MXPA06005395A - Inkjet ink composition exhibiting low gloss - Google Patents

Abstract

Non-visible ink-jet printing ink composition for marking a substrate, comprising at least one marking compound absorbing light outside the visible wavelength range of about 400 - 700 nm, and which comprises a hydrocarbon compound, having two to six carbon atoms carrying two or three hydroxyl groups, as a non-particulate matting agent, so as to adapt the gloss of the ink-jet printed marking to the gloss of the substrate.

Description

INK COMPOSITION FOR INJECTION OF INK THAT EXHIBITS UNDER BRIGHTNESS Field of the Invention The invention is directed to the use of an opaque non-particulate composition in an inkjet printing ink composition, particularly in an ink composition for security marking which exhibits an identical brightness as the substrate carrying the ink. dialing Background of the Invention There is an increased need for security markings on negotiated goods, to prevent fraud and theft of the product. Security markings are also applied for identification purposes on a variety of items including envelopes, checks, stamps, passports, tax stamps, as well as branded or encumbered merchandise. A number of methods and techniques have been used to identify marked items, in an effort to reduce counterfeiting and product theft. In a first type of anti-counterfeiting / anti-subtraction measure, an active ultraviolet (UV active) ink composition was used to mark the product with identification signals. The benefit of using UV active ink is that the marking is not typically visible when it is illuminated with light in the visible spectrum (400-700 nm), but becomes visible when it is illuminated with light in the ÜV spectrum (200-400 nm) ). Thus, counterfeits will be impossible to know if and where the product contains a security mark, observing it only under visible light. Alternative types of safety inkjet marking include the use of infrared laser dyes, which are poorly absorbed in the visible spectrum range of approximately 400 to 700 nm, but which absorb in the near infrared (NIR) range (750 nm up) and can fluoresce in response to radiation absorption in said NIR range. Despite the low visible coloration of the two types of ink described above (UV and NIR), inkjet prints, such as bar codes, can still be displayed at non-normal visible angles due to the difference in brightness between the impressions by injection of ink and the substrate. This is mainly due to the high gloss of the common binders, which are used based on ketone, ink compositions for continuous inkjet fast drying; said compositions are in fact, brighter than most paper or commercial substrates based on cardboard. This is a major drawback, since it allows an easy visual location of the printed information, and criminals involved in falsification and subtraction know where they have to look. Existing ink formulation techniques to reduce the gloss of prints, include the addition of opacifying agents such as inorganic white pigments or mineral fillers. However, in continuous inkjet printing inks, these types of opacifying agents are not suitable, because they have a high tendency to settle in a medium of low viscosity. However, they often strongly alter the use of ink in the printer. To obtain an invisible and covered inkjet security marking to prevent illegal merchandise, it is essential to reduce the brightness of the inkjet ink and match it to the inherent brightness of the substrate. Said security marking may also be applied in the form of a code (bar code or two-dimensional data matrix), to provide a unique identity to each marked product. Said unique code can also be stored in a data management system, to allow tracking capacity and complete authentication of the product marked in this way through the logistical supply chain, but using appropriate and indicated scans for invisible codes.

