WO2006036556A1

WO2006036556A1 - Labels and labeling process

Info

Publication number: WO2006036556A1
Application number: PCT/US2005/032733
Authority: WO
Inventors: Dieu Dai Huynh
Original assignee: Avery Dennison Corporation
Priority date: 2004-09-23
Filing date: 2005-09-14
Publication date: 2006-04-06
Also published as: CN101027373A; WO2006036556B1; KR20070054203A; AU2005289963A1

Abstract

This invention relates to labels, particularly polymeric labels and to a process for printing such polymeric labels. The printed labels are useful for application to food containers, including glass and polymeric containers.

Description

TITLE: LABELS AND LABELING PROCESS

This application claims the benefit of provisional application Serial No. 60/612,331 filed on September 23, 2004, which is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

This invention relates to labels, and more particularly to polymeric film labels for use on food containers, and to a process of printing polymeric film labels.

BACKGROUND OF THE INVENTION

It is common practice to apply labels to food containers or jars formed from glass or polymers. Such containers and jars are available in a wide variety of shapes and sizes for holding many different types of food items, etc. The labels provide information regarding the contents of the containers and other information such as the supplier of the container and the nutritional value of the contents.

Paper labels are commonly used on food containers because they provide almost unlimited art and/or graphics potential. However, paper labels offer little resistance to label damage, particularly in high speed food container filling and conveyance operations.

Polymeric labels provide improved abrasion resistance but at a higher cost. In addition, because the printing surface of some polymeric films is relatively non-receptive to ink, high definition printing is often not possible.

Many polymer labels used for food containers are reverse printed on the underside of the clear polymeric facestock and adhesive is applied to the print layer. Upon application of the label to the container, the print layer is positioned between the polymeric label and the container surface. Alternatively, the polymeric label, which is either clear or colored, is printed on its upper surface and then overlaminated with a second, polymeric film that is clear. The print layer is then sandwiched between the two polymeric films.

Gravure printing is often used to print the high definition graphics and designs onto the polymeric film. In gravure printing, the gravure ink is deposited in image wells in the surface of a gravure cylinder, and the deposited ink image is then transferred to the label facestock. Since gravure printing typically is carried out at high speeds, the gravure ink typically contains volatile organic solvents that dissolve the ink binder components and must be rapidly removed during the drying process.

In order to gravure print ink onto polymeric film facestock, particularly biaxially oriented polypropylene (BOPP), a primer or topcoat layer is first coated onto the polymeric facestock surface. The primer layer improves the adhesion of the gravure ink to the polymeric film. However the addition of the primer layer increases the manufacturing costs and time of the labeling process.

Accordingly, it would be desirable to product labels, in particular, polymeric film labels having a high quality print layer and the durability to withstand the demands of the manufacturing process at reduced cost.

SUMMARY OF THE INVENTION

In one aspect, this invention relates to a food container having provided thereon a label comprising (a) a polymeric facestock having an upper surface and a lower surface; (b) a pressure sensitive adhesive layer in contact with the lower surface of the facestock; (c) a solvent-based ink layer printed on the upper surface of the facestock; and (d) an overprint varnish layer overlying the ink layer.

In one embodiment, the label comprises (a) an unprimed polyolefin facestock having an upper surface and a lower surface; (b) a pressure sensitive adhesive layer in contact with the lower surface of the facestock; (c) a solvent-based ink layer printed on the upper surface of the facestock; and (d) an overprint varnish layer overlying the ink layer.

In another aspect, the invention relates to a method for making gravure printed labels comprising (a) providing an unprimed polyolefin facestock having an upper surface and a lower surface; (b) corona treating the upper surface of the facestock; (c) printing a solvent based ink directly onto the upper surface of the facestock to form a print layer; (d) drying the solvent based ink; (e) coating the print layer with an overprint coating; and (f) applying an adhesive to the lower surface of the facestock. BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of a side view of a label construction of the present invention.

