Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Patent
1997-10-06
1999-06-01
Goodrow, John
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
399307, G03G 1322
Patent
active
059087293
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to improved electrostatic processes for printing or coating on polymer films and surfaces with toner and toner inks. The invention specifically relates to a method of achieving high quality high contrast colored or inulti-colored images in continuous roll printing on transparent, flexible packaging films.
BACKGROUND OF THE INVENTION
The coating of plastic films or surfaces e.g. polyethylene, polypropylene. etc. for aesthetic or functional purposes is of great utility and importance. A major use of such films is in food packaging.
Electrostatic printing has inherent advantages which would appear to make it particularly desirable for printing on plastic films. The inherent advantages include adaptability to short runs economically, high resolution, on demand printing and good visibility. However, at present, printing on transparent films, especially multi-color printing is commercially performed in multi-head presses, and only in long runs.
SUMMARY OF THE INVENTION
It is an object of certain aspects of the present invention to produce improved quality color images electrostatically on transparent plastic films and substrates.
Color integrity of multi-color images is improved by optimizing the image forming and transfer stages of the printing process.
In order to improve the visibility of color images printed on the inner surface of transparent flexible packaging, according to a preferred embodiment of the invention, the color image is overcoated with a substantially opaque toner layer at least in those portions of the packaging which are printed with color toners. Thus on the packaging material, at least one color toner layer is situated closest to the material, and a white or other opaque layer is situated behind the colored layer or layers, i.e., further away from the material. Such images are viewed from the unprinted side of the substrate.
Alternatively, the complete multi-layer image is printed with the opaque layer uppermost on the intermediate transfer member so that, when the image is transferred to the substrate, the opaque layer is closest to the substrate. Such images are viewed from the printed side of the substrate.
Additionally, the white toner layer may also extend past the edges of the colored layers and directly contact the packaging material.
In order to avoid unnecessary alignment and registration steps, the different color images involved are sequentially transferred from an image forming surface onto an intermediate transfer member, each in alignment with previous images. The intermediate transfer member is heated so that each color image coalesces into a cohesive film, in which the respective color pigments are held so that they do not diffuse into other layers. Mixing of colors, especially with the opaque pigment is detrimental to image quality.
Each complete multi-color image is subsequently transferred from the intermediate transfer member to the substrate.
Another object of certain aspects of the present invention is to provide a process for printing toner polymer images on ionomer (high or low molecular weight) or ethylene vinyl acetate coatings on polymer surfaces, thereby achieving improved qualities. The toner polymer images may be based on high molecular weight ionomers, e.g. Surlyns, low molecular weight ionomers, e.g. Aclyns, ionomers having an intermediate molecular weight, ethylene vinyl acetate polymers and ethelene copolymers or terpolymers e.g., Bynels and Nucrels, to achieve improved qualities, such as sealability, adhesiveness, food compatibility, and others.
In other aspects of the invention special toners, including opaque white, silver, gold and fluorescent toners have been prepared by adding pigments to a hot ionomer solution, preferably of low molecular weight ionomers, and stirring the mixture as it cools. This procedure has been used to prepare gold, silver, white opaque TiO.sub.2 based, magnetic and fluorescent inks, respectively.
There is thus provided, in accordance with a preferred embodiment of the
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Ben-Avraham Peretz
Bossidan Becky
Golodetz Galia
Landa Benzion
Teisheb Albert
Goodrow John
Indigo N.V.
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