Patent Publication Number: US-2013251905-A1

Title: Method of applying thermal ink to beverage containers

Description:
FIELD OF THE INVENTION 
     The invention generally relates to methods of applying inks to containers such as beverage containers, and more specifically to methods of applying thermal inks to beverage containers in a controlled manner to reduce the amount of ink used, yet to employ use of the thermal inks to still sufficiently display temperature conditions of the containers. 
     BACKGROUND OF THE INVENTION 
     There are numerous methods of applying indicia to a substrate such as a label of a container, as well as numerous methods of applying indicia directly to a container such as an aluminum can. Sophisticated printing techniques have developed over time allowing containers to employ very ornate and complex container designs. 
     For beverage containers, it is known to apply thermal or thermal/thermochromic ink to the container sidewalls. The thermal ink can be used as an indication of the temperature of the beverage within the container. More specifically, selected thermal inks applied to a container undergo a color change as the beverage changes temperature, and the color(s) displayed by the thermal inks correspond to a known temperature range. Accordingly, beverage containers may incorporate the use of thermal inks to convey information to the consumer as to the temperature of the beverage, and whether it is at an optimum temperature for consumption. 
     Examples of references that disclose the use of thermal inks on beverage containers include the U.S. Pat. Nos. 4,919,983; 5,400,610, and 7,556,425. Other references include the published U.S. Application Publication Nos. 20100308032, 2008084915, and 20030000451. 
     Although thermal inks provide a unique capability for conveying information to a consumer, thermal inks are relatively expensive as compared to other types of inks Furthermore, thermal inks are not easily applied with consistent thicknesses, especially for application upon smooth surfaces such as aluminum. In order to overcome problems associated with applying an adequate amount of thermal ink to a designated area of a container, the preferred practice has been to flood coat a significant portion of the container sidewall with the ink, and then to print over the thermal ink with the remaining portions of the label pattern and lettering. 
     Not only does the use of thermal ink materially increase the cost of manufacturing a container, but use of the thermal ink requires a separate printing step, and a time delay in order for the thermal ink to set prior to finishing the labeling of the container. Even with application of thermal ink to paper-based materials, the thermal ink is applied in a flood coat manner which covers a significant portion of the material, and the remaining printing of the label is then completed in a subsequent printing process. 
     Although thermal inks provide the capability of conveying temperature information to consumers, the disadvantages of using thermal ink make its use on many containers infeasible due to the increased cost associated with the use of the thermal inks Therefore, there is a need to provide thermal inks for containers in which the thermal ink may be incorporated in the container to adequately convey temperature information to a consumer, but significantly reducing the costs of using the thermal inks 
     SUMMARY 
     In accordance with a method of the present invention, in one aspect of the invention, a method is provided to apply thermal inks to discrete portions of a container without the requirement for flood coating a larger continuous area of the container. 
     In another aspect of the invention, the method includes applying ink to portions of the container other than the sidewall of the container, namely, the opening tab of the container mounted to the top surface or end of the container. 
     In yet another aspect of the invention, thermal ink is applied to the opening tab of the container in a selected amount and on a pre-designated area of the tab, which therefore limits the amount of thermal ink used, yet still provides an adequate color indication corresponding to the temperature of the beverage. 
     In yet another aspect of the invention, the method includes calculating an ambient temperature offset that ensures the color displayed to a consumer corresponds to the estimated temperature of the beverage. More specifically, since the opening tab has a significant portion of its area that is not in direct contact with the container, ambient temperatures will more greatly affect the temperature of the exposed surface of the opening tab that has thermal ink applied thereto. Therefore, an offset calculation may be made which takes into consideration how quickly ambient temperature conditions may affect the temperature of the opening tab after it has been removed from a controlled temperature environment such as a refrigerator. 
