A kind of color fluorescent anti-counterfeiting glass and its preparation method

Abstract

The present invention discloses a color fluorescent anti-counterfeiting glass and a preparation method thereof, relating to the technical field of fluorescent anti-counterfeiting. The method is based on porous glass and comprises the following steps: (1) immersing the porous glass in a luminescent solution to obtain a porous glass doped with luminescent ions, wherein the luminescent solution contains single or multiple luminescent ions, with or without co-doping with tin ions; (2) using a carbon dioxide laser to perform micro-area heating on the anti-counterfeiting area of the porous glass doped with luminescent ions to obtain an anti-counterfeiting pattern. The present invention uses a carbon dioxide laser to perform local micro-area heating and scanning on the porous glass, activates the luminescent ions in the doped area at a relatively low temperature to form a high-resolution fluorescent pattern (such as letters, logos), avoids densification caused by high temperature, and the glass still remains in a porous state after treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent anti-counterfeiting technology, and particularly relates to a colored fluorescent anti-counterfeiting glass and a preparation method thereof. Background Art

[0002] Due to its unique optical response characteristics, fluorescent anti-counterfeiting technology has important applications in high-end packaging, currency anti-counterfeiting and other fields. Although traditional fluorescent anti-counterfeiting means (such as fluorescent inks, labels) are low in cost, they have defects such as being easy to copy, poor weather resistance, and low pattern resolution, and it is difficult to meet the high-security requirements. In recent years, fluorescent glass based on inorganic luminescent materials has gradually become a research hotspot, and its excellent chemical stability, high temperature resistance and long life characteristics provide a new direction for fluorescent anti-counterfeiting technology.

[0003] At present, the preparation methods of fluorescent glass include sol-gel method and porous glass doping method. The sol-gel method uniformly disperses luminescent ions in the glass matrix through the sol-gel process, but high-temperature sintering (>800 °C) is likely to cause the closure of nanopores and ion aggregation, and the luminescence efficiency is limited (such as the patent application with the publication number CN107082571A). In addition, the uniform distribution of active ions between the matrix and the crystal exacerbates non-radiative energy transfer (such as quenching effect), and it is difficult to achieve high-brightness luminescence. The porous glass doping method, with its high specific surface area and interconnected nanopore structure, can efficiently adsorb active ions (such as Eu³⁺, Tb³⁺, etc.), and form luminescent nanocrystals (such as SnO2) through heat treatment. For example, the patent application with the publication number CN111847886A discloses a preparation method of nano-crystalline glass containing tin dioxide. Through porous glass solution doping, primary heat treatment (400-900 °C), acid treatment and secondary heat treatment (900-1300 °C), the luminescent ions outside the crystal are selectively removed, and the active ions are enriched inside the SnO2 nanocrystals, significantly improving the luminescence intensity and transparency of the glass. However, this method requires high-temperature densification treatment, resulting in the collapse of the porous structure and the inability to retain the dynamic regulation ability of the porous matrix, which limits its application in patterned anti-counterfeiting. Current technologies mostly focus on the optimization of overall performance. For example, the patent application with the publication number CN102320746A improves white light emission by adjusting the ion distribution, but still does not solve the problem of local control of multicolor fluorescent patterns. Summary of the Invention

[0004] The present invention provides a preparation method of a colored fluorescent anti-counterfeiting glass, which locally scans a porous glass based on laser micro-area activation to activate the luminescent ions in the doped area, thereby forming a high-resolution fluorescent pattern, so as to solve many problems existing in the preparation process of the existing colored fluorescent anti-counterfeiting glass, such as complex preparation process, poor luminescence efficiency, and difficult local control.

[0005] The technical solution adopted by the present invention is as follows:

[0006] One of the objectives of the present invention is to provide a preparation method of a color fluorescent anti-counterfeiting glass, which is based on porous glass and includes the following steps:

[0007] (1) Immerse the porous glass in a luminescent solution to obtain a porous glass doped with luminescent ions. The luminescent solution contains single or multiple luminescent ions, with or without co-doping of tin ions;

[0008] (2) Use a carbon dioxide laser to perform micro-area heating on the anti-counterfeiting area of the porous glass doped with luminescent ions to obtain an anti-counterfeiting pattern. The power of the carbon dioxide laser is 0.3 - 20 W, the spot diameter is 0.1 - 3 mm, and the power density ranges from 1 - 49 W / mm 2 , and the power density is the ratio of the carbon dioxide laser power to the spot area; the scanning speed is 20 - 250 mm / s, the number of scanning times is 20 - 800 times, and finally the cumulative temperature of the micro-area heating is 300 - 700 °C.

