Coating liquid for improving adhesion performance of PMMA (polymethyl methacrylate) film for polaroid

Abstract

The invention provides a coating liquid for improving the attaching performance of a PMMA film for a polaroid. The coating liquid comprises the following components: 2-10 parts of water-based resin, 1-8 parts of a silicon dioxide solution containing an oxazoline copolymer, 3-15 parts of an organic auxiliary agent and 90-110 parts of deionized water. According to the coating liquid designed by the invention, the main component of the adhesive or the component reacting with the adhesive is added, and different production conditions are matched, so that the reaction speed and reaction degree of the coating and the adhesive can be improved, the reaction time of the coating and the adhesive can be shortened, and the coating and the adhesive can be connected more firmly; therefore, the film materials in the polaroid are adhered and are not easy to layer. The coating liquid designed by the invention is stable in property and easy to store, and does not influence the characteristics of PMMA.

Description

Technical Field

[0001] The present invention relates to the field of optical thin films, and in particular to a coating liquid for improving the bonding performance of PMMA films used in polarizers. Background Art

[0002] A polarizer is composed of a PVA film, upper and lower substrates, a protective film, a release film, and a pressure-sensitive adhesive, and is an essential component for the imaging of a display module. Two polarizers are required in an LCD module, which are respectively located on both sides of the glass substrate. The lower polarizer converts the backlight beam into polarized light, and the upper polarizer analyzes the polarized light modulated by liquid crystal electricity. Therefore, no picture can be displayed without any one of the polarizers. And the polarizer obtained by stretching the PVA film is an important part of the entire polarizer. However, the characteristics of the polarizer are fragile, so it is particularly necessary to add protective films on the upper and lower sides of the polarizer.

[0003] The PMMA film can be used as the upper and lower protective films of the polarizer and belongs to a hydrophobic material. Currently, it is the mainstream material of the polarizer. The PMMA film is called polymethyl methacrylate film, commonly known as acrylic film or plexiglass film. It has basic characteristics such as excellent weather resistance and high transmittance, and the light conduction is uniform, so no complex optical simulation and optical structure design are required. In addition, the PMMA film has good heat resistance, high humidity resistance, and good aging resistance. In order to improve the adhesion between the PMMA film and the PVA film and avoid poor adhesion between the film materials, a coating liquid is usually applied to the PMMA film.

[0004] During the lamination process, due to the changes in the manufacturer's adhesive and production conditions, the adhesion between the PMMA film and the polarizer is insufficient, making it difficult to sell the product and causing doubts from downstream factories about the product.

[0005] The coating liquid (Primer) in this application contains an adhesive component or a component that can react and combine with the adhesive, which can effectively increase the adhesion between the PMMA film and the PVA film and prevent the polarizer from delaminating. At the same time, this additive will not affect the properties of the original components and cause product deterioration. And the added components are soluble in water and the original components, and will not cause solution stratification and precipitation. Summary of the Invention

[0006] To overcome the deficiencies of the prior art, the present invention provides a coating liquid for improving the bonding adhesion of PMMA films used in polarizers, which comprises the following components in parts by weight:

[0007]

[0008] More specifically, the aqueous resin is an aqueous polyurethane resin.

[0009] More specifically, the oxazoline-containing copolymer comprises dioxazoline and acrylic acid-grafted oxazoline, preferably a silica solution of dioxazoline.

[0010] More specifically, the method for preparing the silica solution of the oxazoline-containing copolymer comprises the following steps:

[0011] S1. Calcining silicon chloride in a hydrogen and oxygen flame to undergo a high-temperature hydrolysis reaction to generate fumed silica;

[0012] S2. Placing the fumed silica in an aggregator to integrate silica particles, and then collecting them in a cyclone separator and feeding them into a deacidification furnace for deacidification treatment to obtain finished nano-SiO2;

[0013] S3. Uniformly dispersing the finished nano-SiO2 in an oxazoline-containing copolymer solution to obtain a silica solution of the oxazoline-containing copolymer.

