A kind of silk screen fluorescent carbon dot invisible anti-counterfeiting ink and preparation method thereof

Abstract

The present invention relates to a screen fluorescent carbon dot invisible anti-counterfeiting ink and a preparation method thereof, and belongs to the field of anti-counterfeiting technology. The ink comprises the following components: green carbon quantum dots, acrylic resin, rosin resin, biomass dye, ethanol, defoamer and dispersant. The ink preparation process of the present invention is simple, suitable for screen printing, colorless under sunlight, and emits bright green under ultraviolet light. It also has the advantages of good adaptability to screen printing and green and environmentally friendly materials, and can be used for invisible ink, information identification and anti-counterfeiting.

Description

Technical Field

[0001] The invention belongs to the technical field of anti-counterfeiting, and relates to a silk screen fluorescent carbon dot invisible anti-counterfeiting ink and a preparation method thereof. Background Art

[0002] Although traditional anti-counterfeiting methods such as laser holography, barcodes and RFID are effective, they still pose the risk of being counterfeited. Therefore, it is particularly urgent to develop a new, efficient and difficult-to-copy anti-counterfeiting technology.

[0003] In recent years, carbon quantum dots, as an emerging nanomaterial, have attracted widespread attention in the field of anti-counterfeiting due to their unique optical properties and environmental friendliness. Carbon quantum dots have the characteristics of small size, large specific surface area, and adjustable fluorescence properties. They can emit strong fluorescence under the excitation of ultraviolet light, but are almost invisible under natural light, which provides an ideal technical basis for invisible anti-counterfeiting.

[0004] However, conventional carbon quantum dot inks face some challenges in practical applications. First, the dispersion and stability of carbon quantum dots are insufficient, resulting in poor printing adaptability of the ink and difficulty in uniformly adhering to various substrates. Second, the durability of carbon quantum dot inks needs to be improved to meet the needs of long-term storage and use.

[0005] The present invention proposes a screen fluorescent carbon dot invisible anti-counterfeiting ink. The ink uses specially synthesized carbon quantum dots as fluorescent materials, and achieves efficient dispersion and stability of the carbon quantum dots by optimizing the formula. The ink of the present invention is perfectly compatible with the screen printing process, and can print invisible anti-counterfeiting patterns with high resolution and high contrast on the surface of products of various materials.

[0006] The screen fluorescent carbon dot invisible anti-counterfeiting ink of the present invention not only improves the concealment and reliability of anti-counterfeiting technology, but also reduces production costs, simplifies the printing process, and provides strong support for technological innovation and upgrading of the anti-counterfeiting industry. With the further development of technology and the promotion of application, the present invention is expected to become an important representative of the new generation of anti-counterfeiting technology, and contribute to combating counterfeit and shoddy goods and protecting the rights and interests of consumers. Summary of the invention

[0007] The present invention provides a screen fluorescent carbon dot invisible anti-counterfeiting ink and a preparation method thereof. The fluorescent anti-counterfeiting ink is developed for screen printing, which is a simple and feasible printing method and has the characteristics of general anti-counterfeiting inks, such as excellent anti-counterfeiting performance, simple operation, low cost, good concealment, and convenient inspection. It is mainly used as one of the raw materials for the ink formula used for screen printing patterning.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A silk screen fluorescent carbon dot invisible anti-counterfeiting ink, characterized in that it comprises the following components calculated by weight:

[0010] Green carbon quantum dots 0.01~0.1 parts

[0011] 35-50 parts of acrylic resin

[0012] 35-50 parts of rosin resin

[0013] Biomass dye 0.01~0.1 parts.

[0014] As a preferred technical solution of the present invention, the following components are included, calculated by weight:

[0015] Green carbon quantum dots 0.02~0.05 parts

[0016] Acrylic resin 40-45 parts

[0017] 40-45 parts of rosin resin

[0018] Biomass dye 0.02-0.05 parts.

[0019] As a preferred technical solution of the present invention, the following components are also included by weight:

[0020] 5-30 parts of ethanol

[0021] Defoaming agent 0.1~1 part

[0022] Dispersant 5 to 15 parts.

