Heat-transfer label including non-wax release layer

A heat-transfer label including a non-wax, non-silicone release layer for use in decorating an article, such as a glass container, without leaving a visually discernible release residue on the decorated article. In a preferred embodiment, the label includes a transfer portion, the transfer portion comprising a protective lacquer layer, an ink design layer over the protective lacquer layer, and a heat-activatable adhesive layer over the ink design and protective lacquer layers, the adhesive layer extending beyond the peripheries of the ink design and protective lacquer layers. The protective lacquer layer preferably includes a cross-linked phenoxy resin, the ink design layer preferably includes a polyester resin, and the adhesive layer preferably includes a polyester resin and an anti-blocking agent, such as a paraffinic wax. The label also includes a support portion, the transfer portion being positioned over the support portion for transfer of the transfer portion from the support portion to an article upon the application of heat to the support portion while the transfer portion is placed in contact with the article. The support portion includes a carrier, the carrier preferably being a polyester film. The support portion also includes a non-wax, non-silicone release layer positioned over the carrier and in direct contact with the protective lacquer layer and the periphery of the adhesive layer, the release layer preferably being made by (a) coating onto the carrier a composition preferably comprising about 5 to 30 wt % of an alkyl vinyl ether monomer having a carbon chain length of at least 18, about 40 to 80 wt % of a difunctional acrylate monomer, about 5 to 50 wt % of trifunctional acrylate monomer, and about 2 to 8 wt % of a free-radical UV photoinitiator and (b) activating the free-radical UV photoinitator. The release composition may also include up to about 1 wt % of a wetting agent, such as a fluoroalkyl surfactant, a silicone polyether wetting agent, and a silicone defoamer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1 , there is shown a schematic section view of one embodiment of a heat-transfer label constructed according to the teachings of the present invention, said heat-transfer label being represented generally by reference numeral 11 . Label 11 comprises a support portion 13 . Support portion 13 , in turn, comprises a carrier 15 . Carrier 15 may comprise any suitable material conventionally used as a carrier in heat-transfer labels, such as any of the carrier materials described in U.S. Pat. No. 3,922,435. For example, carrier 15 may be a plastic film or paper. Preferably, carrier 15 is a plastic film as plastic films are generally more durable than paper carriers and are comparable in terms of manufacturing costs. In addition, certain plastic films are sufficiently extensible to enable the selective stretching of various regions of a single label for application to atapered or conical article (see U.S. Pat. Nos. 5,709,770 and 5,735,996, both of which are incorporated herein by reference, for examples of labels that are stretched in selected areas for application to tapered articles). More preferably, carrier 15 is a clear plastic film. As can readily be appreciated, one benefit to using a clear material as carrier 15 is that, if desired, one can inspect the quality of the printed matter of the label by looking at said printed matter through carrier 15 (from which perspective said printed matter appears as it will on the labelled article), as opposed to looking at said printed matter through the adhesive layer of the label (from which perspective said printed matter appears as the mirror image of what will appear on the labelled article). A particularly preferred plastic material for use as carrier 15 is a clear polyester film, such as a clear polyethylene terephthalate (PET) film. This is because, at least as compared to some other plastic materials like polyethylene and polypropylene, polyester is a strong plastic material and makes a good substrate to be printed onto. In addition, unlike polyethylene, polyester does not tend to soften and become tacky at the types of temperatures typically encountered during heat-transfer. Examples of suitable polyester films for use in the present invention include the S10 brand 1.5 mil polyester film commercially available from Toray and the SM30 brand 1.5 mil polyester film commercially available from SKC America. Support 13 also includes a release layer 17 overcoated onto carrier 15 . Release layer 17 is a thermoset release material that separates cleanly from the below-described transfer portion of label 11 and is not transferred, to any visually discernible degree, with said transfer portion of label 11 onto an article being labelled. (For purposes of the present specification and claims, the term “visually discernible” is to be construed in terms of an unaided or naked human eye.) Release layer 17 does not contain any waxes or any silicones, except to the limited extent provided below, and the terms “non-wax” and “non-silicone,” when used in the present specification and claims to describe and to define the release layer, are defined herein to exclude from the release layer the presence of any and all waxes and silicones not encompassed by the limited exceptions provided below. Release layer 17 is preferably made by (a) coating