Prime coat composition for optical film as well as preparation method and application of prime coat composition

Abstract

The present invention relates to an undercoat composition for an optical film and a method for preparing the same. The composition comprises the following components in parts by weight: 85-95 parts of double-bond modified waterborne polyurethane with the solid content of 30%, 2-10 parts of a crosslinking agent containing silicon-hydrogen bonds and 1-5 parts of a platinum catalyst. The double-bond modified waterborne polyurethane is prepared by carrying out pH regulation, mixing and heating reaction on an aldehyde solution obtained by hydrolyzing an acetal or hemiacetal compound and a waterborne polyurethane emulsion, and carrying out post-treatment to remove small-molecule byproducts, so as to obtain the high-solid-content modified emulsion. The priming coat working solution is coated on the surface of a PET base material, and after drying and thermocuring, a compact cross-linked structure is formed through a hydrosilylation reaction. According to the invention, the adhesive force between the PET substrate and the acrylate optical resin layer is effectively enhanced, the problem that the original interface is insufficient in bonding force and easy to layer is solved, meanwhile, the process is simple and convenient, the raw material source is wide, and the method is suitable for a brightness enhancement film product for display.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer coating materials, in particular to a primer coating composition for optical film layer materials and a preparation method thereof. BACKGROUND

[0002] Polyethylene terephthalate (PET) substrate is widely used as the base material of optical functional film of brightness enhancement film in display devices due to its excellent optical and mechanical properties. However, the PET surface has high chemical inertness, which makes it difficult for the subsequently coated brightness enhancement film resin layer, usually an acrylate UV-curable resin, to form a firm interfacial bond with it, and easy to cause delamination or peeling phenomenon during use, which seriously affects the reliability of the product. In order to improve the interfacial adhesion, the industry usually introduces a primer coating layer between the PET substrate and the functional layer to achieve the improvement of the bonding force. Waterborne polyurethane is generally used as the primer material in the prior art, and by introducing a functional monomer containing an acrylate type carbon-carbon double bond or other reactive groups during the synthesis of polyurethane, the resin has the ability of light or thermal crosslinking, thereby enhancing the internal strength of the coating and the adhesion to the substrate. However, this method has several obvious limitations: first, the raw material selection flexibility is low and the cost is high, because specific functional monomers need to be introduced during polymerization, it must rely on the synthesis of special polyurethane resin, which makes the research and development cycle long and the process complex, it is difficult to directly select commercially available general-purpose, low-cost and stable performance waterborne polyurethane emulsion; second, the process controllability is poor, the introduction of active groups in the polyurethane chain may affect the storage stability of the emulsion, and cause gelation problems in the subsequent formulation and coating process; in addition, the obtained bonding force improvement effect is still insufficient, especially in the harsh reliability test of humid heat aging, it is difficult to meet the requirements of high-end display products for durable interfacial strength. Therefore, it has become a key problem to be solved in this field to develop a primer coating technology that can significantly and durably improve the interfacial bonding force between the PET substrate and the brightness enhancement film resin based on commercial general-purpose waterborne polyurethane raw materials through a simple modification method. SUMMARY

[0003] The technical problem to be solved is to overcome the shortcomings of the prior art, provide a primer coating composition and a preparation method thereof, which does not rely on special polyurethane synthesis, can be modified using commercially available general-purpose waterborne polyurethane, has flexible process, low cost, and can significantly improve the bonding force and weather resistance between the resin for brightness enhancement film and the PET substrate.

[0004] Technical scheme: A primer coating composition for optical film, characterized by: mixing the following components in parts by weight: an amino group or hydroxyl group containing waterborne polyurethane modified by a non-acrylic carbon-carbon double bond (based on 30% solid content) 85-100 parts; 2~10 parts of crosslinking agent containing silicon-hydrogen bond and non-linear silicon-oxygen main chain; 1~5 parts of platinum catalyst; 0~100000 parts of small molecule solvent.