     Among the many advantages of the invention, which will be made more apparent by a review of the following detailed description of the drawings, provision of a thermal ink on a container is provided that not only reduces the amount of the thermal ink used on the container, but still provides a convenient temperature indicator for the consumer. Another advantage of applying thermal ink to the opening tab is that the opening tab is a portion of the container that the consumer routinely views when opening the container, which therefore provides a convenient location for the user to also view an indication of the temperature of the container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a prior art printing process in which an ink such as thermal ink is applied as a flood coating to a material; 
         FIG. 2  is a schematic diagram of a printing process that is capable of applying thermal ink in registered or pre-designated print rows to achieve the method of the invention; 
         FIG. 3  is another schematic view of a printing process that can be used to achieve the method of the present invention; 
         FIG. 4  is a plan view of a strip of metal, namely, metal stock that had been pre-cut or pre-stamped in three rows of elements for use as opening tabs of containers, and further showing thermal ink applied in the registered print rows corresponding to rows of the opening tabs formed on the tab stock; 
         FIG. 5  is an enlarged fragmentary perspective view of an example gravure cylinder that can be used with a selected printing method to create the registered print rows for applying to a selected material such as the tab stock; and 
         FIG. 6  is a plan view of a container end incorporating an opening tab coated/printed with a selected thermal ink(s). 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a prior art method is illustrated for applying an ink, such as thermal ink, to a material. More specifically, the schematic of  FIG. 1  illustrates an ink source  80  that communicates with a transfer cylinder  82  that transfers ink from the cylinder  82  to a strip of material  88  which is progressively moved by a driving roller  84 . As shown, the strip of material  88  is positioned between the transfer roller  82  and the drive roller  84 , and the ink is uniformly transferred in a flood coating from the transfer roller  82  to the side of the material that faces and contacts the transfer roller  82 . A doctor blade  86  is used to limit or otherwise control the amount of ink that is transferred to the material  88  by adjusting the amount of pressure applied by the doctor blade to the exposed printing surface of the transfer roller  82 . As one can appreciate by reviewing the  FIG. 1 , the flood coating of ink across substantially all of the surface of the material  88  results in use of a significant amount of thermal ink. 
     Referring to  FIG. 2 , an example printing process is shown for a first preferred embodiment of the method of the present invention. In this example, thermal ink is applied by a rotogravure or engraving printing process. The schematic diagram of  FIG. 2  is similar to what is shown in the prior art of  FIG. 1 ; however, the manner in which the ink is transferred to the material is achieved by small engravings or recesses/indentations formed on the gravure cylinder  12 . 
     More specifically, the  FIG. 2  illustrates a source of ink  10 , the gravure cylinder  12 , and an impression cylinder or roller  14 . A doctor blade  16  is also used for controlling an amount of the ink to remain on the cylinder  12 . Registered or aligned print rows  18  are formed after contact of the doctor blade  16  with the exposed surface of the gravure cylinder  12 . That is, the doctor blade  16  wipes off the ink from the roller  12  except for the engraved or recessed portions of the cylinder that hold ink. Referring also to  FIG. 5 , the gravure cylinder  12  is shown with three engravings or recesses that, when filled with ink, form the registered print rows  18 . The remaining portions  24  of the exposed surface of the gravure cylinder, after rotating past the doctor blade  16 , have no observable amounts of ink which remain on the portions  24  because the doctor blade is preferably positioned to effectively scrape or wipe off substantially all of the ink from the portions  24 . Therefore, the resulting registered print rows  18  with ink therein come into contact with the material  20  via the impression roller  14  which places a designated amount of force against the material  20  to contact the registered print rows  18  on the gravure cylinder  12 . The resulting application of the thermal ink is therefore shown in this example as three uniform, spaced, registered print rows  18  that are aligned with designated portions of the material  20 . 
