A multi-color and gradient color anti-counterfeiting ink dependent on multi-wavelength excitation, preparation method thereof, and application thereof

Abstract

The present invention relates to a multi-color and gradient color anti-counterfeiting ink that relies on multi-wavelength excitation, a preparation method thereof, and an application thereof. In the present invention, an anti-counterfeiting ink having different luminescent properties is designed and formulated, and the ink is patterned using screen printing technology. Based on the response differences of materials with different luminescent properties, the prepared anti-counterfeiting pattern exhibits differences in luminescent colors. Typically, the above-mentioned pattern exhibits blue, red, and green luminescence under the excitation of 254nm, 365nm, and 980nm excitation light, respectively; it has green room temperature phosphorescence emission after removing the 365nm excitation; under the coordinated excitation of 254nm and 365nm, the luminescent color can be adjusted from red to blue, and it appears as a gradient color anti-counterfeiting label; under the coordinated excitation of 254nm and 980nm, the luminescent color of the anti-counterfeiting label is adjustable in the range of red to green, and it appears as a gradient color anti-counterfeiting label.

Description

Technical Field

[0001] The present invention relates to the field of anti-counterfeiting technology, and in particular to a multi-color and gradient color anti-counterfeiting ink that relies on multi-wavelength excitation, a preparation method thereof, and an application thereof. Background Art

[0002] As countries, businesses and people around the world suffer huge losses due to the rampant counterfeit and shoddy products, the market is in urgent need of anti-counterfeiting technology with high anti-counterfeiting strength.

[0003] Optical anti-counterfeiting technology has attracted wide attention and favor due to its advantages of strong information encryption capability, easy operation, easy promotion, and high anti-counterfeiting strength. At present, the optical anti-counterfeiting technology used in the market is mainly anti-counterfeiting labels with single visible light emission excited by ultraviolet light.

[0004] However, for experienced counterfeiters, finding alternatives to anti-counterfeiting labels that can emit visible light under ultraviolet light excitation is no longer a problem. In order to meet market demand, anti-counterfeiting labels with higher anti-counterfeiting strength should be developed. At the same time, in order to enhance the anti-counterfeiting strength of optical anti-counterfeiting labels, it is necessary to carefully design their excitation and emission characteristics so that the optical anti-counterfeiting labels have richer optical properties. The ideal method is to achieve a one-to-one correspondence between a specific excitation wavelength and a specific emission light color. Furthermore, the current anti-counterfeiting labels only have a single luminescent color. If multi-color and gradient color anti-counterfeiting labels that respond to different excitation wavelengths can be designed and developed, the anti-counterfeiting labels can have high anti-counterfeiting strength and be difficult to copy, which has important practical significance for the actual anti-counterfeiting application field. Summary of the invention

[0005] In view of the above problems, a multi-color and gradient color anti-counterfeiting ink dependent on multi-wavelength excitation, a preparation method thereof and an application thereof are now provided. In the present invention, based on the synthesized carbon dots, red phosphors and up-conversion phosphors, the screen printing ink is designed and patterned by screen printing technology. The obtained anti-counterfeiting label not only has a high dependence on the excitation light of 254nm, 365nm and 980nm, and has a multi-color anti-counterfeiting label with one-to-one correspondence between excitation and emission, but also can obtain a gradient color anti-counterfeiting label under the synergistic excitation of 254nm, 365nm and 980nm excitation light, which has important practical application value for the actual anti-counterfeiting application field.

[0006] The first aspect of the present invention is to provide a method for preparing a multi-color and gradient color anti-counterfeiting ink that is dependent on multi-wavelength excitation, which has such characteristics, comprising the following steps: uniformly mixing a colorant and a binder to obtain a multi-color anti-counterfeiting ink;

[0007] Among them, the colorant is formed by mixing red phosphor and blue fluorescent carbon dot powder or red phosphor and green fluorescent carbon dot powder or red phosphor, green fluorescent carbon dot powder and blue up-conversion phosphor or red phosphor, blue fluorescent carbon dot powder and green up-conversion phosphor, and the excitation light wavelengths of the red phosphor, up-conversion phosphor and fluorescent carbon dot powder are different.

[0008] Specifically, the preparation method of blue fluorescent carbon dot powder is as follows: citric acid, urea, and a strong base (such as lithium hydroxide, sodium hydroxide, and potassium hydroxide) are dispersed in deionized water, and a hydrothermal reaction is performed to obtain a blue carbon quantum dot solution; anhydrous calcium chloride is added to the blue carbon quantum dot solution to react, and the reaction product is washed with water and ethanol for multiple times and then dried to obtain a blue fluorescent carbon dot powder.