DESCRIPTION OF THE INVENTION

The term "transparent" when referring to one or more layers of the label means any material beneath such layers can be seen through such layers. In reference to the use of the "transparent" or "clear" labels applied to clear containers, such as glass or plastic jars and bottles, the jar or bottle and the food within the jar or bottle are visible through the label.

The term "clear" when referring to one or more layers of the label or to the label itself means the opacity of the layers or label is less than about 5%, and the layers or the label has a haze of less than about 10%. Opacity is measured in accordance with TAPPI Test T425 os, and haze is measured in accordance with ASTM Test Method D-1003.

In one embodiment, the label comprises (a) an unprimed polyolefin facestock having an upper surface and a lower surface; (b) an adhesive layer in contact with the lower surface of the facestock; (c) a print layer comprising a solvent-based gravure ink printed on the upper surface of the facestock; and (d) an overprint layer overlying the ink layer.

In FIG. 1 , label 10 comprises a polymer facestock 11 having an upper surface and a lower surface, a print layer 12 having an upper surface and a lower surface wherein the lower surface of the print layer 12 is in contact with the upper surface of the facestock 11 , an overprint layer 13 in contact with the upper surface of the print layer 12, and an adhesive layer 14 that is in contact with the lower surface of the facestock.

The polymer facestock layer may be a monolayer film or a multilayer film. The multilayer film may comprise from two to ten or more layers. The polymer facestock may be oriented or not oriented. Depending on the end use of the label, the polymer facestock may be transparent or opaque. Opaque facestocks generally comprise a polymer as described below and one or more pigments to provide the facestock, or one layer of a multilayer facestock with the desired color. Pigments useful for this purpose are well known in the art. For example, white films can be prepared by introducing titanium dioxide and other white pigments into the polymer. Carbon black may be introduced to provide a black or grey facestock or film.

A wide variety of polymer film materials are useful in preparing the facestocks of the present invention. For example, the polymer film material may include polymers and copolymers such as at least one polyolefin, polyacrylate, polystyrene, polyamide, polyvinyl alcohol, poly(alkylene acrylate), poly(ethylene vinyl alcohol), poly(alkylene vinyl acetate), polyurethane, polyacrylonitrile, polyester, polyester copolymer, fluoropolymer, polysulfone, polycarbonate, styrene-maleic anhydride copolymer, styrene- acrylonitrile copolymer, ionomers based on sodium or zinc salts of ethylene methacrylic acid, cellulosics, polyacrylonitrile, alkylene-vinyl acetate copolymer, or mixtures of two or more thereof.

The polyolefins that can be utilized as the polymer film material include polymers and copolymers of olefin monomers containing 2 to about 12 carbon atoms such as ethylene, propylene, 1-butene, etc., or blends of mixtures of such polymers and copolymers. In one embodiment the polyolefins comprise polymers and copolymers of ethylene and propylene. In another embodiment, the polyolefins comprise propylene homopolymers, and copolymers such as propylene-ethylene and propylene-1-butene copolymers. Blends of polypropylene and polyethylene with each other, or blends of either or both of them with polypropylene-polyethylene copolymer also are useful. In another embodiment, the polyolefin film materials are those with a very high propylenic content, either polypropylene homopolymer or propylene-ethylene copolymers or blends of polypropylene and polyethylene with low ethylene content, or propylene-1-butene copolymers or blend of polypropylene and poly-1-butene with low butene content. Useful propylene homopolymers and copolymers are described in U.S. Pat. No. 5,709,937 (Adams et al). The copolymers include propylene-ethylene copolymers containing up to about 10% by weight of ethylene, and propylene-1-butene copolymers containing up to about 15% by weight of 1-butene. Oriented films described in the '937 patent are clear films useful as the facestock in the labels of the present invention. The disclosure of U.S. Patent No. 5,709,937 is hereby incorporated by reference. Various polyethylenes can be utilized as the polymer film material including low, medium, and high density polyethylenes, and mixtures thereof. An example of a useful low density polyethylene (LDPE) is Rexene 1017 available from Huntsman. An example of a useful high density polyethylene (HDPE) is Formoline LH5206 available from Formosa Plastics. In one embodiment the polymer film material comprises a blend of 80 to 90% HDPE and 10-20% of LDPE.

