Preparation method and application of UV optical adhesive

Abstract

The present invention discloses a preparation method and application of UV optical adhesive. First, NCO functionalized cellulose acetate, polyoxyethylene 40 hydrogenated castor oil, isophorone diisocyanate and polymer chain extender are polymerized to prepare modified cellulose acetate segmented polyurethane, and then polymerized ionic liquid is introduced into the modified cellulose acetate segmented polyurethane to prepare UV optical adhesive. A low surface energy thin film material is prepared by spin coating the UV optical adhesive on a substrate and performing cyclic oxidation surface modification. The UV optical adhesive of the present invention enhances the adhesion between the film and the substrate and achieves an improvement in light transmittance; the present invention combines the characteristics of intramolecular and intermolecular hydrogen bonds, and the hydrogen bond six-membered ring formed between the imidazole group and the benzoxazine group enhances the mechanical strength and wear resistance of the thin film material, and can be applied to new display devices, chip lithography, nanoimprint molding, photonics, biomedicine, nanomanufacturing and other fields.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a functional adhesive, and in particular to a preparation method and application of a UV optical adhesive. Background Art

[0002] UV optical adhesive is a polymer material with high resolution, high sensitivity, and high precision, suitable for high-end applications such as display device packaging, chip lithography, and nanoimprinting. Its basic principle is to use ultraviolet radiation to trigger a chemical reaction, thereby curing the adhesive layer. The unique structure and chemical properties of UV optical adhesive enable high-precision pattern formation, making it an indispensable material in microelectronics manufacturing. It is also widely used in other fields such as new display devices, chip lithography, nanoimprint molding, photonics, biomedicine, and nanomanufacturing.

[0003] Methods for preparing UV optical adhesives primarily include chemical synthesis and physical synthesis. Chemical synthesis typically utilizes polymer chemistry and cross-linking reactions, where the polymer is typically composed of monomers and cross-linkers. Monomers are used to adjust the properties of the optical adhesive by varying their structure and composition, while cross-linkers are used to control the mechanical strength and brittleness of the adhesive layer. During the chemical synthesis process, factors such as reaction conditions, material ratios, and solvents must be controlled to achieve ideal optical adhesive properties.

[0004] With the continuous advancement of manufacturing technology, the requirements for resolution and precision are becoming higher and higher, which also brings about some key technical barriers. These include how to choose a suitable compounding scheme, how to control the speed and mechanism of chemical reactions, how to further achieve high-resolution and high-precision pattern formation, and how to control the adhesion and peelability of the adhesive layer. CN111995967A discloses a method for preparing a UV-curable optical adhesive film, which uses ethylene-vinyl acetate copolymer as the main body, introduces acrylate monomers, photoinitiators and additives to achieve the preparation of optical adhesive film, and has excellent processing performance and performance. CN111808534A discloses a method for preparing a liquid optical adhesive, the main formula of which includes a tackifying resin, an active oligomer, an active diluent and a photoinitiator. The adhesive liquid is quickly converted into a non-flowing gel through UV pre-curing, and the overflow problem that cannot be overcome by ordinary liquid optical adhesives will not occur in the subsequent bonding process. The adhesive film has moderate bonding strength, which not only has a positioning effect, but also can keep the relative position of the touch screen and the display module from shifting after being bonded, and can also make it easier to separate the touch screen and the display module.

[0005] However, the currently reported synthesis methods mainly rely on the combination of multiple organic resins and lack the reactive design and synthesis of resin monomers. Summary of the Invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a UV optical adhesive with strong stability, good compatibility, high light transmittance and strong adhesion;

[0007] The second object of the present invention is to provide the application of the UV optical adhesive prepared by the above method in low surface energy materials.

[0008] Technical solution: The method for preparing the UV optical adhesive of the present invention comprises the following steps:

[0009] (1) Preparation of -NCO functionalized cellulose acetate;

[0010] (2) polymerizing -NCO functionalized cellulose acetate, hydrogenated castor oil, diisocyanate, organotin catalyst and polymer chain extender to prepare modified cellulose acetate segmented polyurethane;

[0011] (3) The imidazole-type polymeric ionic liquid is compounded with modified cellulose acetate segmented polyurethane and reacted under alkaline conditions to prepare UV optical adhesive.

[0012] The specific preparation process of step (1) is as follows: 4,4'-methylenebis(phenyl isocyanate), dihydroxybenzoxazine monomer, and cellulose acetate are mixed at a molar ratio of -NCO:-OH of 1.2 to 1.3, a tertiary amine catalyst and an inert solvent are added, a condensation reaction occurs, and then the solvent is evaporated under reduced pressure to obtain -NCO functionalized cellulose acetate. Specifically, the tertiary amine catalyst is triethylamine; and the inert solvent is toluene.

