Fluorescent microcapsules and methods for their preparation

Abstract

The present application discloses a fluorescent microcapsule and its preparation method, wherein polyethylene glycol alkene derivative is used as the wall material of the capsule wall, and oily solvent is used as the core material of the capsule core, the oil-soluble fluorescent dye and additive are dissolved in the oily solvent, and the additive is ionic surfactant which can interact with the oil-soluble fluorescent dye. The fluorescent microcapsule has pressure-sensitive characteristics, and is colorless in normal times, but shows specific fluorescent color under ultraviolet lamp irradiation. When the microcapsule is broken by external force, the oil-soluble fluorescent dye will flow out with the oily solvent, so as to develop the stressed area, and realize the rewriting of invisible writing.

Description

Technical Field

[0001] This invention relates to the field of microcapsule technology, and in particular to a fluorescent microcapsule and its preparation method. Background Technology

[0002] Fluorescent microcapsules are shell-core structured nanoparticles. The encapsulated material is called the core, and the material covering the surface of the core is called the wall. They can display fluorescence under ultraviolet light and can be applied to traditional carbonless copy paper.

[0003] Carbonless copy paper is a pressure-sensitive paper made by coating base paper with a copying agent. It develops color through a chemical reaction and is primarily used in the commercial document industry. It consists of three layers (top, middle, and bottom), and while it looks identical to ordinary white paper, its surface is actually coated with microcapsule coatings made of colorless dyes. Depending on the coating, it is divided into CB paper and CF paper. CF paper is mainly coated with an acidic developer, while CB paper is coated with microcapsules containing colorless dyes. When the microcapsules in the CB paper rupture under writing pressure, the colorless dye in the core material transfers to the CF paper, revealing color through a chemical reaction.

[0004] In existing technologies, aiming to simplify carbonless copy paper, there is a desire for a type of copy paper that does not require the use of two parallel lines, possesses anti-counterfeiting properties, and can produce invisible writing. However, the applicant has found that there is currently no commercially available paper of this type. One of the technical challenges is the lack of mature technology for preparing invisible fluorescent microcapsules. In existing fluorescent microcapsules, the fluorescent material is adsorbed onto the microcapsule itself and is not encapsulated in the oil phase within the core. When the microcapsule ruptures under pressure, although the oil phase flows out from the pressure-affected area of ​​the core, no fluorescent material flows out. Therefore, such fluorescent microcapsules cannot be used in carbonless copy paper to achieve invisible writing. Thus, there is a need for an invisible fluorescent microcapsule with pressure-sensitive properties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a fluorescent microcapsule for invisible handwriting copying and its preparation method.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A fluorescent microcapsule includes a capsule wall and a core. The capsule wall is coated on the surface of the core and is formed by the reaction of an aqueous solution and an oil solution. The fluorescent microcapsule uses a polyethylene glycol olefin derivative as the wall material and an oily solvent as the core material. The oily solvent contains an oil-soluble fluorescent dye and an additive. The additive is an ionic surfactant that can interact with the oil-soluble fluorescent dye at the molecular level.

[0008] As a further improvement to the above technical solution:

[0009] The raw materials for the aqueous solution include an emulsifier, a polyethylene glycol olefin derivative, and water, wherein the mass ratio of the emulsifier, the polyethylene glycol olefin derivative, and water is 3–10:0.5–3:15–40.

[0010] The emulsifier is one or more selected from polyvinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, propylene-maleic anhydride copolymer, and isobutylene-maleic anhydride copolymer. The emulsifier is a surfactant with a high molecular chain that stabilizes oil-water microcapsules, possessing numerous hydrophilic groups that can adhere to the surface of oil phase droplets to form a stable emulsion.

[0011] The polyethylene glycol olefin derivative is one or more of polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol fumarate, and olefin-polyethylene glycol-olefin.

