Color-changing microcapsule, color-changing ink, and preparation method and application thereof

Abstract

The present invention discloses a color-changing microcapsule, a color-changing ink, and a preparation method and application thereof, wherein a color-changing microcapsule comprises a capsule core and a capsule wall, wherein the capsule wall is composed of PVA and a wall material in a mass ratio of (5-30): (70-250). The present invention can not only effectively ensure that the capsule wall itself has an isolation effect, effectively isolate the influence of external environmental changes on the capsule core in the capsule wall, avoid the performance of the capsule core from being greatly changed due to environmental interference, and improve the stability of the capsule core; at the same time, it can also better improve the bonding performance with the ink connector, thereby improving the ink adhesion performance, so that after subsequent printing, it will not affect the printing of the ink and can be well attached to the surface of the substrate; the present invention can effectively achieve the effect of taking both stability and adhesion into account.

Description

Technical Field

[0001] The invention relates to the field of inks, and in particular to a color-changing microcapsule, a color-changing ink, and a preparation method and application thereof. Background Art

[0002] Ink is an important material used in printing. It prints or sprays patterns and texts on substrates. It is usually used for printing books, packaging, architectural decoration, electronic circuit boards, etc. With the increase in demand, the variety and output of inks have also expanded and increased accordingly; among them, the color-changing anti-counterfeiting process prepared by anti-counterfeiting color-changing ink is widely used in high-end packaging.

[0003] The anti-counterfeiting color-changing ink disclosed in the prior art usually includes components such as photochromic components, ink connectors, and solvents. The color-changing components are connected by the ink connector to ensure uniform flow of the ink and enhance the ink adhesion performance. For example, Chinese patent document CN101319108A ​​discloses a photochromic ink material in a novel circularly polarized ink and a method for manufacturing the same, wherein mixed liquid crystal is hardened as a color-changing component to form a capsule, and the capsule is then mixed with a binder composed of resin, filler, solvent, etc. to prepare a color-changing ink. Although this method can effectively prepare a color-changing ink, the color-changing material is easily affected by acidity, alkalinity, external factors, organic solvents, etc., resulting in a certain degree of limitation in its application.

[0004] The Japanese patent document JP2006212573A discloses a photochromic microcapsule ink composition using photochromic microcapsules and a production method of photochromic microcapsules, which discloses a technical means of using a polymer film to coat a photochromic agent to form microcapsules. The inside of the microcapsule is blocked from the outside by the polymer film, so the photooxidant and the color-changing pigment are not easily affected by the outside world and have good stability. Although this method can solve the problem of limited application of color-changing materials, the preparation method has the problem of uneven dispersion of the photochromic agent, which leads to the large size of some microcapsules affecting the adhesion performance; and even after removing the larger particulate matter, the ink composed of the microcapsules still has the problem of poor adhesion, so it is extremely easy to be wiped off after printing.

[0005] Furthermore, the photochromic agents used in inks in the prior art are usually photochromic liquid crystal materials, which have a single color change pathway and are subject to significant limitations in application scenarios. Summary of the invention

[0006] Therefore, the first problem to be solved by the present invention is that the existing color-changing ink cannot take into account both stability and adhesion; thus, a color-changing microcapsule, color-changing ink, and a preparation method and application thereof that can solve the above problems are provided.

[0007] Specifically, a color-changing microcapsule includes a capsule core and a capsule wall, wherein the raw materials of the capsule wall include PVA and wall material in a mass ratio of (5-30): (70-250).

[0008] The capsule wall refers to a micro container or packaging with a polymer shell made of natural or synthetic organic or polymer materials through microencapsulation, and its size ranges from a few microns to hundreds of microns. Microencapsulation refers to the process of using solid particles, liquid droplets or gases as the inner material of the capsule to form a continuous and thin capsule on the outside.

[0009] The wall material in the present invention is an organic material that is transparent after forming the capsule wall. Preferably, the wall material is melamine resin or isophorone diisocyanate; the melamine resin is a polymer obtained by the reaction of melamine and formaldehyde, also known as melamine formaldehyde resin, melamine-formaldehyde resin (melamine-formaldehyde resin); the English abbreviation is MF.

[0010] And / or, the capsule core comprises small molecule nematic liquid crystal and a chiral agent.

[0011] The mass ratio of the small molecule nematic liquid crystal to the chiral agent is 100:(35-111);

[0012] If the capsule wall is too thick, the color change effect will not be obvious, and if it is too thin, the protection effect will be poor and the stability will be poor; therefore, the mass ratio of the wall material to the small molecule nematic liquid crystal in the present invention is preferably (70-250):100, which can effectively ensure that the capsule wall thickness is moderate, will not affect the color change effect, and can also ensure stability. Preferably, when the wall material is melamine resin, the mass ratio of the wall material to the small molecule nematic liquid crystal is preferably (70-100):100; when the wall material is isophorone diisocyanate, the mass ratio of the wall material to the small molecule nematic liquid crystal is preferably (100-250):100.

[0013] The second problem to be solved by the present invention is that the ink prepared by the existing process has a single color change pathway; thereby providing a color-changing microcapsule, color-changing ink, and a preparation method and application thereof that enhance product recognition and further expand application scenarios.

[0014] Specifically, the capsule core also includes a viologen compound, and the general structural formula of the viologen compound is as follows: Preferably, the mass ratio of the viologen compound to the small molecule nematic liquid crystal is 50:100.

[0015] A color-changing ink comprises the above-mentioned color-changing microcapsules.

