Marking composition

Abstract

The invention relates to a marking composition, by means of which better protection of goods than hitherto available can be achieved independently of the coloring of the goods. The marking composition comprises an infrared-absorbing particulate component and a carbon derivative, wherein the weight ratio of infrared-absorbing component to carbon derivative is in the range of approx. 10:1 to approx. 10,000:1.

Claims

1. An article comprising one or more infrared-detectable identification markings comprising an infrared-absorbing particulate component, wherein the infrared-absorbing particulate component has a characteristic particle size value d.sub.50 of about 100 nm or less, and a carbon derivative, wherein the weight ratio of the infrared-absorbing particulate component to the carbon derivative is in the range of about 100:1 to about 10,000:1, wherein the one or more infrared-detectable identification markings comprise a finely dispersed particulate mixture of the infrared-absorbing particulate component and the carbon derivative, wherein the one or more infrared-detectable identification markings contain a solid material portion of the infrared-absorbing particulate component of approximately 0.05 to approximately 1 weight-%, and wherein the one or more identification markings exhibit a synergistic emission in the infrared range as a result of the combination of the infrared-absorbing particulate component and the carbon derivative.

2. The article of claim 1 wherein the article comprises a surface and the one or more identification markings are on the surface of the article.

3. The article of claim 1 wherein the one or more markings form a security code or a data matrix code.

4. The article of claim 1 wherein the infrared-absorbing particulate component is an oxide selected from the group consisting of tin oxides, zinc oxides, antimony oxides, indium oxides, molybdenum oxides, tungsten oxides, bismuth oxide, and combinations thereof.

5. The article of claim 1 wherein the infrared-absorbing particulate component comprises a tin oxide doped with an element selected from the group consisting of indium, antimony, fluorine, and combinations thereof.

6. The article of claim 1 wherein the carbon derivative is selected from the group consisting of soot, graphite, fullerenes, graphenes, carbon nanotubes, and combinations thereof.

7. The article of claim 1 wherein the infrared-absorbing particulate component has a characteristic particle size value d50 of about 70 nm or less.

8. The article of claim 1 wherein the carbon derivative is in the form of nanoparticles that extend in at least one direction by about 100 nm or less.

9. The article of claim 1 wherein the article is selected from the group consisting of identification cards, credit cards, debit cards, and combinations thereof.

10. The article of claim 1 wherein the article is a consumer good.

11. The article of claim 1 wherein the article is a textile.

12. The article of claim 1 wherein the article is selected from the group consisting of CD's, DVD's, and combinations thereof.

13. The article of claim 1 wherein the identification markings are visually undetectable.

Description

(1) In the following, these and other advantages of the invention are explained by means of examples and drawings.

(2) Specifically, the individual drawings show:

(3) FIG. 1: UV-VIS-NIR absorption curves of a nanoscale antimony-doped tin oxide, soot, and CNT dispersion, as well as the marking compositions of this invention contained therein, all water-based;

(4) FIG. 2: UV-VIS-NIR absorption curves of dried, antimony-doped tin oxide, soot, and CNT dispersions, as well as the dried marking compositions according to this invention;

(5) FIG. 3: UV-VIS-NIR absorption curves of dried binder-containing ink preparations of the individual components and a marking composition according to this invention;

(6) FIG. 4: Differences of chromatic color values measured and compared against blank white paper, measured at imprints of ink preparations having the nanoscale antimony-doped tin oxide component (white bar); of ink preparations containing the finely dispersed marking compositions according to this invention of the nanoscale antimony-doped tin oxide sample with soot (cross-hatched bar), as well as with carbon nanotubes (black bar); and

(7) FIG. 5: Percentage of color changes of the contrasts in the visual, near infrared, and far infrared range of detection for imprints of ink preparations with the nanoscale, antimony-doped tin oxide component (white bar), of ink preparations containing the finely dispersed marking compositions described in this invention of the nanoscale antimony-doped tin oxide sample with soot (cross-hatched bar), as well as carbon nanotubes (black bar).

