A method for preparing a high refractive index (thiol-containing) uv-cured acrylate film

Abstract

The application provides a preparation method of a high-refractive (mercapto-containing) UV-cured acrylate film, and belongs to the technical field of preparation of light-cured films. The system used in the application is composed of four parts: A. flexible long-chain acrylate monomer; B. aromatic ring-containing acrylate monomer; C. thiofuran or selenothiofuran functional monomer containing mercapto; and D. photo-crosslinking initiator. Since the polymer system contains sulfur or selenium atoms with high molar refractivity, and also contains thiofuran groups or aromatic rings with high molar refractivity and low molar volume, the polymer refractivity is improved by the two. The film prepared by the method has high refractivity, and the refractivity is greater than 1.68. The high-refractive UV-cured acrylate film prepared by the application can be used in the industrial fields of optical materials, electronic packaging and flexible electronics.

Description

Technical Field

[0001] This invention belongs to the field of photocurable film preparation technology, and provides a method for preparing a UV-curable acrylate film with high refractive index (containing mercapto groups). Background Technology

[0002] Acrylic esters are commonly used functional monomers and reactive diluents in UV curing systems. They contain multiple double bonds that can undergo double bond addition reactions or click reactions with thiols, leading to chain or stepwise polymerization reactions. They offer advantages such as low cost, good light transmittance, good chemical stability, low volatility, fast curing rate, good adjustability, and ease of processing, making them widely popular in ultraviolet (UV) curing technology. Among these, research on the UV curing of acrylic acid and its esters, which have high refractive indices, is becoming increasingly extensive.

[0003] Chinese patent CN114853979A discloses a high-performance, high-refractive-index UV resin and its preparation method. Product 1 is synthesized using (meth)acrylate hydroxyl ester, a benzene-ring-containing acid anhydride, and bisphenol A type epoxy resin; Product 2 is synthesized using diisocyanate and (meth)acrylate hydroxyl ester; Product 1 (hydroxyl group) and Product 2 (isocyanate group) are reacted in a specific ratio, and the reaction endpoint is determined by titration and Fourier transform infrared spectroscopy. Although this invention obtains a resin with a high refractive index by introducing a benzene-ring-containing structure and increasing the functionality of the UV resin, and has high cost-effectiveness due to the low cost of the reaction raw materials and the simple synthesis process, making it highly competitive in the market, this system relies solely on the benzene-ring structure to increase the polymer's refractive index. If used in optical or electronic materials, it is prone to yellowing during use, thus affecting performance and interfering with the normal use of optical and electronic components.

[0004] Chinese patent CN109593154B discloses a selenium-containing maleimide polymer, its preparation method, and its applications. This invention polymerizes a novel selenium-containing maleimide monomer with a styrene monomer; additionally, it copolymerizes a novel selenium-containing vinyl monomer with the selenium-containing maleimide. While this invention overcomes the shortcomings of poor thermal stability and uncontrollable molecular weight, and allows for controllable adjustment of the refractive index, thus expanding its application in the optical field to some extent, replacing the UV-curable main monomer in the system with an acrylate monomer could significantly simplify the production process, reduce costs, and be more conducive to large-scale industrial production.

[0005] Chinese patent CN115058215A discloses a high-refractive-index photovoltaic module encapsulating film, its preparation method, and its applications. The polymer is prepared from a high-refractive-index polyolefin elastomer resin (a random or block polymer of ethylene, α-olefin, and amino-functionalized comonomers), a thermal initiator, a crosslinking agent, a coupling agent, an antioxidant, and an ultraviolet absorber. Although the polymer of this invention has a unique amino structure, which to some extent increases the molar refractive index, making the resulting high-refractive-index photovoltaic module encapsulating film similar in refractive index to tempered glass, effectively reducing light loss and slightly improving the light source utilization rate of the photovoltaic module; however, compared to amino groups, the synergistic effect of selenium atoms, sulfur atoms, and thiophene groups, after proportional adjustment, can more accurately obtain the target refractive index, enabling optical devices to meet higher practical application requirements.

