Pressure-sensitive color-changing anti-forgery ink and preparation method thereof

Abstract

The invention discloses pressure-sensitive color-changing anti-forgery ink and a preparation method thereof. The ink is prepared from dye-loaded aerogel particles, four-needle zinc oxide whiskers, water-based acrylic resin, a color developing agent, porous silicon dioxide and a dispersing agent. The stress concentration effect of the four-needle zinc oxide whiskers triggers the aerogel to break and release the dye, so that low-pressure instantaneous color development is realized. Industrial by-products and building material-grade raw materials are adopted, the production cost is low, and mass production can be achieved without complex equipment. The ink trigger pressure is as low as 0.3 MPa, the developing time is less than or equal to 3 seconds, the background color delta E is less than or equal to 0.8, and the method is suitable for public anti-counterfeiting scenes such as food packaging and daily chemical labels.

Description

Technical Field

[0001] The invention relates to the technical field of inks, and specifically provides a pressure-sensitive color-changing anti-counterfeiting ink and a preparation method thereof. Background Art

[0002] Pressure-sensitive color-changing anti-counterfeiting inks, which achieve anti-counterfeiting functionality by triggering color changes through mechanical pressure, are widely used in areas such as product packaging, bills and documents, and high-end consumer goods. Their core principle is to exploit the chemical or physical changes in the material under pressure, causing the ink to transform from its initial state to a visible color, thereby enabling rapid anti-counterfeiting verification. Currently, technological development of this type of ink focuses on improving color change sensitivity, reducing trigger pressure, and simplifying production processes to meet the needs of convenient use in different scenarios.

[0003] Existing pressure-sensitive color-changing anti-counterfeiting inks still face many technical bottlenecks in practical applications. On the one hand, to ensure the stability of the anti-counterfeiting function, most inks rely on complex microencapsulation technology, which achieves on-demand color development by isolating the pressure-sensitive dye and the color developer in the capsule. However, this type of technology often requires high-precision coating equipment and strict process conditions, resulting in high production costs and difficulty in meeting the large-scale application needs of mass consumer products. On the other hand, the trigger pressure of traditional inks is generally high, usually requiring the use of tools to apply a pressure of more than 0.8MPa to achieve a noticeable color change. It cannot be verified by simple methods such as light pressure with a finger, which limits its promotion in daily scenarios.

[0004] In addition, the control of the background color of the ink in the prior art is still a prominent problem. Since the pressure-sensitive dye and the developer may react slightly in advance during storage, or the free dye fails to be completely enclosed, the ink will show a darker background color when it is not under pressure, which significantly reduces the contrast before and after the color change, affecting the recognition accuracy of the anti-counterfeiting information. At the same time, the production process of most inks involves complex steps such as the precise dispersion of nanomaterials, high-temperature and high-pressure reactions, which not only have high energy consumption and low efficiency, but also place high demands on production equipment, further restricting the feasibility of its industrial mass production. Therefore, the development of a pressure-sensitive color-changing anti-counterfeiting ink with low cost, simple process, low pressure triggering and light background color has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] In view of this, the present invention proposes a pressure-sensitive color-changing anti-counterfeiting ink and a preparation method thereof.

[0006] The technical solution of the present invention is achieved as follows: The present invention provides a raw material ratio of a pressure-sensitive color-changing anti-counterfeiting ink, which, calculated by weight, comprises: 15-25 parts of dye-loaded aerogel particles, wherein 10-20 wt% of pressure-sensitive dye is adsorbed inside the aerogel particles; 10-18 parts of four-needle zinc oxide whiskers; 50-65 parts of water-based acrylic resin; 5-10 parts of a developer, wherein the developer is immobilized on the surface of the four-needle zinc oxide whisker; 3-8 parts of porous silica, wherein the porous silica has a pore size of 2-5 nm and a specific surface area of ​​>500 m2 / g; Dispersant 0.5-1 part.

[0007] In some embodiments, the dye-loaded aerogel particles are hydrophobic SiO2 aerogels with a particle size of 1-10 μm, and the pressure-sensitive dye adsorbed therein is crystal violet lactone or a fluorane pressure-sensitive dye.

