Formula and preparation method of UV glue with high refractive index

Abstract

The invention discloses a formula of high-refractive-index UV glue, which comprises the following components: a monofunctional acrylic monomer, a bifunctional acrylic monomer, an acrylic monomer of which the functionality is greater than or equal to three, and a modified nano titanium dioxide dispersion liquid, and discloses a method for preparing the high-refractive-index UV glue by using the formula. Mixing a monofunctional acrylic monomer, a bifunctional acrylic monomer and an acrylic monomer with the functionality greater than or equal to three, uniformly stirring to obtain a resin precursor, adding the modified nano titanium dioxide dispersion liquid into the resin precursor, and uniformly stirring to obtain the high-refractive-index UV glue. The solvent-free high-refractive-index UV glue is prepared by providing a proper formula, preparing a modified nano titanium dioxide dispersion liquid with smaller particle size under high-temperature and high-pressure conditions, providing an adjustable UV glue formula and adjusting the dosage of each monomer, and has the advantages of high refractive index, high transparency, proper flowability and proper viscosity.

Description

Technical Field

[0001] The present invention relates to the field of composite polymer materials and the field of polymer material adhesives, and particularly to a formulation and preparation method of a high refractive index UV adhesive. Background Art

[0002] UV adhesives are irradiated by high-intensity ultraviolet light (300nm to 400nm), generating active free radicals or ionic groups, thereby initiating polymerization, cross-linking and grafting reactions, causing the adhesive to transform from a liquid to a solid state within seconds, thus achieving the bonding effect; UV adhesives have the characteristics of being safe and low-toxic, having good compatibility with materials, good adhesion, easy adjustment of the adhesion effect, low use cost, and convenience, and are widely used in various industries.

[0003] For a type of UV adhesives applied to related electronic fields such as displays and touchscreens, it is required to have good adhesion, transparency, and good refractive index to improve the ability of the adhesive to capture ultraviolet light, thereby enhancing its curing ability and adhesion, and the high refractive index can improve optical transparency, making the coating or bonding layer formed on the surface of the cured object by the adhesive have a refractive index closer to that of air.

[0004] Currently, the refractive index of general UV adhesives is between 1.5 and 1.7, and the transparency is between 90% and 95%. However, with the continuous improvement of the requirements for high refractive index, high-definition display, and high-fidelity display in industries such as chip manufacturing and screens, the requirements for the refractive index and transparency of UV adhesives are further increased. The higher the refractive index of UV adhesives, the corresponding increase in the cost of their raw materials and preparation processes. There are certain limitations in the high refractive index monomers, formulations, and preparation methods of existing technologies for UV adhesives.

[0005] Currently, high refractive index UV adhesives are usually prepared by selecting monomers with high refractive index and adding 50% to 70% of nano-titanium dioxide. This type of method has relatively high requirements for the refractive index of the monomer resin itself. Usually, monomer resins with a refractive index of ≥1.60 or above need to be selected, which limits the selection of monomer resins. The refractive index of the prepared UV adhesives is generally ≤1.80, unable to meet high optical requirements; in addition, some technologies use directly purchased well-dispersed modified nano-titanium dioxide dispersion liquids and increase the addition amount of nano-titanium dioxide to increase the refractive index. This type of method is prone to problems where the compatibility between the resin and the modified nano-titanium dioxide dispersion liquid is uncontrollable, and it is difficult to form, adjust, and improve the optimal matching effect between the resin and the modified nano-titanium dioxide. Therefore, it is difficult to form the matching and control of the overall technical process from raw materials to the preparation of the adhesive, and the stability of the preparation process and the produced UV adhesive finished products is not good.

[0006] Patent CN116535980A discloses a high refractive index ultraviolet curable glue and its preparation method. On the one hand, the modified titanium oxide nanoparticles used in this patent are "the particle size of the modified titanium oxide nanoparticles is not more than 50 nm; preferably, the modified titanium oxide nanoparticles can be obtained from the modified titanium oxide nanoparticle dispersion liquid, and the modified titanium oxide nanoparticle dispersion liquid can adopt the OT-RA205K7 model of Nissan Chemical Industries, Ltd. (the content of modified titanium oxide nanoparticles is 20%)", that is, it can be directly purchased, and what is purchased is the modified titanium oxide nanoparticle dispersion liquid. The purchased dispersion liquid contains organic solvents with more unknown components. During application, although strict screening is carried out on the monofunctional monomer and polyfunctional monomer, the patent does not disclose the organic solvent components contained in the modified titanium oxide nanoparticle dispersion liquid and the process of removing the organic solvent. This unknown organic solvent will cause problems such as uncontrollable compatibility, resulting in uncontrollable effective crosslinking and bonding between the modified titanium oxide nanoparticles and the resin. After preparing the UV glue, it is difficult to control its fluidity, refractive index and transparency; on the other hand, this patent mainly improves the proportion of the monofunctional monomer resin and reduces the proportion of the polyfunctional monomer resin, thereby increasing the proportion of the modified titanium oxide nanoparticles, and it can achieve a high refractive index UV glue with low viscosity and good fluidity. However, the UV glue prepared by this method has a problem of too low viscosity of the UV glue due to the presence of more monofunctional monomer resins with low crosslinking degree. When spin-coating to form a film, the problem of incomplete surface drying is very likely to occur, resulting in the problem that additional treatment methods are required during application. If a surface drying initiator is added, the transparency will be further reduced, and at the same time, the problem of glue shrinkage is likely to occur.