[0012] The raw materials for the oil phase solution include an oil-soluble fluorescent dye, an oil-soluble initiator, an additive, and an oily solvent. The mass ratio of the oil-soluble fluorescent dye, the oil-soluble initiator, and the oily solvent is 5–50:50–300:5000–10000. The mass of the additive is 0.5–2.5 times the mass of the oil-soluble fluorescent dye.

[0013] The ionic surfactant is one or more of sodium alkyl sulfonate, sodium alkylbenzene sulfonate, alkyl ammonium bromide, and alkyl pyridine bromide.

[0014] The oil-soluble fluorescent dyes are europium acetylacetonate (III), tris(4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione) europium (III), o-phenoline·tris(benzoyltrifluoroacetylacetonate) europium (III), bipyridine·tris(benzoyltrifluoroacetylacetonate) europium (III), and di(triphenylphosphine oxide)·tris(benzoyltrifluoroacetylacetonate) europium (III). Europium(III) of o-phenobarline·tris(4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione), Europium(III) of bipyridine·tris(4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione), Europium(III) of di(triphenylphosphine oxide)·tris(4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione) 1,4,4-phenanthroline-tris(benzoyltrifluoroacetylacetone)terbium(III), bipyridine-tris(benzoyltrifluoroacetylacetone)terbium(III), di(triphenylphosphine oxide)-tris(benzoyltrifluoroacetylacetone)terbium(III), 1,4,4-phenanthroline-tris(4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione)terbium(III), bipyridine-tris(4,4, One or more of the following: 4-trifluoro-1-(2-thiophene)-1,3-butanedione (III), bis(triphenylphosphine oxide)·tris(4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione (III), and bis(triphenylphosphine oxide)·tris(4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione (III). The fluorescent molecules in the oil-soluble fluorescent dye are invisible fluorescent molecules, having no effect on the appearance of the active area. The residual fluorescent molecules can be seen with a specific fluorescent color under ultraviolet light, thus achieving both invisibility and anti-counterfeiting functionality.

[0015] The oily solvent is one or more of the following: hexane, cyclohexane, petroleum ether, heptane, octane, 1-bromooctane, nonane, decane, undecane, dodecane, dimethyl phthalate, diethyl phthalate, propylene carbonate, and octanoic / decanoic triglycerides. The oily solvent is colorless, odorless, and volatile, and has no corrosive effect on common materials such as fabrics, paper, metals, wood, and plastics.

[0016] The oil-soluble initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide.

[0017] As a general inventive concept, the present invention also provides a method for preparing the aforementioned fluorescent microcapsules, comprising the following steps:

[0018] S1. Preparation of raw material aqueous solution A and oil solution B:

[0019] Emulsifier and polyethylene glycol olefin derivative are dissolved in water and stirred evenly to obtain aqueous solution A; oil-soluble fluorescent dye, oil-soluble initiator and additive are dissolved in oily solvent and stirred evenly to obtain oily solution B.

[0020] S2. Mix aqueous solution A and oil solution B at a volume ratio of 5:1 to 2:1 and emulsify to form a uniform emulsion;

[0021] S3. After stirring the emulsion at a temperature of 60-80℃, the emulsion is filtered, washed, and dried to obtain fluorescent microcapsules.

[0022] In step S2, the emulsification time is 10 to 40 minutes.

[0023] In step S2, the stirring reaction takes 3 to 6 hours.

[0024] As a general inventive concept, the present invention also provides an invisible pressure-sensitive copy paper coated with fluorescent microcapsules, wherein the fluorescent microcapsules are the aforementioned fluorescent microcapsules or fluorescent microcapsules prepared by the aforementioned method for preparing fluorescent microcapsules.

