Packaging material and products comprising indicia-former which changes from a first visual condition to a second visual condition and indicates a characteristic of the package contents

Abstract

Packaging materials, in particular, film and products that are marked with an energy sensitive indicia-former. The film has at least one heat sensitive indicia-former on at least part of the film. The film comprises a thin film substrate which is substantially transparent to radiant energy. Associated with at least part of the film substrate is an absorbent material which is sufficiently opaque to radiant energy to absorb said radiant energy and convert the radiant energy into heat energy. The indicia-former undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy from the absorbent material. The film is used preferably as a shrink wrap of the open top of drink containers and to identify the contents of the container.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 60/387,366, filed Jun. 10, 2002, and U.S. patent application Ser. No. 10/183,415, filed Jun. 28, 2002, both of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention pertains generally to packaging material and products which comprise (a) a substrate; and (b) an energy sensitive indicia-former carried by the substrate. The invention also pertains, in particular, to the use of such indicia-former on containers, having the capability of indicating the contents of such containers.

BACKGROUND OF THE INVENTION

[0003] In numerous instances, products are made and packaged that do not have markings that would be useful, for example, to identify the product, parts of the product or how to use the product. This is also true for packaging. Product identifiers on packaging material such as labels require time to complete and affix to the package, particularly if used in fast food preparation.

[0004] In fast food outlets, convenience stores and the like, beverage dispensing machines are used which are capable of dispensing a number of beverages of different brands and flavors. These beverages are usually poured into disposable paper cups having advertising printed thereon, but bearing no markings to identify the cups' contents.

[0005] When a beverage order includes a number of different brands and/or flavors, it is extremely difficult to determine the contents of each cup by visual inspection. Identification is further complicated by the placement of thermoformed lids over the cups to prevent spillage.

[0006] As a consequence of this problem, mixups occur and customers get the wrong beverage and do not discover the error until they taste it.

[0007] One way in which this confusion can be avoided is by using paper cups of different colors or having different designs or markings thereon. However, this requires a large inventory of cups, and the person filling the order must be attentive to selecting the appropriate cup in order to avoid the error of filling the selected cup with the incorrect beverage.

[0008] Other ways of solving this problem include the use of labels affixed to the outer surface of the container or thermoformed lids having manually deformable buttons identifying drinks of various kinds. A further approach is marking the identity of the drink onto the container or its lidding with a pen, i.e., by circling the drink type or checking or box a dot next to a specific drink type. These solutions require an inventory of container labels or lids and consistently attentive servers.

SUMMARY OF THE INVENTION

[0009] Accordingly, it is an object of the invention to provide a product comprising a substrate and an energy sensitive indicia-former carried by said substrate that undergoes conversion from a first visual condition to a second visual condition.

[0010] It is another object of this invention to provide a packaging material which comprises such energy sensitive indicia-former. It is a further object of this invention to provide a packaging material which shrinks in a controlled fashion upon exposure to heat of appropriate intensity, i.e. a shrink wrap material, thereby serving as a replacement for plastic lids as closures for drink containers.

[0011] It is a further object of this invention to provide a closure which comprises as the heat sensitive indicia-former, thermochromic ink that is converted from a first visual condition, preferably a visually indistinct, low contrast condition, to a second visual condition, preferably a visually distinctive, high contrast condition, when undergoing a temperature change. The first visual condition is preferably white. The second visual condition is preferably black or another dark hue, so that the conversion from the first to the second condition is clearly visually perceptible, thereby enabling the use of the ink as a marker of the contents of the container to which the closure is applied.

[0012] These and other objects are achieved by the packaging material and products of the present invention which comprise (a) a substrate and (b) an energy sensitive indicia-former carried by the substrate, which undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy. A preferred embodiment of the invention is a flexible packaging material which comprises (a) a substrate that is substantially transparent to radiant energy, (b) an energy absorbent material associated with at least a portion of the substrate, the absorbent material being sufficiently opaque to radiant energy to absorb and convert radiant energy into heat energy, thereby raising the temperature of the absorbent material, and (c) an energy sensitive indicia-former carried by said substrate which undergoes conversion from a first visual condition to a second visual condition upon an increase in temperature resulting from exposure to heat energy from the absorbent material. In a preferred form, the packaging material is a flexible film used to cover open-top containers. Other aspects of the invention include a method of manufacturing the above-described packaging and open-top containers covered by the above-described closures, and a method of filling an open-top container with a beverage and sealing the container with such closures.

