Irreversible thin film display with clearing agent

Information

  • Patent Grant
  • 6270122
  • Patent Number
    6,270,122
  • Date Filed
    Friday, October 22, 1999
    25 years ago
  • Date Issued
    Tuesday, August 7, 2001
    23 years ago
Abstract
Display information is revealed from behind a metal film that can be cleared upon effective contact with a clearing agent. The metal film, while opaque, is generally less than 1000 Angstroms thick and can be cleared by exposure to innocuous agents including food or other household products.
Description




TECHNICAL FIELD




When actuated, irreversible displays undergo permanent changes in appearance. Initially obscured or otherwise hidden information is revealed by the changes of appearance.




BACKGROUND




Changes that take place in irreversible displays generally involve the revelation of indicia, which can range from a patch of color to text and pictures. The indicia can be revealed by chemical or physical agents that change themselves or that produce other changes in the displays. For example, opaque coloring agents can be rendered transparent to reveal underlying indicia, or similar agents can change from one color to another to indicate a change.




Chemical transformations in irreversible displays are sometimes used for security purposes to provide evidence of tampering or counterfeiting. U.S. Pat. No. 4,488,646 to McCorkle hides a warning message behind a solvent-sensitive blush coating to provide evidence of solvent tampering with letters, tickets, and other information-bearing constructions. Upon exposure to a wide range of aromatic or aliphatic solvents, the blush coating is transformed into a transparent state revealing the message. U.S. Pat. No. 4,903,991 to Wright discloses a document security system in which a latent image is developed by rupturing photoactive microcapsules to verify authenticity.




Mechanical transformations are more often used for interactive game pieces. The most common are scratch-off games in which an opaque coating is removed by abrasion to reveal a hidden indicium. Chang et al. in U.S. Pat. No. 5,431,452 separately position a latent image and a removable image-developing device on different portions of a substrate. The image-developing device contains a chromogenic composition that converts the latent image into a visible image.




SUMMARY OF INVENTION




Our irreversible displays exploit features of thin metal films, especially vapor deposited films, for such purposes as temporarily obscuring predetermined indicia from view and subsequently reacting with chemical clearing agents to reveal the predetermined indicia. The thin metal films can be cleared away to reveal underlying indicia, or the indicia can also be formed by clearing the films in predetermined patterns. The clearing process is visually engaging as a preferably lustrous metal progressively disappears.




One example of our irreversible display includes a metal layer having a surface that overlies an indicium, such as a contrasting color, a pattern, or a message. A substrate supports the metal layer and the indicium. A chemical clearing agent is supported on the substrate out of contact with the surface of the metal layer that overlies the indicium. The clearing agent is relatively movable into contact with the surface of the metal layer for inducing a chemical reaction that clears the metal layer and reveals the underlying indicium. The metal layer, which can be formed from a variety of metals including aluminum, zinc, or silver, is preferably thick enough to completely obscure the indicium but thin enough to rapidly disappear when placed in contact with the clearing agent. Thicknesses between 100 and 1000 Angstroms are preferred for these purposes.




The clearing agent can be drawn from a variety of materials including electrolytes, acids, bases, and other agents that participate in localized reactions for corroding or otherwise clearing the metal layer. Among the choices are many safe and environmentally friendly materials including edibles such as juices, carbonated beverages, and even condiments. The reactions that clear the metal layer include localized electrochemical reactions that oxidize the metal layer. In contrast to galvanic or electrolytic electrochemical reactions, the localized electrochemical reactions between the clearing agent and the metal layer produce a mixed electropotential and do not require a net flow of current through the metal layer.




Preferably, the substrate is one of a pair of top and bottom substrates between which the clearing agent is confined within a reservoir out of contact with the surface of the metal layer. The top substrate preferably includes a transparent portion (i.e., a window) that overlies the metal layer and the indicium. A gated pathway between the substrates can be used to direct the clearing agent from the reservoir into contact with the surface of the metal layer.




The reservoir can be arranged adjacent to or even surrounding the surface of the metal layer that overlies the indicium. Squeezing the reservoir forces some of the clearing agent along one or more of the gated pathways into contact with the surface of the metal layer from one or more directions. Alternatively, the clearing agent can be arranged to overlie the metal film at an initial separation set by a spacer. An opening through the spacer allows the clearing agent to be relatively moved into contact with the metal layer. The clearing agent of this overlapping arrangement can be an adhesive for maintaining contact with the surface of the metal layer after being relatively moved through the spacer opening.




Another example of our irreversible display includes a metal film, a display window aligned with the metal film, and an indicium that is aligned with the display window but obscured by the metal film. The window provides access to the metal film for exposing the metal film to a chemical clearing agent that clears a portion of the metal film and reveals the indicium. A separate access opening can also be provided along with a transport medium (e.g., a wick) to transport the clearing agent from the opening to the metal film.




The exemplary display can be activated by adding the clearing agent through the display window or other access opening., Contact between the clearing agent and the metal film produces a localized electrochemical reaction between the clearing agent and the metal film without generating an electromotive force beyond the clearing agent. The localized electrochemical reaction clears the metal film (in an apparent gnawing action) and reveals the indicium within the display window through an opening cleared in the metal film by the reaction with the clearing agent.




Other exemplary approaches for controlling contact between a clearing agent and a metal film include forming a breakable barrier layer and microencapsulating the clearing agent. Mechanical action such as squeezing or bending can be used to breach the barrier layer or release the clearing agent from microencapsulation. Adhesive clearing agents can be separately mounted and temporarily protected by a release liner. Upon removal of the release liner, the adhesive clearing agent can be moved in contact with the metal layer through an opening in the top substrate.




Instead of clearing the metal film to reveal an underlying indicium, the metal film can be cleared in a pattern (e.g., a stencil) that forms its own indicium. For example, a protective layer could be laid out in a pattern on the metal film. Exposing a portion of the metal film that is not covered by the protective layer to a clearing agent changes the exposed metal film from opaque to clear. The remaining portion of the metal film that is covered by the protective layer is sheltered from similar exposure to the clearing agent. The two portions of the metal film are arranged for producing a predetermined pattern upon exposure of the first portion of the metal film to the clearing agent.




