Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1997-07-01
2001-01-23
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S195100, C428S211100, C428S304400, C428S914000
Reexamination Certificate
active
06177187
ABSTRACT:
The invention relates to a recording material for inkjet printing, comprising at least one temporary sheet-like substrate material and a porous recording layer which is arranged thereon and can be converted into a film by the action of heat. After the production of recordings on the recording material by means of the inkjet printing method, it is possible to convert the recording layer into a film by the action of heat and to form a self-supporting film which can readily be detached from the temporary substrate at room temperature.
STATEMENT OF PRIOR ART
DE-A-30 18 342 describes a synthetic paper for inkjet printing, which is rendered transparent after printing in the inkjet printer by the action of heat in order to obtain multicolor inkjet recordings having high recording density, good color reproduction and high water resistance. It is only as a result of the subsequent melting that the print, which initially appears pale, acquires high contrast and becomes water-resistant. Papers of this type then have the disadvantage of low opacity (high transparency). The inventors are attempting to remedy this disadvantage by means of two- or three-ply papers having an opaque ply which cannot be rendered transparent and an outer ply or outer plies which can be rendered transparent and which consist of plastics. However, fiber-containing recording layers always give an inadequate printed image with respect to defined spot diameters and bleeding of the ink in the recording surface.
EP-A-0 575 644 describes a microporous coating by formation of an open-pore polymer matrix on exceeding the solubility limits of the chosen polymer in the solvent (mixture) or by sintering together individual polymer particles. This coating is also said to be printable by inkjet printing, it being possible to render the coating transparent after printing by means of heat, pressure or solvents and, in so doing, to encapsulate the ink dyes. The advantage is the increased durability of the prints after transparency has been imparted, in particular permanent resolution. The production of such layers is extremely difficult since precipitation reactions of polymers and sintering of polymers are difficult to control.
EP-B-0 227 245 describes an inkjet recording material having an outer, porous ink transport layer and an ink absorption layer arranged underneath and present on a preferably transparent substrate. During printing, the ink penetrates through the transport layer and is fixed in the absorption layer located underneath. In a particular embodiment, the ink transport layer can, after printing, be rendered transparent by heat and pressure in order to be able to view the image with high brilliance from the printed side, too. It is also possible to bond the melted transport layer to a substrate during the melting process in order to fix the image thereto. It is not intended here that the substrate of the coatings—a polyester film—can be peeled off. A disadvantage of this process is that the ink absorption layer contains water-soluble or swellable polymers which, under the influence of moisture, tend to destroy the adhesive bond and the printed image.
EP-A-648 611 discloses a three-layer inkjet recording material, comprising a temporary substrate with an ink receiving layer and a (hotmelt) adhesive layer applied thereon. After the unprinted recording material has been bonded to a given substrate, the temporary substrate, which may additionally carry a release layer, is peeled off and the ink absorption layer is free for printing. The disadvantage of this invention is the use of water-soluble ink absorption layers and the necessity of the expensive transfer prior to printing.
DE-A-19 53 8675 describes an overhead projector transparency having coatings which can be peeled off cohesively from the substrate after printing, in order to be reused or recycled.
U.S. Pat. No. 5,242,739 discloses a recording material whose recording layer can be applied in the molten state to other substrate materials. The recording layer contains a film-forming binder and thermoplastic polymer in particle form so that splitting of the layer during melt transfer may take place.
U.S. Pat. No. 5,194,317 describes a recording material for inkjet methods, whose recording layer contains a film-forming binder and plastics pigment, preferably polystyrene beads.
According to the teaching in EP-A-575 644, a recording layer for inkjet methods, which comprises a filler-rich polymer matrix having pores or capillaries perpendicular to the surface, is formed on a substrate.
In recent years, inkjet printing has become widely used. These printers, which in general are also capable of color printing, are used in particular in business sectors but also in the private sector. A further field of use involves large-area prints which can be produced using broad inkjet printers. These are used, for example, in advertising, in trade fair construction, as a substitute for large photographs, etc. Conventional inkjet recording materials therefore comprise a substrate which carries a special coating in order to absorb the generally aqueous inks rapidly and to give a crisp and brilliant image.
For outdoor applications exposed continuously to water, humidity and light, conventional, coated recording materials are not suitable for inkjet printing since the printed images applied are unstable to the stated environmental influences. The fixatives required for fixing the frequently used soluble anionic ink dyes do improve the water resistance in the case of porous coatings, for example those based on SiO
2
, but they generally reduce the light stability and oxidation stability of the recordings. Glossy film and paper coatings comprise water-soluble or water-swellable coatings, some of which are also crosslinked, but which remain extremely water-sensitive after printing and are thus unsuitable for unprotected outdoor use.
To apply protection from environmental influences, it is usual to apply laminated films at high or low temperatures over the recording or to overcoat said recording. Both methods are expensive and require materials tailored to one another in order to achieve optimum effects. Inkjet prints treated by these methods also remain sensitive to water in the case of water-soluble or water-swellable coatings, at least from the edge, unless the edge is specifically sealed. Although the light stability can be increased by overlamination or overcoating, it remains limited since, for example, the cationic polymers used for fixing have an adverse effect in the ink recording layer. In the case of pigmented inkjet inks, the finely divided colored pigments (particle size <0.2 &mgr;m) are generally substantially more light stable but, owing to the low binder content in the inks, the pigment particles cannot be fixed in a truly water- and abrasion-resistant manner. A protective covering is therefore required even when these inks are used for prints intended for outdoors.
Owing to the disadvantages described, it has to date been possible to use conventional inkjet prints outdoors only to a very limited extent. However, conventional printing methods, such as screen printing, are economical only above a certain print run, so that there is a considerable demand for inkjet prints, especially with short print runs for outdoor use.
It is the object of the present invention to provide a recording material for inkjet printing with aqueous inks, which material meets all requirements for outdoor use and recordings of any type produced thereon withstand the influence of humidity or water, light and oxidation for a sufficient time.
SUMMARY OF THE INVENTION
This object is achieved by a recording material for the inkjet method with aqueous inks, containing at least one sheet-like temporary substrate material for an ink absorption layer, selected from paper impregnated and/or coated with silicones, paper impregnated and/or coated with chromium compounds as release agents, a plastics film coated with silicones, paper coated with silicone-free, synthetic polymers, a film of silicone-free po
Liebler Ralf
Niemoller Axel
Sch{umlaut over (a)}fer Manfred
Baker & Daniels
Cronin Chris
Hess Bruce H.
Sinhl GmbH
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