BRIEF DESCRIPTION OF THE DRAWING

[0013] FIG. 1 illustrates a configuration used for the indicia-former.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The invention has many applications. These include use of the indicia-former in packaging, product marking, decorative and labeling material and as a barrier material to protect articles from damage from, for example, water, heat, cold and radiation. The products to be marked can be any product to which the indicia-former can be affixed. The packaging may be any material continuously used for packaging, such as paper, dimensionally stable materials such as cardboard and heat sensitive packaging such as polyurethane or transparent clam shells used to hold take-out food. The packaging material may also be a film, and preferably a flexible film.

[0015] The present invention will be described below with references to thin film closures which are preferably transparent. A particularly preferred type of film is shrink film, commonly referred to as “shrink wrap film.” It should be understood, however, that the packaging material of the invention may also be embodied in a variety of other forms, such as thermoformed lids, packaging for construction materials, paper goods and pharmaceutical containers.

[0016] End uses of these films include food packaging (for example, oxygen and moisture barrier bag for frozen poultry; prime meat cuts and processed meat and cheese products for preservation of freshness and hygienics) and non-food packaging (for example, “overwraps” for protecting goods against damage, soiling, tampering and pilferage) during transporting, distribution, handling and display. A typical end use is in retail sales where the films are wrapped air-tight around single or multiple items of compact disks, audio/video tapes, computer software boxes, magazines, confectionery, boxed products, single serve bowls, etc. Another common end use is in wholesale marketing, where multiple containers of bottled and canned goods such as beverages, condiments and personal hygiene products are sold in bulk. Yet another example is in courier shipping, where singular items of shrink-wrapped sporting goods and household appliances are safely transported without the need for bulky protective cardboard cartons.

[0017] The term “shrink film” refers to a plastic wrapping film which has the capability of shrinking when it is heated to near the melting point of the film. These films are commonly manufactured from plastic resins such as polyvinyl chloride (PVC); polypropylene (PP); linear-low density polyethylene (LLDPE); low density polyethylene (LDPE); high density polyethylene (HDPE); copolymers of ethylene and vinyl acetate (EVA); copolymers of ethylene and vinyl alcohols (EVOH); ionomers (e.g., SURLYN®, a registered trademark of E. I. duPont de Nemours and Co., Wilmington, Del.); copolymers of vinylidene chloride (e.g., PVDC, SARAN, a trademark of the Dow Chemical Company); copolymers of ethylene and acrylic acid (EAA); polyamides (PA); polyester, polystyrene, nylon and copolymers of ethylene and octene.

[0018] Film Substrate

[0019] Films particularly suitable for this purpose are flexible and substantially transparent to radiant energy. It will be appreciated by those skilled in the art that the thickness of the film can be varied without adversely affecting the operation of the present invention. For certain applications, when greater strength is required, substantial film thickness may be appropriate, such as 200-gauge (0.05 mm) and more. Considerations such as price, tear resistance, degree of shrink and clarity will affect the selection of an appropriate film and thickness to suit the commercial objective to be met. When used in contact with food or beverage products, the film should be approved by the appropriate regulatory authorities.

[0020] If the film is a shrink wrap film, the preferred shrink film substrate will have shrink characteristics suitable for the given packaging objectives. Some of these characteristics include the degree and orientation of the shrink and whether the shrink is to occur in both or only in one direction. Most common commercially available shrink film substrates are substantially transparent, meaning that light, infrared radiation and other forms of radiant energy pass through the substrate with very little, if any, absorption. In this case, substantially transparent means that at least 75% and preferably more than 90% of radiant energy passes through said film. Such transparency has led to the utilization of a heat absorbing medium, in physical contact with the film, to provide sufficient heat transfer to cause the desired shrink. A preferred film is a bi-axially oriented thin shrink film, having a preferred thickness of between approximately 50 to 150-gauge (0.0127 mm to 0.0381 mm) with the most preferred range being from 60 to 75-gauge (0.0152 mm to 0.0191 mm). Films meeting these specifications are a 75-gauge (0.0191 millimeter). CLYSAR® polyolefin shrink film sold by Bernis Corporation of Minneapolis, Minn. and a 75-gauge 0.0191 millimeter Exfilm™ polyolefin shrink film sold by Intertape Corp. of Bradenton, Fla.

