Low-refractive-index high-transparency UV inkjet ink and preparation method thereof

Abstract

The invention relates to the technical field of ink-jet ink, and discloses low-refractive-index high-transparency UV ink-jet ink and a preparation method thereof.Fluorine-containing alkenyl zwitterionic monomers obtained through substitution, condensation, quaternization and other reactions are polymerized with UV curing resin prepolymer under the action of a photoinitiator, and pigment, auxiliaries and the like are added to prepare the ink-jet ink; the electronegativity of fluorine atoms is great, and the polarizability is small, so that the propagation speed of light in the ink is accelerated, and the refractive index is relatively low; the fluorine-containing alkenyl zwitterionic monomer can increase the compatibility between the pigment and a solvent, and can form a layer of protective film around pigment particles to prevent the pigment particles from getting close to each other and aggregating, so that the transmittance of the ink is further improved; the prepared UV ink-jet ink is excellent in tensile strength, water resistance, wear resistance, adhesiveness and weather resistance, meets the industrial requirements of ink, and is suitable for ink-jet printing in various fields.

Description

Technical Field

[0001] The invention relates to the technical field of inkjet inks, and in particular to a low-refractive-index and high-transmittance UV inkjet ink and a preparation method thereof. Background Art

[0002] With the rapid development of digital printing technology, inkjet printing, as an efficient and flexible printing method, has been widely used in many fields. Among them, UV inkjet printing, with its unique ultraviolet curing technology, can achieve fast drying and high adhesion, and has become an important development direction of the printing industry in recent years. UV inkjet ink mainly uses the energy of ultraviolet light to trigger base material polymerization and cross-linking reactions between molecules in the coating, so that the ink changes from liquid to solid. Although traditional UV inkjet ink has shown good adhesion on non-absorbent media such as metal and glass, in certain specific applications, such as optical devices and high-transparency materials, higher requirements are placed on the refractive index and transparency of the ink. High-refractive-index inks may cause optical interference or affect visual effects, and the development of low-refractive-index and high-transparency UV inkjet inks is precisely to meet these special needs.

[0003] In the fields of LED display screens, touch screens, solar panels, etc., low refractive index and high transmittance ink can reduce light scattering and reflection and improve the optical performance of products; there are many kinds of UV inkjet inks on the market, but most of them have problems such as high refractive index and insufficient light transmittance; although high refractive index ink can enhance color effect and glossiness, in some application scenarios, such as occasions where color accuracy and clarity need to be maintained, too high refractive index will lead to light scattering and color distortion; in addition, high refractive index ink may also increase the surface roughness of printed products, affecting the visual effect. There are few studies on the low refractive index of ink in the prior art. For example, patent No. CN115368776A discloses ink, light refractive index regulating film and its preparation method and application, which mainly adjusts the refractive index of the light refractive index regulating film by continuously adjusting the concentration of ZrO2 nanocrystals. There are problems such as poor dispersion performance and easy agglomeration, and the transmittance and weather resistance of the ink are not significantly improved.

[0004] Since fluorine has extremely high electronegativity, low refractive index and low polarizability, it has excellent electrical and optical properties; siloxane has outstanding thermal stability, stain resistance and low surface tension; resin is often used as prepolymer in UV ink of the prior art, but this ink has poor film-forming property, and the hardness and strength of the film are poor; the present invention aims to utilize the characteristics of low refractive index of fluorine atoms, good weather resistance of siloxane and effective dispersion of pigments in ink by zwitterions to prepare a low refractive index and high transmittance olefin monomer, which is polymerized with UV resin prepolymer under the action of photoinitiator, and the obtained UV inkjet ink can be widely used in display screens, touch screens and other fields. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and to provide a low-refractive-index and high-transmittance UV inkjet ink and a preparation method thereof. The ink has very good transmittance, adhesion and weather resistance, low refractive index and a wide range of applications.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a low refractive index and high transmittance UV inkjet ink is carried out according to the following steps:

[0008] Step (1), under a nitrogen atmosphere, 100 parts by weight of toluene diisocyanate and 40-60 parts of polytetramethylene ether glycol are added to a reaction flask, stirred evenly, 0.2-0.5 parts of stannous octoate and 0.03-0.08 parts of polymerization inhibitor are added, stirred at 75-90° C. for 1-3 hours, cooled to 50-65° C., 20-35 parts of N-methyldiethanolamine and 5-10 parts of 1,4-butanediol are added, reacted for 0.5-2 hours, 8-15 parts of hydroxyethyl acrylate are added for photosensitive active end-capping, and reacted at 60-75° C. for 0.5 hours to obtain a UV-curable resin prepolymer.

