A thermochromic aqueous ink containing cholesteric liquid crystal microcapsules and a preparation method thereof

Abstract

The present invention provides a thermochromic aqueous ink containing cholesteryl liquid crystal microcapsules and a preparation method thereof, which relates to the technical field of aqueous inks. The aqueous ink provided by the present invention comprises, by weight: 10-20% of cholesteryl liquid crystal microcapsules and the balance of an aqueous ink matrix; wherein the preparation method of the cholesteryl liquid crystal microcapsules comprises the following steps: stirring and mixing cholesteryl liquid crystal with a phycocyanin solution to obtain a mixed solution; emulsifying and gelling the mixed solution to obtain cholesteryl liquid crystal microcapsules. The present invention combines phycocyanin with cholesteryl liquid crystal, which can significantly improve the stability of the thermochromic aqueous ink. At the same time, after microencapsulation, it can protect phycocyanin and cholesteryl liquid crystal, so as to achieve the purpose of enhancing the stability and durability of the aqueous ink.

Description

Technical Field

[0001] The present invention relates to the technical field of water-based inks, and particularly to a thermochromic water-based ink containing cholesteric liquid crystal microcapsules and a preparation method thereof. Background Art

[0002] Due to the unique function of thermochromic materials to change color in response to temperature changes, they have received extensive attention in the field of intelligent materials. These materials show important application prospects in temperature sensing, intelligent packaging, anti-counterfeiting labels, reversible displays, etc. Among them, cholesteric liquid crystal (CLC) is a liquid crystal material with a helical structure. The arrangement of its chiral molecules forms a structure that selectively reflects light of a specific wavelength, resulting in different colors at different temperatures and showing rich optical properties. It is an ideal photochromic material.

[0003] In order to make cholesteric liquid crystal better applied in thermochromic water-based inks, cholesteric liquid crystal is usually made into microcapsule form through emulsification and curing, so as to play a good protective role for cholesteric liquid crystal. Furthermore, when applied to thermochromic water-based inks, the dispersion uniformity and stability of cholesteric liquid crystal can be improved.

[0004] However, although microencapsulation can improve the stability of cholesteric liquid crystal, during long-term use and storage, problems such as rupture, leakage, and degradation are prone to occur in microencapsulation, resulting in the leakage of cholesteric liquid crystal, and further leading to a decline in the thermochromic performance of the ink. Especially in environments such as high temperature, high humidity, or strong light, the problem of microcapsule failure is particularly likely to occur. Therefore, there is an urgent need to provide a solution to improve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a thermochromic water-based ink containing cholesteric liquid crystal microcapsules and a preparation method thereof, which can improve the stability and durability of the water-based ink.

[0006] In a first aspect, a thermochromic water-based ink containing cholesteric liquid crystal microcapsules provided by the present invention comprises, by weight: 10-20% cholesteric liquid crystal microcapsules and the balance of a water-based ink matrix; wherein the preparation method of the cholesteric liquid crystal microcapsules comprises the following steps: stirring and mixing cholesteric liquid crystal with a phycocyanin solution to obtain a mixed solution; emulsifying and gelling the mixed solution to obtain cholesteric liquid crystal microcapsules.

[0007] The thermochromic water-based ink provided by the present invention combines phycocyanin and cholesteric liquid crystal, which can significantly improve the stability of the thermochromic water-based ink. This is because phycocyanin is a natural photosensitive protein with good light stability and antioxidant properties. At the same time, after microencapsulation, it can protect phycocyanin and cholesteric liquid crystal, thereby achieving the purpose of enhancing the stability and durability of the water-based ink.

[0008] Optionally, the water-based ink matrix includes, by mass percentage: 60-70% water-based acrylic resin, 20-30% deionized water, and the balance of functional additives.

[0009] Optionally, the cholesteric liquid crystal includes at least one of cholesteryl oleyl carbonate, cholesteryl nonanoate, cholesteryl benzoate, and cholesteryl propionate.

[0010] Optionally, in the process of emulsifying and gelling the mixed solution to prepare cholesteric liquid crystal microcapsules, it includes: stirring and mixing the mixed solution with a surfactant to obtain an emulsion by emulsifying and dispersing; at 50-60 °C, stirring and mixing the polyurethane prepolymer with the emulsion, and then separating, washing, and drying to obtain cholesteric liquid crystal microcapsules.

