LUMINESCENT INK AND CERAMIC PRODUCT WITH A LABEL PRINTED WITH LUMINESCENT INK

Abstract

The present invention relates to a luminescent ink having a composition in % by weight comprising 20-55% of solvent, 5-55% of diluent; 2-15% of dispersant additive; 5-35% of solid particles with fluorescent properties, and 0.5-15% of solid dopant particles. The invention also relates to a process for obtaining a ceramic product with a printed luminescent label which incorporates a step in which digital printing is performed with said luminescent ink, this printing being applied on the surface substrate of the unfired ceramic part; and wherein the printing is performed with a digital printing machine; subjecting the ceramic part to a subsequent heat treatment in a conventional ceramic furnace at a temperature comprised between 650 and 1400 C.; and obtaining a fired ceramic product comprising a luminescent label visible with ultraviolet light. The invention also relates to a ceramic product obtainable by means of said process for obtaining a ceramic product, as well as to the use of the ink for printing luminescent labels that glow under ultraviolet light on ceramic products.

Claims

1. A luminescent ink which has a composition in % by weight comprising: 20-55% of solvent; being at least one selected from glycols, ethers, esters, aliphatic hydrocarbons, aromatic hydrocarbons, glycol-ether mixtures, or glycol-water mixtures; 5-55% of diluent; being at least one selected from glycols, ethers, esters, aliphatic hydrocarbons, aromatic hydrocarbons, glycol-ether mixtures, glycol-water mixtures; 2-15% of dispersant; being at least one selected from anionic compounds, cationic compounds, non-ionic compounds, short-chain compounds, long-chain compounds, conjugated polymers having a single bond or a double bond; 5-35% of solid particles from the combination of at least one component selected from Zr, W, Mo, and V oxides and salts with fluorescent properties; and 0.1-15% of solid dopant particles from the combination of at least one component selected from Eu.sub.2O.sub.3, Sm.sub.2O.sub.3, Dy.sub.2O.sub.3, Nd.sub.2O.sub.3, Ho.sub.2O.sub.3, and Er.sub.2O.sub.3.

2. The luminescent ink according to claim 1, wherein at least one reducer agent is added, with there being between 0.01 and 2% of reducer in the total mixture, and this reducer being at least one selected from silicon carbide, wood shavings, coal, sugar and its derivatives, glues, celluloses, metals, or organic solvents.

3. The luminescent ink according to claim 1, wherein solid particles which are alkaline oxides are added, with there being between 0.001 and 15% of solid particles in the total mixture, and which alkaline oxides are from the combination of at least one component selected from Li.sub.2O, Na.sub.2O, and K.sub.2O.

4. The luminescent ink according to claim 1, wherein solid co-dopant particles are added, with there being between 0.5 and 15% of solid co-dopant particles in the total mixture, and which particles are from the combination of at least one component selected from CeO.sub.2, Y.sub.2O.sub.3, La.sub.2O.sub.3, Lu.sub.2O.sub.3, Gd.sub.2O.sub.3, Tb.sub.2O.sub.3, and Yb.sub.2O.sub.3

5. The luminescent ink according to claim 1, wherein wetting additives are added, with there being between 0.1 and 10% of wetting additives in the total mixture; this wetting additive being at least one selected from 1,2-hexanediol or 1,6-hexanediol, pentanediol, or glycerin.

6. A process for obtaining a ceramic product with a printed luminescent label, wherein the label is printed inside the actual structure of the ceramic product, the process comprising the following the steps: i) preparing and obtaining an unfired ceramic part, obtaining an unfired support or ceramic part; ii) performing digital printing with luminescent ink according to the features of claim 1, this printing being applied on the surface substrate of the unfired ceramic part; and wherein the printing is performed with a digital printing machine; iii) subjecting the ceramic part to heat treatment in a conventional ceramic furnace at a temperature comprised between 650 and 1400 C.; and iv) obtaining a fired ceramic product comprising a luminescent label visible with ultraviolet light.

7. The process for obtaining a ceramic product with a printed luminescent label according to claim 6, wherein step (ii) of performing digital printing comprises a sub-step of preparing the raw materials of the ink in a digital printer; and a sub-step of printing the ink in the digital printer on the surface substrate of the unfired ceramic part.

8. The process for obtaining a ceramic product with a printed luminescent label according to claim 6, wherein the digital printing machine comprises at least one ink storage reservoir in which the raw material of the ink is arranged; wherein each storage reservoir is connected with a conduit with a head that prints the ink on the surface substrate of the unfired ceramic part, with the design and the printing being managed by a programmable control module of the machine.