[0005] Preferably, the water-based polyurethane emulsion contains one or more of amino groups and hydroxyl groups, and the molecular chain contains one or more of carboxylate, sulfonate, and quaternary ammonium salt groups; the small molecule solvent is one or more of other alcohols, ketones, and water.

[0006] Preferably, the water-based polyurethane containing amino or hydroxyl groups modified by non-acrylic carbon-carbon double bond is prepared by the following steps: S1. Hydrolyze acetal or hemiacetal compound containing non-acrylic carbon-carbon double bond under the condition of pH=1~4 to obtain aqueous solution of aldehyde compound containing non-acrylic carbon-carbon double bond; S2. Adjust the pH value of the hydrolyzed acetal solution of step S1, then mix it with water-based polyurethane emulsion containing amino or hydroxyl groups, and react under heating condition to obtain double bond modified water-based polyurethane; S3. Post-treat the system after step S2 reaction, remove unreacted small molecule by-products and solvent to obtain double bond modified water-based polyurethane emulsion with high solid content.

[0007] The above method for preparing a primer layer composition for optical film includes the following steps: S11. Mix and stir the double bond modified water-based polyurethane, crosslinking agent containing silicon-hydrogen bond and platinum catalyst, and one or more small molecule solvents such as other alcohols, ketones, and water in a predetermined ratio to obtain primer layer working solution; S12. Uniformly coat the primer layer working solution obtained in step S11 on the surface of thin film substrate with a thickness of 6~200µm using one of the wet film preparation tools such as wire bar, anilox roll, and micro-concave roll with a wet film thickness of 1~100µm; S13. Dry the coated substrate at 50~100℃ for 1~60min, then cure it at 90~230℃ for 1~60min to form thin film with improved UV curing oil adhesion.

[0008] Preferably, the acetal or hemiacetal compound in step S1 is propylene glycol or dimethyl acetal, and the initial concentration of the compound in the reaction system is 30%~70%, and the hydrolysis reaction is carried out at 40~80℃ for 0.5~4h.

[0009] Preferably, the hydrolyzed acetal aqueous solution in step S2 is adjusted to pH = 7.0-10.0 by adding NaOH and diluted with water to a solid content of 10%-60% in the aqueous polyurethane emulsion; and / or, Preferably, the hydrolyzed acetal aqueous solution is mixed with the aqueous polyurethane emulsion at a weight ratio of 5:95-15:85; and / or, Preferably, the reaction temperature in step S2 is 50-100℃, and the reaction time is 1-10h.

[0010] Preferably, step S3 includes first diluting the system with water to a solid content of 10%-30%, then performing vacuum distillation at 30-60℃, and finally concentrating the solid content to 20%-50%.

[0011] Preferably, the molar equivalent ratio of the carbon-carbon double bond of the double bond modified aqueous polyurethane to the silicon-hydrogen bond of the crosslinking agent containing a silicon-hydrogen bond is 1:(0.8-1.5), and the film substrate is any one of PET and PA.

[0012] Preferably, the crosslinking agent containing a silicon-hydrogen bond and having a non-linear silicon-oxygen main chain is a hydrogen-terminated T-shaped phenyl polysiloxane.

[0013] Beneficial effects: The optical film primer composition has the following advantages: 1. The present application uses platinum catalyst to catalyze the silicon-hydrogen addition reaction, so that the carbon-carbon double bond on the polyurethane molecular chain reacts with the silicon-hydrogen bond in the crosslinking agent to form a dense chemical crosslinking network structure, greatly enhancing the cohesive strength of the coating itself and improving the interfacial compatibility and force with the PET substrate and the upper bright film resin, so that the final interlayer bonding force is improved by several times, and the rigorous hatch test can be passed.

[0014] 2. The present application breaks the limitation of having to synthesize a specific polyurethane, and the aldehyde group reacts with the active groups such as amino and hydroxyl groups remaining in the polyurethane molecular chain, thereby grafting the carbon-carbon double bond to the polyurethane molecular chain. Any general-purpose aqueous polyurethane emulsion containing amino or hydroxyl groups remaining on the market can be directly selected as the base resin, the selection range is wide, and the cost advantage is obvious.