[0025] Compared with the prior art, the advantages of the present invention are as follows:

[0026] This invention discloses a fluorescent microcapsule with a polyethylene glycol olefin derivative as the wall material and an oily solvent as the core material. The oily solvent contains an oil-soluble fluorescent dye and an additive. The additive is an ionic surfactant capable of molecularly interacting with the oil-soluble fluorescent dye. This ionic surfactant interacts with the oil-soluble fluorescent dye (fluorescent complex) molecules, achieving solubilization and uniform dispersion, thus encapsulating or dissolving the oil-soluble fluorescent dye in the oily solvent and preventing it from being encapsulated by polymer monomers into the capsule wall during later polymerization reactions. The fluorescent microcapsules of this invention have pressure-sensitive properties; they are normally colorless but display a specific fluorescent color under ultraviolet light. When the microcapsule is broken by external force, the oil-soluble fluorescent dye flows out with the oily solvent, thereby revealing color in the stressed area and achieving invisible writing replication.

[0027] The present invention discloses a method for preparing fluorescent microcapsules, which involves emulsifying an aqueous solution and an oil solution and then stirring the mixture to obtain the microcapsules. The preparation process is simple.

[0028] The present invention provides an invisible pressure-sensitive copy paper in which fluorescent microcapsules are coated on the paper surface, which can be directly used as an independent invisible pressure-sensitive copy paper without the need for triple copying. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the fluorescent microcapsules prepared in Example 1.

[0030] Figure 2 This is a scanning electron microscope image of the fluorescent microcapsules prepared in Example 1.

[0031] Figure 3 The image shows a fluorescence photograph of the fluorescent microcapsules prepared in Example 1.

[0032] Figure 4 This is an optical photograph of the fluorescent microcapsules prepared in Example 1 after they were crushed, showing the solvent flowing out of the microcapsules.

[0033] Figure 5 The image shows the fluorescence of the fluorescent microcapsules prepared in Example 1 after they were crushed and the solvent inside the microcapsules flowed out.

[0034] Figure 6 The image shows a scanning electron microscope (SEM) image of the fluorescent microcapsules prepared in Comparative Example 1.

[0035] Figure 7 The image shows the fluorescence of the microcapsules prepared in Comparative Example 1 after the solvent in the microcapsules was squeezed out.

[0036] Figure 8 Here are scanning electron microscope images of the fluorescent microcapsules prepared in Comparative Example 2;

[0037] Figure 9 The image shows the fluorescence of the microcapsules prepared in Comparative Example 2 after the solvent in the microcapsules has flowed out after they have been crushed.

[0038] Figure 10 The image shows a scanning electron microscope (SEM) image of the fluorescent microcapsules prepared in Comparative Example 3.

[0039] Figure 11 The image shows the fluorescence of the microcapsules prepared in Comparative Example 3 after the solvent in the microcapsules flowed out when the capsules were crushed.

[0040] Figure 12 The images shown are optical and fluorescence photographs of the fluorescent microcapsules prepared in Comparative Example 4 after they were crushed and the solvent flowed out. Figure 12 (a) is an optical photograph. Figure 12 (b) is a fluorescence photograph. Detailed Implementation

[0041] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0042] Example 1:

[0043] like Figure 1As shown, a fluorescent microcapsule of this embodiment includes a capsule wall 1 and a core 2. The capsule wall 1 coats the surface of the core 2 and is formed by the mixed reaction of an oil phase solution and an aqueous phase solution. A polyethylene glycol olefin derivative (polyethylene glycol dimethacrylate) is used as the wall material of the capsule wall 1, and an oily solvent (decane) is used as the core material of the core 2. An oil-soluble fluorescent dye (Eu) is dissolved in the oily solvent (decane). 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide) and the additive (dodecyl ammonium bromide), the additive (dodecyl ammonium bromide) can react with oil-soluble fluorescent dyes (Eu... 3+ An ionic surfactant that interacts molecularly with a complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine europium oxide.

[0044] This embodiment describes a method for preparing fluorescent microcapsules, comprising the following steps:

[0045] S1. Dissolve 4g of polyvinyl alcohol and 2g of polyethylene glycol dimethacrylate in 20g of pure water. Stir until completely dissolved to obtain aqueous solution A.

[0046] 10mg of Eu 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide, 50 mg of benzoyl peroxide, and 10 mg of dodecyl ammonium bromide were dissolved in 6 g of decane, completely dissolved, and stirred evenly to obtain an oily solution B.