Our irreversible displays can be manufactured by an in-line press. All of the layers including substrates, metal films, clearing agents, graphics, adhesives, and spacers can be formed from individual webs or from layers applied to the individual webs. The result is a succession of thin flexible displays that can be manufactured quickly at low cost and integrated if desired with other press-produced or otherwise compatible articles.











DRAWINGS





FIG. 1

is a plan view of an irreversible display activated by squeezing a clearing agent from a reservoir. A portion of a metal film is cut away to show a portion of an underlying graphic layer.





FIG. 2

is a cross-sectional view of the display taken along line II—II of FIG.


1


.





FIG. 3

is a cross-sectional view of the display taken along line III—III of FIG.


1


.





FIG. 4

is a top view of an irreversible display activated by folding. The view is taken along line IV—IV of

FIG. 5

with a release liner removed to better view the active surfaces.





FIG. 5

is a cross-sectional view of the entire display taken along line V—V of FIG.


4


.





FIG. 6

is a similar cross-sectional view of the display folded into an activated position.





FIG. 7

is a plan view of an irreversible display arranged in a stack with a portion of a metal film cut away to show a portion of an underlying graphic.





FIG. 8

is a cross-sectional view of the display taken along line VIII—VIII of FIG.


7


.





FIG. 9

is a similar cross-sectional view of the display with the layers reordered to activate the display.





FIG. 10

is a plan view of an irreversible display arranged with a removable spacer between active layers of the display. The metal film is cut away to show a part of pattern hidden behind the metal film.





FIG. 11

is a cross-sectional view of the display taken along line XI—XI of FIG.


10


.





FIG. 12

is a plan view of an irreversible display with a metal film arranged as a switch arm for activating the display.





FIG. 13

is a cross-sectional view of the display taken along line XIII—XIII of

FIG. 12

with the switch in an open position.





FIG. 14

is a similar cross-sectional view of the display with the switch in a closed position.





FIG. 15

is a cross-sectional view of another irreversible display with a breakable barrier layer separating a clearing agent and a metal film.





FIG. 16

is a cross-sectional view of a similar display with the clearing agent microencapsulated to temporarily separate the clearing agent from the metal film.





FIG. 17

is a plan view of an irreversible display having a metal film exposed for applying a clearing agent from an exterior source.





FIG. 18

is a cross-sectional view taken along line XVIII—XVIII of FIG.


17


.





FIG. 19

is a plan view of an irreversible display having a wicking layer for transporting a clearing agent from an exterior source to two different sites covered by metal film.





FIG. 20

is a cross-sectional view taken along line XX—XX of FIG.


19


.





FIG. 21

is a plan view of an irreversible display arranged for progressively clearing a metal film. Graphic indicia underlying the metal film are visible.





FIG. 22

is a cross-sectional view taken along line XXII—XXII of FIG.


21


.





FIG. 23

is a cross-sectional view of an irreversible display having two layers of metal film to protect an intervening graphics layer from discovery until the display is activated.





FIG. 24

is a plan view of an irreversible display in which a protective layer is applied in a pattern over a metal film. A message formed by the pattern is visible.





FIG. 25

is a cross-sectional view taken along line XXV—XXV of FIG.


24


.





FIG. 26

is a cross-sectional view of an irreversible display with clearing agent confined within a reservoir beneath a metal film.





FIG. 27

is a diagram of an in-line press for manufacturing the irreversible displays.











DETAILED DESCRIPTION




The irreversible displays of our invention take a variety of forms actuatable by reacting chemical clearing agents with metal films for revealing indicia. In-line press produced adaptations are preferred for high-volume low-cost manufacture.




One such irreversible display


10


shown in

FIGS. 1-3

includes a pair of top and bottom substrates


12


and


14


supporting between them a graphics layer


16


overlaid in one location by a metal film


18


and in another location by a chemical clearing agent


20


. An adhesive layer


22


bonds the two substrates


12


and


14


together, leaving space for a pocket reservoir


24


that confines the clearing agent


20


and a gated pathway


26


that provides for distributing the clearing agent from the reservoir


24


over a surface


28


of the metal film


18


. Although only one gated pathway


26


is shown, additional gated pathways can be provided for directing the clearing agent


20


to multiple locations on the surface


28


of the metal film


18


. More than one reservoir


24


could also be provided to direct the clearing agent to multiple locations, such as from opposite ends of the surface


28


.




The top substrate


12


is preferably transparent at least in a windowed area


30


aligned with the metal film


18


. The bottom substrate can be entirely opaque. Both can have a single-ply or a multi-ply construction made from a variety of materials including paper and plastic. For example, the top and bottom substrates


12


and


14


can be formed by a combination of low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polyethylene terephtalate (PET). The substrate material is preferably adaptable for web transport.




An indicium


32


of the graphics layer


16


, such as the message “press here”, is preferably viewable through both the top substrate


12


and the clearing agent


20


to provide instructions for activating the display


10


. Similar instructions could also be provided elsewhere on or between the top and bottom substrates


12


and


14


. However, an indicium


34


of the graphics layer


16


such as “you win!” is temporarily blocked from view by the metal film


18


. Any other overlying layers including the windowed area


30


of the top substrate


12


are preferably transparent or at least translucent. Conventional printing techniques with ink can be used to form the graphics layers.




A bulge


36


can be formed in the top substrate


12


to confine additional clearing agent


20


within the reservoir


24


. Vacuum pressure, heat, or stamping can be used to form the bulge


36


. An intervening layer such as a spacer (not shown) between the top and bottom substrates


12


and


14


could also be used to add depth to the reservoir


24


. The adhesive layer


22


, which is preferably a pressure-sensitive adhesive, provides a seal around the reservoir


24


to confine the clearing agent


20


and to isolate the clearing agent


20


from environmental influences. In place of or in addition to the adhesive layer


22


, a heat seal could be formed between the top and bottom substrates


12


and


14


to achieve similar ends.