9. The process for obtaining a ceramic product with a printed luminescent label according to claim 8, wherein at the outlet of the ink storage reservoir there is a pump that pumps the material to the head, with a filter being arranged at the outlet of the pump.

10. The process for obtaining a ceramic product with a printed luminescent label according to claim 9, wherein the conduit connecting the filter with the head comprises a recirculation circuit for excess material to be printed located between the filter and the head.

11. The process for obtaining a ceramic product with a printed luminescent label according to claim 9, wherein the conduit connecting the filter with the head comprises a thermostat(S) located between the filter and the head.

12. A ceramic product with a printed luminescent label obtainable by means of the process for obtaining a ceramic product described in claim 6.

13. (canceled)

Description

BRIEF DESCRIPTION OF THE FIGURES

[0106] In order to complete the description and to help better understand the features of the invention, a set of figures and drawings in which the following is depicted in a non-limiting illustrative manner is provided:

[0107] FIG. 1 schematically shows the different steps for producing a ceramic part comprising a luminescent label that glows under ultraviolet light.

[0108] FIG. 2 schematically shows how a luminescent ink digital printing machine is formed internally and the printing of said ink on the surface substrate of the unfired ceramic part.

[0109] FIGS. 3A-3D show the different results from printing a possible embodiment of the ink on tiles and their corresponding labels which are visible under ultraviolet light.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0110] Different embodiments of the inks such as those described above and in which all the possible components are included, not only the essential components, are described in detail below.

[0111] Tables 1 to 3 show, respectively, the relationship existing between each of the selected components and the formulated inks with respect to the constant solid content, as well as the grinding conditions used in the particle size reduction step.

TABLE-US-00001 TABLE 1 Alkaline Fluorescent host oxides Main dopants Co-dopants Reducer Ink Type % Type % Type % Type % Type % A V.sub.2O.sub.7.sup.2 93 Eu.sub.2O.sub.3 7 B WO.sub.4.sup.2 89.8 K.sub.2O 3.78 Eu.sub.2O.sub.3/Sm.sub.2O.sub.3 6.4 Shaving 0.02 (0.8/0.2) C MoO.sub.4.sup.2 89.2 K.sub.2O 3.55 Eu.sub.2O.sub.3/Sm.sub.2O.sub.3 7.2 Sugar 0.05 (0.5/0.5) D MoO.sub.4.sup.2 89.6 Na.sub.2O 3.59 Eu.sub.2O.sub.3/Sm.sub.2O.sub.3 4.6 Y.sub.2O.sub.3 2.2 Glucose 0.01 (0.8/0.2) E V.sub.2O.sub.7.sup.2 89.0 Na.sub.2O 3.89 Eu.sub.2O.sub.3/Ho.sub.2O.sub.3 4.7 Tb.sub.2O.sub.3 2.4 Coal 0.01 (0.9/0.1) F MoO.sub.4.sup.2 89.1 K.sub.2O 3.17 Eu.sub.2O.sub.3/Er.sub.2O.sub.3 6.8 Yb.sub.2O.sub.3 0.9 Glucose 0.03 (0.9/0.1) G WO.sub.4.sup.2 89.1 K.sub.2O 4.38 Eu.sub.2O.sub.3/Sm.sub.2O.sub.3 5.2 Gd.sub.2O.sub.3 1.3 CSi 0.02 (0.5/0.5) H V.sub.2O.sub.7.sup.2 89.2 Na.sub.2O 3.9 Eu.sub.2O.sub.3/Dy.sub.2O.sub.3 5.8 Lu.sub.2O.sub.3 1.1 (0.8/0.2) I WO.sub.4.sup.2/ 89.1 Li.sub.2O 3.68 Eu.sub.2O.sub.3/Sm.sub.2O.sub.3 5.5 Y.sub.2O.sub.3 1.6 CSi 0.02 MoO.sub.4.sup.2 (1/1) (0.8/0.2) J WO.sub.4.sup.2/ 86.5 Na.sub.2O 1.59 Eu.sub.2O.sub.3 4 Y.sub.2O.sub.3 7.9 Coal 0.01 MoO.sub.4.sup.2 (1/1)

[0112] Table 1 shows the solid components used in the inks with surface fluorescent properties.