The propylene homopolymers that can be utilized as the polymer film material in the invention, either alone, or in combination with a propylene copolymer as described herein, include a variety of propylene homopolymers such as those having melt flow rates (MFR) from about 0.5 to about 20 as determined by ASTM Test D 1238. In one embodiment, propylene homopolymers having MFR's of less than 10, and more often from about 4 to about 10 are particularly useful. Useful propylene homopolymers also may be characterized as having densities in the range of from about 0.88 to about 0.92 g/cm³. A number of useful propylene homopolymers are available commercially from a variety of sources, and some useful polymers include: 5A97, available from Dow Chemical and having a melt flow of 12.0 g/10 min and a density of 0.90 g/cm³; DX5E66, also available from Dow Chemical and having an MFI of 8.8 g/10 min and a density of 0.90 g/cm³; and WRD5-1057 from Dow Chemical having an MFI of 3.9 g/10 min and a density of 0.90 g/cm³. Useful commercial propylene homopolymers are also available from Fina and Montel.

Examples of useful polyamide resins include resins available from EMS American Grilon Inc., Sumter, S. C. under the general tradename Grivory such as CF6S, CR-9, XE3303 and G-21. Grivory G-21 is an amorphous nylon copolymer having a glass transition temperature of 125 ⁰C, a melt flow index (DlN 53735) of 90 ml/10 min and an elongation at break (ASTM D638) of 15. Grivory CF65 is a nylon 6/12 film grade resin having a melting point of 135 ⁰C, a melt flow index of 50 ml/10 min, and an elongation at break in excess of 350%. Grilon CR9 is another nylon 6/12 film grade resin having a melting point of 200 ⁰C, a melt flow index of 200 ml/10 min, and an elongation at break at 250%. Grilon XE 3303 is a nylon 6.6/6.10 film grade resin having a melting point of 200 ⁰C, a melt flow index of 60 ml/10 min, and an elongation at break of 100%. Other useful polyamide resins include those commercially available from, for example, International Paper of Wayne, N.J. under the Uni- Rez product line, and dimer-based polyamide resins available from Bostik, International Paper, Fuller, Henkel (under the Versamid product line). Other suitable polyamides include those produced by condensing dimerized vegetable acids with hexamethylene diamine. Examples of polyamides available from International Paper include Uni-Rez 2665; Uni-Rez 2620; Uni- Rez 2623; and Uni-Rez 2695.

Polystyrenes can also be utilized as the polymer facestock material and these include homopolymers as well as copolymers of styrene and substituted styrene such as alpha-methyl styrene. Examples of styrene copolymers and terpolymers include: acrylonitrile-butene-styrene (ABS); styrene-acrylonitrile copolymers (SAN); styrene butadiene (SB); styrene- maleic anhydride (SMA); and styrene-methyl methacrylate (SMMA); etc. An example of a useful styrene copolymer is KR-10 from Phillips Petroleum Co. KR-10 is believed to be a copolymer of styrene with 1 ,3-butadiene.

Polyurethanes also can be utilized as the polymer film material, and the polyurethanes may include aliphatic as well as aromatic polyurethanes. The polyurethanes are typically the reaction products of (A) a polyisocyanate having at least two isocyanate (--NCO) functionalities per molecule with (B) at least one isocyanate reactive group such as a polyol having at least two hydroxy groups or an amine. Suitable polyisocyanates include diisocyanate monomers, and oligomers.

Useful polyurethanes include aromatic pblyether polyurethanes, aliphatic polyether polyurethanes, aromatic polyester polyurethanes, aliphatic polyester polyurethanes, aromatic polycaprolactam polyurethanes, and aliphatic polycaprolactam polyurethanes. Particularly useful polyurethanes include aromatic polyether polyurethanes, aliphatic polyether polyurethanes, aromatic polyester polyurethanes, and aliphatic polyester polyurethanes.