EXAMPLES

(8) The carbon derivative used in the following examples was lamp black in the form of Printex U from Evonik Industries AG with an average primary particle size of 21 nm or so-called MWCNT (multi-walled carbon nanotubes) in the form of Nanocyl NC 7000 from Nanocyl S.A. with a mean tube diameter of 9.5 nm and a mean fiber length of 1.5 m.

(9) The infrared absorber employed was an antimony-doped tin oxide nanopowder (ATO), available from Sigma-Aldrich Co. under the order number 549541 as antimony tin oxide, nanopowder, having a primary particle size smaller than 50 nm and an antimony oxide content in the range of 7 to 11 weight-%.

(10) Prior to use, the infrared-absorbing component and the carbon derivative were dispersed by means of a nano mill. A dispersing agent and a wetting agent were added to the liquid formulations (25 weight-% of Disperbyk 190 from Byk-Chemie, in relation to the solid material content of the carbon and infrared-absorbing components) until a finely dispersed state with particle sizes of d.sub.50 of approx. 70 nm or smaller was achieved. The particle sizes in a dispersion and thus the dispersed state of the dispersion were determined by utilizing methods of light diffusion.

(11) The polymeric binder was used in Example 3 as a mixture of PVP K12 (polyvinyl pyrrolidone) from Sigma-Aldrich Co. and WALOCEL MW3600 (hydroxyethyl methyl cellulose) from Dow Wolff Cellulosics GmbH in a weight ratio of 1:1, formulated as a 0.02 weight-% solution in water.

(12) The polymeric binder of the ink formulations of Example 4 was available as an aqueous binder dispersion. To this effect, hydrosol 900 (a 35 weight-% watery styrene acrylate copolymer dispersion from Lefatex-Chemie GmbH) was diluted with water to arrive at an approx. 10 weight-% solid material ratio of the polymeric binder (styrene acrylate copolymer).

Example 1

(13) Comparison of the UV-VIS-NIR absorption of a nanoscale antimony-doped tin oxide, soot, and CNT dispersion, as well as the mixtures thereof according to this invention, in water

(14) FIG. 1 shows a comparison of the UV-VIS-NIR absorption A of a nanoscale antimony-doped tin oxide, soot, and CNT dispersion, as well as the mixtures thereof according to this invention, in water.

(15) The absorption curves shown refer to the following dispersions:

(16) Absorption curve (1): distilled water

(17) Absorption curve (2): aqueous dispersion with approx. 0.001 weight-% lamp black

(18) Absorption curve (3): aqueous dispersion with approx. 0.001 weight-% MWCNT

(19) Absorption curve (4): aqueous dispersion with approx. 0.05 weight-% nanoscale, antimony-doped tin oxide (ATO) (d.sub.50 approx. 66 nm)

(20) Absorption curve (5): aqueous dispersion with approx. 0.001 weight-% lamp black and approx. 0.05 weight-% nanoscale, antimony-doped tin oxide (ATO) (d.sub.50 approx. 66 nm)

(21) Absorption curve (6): aqueous dispersion with approx. 0.001 weight-% MWCNT and approx. 0.05 weight-% nanoscale, antimony-doped tin oxide (ATO) (d.sub.50 approx. 66 nm)

(22) As can be seen, the addition of the nanoscale, antimony-doped tin oxide has a significant impact on the absorption characteristics of the dispersion in water under UV-VIS-NIR, but the two carbon derivatives lamp black and MWCNT influence them only slightly in this wavelength range.

Example 2

(23) Comparison of the UV-VIS-NIR absorptions of dried antimony-doped tin oxide, soot, and CNT dispersions, as well as the dried mixtures according to this invention

(24) FIG. 2 shows a comparison of the UV-VIS-NIR absorption A of dried antimony-doped tin oxide, soot, and CNT dispersions with the dried mixtures according to this invention. Here the absorption curves refer to the following solid materials and/or solid material compositions:

(25) Absorption curve (1): approx. 50 l of a dried lamp black dispersion from Example 1 on quartz glass (coating thickness approx. 700 nm)

(26) Absorption curve (2): approx. 50 l of a dried MWCNT dispersion from Example 1 on quartz glass (coating thickness approx. 700 nm)

