Anti-counterfeiting digital invisible ink and application thereof

Abstract

Disclosed are an anti-counterfeiting digital invisible ink and application thereof. The anti-counterfeiting label provided by the present invention is prepared by printing the anti-counterfeiting digital invisible ink on a label followed by heating and drying, wherein the raw material components of the anti-counterfeiting digital invisible ink comprise, in parts by mass: 10-40 parts of an invisible anti-counterfeiting agent, 0.3-3 parts of a polymer, 0.05-1 part of a stabilizer, 5-30 parts of a solvent, and 0.05-5 parts of an auxiliary agent, wherein the invisible anti-counterfeiting agent is selected from one of an invisible anti-counterfeiting core-structured substance and core-shell composite particles; in the present invention, the anti-counterfeiting digital invisible ink is obtained by mixing and stirring the raw material components followed by dispersion treatment. Compared with the prior art, the anti-counterfeiting label prepared in the present invention has the advantage of excellent invisibility, and the anti-counterfeiting digital invisible ink used therein has the advantages of high stability and good weathering resistance.

Description

Anti-counterfeiting digital invisible ink and its application Technical Field

[0001] This invention relates to the field of printing ink technology, and in particular to an anti-counterfeiting digital invisible ink and its application. Background Technology

[0002] "Anti-counterfeiting" primarily embodies prevention, providing solutions to combat counterfeiting at its source. It also possesses universality, offering a usable method for verifying authenticity in daily life. With rapid socio-economic development, various counterfeiting technologies are constantly evolving, leading to increasingly rampant counterfeiting in various manufacturing industries. This not only harms the interests of businesses but also the interests of the nation. Against this backdrop, effective anti-counterfeiting technologies are needed to safeguard confidential documents, goods, and currency, such as digital information anti-counterfeiting, biometric anti-counterfeiting, and printing technology anti-counterfeiting. Among these, anti-counterfeiting inks play a crucial role in printing technology anti-counterfeiting. Technical issues

[0003] CN116200075A discloses a high-resolution anti-counterfeiting electronic ink and its preparation method. By adding nano-cadmium sulfide or nano-titanium dioxide as nano-anti-counterfeiting powder, the color purity is improved, enhancing the ink's anti-counterfeiting performance. However, the ink prepared by this method does not provide a secure seal when printed on a substrate and is easily counterfeited. CN114958092A discloses a thermochromic anti-counterfeiting ink, its preparation method, and its application. Composed of 5-20 parts of a color-changing material, 5-20 parts of acetate microcapsules, 30-50 parts of an aqueous PUA emulsion, 15-30 parts of styrene-acrylic resin, and 5-30 parts of water, the prepared ink can unidirectionally change color at 37-45℃. However, the color-changing temperature of the ink prepared by this method is too low and irreversible, making it prone to failure during natural storage. Technical solutions

[0004] In view of the above-mentioned defects of the prior art, the present invention provides an anti-counterfeiting label made of anti-counterfeiting digital invisible ink. The anti-counterfeiting label made by the present invention has the advantage of good invisibility, and the anti-counterfeiting digital invisible ink used has the advantages of high stability and good weather resistance.

[0005] To achieve the above objectives, the present invention provides a method for preparing anti-counterfeiting digital invisible ink, comprising the following steps, in parts by weight:

[0006] Disperse 10-40 parts of invisible anti-counterfeiting agent, 0.3-3 parts of polymer, 0.05-1 part of stabilizer, 5-30 parts of solvent, and 0.05-5 parts of additives evenly using a high-speed disperser, then grind them in a grinding mill, and finally perform ultrasonic treatment to obtain anti-counterfeiting digital invisible ink.

[0007] More preferably, the material is fed into a grinder to grind to a particle size of less than 10 μm, and the ultrasonic treatment conditions are ultrasonication at 40-100 kHz for 5-15 minutes.

[0008] Preferably, the polymer is selected from at least one of polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene, polyacrylamide, polyacrylic acid, polylactic acid, polyglycolic acid, polylactic acid-glycolic acid copolymer, polycaprolactone, polyvinyl acetate, polydimethylsiloxane, and polyurethane.

[0009] The stabilizer is at least one selected from butanethiol, nonanethiol, dodecanethiol, hexadecanethiol, mercaptoacetic acid, mercaptopropionic acid, 4-mercaptobutyric acid, 8-mercaptoheptanoic acid, 1-mercapto-2-propanone, 4-mercapto-2-pentanone, 3-mercapto-2-butanone, mercaptoethylamine, 3-mercapto-1-propanamine, and 3-mercapto-N-nonylpropionamide.

[0010] The solvent is selected from at least one of water, methanol, ethanol, isopropanol, n-propanol, ethylene glycol, propylene glycol, glycerol, n-butanol, n-octanol, n-nonanol, n-decanol, N-methylpyrrolidone, a mixture of diesters, dimethylformamide, diacetone alcohol, 1,3-dimethylimidazolinone, dimethyl sulfoxide, diethylene glycol monobutyl ether, diethylene glycol acetate, ethylene glycol carbonate, propylene glycol carbonate, 1,4-butyrolactone, toluene, chlorobenzene, dichloromethane, and tetrahydrofuran.

