Coating liquid

Abstract

The invention relates to a coating liquid which comprises the following components in parts by weight: 2-10 parts of water-based resin, 2-10 parts of a resin copolymer, 1-8 parts of silicon dioxide particles, 1-5 parts of a bacteriostatic agent and 95-110 parts of pure water, the water-based resin is water-based polyurethane resin, and the resin copolymer is selected from one or more of an oxazoline copolymer and a carbodiimide copolymer. According to the coating liquid designed by the invention, the waterborne polyurethane resin is taken as matrix resin, and the resin copolymer and the bacteriostatic agent are added, so that the coating liquid has excellent stability and dispersity, is easy to coat and is not easy to generate a coagulation phenomenon.

Description

Technical Field

[0001] The present invention relates to the field of optical thin films, and particularly to a coating liquid. Background Art

[0002] The polarizer is mainly used to control the light of the liquid crystal panel of the LCD. Attaching two polarizers with perpendicular absorption axes to both sides of the liquid crystal panel can control the polarization direction of the light beam. The core material of the polarizer is the polarizer after the PVA film is stretched. Due to the thin and brittle characteristics of the polarizer, it is necessary to attach protective films on both the upper and lower sides of the polarizer to protect it. Because of its stability and moisture impermeability, the PMMA film is the mainstream protective film used for polarizers at present. The structure of the PMMA film is mainly an acrylic base film, but the adhesion between acrylic and the polarizer is not good. It is often necessary to coat a layer of coating liquid that is beneficial for adhesion on the adhesion surface of the PMMA film. This coating liquid can not only increase the adhesion between the glue and the PMMA, but also prevent the film from sticking to each other after the PMMA film is wound up. Basically, the coating liquids on the market all contain anti-sticking silica. However, silica is extremely prone to producing mildew and deteriorating in an aqueous solution for a long time. The deteriorated coating liquid not only reduces the adhesion performance of the PMMA film, but the black mildew also affects the appearance of the PMMA film after coating. Due to its perishable nature, the shelf life of the coating liquid is often short, which is not conducive to storage and use, increasing the cost of PMMA film production.

[0003] The coating liquid formula designed in this application contains an antibacterial agent that can inhibit the growth of bacteria, and can effectively inhibit the deterioration caused by the invasion of microorganisms and the production of mildew in the coating liquid. In addition, the coating liquid of this application has good dispersibility and is not prone to agglomeration phenomena, and will not affect the adhesion performance when the PMMA film is adhered to the polarizer. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the present invention provides a coating liquid formula, which includes the following components in parts by weight:

[0005]

[0006]

[0007] The aqueous resin is an aqueous polyurethane resin;

[0008] The resin copolymer is selected from one or more of oxazoline and carbodiimide.

[0009] More specifically, the aqueous polyurethane resin is polymerized from 5-amino-1,3,3-trimethyl-cyclohexylmethylamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene).

[0010] More specifically, the particle size of the silica particles is 30-100 nm.

[0011] More specifically, the bacteriostatic agent is one or both of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

[0012] More specifically, the resistivity of the pure water is 10 - 18 MΩ·cm, and the pure water is sterilized by ultraviolet light with a wavelength of 180 - 254 nm.

[0013] The present application also provides a method for preparing a coating solution for a PMMA film for a polarizer, comprising the following steps: Step S1: Add pure water and an aqueous resin in sequence by weight, and stir at a speed of 200 - 500 rpm for 20 - 60 min to obtain a first mixed solution;

[0014] Step S2: Add a copolymer of resin and silica particles to the first mixed solution in sequence by weight, and stir at a speed of 250 - 550 rpm for 20 - 60 min to obtain a second mixed solution;

[0015] Step S3: Add a bacteriostatic agent to the second mixed solution by weight, stir at a speed of 250 - 550 rpm for 20 - 60 min, and stand at a pressure of -1 to -0.08 MPa for 3 - 6 h to obtain a coating solution for a PMMA film for a polarizer.

[0016] The present application also provides a method for using the coating solution, comprising the following steps: uniformly coat the coating solution on the surface of the PMMA film, and perform drying after coating;

[0017] Before coating, corona treat the PMMA base film with a power of 1 - 6 kW to reduce the contact angle of the PMMA base film surface to 40° - 65°.

[0018] More specifically, the drying temperature is set at 50 - 150 °C, and the thickness of the coating layer after drying is 200 - 800 nm.

[0019] More specifically, the coating method of the coating solution is selected from any one of wire bar coating, extrusion coating, and microgravure coating.