[0013] The specific preparation process of step (2) is as follows: dissolving diisocyanate and an organotin catalyst in a solvent, adding -NCO functionalized cellulose acetate, hydrogenated castor oil and a polymer chain extender, heating to 40-55° C., reacting under a protective atmosphere for 4-7 hours, and removing the solvent by rotary evaporation to obtain a modified cellulose acetate segmented polyurethane.

[0014] Specifically, the hydrogenated castor oil is polyoxyethylene 40 hydrogenated castor oil; the polymer chain extender includes at least one of stearyl diethanolamine, hydroxyl-terminated polydimethylsiloxane, polyether polyol or polytetrahydrofuran; and the organotin catalyst includes at least one of dibutyltin dilaurate, stannous octoate or di(dodecylsulfide)dibutyltin.

[0015] Wherein, the modified cellulose acetate segmented polyurethane has the following structure:

[0016]

[0017] In step (2), the molar ratio of isocyanate to hydroxyl is 1.2 to 1.35, which is beneficial for maintaining the low viscosity of the polyurethane glue, and is beneficial for storage, use, and subsequent film coating.

[0018] In step (2), the amount of the polymer chain extender introduced is 7-11 wt% of the total mass of the system; and the amount of the catalyst introduced is 0.05-0.07 wt% of the total mass of the system. Within the above ranges, the introduction of the chain extender is beneficial to the extension of the molecular chain, reducing the reduction in molecular weight and the formation of terminal carboxyl groups due to thermal degradation and hydrolysis reactions, thereby weakening the mechanical strength. The introduction of the catalyst is beneficial to the polymerization reaction and reduces the reaction energy barrier.

[0019] Wherein, the specific preparation process of step (3) is:

[0020] The imidazole polymeric ionic liquid was dispersed in dichloromethane, and polymethyl methacrylate was introduced into the solution and aged for 1-1.5 h. The resulting mixture was then pumped at a rate of 1-2 mL min -1 The controlled liquid flow rate is sprayed into non-polar polyethylene terephthalate, and then atomized and dispersed into droplets with a diameter of 5 to 8 μm under the inert gas at a pressure of 10 to 20 kPa, and then sprayed into an ethyl acetate solution of modified cellulose acetate block polyurethane in batches;

[0021] The imidazole polymeric ionic liquid and modified cellulose acetate segmented polyurethane are mixed in a mass ratio of 2:6.5-8.5, the pH value is adjusted to 8.5-9, and the mixture is stirred at 0-5°C under a protective atmosphere for 12-15 hours to obtain a UV optical adhesive. The inert gas may be nitrogen or argon; the protective atmosphere may be nitrogen, a mixture of nitrogen and carbon dioxide, or a mixture of nitrogen and argon.

[0022] The present invention sprays polymeric ionic liquid droplets with diameters within this range into a polymer solution, facilitating uniform and continuous dispersion within the system, thereby avoiding phase separation between the two components during blending due to polarity differences. Furthermore, hydrogen bonding sites are generated in situ, increasing the spatial isomerization of the molecular chains, reducing the regularity of the crystal molecules, lowering crystallinity, and increasing light transmittance.

[0023] Wherein, in step (3), the preparation process of the imidazole type polymeric ionic liquid is as follows: dissolving the ionic liquid and azobisisobutyronitrile in a 25-35wt% acrylate solution, stirring at room temperature under a protective atmosphere for 3-4 hours, then heating to 60-80°C for reaction for 9-11 hours, and rotary evaporating to obtain the imidazole type polymeric ionic liquid. The imidazole type polymeric ionic liquid can provide dense imidazole groups, forming extensive hydrogen bonds with the carbamate groups and oxazine rings on the polymer main chain, weakening the regularity of the molecular arrangement, reducing the crystallinity of the polyurethane material, and increasing the transparency of the material. The structural formula of the imidazole type polymeric ionic liquid is:

[0024]

[0025] The ionic liquid includes at least one of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-ethylimidazolium hexafluorophosphate, and 1-vinyl-3-ethylimidazolium tetrafluoroborate.

[0026] The method for preparing a low surface energy material using the above-mentioned UV optical adhesive comprises the following steps:

[0027] (1) coating a composite of UV optical adhesive and photoinitiator on the surface of a substrate and irradiating with ultraviolet light to form a prefabricated film;

[0028] (2) coating the cerium salt solution on the surface of the prefabricated membrane and irradiating it with ultraviolet light;

[0029] (3) turning off the ultraviolet light irradiation, raising the temperature, and coating the surface of the film with a low-polarity organic solution for modification to obtain the low surface energy material.