The gated pathway


26


is initially closed to isolate the clearing agent


20


from the metal film


18


but can be opened by application of pressure to the reservoir


24


. The initially closed and later opened valve function of the gated pathway


26


can be accomplished by forming a weaker bond between the substrates


12


and


14


across the gated pathway


26


than elsewhere surrounding the reservoir


24


. A weaker adhesive, a release agent, or a cooler heat seal could be used for this purpose. The length of the gated pathway


26


can also be adjusted to influence the valve function.




The metal film


18


is preferably a smooth uniformly thin film of sputtered or vapor-deposited metal, such as zinc, aluminum, or silver, bonded by its manufacturing technique to an underlying transparent (or at least translucent) substrate


38


, such as a thin polyester film. Alternatively, the metal film could be formed by an at least partially self-supporting foil that is thin enough to clear at a desired rate in the presence of the clearing agent


20


. The foil could be laminated or transfer printed onto an intermediate substrate, such as the substrate


28


, or onto the graphics layer


16


of the underlying substrate


14


. For most applications, clearing should take place in less than one minute. Metal film thicknesses between 100 Angstroms and 1000 Angstroms can be cleared at the required rate. The metal film


18


is preferably highly reflective to further obscure the underlying indicium


34


.




The chemical clearing agent


20


preferably takes the form of a liquid or gel, such as a hydrogel, that is movable (e.g., squeezable) from the reservoir


24


through the gated pathway


26


over the surface


28


of the metal film


18


. A wide variety of materials can function as clearing agents including oxidants, acids, salts, and alkalis, as well as combinations of these groups of materials. Other materials including thickeners (e.g., hydrogels) can be added to adjust physical properties such as viscosity, yield value, and surface tension to achieve desired flow and coverage characteristics. Preferred mixtures contain materials that are safe and environmentally friendly. One example formulated for clearing a zinc film contains the following combination of materials:




49% water




35% citric acid




15% potassium chloride




1% gel medium (thickener)




Squeezing the bulge


36


forces the clearing agent


20


from the reservoir


24


through gated pathway


26


and over the surface


28


of the thin metal film


18


. In just a few seconds (e.g., 5 seconds) following exposure to the clearing agent


20


, the metal film


18


disappears revealing the underlying indicium


34


. The thickness and composition of the metal film


18


as well as the amount and composition of the clearing agent


20


can be varied to adjust the rate of clearing. The oxidation, dissolution, or other disappearance of the thin metal film is irreversible.




A collar


39


surrounds the bulge


36


to prevent the bulge from being inadvertently squeezed, especially when the display


10


is wound into a roll together with a succession of similar displays produced by an in-line press. Although shown as a separate substrate, the collar


39


could also be formed by embossing one or more of the other substrates


12


and


14


of the display


10


. As shown, the collar


39


almost completely surrounds the bulge


36


. However, the collar


39


could be limited to diametrical areas at which the bulge


36


is subject to the most pressure upon winding. In addition, while the inner periphery of the collar


39


at least partially envelops the bulge


36


, the outer periphery of the collar can occupy up to all of the remaining surface area of the display


10


.




An irreversible display cell


40


shown in

FIGS. 4-6

is activated by a folding action. A common base substrate


42


supports a thin metal film


44


overlying a graphics layer


46


in one area and a chemical clearing agent


48


in another area. Both areas are surrounded by pressure-sensitive adhesive borders


52


and


54


and covered by a removable liner


56


having a release layer


58


. The metal film


44


is supported on a transparent substrate


60


, but could be replaced by a self-supporting foil.




The clearing agent


48


also preferably takes the form of a pressure-sensitive adhesive. Oxidants, acids, salts, or alkalis can be added to a conventional pressure-sensitive adhesive to adjust its efficacy for clearing the metal film


44


; or the pressure-sensitive adhesive could be reformulated with mildly corrosive properties. The release layer


58


is preferably made of silicone, but other release materials having low adherence to the pressure-sensitive adhesive borders


52


and


54


and the clearing agent


48


could also be used.




The display


40


is activated by removing the liner


56


and folding the substrate


42


about a fold line


62


to move the clearing agent


48


into contact with the metal film


44


. The two pressure-sensitive adhesive borders


52


and


54


also contact each other for securing the display


40


in the folded position. The contact between the clearing agent


48


and the metal film


44


triggers a spontaneous chemical reaction that clears the metal film


44


. Both the clearing agent


48


and at least the overlying portion of the folded substrate


42


are preferably transparent (or at least translucent) to provide a window for viewing the graphics layer


46


, which is revealed by the disappearance of the metal film


44


.




Other instructional or decorative graphics can be located elsewhere on the substrate


42


or the liner


56


. For example, additional graphics could be used to block viewing of the graphics layer


46


through the base substrate


42


. Also, the liner


56


could be limited to covering the clearing agent


48


in the unfolded position, and the clearing agent


48


alone (i.e., without the adhesive borders


52


and


54


) could be used to subsequently secure the display


40


in the folded position.




An irreversible display


70


in a stack configuration is illustrated by

FIGS. 7-9

. A first substrate


72


, which is preferably opaque, supports a metal film


74


over a graphics layer


76


on one side and a release layer


78


on an opposite side. A border


80


surrounds the metal film


74


. The border


80


can be formed by an additional substrate, graphics, or other layer to complete a top surface of the display


70


. A second substrate


82


, which is preferably transparent or at least translucent, supports a chemical clearing agent


84


, preferably in the form of a pressure-sensitive adhesive.




The metal film


74


is again shown in its preferred form deposited onto a transparent (or at least translucent) substrate


86


. However, in contrast to the preceding embodiment, the metal film


74


is exposed to the environment, so appropriate care must be taken to avoid contact with substances that might inadvertently act as clearing agents.




Activating the display


70


is accomplished by removing the second substrate


82


together with the clearing agent


84


from the release layer


78


and remounting the second substrate


82


over the first substrate


72


to move the clearing agent


84


into contact with the metal film


74


. The accompanying disappearance of the metal film


74


reveals an underlying indicium


88


, such as “free refill”. The indicium


88


is visible through both the second substrate


82


and the clearing agent


84


.