[0020] The beneficial effects of the present invention are:

[0021] 1) Through the formula design of the present application, the coating solution 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 lamination performance when the PMMA film is laminated into a polarizer.

[0022] 2) In the coating liquid formulation, 1,2-benzisothiazolin-3-one and / or 2-methyl-4-isothiazolin-3-one bacteriostatic agents are added, which can effectively inhibit the generation of mold caused by microbial invasion in the coating liquid, thereby preventing deterioration. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of mold detected after 3 months for the prior art coating liquid;

[0024] Figure 2 It is a schematic diagram of no mold detected after 6 months for the coating liquid of the present invention;

[0025] Figure 3 It is a schematic diagram of a small amount of mold generated after 9 months of placing the coating liquid of the present invention;

[0026] Figure 4 It is a schematic diagram of the structure of the coating liquid of the present invention coated on the surface of a PMMA film. DETAILED DESCRIPTION OF THE INVENTION

[0027] To make the objectives, technical solutions, and advantages of the implementation of the present invention clearer, the following clearly and completely describes the specific implementation manners of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0028] The present invention provides a coating liquid formulation, which includes the following components in parts by weight:

[0029]

[0030] The coating liquid designed in this application is applicable to optical film layers such as PMMA films, COP films, TAC films, and COP films. It has excellent bacteriostatic effects, can effectively inhibit the deterioration caused by the generation of mold due to microbial invasion in the coating liquid, can protect the polarizer, and extend the service life of the polarizer.

[0031] In some specific embodiments, the water-based resin is selected as the water-based polyurethane resin. The water-based polyurethane resin has good material compatibility, has good film-forming properties and adhesive properties as the main resin, is non-flammable, non-toxic, and has low volatility, is environmentally friendly, and has higher safety during production and use. The water-based polyurethane is polymerized from 5-amino-1,3,3-trimethyl-cyclohexylmethylamine and Α-hydrogen-Ω-hydroxy-poly(oxy-1,4-butylene).

[0032] In some specific embodiments, to enable tight bonding among the PMMA resin in the PMMA film, the aqueous resin in the coating solution, and the adhesive for lamination, the resin copolymer is selected from one or more of oxazoline and carbodiimide.

[0033] In some specific embodiments, to prevent adhesion between the films after the PMMA film is wound up, silica particles with a particle size of 30 - 100 nm are selected.

[0034] In some specific embodiments, to prevent mildew formation on the silica, one or two of the bacteriostatic agents 1,2 - benzisothiazolin - 3 - one and 2 - methyl - 4 - isothiazolin - 3 - one are selected.

[0035] In some specific embodiments, pure water with a resistivity of 10 - 18 MΩ·cm is selected. To prevent bacteria from being introduced into the raw material formulation, the pure water needs to be sterilized by ultraviolet light with a wavelength of 180 - 254 nm before addition.

[0036] This application also provides a method for preparing a coating solution, including the following steps:

[0037] Step S1: Add pure water and aqueous resin in sequence by weight, and stir at a speed of 200 - 500 rpm for 20 - 60 min to obtain a first mixed solution;

[0038] Step S2: Add the resin copolymer and silica particles to the first mixed solution in sequence by weight, and stir at a speed of 250 - 550 rpm for 20 - 60 min to obtain a second mixed solution;

[0039] Step S3: Add the bacteriostatic agent to the second mixed solution by weight, stir at a speed of 250 - 550 rpm for 20 - 60 min, and let it stand at a pressure of - 1 to - 0.08 MPa for 3 - 6 h to obtain the coating solution for the PMMA film of the polarizer.

[0040] This application also provides a method for using the coating solution, including the following steps: Uniformly coat the coating solution on the surface of the PMMA film, and perform drying after coating;

[0041] Before coating, corona - treat the PMMA base film with a power of 1 - 6 kW to reduce the contact angle of the PMMA base film surface to 40° - 65°, improve the wettability of the PMMA base film surface, and facilitate the uniform spreading of the coating solution on the PMMA base film surface. After uniform coating, dry at 50 - 150 °C, and the thickness of the coating layer after drying is 200 - 800 nm.

