Fluorescent ink based on metal ion induced nano aggregate and information encryption and decryption method

Abstract

The invention discloses a metal ion-induced nano aggregate fluorescent ink and an information encryption and decryption method. The method comprises the following steps: step A, designing an encryption pattern; b, full-color metal ion induced nano aggregate fluorescent ink is used for printing the encrypted pattern on non-fluorescent paper; encrypted information is stored in a partial pattern of a specific color, and the encryption is invisible under visible light; interference information and encrypted information in an encrypted pattern are displayed at the same time under an ultraviolet lamp, so that the encrypted information stored in a specific color is difficult to read; and C, quenching interference information by using different quenching agents, and leaving encrypted information with a specific color on the non-fluorescent paper. The colorless and transparent full-color ink is printed on the non-fluorescent paper. Small square matrixes with various fluorescent colors can be seen under ultraviolet rays, information is stored in small squares with specific colors, and a visual interference plus dense effect similar to a color vision check diagram is formed.

Description

Technical Field

[0001] The invention relates to the field of luminescence technology, and in particular to a nano-aggregate fluorescent ink based on metal ion induction and a method for encryption and decryption using the ink. Background Art

[0002] In the digital age, personal information leakage incidents occur frequently, which brings many inconveniences and risks to people's daily lives. Therefore, the method of encrypted information storage has become the focus of public attention. Although simple encryption methods have large security vulnerabilities, overly complicated encryption and decryption processes will bring inconvenience to the reading and display of information. In the face of this challenge, it is urgent to design an information storage method that is both simple and has strong encryption capabilities to achieve effective storage and simple display, while also having multi-level dynamic encryption, multi-layer encryption patterns, and high-sensitivity response large-capacity information storage capabilities. To meet this demand, we propose an innovative information storage solution. This method can not only provide strong encryption protection to prevent information leakage, but also ensure fast reading and intuitive display of information. By adopting advanced encryption technology, our method can simplify the information access process while protecting personal privacy, thereby achieving a balance between security and convenience. The development of this multi-level dynamic encryption, high-sensitivity response and large-capacity information storage method will provide more reliable protection for personal information security and open up new possibilities in the field of information security.

[0003] Eu3+、Tb 3 +, Al3+ ion-induced block nanoaggregates have attracted much attention due to their excellent properties, including strong photoluminescence with fast and highly sensitive response and high quantum yield. In metal complexes, organic ligands can not only serve as connectors of adjacent metal ions, but also as energy ligands, which have a strong enhancement effect on the luminescence of metal ions. However, metal element complexes with organic ligands are limited in practical applications due to poor thermal stability and poor plasticity. In order to alleviate these problems, the complexes are usually incorporated into a stable polymer matrix. The functional groups on the block polymer chains can coordinate with metal ions and self-assemble in specific selective solutions to form small spheres with core-shell structures. The shell of this structure effectively shields the interference of the external environment and stabilizes the coordination structure, thereby solving the limitations of metal complexes due to poor thermal stability and plasticity, while improving the fluorescence properties. Eu3+ and Tb 3+ block nanoaggregates have a fluorescence half-width of about 12nm, showing red and green fluorescence respectively. When 3-hydroxyflavone is used as an organic ligand, Al3+ ion block nanoaggregates show blue fluorescence. In theory, full-color fluorescence can be achieved by further mixing red, green and blue inks and adjusting the proportion of each component and the excitation wavelength to control the color. The increase in fluorescence color is of great significance for improving the capacity of information encryption, because it can increase the dimension and complexity of encrypted information, thereby improving security. These block nanoaggregates not only perform well in fluorescence performance, but also have obvious advantages in cost-effectiveness and processing convenience, making them highly potential materials in the field of information encryption. Therefore, the study of high-security and large-capacity encryption and decryption of optical quantum information of metal ion-induced nanoaggregate fluorescent inks is of great significance to today's information security issues. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an information encryption and decryption method based on metal ion-induced nano-aggregate fluorescent ink in view of the deficiencies in the prior art.

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

[0006] The preparation method of metal ion-induced nanoaggregate fluorescent ink comprises the following steps:

[0007] Step 1: preparing a photoluminescent nanoaggregate solution using a metal ion complex and a polystyrene-polyacrylic acid block copolymer PSx-PAAy;

[0008] Step 2: Mix the photoluminescent nanoaggregate solution with the high molecular polymer solution, heat and stir, and obtain the metal ion induced nanoaggregate fluorescent ink.