[0016] The above-mentioned color-changing ink also includes an organic solvent and an ink connector;

[0017] Preferably, the organic solvent comprises one or more of acetone, ethyl acetate, dipropylene glycol monomethyl ether and dimethyl phthalate; and / or the ink connector comprises polyurethane and / or polyethylene glycol;

[0018] Preferably, the mass ratio of the small molecule nematic liquid crystal to the organic solvent and the ink linker in the color-changing microcapsule is 100:(50-80):(10-25).

[0019] The above-mentioned color-changing ink also includes an auxiliary agent. Preferably, the auxiliary agent includes one or more of a thickener, a defoaming agent and water.

[0020] The thickener is a natural thickener or / and a synthetic thickener; preferably, the natural thickener includes one or more of starch, gum arabic, gelatin, alginate, guar gum and dextrin; and / or the synthetic thickener includes one or more of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium alginate, sodium polyacrylate, polyoxyethylene and polyvinyl pyrrolidone;

[0021] And / or, the defoamer is a non-silicon defoamer or a silicone defoamer; preferably, the non-silicon defoamer includes one or more of an alcohol defoamer, a fatty acid defoamer, a fatty acid ester defoamer, a phosphate defoamer, a mineral oil defoamer and an amide defoamer;

[0022] And / or, based on 100 parts by weight of the small molecule nematic liquid crystal in the color-changing microcapsule, the thickener is 1-10 parts by weight, and / or, the defoamer is 0.1-3 parts by weight, and / or, the water is 10-50 parts by weight.

[0023] A method for preparing color-changing microcapsules, comprising:

[0024] The raw materials of the capsule core are used to prepare the capsule core material;

[0025] PVA and water are used to prepare a PVA aqueous solution, and the PVA aqueous solution, capsule core material and wall material are mixed to prepare a microcapsule solution by an in-situ polymerization method. The microcapsule solution is filtered, washed and dried to obtain color-changing microcapsules.

[0026] The preparation process of the capsule core material is: mixing small molecule nematic phase liquid crystal and chiral agent in different proportions, heating until clear and then cooling to prepare the capsule core material; more preferably, mixing with viologen compound after the cooling step to obtain the capsule core material;

[0027] And / or, the mass concentration of PVA in the PVA aqueous solution is 1-10%.

[0028] When the wall material is melamine resin, the core material and the wall material are mixed and then PVA aqueous solution is added, and the pH value is adjusted to 4-5 and then stirred to react to obtain a microcapsule solution; preferably, the pH value is adjusted using acetic acid solution;

[0029] When the wall material is isophorone diisocyanate, the core material and the PVA aqueous solution are mixed and then the wall material is added to obtain a microcapsule solution through a catalytic reaction; preferably, the catalyst is dibutyltin dilaurate.

[0030] A method for preparing a color-changing ink comprises: mixing the color-changing microcapsules prepared by the above-mentioned preparation method with an organic solvent and an ink connector to prepare the color-changing ink; preferably, an auxiliary agent is also added during the preparation process.

[0031] A color-changing microcapsule or a color-changing ink is used in anti-counterfeiting. Specifically, when the ink to be identified is at different angles between the light source and the ink surface, it presents a mixture of different colors; if the ink is red below 20°C, the color-changing ink of the present invention changes from green, light blue, dark blue, purple, red, orange, and yellow to purple in the process of the temperature rising from 20°C to 80°C; specifically, in the temperature range of about 20-50°C, the color changes approximately every 3-5°C, from green, light blue, dark blue, purple, red, orange to yellow in turn, and changes to purple after the temperature is continuously raised from 50°C to 80°C. According to the color change, it can be judged whether it is an ink containing specific color-changing microcapsules, so as to achieve the purpose of identification and the anti-counterfeiting effect.

[0032] The technical solution of the present invention has the following advantages:

[0033] 1. The color-changing microcapsule provided by the present invention comprises a capsule core and a capsule wall. The present invention optimizes the material composition of the capsule wall and adopts PVA and wall material with a mass ratio of (5-30): (70-250) to form the capsule wall. This can not only effectively ensure that the capsule wall itself has an isolating effect, but also effectively isolate the influence of external environmental changes on the capsule core in the capsule wall, avoid that the performance of the capsule core will change significantly due to environmental interference, and improve the stability of the capsule core; at the same time, it can also better improve the bonding performance with the ink connector, thereby improving the ink adhesion performance. Therefore, after subsequent printing, it will not affect the printing of the ink and can be well attached to the surface of the substrate. Through the optimization of the scheme of the present invention, the effect of taking both stability and adhesion into consideration can be effectively achieved.

[0034] 2. The color-changing microcapsule provided by the present invention further optimizes the composition of the capsule core. The capsule core not only includes a photochromic agent obtained by mixing a conventional small molecule nematic phase liquid crystal and a chiral agent, but also includes a viologen compound, and the mass ratio of the viologen compound to the small molecule nematic phase liquid crystal is 50:100. Through the optimization of the present invention, it not only has photochromic properties, but also has reversible thermochromic properties, effectively achieving a dual color-changing approach. Therefore, the present invention increases the color-changing properties and stability of the color-changing microcapsules, and thus can obtain a color-changing printing ink that can be used in a variety of scenarios and is convenient for the public to identify the authenticity of goods, thereby achieving the effect of enhancing product recognition and effectively expanding the application scenarios;