[0011] Optionally, in the process of emulsifying and gelling the mixed solution to prepare cholesteric liquid crystal microcapsules, it includes: stirring and mixing the mixed solution with a surfactant to obtain an emulsion by emulsifying and dispersing; at 60-70 °C, under an initiator, stirring and mixing the mixed solution with methyl methacrylate, and then separating, washing, and drying to obtain cholesteric liquid crystal microcapsules.

[0012] Optionally, the initiator includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0013] Optionally, in the process of emulsifying and gelling the mixed solution to prepare cholesteric liquid crystal microcapsules, it includes: stirring and mixing the mixed solution with a surfactant to obtain an emulsion by emulsifying and dispersing; at 20-30 °C, under a catalyst, stirring and mixing the mixed solution with tetraethoxysilane, and then separating, washing, and drying to obtain cholesteric liquid crystal microcapsules.

[0014] Optionally, the catalyst includes at least one of ammonia water, sodium hydroxide, and sodium bicarbonate.

[0015] Optionally, the surfactant includes at least one of cetyltrimethylammonium bromide, polyvinyl alcohol, polyethylene glycol, and stearate.

[0016] In a second aspect, the present invention also provides a preparation method of a thermochromic water-based ink, including the following steps: stirring and mixing cholesteric liquid crystal microcapsules with a water-based ink matrix, and then performing vacuum degassing to obtain the thermochromic water-based ink. Detailed implementation manners

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art in the field to which the present invention pertains. The words such as "including" used herein are intended to mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items.

[0018] The embodiments of the present invention provide a thermochromic water-based ink containing cholesteric liquid crystal microcapsules, which includes, by weight percentage: 10-20% of cholesteric liquid crystal microcapsules and the balance of a water-based ink matrix. Among them, the water-based ink matrix is used as a substrate material, and after coating, it can be cured on the surface of an object to form a water-based ink layer, and the cholesteric liquid crystal microcapsules are dispersed in the water-based ink matrix, which can achieve the effect of photo-thermochromism.

[0019] In fact, the water-based ink matrix includes, by mass percentage: 60-70% of a water-based acrylic resin, 20-30% of deionized water, and the balance of functional auxiliaries. Specifically, the water-based acrylic resin used in the water-based ink matrix can be at least one of an acrylic resin emulsion, an acrylic resin aqueous dispersion, and an acrylic resin aqueous solution. Specifically, the acrylic resin can be methyl methacrylate. The functional auxiliaries used include at least one of a thickener, a dispersant, a preservative, a pH regulator, and a wetting agent.

[0020] In fact, the thickener in the functional auxiliaries can be carboxymethyl cellulose, the dispersant can be polyethylene glycol, the preservative can be sodium benzoate, the pH regulator can be at least one of ammonia water, sodium hydroxide, and hydrochloric acid, and the wetting agent can be polyethylene glycol stearate.

[0021] Specifically, the preparation method of the cholesteric liquid crystal microcapsules includes the following steps:

[0022] S1. Stir and mix cholesteric liquid crystal and a phycocyanin solution to obtain a mixed solution;

[0023] S2. Emulsify and gel the mixed solution to obtain cholesteric liquid crystal microcapsules.

[0024] Actually, when performing step S1, phycocyanin is pre-dissolved in deionized water to prepare a phycocyanin solution with a concentration of 1%. Specifically, the cholesteric liquid crystal used in step S1 includes at least one of cholesteryl oleyl carbonate, cholesteryl nonanoate, cholesteryl benzoate, and cholesteryl propionate.

[0025] Actually, the structural formulas, melting points, and clearing points of cholesteryl oleyl carbonate, cholesteryl nonanoate, cholesteryl benzoate, and cholesteryl propionate are different, and their temperature change ranges and color display characteristics in the single-component state are also different. Therefore, different cholesteric liquid crystals can be combined to achieve color display regions within different temperature ranges. At the same time, by adjusting the components and ratios within the cholesteric liquid crystal, the prepared cholesteric liquid crystal microcapsules can achieve color changes among red, green, and blue between 40 - 65°C.