[0042] In some specific embodiments, the coating method of the coating solution is selected from any one of wire bar coating, extrusion coating, and microgravure coating. Wire bar coating means that there are circular linear protrusions on the surface of the coating roller. When the coating roller passes through the liquid tank below, the coating solution can be temporarily stored between the linear protrusions. When the coating roller rolls and contacts the PMMA film above, the coating solution is coated on the PMMA film surface; Extrusion coating means using a T-shaped extrusion orifice, and when the film passes through, the liquid can be evenly coated on the PMMA film surface; Microgravure coating means that there are fine grooves on the surface of the coating roller. When the coating roller passes through the liquid tank, the coating solution can be temporarily stored in the grooves and coated on the PMMA film surface when contacting the film surface.

[0043] In some specific embodiments, the preparation process of the PMMA film used: After melting and extruding the PMMA resin, a PMMA film with a uniform and flat surface is obtained through cooling casting and longitudinal stretching.

[0044] Based on the above ratios, some specific embodiments, comparative examples, and specific performance test results are listed below:

[0045] Example 1

[0046] Coating solution formulation selection: Aqueous resin: 3 parts of the polymer of 5-amino-1,3,3-trimethyl-cyclohexanemethanamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene), resin copolymer: 4 parts of oxazoline, silica: 2 parts with a particle size of 57 nm, bacteriostatic agent: 1 part of 1,2-benzisothiazolin-3-one, and pure water is treated by ultraviolet light.

[0047] Coating solution preparation steps: S1. Add 98 parts of pure water with a resistivity of 12.4 MΩ·cm and irradiated by 250 nm ultraviolet light and 3 parts of the polymer of 5-amino-1,3,3-trimethyl-cyclohexanemethanamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene) in sequence, and stir at a speed of 400 rpm for 40 min to obtain a first mixed solution; S2. Add 4 parts of oxazoline and 2 parts of silica particles with an average particle size of 57 nm to the first mixed solution in sequence, and stir at a speed of 450 rpm for 40 min to obtain a second mixed solution; S3. Add 1 part of 1,2-benzisothiazolin-3-one to the second mixed solution, stir at a speed of 450 rpm for 25 min, and stand for 6 h under a pressure of -0.091 MPa to obtain the coating solution for the PMMA film of the polarizer.

[0048] Coating solution coating: The surface of the PMMA film is treated by corona with a power of 3 kW, and the contact angle of the film surface is 52°. The coating solution is evenly coated on the bonding surface of the PMMA film by wire bar coating, and dried in an oven at 80 °C. The average thickness of the coating layer is measured to be 453 nm.

[0049] The above PMMA film is laminated with a polarizer and a COP film to obtain a polarizing plate.

[0050] Example 2

[0051] Coating solution formulation selection: Aqueous resin: 3 parts of the polymer of 5-amino-1,3,3-trimethyl-cyclohexanemethanamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene), resin copolymer: 4 parts of oxazoline, silica: 2 parts with a particle size of 63 nm, bacteriostatic agent: 1 part of 2-methyl-4-isothiazolin-3-one, pure water treated by ultraviolet light.

[0052] Steps for preparing the coating solution: S1. First, add 102 parts of pure water with a resistivity of 13.1 MΩ·cm and irradiated with ultraviolet light at 250 nm, and 3 parts of the polymer of 5-amino-1,3,3-trimethyl-cyclohexanemethanamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene), and stir at a speed of 450 rpm for 40 min to obtain a first mixed solution; S2. Sequentially add 4 parts of oxazoline and 2 parts of silica particles with an average particle size of 63 nm to the first mixed solution in step S1, and stir at a speed of 450 rpm for 40 min to obtain a second mixed solution; S3. Add 1 part of 2-methyl-4-isothiazolin-3-one to the second mixed solution in step S2, stir at a speed of 450 rpm for 25 min, and let it stand for 6 h under a pressure of -0.094 MPa to obtain the coating solution for the PMMA film of the polarizing plate.

[0053] Coating solution coating: After the PMMA is treated by corona with a power of 3 kW, the contact angle of the film surface is 55°. The coating solution is evenly coated on the bonding surface of the PMMA film by extrusion coating and dried in an oven at 80 °C. The average thickness of the coating layer is measured to be 449 nm.

[0054] The above PMMA film is laminated with a polarizer and a PMMA film to obtain a polarizing plate.

[0055] Example 3

[0056] Coating solution formulation selection: Aqueous resin: 3 parts of the polymer of 5-amino-1,3,3-trimethyl-cyclohexanemethanamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene), resin copolymer: 4 parts of carbodiimide, silica: 2 parts with a particle size of 60 nm, bacteriostatic agent: 1 part of a 1:1 weight mixture of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, pure water treated by ultraviolet light.