[0009] Step (2), 20-40 parts by weight of UV curable resin prepolymer, 10-30 parts by weight of the structural formula The fluorinated olefin zwitterionic monomer and 5-8 parts of photoinitiator are added to a high-speed mixer, stirred and dissolved at 40-60°C, and sent to a grinder for cyclic grinding for 2-4 hours. Then, 12-20 parts of pigment paste, 5-10 parts of moisturizer and 2-4 parts of defoamer are added, dispersed evenly and centrifuged, dispersed at high speed to a particle size of 1-2um, filtered and packaged to obtain a low refractive index and high transmittance UV inkjet ink.

[0010] Preferably, the polymerization inhibitor in step (1) is any one of o-methyl hydroquinone, phenothiazine or p-tert-butyl catechol.

[0011] Preferably, in step (2), the moisturizing agent is any one of glycerol, PEG glyceryl ether or diethylene glycol ethyl ether.

[0012] Preferably, the preparation method of the fluorinated alkenyl zwitterionic monomer in step (2) is carried out according to the following steps:

[0013] Step S1, under a nitrogen atmosphere, add methylvinyldichlorosilane and toluene to a reaction flask, stir evenly, add 3-hydroxy-5-(trifluoromethyl)benzoic acid and sodium hydride, stir to react, filter after the reaction, distill under reduced pressure, recrystallize with a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and dry to obtain a fluorinated alkenylsiloxane carboxylic acid monomer.

[0014] Step S2, under a nitrogen atmosphere, add a fluorinated alkenylsiloxane carboxylic acid monomer, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 4-dimethylaminopyridine and dichloromethane to a reaction flask, stir evenly, add N,N-dimethylethylenediamine, react at 20-35° C. for 12-24 h, concentrate under reduced pressure, and separate by column chromatography (elution with chloroform / methanol = 20:1) to obtain a fluorinated alkenylsiloxane tertiary amine monomer.

[0015] Step S3, under a nitrogen atmosphere, add a fluorinated alkenyl siloxane tertiary amine monomer and N,N-dimethylformamide to a reaction flask, stir evenly, add sodium 2-bromoethane sulfonate, stir to react, filter after the reaction is completed, wash with acetonitrile, and dry to obtain a fluorinated alkenyl zwitterionic monomer.

[0016] Preferably, in step S1, the ratio of methylvinyldichlorosilane, 3-hydroxy-5-(trifluoromethyl)benzoic acid, and sodium hydride is 1 mol:(2.05-2.2) mol:(2.3-2.5) mol.

[0017] Preferably, in step S1, the reaction temperature is 70-90° C. and the reaction time is 8-16 h.

[0018] Preferably, in step S2, the ratio of the fluorinated alkenyl siloxane carboxylic acid monomer, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 4-dimethylaminopyridine, and N,N-dimethylethylenediamine is 1 mol: (1.2-1.5) mol: (0.2-0.4) mol: (2.1-2.35) mol.

[0019] Preferably, in step S3, the ratio of the fluorinated alkenylsiloxane tertiary amine monomer to sodium 2-bromoethane sulfonate is 1 mol:(2.3-2.8) mol.

[0020] Preferably, in step S3, the reaction temperature is 110-135° C., and the reaction time is 24-48 h.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The invention uses methylvinyldichlorosilane, 3-hydroxy-5-(trifluoromethyl)benzoic acid, N,N-dimethylethylenediamine and sodium 2-bromoethanesulfonate as raw materials, and obtains fluorine-containing olefin zwitterionic monomers through substitution, condensation and quaternization reactions. The monomers are polymerized with UV curable resin prepolymers under the action of a photoinitiator, and additives such as pigments, wetting agents and defoaming agents are added to obtain low refractive index and high transmittance UV inkjet ink.

[0023] The electronegativity of fluorine atoms is extremely large and their polarizability is low, which makes the electron cloud tightly arranged around the fluorine atoms, reduces the polarization of the electron cloud, and then reduces the refractive index, which speeds up the propagation of light in the ink, thus showing a lower refractive index; the sodium sulfonate group in the fluorinated olefinic zwitterionic monomer can increase the compatibility between the pigment and the solvent, and can form a protective film around the pigment particles to prevent the pigment particles from approaching each other and agglomerating into clusters, thereby ensuring that the pigment is evenly dispersed in the ink, improving the storage stability of the ink, making the printed colors more vivid and full, and reducing the phenomenon of edge blur and color distortion; the quaternary ammonium salt cationic group can produce electrostatic effects with the anions in the ink, making it difficult for the pigment particles to aggregate, offsetting the cohesive force between the pigment particles, preventing the secondary flocculation of the pigment particles, forming a uniform and stable pigment dispersion, and further improving the transmittance of the ink.

