Method for producing a luminescent inorganic material and luminescent inorganic material produced using the method

Abstract

The present invention relates to a method for producing a luminescent inorganic material based on an oxyfluoride matrix doped with multiple combinations of rare-earth ions (ytterbium (Yb), erbium (Er), thulium (Tm), europium (Eu) and neodymium (Nd)), and which contains micro- and nanostructured phases obtained using a thermal treatment. Advantageously, the material obtained using the method of the present invention generates a luminescence pattern with simultaneous emission in the near infrared spectrum and in the visible spectrum under 980 nm infrared excitation, which enables the material to be used in anti-counterfeiting security devices, such as security inks for printing textiles, paper money or printed circuits, among others.

Description

[0001]

[0002] Procedure for obtaining a luminescent inorganic material and luminescent inorganic material obtained by said procedure.

[0003] TECHNICAL SECTOR

[0004] The present invention relates to a process for obtaining a luminescent inorganic material based on an oxyfluoride matrix doped with multiple combinations of “rare earth” ions (Ytterbium (Yb), Erbium (Er), Thulium (Tm), Europium (Eu), Neodymium (Nd)), and containing micro- and nanostructured phases obtained from a heat treatment of the corresponding bulk precursor glass prepared by melting techniques.

[0005] Using infrared excitation of 980 nm and through photonic processes of spectral conversion (up-conversion and down-conversion) a luminescence pattern is generated with simultaneous emission in the near-infrared spectrum NIR (in the range of 800 nm to 1500 nm) and in the visible spectrum (in the range of 450 nm to 700 nm), which provides a coding based on multiple narrow bands of luminescence and predetermined combinations of positions and relative intensities between them.The luminescent behavior of the material obtained as a result of the procedure and its composition provides a unique 'spectral signature' for each material obtained, so it is possible to design a specific luminescence pattern as desired, that is, to 'encode' the luminescence, which makes the procedure and material of the present invention particularly advantageous for its application in the detection of counterfeits, by incorporating it into security devices or inks for printing on textiles, paper, banknotes or printing electronic circuits, among others.

[0006] PRIOR ART

[0007] The risk of counterfeiting electronic devices, such as integrated circuits, textiles, or printed currency, is a significant and growing concern due to its potential to compromise the performance of critical infrastructure, from healthcare devices to defense equipment and aerospace hardware. Furthermore, the counterfeiting of products ranging from textiles and food to pharmaceuticals affects every citizen as an end user, compromising their safety and even their health. An effective supply chain management program, supported by security features such as tracking and tracing, including luminescent inks and security labels made with luminescent materials, provides an effective deterrent against counterfeiting.

[0008] New luminescent security inks and labels must have characteristics that are more difficult for increasingly sophisticated counterfeiters to imitate. In this regard, the luminescent materials that have been widely used in security inks are based on spectral conversion effects of light to display a visible pattern when excited by ultraviolet (UV) sources, but with the associated drawbacks of relatively harmful UV radiation (N Katumo, BS Richards, et al. Adv. Mater. Technology, 2100047, (2021)), (TM Dung Cao, M. Ferrari, et al. Molecules, 26, 1041 (2021)).

[0009] On the other hand, low-cost luminescent inks activated by near-infrared light (NIR) are known, through spectral conversion effects (up-conversion), an approach that has been attracting much interest in recent years to contribute to improving anti-counterfeiting technology (A. Bañde, JM Meruga, C. Douma, D. Langerman, G. Crawford, JJ Kellar, WM Cross and PS May et al, RSC Advances, 5, 101338 (2015)), (S. Torres-García, C. Hernández-Álvarez, M. Medina- Alayón, P. Acosta-Mora, AC Yanes, J. del-Castillo, A. Menéndez-Velázquez, J. Méndez- Ramos, Ceramics International, 49(14), 24390 (2023)). These materials offer advantages compared to the standard fluorescent dyes used so far, such as the almost negligible background noise due to the zero surface autofluorescence and invisibility under ambient light (M. Wu et al, Nature Photonics 10, 31 (2016)), (W.Yao et al, Journal of Materials Chemistry C 4, 6327 (2016)).

