Patent Application
20120211553
The present invention relates generally to the papermaking arts, and more particularly, to the application of brilliant metallic inks to a paperboard or paper substrate in a printing press using an energy curing system and an energy-curable primer.
Metallic coated paper is useful in a variety of applications, such as in decorative paper, such as for holiday and gift wrapping paper, pouch papers, for product identification purposes such as in tobacco products or canned food labels, in DVD sleeves, in cosmetic packaging, in lottery tickets, and in packaging for health products such as toothpaste and razors. Metallic coated paper is found to be desirable for such uses because of its glossy aluminized appearance and its related ability to attract the attention of a consumer. Generally, the metallic paper is printed with some sort of product identifier or some type of decorative design and may be made to have varying degrees of gloss level and various performance characteristics. For example, gift wrap and canned food labels must be both easily printable and have a high reflective finish. Other properties include suitable properties for high speed filling and resistance to abrasion and heat on conveying lines where plastic overwraps are used.
Metallic-coated paper is conventionally prepared by a vacuum metallization process in which aluminum is vacuum deposited as a layer onto a substrate. In one process, a solvent-based release layer is applied to a substrate plastic layer (e.g., a polyester layer) and the solvent is evaporated in an oven. Aluminum is vacuum deposited onto the release layer in a vacuum metallizer to form an aluminum layer on the plastic layer. Next, an adhesive is applied to the coated plastic layer, which is subsequently laminated to adhere aluminum layer to a paper. The plastic layer is subsequently removed to provide a laminated metallic-coated paper or packaging material.
In an alternate embodiment, aluminum vapor is vacuum deposited onto a plastic layer (e.g., a polyester layer) having thereon a solvent-based release coating in a vacuum metallizer as described above. The aluminum layer, however, is brushed or otherwise manipulated to release the aluminum from the plastic layer in the form of aluminum flakes as a slurry in a solvent. The slurry may then be processed through sieves and classified for particle size distribution and concentrated by the use of a centrifuge. These aluminum flakes may be collected and added to ink which is applied directly to a paper or paperboard via a conventional printing process.
Although these processes form metallic-coated paper or paperboards, these processes possess numerous disadvantages. For example, conventional laminated metallic-coated paper products are costly and create large volumes of waste that do not break down in landfills. Additionally, the plastic components of these materials are not sustainable, i.e., plastic materials are not obtained from a renewable source and are not easily recyclable. In addition, the solvent-based coating process undesirably involves at least three or four different steps, which increases the process cost and opportunity for manufacturing losses. Moreover, such a process is not optimally energy efficient due to the use of an oven or dryer to evaporate the solvent. Also, the metallic paper produced by applying the aluminum by conventional ink printing processes results in papers having undulated (e.g., irregular) surfaces that prevent a coherent scattering light from the paper, thereby reducing its gloss.
Despite the existence metallic papers and processes for making them, there remains a need in the art for a process for making a metallic-coated paper where the process is economically efficient and where the brilliance of the metallic-coated paper is optimized.
It is an object of the present invention to provide a method for forming a brilliant metallic paper or paperboard that include (1) applying an energy-curable primer to a first major surface of a paper or paperboard, (2) curing the energy-curable primer onto the paper or paperboard to form a cured primer layer, (3) applying a metallic ink to the cured primer layer, and (4) drying said metallic ink to form a metallic ink layer. The metallic ink contains a plurality of metallic particles. The energy-curable primer may be cured by passing the paper having thereon the energy-curable primer through an ultraviolet or electron beam curing apparatus. The energy-curable primer facilitates the alignment of said metallic particles in a planar orientation within the metallic ink layer. Such an orientation of the metallic particles minimizes light scattering and maximizes light reflectance to the human eye. Additionally, the energy curable primer and/or the metallic ink may be toned to provide shade and hue differences to said metallic paper or paperboard. In exemplary embodiments, the method may further include applying one or more opaque or transparent inks sequentially onto the metallic ink layer and/or applying a transparent top coat to the metallic ink layer. In addition, the method may include subjecting the cured primer layer to corona discharge prior to applying said metallic ink to the cured primer layer.