[0047] S2. Mix aqueous solution A and oily solution B, and emulsify in a homogenizer for 20 minutes to form a uniform O / W emulsion.

[0048] S3. Pour the emulsion into a round-bottom flask, stir and react at 70°C for 5 hours. After the reaction is complete, filter the mixture, wash it three times with water, and dry it in an oven to obtain fluorescent microcapsules.

[0049] The invisible pressure-sensitive carbon paper of this embodiment is obtained by coating the paper with the fluorescent microcapsules prepared in this embodiment using conventional methods.

[0050] Figure 2 This is a scanning electron microscope image of the fluorescent microcapsules prepared in this embodiment. The fluorescent microcapsules are spherical in shape.

[0051] Figure 3 This is a fluorescence photograph of the fluorescent microcapsules prepared in this embodiment. The fluorescent microcapsules exhibit fluorescence.

[0052] Figure 4This is an optical photograph showing the oily solvent flowing out of the fluorescent microcapsules after they were crushed in this embodiment. The shaded area represents the range of oily solvent flow (the area enclosed by the two dashed lines).

[0053] Figure 5 The fluorescent microcapsules prepared in this embodiment are shown in the fluorescence photograph after the solvent in the microcapsules flows out after being crushed. It can be seen that the range of oily solvent outflow shows strong fluorescence, indicating that the fluorescent molecules of the fluorescent dye can flow out freely with the oily solvent, realizing the copying of invisible writing. The invisible pressure-sensitive carbon paper of this embodiment can be used independently and does not need to be equipped with a triplet.

[0054] Comparative Example 1:

[0055] This comparative example of a fluorescent microcapsule includes a capsule wall 1 and a core 2. The capsule wall 1 coats the surface of the core 2 and is formed by a mixed reaction of an oil phase solution and an aqueous phase solution. A polyethylene glycol olefin derivative (polyethylene glycol dimethacrylate) is used as the wall material of the capsule wall 1, and an oily solvent (decane) is used as the core material of the core 2. An oil-soluble fluorescent dye (Eu) is used. 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide is adsorbed on the capsule wall 1 of the microcapsule.

[0056] This comparative example describes a method for preparing fluorescent microcapsules without the addition of additives, comprising the following steps:

[0057] S1. Dissolve 4g of polyvinyl alcohol and 2g of polyethylene glycol dimethacrylate in 20g of pure water. Stir until completely dissolved to obtain aqueous solution A.

[0058] 10mg of Eu 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and europium triphenylphosphine oxide, and 50 mg of benzoyl peroxide were dissolved in 6 g of decane, completely dissolved and stirred evenly to obtain an oily solution B.

[0059] S2. Mix aqueous solution A and oily solution B, and emulsify in a homogenizer for 20 minutes to form a uniform O / W emulsion.

[0060] S3. Pour the emulsion into a round-bottom flask, stir and react at 70°C for 5 hours. After the reaction is complete, filter the mixture, wash it three times with water, and dry it in an oven to obtain microcapsules.

[0061] The carbon paper used in this comparative example was obtained by coating the paper with the fluorescent microcapsules prepared in this embodiment using conventional methods.

[0062] Figure 6 This is a scanning electron microscope image of the fluorescent microcapsules prepared in this comparative example.

[0063] Figure 7 The image shows the fluorescence of the microcapsules prepared in this comparative example after they were crushed and the solvent flowed out. The area enclosed by the dashed line indicates the range of oily solvent flow. It can be seen that the area where the microcapsules are located shows strong fluorescence, but the range of oily solvent flow does not show fluorescence. This indicates that the fluorescent molecules are only adsorbed onto the capsule wall 1 of the microcapsule and are not encapsulated or dissolved in the oily phase of the microcapsule. Therefore, it can be concluded that the carbon paper of this comparative example cannot be used independently.