[0009] By preparing spherical nanoparticles with red, green and blue fluorescence and then adding polymers that increase the ink printing effect, such as PVP, red, green and blue inks are obtained. By adjusting the ratio of red, green and blue fluorescent nanoparticles, the fluorescence intensity of photoluminescence at different wavelengths is regulated to obtain full-color ink. The interaction between polymers and metal ions in the ink can affect its aggregation state in the solution. Polymer molecules can also act as surface protectants to prevent nanoparticles from aggregating, playing the role of nanoparticle dispersants.

[0010] In step 1, the metal ion complexes are Eu 3+ , Tb 3+ 、Al 3+ ; Corresponding to red, green and blue inks respectively.

[0011] In step 2, the heating and stirring temperature is maintained at 40-60° C. for 4-6 hours.

[0012] In step 1, the polystyrene-polyacrylic acid block copolymer PSx-PAAy is PS 61 -PAA 20 or PS 82 -PAA 26 .

[0013] In step 2, the polymer solution includes but is not limited to polyvinyl pyrrolidone (PVP), polyacrylonitrile (PAN), styrene maleic anhydride, and cellulose acetate.

[0014] In step 2, the high molecular polymer is PVP, the concentration of the PVP solution is 0.3 g / ml, and the volume ratio of the PVP solution to the photoluminescent nanoaggregate solution is 1:1.

[0015] An information encryption and decryption method based on metal ion-induced nanoaggregate fluorescent ink comprises the following steps:

[0016] Step A: Design an encrypted pattern, wherein the encrypted pattern includes encrypted information and interference information, and encrypts and "writes" the encrypted information into a specific color portion of the pattern;

[0017] Step B: Printing the encrypted pattern on non-fluorescent paper using full-color metal ion-induced nanoaggregate fluorescent ink; the encrypted information is stored in a portion of the pattern of a specific color, and the encryption is invisible under visible light; under ultraviolet light, the interference information and the encrypted information in the encrypted pattern appear simultaneously, making it difficult to read the encrypted information stored in the specific color;

[0018] Step C: Use different quenchers to quench the interference information, leaving encrypted information of a specific color on the non-fluorescent paper.

[0019] The information encryption and decryption method is to perform electro-hydraulic inkjet (EHD) printing on a suitable flexible flat substrate non-fluorescent paper, set the bias voltage to 800-1200V, the amplitude voltage to 600-900V, the pulse frequency to 200HZ, the distance from the nozzle to the substrate to 0.15-0.3mm, the duty cycle to 15-35%, the base speed to 2-7mm / s, draw the pattern with CAD and input it into the printer, and use non-fluorescent paper as the printing substrate for printing. After printing, put it in a 40°C oven to dry for 5 minutes.

[0020] The information encryption and decryption method, the encrypted information includes digital passwords, letters or complex patterns.

[0021] Based on the visual interference principle of color vision test charts, we use electrofluidic inkjet printers to print square matrices of different color inks in layers on flexible substrates and non-fluorescent paper, forming rectangular square arrays of multiple colors. These square arrays are invisible under ambient light, achieving the first layer of information encryption; the information is stored in a pattern composed of squares of a specific color, and the rest of the pattern is printed with patterns of other colors of ink, which interferes with the information stored in the correct fluorescent color, achieving the second layer of information encryption. It is also possible to quench the interference information by applying different quenching potions on the non-fluorescent paper with the printed pattern, and observe the remaining fluorescent pattern under ultraviolet light to clearly see the hidden information. This is the third encryption and the final decryption display.