(27) Absorption curve (3): approx. 50 l of a dried antimony-doped tin oxide (ATO) dispersion from Example 1 on quartz glass (coating thickness approx. 700 nm)

(28) Absorption curve (4): approx. 50 l of a dried mixture according to this invention of the lamp black and nanoscale, antimony-doped tin oxide (ATO) dispersions from Example 1 on quartz glass (coating thickness approx. 700 nm)

(29) Absorption curve (5): approx. 50 l of a dried mixture according to this invention of the MWCNT and nanoscale, antimony-doped tin oxide (ATO) dispersions from Example 1 on quartz glass (coating thickness approx. 700 nm)

(30) On examination of the UV-VIS-NIR spectrums of the solid materials obtained by drying the dispersions from Example 1, it may be seen that, according to this invention, the finely dispersed addition of the carbon derivatives lamp black and MWCNT to the nanoscale, antimony-doped tin oxide (ATO) dispersion has only a slight impact on the absorption properties in the ultraviolet and visually visible light range, but that there are significant changes in absorption in the near infrared range.

(31) When one considers the generally very slight absorption of the dried dispersions of both carbon derivatives, it is also evident that it involves not just a purely additive absorption, but that the increased absorption in the near infrared range of light represents a synergistic enhancement effect.

Example 3

(32) Comparison of the UV-VIS-NIR absorptions of dried, binder-containing preparations of the individual components and the heterogeneous mixtures of materials according to this invention

(33) FIG. 3 shows the UV-VIS-NIR absorption A of dried binder-containing preparations of the individual components and heterogeneous mixtures of materials according to this invention. Here the absorption curves represent the following binder preparations:

(34) Absorption curve (1): Polymeric binder on quartz glass (coating thickness approx. 1,800 nm)

(35) Absorption curve (2): Polymeric binder with approx. 0.15 weight-% of nanoscale, antimony-doped tin oxide (ATO) on quartz glass (coating thickness approx. 1,800 nm)

(36) Absorption curve (3): Polymeric binder with a mixture according to the invention of approx. 0.006 weight-% MWCNT and approx. 0.15 weight-% nanoscale, antimony-doped tin oxide on quartz glass (coating thickness approx. 1,800 nm)

(37) Absorption curve (4): Polymeric binder with a mixture according to this invention of approx. 0.006 weight-% lamp black and approx. 0.15 weight-% nanoscale, antimony-doped tin oxide (ATO) on quartz glass (coating thickness approx. 1,800 nm)

(38) The absorption spectrums which, following incorporation of the components and the marking compositions of this invention into an approx. 0.2 weight-% polymeric binder dispersion based on polyvinyl pyrrolidone and hydroxyethyl methyl cellulose, were obtained after drying on a quartz glass, and clearly show that for the finely dispersed marking compositions of this invention, obtained from the carbon derivatives lamp black or MWCNT with the nanoscale, antimony-doped tin oxide (ATO) as the infrared-absorbing component, the absorption properties in the UV and visually noticeable light range are only slightly affected, while they are strongly influenced in the near infrared range. It is also seen that here, too, there is not just a purely additive effect, but a synergistic enhancement effect involving absorption in the near infrared light range.

Example 4

(39) Comparison of visual noticeability and infrared contrasts in imprints of binder-containing ink preparations of the individual components and binder-containing ink preparations using the heterogeneous mixtures of materials of this invention on white printer paper.

(40) The ink preparations in this example were produced with the above-described watery binder dispersion based on Hydrosol 900 and, in the comparison example, 5 weight-% nanoscale, antimony-doped tin oxide (ATO) components were added with respect to the solid material portion of the polymeric binder. In the examples of this invention, in addition to the 5 weight-% nanoscale, antimony-doped tin oxide (ATO) component, 50 ppm lamp black (Printex U) and/or 50 ppm MWCNT (Nanocyl NC 7000) were added, each with respect to the solid material portion of the polymeric binder.