onto carrier 15 a composition comprising (i) a functionalized alkyl monomer having a carbon chain length of at least 18 carbon atoms, (ii) a crosslinking monomer reactive with said functionalized alkyl monomer, and (iii) an initiator for effecting at least a partial cure between said functionalized alkyl monomer and said crosslinking monomer and (b) activating said initiator. The functionalized alkyl monomer of the aforementioned composition is preferably an alkyl vinyl ether monomer having a carbon chain length of at least 18 carbon atoms. More preferably, said alkyl vinyl ether monomer is C n H 2n&plus;1 O—CH&boxH;CH wherein n is at least 18 and no greater than 30. A particularly preferred alkyl vinyl ether monomer is octadecyl vinyl ether, which is commercially available as RAPI-CURE® ODVE from ISP Technologies Inc. (Wayne, N.J.). The foregoing alkyl vinyl ether monomer is preferably present in said composition in an amount constituting about 5 to 30 wt %, more preferably 10 to 20 wt %, of said composition. An example of another type of functionalized alkyl monomer suitable for use in the present invention is an epoxidized alpha olefin having a carbon chain length of at least 18 carbon atoms, such as VIKOLOX® 24-28 epoxidized alpha olefin, which is commercially available from Elf Atochem North America, Inc. (Minneapolis, Minn.). Still another type of functionalized alkyl monomer suitable for use in the present invention is an alkyl acrylate having a carbon chain length of at least 18 carbon atoms. Where the functionalized alkyl monomer of the above-described composition is an alkyl vinyl ether monomer, the crosslinking monomer of the above-described composition preferably is at least one multifunctional acrylate monomer and more preferably is a mixture of a difunctional acrylate monomer and a trifunctional acrylate monomer. (Where the functionalized alkyl monomer is an epoxidized alpha olefin, the crosslinking monomer is preferably an epoxy, and where the functionalized alkyl monomer is an alkyl acrylate, the crosslinking monomer is preferably an acrylate.) The aforementioned mixture of both difunctional and trifunctional acrylate monomers is believed to work better than either acrylate monomer individually as the difunctional acrylate monomer tends to be less polar than the trifunctional acrylate and, therefore, releases better from the heat-activatable adhesive layer of the transfer portion to be described below whereas the trifunctional acrylate monomer tends to form a more extensive network of bonds throughout the layer than does the difunctional acrylate monomer and, therefore, tends to endow the release layer with an improved degree of chemical resistance and hold-out of layers deposited thereonto. In general, the difunctional and trifunctional acrylate monomers are preferably as non-polar for use in the present invention, as may difunctional oligomers with hydrocarbon backbones, such as 1,6-hexane diol diacrylate. An example of a suitable difunctional acrylate monomer for use in the present invention is propoxylated neopentyl glycol diacrylate, which is commercially available from Sartomer Company as SR-9003 propoxylated neopentyl glycol diacrylate. An example of a suitable trifunctional acrylate monomer for use in the present invention is propoxylated trimethylolpropane triacrylate, which is commercially available from Sartomer Company as SR-492 three mole propoxylated TMPTA. The foregoing difunctional acrylate monomer is preferably present in said composition in an amount constituting about 40 to 80 wt %, more preferably about 60 to 70 wt %, of said composition, and the foregoing trifunctional acrylate monomer is preferably present in said composition in an amount constituting about 5 to 50 wt %, more preferably about 10 to 30 wt %, of said composition. The free-radical initiator of the foregoing composition preferably is a free-radical photoinitiator and more preferably is a free-radical UV photoinitiator. An example of a suitable free-radical initiator for use in the present invention is Irgacure® 500 free-radical UV photoinitiator, a commercially available product from CIBA-GEIGY that comprises a mixture of two photoinitiators, 1-hydroxycyclohexyl phenyl ketone and benzophenone. The foregoing free-radical UV photoinitiator is preferably present in said composition in an amount constituting about 2 to 8 wt %, more preferably about 3 to 6 wt %, of said composition. The foregoing release composition may also include a very small amount of a wetting agent to improve the lay-down of the release composition onto carrier 15 and to improve printing of the transfer portion of the label onto release layer 17 . Examples of suitable wetting agents include fluoroalkyl surfactants, silicone polyether wetting agents, and silicone defoamers, said wetting agents being added to the release composition in an amount constituting about 0.1 to 1.0 wt % of said composition. To form release layer 17 , the above-described composition is deposited onto carrier 15 , preferably to a coat weight of at least about 1.0 gram/meter. The deposited composition is then UV cured for a number of seconds or minutes. This may be done, for example, using a Fusion benchtop model curing unit using one Fusion “H” bulb at 55% power and belt speed of 125 fpm. Nitrogen inerting may also be used to displace oxygen to roughly 120 ppm or less of oxygen. Although not wishing to be