Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1999-02-20
2001-11-13
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C347S105000, C428S195100
Reexamination Certificate
active
06316120
ABSTRACT:
FIELD OF INVENTION
This invention relates to films useful as image receptor media for a variety of imaging materials such as inks and toners.
BACKGROUND OF THE INVENTION
Advertising and promotional displays often include graphic images appearing on structural surfaces such as truck sides and awnings, or free-hanging as banners. To prepare the display, an image may be formed on an adhesive-backed image receptor medium, sometimes referred to as a graphic marking film, which is then adhered to the desired substrate. Alternatively, the image may be formed first on a temporary carrier, or image transfer medium, and transferred to the image receptor medium. The image receptor medium usually includes a base material with an additional receptor layer overlying it. The base material is typically a plasticized vinyl film, although paper may also be used.
Although the graphic display may be intended for a long term installation of 5 years or more, it is often a relatively short term (3 months to 1 year) outdoor installation. In the case of a short term display, the image receptor medium is desirably a low cost, weather resistant, durable graphic marking film having good printability and adhesion of inks and/or toners that is easily applied to and removed from a surface. The vinyl base films currently used in graphic marking films are generally too costly for a short term application, and present other problems with plasticizer migration, plasticizer staining and adhesive anchorage. Paper-based media are not sufficiently durable or weather resistant and tear easily when removed. Polyolefin base films are low cost and contain no plasticizer but do not provide good ink/toner adhesion. The application of the receptor layer over the base film usually requires an additional process step, thus adding cost to the manufacturing process.
Images can be created by one of several known methods, such as electrography, screen printing, flexographic printing, lithographic printing, ink jet printing, and thermal mass transfer. Electrography involves passing a substrate, normally a dielectric material, through an electrographic printing device, one type of which is an electrostatic printer. In the printer, the substrate is addressed with static electric charges (e.g., as from a stylus) to form a latent image which is then developed with suitable toners. This technique is especially suitable for producing large scale images for use on posters and signs.
At the conclusion of the electrographic process where the toned image has been developed on the dielectric substrate, the printed substrate can be enclosed between two layers of clear vinyl plastic film and used directly in an outdoor application, such as a sign. Because the typical dielectric substrates are paper-based, however, they frequently lack the weather resistance required for outdoor signs. More durable substrates such as polyvinylchloride (PVC) and polyvinylacetate (PVA) films are difficult to image directly because of their electrical and mechanical properties.
To produce large signs that are suitable for outdoor display, the toned image electrographically deposited on a dielectric substrate can be transferred to a more weather resistant image receptor medium. The dielectric substrate is then known as an image transfer medium. This technique is discussed in U.S. Pat. No. 5,262,259. Image transfer may also be practiced with images created by a variety of other known techniques such as knife coating, roll coating, rotogravure coating, screen printing, and the like.
Transfer of the image from an image transfer medium to an image receptor medium typically requires the application of pressure and heat through, for example, lamination in a heated pressure roll system (hot roll lamination). This type of image transfer system is described in U.S. Pat. No. 5,114,520.
Images may also be created directly on a weatherable, durable image receptor medium using such techniques as screen printing and inkjet printing.
The inkjet printing process is now well known. Recently, wide format printers have become commercially available, making feasible the printing of large format articles such as posters, signs and banners. Inkjet printers are relatively inexpensive as compared with many other hardcopy output devices, such as electrostatic printers. Generally, thermal inkjet inks are wholly or partially water-based, whereas piezo inkjet inks can be solventless or solvent-based. Inkjet images may be printed on plain paper or on a suitable image receptor medium that has been treated or coated to improve its inkjet receptor properties. For example, it is known to apply an additional layer of material to an image receptor medium to improve the receptivity to and adhesion of thermal inkjet inks. The materials commonly found in such an inkjet reception layer do not generally adhere well to many image receptor media base films, such as vinyl or polyester.
Print shops or graphic arts facilities that operate more than one type of printing process must stock a different image receptor medium for each process. Because of this, the inventory of receptor media can be large and expensive.
The industry is addressing a need for low-cost, durable, weather resistant image receptor media that can be used with a variety of inks and toners, such as those disclosed in U.S. Pat. No. 5,721,086 (Emslander et al.).
SUMMARY OF THE INVENTION
There is a need for a low-cost, durable, weather resistant image receptor medium that can be used with a variety of inks and toners and will accept such toners and inks without pretreatment of the receptor medium.
The present invention solves the problems in the art with a film for use as an image receptor medium with a variety of printing and image transfer processes, and a variety of imaging materials such as inks and toners. The image receptor medium accepts images without the need for corona treatment, surface modification or other pretreatment. The present invention benefits from the use of ethylene vinyl acetate carbon monoxide terpolymeric resins to provide excellent screenprint ink receptivity without the requirement of corona treatment. These resins are so effective at promoting screenprint ink adhesion that such resins can be diluted by blending with other resins to produce the same results for ink adhesion with the other resins contributing other desirable physical or chemical properties.
Preferably, the ethylene vinyl acetate carbon monoxide terpolymers are blended with other resins, such as ethylene vinyl acetate resins, ethylene (meth)acrylic acid copolymer resins, polyethylene resins, polypropylene resins, ionomers, ethylene methyl acrylate resins or acid-modified or acid/acrylate modified ethylene vinyl acetate resins to increase viscosity of the resulting blended resin. Increased viscosity improves manufacturing operations, especially extrusion manufacturing, for making receptor media of the present invention. Further choices for co-blended resins include those that are less expensive than ethylene vinyl acetate carbon monoxide terpolymeric resins that do not diminish the ink adhesion properties of the imaging layer.
In one aspect, the image receptor medium includes an image reception layer having two major opposing surfaces. The image reception layer comprises a ketone ethylene ester, preferably an ethylene vinyl acetate carbon monoxide terpolymer. Preferably, but optionally, the image reception layer includes an efficacious amount of a free-radical scavenger such as a hindered amine light stabilizer compound (“HALS” compound). The image reception layer provides properties of image receptivity to the image receptor medium. “Image receptivity” means that an image formed on or applied to the image receptor medium adheres completely or nearly completely after being subjected to a tape snap test in which 3M SCOTCH™ Tape No. 610 (commercially available from 3M Company, St. Paul, Minn., USA) is firmly applied to the image and then removed with a rapid jerking motion. A prime layer is optionally included on a first major surface of the image rece
3M Innovative Properties Company
Hess Bruce H.
Hornickel John H.
Peters Carolyn V.
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