[0009] Specifically, the preparation method of green fluorescent carbon dot powder is: disperse citric acid, resorcinol and phosphoric acid in deionized water, carry out hydrothermal reaction, and obtain green carbon quantum dot solution; take green carbon quantum dot solution, add tetraethyl orthosilicate, react, the reaction product is washed with water and ethanol for multiple times and then dried to obtain green fluorescent carbon dot powder.

[0010] Specifically, the preparation method of the phosphor is as follows:

[0011] 1) completely dissolving a rare earth source in deionized water to obtain a solution 1;

[0012] 2) completely dissolving sodium vanadate in deionized water to obtain solution 2;

[0013] 3) Slowly add the complexing agent solution to solution 1 under stirring, add solution 2 after the solution becomes transparent, and stir until a light yellow uniform solution is obtained. Place the solution in a reactor and react at a certain temperature for a period of time. Wash and dry the precipitate after the reaction, and then calcine it at a certain temperature to obtain an upconversion phosphor.

[0014] Specifically, the complexing agent solution is an aqueous solution of citric acid.

[0015] The second aspect of the present invention is to provide a multi-color and gradient color anti-counterfeiting ink that is multi-wavelength excitation-dependent and prepared according to the above preparation method.

[0016] The third aspect of the present invention is to provide the application of the above-mentioned multi-color and gradient color anti-counterfeiting ink relying on multi-wavelength cooperative excitation in the field of anti-counterfeiting.

[0017] The present application found that by regulating the raw materials of the hydrothermal reaction, a blue carbon dot solution having high-brightness blue fluorescence and a green carbon dot solution having high-brightness green fluorescence can be obtained under 365nm excitation light excitation, and then after powderization, the blue and green fluorescence can still be maintained, and the blue carbon dots have excellent green room temperature phosphorescence; Eu3+ Doping into the YVO4 matrix can obtain excellent red luminescence under 254nm excitation; Tm 3+ / Yb 3+ and Er 3+ / Yb 3+ The upconversion phosphors were co-doped into the YVO4 matrix, and excellent blue and green upconversion luminescence were obtained under 980nm excitation light. The synthesized materials have excellent luminescence performance and good stability, and the corresponding anti-counterfeiting labels have high anti-counterfeiting strength. The hydrothermal reaction technology used is mature and suitable for promotion to practical anti-counterfeiting applications.

[0018] The beneficial effects of the above scheme are:

[0019] 1. The method of the present invention realizes a multi-color anti-counterfeiting label under the excitation of multiple excitation lights in a single anti-counterfeiting pattern and a gradient color anti-counterfeiting label under coordinated excitation;

[0020] 2. The anti-counterfeiting label provided by the present invention has multi-color down-conversion, up-conversion and room temperature phosphorescence multi-mode luminescence, showing high anti-counterfeiting strength;

[0021] 3. The method for preparing carbon dots, red phosphors and up-conversion phosphors of the present invention is simple and can be applied to actual commercial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The morphologies of blue carbon dots (a), green carbon dots (b) and red phosphor (c) in the present invention;

[0023] Figure 2 The emission spectra of the blue fluorescent carbon dots and green fluorescent carbon dots, the red phosphor, and the blue and green up-conversion phosphors in the present invention;

[0024] Figure 3 For Example 1 of the present invention, the printed anti-counterfeiting pattern under single excitation at 254 nm, 365 nm and 980 nm was removed, as well as under synergistic excitation at 254 nm and 980 nm and 254 nm and 365 nm. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0028] The present invention provides a multi-color and gradient color anti-counterfeiting ink that relies on multi-wavelength excitation. The colorant in the above-mentioned ink is formed by a mixture of red fluorescent powder and blue fluorescent carbon dot powder or red fluorescent powder and green fluorescent carbon dot powder or red fluorescent powder, green fluorescent carbon dot powder and blue up-conversion fluorescent powder or red fluorescent powder, blue fluorescent carbon dot powder and green up-conversion fluorescent powder, and the excitation light wavelengths of the red fluorescent powder, up-conversion fluorescent powder and fluorescent carbon dot powder are different.