[0010] The patent document WO2014144892 (“Rare Earth Spatial / Spectral Microparticle Barcodes For Labeling Of Objects And Tissues”) discloses the up-conversion luminescence spectrum under infrared excitation at 980 nm with nanoparticles containing Yb luminescent ions 3+ , Er 3+ and Tm 3+resulting in multiple emissions in the visible range between 400 and 700 nm. However, the invention described therein does not exhibit simultaneous emission in the NIR-NIR range alongside the visible emission, nor does it account for changes in the luminescent characteristics caused by the different glassy and nano / microcrystalline phases obtained by heat treatment of the material. It is in this aspect, among others, that the present invention offers advantages for designing unique “spectral signature” patterns with an increase in encoding capacity and the level of encryption of the light signal, as detailed below.

[0011] On the other hand, in the patent family US20100102250 / WO2010048535 (“Phosphor based authentication system”), the luminescence spectrum is disclosed as an authentication mark. However, the invention described therein only exhibits emissions in the 380 nm to 780 nm range, without any simultaneous emission in the NIR-NIR range, nor any type of pre-designed encoding of the luminescent spectrum emitted by the material. Furthermore, the method described therein is excessively complicated, as it requires the preparation of a mixture of different phosphors (luminescent materials), at least two types, or preferably three or more, compared to the present invention, which is based on the luminescent characteristics and the “spectral signature” of a single type of material with different glassy and micro / nano-crystalline phases.

[0012] Therefore, the applicant of the present invention is unaware of any bulk oxyfluoride materials containing different combinations of rare-earth ions for encoding the emitted luminescent spectrum using simultaneous emissions in the NIR-NIR (800 nm–1500 nm) and visible (400 nm–700 nm) ranges with a luminescent pattern design (“spectral signature”) based on relative intensity changes between components of the same luminescence band resulting from the material's prior heat treatment (not only between different bands as disclosed in WO2014144892). Thus, as detailed below, the present invention allows for obtaining a pre-established luminescent pattern that is impossible to counterfeit, while also offering technical simplicity and low cost in the detection devices used.

[0013] DESCRIPTION OF THE INVENTION

[0014] The present invention provides and claims a method for obtaining a luminescent inorganic material, as well as the material obtained by said method, which can advantageously be incorporated into security elements and luminescent inks, which are activated by low-cost near-infrared (NIR) light, by means of spectral conversion (up-conversion) effects.

[0015] The first aspect of the present invention relates to the process for obtaining the luminescent inorganic material. The present invention is defined according to the set of claims accompanying this specification, such that the claimed process comprises the following steps: a) obtaining a glass by a high-temperature melting technique (between 1000 e C-1500 eC) from a volumetric inorganic oxyfluoride matrix containing SiO2 and Al2O3, and a fluoride or a mixture of fluorides. Thus, the fluoride is CaF2 (in which case the glass is preferably obtained at 1400 e C) or a mixture of PbF2 and CdF2 (in which case the glass is preferably obtained at 1050°C). On the other hand, the bulk inorganic oxyfluoride matrix is ​​doped with at least one of the following rare-earth ions: Yb 3+ , Tm 3+ , Er 3+ , Nd 3+ , Eu 3+ , such that the rare earth ions are present in a proportion of between 0.01-10 mol% with respect to the total matrix, preferably 5%; b) obtaining a micro / nanocrystalline material from a precursor glass, wherein the precursor glass is obtained in the same way as the glass of step a), i.e., by applying the melting technique at a temperature between 1000 e C-1500 eC to volumetric inorganic oxyfluoride matrix containing SiO2 and Al2O3, and CaF2 (in which case the glass is preferably obtained at 1400 e C) or a mixture of PbF2 and CdF2 (in which case the glass is preferably obtained at 1050°C); the volumetric inorganic oxyfluoride matrix being doped with at least one of the following rare earth ions: Yb 3+ , Tm 3+ , Er 3+ , Nd 3+ , Eu 3+ where rare earth ions are present in a proportion of between 0.01 and 10 mol% relative to the total matrix, preferably 5%. The resulting precursor glass is subjected to an additional heat treatment at a temperature between 400 e C-500 e C for at least 24 hours, preferably for 24-48 hours, obtaining the micro / nanocrystalline material.