It is another object of the present invention to provide metallic paper or paperboard that includes (1) a paper web having on a major surface thereof a coating of an energy-cured primer forming a cured primer layer, and (2) a coating of a metallic ink on the cured primer layer and having therein metallic ink particles. The energy-curable primer facilitates the alignment of the metallic particles in a planar orientation in the metallic ink layer which minimizes light scattering and maximizes light reflectance to the human eye. Such a coordinated reflectance of the metallic particles optimizes the brilliance of the paper or paperboard. In at least one exemplary embodiment, the metallic ink is applied to designated areas of the paper or paperboard to create a design or pattern on the paper. The metallic paper or paperboard may also include a transparent top coat positioned on the metallic ink layer and/or one or more layers of opaque or transparent inks sequentially positioned on the metallic ink layer. Also, in certain circumstances, the metallic paper or paperboard is recyclable and repulpable.
It is a further object of the present invention to provide a carton product that includes (1) a metallic paper substrate or paperboard scored and folded into a box having at least three sides, each side having an external face and an internal face, and (2) an interior portion located within the box for containing a product. The metallic paper is a metallic paper as described in the preceding paragraph. The metallic ink layer may be located on the external and/or internal faces of the box.
It is an advantage of the present invention that the primer coating has an adequate surface tension to facilitate optimized wetting, leveling, and adhesion of the brilliant metallic ink.
It is another advantage of the present invention that the primer coating facilitates the planar orientation of the metallic pigment particles, thereby providing optimal reflectance.
It is yet another advantage of the present invention that the metallic-coated paper or paperboard may be over-printed with transparent or opaque printing inks.
It is a further advantage of the present invention that the metallic ink may be applied in a “spot-wise” fashion to designated areas of the paper or paperboard.
It is another advantage of the present invention that the inventive process can be run at a fraction of the cost of conventional Mylar® printing processes.
It is also advantage of the present invention that the printing process may be conducted in-line or off-line.
It is another advantage of the present invention that the inventive process eliminates the use of plastic required in the prior art processes.
It is a feature of the present invention that a corona discharge device may be implemented to assist in vaporizing excess solvent or chemicals from the treated paper or paperboard.
It is another feature of the present invention that the primer coating is cured by an energy curing system such as UV or EB curing.
It is yet another feature of the present invention that the inventive process uses conventional gravure, flexographic, or tower coating operations.
It is also a feature of the present invention that the energy-curable primer may be toned with pigments and/or dyes to provide apparent solidity or to provide shade and hue differences to the final product.
It is a further feature of the present invention that the metallic ink may be toned with pigments and/or dyes to provide the look or effect of colorized metallic.
The foregoing and other objects, features, and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description that follows. It is to be expressly understood, however, that the drawings are for illustrative purposes and are not to be construed as defining the limits of the invention.
The advantages of this invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein:
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. All references cited herein, including published or corresponding U.S. or foreign patent applications, issued U.S. or foreign patents, or any other references, are each incorporated by reference in their entireties, including all data, tables, figures, and text presented in the cited references.
In the drawings, the thickness of the lines, layers, and regions may be exaggerated for clarity. It will be understood that when an element such as a layer, region, substrate, or panel is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. Also, when an element is referred to as being “adjacent” to another element, the element may be directly adjacent to the other element or intervening elements may be present. The terms “top”, “bottom”, “side”, and the like are used herein for the purpose of explanation only. Like numbers found throughout the figures denote like elements. As used herein, the terms “paper” and “paper substrate” may be used interchangeably. In addition, the term “primer” and “curable primer” may be interchangeably used herein. Further, the terms “metallic paper”, “metallized paper”, and “metallic-coated paper” may be used interchangeably in this application.
The present invention is directed to a process for the application of brilliant metallic ink to a paperboard or paper substrate (“paper”) having thereon a curable primer coating. The term “paper” as used herein is meant to include all types of cellulose-based products in sheet or web form, including, but not limited to, paper, paperboard, paper substrates, and cardboard. The curable primer orients the metallic pigment particles to provide a coherent reflectance of light and optimal brilliance. The primer may be cured using an energy curing system such as an ultraviolet (UV) or electron beam (EB) curing system. In addition, the inventive process enables the paper to be “spot-coated” with the metallic ink at pre-designated areas, which can minimize the amount of metallic ink used. Additionally, the metallic-coated paper may be over-coated with a transparent or opaque ink. In certain circumstances, the metallic paper and the end product are recyclable and repulpable.
