INK-JET PRINTABLE COMPOSITE MEDIA HAVING A HOLOGRAPHIC PATTERN ON THEIR IMAGING SURFACES
BACKGROUND OF THE INVENTION
[01] Field of the Invention
[02] The present invention relates to ink-jet printable composite media comprising a polymeric film and paper or magnetic substrate. The composite medium comprises a transparent ink-receptive layer overlaying a holographic pattern on its imaging surface.
[03] Brief Description of the Related Art
[04] Residential consumers are turning to ink-jet printing systems and digital technology to produce creative graphic art materials. With the introduction of new computers, software, digital cameras, ink-jet printers, and imaging media, consumers can now create customized posters, greeting cards, calendars, and the like in the comfort of their own homes. In such projects, the consumer generates a computerized image and sends it to a desktop ink-jet printer that prints the image onto a recording medium. Typically, the recording medium comprises a specially coated paper or film substrate. The image can be a reproduction of any object, for example, a photo, illustration, graphic design, logo, text, and the like. The quality of the printed image is dependent on many factors including the composition of the recording medium and the ink.
[05] Ink-jet printers contain very fine nozzles and liquid ink that is squirted through the nozzles onto the medium. The inks used in most ink-jet printers are aqueous-based inks containing molecular dyes or pigmented colorants. Water is the major component in aqueous-based inks. Small amounts of water-miscible solvents such as glycols and glycol ethers can also be present .
[06] Recently, manufacturers have introduced ink-jet printable papers having a holographic pattern or design on their surfaces. With such products, consumers can create unique and colorful images using the holographic pattern as a background for the images . The holographic pattern provides a multi-colored rainbow, three-dimensional effect as light strikes the surface of the paper sheet . In general, conventional ink-jet holographic products can be made using the following techniques . A holographic pattern can be embossed onto a polymeric film, e.g., a polyester, polyvinyl chloride, polypropylene, polystyrene, or polyethylene film. The film can be coated with a semi-soft or hard coating. The film, containing the embossed holographic pattern, can be subjected to a vacuum metal deposition vapor process, where aluminum is vaporized and deposited onto the embossed holographic surface . After the aluminum metallizing step, the film can be laminated to a paper substrate. Alternatively, a paper substrate can be coated with a thermoplastic coating. In such instances, the coated surface of the paper substrate is heated to a temperature above its softening temperature, and the holographic pattern is embossed onto the softened coating.
[07] Published International PCT Application No. WO 00/35662 (Proctor & Gamble Company) discloses a holographic film for packaging applications. The Application discloses embossing a holographic pattern onto a thermoplastic film. A metallized aluminum layer then is coated over the embossed layer. An aqueous-based acrylic primer coating then is coated over the aluminum layer. A printed ink layer containing organic solvents is applied to the primer coating. For example, the printed ink layer can comprise a white ink containing an ethyl-acetate solvent and a colored ink containing an ethanol solvent. According to the Application, the primer coating forms a barrier to the migration of organic solvents in the printed ink layer.
[08] Overcash et al . , US Patent 6,187,389 Bl discloses a method for producing holographic images on paper and
cardboard container substrates . The method involves applying an image-receptive barrier coating onto a carrier substrate (polyester film) containing a holographic image embossed surface. The carrier substrate is sent through a metallizing process, whereby an opaque evaporated layer is deposited onto the barrier coating. An adhesive (tie) layer is coated onto the metallized layer and a sheet of paper is placed over the adhesive layer. The composite structure is then run through heated rollers with high pressure. This heated lamination process forms a bond between the metallized layer and paper. When the bond between the paper and barrier coating is greater than the bond between the carrier substrate and paper, the barrier coating with the cast image of the holographic embossed surface is released from the carrier and transferred to the paper.
[09] Miekka et al . , US Patent 4,913,858 discloses a method for decorating a paper or plastic film substrate with a holographic pattern. A thermoplastic coating is applied to the surface of the substrate, and the coating is heated to a temperature above its softening temperature. An embossing roller containing the desired holographic pattern contacts the softened coating under pressure to emboss the pattern into the coating. The thermoplastic material can be selected from the group consisting of polyethylene, styrene acrylate, styrene butadiene and polyvinylacetate, and it can contain a hydroxylated polysiloxane release agent .