[0030] Wherein, in step (1), the mass fraction of the photoinitiator in the UV optical adhesive is 1 to 3 wt%; the photoinitiator is at least one of 2-hydroxy-2-methyl-1-phenylpropanone, methyl benzoylformate or 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone; the wavelength range of the ultraviolet light is 365 nm, and the irradiation time is 5 to 10 min.

[0031] In step (1), preferably, the UV optical adhesive and the photoinitiator are compounded and then coated on the surface of the metal thin layer substrate by electrospinning, which can achieve control of the diameter of a single membrane fiber. The ultrafine fiber has a large specific surface area, which can improve the adsorption performance of the material on the metal substrate. At the same time, the fiber purity is high, suitable for continuous preparation, and the preparation process is easy to control. The metal in the metal thin layer is preferably nickel-aluminum metal.

[0032] In step (2), the cerium salt solution comprises at least one of an ammonium cerium sulfate / ethylene glycol solution, an ammonium cerium nitrate / acetone solution, an ammonium cerium nitrate / cyclohexanone solution, or a cerium chloride / hydrochloric acid solution. Preferably, the cerium salt solution is applied to the prefabricated membrane surface in a thin layer; the thickness of the thin layer is 10-20 μm. Thin coating facilitates uniform dispersion of the cerium salt solution on the prefabricated membrane surface, reduces liquid flow caused by excessively thick solution application, and ensures that the functional groups on the membrane surface are fully activated.

[0033] Wherein, in step (2), the wavelength range of the ultraviolet light is 200-225 nm, and the irradiation time is 2-3.5 h.

[0034] Wherein, in step (3), the temperature is raised to 55-70° C., and the surface of the film is evenly coated with a low-polarity organic solution for 3-7 hours; the low-polarity organic solution includes at least one of a tetrahydrofuran solution of hexachlorodecane, a tetrahydrofuran solution of 1H,1H-heptadecafluorononylamine, a tetrahydrofuran solution of (3-chloropropyl)diethoxy(methyl)silane, or a tetrahydrofuran solution of hexadecylamine.

[0035] Principle of the invention: The present invention synthesizes long-chain resin monomers with special functional group structures to directionally regulate the optical and physical properties of optical adhesives to meet various application requirements in the field of photoresists.

[0036] The inherent compatibilizing properties of hydrogenated castor oil enhance the compatibility between the soft and hard segments of the system, preventing microphase separation and the resulting macrophase separation. The introduction of -NCO-functionalized cellulose acetate increases the concentration of the rigid component, reducing the molecular polarity of the material and promoting a reduction in surface energy. The introduction of chain extender molecules containing ether bonds and long flexible chains balances the material's excessive brittleness to a certain extent, improving the film's mechanical properties and providing a buffer for steric hindrance between molecular segments, preventing interfacial warping caused by excessive polymerization. The widely distributed hydrophilic ether bonds and unreacted hydroxyl sites within the molecular segments react with functional groups on many substrate surfaces to form strong chemical bonds, enhancing adhesion between the film and the substrate.

[0037] The resin molecules contain a large number of long alkane chains and -NCO functionalized cellulose acetate blocks, which migrate to the interface during the film formation process, constructing a low-energy surface and having low peel strength.

[0038] Ultraviolet light with a wavelength of about 200nm combined with a suitable photosensitizer can activate the C-H bond through a light-excited secondary reaction. Based on the "surface-limited reaction" theory, when a cerium salt solution is placed on the surface of a polymer substrate in a thin layer and irradiated with UV light, Ce 3+ Photooxidation to form Ce 4+ , and then the in situ formed Ce 4+ Oxidative cleavage of the CH bonds on the polymer surface forms surface free radicals, while Ce 4+ Reduced to Ce 3+ and release H + , forming a new cyclic oxidation reaction. This reaction system avoids Ce 4+On the other hand, the instability when coexisting with reducing agents is conducive to the efficient generation of surface free radicals, and the chemical modification method is sustainable and strong. The surface free radicals formed can directly convert the CH bonds on the polymer surface into small molecule functional groups and polymer brushes through coupling or initiation reactions. By introducing small molecule functional groups with low surface energy and non-polarity on the surface of the material, the surface energy and adhesion of the material surface can be further reduced; by chemical modification, long molecular chains are attached to the surface of the material to form a brush-like structure, providing more non-polar functional groups and a smaller specific surface area, so that the outer surface of the low surface energy film material has lower adhesion. Polymer brushes can also achieve precise control of the surface properties of the material by changing the chemical structure and physical morphology of the brush layer, thereby improving its performance. In addition, due to the low incidence depth of ultraviolet light, the reaction can be limited to the outer surface of the substrate without affecting the structure and properties of the film substrate, and is expected to become a green and economical industrial polymer surface modification method.