[0007] Patent CN116478493A discloses a high refractive index resin and its preparation method, a UV glue and its preparation method, and a film. A high refractive index resin is prepared by using a titanium alkoxide (specifically, tetraisopropyl titanate or tetrabutyl titanate or tetraethyl titanate) and an acid containing a terminal double bond (specifically, β-(acryloyloxy)propionic acid or 3-butenoic acid). Then, a high refractive index and high transparency UV glue is prepared by using the high refractive index resin, acrylic monomers, organic solvents, photoinitiators, and additives (leveling agents, defoaming agents). Although this patent discloses the preparation process of the UV glue, the process of preparing the high refractive index resin is only to mix and stir the titanium alkoxide and the acid containing a terminal double bond, and remove the solvent under reduced pressure. Moreover, the process of preparing the UV glue is also only to mix and stir each component in proportion. On the one hand, the acquisition or preparation process of the titanium alkoxide is not disclosed, and the process of preparing the high refractive index resin is too simple. There are problems such as the uncontrollable compatibility between the unknown components contained in the titanium alkoxide and the acrylic monomer resin when preparing the UV glue. On the other hand, after being verified by those skilled in the art, according to the simple mixing and stirring method of this preparation process, a UV glue with high refractive index and high transparency as disclosed cannot be obtained. That is to say, this patent does not fully disclose the preparation processes of the high refractive index resin and the UV glue, and the disclosed content is too simple, resulting in the problem of not being able to obtain an effective product.

[0008] Patent CN117447921A discloses a high refractive index optical organic glue composition and its preparation method. A high refractive index organic glue is prepared by using high refractive index monomers, strength enhancing monomers (specifically, 1,6 - hexanediol diacrylate), interface enhancing monomers (2,2,2 - trifluoroethyl acrylate), a first high refractive index inorganic nano - filler (specifically, zirconium - doped titanium oxide nanoparticles), a second high refractive index inorganic nano - filler (specifically, zirconia nanoparticles coated with silane coupling agent), light - stable additives, photoinitiators, and antioxidants. Although this patent can form an organic glue with a relatively high refractive index, it mainly improves the refractive index by introducing zirconium particles and preparing zirconium - doped titanium oxide nanoparticles, and improves the interfacial adhesion and reduces interfacial scattering by coating silane coupling agent on zirconia nanoparticles to improve the refractive index. It can be seen that it introduces other particles besides resin and titanium dioxide to assist in improving the refractive index, does not make a substantial improvement in the particle size and dispersibility of titanium dioxide itself, and has complex materials and a complex preparation process, resulting in too many uncontrollable factors, a high cost of forming the product, and a greater negative impact on the environment.

[0009] Based on the above background, there is a need to provide a UV glue with higher refractive index and transparency, and a preparation method for forming this glue. Summary of the Invention

[0010] The main purpose of the present invention is to improve the problems in the current formulation used in the preparation of high refractive index UV adhesives, where the modified nano-titanium dioxide particles contain more uncontrollable solvent components, have a low cross-linking and matching degree with the monomer resin, a high uncontrollable compatibility, and a complex preparation process. First, a formulation of a solvent-free high refractive index UV adhesive is provided, and the formulation comprises the following components in parts by weight:

[0011] Mono-functional acrylic monomer: 4 parts to 6 parts;

[0012] Di-functional acrylic monomer: 0 parts to 3 parts;

[0013] Acrylic monomer with a functionality of greater than or equal to three: 3 parts to 6 parts;

[0014] Modified nano-titanium dioxide dispersion: 40 parts to 400 parts.