[10] Although conventional ink-jet printable holographic papers may be capable of providing digital images of adequate quality for some applications, there is a need for holographic media capable of producing improved images. The present invention provides such media. The media of this invention are capable of producing brightly colored images that dry faster than images printed on conventional ink-jet holographic products.
SUMMARY OF THE INVENTION [11] The present invention relates to an ink-jet printable composite medium comprising: a) a polymeric film having a first and second surface, and b) a paper or magnetic substrate . The first surface of the film comprises a holographic pattern and a transparent ink-receptive layer overlaying the holographic pattern, and the second surface of the film is laminated to the paper. The ink-receptive layer comprises a binder resin selected from the group consisting of polyvinyl alcohols, poly(vinyl pyrrolidone) , poly (2-ethyl-2-oxazoline) , polyethylene oxide, and cellulose resins. The composite medium has an imaging surface smoothness of no greater than 125 SU. Preferably, the imaging surface smoothness is in the range of about 5 SU to about 90 SU.
[12] Suitable polymeric films include, for example, polyester, polyvinyl chloride, polypropylene, polystyrene, and polyethylene films, and preferably a polyester film is used. Suitable paper substrates include bond, clay-coated, and polyolefin-coated papers, and preferably a bond paper is used.
[13] The ink-receptive layer can further comprise particulate such as calcium carbonate, silica, alumina, clays, glass, polystyrene, starch, poly (methyl methacrylate) , and polytetrafluoroethylene particles. In addition, the ink-receptive layer can comprise additives such as anti-static agents, optical brighteners, and UV light stabilizers. The dry coat weight of the ink- receptive layer can be in the range of about 1 to about 50 grams / square meter. The total thickness of the medium can be in the range of about 2 mils to about 10 mils.
[14] If a paper substrate is used, the surface of the composite medium, opposite to the surface coated with the ink-receptive layer, can be coated with a polymeric coating to provide dimensional stability to the medium. For example, an acrylic-based coating can be used on the back
surface of the medium. The dry coat weight of the polymeric coating can be in the range of about 1 to about 20 grams / square meter.
DETAILED DESCRIPTION OF THE INVENTION
[15] The present invention relates to ink-jet printable composite media comprising: a) a polymeric film having a first and second surface, and b) a paper or magnetic substrate, wherein the first surface of the film comprises a holographic pattern and a transparent ink-receptive layer overlaying said holographic pattern. The second surface of the film is laminated to the paper or magnetic substrate.
[16] A polymeric film comprising a holographic pattern on its surface is first prepared. The thickness of the film can vary, but it is typically in the range of about 0.25 mils (6.35 μm) to about 4 mils (lOO.lδμm). The holographic pattern can be embossed onto the film of this invention using conventional techniques. As described above, these techniques typically involve first selecting a desired holographic pattern that is embossed onto the surface of a roller or plate. Then, the roller or plate embosses the holographic image onto a polymeric film, e.g., a polyester, polyvinyl chloride, polypropylene, polystyrene, or polyethylene film. The film, comprising the embossed holographic pattern, is subjected to a vacuum metal deposition vapor process, where aluminum is vaporized and deposited onto the embossed holographic surface. Other conventional methods such as laser etching can be used to emboss the holographic pattern onto the surface of the film.
[17] The polymeric film comprising the embossed holographic surface is laminated to a paper substrate. Examples of suitable paper substrates include bond papers, clay-coated papers, and polyolefin resin-coated papers (e.g., polyethylene-coated papers) . The thickness of the paper substrate can vary, but it is typically in the range of about 2 mils (51 μm) to about 15 mils (381 μm) . In an
alternative embodiment, the film comprising the embossed holographic surface is laminated to a magnetic substrate. The film can be laminated to the paper or magnetic substrate using a conventional adhesive such as acrylic, styrene butadiene rubber (SBR) , or natural rubber. The film is laminated to the paper or magnetic substrate such that the holographic surface faces upwards, i.e., the holographic surface, is exposed.