[0039] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0040] (1) The present invention combines the characteristics of intramolecular and intermolecular hydrogen bonds. The hydrogen bonded six-membered ring formed between the imidazole group and the benzoxazine group improves the stability of the UV optical adhesive. The components of the optical adhesive have good compatibility, overcoming the macroscopic phase separation caused by the mutual repulsion between the polar segments and the non-polar segments. The widely distributed hydrophilic ether bonds and unreacted hydroxyl sites in the molecular segments of the UV optical adhesive can react with the functional groups on the surface of many substrates to form strong chemical bonds, thereby enhancing the adhesion between the film and the substrate. The chair structure of the benzoxazine ring dislocates the spatial arrangement of the cellulose acetate molecules, and the formation of extensive intramolecular and intermolecular hydrogen bonds exacerbates the irregularity of the molecular structure. These two methods reduce the crystallinity of the polymer and achieve an increase in light transmittance.

[0041] (2) The present invention sprays the polymerized ionic liquid droplets of a specific particle size range formed by atomization into the polymer solution, which is conducive to uniform and continuous dispersion in the system, avoiding the phase separation of the two components during the blending process due to polarity differences, and further improving the compatibility; at the same time, hydrogen bonding sites are generated in situ, increasing the spatial isomerization of the molecular chain, reducing the regularity of the arrangement of the crystal molecules, reducing the crystallinity, and further increasing the transmittance of the UV optical adhesive.

[0042] (3) Compared with the traditional single coating resin structure low surface energy film, the UV optical adhesive prepared by this method is coated to form a low surface energy composite film material, which combines the characteristics of intramolecular and intermolecular hydrogen bonds. The hydrogen bond six-membered ring formed between the imidazole group and the benzoxazine group gives the material high mechanical strength and wear resistance. In addition, the generation of intermolecular hydrogen bonds caused by benzoxazine self-polymerization is avoided, while extensive intermolecular hydrogen bonds will increase the brittleness of the film and reduce the strength of use. Polar fragments are distributed on the contact interface between the film and the substrate. The film and the substrate are tightly bonded by van der Waals forces and ionic bonds, and the adhesion is greatly enhanced. The non-polar fragments spontaneously migrate to the surface of the film in contact with the air due to mutual repulsion, forming a low surface energy on a macro scale;

[0043] (4) By using electrospinning technology, UV optical adhesive and photoinitiator are compounded and then coated on the surface of the metal thin layer substrate, which can realize the control of the diameter of a single membrane fiber. The ultrafine fiber has a large specific surface area, which can improve the adsorption performance of the material on the metal substrate. At the same time, the fiber purity is high, which is suitable for continuous preparation and the preparation process is easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a water contact angle diagram of the UV optical adhesive film of Example 1;

[0045] Figure 2 This is a water contact angle diagram of the UV optical adhesive film of Example 2;

[0046] Figure 3 This is a water contact angle diagram of the UV optical adhesive film of comparative example 1;

[0047] Figure 4 This is a water contact angle diagram of the UV optical adhesive film of Control Example 1 after standing for 30 seconds;

[0048] Figure 5 This is a water contact angle diagram of the UV optical adhesive film of comparative example 2;

[0049] Figure 6 This is a water contact angle diagram of the UV optical adhesive film of comparative example 3;

[0050] Figure 7 This is a water contact angle diagram of the UV optical adhesive film of Control Example 3 after standing for 30 seconds;

[0051] Figure 8 This is a water contact angle diagram of the UV optical adhesive film of comparative example 4;

[0052] Figure 9 This is the water contact angle diagram of the UV optical adhesive film of Control Example 5. DETAILED DESCRIPTION

[0053] The present invention is described in further detail below.

[0054] Example 1

[0055] Preparation of UV optical adhesive:

[0056] (1) Preparation of -NCO functionalized cellulose acetate: 4,4'-methylenebis(phenyl isocyanate), dihydroxybenzoxazine monomer and cellulose acetate were mixed and dissolved in a toluene solution at a -NCO:-OH molar ratio of 1.2, 2-3 drops of triethylamine were added, the temperature was raised to 70°C and the reaction was carried out overnight, and then the solvent was evaporated under reduced pressure to obtain -NCO functionalized cellulose acetate.