[0026] Specifically, after the preparation in step S2, the particle size of the prepared cholesteric liquid crystal microcapsules is 3 - 10 μm. The cholesteric liquid crystal microcapsules within this particle size range can be well-dispersed in the water-based coating and can also be well-dispersed inside the coating after the coating is cured to form a film.

[0027] In some embodiments, during the execution of step S2, it includes:

[0028] S2.1. Stir and mix the mixed solution with a surfactant and then emulsify and disperse to obtain an emulsion;

[0029] S2.2. At 50 - 60°C, stir and mix the polyurethane prepolymer with the emulsion, and then separate, wash, and dry to obtain cholesteric liquid crystal microcapsules.

[0030] In other embodiments, during the execution of step S2, it includes:

[0031] S2.1. Stir and mix the mixed solution with a surfactant and then emulsify to obtain an emulsion;

[0032] S2.2. At 60 - 70°C, under an initiator, stir and mix the mixed solution with methyl methacrylate, and then separate, wash, and dry to obtain cholesteric liquid crystal microcapsules.

[0033] Actually, during the execution of step S2.2, the initiator used includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0034] In still other embodiments, during the execution of step S2, it includes:

[0035] S2.1. Stir and mix the mixed solution with a surfactant and then emulsify and disperse to obtain an emulsion;

[0036] S2.2. Stir and mix the mixed solution with tetraethoxysilane under a catalyst at 20 - 30°C, and then separate, wash, and dry to obtain cholesteric liquid crystal microcapsules.

[0037] Actually, the catalyst used in the process of performing step S2.2 includes at least one of ammonia water, sodium hydroxide, and sodium bicarbonate.

[0038] Specifically, in the process of performing any of the above step S2.1, the surfactant used includes at least one of cetyltrimethylammonium bromide, polyvinyl alcohol, polyethylene glycol, and stearate.

[0039] The present invention also provides a preparation method of a thermochromic water-based ink, including the following steps: Stir and mix cholesteric liquid crystal microcapsules with a water-based ink matrix, and then vacuum degas to obtain the thermochromic water-based ink.

[0040] Preparation Example 1

[0041] This Preparation Example 1 provides a preparation method of cholesteric liquid crystal microcapsules, including the following steps:

[0042] S1. Stir and mix 10 g of cholesteryl oleyl carbonate (CAS: 17110 - 51 - 9, purchased from Hubei Yunmei Technology Co., Ltd.), 60 g of cholesteryl nonanoate (CAS: 1182 - 66 - 7, purchased from Wuhan Karnos Technology Co., Ltd.), 20 g of cholesteryl benzoate (CAS: 604 - 32 - 0, purchased from Shandong Xiya Chemical Co., Ltd.) with 1 L of an aqueous solution of phycocyanin (CAS: 11016 - 15 - 2, purchased from Guangdong Hongyou Biotechnology Co., Ltd.) with a mass concentration of 1% to obtain a mixed solution;

[0043] S2. Stir and mix the mixed solution with 5 g of polyethylene glycol 2000 (purchased from Jiangsu Rayen Environmental Protection Technology Co., Ltd.), and then stir and emulsify at a rotation speed of 3000 rpm to obtain an emulsion; heat the emulsion to 55°C in a water bath environment, then stir and mix 50 g of polyurea prepolymer with the emulsion for 4 h, and then centrifuge at a rotation speed of 1000 rpm to obtain crude microcapsules. After rinsing the crude microcapsules with deionized water, place them in a drying oven at 40°C and dry until the weight does not change to obtain cholesteric liquid crystal polyurea microcapsules with an average particle size of 5 μm.

[0044] Specifically, the preparation method of the polyurea prepolymer used in Preparation Example 1 is as follows: Dehydrate 3 kg of the JH334 amine chain extender purchased from Junhe Chemical Industry (Shanghai) Co., Ltd. until the water content is less than 300 ppm, then add 2 kg of isocyanate (CAS: 75 - 13 - 8, purchased from Shandong Xuchen Chemical Technology Co., Ltd.) at 45°C, and control the reaction temperature during the dropping process to be 50 - 60°C, and then keep the temperature for reaction for 5 h to obtain the polyurea prepolymer.

