Heat-transfer label assembly

Details Heat-transfer label assembly Heat-transfer label assembly

2001-01-19

2003-03-25

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

C428S195100, C428S348000, C428S349000, C428S352000, C428S200000, C428S913000, C428S914000

Reexamination Certificate

active

06537651

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to heat-transfer label assemblies and more particularly to a novel heat-transfer label assembly.
Heat-transfer labels are implements commonly used to decorate and/or to label commercial articles, such as, and without limitation to, containers for beverages (including alcoholic beverages, such as beer), essential oils, detergents, adverse chemicals, as well as health and beauty aids. As can readily be appreciated, heat-transfer labels are desirably resistant to abrasion and chemical effects in order to avoid a loss of label information and desirably possess good adhesion to the articles to which they are affixed. Heat-transfer labels are typically constructed as part of a heat-transfer label assembly, with one or more heat-transfer labels printed on a removable carrier web.
One of the earliest types of heat-transfer label assemblies is described in U.S. Pat. No. 3,616,015, inventor Kingston, which issued October, 1971, and which is incorporated herein by reference. In the aforementioned patent, there is disclosed a heat-transfer label assembly comprising a paper sheet or web, a wax release layer affixed to the paper sheet, and an ink design layer printed on the wax release layer. In the heat-transfer labelling process, the label-carrying web is subjected to heat, and the label is pressed onto an article with the ink design layer making direct contact with the article. As the paper sheet is subjected to heat, the wax layer begins to melt. This enables the paper sheet to be released from the ink design layer, with a portion of the wax layer being transferred with the ink design layer onto the article and with a portion of the wax layer remaining with the paper sheet. After transfer of the design to the article, the paper sheet is immediately removed, leaving the design firmly affixed to the article and the wax transferred therewith exposed to the environment. The wax layer is thus intended to serve two purposes: (1) to provide release of the ink design from the web upon application of heat to the web and (2) to form a protective layer over the transferred ink design. After transfer of the label to the article, the transferred wax release layer is typically subjected to a post-flaming or post-heating technique which enhances the optical clarity of the wax protective layer (thereby enabling the ink design layer therebeneath to be better observed) and which enhances the protective properties of the transferred wax release.
Many heat-transfer label assemblies include, in addition to the layers described above, an adhesive layer (comprising, for example, a polyamide, phenoxy, or polyester adhesive) deposited over the ink design to facilitate adhesion of the label onto a receiving article. An example of a heat-transfer label assembly having an adhesive layer is disclosed in U.S. Pat. No. 4,548,857, inventor Galante, which issued Oct. 22, 1985, and which is incorporated herein by reference. Additionally, many heat-transfer label assemblies additionally include a protective lacquer layer interposed between the wax release layer and the ink layer. An example of such a label assembly is disclosed in U.S. Pat. No. 4,426,422, inventor Daniels, which issued Jan. 17, 1984, and which is incorporated herein by reference.
One phenomenon that has been noted with heat-transfer label assemblies of the type described above containing a wax release layer is that, quite often, a degree of hazing or a “halo” is noticeable over the transferred label when the transfer is made onto clear materials. This “halo” effect, which persists despite post-flaming or post-heating and which may detract from the appearance of the label, is caused by the presence of the wax coating around the outer borders of the transferred ink design layer. Hazing due to the wax release layer may also appear in “open-copy” areas of the label, i.e., areas of the label where no ink and no protective or adhesive lacquers are present, and also may detract from the appearance of the label.
In addition to and related to the aforementioned problem of hazing, when heat-transfer labels of the type described above are applied to dark-colored containers, the outer wax layer of the label often appears as a whitish coating on the container, which effect is undesirable in many instances. Furthermore, scratches and similar abrasions to the outer wax layer of the label can occur easily and are readily detectable.
Accordingly, to address the aforementioned issues, considerable effort has been expended in replacing or obviating the need for a wax release layer. One such approach to this problem is disclosed in U.S. Pat. No. 4,935,300, inventors Parker et al., which issued Jun. 19, 1990, and which is incorporated herein by reference. In the aforementioned Parker patent, the label assembly, which is said to be particularly well-suited for use on high density polyethylene, polypropylene, polystyrene, polyvinylchloride and polyethylene terephthalate surfaces or containers, comprises a paper carrier web which is overcoated with a layer of thermoplastic polyethylene. A protective lacquer layer comprising a polyester resin and a relatively small amount of a nondrying oil is printed onto the polyethylene layer. An ink design layer comprising a resinous binder base selected from the group consisting of polyvinylchloride, acrylics, polyamides and nitrocellulose is then printed onto the protective lacquer layer. A heat-activatable adhesive layer comprising a thermoplastic polyamide adhesive is then printed onto the ink design layer.
Although the above-described Parker label assembly substantially reduces the wax-related effects discussed previously, said label assembly does not quite possess the same release characteristics of heat-transfer label assemblies containing a wax release layer. In fact, when put to commercial use, the polyethylene release layer of the Parker label assembly was found to become adhesive when subjected to the types of elevated temperatures typically encountered during label transfer. Accordingly, another type of heat-transfer label assembly differs from the Parker heat-transfer label assembly in that a very thin layer or “skim coat” of carnauba wax is interposed between the polyethylene release layer and the protective lacquer layer to improve the release of the protective lacquer from the polyethylene-coated carrier web. The thickness of the skim coat corresponds to approximately 0.1-0.4 lbs. of the wax spread onto about 3000 square feet of the polyethylene release layer. The aforementioned “skim coat-containing” heat-transfer label assembly also differs from the Parker label assembly in that the heat-activatable adhesive of the “skim coat” label assembly is printed over the entirety of the ink and protective lacquer layers, with the peripheral edges of the adhesive layer in direct contact with the wax skim coat.
In addition to improving the release characteristics of the label assembly, the aforementioned wax skim coat also enables the label to be stretched non-uniformly, if desired, for application to articles of tapered cross-section.
An example of a “skim coat-containing” heat-transfer label assembly of the type described above is disclosed in U.S. Pat. No. 5,800,656, inventors Geurtsen et al., which issued Sep. 1, 1998, and which is incorporated herein by reference. According to one embodiment, the aforementioned Geurtsen label assembly is designed for use with silane-treated glass containers of the type that are subjected to pasteurization conditions, the label assembly including a support portion, a skim coat positioned on top of the support portion and a transfer portion positioned on top of the support portion. The support portion includes a sheet of paper overcoated with a release layer of polyethylene. The transfer portion includes an organic solvent-soluble phenoxy resin protective lacquer layer, an organic solvent-soluble polyester resin ink layer over the protective lacquer layer, and a water-dispersible acrylic adhesive resin layer over the ink and protec

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