[0016] Preferably, both in obtaining the glass in step a) and in obtaining the precursor glass in step b), the melting is carried out using a heating ramp of 10 e C / min, starting from room temperature, until reaching the melting temperature of the volumetric inorganic oxyfluoride matrix (at a temperature between 1000 e C-1500 e C). This temperature is maintained for at least 30 minutes, preferably not exceeding 60 minutes, and then proceeding to a sudden (not progressive) cooling of the molten volumetric inorganic matrix to obtain the glass, for example, by pouring it onto stainless steel plates at room temperature.

[0017] Once the glass from step a) with an amorphous structure and the micro / nanocrystalline material from step b) have been obtained, they are mixed together in any desired proportion from 1% to 99% for each of them, obtaining the luminescent inorganic material, which is also the subject of the invention according to a second aspect thereof.

[0018] As a result of the different arrangements of matter present in the obtained luminescent inorganic material, as well as the presence of rare earth ions, the material exhibits a luminescence pattern with simultaneous emission in the near infrared (NIR) spectrum and the visible spectrum under infrared excitation of 980 nm, which is a feature of practical use in the field of security, since the material will only show the luminescence pattern under that wavelength.

[0019] The pre-heat treatment of the precursor material allows for the modification of specific luminescent characteristics, originating from the different vitreous and nano / micro-crystalline phases the material may exhibit, to create unique patterns that constitute a "spectral signature," making it impossible to counterfeit. This "spectral signature," acting as a light key, allows for the introduction of narrow secondary luminescence peaks within a main spectrum dominated by primary luminescent bands. This is achieved, for example, by changing the intensity ratios between components within the same narrow luminescence band in the 580 nm–620 nm range. This significantly increases the encoding capacity and the level of light signal capture provided by the material under infrared excitation, making it ideal for use in security inks.

[0020] According to a third aspect of the present invention, the luminescent inorganic materials that are the subject of the same are applicable for use in safety elements in textiles, paper and electronic circuit boards, among other non-limiting examples of application of the present invention.

[0021] Thus, the luminescent inorganic material can be incorporated into commercially available printable inks used in the offset printing industry. To achieve this, the luminescent inorganic material of the invention can be ground to a particle size smaller than a millimeter, and then mixed and incorporated in a specific weight proportion with the base offset ink for subsequent validation in print tests. Preferably, the concentration of the luminescent inorganic material in the printing ink will be 0.1%–50% by weight, more preferably 10% by weight.

[0022] Advantageously, the luminescent inorganic material of the invention remains unaltered after the milling process, dispersion in commercial offset printing ink and subsequent actual printing on different substrates, being equally stable against temperature increases of up to 700 e C, which entails the invariance of the luminescence pattern (“spectral signature”) that constitutes a code for security purposes. Therefore, the present invention demonstrates its applicability in the production of security luminescent inks for developing security features in banknotes and confidential documents, as well as for printing on textiles, paper, and coatings for electronic circuit boards.

[0023] On the other hand, it is important to highlight that the encapsulated luminescent patterns of the materials of the present invention can be activated and detected with simple, low-cost excitation sources and small, low-cost point sensors (mainly silicon sensors), without the need for sophisticated additional elements such as diffraction gratings or higher-quantity optical filters, which opens the way to multiple real commercial applications.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To complement the description that follows and to aid in a better understanding of the characteristics of the invention, in accordance with the preferred examples of its practical embodiment detailed below, a set of figures is included as an integral part of said description, in which, for illustrative and non-limiting purposes, the following has been represented:

[0026] Figure 1 shows the emission spectrum (Fig. 1.A) in the visible range by up-conversion under infrared excitation of 980 nm and the energy level diagram (Fig. 1.B) for the material with a volumetric matrix of 40 mol% SiO2, 15 mol% Al2O3 and 40 mol% CaF2, containing the rare earth ions Yb 3+ -Er 3+ -Eu 3+ in a concentration of 2 mol% of Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% Eu 3+ (Example 1 of preferred embodiment). In the figure

[0027] 1.A The wavelength in nm is represented on the x-axis, while the up-conversion emission in arbitrary units is represented on the y-axis. In Figure 1.B, the different elements are represented on the x-axis, while the energy level in cm is represented on the y-axis. -1 .