[0011] The auxiliary agent is selected from at least one of the perfluorinated surfactants BOK-B-100, BOK-B-101, BOK-B-102, and BOK-B-103.

[0012] More preferably, the solvent is isopropanol and water mixed in a mass ratio of 1-5:1-5.

[0013] Preferably, the invisible anti-counterfeiting agent is selected from one of invisible anti-counterfeiting nuclear structure materials and core-shell composite particles.

[0014] Preferably, the preparation method of the stealth anti-counterfeiting nuclear structure material includes the following steps, in parts by weight:

[0015] Mix 1-5 parts of 1,3-dimethylbarbituric acid, 0.1-1.5 parts of furfural, and 10-30 parts of water thoroughly, and react at 20-40℃ and 800-1000rpm for 1-3 hours. Then collect the precipitate, dissolve it in dichloromethane, and extract it with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 1-5 parts of compound 1, 0.1-1.5 parts of diethylamine, and 10-30 parts of water thoroughly, and react at 20-40℃ and 800-1000rpm for 1-3 hours. Then remove the solvent using a rotary evaporator to obtain DASA, i.e., the donor-acceptor Steinhaus adduct molecule.

[0016] As a further explanation of the present invention, the donor-acceptor Steinhaus adduct molecule DASA can mainly exist in two states: linear and cyclic, and these two states can interconvert. Under visible light, the donor-acceptor Steinhaus adduct molecule DASA transforms from its initial colored state into a colorless closed-ring isomer, remaining colorless under visible light, but exhibiting color under specific ultraviolet light. DASA can bind to water molecules and transform into a colorless and structurally stable cyclic donor-acceptor Steinhaus adduct hydrate. The cyclic donor-acceptor Steinhaus adduct hydrate loses its bound water molecules when heated to approximately 160°C, rapidly transforming into purple linear DASA within about 5 seconds.

[0017] Preferably, the preparation method of the core-shell composite particles includes the following steps, in parts by weight:

[0018] Step 1: Mix 1-5 parts of 1,3-dimethylbarbituric acid, 0.1-1.5 parts of furfural, and 10-30 parts of water thoroughly. React at 20-40℃ and 800-1000 rpm for 1-3 hours. Collect the precipitate, dissolve it in dichloromethane, and extract with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 1-5 parts of compound 1, 0.1-1.5 parts of diethylamine, and 10-30 parts of water thoroughly. React at 20-40℃ and 800-1000 rpm for 1-3 hours. The reaction was carried out at -1000 rpm for 1-3 h, and then the solvent was removed by rotary evaporation to obtain DASA; 5-15 parts of PAMAM dendritic polymer and 1-5 parts of DASA were added to 30-60 parts of tetrahydrofuran and mixed evenly, and then reacted at 60-100℃ and 800-1000 rpm for 2-4 h; then centrifuged at 2000-4000 rpm, the solid was collected, and dried at 60-100℃ for 4-8 h to obtain core-structured DASA dendritic polymer microspheres;

[0019] Step 2: Mix 1-5 parts of silica with 5-10 parts of 5-15 wt% HCl and stir for 1-3 hours. Then centrifuge at 2000-4000 rpm, collect the solid, wash the solid with water until the supernatant is neutral, and dry the washed solid at 60-100℃ for 4-8 hours to obtain activated silica. Mix 1-5 parts of activated silica with 5-10 parts of ethanol evenly, add 0.1-1 parts of ammonia and 0.1-1 parts of silane coupling agent, react at 50-70℃ and 800-1000 rpm for 16-48 hours, then centrifuge at 2000-4000 rpm, collect the solid, wash the solid with ethanol until the supernatant is neutral, and dry the washed solid at 60-100℃ for 4-8 hours to obtain modified silica.

[0020] Step 3: Mix 1-10 parts of modified silica with 10-50 parts of tetrahydrofuran until homogeneous, then add 5-10 parts of core-structured DASA dendritic polymer microspheres, react at 20-60℃ and 800-1000rpm for 2-4h, then centrifuge at 2000-4000rpm, collect the solid, and dry at 60-100℃ for 4-8h to obtain composite modified silica, i.e., core-shell composite particles.

[0021] More preferably, step three can also be:

[0022] Mix 1-10 parts of modified silica with 10-50 parts of tetrahydrofuran until homogeneous, then add 5-10 parts of core-structured DASA dendritic polymer microspheres. React at 20-60℃ and 800-1000rpm for 2-4 hours, then centrifuge at 2000-4000rpm to collect the solid, and dry at 60-100℃ for 4-8 hours to obtain composite modified silica. Mix 1-5 parts of composite modified silica with 1-50 parts of isopropanol until homogeneous, then add 1-5 parts of phenolic resin. React at 80-120℃ and 800-1000rpm for 2-4 hours, cool to room temperature, then centrifuge at 2000-4000rpm to collect the solid, and dry the solid at 60-100℃ for 4-8 hours to obtain core-shell composite particles.