(41) For marking compositions that are formulated as marking inks, in particular, the recommended weight relationship between the infrared-absorbing component and the carbon derivative is in the range of approx. 100:1 to approx. 10,000:1. Even when the carbon derivative portion in the marking composition is so extremely low, the present Example 4 shows a marked synergistic effect.

(42) In FIG. 4, the differences between the chromatic color values, measured by means of the X-Rite MA68 colorimeter (X-Rite, Inc.), of the imprints of the ink preparations containing only the nanoscale, antimony-doped tin oxide (ATO) component (white bar) were compared to the differences between the chromatic color values of the imprints of the inks with the finely dispersed mixtures of materials of this invention containing the nanoscale, antimony-doped tin oxide (ATO) sample mixed with lamp black (cross-hatched bar) and/or with MWCNT (black bar) against blank white paper. The angles given as X-Rite measurement geometry hereby reflect, by definition, the angular distance from the glancing angle.

(43) Under normal print conditions, the imprints of the formulations mentioned in the examples are transparent and color-neutral. To allow for visual checking and evaluation by means of color measurements, in this particular example, in each case in connection with the results shown in FIGS. 4 and 5, the imprints as to the number of overprints and the print density (dpi) were performed in such a way that for the imprints from the ink preparations, which contain only the usual nanoscale, antimony-doped tin oxide (ATO) component (comparison example, white bar), a chromatic color value difference E of approx. 1 against the white paper was obtained, at an X-Rite measurement geometry of 45. The imprints are subsequently weakly visible and so easier to differentiate.

(44) For imprints of inks with the finely dispersed mixtures of materials according to this invention (the examples according to this invention, cross-hatched and black bars), the relevant imprints were performed using analog print parameters, i.e., the number of overprints and the print density (dpi) were the same as for the comparison example that contained only the ATO.

(45) The chromatic color value differences E are shown in FIG. 4 for the visible wavelength range of 400 to 720 nm. As can be seen, the imprints from the inks containing the finely dispersed mixtures of this invention of tin oxide as the infrared-absorbing component with the carbon derivatives, change colors only to a slight degree over several angles of observation.

(46) In FIG. 5, based on the imprints described in connection with FIG. 4, the percentage of the color changes in the visible range (VIS: 400 to 720 nm; X-Rite measurement geometry 110) was compared to the percentage of contrast changes in the near infrared detection range (NIR: 720 to 2,500 nm), obtained upon stimulation in the near infrared range, and the far infrared detection range (FIR: 2.5 to 14 m).

(47) Values were measured for the following imprints, respectively, by means of suitable infrared cameras: Ink preparations with the nanoscale, antimony-doped tin oxide (ATO) component (white bar), Ink preparations containing the finely dispersed mixtures of materials of the nanoscale, antimony-doped tin oxide (ATO) sample according to this invention with lamp black (cross-hatched bar), and/or with MWCNT (black bar).

(48) The contrast changes are calculated based on the intensity values, previously determined by means of near infrared and far infrared cameras, using the following formula:

(49) $\mathrm{Contrast}=\frac{I_{\mathrm{Background}}-I_{\mathrm{Marking}}}{I_{\mathrm{Background}}+I_{\mathrm{Marking}}}.Math.100\%$

(50) As can be seen, in the visible range of the detection, the color changes and thus the visual noticeability of the imprints behave, in terms of percentages, similar to the achievable contrasts in the near infrared range, but in the far infrared detection range very much higher contrasts are obtained for the marking compositions of antimony-doted tin oxide and the carbon derivatives soot and CNT of this invention.

(51) Particularly for inks containing the mixture with the CNT of this invention, extremely increased far infrared contrasts are obtained when compared to the visually noticeable color changes. When the relevant near infrared absorption of the mixtures of this invention containing soot and CNT in FIG. 3 is compared to the resultant far infrared contrasts in FIG. 5, it is clearly seen that, due to the increased absorption of the mixtures of this invention containing soot or CNT (see FIG. 3), the energy intake by absorption is not the sole reason for the considerable increase in the far infrared contrasts. Rather, the effects of heat conductivity and emissivity, caused by the influence of the soot or CNT components, obviously contribute to the enhanced far infrared contrasts.