TABLE-US-00002 TABLE 2 Grinding Other Ink solvent Diluents Dispersant additives A Ethyl cocoate 2-ethylhexanol Polymeric palmitate hyperdispersants with a single bond B Tripropylene Dipropylene Polymeric 1,2- glycol methyl glycol hyperdispersants with hexanediol ether a single bond C Tripropylene 2-ethylhexanol Polymeric glycol methyl palmitate hyperdispersants with ether a single bond D Dioctyl adipate Dioctyl adipate Polymeric hyperdispersants with a single bond E Isotridecyl Ethyl cocoate Polymeric stearate hyperdispersants with a single bond F 2-ethylhexanol Ethyl cocoate Polymeric palmitate hyperdispersants with a single bond G 2-ethylhexanol Dioctyl adipate Polymeric stearate hyperdispersants with a single bond H Mixture of 2-ethylhexanol Polymeric isobutyl esters palmitate hyperdispersants with a single bond I Dioctyl adipate Mixture of Polymeric isobutyl esters hyperdispersants with a single bond J Ethyl cocoate 2-ethylhexanol Polymeric palmitate hyperdispersants with a single bond

[0113] Table 2 shows the liquid components used in the inks with surface fluorescent properties.

TABLE-US-00003 TABLE 3 CS Solvent Diluent Dispersant KWh/kg of Ink (wt)% (wt)% (wt)% (wt)% solid A 44.200 35.002 15.000 5.750 0.85 B 44.100 40.197 10.000 5.730 0.87 C 44.000 31.575 20.000 4.402 0.89 D 44.000 31.575 20.000 4.402 0.90 E 44.000 37.219 10.000 8.797 0.88 F 44.000 38.703 12.000 5.282 0.97 G 44.000 35.703 15.000 5.282 1.02 H 44.000 40.703 10.000 5.282 1.00 I 44.000 40.703 10.000 5.282 1.08 J 44.000 40.703 10.000 5.282 1.08

[0114] Table 3 shows the compositions and grinding conditions of the inks formulated and developed with the ratio by weight (wt) %.

[0115] Table 4 below shows the results of the physical properties of the different formulated inks.

TABLE-US-00004 TABLE 4 Dynamic surface Viscosity at tension 45 C. (mPa .Math. s) Density at 45 C. Particle size distribution (m) 12 20 Sedimentation Agglomeration 25 C. (mN/m) Ink D.sub.10 D.sub.50 D.sub.90 D.sub.100 rpm rpm at 45 C. (%) at 45 C. (%) (g/cm.sup.3) 10 ms A 0.345 0.638 0.981 1.451 18.70 18.81 10.60 1.80 1.280 33.2 B 0.347 0.677 0.947 1.425 20.90 20.06 5.80 2.00 1.280 33.1 C 0.347 0.715 0.995 1.389 23.40 23.58 4.40 1.55 1.280 32.9 D 0.342 0.720 0.985 1.397 18.25 18.45 12.90 1.30 1.280 33.5 E 0.346 0.701 0.895 1.256 19.50 19.56 10.55 1.25 1.280 33.5 F 0.345 0.687 0.901 1.155 21.50 21.63 10.00 2.00 1.280 33.1 G 0.374 0.485 0.588 0.608 22.15 21.81 8.20 0.60 1.280 35.2 H 0.372 0.388 0.397 0.403 25.45 24.33 8.10 0.40 1.280 34.4 I 0.373 0.589 0955 1.209 26.25 25.02 7.85 1.20 1.280 35.9 J 0.347 0.482 0.592 0.609 23.20 22.83 4.00 0.60 1.280 33.8

[0116] After obtaining any of those possible embodiments of an ink that is visible under ultraviolet light (inks A-J), the second object is to define the process which allows obtaining a ceramic product with a printed luminescent label inside its very structure, wherein this process comprises the steps of: [0117] i) Preparing and obtaining an unfired ceramic part through conventional means, obtaining an unfired support or ceramic part; [0118] ii) performing digital printing with luminescent ink such as the one defined above in the form of a label or equivalent decorative element, wherein the composition of the ink allows it to be visible under ultraviolet light, and this printing being applied on the surface substrate of the unfired ceramic part; and wherein the printing is performed with a digital printing machine; [0119] iii) subjecting the ceramic part to heat treatment in a conventional ceramic furnace at a temperature comprised between 650 and 1400 C.; with the temperature depending on the final product to be obtained; and [0120] iv) obtaining a fired ceramic product comprising a luminescent label visible with ultraviolet light.

