A method for preparing a thermochromic anti-counterfeiting coating

Abstract

The application discloses a kind of thermochromic anti-counterfeiting coating and preparation method thereof, belong to optical anti-counterfeiting field.The color-changing anti-counterfeiting coating is composed of three-layer structure, and the upper and lower two layers are the thin layer obtained by heating and curing different concentrations of polymer solution, and the middle layer is the structural color phase change thin layer obtained by spraying structural color phase change coating and heating solvent volatilization, wherein the structural color phase change coating is obtained by mixing structural color nano pigment with monodisperse characteristics and phase change material in ethanol.The thermochromic anti-counterfeiting coating can present different colors when heated to different temperatures, and the coating can recover to the initial color after cooling, and the multiple color changes make it have broad application prospects in the field of high-level anti-counterfeiting.

Description

Technical Field

[0001] This invention belongs to the field of optical anti-counterfeiting, specifically relating to a thermochromic anti-counterfeiting coating and its preparation method. Background Technology

[0002] Counterfeiting is a growing global problem, causing significant damage to national reputation and industry economies. Therefore, developing new anti-counterfeiting technologies to distinguish genuine products from fakes and prevent counterfeiting is crucial for enhancing national image and promoting enterprise development. Among numerous anti-counterfeiting technologies, optical anti-counterfeiting technology, based on the human eye's ability to distinguish colors, is simple and reliable, offering significant advantages in public anti-counterfeiting and is widely used in currency, food, pharmaceuticals, and clothing. However, common static optical anti-counterfeiting technologies such as watermarks, hot stamping, and holograms are easily cracked and counterfeited because their images and colors are fixed and visible. Therefore, there is an urgent need to develop new optical anti-counterfeiting technologies with responsiveness to stimuli and diverse color changes.

[0003] This invention discloses a thermochromic anti-counterfeiting coating and its preparation method. The coating consists of three layers: the top and bottom layers are thin layers obtained by heating and curing polymer solutions of different concentrations; the middle layer is a structural color phase change coating obtained by spraying a structural color phase change paint and then heating to evaporate the solvent. The structural color phase change paint is obtained by mixing structural color nano-pigments with monodisperse properties with a phase change material in ethanol. This thermochromic anti-counterfeiting coating exhibits different colors when heated to different temperatures, and it can revert to its initial color after cooling. This multi-color change makes it promising for applications in advanced anti-counterfeiting fields. Summary of the Invention

[0004] This invention discloses a thermochromic anti-counterfeiting coating and its preparation method. The coating consists of three layers: the top and bottom layers are thin layers obtained by heating and curing polymer solutions of different concentrations; the middle layer is a structural color phase change coating obtained by spraying a structural color phase change paint and then heating to evaporate the solvent. The structural color phase change paint is obtained by mixing structural color nano-pigments with monodisperse properties with a phase change material in ethanol. This thermochromic anti-counterfeiting coating exhibits different colors when heated to different temperatures, and returns to its initial color after cooling. This multi-color change makes it promising for applications in advanced anti-counterfeiting fields. This invention also provides a method for preparing the thermochromic anti-counterfeiting coating, comprising the following steps:

[0005] (1) The structural color nano pigments with monodisperse characteristics and the phase change materials were mixed in ethanol at a certain mass ratio and stirred at 40~60 ℃ for 1~3 h to make them uniformly mixed, so as to prepare structural color phase change coatings with different structural colors.

[0006] (2) A thin polymer layer is obtained by brushing a uniform polymer solution onto the substrate and drying it in an oven at 70~90 ℃. Then, the structural color phase change coating with different structural colors prepared in step (1) is sprayed onto the substrate and dried in an oven at 50~70 ℃. A low-concentration polymer solution is brushed onto the surface of the obtained coating and placed in an oven at 70~90 ℃ for drying to obtain a thermochromic anti-counterfeiting coating with a "sandwich" structure (polymer / structural color phase change coating / polymer).

[0007] Preferably, in the above-mentioned thermochromic anti-counterfeiting coating, the structural color nano-pigment in the structural color phase change coating has a mass fraction of 60%~75% and a mass fraction of phase change material of 25%~40%.