[0015] 3. The step-by-step reaction of the present application makes the process window wide and easy to control in industrial production. The final primer layer working solution is an aqueous system, which is environmentally friendly and non-polluting, and the coating process is mature. DETAILED DESCRIPTION

[0016] Synthesis Example 1 The hydroxyl-containing polyurethane resin was synthesized according to the following steps: Hexamethylene diisocyanate, polycaprolactone diol with molecular weight of 540 (trade name CAPA 2054), dimethylol propionic acid, acetone were mixed in a mass ratio of 10:20:2.2:30, heated to 55°C under nitrogen protection, and stirred for 8 h; 0.4 parts by mass of hydroxyethyl ethylenediamine was added and the reaction was continued for 0.5 h; 1.6 parts by mass of triethylamine was added; emulsification was carried out by gradually adding 80 g of water under stirring at 1000 rpm; the above emulsion was distilled under reduced pressure at 40°C to a solid content of 30%, and an aqueous polyurethane containing hydroxyl and amino groups was obtained.

[0017] Synthesis Example 2 The polyurethane resin containing acrylic type carbon-carbon double bond was synthesized according to the following steps: Hexamethylene diisocyanate, polycaprolactone diol with molecular weight of 540 (trade name CAPA 2054), dimethylol propionic acid, acetone were mixed in a mass ratio of 10:20:2.2:30, heated to 55°C under nitrogen protection, and stirred for 8 h; 0.7 parts by mass of hydroxyethyl methacrylate was added and the reaction was continued for 1 h; 1.6 parts by mass of triethylamine was added; emulsification was carried out by gradually adding 80 g of water under stirring at 1000 rpm; the above emulsion was distilled under reduced pressure at 40°C to a solid content of 30%, and an aqueous polyurethane modified with acrylic double bond was obtained.

[0018] Synthesis Example 3 The polyurethane resin containing acrylic type carbon-carbon double bond was synthesized according to the following steps: Hexamethylene diisocyanate, polycaprolactone diol with molecular weight of 540 (trade name CAPA 2054), dimethylol propionic acid, acetone were mixed in a mass ratio of 10:20:2.2:30, heated to 55°C under nitrogen protection, and stirred for 8 h; 0.7 parts by mass of hydroxyethyl methacrylate was added and the reaction was continued for 1 h; 1.6 parts by mass of triethylamine was added; emulsification was carried out by gradually adding 80 g of water under stirring at 1000 rpm; the above emulsion was distilled under reduced pressure at 40°C to a solid content of 30%, and an aqueous polyurethane modified with acrylic double bond was obtained.

[0019] Example 1

[0020] A preparation method of an optical film primer composition, comprising the following steps: S11. A double bond modified polyurethane with a solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, and water were mixed in a weight ratio of 100:6:0.1:15:100:900 to obtain a primer working solution with a solid content of 3.2%; S12. The primer working solution obtained in step S11 was bar coated on the surface of 75 pm PET substrate at a wet film thickness of 6 pm; S13. After drying the coated PET substrate at 80°C for 10 min, and curing at 150°C for 10 min, a primer layer firmly attached to the PET substrate was formed.

[0021] The double-bond modified waterborne polyurethane was prepared by the following steps: S1. Acrolein diethyl acetal was prepared into a solution with water according to a mass ratio of 40:60, and the solution pH was adjusted to 4 with 1 mol / L hydrochloric acid, and a hydrolyzed acetal solution was obtained by reacting at 60°C for 2 h; S2. The hydrolyzed acetal solution obtained in step S1 was adjusted to pH 7.5 with NaOH, and diluted with water to a solid content of 36.5%, and then mixed with waterborne polyurethane BASF Joncryl U 4190 emulsion with a solid content of 36.5% according to a weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 h to complete the reaction; S3. The solution obtained in step S2 was diluted with water to a solid content of 25%, and distilled at 40°C under reduced pressure to a final solid content of 30% to remove residual unreacted acrolein diethyl acetal and acrolein, ethanol, to obtain a double-bond modified polyurethane with a solid content of 30%.