SUMMARY OF THE INVENTION In view of the disadvantages stated aboveThere is one. need to improve the formulation of inkjet inks for "invisible" marking, to make prints as coated as possible by matching the brightness of inkjet printing to the inherent gloss of the substrate. However, the improved formulation is directed not to contain particulate materials, to avoid blocking of the ink jet printer nozzles and to reduce the waiting time of the printing equipment. These objects of the invention are solved by an ink formulation comprising a non-particulate opaque compound, in accordance with the features of the independent claim. In use of the at least one hydrocarbon compound having two or three hydroxyl groups, said hydrocarbon compound has a carbon chain (linear or branched) of two, three, four, five or six carbon atoms in an ink composition of Inkjet printing as a non-particulate opaque composite allows the brightness of the printed ink composition to be adapted in such a way that the brightness of the printed marking or signal is identical to the brightness of the non-printing substrate. The marking thus obtained is not perceptible from the substrate only with the eye. The non-particulate opaque compound is preferably selected from divalent or trivalent alcohols (diols or triols) of short chain alkyl compounds. In the context of the present invention, short chain alkyl compounds include compounds having a chain length of two to six carbon atoms. Preferred divalent or trivalent alcohols suitable as opacifying compounds include pentanediol, butanediol, propanediol or glycerol, and their corresponding isomers. As used herein, an "opaque compound" is a compound that has an opacifying effect on inkjet printing ink compositions. Typically, the opaque compound is incorporated in the ink composition at a concentration level between 0.5 to 10% by weight, more preferably between 1 to 8% by weight of the total ink composition. In specific formulations, the amount of opacifying compound can still vary from 0.3 to 20% by weight of the total ink composition. In printing, the main solvent becomes evaporated, leaving in the substrate the binder and the opaque compound, which has a boiling point higher than the main solvent. As the binder is insoluble in such opaque compound, the binder precipitates and forms an imperfect film which is opaque in appearance. The labeling comprises labeling compounds which do not exhibit light absorption in the visible area of the electromagnetic spectrum (400 to 700 nm). These compounds can absorb either at wavelength shorter than 400 nm (UV-) or at a wavelength longer than 700 nm. (IR radiation). They can also be luminescent compounds, either of the up or down conversion type, that is, they can emit radiation either at shorter wavelengths or at wavelengths longer than the wavelength of the light absorbed. The inkjet printing ink composition further comprises: at least one solvent, at least one binder, at least one marking compound that absorbs light outside the visible range, and optionally additional additives.

Brief Description of the Figures Figures la-c show the results of the brightness measurements of the inks printed with binders of examples 1 to 3 on Kraft paper. Figures 2a-d show some different results for the brightness measurements of the inks printed on FID paper of Examples 1 to 4.

Detailed Description of the Invention In the context of the present invention, at least one solvent is selected from fast-drying solvents such as ketones, especially acetone and methyl ethyl ketone; Acetic or alcohol based solvents such as methyl or ethyl acetate or methanol can also be used. The solvent can also be a mixture of two or more of the mentioned solvents. Preferably, the solvent does not contain water, except water included in the solvent or other components of the ink as an impurity. Thus, the ink is preferably free of water. The solvent is present in an amount ranging from 40 to 90% by weight or more, preferably ranging from 70 to 90% by weight of the total ink composition. Solvents which have slower evaporation properties than the said solvents, such as isopropanol, isopropyl acetate, ethanol or propanol, can also be included in the composition of the solvent. Such solvents are, however, only incorporated in minor amounts, for a fine tempering of the total ink properties. The binder is selected from the group of vinyl resins, cellulose derivatives, polyacetal resins, acrylic resins or styrene-maleic copolymer resins. Preferably, the binders are selected from copolymers of vinyl acetate and vinyl chloride, nitrocellulose or polyvinyl butyral. The amount of the binder incorporated in the ink composition varies between 3 to 30% by weight, more preferably between 4 to 20% by weight, of the total ink composition. The labeling compound is preferably selected from the group of dyes which do not show absorbance in the visible range of the electromagnetic spectrum, ie at wavelengths between 400 to 700 nm, but which are visible on or after exposure to light ultraviolet (200 to 400 nm) or infrared (700 to 2500 nm). Suitable dyes include ÜV markers such as optical brighteners, rare iron chelates, as well as NIR dyes, such as laser NIR dyes. Typical levels of incorporation vary from 0.0001 to 10% by weight, preferably from 0.001 to 5% by weight, and more preferably from 0.1 to 2% by weight of the total ink composition.

Additional additives which can be incorporated into the ink composition include salts and conductivity humectants. Suitable salts for imparting ink conductivity can be selected from inorganic salts such as LINO3, organic salts such as alkylammonium acetate, and mixed salts such as potassium acetate. The conductivity of the salt should be sufficiently high to reach approximately 1 mS to 1% by weight of incorporation level. The salt is preferably incorporated in an amount ranging from 0.3 to 5% by weight, more preferably ranging from 0.5 to 3% by weight of the total ink composition. The humectant is added to the ink composition to prevent clogging of the nozzle when the highly volatile solvent evaporates. Suitable humectants are, for example, glycols and glycol ester, N-methyl-pyrrolidone (NMP), glycerol esters, long-chain alkylamides or the like; typically, these compounds to be used as humectants have a higher boiling point than said highly volatile solvents commonly used in inkjet printing ink compositions. The humectant is typically incorporated at levels ranging from 0.2 to 20% by weight, and more preferably ranging from 0.5 to 5% by weight of the total ink composition.