     It shall be appreciated that the size of the elements shown in the  FIG. 2  are not to scale, and are provided for schematic illustrative purposes only to adequately convey how the methods of the invention can be achieved. In practice, the rollers may be quite large as compared to the width of the strip of metal stock, and therefore it is possible to apply thermal ink to much larger sized pieces of metal stock. Additionally, although only one ink is shown in the ink source  10 , it is also contemplated with the method of the invention to use more than one ink. This can be achieved by sectioning or isolating the ink source  10  into a plurality of ink containers or wells, and each well having a pre-selected type of thermal ink. In some circumstances, it may be desirable to use more than one thermal ink on a beverage container to convey different temperature ranges to a consumer. Additionally, it is contemplated that application of the different inks can be applied to pre-selected and different portions of the container in order to convey temperature information. For example, the opening tab could include one or two inks, and the container sidewall could include one or more different inks in pre-selected patterns, but not a flood coating. 
       FIG. 2  is also intended to generally illustrate gravure printing. However, the method of the invention can be achieved with other types of printing processes. For example, referring to  FIG. 3 , another printing process that may achieve the method of the present invention includes flexography or letter press printing in which the image is transferred to the targeted material by a flexible relief plate as opposed to engravings. The relief plate has very small raised surfaces or protrusions that represent the particular pattern which is desired to be printed on the material. 
     This flexographic printing method may be achieved with a series of cylinders/rollers as shown in  FIG. 3 . More specifically,  FIG. 3  illustrates a first ink supply roller or cylinder  26  whose purpose is to pick up and deliver a relatively heavy flow of ink from the ink source  10 . The ink supply cylinder  26  contacts an anilox roll  27 . Typically, the anilox roll  27  is a chrome or ceramic plated roll covered with a continuous series of very small engravings. For example, the number of engravings or cells may range from 100-1000 cells per linear inch. The purpose of the anilox roll  27  is to supply a very fine film of ink to printing plates  29  that are secured to a printing plate cylinder  28 . As also shown, a reverse angled doctor blade can be used to wipe excess ink from the anilox roll  27 . The printing plate cylinder  28  is installed between the anilox roll  27  and the impression cylinder or roller  14 . The raised surfaces of the printing plates  29  pick up ink from the anilox roll and transfer it to the material  20  which is positioned between the impression cylinder  14  and printing plate cylinder  28 . Typically, the impression cylinder  14  has a smooth and highly polished exposed surface that supports the material when it contacts the printing plates  29 . Obviously, the speeds of rotation of the cylinders must match one another in order to advance the material  20  at a controlled, steady rate. 
     Another type of printing that is contemplated with the method of the invention also includes lithography printing. According to present methods of lithography, the image to be replicated on a targeted material is achieved by use of an image that is made of a polymer coating applied to a flexible plate, such as aluminum. The flexible metallic plate is then placed in contact with an image accepting surface, such as lithographic limestone or a metallic surface. This image accepting surface is slightly roughened or etched and divided into two regions. The first region is a hydrophilic region that accepts a film of water, and thereby repels inks which are typically oil-based. The other region is a hydrophobic region that repels water and therefore accepts the ink because the surface tension is greater on the image area in which the ink is found, and therefore this region remains dry. The image can be transferred directly from the image accepting surface, in which case the orientation of the image is reversed, or the image can be transferred by an offset element, that is, by transferring the image onto a flexible sheet of material such as rubber. Additionally, modern offset lithographic processes may also be used taking advantage of known photographic processes in which the printing plates have brushed or roughened texture surfaces covered with a photo-sensitive emulsion. A photographic negative of the desired image is placed in contact with the emulsion. The printing plate is then exposed to ultraviolet light, and after development, the emulsion shows a reverse of the negative image which is thus a duplicate of the original image. The printing plate can be made of material such as flexible aluminum, polyester, or milar, and is then affixed to a cylinder in the printing press. Dampening rollers apply water that covers the blank portions of the plate, but the water is repelled by the emulsion of the image area. Hydrophobic ink, which repels water, therefore only adheres to the emulsion of the image area. The hydrophobic ink is then applied by inking rollers to the material. The emulsion of the image area can be configured to correspond to precisely how a user wishes to apply the ink, and in the present case, a thermal ink to be applied to a component of a container, such as ink applied to create the registered print rows  18 . 