[0015] Furthermore, the formulation of the modified nano-titanium dioxide dispersion comprises the following components in parts by weight:

[0016] Tetrabutyl titanate: 10 parts to 100 parts;

[0017] Oleic acid: 100 parts to 500 parts;

[0018] Hexadecyltrimethoxysilane: 1 part to 20 parts;

[0019] Dispersant: 1 part to 10 parts;

[0020] Absolute ethanol: 50 parts to 500 parts;

[0021] Ethyl acetate: 5 parts to 20 parts.

[0022] Furthermore, the formulation further comprises the following components in parts by weight:

[0023] Polymerization inhibitor: 0.02 parts to 0.06 parts;

[0024] Defoamer: 0.02 parts to 1 part;

[0025] Leveling agent: 0.2 parts to 1 part;

[0026] Photoinitiator: 0.1 parts to 0.8 parts.

[0027] Optionally, the refractive index of the mono-functional acrylic monomer is ≥ 1.45.

[0028] Optionally, the refractive index of the di-functional acrylic monomer is ≥ 1.45.

[0029] Optionally, the particle size of the modified nano-titanium dioxide dispersion is 8 nm to 50 nm.

[0030] Secondly, a preparation method of a high refractive index UV glue is also provided. Using the above formula, it is prepared according to the following steps:

[0031] S10: Prepare the modified nano-titanium dioxide dispersion:

[0032] S110: Add the tetrabutyl titanate to the oleic acid and disperse it at room temperature to obtain a titanate precursor;

[0033] S120: Transfer the titanate precursor to a high-temperature and high-pressure reactor for reaction, then naturally cool it, add the cetyltrimethoxysilane, continue the reaction, then cool it to room temperature, centrifuge and wash it with anhydrous ethanol, and then dry it to obtain modified titanium dioxide powder;

[0034] S130: Add the dispersant to the ethyl acetate solvent, disperse it and then add the modified titanium dioxide powder, and stir to prepare the modified nano-titanium dioxide dispersion;

[0035] S20: Prepare the high refractive index UV glue:

[0036] S210: Mix the monofunctional acrylic monomer, difunctional acrylic monomer and acrylic monomer with a functionality of greater than or equal to three, and stir evenly to obtain a resin precursor;

[0037] S220: Add the modified nano-titanium dioxide dispersion to the resin precursor and stir evenly to obtain a high refractive index UV glue.

[0038] Optionally, obtaining the resin precursor further includes: mixing the monofunctional acrylic monomer, difunctional acrylic monomer and acrylic monomer with a functionality of greater than or equal to three, stirring evenly, and then adding the inhibitor and further stirring evenly to obtain the resin precursor.

[0039] Optionally, obtaining the high refractive index UV glue further includes: adding the modified nano-titanium dioxide dispersion to the resin precursor, stirring evenly, and then sequentially adding the defoaming agent, the leveling agent, and the photoinitiator under stirring conditions, and further stirring to obtain a preliminary high refractive index UV glue, and performing a low-temperature evaporation treatment on the preliminary high refractive index UV glue, and at the same time adding a monofunctional acrylic monomer until the measured solid content reaches 99% to 100% to obtain the high refractive index UV glue.

[0040] Optionally, the high refractive index UV glue satisfies at least one of the following conditions:

[0041] (A) Refractive index ≥ 1.88;

[0042] (B) Cross-cut test is grade 0;

[0043] (C) Transparency ≥ 99%.

[0044] The technical solution of the present invention provides a formulation for a high refractive index UV glue. For the formulation of the modified nano-titanium dioxide dispersion, a formulation with clear components is provided independently. Through this formulation, titanium dioxide is modified, and by using a reaction under necessary high temperature and high pressure conditions, the crystal structure of titanium dioxide can be changed to make it more stable. And by using methods such as release cleaning treatment and constant temperature fixed stirring, a dispersion containing modified titanium dioxide with smaller particle size is prepared, providing a prerequisite for subsequent mixing with resin to form a UV glue with more controllable compatibility and more excellent stability. An organic solvent that can provide good dissolution and other auxiliary effects during the preparation process and is easy to evaporate at low temperature after preparation is used, so that the organic solvent in the subsequent formed UV glue volatilizes fully, avoiding the influence of the organic solvent on the properties such as the viscosity and fluidity of the UV glue.

[0045] For the formulation of the high refractive index UV glue, by adjusting the ratio of three resins: monofunctional acrylic monomer, difunctional acrylic monomer, and acrylic monomer with trifunctional or more, and using difunctional acrylic monomer to replace part of the amount of acrylic monomer with trifunctional or more, the comprehensive properties of the fluidity, viscosity, and surface dry performance after spin coating of the glue can be effectively controlled and balanced.