limited to any theory behind the invention, the present inventors believe that, in those instances in which the subject composition includes the aforementioned alkyl vinyl ether monomer, difunctional acrylate monomer, and trifunctional acrylate monomer, the cured product is a partially-cured release coating, with a portion of the allyl vinyl ether monomer bonded to the difunctional acrylate monomer and/or the trifunctional acrylate monomer and a portion of the alkyl vinyl ether monomer not bonded to either of the difunctional acrylate monomer or the trifunctional acrylate monomer. The present inventors believe that the presence of some unbonded alkyl vinyl ether monomer in the release coating may be beneficial in endowing the release coating with its release properties. Although release layer 17 is particularly well-suited for use as a release coating in a heat-transfer label, release layer 17 may also be useful as a release coating for metal sheets in foil stamping techniques and as a release coating for certain pressure sensitive adhesives and adhesive tapes, such as Scotch brand adhesive tape &num;810. Label 11 further comprises a transfer portion 21 (it being understood that a plurality of transfer portions 21 may be spaced apart on a single support portion 13 ). Transfer portion 21 , in turn, includes (i) a protective lacquer layer 23 printed directly on top of a desired area of release layer 17 , (ii) an ink design layer 25 printed directly onto a desired area of lacquer layer 23 , and (iii) a heat-activatable adhesive layer 27 printed directly onto ink design layer 25 , any exposed portions of lacquer layer 23 and a surrounding area of release layer 17 . Where the article being labelled is a glass article, such as a silane-treated glass container, protective lacquer layer 23 preferably is a phenoxy protective lacquer layer, such as that described in U.S. Pat. No. 5,800,656, or is a cross-linked phenoxy lacquer layer such as that disclosed in U.S. patent application Ser. No. 09/093,150, which is incorporated herein by reference. This is because phenoxy protective lacquer layers tend to possess the high degree of scuff resistance and chemical resistance preferred for glass articles. It should be understood, however, that release layer 17 releases well from a variety of protective lacquer layers of different compositions and that other types of protective lacquer resins may also be suitable for use in layer 23 depending upon the type of article being labelled and the use to which the decorated article is to be put. Examples of phenoxy lacquer resins suitable for use in the aforementioned phenoxy or crosslinked phenoxy protective lacquer layer include the UCAR® Phenoxy Resins (Phenoxy Associates, Rock Hill, S.C.), which have the following chemical structure: 1 A particularly preferred UCAR® Phenoxy Resin is PKHH, a medium weight grade of the above structure which, at 40% solids, by weight, in methyl ethyl ketone (MEK), has a solution viscosity of 4500 to 7000 mPa·s(cP). Examples of a suitable cross-linker for cross-linking the aforementioned phenoxy resin include partially methylated melamine-formaldehyde resins of the type present in the CYMEL 300 series of partially methylated melamine-formaldehyde resin solutions (Cytec, Industries, Inc., West Paterson, N.J.) and, in particular, CYMEL 370 partially methylated melamine-formaldehyde resin solution (88±2% nonvolatiles, iBuOH solvent). Preferably, the solids of the aforementioned CYMEL 370 resin solution constitute no more than about 5%, by weight, of lacquer layer 23 (with the remainder of lacquer layer 23 being the aforementioned phenoxy resin) since amounts of CYMEL 370 in excess thereof may cause lacquer layer 23 to become tacky. To form a cross-linked phenoxy lacquer layer 23 , a lacquer composition comprising the above-identified phenoxy lacquer resin, a suitable cross-linker and one or more suitable volatile solvents are deposited onto a desired area of release layer 17 , preferably by gravure printing or a similar technique. After deposition of the lacquer composition onto the desired area of layer 17 , the volatile solvent(s) evaporate(s), leaving only the non-volatile components thereof to make up lacquer layer 23 . In a preferred embodiment, the lacquer composition comprises about 20%, by weight, PKHH; about 1%, by weight, CYMEL 370 resin solution; about 59%, by weight, methyl ethyl ketone; and about 20%, by weight, toluene. Ink design layer 25 of transfer portion 21 , which layer may actually comprise either a single ink layer or a plurality of ink layers, may be made using one or more conventional inks, such as polyester inks, polyester/vinyl inks, polyamide inks and/or acrylic inks, as well as the phenoxy ink described in commonly-assigned, co-pending U.S. Ser. No. 09/204,424, which is incorporated herein by reference. Such inks typically comprise a resin of the type described above, a suitable pigment or dye, and one or more suitable volatile solvents. Ink design layer 25 is formed in the conventional manner by depositing, preferably by gravure printing, one or more ink compositions of the type described above onto one or more desired areas of lacquer layer 23 and, thereafter, allowing the volatile solvent(s) of the ink composition(s) to evaporate, leaving only the non-volatile ink components to form layer 25 . An example of polyester ink suitable for use in forming layer 25 comprises 18 