[0023] More preferably, the silane coupling agent in step two is selected from at least one of trimethoxy[2-(7-oxadicyclo[4.1.0]hept-3-yl)ethyl]silane.

[0024] As a further explanation of the present invention, the core-shell structure is a special composite material composed of a core and one or more outer shells surrounding the core. PAMAM dendritic polymers possess a unique topological structure and excellent temperature-sensitive properties, enabling them to spontaneously assemble with DASA into microspheres as the core structure. The shell structure is modified silica, phenolic resin, or a combination of modified silica and phenolic resin, assembled into core-shell composite particles through adsorption and / or chemical reactions. The use of silane coupling agents in the core-shell composite particles can promote chemical bonding between modified silica and DASA dendritic polymer microspheres, forming a stable core-shell structure. Modified silica and phenolic resin may form a physical network structure within the particles. The outer shell of the core-shell structure can improve the dispersibility of the core in the ink, reduce particle aggregation, thereby improving ink stability, and can also effectively limit particle aggregation and sedimentation. Furthermore, the outer shell of the core-shell structure may also form a protective layer on the particle surface. This protective layer can mitigate the effects of external factors such as temperature, humidity, and pH on the core, thereby improving the weather resistance and stability of the ink.

[0025] This invention also provides the application of the aforementioned anti-counterfeiting digital invisible ink on anti-counterfeiting labels. The specific application is as follows: the anti-counterfeiting label is prepared by printing the anti-counterfeiting digital invisible ink onto the label, and drying it at 80-100℃ for 1-3 hours. The printed content is invisible initially, but becomes purple upon heating. Beneficial effects

[0026] 1. Compared with existing technologies, this invention, through reasonable formulation and the interaction between various substances, prepares anti-counterfeiting digital invisible ink. This ink is then printed on labels to create anti-counterfeiting tags. The anti-counterfeiting digital invisible ink provided by this invention not only possesses an invisible effect, displaying graphic information under specific lighting conditions, thus giving traditional wearable tags anti-counterfeiting properties, but also exhibits good stability and acid and alkali resistance. This invention introduces core-shell composite particles to prepare the anti-counterfeiting digital invisible ink, improving its stability. The anti-counterfeiting digital invisible ink prepared by this invention, after being placed at 42±1℃ for 21 days, showed a sedimentation rate of only 0.99%.

[0027] 2. Compared with the prior art, the present invention adds core-shell composite particles in the preparation process of anti-counterfeiting digital invisible ink. Modified silica and phenolic resin are added to the core-shell composite particles at the same time, which may form a physical network structure in the core-shell composite particles, which can effectively limit the aggregation and sedimentation of particles. After being placed at 42±1℃ for 21 days, the sedimentation rate of the anti-counterfeiting digital invisible ink of the present invention is only 0.99%, indicating that the ink of the present invention has better stability during storage and use.

[0028] 3. Compared to existing technologies, the anti-counterfeiting digital invisible ink of this invention produces labels with a color development temperature of 210℃ and a color development time of 35 seconds, which is higher than that of ordinary DASA ink and requires a longer development time. This means that the anti-counterfeiting labels of this invention are more difficult to illegally copy because higher temperatures and more precise conditions are required for the printed content to appear. Embodiments of the present invention

[0029] The parameters and sources of some raw materials in this embodiment of the invention are as follows:

[0030] Silica, particle size: <150μm;

[0031] The perfluorinated surfactant BOK-B-100 is sourced from Guangzhou Xinrui Chemical Materials Co., Ltd.

[0032] Phenolic resin, grade: S607, sourced from Jiangsu Senbo New Materials Co., Ltd.

[0033] PAMAM dendritic polymer, product number: P475373, molecular weight 516.68, is sourced from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0034] Polyvinylpyrrolidone, product number: P110611, average molecular weight 10000, sourced from Shanghai Aladdin Biochemical Technology Co., Ltd. Example 1

[0035] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink includes the following steps:

[0036] Step a: Disperse 200g of invisible anti-counterfeiting core structure material, 10g of polyvinylpyrrolidone, 2g of butanethiol, 200g of isopropanol, 50g of water, and 2g of perfluorinated surfactant BOK-B-100 evenly using a high-speed disperser. Then, grind the mixture in a grinder until the particle size is less than 10μm. Finally, ultrasonically treat the mixture at 50kHz for 10 minutes to obtain the anti-counterfeiting digital invisible ink.

[0037] Step b: Print the anti-counterfeiting digital invisible ink obtained in step a onto the label, and dry it at 90℃ for 2 hours to obtain an anti-counterfeiting label with invisible printed content; the printed content of the anti-counterfeiting label will turn purple after heating.