[0046] The preparation method provided by the present invention uses a proportion of acrylic monomer with trifunctional or more ≥ 40% and an appropriate amount of difunctional acrylic monomer, which can not only make the glue have a lower viscosity and better fluidity, but also be completely surface dry after spin coating during drying, eliminating the phenomena of shrinkage glue and bubbles; when preparing the UV glue, all components used in the preparation process are clear, and no unknown components or other auxiliary components are added, making the preparation process complete and sufficient, effectively reducing the uncontrollable influence of unknown components or complex components on the preparation process; and through the low-temperature evaporation treatment technology, the residual solvent inside the prepared UV glue is removed, improving the selection range of the fluidity and thickness of the glue, which can meet the spin coating thickness requirements from 10 nm to 10 μm, thus meeting the application in a wider field. Description of the Drawings

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0048] Figure 1 It is a process flow chart of the preparation method for the embodiments of the present invention

[0049] Figure 2 These are the appearance diagrams of samples of three different modified nano-titanium dioxide dispersions after standing for 15 days;

[0050] Figure 3 This is the particle size test diagram of a general ordinary modified nano-titanium dioxide dispersion;

[0051] Figure 4 This is the particle size test diagram of the modified nano-titanium dioxide dispersion purchased from Nissan Chemical Industries, Ltd.;

[0052] Figure 5 This is the particle size test diagram of the modified nano-titanium dioxide dispersion prepared by the implementation mode of the present invention;

[0053] Figure 6 These are the appearance diagrams of the high refractive index UV glue samples prepared by using Example 2 (left) and Example 3 (right) of the implementation mode of the present invention. Specific implementation mode

[0054] Next, in combination with the accompanying drawings in the implementation mode of the present invention, the technical solutions in the implementation mode of the present invention will be clearly and completely described. Obviously, the described implementation mode is only a part of the implementation modes of the present invention, rather than all the implementation modes. Based on the implementation modes in the present invention, all other implementation modes obtained by those of ordinary skill in the art without making creative efforts belong to the scope protected by the present invention.

[0055] In the present invention, descriptions such as "first", "second", etc. are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first", "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0056] Please refer to Figure 1 , Figure 1 This is the process flow chart of the preparation method of the implementation mode of the present invention.

[0057] The implementation mode of the present invention first provides a formulation of a high refractive index UV glue, which includes the following components in parts by weight:

[0058] Monofunctional acrylic monomer: 4 parts to 6 parts; optionally one or a mixture of two or more of 2-phenoxyethyl acrylate, 4-tert-butylcyclohexyl acrylate TBCHA, phenoxybenzyl acrylate, o-phenoxyphenethyl acrylate, dicyclopentenyl acrylate.

[0059] In the process of preparing the UV glue, the monofunctional acrylic monomer of this embodiment forms a relatively low crosslinking degree, which can play a role in reducing the viscosity of the UV glue and improving the fluidity of the UV glue; in this embodiment, the refractive index of the monofunctional acrylic monomer ≥ 1.45; in this embodiment, there is no need to specifically select a monofunctional acrylic monomer with a high refractive index, and a resin with a normal refractive index can be selected, and the refractive index requirement for the monomer resin itself is generally average.

[0060] Bifunctional acrylic monomer: 0 parts to 3 parts; optionally one or a mixture of two or more of tripropylene glycol diacrylate TPGDA, hexanediol diacrylate, dipropylene glycol diacrylate, 9,9-bis(4-(2-acryloyloxyphenyl)fluorene) diacrylate.

[0061] The bifunctional acrylic monomer of this embodiment replaces a part of the relative amount of acrylic monomers with trifunctionality or higher. In the process of forming the UV glue, its crosslinking degree is between that of the monofunctional acrylic monomer and the acrylic monomer with trifunctionality or higher, and it has a good effect of regulating the viscosity and fluidity of the UV glue; in this embodiment, the refractive index of the bifunctional acrylic monomer ≥ 1.45; similarly, the refractive index requirement for the bifunctional acrylic monomer itself is also average.

[0062] Acrylic monomers with trifunctionality or higher: 3 parts to 6 parts; optionally one or a mixture of two or more of trimethylolpropane triacrylate TMPTA, ethoxylated trimethylolpropane triacrylate, bis-pentaerythritol hexaacrylate DPHA, pentaerythritol acrylate.

[0063] In the process of preparing and forming the UV glue, the acrylic monomer with trifunctionality or higher in this embodiment has a greater crosslinking degree and a faster curing rate, resulting in a greater viscosity. Therefore, it has the effect of improving the fluidity of the UV glue.

[0064] Modified nano-titanium dioxide dispersion: 40 parts to 400 parts; optionally the mass fraction of modified nano-titanium dioxide is 10% to 30%.