[0022] The present invention proposes an information encryption system based on the fluorescence characteristics of metal ion-induced polystyrene-block-polyacrylic acid (PS-PAA) nanoaggregates (MIPAs). MIPA is a kind of 3+ , Tb 3+ and Al 3+ The red, green and blue primary color inks were prepared by combining with polyvinylpyrrolidone (PVP) and the ratio of the central ion nanoaggregates of these inks was precisely adjusted to achieve the regulation of the photoluminescence fluorescence intensity of different emission wavelengths, thus obtaining a full-color fluorescent ink. The increase in fluorescent color is of great significance for improving the capacity of information encryption. Using an electrofluidic inkjet printer, we printed the colorless and transparent full-color ink on non-fluorescent paper. Under ultraviolet light, a small square matrix of multiple fluorescent colors was visible, and the information was stored in the small squares of specific colors, forming a visual interference encryption effect similar to a color vision test chart. Further, we used different quenching molecules and multiple quenching mechanisms to read and display information, including static quenching, dynamic quenching effect, and a combination of inner filter effect and dynamic quenching effect. The use of these quenching mechanisms not only improves the security of information encryption, but also enhances the efficiency of information storage and display detection. Finally, we successfully achieved the storage and display detection goals of information, providing an effective solution for high-security and large-capacity information encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 TEM images in Example 1; (a) is EuPAs; (b) is TbPAs; (c) is AlPAs; (d) is the particle size distribution diagram of EuPAs; (e) is the particle size distribution diagram of TbPAs; (f) is the particle size distribution diagram of AlPAs.

[0024] Figure 2 The excitation spectra (a) and emission spectra (b) of the photoluminescence performance of EuPAs, TbPAs, and AlPAs before and after adding PVP in Example 1.

[0025] Figure 3 (a) is the fluorescence emission spectrum of green ink before and after quenching with 0.1 mol / L HAC (acetic acid) quencher (b) is the fluorescence emission spectrum of green ink after quenching with 0.1 mol / L Fe 3+ The fluorescence emission spectra before and after (c) are the green ink with the addition of quencher 0.1 mol / L Mn 2+ The fluorescence emission spectra before and after (d) are the green ink with the addition of quencher 0.1 mol / L pNP (p-nitrophenol) and the fluorescence emission spectra before and after quenching (e) are the blue ink with the addition of quencher 0.1 mol / L HAC / Mn 2+ The fluorescence emission spectra before and after (f) are the fluorescence emission spectra before and after the addition of quencher 0.1 mol / L pNP to the red ink.

[0026] Figure 4 This is an example of encryption and decryption of the metal ion-induced nanoaggregate fluorescent ink and information encryption and decryption method in Example 2, that is, by applying a quencher, a combined multi-level encryption of fluorescence emission / quenching is performed.

[0027] Figure 5 This is an example of encryption and decryption of the metal ion-induced nanoaggregate fluorescent ink and information encryption and decryption method in Example 3, that is, by applying a quencher, a combined multi-level encryption of fluorescence emission / quenching is performed.

[0028] Figure 6 It is an overview of the quenching mechanisms of different quenchers of the present invention. Figure 6 (a) Kinetic decay curve of green ink after adding quencher 0.1 mol / L HAC (acetic acid); Figure 6 (b) Add quencher 0.1 mol / L Fe 3+ The kinetic decay curve of the back green ink; Figure 6 (c) Add quencher 0.1 mol / L Mn 2+ Dynamic decay curve of post-green ink; Figure 6 (d) Kinetic decay curve of green ink after adding quencher 0.1 mol / L pNP (p-nitrophenol). The spectrum distinguishes whether different quenchers are dynamic quenching or static quenching. Figure 6 (e) shows the XRD curves of the ink after adding different quenchers and comparing them with the curve of the green ink. There is no obvious change in the XRD curves before and after adding the quencher, indicating that the crystal structure is not destroyed and is very stable. Therefore, the fluorescence quenching effect caused by system collapse can be ruled out. Figure 6 (f) is the UV-visible absorption spectra of the quencher and red and green inks, from which it can be analyzed that Fe3+ and pNP have a unique inner filter quenching effect. Figure 6 (g) shows that the quencher is Mn 2+The fluorescence intensity of the ink changes with the quencher concentration, and the quenching efficiency of the quencher is evaluated. The relationship between the fluorescence intensity and the quencher concentration is plotted, indicating that there is a robust linear relationship between its concentration and the fluorescence color contrast, and the position of the fluorescence emission peak does not move. This linear relationship means that the charge transfer mechanism between the quencher and the green ink is a dynamic mechanism. Figure 6 (h) shows the curve of the fluorescence intensity of the ink changing with the quencher concentration when the quencher is pNP (p-nitrophenol), and the quenching efficiency of the quencher is evaluated. A graph of the relationship between the fluorescence intensity and the quencher concentration is plotted, indicating that there is a robust linear relationship between its concentration and the fluorescence color contrast, and the position of the fluorescence emission peak does not move. This linear relationship means that the charge transfer mechanism between the quencher and the green ink is a dynamic mechanism. Figure 6 (i) shows that the quencher is Fe 3+ The fluorescence intensity of the ink changes with the quencher concentration, and the quenching efficiency of the quencher is evaluated. The relationship between the fluorescence intensity and the quencher concentration is plotted, indicating that there is a robust linear relationship between its concentration and the fluorescence color contrast, and the position of the fluorescence emission peak does not move. This linear relationship means that the charge transfer mechanism between the quencher and the green ink is a dynamic mechanism. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with specific embodiments.