wt % ViTEL® 2700 (a copolyester resin commercially available from Bostik, Middleton, Mass., having a high tensile strength (7000 psi) and a low elongation (4% elongation)), 6 wt % pigment, 30.4 wt % n-propyl acetate and 45.6 wt % toluene. An example of another suitable polyester ink comprises ViTEL® 2300 polyester resin (a copolyester resin also commercially available from Bostik having a high tensile strength (8000 psi) and a low elongation (7% elongation)). In those instances in which release layer 17 is formed using the above-described composition comprising an alkyl vinyl ether monomer, a difunctional acrylate monomer and a trifunctional acrylate monomer, adhesive layer 27 of transfer portion 21 preferably comprises a polyester-based adhesive; however, it is to be understood that other types of adhesive materials may also be suitable for use as layer 27 depending upon their release from release layer 17 (the periphery of adhesive layer 27 being in direct contact with release layer 17 ). Adhesive layer 27 is preferably formed by depositing, by gravure printing or the like, onto (i) ink layer 25 , (ii) exposed portions of lacquer layer 23 and (iii) a surrounding area of release layer 17 an adhesive composition comprising an adhesive resin and one or more volatile solvents and then evaporating the volatile component(s) of the composition (for example, by oven-heating for 30 seconds at 200° F.), leaving only the non-volatile solid component(s) thereof to form layer 27 . An example of a suitable polyester-based adhesive composition for use in forming a polyester-based adhesive of the type mentioned above comprises about 10.7 wt % of ViTEL® 2700 polyester resin, about 10.7 wt % of ViTEL® 2300, about 1.1 wt % of BENZOFLEX® S404 glyceryl tribenzoate plasticizer (commercially available from Velsicol Chemical Corporation, Chicago, Ill.), about 1.1 wt % HULS 512 adhesion promoter (commercially available from Sivento Inc., Piscataway, N.J.), about 19.20 wt % toluene and about 57.10 wt % methyl ethyl ketone. Adhesive layer 27 may additionally include an anti-blocking agent for use in preventing adhesive layer 27 from adhering to the underside of carrier 15 when a label assembly comprising a plurality of transfer portions 21 on a single support portionl 3 is wound into a roll. The inclusion of said anti-blocking agent in said adhesive may be particularly desirable in those instances in which adhesive layer 27 and carrier 15 have a high degree of adherence to one another, such as where adhesive layer 27 comprises a polyester-based adhesive and carrier 15 is a polyester film. An example of a suitable anti-blocking agent is a wax, such as a paraffinic wax, which is added to the adhesive composition used to form adhesive layer 27 in an amount constituting about 1 wt % of said composition. In those instances in which a wax is included in adhesive layer 27 , a percentage of said wax is believed to migrate to other layers of label 11 , including to the interface between release layer 17 and protective lacquer layer 23 . Evidence of said migration can be seen in FIG. 2 , where the oxygen content at the surface of various layers of a three-layer label assembly was measured by XPS, said assembly being made up of the above-described alkyl vinyl ether/acrylate release layer, the above-described cross-linked phenoxy protective lacquer positioned on top of said release layer and the above-described polyester with wax adhesive layer positioned on top of said phenoxy protective lacquer layer. Moreover, as seen in FIG. 3 , said wax migration appears to improve the release of protective lacquer layer 23 and adhesive layer 27 from release layer 17 . Nevertheless, notwithstanding the presence of said minute quantities of wax at the surface of release layer 17 , the present inventors did not detect any visually discernible amount of wax that was transferred from the release layer to the labelled article. Any such quantities of migrated wax do not render a release layer of the present invention outside the meaning of the term “non-wax.” Label 11 may be used in the conventional manner by contacting adhesive layer 27 with a desired article, such as a pre-heated, silane-treated clear glass container, while applying sufficient heat to the bottom of carrier 15 (about 300 to 450° F.) so as to cause transfer portion 21 to be released from support portion 13 and so as to cause adhesive layer 27 to become heat-activated for bonding to the desired article. Heat-transfer may alternatively be effected by directly heating or pre-heating the container only (so as to activate the heat-activatable adhesive placed in contact with the heated container) and not by directly heating the heat-transfer label itself. The present inventors have noted that, when label 11 is used to decorate silane-treated, clear glass containers, a good degree of label adherence and scuffresistance is achieved (i.e., at least about 5H pencil hardness, as measured by ASTM standard D3363-92a for film hardness on a substrate). One of the advantages associated with the use of a release layer like release layer 17 is that transfer portion 21 of label 11 can be of the “wrap-around” variety that completely encircles a container. The present invention may more clearly be understood by reference to the following examples, it being understood that such examples are illustrative and not to be considered as limiting of the invention. 