[0065] In the embodiment of the present invention, by using acrylic monomers with different functionalities (i.e., monomer resins with different functionalities) and precisely controlling the dosage of each monomer, a comprehensive performance of effectively regulating the fluidity, viscosity, and surface drying performance after spin-coating of the UV glue is formed.

[0066] In this embodiment, the formulation of the modified nano-titanium dioxide dispersion contains the following components in parts by weight:

[0067] Tetrabutyl titanate: 10 parts to 100 parts;

[0068] Oleic acid: 100 parts to 500 parts;

[0069] Hexadecyltrimethoxysilane: 1 part to 20 parts;

[0070] Dispersant: 1 part to 10 parts, optionally one or a mixture of two or more of BYK-130, BYK-140, BYK-161 or BYK-163;

[0071] Absolute ethanol: 50 parts to 500 parts;

[0072] Ethyl acetate: 5 parts to 20 parts.

[0073] The formulation of the modified nano-titanium dioxide dispersion in this embodiment adopts a self-provided formulation with clear components, and uses an organic solvent that can provide good dissolution and other auxiliary effects during the preparation process and is easy to evaporate at low temperature after preparation, so as to fully volatilize the organic solvent after the subsequent preparation of the UV glue.

[0074] In this embodiment, the formulation further comprises the following components in parts by weight:

[0075] Polymerization inhibitor: 0.02 part to 0.06 part; optionally one or a mixture of two or more of p-methoxyphenol, hydroquinone methyl ether, catechol.

[0076] Leveling agent: 0.02 part to 1 part; optionally one or a mixture of two or more of BYK-301, BYK-302, BYK-332, BYK-348.

[0077] Light stabilizer: 0.2 part to 1 part; optionally one or two mixtures of bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1-(methyl)-8-(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate).

[0078] Photoinitiator: 0.1 part to 0.8 part; optionally one or a mixture of two or more of methyl o-benzoylbenzoate, methyl benzoylformate, 1-hydroxycyclohexyl phenyl ketone, dialkoxyacetophenone.

[0079] This embodiment of the present invention also provides a method for preparing a high refractive index UV glue, using the above formulation and preparing according to the following steps:

[0080] Please refer to Figures 2 to 5 ; Figure 2 It is the appearance diagram of the samples of three different modified nano-titanium dioxide dispersions after standing for 15 days; Figure 3 It is the particle size test diagram of a general ordinary modified nano-titanium dioxide dispersion; Figure 4 It is the particle size test diagram of the modified nano-titanium dioxide dispersion purchased from Nissan Chemical Industries, Ltd.; Figure 5It is a particle size test chart of the modified nano-titanium dioxide dispersion liquid prepared by the embodiment of the present invention.

[0081] First, step S10 is to prepare a modified nano-titanium dioxide dispersion liquid:

[0082] Step S110:

[0083] Take 50 g of tetrabutyl titanate and add it to 250 g of oleic acid. Stir at a speed of 1000 r / min for 2 hours at room temperature using a dispersion disk to obtain a titanate precursor.

[0084] Step S120:

[0085] Transfer the titanate precursor to a high-temperature and high-pressure reactor, react at 250 °C and 8 MPa for 12 hours; then naturally cool to 100 °C, add 10 g of cetyltrimethoxysilane, continue to react for 2 hours, then cool to room temperature, use absolute ethanol as a solvent, centrifugally wash 5 times, and then dry at 40 °C for 12 h to obtain modified titanium dioxide powder.

[0086] Step S130:

[0087] Take 2 g of dispersant and add it to 160 g of ethyl acetate solvent. After dispersing evenly, add 40 g of modified titanium dioxide powder, and stir at a speed of 500 r / min in a water bath at 50 °C for 1 hour to prepare a modified nano-titanium dioxide dispersion liquid with a mass fraction of 20% of modified nano-titanium dioxide.

[0088] In this embodiment, the particle size of the modified nano-titanium dioxide dispersion liquid is 8 nm to 50 nm; the particle size of the modified nano-titanium dioxide dispersion liquid prepared by the above method is smaller and more uniform after testing compared with that of other modified nano-titanium dioxide dispersion liquids, and the average particle size of the modified titanium dioxide particles in the dispersion liquid can reach ≤20 nm.

[0089] This embodiment can change the structure of the titanium dioxide crystal to make it more stable by using the reaction under necessary high-temperature and high-pressure conditions, and prepares a dispersion liquid containing modified titanium dioxide with smaller particle size and more controllable compatibility by using methods such as release cleaning treatment and constant-temperature fixed stirring.