[0022] Example 2

[0023] A preparation method of a primer composition for an optical film, comprising the following steps: S11. Double-bond modified polyurethane with a solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, and water were prepared into a primer working solution with a solid content of 3.6% according to a weight ratio of 100:10:0.1:15:100:900; S12. The primer working solution obtained in step S11 was bar coated on the surface of 75 pm PET substrate at a wet film thickness of 6 pm; S13. After drying the coated PET substrate at 80°C for 10 min, and curing at 150°C for 10 min, a primer layer firmly attached to the PET substrate was formed.

[0024] The double-bond modified waterborne polyurethane was prepared by the following steps: S1. Acrolein diethyl acetal was prepared into a solution with water according to a mass ratio of 40:60, and the solution pH was adjusted to 4 with 1 mol / L hydrochloric acid, and a hydrolyzed acetal solution was obtained by reacting at 60°C for 2 h; S2. The hydrolyzed acetal solution of step S1 was adjusted to pH 7.5 with NaOH and diluted with water to a solid content of 36.5%, and then mixed with the waterborne polyurethane BASF Joncryl U 4190 emulsion of the same solid content at a weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 hours to completion; S3. The solution of step S2 was diluted with water to a solid content of 25%, and distilled at reduced pressure at 40°C to a final solid content of 30% to remove residual unreacted hydrolyzed acetal and acrolein, ethanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0025] Example 3

[0026] A method for preparing an optical film primer composition, comprising the following steps: S11. A double bond modified polyurethane with a solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water were prepared at a weight ratio of 100:2:0.1:15:100:900 to obtain a primer working solution with a solid content of 2.9%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of a 75 μm PET substrate with a wire bar at a wet film thickness of 6 μm; S13. After drying the coated PET substrate at 80°C for 10 min, and curing at 150°C for 10 min, a primer layer firmly attached to the PET substrate was formed.

[0027] wherein the double bond modified waterborne polyurethane is prepared by the following steps: S1. Acrolein diethyl acetal was prepared into a solution with water at a mass ratio of 40:60, and the solution pH was adjusted to 4 with 1 mol / L hydrochloric acid, and reacted at 60°C for 2 h to obtain a hydrolyzed acetal solution; S2. The hydrolyzed acetal solution of step S1 was adjusted to pH 7.5 with NaOH and diluted with water to a solid content of 36.5%, and then mixed with the waterborne polyurethane BASF Joncryl U 4190 emulsion of the same solid content at a weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 hours to completion; S3. The solution of step S2 was diluted with water to a solid content of 25%, and distilled at reduced pressure at 40°C to a final solid content of 30% to remove residual unreacted hydrolyzed acetal and acrolein, ethanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0028] Example 4

[0029] A method for preparing an optical film primer composition, comprising the following steps: S11. A double bond modified polyurethane with a solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Winco, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water were mixed in a weight ratio of 100:6:0.1:15:100:900 to obtain a primer working solution with a solid content of 3.2%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of a 75 μm PET substrate with a wire bar at a wet film thickness of 6 μm; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer firmly attached to the PET substrate was formed after curing at 150°C for 10 min.

[0030] The double bond modified waterborne polyurethane was prepared by the following steps: S1. Acetaldehyde diethyl acetal was prepared into a solution with water in a mass ratio of 40:60, and the solution pH was adjusted to 4 with 1 mol / L hydrochloric acid, and the solution was reacted at 60°C for 2 h to obtain a hydrolyzed acetal solution; S2. The hydrolyzed acetal solution obtained in step S1 was adjusted to pH 7.5 with NaOH, and diluted with water to a solid content of 36.5%, and then mixed with waterborne polyurethane BASF Joncryl U 4190 emulsion with a solid content of 36.5% in a weight ratio of 15:85, and reacted at 70°C for 4 h to complete the reaction; S3. The solution obtained in step S2 was diluted with water to a solid content of 25%, and distilled at 40°C under reduced pressure to a final solid content of 30% to remove residual unreacted acetaldehyde diethyl acetal, acetaldehyde and ethanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0031] Example 5

[0032] A preparation method of an optical film primer composition, comprising the following steps: S11. A double bond modified polyurethane with a solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Winco, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water were mixed in a weight ratio of 100:6:0.1:15:100:900 to obtain a primer working solution with a solid content of 3.2%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of a 75 μm PET substrate with a wire bar at a wet film thickness of 6 μm; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer firmly attached to the PET substrate was formed after curing at 150°C for 10 min.