[0014] More specifically, the particle size of the silica particles in the silica solution of the oxazoline-containing copolymer is 40-110 nm.

[0015] More specifically, the organic auxiliary agent is selected from one or more of a modified acrylamide monomer, acryloylmorpholine, and carbodiimide.

[0016] More specifically, the modified acrylamide monomer comprises a urethane-modified acrylamide and a hydroxyethyl-modified acrylamide, preferably a hydroxyethyl-modified acrylamide.

[0017] More specifically, the resistivity of the deionized water is 10-20 MΩ·cm.

[0018] This application also provides a method for preparing a coating solution used for improving the adhesion of the PMMA film for a polarizer, comprising the following steps:

[0019] S4. Mixing a modified acrylamide monomer, acryloylmorpholine, carbodiimide, and an aqueous resin by weight, and stirring at a speed of 250-500 rpm for 20-60 min to obtain a first mixed solution;

[0020] S5. Adding the first mixed solution to deionized water and stirring at a speed of 200-400 rpm for 20-60 min to obtain a second mixed solution;

[0021] S6. Add a silica solution containing an oxazoline copolymer to the second mixed solution, stir at a speed of 200 - 500 rpm for 20 - 40 min. After stirring evenly, filter it through a filter cyclically for 20 - 60 min. After cyclic filtration, let it stand in a low-pressure environment of 0 to -0.1 Mpa for 3 - 6 h until the bubbles completely disappear to obtain the coating liquid for the PMMA film for polarizers.

[0022] More specifically, in step S5, the pore size of the filter element of the filter is 1 - 10 μm.

[0023] This application also provides a polarizer. The main part of the polarizer consists of an upper protective film, a polarizer, and a lower protective film from top to bottom. The upper protective film can be selected as a PMMA film, the polarizer is an extended polyvinyl alcohol film, and the lower protective film can be selected as one of a PMMA film, a COP film, and a TAC film. Among them, between the PMMA protective film and the polarizer, it is adhered by the above-mentioned Primer containing organic additives and an adhesive.

[0024] Advantages of the present invention:

[0025] 1. The main component of the adhesive or a component that reacts with the adhesive is added to this coating liquid. With different production conditions, it can improve the reaction speed and degree between the coating and the adhesive, and shorten the reaction time between the coating and the adhesive, making the connection between the two stronger.

[0026] 2. This coating liquid has excellent stability and dispersibility, is not prone to agglomeration, is easy to coat, does not affect the optical properties of the PMMA film, and does not affect the laminating performance when the PMMA film is laminated into a polarizer. Description of the drawings

[0027] Figure 1 It is a schematic diagram of adding to a polarizer with a PMMA + PMMA structure of the present invention;

[0028] Figure 2 It is a schematic diagram of adding to a polarizer with a PMMA + TAC structure of the present invention;

[0029] Figure 3 It is a schematic diagram of the additive for a polarizer with a PMMA + COP structure of the present invention;

[0030] Figure 4 It is a photo of the delaminated structure observed by SEM after slicing a polarizer without using the coating liquid of the present invention;

[0031] Figure 5 It is a photo of the tight structure observed by SEM after slicing a polarizer using the coating liquid of the present invention. Detailed implementation manners

[0032] To make the purpose, technical solutions, and advantages of the implementation of the present invention clearer, the following provides a clear and complete description of the specific implementation manners of the present invention. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0033] A coating solution for improving the adhesion of PMMA film used in polarizers, comprising the following components in parts by weight: 2 - 10 parts of water-based resin, 1 - 8 parts of silica solution containing oxazoline copolymer, 3 - 15 parts of organic auxiliary, and 90 - 110 parts of deionized water.

[0034] In some specific embodiments, the water-based resin is selected as a one-component water-soluble polyurethane. The one-component water-soluble polyurethane has good material compatibility, and as the main resin, it has good film-forming properties and adhesion performance. It is not flammable, non-toxic, and has low volatility, being environmentally friendly and having higher safety during production and use.