[0035] Specifically, the molecules of small molecule nematic liquid crystal are arranged in layers, and there is a slight twist angle between the long axes of the molecules in each layer. The arrangement direction of the multilayer molecules is gradually twisted, forming a spiral structure, and the degree of spirality is characterized by the pitch P. When the period of the spiral structure is of the same order of magnitude as the wavelength of the incident light, the pitch acts as a diffraction grating, and the spiral structure selectively reflects the polarization component of the light, thereby presenting different colors. In addition, when the temperature changes slightly, the pitch will also change, thereby presenting a change in color. Adding a chiral agent to a nematic phase liquid crystal can form a spiral structure, and the pitch of the resulting liquid crystal mixture will change with the amount of chiral agent added, thereby presenting different colors; therefore, the ratio of small molecule nematic phase liquid crystal and chiral agent can be determined according to the desired ink color; for example: red when the ratio is 100:35, orange when 100:50, yellow when 100:58, green when 100:74, cyan when 100:88, blue when 100:95, and purple when 100:111; the present invention forms a photochromic agent by the cooperation of small molecule nematic phase liquid crystal and chiral agent;

[0036] At the same time, the viologen compound of the present invention has two positive charges (V 2+ ), which has electron-deficient characteristics; therefore, it is easily reduced under external conditions such as light, heat, electricity or solvation to generate viologen free radical cations (V ·+ ), or it can continue to generate electrons to generate the neutral product V of violacein. The colors of these three different charged violaceins are significantly different. When violacein V 2+ Get an electron and turn it into V ·+ Finally, due to the different charges on the pyridine N, the charge can be delocalized on the entire pyridine ring, and the viologen radical cation V ·+Usually it will show a darker color, and the free radical is unstable and can quickly lose an electron to turn back to the original substance, so the viologen compound can show rich and reversible color changes. It can be seen from this that in fact, the viologen compound is very susceptible to interference from the external environment, resulting in unexpected color changes. It is precisely because of its various color change pathways that its color change pathways are not easy to be used in inks, and viologen compounds are usually not used in inks; but in the present invention, the viologen compound is isolated by the capsule wall, and other color change pathways except temperature are eliminated, and only the temperature color change pathway is retained; and the study found that the two materials will not react with each other, and will not cause the color change to fail. The two are evenly mixed and exist in the microcapsule at the same time, and can achieve color change in different pathways; in this way, the viologen compound and the photochromic agent cooperate with each other to achieve the temperature change effect while not affecting the light change pathway.

[0037] 3. The preparation method of the color-changing microcapsules provided by the present invention adopts an in-situ polymerization method and relies on the in-situ polymerization of monomers or prepolymers at the oil-water interface to form a polymer capsule wall on the surface of the dispersed phase core material. This method is easy to operate, the product is easy to form into balls, the reaction is easy to control, the cost is low, and it is suitable for industrial production. DETAILED DESCRIPTION

[0038] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0039] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0040] Example 1

[0041] A color-changing microcapsule uses melamine resin as a wall material. The raw materials of the microcapsule include: 100 parts of small molecule nematic phase liquid crystal, 35 parts of a chiral agent, 50 parts of a viologen compound, 10 parts of PVA, and 80 parts of a melamine resin prepolymer. The raw materials of the melamine resin prepolymer include melamine, formaldehyde, and deionized water in a mass ratio of about 10:30:40.

[0042] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 60 parts of an organic solvent, 15 parts of an ink connector, and 25 parts of deionized water; wherein the organic solvent is ethyl acetate and the ink connector is polyethylene glycol.

[0043] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0044] Step 1: Preparation of capsule core material.

[0045] 100 g of small molecule nematic liquid crystal and 35 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0046] Step 2: Preparation of color-changing microcapsules.

[0047] Firstly, a PVA aqueous solution and a melamine resin prepolymer are prepared respectively;

[0048] The preparation of the PVA aqueous solution is as follows: 10 g of PVA is dissolved in water to prepare a PVA aqueous solution, wherein the mass concentration of the PVA aqueous solution is 5%;

[0049] The preparation of the melamine resin prepolymer is as follows: according to the mass ratio of melamine to formaldehyde of 1:3, melamine and a formaldehyde solution with a concentration of 37% are weighed and mixed; the pH value is adjusted to 8-9 with a triethanolamine aqueous solution, the temperature is raised to 60°C with stirring, and the melamine is reacted until the melamine is completely dissolved; the formaldehyde is diluted with water of the same volume, the reaction is continued for 20 minutes, and the melamine resin prepolymer is obtained, and the constant temperature of 60°C is maintained for standby use;

[0050] The reserved capsule core material is stirred at a constant temperature of 60°C for 20 minutes at a speed of 1500 r / min; 80 g of melamine resin prepolymer is slowly added to the capsule core material in step 1, and then the PVA aqueous solution prepared above is added as a protective colloid, and the pH value of the system is adjusted to 4-5 with acetic acid solution at a constant temperature of 1000 r / min, and stirred at a constant temperature of 400 r / min for 2.5 hours; after cooling, it is filtered, washed and dried to obtain color-changing microcapsules.

[0051] Step 3: Preparation of color-changing ink.

[0052] The color-changing ink was prepared by adding 60 g of organic solvent, 15 g of ink connector and 25 g of deionized water to the color-changing microcapsules prepared in step 2 and stirring evenly.

[0053] The color-changing ink prepared in this embodiment appears red when the temperature is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0054] Example 2

[0055] A color-changing microcapsule uses isophorone diisocyanate as a wall material and dibutyltin dilaurate as a catalyst. The raw materials include: 100 parts of small molecule nematic liquid crystal, 58 parts of a chiral agent, 50 parts of a viologen compound, 20 parts of PVA, 200 parts of isophorone diisocyanate, and 10 parts of dibutyltin dilaurate.