[0030] Example 1

[0031] Preparation of red ink

[0032] (1) 9.36 g styrene, 0.263 g Raft, and 0.054 g AIBN as initiator were dissolved in a flask containing 10 ml dioxane, nitrogen was introduced for 30 min, and then heated and stirred at 75 ° C for 10 h. The reaction mixture was placed in a large amount of methanol, and the unreacted monomers were removed four times, and then filtered. The polymer PS was obtained by vacuum drying. 61 Take the PS synthesized in the previous step 61 1.2g, 0.378g acrylic acid (AA), 0.054g AIBN were dissolved in a 12ml flask, nitrogen was introduced for 30min, and heated and stirred at 60℃ for 10h. The reactants were placed in a large amount of petroleum ether, left to stand for 12h, filtered to remove unreacted monomers, and dried in vacuum to obtain PS 61 -PAA 20 .

[0033] (2) The obtained PS 61 -PAA 20 Dissolve in DMF to make a 0.4 mol / L solution, add 0.2 mL of PS in a flask containing 10 ml of DMF. 61 -PAA20 solution, add 0.0534g tta and 0.0158g phen, and finally add 0.0292g EuCl 3 .6H 2 O. Stir at 60 ° C for 6 h to obtain photoluminescent nanoaggregates Eu (tta) 3 phen@PS 61 - Red photoluminescent solution with uniform distribution of PAA20 (EuPAs).

[0034] (3) PVP powder was dissolved in 10 ml of DMF and stirred at 55 °C for 3 h to prepare a 0.3 g / ml solution. 1 mL of PVP solution and 1 mL of EuPAs solution were placed in a flask and stirred at 55 °C for 5 h to obtain EuPAs@PVP red ink.

[0035] (4) The prepared solution was injected into a syringe with a volume of 1 ml as the ink of the electrohydrodynamic inkjet printer (EHD). The bias voltage was set to 1050 V, the amplitude voltage was set to 800 V, the pulse frequency was set to 200 Hz, the distance from the nozzle to the substrate was set to 0.21 mm, the duty cycle was set to 23%, and the base speed was set to 4 mm / s. The pattern was drawn using CAD and input into the printer. Non-fluorescent paper was used as the printing substrate for printing. After printing, it was placed in a 40°C oven to dry for 5 minutes.

[0036] Preparation of green ink

[0037] (1) 12.48 g of styrene, 0.263 g of Raft reagent, and 0.054 g of AIBN as an initiator were dissolved in a flask containing 10 ml of dioxane, and nitrogen was introduced for 30 min. Then, the mixture was heated and stirred at 75°C for 10 h. The reaction mixture was placed in a large amount of methanol, and the unreacted monomers were removed four times, and then filtered. The polymer PS was obtained by vacuum drying. 82 Take the PS synthesized in the previous step 82 1.2g, 0.378g acrylic acid (AA), 0.054g AIBN were dissolved in a 12ml flask, nitrogen was introduced for 30min, and heated and stirred at 60℃ for 10h. The reactants were placed in a large amount of petroleum ether, left to stand for 12h, filtered to remove unreacted monomers, and dried in vacuum to obtain PS 82 -PAA 26 .

[0038] (2) The obtained PS 82 -PAA 26 Dissolve in DMF to make a 0.4 mol / L solution, add 0.2 mL of PS in a flask containing 10 ml of DMF. 82 -PAA 26solution, add 0.018g 4-benzoylbenzoic acid (4-BBA) and 0.01248g 2,2-bipyridine (BPA), and finally add 0.0298g TbCl 3 .6H2O. Stir at 60℃ for 6h to obtain photoluminescent nanoaggregates Tb(4-BBA)3bpa@PS 82 -PAA 26 (TbPAs) uniformly distributed green photoluminescent solution.