[0006] This invention provides a method for preparing a high-refractive-index (thiol-containing) UV-curable acrylate film. The invention involves preparing a mixed solution system of acrylate, which, after UV curing, yields a high-refractive-index UV-curable acrylate film. The polymer system of this invention incorporates sulfur and selenium atoms with high molar refractive indices, as well as thiophene groups and aromatic rings with high molar refractive indices and low molar volumes, working synergistically to increase the polymer's refractive index. This polymer exhibits high optical transmittance, low dispersion, excellent mechanical properties, and stability. The introduction of flexible long-chain acrylate monomers adjusts the polymer's viscosity and mechanical properties, facilitating molding and processing. The high-refractive-index acrylate UV film provided by this invention achieves a balance between high refractive index, good processability, and thermal stability. Furthermore, the synthetic route for the acrylate UV-curable film provided by this invention is simple and efficient, which is beneficial for expanding its applications in optical materials, electronic packaging, and flexible electronics. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing high-refractive-index materials in practical applications and to provide a method for preparing a high-refractive-index (thiol-containing) UV-curable acrylate film. This method is simple to operate, has mild and easily controllable conditions, and achieves high utilization of selenium and sulfur atoms. By introducing sulfur and selenium atoms with high molar refractive indices, as well as thiophene groups and aromatic rings with high molar refractive indices and low molar volumes, they work synergistically to improve the polymer's refractive index. The resulting polymer exhibits high optical transmittance, low dispersion, excellent mechanical properties, and stability. The introduction of flexible long-chain acrylate monomers adjusts the polymer's viscosity and mechanical properties, facilitating molding and processing.

[0008] In a first aspect, the present invention provides a method for preparing a UV-curable acrylate film with high refractive index (containing mercapto groups), comprising a flexible long-chain acrylate monomer, an aromatic ring acrylate monomer, a thiophene or selenothiophene functional monomer containing mercapto groups, and a photocrosslinking initiator, wherein the flexible long-chain acrylate monomer can be represented by the following structure:

[0009] All R groups are (-CH2-)n (n=0, 1, 2, 3, 4, 5);

[0010] Furthermore, the aromatic ring-containing acrylate monomer can be represented by the following structure:

[0011] Where the R base is (-CH2-)n (n=0, 1, 2, 3, 4, 5);

[0012] Furthermore, the thiophene or selenothiophene functional monomer containing a mercapto group includes any one of 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene (A), 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl diselenothiophene (B), and 2,5-bis[(2-mercapto)ethylthio]selenothiophene (C), the structure of which is represented as follows:

[0013]

[0014] Furthermore, the photocrosslinking initiator includes one or more of benzo[a]one, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, 2-hydroxy-2-methyl-1-phenylacetone, 1-hydroxy-cyclohexylacetone, hydroxybenzophenone, benzoyldiphenylphosphine, benzophenone, and 2,2'-azobis(2-methylpropionitrile).

[0015] Preferably, the photocrosslinking initiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

[0016] Furthermore, the preparation of a UV-curable acrylate film with high refractive index (containing thiol groups) involves the following specific steps:

[0017] (1) Preparation of thiophene or selenthiophene functional monomers containing mercapto groups, the specific steps are as follows:

[0018] ① Synthetic steps of 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene: 2,5-dichloro-3,4-ethyl dithiothiophene (14.7 mmol), potassium tert-butoxide (29.4 mmol), 1,2-ethanedithiol (29.4 mmol), and N,N-dimethylformamide (40 ml) were mixed and stirred overnight at 120°C. The solvent was then removed under reduced pressure. The crude product was subjected to oxidation with n-hexane (R...f The product was purified by silica gel column chromatography eluted with 0.3 g / L to give the solid product 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene.