[0038] The preparation method of the stealth anti-counterfeiting nuclear structure material includes the following steps:

[0039] 30g of 1,3-dimethylbarbituric acid, 10g of furfural, and 200g of water were mixed evenly and reacted at 30℃ and 900rpm for 2h. The precipitate was then collected, dissolved in dichloromethane, and extracted with water and saturated sodium chloride. The organic phase was collected and the solvent was removed by rotary evaporation to obtain compound 1. 30g of compound 1, 10g of diethylamine, and 200g of water were mixed evenly and reacted at 30℃ and 900rpm for 2h. The solvent was then removed by rotary evaporation to obtain DASA. This yielded the stealth anti-counterfeiting nuclear structure material. Example 2

[0040] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink includes the following steps:

[0041] Step a: According to the mass fraction of each raw material component, 200g of core-structured DASA dendritic polymer microspheres, 10g of polyvinylpyrrolidone, 2g of butanethiol, 200g of isopropanol, 50g of water, and 2g of BOK-B-100 are dispersed evenly using a high-speed disperser, then fed into a grinder and ground until the particle size is less than 10μm, and then ultrasonically treated at 50kHz for 10min to obtain anti-counterfeiting digital invisible ink;

[0042] Step b: Print the anti-counterfeiting digital invisible ink obtained in step a onto the label, and dry it at 90℃ for 2 hours to obtain an anti-counterfeiting label with invisible printed content; the printed content of the anti-counterfeiting label will turn purple after heating.

[0043] The preparation method of the core-structured DASA dendritic polymer microspheres includes the following steps:

[0044] 30 g of 1,3-dimethylbarbituric acid, 10 g of furfural, and 200 g of water were mixed evenly and reacted at 30 °C and 900 rpm for 2 h. The precipitate was then collected, dissolved in dichloromethane, and extracted with water and saturated sodium chloride. The organic phase was collected and the solvent was removed by rotary evaporation to obtain compound 1. 30 g of compound 1, 10 g of diethylamine, and 200 g of water were mixed evenly and reacted at 30 °C and 900 rpm for 2 h. The solvent was then removed by rotary evaporation to obtain DASA. 100 g of PAMAM dendritic polymer and 30 g of DASA were added to 450 g of tetrahydrofuran and mixed evenly. The mixture was then reacted at 80 °C and 900 rpm for 3 h. The solid was then collected by centrifugation at 3000 rpm and dried at 80 °C for 6 h to obtain core-structured DASA dendritic polymer microspheres. Example 3

[0045] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink includes the following steps:

[0046] Step a: Disperse 200g of core-shell composite particles, 10g of polyvinylpyrrolidone, 2g of butanethiol, 200g of isopropanol, 50g of water, and 2g of BOK-B-100 evenly using a high-speed disperser, then grind them in a grinder until the particle size is less than 10μm, and then sonicate them at 50kHz for 10min to obtain anti-counterfeiting digital invisible ink.

[0047] Step b: Print the anti-counterfeiting digital invisible ink obtained in step a onto the label, and dry it at 90℃ for 2 hours to obtain an anti-counterfeiting label with invisible printed content; the printed content of the anti-counterfeiting label will turn purple after heating.

[0048] The preparation method of the core-shell composite particles includes the following steps:

[0049] Step 1: Mix 30g of 1,3-dimethylbarbituric acid, 10g of furfural, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then collect the precipitate, dissolve it in dichloromethane, and extract with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 30g of compound 1, 10g of diethylamine, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then remove the solvent using a rotary evaporator to obtain DASA. Add 100g of PAMAM dendritic polymer and 30g of DASA to 450g of tetrahydrofuran and mix thoroughly. Then react at 80℃ and 900rpm for 3h. Then centrifuge at 3000rpm, collect the solid, and dry at 80℃ for 6h to obtain core-structured DASA dendritic polymer microspheres.

[0050] Step 2: Mix 30g of silica with 80g of 10wt% HCl and stir for 2h. Then centrifuge at 3000rpm and collect the solid. Wash the solid with water until the supernatant is neutral. Dry the washed solid at 80℃ for 6h to obtain activated silica. Mix 30g of activated silica with 80g of ethanol evenly, add 5g of ammonia and 5g of trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane, react at 60℃ and 900rpm for 24h, then centrifuge at 3000rpm and collect the solid. Wash the solid with ethanol until the supernatant is neutral. Dry the washed solid at 80℃ for 6h to obtain modified silica.