[0021] An alternate film is a shrink film that is made of polyvinyl chloride and sold under the trade name #2024 REYNOLON®, a trade name of Reynolds Metals Company of Richmond, Va. Such films are disclosed in U.S. Pat. No. 6,291,037 B1 to Bakker, the contents of which are incorporated by reference herein.

[0022] Energy Absorbent Material

[0023] The energy absorbent material used in practicing this invention is a material which is adapted to be associated with at least a portion of the film substrate and is sufficiently opaque to absorb energy, preferably radiant energy. Radiant energy includes electromagnetic energy. See The Condensed Chemical Dictionary, 8th Edition, Revised by Hawley, Gessner G. (Van Nostrand Reinhold Company, New York, 1971) p. 750, in which radiation is defined as “energy in the form of electromagnetic waves (also called radiant energy or light).” The energy absorbent material functions to convert radiant (electromagnetic) energy into heat energy, thereby causing an increase in temperature of the film.

[0024] The absorbent material may be formed on the film by a variety of well-known methods such as printing means (flexographic, rotogravure, screen, transfer, etc.), brushing, spray coating, electrostatic coating, electrodeposition coating, flow coating, roller coating, dip coating, and the like. Printing is the preferred method (e.g., using flexographic or rotogravure techniques). The energy absorbent material includes at least one radiant energy absorbing component such as carbon black, graphite, iron oxide or the like. It will be appreciated by those skilled in the art that while certain specific energy absorbing materials have been identified, other material will also be suitable. What is desired is that the energy absorption rate of the material be sufficient so that upon exposure of the material to radiant energy, the heat generated will cause the desired degree of shrinkage of the film substrate in a predetermined amount of time.

[0025] In some cases, such films may require special treatment to be made more adaptable to printing of the energy absorbent material thereon, such as the application of a charged electric field, known as corona treating, which is done before printing to ensure adhesion of the absorbent material, and its carrier vehicle, if any. Other methods of promoting adhesion of the absorbent material include flame treatment or chemical primer application. For other films, such as polyvinyl chloride shrink films, corona treating is not necessary for good printing results.

[0026] In an alternate embodiment, the absorbent material may be physically incorporated into the film substrate and absorbs the radiant energy from within the film. This latter approach is less preferred to printing the absorbent material onto the film, since incorporating the absorbent material into the film may change the heat shrink characteristics of the film, such as flexibility, degree of shrink and the like.

[0027] According to the present invention, radiant energy means energy which may be transmitted from a suitable source to the absorbent layer, where it is absorbed to produce heat. In a preferred embodiment, the radiant energy is infrared radiation, which is efficiently absorbed by the absorbent layer, but not the film. In this way, heat energy is provided directly to the heat shrinkable film, thus avoiding the necessity of using any other heating medium, such as hot water or air, as in the past to carry the heat to the film. Thus, radiant energy in this context means any form of radiant energy that is transmissible through a medium such as air, without being substantially absorbed thereby. In a preferred embodiment, the radiant energy is supplied by a halogen bulb.

[0028] Carbon black provides good results when incorporated as the energy absorbent material on or in the film substrate. In particular, carbon black responds readily to the radiant energy output of a halogen bulb, which emits energy primarily in the visible and near infrared spectrum. Carbon black is a standard pigment in printing inks. This combined ability to blend with existing printing inks, and to absorb radiant energy such as infrared radiation, makes it well suited for use in the present invention.

[0029] A preferred energy absorbing material is carbon pigment-containing black ink sold by Coates Ink, a division of Sun Chemical, under the trade name Brazilia TN15787. This ink is readily adapted for printing onto the film substrate. The Brazilia inks are available in many colors and are broadly usable as absorbing materials according to the invention if the ink meets the requirements specified hereinabove. In a preferred embodiment, a reflective coating, preferably composed of white ink, is overlaid on the energy absorbent material in an amount sufficient to provide appropriate contrast with the areas the indicia-former, after it is caused to change from the first visual condition to the second visual condition, so that the latter is more easily observed. A preferred white ink is also sold by Coates Ink under the trade names Lunar TN12316 and Alfalam. The use of a white ink overlay depends on whether a black or white background is more effective in facilitating visual observation of the change in the indicia-former from a preferred low contrast, first visual condition to the high contrast, second visual condition.