[0057] Coating solution preparation steps: S1. Add 98 parts of pure water with a resistivity of 12.7 MΩ·cm and irradiated with 250-nm ultraviolet light and 3 parts of waterborne polyurethane resin in sequence, and stir at a speed of 450 rpm for 40 min to obtain a first mixed solution; S2. Add 4 parts of carbodiimide and 2 parts of silica particles with an average particle size of 60 nm to the first mixed solution in step S1 in sequence, and stir at a speed of 450 rpm for 40 min to obtain a second mixed solution; S3. Add 1 part of a mixture of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one with a weight ratio of 1:1 to the second mixed solution in step S2, stir at a speed of 450 rpm for 25 min, and let it stand for 6 h under a pressure of -0.090 MPa to obtain a coating solution for a PMMA film for a polarizer.

[0058] Coating solution coating: After corona treatment of PMMA with a power of 3 kW, the contact angle of the film surface is 54°. The coating solution is evenly coated on the bonding surface of the PMMA film by microgravure coating, and dried in an 80°C oven. The average thickness of the coating layer is measured to be 455 nm.

[0059] Bond the above PMMA film, polarizer, and TAC film together to prepare a polarizer.

[0060] Comparative Example 1

[0061] Coating solution formulation selection: 3 parts of a polymer of 5-amino-1,3,3-trimethyl-cyclohexylmethylamine and Α-hydrogen-Ω-hydroxy-poly(oxy-1,4-butylene) as the waterborne resin, 4 parts of oxazoline as the resin copolymer, 2 parts of silica with a particle size of 60 nm, no bacteriostatic agent added, and pure water is ultraviolet-treated.

[0062] Coating solution preparation steps: S1. Add 98 parts of pure water with a resistivity of 12.8 MΩ·cm and irradiated with 250-nm ultraviolet light and 3 parts of waterborne polyurethane resin in sequence, and stir at a speed of 400 rpm for 40 min to obtain a first mixed solution; S2. Add 4 parts of oxazoline and 2 parts of silica particles with an average particle size of 59 nm to the first mixed solution in step S1 in sequence, and stir at a speed of 450 rpm for 40 min, and let it stand for 6 h under a pressure of -0.090 MPa to obtain a coating solution for a PMMA film for a polarizer.

[0063] Coating solution coating: After corona treatment of PMMA with a power of 3 kW, the contact angle of the film surface is 53°. The coating solution is evenly coated on the bonding surface of the PMMA film by wire bar coating, and dried in an 80°C oven. The average thickness of the coating layer is 456 nm.

[0064] Bond the above PMMA film, polarizer, and COP film together to prepare a polarizer.

[0065] Comparative Example 2

[0066] Coating solution formulation selection: Aqueous resin: 3 parts of the polymer of 5-amino-1,3,3-trimethyl-cyclohexanemethanamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene); Resin copolymer: 4 parts of carbodiimide; Silicon dioxide: 2 parts with a particle size of 55 nm; Bacteriostat: 1 part of 1,2-benzisothiazol-3-one; Pure water is not treated by ultraviolet light.

[0067] Coating solution preparation steps: S1. Add 98 parts of untreated pure water and 3 parts of aqueous polyurethane resin in sequence, and stir at a speed of 400 rpm for 40 min to obtain a first mixed solution; S2. Add 4 parts of carbodiimide and 2 parts of silicon dioxide particles with an average particle size of 55 nm to the first mixed solution in step S1 in sequence, and stir at a speed of 450 rpm for 40 min to obtain a second mixed solution; S3. Add 1 part of 1,2-benzisothiazol-3-one to the second mixed solution in step S2, stir at a speed of 450 rpm for 25 min, and let it stand at a pressure of -0.094 MPa for 6 h to obtain a coating solution for the PMMA film of the polarizer.

[0068] Coating solution coating: The PMMA film is not treated by corona discharge, the contact angle of the film surface is 75°, and the coating solution is evenly coated on the bonding surface of the PMMA film by wire bar coating, and dried in an oven at 80 °C to obtain a PMMA film with a coating layer thickness of 455 nm.

[0069] Comparative Example 3

[0070] Coating solution formulation selection: Aqueous resin: 3 parts of the polymer of 5-amino-1,3,3-trimethyl-cyclohexanemethanamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene); Resin copolymer: 4 parts of oxazoline; Silicon dioxide: 2 parts with a particle size of 111 nm; Bacteriostat: 1 part of 1,2-benzisothiazol-3-one; Pure water is treated by ultraviolet light.