[0057] (2) Preparation of -NCO functionalized cellulose acetate block polyurethane: 2.23 g of isophorone diisocyanate and 4 drops of dibutyltin dilaurate were dissolved in 10 mL of dichloromethane and then poured into a three-necked round-bottom flask equipped with a condenser, a dropping funnel, a nitrogen inlet, and a magnetic stirring bar. Thereafter, 1.876 g of polyoxyethylene 40 hydrogenated castor oil, 0.4 g of -NCO functionalized cellulose acetate, and 0.718 g of stearyl diethanolamine were dissolved in 40 mL of dichloromethane, and the solution was added dropwise to the flask under a nitrogen atmosphere over 0.5 h. The resulting mixture was stirred at 40° C. under nitrogen for 4 h. Then, the solvent was removed from the mixture by rotary vacuum evaporation to obtain -NCO functionalized cellulose acetate block polyurethane, i.e., modified cellulose acetate block polyurethane.

[0058] (3) Preparation of UV optical adhesive: 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and AIBN were dissolved in a 25 wt% acrylate solution, stirred at room temperature under argon atmosphere for 3 h, then heated to 60 °C for 9 h, and rotary evaporated to obtain an imidazole-type polymeric ionic liquid;

[0059] 2 g of imidazole-type polymeric ionic liquid was dispersed in dichloromethane, and polymethyl methacrylate was subsequently introduced into the solution and aged for 1 h. The resulting mixture was then pumped at a rate of 1 mL min -1 The controlled liquid flow rate was sprayed into non-polar polyethylene terephthalate, and was carried and atomized by N2 at a pressure of 10 kPa to disperse into droplets with a diameter of 5 μm, and then sprayed into an ethyl acetate solution containing 7 g of modified cellulose acetate segmented polyurethane in batches. After adjusting the pH value to 8.5, the mixture was stirred at 0°C under a nitrogen atmosphere for 12 hours to obtain UV optical adhesive.

[0060] Application of UV optical adhesive:

[0061] UV optical adhesive and 1% photoinitiator 1173 were compounded and spin-coated on the surface of the substrate, and irradiated with ultraviolet light of a wavelength of 365nm for 5 minutes to form a prefabricated film; ammonium cerium sulfate / ethylene glycol solution was coated on the surface of the prefabricated film in a thin layer, wherein the thickness of the thin layer was 10μm; and irradiated with ultraviolet light of a wavelength of 200nm for 2h; the ultraviolet light irradiation was turned off, the temperature was raised to 55°C, and the surface of the film was evenly coated with a 15% tetrahydrofuran solution of hexadecane chloride and treated for 3h to obtain a low surface energy film.

[0062] The light transmittance of the low surface energy film is 95%, the substrate peel strength is 45.765 gf / in, and the interface peel strength is 13.661 gf / in. Figure 1 , the water contact angle is about 121°.

[0063] Example 2

[0064] Preparation of UV optical adhesive:

[0065] (1) Preparation of -NCO functionalized cellulose acetate: 4,4'-methylenebis(phenyl isocyanate), dihydroxybenzoxazine monomer and cellulose acetate were mixed and dissolved in a toluene solution at a -NCO:-OH molar ratio of 1.24. 2-3 drops of triethylenediamine were added and the temperature was raised to 70°C for overnight reaction. The solvent was then evaporated under reduced pressure to obtain -NCO functionalized cellulose acetate.

[0066] (2) Preparation of -NCO functionalized cellulose acetate block polyurethane: 3.114 g of isophorone diisocyanate and 3 drops of dibutyltin dilaurate were dissolved in 15 mL of dichloromethane and then poured into a three-necked round-bottom flask equipped with a condenser, a dropping funnel, a nitrogen inlet, and a magnetic stirring bar. Thereafter, 2.145 g of polyoxyethylene 40 hydrogenated castor oil, 0.71 g of -NCO functionalized cellulose acetate, and 0.996 g of stearyl diethanolamine were dissolved in 60 mL of dichloromethane and the solution was added dropwise to the flask under a nitrogen atmosphere over 0.5 h. The resulting mixture was stirred at 45 °C under nitrogen for 5 h. Then, the solvent was removed from the mixture by rotary vacuum evaporation to obtain -NCO functionalized cellulose acetate block polyurethane.

[0067] (3) Preparation of UV optical adhesive: 1-vinylimidazole bis(trifluoromethanesulfonyl)imide and AIBN were dissolved in 25 wt% acrylate solution, stirred at room temperature under argon atmosphere for 4 h, then heated to 60 °C for reaction for 9 h, and rotary evaporated to obtain imidazole type polymeric ionic liquid.

[0068] 4 g of imidazole-type polymeric ionic liquid was dispersed in dichloromethane, and polymethyl methacrylate was subsequently introduced into the solution and aged for 1 h. The resulting mixture was then pumped at a rate of 1 mL min using a syringe pump. -1The controlled liquid flow rate was sprayed into non-polar polyethylene terephthalate, and was carried and atomized by N2 at a pressure of 15 kPa to disperse into droplets with a diameter of 6 μm, and then sprayed into an ethyl acetate solution containing 14.3 g of modified cellulose acetate segmented polyurethane in batches. After adjusting the pH value to 8.5, the solution was stirred at 0°C under a nitrogen atmosphere for 12 hours to obtain UV optical adhesive.