 EXAMPLE 1 A release formulation of the following composition was manually coated onto a 1.5 mil polyester film to a coat weight of about 1.0 gram/meter 2 : 1 Component Amount (% by weight) Sartomer Company SR90003 Propoxylated Neo- 60% pentyl Glycol Diacrylate Sartomer Company SR492 Propoxylated 21% Trimethylolpropane Triacrylate BASF Corp. ODVE octadecyl vinyl ether 15% Ciba-Geigy Irgacure 500 free-radical 3.9% photoinitiator 3M FC430 non-ionic fluorochemical surfactant 0.1% The coating was then cured with a Fusion benchtop model curing using one Fusion “H” bulb at 55% power and belt speed of 125 fpm. Nitrogen inerting was used to displace oxygen to roughly 120 ppm or less of oxygen. A transfer portion comprising a cross-linked phenoxy protective lacquer, a polyester ink and a polyester with wax adhesive as described above was printed onto the foregoing coated polyester film in the conventional manner. The thus-assembled label was then transferred onto a 275° F. glass bottle using a 180° F. platen. The decorated bottle was then visually inspected for the quality of the release and rated a “2” on a scale from “1” through “5,” with “1” being the best. 
 EXAMPLE 2 The procedure of Example 1 was repeated, except that the release composition was coated onto a 1.5 mil polyester film using a 7-roll coating machine applying roughly 1.0 gram/ 2 at a speed of 600 fpm and the coating was then cured with two banks of Fusion “H” bulbs, with nitrogen inerting to less than 50 ppm. The decorated bottle was again rated a “2.” 
 EXAMPLE 3 The procedure of Example 1 was repeated, except that the following release composition was used: 2 Component Amount (% by weight) Sartomer Company SR90003 Propoxylated Neo- 60% pentyl Glycol Diacrylate Sartomer Company SR492 Propoxylated 21% Trimethylolpropane Triacrylate BASF Corp. ODVE octadecyl vinyl ether 15% Ciba-Geigy Irgacure 500 free-radical 3.9% photoinitiator Byk-Chemie BYK-080 polysiloxane copolymer 0.1% The decorated bottle was rated a “2 to 3.” 
 EXAMPLE 4 The procedure of Example 1 was repeated, except that the following release composition was used: 3 Component Amount (% by weight) Sartomer Company SR90003 Propoxylated Neo- 77.5% pentyl Glycol Diacrylate Sartomer Company SR492 Propoxylated 7.5% Trimethylolpropane Triacrylate BASF Corp. ODVE octadecyl vinyl ether 10% Ciba-Geigy Irgacure 500 free-radical 4% photoinitiator Goldschmidt RC726 silicone release agent, 1% acrylate modified The decorated bottle was rated a “2,” but there was severe dewetting of the ink layer (presumably due to the presence of silicone in the release layer). 