[0056] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 80 parts of an organic solvent, 20 parts of an ink connector, and 30 parts of deionized water; wherein the organic solvent is dipropylene glycol monomethyl ether, and the ink connector is polyurethane.

[0057] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0058] Step 1: Preparation of capsule core material.

[0059] 100 g of small molecule nematic liquid crystal and 58 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0060] Step 2: Preparation of color-changing microcapsules.

[0061] The PVA aqueous solution is prepared first and then the color-changing microcapsules are prepared.

[0062] The preparation process of the PVA aqueous solution is as follows: 20 g of PVA is dissolved in water to prepare the PVA aqueous solution, and the mass concentration of the PVA aqueous solution is 10%.

[0063] The preparation of color-changing microcapsules is as follows: the reserved capsule core material is mixed evenly with the prepared PVA aqueous solution to obtain an emulsion, the mixing method is stirring, the stirring speed is 1000-3000r / min, and the speed of 1500r / min is used for 6min in this embodiment; 200g of isophorone diisocyanate (IPDI) is slowly added to the above emulsion, and emulsified at the same emulsification rate for 6min. Then transfer it to a three-necked flask, add 10g of catalyst dibutyltin dilaurate (DBTDL), and react for 6h at a certain stirring rate, the stirring rate is 500-2500r / min, and 1000r / min is used in this embodiment, and the reaction temperature is 40°C. After the reaction is completed, filter and vacuum dry to obtain color-changing microcapsules.

[0064] Step 3: Preparation of color-changing ink.

[0065] Add 80 g of organic solvent, 20 g of ink connector and 30 g of deionized water to the color-changing microcapsules prepared in step 2, and stir evenly to prepare the color-changing ink.

[0066] The color-changing ink prepared in this embodiment appears yellow when the temperature is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0067] Example 3

[0068] A color-changing microcapsule uses melamine resin as a wall material. The raw materials of the microcapsule include: 100 parts of small molecule nematic phase liquid crystal, 88 parts of a chiral agent, 50 parts of a viologen compound, 5 parts of PVA, and 70 parts of a melamine resin prepolymer. The raw materials of the melamine resin prepolymer include melamine, formaldehyde, and deionized water in a mass ratio of about 10:30:40.

[0069] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 50 parts of an organic solvent, 10 parts of an ink connector, and 50 parts of deionized water; wherein the organic solvent is ethyl acetate and the ink connector is polyethylene glycol.

[0070] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0071] Step 1: Preparation of capsule core material.

[0072] 100 g of small molecule nematic liquid crystal and 88 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0073] Step 2: Preparation of color-changing microcapsules.

[0074] Firstly, a PVA aqueous solution and a melamine resin prepolymer are prepared respectively;

[0075] The preparation of the PVA aqueous solution is as follows: 5 g of PVA is dissolved in water to prepare a PVA aqueous solution, wherein the mass concentration of the PVA aqueous solution is 5%;

[0076] The preparation of melamine resin prepolymer is as follows: according to the mass ratio of melamine to formaldehyde of 1:3, melamine and formaldehyde solution with a concentration of 37% are weighed and mixed; the pH value is adjusted to 8-9 with triethanolamine aqueous solution, the temperature is raised to 60°C with stirring, and the melamine is reacted until the melamine is completely dissolved; the formaldehyde is diluted with water of the same volume, the reaction is continued for 20 minutes, and the melamine resin prepolymer is obtained, and the constant temperature of 60°C is maintained for standby use;

[0077] The reserved capsule core material is stirred at a constant temperature of 60°C for 20 minutes at a speed of 1500 r / min; 70 g of melamine resin prepolymer is slowly added to the capsule core material in step 1, and then the PVA aqueous solution prepared above is added as a protective colloid, and the pH value of the system is adjusted to 4-5 with acetic acid solution at a constant temperature of 1000 r / min, and stirred at a constant temperature of 400 r / min for 2.5 hours; after cooling, it is filtered, washed and dried to obtain color-changing microcapsules.

[0078] Step 3: Preparation of color-changing ink.

[0079] Add 50 g of organic solvent, 10 g of ink connector and 50 g of deionized water to the color-changing microcapsules prepared in step 2, and stir evenly to prepare the color-changing ink.

[0080] The color-changing ink prepared in this embodiment is cyan when it is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, changing one color at about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0081] Example 4

[0082] A color-changing microcapsule uses melamine resin as a wall material. The raw materials of the microcapsule include: 100 parts of small molecule nematic phase liquid crystal, 111 parts of a chiral agent, 50 parts of a viologen compound, 30 parts of PVA, and 100 parts of a melamine resin prepolymer. The raw materials of the melamine resin prepolymer include melamine, formaldehyde, and deionized water in a mass ratio of about 10:30:40.

[0083] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 80 parts of an organic solvent, 25 parts of an ink connector, and 10 parts of deionized water; wherein the organic solvent is ethyl acetate and the ink connector is polyethylene glycol.

[0084] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0085] Step 1: Preparation of capsule core material.

[0086] 100 g of small molecule nematic liquid crystal and 111 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0087] Step 2: Preparation of color-changing microcapsules.