     In addition to lithography or offset lithography, it is also contemplated that thermal inks can be applied by a screen printing process as well. As understood by those skilled in the art, screen printing is achieved by the transfer of ink or another printing medium through a mesh or screen that has been tightly stretched over a frame, and to which a stencil has been applied. The particular pattern of openings in the stencil determines the image that is transferred to the targeted material. The ink is forced through the screen, such as by a squeegee device, and the ink is therefore imparted onto the material according to the particular stencil image selected. As applied to the present invention, the particular configuration of the stencil can therefore be selected to avoid a flood coating and to only apply thermal ink to the pre-designated areas of the container components. 
     Now referring to  FIG. 4 , a strip of material  20  is illustrated in the form of a metallic stock which is used to form a plurality of opening tabs  30 . The strip of material, also referred to herein as tab stock, has numerous score lines  32  that define the outer shape of the opening tabs  30 . A plurality of openings or apertures is punched in the tab stock  20  and corresponds to other features of the opening tabs  30 . For example, a plurality of hinge point openings  34  are provided that receive rivets attached to the container ends for securing the opening tabs to the ends of the containers. A plurality of other apertures  36  are also shown that correspond to other features of the opening tab  30 . In the example of  FIG. 4 , there are three registered rows of printed thermal ink  18  that have been printed on the tab stock that correspond to pre-designated areas on the tab stock to receive the ink. These pre-designated areas are shown as continuous stripes or strips that cover the central portions of each of the opening tabs  30 . As also illustrated in  FIG. 4 , the thermal ink can be applied in very finely defined areas on the tab stock. Therefore, it is apparent that, as compared to traditional flood coating, incorporation of registered print rows results in savings in the amount of ink used, and also provides selective and controllable areas in which the ink can be applied. Further, the various openings  34  and  36  that are punched in the tab stock are not filled with ink. Since the tab stock is of a known thickness, the distance between the impression roller and gravure cylinder can be calibrated such that only ink is applied to the exposed surface of the tab stock. Therefore, additional savings of thermal ink can be realized since the registered print rows do not result in ink being applied into the openings/apertures  34  and  36 . 
       FIG. 4  provides just one example of how thermal ink could be applied to the opening tabs  30 , and a user has the capability in accordance with the method of the invention to choose an almost limitless number of patterns that could be applied to not only the opening tabs, but also the container sidewalls, main panels of the container ends, and combinations thereof. 
     Since at least the exposed upper surface of an opening tab is not in direct contact with the container, it may experience greater susceptibility to ambient temperature conditions after the beverage has been removed from a controlled temperature environment (such as a refrigerator). Accordingly, as contemplated within the method of the invention, a type of ink can be selected that compensates for an average amount of time it may take for a consumer to view and open the container. For example, at a typical social event, a few of the beverages may be opened immediately after being removed from a refrigerated environment, but there may be a significant number of beverages that are not immediately consumed. Therefore, there can be extended time periods in which these containers may be exposed to the warmer ambient temperatures and therefore, the opening tabs may heat faster than the beverages within the containers. To address this possibility, it is contemplated that slower reacting thermal inks can be used in which the inks are slower to change color based on ambient temperature conditions. Also, multiple different types of inks could be used to provide a more accurate and continuing temperature indication, which could include a combination of faster and slower reacting thermal inks Finally, depending upon the particular construction and shape of the opening tabs used, and the manner in which the tabs are mounted on the container ends, data can be gathered to estimate how ambient temperature conditions could affect the upper surface temperature of the opening tabs, and types and patterns of inks could be selected accordingly. 
     In summary, applying thermal ink(s) to opening tabs results in a reduced amount of thermal ink used as opposed to flood coating a portion of the sidewall of the container. Yet, applying the thermal ink(s) to the opening tabs still provides an effective manner in which to present thermal inks to a consumer so the consumer can easily judge the temperature of the beverage based upon the color(s) of the thermal inks used. 
     Although the above described methods of the invention have been described with respect to various preferred forms or types of printing processes, it shall be understood that the invention may depart from the teachings of these preferred printing processes commensurate with the scope of the claims appended hereto.