Anti-counterfeiting anti-uncovering label and preparation method thereof

Abstract

The invention is applicable to the technical field of preparation of anti-counterfeit labels, and provides an anti-counterfeit and anti-tamper label and a preparation method of the anti-counterfeit and anti-tamper label. A water-based ink normal-temperature information layer, a temperature-force double-response composite ink layer, a cross-linking density gradient interpenetrating network (IPN) covering layer, a transparent polyurethane protection ink layer, a temperature-sensitive double-layer wall material microcapsule-acrylate pressure-sensitive adhesive layer and Glasin release paper are sequentially arranged from bottom to top. In the preparation process, interlayer bonding is ensured through interface pretreatment, the microcapsules are prepared by adopting double-layer emulsification-in-situ polymerization, the IPN layer is prepared by adopting partition spraying-gradient curing, and process abnormality response measures are defined. The problems that an existing anti-counterfeit label does not develop color at high temperature and the like are solved, the collaborative anti-counterfeit effect of developing blue at normal temperature, developing red at high temperature and developing brown at high temperature is achieved, the storage life reaches 1.5 years or above, and the anti-counterfeit label is suitable for multiple scenes such as universal packaging, valuables and cold-chain food.

Description

Technical Field

[0001] This invention belongs to the field of anti-counterfeiting label preparation technology, and particularly relates to an anti-counterfeiting and tamper-evident label and its preparation method. Background Technology

[0002] With the continuous expansion of the global market and the diversification of consumer goods, the threat of counterfeit and substandard products is also gradually increasing. To ensure product authenticity and protect consumer rights, anti-counterfeiting technology has emerged and is widely used in various packaging materials. Anti-counterfeiting labels, due to their wide application range, low cost, and mature technology, have become an important anti-counterfeiting measure. They are not only used to protect the integrity of goods but also play an important functional role in logistics transportation and document sealing. The core function of tamper-evident labels is to leave irreversible marks or markings on the packaging surface or the label itself when opened or torn. These labels typically cannot be restored to their original state after being torn, revealing clear anti-counterfeiting markings and thus indicating to the user that the packaging has been opened or tampered with. For example, security reveal labels, when peeled off, will display preset text, patterns, or symbols (such as "VOID," "OPENED," etc.) on the packaging surface or the label itself. Once these markings appear, they cannot be restored, clearly indicating that the packaging has been opened.

[0003] Existing anti-counterfeiting labels can reveal preset text, patterns, or symbols when peeled off at room temperature. However, when peeled off at high temperatures—such as by using a hairdryer to blow hot air while peeling—the preset anti-counterfeiting information will not appear. This shortcoming of existing anti-counterfeiting labels poses a significant risk. Unauthorized individuals can use this method to open the packaging, rendering the anti-counterfeiting label ineffective. Furthermore, a single anti-counterfeiting mechanism is easily counterfeited, lacking multi-dimensional and cross-verifiable anti-counterfeiting measures.

[0004] This invention provides a label that can display anti-counterfeiting information when peeled off at both room temperature and high temperature, effectively eliminating the security risks of existing anti-counterfeiting labels and having great practical significance. Summary of the Invention

[0005] This invention provides an anti-counterfeiting and tamper-evident label and its preparation method, aiming to solve the above-mentioned problems.

[0006] This invention is implemented as follows: an anti-counterfeiting and tamper-evident label, comprising, from bottom to top:

[0007] (1) Substrate layer: Modified nanocellulose-enhanced fluorescent PET film, thickness 30-60μm; its composition by mass fraction is: PET chips 90-95wt%, modified nanocellulose (KH550 modified, length 500-800nm, diameter 20-30nm) 3-7wt%, SrAl2O4:Eu 2+Fluorescent powder (excited by 254nm ultraviolet light, exhibiting green fluorescence, emission wavelength 520nm) 0.5-1wt%;

[0008] (2) Room temperature information layer: "VOID" pattern (font size 8-12, spacing 4-6mm) printed with water-based red ink (solid content 5-30wt%, viscosity 200-300mPa·s (25℃), pigment content 15-18wt%), thickness 1-3μm;

[0009] (3) The high-temperature responsive information layer is a temperature-force dual-response composite ink layer: thickness 8-10μm, components by mass fraction are: spiropyran derivative (red at 60-120℃, reversible thermochromic but irreversible trace) 6-7wt%, triarylmethane lactone derivative (blue after ≥5N tearing, irreversible) 4-4.5wt%, polyurethane acrylate (containing hydroxyl groups, crosslinking binder) 22-23wt%, mixed solvent (ethyl acetate: propylene glycol methyl ether acetate = 3:1) 62.7-63.5wt%, 2-hydroxy-4-methoxybenzophenone (UV absorber) 0.3-0.5wt%, hydrogenated castor oil (anti-migration agent, prevents component migration) 1.5-1.8wt%; This layer has a "temperature-force threshold cross-locking" mechanism: it only turns blue when torn at room temperature (25℃) ≥5N, only turns red when torn at high temperature (60-120℃ for ≥3s), and turns brown when torn at high temperature + ≥5N (the strength increases with increasing temperature / force);

[0010] Threshold cross-locking implementation principle:

[0011] The "temperature-force threshold cross-locking mechanism" achieves "AND" logic control through the intermolecular interactions of spiropyran derivatives (temperature-sensitive), triarylmethane lactone derivatives (force-sensitive), and cross-linking agents (polyurethane acrylate). The specific principle is as follows:

[0012] At room temperature (20-30℃) + ≥5N tear: turns blue

[0013] At room temperature, spiropyran derivative molecules are in a closed-ring, colorless state (no temperature change triggering). However, under a tear force of ≥5N, the CO bonds in the triarylmethane lactone derivative molecules break, generating a blue chromophore with a conjugated structure. At the same time, the hydroxyl groups (-OH) on the polyurethane acrylate molecular chain form hydrogen bonds and other physical interactions with the lactone ring structure (-OC(=O)-) of the triarylmethane lactone derivative. This interaction can enhance the stability of the CO bonds in the triarylmethane lactone molecule, restricting their breakage under low force (<5N), ensuring that the CO bonds break and turn blue only when the tear force is ≥5N.