Examples of commercial polyurethanes include Sancure 2710^® and/or Avalure UR 44-5^® (which are equivalent copolymers of polypropylene glycol, isophorone diisocyanate, and 2,2-dimethylolpropionic acid, having the International Nomenclature Cosmetic Ingredient name "PPG-17/PPG- 34/IPDI/DMPA Copolymer"), Sancure 878^®, Sancure 815^®, Sancure 1301^®, Sancure 2715^®, Sancure 1828^®, Sancure 2026^®, and Sancure 12471^® (all of which are commercially available from Noveon, Cleveland, Ohio), Bayhydrol DLN (commercially available from Bayer Corp., McMurray, Pa.), Bayhydrol LS-2033 (Bayer Corp.), Bayhydrol 123 (Bayer Corp.), Bayhydrol PU402A (Bayer Corp.), Bayhydrol 110 (Bayer Corp.), Witcobond W-320 (commercially available from Witco Performance Chemicals), Witcobond W-242 (Witco Performance Chemicals), Witcobond W-160 (Witco Performance Chemicals), Witcobond W-612 (Witco Performance Chemicals), Witcobond W-506 (Witco Performance Chemicals), NeoRez R-600 (a polytetramethylene ether urethane extended with isophorone diamine commercially available from Avecia, formerly Avecia Resins), NeoRez R-940 (Avecia), and NeoRez R-960 (Avecia).

Examples of such aliphatic polyether polyurethanes include Sancure 2710^® and/or Avalure UR 445^®, Sancure 878^®, NeoRez R-600, NeoRez R- 966, NeoRez R-967, and Witcobond W-320.

In one embodiment, the facestocks comprises at least one polyester polyurethane. Examples of these urethanes include those sold under the names "Sancure 2060" (polyester-polyurethane), "Sancure 2255" (polyester- polyurethane), "Sancure 815" (polyester-polyurethane), "Sancure 878" (polyether-polyurethane) and "Sancure 861" (polyether-polyurethane) by the company Sanncor, u nder the names "Neorez R-974" (polyester- polyurethane), "Neorez R-981" (polyester-polyurethane) and "Neorez R-970" (polyether-polyurethane) by the company Avecia, and the acrylic copolymer dispersion sold under the name "Neocryl XK-90" by the company Avecia.

Polyesters prepared from various glycols or polyols and one or more aliphatic or aromatic carboxylic acids also are useful film materials. Polyethylene terephthalate (PET) and PETG (PET modified with cyclohexanedimethanol) are useful film forming materials that are available from a variety of commercial sources including Eastman. For example, Kodar 6763 is a PETG available from Eastman Chemical. Another useful polyester from duPont is Selar PT-8307 which is polyethylene terephthalate.

Acrylate polymers and copolymers and alkylene vinyl acetate resins (e.g., EVA polymers) also are useful as the film forming materials in the preparation of the constructions of the invention. Commercial examples of available polymers include Escorene UL-7520 (Exxon), a copolymer of ethylene with 19.3% vinyl acetate; Nucrell 699 (duPont), an ethylene copolymer containing 11 % of methacrylic acid, etc. lonomers (polyolefins containing ionic bonding of molecular chains) also are useful. Examples of ionomers include ionomeric ethylene copolymers such as Surlyn 1706 (duPont) which is believed to contain interchain ionic bonds based on a zinc salt of ethylene methacrylic acid copolymer. Surlyn 1702 from duPont also is a useful ionomer.

Polycarbonates also are useful, and these are available from the Dow Chemical Co. (Calibre) G. E. Plastics (Lexan) and Bayer (Makrolon). Most commercial polycarbonates are obtained by the reaction of bisphenol A and carbonyl chloride in an interfacial process. Molecular weights of the typical commercial polycarbonates vary from about 22,000 to about 35,000, and the melt flow rates generally are in the range of from 4 to 22 g/10 min.