[0121] In a possible embodiment of the invention, the process for the specific case of obtaining a tile with said luminescent label is defined. This process can be schematically seen in FIG. 1 with references (A)-(H) that correspond with the different steps of the process, wherein the process precisely comprises the steps of: [0122] (A) preparing and homogenizing the raw materials which form a ceramic paste, these materials being fundamentally clays, feldspars, sand, carbonates, and kaolins, among others; [0123] (B) milling the different materials of the ceramic paste; comprising at least one of mixing, dispersion, grinding, granulation; [0124] (C) compacting the milled ceramic paste by uniaxial pressing or isostatic pressing, obtaining a ceramic part formed by the press; [0125] (D) drying the ceramic part or support thus obtained, wherein the ceramic part is subjected to a temperature of up to 110 C.; [0126] (E) applying, after crushing the support, engobe, glaze, or engobe-glaze, wherein this ceramic part has yet to be subjected to firing; [0127] (F) performing digital printing with luminescent ink such as the one defined above in the form of a label, wherein the composition of the ink allows it to be visible under ultraviolet light, and this printing being applied on the surface substrate of the unfired ceramic part; and wherein the printing is performed with a digital printing machine. [0128] (G) subjecting the ceramic part to heat treatment in a conventional ceramic furnace at a temperature between 900 and 1250 C.; and [0129] (H) obtaining a fired ceramic product comprising a luminescent label visible with ultraviolet light, in the case of this possible embodiment, a tile.

[0130] To improve the description, FIG. 2 schematically shows how the digital printing machine is, as indicated above the machine comprises, in a possible embodiment of the invention, ink storage reservoirs (1) in which the ink described above in the preceding sections is arranged; wherein each storage reservoir (1) is connected with a head (2) which is the device that prints on the surface substrate of the unfired ceramic part (UCP). At the outlet of the ink storage reservoir there is a pump (3) that pumps the material to the head, with a filter (4) being arranged at the outlet of the pump to ensure the particle size, a conduit connecting the filter with the head, comprising a recirculation circuit (5) in the case of pumping more material that is to be printed, and a thermostat (6) which regulates the temperature of the raw material can also be arranged before the head, all of them being managed by a programmable control module (7) of the machine in which the label to be printed is designed and the parameters for printing the ink on the substrate of the unfired ceramic part are managed.

[0131] By way of example, FIG. 3A shows a luminescent label developed according to the example of ink A (Tables 1 to 4) at the firing temperature of 1220 C. and a weight of 12 g/m.sup.2. The image on top shows the inspection of a tile by means of (excitation-free) daylight; whereas the image at the bottom shows an authenticity-certifying label which is visible by means of visual inspection with UV light at a wavelength of 360-380 nm.

[0132] FIG. 3B shows a luminescent label developed according to the example of ink B (Tables 1 to 4) at the firing temperature of 1200 C. and with a weight of 10 g/m.sup.2. The image on top shows the inspection of a tile by means of (excitation-free) daylight; whereas the image at the bottom shows an authenticity-certifying label in the form of a fingerprint which is visible by means of visual inspection with UV light at a wavelength of 360-380 nm.

[0133] FIG. 3C shows a luminescent label developed according to the example of ink I (Tables 1 to 4) at the firing temperature of 1150 C. and with a weight of 12 g/m.sup.2. The image on top shows the inspection of a tile by means of (excitation-free) daylight; whereas the image at the bottom shows an authenticity-certifying label in the form of a QR code which is visible by means of visual inspection with UV light at a wavelength of 360-380 nm.

[0134] FIG. 3D shows a luminescent label developed according to the example of ink J (Tables 1 to 4) at the firing temperature of 1120 C. and with a weight of 10 g/m.sup.2. The image on top shows the inspection of a tile by means of (excitation-free) daylight; whereas the image at the bottom shows an authenticity-certifying label in the shape of a star which is visible by means of visual inspection with UV light at a wavelength of 360-380 nm.

[0135] Taking all the preceding aspects into account, the present invention solves the problems of enabling the firing of ceramic product such that a luminescent label is printed inside the actual product, and such that the firing process does not affect the luminescent properties of said label. As indicated throughout the description, this allows obtaining a special advantage or application intended for the field of certifying the authenticity of said ceramic products given that, by obtaining a luminescent label that glows under ultraviolet light conditions, this label is invisible under normal conditions of use (FIGS.A-3D).