[0023] As a preferred technical solution of the present invention, the following components are also included by weight:

[0024] 15-25 parts of ethanol

[0025] Defoaming agent 0.3~0.7 parts

[0026] Dispersant 8-12 parts.

[0027] As a preferred technical solution of the present invention, the green carbon quantum dots are prepared by the following steps:

[0028] W1. Weigh 0.5g of o-phenylenediamine and dissolve it in 20ml of butyl acrylate, stir and dissolve it at 25°C, put it into a 50mL reactor with a polytetrafluoroethylene liner, react at 180°C for 12h, cool it to room temperature and take it out to obtain a synthesized CDs solution;

[0029] W2. Dry at 50°C to obtain black powder, dissolve the black powder in anhydrous ethanol, and finally obtain green carbon dot ethanol solution.

[0030] As a preferred technical solution of the present invention, the biomass dye is composed of 4 to 10 parts of indigo dye and 10 parts of shikonin dye calculated by weight.

[0031] As a preferred technical solution of the present invention, the indigo dye is prepared by the following steps:

[0032] X1. Soak the indigo leaves in water, add lime, let it stand for 5 to 10 minutes, remove the supernatant to obtain indigo paste, boil it, add acid to neutralize it, obtain indigo extract, filter and wash it 3 to 5 times, filter press, and dry it to obtain dry indigo.

[0033] As a preferred technical solution of the present invention, the acid addition and neutralization comprises the following steps:

[0034] Y1. Mix indigo paste: water = 500g: 4500mL and place in a constant temperature heated magnetic stirrer at 80℃ and stir for 1h, then slowly add 20% hydrochloric acid solution until the pH value is 3-4, continue stirring and react for 30min, centrifuge, wash the lower layer of solid with boiling water until neutral, and then dry in a 60℃ oven, then grind and sieve to obtain indigo extract.

[0035] As a preferred technical solution of the present invention, the shikonin dye is prepared by the following steps:

[0036] Z1. After crushing the lithospermum officinale, put it into a sealed container, pour in 95% ethanol, soak for 24 hours, pour out the solution, and then soak in 95% ethanol for 6 hours, repeat twice, and finally mix all the solutions and filter to obtain shikonin dye solution.

[0037] A silk screen fluorescent carbon dot invisible anti-counterfeiting ink prepared according to the preparation method.

[0038] Beneficial effects of the present invention:

[0039] (1) The screen fluorescent carbon dot invisible anti-counterfeiting ink of the present invention has a large proportion of rosin resin, which replaces the industrial-grade connecting material to a certain extent. The use of biomass resin is more environmentally friendly and the raw materials are more economical. The dyes used are also extracted from plants and have a wide range of sources and can be obtained in large quantities.

[0040] (2) The carbon dots prepared at present appear yellow under sunlight and green under ultraviolet excitation. The present invention uses indigo and shikonin to correct the color of the carbon dot solution under sunlight using the principle of color light subtraction, so that the color of the ink under sunlight is similar to that of the paper base, L*=92.1, a*=0.25, b*=0.55, and is completely different from the color under ultraviolet light, L*=75, a*=-34, b*=-9, thereby effectively achieving the purpose of anti-counterfeiting.

[0041] (3) The screen fluorescent carbon dot invisible anti-counterfeiting ink of the present invention has a simple carbon dot preparation method, the synthesized ink has good printability, and the dye is as thin as 0.05-0.45 microns, which improves the fineness of the ink to prevent clogging of the mesh. The printed ink film has good wear resistance and glossiness, and can be mass-produced.

[0042] (4) The surface of the g-CDs of the present invention contains a large number of amine groups, carboxyl groups and oxygen-containing functional groups, which can enhance the interaction between g-CDs and the paper-based surface by interacting with the hydroxyl groups on the surface of the paper-based fibers. The dye used is weakly acidic, similar to the carbon quantum dot solution, and there is no chemical reaction between the two, and they can exist stably; and the configured dye solution has a certain degree of transparency, which can prevent the fluorescent color of the carbon dots from being covered. The dye is an organic compound that can directly dye the paper-based fibers, and its molecules and cellulose molecules form more than two hydrogen bonds and van der Waals forces to color the fibers, thereby obtaining a firm color on the paper base.