Another irreversible display


90


constructed with similar layers is shown in

FIGS. 10 and 11

. Between top and bottom substrates


92


and


94


is a progression of layers including a chemical clearing agent


96


surrounded by a border


98


(such as an adhesive or other confining material) and a metal film


100


overlying a graphics layer


102


. The top substrate


92


and the clearing agent


96


are preferably transparent or at least translucent. The bottom substrate


94


is preferably opaque.




A removable spacer


104


having a release layer


106


separates the clearing agent


96


from the metal film


100


. The release layer


106


exhibits little adhesion to the clearing agent


96


or to its border


98


. The display


90


is activated by removing the spacer


104


and moving the clearing agent


96


into contact with the metal film


100


. The clearing agent


96


is preferably a gel or an adhesive that can maintain contact with the metal film


100


until the film disappears revealing the underlying graphic


102


. An exemplary indicium


108


formed by the graphic


102


and revealed through the windowed structure of the display


90


is a picture of a cup.




An irreversible display


110


with internal switching capabilities is shown in

FIGS. 12-14

. Top and bottom substrates


112


and


114


are again used along with a spacer


116


. A graphics layer


118


is printed on the top substrate


112


providing instructions, information, or decorative design. The top substrate


112


and the spacer


116


capture between them a metal film


120


that straddles an opening


122


in the spacer


116


. The preferred metal film


120


is deposited onto a surface of a transparent substrate


124


facing the bottom substrate


114


.




A chemical clearing agent


126


, which has the form of an adhesive, overlies a graphics layer


128


on the bottom substrate


114


within the spacer opening


122


. Surrounding layers of adhesive


130


and


132


bond the top substrate


112


to the spacer


116


and bond the spacer


116


to the bottom substrate


114


. A fixed end


134


of the metal film


120


is firmly anchored between the top substrate


112


and the spacer


116


, but a free end


136


is only temporarily captured between the same layers.




Squeezing the top and bottom substrates


112


and


114


together where shown by arrows


138


in

FIG. 14

deforms the two substrates


112


and


114


, disengages the free end


136


of the metal film


120


from between the top substrate


112


and the spacer


116


, and moves the metal film


120


into contact with the adhesive clearing agent


126


. The top and bottom substrates


112


and


114


are both preferably resilient and return to their original shape after the squeezing action is discontinued. However, the free end


136


of the metal film


120


remains in contact with the adhesive clearing agent


126


, thereby separating from the top substrate


112


.




Contact between the metal film


120


and the clearing agent


126


clears the metal film


120


in the usual manner, revealing the underlying graphics layer


128


along with any indicia formed by the graphics layer


128


. Both the top substrate


112


and the clearing agent


126


should be transparent or at least translucent for viewing the underlying graphics layer


128


through a window


140


framed by the graphics layer


118


and the spacer


116


.




Similar results can be obtained by supporting the adhesive clearing agent


126


for movement through the opening


122


into contact with the metal film


120


. In addition, a hidden graphics layer could be positioned between the metal film


120


and the top substrate


112


for viewing a change in the display through the bottom substrate


114


.




Two more irreversible displays


150


and


170


with internal switching mechanisms are shown in

FIGS. 15 and 16

. Both have similar top substrates


152


,


172


and bottom substrates


154


,


174


. The bottom substrates


154


and


174


support similar graphics layers


156


and


176


that are overlain by metal films


158


and


178


. Clearing agents


160


and


180


are also supported between the top and bottom substrates


152


,


154


and


172


,


174


. Adhesive layers


162


,


182


surround the clearing agents


160


,


180


; and adhesive layers


164


,


184


surround the metal films


158


,


178


.




The display


150


has a temporary barrier layer


166


in the form of a stratum separating the clearing agent


160


from the metal film


158


. The barrier layer


166


can be formed by a varnish or other material that does not react with the metal film


158


and that can be ruptured by an external force or moment.




For example, arrows


168


represent a moment that can be applied to the display


150


to rupture the barrier layer


166


and allow the clearing agent


160


to contact the metal film


158


. Clearing the metal film


158


renders the underlying graphics layer


156


visible through the top substrate


152


, the clearing agent


160


, and any remaining portion of the barrier layer


166


. Any substrate on which the metal film is supported should also be transparent or at least translucent, consistent with all of the earlier examples.




Instead of a distinct barrier layer, the display


170


microencapsulates the clearing agent


180


for temporarily separating the clearing agent


180


from the metal film


178


. Squeezing the top and bottom substrates


172


and


174


together as indicated by arrows


188


releases the clearing agent


180


from microencapsulation and allows contact between the clearing agent


180


and the metal film


178


. The intended reaction clears the metal film


178


, rendering the underlying graphics layer


176


visible through the top substrate


172


.




In place of microencapsulation, the corrosive chemical effects of the clearing agent


180


could be temporarily blocked, such as by freezing the clearing agent


180


. Upon thawing, the corrosive properties of the clearing agent


180


would be restored. The temperature at which the clearing agent


180


thaws can be adjusted by the composition of the clearing agent. An irreversible record of the thaw is provided by the cleared metal film


178


.




Similar to the earlier examples, the hidden graphics layers


156


and


176


of the irreversible displays


150


and


170


could be located adjacent to what is now their top substrates


152


and


172


and the viewing of the repositioned graphics layers


156


and


176


could take place through what is now their bottom substrates


154


and


174


. The clearing agents


160


and


180


preferably have a liquid or gel form that is flowable upon release from confinement or encapsulation.




An irreversible display


180


depicted in

FIGS. 17 and 18

relies on an external supply of chemical clearing agent to change states. Top and bottom substrates


182


and


184


joined together by an adhesive layer


186


provide the desired support for a metal film


188


and an underlying graphics layer


190


. However, openings


192


,


194


, and


196


in the top substrate


182


expose different portions of the metal film


188


to the surrounding environment.