Although any conventional gravure, flexographic, roll coater, curtain coater, tower coating operation or other coating devices may be used in conjunction with the inventive process, for ease of discussion, a gravure process will be discussed herein. Turning to
Aside from the relative smoothness of the paper, the paper is not particularly limited. The paper may be produced as a single layer or a multi-layer paper having two or more layers. Additionally, the paper may or may not be calendared.
The paper is provided as a web containing cellulosic pulp fibers such as fibers derived from hardwood trees, softwood trees, or a combination of hardwood and softwood trees. The fibers may be prepared for use in a papermaking furnish by any known suitable digestion, refining, and bleaching operations. The paper may optionally contain recycled fibers and/or virgin fibers. It is to be appreciated that recycled fibers differ from virgin fibers in that the recycled fibers have gone through a drying process at least once. In certain embodiments, at least a portion of the fibers may be provided from non-woody herbaceous plants including, but not limited to, kenaf, hemp, jute, flax, sisal, or abaca, although legal restrictions and other considerations may make the utilization of hemp and other fiber sources impractical or even impossible. Additionally, the paper may include conventional additives such as, for example, starch, mineral fillers, sizing agents, retention aids, and strengthening polymers. Among the fillers that may be used are organic and inorganic pigments such as, for example, polymeric particles such as polystyrene latexes and polymethylmethacrylate, and minerals such as calcium carbonate, kaolin, and talc. In some embodiments, the paper may also include hollow microspheres.
Either bleached or unbleached pulp fiber may be utilized. In exemplary embodiments, the source of the cellulosic pulp fibers is from softwood and/or hardwood trees. The cellulosic fibers in the paper may include from about 0% to about 100% or from about 20% to about 80% by weight dry basis softwood fibers and from about 0% to about 100% or from about 20% to about 80% by weight dry basis hardwood fibers.
After the paper 10 has been coated with the energy-curable primer, such as by impression cylinder “C” and engraved gravure cylinder “G” in the first print unit 20, the coated paper 14 bypasses the dryer 30 in the first print unit 20 (not depicted) and proceeds to the energy curing device 40 located external to the paper printing process 12. It is to be appreciated that in some exemplary printing units, the dryer 30 may be removed from the first print unit 20. The energy curing device 40 cures the primer onto the paper 10 forming a cured primer layer. Non-limiting examples of suitable energy curing apparatuses include UV (ultraviolet) curing and EB (electron beam) curing. The energy-curable primer facilitates the orientation of the metallic particles in a planar fashion on the paper 10 so that a coherent reflectance off of the particles is achieved and optimized brilliance is obtained. “Brilliance”, as used herein, is meant to denote the high brightness or shine of light reflecting from the surface of the paper. As discussed in detail below, a coherent reflection off the metallic particles 45 causes minimal light scattering, thereby directing more light to the human eye and creating a more brilliant paper.
The primer may be any suitable primer that can be energy cured and which has sufficient surface tension to facilitate optimized wetting, leveling, and adhesion of the brilliant metallic ink to the paper 10. In addition, the primer should be applied at a sufficiently low and Newtonian viscosity so that it provides a level surface after printing and curing. Surfactants may be used in the primer formulation to facilitate leveling. Both the UV and EB curable primers include energy activated monomers and oligomers as well as various optional modifiers including waxes, anti-foaming agents, defoamers, etc. to adjust surface slip and surface tension. In UV primer coatings, a photo-initiator is used to promote cross-linking or photo-polymerization when the monomers or oligomers are exposed to UV energy from the energy curing device 40. Such photo-polymerization causes crosslinking of the monomers and/or oligomers and turns the applied liquid coating to a uniform, plastic-like solid.
Additionally, nitrogen may be used to blanket the applied coating during the curing process to minimize the amount of oxygen present in the system because oxygen may have an inhibitory effect on the energy-curing process. Also, the viscosity of the primer may be further reduced at press-side by inputting thermal energy into the coating supply sump “S”. Alternatively (or additionally), thermal energy may be added by heating the coating within the circulating energy coating system 40. Other energy inputs such as ultrasonic energy (not shown) may also be utilized to facilitate coating and ink flow-out/leveling either prior to or subsequent to the coated paper 14 passing through the energy curing device 40. Heat from print unit dryers 50, 65, 75, 85 can also be used to warm the paper and may therefore facilitate improved coating flow-out and leveling of the primer. Non-limiting examples of suitable primers for use in conjunction with the inventive process include ProCure EB primer coating (commercially available from Inx International) and Suncure (commercially available from Sun Chemical).