[0029] Specifically, the preparation method of blue fluorescent carbon dot powder is as follows: 0.2g citric acid, 0.8g urea, and 0.2g sodium hydroxide are dispersed in 25mL deionized water, and then hydrothermally reacted at 200°C to obtain a blue carbon quantum dot solution; 12.5mL of the blue carbon quantum dot solution is taken, 0.6215g of anhydrous calcium chloride is added, and the reaction is carried out at 150°C, and the reaction product is washed with water and ethanol for multiple times and then dried to obtain a blue fluorescent carbon dot powder. The above blue fluorescent carbon dot powder has high-brightness blue fluorescence under 365nm excitation light excitation, and has excellent green room temperature phosphorescence after removing the excitation.

[0030] Specifically, the preparation method of green fluorescent carbon dot powder is as follows: 0.2g citric acid, 0.1g resorcinol and 5mL phosphoric acid are dispersed in 20mL deionized water, and then hydrothermally reacted at 200°C to obtain a green carbon quantum dot solution; 10mL of green carbon quantum dot solution is taken, 2mL of ethyl orthosilicate is added, and the reaction is carried out at 150°C, and the reaction product is washed with water and ethanol for multiple times and then dried to obtain green fluorescent carbon dot powder. The above green fluorescent carbon dot powder has green fluorescence characteristics under 365nm excitation light excitation.

[0031] Specifically, the preparation method of the red phosphor is as follows: 1) 0.0440g of europium chloride hexahydrate and 0.6917g of yttrium chloride hexahydrate are completely dissolved in 5mL of deionized water to obtain solution 1; 2) 0.4414g of sodium vanadate is completely dissolved in 15mL of deionized water to obtain solution 2; 3) 1.8822g of citric acid is completely dissolved in 10mL of deionized water to obtain a complexing agent solution; 4) the complexing agent solution is slowly added to solution 1 under stirring, and solution 2 is added after the solution becomes transparent, and stirred to a light yellow uniform solution, and the solution is placed in a reactor to react at 180°C for 12h, and the precipitate after the reaction is washed with water and ethanol and then dried, and calcined at 800°C for 2h to obtain a red phosphor. The above red phosphor has red fluorescence characteristics under 254nm excitation light excitation.

[0032] Specifically, the preparation method of the blue up-conversion phosphor is as follows: 1) 0.0092g of thulium chloride hexahydrate, 0.0930g of ytterbium chloride hexahydrate and 0.6480g of yttrium chloride hexahydrate are completely dissolved in 5mL of deionized water to obtain solution 1; 2) 0.4414g of sodium vanadate is completely dissolved in 15mL of deionized water to obtain solution 2; 3) 1.8822g of trisodium citrate is completely dissolved in 10mL of deionized water to obtain a complexing agent solution; 4) the complexing agent solution is slowly added to solution 1 under stirring, and solution 2 is added after the solution becomes transparent, and stirred to a light yellow uniform solution, and the solution is placed in a reactor to react at 180°C for 12h, and the precipitate after the reaction is washed with water and ethanol and then dried, and calcined at 800°C for 2h to obtain a blue up-conversion phosphor. The above blue up-conversion phosphor has blue up-conversion luminescence performance under 980nm excitation light.

[0033] Specifically, the preparation method of the green up-conversion phosphor is as follows: 1) 0.0183g of erbium chloride hexahydrate, 0.0930g of ytterbium chloride hexahydrate and 0.6407g of yttrium chloride hexahydrate are completely dissolved in 5mL of deionized water to obtain solution 1; 2) 0.4414g of sodium vanadate is completely dissolved in 15mL of deionized water to obtain solution 2; 3) 1.8822g of trisodium citrate is completely dissolved in 10mL of deionized water to obtain a complexing agent solution; 4) the complexing agent solution is slowly added to solution 1 under stirring, and solution 2 is added after the solution becomes transparent, and stirred to a light yellow uniform solution, and the solution is placed in a reactor to react at 180°C for 12h, and the precipitate after the reaction is washed with water and ethanol and then dried, and calcined at 800°C for 2h to obtain a green up-conversion phosphor. The above green up-conversion phosphor has green up-conversion luminescence performance under 980nm excitation light.