 EXAMPLE 5 The procedure of Example 1 was repeated, except that the following release composition was used: 4 Component Amount (% by weight) Sartomer Company SR90003 Propoxylated Neo- 78% pentyl Glycol Diacrylate Sartomer Company SR492 Propoxylated 8% Trimethylolpropane Triacrylate BASF Corp. ODVE octadecyl vinyl ether 10% Ciba-Geigy Irgacure 500 free-radical 4% photoinitiator The decorated bottle was not rated numerically but was reported to have exhibited a good release, without dewetting of the ink layer. 
 EXAMPLE 6 The procedure of Example 1 was repeated, except that the following release composition was used: 5 Component Amount (% by weight) Allied Signal VE 4020 Pentanedioic acid, 74% bis&lsqb;4-&lsqb;(ethenyloxy)methyl&rsqb;cyclohexyl&rsqb;methylester BASF Corp. ODVE octadecyl vinyl ether 20% Union Carbide UVI-6974 onium salt initiator - 6% photoacid This release composition is an all-vinyl ether release system. Initially, the decorated bottle was rated a “2”, but with post-baking at 230° F. for 20 minutes to simulate adhesive blocking of the type that might be caused by storing the label in a truck at 140° F. in the summer, the bottle was later re-rated a “4 to 5.” 
 EXAMPLE 7 The procedure of Example 1 was repeated, except that the following release composition was used: 6 Component Amount (parts) Lord Photoglaze T038 (a di- and tri-acrylate system 100 parts with Irgacure 500 photoinitiator) BASF Corp. ODVE octadecyl vinyl ether 20 parts The decorated bottle was not rated numerically but was reported to have exhibited a good release. 
 EXAMPLE 8 The procedure of Example 1 was repeated, except that the following release composition was used: 7 Component Amount (parts) Lord Photoglaze T038 (a di- and tri-acrylate system 100 parts with Irgacure 500 photoinitiator) BASF Corp. ODVE octadecyl vinyl ether 40 parts The decorated bottle was not rated numerically but was reported to have exhibited a very poor release. In addition, solvent in the adhesive caused a discoloration in the release film. The release formulation of this example contains approximately 40 wt % ODVE alkyl vinyl ether, as compared to the approximately 20 wt % ODVE alkyl vinyl ether of Example 7. 
 EXAMPLE 9 The procedure of Example 1 was repeated, except that the following release composition was used: 8 Component Amount (% by weight) Sartomer Company SR90003 Propoxylated 80% Neopentyl Glycol Diacrylate Sartomer Company SR492 Propoxylated 16% Trimethylolpropane Triacrylate BASF Corp. ODVE octadecyl vinyl ether 0% Ciba-Geigy Irgacure 500 free-radical 4% photoinitiator The above formula has no octadecyl vinyl ether and is comparatively low in triacrylate. The decorated bottle was rated a “3 to 4,” which was considered a poor release. 
 EXAMPLE 10 The procedure of Example 1 was repeated, except that the following release composition was used: 9 Component Amount (% by weight) Sartomer Company SR90003 Propoxylated 80% Neopentyl Glycol Diacrylate Sartomer Company SR492 Propoxylated 0% Trimethylolpropane Triacrylate BASF Corp. ODVE octadecyl vinyl ether 16% Ciba-Geigy Irgacure 500 free-radical 4% photoinitiator The above formula has no triacrylate. The decorated bottle was rated a “3,” which was considered better than that for Example 9 but still not a very good release. 
 EXAMPLE 11 The procedure of Example 1 was repeated, except that the following release composition was used: 10 Component Amount (% by weight) Sartomer Company SR90003 Propoxylated 0% Neopentyl Glycol Diacrylate Sartomer Company SR492 Propoxylated 80% Trimethylolpropane Triacrylate BASF Corp. ODVE octadecyl vinyl ether 16% Ciba-Geigy Irgacure 500 free-radical 4% photoinitiator The above formula has no diacrylate. The decorated bottle was rated a “3 to 4,” which was considered a poor release. The embodiments of the present invention recited herein are intended to be merely exemplary and those skilled in the art will be able to make numerous variations and modifications to it without departing from the spirit of the present invention. For example, it should be appreciated that one may add, either directly or through trans-layer migration, trace or non-functional minor amounts of waxes or silicones to the release layer described herein as “non-wax” and “non-silicone” without being outside the scope of applicants' invention. Thus, the terms “non-wax” and “non-silicone” as used herein is intended to embrace this possibility. All such variations and modifications are intended to be within the scope of the present invention as defined by the claims appended hereto.