In a further aspect, the invention describes a method of applying an invisible security marking to a substrate. The method comprises the steps of: Providing an inkjet printing ink comprising at least one hydrocarbon compound having two or three hydroxyl groups, said hydrocarbon compound having a linear or branched carbon chain of two, three, four , five or six carbon atoms, as a non-particulate opaque compound; e - printing a security marking on a substrate; and characterized in that the printed security label exhibits the same level of brightness as the brightness of the substrate. Another aspect of the invention is a substrate bearing a printed marking, which is printed with an inkjet ink according to the invention, and which exhibits the same level of brightness as the substrate. The invention is now described in more detail by means of examples: Example 1: UCAR VMCH (vinyl resin, DOW); Example 2: Scripset 520 (anhydrous maleic and styrene copolymer, Hercules Inc.); Example 3: Pioloform BL 18 (Polybutyl butyral, Wacker Chemies); Example 4: DHX 3/5 Nitrocellulose (Noble Enterprises); Example 5: Joncryl 671 (acrylic resin, SC Johnson &Son); Example 6: Paraloid A-12 (acrylic resin, Rohm &Hass).

The inks, which include combinations of opaque and binder compounds as listed in Table 1, further contain 1% by weight of tetrabutylammonium tetrafluoroborate (Fluka) as the conductive salt, 2% by weight of dipropylene glycol monomethyl ether (DPM) (DOW) ) as a humectant and 0.002% by weight of UVITEX OB (Ciba SC) as UV fluorescent opaque compound, and the remaining part of the composition is acetone.The amount of binder added is given in Table 1. For brightness test purposes , 1 ml of ink is then allowed to evaporate on a thin-film substrate and the opaque effect is observed as a bleaching of the drying film ..

Table 1: Combinations of binder and opaque compound.

To determine the intensity of the opaque effect for various combinations of binder and opacifying compound, Kbar films of the previous inks were printed on several representative substrates, namely, Fiduciary paper (FID) and Kraft. The gloss at 60 ° C was then measured as a function of the amount (in weight%) of opaque diol or triol in the ink composition using a LANGE REFO 60 brightness meter. Figures la-c show the results of the gloss measurements of the inks printed with binders of examples 1 to 3 on Kraft paper. The opacifying compounds in Example 1 are 1,5-pentanediol (triangle) and 1, 2-butanediol (diamond) see figure la. The opacifying compounds in Example 2 are 1,5-pentane-diol (triangle) and monopropylene glycol (diamond) see figure Ib.

The opacifying compounds in Example 3 are monopropylene glycol (triangle) and glycerol (diamond) see figure le. The boxes represent the brightness of the substrate. For the vinyl binder, an amount of at least 7% by weight of the opaque compound is required to achieve a significant reduction in gloss. For anhydrous maleic and styrene copolymers (Hercules Scripset), less of the opaque compound has been added compared to the vinyl binder. Both opacifying compounds used exhibit a similar brightness reduction with an increased amount of the aggregate opaque compound. A strong decrease in brightness can be observed for a polyvinyl butyral binder (Pioloform) in addition to about 6% by weight of glycerol. Contrary to this monopropylene glycol, it is not suitable to reduce the gloss when it is added to a polyvinylbutyral binder and printed on Kraft paper. Figures 2a-d show some different results for the brightness measurements of the inks printed on FID paper of examples 1 to 4. The ink containing a vinyl resin as a binder (example 1), requires a high amount of about 9% by weight of 1,5-pentane-diol to exhibit a clear reduction in brightness, see Figure 2a. An ink with binder of Example 2 (maleic anhydro and styrene), requires less opaque compound, if especially 1,5-pentanediol is used, see Figure 2b. Even the least opaque compound is necessary if polyvinyl butyral is used (binder example 3, see figure 2c). Approximately 4% by weight of monopropylene glycol are capable of reducing the brightness of the printed ink at the substrate level. Similar amounts of monopropylene glycol or glycerol are necessary to reduce the brightness of an ink containing a nitrocellulose binder at the substrate level. In a further experiment, a selected amount of the opaque compound is incorporated into inkjet inks and a UV-readable dimensional code was printed on different substrates, i.e., Kraft paper, cardboard and FID paper. Since the amount of ink printed was also low to reproducibly measure the brightness of these low-gloss substrates, the level of invisibility of ink-jet printing was assessed based on the following criteria: ++ = inkjet printing is invisible because it is much more shiny; + = inkjet printing is slightly visible because it is brighter; 0 = inkjet printing is completely invisible because it has the same level of brightness as the substrate; - Inkjet printing is slightly visible because it is more opaque; - = inkjet printing is very visible because it is much more opaque than the substrate. Results are shown in table 2.