[0034] Example 1

[0035] In this embodiment, 0.05g of red fluorescent powder, 0.1g of green fluorescent carbon dot powder, 0.05g of blue up-conversion phosphor and 2mL of binder (formed by dissolving 1.5g of carboxymethyl cellulose V in 30mL of deionized water in this embodiment) are mixed evenly to obtain multi-color and gradient color anti-counterfeiting ink 1; then 0.05g of red fluorescent powder, 0.1g of blue fluorescent carbon dot powder and 0.05g of green up-conversion phosphor and 2mL of binder (formed by dissolving 1.5g of carboxymethyl cellulose V in 30mL of deionized water in this embodiment) are mixed evenly to obtain multi-color and gradient color anti-counterfeiting ink 2.

[0036] In this embodiment, the two configured inks are printed once and overprinted multiple times using screen printing technology to form an anti-counterfeiting pattern.

[0037] like Figure 3 As shown, the anti-counterfeiting pattern in the present invention is red under 254nm excitation; blue and green are respectively presented under 365nm excitation. After removing the 365nm excitation, the pattern has bright green room temperature phosphorescence. Blue and green carbon dots have better emission under 365nm excitation than 254nm excitation, and red phosphor has better emission under 254nm excitation than 365nm excitation. Through the synergistic excitation of 254nm and 365nm, the luminescent color of the anti-counterfeiting label can be adjusted from red to blue and green respectively; and under 980nm excitation, the above pattern has blue and green up-conversion luminescence. Under the synergistic excitation of 254nm and 980nm, by adjusting the exposure time under 254nm ultraviolet light, the luminescent color of the anti-counterfeiting label can be adjusted from red to green and blue respectively.

[0038] From the above, it is explained that the anti-counterfeiting label in this embodiment is a gradient color anti-counterfeiting label.

[0039] Example 2

[0040] In this embodiment, 0.05 g of red fluorescent powder, 0.1 g of green fluorescent carbon dot powder and 2 mL of binder (formed by dissolving 1.5 g of carboxymethyl cellulose V in 30 mL of deionized water in this embodiment) are mixed evenly to obtain multi-color and gradient color anti-counterfeiting ink.

[0041] In this embodiment, the screen printing technology is used to perform a single printing and multiple overprinting of the configured ink to form an anti-counterfeiting pattern.

[0042] In the present invention, green carbon dots have better emission when excited at 365nm than at 254nm, and red phosphor has better emission when excited at 254nm than at 365nm. Since the ink contains the above two luminescent materials, after printing it into a pattern, in the coordinated excitation of 254nm and 365nm excitation wavelengths, the 254nm excitation source and the anti-counterfeiting label are fixed, and the distance between the 365nm excitation source and the anti-counterfeiting label is adjusted. Based on the change in the relative intensity of the excitation light, the relative change in the red and green luminous intensities is caused, so that the luminous color changes in the range of red to green.

[0043] From the above, it is explained that the multi-color and gradient color anti-counterfeiting labels are obtained in this embodiment.

[0044] Example 3

[0045] In this embodiment, 0.05 g of red fluorescent powder, 0.1 g of green fluorescent carbon dot powder, 0.05 g of blue up-conversion fluorescent powder and 2 mL of binder (formed by dissolving 1.5 g of carboxymethyl cellulose V in 30 mL of deionized water in this embodiment) are mixed evenly to obtain multi-color and gradient anti-counterfeiting ink.

[0046] In this embodiment, the screen printing technology is used to perform a single printing and multiple overprinting of the configured ink to form an anti-counterfeiting pattern.

[0047] In this embodiment, a blue up-conversion phosphor is further introduced on the basis of the ink in Example 2, so that the obtained ink and anti-counterfeiting label not only have the luminescence characteristics of Example 2, but also in the coordinated excitation of 254nm and 980nm excitation wavelengths, the excitation time of the 254nm excitation source is adjusted and switched. Based on controlling the excitation time of the 254nm excitation source, the relative intensity of the red luminescence and the blue luminescence can be adjusted to form a relative intensity change between red and blue, so that the luminescent color varies in the range of red to blue.

[0048] From the above, it is explained that the multi-color and gradient color anti-counterfeiting labels are obtained in this embodiment.

[0049] Example 4

[0050] In this embodiment, 0.05 g of red fluorescent powder, 0.1 g of blue fluorescent carbon dot powder and 2 mL of binder (formed by dissolving 1.5 g of carboxymethyl cellulose V in 30 mL of deionized water in this embodiment) are mixed evenly to form a multi-color and gradient anti-counterfeiting ink that depends on multi-wavelength excitation.

[0051] In this embodiment, the screen printing technology is used to perform a single printing and multiple overprinting of the configured ink to form an anti-counterfeiting pattern.