[0009] In the present invention, the porous glass can be obtained commercially, or can be prepared according to the methods recorded in the literature or by self-made methods. The methods recorded in the literature include any of the following methods recorded in the literature:

[0010] (1) D. Chen, H. Miyoshi, T. Akai, T. Yazawa, Colorless transparent fluorescence material: sintered porous glass containing rare-earth and transition-metal ions, Appl. Phys. Lett. 86 (2005), 231908 - 231908.

[0011] (2) Q. Zhang, Y. B. Qiao, B. Qian, G. P. Dong, J. Ruan, X. F. Liu, Q. L. Zhou, Q. X. Chen, J. R. Qiu, D. P. Chen, Luminescence properties of the Eu-doped porous glass and spontaneous reduction of Eu 3+ to Eu 2+ , J. Lumines.129(11), (2009) 1393 - 1397.

[0012] (3)Y. Shen, S. Zheng, Q. Sheng, S. Liu, W. Li, D. Chen, Synthesis of nano - colloidal silica particles and their effects on the luminescence properties of Eu 2+ -doped High silica glass, Mater. Lett. 139, (2015) 373 - 376.

[0013] The self - preparation steps of the porous glass are as follows: Mix the powder raw materials of SiO2, B2O3, Al2O3, Na2CO3 and CaO according to the weight percentages of (49 - 52):(28 - 30):1.6:(12 - 14):5.4 respectively, fire at high temperature, pour out the glass melt and press it thin, put it into a muffle furnace for heat treatment for phase separation, and then soak it in hot acid to obtain the porous glass; A more preferred self - preparation step of the porous glass is: Mix the powder raw materials of SiO2, B2O3, Al2O3, Na2CO3 and CaO according to the weight percentages of 51:29:1.6:13:5.4 respectively, fire at 1400 °C for 2 hours, pour out the glass melt and press it thin, put it into a 600 °C muffle furnace for heat treatment for 24 hours for phase separation, and then soak it in 100 °C 1 mol / L hot hydrochloric acid for 24 hours to obtain the porous glass.

[0014] Furthermore, the porous glass is porous silica glass, and the pore diameter of the porous glass is 4 - 1000 nm.

[0015] Even further, the pore diameter of the porous glass is 4 - 50 nm.

[0016] Even further, the porous glass is porous high - silica glass with uniformly distributed nano - micropores inside.

[0017] Furthermore, the time for the porous glass to be immersed in the luminescent solution is 20 minutes - 24 hours.

[0018] Even further, the time for the porous glass to be immersed in the luminescent solution is 30 minutes.

[0019] Furthermore, the concentration of the tin ions is 0.1 - 2 mol / L, and the concentration of the luminescent ions is 0.05 - 1 mol / L.

[0020] Even further, the concentration of the tin ions is 0.8 mol / L, and the concentration of the luminescent ions is 0.4 mol / L.

[0021] Further, the luminescent ions are one or more of europium (Eu) ions, chromium (Cr) ions, manganese (Mn) ions, erbium (Er) ions, nickel (Ni) ions, cerium (Ce) ions, terbium (Tb) ions, ytterbium (Yb) ions, neodymium (Nd) ions, thulium (Tm) ions, praseodymium (Pr) ions, samarium (Sm) ions, and copper (Cu) ions.

[0022] The second object of the present invention is to provide a colored fluorescent anti-counterfeiting glass prepared by the above preparation method.

[0023] In summary, compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. The present invention uses a carbon dioxide laser to locally heat and scan a porous glass, activating the luminescent ions in the doped region at a relatively low temperature to form a high-resolution fluorescent pattern (such as letters and logos), avoiding densification caused by high temperature, and the glass still remains porous after treatment.

[0025] 2. Through the co-doping and selective activation of different luminescent ions (such as SnO2:Eu³⁺ red light, Tb³⁺ green light, Eu²⁺ blue light), the present invention can achieve multi-color anti-counterfeiting on a single substrate. For example, through the co-doping of Sn ions and Eu³⁺, under the scanning of a carbon dioxide laser, Sn ions form a SnO2 lattice and Eu³⁺ enters the SnO2 lattice and remains Eu³⁺, thus realizing red fluorescence; green fluorescence is realized by doping Tb; in the case of no Sn doping, Eu³⁺ is easily formed after directly contacting the porous glass (i.e., the SiO2 component) under the scanning of a carbon dioxide laser, 2+ ions, thus realizing blue fluorescence; in addition, Tb can be doped first to achieve an overall green background, and then local blue and red fluorescent patterns can be formed.