[0088] Firstly, a PVA aqueous solution and a melamine resin prepolymer are prepared respectively;

[0089] The preparation of the PVA aqueous solution is as follows: 30 g of PVA is dissolved in water to prepare a PVA aqueous solution, wherein the mass concentration of the PVA aqueous solution is 10%;

[0090] The preparation of melamine resin prepolymer is as follows: according to the mass ratio of melamine to formaldehyde of 1:3, melamine and formaldehyde solution with a concentration of 37% are weighed respectively, and mixed; the pH value is adjusted to 8-9 with triethanolamine aqueous solution, the temperature is raised to 60°C with stirring, and the melamine is reacted until the melamine is completely dissolved; the formaldehyde is diluted with water of the same volume, the reaction is continued for 20 minutes, and the melamine resin prepolymer is obtained, and the constant temperature of 60°C is maintained for standby use;

[0091] The reserved capsule core material is stirred at a constant temperature of 60°C for 20 minutes at a speed of 1500 r / min; 100 g of melamine resin prepolymer is slowly added to the capsule core material in step 1, and then the PVA aqueous solution prepared above is added as a protective colloid, and the pH value of the system is adjusted to 4-5 with acetic acid solution at a constant temperature of 1000 r / min, and stirred at a constant temperature of 400 r / min for 2.5 hours; after cooling, it is filtered, washed and dried to obtain color-changing microcapsules.

[0092] Step 3: Preparation of color-changing ink.

[0093] The color-changing ink was prepared by adding 80 g of organic solvent, 25 g of ink connector and 10 g of deionized water to the color-changing microcapsules prepared in step 2 and stirring evenly.

[0094] The color-changing ink prepared in this embodiment appears purple when it is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, changing one color at about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0095] Example 5

[0096] A color-changing microcapsule uses isophorone diisocyanate as a wall material and dibutyltin dilaurate as a catalyst. The raw materials include: 100 parts of small molecule nematic liquid crystal, 35 parts of a chiral agent, 50 parts of a viologen compound, 15 parts of PVA, 100 parts of isophorone diisocyanate, and 10 parts of dibutyltin dilaurate.

[0097] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 50 parts of an organic solvent, 10 parts of an ink connector, and 40 parts of deionized water; wherein the organic solvent is dipropylene glycol monomethyl ether, and the ink connector is polyurethane.

[0098] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0099] Step 1: Preparation of capsule core material.

[0100] 100 g of small molecule nematic liquid crystal and 35 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0101] Step 2: Preparation of color-changing microcapsules.

[0102] The PVA aqueous solution is prepared first and then the color-changing microcapsules are prepared.

[0103] The preparation process of the PVA aqueous solution is as follows: 15 g of PVA is dissolved in water to prepare the PVA aqueous solution, and the mass concentration of the PVA aqueous solution is 1%.

[0104] The preparation of color-changing microcapsules is as follows: the reserved capsule core material is evenly mixed with the prepared PVA aqueous solution to obtain an emulsified liquid, and the mixing method is stirring, and the stirring speed is 1000-3000r / min. In this embodiment, the speed of 3000r / min is used for 6min; 100g of isophorone diisocyanate (IPDI) is slowly added to the above emulsified liquid, and emulsified at the same emulsification rate for 6min. Then transfer it to a three-necked flask, add 10g of catalyst dibutyltin dilaurate (DBTDL), and react for 6h at a certain stirring speed, which is 500-2500r / min. In this embodiment, 500r / min is used, and the reaction temperature is 40°C. After the reaction is completed, filter and vacuum dry to obtain color-changing microcapsules.

[0105] Step 3: Preparation of color-changing ink.

[0106] Add 50 g of organic solvent, 10 g of ink connector and 40 g of deionized water to the color-changing microcapsules prepared in step 2, and stir evenly to prepare the color-changing ink.

[0107] The color-changing ink prepared in this embodiment appears red when the temperature is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0108] Example 6

[0109] A color-changing microcapsule uses isophorone diisocyanate as a wall material and dibutyltin dilaurate as a catalyst. The raw materials include: 100 parts of small molecule nematic liquid crystal, 95 parts of a chiral agent, 50 parts of a viologen compound, 30 parts of PVA, 250 parts of isophorone diisocyanate, and 10 parts of dibutyltin dilaurate.

[0110] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 80 parts of an organic solvent, 25 parts of an ink connector, and 20 parts of deionized water; wherein the organic solvent is dipropylene glycol monomethyl ether, and the ink connector is polyurethane.

[0111] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0112] Step 1: Preparation of capsule core material.

[0113] 100 g of small molecule nematic liquid crystal and 95 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0114] Step 2: Preparation of color-changing microcapsules.

[0115] The PVA aqueous solution is prepared first and then the color-changing microcapsules are prepared.

[0116] The preparation process of the PVA aqueous solution is as follows: 30 g of PVA is dissolved in water to prepare the PVA aqueous solution, and the mass concentration of the PVA aqueous solution is 10%.

[0117] The preparation of color-changing microcapsules is as follows: the reserved capsule core material is evenly mixed with the prepared PVA aqueous solution to emulsify and obtain an emulsion, the mixing method is stirring, the stirring speed is 1000-3000r / min, and the speed of 1000r / min is used for 6min in this embodiment; 250g of isophorone diisocyanate (IPDI) is slowly added to the above emulsion, and emulsified at the same emulsification rate for 6min. Then transfer it to a three-necked flask, add 10g of catalyst dibutyltin dilaurate (DBTDL), and react for 6h at a certain stirring rate, the stirring rate is 500-2500r / min, and 2500r / min is used in this embodiment, and the reaction temperature is 40°C. After the reaction is completed, filter and vacuum dry to obtain color-changing microcapsules.

[0118] Step 3: Preparation of color-changing ink.

[0119] Add 80 g of organic solvent, 25 g of ink connector and 20 g of deionized water to the color-changing microcapsules prepared in step 2, and stir evenly to prepare the color-changing ink.