[18] If desired, a transparent, acrylic-based coating can be applied over the embossed holographic surface to prevent dirt and other foreign matter from soiling the surface during handling of the film/paper composite. In addition, an optional primer coating comprising adhesion promoters such as polyurethanes, polyesters, acrylics, and cellulose ethers can be coated over the acrylic coating. If no acrylic coating is present, the primer coating can be coated directly over the holographic surface. The primer coating can enhance adhesion of the ink-receptive layer to the film/paper composite.
[19] In accordance with this invention, a transparent ink- receptive layer is coated over the holographic surface . The ink-receptive layer of the present invention helps provide the composite medium with a relatively smooth and clear imaging surface versus conventional products. Particularly, the imaging surface of a composite medium of this invention has a Sheffield Smoothness of no greater than 125 SU. Preferably, the Sheffield Smoothness is in the range of about 5 to about 90 SU. It is believed that the relatively smooth and clear imaging surface makes the medium capable of producing brightly colored images. In contrast, conventional products have rough and hazy imaging surfaces that can deteriorate a colored image and cause other imaging defects. Further, the smooth surface of the composite medium of this invention helps .enhance feeding of the medium through the ink-jet printer. Thus, the media sheets tend not to jam together and cause printer break-downs as they are fed through the machine.
[20] Particularly, the ink-receptive layer comprises a binder resin selected from the group consisting of polyvinyl alcohols, poly(vinyl pyrrolidone) , poly (2-ethyl-2- oxazoline) , polyethylene oxide, and cellulose resins. Copolymers and mixtures of the foregoing compounds are suitable. The binder resin is generally water-soluble. By the term "cellulose resins", it is meant natural polysaccharide resins and chemically modified cellulose resins such as cellulose ethers (e.g., methylcellulose and ethylcellulose) . The binder resins of the present invention can form a polymeric matrix that helps the ink-receptive layer absorb the aqueous ink vehicle. Further, the binder resins help impart a relatively smooth and clear imaging surface to the finished composite medium. Preferably, the ink-receptive layer comprises at least 60% by weight of the binder resin based on total dry weight of the layer.
[21] The ink-receptive layer can comprise particulate to improve ink absorption properties and modify surface friction of the finished product. For example, calcium carbonate, silica, alumina, alumina hydrate, clays, glass, polystyrene, starch, poly(methyl methacrylate) , polytetrafluoroethylene, and the like can be added to the coating. However, the ink-receptive layer should comprise particulate in an amount no greater than 40% by weight based on total dry weight of the layer. If the ink-receptive layer contains particulate in an amount greater than 40% by weight, the surface can be rough and its smoothness may be greater than 125 SU. Further, the particles used in the ink-receptive layer preferably have a mean diameter size in the range of about 80 to about 100 microns.
[22] In addition, surface active agents that control the wetting or spreading action of the coating, anti-static agents, suspending agents, acidic compounds to control the pH of the coating, optical brighteners, UV light stabilizers, defoaming agents, waxes, plasticizers, and the like may be added to the coating formulation. Further, the
coating can comprise generally water-insoluble resins such as poly (vinyl chloride), polyester, poly (vinylidene fluoride) , methyl methacrylate, ethyl acrylate, styrene- acrylonitrile polymers, polyurethane, butadiene, N- hydroxyethyl acrylamide, N-hydroxymethylacrylamide, and polycarbonate .
[23] Multiple ink-receptive layers can be applied to the composite film/paper medium. For example, a first coating formulation (i.e., an inter-coat or under layer) comprising poly (2-ethyl-2-oxazoline) , cellulose acetate propionate, poly (vinyl pyrrolidone) , and organic solvents can be applied to the composite. Generally, the inter-coat is hydrophobic. After this first coating formulation has dried, a second coating formulation (i.e., top coat or upper layer) comprising methylcellulose, polyethylene oxide, alumina, and water can be applied over the first coating. Generally, the top-coat is hydrophilic. This two-step coating process creates a synergistic combination of ink-receptive layers on the composite medium.