[0039] (3) PVP powder was dissolved in 10 ml of DMF and stirred at 55 °C for 3 h to prepare a 0.3 g / ml solution. 1 mL of PVP solution and 1 mL of TbPAs solution were placed in a flask and stirred at 55 °C for 5 h to obtain TbPAs@PVP green ink.

[0040] (4) The prepared solution was injected into a syringe with a volume of 1 ml as the ink of the electrohydrodynamic inkjet printer (EHD). The bias voltage was set to 1050 V, the amplitude voltage was set to 800 V, the pulse frequency was set to 200 Hz, the distance from the nozzle to the substrate was set to 0.21 mm, the duty cycle was set to 23%, and the base speed was set to 4 mm / s. The pattern was drawn using CAD and input into the printer. Non-fluorescent paper was used as the printing substrate for printing. After printing, it was placed in a 40°C oven to dry for 5 minutes.

[0041] Preparation of blue ink

[0042] (1) The obtained PS 61 -PAA 20 Dissolve in DMF to make a 0.4 mol / L solution, add 0.2 mL of PS in a flask containing 10 ml of DMF. 61 -PAA 20 solution, add 0.0216g trihydroxyflavone (3-HF), and finally add 0.03gAl(NO 3 ) 3 .9H2O. Stir at 60℃ for 6h to obtain photoluminescent nanoaggregates Al(3-HF)@PS 61 -PAA 20 (AlPAs) uniformly distributed blue photoluminescent solution.

[0043] (2) PVP powder was dissolved in 10 ml of DMF and stirred at 55°C for 3 h to prepare a 0.3 g / ml solution. 1 mL of PVP solution and 1 mL of AlPAs solution were placed in a flask and stirred at 55°C for 5 h to obtain AlPAs@PVP ink.

[0044] (3) The prepared solution was injected into a syringe with a volume of 1 ml as the ink of the electrofluidic inkjet printer (EHD). The bias voltage was set to 1050 V, the amplitude voltage was set to 800 V, the pulse frequency was set to 200 Hz, the distance from the nozzle to the substrate was set to 0.21 mm, the duty cycle was set to 23%, and the base speed was set to 4 mm / s. The pattern was drawn using CAD and input into the printer. Non-fluorescent paper was used as the printing substrate for printing. After printing, it was placed in a 40°C oven to dry for 5 minutes.

[0045] Figure 1 TEM images of EuPAs, TbPAs, and AlPAs and their particle size distribution. Figure 1 It can be seen that the microstructure of EuPAs, TbPAs and AlPAs presents a spherical structure and is very evenly dispersed.

[0046] Figure 2 It is a characterization of the photoluminescence properties of red, green and blue inks. Figure 2 It can be found that after adding PVP, the emission peak wavelengths of red, green and blue inks remain unchanged and the fluorescence intensity is enhanced.

[0047] Example 2

[0048] First, use CAD software to design the information encryption content, and then import it into the electrofluidic inkjet printer. The amplitude voltage is set to 650V, the bias voltage is set to 900V, the duty cycle is 25%, the pulse frequency is 200HZ, the distance from the printer nozzle to the substrate is 1.78mm, and the base movement speed is 5mm / S. Use blue and green inks to print and take out the printed pattern. "Mn, HAC" The small rectangles printed with blue ink constitute the pattern "Mn, HAC" The small rectangles printed with green ink cover the paper surface (it can also be designed into a unique pattern). Because the ink is colorless and transparent, the pattern is invisible under visible light. Wrong decryption method: Directly irradiate the material surface with UV ultraviolet light. At this time, because multi-color inks are used for printing, the pattern information formed by other color inks will interfere with it. When you don’t know which color ink stores the correct information, you can’t judge the accurate information. Correct decryption method: Use a quencher of 0.1mol / L MnCl 3 \HAC solution is applied on the pattern. Due to the dynamic quenching mechanism of manganese chloride solution on green ink and the static quenching mechanism of acetic acid solution on green ink, when manganese chloride solution and acetic acid solution are used as decryption agents on the pattern surface, the green fluorescent nanopattern is quenched by the decryption agent, while the blue fluorescent pattern is not affected. At this time, the blue fluorescent information "Mn, HAC" is observed by irradiating with ultraviolet light.