[0120] The color-changing ink prepared in this embodiment appears blue when it is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of liquid crystals under light.

[0121] Example 7

[0122] A color-changing microcapsule uses melamine resin as a wall material. The raw materials of the microcapsule include: 100 parts of small molecule nematic phase liquid crystal, 35 parts of a chiral agent, 50 parts of a viologen compound, 10 parts of PVA, and 80 parts of a melamine resin prepolymer. The raw materials of the melamine resin prepolymer include melamine, formaldehyde, and deionized water in a mass ratio of about 10:30:40.

[0123] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 60 parts of an organic solvent, 15 parts of an ink connector, 25 parts of deionized water, 3 parts of a thickener, and 1 part of a defoamer; wherein the organic solvent is ethyl acetate, the ink connector is polyethylene glycol, the thickener is gum arabic, and the defoamer is a fatty acid ester defoamer.

[0124] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0125] Step 1: Preparation of capsule core material.

[0126] 100 g of small molecule nematic liquid crystal and 35 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0127] Step 2: Preparation of color-changing microcapsules.

[0128] Firstly, a PVA aqueous solution and a melamine resin prepolymer are prepared respectively;

[0129] The preparation of the PVA aqueous solution is as follows: 10 g of PVA is dissolved in water to prepare a PVA aqueous solution, wherein the mass concentration of the PVA aqueous solution is 5%;

[0130] The preparation of melamine resin prepolymer is as follows: according to the mass ratio of melamine to formaldehyde of 1:3, melamine and formaldehyde solution with a concentration of 37% are weighed and mixed; the pH value is adjusted to 8-9 with triethanolamine aqueous solution, the temperature is raised to 60°C with stirring, and the melamine is reacted until the melamine is completely dissolved; the formaldehyde is diluted with water of the same volume, the reaction is continued for 20 minutes, and the melamine resin prepolymer is obtained, and the constant temperature of 60°C is maintained for standby use;

[0131] The reserved capsule core material is stirred at a constant temperature of 60°C for 20 minutes at a speed of 1500 r / min; 80 g of melamine resin prepolymer is slowly added to the capsule core material in step 1, and then the PVA aqueous solution prepared above is added as a protective colloid, and the pH value of the system is adjusted to 4-5 with acetic acid solution at a constant temperature of 1000 r / min, and stirred at a constant temperature of 400 r / min for 2.5 hours; after cooling, it is filtered, washed and dried to obtain color-changing microcapsules.

[0132] Step 3: Preparation of color-changing ink.

[0133] The color-changing ink was prepared by adding 60 g of organic solvent, 15 g of ink connector, 25 g of deionized water, 3 g of thickener and 1 g of defoamer to the color-changing microcapsules prepared in step 2 and stirring evenly.

[0134] The color-changing ink prepared in this embodiment appears red when the temperature is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0135] Example 8

[0136] A color-changing microcapsule uses isophorone diisocyanate as a wall material and dibutyltin dilaurate as a catalyst. The raw materials include: 100 parts of small molecule nematic liquid crystal, 58 parts of a chiral agent, 50 parts of a viologen compound, 20 parts of PVA, 200 parts of isophorone diisocyanate, and 10 parts of dibutyltin dilaurate.

[0137] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 80 parts of an organic solvent, 20 parts of an ink connector, 30 parts of deionized water, 3 parts of a thickener, and 1 part of a defoamer; wherein the organic solvent is dipropylene glycol monomethyl ether, the ink connector is polyurethane, the thickener is carboxymethyl cellulose, and the defoamer is an amide defoamer.

[0138] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0139] Step 1: Preparation of capsule core material.

[0140] 100 g of small molecule nematic liquid crystal and 58 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0141] Step 2: Preparation of color-changing microcapsules.

[0142] The PVA aqueous solution is prepared first and then the color-changing microcapsules are prepared.

[0143] The preparation process of the PVA aqueous solution is as follows: 20 g of PVA is dissolved in water to prepare the PVA aqueous solution, and the mass concentration of the PVA aqueous solution is 10%.

[0144] The preparation of color-changing microcapsules is as follows: the reserved capsule core material is evenly mixed with the prepared PVA aqueous solution to emulsify and obtain an emulsion, the mixing method is stirring, the stirring speed is 1000-3000r / min, and the speed of 1500r / min is used for 6min in this embodiment; 200g of isophorone diisocyanate (IPDI) is slowly added to the above emulsion, and emulsified at the same emulsification rate for 6min. Then transfer it to a three-necked flask, add 10g of catalyst dibutyltin dilaurate (DBTDL), and react for 6h at a certain stirring rate, the stirring rate is 500-2500r / min, and 1000r / min is used in this embodiment, and the reaction temperature is 40°C. After the reaction is completed, filter and vacuum dry to obtain color-changing microcapsules.

[0145] Step 3: Preparation of color-changing ink.

[0146] Add 80 g of organic solvent, 20 g of ink connector, 30 g of deionized water, 3 g of thickener and 1 g of defoamer to the color-changing microcapsules prepared in step 2, and stir evenly to prepare the color-changing ink.

[0147] The color-changing ink prepared in this embodiment appears yellow when the temperature is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0148] Example 9

[0149] A color-changing microcapsule uses isophorone diisocyanate as a wall material and dibutyltin dilaurate as a catalyst. The raw materials include: 100 parts of small molecule nematic liquid crystal, 58 parts of a chiral agent, 50 parts of a viologen compound, 20 parts of PVA, 200 parts of isophorone diisocyanate, and 10 parts of dibutyltin dilaurate.