[0051] Step 3: Mix 50g of modified silica evenly in 300g of tetrahydrofuran, then add 80g of core-structured DASA dendritic polymer microspheres, react at 40℃ and 900rpm for 3h, then centrifuge at 3000rpm, collect the solid, and dry at 70℃ for 6h to obtain composite modified silica, i.e., core-shell composite particles. Example 4

[0052] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink differs from Example 2 in that the preparation method of the core-shell composite particles includes the following steps:

[0053] Step 1: Mix 30g of 1,3-dimethylbarbituric acid, 10g of furfural, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then collect the precipitate, dissolve it in dichloromethane, and extract with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 30g of compound 1, 10g of diethylamine, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then remove the solvent using a rotary evaporator to obtain DASA. Add 100g of PAMAM dendritic polymer and 30g of DASA to 450g of tetrahydrofuran and mix thoroughly. Then react at 80℃ and 900rpm for 3h. Centrifuge at 3000rpm, collect the solid, and dry at 80℃ for 6h to obtain core-structured DASA dendritic polymer microspheres.

[0054] Step 2: Mix 30g of silica with 80g of 10wt% HCl and stir for 2 hours. Then centrifuge at 3000rpm and collect the solid. Wash the solid with water until the supernatant is neutral. Dry the washed solid at 80℃ for 6 hours to obtain activated silica. Mix 30g of activated silica with 80g of ethanol evenly, add 5g of ammonia and 5g of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, react at 60℃ and 900rpm for 24 hours, then centrifuge at 3000rpm and collect the solid. Wash the solid with ethanol until the supernatant is neutral. Dry the washed solid at 80℃ for 6 hours to obtain modified silica.

[0055] Step 3: Mix 50g of modified silica evenly in 300g of tetrahydrofuran, then add 80g of core-structured DASA dendritic polymer microspheres, react at 40℃ and 900rpm for 3h, then centrifuge at 3000rpm, collect the solid, and dry at 70℃ for 6h to obtain composite modified silica, i.e., core-shell composite particles. Example 5

[0056] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink differs from Example 2 in that the preparation method of the core-shell composite particles includes the following steps:

[0057] Step 1: Mix 30g of 1,3-dimethylbarbituric acid, 10g of furfural, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then collect the precipitate, dissolve it in dichloromethane, and extract with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 30g of compound 1, 10g of diethylamine, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then remove the solvent using a rotary evaporator to obtain DASA. Add 100g of PAMAM dendritic polymer and 30g of DASA to 450g of tetrahydrofuran and mix thoroughly. Then react at 80℃ and 900rpm for 3h. Then centrifuge at 3000rpm, collect the solid, and dry at 80℃ for 6h to obtain core-structured DASA dendritic polymer microspheres.

[0058] Step 2: Mix 30g of silica with 80g of 10wt% HCl and stir for 2 hours. Then centrifuge at 3000rpm and collect the solid. Wash the solid with water until the supernatant is neutral. Dry the washed solid at 80℃ for 6 hours to obtain activated silica. Mix 30g of activated silica with 80g of ethanol evenly, add 5g of ammonia and 5g of γ-mercaptopropyltrimethoxysilane, and react at 60℃ and 900rpm for 24 hours. Then centrifuge at 3000rpm and collect the solid. Wash the solid with ethanol until the supernatant is neutral. Dry the washed solid at 80℃ for 6 hours to obtain modified silica.

[0059] Step 3: Mix 50g of modified silica evenly in 300g of tetrahydrofuran, then add 80g of core-structured DASA dendritic polymer microspheres, react at 40℃ and 900rpm for 3h, then centrifuge at 3000rpm, collect the solid, and dry at 70℃ for 6h to obtain composite modified silica, i.e., core-shell composite particles. Example 6

[0060] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink differs from Example 2 in that the preparation method of the core-shell composite particles includes the following steps:

[0061] Step 1: Mix 30g of 1,3-dimethylbarbituric acid, 10g of furfural, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then collect the precipitate, dissolve it in dichloromethane, and extract with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 30g of compound 1, 10g of diethylamine, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then remove the solvent using a rotary evaporator to obtain DASA. Add 100g of PAMAM dendritic polymer and 30g of DASA to 450g of tetrahydrofuran and mix thoroughly. Then react at 80℃ and 900rpm for 3h. Centrifuge at 3000rpm, collect the solid, and dry at 80℃ for 6h to obtain core-structured DASA dendritic polymer microspheres.

[0062] Step 2: Mix 30g of silica with 80g of 10wt% HCl and stir for 2h. Then centrifuge at 3000rpm and collect the solid. Wash the solid with water until the supernatant is neutral. Dry the washed solid at 80℃ for 6h to obtain activated silica. Mix 30g of activated silica with 80g of ethanol evenly, add 5g of ammonia and 5g of trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane, react at 60℃ and 900rpm for 24h, then centrifuge at 3000rpm and collect the solid. Wash the solid with ethanol until the supernatant is neutral. Dry the washed solid at 80℃ for 6h to obtain modified silica.