In one embodiment, the facestock polymer material may comprise fluorinated polymer. The fluorinated polymer includes a thermoplastic fluorocarbon such as polyvinylidene fluoride (PVDF). The fluorinated polymer also can include copolymers and terpolymers of vinylidene fluoride. A useful thermoplastic fluorocarbon is the polyvinylidene fluoride known as Kynar, a trademark of Pennwalt Corp. This polymer is a high molecular weight (400,000) polymer that provides a useful blend of durability and chemical resistance properties. Generally, a high molecular weight PVDF resin, with a weight average molecular weight of about 200,000 to about 600,000 is used.

The polymer facestock material may be free of inorganic fillers and/or pigments for clear facestocks and clear labels, or the polymer facestock material may be cavitated and/or contain inorganic fillers and other organic or inorganic additives to provide desired properties such as appearance properties (opaque or colored films), durability and processing characteristics. Nucleating agents can be added to increase crystailinity and thereby increase stiffness. Examples of useful materials include calcium carbonate, titanium dioxide, metal particles, fibers, flame retardants, antioxidant compounds, heat stabilizers, light stabilizers, ultraviolet light stabilizers, antiblocking agents, processing aids, acid acceptors, etc. Opaque and/or white facestocks are often utilized when the labels described herein dD not contain a metal layer overlying the facestock layer.

The polymer facestock material is chosen to provide a continuous polymer film in the film structures of this invention with the desired properties such as improved tensile strength, elongation, impact strength, tear resistance, and optics (haze and gloss). The choice of polymeric facestock forming material also is determined by its physical properties such as melt viscosity, high speed tensile strength, percent elongation etc. In one embodiment, clear or transparent facestocks are used in the label construction when clear or transparent labels are desired.

The thickness of the polymer facestock is from about 0.1 to about 10 mils, or from about 1 to about 5 mils. In one embodiment the thickness of the facestock is from about 1 to about 3 mils. The facestock may comprise a single layer, or the film can be a multilayer film of two or more adjacent layers. For example the film can comprise one layer of a polyolefin and one layer of a blend of a polyolefin and a copolymer of ethylene and vinyl acetate (EVA). In another embodiment the film comprises three layers, a base or core layer of, for example, a polyolefin, and skin layers in both sides of the base or core layer which may be comprised of the same or different polymer blends. The individual layers of a multilayer facestock may be selected to provide desirable properties.

The monolayer and multilayer film facestocks useful in the labels useful herein can be manufactured by those processes known to those skilled in the art such as by casting or extrusion. In one embodiment, the films are manufactured by polymer extrusion or coextrusion processes. The extrudate or coextrudate of polymeric film materials is formed by simultaneous extrusion from a suitable known type of extrusion or co-extrusion die, and in the case of a coextrudate, the layers are adhered to each other in a permanently combined state to provide a unitary coextrudate.

In addition to coextrusion, the multilayer film facestocks useful in the present invention may be prepared by extrusion of a continuous film to form one layer followed by the application of one or more additional layers on the extruded layer by extrusion of one or more additional layers; by lamination of a preformed polymer film to a preformed functional film; or by deposition of additional layers on the preformed film from an emulsion or solution of a polymeric film forming material.

In one embodiment, the facestocks used in the present invention are not oriented. That is, the facestock and films are not subjected to a hot- stretching and annealing step. In other embodiments, the facestock contained in the labels used in the present invention may be oriented in the machine direction (uniaxially) or in both the machine and cross directions (biaxially) by hot-stretching and annealing by techniques well known to those skilled in the art. For example, the films may be hot-stretched in the machine direction only at a ratio of at least 2:1 and more often, at a ratio of between about 2:1 to about 9:1. After the film has been hot stretched, it is generally passed over annealing rolls where the film is annealed or heat-set at temperatures in the range of from about 50 ⁰C, more often 100°C to about 1 50 ⁰C, followed by cooling. In another embodiment, the facestock is a biaxially oriented.

It is desirable that the films exhibit a degree of stiffness in the machine direction and the cross direction to facilitate handling, printing and dispensing. Thus, in one embodiment, the stiffness in the machine direction, and the cross direction should be at least about 14 Gurley (mg), as determined using TAPPI Test T543 pm and in a further embodiment the Gurley stiffnesses in both directions are within about 5 Gurley units (sometimes referred to as a balanced stiffness).