[0035] In some specific embodiments, a silica solution fully dissolved in dioxazoline is used, and the solution preparation method includes the following steps:

[0036] S1. Calcinate silicon chloride in a hydrogen and oxygen flame to undergo a high-temperature hydrolysis reaction to generate fumed silica;

[0037] S2. Place the fumed silica in an aggregator to integrate silica particles, and then collect them through a cyclone separator and perform deacidification treatment in a deacidification furnace to obtain the finished product nano-SiO2;

[0038] S3. Uniformly disperse the finished product nano-SiO2 in a dioxazoline solution to obtain a silica solution containing oxazoline copolymer.

[0039] In some specific embodiments, considering that the film material is produced in the form of a roll, to prevent adhesion between film materials and without affecting the light transmittance of the film material, the particle size of silica particles in the silica solution containing oxazoline copolymer is 40 - 110 nm.

[0040] In some specific embodiments, the organic auxiliary is selected from one or more of modified acrylamide monomers, acryloylmorpholine, and carbodiimide.

[0041] In some specific embodiments, to avoid the reaction between impurity ions and each component during preparation, which may affect the performance of the finished coating solution, the resistivity of the deionized water is required to be 10 - 20 MΩ·cm.

[0042] The present application also provides a preparation method of a coating liquid for improving the adhesion of PMMA film used for polarizing films, comprising the following steps:

[0043] S4. Mix a modified acrylamide monomer, acryloylmorpholine, carbodiimide and an aqueous resin by weight, and stir at a rotation speed of 250 - 500 rpm for 20 - 60 min to obtain a first mixed solution;

[0044] S5. Add the first mixed solution to deionized water, and stir at a rotation speed of 200 - 400 rpm for 20 - 60 min to obtain a second mixed solution;

[0045] S6. Add a silica solution containing an oxazoline copolymer to the second mixed solution, stir at a rotation speed of 200 - 500 rpm for 20 - 40 min, stir evenly, then circulate and filter through a filter for 20 - 60 min. After circulation filtration, let it stand in a low - pressure environment of 0 to - 0.1 Mpa for 3 - 6 h. When the bubbles completely disappear, a coating liquid for PMMA film used for polarizing films is obtained.

[0046] In some specific embodiments, to better eliminate the tiny bubbles remaining in the coating liquid, in step S5, a filter with a filter element pore size of 1 - 10 μm is used.

[0047] In some specific embodiments, when the coating liquid designed in the present application is canned from the tank to the packaging barrel, preferably, the pressure of the tank is between - 0.1 and 1 MPa, the pressure of the canning pump ≤ 0.2 MPa. It is required that the pipeline at the canning port uses a plastic soft belt, and the plastic soft belt is connected to the bottom of the packaging barrel. When coating on the PMMA base film, preferably, the Coater roller is an extrusion - type steel wire squeegee D - Bar, with a length of 1 - 2 meters, an angle of 0° - 85°, a squeegee diameter of 9 - 12 mm, and a surface treatment of HCr hard chromium, which can obtain a better coating effect without contaminating the coating liquid.

[0048] Based on the above ratios, the following lists some specific examples, comparative examples and specific performance test results:

[0049] Example 1:

[0050] Coating liquid formula: one - component water - soluble polyurethane, 5 parts; organic auxiliary agent: hydroxyethyl - modified acrylamide, 3 parts; SiO2 solution dissolved in dioxazoline, 3 parts.

[0051] Preparation steps of the coating solution: S1. Add 3 parts of hydroxyethyl-modified acrylamide and 5 parts of one-component water-soluble polyurethane in sequence by weight, and stir for 30 min at a rotation speed of 250 rpm to obtain a first mixed solution; S2. Add the first mixed solution to 96 parts of deionized water, and stir for 30 min at a rotation speed of 250 rpm to obtain a second mixed solution; S3. Add 3 parts of silica solution containing dioxazoline to the second mixed solution in step S2, and stir for 30 min at a rotation speed of 300 rpm; S4. Insert the two inlet and outlet tubes of the filter into the solution, circulate the solution through a 5-μm filter element for 30 min, and let it stand for 4 h under a pressure of -0.096 MPa. After the bubbles are completely eliminated, the coating solution for the PMMA film of the polarizer is obtained.