[0028] Figure 2 shows the emission spectrum (Fig. 2.A) in the visible range by up-conversion under infrared excitation of 980 nm and the energy level diagram (Fig. 2.B) for the material with a volumetric matrix of 40 mol% SiO2, 15 mol% Al2O3 and 40 mol% CaF2, containing the rare earth ions Yb 3+ -Er 3+ in a concentration of 4.5 mol% of Yb 3+ and 0.5 mol% of Er 3+ (Example 2 of preferred embodiment). In Figure 2.A, the wavelength in nm is represented on the x-axis, while the up-conversion emission in arbitrary units is represented on the y-axis. In the figure

[0029] 2.B The different elements have been represented on the x-axis, while the energy level in cm has been represented on the y-axis. 1 .

[0030] Figure 3 shows the emission spectra in the near-infrared (NIR-NIR) range from 800 nm to 1500 nm under infrared excitation of 980 nm (solid box, NIR-NIR), simultaneous with the emission in the visible range from 450 nm to 700 nm (dashed box, VIS), for Example 2 embodiment, in which the volumetric matrix has 40 mol% SiO2, 15 mol% Al2O3 and 40 mol% CaF2, containing the rare earth ions Yb 3+ -Er 3+ , in a concentration of 4.5 mol% of Yb3+ and 0.5 mol% of Er 3+ The wavelength in nm is represented on the x-axis, while the photon flux units are represented on the y-axis.

[0031] Figure 4 shows the emission spectrum in the visible range by up-conversion under 980 nm infrared excitation for the material of Example 4 embodiment in which the bulk inorganic matrix comprises 30 mol% SiO2, 15 mol% Al2O3, 29 mol% CdF2, 22 mol% PbF2, containing the rare earth ions Yb 3+ Er 3+ -Eu 3+ , at a concentration of 1 mol% of Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% Eu 3+ In figures 4.A and 4.B, the wavelength in nm has been represented on the abscissa axis, while the up-conversion emission in arbitrary units has been represented on the ordinate axis.

[0032] Figure 5 shows a CIE chromaticity diagram, where the numbers on the curve correspond to the wavelength in nm, and where the color coordinates on the diagram corresponding to the visible emission by up-conversion under infrared excitation of 980 nm for the materials of Example 1 embodiment (volumetric array of 40 mol% SiO2, 15 mol% Al2O3, 40 mol% CaF2, 2 mol% Yb) have been marked. 3+ 0.5 mol% of Er 3+ and 2.5 mol% Eu 3+ ) and from Example 2 of implementation (volumetric matrix of 40 mol% SiO2, 15 mol% Al2O3, 40 mol% CaF2, 4.5 mol% Yb 3+ and 0.5 mol% of Er 3+ The photograph inserted in the graphic represents the material of Example 1 of the embodiment emitting visible light under infrared excitation of 980 nm.

[0033] Figure 6 shows the emission spectra in the near-infrared (NIR-NIR) range from 825 to 1100 nm under infrared excitation of 980 nm (Figure 6.B), simultaneous with emission in the visible range from 450 to 700 nm (Figure 6.A), for the material of Example 3, with a volumetric matrix of 40 mol% SiO2, 15 mol% Al2O3 and 40 mol% CaF2, containing the rare-earth ions Yb 3+ , Tm 3+ and Nd 3+ , in a concentration of 3 mol% of Yb 3+ and 0.5 mol% of Tm 3+ and 1.5 mol% of Nd 3+ In figures 6.A and 6.B, the wavelength in nm has been represented on the abscissa axis, while the up-conversion emission in arbitrary units has been represented on the ordinate axis.

[0034] Figure 7 shows the emission spectrum in the visible range by up-conversion under 980 nm infrared excitation for a commercial offset printing ink (SIEGWERG™ brand) containing a concentration of 10 wt% of the luminescent inorganic material according to Example 2 of embodiment (volumetric inorganic matrix of 40 mol% SiO2, 15 mol% Al2O3 and 40 mol% CaF2, containing rare earth ions Yb 3+ -Er 3+ , at a concentration of 4.5 mol% of Yb 3+ and 0.5 mol% of Er 3+), where the x-axis represents the wavelength in nm, while the y-axis represents the up-conversion emission in arbitrary units. The 'Composite inks' data series refers to the measurement performed on the commercial offset ink after the integration process of the luminescent inorganic material of the invention, while the 'Printing test' data series refers to the measurement performed on a pattern printed with said ink.