[0024] The carbon-fluorine bond has a large bond energy, and the fluorine atoms are closely arranged around the carbon-carbon main chain, which plays a role in protecting the main chain and has good heat resistance and solvent resistance; the flexibility of siloxane gives the material good shear resistance and wear resistance, so that it can maintain a low wear rate and stable friction performance when subjected to high load and high-speed friction; the UV curing resin prepolymer uses polyurethane as a skeleton material and hydroxyethyl acrylate as a capping material, and initiates polymerization with fluorinated alkenyl zwitterionic monomers at the same time to form a network structure similar to a semi-interpenetrating polymer, which not only retains the excellent properties of polyurethane and polyacrylate, but also plays the characteristics of organic silicon and organic fluorine in functional monomers, so that they complement each other organically, and improve the mechanical properties, yellowing and weather resistance of the ink cured film. The UV inkjet ink prepared by the present invention is excellent in tensile strength, water resistance, wear resistance, adhesion and weather resistance, meets the industry requirements of ink, and is suitable for inkjet printing in various fields. DETAILED DESCRIPTION

[0025] The technical scheme in the embodiment of the present invention will be clearly and completely described below. Obviously, the described embodiment is only a part of the embodiment of the present invention, rather than all embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Unless otherwise indicated, the raw materials and reagents used in this application are all commercially available products, or can be prepared by known methods.

[0026] Methylvinyldichlorosilane, CAS number is 124-70-9.

[0027] 3-Hydroxy-5-(trifluoromethyl)benzoic acid 328-69-8.

[0028] N,N-Dimethylethylenediamine, CAS number is 108-00-9.

[0029] Sodium 2-bromoethane sulfonate, CAS number is 4263-52-9.

[0030] Example 1

[0031] (1) Under a nitrogen atmosphere, 60 mmol of methylvinyldichlorosilane and 240 mL of toluene were added to a reaction flask, and after stirring, 128 mmol of 3-hydroxy-5-(trifluoromethyl)benzoic acid and 145 mmol of sodium hydride were added, and the mixture was reacted at 80° C. for 12 h, filtered, and distilled under reduced pressure. Recrystallization was performed using a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and the fluorinated alkenylsiloxane carboxylic acid monomer was obtained after drying.

[0032] (2) Under a nitrogen atmosphere, 50 mmol of a fluorinated alkenylsiloxane carboxylic acid monomer, 65 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 15 mmol of 4-dimethylaminopyridine and 325 mL of dichloromethane were added to a reaction flask. After stirring evenly, 110 mmol of N,N-dimethylethylenediamine was added, and the mixture was reacted at 25° C. for 16 h. The mixture was concentrated under reduced pressure and separated by column chromatography (elution with chloroform / methanol = 20:1) to obtain a fluorinated alkenylsiloxane tertiary amine monomer.

[0033] (3) Under nitrogen atmosphere, 45 mmol of fluorinated alkenyl siloxane tertiary amine monomer and 540 mL of N,N-dimethylformamide were added to the reaction flask, and after stirring, 117 mmol of sodium 2-bromoethane sulfonate was added, and the mixture was reacted at 125° C. for 32 h, filtered, washed with acetonitrile, and dried to obtain a fluorinated alkenyl zwitterionic monomer. The preparation reaction formula is as follows:

[0034]

[0035] (4) Under a nitrogen atmosphere, 100 g of toluene diisocyanate and 50 g of polytetramethylene glycol were added to a reaction flask and stirred evenly. 0.4 g of stannous octoate and 0.06 g of hydroquinone were added and stirred at 85 °C for 2 h. The temperature was lowered to 55 °C, 25 g of N-methyldiethanolamine and 8 g of 1,4-butanediol were added and reacted for 1 h. 12 g of hydroxyethyl acrylate was added for photosensitive active end-capping and the reaction was carried out at 65 °C for 0.5 h to obtain a UV-curable resin prepolymer.

[0036] (5) 40 g of UV curable resin prepolymer, 10 g of fluorinated alkenyl zwitterionic monomer and 6 g of photoinitiator PI 1173 were added to a high-speed mixer, stirred and dissolved at 50° C., and sent to a grinder for cyclic grinding for 3 h. Then, 15 g of quinacridone, 8 g of propylene glycol and 3 g of defoamer BYK024 were added, and the mixture was evenly dispersed and centrifuged. The mixture was dispersed at high speed to a particle size of 1.5 μm, filtered and packaged to obtain a low refractive index and high transmittance UV inkjet ink.

[0037] Example 2

[0038] (1) Under a nitrogen atmosphere, 150 mmol of methylvinyldichlorosilane and 300 mL of toluene were added to a reaction flask, and after stirring, 307.5 mmol of 3-hydroxy-5-(trifluoromethyl)benzoic acid and 345 mmol of sodium hydride were added, and the mixture was reacted at 90° C. for 8 h, filtered, and distilled under reduced pressure. Recrystallization was performed using a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and the fluorinated alkenylsiloxane carboxylic acid monomer was obtained after drying.