[24] Various methods can be used to apply the ink-receptive coating formulation(s) to the imaging surface of the composite medium. These coating methods include Meyer-rod, roller, blade, wire-bar, dip, solution extrusion, air-knife, curtain, slide, doctor-knife, and gravure methods. The coated composite medium can be fed through forced hot air ovens to dry the coatings. Generally, the dry coat weight of the ink-receptive layer (s) is in the range of about 1 to about 50 grams / square meter (gsm) , and the preferable weight is about 2 to about 20 gsm.
[25] The above-described coating formulations are applied to the front (i.e., imaging) surface of the composite medium. If a paper substrate is used, the opposite (i.e., non- imaging or back) surface of the composite medium can be non- coated, coated with the same compositions used on the front surface, or coated with a different composition than used on the front surface. If the same coating compositions are
used on the front and back surfaces of the substrate, the medium may be referred to as having symmetrical coatings . If different coating compositions are used on the front and back surfaces, the medium may be referred to as having asymmetrical coatings. For example, an acrylic-based coating comprising an acrylic emulsion and pigments can be used. Such a polymeric coating on the back surface of the paper enhances the paper's dimensional stability and stiffness and helps minimize physical curling. If a polymeric coating is applied to the back surface, the dry coat weight of the polymeric layer is generally in the range of about 1 to about 20 gsm, and the preferable weight is about 2 to about 10 gsm. In general, the total thickness of the composite film/paper medium can vary, but it is typically in the range of about 2 mils (51 μm) to about 15 mils (381 μm) .
[26] The ink-jet printable composite media of this invention are characterized as having a smooth and clear imaging surface. Particularly, the imaging surface of the medium has a Sheffield Smoothness of no greater than 125 SU. It is believed that the relatively smooth and clear imaging surface allows for the production of brightly colored images. Further, printed images on the media of this invention can dry faster than printed images on conventional media as shown in the following examples .
[27] The present invention is further illustrated by the following examples, but these examples should not be construed as limiting the scope of the invention. The ink- jet recording composite media samples prepared in the following Examples were tested and evaluated using the below Test Methods .
[28] Test Methods [29] Ink Drying Time
[30] The samples were imaged using an Epson Stylus Photo 750 ink-jet printer available from Epson. The ink-jet printer
contained standard aqueous-based inks as provided by the manufacturer. The printer was set at photo mode, 720 dpi, and photo media setting. The samples were imaged in ambient conditions (about 23°C) . The samples were imaged with the inks such that the amount of ink in an imaged area was in the range of about 25 to about 50% by weight based on the weight of the coated ink-receptive layer in the area that was imaged. The amount of ink was determined by the weight difference of the sample as measured within about thirty (30) seconds of imaging (printing) the sample. The weight of the coated ink-receptive layer was in the range of about 10 to about 20 grams/ square meter (gsm) .
[31] A sheet of plain copy paper was weighed (Wl) and placed on the imaged surface of the imaged samples, and a four (4) pound roller was rolled over the copy paper at the following time intervals: TO (30 to 60 seconds after imaging), T2 (2 minutes after imaging) , and T5 (5 minutes after imaging) . After the rolling step at each time interval, the copy paper was removed and weighed (W2) to determine the amount of ink that transferred to the paper based on the weight difference (W2 - Wl) of the paper.
[32] Sheffield Smoothness
[33] The Sheffield Smoothness of the imaging surface of the ink-jet printable media was measured using a Hagerty Smoothness Tester (Model 538, Hagerty Technologies, Inc.) according to the manufacturer's standard instruction manual. Generally, the Sheffield Smoothness of a medium is an indication of the roughness of the medium. A relatively high Sheffield Smoothness value indicates a rougher surface, while a relatively low Sheffield Smoothness value indicates a smoother surface.
[34] Brightness
[35] As described above, the samples were imaged using a
Epson Stylus Photo 750 ink-jet printer available from Epson. The samples were imaged with a print test pattern comprising colored squares . The test pattern included squares of
black, green, yellow, red, blue, and pink colors. The percentages of light reflectance of the colored squares were measured using a Photovolt Brightness Rating meter (Seragen Diagnostics, Indianapolis, IN 46225) according to the manufacturer's standard instruction manual. Average values are reported in Table 1 below. Generally, light % reflectance is an indication of color brightness. Relatively bright colors have a higher light % reflectance.