[0019]

[0020] ②Synthetic steps of 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyldiselenothiophene: 2,5-dichloro-3,4-ethyldiselenothiophene (14.7 mmol), potassium tert-butoxide (29.4 mmol), 1,2-ethanedithiol (29.4 mmol), and N,N-dimethylformamide (40 ml) were mixed and stirred overnight at 120°C. The solvent was then removed under reduced pressure. The crude product was subjected to oxidation with n-hexane (R... f Purified by silica gel column chromatography eluted with 0.3 g / L to give solid product 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyldiselenothiophene;

[0021]

[0022] ③ Synthesis steps of 2,5-bis[(2-mercapto)ethylthio]selenothiophene: 2,5-dibromoselenothiophene (14.7 mmol), potassium tert-butoxide (29.4 mmol), 1,2-ethanedithiol (29.4 mmol), and N,N-dimethylformamide (40 ml) were mixed and stirred overnight at 120°C. The solvent was then removed under reduced pressure. The crude product was subjected to oxidation with n-hexane (R... f Purified by silica gel column chromatography eluted with 0.3 g / L to obtain the solid product 2,5-bis[(2-mercapto)ethylthio]selenothiophene.

[0023]

[0024] (2) Preparation of acrylate mixed solution

[0025] Under N2 atmosphere, room temperature and in the dark, acrylate monomers containing flexible long chains, acrylate monomers containing aromatic rings, thiophene or selenothiophene functional monomers containing mercapto groups and photocrosslinking initiators are added to a stainless steel container at a monomer molar ratio of 0-8:0-6:2-5:0.1-0.5 and stirred at 300-380 rpm for 60 min, and then allowed to stand for 40 min to obtain an acrylate mixed solution.

[0026] (3) Preparation of high refractive index (containing mercapto) UV-cured acrylate film

[0027] ① Spin-coat the acrylate mixed solution prepared in step (2) onto a silicone plate;

[0028] ② Place the silicone plate from (3) ① under ultraviolet light with a wavelength of 190-400nm for 50-1200s to cure and form a UV film of 0.01-4mm, thus obtaining a high refractive index UV-cured acrylate film.

[0029] Furthermore, a UV-curable acrylate film with a high refractive index (containing mercapto groups) was prepared, with a refractive index greater than 1.6 and a transmittance of over 87% for wavelengths of 450-830 nm.

[0030] Beneficial effects:

[0031] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0032] The inventive point of this invention lies in the fact that by introducing selenium or sulfur atoms with high molar refractive index and aromatic rings with high molar refractive index and low molar volume, the mechanical and thermal properties of the polymer can be improved while simultaneously increasing the polymer's refractive index to above 1.6. The introduction of flexible long-chain acrylate monomers adjusts the polymer's viscosity and mechanical properties, facilitating molding and processing, thereby broadening its application areas. Detailed Implementation

[0033] The specific steps for preparing thiophene or selenthiophene functional monomers containing thiol groups are as follows:

[0034] (1) 2,5-Dichloro-3,4-ethyldithiophene (14.7 mmol), potassium tert-butoxide (29.4 mmol), 1,2-ethanedithiol (29.4 mmol), and N,N-dimethylformamide (40 ml) were mixed and stirred overnight at 120 °C. The solvent was then removed under reduced pressure. The crude product was subjected to treatment with n-hexane (R... f Purified by silica gel column chromatography eluted with 0.3 g / L to give solid product 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene (21.7 mmol, 67.7%).

[0035] (2) Preparation of acrylate mixed solution

[0036] Under N2 atmosphere, room temperature, and in the dark, ethyl acrylate, benzoyl acrylate, 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene, and photocrosslinking initiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone were added to a stainless steel container at a monomer molar ratio of 4:2:1:0.3 and stirred at 320 rpm for 60 min, followed by standing for 40 min to obtain an acrylate mixed solution.

[0037] (3) Preparation of high refractive index (containing mercapto) UV-cured acrylate film

[0038] ① Spin-coat the acrylate mixed solution prepared in step (2) onto a silicone plate;

[0039] ② Place the silicone plate from ① under ultraviolet light with a wavelength of 395nm for 100s to cure and form a 0.12mm UV film, thus obtaining a high refractive index (containing mercapto) UV-cured acrylate film.