[0026] 3. The present invention abandons the traditional high-temperature sintering and acid treatment steps, and only requires one-step laser treatment, significantly reducing the energy consumption and time cost. Description of the Drawings

[0027] Figure 1 Monochromatic fluorescent patterns of blue, green, and red prepared in Examples 1 to 3.

[0028] Figure 2 Green background + blue pattern, green background + red pattern, and three-color mixed letter fluorescent patterns prepared in Examples 4 to 6.

[0029] Figure 3 Laser engraving pattern prepared in Comparative Example 1. Detailed Description of the Invention

[0030] The present invention will be specifically described below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be presented more clearly therefrom. Those skilled in the art should understand that these specific embodiments and examples are used to illustrate the present invention, rather than limiting the present invention.

[0031] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as the general understanding of those skilled in the art to which the present invention pertains. In case of any contradiction, this specification shall prevail.

[0032] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0033] The present application will be described in detail below in conjunction with examples and experimental data.

[0034] Example 1

[0035] This example provides a method for preparing a colored fluorescent glass, and the specific steps are as follows:

[0036] (1) Doping of porous glass solution;

[0037] Prepare a mixed aqueous solution of SnCl4 and EuCl3, wherein the concentration of Sn 4+ is 0.8 mol / L, and the concentration of Eu 3+ is 0.4 mol / L. Immerse the porous glass in the above mixed solution for 30 minutes; take it out and dry it at 10°C to 120°C (it can also be air-dried) for later use.

[0038] The preparation process of the porous glass in this example is as follows: Mix the powder raw materials of SiO2, B2O3, Al2O3, Na2CO3, and CaO according to the weight percentages of 51: 29: 1.6: 13: 5.4, fire at 1400°C for 2 hours, pour out the glass melt and press it thin, put it in a muffle furnace at 600°C for heat treatment for 24 hours for phase separation, and then soak it in hot hydrochloric acid at 100°C and 1 mol / L for 24 hours to obtain the porous glass; the pore size range of the porous glass is 4 to 50 nm.

[0039] (2) Carbon dioxide laser scanning heating; Scan the letter E. The power is 2W, the spot diameter is 0.5mm, and the power density is about 10 W / mm 2 , the scanning speed is 100 mm / s, and the number of scans is 200 times. As shown in Figure c of Figure 1 , the colored fluorescent glass obtained by scanning shows the red letter E under ultraviolet light excitation.

[0040] Example 2

[0041] The implementation method is the same as that of Example 1, except that in this example, the mixed solution of SnCl4 and EuCl3 is replaced with a separate Tb ion solution. As shown in Figure 1 Figure b, the scanned colored fluorescent glass presents a green letter E under ultraviolet light excitation.

[0042] Example 3

[0043] The implementation method is the same as that of Example 1, except that in this example, the mixed solution of SnCl4 and EuCl3 is replaced with a separate Eu 3+ ion solution. As shown in Figure 1 Figure a, the formation of SnO2 is missing. After scanning, Eu directly contacts SiO2 and is easily converted into Eu 2+ , and the obtained colored fluorescent glass presents a blue letter E under ultraviolet light excitation.

[0044] Example 4

[0045] This example provides a method for preparing colored fluorescent glass, and the specific steps are as follows:

[0046] (1) Prepare aqueous solutions of 0.4 mol / L TbCl3 and EuCl3 separately for later use;

[0047] (2) Immerse the porous glass in the above Tb ion solution for 30 minutes; take it out and dry it at 10°C to 120°C;

[0048] (3) Carry out a CO2 laser overall scan on the porous glass doped with Tb ions, with a power of 20 W, a spot diameter of 3 mm, and a power density of about 2.8 W / mm 2 , a scanning speed of 100 mm / s, and 200 scanning times;

[0049] (4) Immerse the overall scanned porous glass in the above Eu 3+ ion solution for 30 minutes; take it out and dry it at 10°C to 120°C;

[0050] (5) Carry out a CO2 laser scan on the porous glass doped with Eu ions for the second time, with a power of 2 W, a spot diameter of 0.5 mm, and a power density of about 10 W / mm 2 , a scanning speed of 100 mm / s, and 200 scanning times to obtain the pattern E.