[0039] (2) Under a nitrogen atmosphere, 135 mmol of a fluorinated alkenylsiloxane carboxylic acid monomer, 162 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 27 mmol of 4-dimethylaminopyridine and 675 mL of dichloromethane were added to a reaction flask. After stirring evenly, 283.5 mmol of N,N-dimethylethylenediamine was added, and the mixture was reacted at 35° C. for 12 h. The mixture was concentrated under reduced pressure and separated by column chromatography (elution with chloroform / methanol = 20:1) to obtain a fluorinated alkenylsiloxane tertiary amine monomer.

[0040] (3) Under nitrogen atmosphere, 120 mmol of fluorinated olefinic siloxane tertiary amine monomer and 1200 mL of N,N-dimethylformamide were added to a reaction flask, and after stirring, 276 mmol of sodium 2-bromoethane sulfonate was added, and the mixture was reacted at 135° C. for 24 h. The mixture was filtered, washed with acetonitrile, and dried to obtain a fluorinated olefinic zwitterionic monomer.

[0041] (4) Under a nitrogen atmosphere, 100 g of toluene diisocyanate and 40 g of polytetramethylene glycol were added to a reaction flask and stirred evenly. 0.2 g of stannous octoate and 0.03 g of phenothiazine were added and stirred at 90 °C for 1 h. The temperature was lowered to 65 °C, 20 g of N-methyldiethanolamine and 5 g of 1,4-butanediol were added and reacted for 0.5 h. 8 g of hydroxyethyl acrylate was added for photosensitive active end-capping and the mixture was reacted at 75 °C for 0.5 h to obtain a UV-curable resin prepolymer.

[0042] (5) 35 g of UV curable resin prepolymer, 15 g of fluorinated alkenyl zwitterionic monomer and 5 g of photoinitiator PI 1173 were added to a high-speed mixer, stirred and dissolved at 60° C., and sent to a grinder for cyclic grinding for 2 h. Then, 12 g of quinacridone, 5 g of PEG glycerol ether and 2 g of defoamer BYK024 were added, and the mixture was evenly dispersed and centrifuged. The mixture was dispersed at high speed to a particle size of 1 um, filtered and packaged to obtain a low refractive index and high transmittance UV inkjet ink.

[0043] Example 3

[0044] (1) Under a nitrogen atmosphere, 40 mmol of methylvinyldichlorosilane and 200 mL of toluene were added to a reaction flask, and after stirring, 88 mmol of 3-hydroxy-5-(trifluoromethyl)benzoic acid and 100 mmol of sodium hydride were added, and the mixture was reacted at 70° C. for 16 h, filtered, and distilled under reduced pressure. Recrystallization was performed with a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and the fluorinated alkenylsiloxane carboxylic acid monomer was obtained after drying.

[0045] (2) Under a nitrogen atmosphere, 32 mmol of a fluorinated alkenylsiloxane carboxylic acid monomer, 48 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 12.8 mmol of 4-dimethylaminopyridine and 256 mL of dichloromethane were added to a reaction flask. After stirring evenly, 75.2 mmol of N,N-dimethylethylenediamine was added, and the mixture was reacted at 20° C. for 24 h. The mixture was concentrated under reduced pressure and separated by column chromatography (elution with chloroform / methanol = 20:1) to obtain a fluorinated alkenylsiloxane tertiary amine monomer.

[0046] (3) Under nitrogen atmosphere, 28 mmol of fluorinated olefinic siloxane tertiary amine monomer and 420 mL of N,N-dimethylformamide were added to a reaction flask, and after stirring, 78.4 mmol of sodium 2-bromoethane sulfonate was added, and the mixture was reacted at 110° C. for 48 h. The mixture was filtered, washed with acetonitrile, and dried to obtain a fluorinated olefinic zwitterionic monomer.

[0047] (4) Under a nitrogen atmosphere, 100 g of toluene diisocyanate and 60 g of polytetramethylene glycol were added to a reaction flask and stirred evenly. 0.5 g of stannous octoate and 0.08 g of tert-butyl catechol were added and stirred at 75 °C for 3 h. The temperature was lowered to 50 °C, 35 g of N-methyldiethanolamine and 10 g of 1,4-butanediol were added and reacted for 2 h. 15 g of hydroxyethyl acrylate was added for photosensitive active end-capping and the mixture was reacted at 60 °C for 0.5 h to obtain a UV-curable resin prepolymer.