[0090] Please continue to refer to Figure 2 , it can be seen that the modified nano-titanium dioxide dispersion prepared by the embodiment of the present invention (the sample on the right in the figure) is in a clear semi-transparent state as a whole. After standing for 15 days, the system is still in a clear semi-transparent state without precipitation, indicating that the particle size is small and uniform and the dispersibility is good.

[0091] For a general ordinary modified nano-titanium dioxide dispersion (the sample on the left in the figure), the overall sample is in an opaque milky white state. After standing for 15 days, the system remains in an opaque milky white state, and there are obvious precipitates, indicating that the particle size is large and uneven, and the dispersibility is poor; for the modified nano-titanium dioxide dispersion purchased from Nissan Chemical Industries, Ltd. (the sample in the middle in the figure), the overall sample is in a clear and slightly transparent state. After standing for 15 days, the system is in a slightly translucent state, and there are fewer precipitates, indicating that the particle size is small, there is unevenness, and the dispersibility is good.

[0092] Please continue to refer to Figures 3 to 5 ; Figure 3 is the particle size test chart of the general ordinary modified nano-titanium dioxide dispersion; Figure 4 is the particle size test chart of the modified nano-titanium dioxide dispersion purchased from Nissan Chemical Industries, Ltd.; Figure 5 is the particle size test chart of the modified nano-titanium dioxide dispersion prepared by the embodiment of the present invention.

[0093] By respectively testing the particle sizes of the modified nano-titanium dioxide contained in the three modified nano-titanium dioxide dispersions, it can be seen that Figure 5 the particle size of the modified nano-titanium dioxide contained in the modified nano-titanium dioxide dispersion prepared in this embodiment is distributed around 10 nm, the particle size is small and uniform, Figure 3 the particle size distribution is around 60 nm, and the particle size is relatively large, Figure 4 the particle size distribution is around 50 nm, and the particle size is relatively large.

[0094] Subsequently, step S20 is to prepare a high refractive index UV glue:

[0095] Step S210:

[0096] Mix a monofunctional acrylic monomer, a bifunctional acrylic monomer, and an acrylic monomer with a functionality of greater than or equal to trifunctional, stir evenly, and then add an inhibitor and stir further evenly to obtain a resin precursor.

[0097] Step S220:

[0098] Add the modified nano-titanium dioxide dispersion to the resin precursor, stir evenly, and then sequentially add an antifoaming agent, a leveling agent, and a photoinitiator under stirring conditions, and stir further to obtain a preliminary high refractive index UV glue. Perform low-temperature evaporation treatment on the preliminary high refractive index UV glue, and at the same time add a monofunctional acrylic monomer until the measured solid content reaches 99% to 100% to obtain a high refractive index UV glue.

[0099] The key indicators of the high refractive index UV glue prepared through the above process are:

[0100] (A)Refractive index ≥ 1.88; (B) Crosshatch test is grade 0; (C) Transparency ≥ 99%.

[0101] To further illustrate the effects of the embodiments of the present invention on the film thickness, refractive index, transparency, and adhesion of the UV glue, experiments and tests were carried out according to the component ratios of Examples 1 to 3 and Comparative Examples 1 to 5 in Table 1 respectively (wherein: the monomer resins with different functionalities and the modified nano-titanium dioxide dispersion liquid in the formula are the main agents, and the remaining components are auxiliaries).

[0102] Table 1:

[0103]

[0104] Example 1:

[0105] Step S210:

[0106] Take a monofunctional acrylic monomer, a bifunctional acrylic monomer, and an acrylic monomer with a functionality of greater than or equal to trifunctional, add them to a beaker and mix. Use a magnetic stirrer to stir at a speed of 500 r / min at room temperature for 30 min, then add an inhibitor and stir for another 10 min to obtain a resin precursor.

[0107] Step S220:

[0108] Add the modified nano-titanium dioxide dispersion liquid to the resin precursor, stir at a speed of 700 r / min at room temperature for 60 min, then sequentially add an antifoaming agent, a leveling agent, and a photoinitiator under stirring conditions, and continue to stir at a speed of 700 r / min for 60 min to obtain a preliminary high-refractive-index UV glue. Use a rotary evaporator to rotary evaporate the preliminary high-refractive-index UV glue at 60 °C for 40 min to 60 min. When the solid content is tested to be between 97% and 98%, continue to add a monofunctional monomer resin accounting for 1% to 2% of the total mass ratio, and continue to rotary evaporate for 5 min to 10 min until the solid content is 99% to 100% to obtain a solvent-free high-refractive-index UV glue.

[0109] Example 2:

[0110] Use the respective component ratios corresponding to Example 2 in Table 1 and prepare according to the same preparation method as Example 1.

[0111] Example 3:

[0112] Use the respective component ratios corresponding to Example 3 in Table 1 and prepare according to the same preparation method as Example 1.