[0069] Application of UV optical adhesive:

[0070] UV optical adhesive and 1.5% photoinitiator 1173 were compounded and spin-coated on the surface of the substrate, and irradiated with ultraviolet light of a wavelength of 365nm for 5 minutes to form a prefabricated film; a thin layer of ammonium cerium nitrate / acetone solution was coated on the surface of the prefabricated film, wherein the thickness of the thin layer was 15μm; and the film was irradiated with ultraviolet light of a wavelength of 200nm for 3 hours; the ultraviolet light was turned off, the temperature was raised to 65℃, and the surface of the film was evenly coated with a 15% THF solution of 1H,1H-heptadecafluorononylamine and treated for 3 hours to obtain a low surface energy film.

[0071] The light transmittance of the low surface energy film is 93.64%, the substrate peel strength is 55.304 gf / in, and the interface peel strength is 11.078 gf / in. Figure 2 , the water contact angle is about 127°.

[0072] Example 3

[0073] Preparation of UV optical adhesive:

[0074] (1) Preparation of -NCO functionalized cellulose acetate: 4,4'-methylenebis(phenyl isocyanate), dihydroxybenzoxazine monomer and cellulose acetate were mixed and dissolved in an acetone solution at a -NCO:-OH molar ratio of 1.27. 2-3 drops of triethylenediamine were added and the temperature was raised to 75°C for overnight reaction. The solvent was then evaporated under reduced pressure to obtain -NCO functionalized cellulose acetate.

[0075] (2) Preparation of -NCO functionalized cellulose acetate block polyurethane: 4.443 g of isophorone diisocyanate and 4 drops of dibutyltin dilaurate were dissolved in 20 mL of dichloromethane and then poured into a three-necked round-bottom flask equipped with a condenser, a dropping funnel, a nitrogen inlet, and a magnetic stirring bar. Thereafter, 3.014 g of polyoxyethylene 40 hydrogenated castor oil, 0.873 g of -NCO functionalized cellulose acetate, and 0.614 g of stearyl diethanolamine were dissolved in 70 mL of dichloromethane and the solution was added dropwise to the flask under a nitrogen atmosphere over 0.5 h. The resulting mixture was stirred at 50°C under nitrogen for 6 h. Then, the solvent was removed from the mixture by rotary vacuum evaporation to obtain -NCO functionalized cellulose acetate block polyurethane.

[0076] (3) Preparation of UV optical adhesive: 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and AIBN were dissolved in a 30 wt% acrylate solution, stirred at room temperature under argon atmosphere for 3 h, then heated to 70 °C for reaction for 10 h, and rotary evaporated to obtain an imidazole-type polymeric ionic liquid.

[0077] 3.5 g of imidazole-type polymeric ionic liquid was dispersed in dichloromethane, and polymethyl methacrylate was subsequently introduced into the solution and aged for 1.5 h. The resulting mixture was then pumped at a rate of 1.5 mL min -1 The controlled liquid flow rate was sprayed into non-polar polyethylene terephthalate, and was carried and atomized by N2 at a pressure of 15 kPa to disperse into droplets with a diameter of 7 μm, and then sprayed into an ethyl acetate solution containing 13.5 g of modified cellulose acetate segmented polyurethane in batches. After adjusting the pH value to 9, the mixture was stirred at 0°C under a nitrogen atmosphere for 14 hours to obtain UV optical adhesive.

[0078] Application of UV optical adhesive:

[0079] UV optical adhesive and 1% photoinitiator 1173 were compounded and spin-coated on the surface of the substrate, and irradiated with ultraviolet light of a wavelength of 365nm for 10 minutes to form a prefabricated film; a thin layer of ammonium cerium nitrate / cyclohexanone solution was coated on the surface of the prefabricated film, wherein the thickness of the thin layer was 16μm; and irradiated with ultraviolet light of a wavelength of 210nm for 2.5h; the ultraviolet light was turned off, the temperature was raised to 60℃, and the surface of the film was evenly coated with a 15% hexadecylamine THF solution and treated for 3h to obtain a low surface energy film.

[0080] The low surface energy adhesive film has a light transmittance of 91.2%, a substrate peel strength of 64.347 gf / in, and an interface peel strength of 7.486 gf / in.