[0064] Comparative Example 2:

[0065] This comparative example of a fluorescent microcapsule includes a capsule wall 1 and a core 2. The capsule wall 1 coats the surface of the core 2 and is formed by a mixed reaction of an oil phase solution and an aqueous phase solution. The capsule wall 1 uses polyethylene glycol olefin derivatives (methyl methacrylate, 1,4-butanediol diacrylate) as the wall material, and an oily solvent (decane) as the core material. An oil-soluble fluorescent dye (Eu) is used. 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide is adsorbed on the capsule wall 1 of the microcapsule.

[0066] This comparative example describes a method for preparing fluorescent microcapsules, using the polymer monomers methyl methacrylate and 1,4-butanediol diacrylate as the wall material of the capsule wall 1, comprising the following steps:

[0067] S1. Dissolve 4g of polyvinyl alcohol in 20g of pure water, stir until completely dissolved and homogeneous to obtain aqueous solution A.

[0068] 10mg of Eu 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide, 50 mg of benzoyl peroxide, 10 mg of dodecyl ammonium bromide, 2 g of methyl methacrylate, and 1 g of 1,4-butanediol diacrylate were dissolved in 6 g of decane, and the solution was completely dissolved and stirred evenly to obtain an oily solution B.

[0069] S2. Mix aqueous solution A and oily solution B, and emulsify in a homogenizer for 20 minutes to form a uniform O / W emulsion.

[0070] S3. Pour the emulsion into a round-bottom flask, stir and react at 70°C for 5 hours. After the reaction is complete, filter the mixture, wash it three times with water, and dry it in an oven to obtain microcapsules.

[0071] The carbon paper used in this comparative example was obtained by coating the paper with the fluorescent microcapsules prepared in this embodiment using conventional methods.

[0072] Figure 8This is a scanning electron microscope image of the fluorescent microcapsules prepared in this comparative example.

[0073] Figure 9 The image shows the fluorescence of the microcapsules prepared in this comparative example after they were crushed and the solvent flowed out. The area enclosed by the dashed line indicates the range of oily solvent flow. It can be seen that the area where the microcapsules are located shows strong fluorescence, but the solvent flow range does not show fluorescence. This indicates that the fluorescent molecules are only adsorbed onto the capsule wall 1 of the microcapsule and are not encapsulated or dissolved in the oil phase of the microcapsule. Therefore, it can be concluded that the carbon paper of this comparative example cannot be used independently.

[0074] Comparative Example 3:

[0075] This comparative example of a fluorescent microcapsule includes a capsule wall 1 and a core 2. The capsule wall 1 coats the surface of the core 2 and is formed by a mixed reaction of an oil phase solution and an aqueous phase solution. Polyethylene glycol olefin derivative (methyl methacrylate) is used as the wall material of the capsule wall 1, and an oily solvent (decane) is used as the core material of the core 2. An oil-soluble fluorescent dye (Eu) is used. 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide is adsorbed on the capsule wall 1 of the microcapsule.

[0076] This comparative example describes a method for preparing fluorescent microcapsules, using the polymer monomer ethylene glycol dimethacrylate as the wall material of the capsule wall 1, comprising the following steps:

[0077] S1. Dissolve 4g of polyvinyl alcohol in 20g of pure water, stir until completely dissolved and homogeneous to obtain aqueous solution A.

[0078] 10mg of Eu 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and europium triphenylphosphine oxide, 50 mg of benzoyl peroxide, 10 mg of dodecyl ammonium bromide, and 2 g of ethylene glycol dimethacrylate were dissolved in 6 g of decane, and the solution was completely dissolved and stirred evenly to obtain an oily solution B.

[0079] S2. Mix aqueous solution A and oily solution B, and emulsify in a homogenizer for 20 minutes to form a uniform O / W emulsion.

[0080] S3. Pour the emulsion into a round-bottom flask, stir and react at 70°C for 5 hours. After the reaction is complete, filter the mixture, wash it three times with water, and dry it in an oven to obtain fluorescent microcapsules.