[0035] Figure 8 shows the emission spectrum in the visible range by up-conversion under 980 nm infrared excitation for the luminescent inorganic material according to Example 2 of embodiment (volumetric inorganic matrix of 40 mol% SiO2, 15 mol% Al2O3 and 40 mol% CaF2, containing rare earth ions Yb 3+ -Er 3+ , at a concentration of 4.5 mol% of Yb 3+ and 0.5 mol% of Er 3+), where the x-axis represents the wavelength in nm, while the y-axis represents the up-conversion emission in arbitrary units. The data series 'Yb-Er-SACC40' refers to the measurement performed on the luminescent inorganic material obtained by the process of the invention, while the data series 'Heat treated at 700 e C' refers to the measurement taken on the same material after being subjected to a temperature increase of up to 700 e C.

[0036] PREFERRED EMBODIMENT OF THE INVENTION

[0037] The following are illustrated with some examples and figures of different embodiments which are not intended to limit the present invention, but serve to show the procedure and the reagents that can be used for its preparation.

[0038] Example 1

[0039] According to a first embodiment of the invention, the volumetric inorganic oxyfluoride matrix contains 40 mol% SiOs, 15 mol% Al2O3 and 40 mol% CaF2, the volumetric inorganic matrix being doped with 2 mol% Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% of Eu 3+ .

[0040] Example 2

[0041] According to a second embodiment of the invention, the volumetric inorganic oxyfluoride matrix contains 40 mol% SiO2, 15 mol% Al2C3 and 40 mol% CaF2, the volumetric inorganic matrix being doped with 4.5 mol% Yb 3+ and 0.5 mol% of Er 3+ .

[0042] Example 3

[0043] According to a third embodiment of the invention, the volumetric inorganic oxyfluoride matrix contains 40 mol% SiO2, 15 mol% Al2C3, and 40 mol% CaF2, the volumetric inorganic matrix being doped with 3 mol% Yb3+ , 0.5 mol% of Tm 3+ and 1.5 mol% of Nd 3+ .

[0044] Example 4

[0045] According to a fourth embodiment of the invention, the volumetric inorganic oxyfluoride matrix contains 30 mol% SiO2, 15 mol% Al2C3, 29 mol% CdF2, and 22 mol% PbF2, the volumetric inorganic matrix being doped with 1 mol% Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% of Eu 3+ .

[0046] Figures 1 and 2 show the experimental results of embodiments 1 and 2, respectively. On the left is the visible emission spectrum obtained by up-conversion under infrared excitation of the material at 980 nm, using a low-cost commercial diode. To the right of each spectrum are the corresponding energy level diagrams along with the electronic transitions responsible for each emission band (indicated in nm) for the rare-earth ions involved. As can be seen in Figures 1 and 2, the infrared-to-visible energy conversion process yields simultaneous emissions in the near-infrared (NIR) and visible regions, corresponding to the electronic transitions of the rare-earth ions used as dopants.

[0047] On the other hand, Figure 3, which corresponds to Example 2 of the embodiment, serves to illustrate the concept of “spectral signature” in the context of the present invention. Indeed, in this figure it can be seen that the encoding of the luminescence pattern emitted by the material as a light key code should be understood as the presence of multiple narrow bands and predetermined combinations of their corresponding positions and relative intensities, both in the near-infrared (NIR-NIR) range and simultaneously in the visible (VIS) range.

[0048] As detailed above, the heat treatment applied in the proposed procedure allows for the modification of specific luminescent characteristics, enabling the design of unique “spectral signature” patterns. This is achieved by changing the intensity ratios between components of certain narrow luminescence bands. In the case of Example 4, Figure 4 shows how, in the 580 nm–620 nm range (Figure 4), which uses the properties of Eu 3+ as a probe ion of the local crystal structure of the material. Thus, in Figure 4.A, the box indicates the presence of Eu ion emission. 3+ in the 580-620 nm range, as additional security features of the spectral code. Furthermore, Figure 4.B shows an enlarged detail of the intensity ratio change between the components of the Eu ion emission band. 3+between 580 nm and 620 nm due to the heat treatment that gives rise to the different glassy and nano / micro crystalline phases that the material can exhibit. In this way, narrow peaks of luminescence, tunable in intensity and position, can be introduced as extra security features, hidden from the naked eye, within a spectrum formed by main luminescent bands in the green and red range of the spectrum (between 550 nm and 660 nm), which significantly increases the encoding capacity and the level of encryption of the light signal.