[0033] wherein the double bond modified waterborne polyurethane is prepared by the following steps: S1. Acrolein diethyl acetal is prepared into a solution with water according to the mass ratio of 40:60, and the solution pH is adjusted to 4 with 1 mol / L hydrochloric acid, and a hydrolyzed acetal solution is obtained by reacting at 60°C for 2 h; S2. The hydrolyzed acetal solution of step S1 is adjusted to pH 7.5 with NaOH, and then diluted with water to a solid content of 36.5%, and then mixed with the hydroxyl-containing waterborne polyurethane as described in Synthesis Example 1 according to the weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 h to complete; S3. The solution of step S2 is diluted with water to a solid content of 25%, and then distilled at 40°C under reduced pressure to a final solid content of 30% to remove residual unreacted acrolein diethyl acetal and acrolein, ethanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0034] Example 6

[0035] A preparation method of an optical film primer composition, comprising the following steps: S11. A double bond modified polyurethane with a solid content of 30%, a T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water are mixed according to the weight ratio of 100:6:0.1:15:100:900 to obtain a primer working solution with a solid content of 3.2%; S12. The primer working solution obtained in step S11 is uniformly coated on the surface of a 75 µm PET substrate with a wire bar at a wet film thickness of 6 µm; S13. After drying the coated PET substrate at 80°C for 10 min, and curing at 150°C for 10 min, a primer layer firmly attached to the PET substrate is formed.

[0036] wherein the double bond modified waterborne polyurethane is prepared by the following steps: S1. Acrolein dimethyl acetal is prepared into a solution with water according to the mass ratio of 40:60, and the solution pH is adjusted to 4 with 1 mol / L hydrochloric acid, and a hydrolyzed acetal solution is obtained by reacting at 60°C for 2 h; S2. The hydrolyzed acetal solution of step S1 is adjusted to pH 7.5 with NaOH, and then diluted with water to a solid content of 36.5%, and then mixed with the waterborne polyurethane BASF Joncryl U 4190 emulsion with the same solid content according to the weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 h to complete; S3. Dilute the solution obtained in step S2 with water to a solid content of 25%, and distill under reduced pressure at 40°C to a final solid content of 30% to remove residual unreacted propylene glycol acetal and propionaldehyde, methanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0037] Comparative Example 1 A preparation method for an optical film primer composition, comprising the following steps: S11. An aqueous polyurethane BASF Joncryl U 4190 with a solid content of 36.5%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water were prepared according to a weight ratio of 100:6:0.1:15:100:900 to obtain a primer working solution with a solid content of 3.8%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of a 75 μm PET substrate with a wire bar at a wet film thickness of 6 μm; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer was formed after curing at 150°C for 10 min.

[0038] Comparative Example 2 A preparation method for an optical film primer composition, comprising the following steps: S11. A double bond modified polyurethane with a solid content of 30%, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water were prepared according to a weight ratio of 100:0.1:15:100:900 to obtain a primer working solution with a solid content of 2.7%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of a 75 μm PET substrate with a wire bar at a wet film thickness of 6 μm; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer was formed after curing at 150°C for 10 min.