[0063] Step 3: Mix 50g of modified silica evenly with 300g of tetrahydrofuran, then add 80g of core-structured DASA dendritic polymer microspheres, react at 40℃ and 900rpm for 3h, then centrifuge at 3000rpm, collect the solid, and dry at 80℃ for 6h to obtain composite modified silica; mix 25g of composite modified silica and 300g of isopropanol evenly, then add 25g of phenolic resin, react at 100℃ and 900rpm for 3h, cool to room temperature, then centrifuge at 3000rpm, collect the solid, and dry the solid at 80℃ for 6h to obtain core-shell composite particles. Comparative Example 1

[0064] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink differs from Example 2 in that the preparation method of the core-shell composite particles includes the following steps:

[0065] Step 1: Mix 30g of 1,3-dimethylbarbituric acid, 10g of furfural, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then collect the precipitate, dissolve it in dichloromethane, and extract with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 30g of compound 1, 10g of diethylamine, and 200g of water thoroughly and react at 30℃ and 900rpm for 2h. Then remove the solvent using a rotary evaporator to obtain DASA. Add 100g of PAMAM dendritic polymer and 30g of DASA to 450g of tetrahydrofuran and mix thoroughly. Then react at 80℃ and 900rpm for 3h. Centrifuge at 3000rpm, collect the solid, and dry at 80℃ for 6h to obtain core-structured DASA dendritic polymer microspheres.

[0066] Step 2: Mix 50g of silica evenly with 300g of tetrahydrofuran, then add 80g of core-structured DASA dendritic polymer microspheres, react at 40℃ and 900rpm for 3h, then centrifuge at 3000rpm, collect the solid, and dry at 70℃ for 6h to obtain core-shell composite particles. Comparative Example 2

[0067] A method for preparing an anti-counterfeiting label using anti-counterfeiting digital invisible ink differs from Example 2 in that the preparation method of the core-shell composite particles includes the following steps:

[0068] Step 1: Mix 30g of 1,3-dimethylbarbituric acid, 10g of furfural, and 200g of water thoroughly. React at 30℃ and 800-1000rpm for 1-3h. Collect the precipitate, dissolve it in dichloromethane, and extract with water and saturated sodium chloride. Collect the organic phase and remove the solvent using a rotary evaporator to obtain compound 1. Mix 1-5 parts of compound 1, 0.1-1.5 parts of diethylamine, and 10-30 parts of water thoroughly. React at 20-40℃ and 800-1000rpm for 1-3h. Remove the solvent using a rotary evaporator to obtain DASA. Add 100g of PAMAM dendritic polymer and 30g of DASA to 450g of tetrahydrofuran and mix thoroughly. React at 80℃ and 900rpm for 3h. Centrifuge at 3000rpm, collect the solid, and dry at 80℃ for 6h to obtain core-structured DASA dendritic polymer microspheres.

[0069] Step 2: Mix 50g of phenolic resin and 300g of tetrahydrofuran evenly, then add 80g of core-structured DASA dendritic polymer microspheres. React at 40℃ and 900rpm for 3h, then centrifuge at 3000rpm, collect the solid, and dry at 70℃ for 6h to obtain core-shell composite particles. Test Example 1

[0070] Stability test

[0071] 100 mL (V1) of the anti-counterfeiting digital invisible inks prepared in Examples 1-6 and Comparative Examples 1-2 were taken as test samples and placed at 42±1℃ for 21 days. The sedimentation of the ink in each test sample was observed, and the volume of non-settled ink (V2) was recorded. The ink sedimentation rate (S) was calculated based on the change in ink sedimentation volume. The smaller the sedimentation rate, the better the stability of the ink. The formula for calculating the ink sedimentation rate is shown below:

[0072] S = (V1 - V2) / V1 × 100%;

[0073] In the formula, V1 is the initial volume in mL; V2 is the unsettled volume in mL; S is the settling rate in %. The results are shown in Table 1.

[0074] Table 1 Settlement Rate

[0075]

[0076] By comparing Examples 1-6 and Comparative Examples 1-2, it can be found that the sedimentation rates of Examples 2-6 and Comparative Examples 1-2 are significantly lower than those of Example 1, with Example 6 having the lowest sedimentation rate of 0.99%. The reason for this may be that the core-shell composite particles added in Example 6 have better dispersibility and stability.

[0077] A comparison of Examples 2-5 reveals that the sedimentation rate of Example 3 is lower than that of Examples 4 and 5. This may be because Example 2 uses DASA dendritic polymer microspheres, while Example 3 uses β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane to modify silica, resulting in modified silica. The silica modified by β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane can undergo ring-opening reactions with the hydroxyl or amino groups in the DASA dendritic polymer microspheres and the polymer, forming covalent bonds and enhancing the interaction between the polymer and silica, thereby improving the system's stability. Examples 4 and 5 use N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane, which contain amino and mercapto groups respectively. These can form hydrogen bonds or coordinate bonds with the hydroxyl groups on the silica surface, enhancing the interaction between silica and the polymer and also improving the system's stability. Although these methods improve stability, the effect is less pronounced than in Example 3.