[0014] High temperature only (60-120℃ for ≥3 seconds): turns red

[0015] At high temperatures, spiropyran derivative molecules absorb heat and undergo a spiro-ring-opening isomerization reaction (closed-ring colorless spiropyran → open-ring red anthocyanin structure); at this time, there is no tearing force, the triarylmethane lactone molecule does not break and remains colorless; and the high temperature (<120℃) does not destroy the weak interaction between polyurethane acrylate and spiropyran, and only needs to be sustained for ≥3s to ensure complete isomerization, avoiding false triggering caused by instantaneous high temperature (such as 50℃ for 10s).

[0016] High temperature (60-120℃) + ≥5N tearing: turns brown

[0017] High temperature causes spiropyran to turn red and triarylmethane lactone to turn blue upon cleavage. At the same time, rhodamine B reacts with the cleavage product of triarylmethane lactone to turn yellow. The combination of these three factors results in a final brown color (the intensity of which increases with increasing temperature / pressure).

[0018] The response threshold can be precisely controlled by adjusting the mass fraction of the following components, with the specific correspondence as follows:

[0019] Spiropyran derivatives: Increased content leads to a decrease in temperature change triggering temperature (e.g., 55°C triggering at 7wt%, 65°C triggering at 5wt%). This application preferably uses 6-7wt% to ensure that 60°C is the triggering starting point and avoids false triggering at low temperatures.

[0020] Triarylmethane lactone derivatives: Increased content reduces the triggering force (e.g., 4N triggering at 5wt%, 6N triggering at 3wt%). This application preferably uses 4-4.5wt% to ensure ≥5N triggering, matching the conventional tearing force.

[0021] Polyurethane acrylate: As the content increases, hydrogen bonding increases, the force threshold increases, and the temperature response delay increases. This application preferably uses 22-23 wt% to balance the sensitivity of the two responses and avoid threshold drift.

[0022] (4) Crosslinking density gradient IPN cover layer: 12-18 μm thick, crosslinking degree ≥85% on the information layer side, crosslinking degree ≤60% on the surface side, and a gradient transition layer of 70-80% in the middle; it is made by in-situ polymerization of methyl methacrylate (MMA) monomer, diisocyanate (6wt% on the information layer side and 4wt% on the surface side), and azobisisobutyronitrile (1wt% on the information layer side and 0.6wt% on the surface side);

[0023] (5) Protective ink layer: transparent polyurethane ink, thickness 4-6μm;

[0024] (6) Temperature-sensitive double-layer wall material microcapsule-pressure-sensitive adhesive layer: thickness 18-22μm; the main body of the pressure-sensitive adhesive is 70-80wt% of acrylate copolymer (butyl acrylate: methyl methacrylate: acrylic acid = 85:10:5), with added temperature-sensitive double-layer wall material microcapsules (5-10wt%), hydrogenated rosin glycerol ester (tackifying resin, 8-20wt%), 2,6-di-tert-butyl-p-cresol (antioxidant, 0.3-0.5wt%), and silicone defoamer (0.1-0.2wt%); the inner layer of the microcapsule is polyurea formaldehyde (0.3-0.5μm, softens and cracks above 60℃), the outer layer is polymethyl methacrylate (PMMA, 0.2-0.3μm, room temperature, isolated environment), and the core material is Rhodamine B colorant (reacts with ink to turn yellow);

[0025] The colorimetric reaction mechanism of Rhodamine B (core material) with the metronochromic component (triarylmethane lactone derivative):

[0026] Rhodamine B characteristics: At room temperature, it has a colorless lactone structure. In acidic environments or when it reacts with compounds containing active hydrogen, the lactone ring opens to form a yellow conjugated structure.

[0027] Characteristics of triarylmethane lactone derivatives: After tearing and breaking, they generate blue chromophores containing phenolic hydroxyl groups (-OH, active hydrogen);

[0028] Reaction process: At high temperature, the microcapsules rupture and release Rhodamine B, which reacts with the "blue chromophore (containing -OH)" generated by tearing, opening the Rhodamine B lactone ring and forming a yellow conjugated structure; the yellow and blue superimpose to finally present green (when tearing at room temperature) or the yellow and purple-red superimpose to present brown (when tearing at high temperature).

[0029] (7) Release paper layer: white glassine release paper.

[0030] The present invention also provides a method for preparing the above-mentioned anti-counterfeiting and tamper-evident label, comprising the following steps:

[0031] S1. Substrate preparation: PET chips, modified nanocellulose, and fluorescent powder are mixed and extruded through a twin-screw extruder (speed 200r / min, barrel temperature 260-280℃), biaxially stretched (3.5 times in the longitudinal direction and 4 times in the transverse direction), heat-set (200℃, 30s), corona treated (surface tension ≥42mN / m), and wound up to obtain the substrate;

[0032] S2. Room temperature information layer printing: Flexographic printing is used to coat the non-corona-electrode surface of the substrate with water-based red ink, dry at 70-75℃ for 30-40s, control the thickness to 1-3μm, and perform corona treatment (≥45mN / m).

[0033] S3. High-temperature responsive information layer, i.e. temperature-force dual-responsive ink layer printing: The composite ink used for the high-temperature responsive information layer is coated onto the room temperature information layer using a 300-mesh anilox roller, and pre-dried at 60-65℃ for 25-35s, with a thickness of 8-10μm;

[0034] S4. Preparation of gradient IPN masking layer:

[0035] S41. Spraying MMA mixture in sections: Spraying MMA mixture containing 6wt% diisocyanate and 1wt% azobisisobutyronitrile on the information layer side, and spraying MMA mixture containing 4wt% diisocyanate and 0.6wt% azobisisobutyronitrile on the surface side.

[0036] S42. Gradient curing: Ultraviolet light (365nm, 900mJ / cm² on the information layer side) 2 Surface side 700mJ / cm 2 Cure for 10-15 seconds, then dry at 85-90℃ for 90-120 seconds to form a cross-linked density gradient IPN layer with a thickness of 12-18μm.

[0037] S5. Protective ink layer printing: Flexographic printing of transparent polyurethane ink, drying at 85-95℃ for 15-25s, thickness 4-6μm, plasma treatment;

[0038] S6. Microcapsule-pressure sensitive adhesive coating:

[0039] S61. Microcapsule preparation: The double-layer emulsification method was adopted. First, the Rhodamine B core material was emulsified with polyurea formaldehyde prepolymer (inner layer), and then PMMA outer layer was wrapped and dried to obtain double-layer wall material microcapsules.

[0040] S62. Adhesive layer preparation: Mix the microcapsules with the acrylate matrix, tackifying resin, antioxidant, and defoamer (stirring at 800 r / min for 30 min);

[0041] S63. Coating and Drying: Coat the adhesive onto the protective ink layer and dry at 85-90℃ for 60-90s, with a thickness of 18-22μm;

[0042] S7. Release paper lamination: Lay qualified Racine release paper under a pressure of 0.2-0.4MPa;

[0043] S8. Treat the corona-treated surface of the substrate and dry at 100-110℃ for 25-35 seconds;

[0044] S9. Slitting: Slitting into rolls or slices as needed.

[0045] Preferably, the modified nanocellulose is prepared as follows:

[0046] Add 10-15 parts of unmodified nanocellulose to 80-90 parts of anhydrous ethanol and disperse for 30-40 minutes using a high-speed disperser (3000-4000 r / min) to form a uniform suspension; then add 5-10 parts of deionized water and continue dispersing for 10-15 minutes to prevent the unmodified nanocellulose from agglomerating.

[0047] Add 1-2 parts of KH550 to 2-3 parts of anhydrous ethanol, add 0.1-0.3 parts of glacial acetic acid to adjust the pH to 4-5, and stir in a water bath at 30-35℃ (500-800 r / min) for 15-20 min to allow KH550 to be fully hydrolyzed to generate silanol groups.

[0048] Slowly add the KH550 hydrolysate to the modified nanocellulose dispersion at a rate of 1-2 drops / second. After the addition is complete, heat the mixture to a water bath at 60-70℃ and stir (800-1000 r / min) for 2-3 hours to allow the hydrolyzed KH550 to undergo a grafting reaction with the hydroxyl groups on the surface of the modified nanocellulose.

[0049] After the reaction was completed, the mixture was transferred to centrifuge tubes and centrifuged for 15-20 minutes using a high-speed centrifuge (8000-10000 r / min). The supernatant was discarded. The precipitate was washed repeatedly with anhydrous ethanol 3-4 times (centrifuged for 10 minutes each time) to remove unreacted KH550 and impurities. Finally, the precipitate was placed in a vacuum drying oven (temperature 60-65℃, vacuum degree -0.08~-0.09MPa) and dried for 4-5 hours. The precipitate was then pulverized through a 100-mesh sieve to obtain KH550 modified nanocellulose powder.

[0050] Preferably, the method for preparing the temperature-sensitive double-walled microcapsules is as follows:

[0051] Add 5-8 parts of Rhodamine B to 20-25 parts of deionized water and stir (500 rpm) for 10-15 minutes until completely dissolved. Add 0.1-0.2 parts of defoamer and continue stirring for 5 minutes.

[0052] Add 15-20 parts of polyurea-formaldehyde prepolymer to the above core material dispersion, add 1-1.5 parts of Tween 80, and emulsify for 20-30 minutes using a high-speed emulsifier (1500-2000 r / min) to form an oil-in-water (O / W) type inner layer emulsion. The emulsion particle size is controlled at 1.5-2 μm (monitored by a laser particle size analyzer).

[0053] Transfer the inner layer emulsion to a four-necked flask, heat to a water bath at 50-55℃, stir (600-800 r / min), slowly add 10% hydrochloric acid to adjust the pH to 3-4, and keep warm for 2-2.5 hours to allow the polyurea-formaldehyde prepolymer to crosslink and form the inner layer wall material; after curing, cool to room temperature to obtain the inner layer microcapsule suspension.

[0054] Mix 8-12 parts MMA with 0.2-0.3 parts AIBN and stir (300 r / min) for 10 min to completely dissolve the AIBN, thus obtaining an MMA monomer solution.

[0055] Add the inner microcapsule suspension to 40-50 parts of deionized water, add 0.8-1.2 parts of Span 80, and stir (800 r / min) for 15 min; then slowly add MMA monomer solution at a rate of 0.5-1 mL / min. After the addition is complete, emulsify using a high-speed emulsifier (1200-1500 r / min) for 15-20 min to form a water-in-oil-in-water (W / O / W) bilayer emulsion. The particle size of the bilayer emulsion is controlled at 2-3 μm.

[0056] Transfer the bilayer emulsion to a four-necked flask, purge with nitrogen (flow rate 50-100 mL / min), heat to 70-75℃ in a water bath, and maintain the temperature with stirring (600-800 r / min) for 3-3.5 h to allow MMA to polymerize under the initiation of AIBN to form the PMMA outer layer; after polymerization, heat to 80℃ and maintain the temperature for 1 h to ensure complete polymerization, then cool to room temperature.

[0057] Purification: Dilute the double-layer microcapsule suspension with deionized water, centrifuge at a medium speed (5000-6000 r / min) for 10-15 min, and discard the supernatant; wash the precipitate repeatedly with deionized water 2-3 times to remove unreacted MMA, emulsifier and AIBN until the supernatant is clear.

[0058] Drying: The purified microcapsule precipitate was placed in a freeze dryer (temperature -50~-40℃, vacuum degree ≤10Pa) and dried for 8-10 hours to avoid softening of the microcapsule wall material due to high temperature; after drying, it was pulverized and passed through an 80-mesh sieve to obtain temperature-sensitive double-layer wall material microcapsule powder (inner layer thickness 0.3-0.5μm, outer layer thickness 0.2-0.3μm).

[0059] Preferably, an interface pretreatment structure is provided between adjacent layers: the room temperature information layer and the high temperature response information layer are corona treated, with a surface tension ≥45mN / m; a water-based acrylic primer with a thickness of 0.5-1μm is coated between the cover layer and the protective ink layer; and the protective ink layer and the pressure-sensitive adhesive layer are treated with plasma at a power of 300-400W for 10-15s and a vacuum degree of -0.06 to -0.07MPa.

[0060] Preferably, the treatment of the corona-electrode surface of the substrate is carried out in one of the following ways:

[0061] Method 1: Coat with polydimethylsiloxane release agent, 1-2 μm thick, and dry at 100-110℃ for 25-35 seconds;

[0062] Method 2: First, apply water-based ink to a thickness of 1-3 μm, dry at 70-75℃ for 30-40 seconds, and then apply polydimethylsiloxane release agent.

[0063] Method 3: Apply varnish to a thickness of 2-4μm, and dry at 90-100℃ for 20-30 seconds;

[0064] Method 4: Apply matte oil to a thickness of 2-4μm, and dry at 85-95℃ for 20-30s. 0.5-1wt% of silica matting powder (particle size 2-5μm) can be added to the matte oil to enhance the matte effect.

[0065] Performance testing methods

[0066] False trigger rate test

[0067] Testing standard: Refer to QB / T 4873-2015 "General Technical Conditions for Anti-counterfeiting Labels";

[0068] Sample preparation: Cut 100 5cm×5cm label samples and attach them to PET packaging substrate (surface tension ≥42mN / m);

[0069] Testing equipment: small tensile testing machine (accuracy ±0.1N), constant temperature oven (temperature control accuracy ±1℃);

[0070] Test steps:

[0071] Apply a constant tensile force of 3N (speed 100mm / min) to 50 samples and observe whether color development occurs;

[0072] Another 50 samples were placed in a 50℃ oven for 10 seconds (instantaneous high temperature), and then observed to see if color development occurred.

[0073] False trigger rate = (number of color samples / total number of samples) × 100%, with a passing grade of ≤1%.

[0074] Crack uniformity test

[0075] Test standard: Refer to the self-made method (observed with an optical microscope; specific operation is as follows);

[0076] Testing equipment: Metallurgical microscope (200x, with image analysis software);

[0077] Test steps:

[0078] After tearing off the label, take a sample of the cracked area (2cm×2cm);

[0079] Microscopic observation was conducted to determine the percentage of effective cracks with a crack spacing of 0.5-1 mm and a width of 1-3 μm.

[0080] Crack uniformity = (effective crack area / total area of ​​the observation area) × 100%, with a pass rate of ≥95%.

[0081] interlayer peel strength test

[0082] Testing standard: GB / T 2792-2014;

[0083] Testing equipment: Electronic tensile testing machine (300mm / min);

[0084] Test steps:

[0085] The sample was bonded to a stainless steel plate (Ra=0.8μm) and rolled three times with a 2kg roller;

[0086] Average force measured by 180° peel test; qualified index ≥15N / 25mm.

[0087] Microcapsule stability test

[0088] Test standard: GB / T 29602-2013;

[0089] Test equipment: HPLC;

[0090] Test steps:

[0091] After storage at 25℃ for 6 months, the Rhodamine B leakage rate was measured, and the acceptable standard was ≤0.5%.

[0092] Fluorescence intensity test

[0093] Test equipment: Fluorescence spectrophotometer (254nm excitation);

[0094] Test steps:

[0095] Measure the emission intensity at 520nm;

[0096] The retention rate was measured after aging at 40℃ / 85% RH for 1 year. The qualified indicators are: initial ≥5000 a.u., retention rate ≥80%.

[0097] Compared with the prior art, the embodiments of this application have the following main advantages:

[0098] The anti-counterfeiting and tamper-evident label provided by this invention achieves a dual verification mechanism through the synergistic effect of multi-level composite structure design and temperature-sensitive double-layer wall material microcapsules. This mechanism hides information at room temperature and triggers the appearance of anti-counterfeiting marks with a color reaction at high temperature, significantly improving the security and recognizability of the label.

[0099] The outer PMMA layer of the microcapsule is temperature-sensitive, and the inner polyurea-formaldehyde layer is fully encapsulated, ensuring that the colorimetric reaction is reversible and has good repeatability.

[0100] By combining interface preprocessing technology, the adhesion between functional layers is enhanced, effectively preventing delamination or detachment during use and ensuring the stability and durability of the label in complex environments.

[0101] By adjusting the type and ratio of phase change materials in microcapsules, colorimetric responses at different temperature thresholds can be achieved, expanding their application potential in temperature-controlled scenarios such as cold chain logistics and pharmaceutical packaging. Attached Figure Description

[0102] Figure 1 This is a flowchart of a method for preparing an anti-counterfeiting and tamper-evident label provided by the present invention.

[0103] Figure 2 This is a structural schematic diagram of an anti-counterfeiting and anti-tamper label provided by the present invention.

[0104] Figure label annotations: 1. Substrate; 2. Room temperature information layer; 3. High temperature response information layer; 4. Covering layer; 5. Protective ink layer; 6. Pressure-sensitive adhesive layer; 7. Release paper layer. Detailed Implementation

[0105] 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 this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0106] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0107] Example 1: Standard General Packaging

[0108] This invention provides an anti-counterfeiting and tamper-evident label, which comprises the following raw materials:

[0109] Substrate: 92wt% PET chips, 5wt% modified nanocellulose (grafting rate 6.5%), 0.8wt% phosphor, thickness 50μm;

[0110] Room temperature information layer: water-based red ink (solid content 28wt%, viscosity 250mPa·s), 10-point font "VOID", thickness 2μm;

[0111] High-temperature response information layer: 6.5wt% spiropyran, 4.2wt% triarylmethane lactone, 22.5wt% polyurethane acrylate, 63wt% mixed solvent, 0.4wt% UV absorber, 1.6wt% anti-migration agent, thickness 9μm;

[0112] Gradient IPN: 6% diisocyanate + 1% AIBN on the information layer side, 4% + 0.6% on the surface side, UV energy 900 / 700 mJ / cm 2 Dry at 85℃ for 100 seconds to achieve a thickness of 15μm;

[0113] Protective ink: Polyurethane ink (solid content 42wt%, hardness 2H), thickness 5μm;

[0114] Pressure-sensitive adhesive: 75wt% acrylate matrix, 8wt% temperature-sensitive double-layer wall material microcapsules (inner layer 0.4μm, outer layer 0.25μm), 15wt% tackifying resin, 0.4wt% antioxidant, 0.1wt% defoamer, thickness 20μm;

[0115] Corona treatment: S81 (silicone release agent 1.5μm, dried at 105℃ for 30s).

[0116] The modified nanocellulose is prepared as follows:

[0117] 12 parts of unmodified nanocellulose were added to 85 parts of anhydrous ethanol and dispersed for 35 minutes using a high-speed disperser (3500 r / min) to form a uniform suspension. Then, 8 parts of deionized water were added dropwise and the dispersion was continued for 12 minutes to prevent the unmodified nanocellulose from agglomerating.

[0118] Add 1.5 parts of KH550 to 2.5 parts of anhydrous ethanol, add 0.2 parts of glacial acetic acid to adjust the pH to 4-5, and stir in a 32℃ water bath (650 r / min) for 18 min to allow KH550 to be fully hydrolyzed to generate silanol groups.

[0119] The KH550 hydrolysate was slowly added dropwise to the modified nanocellulose dispersion at a rate of 1 drop / second. After the addition was complete, the temperature was raised to 65°C in a water bath and stirred (900 r / min) for 2.5 h to allow the hydrolyzed KH550 to undergo a grafting reaction with the hydroxyl groups on the surface of the modified nanocellulose.

[0120] After the reaction was completed, the mixture was transferred to a centrifuge tube and centrifuged for 18 min using a high-speed centrifuge (9000 r / min). The supernatant was discarded. The precipitate was washed repeatedly with anhydrous ethanol 4 times (centrifuged for 10 min each time) to remove unreacted KH550 and impurities. Finally, the precipitate was placed in a vacuum drying oven (temperature 62℃, vacuum degree -0.08MPa) and dried for 4.5 h. It was then pulverized and passed through a 100-mesh sieve to obtain KH550 modified nanocellulose powder.

[0121] In this embodiment, the preparation method of the temperature-sensitive double-walled microcapsules is as follows:

[0122] Add 6 parts of Rhodamine B to 22 parts of deionized water and stir (500 rpm) for 13 minutes until completely dissolved. Add 0.15 parts of defoamer and continue stirring for 5 minutes.

[0123] Add 18 parts of polyurea-formaldehyde prepolymer to the above core material dispersion, add 1.2 parts of Tween 80, and emulsify for 25 minutes using a high-speed emulsifier (1800 r / min) to form an oil-in-water (O / W) type inner layer emulsion. The emulsion particle size is controlled at 1.5-2 μm (monitored by a laser particle size analyzer).

[0124] The inner layer emulsion was transferred to a four-necked flask, heated to a water bath at 52°C, stirred (700 rpm), and 10% hydrochloric acid was slowly added dropwise to adjust the pH to 3-4. The mixture was kept at this temperature for 2.2 hours to allow the polyurea-formaldehyde prepolymer to crosslink and form the inner layer wall material. After curing, the mixture was cooled to room temperature to obtain the inner layer microcapsule suspension.

[0125] Mix 10 parts MMA with 0.25 parts AIBN and stir (300 r / min) for 10 min to completely dissolve AIBN, thus obtaining an MMA monomer solution.

[0126] The inner microcapsule suspension was added to 45 parts of deionized water and 1 part of Span 80, and stirred (800 r / min) for 15 min. Then, the MMA monomer solution was slowly added dropwise at a rate of 0.8 mL / min. After the addition was completed, the mixture was emulsified for 18 min using a high-speed emulsifier (1300 r / min) to form a water-in-oil-in-water (W / O / W) bilayer emulsion. The particle size of the bilayer emulsion was controlled at 2-3 μm.

[0127] The bilayer emulsion was transferred to a four-necked flask, protected with nitrogen (flow rate 75 mL / min), heated to 72°C in a water bath, and stirred at 700 r / min for 3.2 h to allow MMA to polymerize under the initiation of AIBN to form the PMMA outer layer. After polymerization, the temperature was raised to 80°C and held for 1 h to ensure complete polymerization, and then cooled to room temperature.

[0128] Purification: Dilute the bilayer microcapsule suspension with deionized water, centrifuge at medium speed (5500 r / min) for 12 min, and discard the supernatant; wash the precipitate repeatedly with deionized water 3 times to remove unreacted MMA, emulsifier and AIBN until the supernatant is clear.

[0129] Drying: The purified microcapsule precipitate was placed in a freeze dryer (temperature -45℃, vacuum degree ≤10Pa) and dried for 9 hours to avoid softening of the microcapsule wall material due to high temperature; after drying, it was pulverized and passed through an 80-mesh sieve to obtain temperature-sensitive double-layer wall material microcapsule powder (inner layer thickness 0.3-0.5μm, outer layer thickness 0.2-0.3μm, rupture rate of 98% at 60℃, leakage rate of 0.3% after 6 months of storage at 25℃).

[0130] like Figure 1-2 As shown, the method for preparing the anti-counterfeiting and tamper-evident label includes the following steps:

[0131] S1. Substrate preparation: PET chips, modified nanocellulose, and fluorescent powder are mixed and extruded through a twin-screw extruder (speed 200r / min, barrel temperature 270℃), biaxially stretched (3.5 times in the longitudinal direction and 4 times in the transverse direction), heat-set (200℃, 30s), corona treated (surface tension ≥42mN / m), and wound up to obtain the substrate;

[0132] S2. Room temperature information layer printing: Flexographic printing is used to coat the non-corona-electrode surface of the substrate with water-based red ink, dry at 72℃ for 35s, control the thickness to 1-3μm, perform corona treatment on the surface of the room temperature information layer, control the surface tension to 48mN / m, and process at a speed of 6m / min.

[0133] S3. Temperature-force dual-response ink layer printing: The composite ink is coated onto the information layer at room temperature using a 300-mesh anilox roller, and then pre-dried at 62℃ for 30 seconds to a thickness of 8-10μm.

[0134] S4. Preparation of gradient IPN masking layer: Coated with water-based acrylic primer (30wt% solids content), 0.8μm thick, and dried at 62℃ for 18s.

[0135] S41. Spraying MMA mixture in sections: Spraying MMA mixture containing 6wt% diisocyanate and 1wt% azobisisobutyronitrile on the information layer side, and spraying MMA mixture containing 4wt% diisocyanate and 0.6wt% azobisisobutyronitrile on the surface side.

[0136] S42. Gradient curing: Ultraviolet light (365nm, 900mJ / cm² on the information layer side) 2 Surface side 700mJ / cm 2 Curing for 12 seconds, then drying at 88℃ for 105 seconds, forms a cross-linked density gradient IPN layer with a thickness of 12-18μm;

[0137] S5. Protective ink layer printing: flexographic printing of transparent polyurethane ink, drying at 90℃ for 20s, thickness 4-6μm, plasma treatment, power 350W, time 12s, vacuum degree -0.065MPa;

[0138] S6. Microcapsule-pressure sensitive adhesive coating:

[0139] S61. Microcapsule preparation: The double-layer emulsification method was adopted. First, the Rhodamine B core material was emulsified with polyurea formaldehyde prepolymer (inner layer), and then PMMA outer layer was wrapped and dried to obtain double-layer wall material microcapsules.

[0140] S62. Adhesive layer preparation: Mix the microcapsules with the acrylate matrix, tackifying resin, antioxidant, and defoamer (stirring at 800 r / min for 30 min);

[0141] S63. Coating and Drying: Coat the adhesive onto the protective ink layer and dry at 88℃ for 75 seconds, with a thickness of 18-22μm;

[0142] S7. Release paper lamination: Lay qualified Racine release paper under a pressure of 0.3MPa;

[0143] S8. Treat the corona-treated surface of the substrate (Method 1: apply 1.5μm of silicone release agent and dry at 105℃ for 30s);

[0144] S9. Slitting: Slitting into rolls or slices as needed.

[0145] The performance test results are shown in Table 1 below:

[0146]

[0147]

[0148] Further verification experiments were conducted based on Example 1:

[0149] Experiment 1: Adjusting only the spiropyran content to 5wt%, keeping everything else unchanged → the high-temperature trigger temperature rises to 65℃, which conforms to the rule of "content ↑ → temperature ↓";

[0150] Experiment 2: Only the triarylmethane lactone was adjusted to 3 wt%, while the rest remained unchanged → the force triggering force increased to 6 N, which conforms to the rule of "content ↑ → force ↓";

[0151] Experiment 3: Without polyurethane acrylate → the force threshold drops to 3N (false triggering), and the temperature response is unstable (it turns red at 50℃), proving the key role of the binder.

[0152] Example 2: High-adhesion version for valuable items

[0153] The difference from Example 1 is as follows:

[0154] Pressure-sensitive adhesive: 68wt% acrylate matrix, 10wt% microcapsules, 20wt% tackifying resin, 0.5wt% antioxidant, 0.2wt% defoamer, thickness 22μm;

[0155] Substrate thickness: 60μm (7wt% modified nanocellulose to improve mechanical strength).

[0156] Corona treatment (Method 2: 2μm transparent acrylic ink / 72℃ drying for 35s, 1.5μm silicone release agent)

[0157] Performance testing

[0158] The results are shown in Table 2 below:

[0159]

[0160]

[0161] Example 3: Low-Temperature Adapted Version for Cold Chain Foods

[0162] The difference from Example 1 is as follows:

[0163] Composite ink: 5.8 wt% spiropyran (adjusted temperature change threshold to 50℃ trigger), 4.5 wt% triarylmethane lactone, thickness 10 μm;

[0164] Microcapsule inner layer: 0.5μm polyurea formaldehyde (softens and ruptures at 50℃, suitable for cold chain high-temperature tampering);

[0165] Substrate: 40μm thick, with 1wt% low-temperature resistant agent (dioctyl adipate);

[0166] Corona treatment (Method 3: UV varnish 3μm, solid content 40wt%, 365nm 700mJ / cm) 2 Curing time 12 seconds, then drying at 95°C for 25 seconds.

[0167] The performance test results are shown in Table 3 below:

[0168]

[0169] Example 4: Mildew-resistant version for high humidity environments

[0170] The difference from Example 1 is as follows:

[0171] Pressure-sensitive adhesive: 0.3wt% mildew inhibitor (isothiazolinone) added;

[0172] Substrate: 0.5wt% moisture resistant agent (polyethylene glycol 400) added;

[0173] Protective ink: Add 0.2wt% mildew inhibitor, thickness 6μm;

[0174] Corona treatment (Method 4: water-based matte oil 3μm, solid content 38wt%, add 0.8wt% silica (particle size 3μm), dry at 90℃ for 25s).

[0175] The performance test results are shown in Table 4 below:

[0176]

[0177] Example 5: Ultra-thin electronic tag

[0178] The difference from Example 1 is as follows:

[0179] Substrate thickness: 30μm (95wt% PET chips, 3wt% modified nanocellulose, 0.5wt% fluorescent powder);

[0180] Gradient IPN thickness: 12μm (55% cross-linking degree on the surface side, improving flexibility);

[0181] Pressure-sensitive adhesive thickness: 18μm;

[0182] Corona treatment (Method 1: 1μm silicone release agent, dry at 100℃ for 25s).

[0183] The performance test results are shown in Table 5 below:

[0184]

[0185]

[0186] In summary, the temperature-sensitive anti-counterfeiting label provided by this invention exhibits excellent stability and response characteristics in various application environments. It also features low-temperature toughness, high-humidity mildew resistance, ultra-thin flexibility, and fluorescent recognition functions. It is suitable for complex scenarios such as cold chain transportation, electronic device identification, and high-humidity storage, and has good prospects for industrial application.

[0187] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0188] It should be understood that the disclosed apparatus can be implemented in other ways, as illustrated in the embodiments provided in this application. For example, the apparatus embodiments described above are merely illustrative; the division of units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or communication connections shown or discussed may be through some interfaces; the indirect coupling or communication connections between devices or units may be telecommunications or other forms.

[0189] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0190] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A tamper-evident label, characterized in that, From bottom to top, it includes a substrate layer, a room temperature information layer, a high temperature response information layer, a masking layer, a protective ink layer, a pressure-sensitive adhesive layer, and a release paper layer; The room temperature information layer is used to display a physical anti-counterfeiting pattern when the device is opened at room temperature. The high-temperature response information layer contains a temperature-sensitive color-developing component, which is used to display a physical anti-counterfeiting pattern when the surface is opened at high temperatures. The pressure-sensitive adhesive layer contains thermosensitive microcapsules, the core material of which is a color developer. The thermosensitive microcapsules rupture and release the color developer at ≥50°C, which then reacts with the mechanochromic components of the high-temperature response information layer to produce a color development reaction.

2. The anti-counterfeiting and tamper-evident label as described in claim 1, characterized in that, The high-temperature responsive information layer is a temperature-force dual-responsive composite ink layer, the temperature-sensitive color-developing component is a spiropyran derivative, and the composite ink layer also contains a triarylmethane lactone derivative as a force-induced color-developing component; the spiropyran derivative shows red at 60-120℃, and the triarylmethane lactone derivative breaks down into a blue chromophore containing phenolic hydroxyl groups when the tear force is ≥5N, and the blue chromophore can undergo a secondary color-developing reaction with the color developer released by the pressure-sensitive adhesive layer.

3. The anti-counterfeiting and tamper-evident label as described in claim 2, characterized in that, The temperature-force dual-response composite ink layer has a "temperature-force threshold cross-locking" mechanism: it only appears blue at room temperature (20-30℃) and tear force ≥5N; it only appears red at high temperature (60-120℃ and lasting ≥3s); at high temperature (60-120℃) and tear force ≥5N, the spiropyran derivative and the triarylmethane lactone derivative synergistically develop color, and at the same time, the rhodamine B released by the pressure-sensitive adhesive layer reacts with the fracture products of the triarylmethane lactone derivative to develop color, ultimately resulting in a brown color.

4. The anti-counterfeiting and tamper-evident label as described in claim 3, characterized in that, The temperature-force dual-response composite ink layer, by mass fraction, further includes 20-25 wt% crosslinking binder, 60-65 wt% mixed solvent, 0.3-0.5 wt% ultraviolet absorber, and 1-2 wt% anti-migration agent; the crosslinking binder is a hydroxyl-containing polyurethane acrylate, the mixed solvent is a mixture of ethyl acetate and propylene glycol methyl ether acetate in a mass ratio of 3:1, and the anti-migration agent is hydrogenated castor oil.

5. The anti-counterfeiting and tamper-evident label as described in claim 1, characterized in that, The masking layer is a cross-linked density gradient interpenetrating network structure. The side of the masking layer closer to the high-temperature response information layer is the information layer side with a cross-linking degree ≥85%, and the side closer to the protective ink layer is the surface side with a cross-linking degree ≤60%. A gradient transition layer with a cross-linking degree of 70-80% is provided between the information layer side and the surface side.

6. The anti-counterfeiting and tamper-evident label as described in claim 5, characterized in that, The covering layer is formed by in-situ polymerization of methyl methacrylate monomer, diisocyanate crosslinking agent and azobisisobutyronitrile initiator; wherein, the amount of diisocyanate added on the information layer side is 6% of the mass of methyl methacrylate monomer and the amount of azobisisobutyronitrile added is 1% of the mass of methyl methacrylate monomer; the amount of diisocyanate added on the surface side is 4% of the mass of methyl methacrylate monomer and the amount of azobisisobutyronitrile added is 0.6% of the mass of methyl methacrylate monomer.

7. The anti-counterfeiting and tamper-evident label as described in claim 1, characterized in that, The temperature-sensitive microcapsule has a double-layer wall structure. The inner wall material is polyurea-formaldehyde with a thickness of 0.3-0.5 μm; the outer wall material is polymethyl methacrylate with a thickness of 0.2-0.3 μm; the core material is Rhodamine B color developer, which reacts with the mechanochromic component of the high-temperature response information layer to produce a yellow color.

8. The anti-counterfeiting and tamper-evident label as described in claim 7, characterized in that, The pressure-sensitive adhesive layer comprises, by mass fraction, 70-80 wt% acrylate copolymer, 5-10 wt% thermosensitive microcapsules, 8-20 wt% tackifying resin, 0.3-0.5 wt% antioxidant, and 0.1-0.2 wt% defoamer; the acrylate copolymer is copolymerized from butyl acrylate, methyl methacrylate, and acrylic acid in a mass ratio of 85:10:5, and the tackifying resin is hydrogenated rosin glycerol ester.

9. The anti-counterfeiting and tamper-evident label as described in claim 1, characterized in that, The substrate layer is a modified nanocellulose-enhanced fluorescent PET film, comprising 90-95 wt% PET chips, 3-7 wt% KH550 modified nanocellulose, and SrAl2O4:Eu by mass fraction. 2+ The fluorescent powder is 0.5-1 wt%; the modified nanocellulose has a grafting rate of 5-8%, a length of 500-800 nm, and a diameter of 20-30 nm; the substrate layer has a thickness of 30-60 μm.

10. A method for preparing an anti-counterfeiting and tamper-evident label as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Preparation of substrate layer: PET chips, modified nanocellulose and fluorescent powder are mixed, and the mixture is subjected to twin-screw extrusion, biaxial stretching, heat setting and corona treatment to obtain the substrate; S2. Printing the information layer at room temperature: Coating the non-corona-electrode surface of the substrate with water-based ink to print the anti-counterfeiting pattern, and then drying; S3. Printing a high-temperature responsive information layer: Coat the surface of the room-temperature information layer with an ink containing a temperature-sensitive color-developing component, and then pre-dry it; S4. Preparation of the masking layer: The polymerization system is sprayed onto the surface of the high-temperature response information layer in sections, and then cured and dried in a gradient manner to form the masking layer; S5. Printing protective ink layer: Coat the surface of the masking layer with transparent polyurethane ink and dry; S6. Coating pressure-sensitive adhesive layer: Mix the temperature-sensitive microcapsules with the pressure-sensitive adhesive components, coat the surface of the protective ink layer, and dry; S7. Laying release paper: Laying white glassine release paper onto the surface of the pressure-sensitive adhesive layer; S8. Treat the corona-treated surface of the substrate, dry it, and then cut it to obtain the finished product.

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