[0039] The double bond modified aqueous polyurethane was prepared by the following steps: S1. Propylene glycol acetal was prepared by mixing with water according to a mass ratio of 40:60, and the solution pH was adjusted to 4 with 1 mol / L hydrochloric acid, and the solution was reacted at 60°C for 2 h to obtain a hydrolyzed acetal solution; S2. The hydrolyzed acetal solution obtained in step S1 was adjusted to a pH of 7.5 with NaOH, and diluted with water to a solid content of 36.5%, and then mixed with an aqueous polyurethane BASF Joncryl U 4190 emulsion with a solid content of 36.5% according to a weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 h to complete the reaction; S3. Dilute the solution obtained in step S2 to a solid content of 25% with water, and distill at 40°C under reduced pressure to a final solid content of 30% to remove residual unreacted diethyl acetal of propionaldehyde and propionaldehyde, ethanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0040] Comparative Example 3 A preparation method of a primer coating composition for an optical film includes the following steps: S11. A double bond modified polyurethane with a solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water are mixed in a weight ratio of 100:25:0.1:15:100:900 to obtain a primer coating working solution with a solid content of 4.9%; S12. The primer coating working solution obtained in step S11 is uniformly coated on the surface of a 75 μm PET substrate with a wire bar at a wet film thickness of 6 μm; S13. After drying the coated PET substrate at 80°C for 10 min, a primer coating is formed after curing at 150°C for 10 min.

[0041] The double bond modified waterborne polyurethane is prepared by the following steps: S1. Diethyl acetal of propionaldehyde is prepared by mixing propionaldehyde with water in a mass ratio of 40:60, adjusting the pH of the solution to 4 with 1 mol / L hydrochloric acid, and reacting at 60°C for 2 h to obtain a hydrolyzed acetal solution; S2. The hydrolyzed acetal solution obtained in step S1 is adjusted to a pH of 7.5 with NaOH, diluted with water to a solid content of 36.5%, and then mixed with waterborne polyurethane BASF Joncryl U 4190 emulsion with a solid content of 36.5% at a weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 h to complete the reaction; S3. Dilute the solution obtained in step S2 to a solid content of 25% with water, and distill at 40°C under reduced pressure to a final solid content of 30% to remove residual unreacted diethyl acetal of propionaldehyde and propionaldehyde, ethanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0042] Comparative Example 4 A preparation method of a primer coating composition for an optical film includes the following steps: S11. A double bond modified polyurethane with a solid content of 30%, linear hydrogen-containing silicone oil YK-203 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water are mixed in a weight ratio of 100:7:0.1:15:100:900 to obtain a primer coating working solution with a solid content of 3.3%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of 75 pm PET substrate with a wire bar at a wet film thickness of 6 pm; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer was formed after curing at 150°C for 10 min.

[0043] wherein the double bond modified waterborne polyurethane is prepared by the following steps: S1. Acrolein diethyl acetal was prepared into a solution according to a mass ratio of 40:60 with water, and the solution pH was adjusted to 4 with 1 mol / L hydrochloric acid, and a hydrolyzed acetal solution was obtained after reacting at 60°C for 2 h; S2. The hydrolyzed acetal solution obtained in step S1 was adjusted to pH 7.5 with NaOH, and diluted with water to a solid content of 36.5%, and then mixed with waterborne polyurethane BASF Joncryl U 4190 emulsion with a solid content of 36.5% according to a weight ratio of hydrolyzed acetal solution: polyurethane of 5:95, and reacted at 70°C for 4 h to complete the reaction; S3. The solution obtained in step S2 was diluted with water to a solid content of 25%, and distilled at 40°C under reduced pressure to a final solid content of 30% to remove residual unreacted acrolein diethyl acetal and acrolein, ethanol, to obtain a double bond modified polyurethane with a solid content of 30%.

[0044] Comparative Example 5 A preparation method of an optical film primer composition, comprising the following steps: S11. Acrolein diethyl acetal was prepared into a solution according to a mass ratio of 40:60 with water, and the solution pH was adjusted to 4 with 1 mol / L hydrochloric acid, and a hydrolyzed acetal solution was obtained after reacting at 60°C for 2 h; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of 75 pm PET substrate with a wire bar at a wet film thickness of 6 pm; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer was formed after curing at 150°C for 10 min.

[0045] Comparative Example 6 A preparation method of an optical film primer composition, comprising the following steps: S11. An aqueous polyurethane with solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water were prepared according to the weight ratio of 100:6:0.1:15:100:900 to obtain a primer working solution with a solid content of 3.2%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of a 75 μιη PET substrate with a wire bar at a wet film thickness of 6 μιη; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer on the PET substrate was formed after curing at 150°C for 10 min.