[0078] A comparison of Examples 2-3, Example 6, and Comparative Examples 1-2 reveals that, compared to Example 2 (which uses DASA dendritic polymer microspheres with a core structure to prepare invisible ink), Comparative Example 1 (which uses DASA dendritic polymer microspheres with a core structure and silica to prepare core-shell composite particles), and Comparative Example 2 (which uses DASA dendritic polymer microspheres with a core structure and phenolic resin to prepare core-shell composite particles), Example 6, which uses DASA dendritic polymer microspheres with a core structure, modified silica, and phenolic resin to prepare invisible ink with core-shell composite particles, exhibits the lowest sedimentation rate. The stability was 0.99%, significantly higher than Comparative Example 1 and Comparative Example 2. The reason for this may be that the modified silica and phenolic resin may form a physical network structure in the core-shell composite particles, which can effectively limit the aggregation and sedimentation of particles. The cross-linking points in the network structure can capture and fix the particles, reducing their free movement in the ink. At the same time, it can improve the overall chemical stability of the core-shell composite particles and reduce degradation during storage and use, thereby improving the stability of the ink. Adding silica or phenolic resin alone can improve the stability of the ink to a certain extent, but the effect is not as good as in Example 6. Test Example 2

[0079] Ink color development temperature and time test

[0080] The anti-counterfeiting digital invisible inks prepared in Examples 1-3, Example 6, and Comparative Examples 1-2 were printed on labels, and the prepared labels were recorded as Group 1-3, Group 5, and Comparative Examples 1-2, respectively. Then, the labels of each group were heated, and the color development temperature and color development time of the labels were tested. Among them, the color development temperature refers to the temperature at which the label color changes, and the color development time refers to the time required for the label to develop color. The specific test results are shown in Table 2 below.

[0081] Ink acid and alkali resistance test

[0082] The anti-counterfeiting digital invisible inks prepared in Examples 1-3, Example 6, and Comparative Examples 1-2 were used to prepare ink samples according to the standard GB / T18724-2008 "Printing Technology: Determination of Resistance to Various Reagents of Printed Matter and Printing Inks". These samples were recorded as groups 1-3, 6, and 1-2. The acid and alkali resistance of each group of inks was tested according to the standard method of GB / T18724-2008 "Printing Technology: Determination of Resistance to Various Reagents of Printed Matter and Printing Inks". The samples were considered qualified if there was no peeling, bubbling, or discoloration. The specific test results are shown in Table 2 below.

[0083] Table 2

[0084]

[0085] A comparison of Examples 1-3, Example 6, and Comparative Examples 1-2 reveals that, compared to Example 2 (preparing invisible ink by introducing core-structured DASA dendritic polymer microspheres), Comparative Example 1 (preparing ink with core-shell composite particles by introducing core-structured DASA dendritic polymer microspheres and silica), and Comparative Example 2 (preparing ink with core-shell composite particles by introducing core-structured DASA dendritic polymer microspheres and phenolic resin), Example 6, which simultaneously introduces core-structured DASA dendritic polymer microspheres with modified silica and phenolic resin to prepare invisible ink with core-shell composite particles, demonstrates superior performance. The ink developed at a temperature of 210℃ and a time of 35 seconds, exhibiting satisfactory acid and alkali resistance. The reason for this is likely due to the simultaneous addition of modified silica and phenolic resin during the preparation of the core-shell composite particles. The modified silica and phenolic resin may cross-link with the phenolic resin, forming a physical network structure within the core-shell particles and simultaneously creating a protective layer on the surface. This protective layer slows down the heat transfer to the DASA molecules, thus requiring a higher temperature and longer development time for color development. Simultaneously, this protective layer reduces the impact of external acid and alkali properties on the core, improving acid and alkali resistance. The core-shell structures of Comparative Examples 1-2 also formed a protective layer to reduce the impact of external acid and alkali properties on the core, but their performance was weaker than that of Example 6 when the color development temperature and time were increased.