[0030] Energy Sensitive Indicia-Former

[0031] As described hereabove, the energy sensitive indicia-former changes from one visual condition to a second visual condition. Change in visual condition would include but not be limited to change in appearance, hue, shade, perceptibility, including an enhancement in perceptibility, brightness, lightness, reflectiveness, absorptivity and color, including, for example, light gray to dark gray and white to black.

[0032] The preferred indicia-former is a thermochromic pigment or dye, which may be dispersed in a suitable carrier. These thermochromic materials are preferably used in the form of a thermochromic ink incorporating a thermochromic pigment or dye in a carrier vehicle. The thermochromic ink may be applied to the film substrate by the methods identified above for applying the absorbent material to the substrate. The preferred method is printing the thermochromic ink onto the substrate. The energy sensitive indicia-former is preferably an irreversible thermochromic ink that undergoes a change from white to black when adequately heated. A preferred thermochromic ink, (sold by Sherwood Technologies Limited of Nottingham, UK under the trade name Sherwood Type 90) is white below about 90° C. and undergoes an irreversible color change to black above about 90° C. Those of ordinary skill in the art will understand there are a variety of ink systems comprising one or more inks that can function as the radiant energy absorbent material and as the heat sensitive indicia-former.

[0033] Those of ordinary skill in the art will understand that a variety of ink colors can be used to obtain satisfactory results with the present invention and that a variety of energy sensitive indicia-formers other than thermochromic ink can also be used. Other inks that can be used in the invention as indicia-former are photochromic ink and electrochromic ink, such as those disclosed in U.S. Pat. No. 5,830,529 to Ross, the entire disclosure of which is incorporated herein by reference. Of course, photochromic and electrochromic inks, when employed as the indicia-former, would not require an absorbent layer. Instead, the indicia-former would be exposed directly to energy capable of causing the desired visual transformation of the indicia-former. In addition, those of ordinary skill in the art will understand that it is not necessary to coat the entire film substrate with ink. Moreover, those of ordinary skill in the art will appreciate that ink patterns can be used in applying the indicia-former to the substrate.

[0034] Preferred Applications of Absorbent and Indicia-Former Layers

[0035] As noted above, in a particularly preferred embodiment relating to films used to cover drink containers, an absorbent material comprising an ink composition containing carbon black is printed onto the film substrate. As this ink composition is black in appearance due to its carbon black content, white ink, for example, is applied over the portions of the black ink on which the indicia-former is to be located to show the contents of the container, in order to provide appropriate contrast for the indicia-former. Then the indicia-former is superimposed on the areas of white ink, preferably by printing.

[0036] There are, of course, numerous possible combinations of the absorbent layer, optional contrast layer and energy sensitive indicia-former that can be employed in carrying out the invention.

[0037] Those of ordinary skill in the art will understand that a variety of ink concentrations can achieve satisfactory results in the present invention. The second ink which acts as an energy sensitive indicia-former may be, as identified above, an ink that undergoes conversion from one color to another that contrasts with the color of the absorbent material upon a predetermined increase in temperature. Alternatively, it may be an ink that undergoes a different sort of visually observable conversion, such as a dye or luminescent pigment that is covered by a patch that disintegrates upon a specific increase in temperature. The requirements for the energy sensitive indicia-former are that they undergo a conversion from a first visual state to a second visual state upon exposure to appropriate energy, and that such changes in visual state or condition are perceptible to the human eye.

[0038] Radiant Energy Source

[0039] According to one embodiment of the invention, the radiant energy source produces radiant energy by emitting light having wave lengths in the visible and near infrared range. Those of ordinary skill in the art will understand that the wave length of the energy emitted by the radiant energy source is not particularly critical, provided that the absorbent material chosen is sufficiently absorbent within the range of the wave lengths emitted, so that conversion of the radiant energy into heat energy and increased temperature of the film is reasonably rapid.

[0040] A preferred radiant energy source is a conventional halogen lamp emitting light energy having wave lengths between about 600 nm to about 1400 nm. It has been found that tungsten halogen lamps are a preferred radiant energy source. However, those of ordinary skill in the art will understand that a number of different radiant energy sources are available which produce sufficient visible and near infrared radiation, such as xenon arc lamps. The energy source is preferred to have a total wattage of between 50 and 150 watts, and most preferably comprises one 100-watt bulb. The wattage should be chosen to provide sufficient energy to shrink the film without burning through the film. One radiant energy source that has been successfully used is a Osram JC24V-100 WG6.35 from Osram Sylvania, Inc., of Danvers, Mass.