[0071] Coating solution preparation steps: S1. Add 98 parts of pure water with a resistivity of 12.7 MΩ·cm and irradiated by 250 nm ultraviolet light and 3 parts of aqueous polyurethane resin in sequence, and stir at a speed of 400 rpm for 40 min to obtain a first mixed solution; S2. Add 4 parts of oxazoline and 2 parts of silicon dioxide particles with an average particle size of 55 nm to the first mixed solution in step S1 in sequence, and stir at a speed of 450 rpm for 40 min to obtain a second mixed solution; S3. Add 1 part of 1,2-benzisothiazol-3-one to the second mixed solution in step S2, stir at a speed of 450 rpm for 25 min, and let it stand at a pressure of -0.094 MPa for 6 h to obtain a coating solution for the PMMA film of the polarizer.

[0072] Coating solution coating: The PMMA film was not treated by corona discharge, and the contact angle of the film surface was 75°. The coating solution was evenly coated on the bonding surface of the PMMA film by rod coating, and dried in an oven at 80 °C. The PMMA film with a coating layer thickness of 455 nm was obtained.

[0073] Table 1: Composite materials and performance evaluation results of examples and comparative examples

[0074]

[0075] It can be seen from the performance test results that in Examples 1 to 3, no mold was detected in the finished coating solution after 6 months when the bacteriostatic agent was added to the coating solution formulation. Comparing Examples 1 to 3 with Comparative Example 1, if the bacteriostatic agent was not added, mold was detected in the finished coating solution after 3 months. Comparing Example 1 with Comparative Example 2, if the bacteriostatic agent was added but the pure water was not sterilized, mold was detected in the finished coating solution after 5 months. Thus, it can be proved that the coating solution after adding the bacteriostatic agent and sterilizing the pure water is not likely to produce mold again, and the storage period of the coating solution can be greatly increased. Comparing Example 1 with Comparative Example 2, if the bonding surface of the PMMA film was not treated by corona discharge before coating the coating solution, the bonding performance of the PMMA film would be affected. Comparing Example 1 with Comparative Example 3, if the particle size of the silica particles in the coating solution was not in the range of 30 to 100 nm, the bonding property of the PMMA film would be affected.

[0076] 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 principle 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 liquid, characterized in that, It comprises the following components in parts by weight: The aqueous resin is aqueous polyurethane; The resin copolymer is selected from one or more of oxazoline copolymers and carbodiimide copolymers.

2. The coating liquid according to claim 1, wherein The aqueous polyurethane resin is polymerized from 5-amino-1,3,3-trimethyl-cyclohexylmethylamine and Α-hydro-Ω-hydroxy-poly(oxy-1,4-butylene).

3. The coating liquid according to claim 1, wherein The particle size of the silica particles is 30 to 100 nm.

4. The coating liquid according to claim 1, wherein The bacteriostatic agent is selected from one or more of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

5. The coating liquid according to claim 1, characterized in that, The resistivity of the pure water is 10 to 18 MΩ·cm.

6. The coating liquid according to claim 1, wherein The pure water is treated by ultraviolet light sterilization at 180 to 254 nm.

7. A preparation method of the coating liquid according to any one of claims 1-5, characterized in that, It comprises the following steps: Step S1: Add pure water and aqueous resin in sequence by weight, and stir at a speed of 200 to 500 rpm for 20 to 60 min to obtain a first mixed solution; Step S2: Add the resin copolymer and silica particles to the first mixed solution in sequence by weight, and stir at a speed of 250 to 550 rpm for 20 to 60 min to obtain a second mixed solution; Step S3: Add the bacteriostatic agent to the second mixed solution by weight, stir at a speed of 250 to 550 rpm for 20 to 60 min, and stand at a pressure of -1 to -0.08 MPa for 3 to 6 h to obtain a coating liquid for the PMMA film for polarizers.

8. A method for using the coating liquid according to any one of claims 1-5, characterized in that, It comprises the following steps: uniformly coat the coating liquid on the surface of the PMMA film, and dry it after coating; before coating, treat the PMMA base film with corona at a power of 1 to 6 kW to reduce the contact angle of the PMMA base film surface to 40° to 65°.

9. The method for using the coating liquid according to claim 8, characterized in that, The drying temperature is set at 50 to 150 °C, and the thickness of the coating layer after drying is 200 to 800 nm.

10. The method for using the coating liquid according to claim 8, wherein The coating method of the coating liquid is selected from any one of wire bar coating, extrusion coating, and microgravure coating.

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