Any number of prescribed clearing agents can be applied to the exposed portions of the metal film by separately adding one of the clearing agents through the openings


192


,


194


,


196


or by immersing the entire display


180


in one of the clearing agents. A separate substrate could also be provided to support or confine the clearing agent until needed to activate the display. Spontaneous chemical reactions resulting from the addition of the clearing agent through the openings


192


,


194


, and


196


clear localized areas of the metal film


188


revealing indicia


198


,


200


, and


202


formed in the graphics layer


190


.




Another irreversible display


210


requiring an external supply of clearing agent is depicted in

FIGS. 19 and 20

. A top substrate


212


and a bottom substrate


214


support intervening layers including a graphics layer


216


and two separate metal films


220


and


222


laid out over different portions of the graphics layer


216


. Adhesive layer


224


bonds the two substrates


212


and


214


together.




A wicking layer


226


contacts both metal films


220


and


222


and is exposed to the surrounding environment through an opening


228


in the top substrate


212


. Another graphics layer


230


is printed on the top substrate


212


, which is preferably otherwise transparent, to provide instructions and other information related to the function of the display


210


and to define windows


232


and


234


through which the metal films


220


and


222


are visible. The wicking layer


226


can be made of paper or other material that can absorb and transport a chemical clearing agent having a liquid or gel form.




Clearing agents added through the opening


228


in the top substrate


212


are absorbed by the wicking layer


226


and are transported by capillary action into contact with the two metal films


220


and


222


. Clearing first takes place at the metal film


220


and is later followed by clearing at the metal film


222


. Indicia


236


and


238


, which are revealed in the graphics layer


216


, can be meaningfully sequenced to attract and hold a viewer's attention.




Capillary action can also be used to transport the clearing agent stored within a display reservoir to one or more metal films or to one or more portions of the same metal film. The clearing agent can be transported along wicks in more than one direction to display different indicia at once or in a single direction to display indicia in sequence.




In addition to clearing areas of the metal film overlapped by the clearing agent, adjacent areas can be progressively cleared along a common boundary between the clearing agent and the metal film. An irreversible display


240


exemplifying this progressive clearing function is illustrated in

FIGS. 21 and 22

. Top and bottom substrates


242


and


244


joined by an adhesive layer


246


confine between them in separate locations a chemical clearing agent


248


and a metal film


250


overlying a graphic layer


252


.




The clearing agent


248


, which is in a flowable form, is initially confined within a reservoir


254


bounded by the top and bottom substrates


242


and


244


and the adhesive layer


246


. A bulge


256


is formed in the top substrate


242


to expand the reservoir


254


. A protective coating


258


made from an inert material such as a varnish or an adhesive is applied over a portion of the metal film


250


remote from the reservoir


254


. A graphics layer


260


applied to the top substrate


242


, which is preferably transparent, defines a series of windows


262


,


264


,


266


, and


268


.




The window


262


exposes the reservoir


254


of clearing agent


248


, revealing an instructional indicium


270


(“press here”) in the graphics layer


252


. Squeezing the reservoir


254


as instructed forces the clearing agent


248


through a gated pathway


272


over a first portion of the metal film


250


, revealing the underlying indicium


274


(“start”). The protective coating


258


blocks further flows of the clearing agent


248


over the metal film


250


. However, after the overlapped portion of the metal film


250


is cleared within the window


264


, an edge


276


of the metal film


250


remains in contact with the clearing agent


248


. Clearing continues at a slower pace but in a progressive manner at the edge


276


, which forms a common boundary between the clearing agent


248


and the metal film


250


.




As the edge


276


retreats into the remaining metal film


250


, a further indicium


278


in the form of a pattern is progressively revealed in the window


264


. During the retreat, the area occupied by the clearing agent


248


progressively expands and the area occupied by the metal film


250


progressively diminishes. The rate of edge retreat can be adjusted to provide a timing function, particularly by controlling the percentage of active ingredients in the clearing agent


248


.




The graphics layer


260


blocks a view along a portion of the path of edge retreat in advance of the window


268


to provide a period of delay. The edge retreat continues out of sight until the edge


276


becomes visible in the window


268


. Another indicium


280


(“end”) in the graphics layer


252


is revealed in the window


268


following the disappearance of the overlying metal film


250


behind the edge


276


.




The number, size, shape, and contents of the windows can be varied to suit particular applications. Except for the metal film


250


, all of the layers that overlie the graphics layer


252


within the windows are preferably transparent or at least translucent. The progressive clearing of the metal film


250


along a retreating edge


276


can take place in more than one direction and can be rendered visible throughout any or all of the path of retreat.




An irreversible display


290


shown in

FIG. 23

is arranged to be particularly useful for security purposes in such instruments as coupons, tickets, vouchers, and seals. The display


290


highlights security features that are otherwise adaptable to any or all of the embodiments previously illustrated.




For example, a first metal film


292


deposited onto a transparent substrate


294


is exposed through an opening


296


in a top substrate


298


. The opening


296


provides access for moving a chemical clearing agent (not shown) into contact with the first metal film


292


. However, the clearing agent could also be supplied from an adjacent or overlying reservoir in accordance with the earlier embodiments.




In contrast with the preceding embodiments, a first graphics layer


300


is applied to a back surface of the substrate


294


and is covered by a second metal film


302


that is deposited over the first graphics layer


300


. A second graphics layer


304


is located between the second metal film


302


and a bottom substrate


306


. An adhesive layer


308


bonds the top and bottom substrates


298


and


306


together.




The first metal film


292


provides the usual function of blocking the immediately underlying first graphics layer


300


from sight until acted on by a clearing agent. The second metal film


302


, which is preferably deposited over the first graphics layer


300


, blocks sight of the first graphics layer


300


from an opposite direction. If necessary, a median layer, such as an adhesive, can be applied over the first graphics layer


300


to support the deposition of the second metal film


302


. Alternatively, the first graphics layer


300


could also be positioned between the first metal film


292


and the substrate


294


, which could be opaque obviating the need for the second metal film


302


and the second graphics layer


304


.




The metal films


292


and


302


are preferably smooth, reflective, and have thicknesses measured in hundreds of Angstroms. Tampering with these metal films


292


and


294


is likely to result in permanently damaging them, which would be readily apparent. In addition, the metal films


292


and


302


cannot be easily repaired or reproduced. The application of most chemical solvents will also produce visible damage to these films


292


and


302


.