[0150] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 80 parts of an organic solvent, 20 parts of an ink connector, 30 parts of deionized water, 1 part of a thickener, and 3 parts of a defoamer; wherein the organic solvent is dipropylene glycol monomethyl ether, the ink connector is polyurethane, the thickener is polyvinyl pyrrolidone, and the defoamer is a mineral oil defoamer.

[0151] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0152] Step 1: Preparation of capsule core material.

[0153] 100 g of small molecule nematic liquid crystal and 58 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0154] Step 2: Preparation of color-changing microcapsules.

[0155] The PVA aqueous solution is prepared first and then the color-changing microcapsules are prepared.

[0156] The preparation process of the PVA aqueous solution is as follows: 20 g of PVA is dissolved in water to prepare the PVA aqueous solution, and the mass concentration of the PVA aqueous solution is 10%.

[0157] The preparation of color-changing microcapsules is as follows: the reserved capsule core material is evenly mixed with the prepared PVA aqueous solution to emulsify and obtain an emulsion, the mixing method is stirring, the stirring speed is 1000-3000r / min, and the speed of 1500r / min is used for 6min in this embodiment; 200g of isophorone diisocyanate (IPDI) is slowly added to the above emulsion, and emulsified at the same emulsification rate for 6min. Then transfer it to a three-necked flask, add 10g of catalyst dibutyltin dilaurate (DBTDL), and react for 6h at a certain stirring rate, the stirring rate is 500-2500r / min, and 1000r / min is used in this embodiment, and the reaction temperature is 40°C. After the reaction is completed, filter and vacuum dry to obtain color-changing microcapsules.

[0158] Step 3: Preparation of color-changing ink.

[0159] To the color-changing microcapsules prepared in step 2, add 80 g of organic solvent, 20 g of ink connector, 30 g of deionized water, 1 g of thickener, and 3 g of defoamer, and stir evenly to prepare the color-changing ink.

[0160] The color-changing ink prepared in this embodiment appears yellow when the temperature is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0161] Example 10

[0162] A color-changing microcapsule uses isophorone diisocyanate as a wall material and dibutyltin dilaurate as a catalyst. The raw materials include: 100 parts of small molecule nematic liquid crystal, 58 parts of a chiral agent, 50 parts of a viologen compound, 20 parts of PVA, 200 parts of isophorone diisocyanate, and 10 parts of dibutyltin dilaurate.

[0163] A color-changing ink comprises color-changing microcapsules prepared from the above raw materials, 80 parts of an organic solvent, 20 parts of an ink connector, 30 parts of deionized water, 10 parts of a thickener, and 0.1 parts of a defoamer; wherein the organic solvent is dipropylene glycol monomethyl ether, the ink connector is polyurethane, the thickener is dextrin, and the defoamer is a silicone-type defoamer.

[0164] The preparation method of the above color-changing microcapsules and color-changing ink is as follows:

[0165] Step 1: Preparation of capsule core material.

[0166] 100 g of small molecule nematic liquid crystal and 58 g of chiral agent were mixed, heated until clear and mixed evenly, and cooled; after cooling, 50 g of viologen compound was evenly mixed to obtain capsule core material, which was set aside.

[0167] Step 2: Preparation of color-changing microcapsules.

[0168] The PVA aqueous solution is prepared first and then the color-changing microcapsules are prepared.

[0169] The preparation process of the PVA aqueous solution is as follows: 20 g of PVA is dissolved in water to prepare the PVA aqueous solution, and the mass concentration of the PVA aqueous solution is 10%.

[0170] The preparation of color-changing microcapsules is as follows: the reserved capsule core material is evenly mixed with the prepared PVA aqueous solution to emulsify and obtain an emulsion, the mixing method is stirring, the stirring speed is 1000-3000r / min, and the speed of 1500r / min is used for 6min in this embodiment; 200g of isophorone diisocyanate (IPDI) is slowly added to the above emulsion, and emulsified at the same emulsification rate for 6min. Then transfer it to a three-necked flask, add 10g of catalyst dibutyltin dilaurate (DBTDL), and react for 6h at a certain stirring rate, the stirring rate is 500-2500r / min, and 1000r / min is used in this embodiment, and the reaction temperature is 40°C. After the reaction is completed, filter and vacuum dry to obtain color-changing microcapsules.

[0171] Step 3: Preparation of color-changing ink.

[0172] To the color-changing microcapsules prepared in step 2, add 80 g of organic solvent, 20 g of ink connector, 30 g of deionized water, 10 g of thickener, and 0.1 g of defoamer, and stir evenly to prepare the color-changing ink.

[0173] The color-changing ink prepared in this embodiment appears yellow when the temperature is below 20°C, and as the temperature rises, the liquid crystal appears green, light blue, dark blue, purple, red, orange, and yellow in sequence, with a color change of about 3 to 5°C. The color-changing temperature is between 20°C and 50°C, and continuous heating to 80°C will cause purple to appear due to the viologen compound. The color-changing ink prepared in this embodiment appears as a colorful mixture of the motley colors of the liquid crystal under light.

[0174] Comparative Example 1

[0175] The difference from Example 1 is that water of the same mass is used to replace the PVA aqueous solution, and the rest is the same as Example 1.

[0176] The red ink prepared in this comparative example is unevenly mixed and contains some relatively large particles. The large particles cannot fill the gaps in the substrate during printing, the adhesion is poor, and the color is easily wiped off after printing.

[0177] Comparative Example 2

[0178] The difference from Example 2 is that water of the same mass is used to replace the PVA aqueous solution, and the rest is the same as Example 2.