[0052] When the coating solution is filled from the tank into the packaging barrel, the pressure of the tank is 0.01 MPa, and the pressure of the filling pump is 0.18 MPa. It is required that the pipeline at the filling port uses a plastic soft belt, and the plastic soft belt is connected to the bottom of the packaging barrel.

[0053] When the prepared coating solution is coated on the PMMA base film, the Coater roller used is an extrusion type steel wire squeegee D-Bar, with a length of 1.9 m, an angle of 45°, a squeegee diameter of 9 mm, and a surface treatment of HCr hard chromium. Then, the above PMMA film, polarizer, and PMMA film are laminated between the three layers to obtain a polarizer as shown in Figure 1 the figure.

[0054] Example 2:

[0055] Coating solution formula: 5 parts of one-component water-soluble polyurethane; organic additives: 3 parts of hydroxyethyl-modified acrylamide, 3 parts of 4-acryloylmorpholine; 3 parts of SiO2 solution dissolved in dioxazoline.

[0056] Preparation steps of the coating solution: S1. Add 3 parts of hydroxyethyl-modified acrylamide, 3 parts of 4-acryloylmorpholine, and 5 parts of one-component water-soluble polyurethane in sequence by weight, and stir for 30 min at a rotation speed of 250 rpm to obtain a first mixed solution; S2. Add the first mixed solution in step S1 to 93 parts of deionized water, and stir for 30 min at a rotation speed of 250 rpm to obtain a second mixed solution; S3. Add 3 parts of silica solution containing dioxazoline to the second mixed solution in step S2, and stir for 30 min at a rotation speed of 300 rpm; S4. Insert the two inlet and outlet tubes of the filter into the solution, circulate the solution through a 5-μm filter element for 30 min, and let it stand for 4 h under a pressure of -0.095 MPa. After the bubbles are completely eliminated, the coating solution for the PMMA film of the polarizer is obtained.

[0057] When the coating liquid is filled from the tank into the packaging barrel, the pressure of the tank is 0.01 MPa, and the pressure of the filling pump is 0.18 MPa. It is required that the pipeline at the filling port uses a plastic flexible belt, and the plastic flexible belt is connected to the bottom of the packaging barrel.

[0058] When the prepared coating liquid is coated on the PMMA base film, the Coater roller used is an extrusion type wire squeegee D-Bar, with a length of 1.9 meters, an angle of 45°, a squeegee diameter of 9 mm, and a surface treatment of HCr hard chromium. Then, the above PMMA film is laminated with a polarizer and a COP film to obtain a polarizer as Figure 3 shown.

[0059] Example 3:

[0060] Coating liquid formula: 5 parts of one-component water-soluble polyurethane; organic auxiliary agent: 3 parts of hydroxycarbodiimide; 3 parts of SiO2 solution dissolved in dioxazoline.

[0061] Preparation steps of the coating liquid: S1. Add 3 parts of carbodiimide and 5 parts of one-component water-soluble polyurethane in sequence, and stir at a speed of 250 rpm for 30 min to obtain a first mixed solution; S2. Add the first mixed solution in step S1 to 96 parts of deionized water, and stir at a speed of 250 rpm for 30 min to obtain a second mixed solution; S3. Add 3 parts of silica solution containing dioxazoline to the second mixed solution in step S2, and stir at a speed of 300 rpm for 30 min; S4. Insert the two inlet and outlet tubes of the filter into the solution, circulate the solution through a 5-micron filter element for 30 min, and let it stand at a pressure of -0.094 MPa for 4 h. After the bubbles are completely eliminated, the coating liquid for the PMMA film of the polarizer is obtained.

[0062] When the coating liquid is filled from the tank into the packaging barrel, the pressure of the tank is 0.01 MPa, and the pressure of the filling pump is 0.18 MPa. It is required that the pipeline at the filling port uses a plastic flexible belt, and the plastic flexible belt is connected to the bottom of the packaging barrel.