[0048] (5) 30 g of UV curable resin prepolymer, 20 g of fluorinated alkenyl zwitterionic monomer and 8 g of photoinitiator PI 1173 were added to a high-speed stirrer, stirred and dissolved at 40° C., and sent to a grinder for cyclic grinding for 4 h. Then, 20 g of quinacridone, 10 g of diethylene glycol ethyl ether and 4 g of defoamer BYK024 were added, and the mixture was evenly dispersed and centrifuged. The mixture was dispersed at high speed to a particle size of 2 μm, filtered and packaged to obtain a low refractive index and high transmittance UV inkjet ink.

[0049] Example 4

[0050] (1) Under a nitrogen atmosphere, 90 mmol of methylvinyldichlorosilane and 315 mL of toluene were added to a reaction flask, and after stirring, 193.5 mmol of 3-hydroxy-5-(trifluoromethyl)benzoic acid and 220.5 mmol of sodium hydride were added, and the mixture was reacted at 85° C. for 156 h, filtered, and distilled under reduced pressure. Recrystallization was performed using a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and the fluorinated alkenylsiloxane carboxylic acid monomer was obtained after drying.

[0051] (2) Under a nitrogen atmosphere, 80 mmol of a fluorinated alkenylsiloxane carboxylic acid monomer, 108 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 20 mmol of 4-dimethylaminopyridine and 520 mL of dichloromethane were added to a reaction flask. After stirring evenly, 180 mmol of N,N-dimethylethylenediamine was added, and the mixture was reacted at 30° C. for 20 h. The mixture was concentrated under reduced pressure and separated by column chromatography (elution with chloroform / methanol = 20:1) to obtain a fluorinated alkenylsiloxane tertiary amine monomer.

[0052] (3) Under a nitrogen atmosphere, 65 mmol of a fluorinated alkenyl siloxane tertiary amine monomer and 910 mL of N,N-dimethylformamide were added to a reaction flask, and after stirring, 156 mmol of sodium 2-bromoethane sulfonate was added, and the mixture was reacted at 120° C. for 35 h. The mixture was filtered, washed with acetonitrile, and dried to obtain a fluorinated alkenyl zwitterionic monomer.

[0053] (4) Under a nitrogen atmosphere, 100 g of toluene diisocyanate and 55 g of polytetramethylene glycol were added to a reaction flask and stirred evenly. 0.35 g of stannous octoate and 0.06 g of hydroquinone were added and stirred at 85 °C for 2 h. The temperature was lowered to 55 °C, 25 g of N-methyldiethanolamine and 7 g of 1,4-butanediol were added and reacted for 1.5 h. 12 g of hydroxyethyl acrylate was added for photosensitive active end-capping and the mixture was reacted at 70 °C for 0.5 h to obtain a UV-curable resin prepolymer.

[0054] (5) 25 g of UV curable resin prepolymer, 25 g of fluorinated alkenyl zwitterionic monomer and 7 g of photoinitiator PI 1173 were added to a high-speed mixer, stirred and dissolved at 55° C., and sent to a grinder for cyclic grinding for 3 h. Then, 16 g of quinacridone, 8 g of propylene glycol and 4 g of defoamer BYK024 were added, and the mixture was evenly dispersed and centrifuged. The mixture was dispersed at high speed to a particle size of 2 μm, filtered and packaged to obtain a low refractive index and high transmittance UV inkjet ink.

[0055] Example 5

[0056] (1) Under a nitrogen atmosphere, 35 mmol of methylvinyldichlorosilane and 125 mL of toluene were added to a reaction flask, and after stirring, 74.2 mmol of 3-hydroxy-5-(trifluoromethyl)benzoic acid and 82.6 mmol of sodium hydride were added, and the mixture was reacted at 75° C. for 12 h, filtered, and distilled under reduced pressure. Recrystallization was performed using a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and the fluorinated alkenylsiloxane carboxylic acid monomer was obtained after drying.

[0057] (2) Under a nitrogen atmosphere, 30 mmol of a fluorinated alkenylsiloxane carboxylic acid monomer, 42 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 8.4 mmol of 4-dimethylaminopyridine and 205 mL of dichloromethane were added to a reaction flask. After stirring evenly, 66 mmol of N,N-dimethylethylenediamine was added, and the mixture was reacted at 30° C. for 24 h. The mixture was concentrated under reduced pressure and separated by column chromatography (elution with chloroform / methanol = 20:1) to obtain a fluorinated alkenylsiloxane tertiary amine monomer.

[0058] (3) Under a nitrogen atmosphere, 20 mmol of a fluorinated alkenyl siloxane tertiary amine monomer and 27 mL of N,N-dimethylformamide were added to a reaction flask, and after stirring, 52 mmol of sodium 2-bromoethane sulfonate was added, and the mixture was reacted at 130° C. for 40 h. The mixture was filtered, washed with acetonitrile, and dried to obtain a fluorinated alkenyl zwitterionic monomer.