[0043] (5) The color of the ink in the present invention is divided into two parts: one is the color of the carbon quantum dots themselves and the color of the dye under sunlight, which is light gray due to the principle of color light subtraction. The principle is as follows: the emission spectrum band of the carbon quantum dot solution itself corresponds to 550nm, and the reflectivity is 20%-30%. The emission spectrum band of the dye solution corresponds to 450nm and 400nm. After the dye and the carbon quantum dots are fused, the effect of gray light is achieved; the second part is the corresponding wavelength emitted by the carbon quantum dots under ultraviolet light. Transparency is an indicator related to the combined influence of the color and turbidity of the solution. When the mass fraction of the dye reaches less than 1%, the ink has light transmittance, which can achieve the purpose of not hindering the luminescence of the carbon dots and having good light transmittance under sunlight.

[0044] (6) The viscosity of the fluorescent anti-counterfeiting ink based on carbon quantum dots of the present invention is about 4000-10000 mPa·s, and the surface tension is 39 mN / m. It can be screen-printed on various substrates such as white cardboard, kraft paper, coated paper, PET film, etc. When there is no ultraviolet light source, it is colorless or nearly colorless. Under the irradiation of a specific ultraviolet light source, it appears green, has good stability, and can achieve a good anti-counterfeiting effect.

[0045] (7) The ink of the present invention is a transparent light yellow liquid. After being sprayed onto a substrate, the color is relatively light. After being irradiated by ultraviolet light, it shows a brilliant green color. It has a strong concealment property and can effectively prevent copying and counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0047] Figure 1 It is the indigo structural formula;

[0048] Figure 2 is the structural formula of shikonin;

[0049] Figure 3 These are the pictures before ink coloring, the left picture is under UV, and the right picture is under sunlight;

[0050] Figure 4 The pictures after ink toning, the left picture is under UV, the right picture is under sunlight;

[0051] Figure 5 The effect of screen printing on bond paper after ink color matching, left side is under UV, right side is under daylight. DETAILED DESCRIPTION

[0052] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0053] The rosin resin used in the present invention is purchased from Guangdong Kemao Forest Products Co., Ltd., the model is Y308, and the viscosity value is 3000-8000 centipoise.

[0054] The present invention adopts W358A resin as a connecting material of fluorescent anti-counterfeiting ink, the main component of W358A resin is polyacrylate, and the solvent is 15% by mass of n-butanol. Since the resin does not contain toxic substances such as formaldehyde, nitrosamines, polycyclic aromatic hydrocarbons, radioactive substances, etc., and complies with EU RoHS Directive 2011 / 65 / EC, it is an environmentally friendly resin. W358A resin is relatively viscous, and the glossiness of the printed product is high and has certain wear resistance. Other composite resins contain organic matrix, colorant, fluorescent brightener, which have a greater impact on the fluorescence intensity and color of fluorescent carbon dots, so a connecting material with a single component needs to be used.

[0055] The W358A resin used in the present invention can promote the solid-state luminescence of carbon quantum dots, increase the distance between carbon dots, reduce fluorescence quenching caused by collision, and simultaneously form a cross-linked supramolecular skeleton with the carbon quantum dots to increase the distance between the carbon quantum dots in space.

[0056] The dispersant used in the present invention is water-based and has a small molecular weight. It is purchased from Foshan Banyue Chemical Co., Ltd. and can be dissolved in ethanol or deionized water after sufficient stirring to form a stable solution. The dispersant with anions can disperse the dye particles in the dye solution, so that the dye solution can form a relatively stable dispersion system. The organosilicon defoamer is purchased from Foshan Banyue Chemical Co., Ltd., model LY-198, and can be dissolved in ethanol or deionized water to form a stable solution.

[0057] Example

[0058] A certain volume of CDs solution was measured and added to W358A resin, and the following mass fractions of dispersant, defoamer and biomass dye were added. The solution was placed in a magnetic stirrer and stirred for 20 minutes to mix the solution evenly, thereby obtaining a silk screen fluorescent carbon dot invisible anti-counterfeiting ink.