[0081] The carbon paper used in this comparative example was obtained by coating the paper with the fluorescent microcapsules prepared in this embodiment using conventional methods.

[0082] Figure 10This is a scanning electron microscope image of the fluorescent microcapsules prepared in this comparative example.

[0083] Figure 11 The image shows the fluorescence of the microcapsules prepared in this comparative example after they were crushed and the solvent flowed out. The area enclosed by the dashed line indicates the range of oily solvent flow. It can be seen that the area where the microcapsules are located shows strong fluorescence, but the solvent flow range does not show fluorescence. This indicates that the fluorescent molecules are only adsorbed onto the capsule wall 1 of the microcapsule and are not encapsulated or dissolved in the oil phase of the microcapsule. Therefore, it can be concluded that the carbon paper of this comparative example cannot be used independently.

[0084] Comparative Example 4:

[0085] This comparative example of a fluorescent microcapsule includes a capsule wall 1 and a core 2. The capsule wall 1 coats the surface of the core 2 and is formed by a mixed reaction of an oil phase solution and an aqueous phase solution. A polyethylene glycol olefin derivative (polyethylene glycol dimethacrylate) is used as the wall material of the capsule wall 1, and an oily solvent (decane) is used as the core material of the core 2. An oil-soluble fluorescent dye (Eu) is used. 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide is adsorbed on the capsule wall 1 of the microcapsule.

[0086] This comparative example describes a method for preparing fluorescent microcapsules, using dodecylphenol polyoxyethylene ether (OP-10) as an additive, and includes the following steps:

[0087] S1. Dissolve 4g of polyvinyl alcohol and 2g of polyethylene glycol dimethacrylate in 20g of pure water. Stir until completely dissolved to obtain aqueous solution A.

[0088] 10mg of Eu 3+ The complex formed with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and triphenylphosphine oxide, 50 mg of benzoyl peroxide, and 10 mg of OP-10 were dissolved in 6 g of decane, completely dissolved, and stirred until homogeneous to obtain oily solution B.

[0089] S2. Mix aqueous solution A and oily solution B, and emulsify in a homogenizer for 20 minutes to form a uniform O / W emulsion.

[0090] S3. Pour the emulsion into a round-bottom flask, stir and react at 70°C for 5 hours. After the reaction is complete, filter the mixture, wash it three times with water, and dry it in an oven to obtain microcapsules.

[0091] The carbon paper used in this comparative example was obtained by coating the paper with the fluorescent microcapsules prepared in this embodiment using conventional methods.

[0092] Figure 12The images shown are optical and fluorescent photographs of the fluorescent microcapsules prepared in this comparative example after they were crushed and the solvent flowed out. The area enclosed by the dashed line indicates the range of oily solvent flow. It can be seen that the area where the microcapsules are located shows strong fluorescence, but the solvent flow range does not show fluorescence. This indicates that the fluorescent molecules are only adsorbed onto the capsule wall 1 of the microcapsule and are not encapsulated or dissolved in the oil phase of the microcapsule. Therefore, it can be concluded that the carbon paper of this comparative example cannot be used independently.

[0093] Example 2:

[0094] A fluorescent microcapsule of this embodiment includes a capsule wall 1 and a capsule core 2. The capsule wall 1 covers the surface of the capsule core 2 and is formed by the mixed reaction of an oil phase solution and an aqueous phase solution. The capsule wall 1 is made of polyethylene glycol olefin derivative (polyethylene glycol fumarate) and the capsule core 2 is made of an oily solvent (caprylic acid / capric acid triglyceride). The oily solvent (caprylic acid / capric acid triglyceride) contains an oil-soluble fluorescent dye (o-phenanthroline tri(benzoyltrifluoroacetylacetone) terbium (III)) and an additive (hexadecyl pyridine bromide). The additive (hexadecyl pyridine bromide) is an ionic surfactant that can interact with the oil-soluble fluorescent dye (o-phenanthroline tri(benzoyltrifluoroacetylacetone) terbium (III)) through molecular interaction.