[0059] (4) Under a nitrogen atmosphere, 100 g of toluene diisocyanate and 45 g of polytetramethylene glycol were added to a reaction flask and stirred evenly. 0.5 g of stannous octoate and 0.08 g of phenothiazine were added and stirred at 90 ° C for 2 h. The temperature was lowered to 60 ° C. 25 g of N-methyldiethanolamine and 10 g of 1,4-butanediol were added and reacted for 2 h. 12 g of hydroxyethyl acrylate was added for photosensitive active end-capping. The reaction was carried out at 60 ° C for 0.5 h to obtain a UV-curable resin prepolymer.

[0060] (5) 20 g of UV curable resin prepolymer, 30 g of fluorinated alkenyl zwitterionic monomer and 6 g of photoinitiator PI 1173 were added to a high-speed mixer, stirred and dissolved at 55° C., and sent to a grinder for cyclic grinding for 3 h. Then, 15 g of quinacridone, 9 g of PEG glycerol ether and 4 g of defoamer BYK024 were added, and the mixture was evenly dispersed and centrifuged. The mixture was dispersed at high speed to a particle size of 1.2 μm, filtered and packaged to obtain a low refractive index and high transmittance UV inkjet ink.

[0061] Comparative Example 1

[0062] (1) Under nitrogen atmosphere, 60 mmol of methylvinyldichlorosilane and 240 mL of toluene were added to a reaction flask. After stirring, 128 mmol of p-hydroxybenzoic acid (CAS No. 99-96-7, structural formula: ) and 145 mmol sodium hydride, react at 80° C. for 12 h, filter, distill under reduced pressure, recrystallize with a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and dry to obtain an alkenylsiloxane carboxylic acid monomer.

[0063] (2) Under a nitrogen atmosphere, 50 mmol of alkenylsiloxane carboxylic acid monomer, 65 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 15 mmol of 4-dimethylaminopyridine and 325 mL of dichloromethane were added to a reaction flask, and after stirring evenly, 110 mmol of N,N-dimethylethylenediamine was added, and the mixture was reacted at 25° C. for 16 h. The mixture was concentrated under reduced pressure, and separated by column chromatography (elution with chloroform / methanol = 20:1) to obtain an alkenylsiloxane tertiary amine monomer.

[0064] (3) Under nitrogen atmosphere, 45 mmol of alkenyl siloxane tertiary amine monomer and 540 mL of N,N-dimethylformamide were added to the reaction flask, and after stirring, 117 mmol of sodium 2-bromoethane sulfonate was added, and the mixture was reacted at 125° C. for 32 h, filtered, washed with acetonitrile, and dried to obtain an alkenyl zwitterionic monomer (structural formula: ).

[0065] (4) 40 g of UV curable resin prepolymer (prepared in Example 1), 10 g of alkenyl zwitterionic monomer and 6 g of photoinitiator PI 1173 were added to a high-speed stirrer, stirred and dissolved at 50° C., and sent to a grinder for cyclic grinding for 3 h. Then, 15 g of quinacridone, 8 g of propylene glycol and 3 g of defoamer BYK024 were added, and after uniform dispersion, centrifugation was performed, and high-speed dispersion was performed to a particle size of 1.5 um. The mixture was filtered and packaged to obtain a high-transmittance UV inkjet ink.

[0066] Comparative Example 2

[0067] 40 g of UV curable resin prepolymer (prepared in Example 1), 10 g of fluorinated alkenyl siloxane carboxylic acid monomer (prepared in Example 1) and 6 g of photoinitiator PI 1173 were added to a high-speed stirrer, stirred and dissolved at 50° C., and sent to a grinder for cyclic grinding for 3 h. Then, 15 g of quinacridone, 8 g of propylene glycol and 3 g of defoamer BYK024 were added, and the mixture was evenly dispersed and centrifuged, dispersed at high speed to a particle size of 1.5 um, filtered and packaged to obtain a low refractive index UV inkjet ink.

[0068] Comparative Example 3

[0069] 50 g of UV curable resin prepolymer (prepared in Example 1) and 6 g of photoinitiator PI 1173 were added to a high-speed stirrer, stirred and dissolved at 50° C., and sent to a grinder for cyclic grinding for 3 h. Then, 15 g of quinacridone, 8 g of propylene glycol and 3 g of defoamer BYK024 were added, and the mixture was evenly dispersed and centrifuged, dispersed at high speed to a particle size of 1.5 um, filtered and packaged to obtain UV inkjet ink.

[0070] Preparation of cured coating film: The prepared UV inkjet ink was evenly coated on the surface of quartz glass using a 50 μm wire rod coater and cured into a film under a UV curing machine.