[0041] In a preferred embodiment, the invention is used on packaging film which shrinks to form at least part of the package when exposed to heat. The packaging film includes a thin film substrate that contracts or shrinks when heated and which is substantially transparent to radiant energy. The film also includes an absorbent material that is sufficiently opaque to radiant energy to absorb and transfer to the substrate enough heat energy to cause the substrate to shrink when the film is exposed to a source of radiant energy. In a particularly preferred embodiment, the packaging film performs the function of a beverage container lid.

[0042] In use, radiant energy is caused to impinge on the film covering the container. The film has several marking options, such as “soda,” “diet cola,” and “water,” imprinted on the film. Next to each option is an indicia area having absorbent and thermochromic ink layers.

[0043] In a particularly preferred form, the marking options printed onto the film have absorbent, reflective or contrast-enhancing and thermochromic layers. Accordingly, after the container is filled with a specific beverage, radiant energy is directed to the film at the beverage option selected. The radiant energy may be directed by indexing a variable mask situated, between the radiant energy source and the indicia-former. The radiant energy source may comprise one lamp or more than one lamp. The radiant energy mask may have one orifice or several orifices through which the radiant energy is directed to the film. If the radiant energy is directed to the film at the beverage option selected through one orifice, the radiant energy results in the heating of the absorbent material precisely at the beverage option selected and thereby causes a localized increase in temperature of the indicia-former identifying that option. The increase in temperature causes the indicia-former identifying that option to change color (e.g., from white to black). The resultant black marking identifies the option selected, thus indicating the contents of the container. As radiant energy is not directed at the indicia-formers identifying other drink options, those indicia-formers do not change color. Accordingly, the beverage option selected is identified by the color change of the particular indicia-former identifying that option.

[0044] For example, if the container is filled with diet cola, the radiant energy is directed to, and causes the indicia-former identifying “diet cola” to change color, preferably from white to black. In this embodiment, the indicia-former changes to a color that contrasts with the background, so that the mark formed is easily identifiable. The identification marking can take numerous configurations. Preferred configurations are a circle enclosing the letter “x,” a check mark, or even a word or words identifying the beverage. An illustration of one of these configurations, namely the circle enclosing the letter “x,” is shown in FIG. 1. Preferably, the source of the radiant energy is positioned about 0.5 inch away from the film. In a most preferred form, the film is 0.932 inch from the center of the bulb filament and 0.464 inch from the top of the bulb. If the radiant energy source is one 100-watt halogen bulb, the film is exposed to the activated source typically for one-quarter second, with the power applied at 30% of capacity.

[0045] Alternatively, radiant energy can be directed to the film precisely at the beverage options not selected so that the beverage option selected would be the only option identified that did not undergo a change from one visual condition to a second visual condition. This process can be accomplished by directing the radiant energy through several orifices in the variable mask. The orifices are aligned to ensure that the radiant energy is directed to the film precisely at the indicia-former identifying the beverage options not selected.

[0046] In a preferred embodiment, this marking of the identification of the drink is carried out in the same sequence of operations during which the container is filled and the shrink wrap film cover is applied to the open top of the container; however, the energy source used for the marking operation is distinct from the energy source used to shrink wrap the cover over the open container.

[0047] The invention also includes a method of manufacturing the film of the invention. According to this method, an absorbent material is applied onto at least a portion of a thin film substrate which is substantially transparent to radiant energy. The absorbent material is sufficiently opaque to radiant energy to absorb radiant energy and convert it to heat energy. Then an energy sensitive indicia-former which undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy is applied onto the film substrate. The preferred methods of application are by printing.

[0048] The invention also is directed to drink containers covered by heat shrinkable flexible films. According to this embodiment of the invention, an open-top container is covered by a heat shrinkable, flexible packaging film having at least one heat sensitive indicia-former on the surface thereof. The film material comprises a thin film substrate which is flexible and contracts when heated, and which is substantially transparent to radiant energy, thereby remaining substantially unchanged by radiant energy. An absorbent material overlays at least a portion of the film substrate. The absorbent material is sufficiently opaque to radiant energy to absorb and convert radiant energy into heat energy. This heat energy causes the heat sensitive indicia-former carried by the film to undergo conversion from a first visual condition to a second visual condition. This change in visual condition preferably occurs at a temperature below that at which the film is caused to shrink.