[0046] Comparative Example 7 A preparation method for an optical film primer composition, comprising the following steps: S11. An aqueous polyurethane with solid content of 30%, T-shaped hydrogen-containing silicone oil YK-233-5000 from Zhejiang Yingke, Dow Syl OFF 4000 platinum catalyst, acetone, isopropyl alcohol, water were prepared according to the weight ratio of 100:6:0.1:15:100:900 to obtain a primer working solution with a solid content of 3.2%; S12. The primer working solution obtained in step S11 was uniformly coated on the surface of a 75 μιη PET substrate with a wire bar at a wet film thickness of 6 μιη; S13. After drying the coated PET substrate at 80°C for 10 min, a primer layer on the PET substrate was formed after curing at 150°C for 10 min.

[0047] wherein the aqueous polyurethane is prepared by the following steps: S1. Acetaldehyde diethyl acetal was prepared by mixing with water according to the mass ratio of 40:60 to prepare an acetal solution, adjusting the pH to 7.5 with NaOH, and diluting with water to a solid content of 36.5%, and then mixing with an aqueous polyurethane BASF Joncryl U 4190 emulsion with a solid content of 36.5% according to the weight ratio of acetal solution: polyurethane of 5:95, and reacting at 70°C for 4 hours to complete; S2. Step S1 was diluted with water to a solid content of 25%, and distilled at 40°C under reduced pressure to a final solid content of 30% to remove residual unreacted acetaldehyde diethyl acetal, to obtain an aqueous polyurethane with a solid content of 30%.

[0048] Performance test: Test Example 1 Bartest: The acrylic UV-curable oil for optical brightening film was applied on the 75 μm PET base film coated with the primer layer by a doctor blade with a wet film thickness of 15 μm, and then cured by irradiation with 600 mW / cm 2 of 365 nm UV irradiation power for 10 s after air insulation by a release film. After the curing was completed, the release film was removed, and the adhesion was tested according to ASTM D3359-09 using 3M 600 tape.

[0049] Test Example 2 Retention rate: The UV-cured film sample prepared as in Test Example 1 was again tested for crosshatch adhesion according to ASTM D3359-09 using 3M 600 tape after aging at 85°C, 85% humidity for 72 h.

[0050] Test Example 3 Gel rate: About 20 g of the coating solution prepared as in each of the examples and comparative examples was poured into an aluminum pan, dried at 80°C for 4 h, and then cured at 150°C for 10 min. The obtained solid was immersed in dimethyl sulfoxide at a weight ratio of 1:10, and dissolved at 120°C for 1 h. The insoluble matter was weighed, and the gel rate, i.e., the proportion of the polymer that had undergone crosslinking reaction, was calculated based on the weight ratio to the original dried solid.

[0051] Table 1 is the performance test of Examples 1-6 and Comparative Examples 1-5 Initial preparation of the cross-hatch test 85°C 85% 72h after cross-hatch test Gel fraction Example 1 5B 5B 93% Example 2 5B 4B 88% Example 3 4B 4B 88% Example 4 5B 4B 95% Example 5 5B 5B 92% Example 6 5B 4B 96% Comparative Example 1 0B 0B 0% (dissolved) Comparative Example 2 0B 0B 0% (dissolved) Comparative Example 3 1B 0B 22% Comparative Example 4 1B 1B 82% Comparative Example 5 4B 5B 90% Comparative Example 6 0B 0B 0% (dissolved) Comparative Example 7 0B 0B 0% (dissolved) It is apparent that the above-described examples are merely illustrative for the sake of clarity and are not intended to limit the scope of the embodiments. Other changes or modifications that one ordinarily skilled in the art can make based on the above description are also possible. It is not necessary or possible to exhaust all the embodiments. The changes or modifications that are thus extended are still within the scope of the present invention.