[0052] In the present invention, the anti-counterfeiting pattern is red under 254nm excitation; it is blue under 365nm excitation. After removing the 365nm excitation, the pattern has bright green room temperature phosphorescence. Blue carbon dots have better emission under 365nm excitation than 254nm excitation, and red phosphor has better emission under 254nm excitation than 365nm excitation. Since the ink contains the above two luminescent materials, after printing it into a pattern, in the synergistic excitation of 254nm and 365nm excitation wavelengths, the 254nm excitation source and the anti-counterfeiting label are fixed, and the distance between the 365nm excitation source and the anti-counterfeiting label is adjusted. The relative change of the red and blue luminous intensity is caused based on the change of the relative intensity of the excitation light, so that the luminous color changes in the range of red to blue.

[0053] From the above, it is explained that the multi-color and gradient color anti-counterfeiting labels are obtained in this embodiment.

[0054] It should be noted that in this application, only Eu 3+ 、Tm 3+ / Yb 3+ , Er 3+ / Yb 3+ As an example of obtaining a specific phosphor, it can be understood that in the prior art, such as adding Eu 3+ 、Tm 3+ / Yb 3+ , Er 3+ / Yb 3+ The red phosphor, blue up-conversion phosphor, green up-conversion phosphor, etc. prepared by doping into REVO4 (RE=Y, La, Gd, Lu) matrix can still be prepared to form ink by referring to the present application.

[0055] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a multi-color and gradient color anti-counterfeiting label dependent on multi-wavelength excitation, characterized in that: The anti-counterfeiting pattern in the anti-counterfeiting label is formed by a multi-color anti-counterfeiting ink through single printing and multiple overprinting; The multi-color anti-counterfeiting ink is formed by uniformly mixing a colorant and a binder, wherein the colorant is formed by mixing red fluorescent powder and blue fluorescent carbon dot powder, or red fluorescent powder and green fluorescent carbon dot powder, or red fluorescent powder, green fluorescent carbon dot powder and blue up-conversion fluorescent powder, or red fluorescent powder, blue fluorescent carbon dot powder and green up-conversion fluorescent powder, and the excitation wavelengths of the red fluorescent powder, the up-conversion fluorescent powder and the fluorescent carbon dot powder are 254 nm, 980 nm and 365 nm respectively; The preparation method of the blue fluorescent carbon dot powder is as follows: citric acid, urea and strong alkali are dispersed in deionized water, and a hydrothermal reaction is performed to obtain a blue carbon quantum dot solution; anhydrous calcium chloride is added to the blue carbon quantum dot solution to react, and the reaction product is washed with water and ethanol for multiple times in sequence and then dried to obtain a blue fluorescent carbon dot powder; The preparation method of the green fluorescent carbon dot powder is as follows: citric acid, resorcinol and phosphoric acid are dispersed in deionized water, and a hydrothermal reaction is performed to obtain a green carbon quantum dot solution; tetraethyl orthosilicate is added to the green carbon quantum dot solution to react, and the reaction product is sequentially washed with water and ethanol for multiple times and then dried to obtain a green fluorescent carbon dot powder; The red phosphor is composed of Eu 3+ The blue up-conversion phosphor is formed by doping YVO4 matrix; 3+ , Yb 3+ The green up-conversion phosphor is formed by doping YVO4 matrix; 3+ , Yb 3+ Doped YVO4 matrix is ​​formed.

2. The preparation method according to claim 1, characterized in that: The blue fluorescent carbon dot powder has a blue fluorescent property under the excitation of an excitation light, and the blue fluorescent carbon dot powder has a green room temperature phosphorescence emission property after the excitation is removed.

3. The preparation method according to claim 1, characterized in that: The green fluorescent carbon dot powder has green fluorescent properties under the excitation of excitation light.

4. The preparation method according to claim 1, characterized in that: The red phosphor has red fluorescence characteristics under the excitation of excitation light.

5. The preparation method according to claim 1, characterized in that: The blue upconversion phosphor has blue upconversion luminescence performance under the excitation of excitation light.

6. The preparation method according to claim 1, characterized in that: The green upconversion phosphor has green upconversion luminescence performance under the excitation of excitation light.

7. A multi-color and gradient color anti-counterfeiting label dependent on multi-wavelength excitation, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 6.

8. Application of the multi-color and gradient color anti-counterfeiting label dependent on multi-wavelength excitation as claimed in claim 7 in the field of anti-counterfeiting.

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