[0049] The invention is further directed to a method of preparing and sealing beverage containers. According to this embodiment of the invention, an open-top container is filled with a beverage. The open-top container is then covered with the film of the invention. The film material is then subjected to energy, which is converted to heat energy. The heat energy causes the film material to shrink to form a seal over the open top, and the indicia-former is thereafter exposed to heat sufficient to transform it from the first visual condition to the second visual condition. Alternatively, the sealing step can be carried out simultaneously with or after the step of transforming the indicia former from a first visual condition to a second visual condition.

EXAMPLE 1

[0050] A test was performed to confirm the ability of the combination of the thermochromic and absorbing inks to form in the indicia-former after it undergoes exposure to radiant energy in the form of a lightbulb. A 75-gauge CLYSAR film manufactured by Bernis Corporation was printed with an absorbent material consisting of a black ink that contains carbon pigment sold under the name Brazilia TN15787 by Coates Ink, a division of Sun Chemical. Then a white ink sold by Coates Ink under the trade name Lunar TN12316 was printed over discrete portions of the black layer of absorbent material to provide indicia areas showing the various types of drink options, resulting in each indicia area having a gray color which serves to provide a contrasting background for the indicia formed upon conversion to the second visual condition. Next, an indicia-former composed of a white thermochromic ink manufactured by Sherwood Technologies, LLD, Nottingham, UK, under the trade name Sherwood Type 90 was printed over each gray-colored indicia area. The resulting indicia areas were gray in color.

[0051] The film was exposed to a 350-watt halogen lightbulb, causing the thermochromic ink to turn from gray to black. The change in color of the indicia area was visible, but it was felt that the contrast could be improved as described in EXAMPLE 2

EXAMPLE 2

[0052] The test procedure used in EXAMPLE 1 was repeated, except that additional white ink was provided for contrast on each indicia area, resulting in the indicia area having a white appearance relative to the gray appearance in EXAMPLE 1 above. Then the thermochromic indicia-former was added over the white layer and exposed to the same 350-watt halogen lightbulb, causing the indicia-former to change from white to black. Accordingly, the color change of the thermochromic ink in EXAMPLE 2 was more pronounced and easier to see.

EXAMPLE 3

[0053] The film substrate was treated with the absorbent ink for radiant energy absorption, white ink to provide contrast and thermochromic ink as the indicia-former, as in EXAMPLE 1. The treated film was exposed to the 350-watt halogen lightbulb for one-half second at a distance of 0.5 inch. Following such exposure, the thermochromic layer changed from white to black.

EXAMPLE 4

[0054] A packaging film was prepared as in EXAMPLE 3. The period of exposure of the treated film to the 350-watt halogen lightbulb at a distance of 0.5 inch was changed from 0.5 second to 1.0 second. The resulting heat melted the film, causing a hole to form in the film, indicating over-treatment.

EXAMPLE 5

[0055] The film of EXAMPLE 1 was exposed to radiant energy from a 100-watt halogen bulb for one-quarter of a second. The halogen bulb was operating at 30% of full power (duty cycle energized 30% of the time during activation period). Radiant energy was applied to the film at a distance of 0.5 inch. These conditions resulted in the transformation of the thermochromic ink from white to black, without any noticeable deleterious effect on the thermochromic ink layer.

EXAMPLE 6

[0056] The film of EXAMPLE 2 was exposed to radiant energy from a 100-watt halogen bulb for one-quarter of a second. The halogen bulb was operating at 30% of full power (duty cycle energized 30% of the time during activation period). Radiant energy was applied to the film at a distance of 0.5 inch. These conditions resulted in the transformation of the thermochromic ink from white to black, without any noticeable deleterious effect on the thermochromic ink layer.

EXAMPLE 7

[0057] The film of EXAMPLE 1 was treated with the black energy absorbent ink, two layers of white ink for contrast and thermochromic ink. The thermochromic ink was applied in the configuration of a circle enclosing the letter “x.” The film was exposed to radiant energy from a 100-watt halogen bulb for one-quarter of a second. The halogen bulb was operating at 30% of full power (duty cycle energized 30% of time during activation period). Radiant energy was applied to the film of a distance of 0.5 inch. The condition resulted in the transformation of the thermochromic ink from white to black, resulting in a very distinct circle enclosing the letter “x.”

[0058] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only with a true scope and spirit of the invention being indicated by the following claims.

Claims

1. A packaging material which comprises:

a) a substrate; and

b) at least one indicia-former carried by said substrate which undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy.

