Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2003-01-10
2004-09-07
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S084000, C522S086000, C522S071000, C522S074000, C522S096000, C522S100000, C522S104000, C522S090000, C522S150000, C522S152000, C522S153000, C522S154000, C522S162000, C522S165000, C106S031130, C427S508000, C427S510000, C427S511000, C427S514000, C428S411100, C428S413000, C428S423100, C428S500000, C101S150000, C101S155000, C101S170000, C101S491000
Reexamination Certificate
active
06787583
ABSTRACT:
The invention relates to an intaglio ink composition, a method of manufacturing and applying said composition, a use of said composition in an intaglio printing process and a method of precipitating the resulting wiping solution, as well as a security document realized by intaglio printing using said composition. The said ink composition comprises components which are polymerizable via a radical reaction path by irradiation with electromagnetic or electron beam radiation. The said ink composition additionally exhibits a suitable dispersibility in wiping solutions of low sodium hydroxide concentration.
The printing of security documents requires an outstanding printing quality and particular measures to prevent counterfeiting and forgery of the printed documents.
Security documents are printed preferably by the intaglio printing process. The term “intaglio printing” as used in this application shall apply to the so-called “engraved steel die” or “copper plate” printing process which is well known to the skilled in the art. The printing plates used herein are usually chromium plated, engraved nickel plates or cylinders, made by galvanic replication of an—often hand-engraved—original copper plate. The following shall not apply to the also well known rotogravure or gravure printing processes, which rely on a different type of ink.
In engraved steel die rotary printing, a rotating engraved steel cylinder carrying the pattern or image to be printed, is supplied with ink by one or more template inking cylinders by which a pattern of inks of different color is transferred to the printing cylinder. Subsequent to inking, any excess of ink on the plain surface of the printing cylinder is wiped off by a rotating wiping cylinder covered by a plastisol. Then, the remaining ink in the engraving of the printing cylinder is transferred under pressure onto the substrate to be printed, which may be paper or plastic material in sheet or web form. The wiping cylinder, in turn, is continuously cleaned using diluted aqueous sodium hydroxide as an emulsifying medium for the wiped-off excess ink, or a paper/calico wiping device, or an organic solvent such as trichloroethylene. These process steps and the machines used for engraved steel die printing are known to the skilled in the art.
Printing inks for the printing of security documents by the engraved steel die method on presently used sheet fed or web fed intaglio presses must satisfy to the following requirements:
correct rheological properties at the moment of ink transfer to the printing cylinder and at the moment of printing (rheology).
The ability of the ink to be easily and quantitatively removed from the non printing areas of the printing die surface (wipeability).
The ease of cleaning of the wiping cylinder with an aqueous solution containing 0.1 to 1% of caustic soda and a similar concentration of a detergent, or even with pure water (detergeability);
Stability of the ink before printing, on the inking rollers, until the moment of printing;
Film forming characteristics such that they allow further manipulation of sheets or webs carrying printed films of up to 200 microns thickness at latest 24 hours after printing or, preferably, immediately after printing;
Non-offsetting properties: In the case of printing on continuous web at speeds going up to 150 m/minute, the immediate rewinding of the printed substrate is mandatory. The ink system must assure that there is no ink transfer from the freshly printed surface to the backside of the enrolled substrate which is in contact with it. In the case of web printing machines equipped with hot air drying devices (as supplied e.g. from TEC-Systems, W.R. Grace & Co.), web printing speeds of up to 150 m/min. have to be withstood, using engraving depths of up to 200 microns. On sheet fed presses, 500 to 10,000 sheets, depending on the particular printing substrate and on the depth of the engravings, must be stacked on piles right after printing, without interleaving sheets;
outstanding chemical and mechanical resistance of the printing according to specifications established by INTERPOL at the 5
th
International Conference on Currency and Counterfeiting in 1969, or to the Bureau of Engraving and Printing's test methods as stated in BEP-88-214 (TN) section M5;
acceptable toxicologic and environmental properties.
As it is known in the art of printing, the printed substrate must generally be dried in order to allow subsequent processing, and to achieve the required resistance properties of the final product.
By the term “drying”, three different mechanisms are addressed, as it is well known to the man skilled in the art of printing. Two mere physical drying processes refer to the evaporation of volatile solvent from the printed ink paste, leaving back its solid resin and pigment components, and to the resorption (sucking) of nonvolatile ink solvent into the substrate. A third, chemical drying process, also called hardening or curing, refers to the transformation of a liquid composition into the solid state by a chemical polymerization or cross-linking reaction. One or more of these drying processes may be implied in the drying of a same particular printing ink, and the printer does generally not make a difference between physical and chemical drying.
Intaglio inks are usually cured by an oxidation reaction. This is a rather slow drying method, and documents correspondingly printed and stacked as sheets cannot usually be handled for further processing before a drying time period of one to several days.
The curing of printed inks by UV radiation is known and widely introduced in the art of printing. UV curing allows a rapid, almost instantaneous drying of the printed ink film, and hence opens the way to increase production speed. The chemical curing reaction is in most cases initiated by radicals, created by the UV irradiation. To obtain sufficient sensitivity to the UV radiation, it is necessary to incorporate a photoinitiator into the printing ink, said photoinitiator being decomposed under the influence of the UV radiation, forming free radicals, which in turn initiate the curing reaction.
FR 2274669 describes an intaglio printing ink based on a varnish (binder) based on tung oil and unsaturated aliphatic dicarboxylic acids, which can be cured by UV irradiation in the presence of oxygen. Due to the type of chemical compounds used, the curing (polymerization) speed of this kind of binder is rather low, thus requiring a long period of time to complete reaction. This intaglio ink is further described to be dispersible in caustic alkali solutions wherein the concentration of the caustic alkali compound usually ranges from 0.5 to 2% by weight. In order to promote the dispersion in the wiping solution, surface tension active molecules (surfactants) like sulfonated castor oil or sodium laurylsulfate must be added.
EP 432093 describes another intaglio ink which is dispersible in caustic alkali solution. The concentration range of the caustic alkali solution is the same as in the aforementioned patent. The said intaglio ink cures upon UV irradation via a cationic polymerization process. The proposed photoinitiators are representing toxicological hazards, however, as they contain toxic chemical elements such as As, Sb, or F, respectively.
It is an object of the present invention to overcome the shortcomings of the prior art; in particular by disclosing an intaglio ink composition which can be easily and completely cured, which requires less environmentally demanding compounds for the necessary post-wiping treatment on the printing press, and which does not contain toxicologically problematic additives. A further property of the disclosed intaglio ink is the water solubility of the ink and a simple, fast and economic way to precipitate the dissolved ink from the wiping solution.
Another object of the present invention is to provide printing inks which are curable by UV- or by shortwave visible light radiation, for the printing of security documents by the engraved steel die printing method. Still another obje
Amrein Olivier
Christinat Alexia
Veya Patrick
McClendon Sanza L.
Seidleck James J.
Shoemaker and Mattare
SICPA Holding S.A.
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