[0008] Preferably, the structural color nano-pigment in the structural color phase change coating of the above-mentioned thermochromic anti-counterfeiting coating is any one of hollow silicon dioxide, hollow titanium dioxide, hollow zirconium dioxide, hollow tin dioxide, or hollow copper oxide microspheres.

[0009] Preferably, the phase change material in the above-mentioned thermochromic anti-counterfeiting coating is any one of stearic acid, lauric acid, palmitic acid, myristic acid, or decanoic acid.

[0010] Preferably, the polymer solution in the above-mentioned thermochromic anti-counterfeiting coating is any one of water-based acrylic resin, water-based polyurethane, polyacrylic resin, epoxy resin, or polyethylene.

[0011] Preferably, the mass fraction of the low-concentration polymer solution in the above-mentioned thermochromic anti-counterfeiting coating is 2-5%.

[0012] Beneficial effects: The thermochromic anti-counterfeiting coating prepared by this invention exhibits a variety of different colors with temperature changes and possesses reversible thermochromic properties, making its diverse color changes difficult to imitate. Secondly, the thermochromic anti-counterfeiting coating prepared by this invention is easy to use; it can easily achieve patterned effects through spraying, and has broad application prospects in the field of advanced anti-counterfeiting. Attached Figure Description

[0013] Figure 1 Optical photographs taken during the heating and cooling process of the thermochromic anti-counterfeiting coating prepared in Example 1;

[0014] Figure 2 The reflection spectrum of the thermochromic anti-counterfeiting coating prepared in Example 1 during the heating and cooling process is shown. Detailed Implementation

[0015] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0016] Example 1:

[0017] (1) A structural color phase change coating was prepared by blending. The specific operation steps are as follows: Hollow silica microspheres with monodisperse characteristics and a particle size range of 200~500 nm were used as the color-generating component and stearic acid was used as the phase change component. The two were blended in ethanol at a certain mass ratio (65% of the mass fraction of hollow silica microspheres and 35% of the mass fraction of stearic acid) and stirred at 40 °C for 3 h to make them uniformly mixed, thus preparing a structural color phase change coating with different structural colors.

[0018] (2) A thermochromic anti-counterfeiting coating was prepared by brushing, spraying, and heat curing. The specific steps are as follows: First, a layer of water-based acrylic resin solution was brushed onto a glass slide and dried in an oven at 70 ℃ to form a thin layer of acrylic resin. Then, the structural color phase change coating prepared in step (1) was sprayed onto the slide and dried in an oven at 50 ℃. After drying, a water-based acrylic resin solution (mass fraction 2%) was brushed onto the surface and dried in an oven at 70 ℃ to form a thermochromic anti-counterfeiting coating. By using hollow silica microspheres of different particle sizes as the color-generating component, thermochromic anti-counterfeiting coatings with different colors can be prepared.

[0019] In this embodiment, purple, green, and blue structural color-changing coatings were prepared by blending purple, blue, and green hollow silica microspheres with particle sizes of 316 nm, 342 nm, and 402 nm with stearic acid, respectively. These coatings were then applied by brushing and heat curing to obtain colored thermochromic anti-counterfeiting coatings. Optical photographs of the coatings during the heating and cooling processes are shown below. Figure 1As shown in the figure. During the heating process, the coating exhibits a bright color at 67 ℃. Above 67 ℃ but below 70 ℃, the color gradually changes from purple, green, and blue to black. When the temperature is heated from 70 ℃ to 100 ℃, the color remains black. Above 100 ℃ but below 110 ℃, the color gradually changes from black to the initial purple, green, and blue, and remains multicolored at 110 ℃. During the cooling process, below 110 ℃ but above 100 ℃, the color gradually changes from purple, green, and blue to black. When the temperature is lowered from 100 ℃ to 70 ℃, the color remains black. Below 70 ℃ but above 64 ℃, the color gradually changes from black to purple, green, and blue, and remains multicolored at 64 ℃. The reflectance spectrum of the obtained thermochromic coating during heating and cooling processes is shown in the figure. Figure 2 As shown.

