "raised-images" (not to be confused with the 'raised-image' relief pattern images on the printing plate 4) of adhesive and possess highly defined sharp edges in ~ n~ri~n with consistent uniform thickness ~icrrihlltion throughout the solid areas of the printed image. The substrate 1, replete with printed adhesive images 8, then passes through a curing mechanism 9, such as a U.V. Iamp2 o system which initiates the curing process of the adhesive images 8 .When utilr~ing a special adhesive such as that supplied by 3M Canada Inc. under the designation given earlier, the adhesive images after passing through the curing mechanism 9, exhibit several unique .ll~ , including; a) semi-r~ i7:~li.n of the raised printed adhesive images 8, b) after a short period of time the said images 8 become tacky and 25 remain so for a ,u.~7 ":J length of time. In essence, a window of tackiness is created after curmg has been initia.ed, with the delay in the initial onset of tackiness and subsequent transition to non-tackiness being ~ull~l~ " ' ' through the forml~ it)n of the a&esive. It is during the time period of this window of adhesion that it becomes possible to perform rnany new and novel transfers of various decorative andior 3 o security media to the discrete, sharp-edged raised-images 8 printed onto substrate 1.
The variation of the Cold Image Transfer Process shown in Figure 3 is for cold foil lamination. At some point duw~Llca~l from the curing mechanism 9, the printed adhesive raised-images become tacky and are then processed through a foil laminator 10. The lamirlator 10 consists of a roll of metalli_ed foil 11, as is currently 2~ 901 1 3 used in the various hot transfer processes, retained on a controlled tension unwind syStem 14, a driven base roll 12, a driven nip roll 13, and a controlled tension rewind system lS . The foil 11 is unwound from the unwind system 14 and brought into contact with and nipped to the substrate 1 at the pomt of contact between the base roll 5 12 and the nip roll 13. It is along the nip line between these two rolls that the metal particle layer is released from the foil carrier layer and adhered to the still tacky semi-rigidized raised printed adhesive images. Because the a&esive images are still in a semi-rigid state, the contact pressure at the nip line must be fnely controlled in order to achieve optimum transfer of the metal particles. Exiting from the nip point, the 10 remainder of the foil carrier web (missing the trarlsferred foil images) is separated from the substrate 1 and ' ' by the tension controlled rewind system 15.
The substrate 1, replete with laminated images 16, then exits the laminator 10 and proceeds downstream to the next print head li, where another printed image, either of ink, varnish or a&esive, can be transferred when desired to the substrate. Curing of 15 the adhesive images contmues to completion after lamination. Time required for total cure of the a&esive is dependent on the a&esive rO".,.,~
Figure 4 is a schematic side elevational view of a specific application ("particle dusting") of the proposed new Cold Image Transfer Process. In this 2 o Arrli~tinn the printing and curing of the special adhesive is identical to that shown in Figure 3; however, instead of the use of a foil lamination unit 10 as shown m Figure 3, a "cold dusting" chamber 23, or equivalent, is used. The coating to be applied to the tacky adhesive surface could be in liquid or solid form, such as powder, and be applied to the a&esive image using methods such as, but not limited to; spraying, 25 roller coating, brushing, pressure coating and/or immersion. This method may be used with or without a nipping mecharusm and/or substrate surface brushing unit.
Figure 5 shows a simplified cross-sectlon through a typical foil laminate, including a polymer carrier layer 30, a heat activated release coating layer 32, a 3 o . lacquer layer 34, a metallized foil layer 36 which may be vacuum deposited, and a heat sensitive adhesive layer ("sizing") 38. Also illustrated are a die 40 and asubstrate 42. The adhesive layer 38 is not essential when performing the method of this invention. This is a simplified cross-section, as there may be additional layers present in special foil laminates.

~i 90~ 13 While several ~ of this invention have been illustrated in the d~,o~ ul~ drwings and described Ik~ dlJuv~ it will be evident to those skilled in the art that cbdnges and ~ .I;r~ i""~ may be made therein, withont departing from the essence of this invention, as set forth in tbe appended clairns.

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for transferring particles of a liquid or solid medium to a substrate, comprising the steps:
a) printing a plurality of discrete, sharp-edged, raised images on the substrate, the said images including ultra-violet-polymerizable adhesive, b) using ultra-violet radiation to begin to polymerize the adhesive in said images so that the raised images adhesive becomes semi-rigid, tacky, and remains tacky for a predetermined length of time, c) within said predetermined length of time, bringing the media particles together with the substrate at a common transfer point, such that said particles are adhesively retained by said semi-rigid raised images on the substrate, and d) permitting said predetermined length of time to expire before contacting the raised images during a storage procedure.

2. The method claimed in claim 1, in which said substrate is a continuous, moving, elongate web, in which a carrier means is used to transfer the particles to the web substrate, and in which, at a location downstream of said transfer point, the carrier means is removed from contact with the web substrate and discarded.

3. The method claimed in claim 1, in which said substrate is a continuous moving, elongate web, in which a carrier means is used to transfer the particles to the web substrate, in which the nip between two nip rolls defines the transfer point, and in which the remainder of the carrier means is entrained around and maintained against at least part of the periphery of one nip roll, thereby to enhance the traction on said remainder of the carrier means.

4. The method claimed in claim 1, in which liquid or solid media particles are directly transferred to the printed raised adhesive images without the use of a continuous carrier, such transfer being accomplished by a process selected from the group consisting of: spraying, blowing, rolling, dipping, immersion.

5. The method claimed in claim 4, in which a rotary nipping mechanism is used on the substrate downstream of the media transfer point to iron the media-laden raised adhesive images.

6. Apparatus for transferring discrete portions of foil from a continuous foil web to a continuous moving substrate, comprising:
a) printing means for printing, on the moving substrate, a plurality of discrete, sharp-edged, raised images which include an adhesive which, when subjected to ultra-violet radiation, is at least partly polymerized so as to become tacky and semi-rigid, and remain tacky for a predetermined length of time, b) ultra-violet radiation means downstream of the printing means to begin polymerizing the adhesive in said images, c) roll means downstream of the ultra-violet radiation means, said roll means including a drive roll and a web nip roll, one of said rolls having a resilient surface, the other of said rolls having a non-resilient surface, said rolls defining a nip through which said moving substrate and said foil web can pass together, such that when passage through said nip takes place within said predetermined length of time, said discrete portions of foil are adhesively retained by said images on the substrate, d) separation means at a location downstream of said nip, for separating the remainder of the foil web from the substrate, and e) first rewind means for rewinding the remainder of the foil web, and second rewind means for rewinding the moving substrate, said second rewind means being sufficiently far downstream of the ultra-violet radiation means that said predetermined length of time expires before the substrate reaches the second rewind means.

7. The apparatus claimed in claim 6, in which said roll means is such as to entrain the remainder of the foil web around, and maintain it against, at least part of the periphery of the roll in contact with the foil web, thereby to enhance the traction on said remainder of the foil web.