[0095] This embodiment describes a method for preparing fluorescent microcapsules, comprising the following steps:

[0096] S1. Dissolve 6g of polyvinyl alcohol and 2g of polyethylene glycol fumarate in 30g of pure water. Stir until completely dissolved to obtain aqueous solution A.

[0097] 5 mg of o-phenoxyline tri(benzoyltrifluoroacetylacetone) terbium(III), 50 mg of azobisisobutyronitrile, and 10 mg of hexadecylpyridine bromide were dissolved in 6 g of caprylic / capric triglyceride. The solution was completely dissolved and stirred until homogeneous to obtain oily solution B.

[0098] S2. Mix aqueous solution A and oily solution B, and emulsify in a homogenizer for 20 minutes to form a uniform O / W emulsion.

[0099] S3. Pour the emulsion into a round-bottom flask, stir and react at 70°C for 5 hours. After the reaction is complete, filter the mixture, wash it three times with water, and dry it in an oven to obtain fluorescent microcapsules.

[0100] The invisible pressure-sensitive carbon paper of this embodiment is obtained by coating the paper with the fluorescent microcapsules prepared in this embodiment using conventional methods.

[0101] Example 3:

[0102] A fluorescent microcapsule of this embodiment includes a capsule wall 1 and a capsule core 2. The capsule wall 1 covers the surface of the capsule core 2 and is formed by the mixed reaction of an oil phase solution and an aqueous phase solution. The capsule wall 1 is made of polyethylene glycol olefin derivative (polyethylene glycol diacrylate) and the capsule core 2 is made of an oily solvent (1-bromooctane). The oily solvent (1-bromooctane) contains an oil-soluble fluorescent dye (bipyridine tri(benzoyltrifluoroacetylacetone) europium(III)) and an additive (sodium dodecyl sulfonate). The additive (sodium dodecyl sulfonate) is an ionic surfactant that can interact with the oil-soluble fluorescent dye (bipyridine tri(benzoyltrifluoroacetylacetone) europium(III)).

[0103] This embodiment describes a method for preparing fluorescent microcapsules, comprising the following steps:

[0104] S1. Dissolve 3g of styrene-maleic anhydride copolymer and 3g of polyethylene glycol diacrylate in 20g of pure water. Stir until completely dissolved to obtain aqueous solution A.

[0105] 10 mg of bipyridine tri(benzoyltrifluoroacetylacetone) europium(III), 80 mg of azobisisoheptanenitrile, and 20 mg of sodium dodecyl sulfonate were dissolved in 6 g of 1-bromooctane, and the solution was completely dissolved and stirred evenly to obtain an oily solution B.

[0106] S2. Mix aqueous solution A and oily solution B, and emulsify in a homogenizer for 20 minutes to form a uniform O / W emulsion.

[0107] S3. Pour the emulsion into a round-bottom flask, stir and react at 70°C for 5 hours. After the reaction is complete, filter the mixture, wash it three times with water, and dry it in an oven to obtain fluorescent microcapsules.

[0108] The invisible pressure-sensitive carbon paper of this embodiment is obtained by coating the paper with the fluorescent microcapsules prepared in this embodiment using conventional methods.

[0109] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A fluorescent microcapsule, comprising a capsule wall (1) and a capsule core (2), wherein the capsule wall (1) coats the surface of the capsule core (2) and is formed by mixing and reacting an aqueous solution and an oil solution, characterized in that: The fluorescent microcapsule has a polyethylene glycol alkylene derivative as a wall material of a capsule wall (1), and has an oily solvent as a core material of a capsule core (2), wherein the oily solvent has dissolved therein an oil-soluble fluorescent dye and an additive which can have a molecular interaction with the oil-soluble fluorescent dye; The raw materials of the aqueous solution include an emulsifier, a polyethylene glycol alkylene derivative, and water; The polyethylene glycol alkylene derivative is one or more of polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol fumarate, and alkylene-polyethylene glycol-alkylene. The raw materials of the oily solution include an oil-soluble fluorescent dye, an oil-soluble initiator, an additive, and an oily solvent.