Polymer facestocks useful in the labels of the present invention are available commercially from a variety of sources including Avery Dennison Corp., Painesville, Ohio. Clear films and white films are available.

The surface energy of both surfaces of the facestock can be enhanced by treatments such as corona discharge, flame, plasma, etc. to provide the surfaces with desirable properties such as improved adhesion to subsequently applied layers. Procedures for corona treating and flame treating of polymer films are well known to those skilled in the art. In one embodiment, a facestock is corona discharge treated on the upper surface and flame treated on the lower surface.

The polymer facestock 11 in one embodiment comprises a biaxially oriented polypropylene (BOPP) film. BOPP films useful in the labels of the present invention are available commercially from a variety of sources, particularly Fasson Roll Materials, a division of Avery Dennison Corp., Painesville, Ohio. Other sources include AMTOPP, a division of lnterplast Group LTD, Livingston, New Jersey; Exxon Mobil Chemical Co., Macdon, New York; AET Films, New Castle, Delaware; UCB Films Inc., Smyrna, Georgia; and Vifan USA, a division of Vibac, Montreal, Canada.

The BOPP facestock film is not topcoated or coated with a primer prior to gravure printing of the solvent-based ink. The solvent-based ink is printed directly onto the BOPP film. The surface energy of the BOPP facestock can be enhanced by treatments such as corona discharge, flame, or plasma to provide a surface with improved adhesion to subsequently applied layers, including the ink applied to the upper surface. In one embodiment, the BOPP facestock is corona discharge treated on press on the upper surface of the facestock.

The print layer 12 is in contact with the upper surface of the polymeric facestock. The print layer may be an ink or graphics layer, and the print layer may be a mono-colored or multi-colored print layer depending on the printed message and/or the intended pictorial design. These include variable imprinted data such as serial numbers, bar codes, trademarks, nutritional information, etc. The thickness of the print layer is typically in the range of about 0.5 to about 10 microns, and in one embodiment, about 1 to about 5 microns, and in another embodiment about 1 to about 3 microns. The inks used in the print layer include commercially available solvent-based inks .

In one embodiment, the print layer is formed by depositing by gravure printing an ink composition comprising a resin, a suitable pigment or dye and one or more suitable volatile solvents onto the upper surface of the polymeric facestock. After application of the ink composition, the volatile solvent component(s) of the ink composition evaporate(s), leaving only the non¬ volatile ink components to form the print layer.

The solvent-based ink composition comprises at least one solvent- soluble resin, a colorant and an organic solvent. Non-limiting examples of the resin include polyurethanes, polyolefins, polyacryls, polymethacryls, polyamides, polyvinyl acetates, polyvinyl alcohols, polyvinyl ethers, polyacrylonitriles, polystyrenes, polyvinyl pyrrolidones, polyvinyl chlorides, poly(alkylene oxides), cellulosic polymers, and copolymers of one or more monomers including olefins, (meth) acrylates, vinyl acetates, allyl acetates, vinyl chlorides, acrylonitriles, N-vinyl pyrrolidones, N-vinyl oxazolidones, vinyl ethers and other allylic and vinylic monomers, and mixtures of two or more thereof.

The colorants may include soluble dyes, pigments or mixtures thereof. The classes of dyes include acid dyes, natural dyes, direct dyes either cationic or anionic direct dyes, basic dyes and reactive dyes. The pigments may be any conventional organic or inorganic pigment.

Useful organic solvents for gravure printing inks include, but are not limited to ester solvents such as ethyl acetate, propyl acetate, isopropyl acetate, etc., alcohols such as methanol, ethanol, n-propanol, isopropanol and solvents such as an ester/alcohol mixture.

The solvent-based ink composition may also contain one or more additives to adjust flow, surface tension, and gloss of a cured ink. Such additives typically comprise polymeric dispersants, surface active agents, fillers, waxes, or a combination thereof. The additives may function as leveling agents, optical brighteners, plasticizers, drying promoters, viscosity regulators, extenders, anti-fouling agents, anti-blocking agents, anti-slip agents, anti-static agents, wetting agents, dispersants, defrothers, deareators, and/or adhesions promoters, or other additives may be used to provide a specific function.