[0049] Example 3

[0050] First, use CAD software to design the information encryption content, and then import it into the electro-fluid inkjet printer. The amplitude voltage is set to 650V, the bias voltage is set to 900V, the duty cycle is 25%, the pulse frequency is 200HZ, the distance from the printer nozzle to the substrate is 1.78mm, and the base moving speed is 5mm / S. Use blue and green inks to print and take out the printed pattern. "pNP" The small rectangles printed with red ink constitute the pattern "pNP" The small rectangles printed with green ink cover the paper surface (it can also be designed into a unique pattern). Because the ink is colorless and transparent, the pattern is invisible under visible light. Wrong decryption method: Directly irradiate the material surface with UV ultraviolet light At this time, because multi-color inks are used for printing, the pattern information formed by other color inks will interfere with the correct fluorescent stored information. When you don't know which color ink stores the correct information, you can't judge the accurate information. Correct decryption method: Use 0.1 mol / L p-nitrophenol (pNP) solution as a decryption agent to apply on the pattern. Due to the internal filtration effect and dynamic quenching mechanism of the pNP solution, when the pNP solution acts on the pattern, the green fluorescent nanopattern surface is quenched by the decryption agent, while the red fluorescent pattern part is not affected. At this time, the red fluorescent information "pNP" can be observed under ultraviolet light.

[0051] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for preparing a fluorescent ink based on metal ion-induced nanoaggregates, characterized in that: The following steps are involved: Step 1: preparing a photoluminescent nanoaggregate solution using a metal ion complex and a polystyrene-polyacrylic acid block copolymer PSx-PAAy; Step 2: Mix the photoluminescent nanoaggregate solution with the high molecular polymer solution, heat and stir, and obtain the metal ion induced nanoaggregate fluorescent ink.

2. The preparation method according to claim 1, characterized in that: In step 1, the metal ion complexes are Eu 3+ , Tb 3+ 、Al 3+ ; Corresponding to red, green and blue inks respectively.

3. The preparation method according to claim 1, characterized in that: In step 2, the heating and stirring temperature is maintained at 40-60° C. for 4-6 hours.

4. The preparation method according to claim 1, characterized in that: In step 1, the polystyrene-polyacrylic acid block copolymer PSx-PAAy is PS 61 -PAA 20 or PS 82 -PAA 26 .

5. The preparation method according to claim 1, characterized in that: In step 2, the high molecular polymer solution includes polyvinyl pyrrolidone (PVP), polyacrylonitrile (PAN), styrene maleic anhydride and cellulose acetate.

6. The preparation method according to claim 1, characterized in that: In step 2, the high molecular polymer is PVP, the concentration of the PVP solution is 0.3 g / ml, and the volume ratio of the PVP solution to the photoluminescent nanoaggregate solution is 1:

1.

7. The metal ion-induced nanoaggregate fluorescent ink obtained according to the preparation method according to any one of claims 1 to 6.

8. An information encryption and decryption method based on the metal ion induced nanoaggregate fluorescent ink according to claim 7, comprising the following steps: Step A: Design an encrypted pattern, wherein the encrypted pattern includes encrypted information and interference information, and encrypts and "writes" the encrypted information into a specific color portion of the pattern; Step B: Printing the encrypted pattern on non-fluorescent paper using full-color metal ion-induced nanoaggregate fluorescent ink; the encrypted information is stored in a portion of the pattern of a specific color, and the encryption is invisible under visible light; under ultraviolet light, the interference information and the encrypted information in the encrypted pattern appear simultaneously, making it difficult to read the encrypted information stored in the specific color; Step C: Use different quenchers to quench the interference information, leaving encrypted information of a specific color on the non-fluorescent paper.

9. The information encryption and decryption method according to claim 8, characterized in that: Perform electro-hydraulic inkjet (EHD) printing on a suitable flexible flat substrate non-fluorescent paper, set the bias voltage to 800-1200V, the amplitude voltage to 600-900V, the pulse frequency to 200HZ, the distance from the nozzle to the substrate to 0.15-0.3mm, the duty cycle to 15-35%, the base speed to 2-7mm / s, draw the pattern in CAD and input it into the printer, use non-fluorescent paper as the printing substrate for printing. After printing, put it in a 40℃ oven to dry for 5 minutes.

10. The information encryption and decryption method according to claim 8, characterized in that: The encrypted information includes digital passwords, letters or complex patterns.

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