[0020] Examples 2-5:

[0021] Hollow titanium dioxide, hollow zirconium dioxide, hollow tin dioxide, and hollow copper oxide microspheres were used instead of the hollow silica microspheres in Example 1 as structural color nanopigments, and other conditions were the same as in Example 1. Coatings with reversible thermochromic effects could also be obtained.

[0022] Example 6:

[0023] (1) A structural color phase change coating was prepared by blending. The specific operation steps are as follows: Hollow silica microspheres with monodisperse characteristics and a particle size range of 200~500 nm were used as the color-generating component and lauric acid was used as the phase change component. The two were blended in ethanol at a certain mass ratio (60% mass fraction of hollow silica microspheres and 40% mass fraction of lauric acid) and stirred at 50 °C for 2 h to make them uniformly mixed, thus preparing a structural color phase change coating with different structural colors.

[0024] (2) A thermochromic anti-counterfeiting coating was prepared by brushing, spraying, and heat curing. The specific steps are as follows: First, a layer of water-based polyurethane solution was brushed onto a glass slide and dried in an oven at 80 ℃ to form a thin polyurethane layer. Then, the structural color phase change coating prepared in step (1) was sprayed onto the slide and dried in an oven at 60 ℃. After drying, a water-based polyurethane solution (mass fraction 3%) was brushed onto the surface and dried in an oven at 80 ℃ to form a thermochromic anti-counterfeiting coating. By using the above method, thermochromic anti-counterfeiting coatings with different colors can be prepared by using hollow silica microspheres of different particle sizes as the color-generating component.

[0025] Examples 7-10:

[0026] Hollow titanium dioxide, hollow zirconium dioxide, hollow tin dioxide, and hollow copper oxide microspheres were used instead of the hollow silica microspheres in Example 6 as structural color nanopigments, and other conditions were the same as in Example 6. Coatings with reversible thermochromic effects could also be obtained.

[0027] Example 11:

[0028] (1) A structural color phase change coating was prepared by blending. The specific operation steps are as follows: Hollow silica microspheres with monodisperse characteristics and a particle size range of 200~500 nm were used as the color-generating component, and palmitic acid was used as the phase change component. The two were blended in ethanol at a certain mass ratio (the mass fraction of hollow silica microspheres was 70% and the mass fraction of palmitic acid was 30%), and stirred at 60 °C for 1 h to make them uniformly mixed, thus preparing a structural color phase change coating with different structural colors.

[0029] (2) A thermochromic anti-counterfeiting coating was prepared by brushing, spraying, and heat curing. The specific steps are as follows: First, a layer of polyacrylic acid resin solution was brushed onto a glass slide and dried in an oven at 90 ℃ to form a thin layer of polyacrylic acid resin. Then, the structural color phase change coating prepared in step (1) was sprayed onto the slide and dried in an oven at 70 ℃. After drying, a polyacrylic acid resin solution (mass fraction 4%) was brushed onto the surface and dried in an oven at 90 ℃ to form a thermochromic anti-counterfeiting coating. By using hollow silica microspheres of different particle sizes as the color-generating component, thermochromic anti-counterfeiting coatings with different colors can be prepared.

[0030] Examples 12-15:

[0031] Hollow titanium dioxide, hollow zirconium dioxide, hollow tin dioxide, and hollow copper oxide microspheres were used instead of the hollow silica microspheres in Example 11 as structural color nanopigments, and other conditions were the same as in Example 11. Coatings with reversible thermochromic effects could also be obtained.

[0032] Example 16:

[0033] (1) A structural color phase change coating was prepared by blending. The specific operation steps are as follows: Hollow silica microspheres with monodisperse characteristics and a particle size range of 200~500 nm were used as the color-generating component and myristic acid was used as the phase change component. The two were blended in ethanol at a certain mass ratio (the mass fraction of hollow silica microspheres was 75% and the mass fraction of palmitic acid was 25%) and stirred at 40 °C for 3 h to make them uniformly mixed, thus preparing a structural color phase change coating with different structural colors.