Solvent-based inks are commercially available. Examples of such inks include those available from Sicpa under the tradename BARGOFOR. Pigments for solvent based printing inks are commercially available from Sun Chemical under the trade names SUNBRITE^®, SUNFAST^® and FASTOGEN^®. Nitrocellulose based inks are available from Siegwerk as the MRH 23 series of inks. Solvent based inks available from XSYS Print Solutions include nitrocellulose based, polyamide based, polyvinyl butyral based, and polyvinyl chloride based inks.

In one embodiment, the printing ink comprises reflective metal flakes that have been embossed. Printing inks containing embossed metallic leafing pigments are described in US Patent 5,672,410, which is incorporated by reference herein. In one embodiment, embossed fine particulate thin metallic flakes having high levels of brightness and color intensity are produced by providing a release surface on a carrier, embossing the release surface with a diffraction grating pattern having an angular ruling pattern greater than 45°, metalizing the embossed release surface with a thin reflective metal film, removing the metal film from the release surface to form a solvent dispersion of embossed metal flakes that have replicated the diffraction grating pattern, and controlling the particle size of the flakes contained in the dispersion to maintain the embossed flakes contained therein at a D50 particle size at or above 75 microns. The embossed flakes can be used to produce printing inks having extremely high brightness characterized as an optically apparent glitter or sparkle effect in combination with high color intensity or chromaticity. The embossed metal flakes can be combined with an acrylic and/or nitrocellulosic resin binder to produce a printing ink. Printing ink containing embossed metallic flakes is commercially available from Eckart GmbH.

A transparent overprint layer 13 overlies the print layer. The protective overprint layer provides desirable properties to the label before and after the label is affixed to the container. The presence of the transparent overprint layer may, in some embodiments, provide additional properties such as antistatic properties, stiffness and/or weatherability, and the overprint layer may protect the print layer from, e.g., weather, sun, abrasion, moisture, water, etc. The transparent overprint layer can enhance the properties of the underlying print layer to provide a glossier and richer image. The protective overprint layer may also be designed to be abrasion resistant, radiation resistant (e.g., UV), chemically resistant, thermally resistant thereby protecting the label and, particularly the print layer from degradation from such causes. The overprint layer may also contain antistatic agents, or anti-block agents to provide fro easier handling when the labels are being applied to containers at high speeds. The overprint layer may also be selected to provide labels useful on containers subjected to subsequent washing/rinsing, filling and pasteurization, or liquid immersion (e.g., ice bath) without displaying adverse consequences such as label lifting or hazing. The overprint layer may be applied to the print layer from a solution. The thickness of the overprint layer is generally in the range of about 0.5 to about 5 mils, and in one embodiment about 1 to about 3 mils.

In one embodiment, the overprint layer comprises a two component, solvent based, chlorine-free, high-gloss varnish commercially available from Sicpa (Switzerland) under the tradename BARGOFLEX L726-2. A hardener, CFA 4488 also from Sicpa, is used with the two component varnish. In another embodiment, the overprint layer comprises a single component varnish. UV flexo cationic varnishes are available from Sicpa, Sun Chemical (New Jersey) and XSYS Print Systems.

The adhesive layer 14 of the label comprises a pressure sensitive adhesive (PSA). A description of useful pressure sensitive adhesives may be found in Encyclopedia of Polymer Science and Engineering, Vol. 13. Wiley- lnterscience Publishers (New York, 1988). Additional description of useful PSAs may be found in Polymer Science and Technology, Vol. 1 , lnterscience Publishers (New York, 1964). Conventional PSAs, including acrylic-based PSAs, rubber-based PSAs and silicone-based PSAs are useful. The PSA may be a solvent based or may be a water based adhesive.