2. The fluorescent microcapsule according to claim 1, characterized in that: The mass ratio of the emulsifier, the polyethylene glycol alkylene derivative, and the water is 3-10:0.5-3:15-40.

3. The fluorescent microcapsule according to claim 2, characterized in that: The emulsifier is one or more of polyvinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, propylene-maleic anhydride copolymer, and isobutylene-maleic anhydride copolymer.

4. The fluorescent microcapsule according to claim 1, characterized in that: The mass ratio of the oil-soluble fluorescent dye, the oil-soluble initiator, and the oily solvent is 5-50:50-300:5000-10000, and the mass of the additive is 0.5-2.5 times the mass of the oil-soluble fluorescent dye.

5. The fluorescent microcapsule according to claim 4, wherein: The ionic surfactant is one or more of sodium alkyl sulfonate, sodium alkyl benzene sulfonate, alkyl ammonium bromide, and alkyl pyridine bromide. The oil-soluble fluorescent dye is one or more of acetylacetone europium (III), tris (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) europium (III), o-phenanthroline · tri (benzoyl trifluoroacetylacetone) europium (III), bipyridine · tri (benzoyl trifluoroacetylacetone) europium (III), bis (triphenylphosphine oxide) · tri (benzoyl trifluoroacetylacetone) europium (III), o-phenanthroline · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) europium (III), bipyridine · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) europium (III), bis (triphenylphosphine oxide) · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) europium (III), o-phenanthroline · tri (benzoyl trifluoroacetylacetone) terbium (III), bipyridine · tri (benzoyl trifluoroacetylacetone) terbium (III), bis (triphenylphosphine oxide) · tri (benzoyl trifluoroacetylacetone) terbium (III), o-phenanthroline · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) terbium (III), bipyridine · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) terbium (III), bis (triphenylphosphine oxide) · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) terbium (III), bis (triphenylphosphine oxide) · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) terbium (III), bis (triphenylphosphine oxide) · tri (4, 4, 4-trifluoro-1- (2-thiophene) -1, 3-butanedione) terbium (III).

6. The fluorescent microcapsule according to claim 4, characterized in that: The oily solvent is one or more of hexane, cyclohexane, petroleum ether, heptane, octane, 1-bromooctane, nonane, decane, undecane, dodecane, dimethyl phthalate, diethyl phthalate, propylene carbonate, caprylic / capric triglyceride; The oil-soluble initiator is one or more of azobisisobutyronitrile, azobisisoheptyl nitrile, benzoyl peroxide.

7. A method of producing the fluorescent microcapsule according to any one of claims 1 to 6, characterized by: The method comprises the following steps: S1, preparation of raw material aqueous solution A and oily solution B: The emulsifier, polyethylene glycol alkene derivative is dissolved in water, and the aqueous solution A is obtained after uniform stirring; the oil-soluble fluorescent dye, oil-soluble initiator, additive are dissolved in the oily solvent, and the oily solution B is obtained after uniform stirring; S2, the aqueous solution A and the oily solution B are mixed in a volume ratio of 5:1 to 2:1, and then emulsified to form a uniform emulsion; S3, the emulsion is stirred and reacted at a temperature of 60-80℃, and then filtered, washed and dried to obtain the fluorescent microcapsule.

8. The method for preparing fluorescent microcapsules according to claim 7, characterized in that: In step S2, the emulsification time is 10-40 min.

9. The method for preparing fluorescent microcapsules according to claim 7, characterized in that: In step S2, the stirring reaction time is 3-6 h.

10. A covert pressure sensitive copy paper coated with fluorescent microcapsules, characterized in that: The fluorescent microcapsule is the fluorescent microcapsule prepared according to the method for preparing the fluorescent microcapsule according to any one of claims 1-6 or the fluorescent microcapsule according to any one of claims 7-9.

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