[0008] The hydrophobic SiO2 aerogel, with its nanoscale pores providing a high surface area, can absorb 10-20wt% of pressure-sensitive dye. The aerogel surface is modified with the silane coupling agent KH-550 to form a hydrophobic layer, preventing premature dye release during storage due to moisture absorption, thereby eliminating background color.

[0009] In some embodiments, the surface of the four-needle zinc oxide whisker is modified by a silane coupling agent KH-550, the color developer is bisphenol A, and the color developer is immobilized on the surface of the four-needle zinc oxide whisker through hydrogen bonds.

[0010] The four-needle zinc oxide whiskers act as stress concentrators. Their tip curvature radius is ≤200nm, creating a stress concentration effect under pressure. The localized pressure can reach over three times the external pressure, allowing them to precisely penetrate the aerogel and release the dye. The four-needle zinc oxide whiskers, modified with KH-550, immobilize the color developer, bisphenol A, through hydrogen bonding, ensuring uniform distribution and resistance to dislodging within the ink.

[0011] In some embodiments, the porous silica has an adsorption capacity of free dyes ≥ 100 mg / g, and is used to eliminate the background color of ink.

[0012] Select pore size 2-5nm, specific surface area > 500m 2 / g of mesoporous silica, the adsorption capacity of its microporous structure for free dyes is ≥100mg / g, which can efficiently capture dye molecules that are not adsorbed by aerogel, making the background color ΔE value ≤0.8.

[0013] In some embodiments, the mass ratio of the dye-loaded aerogel particles to the four-needle zinc oxide whiskers is (1.2-2):1.

[0014] A second aspect of the present invention provides a method for preparing the above-mentioned ink, comprising the following steps: (1) The hydrophobic SiO2 aerogel was impregnated in a 10-20 wt% pressure-sensitive dye / ethanol solution, dried at 60°C, and sieved to obtain dye-loaded aerogel particles; (2) Immerse the four-needle zinc oxide whiskers in a 2 wt% KH-550 ethanol solution, treat at 80°C for 1 hour, filter, and then spray with a 10 wt% bisphenol A / acetone solution, filter and dry to obtain the four-needle zinc oxide whiskers with a color developer immobilized on the surface; (3) Mix the water-based acrylic resin with the dispersant, add the four-needle zinc oxide whiskers with a surface-immobilized color developer, dye-loaded aerogel particles, and porous silica in sequence, and stir at 400 rpm for 20 minutes.

[0015] In some embodiments, in step (1), a 200-mesh sieve is used for sieving, and aerogel particles with a particle size of 1-10 μm are retained.

[0016] In some embodiments, in step (2), after spraying the bisphenol A / acetone solution, vacuum drying is performed at 60° C. for 2 hours.

[0017] In some embodiments, in step (3), the stirring temperature is controlled at 25±5° C., and after stirring is completed, the mixture is filtered through a 200-mesh sieve.

[0018] The present invention has the following beneficial effects compared to the prior art: The stress concentration effect of the four-pin zinc oxide whiskers amplifies external pressure by more than three times, reducing the ink trigger pressure to as low as 0.3 MPa. Color development occurs with just a light finger pressure, significantly lower than the 0.8 MPa of traditional microcapsule inks. Once released, the dye quickly diffuses to the developer through the microchannel network created by the aerogel's shattering, resulting in a short color development time, meeting the needs of instant verification.

[0019] The porous silica's microporous structure has an adsorption capacity of ≥100 mg / g for free dyes. Combined with the hydrophobic modification of the aerogel, the background color ΔE value can be controlled below 0.8, far superior to the existing ΔE>15. The resulting color contrast is clearly discernible, making it suitable for high-precision anti-counterfeiting scenarios. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0022] Unless otherwise specified, the methods used in the following examples are conventional methods. The materials, reagents, and instruments used are conventional materials, reagents, and instruments in the art, unless otherwise specified, and can be obtained commercially by those skilled in the art.

[0023] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. In the present specification and claims, range definitions may be combined and / or interchanged, and if not otherwise stated, such ranges include all subranges contained therein.