[0049] Figure 5 shows the color coordinates in the CIE chromaticity diagram corresponding to the visible up-conversion emission under 980 nm infrared excitation for the material of Example 1 (Yb-doped matrix) 3+ -Er 3+ -Eu 3+ ) and the material from Example 2 (Yb-doped matrix 3+ -Er 3+). As can be observed, there is a full match of the CIE coordinates for both examples of embodiment, which makes them indistinguishable to the naked eye, and only discernible through detailed spectroscopic analysis of their “spectral signatures” shown in figures 1 and 2.

[0050] In Figure 6, which corresponds to Example 3 of implementation, you can see the presence of multiple narrow bands and predetermined combinations of their corresponding positions and relative intensities among them, both in the near infrared range (NIR-NIR) and simultaneously in the visible (VIS), as a light key / code.

[0051] Finally, Figures 7 and 8 illustrate an additional advantage of the materials obtained according to the procedure of the present invention, namely the persistence of the material's spectral signature after its integration into a commercial ink and subsequent printing with it, and after subjecting the material to high temperatures, respectively. Thus, Figure 7 illustrates the persistence of the spectral signature after the integration of the material from Example 2 into a commercial offset ink, as evidenced by the spectra shown in that figure. Similarly, Figure 8 shows the stability of the material from Example 2 after subjecting it to temperature increases of up to 700°C. e C.

[0052] Detailed experimental results show that the procedure of the present invention allows the development of elements with customized and stable luminescence patterns, making the luminescent inorganic materials of the present invention optimal for security applications in legal tender banknotes, which use offset printing techniques, as well as for printing on textiles, paper and coatings of electronic circuit boards.