Table 2: Comparison of gloss effects of printed 2D codes.

Claims (16)

NOVELTY OF THE INVENTION Having described the present is considered as a novelty, and therefore, it is claimed as property contained in the following: CLAIMS

1. Use of at least one hydrocarbon compound having a carbon chain of two to six carbon atoms, two or three hydroxyl groups in an inkjet printing ink composition as an opaque non-particulate compound, to adapt the brightness of a marking printed on the brightness of a substrate carrying said marking, such that said marking is not perceptible only with the eye.

2. Use according to claim 1, wherein the opaque compound is incorporated in the composition in an amount ranging from 0.5 to 10% by weight, preferably from 1.0 to 8.0% by weight of the total composition.

3. Use according to claim 1 or 2, wherein the opaque compound is selected from the group consisting of 1,5-pentanediol, ethylenediol, butanediol, propanediol, glycerol and mixtures thereof.

4. Use according to one of claims 1 to 3, wherein the inkjet printed ink composition comprises at least one solvent, at least one binder, at least one marking compound that absorbs light outside the wavelength range visible, and optional additives.

5. Use according to claim 4, wherein the solvent is selected from the group consisting of ketones, acetate esters, alcohols and mixtures thereof.

6. Use according to claim 5, wherein the solvent is selected from the group consisting of acetone, methyl ethyl ketone, ethyl acetate, methyl acetate, methanol, isopropanol, isopropyl acetate, ethanol, propanol and mixtures thereof.

7. Use according to one of claims 4 to 6, wherein the amount of the solvent ranges from 40 to 95% by weight, preferably 70 and 90% by weight of the total ink composition.

8. Use according to one of claims 4 to 7, wherein the binder comprises a resin selected from the group consisting of vinyl, cellulose, acrylic, polyacetalic, styrene-maleic copolymer resins and mixtures thereof.

9. Use according to one of claims 4 to 8, wherein the binder is incorporated in the composition in an amount ranging from 3 to 30% by weight, preferably 4 and 20% by weight of the total ink composition. .

10. Use according to one of claims 4 to 9, wherein the additives comprise at least one conductivity of the salt, a humectant and / or a stabilizer.

11. Use according to claim 10, wherein the conductivity of the salt is selected from the group consisting of lithium nitrate, alkylamino acetate, potassium acetate and mixtures thereof.

12. Use according to one of claims 10 or 11, wherein the conductivity of the salt is included in the composition in an amount ranging from 0.3 to 5% by weight, preferably between 0.5 and 3% by weight of the composition of total ink.

13. Use according to one of claims 4 to 12, wherein the opaque compound is incorporated in the composition in an amount ranging from 0.0001 to 10% by weight, preferably 0.01 to 2% by weight of the ink composition. total. A substrate carrying a printed security label, preferably printed with an ink jet printing ink composition, characterized in that it comprises a non-particulate opaque composite, with preferably at least one hydrocarbon compound having a linear carbon chain or branched from two to six carbon atoms, carrying two or three hydroxyl groups, wherein said security label is adapted to the brightness of the substrate. 15. Method for applying an invisible security marking to a substrate, characterized in that it comprises the steps of: - providing an inkjet printing ink comprising at least one opaque non-particulate compound; e - printing with said ink a security marking on a substrate, wherein the brightness of the printed security marking is adapted to the brightness of the substrate, in which at least one opaque non-particulate compound is a hydrocarbon compound having a chain linear or branched carbon of two to six carbon atoms carrying two or three hydroxyl groups. 16. Inkjet printing ink comprising at least one solvent, at least one binder and at least one marking compound, said marking compound absorbs light of a non-visible wavelength, and optionally additives, characterized in that the ink it further comprises a non-particulate opaque compound, selected from the group of hydrocarbon compounds having a linear or branched carbon chain of two or six carbon atoms, bearing two or three hydroxyl groups.