[0024] Example 1 Raw material preparation Hydrophobic SiO2 aerogel (building material grade, particle size 1-10μm, porosity 90%); Four-needle zinc oxide whiskers (purity 85%, needle length 10-50 μm, tip curvature radius 200 nm); Crystal violet lactone (CVL, technical grade, purity 95%); Bisphenol A (developer, industrial grade); Porous silica (mesopores, pore size 3nm, specific surface area 600m 2 / g); Water-based acrylic resin (solid content 50%); Silane coupling agent KH-550 (industrial grade); OP-10 dispersant (industrial grade).

[0025] 2. Preparation Steps (1) Preparation of dye-loaded aerogel: 100 g of hydrophobic SiO2 aerogel was immersed in 500 g of 15 wt% CVL / ethanol solution, stirred at room temperature for 2 h, dried under reduced pressure at 60 °C to constant weight, and passed through a 200 mesh sieve to obtain dye-loaded aerogel particles (dye loading 15 wt%).

[0026] (2) ZnO-T functionalization: Take 50g ZnO-T and add 500g 2wt% KH-550 ethanol solution, reflux at 80℃ for 1h, filter and spray with 100g 10wt% bisphenol A / acetone solution, and vacuum dry at 60℃ for 2h to obtain ZnO-T with surface-immobilized color developer (bisphenol A loading amount 8mg / g).

[0027] (3) Ink preparation: 550 g of water-based acrylic resin and 5 g of OP-10 were added to a stirring kettle. Under stirring at 25°C and 400 rpm, 150 g of functionalized ZnO-T, 200 g of dye-loaded aerogel, and 50 g of porous silica were added in sequence. The mixture was stirred for 20 min and filtered through a 200-mesh sieve to obtain a pressure-sensitive color-changing anti-counterfeiting ink.

[0028] Example 2 The difference from Example 1 is: The particle size of hydrophobic SiO2 aerogel is controlled to 5 μm (achieved by adjusting the pH of the sol-gel reaction to 4.5); The rest of the ingredients are the same as in the steps.

[0029] Example 3 The difference from Example 1 is: The curvature radius of the ZnO-T tip was adjusted to 100 nm; The rest of the ingredients are the same as in the steps.

[0030] Example 4 The difference from Example 1 is: The amount of porous silica is increased to 80g (accounting for 8 parts); The rest of the ingredients are the same as in the steps.

[0031] Comparative Example 1 The difference from Example 1 is: Differentiating steps (1) Preparation of CVL microcapsules: Oil phase: Dissolve 15g of crystal violet lactone (CVL) and 20g of toluene diisocyanate (TDI) in 50g of cyclohexane and stir until dissolved; Aqueous phase: Dissolve 5 g of polyvinyl alcohol (PVA) in 500 mL of deionized water at 80°C and then cool to 40°C. Emulsification: Add the oil phase to the water phase and stir at 3000 rpm for 30 minutes to form an emulsion (particle size 5-10 μm); Curing: add 5 g of ethylenediamine, stir at 60°C for 4 h, filter, wash and dry to obtain CVL-coated polyurethane microcapsules (containing 15 wt% CVL).

[0032] (2) Ink preparation (direct dispersion of developer): Take 550g of water-based acrylic resin, add 10g of bisphenol A (color developer, 5-10 parts in Comparative Example 1, 10 parts here to enhance the color development effect), and stir at 2000rpm for 30min to disperse the bisphenol A (not fixed, free in the resin); 200 g of the above-mentioned CVL microcapsules, 5 g of OP-10, and 50 g of porous silica were added, and the mixture was stirred at 400 rpm for 20 min to obtain a comparative ink.

[0033] Comparative Example 2 The difference from Example 1 is: The aerogel was eliminated and 30 g of CVL was directly dispersed in the waterborne acrylic resin; The rest of the ingredients are the same as in the steps.

[0034] Comparative Example 3 The difference from Example 1 is: Removal of porous silica; The rest of the ingredients are the same as in the steps.

[0035] Comparative Example 4 The difference from Example 1 is: ZnO-T was not modified with KH-550 and was directly added to the bisphenol A solution (no hydrogen bonding immobilization); The rest of the ingredients are the same as in the steps.

[0036] The performance test of the anti-counterfeiting ink prepared in the above examples and comparative examples includes the following steps: The ink to be tested was evenly printed on a PET substrate using a coater and dried at 80°C for 30 min. The dry film thickness was controlled to be 20±2 μm.