Claims

1. A UV-curable acrylate film, characterized in that, The UV-curable acrylate film is made of acrylate monomers containing flexible long chains, acrylate monomers containing aromatic rings, thiophene or selenothiophene functional monomers containing mercapto groups, and a photocrosslinking initiator. The thiophene or selenothiophene functional monomers containing mercapto groups include any one of 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene (A), 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl diselenothiophene (B), and 2,5-bis[(2-mercapto)ethylthio]selenothiophene (C), the structures of which are shown below: ； The UV-curable acrylate film is prepared by the following method, with the specific steps as follows: (1) The preparation of thiophene or selenthiophene functional monomers containing mercapto groups, the specific steps are as follows: The synthesis steps of 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene: 14.7 mmol of 2,5-dichloro-3,4-ethyl dithiothiophene, 29.4 mmol of potassium tert-butoxide, 29.4 mmol of 1,2-ethanedithiol, and 40 ml of N,N-dimethylformamide were mixed and stirred overnight at 120 °C. The solvent was then removed under reduced pressure. The crude product was subjected to reconstitution with n-hexane R... f Purified by silica gel column chromatography eluted with 0.3 g / L to give solid product 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyl dithioselenothiophene; The synthesis steps of 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyldiselenothiophene were as follows: 14.7 mmol of 2,5-dichloro-3,4-ethyldiselenothiophene, 29.4 mmol of potassium tert-butoxide, 29.4 mmol of 1,2-ethanedithiol, and 40 ml of N,N-dimethylformamide were mixed and stirred overnight at 120 °C. The solvent was then removed under reduced pressure. The crude product was subjected to reconstitution with n-hexane R... f Purified by silica gel column chromatography elution with a 0.3 elution ratio, the solid product 2,5-bis[(2-mercapto)ethylthio]-3,4-ethyldiselenothiophene was obtained. The synthesis steps of 2,5-bis[(2-mercapto)ethylthio]selenothiophene: 14.7 mmol of 2,5-dibromoselenothiophene, 29.4 mmol of potassium tert-butoxide, 29.4 mmol of 1,2-ethanedithiol, and 40 ml of N,N-dimethylformamide were mixed and stirred overnight at 120 °C. The solvent was then removed under reduced pressure. The crude product was subjected to reconstitution with n-hexane R... f Purified by silica gel column chromatography eluted with 0.3 g, the solid product 2,5-bis[(2-mercapto)ethylthio]selenothiophene was obtained. (2) The preparation of the acrylate mixed solution is as follows: Under N2 atmosphere, room temperature and light-protected conditions, acrylate monomers containing flexible long chains, acrylate monomers containing aromatic rings, thiophene or selenothiophene functional monomers containing mercapto groups and photocrosslinking initiators were added to a stainless steel container in a molar ratio of 4:2:1:0.3 and stirred at 300-380 rpm for 60 min, and then allowed to stand for 40 min to obtain an acrylate mixed solution. (3) The specific steps for preparing UV-cured acrylate films are as follows: ① Spin-coat the acrylate mixed solution prepared in step (2) onto a silicone plate; ② Place the silicone plate from step ① under ultraviolet light with a wavelength of 190-400nm for 50-1200s to cure and form a UV film of 0.01-4mm, thus obtaining a UV-cured acrylate film.

2. The UV-curable acrylate film according to claim 1, characterized in that, Acrylate monomers containing flexible long chains are represented by the following structures: In this case, all R groups are (-CH2-)n, where n = 0, 1, 2, 3, 4, 5.

3. The UV-curable acrylate film according to claim 1, characterized in that, The aromatic ring-containing acrylate monomer is represented by the following structure: Wherein, the R group is (-CH2-)n, where n = 0, 1, 2, 3, 4, 5.

4. The UV-curable acrylate film according to claim 1, characterized in that, The photocrosslinking initiator includes one or more of benzo[a]one, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, 2-hydroxy-2-methyl-1-phenylacetone, 1-hydroxy-cyclohexylacetone, hydroxybenzophenone, benzoyldiphenylphosphine, and benzophenone.

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