[0071] Refractive index test: Referring to GB / T 6488-2008 standard, a multi-wavelength Abbe refractometer was used to measure the refractive index of the ink at 25°C.

[0072] Transmittance test: UV-visible spectrophotometer was used for testing, with a scanning range of 380-800nm ​​and a scanning wavelength interval of 1nm.

[0073] Table 1 Refractive index and transmittance test

[0074] Refractive Index Transmittance (%) Example 1 1.4351 90.5 Example 2 1.4026 93.6 Example 3 1.3765 95.2 Example 4 1.3523 96.8 Example 5 1.3508 97.1 Comparative Example 1 1.6792 90.3 Comparative Example 2 1.4381 83.1 Comparative Example 3 1.6836 82.6

[0075] From the test results in the above table, it can be seen that with the increase of the content of fluorinated alkenyl zwitterionic monomers, the refractive index of UV inkjet ink gradually decreases. The refractive index in Example 4 is 1.3523, which is relatively low. This is because the electronegativity of fluorine atoms is extremely large and the polarizability is small, which makes the electron cloud closely arranged around the fluorine atoms, reduces the polarization of the electron cloud, and then reduces the refractive index, so that the propagation speed of light in the ink is accelerated, thereby showing a lower refractive index. Comparative Example 1 does not contain organic fluorine, has a high refractive index, and is not suitable for applications in the fields of LED display screens, touch screens, solar panels, etc.

[0076] After UV inkjet ink is evenly dispersed, the transmittance will become higher, because the pigment particles in the evenly dispersed ink are smaller and evenly distributed, and the scattering and reflection of light are reduced, making it easier for light to pass through the ink layer, thereby improving transparency; With the increase of the content of fluorinated alkenyl zwitterionic monomers, the transmittance of ink is improved, because on the one hand, the sodium sulfonate group can increase the compatibility between the pigment and the solvent, and a protective film can be formed around the pigment particles to prevent the pigment particles from approaching each other and agglomerating into a group, thereby ensuring that the pigment is evenly dispersed in the ink, improving the storage stability of the ink, making the color printed more vivid and full, reducing the phenomenon of edge fuzziness and color distortion; On the other hand, the electrostatic effect that the quaternary ammonium salt cationic group can produce with the anion in the ink makes the pigment particles difficult to aggregate, offsets the cohesive force between the pigment particles, prevents the secondary flocculation of the pigment particles, forms a uniform and stable pigment dispersion, and further improves the transmittance of the ink. In Comparative Example 2, zwitterions are not contained, and the dispersibility of the ink is poor, and the transmittance is low.

[0077] Tensile strength test: Referring to GB / T 1040.3-2006 standard, the cured coating film was made into a sample with a length of 150 mm, a width of 50 mm, and a height of 10 mm. The tensile properties were measured using a tensile testing machine with a tensile rate of 50 mm / min.

[0078] Water absorption test: refer to HG / T 3344-2012 standard, add the cured coating into 50mL of distilled water, soak for 24h, then take out and drain the excess water, weigh and measure the water absorption W, W=(M 吸水后 -M 吸水前 ) / M 吸水前 .

[0079] Wear resistance test: Use a friction tester to cut the prepared inkjet ink cured film into 250mm×500mm samples, use standard coated paper to rub the sample back and forth 100 times, wipe off the floating debris, weigh it, and the difference in mass before and after grinding is the film weight loss. The friction pressure is 20N and the friction speed is 3cpm.

[0080] Adhesion performance test: refer to GB / T 9296-88 tape method for testing, stick the tape on the ink layer, press it tightly, and tear it off. If the film layer does not fall off, it is considered qualified. If the ink layer is attached to the tape and torn off together, it is considered unqualified. The test temperature is 25℃ and the humidity is 50%.

[0081] Weather resistance test: Tested in accordance with ASTMG-151 standard.

[0082] Table 2 Ink performance test

[0083]

[0084]

[0085] It can be seen from the test results in the above table that the UV inkjet ink prepared by the present invention has excellent tensile strength, water resistance, wear resistance, adhesion and weather resistance, meets the industry requirements of ink, and is suitable for inkjet printing; this is because on the one hand, the carbon-fluorine bond has a large bond energy, and the fluorine atoms are closely arranged around the carbon-carbon main chain, which plays a role in protecting the main chain and has good heat resistance and solvent resistance; the flexibility of siloxane gives the material good shear resistance and wear resistance, so that it can maintain a low wear rate and stable friction performance when subjected to high load and high-speed friction; on the other hand, the UV-curable resin prepolymer in the ink uses polyurethane as a skeleton material and hydroxyethyl acrylate as a capping material, and simultaneously initiates polymerization with a fluorinated alkenyl zwitterionic monomer to form a network structure similar to a semi-interpenetrating polymer, which not only retains the excellent properties of polyurethane and polyacrylate, but also gives play to the characteristics of organic silicon and organic fluorine in the functional monomer, so that they are organically complementary, and the mechanical properties, yellowing and weather resistance of the ink cured film are improved.