EXAMPLES
[36] In the following examples, percentages are by weight based on the weight of the coating formulation, unless otherwise indicated.
[37] Example 1
[38] A 0.48 mil polyester film available from Spectratek
Technologies, Inc. (Los Angeles, CA) containing an embossed holographic pattern and metallized aluminum coating was laminated to a 100 lb. bond paper available from Champion International Corp (Stamford, CT) . The embossed holographic surface of the film was first coated with an acrylic-based coating and a polyurethane primer coating. The surface of the film was then coated with two ink-receptive layers, an inter-coat and a top-coat. The inter-coat formulation, as described below, was applied to the film at a thickness of about 13 grams per square meter (gsm) using a reverse roll coating method and dried under forced hot air in an oven at 200°C for about 5 to 60 seconds. The inter-coat layer contained 75 wt.% poly(2-ethyl-2-oxazoline) , 7 wt.% poly (vinyl pyrrolidone) , 17 wt.% cellulose acetate propionate, and 1 wt.% citric acid based on dry weight of the coated layer. The top-coat formulation, as described below, was then coated over the inter-coat at a thickness of about 2 gsm using a Meyer rod and dried under forced hot air in an oven at 200°C for about 5 to 60 seconds. The top-coat layer contained 84 wt.% alumina particulate, 5 wt.% methyl cellulose, and 11 wt.% polyethylene oxide based on dry weight of the coated layer. The back surface of the film/paper composite was coated with a back-coat, as
described below, at a thickness of about 8 gsm using a Meyer rod and dried under forced hot air in an oven at 200°C for about 5 to 60 seconds. The finished composite media samples were imaged using an Epson Stylus Photo 750 ink-jet printer and evaluated as described in the above Test Methods . Results are reported below in Tables 1, 2, and 3.
[39] Inter-Coat
Aquazol Al1 13 wt.%
Cellulose Acetate Propionate2 3 wt.%
Poly (vinyl pyrrolidone)3 K 90 1.3 wt.%
Ethyl Alcohol 16 wt.%
Phenylmethyl (PM) Solvent 20 wt.%
Methyl Ethyl Ketone 46.0 wt.%
Citric Acid 0.1 wt.%
1 Poly (2-ethyl-2-oxazoline) available from Polymer Chemistry Innovations (Tucson, AZ) .
2 Cellulose acetate propionate available from Lawter International (Pleasant Prarie, Wl) .
3 Poly (vinyl pyrrolidone) available from ISP Corporation (Wayne, NJ) .
[40] Top-Coat
Methyl cellulose4 0.4 wt.%
Poly (ethylene oxide)5 1.0 wt.%
Alumina sol6 25 wt.%
Water 53 wt.%
4 Methyl cellulose available from Dow Chemical (Midland,
MI) .
Poly (ethylene oxide) available from Dow Chemical (Midland, MI) .
6 Alumina sol available from Sasol North America (Houston, X) .
[41] Back-Coat
Joncryl 6247 62 wt.%
Syloid8 7 wt.%
Water 31 wt.%
7 acrylic resin available from SC Johnson. Polymer (Sturtevant, Wl) silica pigment available from Grace Davision (Baltimore,
MD)
[42] Example 2
[43] A 2 mil polyester film available from Spectratek
Technologies, Inc. (Los Angeles, CA) containing an embossed holographic pattern and metallized aluminum coating was laminated to a magnetic substrate available from Magnetic Specialty, Inc. (Marietta, OH) . The embossed holographic surface of the film was first coated with an acrylic-based coating and a polyurethane primer coating as described in above Example 1. The surface of the film was then coated with two (2) ink-receptive layers (an inter-coat and topcoat) as described in above Example 1. The finished composite media samples were imaged using an Epson Stylus Photo 750 ink-jet printer and evaluated as described in the above Test Methods. Results are reported below in Tables 1, 2 , and 3.