[0051] As shown in Figure 2 Figure a, the scanned colored fluorescent glass presents a green background + a blue letter E under ultraviolet light excitation.

[0052] Example 5

[0053] The implementation method is the same as that of Example 4, except that in this example, the Eu solution for secondary doping is replaced with a mixed solution of SnCl4 and EuCl3. As shown in Figure b of , the scanned colored fluorescent glass exhibits a green background + red letter E under ultraviolet light excitation. 3+ The Figure 2

[0054] Example 6

[0055] This example provides a method for preparing colored fluorescent glass, and the specific steps are as follows:

[0056] Divide the glass into 3 regions, and dope Eu+Sn, Tb, and Eu solutions in the 3 regions respectively according to the above doping steps. Then, scan the letters J, N, and U in the three regions with a carbon dioxide laser respectively. 3+ 3+

[0057] As Figure 2 shown in Figure c of , the scanned colored fluorescent glass exhibits red letter J, green letter N, and blue letter U under ultraviolet light excitation.

[0058] Comparative Example 1

[0059] The implementation method is the same as that of Example 1, except that in this example, the power of the carbon dioxide laser scanning and heating is changed to 10 W, and the power density reaches about 51 W / mm. The glass appearance is etched with a dented letter E. As shown in , obvious etch marks can be observed with the naked eye under natural light. 2 Figure 3

[0060] Comparative Example 2

[0061] The implementation method is the same as that of Example 1, except that in this example, the diameter of the carbon dioxide laser spot is changed to 0.2 mm, and the power density reaches about 63 W / mm. The glass appearance is etched with dents. 2

[0062] It is not difficult to see from Comparative Example 1 and Comparative Example 2 that when using carbon dioxide laser scanning and heating to form fluorescent patterns or marks, with a power density (power / spot area) comparable to the prior art, it is easy to etch dents on the glass, while a lower power density can obtain fluorescent patterns or marks.

[0063] ​​​​​​Finally, it should also be noted that the terms "comprising", "including" or any other variant are intended to cover non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn of the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0064] The above-described embodiments merely represent the specific implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several variations and improvements can still be made, and these all fall within the protection scope of the present application.

Claims

1. A method for preparing a color fluorescent anti-counterfeiting glass, characterized in that, The method is based on porous glass and includes the following steps: (1) Immerse porous silica glass with a pore size of 4 - 50 nm in a luminescent solution for 20 minutes to 24 hours to obtain a porous glass doped with luminescent ions. The luminescent solution contains single or multiple luminescent ions, with or without co-doping of tin ions. The luminescent ions are one or more of europium ions, chromium ions, manganese ions, erbium ions, nickel ions, cerium ions, terbium ions, ytterbium ions, neodymium ions, thulium ions, praseodymium ions, samarium ions, and copper ions; (2) The anti-counterfeiting area of the porous glass doped with luminescent ions is micro-regionally heated using a carbon dioxide laser to obtain an anti-counterfeiting pattern. The power of the carbon dioxide laser is 0.3 - 20 W, the spot diameter is 0.1 - 3 mm, and the energy density ranges from 1 - 49 W / mm 2 . The energy density is the ratio of the carbon dioxide laser power to the spot area; the scanning speed is 20 - 250 mm / s, the number of scans is 20 - 800 times, and finally the cumulative temperature of the micro-region heating is achieved to be 300 - 700 °C.

2. The preparation method of the color fluorescent anti-counterfeiting glass according to claim 1, characterized in that, The porous glass is porous high-silica glass with uniformly distributed nano micropores inside.

3. The preparation method of the color fluorescent anti-counterfeiting glass according to claim 1, characterized in that, The time for immersing the porous glass in the luminescent solution is 30 minutes.

4. The preparation method of the color fluorescent anti-counterfeiting glass according to claim 1, characterized in that, The concentration of the tin ions is 0.1 - 2 mol / L, and the concentration of the luminescent ions is 0.05 - 1 mol / L.

5. The preparation method of the color fluorescent anti-counterfeiting glass according to claim 4, characterized in that, The concentration of the tin ions is 0.8 mol / L, and the concentration of the luminescent ions is preferably 0.4 mol / L.

6. The colored fluorescent anti-counterfeiting glass prepared by the method for preparing colored fluorescent anti-counterfeiting glass according to any one of claims 1 - 5.

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