[0086] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a low refractive index and high transmittance UV inkjet ink, characterized in that: The preparation method is carried out according to the following steps: Step (1), under a nitrogen atmosphere, adding 100 parts by weight of toluene diisocyanate and 40-60 parts of polytetramethylene glycol to a reaction flask, stirring evenly, adding 0.2-0.5 parts of stannous octoate and 0.03-0.08 parts of a polymerization inhibitor, stirring at 75-90° C. for 1-3 hours, cooling to 50-65° C., adding 20-35 parts of N-methyldiethanolamine and 5-10 parts of 1,4-butanediol, reacting for 0.5-2 hours, adding 8-15 parts of hydroxyethyl acrylate for photosensitive active end-capping, and reacting at 60-75° C. for 0.5 hours to obtain a UV-curable resin prepolymer; Step (2), 20-40 parts by weight of UV curable resin prepolymer, 10-30 parts by weight of the structural formula The fluorinated olefin zwitterionic monomer and 5-8 parts of photoinitiator are added to a high-speed mixer, stirred and dissolved at 40-60°C, and sent to a grinder for cyclic grinding for 2-4 hours. Then, 12-20 parts of pigment paste, 5-10 parts of moisturizer and 2-4 parts of defoamer are added, dispersed evenly and centrifuged, dispersed at high speed to a particle size of 1-2um, filtered and packaged to obtain a low refractive index and high transmittance UV inkjet ink.

2. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 1, characterized in that: The polymerization inhibitor in step (1) is any one of o-methyl hydroquinone, phenothiazine or p-tert-butyl catechol.

3. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 1, characterized in that: In the step (2), the moisturizing agent is any one of glycerol, PEG glyceryl ether or diethylene glycol ethyl ether.

4. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 1, characterized in that: The preparation method of the fluorinated alkenyl zwitterionic monomer in step (2) is carried out according to the following steps: Step S1, under a nitrogen atmosphere, adding methylvinyldichlorosilane and toluene to a reaction flask, stirring evenly, adding 3-hydroxy-5-(trifluoromethyl)benzoic acid and sodium hydride, stirring for reaction, filtering after the reaction, distilling under reduced pressure, recrystallizing with a mixed solvent of toluene and petroleum ether in a volume ratio of 1:1, and drying to obtain a fluorinated alkenylsiloxane carboxylic acid monomer; Step S2, under a nitrogen atmosphere, add a fluorinated alkenylsiloxane carboxylic acid monomer, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 4-dimethylaminopyridine and dichloromethane to a reaction flask, stir evenly, add N,N-dimethylethylenediamine, react at 20-35° C. for 12-24 h, concentrate under reduced pressure, and separate by column chromatography to obtain a fluorinated alkenylsiloxane tertiary amine monomer; Step S3, under a nitrogen atmosphere, add a fluorinated alkenyl siloxane tertiary amine monomer and N,N-dimethylformamide to a reaction flask, stir evenly, add sodium 2-bromoethane sulfonate, stir to react, filter after the reaction is completed, wash with acetonitrile, and dry to obtain a fluorinated alkenyl zwitterionic monomer.

5. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 4, characterized in that: In the step S1, the ratio of methylvinyldichlorosilane, 3-hydroxy-5-(trifluoromethyl)benzoic acid and sodium hydride is 1 mol: (2.05-2.2) mol: (2.3-2.5) mol.

6. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 4, characterized in that: In step S1, the reaction temperature is 70-90° C. and the reaction time is 8-16 hours.

7. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 4, characterized in that: In the step S2, the ratio of the fluorinated alkenyl siloxane carboxylic acid monomer, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 4-dimethylaminopyridine, and N,N-dimethylethylenediamine is 1 mol: (1.2-1.5) mol: (0.2-0.4) mol: (2.1-2.35) mol.

8. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 4, characterized in that: In the step S3, the ratio of the fluorinated alkenylsiloxane tertiary amine monomer to sodium 2-bromoethane sulfonate is 1 mol:(2.3-2.8) mol.

9. The method for preparing the low refractive index and high transmittance UV inkjet ink according to claim 4, characterized in that: In step S3, the reaction temperature is 110-135° C. and the reaction time is 24-48 hours.

10. A low refractive index and high transmittance UV inkjet ink, characterized in that: Obtained by the preparation method according to any one of claims 1 to 9.

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