[0113] Comparative Example 1:

[0114] Prepare according to the respective component ratios corresponding to Comparative Example 1 in Table 1 using the same preparation method as in Example 1.

[0115] Comparative Example 2:

[0116] Prepare according to the respective component ratios corresponding to Comparative Example 2 in Table 1 using the same preparation method as in Example 1.

[0117] Comparative Example 3:

[0118] Prepare according to the respective component ratios corresponding to Comparative Example 3 in Table 1 using the same preparation method as in Example 1.

[0119] Comparative Example 4:

[0120] Prepare according to the respective component ratios corresponding to Comparative Example 4 in Table 1 using the same preparation method as in Example 1.

[0121] Comparative Example 5:

[0122] Prepare according to the respective component ratios corresponding to Comparative Example 5 in Table 1 using the same preparation method as in Example 1.

[0123] Perform performance verification tests on the UV glues respectively prepared according to the respective component ratios of Examples 1 to 3 and Comparative Examples 1 to 5.

[0124] Test method:

[0125] Drop the UV glues prepared in Examples 1 to 3 and Comparative Examples 1 to 5 respectively on silicon wafers, spin-coat them on a spin coater at a speed of 1000 rpm, and then irradiate them with a UV lamp for 1 minute to obtain a high refractive index surface coating after curing.

[0126] Measure the thickness, refractive index, transparency, and adhesion of the coatings; the test results are shown in Table 2.

[0127] Table 2:

[0128]

[0129] It can be seen from the test data of Examples 1 to 3 that among them, the addition ratio of the modified nano-titanium dioxide in Example 1 to the main agent is relatively small, less than 80%, but its refractive index is already > 1.8 and the transparency is > 99%; the addition ratios of the modified nano-titanium dioxide in Examples 2 and 3 to the main agent are both > 80%, and their refractive indices have increased significantly, reaching ≥ 1.88, and even ≥ 1.9.

[0130] This phenomenon indicates that the modified nano-titanium dioxide dispersion prepared by this embodiment has a relatively small average particle size, about ≤20 nm, and good dispersion uniformity. Compared with the addition amount of 50% to 70% in the prior art, when the addition amount of the modified nano-titanium dioxide in this embodiment is ≥80%, it is still possible to prepare a high refractive index UV glue with a refractive index ≥1.88 and a transparency ≥99%.

[0131] It can be seen from Example 3 that as the addition ratio of the modified nano-titanium dioxide dispersion continues to increase, although the refractive index will continue to increase, the transparency will show a relatively obvious decrease. This shows that under the particle size conditions and dispersion uniformity conditions of the modified nano-titanium dioxide in this embodiment, and under the content ratio conditions of the monomer resin, the optimal addition amount of the modified nano-titanium dioxide in the main agent is about 80%; for the modified nano-titanium dioxide dispersion, the smaller the particle size of the modified nano-titanium dioxide and the better the dispersion uniformity, the relatively larger the addition ratio can be, and the better the refractive index and transparency. The particle size of the modified nano-titanium dioxide dispersion in this embodiment has reached an optimal level.

[0132] Please refer to Figure 6 ; Figure 6 It is a diagram of the appearance of the high refractive index UV glue samples prepared by Example 2 (left) and Example 3 (right) adopting the embodiment of the present invention.

[0133] It can be seen that the appearance of the high refractive index UV glue samples prepared by Example 2 (left) and Example 3 (right) is uniform, clear and transparent, indicating that the modified nano-titanium dioxide dispersion in this embodiment has good dispersion in the colloid and good cross-linking and binding states with other components.

[0134] It can be seen from the test data of Comparative Example 1 to Comparative Example 5 that by adjusting the ratio of the monofunctional acrylic monomer, the bifunctional acrylic monomer, and the acrylic monomer with a functionality of greater than or equal to three, when the ratio of the monofunctional acrylic monomer is ≥60%, the surface drying of the spin-coated UV glue is incomplete during the drying process. When the ratio of the monofunctional acrylic monomer to the acrylic monomer with a functionality of greater than or equal to three is 1:1, the viscosity of the glue is relatively large, and problems such as glue shrinkage and uneven coating are likely to occur during spin coating; when 10% of the bifunctional acrylic monomer is used to replace the acrylic monomer with a functionality of greater than or equal to three, the fluidity is better and the viscosity decreases significantly.

[0135] This shows that by preparing a modified nano-titanium dioxide dispersion with a low particle size (particle size ≤20 nm) and adding a certain amount of bifunctional acrylic monomer, a high refractive index UV glue can be prepared, and its transparency and fluidity can be improved.