[0081] Example 4

[0082] Preparation of UV optical adhesive:

[0083] (1) Preparation of -NCO functionalized cellulose acetate: 4,4'-methylenebis(phenyl isocyanate), dihydroxybenzoxazine monomer and cellulose acetate were mixed and dissolved in a dichloromethane solution at a -NCO:-OH molar ratio of 1.3. 2-3 drops of triethylenediamine were added and the temperature was raised to 80°C for overnight reaction. The solvent was then evaporated under reduced pressure to obtain -NCO functionalized cellulose acetate.

[0084] (2) Preparation of -NCO functionalized cellulose acetate block polyurethane: 1.764 g of isophorone diisocyanate and 3 drops of dibutyltin dilaurate were dissolved in 10 mL of dichloromethane and then poured into a three-necked round-bottom flask equipped with a condenser, a dropping funnel, a nitrogen inlet, and a magnetic stirring bar. Thereafter, 0.814 g of polyoxyethylene 40 hydrogenated castor oil, 0.21 g of -NCO functionalized cellulose acetate, and 0.205 g of stearyl diethanolamine were dissolved in 30 mL of dichloromethane and the solution was added dropwise to the flask under a nitrogen atmosphere over 0.5 h. The resulting mixture was stirred at 40°C under nitrogen for 5 h. Then, the solvent was removed from the mixture by rotary vacuum evaporation to obtain -NCO functionalized cellulose acetate block polyurethane.

[0085] (3) Preparation of UV optical adhesive: 1-vinyl-3-ethylimidazolium tetrafluoroborate and AIBN were dissolved in a 35 wt% acrylate solution, stirred at room temperature under argon atmosphere for 4 h, then heated to 60 ° C for 10 h, and rotary evaporated to obtain an imidazole-type polymeric ionic liquid.

[0086] 3 g of imidazole-type polymeric ionic liquid was dispersed in dichloromethane, and polymethyl methacrylate was subsequently introduced into the solution and aged for 1.5 h. The resulting mixture was then pumped at a rate of 2 mL min -1 The controlled liquid flow rate was sprayed into non-polar polyethylene terephthalate, and was carried and atomized by N2 at a pressure of 20 kPa to disperse into droplets with a diameter of 8 μm, and then sprayed in batches into an ethyl acetate solution containing 9.72 g of modified cellulose acetate segmented polyurethane. After adjusting the pH value to 8.5, the solution was stirred at 2°C under a nitrogen atmosphere for 15 hours to obtain UV optical adhesive.

[0087] Application of UV optical adhesive:

[0088] UV optical adhesive and 2% photoinitiator 1173 were compounded and spin-coated on the surface of the substrate, and irradiated with ultraviolet light of a wavelength of 365nm for 10 minutes to form a prefabricated film; ammonium cerium nitrate / acetone solution was coated on the surface of the prefabricated film in a thin layer, wherein the thickness of the thin layer was 20μm; and irradiated with ultraviolet light of a wavelength of 250nm for 2.5h; the ultraviolet light irradiation was turned off, the temperature was raised to 70°C, and the surface of the film was evenly coated with a THF solution of 15% (3-chloropropyl)diethoxy(methyl)silane and treated for 3h to obtain a low surface energy film.

[0089] The low surface energy film has a light transmittance of 97.7%, a substrate peel strength of 71.674 gf / in, and an interface peel strength of 6.664 gf / in.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that no -NCO functionalized cellulose acetate is added.

[0092] See also Figure 3 , the water contact angle of the film surface decreases, see Figure 4 ,After 30s, the water droplets gradually penetrated into the interior of the film, and the interfacial properties of the material were weakened.

[0093] The low surface energy adhesive film has a light transmittance of 90.1%, a substrate peel strength of 43.334 gf / in, and an interface peel strength of 38.565 gf / in.

[0094] Comparative Example 2

[0095] The difference from Example 2 is that the surface of the prefabricated membrane is not subjected to cyclic oxidation modification.

[0096] See also Figure 5 , the water contact angle on the film surface decreases, that is, the surface energy increases.

[0097] The low surface energy adhesive film has a light transmittance of 88.3%, a substrate peel strength of 37.674 gf / in, and an interface peel strength of 46.654 gf / in.

[0098] Comparative Example 3

[0099] The difference from Example 1 is that unmodified cellulose acetate is added.

[0100] See also Figure 6 , the water contact angle of the film surface decreases, see Figure 7 After 30s, the water droplets gradually penetrated into the film, the contact angle further decreased, and the interface performance of the material was weakened.

[0101] The low surface energy film has a light transmittance of 77.2%, a substrate peel strength of 64.195 gf / in, and an interface peel strength of 54.611 gf / in.

[0102] Comparative Example 4

[0103] The difference from Example 3 is that single 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide is used.

[0104] See also Figure 8 , the water contact angle on the film surface decreases, that is, the surface energy increases.