[0063] When the prepared coating liquid is coated on the PMMA base film, the Coater roller used is an extrusion type wire squeegee D-Bar, with a length of 1.8 meters, an angle of 45°, a squeegee diameter of 9 mm, and a surface treatment of HCr hard chromium. Then, the above PMMA film is laminated with a polarizer and a TAC film to obtain a polarizer as Figure 2 shown.

[0064] Comparative Example 1:

[0065] Coating liquid formula: 5 parts of one-component water-soluble polyurethane; 3 parts of SiO2 solution containing dioxazoline.

[0066] Preparation steps of the coating solution: S1. Add 99 parts of deionized water and 5 parts of one-component water-soluble polyurethane in sequence, and stir for 30 min at a rotation speed of 250 rpm to obtain a first mixed solution; S2. Add 3 parts of silica solution containing dioxazoline to the first mixed solution in step S1, and stir for 30 min at a rotation speed of 300 rpm; S3. Insert the two inlet and outlet tubes of the filter into the solution, circulate the solution through a 5-μm filter element for 30 min, and let it stand for 4 h under a pressure of -0.096 MPa. After the bubbles are completely eliminated, the coating solution for the PMMA film for polarizers is obtained.

[0067] When the coating solution is filled from the tank into the packaging barrel, the pressure of the tank is 0.01 MPa, and the pressure of the filling pump is 0.18 MPa. It is required that the pipeline at the filling port uses a plastic soft belt, and the plastic soft belt is connected to the bottom of the packaging barrel.

[0068] When the prepared coating solution is coated on the PMMA base film, the Coater roller used is an extrusion type wire scraping bar D-Bar, with a length of 1.9 m, an angle of 45°, a scraping bar diameter of 9 mm, and a surface treatment of HCr hard chromium. The above PMMA film is laminated with the polarizer and the PMMA film to prepare a polarizer.

[0069] Comparative Example 2:

[0070] Coating solution formula: 5 parts of one-component water-soluble polyurethane; organic auxiliary agent: 3 parts of hydroxyethyl-modified acrylamide; 3 parts of SiO2 solution dissolved in dioxazoline.

[0071] Preparation steps of the coating solution: S1. Add 3 parts of hydroxyethyl-modified acrylamide and 5 parts of one-component water-soluble polyurethane in sequence, and stir for 30 min at a rotation speed of 250 rpm to obtain a first mixed solution; S2. Add the first mixed solution in step S1 to 96 parts of deionized water, and stir for 30 min at a rotation speed of 250 rpm to obtain a second mixed solution; S3. Add 3 parts of silica solution containing dioxazoline to the second mixed solution in step S2, and stir for 30 min at a rotation speed of 300 rpm, and let it stand for 4 h under a pressure of -0.096 MPa. After the bubbles are completely eliminated, the coating solution for the PMMA film for polarizers is obtained.

[0072] When the coating solution is filled from the tank into the packaging barrel, the pressure of the tank is 0.01 MPa, and the pressure of the filling pump is 0.18 MPa. It is required that the pipeline at the filling port uses a plastic soft belt, and the plastic soft belt is connected to the bottom of the packaging barrel. When the prepared coating solution is coated on the PMMA base film, the Coater roller used is an extrusion type wire scraping bar D-Bar, with a length of 1.9 m, an angle of 45°, a scraping bar diameter of 9 mm, and a surface treatment of HCr hard chromium. Then the above PMMA film is laminated with the polarizer and the PMMA film to prepare a polarizer.

[0073] Table 1: Composite Materials and Performance Evaluation Results of Examples and Comparative Examples

[0074]

[0075]

[0076] From the appearance inspection and peel strength test of Examples 1 to 3, it can be seen that the coating liquid designed in this application is applicable to different polarizer structural layers, including the bonding ability after bonding with different types of additives in the PMMA + polarizer + PMMA structure, PMMA + polarizer + COP structure, and PMMA + polarizer + TAC structure has been improved.