2. The packaging material according to claim 1, wherein the material is flexible.

3. The packaging material according to claim 1, wherein the material is dimensionally stable.

4. The film according to claim 1, wherein the absorbent material comprises at least one radiant energy absorbing component selected from the group consisting of carbon black, graphite and iron oxide.

5. The flexible material according to claim 1, wherein the indicia-former undergoes a change in perceptibility.

6. The flexible material according to claim 1, wherein the indicia-former undergoes a change in appearance.

7. The flexible material according to claim 1, wherein the indicia-former undergoes a change in hue.

8. The flexible material according to claim 1, wherein the indicia-former undergoes a change in shade.

9. The flexible material according to claim 1, wherein the indicia-former undergoes a change in brightness.

10. The flexible material according to claim 1, wherein the indicia-former undergoes a change in lightness.

11. The flexible material according to claim 1, wherein the indicia-former undergoes a change in saturation.

12. The flexible material according to claim 1, wherein the indicia-former undergoes a change in color.

13. The flexible material according to claim 1, wherein the indicia-former undergoes a change in reflectiveness.

14. The flexible material according to claim 1, wherein the indicia-former undergoes a change in absorbtivity.

15. The flexible material according to claim 1, wherein the indicia-former undergoes a change from white to black.

16. The flexible material according to claim 1, wherein the indicia-former undergoes a change from light gray to dark gray.

17. The film according to claim 1, wherein the indicia-former is configured to comprise a circle enclosing the letter “x.”

18. The film according to claim 1, wherein the indicia-former is configured to comprise a check mark.

19. The film according to claim 1, wherein the indicia-former is configured to comprise words identifying beverage options.

20. The film according to claim 1, wherein the heat sensitive indicia-former comprises thermochromic ink.

21. The film according to claim 20, wherein the thermochromic ink undergoes conversion from white to black upon exposure to heat energy from the absorbent material.

22. The film according to claim 20, wherein the thermochromic ink is applied onto the film substrate by printing.

23. The film according to claim 22, wherein the thermochromic ink is applied onto the film substrate by flexographic printing.

24. A product which comprises:

a) a substrate; and

b) at least one indicia-former carried by said substrate which undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy.

25. A flexible material which comprises:

a) a thin film substrate which is substantially transparent to radiant energy;

b) an absorbent material associated with at least a portion of the substrate, said absorbent material being sufficiently opaque to radiant energy to absorb said radiant energy and convert said energy into heat energy; and

c) at least one indicia-former carried by said film substrate which undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy from said absorbent material.

26. A heat-shrinkable flexible packaging film, said film having at least one energy sensitive indicia-former on the surface thereof, said film comprising:

a) a thin film substrate which is flexible and shrinks when heated, and which is substantially transparent to radiant energy, thereby remaining substantially unchanged on exposure to radiant energy;

b) an absorbent material associated with at least a portion of said substrate, said absorbent material being sufficiently opaque to radiant energy to absorb said energy and convert said radiant energy into heat energy, with said heat energy being transferred to said indicia-former; and

c) said energy sensitive indicia-former carried by said film being caused to undergo conversion from a first visual condition to a second visual condition upon exposure to said heat energy.

27. The packaging film according to claim 26, wherein the temperature at which the energy sensitive indicia-former undergoes conversion from one visual condition to another is lower than the temperature at which said film is caused to shrink.

28. The packaging film according to claim 26, wherein the film substrate is selected from the group consisting of polyvinyl chloride, polyolefins such as polypropylene, linear-low density polyethylene, low density polyethylene, high density polyethylene, copolymers of ethylene and vinyl acetate, copolymers of ethylene and vinyl alcohols, isonomers; copolymers of vinylidone chloride, copolymers of ethylene and acrylic acid, polyamides, polyesters, polystyrene, nylon and copolymers of ethylene and octenes.

29. The packaging film according to claim 28, wherein the film substrate is a polyvinyl chloride or a polyolefin.

30. The packaging film according to claim 29, wherein the film substrate is a bi-axially oriented shrink film having a thickness of between about 0.0127 millimeters and about 0.0381 millimeters.

31. The packaging film according to claim 26, wherein the absorbent material comprises at least one radiant energy absorbing component selected from the group consisting of carbon black, graphite and iron oxide.