[0045] Preparation Example 2

[0046] This Preparation Example 2 provides a method for preparing cholesteric liquid crystal microcapsules, comprising the following steps:

[0047] S1. 10 g of cholesteryl oleyl carbonate (CAS: 17110-51-9, purchased from Hubei Yunmei Technology Co., Ltd.), 60 g of cholesteryl nonanoate (CAS: 1182-66-7, purchased from Wuhan Karnos Technology Co., Ltd.), 20 g of cholesteryl benzoate (CAS: 604-32-0, purchased from Shandong Xiya Chemical Co., Ltd.) and 1 L of an aqueous solution of phycocyanin (CAS: 11016-15-2, purchased from Guangdong Hongyou Biotechnology Co., Ltd.) with a mass concentration of 1% were stirred and mixed to obtain a mixed solution;

[0048] S2. After the mixed solution was stirred and mixed with 5 g of polyvinyl alcohol 1799 (purchased from Shandong Hongquan Chemical Technology Co., Ltd., grade PVA088-20), it was stirred and emulsified at a rotation speed of 3000 rpm to obtain an emulsion; after the emulsion was heated to 65 °C in a water bath environment, 50 g of methyl methacrylate (CAS: 80-62-6, purchased from Shandong Xingshun Chemical Co., Ltd.), 5 g of ammonium persulfate (CAS: 7727-54-0, purchased from Changzhou Qidi Chemical Co., Ltd.) and the emulsion were stirred and mixed for 4 h, and then centrifuged at a rotation speed of 1000 rpm to obtain crude microcapsules. After the crude microcapsules were rinsed with deionized water, they were placed in a drying oven at 40 °C and dried until the weight did not change, and cholesteric liquid crystal methyl methacrylate microcapsules with an average particle size of 5 μm were prepared.

[0049] Preparation Example 3

[0050] This Preparation Example 3 provides a method for preparing cholesteric liquid crystal microcapsules, comprising the following steps:

[0051] S1. 10 g of cholesteryl oleyl carbonate (CAS: 17110-51-9, purchased from Hubei Yunmei Technology Co., Ltd.), 60 g of cholesteryl nonanoate (CAS: 1182-66-7, purchased from Wuhan Karnos Technology Co., Ltd.), 20 g of cholesteryl benzoate (CAS: 604-32-0, purchased from Shandong Xiya Chemical Co., Ltd.) and 1 L of an aqueous solution of phycocyanin (CAS: 11016-15-2, purchased from Guangdong Hongyou Biotechnology Co., Ltd.) with a mass concentration of 1% were stirred and mixed to obtain a mixed solution;

[0052] S2. After stirring and mixing the mixed solution with 5 g of cetyltrimethylammonium bromide (CAS: 57-09-0, purchased from Shandong Shouhua Chemical Co., Ltd.), emulsify it by stirring at a speed of 3000 rpm to obtain an emulsion; at room temperature of 25 °C, stir and mix the emulsion with 50 g of tetraethoxysilane (purchased from Shandong Qiyun Chemical Technology Co., Ltd., product number QY-8956956) and 4 mL of 27% ammonia water for 4 h, then centrifuge at a speed of 1000 rpm to obtain crude microcapsules. After rinsing the crude microcapsules with deionized water, place them in a drying oven at 40 °C and dry until the weight remains unchanged to obtain cholesteric liquid crystal methyl methacrylate microcapsules with an average particle size of 5 μm.

[0053] Preparation Example 4

[0054] This Preparation Example 4 provides a method for preparing cholesteric liquid crystal microcapsules, which includes the following steps:

[0055] S1. Stir and mix 20 g of cholesteryl oleyl carbonate (CAS: 17110-51-9, purchased from Hubei Yunmei Technology Co., Ltd.), 60 g of cholesteryl nonanoate (CAS: 1182-66-7, purchased from Wuhan Karnos Technology Co., Ltd.), and 20 g of cholesteryl benzoate (CAS: 604-32-0, purchased from Shandong Xiya Chemical Co., Ltd.) and disperse them in 1 L of deionized water to obtain a mixed solution;

[0056] S2. After stirring and mixing the mixed solution with 5 g of polyethylene glycol 2000 (purchased from Jiangsu Rayen Environmental Protection Technology Co., Ltd.), emulsify it by stirring at a speed of 3000 rpm to obtain an emulsion; heat the emulsion to 55 °C in a water bath environment, then stir and mix 50 g of polyurea prepolymer with the emulsion for 4 h, and then centrifuge at a speed of 1000 rpm to obtain crude microcapsules. After rinsing the crude microcapsules with deionized water, place them in a drying oven at 40 °C and dry until the weight remains unchanged to obtain cholesteric liquid crystal polyurethane microcapsules with an average particle size of 5 μm.

