Labeling method employing radiation curable adhesive

Details Labeling method employing radiation curable adhesive Labeling method employing radiation curable adhesive

2000-11-02

2003-02-04

Ball, Michael W. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C156S275500, C156S257000, C156SDIG002

Reexamination Certificate

active

06514373

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to a labeling apparatus and method for applying labels to containers, and more particularly to a labeling apparatus and method employing a radiation curable adhesive for adhering a label to a container. The labels employable in this invention are in the form of plastic, sheet fed/cut and stack labels, and can be formed of films that are transparent or opaque (including metallized films). Most preferably the radiation curable adhesive is a UV curable adhesive.
BACKGROUND ART
A number of prior art systems exist for applying labels to containers. These systems employ either continuous roll fed labels or cut and stack labels.
Prior art labeling apparatus and methods employing labels in continuous roll form include label cutting and registration means for severing discrete labels from the roll and then registering them for attachment to the containers through a vacuum transfer drive system. In these prior art systems a hot melt adhesive generally is employed; being applied to both the leading and trailing edge of the back side of the labels for permitting attachment of the labels to the containers.
Although the above-described system is being commercially utilized, it does include a number of drawbacks for various applications. First, continuous roll fed labeling systems require both label cutting and registration units, which increase the complexity of the system. Second, hot melt adhesives are, at best, generally cloudy or milky in appearance and therefore are not effectively utilized to apply clear or transparent labels in a uniform fashion to clear containers. The uniform attachment of clear or transparent labels to clear containers, e.g., clear glass or plastic beer and soda bottles, is very desirable, providing a very clean finish, and also permitting the product inside of the bottle to be clearly and easily viewed through the label. A further deficiency in connection with the use of hot melt adhesives is that they generally are difficult to apply as a smooth, continuous layer to the label stock.
It is known to employ continuous rolls oftransparent pressure sensitive labels for application to clear containers. However, as discussed above, the use of these continuous rolls require cutting and registration units that increase the complexity of the system. Moreover, the rolls of pressure sensitive labels often include a release liner covering the adhesive surface, thereby necessitating the removal of the release liner from the label during the continuous process. This also introduces an undesired complexity and cost into the system.
It also is known to apply sheet fed/cut and stack labels (i.e., labels that have been cut off line and are retained in a stack within a dispensing magazine) to containers, such as bottles, in a continuous label application system. These latter prior art systems often employ a cold glue adhesive, which is water soluble, and sometimes employ a hot melt adhesive. When a cold glue adhesive is employed it is applied to a glue transfer pad by a rubber transfer roll, and then the glue transfer pad is moved into contact with the lower label of the stack to both apply the glue to that label and remove the label from the stack through surface adhesion between the label and the adhesive. Thereafter, the label, with the cold glue adhesive thereon, is moved to a transfer drum, from where it is then applied to a container, such as a glass bottle. These cold glue adhesives generally have been utilized only in connection with paper labels that are capable of absorbing the moisture from the water soluble adhesives. In other words, systems employing water soluble cold glue adhesives are not well suited for use with non-porous, plastic labels. Although hot melt adhesives also have been employed with cut and stack labels, they are subject to the same deficiencies discussed above with respect to the use of such adhesives on continuous label stock.
Based on the deficiencies of the existing prior art systems, a need exists for a labeling apparatus and method that is not required to handle an excessively tacky adhesive throughout the label handling and applying operations, and that is effective for use with plastic labels, preferably transparent plastic labels, for adhering such labels to containers; preferably clear glass bottles such as beer or soda bottles. Most preferably a need exists for the aforementioned type of system that does not require the use of label cutting and registration units of the type generally employed in labeling apparatus and methods that handle continuous roll fed labels.
OBJECTS OF THIS INVENTION
It is a general object of this invention to provide a method and apparatus for applying plastic labels to containers that are reliable in operation.
It is a further object of this invention to provide a method and apparatus for applying plastic labels devoid of any release liner to containers in a reliable manner.
It is a further object of the most preferred embodiment of this invention to provide a method and apparatus for applying transparent plastic labels to clear containers in a reliable manner.
It is a further object of the most preferred embodiment of this invention to provide a sheet fed, cut and stack, labeling method and apparatus for applying plastic labels to containers that do not require the use of label cutting and registration devices of the type included in labeling systems that handle labels in continuous roll form.
It is still a further object of this invention to provide a method and apparatus for applying a plastic label to a container wherein an excessively tacky adhesive is not required to be handled throughout the entire label forming and applying operations.
It is yet a further object of this invention to provide a method and apparatus for applying a plastic label to a container wherein an adhesive is rendered sufficiently tacky to effectively adhere it to the container just prior to applying the label to the container; the result being equivalent to utilizing a conventional pressure-sensitive label but without the attendant drawbacks thereof, as discussed earlier.
SUMMARY OF THE INVENTION
The above and other objects ofthis invention are achieved in a labeling apparatus and method wherein a radiation curable adhesive, which is not excessively tacky prior to curing (or partial curing), is applied to the surface of a label to be attached to a bottle, and the label, with the radiation curable adhesive thereon, is then sequentially fed through a curing operation to render the adhesive sufficiently tacky to adhere the label to a container, and then to a station for immediately applying the label to a surface of the container through the tacky adhesive on the label.
It is within the scope of this invention to cure the adhesive to a full pressure sensitive state in the curing operation. In this condition, additional curing of the adhesive after the label is applied to the container is not required to take place, and in fact, does not take place; the adhesive being sufficiently tacky to assure that the label remains permanently adhered to the container during normal handling of the container. It also is within the scope of this invention to only partially cure the adhesive in the radiation curing step to render the adhesive sufficiently tacky to initially adhere the label to a container. However, thereafter the adhesive will continue to cure, or set-up, to assure that the label remains permanently adhered to the container during normal handling ofthe container.
In accordance with the most preferred embodiment of this invention, the radiation curable adhesive is curable with ultraviolet radiation, although it is within the scope of the broadest aspects of this invention to employ other types of radiation curable adhesives, such as adhesives curable by radio frequency radiation and electron beam radiation. The most preferred adhesives useable in this invention should have a sufficiently low viscosity to permit them to be applied by an adhesive applicator roll to outer surfaces of tra

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