[0179] The yellow ink prepared in this comparative example is unevenly mixed and contains some relatively large particles. The large particles cannot fill the gaps in the substrate during printing, and the adhesion is poor. The color is easy to wipe off after printing.

[0180] By comparing the data of the embodiment and the comparative example in the above table, it can be known that adding PVA to the capsule wall can not only effectively refine the particle size, but also effectively improve the adhesion effect of the color-changing microcapsules after being prepared into ink, and effectively ensure the printing effect. At the same time, through the color-changing ink prepared in this embodiment, through the cooperation of the violet compound and the liquid crystal, the liquid crystal can be presented in green, light blue, dark blue, purple, red, orange, and yellow at a temperature of 20°C to 50°C, and a color change of about 3 to 5°C will appear. Continuous heating to 80°C will show the purple color displayed by the violet compound; the color-changing ink prepared in this embodiment appears as a colorful color mixed with the mottled colors of the liquid crystal under light. Through the mutual cooperation of the color-changing materials of the capsule wall and the capsule core, the dual color-changing performance of light color change and temperature color change is achieved, and the temperature color change can be carried out in a wider range, effectively broadening the application scene.

[0181] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A color-changing microcapsule, characterized in that: The capsule comprises a capsule core and a capsule wall, wherein the raw materials of the capsule wall include PVA and a wall material in a mass ratio of (5-30): (70-250); The capsule core comprises a small molecule nematic liquid crystal, a chiral agent and a viologen compound, wherein the mass ratio of the small molecule nematic liquid crystal to the chiral agent is 100:(35-111), the mass ratio of the viologen compound to the small molecule nematic liquid crystal is 50:100; and the mass ratio of the wall material to the small molecule nematic liquid crystal is (70-250):

100.

2. The color-changing microcapsule according to claim 1, characterized in that: The wall material is melamine resin or isophorone diisocyanate.

3. A color-changing ink, characterized in that: The invention comprises the color-changing microcapsule as described in any one of claims 1 to 2.

4. The color-changing ink according to claim 3, characterized in that: Also includes organic solvents and ink connectors.

5. The color-changing ink according to claim 4, characterized in that: The organic solvent includes one or more of acetone, ethyl acetate, dipropylene glycol monomethyl ether and dimethyl phthalate; and / or the ink connector includes one or more of polyurethane and polyethylene glycol.

6. The color-changing ink according to claim 4, characterized in that: Based on 100 parts by weight of the small molecule nematic phase liquid crystal in the color-changing microcapsule, the added amount of the organic solvent is 50-80 parts by weight, and the added amount of the ink connector is 10-25 parts by weight.

7. The color-changing ink according to claim 4, characterized in that: The invention also comprises auxiliary agents, which include one or more of a thickener, a defoaming agent and water.

8. The color-changing ink according to claim 7, characterized in that: The thickener is a natural thickener and / or a synthetic thickener; And / or, the defoamer is a non-silicon defoamer or a silicone defoamer.

9. The color-changing ink according to claim 7, characterized in that: Based on 100 parts by weight of the small molecule nematic phase liquid crystal in the color-changing microcapsule, the thickener is 1-10 parts by weight, and / or the defoamer is 0.1-3 parts by weight, and / or the water is 10-50 parts by weight.

10. The color-changing ink according to claim 8, characterized in that: The natural thickener includes one or more of starch, gum arabic, gelatin, alginate, guar gum and dextrin; and / or, the synthetic thickener comprises one or more of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium alginate, sodium polyacrylate, polyoxyethylene and polyvinyl pyrrolidone; And / or, the non-silicon defoamer includes one or more of alcohol defoamers, fatty acid defoamers, fatty acid ester defoamers, phosphate ester defoamers, mineral oil defoamers and amide defoamers.

11. A method for preparing a color-changing microcapsule according to any one of claims 1 to 2, characterized in that: include: The raw materials of the capsule core are used to prepare the capsule core material; PVA and water are used to prepare a PVA aqueous solution, and the PVA aqueous solution, capsule core material and wall material are mixed to prepare a microcapsule solution by an in-situ polymerization method. The microcapsule solution is separated and dried to obtain color-changing microcapsules.

12. The preparation method according to claim 11, characterized in that: The preparation process of the capsule core material is: mixing small molecule nematic phase liquid crystal and chiral agent, heating and then cooling; And / or, the mass concentration of PVA in the PVA aqueous solution is 1-10%.

13. The preparation method according to claim 12, characterized in that: After the cooling step, the material is mixed with the viologen compound to obtain the capsule core material.

14. The preparation method according to any one of claims 11 to 13, characterized in that: When the wall material is melamine resin, the core material and the wall material are mixed and then PVA aqueous solution is added, and the pH value is adjusted to 4-5 and then stirred to react to obtain a microcapsule solution; When the wall material is isophorone diisocyanate, the core material and the PVA aqueous solution are mixed and then the wall material is added to obtain a microcapsule solution through a catalytic reaction.

15. The preparation method according to claim 14, characterized in that: The pH value was adjusted using acetic acid solution; And / or, the catalyst is dibutyltin dilaurate.

16. A method for preparing a color-changing ink, characterized in that: include: The color-changing microcapsules prepared by the preparation method according to any one of claims 11 to 15 are mixed with an organic solvent and an ink connector to prepare a color-changing ink.

17. The preparation method according to claim 16, characterized in that: Additives are also added during the preparation of the color-changing ink.

18. Use of the color-changing microcapsule according to any one of claims 1 to 2 or the color-changing ink according to any one of claims 3 to 10 in anti-counterfeiting.