Claims

1. A method for preparing anti-counterfeiting digital invisible ink, characterized in that, The process includes the following steps, by weight: 10-40 parts of invisible anti-counterfeiting agent, 0.3-3 parts of polymer, 0.05-1 part of stabilizer, 5-30 parts of solvent, and 0.05-5 parts of additives are dispersed evenly in a high-speed disperser, then ground in a grinding mill, and then ultrasonically treated to obtain anti-counterfeiting digital invisible ink. The invisible anti-counterfeiting agent is selected from one of the following: core-structured DASA dendritic polymer microspheres and core-shell composite particles. The preparation method of the core-structured DASA dendritic polymer microspheres includes the following steps, by weight: 1-5 parts of 1,3-dimethylbarbituric acid, 0.1-1.5 parts of furfural, and 10-30 parts of water are mixed evenly and reacted at 20-40℃ and 800-1000 rpm for 1-3 hours. The precipitate is then collected, dissolved in dichloromethane, extracted with water and saturated sodium chloride, and the organic phase is collected. The solvent is removed by rotary evaporation to obtain compound 1. 1-5 parts of compound 1, 0.1-1.5 parts of diethylamine, and 10-30 parts of water are then mixed... Mix thoroughly and react at 20-40℃ and 800-1000rpm for 1-3h. Then remove the solvent using a rotary evaporator to obtain DASA. Add 5-15 parts of PAMAM dendritic polymer and 1-5 parts of DASA to 30-60 parts of tetrahydrofuran and mix thoroughly. Then react at 60-100℃ and 800-1000rpm for 2-4h. Then centrifuge at 2000-4000rpm, collect the solid, and dry at 60-100℃ for 4-8h to obtain core-structured DASA dendritic polymer microspheres. The preparation method of the core-shell composite particles includes the following steps, in parts by weight: Mix 1-5 parts of silica with 5-10 parts of 5-15 wt% HCl and stir for 1-3 hours. Then centrifuge at 2000-4000 rpm, collect the solid, wash the solid with water until the supernatant is neutral, and dry the washed solid at 60-100℃ for 4-8 hours to obtain activated silica. Mix 1-5 parts of activated silica with 5-10 parts of ethanol evenly, add 0.1-1 parts of ammonia and 0.1-1 parts of silane coupling agent, react at 50-70℃ and 800-1000 rpm for 16-48 hours, then centrifuge at 2000-4000 rpm, collect the solid, wash the solid with ethanol until the supernatant is neutral, and dry the washed solid at 60-100℃ for 4-8 hours to obtain modified silica. Mix 1-10 parts of modified silica with 10-50 parts of tetrahydrofuran until homogeneous, then add 5-10 parts of core-structured DASA dendritic polymer microspheres. React at 20-60℃ and 800-1000rpm for 2-4 hours, then centrifuge at 2000-4000rpm, collect the solid, and dry at 60-100℃ for 4-8 hours to obtain composite modified silica, i.e., core-shell composite particles; or, mix 1-10 parts of modified silica with 1-50 parts of tetrahydrofuran until homogeneous, then add 5-10 parts of DASA dendritic polymer microspheres. React at 0℃ and 800-1000 rpm for 2-4 hours, then centrifuge at 2000-4000 rpm to collect the solid, and dry at 60-100℃ for 4-8 hours to obtain composite modified silica; mix 1-5 parts of composite modified silica and 1-50 parts of isopropanol evenly, then add 1-5 parts of phenolic resin, and react at 80-120℃ and 800-1000 rpm for 2-4 hours, cool to room temperature, then centrifuge at 2000-4000 rpm to collect the solid, and dry the solid at 60-100℃ for 4-8 hours to obtain core-shell composite particles.

2. The method for preparing anti-counterfeiting digital invisible ink as described in claim 1, characterized in that, The polymer is selected from at least one of polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene, polyacrylamide, polyacrylic acid, polylactic acid, polyglycolic acid, polylactic-glycolic acid copolymer, polycaprolactone, polyvinyl acetate, polydimethylsiloxane, and polyurethane; the stabilizer is selected from at least one of butanethiol, nonanethiol, dodecanethiol, hexadecanethiol, mercaptoacetic acid, mercaptopropionic acid, 4-mercaptobutyric acid, 8-mercaptoheptanoic acid, 1-mercapto-2-propanone, 4-mercapto-2-pentanone, 3-mercapto-2-butanone, mercaptoethylamine, 3-mercapto-1-propanamine, and 3-mercapto-N-nonylpropionamide; the solvent is selected from at least one of... The additive is selected from at least one of the following: water, methanol, ethanol, isopropanol, n-propanol, ethylene glycol, propylene glycol, glycerol, n-butanol, n-octanol, n-nonanol, n-decanol, N-methylpyrrolidone, a mixture of diesters, dimethylformamide, diacetone alcohol, 1,3-dimethylimidazolinone, dimethyl sulfoxide, diethylene glycol monobutyl ether, diethylene glycol acetate, ethylene glycol carbonate, propylene glycol carbonate, 1,4-butyrolactone, toluene, chlorobenzene, dichloromethane, and tetrahydrofuran; the additive is selected from at least one of the perfluorinated surfactants BOK-B-100, BOK-B-101, BOK-B-102, and BOK-B-103.

3. The method for preparing anti-counterfeiting digital invisible ink as described in claim 1, characterized in that: The silane coupling agent is selected from at least one of trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane.

4. Anti-counterfeiting digital invisible ink, prepared by the method described in any one of claims 1-3.

5. The application of the anti-counterfeiting digital invisible ink as described in claim 4 on anti-counterfeiting labels, characterized in that: The anti-counterfeiting label is prepared by printing anti-counterfeiting digital invisible ink on the label and drying it at a temperature of 80-100℃ for 1-3 hours. The printed content is invisible at this time, and the printed content turns purple after heating.

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