Claims

CLAIMS 1 a . Procedure for obtaining a luminescent inorganic material comprising the steps of: c) obtaining a glass by melting technique, at a temperature between 1000 e C-1500 e C, from a bulk inorganic oxyfluoride matrix containing SiO2 and Al2O3, and a fluoride; wherein the fluoride is CaF2 or a mixture of PbF2 and CdF2; the bulk inorganic oxyfluoride matrix being doped with at least one of the following rare-earth ions: Yb 3+ , Tm 3+ , Er 3+ , Nd 3+ , Eu 3+, such that rare earth ions are present in a proportion of between 0.01 and 10 mol% relative to the total matrix; ) from a volumetric inorganic oxyfluoride matrix containing SiO2 and Al2O3, and a fluoride or a mixture of fluorides. Thus, the fluoride is CaF2 or a mixture of PbF2 and CdF2; d) obtaining a micro / nanocrystalline material from a precursor glass, where the precursor glass is obtained by a melting technique at a temperature between 1000 e C-1500 e C from a bulk inorganic oxyfluoride matrix containing SiO2 and Al2O3, and a fluoride; wherein the fluoride is CaF2 or a mixture of PbF2 and CdF2; the bulk inorganic oxyfluoride matrix being doped with at least one of the following rare-earth ions: Yb 3+ , Tm 3+ , Er 3+ , Nd 3+ , Eu 3+, with the rare earth ions present in a proportion of between 0.01 -10 mol% with respect to the total matrix; so that the precursor glass is subjected to a heat treatment at a temperature of between 400 e C-500 e C for at least 24 hours, obtaining the micro / nanocrystalline material; and e) mixing the glass and the micro / nanocrystalline material, in any desired proportion for each of them from 1% to 99%, to obtain the luminescent inorganic material; so that the luminescent inorganic material exhibits a luminescence pattern with simultaneous emission in the near-infrared (NIR) spectrum and the visible spectrum under infrared excitation of 980 nm. 2 a . Method for obtaining a luminescent inorganic material according to claim 1 acharacterized in that in obtaining the glass of step a) and / or in obtaining the precursor glass of step b) the melting is carried out using a heating ramp of 10 e C / min starting from ambient temperature, until reaching a temperature between 1000 e C-1400 e C, maintaining this temperature for at least 30 minutes and then proceeding to a rapid cooling of the molten volumetric inorganic matrix to obtain the glass. 3 a . Method for obtaining a luminescent inorganic material according to claim 1 a or 2 a characterized in that the bulk inorganic matrix contains 40 mol% of SiO2, 15 mol% of Al2O3 and 40 mol% of CaP2, the bulk inorganic matrix being doped with 2 mol% of Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% of Eu 3+ . 4 a. Method for obtaining a luminescent inorganic material according to claim 1 a or 2 a characterized in that the bulk inorganic matrix contains 40 mol% of SiO2, 15 mol% of Al2O3 and 40 mol% of CaP2, the bulk inorganic matrix being doped with 4.5 mol% of Yb 3+ and 0.5 mol% of Er 3+ . 5 a . Method for obtaining a luminescent inorganic material according to claim 1 a or 2 a characterized in that the bulk inorganic matrix contains 40 mol% of SiO2, 15 mol% of Al2O3, 40 mol% of CaP2, the bulk inorganic matrix being doped with 3 mol% of Yb 3+ , 0.5 mol% of Tm 3+ and 1.5 mol% of Nd 3+ . 6 a . Method for obtaining a luminescent inorganic material according to claim 1 a or 2 acharacterized in that the bulk inorganic matrix contains 30 mol% of SiO2, 15 mol% of Al2O3, 29 mol% of CdP2, 22 mol% of PbP2, the bulk inorganic matrix being doped with 1 mol% of Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% of Eu 3+ . 7 a Luminescent inorganic material obtained according to the process of any of the preceding claims, characterized in that it comprises a mixture of a glass and a micro / nanocrystalline material obtained from a bulk inorganic oxyfluoride matrix containing SiO2 and Al2O3, and a fluoride, wherein the fluoride is CaP2 or a mixture of PbP2 and CdP2, the bulk inorganic oxyfluoride matrix being doped with at least one of the following rare-earth ions: Yb 3+ , Tm 3+ , Er 3+ , Nd 3+ , Eu 3+ , and with rare earth ions present in a proportion between 0.01-10%; so that the luminescent inorganic material exhibits a luminescence pattern with simultaneous emission in the near infrared (NIR) spectrum and the visible spectrum under infrared excitation of 980 nm. 8 a . Luminescent inorganic material according to claim 7 a characterized in that the bulk inorganic matrix contains 40 mol% of SiO2, 15 mol% of Al2O3 and 40 mol% of CaF2, the bulk inorganic matrix being doped with 2 mol% of Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% of Eu 3+ . 9 a . Luminescent inorganic material according to claim 7 a characterized in that the bulk inorganic matrix contains 40 mol% of SiO2, 15 mol% of Al2O3 and 40 mol% of CaF2, the bulk inorganic matrix being doped with 4.5 mol% of Yb 3+ and 0.5 mol% of Er 3+ . 10 a . Luminescent inorganic material according to claim 7 a characterized in that the bulk inorganic matrix contains 40 mol% of SiO2, 15 mol% of Al2O3, 40 mol% of CaF2, the bulk inorganic matrix being doped with 3 mol% of Yb 3+ , 0.5 mol% of Tm 3+ and 1.5 mol% of Nd 3+ . 11 a . Luminescent inorganic material according to claim 7 a characterized in that the bulk inorganic matrix contains 30 mol% of SiO2, 15 mol% of Al2O3, 29 mol% of CdF2, 22 mol% PbF2, the bulk inorganic matrix being doped with 1 mol% of Yb 3+ 0.5 mol% of Er 3+ and 2.5 mol% of Eu 3+ . 12 a Printing ink characterized in that it contains the luminescent inorganic material according to any one of the claims of claim 7 a at 11 13 a Printing ink, according to claim 12a , characterized in that the luminescent inorganic material contained in the ink is ground to an average grain size of less than 1 micron. 14 a Printing ink, according to claim 12 a or 13 a , characterized by having a concentration of the luminescent inorganic material of 0.1%-50% by weight. 15 a . Printing ink, according to claim 14 a , characterized by having a concentration of the luminescent inorganic material of 10% by weight. 16 a Use of the luminescent inorganic material, according to any one of the claims in claim 7 a at 11 a , for obtaining security elements in textiles, paper and electronic circuit boards. 17 a Use of the printing ink, according to any one of the claims in claim 12 a at 3 pm a, for obtaining security elements in textiles, paper and electronic circuit boards.

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