In one embodiment, the printed labels are produced by (a) providing an unprimed biaxially oriented polypropylene facestock having an upper surface and a lower surface; (b) corona treating the upper surface of the facestock; (c) printing a solvent based ink directly onto the upper surface of the facestock to form a print layer; (d) drying the solvent based ink; (e) coating the print layer with an overprint coating; and (f) applying an adhesive to the lower surface of the facestock. The solvent based ink may be printed directly onto the facestock by gravure printing.

The labels of the present invention have particular utility in the food industry, wherein the containers are subjected to relatively rough handling. The operations the labeled containers have to withstand may include filling, packing, shipping and storage, as well as pasteurization and recycling operations. During conveying operations, the labeled containers are subjected to considerable line pressures, as well as abrading of one container against another. The labels may be applied to glass, polymeric and metal containers. The polymeric containers may be rigid or flexible. Flexible containers include squeezable food containers. Clear polymeric film may be used to achieve a no label look where the presence of the label is not very apparent to the consumer.

EXAMPLES

The following are examples of labels prepared in accordance with the present invention, and the application of the labels to glass containers.

Label graphics are printed using a solvent based gravure ink onto the surface of 2 mil thick, clear BOPP films from Fasson, Painesville, Ohio identified as BEV/MDO A, BEV/MDO B and BEV/MDO C.

The films used are not primed or topcoated. Immediately prior to application of the ink, the print surface of the films is corona treated.

Ink is gravure printed onto the surface of the films using a solvent based ink available from Sicpa (Switzerland) under the trade name BARGOFOR. Multiple colors of ink are used. The gravure cylinder used to apply the inks has cell depths of 5 microns to about 120 microns, depending on the engraving process technology. After application of the inks, the printed film is heated to evaporate the ink solvent. An overprint varnish is then applied over the print layer and allowed to dry.

As understood by those skilled in the art, multiple layers of ink may be deposited in order to achieve the desired print effect, color and/or quality. The ink deposited may be the same or different.

The labels produced pass a pasteurization test in which the labels are placed in an oven for 50 minutes at room temperature (about 25°C), heated to 70⁰C and then cooled to room temperature. The labels produced also pass an abrasion test designed to simulate the conveying operation wherein labeled containers are manually rubbed against each other for 2 minutes under dry conditions, 2 minutes under wet conditions and another 2 minutes under dry conditions. While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be under stood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims.

Claims

What is claimed is:

1. A food container having provided thereon a label comprising (a) a polymeric facestock having an upper surface and a lower surface; a pressure sensitive adhesive layer in contact with the lower surface of the facestock; a solvent-based ink layer printed on the upper surface of the facestock; and an overprint coating overlying the ink layer.

2. The container of claim 1 wherein the upper surface of the facestock is corona treated.

3. The container of claim 1 wherein the overprint coating comprises a two component varnish.

4. The container of claim 1 wherein the overprint coating comprises a cationic varnish.

5. The container of claim 1 wherein the facestock comprises biaxially oriented polypropylene.

6. The container of claim 1 wherein the overprint coating is the exterior layer of the label.

7. The container of claim 1 wherein the container is formed from glass.

8. The container of claim 1 wherein the container is formed from at least one polymer.

9. The container of claim 8 wherein the container is rigid.

10. The container of claim 8 wherein the container is flexible.

11. The container of claim 1 wherein the ink comprises embossed metallic flakes.

12. A method for making printed labels for food containers comprising: providing an unprimed biaxially oriented polypropylene facestock having an upper surface and a lower surface; corona treating the upper surface of the facestock; printing a solvent based ink directly onto the upper surface of the facestock to form a print layer; drying the solvent based ink; coating the print layer with an overprint coating; and applying an adhesive to the lower surface of the facestock.

13. The method of claim 12 wherein the overprint coating comprises a two component varnish.

14. The method of claim 12 wherein the adhesive comprises a pressure sensitive adhesive.

15. The method of claim 12 further comprising applying the adhesive of the label to a food container.

16. The method of claim 12 wherein the printing comprises gravure printing.

17. The method of claim 12 wherein the ink comprises embossed metallic flakes.