[0059] Table 1 Raw materials of the embodiment

[0060]

[0061]

[0062] Table 2 L*, a*, b* values ​​of carbon dot solution under sunlight

[0063] L* a* b* g-CDs 94.9 -1.1 20

[0064] Table 3 L*, a*, b* values ​​of carbon dot solution under sunlight after color correction

[0065] Color combination Dye dosage L* a* b* g-CDs Indigo 0.033, Violet 0.115 92.1 0.25 0.55 g-CDs Indigo 0.036, Violet 0.236 92.2 0.18 -0.50

[0066] Table 4 Changes in dye ratio with pH value

[0067]

[0068]

[0069] Table 5 Color characteristics of shikonin dyed silk fabrics

[0070] pH L* a* b* C* λmax / nm K / S value 3.0 66.73 9.08 4.78 10.26 500 0.697 4.0 60.74 4.66 -0.14 4.66 560 0.956 5.0 61.51 3.93 -0.81 4.01 560 0.906 6.0 58.97 4.77 -1.53 5.01 570 1.101 7.0 62.54 0.80 -2.45 2.58 580 0.889 8.0 62.21 1.89 -1.71 2.55 580 0.892 9.0 56.51 1.64 -3.30 3.68 580 1.364 10.0 58.09 1.62 -2.15 2.70 580 1.201

[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A silk screen fluorescent carbon dot invisible anti-counterfeiting ink, characterized in that: Calculated by mass, it contains the following components: Green carbon quantum dots 0.01~0.1 parts Acrylic resin 35~50 parts 35~50 parts of rosin resin Biomass dye 0.01~0.1 part; Calculated by mass, it also contains the following components: Ethanol 5~30 parts Defoaming agent 0.1~1 part Dispersant 5-15 parts; The green carbon quantum dots are prepared by the following steps: W1. Weigh 0.5g of o-phenylenediamine and dissolve it in 20ml of butyl acrylate, stir and dissolve it at 25℃, put it into a 50mL reactor with a polytetrafluoroethylene liner, react it at 180℃ for 12h, cool it to room temperature and take it out to obtain the synthesized CDs solution; W2. Dry at 50°C to obtain a black powder, dissolve the black powder in anhydrous ethanol, and finally obtain a green carbon dot ethanol solution; Calculated by weight, the biomass dye consists of 4 to 10 parts of indigo dye and 10 parts of shikonin dye.

2. The screen fluorescent carbon dot invisible anti-counterfeiting ink according to claim 1, characterized in that: Calculated by mass, it contains the following components: Green carbon quantum dots 0.02~0.05 parts Acrylic resin 40~45 parts Rosin resin 40~45 parts Biomass dye 0.02~0.05 parts.

3. The screen fluorescent carbon dot invisible anti-counterfeiting ink according to claim 1, characterized in that: Calculated by mass, it also contains the following components: 15~25 parts of ethanol Defoaming agent 0.3~0.7 parts Dispersant 8~12 parts.

4. The screen fluorescent carbon dot invisible anti-counterfeiting ink according to claim 1, characterized in that: The indigo dye is prepared by the following steps: X1. Soak the indigo leaves in water, add lime, let it stand for 5 to 10 minutes, remove the supernatant to obtain indigo paste, boil it, add acid to neutralize it, obtain indigo extract, filter and wash it 3 to 5 times, filter press, and dry it to obtain dry indigo.

5. The screen fluorescent carbon dot invisible anti-counterfeiting ink according to claim 4, characterized in that: The acid addition and neutralization comprises the following steps: Y1. Mix indigo paste and water at a ratio of 500 g to 4500 mL and place in a constant temperature heated magnetic stirrer at 80°C and stir for 1 hour. Then slowly add 20% hydrochloric acid solution until the pH value is 3-4. Continue stirring and reacting for 30 minutes. Centrifuge. Wash the lower layer of solid with boiling water until it is neutral and dry in a 60°C oven. Then grind and sieve to obtain indigo extract.

6. The screen fluorescent carbon dot invisible anti-counterfeiting ink according to claim 1, characterized in that: The shikonin dye is prepared by the following steps: Z1. Crush the lithospermum officinale, put it into a sealed container, pour in 95% ethanol, soak for 24 hours, pour out the solution, and then soak in 95% ethanol for 6 hours. Repeat twice, and finally mix and filter all the solutions to obtain shikonin dye solution.

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