As a ready check against tampering, the second graphics layer


304


is rendered at least partially visible upon the clearing of the first metal film


292


if any portion of the second metal film


302


is damaged. Alternatively, the second metal film


302


could be intentionally cleared by exposure to a chemical clearing agent to produce a compound display, where the two graphics layers


300


and


304


are revealed simultaneously or in sequence.




An irreversible display


310


that does not rely on an underlying graphics layer to reveal new information is illustrated by

FIGS. 24 and 25

. A metal film


312


, which can be deposited onto an underlying substrate


314


as illustrated or which can be a self-supporting foil, is mounted on a bottom substrate


316


. Either substrate


314


or


316


can be opaque. An adhesive layer (not shown) can be supplied to secure the metal film


312


to the bottom substrate


316


.




A clear protective layer


318


, such as a varnish or adhesive, is applied in a pattern over the metal film


312


. A temporary barrier layer


320


separates the protective layer


318


and the remaining portion of the metal film


312


from a chemical clearing agent


322


. A top substrate


324


together with an adhesive layer


326


confines the clearing agent


322


within the display


310


.




The metal film


312


is preferably clearly visible through the top substrate


324


, the clearing agent


322


, and the barrier layer


320


. However, the protective layer


318


preferably does not exhibit sufficient contrast to be distinguished from the metal film


312


. Upon rupturing the barrier layer


320


, the clearing agent


322


moves into contact with the exposed areas of the metal film


312


. The protective layer


318


prevents the clearing agent


322


from contacting remaining portions of the metal film


312


. Clearing takes place in a pattern complementary to the pattern of the protective layer


318


, revealing an indicium


326


(“win”) formed by a contrast between the cleared and not cleared portions of the metal film


312


. An underlying graphics layer (not shown) can be provided to enhance the contrast.




An irreversible display


330


of

FIG. 26

demonstrates yet other possibilities for arranging layers and displaying indicia. A bottom substrate


332


supports a reservoir of clearing agent


334


within a boundary set by an adhesive


336


. A metal film


338


is supported on a perforated substrate


340


over the clearing agent


334


and is further separated from the clearing agent


334


by a barrier layer


342


, such as a varnish.




In contrast to other embodiments, the film substrate


340


is made opaque or is otherwise modified to provide some form of indicia, if nothing more than a patch of color, beneath the metal film


338


. Although a separate graphics layer is generally preferred for forming indicia, the corresponding substrates underlying the metal film of the earlier embodiments could also be used to form or support a desired indicia.




Openings


344


through the metal film


338


and the underlying substrate


340


together with the barrier layer


342


provide gated pathways between the clearing agent


334


and the metal film


338


. A transparent top substrate


346


is bonded over the metal film


338


with an adhesive


348


leaving space for the clearing agent


334


to flow over the exposed surface of the metal film


338


.




Activation is accomplished by squeezing the top and bottom substrates


346


and


332


together, thereby rupturing the barrier layer


342


and forcing the clearing agent


334


through the openings


344


and across a surface of the metal film


338


. Localized reactions, as described earlier, clear the metal film


338


and reveal the indicium embodied in the immediately underlying substrate


340


.




The irreversible displays described above can be used for a variety of purposes including stand-alone devices and display components of other products or devices. For example, the displays can be used as game pieces, message cards, security devices, or elapsed time indicators. Layers of adhesive and release can also be added to the substrates to incorporate the displays into pressure-sensitive sensitive labels or other printable products. The displays can also be formed as integral parts of the packaging of other products.




The displays can be switched from a first state in which the thin metal film is opaque to a second state in which a predetermined area of the thin metal film becomes substantially transparent, but the displays cannot be restored to the first state. The clearing that takes place in the thin metal films to reveal indicia is irreversible. Preferably, the revealed indicia remain permanently displayed. Although the indicia preferably underlie the metal film, the indicia can also be formed as patterns in the metal film itself. The revealed indicia can also be used to transform, replace, contrast, or complete another overlying or underlying image.




The underlying indicia, which can range from a patch of color to patterns, symbols, or other more imaginative forms, is preferably formed prior to being overlaid by the metal film. However, the indicia could also be formed later in an underlying medium (i.e., after the medium is covered by the metal film) by a developing mechanism, such as a thermal color-developing mechanism. Unique, timely, or interactive information could be printed on demand just prior to distribution or use.




The composition, amount, and physical properties (e.g., viscosity, yield value, and adhesion) of the chemical clearing agent can be adjusted to match the needs of particular applications. A compound change in display can be achieved by adding other chemical transformation components to the clearing agent. For example, a pH-indicating solution that undergoes a color change in the presence of the oxidizing reaction on the metal film can be added to the clearing agent. The pH of the clearing agent can change as the metal film is cleared, resulting in a color change that can tint any underlying graphics.




The thin metal films are preferably formed by deposition onto substrates, which are preferably transparent or at least translucent, unless also intended to embody or otherwise participate in forming an underlying opaque indicium. Deposition methods include vacuum evaporation, cathode sputtering, electroplating, and various chemical reactions in a controlled atmosphere or electrolyte. In addition, the metal films are preferably smooth, shiny, and thick enough to obscure the view of underlying layers. Thicknesses between 100 and 1000 Angstroms are preferred. Thicker metal films, including at least partially self-supporting metal foils, can also be used, particularly for applications requiring slower clearing rates.




The individual substrates that provide support for the displays can be formed as single layers or as laminations for such purposes as providing color patterns, further rigidity, or better sealing capabilities. However, all of the substrates, including the substrate that normally supports the thin metal film, are preferably supplied in rolls that can be unwound into an in-line press. Stress relief can be applied if the substrates are too inflexible for winding. All of the other layers, including the graphics layers, clearing agents, and the adhesives are preferably applied in patterns or injected into predetermined positions on one of the substrates by stations arranged along the press. Flexographic printing is preferred where possible, especially for laying down inks, but other printing techniques including extrusion or injection can be used where needed to lay down layers of clearing agent and adhesive.