[0057] Specifically, the preparation method of the polyurea prepolymer used in Preparation Example 4 is as follows: Dehydrate 3 kg of the JH334 amine chain extender purchased from Junhe Chemical Industry (Shanghai) Co., Ltd. until the water content is less than 300 ppm, then add 2 kg of isocyanate (CAS: 75-13-8, purchased from Shandong Xuchen Chemical Technology Co., Ltd.) at 45 °C, and control the reaction temperature during the dropping process to be 50-60 °C, and then keep the reaction at this temperature for 5 h to obtain the polyurea prepolymer.

[0058] Preparation Example 5

[0059] Preparation Example 5 provided a method for preparing an aqueous ink matrix. By mass, it included mixing 70 parts of methyl methacrylate (CAS: 80-62-6, purchased from Shandong Xingshun Chemical Co., Ltd.), 2 parts of sodium carboxymethyl cellulose (purchased from Shandong Luson Biotechnology Co., Ltd.) as a thickening agent, 2 parts of polyethylene glycol 800 (purchased from Jiangsu Rain Environmental Protection Technology Co., Ltd.) as a dispersant, 1 part of sodium benzoate (CAS: 532-32-1, purchased from Jinan Xinying Chemical Co., Ltd.) as a preservative, 1 part of sodium hydroxide as a pH regulator, 1 part of polyethylene glycol 600 (purchased from Jiangsu Rain Environmental Protection Technology Co., Ltd.) as a wetting agent, and 23 parts of deionized water. After stirring and mixing the above raw materials, an aqueous ink matrix was prepared.

[0060] Examples 1 to 5 and Comparative Example 1 respectively provided a thermochromic aqueous ink containing cholesteryl liquid crystal microcapsules, and their components and contents were shown in Table 1.

[0061] Table 1 Components and Contents

[0062] Cholesterol liquid crystal microcapsules and content Aqueous ink matrix and content Example 1 10% Preparation Example 1 90% Preparation Example 5 Example 2 20% Preparation Example 1 80% Preparation Example 5 Example 3 15% Preparation Example 1 85% Preparation Example 5 Example 4 15% Preparation Example 2 90% Preparation Example 5 Example 5 15% Preparation Example 3 90% Preparation Example 5 Comparative Example 1 15% Preparation Example 4 90% Preparation Example 5

[0063] Performance Detection

[0064] The thermochromic aqueous inks prepared in Examples 1 to 5 and Comparative Example 1 were coated on a stainless steel substrate, cured at 120°C to form a color-changing oil film, cooled to room temperature, and the color change was observed in an environment of 17 - 30°C. The results of the hue change were shown in Table 2 below; after the corresponding color-changing oil films of Examples 1 to 5 and Comparative Example 1 were aged in a pure oxygen atmosphere at 40°C for 240 h, the color change was observed in an environment of 17 - 30°C. The results of the hue change were shown in Table 2 below.

[0065] The thermochromic aqueous inks prepared in Examples 1 to 5 and Comparative Example 1 were respectively roll-coated on a 10 cm × 10 cm stainless steel plate with a coating thickness of 1 mm, and transferred to an oven at 120°C for film curing. The film curing time was calculated as shown in Table 3 below.

[0066] Table 2 Hue Change before and after Aging

[0067]

[0068]

[0069] It can be seen from Table 2 that adding phycocyanin would affect the phase transition behavior of the liquid crystal and the color change of the hue, making the aqueous ink have more abundant hue changes, and at the same time, it could significantly improve the color change stability and durability of the color-changing ink.