The energy-curable primer is applied to the paper 10 in an amount sufficient to achieve a planar orientation of the metallic particles in the metallic ink. Although not wishing to be bound by theory, it is believed that the primer coating application volume should be optimized in to facilitate essentially Newtonian coating flow and applied coating film smoothness. Specifically, it is believed that that the primer coating must be optimized to aid in the Newtonian rheology or pre-cured flow of the energy-curable primer coating for best visual/optical brilliance results.
The cured, primer-coated paper 15 is returned to the printing apparatus 12 at the second print unit 50 where the metallic ink is applied to the coated surface of the paper 15. The metallic ink used in the inventive process and paper is not particularly limited, and may include metallic inks having colors such as silver, gold, and bronze. Non-limiting examples of metallic inks for use in the present invention include metallic inks manufactured by Inx International, Flint Group, and Sun Chemical.
The metallic ink may be applied on the cured primer on the major surface of the paper 15 such as by impression cylinder “C1” and engraved gravure cylinder “G1” within the second print unit 50. In addition, the metallic ink may be toned with pigments and/or dyes to provide the look or effect of colorized metallic. The water-based metallic ink may be applied to the coated paper 12 from the gravure cylinder “G1” in an amount from about 0.3 pounds per thousand square feet to about 3.0 pounds per thousand square feet of printed and coated paper. The particles within the metallic ink essentially flatten out (e.g., are aligned to be parallel or substantially parallel to the paper and coated surface) in the metallic ink positioned on the cured primer.
As illustrated in
Additionally, it is to be understood that the energy-curable primer and the metallic ink may be applied to specific, desired areas on the paper. Such “spot-coating” enables a design or pattern (e.g., a logo) to be created on the paper. As one example, the metallic ink may be applied to predetermined areas of the cured primer layer to form designs or logos on the cured primer layer (and thus the paper). In addition, by applying the metallic ink to specific portions of the paper, less metallic ink is needed, particularly when compared to an embodiment where the entire paper is coated with the metallic ink. The use of less primer and/or less of the relatively costly metallic ink correlates to a reduction in manufacturing and product costs.
Turning back to
It is to be understood that additional print units (or fewer print units) than those depicted in
Alternatively, the metallic paper 55 may not pass through such additional printing towers (not illustrated) and retain a non-colored brilliant metallic ink surface. In such an instance, the metallic paper 55 may be sheeted and transferred for additional processing after it emerges from the dryer 50. It is to be appreciated that subsequent steps, such as, but not including applying a final coating to the paper, cutting the continuous coated paper into desired lengths, scoring, and folding the scored blanks into cartons, although not illustrated for purposes of simplicity, are considered within the purview of the invention.
It is also to be understood that
The color-enhanced metallic paper 90 or non-colored metallic paper 55 may further be at least partially coated with at least one transparent top coating layer (not shown). The top coating layer may be applied to the surface of the metallic ink in the metallic paper 55 or to the surface of the color layer(s) formed on the metallic ink in the color-enhanced metallic paper 90. The coating layer may contain a binder and optionally a pigment. The coating provides additional abrasion resistance and/or slip, apparent depth, and/or gloss to the finished product. Wax and/or other particles contained within the coating(s) may cause light-scattering which could diminish the apparent brilliance of the finished product. Therefore, it may be necessary to use particulate-free slip and anti-abrasion compounds that are soluble in the system to prevent undesirable random light-scattering. Other ingredients of the coating layer may include surfactants, dispersion aids, and other additives conventionally used in printing compositions. Such a top coating layer may provide a protective layer and/or enhance the brilliance and gloss of the metallic ink forming the metallic ink layer 35 (see
In at least one exemplary embodiment, depicted in
The invention of this application has been described above both generically and with regard to specific embodiments. Although the invention has been set forth in what is believed to be the preferred embodiments, a wide variety of alternatives known to those of skill in the art can be selected within the generic disclosure. The invention is not otherwise limited, except for the recitation of the claims set forth below.
This application is a continuation of and claims the benefit of U.S. patent application Ser. No. 13/010147, filed Jan. 20, 2011, herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13010147 | Jan 2011 | US |
| Child | 13438980 | US |