[0105] The low surface energy adhesive film has a light transmittance of 82.1%, a substrate peel strength of 44.495 gf / in, and an interface peel strength of 58.948 gf / in.

[0106] Comparative Example 5

[0107] The difference from Example 4 is that no cerium salt solution is used for surface cyclic oxidation modification.

[0108] See also Figure 9 , the water contact angle of the film surface decreases and the surface energy increases.

[0109] The low surface energy adhesive film has a light transmittance of 92.1%, a substrate peel strength of 55.556 gf / in, and an interface peel strength of 45.538 gf / in.

Claims

1. A method for preparing UV optical adhesive, characterized in that: The following steps are involved: (1) Preparing -NCO functionalized cellulose acetate; the specific preparation process is: mixing 4,4'-methylenebis(phenyl isocyanate), dihydroxybenzoxazine monomer and cellulose acetate at a molar ratio of -NCO:-OH of 1.2 to 1.3, adding a tertiary amine catalyst and an inert solvent, causing a condensation reaction, and then evaporating under reduced pressure to remove the solvent to obtain -NCO functionalized cellulose acetate; (2) polymerizing -NCO functionalized cellulose acetate, hydrogenated castor oil, diisocyanate, organotin catalyst and polymer chain extender to prepare modified cellulose acetate segmented polyurethane; (3) The imidazole-type polymeric ionic liquid is compounded with modified cellulose acetate segmented polyurethane and reacted under alkaline conditions to prepare UV optical adhesive.

2. The method for preparing UV optical adhesive according to claim 1, wherein: The specific preparation process of step (2) is as follows: dissolving diisocyanate and an organotin catalyst in a solvent and mixing them, then adding -NCO functionalized cellulose acetate, hydrogenated castor oil and a polymer chain extender, heating to 40-55° C., reacting under a protective atmosphere for 4-7 hours, and removing the solvent by rotary evaporation to obtain a modified cellulose acetate segmented polyurethane.

3. The method for preparing UV optical adhesive according to claim 1, wherein: The modified cellulose acetate segmented polyurethane has the following structure:

4. The method for preparing UV optical adhesive according to claim 1, wherein: In step (2), the molar ratio of isocyanate to hydroxyl is 1.2 to 1.

35.

5. The method for preparing UV optical adhesive according to claim 1, characterized in that: In step (2), the amount of the polymer chain extender introduced is 7 to 11 wt% of the total mass of the system; and the amount of the catalyst introduced is 0.05 to 0.07 wt% of the total mass of the system.

6. The method for preparing UV optical adhesive according to claim 1, characterized in that: The specific preparation process of step (3) is: The imidazole polymeric ionic liquid was dispersed in dichloromethane, and polymethyl methacrylate was introduced into the solution and aged for 1 to 1.5 hours. The resulting mixture was then heated at 1 to 2 mL min -1 The controlled liquid flow rate is sprayed into non-polar polyethylene terephthalate, and then atomized and dispersed into droplets with a diameter of 5 to 8 μm under the inert gas at a pressure of 10 to 20 kPa, and then sprayed into an ethyl acetate solution of modified cellulose acetate block polyurethane in batches; The mass ratio of imidazole type polymeric ionic liquid and modified cellulose acetate segmented polyurethane is 2:6.5-8.5, the pH value is adjusted to 8.5-9, and the mixture is continuously stirred for 12-15 hours at 0-5 DEG C in a protective atmosphere to obtain UV optical adhesive.

7. The method for preparing UV optical adhesive according to claim 1, characterized in that: In step (3), the preparation process of the imidazole type polymeric ionic liquid is as follows: dissolving the ionic liquid and azobisisobutyronitrile in a 25-35wt% acrylate solution, stirring for 3-4h at room temperature under a protective atmosphere, then heating to 60-80°C for reaction for 9-11h, and rotary evaporating to obtain the imidazole type polymeric ionic liquid.

8. Use of the UV optical adhesive prepared by the method according to claim 1 in low surface energy materials, characterized in that: The following steps are involved: (1) coating a composite of UV optical adhesive and photoinitiator on the surface of a substrate and irradiating with ultraviolet light to form a prefabricated film; (2) coating the cerium salt solution on the surface of the prefabricated membrane and irradiating it with ultraviolet light; (3) turning off the ultraviolet light irradiation, raising the temperature, and coating the surface of the film with a low-polarity organic solution for modification to obtain the low surface energy material.

9. The use of UV optical adhesive in low surface energy materials according to claim 8, characterized in that: In step (2), the cerium salt solution includes at least one of ammonium cerium sulfate / ethylene glycol solution, ammonium cerium nitrate / acetone solution, ammonium cerium nitrate / cyclohexanone solution or cerium chloride / hydrochloric acid solution.

Images