The thin metal films are preferably predeposited onto substrates in advance of any press operations. However, thin metal film could also be transfer printed from a temporary carrier to the substrate along the press, such as by hot or cold stamping. For example, a thin metal film could be transferred from the temporary carrier by cold stamping in a pattern that matches an adhesive pattern on a substrate. Self-supporting metal foils could also be used if thin enough to clear within a required time span. Our preferred metal films are made of aluminum, zinc, or silver; but many other metals, including metal alloys, can be used.




An exemplary in-line press


350


for making our irreversible displays, particularly the display of

FIGS. 1-3

, is depicted in

FIG. 27. A

bottom substrate (web)


352


is unwound from a roll


354


and advanced to a print station


356


that applies a graphics layer. A metal film


358


on a transparent supporting substrate (web) is unwound from a roll


360


. A laminator


362


joins the metal film to the bottom substrate


352


, and a die-cut station


364


cuts the metal film into a succession of patterns. An adhesive or other bonding agent can be used to secure the metal film


358


to the bottom substrate


352


. The metal film


358


could also be mounted in a variety of other ways such as by transfer printing or by substituting a metal foil.




An adhesive station


368


applies adhesive in patterns surrounding both the successions of die-cut metal film and reservoirs (not shown) for confining a clearing agent. Thinner or otherwise weaker portions of the adhesive patterns form gated pathways (not shown) between the reservoirs and the die-cut metal film. A dispensing station


370


injects the clearing agent into the reservoirs. A transparent top substrate (web)


372


is unwound from a roll


374


and is directed through a vacuum forming station


376


for forming a succession of bulges through the top substrate


372


for increasing reservoir volumes. A laminator


378


joins the top and bottom substrates


372


and


352


, sealing the clearing agent within the reservoirs. Heat sealing (not shown) can be used in combination with or as a substitute for the adhesive to join the two substrates together. An embossing station


380


forms collars around the reservoirs in advance of a rewind station


382


to reduce pressure on the reservoirs when a resulting succession of displays


384


are roll wound. The collars could also be formed by a separate substrate or embossments in the top substrate alone. In place of reservoirs, successions of openings can be formed in the top substrate


372


to provide access to the metal film. Similar adaptations can be made for producing the other embodiments on press.




Such in-line processing can be used to produce successions of irreversible display cells in large volumes at low cost. Additional stations, such as die cutters, can be used to separate succeeding displays and to adapt the displays for their intended use as stand-alone displays or as displays incorporated within other products or product packages. A similar arrangement of in-line stations can be used to produce other embodiments of our displays including the addition or substitution of stations for applying layers such as barrier layers, protective layers, graphics layers, or layers of release. Additional rolls of substrates including liners and spacers can also be appended to the press.