32. The flexible material according to claim 26, wherein the indicia-former undergoes a change in perceptibility.

33. The flexible material according to claim 32, wherein the indicia-former undergoes an enhancement in perceptibility.

34. The packaging film according to claim 26, wherein the heat sensitive indicia-former comprises an ink elected from the group of thermochromic pigment, thermochromic dye and thermochromic ink.

35. The packaging film according to claim 34, wherein the heat sensitive indicia-former comprises thermochromic ink.

36. The packaging film according to claim 35, wherein the thermochromic ink undergoes conversion from white to black upon an increase in temperature due to heat energy from the absorbent material.

37. The packaging film according to claim 26, wherein the heat sensitive indicia-former is applied to the film substrate by printing.

38. The packaging film according to claim 37, wherein the thermochromic ink is applied onto the film substrate by flexographic printing.

39. The packaging film of claim 26, wherein the thermochromic ink is applied to the film surface by brushing.

40. The film according to claim 26, wherein the indicia-former is configured to comprise a circle enclosing the letter “x.”

41. The film according to claim 26, wherein the indicia-former is configured to comprise a check mark.

42. The film according to claim 26, wherein the indicia-former is configured to comprise words identifying beverage options.

43. A method of sealing a beverage in an open-top container, said method comprising the steps of

a) filling the container with the beverage;

b) applying over the open top of the container the heat-shrinkable flexible packaging film of claim 26; and

c) exposing the film to at least one radiant energy source, resulting in the conversion of the radiant energy to heat energy that causes the film to shrink and seal the open top of the container and change the indicia-former from a first visual condition to a second visual condition.

44. The method according to claim 43, wherein the radiant energy sources used to shrink and seal the film and to change the indicia-former from the first visual condition to the second visual condition are distinct.

45. The method according to claim 43, wherein the radiant energy source is a halogen lamp.

46. The method according to claim 43, wherein the radiant energy source is a tungsten halogen lamp emitting light energy having wave lengths of between about 600 nm and about 1400 nm.

47. In combination, an open-top container, the open top of which is covered by a heat-shrinkable flexible packaging film, said film comprising:

a) a thin film substrate which is flexible and shrinks when heated, and which is substantially transparent to radiant energy, thereby remaining substantially unchanged by radiant energy;

b) an absorbent material associated with at least a portion of said substrate, said absorbent material being sufficiently opaque to radiant energy to absorb said radiant energy and convert said radiant energy into heat energy; and

c) an energy sensitive indicia-former carried by said film and comprising an ink formulation which undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy converted from the absorbent material.

48. The combination of claim 47, wherein the indicia-former undergoes conversion at a temperature below that at which said film is caused to shrink.

49. The combination of claim 47, wherein the absorbent material comprises at least one radiant energy absorbing component selected from the group consisting of carbon black, graphite and iron oxide.

50. The combination of claim 47, wherein the heat sensitive indicia-former is selected from the group consisting of thermochromic pigment, thermochromic dye and thermochromic ink.

51. The combination of claim 47, wherein the heat sensitive indicia-former is thermochromic ink.

52. The combination of claim 47, wherein the open-top container is a beverage container.

53. The combination according to claim 47, wherein the indicia-former is configured to comprise a circle enclosing the letter “x.”

54. The combination according to claim 47, wherein the indicia-former is configured to comprise a check mark.

55. The combination according to claim 47, wherein the indicia-former is configured to comprise words identifying beverage options.

56. A method of manufacturing a flexible film packaging material, said method comprising the steps of:

a) applying to a thin film substrate an absorbent material being sufficiently opaque to radiant energy to absorb said radiant energy and convert said radiant energy into heat energy; and

b) applying to the substrate of the film a heat sensitive indicia-former which undergoes conversion from a first visual condition to a second visual condition upon exposure to heat energy.

57. The method according to claim 56, wherein application steps (a) and (b) are carried out by printing the absorbent material and heat sensitive indicia-former onto the film.

58. A heat shrinkable flexible packaging film, said film having at least one energy sensitive indicia-former on the surface thereof, said film comprising:

a) a thin film substrate which is flexible and shrinks when heated, and which is substantially transparent to energy, thereby remaining substantially unchanged on exposure to energy; and

b) said energy sensitive indicia-former carried by said film comprising an ink formulation which undergoes conversion from a first visual condition to a second visual condition upon exposure to energy.

59. The heat shrinkable flexible packaging film according to claim 58, wherein the indicia-former is selected from the group consisting of photochromic ink and electrochromic ink.