Claims

1. A base coating composition for optical films, characterized in that: It is composed of the following components in parts by weight: 85-100 parts of a waterborne polyurethane containing amino or hydroxyl groups modified from non-acrylic carbon-carbon double bonds, with a solid content of 30%; 2-10 parts of a crosslinking agent containing silane bonds and with a nonlinear silicon-oxygen backbone; 1-5 parts platinum catalyst; Small molecule solvents: 0-100,000 parts.

2. The undercoating composition for optical films according to claim 1, characterized in that: The aqueous polyurethane emulsion is a polyurethane containing one or more amino groups and hydroxyl groups, and the molecular chain contains one or more carboxylate, sulfonate, and quaternary ammonium salt groups; the small molecule solvent is one or more other alcohols, ketones, or water.

3. The undercoating composition for optical films according to claim 1, characterized in that: The aforementioned waterborne polyurethane containing amino or hydroxyl groups, modified from non-acrylic carbon-carbon double bonds, is prepared through the following steps: S1. Under pH conditions of 1 to 4, acetal or hemiacetal compounds containing non-acrylic acid carbon-carbon double bonds are hydrolyzed to obtain an aqueous solution of aldehyde compounds containing non-acrylic acid carbon-carbon double bonds. S2. The pH value of the hydrolyzed acetal solution from step S1 is adjusted, and then it is mixed with an aqueous polyurethane emulsion containing amino or hydroxyl groups and reacted under heating conditions to obtain a double-bond modified aqueous polyurethane. S3. Post-process the system after the reaction in step S2 to remove unreacted small molecule byproducts and solvents, and obtain a waterborne polyurethane emulsion with high solid content and modified double bonds.

4. The method for preparing a base coating composition for an optical film according to claim 1, characterized in that: Includes the following steps: S11. Mix the double-bond modified waterborne polyurethane, the crosslinking agent containing silicon-hydrogen bonds and the platinum catalyst, other alcohols, ketones, and one or more small molecule solvents in water in a preset ratio and stir evenly to obtain the base coating working solution. S12. The base coating working liquid obtained in step S11 is uniformly coated onto the surface of a film substrate with a thickness of 6-200µm and a temperature resistance of 100℃ or higher using a wet film preparation tool of wire bar, anilox roller, or micro-grooving roller with a wet film thickness of 1-100µm. S13. After drying the coated substrate at 50~100℃ for 1~60 min, it is cured at 90~230℃ for 1~60 min to form a film with improved UV curing oil adhesion.

5. The undercoating composition for an optical film according to claim 3, characterized in that: The acetal or hemiacetal compound mentioned in step S1 is acrolein diethanol acetal or acrolein diethanol acetal, and the initial concentration of the compound in the reaction system is 30%~70%, and the hydrolysis reaction is carried out at 40~80℃ for 0.5~4 h.

6. The undercoating composition for an optical film according to claim 3, characterized in that: In step S2, the hydrolyzed acetal aqueous solution is adjusted to pH 7.0-10.0 with NaOH, and diluted with water until the solid content of the waterborne polyurethane emulsion is 10%-60%; and / or, The hydrolyzed acetal aqueous solution and the aqueous polyurethane emulsion are mixed at a weight ratio of 5:95 to 15:85; and / or, In step S2, the reaction temperature is 50~100℃ and the reaction time is 1~10h.

7. The undercoating composition for an optical film according to claim 3, characterized in that: Step S3 includes first adding water to dilute the system to a solid content of 10%~30%, then performing vacuum distillation at 30~60℃ to finally concentrate the solid content to 20%~50%.

8. The undercoating composition for an optical film according to claim 1, characterized in that: The molar equivalent ratio of the carbon-carbon double bonds to the silane-hydrogen bonds of the crosslinking agent containing silane-hydrogen bonds in the double-bond modified waterborne polyurethane is 1:(0.8~1.5); and / or, The film substrate can be either PET or PA.

9. The undercoating composition for an optical film according to claim 1, characterized in that: The crosslinking agent containing silane-hydrogen bonds and having a nonlinear silicon-oxygen backbone is a hydrogen-terminated T-type phenyl polysiloxane.