[0136] For some high-refractive-index UV glue coatings that require a coating thickness reaching the micron level, solvent-based high-refractive-index UV glue is difficult to meet the requirements; in this embodiment, after evaporating the excess solvent, a solvent-free high-refractive-index UV glue with a solid content of 99% to 100% is formed, which is suitable for making high-refractive-index coatings with different thicknesses.

[0137] Furthermore, the embodiment of the present invention can inversely adjust the dosages of monofunctional acrylic monomers, difunctional acrylic monomers, and acrylic acids with a functionality of greater than or equal to three, as well as adjust the final solid content according to the required film thickness of the UV glue, so as to form a formulation and preparation process with flexible controllability.

[0138] The above is only the preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A formula of high refractive index UV glue, characterized by: The formulation comprises the following components in parts by weight: Monofunctional acrylic monomer: 4 to 6 parts; Difunctional acrylic monomer: 0 to 3 parts; Acrylic acid monomer with trifunctionality or above: 3 to 6 parts; Modified nano titanium dioxide dispersion: 40 to 400 parts.

2. The formula of a high refractive index UV glue according to claim 1, characterized in that: The formula of the modified nano titanium dioxide dispersion comprises the following components in parts by weight: Tetrabutyl titanate: 10 to 100 parts; Oleic acid: 100 to 500 parts; Hexadecyltrimethoxysilane: 1 to 20 parts; Dispersant: 1 to 10 parts; Anhydrous ethanol: 50 to 500 parts; Ethyl acetate: 5 parts 20 parts.

3. A formula of a high refractive index UV glue according to claim 1 or 2, characterized in that: The formulation also comprises the following components in parts by weight: Inhibitor: 0.02 to 0.06 parts; Defoaming agent: 0.02 to 1 part; Leveling agent: 0.2 to 1 part; Photoinitiator: 0.1 to 0.8 parts.

4. The formula of a high refractive index UV glue according to claim 1, characterized in that: The refractive index of the monofunctional acrylic monomer is ≥1.

45.

5. The formula of a high refractive index UV glue according to claim 1, characterized in that: The refractive index of the bifunctional acrylic monomer is ≥1.

45.

6. A formula of a high refractive index UV glue according to claim 1 or 2, characterized in that: The particle size of the modified nano titanium dioxide dispersion is 8nm to 50nm.

7. A method for preparing high refractive index UV glue, characterized in that: The preparation method uses the formulation according to any one of claims 3 to 6 and is prepared according to the following steps: S10: preparing the modified nano titanium dioxide dispersion: S110: adding the tetrabutyl titanate to the oleic acid and dispersing them at room temperature to obtain a titanate precursor; S120: transferring the titanate precursor to a high-temperature and high-pressure reactor for reaction, then cooling naturally, adding the hexadecyltrimethoxysilane, continuing the reaction, then cooling to room temperature, washing by centrifugation with the anhydrous ethanol, and then drying to obtain modified titanium dioxide powder; S130: adding the dispersant to the ethyl acetate solvent, adding the modified titanium dioxide powder after dispersion, stirring, and preparing the modified nano titanium dioxide dispersion; S20: preparing the high refractive index UV glue: S210: mixing the monofunctional acrylic monomer, the difunctional acrylic monomer and the trifunctional acrylic monomer, and stirring them evenly to obtain a resin precursor; S220: adding the modified nano titanium dioxide dispersion into the resin precursor, stirring evenly, and obtaining a high refractive index UV glue.

8. The method for preparing a high refractive index UV glue according to claim 7, characterized in that: The step of obtaining the resin precursor further comprises: mixing the monofunctional acrylic monomer, the difunctional acrylic monomer and the acrylic monomer with a functionality greater than or equal to three, stirring evenly, then adding the polymerization inhibitor, and further stirring evenly to obtain the resin precursor.

9. The method for preparing a high refractive index UV glue according to claim 7, characterized in that: The method of obtaining the high-refractive index UV glue also includes: adding the modified nano-titanium dioxide dispersion to the resin precursor, stirring evenly, then adding the defoamer, the leveling agent, and the photoinitiator in sequence under stirring conditions, and further stirring to obtain an initial high-refractive index UV glue, performing a low-temperature evaporation treatment on the initial high-refractive index UV glue, and adding a monofunctional acrylic monomer at the same time until the tested solid content reaches 99% to 100%, thereby obtaining the high-refractive index UV glue.

10. The method for preparing a high refractive index UV glue according to any one of claims 7 to 9, characterized in that: The high refractive index UV glue meets at least one of the following conditions (A) to (C): (A) Refractive index ≥ 1.88; (B) Adhesion test: 0 level; (C) Transparency ≥ 99%.

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