[0037] 1. Trigger pressure detection: Take a 2cm×2cm sample and fix it on the lower platform of the pressure testing machine. Start from 0.05MPa and increase the pressure at a rate of 0.05MPa / min. Hold for 10s after each application of 0.05MPa. Use a colorimeter (see below) to detect the color development ΔE; the pressure value when ΔE ≥ 30 appears for the first time is the "trigger pressure" (test 5 times in parallel and take the average value).

[0038] 2. Color development time detection method: Use a colorimeter to detect the ΔE value of the color-developing area every 0.5s (take the average value of 3 measuring points); when the ΔE value fluctuation of 3 consecutive tests is ≤1, stop timing, and the time at this time is the "color-developing time" (test 5 times in parallel and take the average value).

[0039] 3. Background color ΔE value detection method: Definition: The color difference between the initial ink color and the standard white plate when no pressure is applied Randomly select five non-edge areas on the sample surface (avoiding substrate defects) and measure the L*, a*, and b* values ​​using a colorimeter. Calculate the color difference from the standard white plate using the formula:

[0040] ΔL*=Lsample-Lstandard, Δa*=asample-astandard, Δb*=bsample-bstandard.

[0041]

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pressure-sensitive color-changing anti-counterfeiting ink, characterized in that: The raw materials are calculated by mass and include: 15-25 parts of dye-loaded hydrophobic aerogel particles, wherein 10-20 wt% of pressure-sensitive dye is adsorbed inside the hydrophobic aerogel particles; 10-18 parts of four-needle zinc oxide whiskers, the tip curvature radius of the four-needle zinc oxide whiskers is ≤200nm; 50-65 parts of water-based acrylic resin; 5-10 parts of a developer, wherein the developer is immobilized on the surface of the four-needle zinc oxide whisker; 3-8 parts of porous silica, the pore size of the porous silica is 2-5nm, and the specific surface area is greater than 500m 2 / g; Dispersant 0.5-1 part.

2. The pressure-sensitive color-changing anti-counterfeiting ink according to claim 1, characterized in that: The dye-loaded aerogel particles are hydrophobic SiO2 aerogels with a particle size of 1-10 μm, and the pressure-sensitive dye adsorbed inside is crystal violet lactone or fluorane pressure-sensitive dye.

3. The pressure-sensitive color-changing anti-counterfeiting ink according to claim 1, characterized in that: The surface of the four-needle zinc oxide whisker is modified by a silane coupling agent KH-550, the color developer is bisphenol A, and the color developer is immobilized on the surface of the four-needle zinc oxide whisker through hydrogen bonds.

4. The pressure-sensitive color-changing anti-counterfeiting ink according to claim 1, characterized in that: The mass ratio of the dye-loaded aerogel particles to the four-needle zinc oxide whiskers is (1.2-2):

1.

5. The method for preparing the pressure-sensitive color-changing anti-counterfeiting ink according to any one of claims 1 to 4, characterized in that: The steps include: (1) The hydrophobic SiO2 aerogel was impregnated in a 10-20 wt% pressure-sensitive dye / ethanol solution, dried at 60°C, and sieved to obtain dye-loaded aerogel particles; (2) Immerse the four-needle zinc oxide whiskers in a 2 wt% KH-550 ethanol solution, treat at 80°C for 1 hour, filter, and then spray with a 10 wt% bisphenol A / acetone solution, filter and dry to obtain the four-needle zinc oxide whiskers with a color developer immobilized on the surface; (3) Mix the water-based acrylic resin with the dispersant, add the four-needle zinc oxide whiskers with a surface-immobilized color developer, dye-loaded aerogel particles, and porous silica in sequence, and stir at 400 rpm for 20 minutes.

6. The preparation method according to claim 5, wherein In the step (1), a 200-mesh sieve is used for sieving, and aerogel particles with a particle size of 1-10 μm are retained.

7. The preparation method according to claim 5, wherein In the step (2), after spraying the bisphenol A / acetone solution, vacuum drying is performed at 60° C. for 2 hours.

8. The preparation method according to claim 5, wherein In the step (3), the stirring temperature is controlled at 25±5°C, and after the stirring is completed, the mixture is filtered through a 200-mesh sieve.

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