[0070] Table 3 Curing Time

[0071] Curing time / min Example 1 58.3 Example 2 55.7 Example 3 62.4 Example 4 51.6 Example 5 53.1 Comparative Example 1 74.5

[0072] As can be seen from Table 3, after adding cholesterol microcapsules complexed with phycocyanin into the thermotropic aqueous ink, the curing time of the aqueous ink can be reduced. This is because phycocyanin can absorb light energy and convert it into heat energy, thereby promoting the endothermic process of the aqueous ink and facilitating the curing reaction, thus shortening the curing time. At the same time, phycocyanin can also increase the specific surface area of the cholesterol microcapsules, thereby forming a heat conduction network in the aqueous ink, which is conducive to the rapid reaching of the curing temperature of the aqueous ink for curing.

[0073] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.

Claims

1. A thermochromic water-based ink containing cholesteric liquid crystal microcapsules, characterized in that: The invention comprises, by weight percentage, 10-20% of cholesteric liquid crystal microcapsules and the remainder of aqueous ink matrix; wherein the preparation method of the cholesteric liquid crystal microcapsules comprises the following steps: stirring and mixing cholesteric liquid crystal and phycocyanin solution to obtain a mixed solution; emulsifying the mixed solution and gelling it to obtain cholesteric liquid crystal microcapsules; The mixed solution is prepared by stirring and mixing the cholesterol liquid crystal and the phycocyanin solution, specifically: 10g of cholesterol oleyl carbonate, 60g of cholesterol nonanoate, 20g of cholesterol benzoate and 1L of phycocyanin aqueous solution with a mass concentration of 1% are stirred and mixed to prepare the mixed solution; The preparation method of the aqueous ink matrix is ​​specifically as follows: by weight, 70 parts of methyl methacrylate, 2 parts of sodium carboxymethyl cellulose as a thickener, 2 parts of polyethylene glycol 800 as a dispersant, 1 part of sodium benzoate as a preservative, 1 part of sodium hydroxide as a pH regulator, 1 part of polyethylene glycol 600 as a wetting agent and 23 parts of deionized water are stirred and mixed to obtain the aqueous ink matrix.

2. The thermochromic water-based ink according to claim 1, characterized in that: The process of preparing cholesteric liquid crystal microcapsules by emulsifying and gelling the mixed solution includes: stirring and mixing the mixed solution with a surfactant and then emulsifying and dispersing to obtain an emulsion; stirring and mixing a polyurethane prepolymer with the emulsion at 50-60°C, separating, washing and drying to obtain cholesteric liquid crystal microcapsules.

3. The thermochromic water-based ink according to claim 1, characterized in that: The process of emulsifying the mixed solution and gelling it to obtain cholesterol liquid crystal microcapsules includes: stirring and mixing the mixed solution with a surfactant and then emulsifying and dispersing it to obtain an emulsion; stirring and mixing the mixed solution with methyl methacrylate at 60-70°C in the presence of an initiator, and then separating, washing, and drying to obtain cholesterol liquid crystal microcapsules.

4. The thermochromic water-based ink according to claim 3, characterized in that: The initiator includes at least one of ammonium persulfate, potassium persulfate and sodium persulfate.

5. The thermochromic water-based ink according to claim 1, characterized in that: The process of emulsifying the mixed solution and gelling it to obtain cholesterol liquid crystal microcapsules includes: stirring and mixing the mixed solution with a surfactant and then emulsifying and dispersing it to obtain an emulsion; stirring and mixing the mixed solution with tetraethoxysilane at 20-30°C in the presence of a catalyst, and then separating, washing and drying it to obtain cholesterol liquid crystal microcapsules.

6. The thermochromic water-based ink according to claim 5, characterized in that: The catalyst includes at least one of ammonia water, sodium hydroxide and sodium bicarbonate.

7. The thermochromic water-based ink according to any one of claims 2 to 6, characterized in that: The surfactant includes at least one of cetyltrimethylammonium bromide, polyvinyl alcohol, polyethylene glycol, and stearate.

8. A method for preparing the thermochromic water-based ink according to any one of claims 1 to 7, characterized in that: The following steps are involved: The cholesteric liquid crystal microcapsules and the water-based ink matrix are stirred and mixed, and the thermochromic water-based ink is prepared after vacuum degassing.

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