[0034] (2) A thermochromic anti-counterfeiting coating was prepared by brushing and heating curing. The specific steps are as follows: First, an epoxy resin solution was brushed onto a glass slide and dried in an oven at 70 ℃ to form a thin epoxy resin layer. Then, the structural color phase change coating prepared in step (1) was brushed onto the slide using the same brushing method. After drying in an oven at 50 ℃, an epoxy resin solution (mass fraction 5%) was brushed onto its surface and dried in an oven at 70 ℃ to form a thermochromic anti-counterfeiting coating. By using the above method, thermochromic anti-counterfeiting coatings with different colors can be prepared by using hollow silica microspheres of different particle sizes as color-generating components.

[0035] Examples 17-20:

[0036] Hollow titanium dioxide, hollow zirconium dioxide, hollow tin dioxide, and hollow copper oxide microspheres were used instead of the hollow silica microspheres in Example 16 as structural color nanopigments, and other conditions were the same as in Example 16. Coatings with reversible thermochromic effects could also be obtained.

[0037] Example 21:

[0038] (1) A structural color phase change coating was prepared by blending. The specific operation steps are as follows: Hollow silica structural color nano-pigments with monodisperse characteristics and a particle size range of 200~500 nm were used as the color-generating component, and decanoic acid was used as the phase change component. The two were blended in ethanol at a certain mass ratio (60% mass fraction of hollow silica microspheres and 40% mass fraction of palmitic acid), and stirred at 50 °C for 2 h to make them uniformly mixed, thus preparing a structural color phase change coating with different structural colors.

[0039] (2) A thermochromic anti-counterfeiting coating was prepared by brushing and heating curing. The specific steps are as follows: First, a layer of polyethylene solution was brushed onto a glass slide in one pass and dried in an oven at 80 ℃ to form a thin polyethylene layer. Then, the structural color phase change coating prepared in step (1) was brushed onto the slide using the same brushing method. After drying in an oven at 60 ℃, a polyethylene solution (mass fraction 2%) was brushed onto the surface and dried in an oven at 80 ℃ to form a thermochromic anti-counterfeiting coating. By using the above method, thermochromic anti-counterfeiting coatings with different colors can be prepared by using hollow silica microspheres of different particle sizes as the color-generating components.

[0040] Examples 22-25:

[0041] Hollow titanium dioxide, hollow zirconium dioxide, hollow tin dioxide, and hollow copper oxide microspheres were used instead of the hollow silica microspheres in Example 21 as structural color nanopigments, and other conditions were the same as in Example 21. Coatings with reversible thermochromic effects could also be obtained.

[0042] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for the preparation of a thermochromic anti-counterfeiting coating, characterized in that It comprises the following steps: (1) blending the structural color nano pigment with monodisperse properties and phase change material in ethanol with a certain mass ratio, and stirring at 40-60 ℃ for 1-3 h to make them uniformly mixed, to prepare a structural color phase change coating with different structural colors; the structural color nano pigment in the structural color phase change coating is any one of hollow silica, hollow titanium dioxide, hollow zirconium dioxide, hollow tin dioxide or hollow copper oxide microspheres; (2) brushing a uniform layer of polymer solution on the substrate, drying in an oven at 70-90 ℃ to obtain a thin layer of polymer, then spraying the different structural color phase change coating prepared in step (1), drying in an oven at 50-70 ℃, then brushing a low-concentration polymer solution on the surface of the obtained coating, and drying in an oven at 70-90 ℃ to obtain a heat-induced color-changing anti-counterfeiting coating with a sandwich structure.

2. A method of preparing a thermochromic anti-counterfeiting coating according to claim 1, characterized in that The mass fraction of the structural color nano pigment in step (1) is 60%-75%, and the mass fraction of the phase change material is 25%-40%.

3. A method of preparing a thermochromic anti-counterfeiting coating according to claim 1, characterized in that The phase change material in step (1) is any one of stearic acid, lauric acid, palmitic acid, myristic acid or capric acid.

4. A method of preparing a thermochromic anti-counterfeiting coating according to claim 1, characterized in that The polymer solution in step (2) is any one of water-based acrylic resin, water-based polyurethane, polyacrylic acid resin, epoxy resin or polyethylene.

5. A method of preparing a thermochromic anti-counterfeiting coating according to claim 1, characterized in that The mass fraction of the low-concentration polymer solution in step (2) is 2-5%.

Images