Claims
  • 1. A method of displaying information with an irreversible display comprising the steps of:adding a chemical agent to a metal film; producing a localized electrochemical reaction between the chemical agent and the metal film without generating an electromotive force beyond the chemical agent; clearing the metal film by the localized electrochemical reaction with the chemical agent; and revealing information through an opening cleared in the metal film by the reaction with the chemical agent.
  • 2. The method of claim 1 in which said step of adding includes applying the chemical agent to the metal film through a display window for also viewing the revealed information.
  • 3. The method of claim 1 including a further step of storing the chemical agent within the display out of contact with the metal film.
  • 4. The method of claim 1 in which the metal film is deposited onto a substrate.
  • 5. The method of claim 1 in which the metal film is a foil.
  • 6. The method of claim 1 in which the metal film has a thickness of no more than 1000 Angstroms.
  • 7. The method of claim 1 in which the revealed information is formed by a graphics layer that underlies the metal film.
  • 8. The method of claim 1 in which the step of adding includes obtaining the chemical agent from a supply external to the display.
  • 9. The method of claim 3 including a further step of applying a mechanical force to move the chemical agent into contact with the metal film.
  • 10. The method of claim 9 in which the step of storing the chemical agent includes confining the chemical agent within a reservoir.
  • 11. The method of claim 10 in which the chemical agent is safely edible.
  • 12. A display method of temporarily obscuring and subsequently revealing an indicium comprising the steps of:supporting a metal layer having a thickness no greater than 1000 Angstroms on a substrate; obscuring the indicium from view through a surface of the metal layer; triggering a non-galvanic non-electrolytic electrochemical reaction by applying a chemical agent to the surface of the metal layer that obscures the indicium from view; and revealing the indicium through an opening in the surface of the metal layer cleared by the electrochemical reaction.
  • 13. The display method of claim 12 in which the electrochemical reaction is a localized electrochemical reaction that does not require a net flow of current through the metal layer.
  • 14. The display method of claim 12 including a step of temporarily separating the chemical agent from the surface of the metal layer that obscures the indicium.
  • 15. The display method of claim 14 in which the step of temporarily separating includes supporting the chemical agent on a different portion of the substrate.
  • 16. The display method of claim 14 in which the substrate is a first of two substrates and the step of temporarily separating includes supporting the chemical agent on a second of the two substrates.
  • 17. The display method of claim 14 in which the step of emporarily separating includes encapsulating the chemical agent.
  • 18. The display method of claim 14 in which the step of temporarily separating includes separating the chemical agent from the metal layer with a spacer.
  • 19. The display method of claim 14 in which the substrate is one of a pair of top and bottom substrates and the step of triggering includes applying the chemical agent to the surface of the metal layer through an opening in one of the top and bottom substrates.
  • 20. The display method of claim 15 in which the step of triggering includes moving the chemical agent across the substrate into contact with the surface of the metal layer.
  • 21. The display method of claim 16 in which the step of riggering includes laminating the two substrates together.
  • 22. The display method of claim 17 in which the step of temporarily separating includes microencapsulating the chemical agent.
  • 23. The display method of claim 17 in which the step of triggering includes rupturing an encapsulating medium.
  • 24. The display method of claim 18 in which the step of triggering includes relatively moving the chemical agent into contact with the surface of the metal layer through an opening in the spacer.
  • 25. The display method of claim 19 in which the step of triggering includes applying the chemical agent to the surface of the metal layer through a display window in the top substrate.
  • 26. An irreversible display having a clearing mechanism for revealing an indicium comprising:a metal layer having a surface that overlies the indicium; a substrate supporting the metal layer and the indicium; a clearing agent supported on the substrate out of contact with the surface of the metal layer that overlies the indicium; and the clearing agent being relatively movable into contact with the surface of the metal layer for inducing a chemical reaction that clears the metal layer and reveals the underlying indicium.
  • 27. The display of claim 26 further comprising a reservoir for confining the clearing agent out of contact with the surface of the metal layer.
  • 28. The display of claim 26 in which the substrate is one of a pair of top and bottom substrates between which the clearing agent is confined.
  • 29. The display of claim 26 in which the substrate is one of two substrates between which the clearing agent is supported out of contact with the surface of the metal layer.
  • 30. The display of claim 26 in which the chemical reaction induced by relative movement of the clearing agent into contact with the metal layer is a localized electrochemical reaction that clears the metal layer without generating an electromotive force beyond the clearing agent.
  • 31. A method of activating the display of claim 26 comprising the step of relatively moving the clearing agent into contact with the surface of the metal layer for inducing a chemical reaction that clears the metal layer and reveals the underlying indicium.
  • 32. The display of claim 27 in which the reservoir underlies the metal film.
  • 33. The display of claim 27 in which the reservoir overlies the metal film.
  • 34. The display of claim 27 in which the reservoir and the metal film occupy separate areas of the substrate.
  • 35. The display of claim 27 further comprising a gated pathway along which the clearing agent is movable from the reservoir into contact with the surface of the metal layer.
  • 36. The display of claim 35 in which the reservoir is compressible for moving the clearing agent out of the reservoir.
  • 37. The display of claim 36 in which the reservoir surrounds at least a portion of the surface of the metal layer that overlies the indicium.
  • 38. The display of claim 37 in which the gated pathway is one of a plurality of gated pathways that guide the clearing agent into contact with the surface of the metal layer from a plurality of directions.
  • 39. The display of claim 28 in which the top substrate includes a transparent portion that overlies the metal layer and the indicium.
  • 40. The display of claim 28 in which the clearing agent is transparent and also overlies the indicium.
  • 41. The display of claim 40 in which a spacer separates the clearing agent from the surface of the metal layer through an opening aligned with the indicium.
  • 42. The display of claim 40 in which the clearing agent is an adhesive for maintaining contact with the surface of the metal layer after being moved into contact through the opening.
  • 43. The display of claim 29 in which one of the two substrates is removable from the clearing agent.
  • 44. The display of claim 43 in which the clearing agent is an adhesive and the removable substrate includes a release layer.
  • 45. The method of claim 31 in which the step of relatively moving includes moving the clearing agent from a reservoir into contact with the metal layer.
  • 46. The method of claim 31 in which the step of relatively moving includes folding the substrate supporting both the metal film and the clearing agent.
  • 47. The method of claim 31 in which the step of relatively moving includes relatively removing the clearing agent from the substrate and relatively positioning the clearing agent in contact with the metal film.
  • 48. The method of claim 31 in which the step of relatively moving is preceded by a step of removing a spacer separating the clearing agent from the metal film.
  • 49. The method of claim 31 in which the step of relatively moving includes moving the metal film from a position out of contact with the clearing agent into a position of contact with the clearing agent.
  • 50. The method of claim 31 in which the step of relatively moving includes breaking a barrier separating the clearing agent from the metal film.
  • 51. The method of claim 31 in which the step of breaking the barrier includes releasing the clearing agent from encapsulation.
  • 52. An irreversible display comprising:a clearing agent, a metal film, and an indicium supported by a common substrate; the metal film being opaque; the indicium being obscured from view behind the metal film; and the clearing agent being: (a) at least partially transparent, (b) temporarily maintained out of operative engagement with the metal film, and (c) operatively engageable with the metal film for starting a chemical reaction that clears the metal film and reveals the indicium obscured behind the metal film.
  • 53. The display of claim 52 in which the clearing agent, the metal film, and the indicium are arranged in a stack.
  • 54. The display of claim 52 in which the clearing agent is an adhesive.
  • 55. The display of claim 52 in which the clearing agent is a hydrogel.
  • 56. The display of claim 52 in which the clearing agent is flowable from a position out of operative engagement with the metal film to a position in operative engagement with the metal film.
  • 57. The display of claim 53 in which the clearing agent is temporarily maintained out of operative engagement by being temporarily maintained at a reduced temperature.
  • 58. The display of claim 53 in which the clearing agent is separated from the metal film by a spacer.
  • 59. The display of claim 57 in which the clearing agent is operatively engageable with the metal film by being increased in temperature.
  • 60. The display of claim 58 in which the spacer has an opening through which the clearing agent is engageable with the metal film.
  • 61. A display that irreversibly changes state from a first display state to a second display state, said display having a metal film that obscures an indicium in the first display state and a chemical clearing agent relatively movable from a first position out of contact with the metal film to a second position in contact with the metal film thereby triggering a chemical reaction between the clearing agent and the metal film that clears the metal film and reveals the indicium in the second display state.
  • 62. The display of claim 61 in which the metal film and the clearing agent are supported on a common substrate.
  • 63. The display of claim 61 further comprising a reservoir for confining the clearing agent out of contact with the metal film.
  • 64. The display of claim 61 in which the clearing agent is transparent and also overlies the indicium.
  • 65. The display of claim 61 in which the chemical reaction triggered by relative movement of the clearing agent into contact with the metal film is a localized electrochemical reaction that clears the metal film without generating an electromotive force beyond the clearing agent.
  • 66. The display of claim 61 in which the metal film has a thickness no greater than 1000 Angstroms.
  • 67. The display of claim 63 further comprising a gated pathway along which the clearing agent is movable from the reservoir into contact with the metal film.
  • 68. The display of claim 64 in which a spacer separates the clearing agent from the metal film through an opening aligned with the indicium.
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5431452 Chang et al. Jul 1995
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