[44] Example 3
[45] A 0.48 mil polyester film available from Spectratek
Technologies, Inc. (Los Angeles, CA) containing an embossed holographic pattern and metallized aluminum coating was laminated to a 100 lb. bond paper available from Champion International Corp (Stamford, CT) . The embossed holographic surface qf the film was first coated with an acrylic-based coating and a polyurethane primer coating. The surface of the film was then coated with two ink-receptive layers, an inter-coat and a top-coat. The inter-coat formulation, as described below, was applied to the film at a thickness of about 11 grams per square meter (gsm) using a Meyer rod and dried under forced hot air in an oven at 125°C for about 1
to 2 minutes. The inter-coat layer contained 79 wt.% poly (2- ethyl-2-oxazoline) , 9 wt.% silica pigment,, and 14 wt.% surfactant, < 1 wt.% constarch, and < 1 wt.% citric acid based on dry weight of the coated layer. The top-coat formulation, as described below, was then coated over the inter-coat at a thickness of about 2 gsm using a Meyer rod and dried under forced hot air in an oven at 125°C for about 1 to 2 minutes. The top-coat layer contained 41 wt.% alumina particulate and 59 wt.% methyl cellulose based on dry weight of the coated layer. The back surface of the film/paper composite was coated with a back-coat, as described in above Example 1, at a thickness of about 8 gsm using a Meyer rod and dried under forced hot air in an oven at 200°C for about 5 to 60 seconds. The finished composite media samples were imaged using an Epson Stylus Photo 750 ink-jet printer and evaluated as described in the above Test Methods. Results are reported below in Tables 1, 2, and 3.
[46] Inter-Coat
A uazol Al 18 wt.%
Methyl Ethyl Ketone 42 wt.%
Phenylmethyl (PM) Solvent 29 wt.%
Citric Acid 1 wt.%
Syloid 1.96 wt.%
Surcol SP-79 8 wt.%
Cornstarch 0.04 wt.%
a surfactant available from Ciba Specialty Chemicals Corp.
[47] Top-Coat
Methyl cellulose 5 wt.%
Alumina sol 13 wt . %
Water 82 wt.%
[48] Comparative Example A
[49] Commercial holographic sheets (W324C) having a holographic pattern on their imaging surfaces, available from Southwbrth Company (Agawam, MA) , were imaged using an Epson Stylus Photo 750 ink-jet printer and evaluated as described in the above Test Methods. Results are reported below in Tables 1 , 2 , and 3.
[50] TABLE 1 (SURFACE SMOOTHNESS)
Sample Smoothness (Sheffield Units)
Example 1 54.2 SU
Example 2 7.2 SU
Example 3 87.4 SU
Comp. Ex. A 174.5 SU
[51] As shown in Table 1, the media of this invention have smooth and clear imaging surfaces . Particularly, the imaging surfaces have a smoothness of no greater than 125 Sheffield Units. In contrast, conventional holographic sheets have a rough and hazy surface as illustrated in Comparative Example A.
[52] TABLE 2 (INK DRY TIME)
Amount of Ink Transfer (Grams) At Time Intervals (TO, T2, and T5)
Sample TO T2 T5 Example 1 0.005 g 0.003 g 0.002 g
Example 2 0.005 g 0.003 g 0.001 g
Example 3 0.007 g 0.002 g 0.000 g
Comp. Ex. A 0.050 g 0.022 g 0.006 g
TO (30 to 60 seconds after imaging) T2 (2 minutes after imaging) T5 (5 minutes after imaging) .
[53] As shown in Table 2, images printed on the media of this invention have a relatively faster drying rate than images printed on conventional holographic sheets. As described above in the testing methods, the ink dry time was obtained by measuring the amount of ink that transferred from the printed media to a sheet of copy paper placed over the media after pressing the sheet with a roller. The amount of ink transfer was measured at different time intervals .
[54] TABLE 3 (BRIGHTNESS %)
Sample Black Green Yellow Red Blue
Pink
Ex. 1 6% 16% 64% 35% 9%
36%
Ex. 2 6% 15% 56% 33% 7%
32%
Ex. 3 4% 15% 55% 30% 6%
30%
Comp. 4% 14% 44% 28% 5%
26%
Ex. A
[55] As shown in Table 3, images printed on the media of this invention have relatively brighter colors versus images printed on conventional holographic sheets as measured by light reflectance .
[56] It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims .