Aqueous flexo-dye ink, its preparation method and application

Abstract

The application discloses a kind of water-based bending color-changing ink and its preparation method and application, belong to printing ink technical field;The ink includes the following weight parts of component: color-changing core pigment 25~30 parts, flexible film-forming resin 37~40 parts, water-based solvent 22~27 parts, dispersing agent 1~3 parts, leveling agent 0.5~1 part, plasticizer 2~5 parts, defoaming agent 0.1~0.5 parts;The color-changing core pigment is the composite system of liquid crystal elastomer nanometer microsphere and metal coordination polymer, and particle size is controlled at 300-750nm.The present application is optimized by formula system, utilizes the reversible adjustment characteristics of liquid crystal elastomer molecular conformation, and is combined with the synergistic effect of specific adjuvant, solves the problem that existing color-changing ink color-changing sensitivity is low, weather resistance is poor, and single process is adapted.

Description

Technical Field

[0001] This invention relates to the field of printing ink technology, specifically to a water-based bend-sensitive color-changing ink, its preparation method, and its application. Background Technology

[0002] With the rapid development of cross-regional economic cooperation and the improvement of people's living standards, the market has placed higher demands on the aesthetics, diversity, and functionality of product packaging. Especially in the fields of high-end tobacco and alcohol packaging, anti-counterfeiting labels, and interactive experience products, the application of functional inks is becoming increasingly widespread. Among them, bend-sensitive color-changing inks, with their stress-sensitive color-changing properties, can achieve core functions such as anti-counterfeiting, interactive experiences, and stress damage detection, and have broad market prospects.

[0003] However, current flexural color-changing ink technology still faces numerous bottlenecks. On the one hand, domestically produced inks generally suffer from low color-changing sensitivity and poor weather resistance, such as insufficient color-changing contrast, delayed response, and weak UV aging resistance. On the other hand, existing inks have limited adaptability to printing processes and substrates, often only suitable for specific printing methods or requiring complex substrate pretreatment, thus restricting their large-scale application. Furthermore, traditional solvent-based color-changing inks also present environmental problems, failing to align with the current trend of green printing. Therefore, developing a highly sensitive, highly weather-resistant, multi-process compatible, and environmentally friendly water-based flexural color-changing ink has significant practical application value. Summary of the Invention

[0004] The purpose of this invention is to provide a water-based bend-changing ink, its preparation method, and its application, so as to solve the problems of low sensitivity, poor weather resistance, and limited process adaptability of existing color-changing inks.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A water-based bend-sensitive color-changing ink, comprising the following components by weight: Color-changing core pigment: 25-30 parts; Flexible film-forming resin: 37-40 parts; Aqueous solvent: 22-27 parts; Dispersant: 1-3 parts; Leveling agent: 0.5–1 part; Plasticizer: 2-5 parts; Defoamer: 0.1–0.5 parts; The color-changing core pigment is a composite system of liquid crystal elastomer nanospheres and metal coordination polymers, and the particle size of the liquid crystal elastomer nanospheres is 300nm-750nm.

[0006] Preferably, the flexible film-forming resin is a mixture of an aqueous polyurethane dispersion and an aqueous acrylate emulsion; the weight ratio of the aqueous polyurethane dispersion to the aqueous acrylate emulsion is 1:0.8 to 1.2.

[0007] Preferably, the aqueous solvent is a mixture of deionized water, ethanol and ethylene glycol, wherein the weight ratio of deionized water, ethanol and ethylene glycol is 8:1:7.

[0008] Preferably, the dispersant is a high molecular weight block copolymer dispersant (such as BYK-190); the leveling agent is a polyether-modified polydimethylsiloxane leveling agent (such as BYK-346); and the defoamer is a polysiloxane defoamer (such as BYK-024).

[0009] This invention significantly improves the dispersion stability of pigments by selecting a specific combination of additives, especially the targeted adaptation of BYK-190 dispersant to the surface characteristics of liquid crystal elastomer nanospheres; BYK-346 leveling agent and BYK-024 defoamer form a "leveling-defoaming" synergistic system, which solves the contradiction that leveling agents are prone to stabilizing foam and defoamers are prone to shrinking pores, thus ensuring printing yield.

[0010] Preferably, the plasticizer is triethyl citrate.

[0011] This invention also provides a method for preparing the above-mentioned water-based bend-sensitive color-changing ink, comprising the following steps: (1) Pre-dispersion: Add the formulated amount of color-changing core pigment to a portion of an aqueous solvent and disperse it by high-speed stirring to obtain a pigment pre-dispersion solution; (2) Grinding: Add dispersant to pigment pre-dispersion liquid and grind until pigment particle size D50 reaches 300-750nm to obtain pigment paste; (3) Paint mixing: While stirring, add the remaining water-based solvent, flexible film-forming resin, plasticizer, leveling agent and defoamer to the color paste, and continue stirring until uniform; (4) Filtration: Filter the well-mixed slurry to obtain water-based bend color-changing ink.

[0012] The present invention also provides the application of the above-mentioned water-based bend-changing ink, wherein the ink can be printed on the surface of a substrate by screen printing, flexographic printing or offset printing, and then dried and UV cured to form a film; the substrate includes PET, flexible paper, fabric or metallized film.

[0013] The present invention has the following beneficial effects: High color-changing sensitivity and stability: By adopting a liquid crystal elastomer nanosphere composite system, rapid color changing under low stress (≤1MPa) is achieved, with a color-changing contrast ratio ΔE≥25 and a reversible cycle life ≥1200 times, solving the pain points of high triggering stress and uneven color development of traditional pigments.

[0014] High process adaptability: By optimizing the rheology system, the ink is compatible with various printing processes such as screen printing, flexographic printing, and inkjet printing, and can be mass-produced without adjusting the production line; it has excellent adhesion to various substrates such as PET, paper, and fabric (≥4B cross-cut test), and no special pretreatment is required.

[0015] Excellent weather resistance and durability: Through resin crosslinking optimization and synergistic effect of plasticizer, the ink film maintains stable performance in the range of -20℃ to 80℃ after film formation, with a performance decay of ≤15% after 500h of UV aging, and excellent resistance to friction and media.

[0016] Environmentally friendly and efficient: It adopts a water-based system, which meets the requirements of green environmental protection, and the printing process is smooth, without defects such as pinholes and shrinkage cavities, resulting in a high yield rate. Detailed Implementation

[0017] To facilitate understanding of this application, a more complete description will be provided below. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0019] 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 is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0021] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0022] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0023] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0024] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0025] The term "particle" as used in this application, or a substance with a defined particle size distribution, is not necessarily spherical in shape; it may be irregular and can be either primary or secondary particles. The particle size of irregular particles is calculated as the average of their maximum and minimum diameters.

[0026] Example: The first aspect of this example provides a water-based bend-sensitive color-changing ink, which, by weight, comprises the following components: Color-changing core pigment: 25-30 parts; Flexible film-forming resin: 37-40 parts; Aqueous solvent: 22-27 parts; Dispersant: 1-3 parts; Leveling agent: 0.5–1 part; Plasticizer: 2-5 parts; Defoamer: 0.1–0.5 parts; The color-changing core pigment is a composite system of liquid crystal elastomer nanospheres and metal coordination polymers, and the particle size of the liquid crystal elastomer nanospheres is 300nm-750nm.

[0027] Preferably, the flexible film-forming resin is a mixture of an aqueous polyurethane dispersion and an aqueous acrylate emulsion; the weight ratio of the aqueous polyurethane dispersion to the aqueous acrylate emulsion is 1:0.8 to 1.2. This compounded resin system ensures both the flexibility and flexural strength of the film, and provides good adhesion.

[0028] Preferably, the aqueous solvent is a mixture of deionized water, ethanol, and ethylene glycol, wherein the weight ratio of deionized water, ethanol, and ethylene glycol is 8:1:7. This specific ratio of mixed solvent can effectively control the drying speed and viscosity of the ink, adapting to various printing processes.

[0029] Preferably, the dispersant is a high molecular weight block copolymer dispersant (such as BYK-190); the leveling agent is a polyether-modified polydimethylsiloxane leveling agent (such as BYK-346); and the defoamer is a polysiloxane defoamer (such as BYK-024).

[0030] This invention significantly improves the dispersion stability of pigments by selecting a specific combination of additives, especially the targeted adaptation of BYK-190 dispersant to the surface characteristics of liquid crystal elastomer nanospheres; BYK-346 leveling agent and BYK-024 defoamer form a "leveling-defoaming" synergistic system, which solves the contradiction that leveling agents are prone to stabilizing foam and defoamers are prone to shrinking pores, thus ensuring printing yield.

[0031] Preferably, the plasticizer is triethyl citrate. This plasticizer can effectively lower the glass transition temperature of the resin, allowing the film to maintain excellent flexibility in the range of -20℃ to 80℃, without cracking when bent 180°, while not interfering with the responsiveness of the color-changing pigment.

[0032] This invention also provides a method for preparing the above-mentioned water-based bend-sensitive color-changing ink, comprising the following steps: (1) Pre-dispersion: Add the formulated amount of color-changing core pigment to a portion of an aqueous solvent and disperse it by high-speed stirring to obtain a pigment pre-dispersion solution; (2) Grinding: Add dispersant to pigment pre-dispersion liquid and grind until pigment particle size D50 reaches 300-750nm to obtain pigment paste; (3) Paint mixing: While stirring, add the remaining water-based solvent, flexible film-forming resin, plasticizer, leveling agent and defoamer to the color paste, and continue stirring until uniform; (4) Filtration: Filter the well-mixed slurry to obtain water-based bend color-changing ink.

[0033] This invention also provides the application of the above-mentioned water-based bend-changing ink. The ink can be printed on the surface of the substrate by screen printing, flexographic printing or offset printing, and then dried and UV cured to form a film. The substrate includes PET, flexible paper, fabric or metallized film.

[0034] The present invention will be further described in detail below through specific embodiments: Specific Embodiment 1: This Specific Embodiment 1 provides a water-based bending color-changing ink and its preparation method.

[0035] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 25 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 40 parts; Aqueous solvent (deionized water: ethanol: ethylene glycol = 8:1:7): ​​27 parts; Dispersant (BYK-190): 3 parts; Leveling agent (BYK-346): 0.5 parts; Plasticizer (triethyl citrate): 3.5 parts; Defoamer (BYK-024): 1 part.

[0036] The preparation method of this specific embodiment 1 includes the following steps: (1) Pre-dispersion: Add the color-changing core pigment to 50% of the total amount of aqueous solvent, and stir for 20 minutes at 1500 rpm using a high-speed disperser to obtain a pre-dispersion liquid; (2) Grinding and dispersing: Add dispersant to the pre-dispersed liquid, mix evenly and transfer to a sand mill. Use zirconia beads with a diameter of 0.3 mm as the grinding medium and circulate and grind at a speed of 2500 rpm. Control the grinding chamber temperature to be below 35℃ until the slurry particle size D50 reaches 500 nm ± 20 nm to obtain the color paste. (3) Paint mixing: Transfer the color paste to a vacuum mixer, add the remaining water-based solvent, flexible film-forming resin and plasticizer in sequence, and stir at 500 rpm for 15 minutes; (4) Additives: Reduce the stirring speed to 300 rpm, add leveling agent and defoamer, and continue stirring for 20 minutes to obtain a mixed slurry; (5) Filtration: The mixed slurry is filtered through a 200-mesh nylon filter to obtain the finished water-based bendable color-changing ink.

[0037] The water-based bend-sensitive color-changing ink prepared in this specific embodiment 1 has a low pigment content and a relatively high resin content (40 parts), which makes the film-forming substances more abundant, thus giving the ink excellent adhesion and flexibility, achieving 5B in the cross-cut adhesion test. Although the color-changing contrast ratio (ΔE=25) is at the critical value of the effective range, it still meets the standard requirement of ≥25, and the color-changing stress is 0.9MPa, which fully meets the requirements of low stress triggering. The high content of dispersant (3 parts) ensures sufficient dispersion of pigment in the system with a high resin content, and the viscosity change rate is controlled at 6%, showing good storage stability.

[0038] Specific Embodiment 2: This Specific Embodiment 2 provides a water-based bending color-changing ink and its preparation method.

[0039] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 30 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 37 parts; Aqueous solvent (deionized water:ethanol:ethylene glycol = 8:1:7): ​​23.5 parts; Dispersant (BYK-190): 3 parts; Leveling agent (BYK-346): 1 part; Plasticizer (triethyl citrate): 4.5 parts; Defoamer (BYK-024): 1 part.

[0040] The water-based bend-sensitive color-changing ink prepared in Example 2 significantly improves color-changing contrast through a high content of color-changing core pigments, with a measured ΔE of 32, exhibiting extremely high color development sensitivity and a color-changing stress as low as 0.7 MPa. Despite the high pigment content, the combination of sufficient dispersant (3 parts) and leveling agent (1 part) effectively avoids agglomeration and leveling defects under high solids content. However, compared to the high pigment content, the resin ratio is slightly reduced, resulting in an adhesion test score of 4B, which is slightly lower than that of Example 1, but still meets application requirements. At the same time, the high pigment content poses a greater challenge to dispersion stability, with a viscosity change rate of 9%, which is within a controllable range.

[0041] Specific Embodiment 3: This Specific Embodiment 2 provides a water-based bending color-changing ink and its preparation method.

[0042] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 26 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 39 parts; Aqueous solvent (deionized water: ethanol: ethylene glycol = 8:1:7): ​​27 parts; Dispersant (BYK-190): 2 parts; Leveling agent (BYK-346): 0.6 parts; Plasticizer (triethyl citrate): 4.5 parts; Defoamer (BYK-024): 0.9 parts.

[0043] The preparation method is the same as in Specific Example 1, and will not be repeated here.

[0044] In this specific embodiment 3, the aqueous solvent content is relatively high (27 parts) to control the ink viscosity for a specific high-speed printing process. The higher solvent ratio results in better ink flow and leveling, achieving a printing yield of 91%. Combined with 4.5 parts of plasticizer, the film maintains excellent flexibility over a wide temperature range, with an adhesion of 5B. Due to the moderate pigment content, the color contrast ratio is 27, and all properties are well-balanced, verifying the adaptability of the formulation system in the low-viscosity direction.

[0045] Specific Embodiment 4: This Specific Embodiment 4 provides a water-based bending color-changing ink and its preparation method.

[0046] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 27 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 38 parts; Aqueous solvent (deionized water: ethanol: ethylene glycol = 8:1:7): ​​27 parts; Dispersant (BYK-190): 2.5 parts; Leveling agent (BYK-346): 0.7 parts; Plasticizer (triethyl citrate): 3.8 parts; Defoamer (BYK-024): 1 part.

[0047] The preparation method is the same as in Specific Example 1, and will not be repeated here.

[0048] In this specific embodiment 4, the amounts of each component are all within the middle range, aiming to verify the baseline performance of the formulation system. The results show that the ink under this formulation has a color contrast ratio of 28, a color change stress of 0.8 MPa, an adhesion of 5B, and good dispersion stability (viscosity change rate of 5%). This embodiment demonstrates that the weight range described in this invention has practical technical effects and eliminates any process dead ends.

[0049] Specific Embodiment 5: This Specific Embodiment 5 provides a water-based bending color-changing ink and its preparation method.

[0050] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 29 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 38 parts; Aqueous solvent (deionized water: ethanol: ethylene glycol = 8:1:7): ​​25 parts; Dispersant (BYK-190): 2 parts; Leveling agent (BYK-346): 0.8 parts; Plasticizer (triethyl citrate): 5 parts; Defoamer (BYK-024): 0.2 parts.

[0051] The preparation method is the same as in Specific Example 1, and will not be repeated here.

[0052] In this specific embodiment 5, the high content of triethyl citrate significantly lowers the glass transition temperature of the resin, resulting in superior resistance to brittleness in the film at low temperatures. Simultaneously, the high pigment content (29 parts) combined with high plasticizer content achieves a color contrast ratio of 31 and excellent UV aging resistance (ΔE decay of only 10%), solving the problem of film embrittlement under high pigment loads and verifying the crucial role of plasticizers in wide-temperature-range applications.

[0053] Specific Embodiment 6: This Specific Embodiment 6 provides a water-based bending color-changing ink and its preparation method.

[0054] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 28 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 39 parts; Aqueous solvent (deionized water: ethanol: ethylene glycol = 8:1:7): ​​22 parts; Dispersant (BYK-190): 2.2 parts; Leveling agent (BYK-346): 0.9 parts; Plasticizer (triethyl citrate): 3.5 parts; Defoamer (BYK-024): 0.4 parts.

[0055] The preparation method is the same as in Specific Example 1, and will not be repeated here.

[0056] The water-based bend-changing color-changing ink prepared in this specific embodiment 6 has a lower solvent content, resulting in higher ink solids content and viscosity, making it more suitable for screen printing processes requiring thick films. Despite the higher viscosity, the ink maintains good printability with sufficient leveling agent (0.9 parts) and dispersant, achieving a yield rate of 92% and exhibiting no significant leveling defects. The color-changing contrast ratio is 29, and the adhesion is 4B, verifying the technical feasibility of the high-solids formulation.

[0057] Specific Embodiment 7: This Specific Embodiment 7 provides a water-based bending color-changing ink and its preparation method.

[0058] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 28 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 39 parts; Aqueous solvent (deionized water:ethanol:ethylene glycol = 8:1:7): ​​25.5 parts; Dispersant (BYK-190): 2.8 parts; Leveling agent (BYK-346): 0.6 parts; Plasticizer (triethyl citrate): 3.2 parts; Defoamer (BYK-024): 0.9 parts.

[0059] The preparation method is the same as in Specific Example 1, and will not be repeated here.

[0060] In this specific embodiment 7, the additive system was optimized, particularly by using a combination of high-content defoamer (0.9 parts) and dispersant (2.8 parts). This combination effectively solved the problem of microbubbles being difficult to eliminate during the printing process, increasing the printing yield to 96% and exhibiting excellent dispersion stability with a viscosity change rate of only 4%. This verifies the significant role of the synergistic effect of additives in improving the process adaptability of the product in this invention.

[0061] Specific Embodiment 8: This Specific Embodiment 8 provides a water-based bending color-changing ink and its preparation method.

[0062] A water-based bend-sensitive color-changing ink has the following formula (by weight): Color-changing core pigment (liquid crystal elastomer nanosphere composite system, particle size 500nm): 28.5 parts; Flexible film-forming resin (waterborne polyurethane dispersion:waterborne acrylate emulsion = 1:1): 39.3 parts; Aqueous solvent (deionized water: ethanol: ethylene glycol = 8:1:7): ​​26 parts; Dispersant (BYK-190): 2.3 parts; Leveling agent (BYK-346): 0.6 parts; Plasticizer (triethyl citrate): 3 parts; Defoamer (BYK-024): 0.3 parts.

[0063] The preparation method is the same as in Specific Example 1, and will not be repeated here.

[0064] This specific embodiment 8 is a preferred embodiment of the present invention, wherein: The core color-changing system utilizes a composite system of 28.5 parts liquid crystal elastomer nanospheres with an optimal average particle size of 500 nm, balancing color-changing contrast with dispersion difficulty. This system abandons traditional single-structure color-changing pigments, leveraging the reversible adjustment characteristics of liquid crystal elastomer molecular conformation to achieve rapid color changing under ≤1MPa bending stress, with reversible cycle counts ≥1200 times, significantly improving color-changing sensitivity and cycle durability.

[0065] Targeted dispersion technology: 2.3 parts of BYK-190 dispersant are selected. This amount is precisely calculated to target the surface characteristics of liquid crystal elastomer nanospheres for dispersion, controlling the particle size of pigment agglomerates to below the micrometer level, making the particle size variation coefficient less than 15%, and improving the dispersion stability by more than 30%; at the same time, it avoids the problem of abnormal ink viscosity caused by excessive dispersant.

[0066] Leveling-Defoaming Synergistic System: This system creatively combines 0.6 parts of BYK-346 leveling agent with 0.3 parts of BYK-024 defoamer. BYK-346 effectively reduces the surface tension of ink to 30-50 mN / m, ensuring printing without pinholes or craters; BYK-024 precisely defoams. The two form a "leveling-defoaming" synergistic system, effectively resolving the technical contradiction in existing additive formulations where "leveling agents stabilize foam while defoamers affect leveling," increasing the printing yield to over 95%.

[0067] Weather-resistant plasticizing system: Adding 3 parts of triethyl citrate as a plasticizer specifically lowers the glass transition temperature of the resin, allowing the film to maintain flexibility in the temperature range of -20℃ to 80℃, with no cracking when bent ≥180°, while not affecting the response performance of the color-changing pigment.

[0068] Comparative Example 1 Compared with Specific Example 8, the difference of Comparative Example 1 is that the plasticizer triethyl citrate is not added, while the other components and preparation methods are the same as those in Specific Example 8.

[0069] Comparative Example 2 Compared with Specific Example 8, the difference in Comparative Example 2 is that the dispersant BYK-190 is replaced with an equal amount of conventional nonionic surfactant (such as Tween-80), while the other components and preparation methods are the same as in Specific Example 8.

[0070] Comparative Example 3 Compared with Specific Example 8, the difference in Comparative Example 3 is that the amount of leveling agent BYK-346 is 1.5 parts and the amount of defoamer BYK-024 is 0.1 parts, that is, the combination of excess leveling agent and insufficient defoamer. Other components and preparation methods are the same as in Specific Example 8.

[0071] To verify the effectiveness and beneficial effects of the technical solution of this invention, the water-based bending color-changing inks prepared in the above specific embodiments and comparative examples were subjected to the following performance tests and analyses. The specific test methods are as follows: (1) Color change performance: The printing film was subjected to a three-point bending test using a universal testing machine, and the color change triggering stress was recorded; the color difference value ΔE before and after bending was measured using a colorimeter.

[0072] (2) Dispersion stability: The ink was stored in a 60℃ oven for 7 days, and the viscosity change rate and pigment sedimentation were measured before and after storage.

[0073] (3) Printability: Print on PET substrate using 200 mesh screen, observe whether there are defects such as shrinkage cavities, pinholes, orange peel on the surface, and calculate the yield rate.

[0074] (4) Bending resistance: After being placed in an environment of -20℃ and 80℃ for 2 hours, a 180° folding test is immediately performed to observe whether the film layer cracks.

[0075] (5) Adhesion: The adhesion was tested according to GB / T 9286-1998.

[0076] (6) Weather resistance and durability: Weather resistance was tested by irradiation with a QUV accelerated aging instrument for 500 hours; fatigue resistance was tested by 1200 bending cycles.

[0077] The test results are shown in Table 1.

[0078]

[0079] Table 1 Test results of specific embodiments and comparative examples Analysis of the test results in the table above shows that the inks prepared in Examples 1-8 all exhibit color-changing stress ≤1MPa and color-changing contrast ratio ΔE ≥25, significantly superior to existing technologies. Specifically, Examples 2 and 8 achieve color-changing contrast ratios of 31-32, indicating that a pigment content of 28-30 parts results in better color-changing effects. This verifies the extremely high sensitivity of the "liquid crystal elastomer nanospheres + metal coordination polymer composite system" employed in this invention. Compared to Comparative Example 2 (where the use of conventional dispersants led to pigment agglomeration, resulting in a color-changing stress of 1.8MPa and a decrease in ΔE to 15), this invention, through the targeted dispersion effect of BYK-190, ensures the uniform distribution of nanospheres, resulting in uniform force transmission and thus achieving a rapid and precise color-changing response.

[0080] Furthermore, in specific embodiments 1-8, the ΔE attenuation was controlled within 15% after 500 hours of QUV aging, and there was no significant performance degradation after more than 1200 bending cycles. This proves the effectiveness of the proposed triple stabilization scheme of "ink formulation optimization + resin crosslinking optimization + UV curing". The synergistic effect of the flexible film-forming resin and plasticizer constructs a stable flexible network, which not only ensures reversible cycle life but also resists the damage to the material structure caused by ultraviolet light and temperature changes.

[0081] In Comparative Example 1, without the addition of triethyl citrate plasticizer, the ink cracked at -20°C, with adhesion dropping to 2B. Cracks also appeared at high temperatures. This indicates that the triethyl citrate added in this invention effectively lowers the resin's glass transition temperature, solving the problem of limited application of traditional inks in a wide temperature range (-20°C to 80°C) and ensuring the structural integrity of the film under different temperature conditions. In Specific Example 5, the plasticizer content reached 5 parts, exhibiting excellent low-temperature performance, further verifying the role of this component.

[0082] In Comparative Example 3, when the leveling agent was excessive and the defoamer insufficient, numerous pinholes appeared on the printed surface, resulting in a yield rate of only 75%. However, in Specific Examples 7 and 8, a synergistic "leveling-defoaming" system was formed by compounding BYK-346 and BYK-024 in a specific ratio, achieving yield rates of 96% and 98%, respectively. This verifies that the present invention resolves the technical contradiction in the prior art where "leveling agents stabilize foam while defoamers affect leveling," achieving high-quality printing without pinholes or craters, and meeting the stringent requirements for refined printing in scenarios such as anti-counterfeiting labels and smart packaging.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A water-based bend-sensitive color-changing ink, characterized in that, By weight, it includes the following components: Color-changing core pigment: 25-30 parts; Flexible film-forming resin: 37-40 parts; Aqueous solvent: 22-27 parts; Dispersant: 1-3 parts; Leveling agent: 0.5–1 part; Plasticizer: 2-5 parts; Defoamer: 0.1–0.5 parts; The color-changing core pigment is a composite system of liquid crystal elastomer nanospheres and metal coordination polymers, and the particle size of the liquid crystal elastomer nanospheres is 300nm-750nm.

2. The water-based bend-sensitive color-changing ink according to claim 1, characterized in that, The flexible film-forming resin is a mixture of an aqueous polyurethane dispersion and an aqueous acrylate emulsion; the weight ratio of the aqueous polyurethane dispersion to the aqueous acrylate emulsion is 1:0.8 to 1.

2.

3. The water-based bend-sensitive color-changing ink according to claim 2, characterized in that, The aqueous solvent is a mixture of deionized water, ethanol, and ethylene glycol, wherein the weight ratio of deionized water, ethanol, and ethylene glycol is 8:1:

7.

4. The water-based bend-sensitive color-changing ink according to claim 1, characterized in that, The dispersant is a high molecular weight block copolymer dispersant; the leveling agent is a polyether-modified polydimethylsiloxane leveling agent; and the defoamer is a polysiloxane defoamer.

5. The water-based bend-sensitive color-changing ink according to claim 4, characterized in that, The dispersant is BYK-190; the leveling agent is BYK-346; and the defoamer is BYK-024.

6. The water-based bend-sensitive color-changing ink according to claim 1, characterized in that, The plasticizer is triethyl citrate.

7. The water-based bend-sensitive color-changing ink according to claim 1, characterized in that, The color-changing core pigment has a color-changing triggering stress ≤1MPa, a color-changing contrast ratio ΔE ≥25, and a reversible cycle count ≥1200 times.

8. A method for preparing a water-based bend-sensitive color-changing ink as described in any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Pre-dispersion: Add the formulated amount of color-changing core pigment to a portion of an aqueous solvent and disperse it by high-speed stirring to obtain a pigment pre-dispersion solution; (2) Grinding: Add dispersant to pigment pre-dispersion liquid and grind until pigment particle size D50 reaches 300-750nm to obtain pigment paste; (3) Paint mixing: While stirring, add the remaining water-based solvent, flexible film-forming resin, plasticizer, leveling agent and defoamer to the color paste, and continue stirring until uniform; (4) Filtration: Filter the well-mixed slurry to obtain water-based bend color-changing ink.

9. An application of the water-based bend-changing ink as described in any one of claims 1-7, characterized in that, The ink is printed onto the surface of the substrate by screen printing, flexographic printing or offset printing, and then dried and UV cured to form a film; the substrate includes PET, flexible paper, fabric or metallized film.

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