[0077] Comparing Example 1 with Comparative Example 1, for the hydrophobic polarizer of PMMA film + polarizer + PMMA film, after adding the organic auxiliary agent, the peel strength of Example 1 is higher than that of Comparative Example 1 when actually laminating the polarizer, improving the adhesion between the polarizer layers.

[0078] Comparing Example 1 with Comparative Example 2, for the polarizer of PMMA film + polarizer + PMMA structure, after using filtration and circulation, with the single stirring method of Comparative Example 2, after online coating and laminating with the polarizer, the peel strength of Example 1 is higher than that of Comparative Example 2. The adhesion ability of Example 1 is better than that of Comparative Example 2.

[0079] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principles and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.

Claims

1. A coating solution for improving the bonding adhesion of PMMA film for polarizer, characterized in that, It comprises the following components by weight parts: 2 - 10 parts of aqueous resin; 1 - 8 parts of silica solution containing oxazoline copolymer; 3 - 15 parts of organic auxiliary agent; 90 - 110 parts of deionized water.

2. The coating liquid for improving the adhesion of the PMMA film for the polarizer according to claim 1, wherein The aqueous resin is aqueous polyurethane resin.

3. The coating liquid for improving the adhesion of the PMMA film for the polarizer according to claim 1, wherein, The silica solution containing oxazoline copolymer is preferably silica solution of dioxazoline.

4. The coating liquid for improving the adhesion of the PMMA film for the polarizer according to claim 1, wherein The silica solution containing oxazoline copolymer is prepared by the following steps: S1. Calcinate silicon chloride in a hydrogen and oxygen flame to undergo a high - temperature hydrolysis reaction to generate fumed silica; S2. Place the fumed silica in an aggregator to integrate into silica particles, and then collect them in a cyclone separator and put them into a deacidification furnace for deacidification treatment to obtain the finished nano - SiO₂; S3. Uniformly disperse the finished nano - SiO₂ in the oxazoline copolymer solution to obtain the silica solution containing oxazoline copolymer.

5. The coating liquid for improving the adhesion of the PMMA film for the polarizer according to claim 1, characterized in that, The particle size of silica particles in the silica solution containing oxazoline copolymer is 20 - 110 nm.

6. The coating liquid for improving the adhesion of the PMMA film for the polarizer according to claim 1, characterized in that, The organic auxiliary agent is selected from one or more of modified acrylamide monomer, acrylmorpholine, and carbodiimide.

7. The coating liquid for improving the adhesion of the PMMA film for the polarizer according to claim 6, characterized in that, The modified acrylamide monomer is preferably hydroxyethyl - modified acrylamide.

8. The coating liquid for improving the adhesion of the PMMA film for the polarizer according to claim 1, wherein, The resistivity of the deionized water is 10 - 20 MΩ·cm.

9. A preparation method of a coating liquid for improving the adhesion of a PMMA film for a polarizer as described in any one of claims 1-8, characterized in that, It includes the following steps: S4. Mix the modified acrylamide monomer, acrylmorpholine, carbodiimide and aqueous resin by weight parts, and stir at a speed of 250 - 500 rpm for 20 - 60 min to obtain a first mixed solution; S5. Add the first mixed solution to deionized water, and stir at a speed of 200 - 400 rpm for 20 - 60 min to obtain a second mixed solution; S6. Add the silica solution containing oxazoline copolymer to the second mixed solution, stir at a speed of 200 - 500 rpm for 20 - 40 min, stir evenly and then circulate and filter through a filter for 20 - 60 min. After circulation filtration, let it stand in a low - pressure environment of 0 - -0.1 Mpa for 3 - 6 h until the bubbles completely disappear to obtain the coating liquid for PMMA film of polarizer.

10. The preparation method of the coating liquid for enhancing the adhesion of the PMMA film for the polarizer according to claim 9, wherein, In step S5, the pore of the filter element of the filter is 1 - 10 μm.

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