A high dimensional stability release film base film for polarizers

Abstract

This invention relates to the field of optical thin film technology, specifically disclosing a high-dimensional stability release film base film for polarizers and its preparation method. The base film has an ABC three-layer co-extrusion structure. Layer A contains intercalated modified montmorillonite functional filler prepared by a specific ATRP method, simultaneously grafted with styrene, methacrylic acid, glycidyl methacrylate, and KH570 modified nano-SiO₂. Layer B uses special polyester chips obtained by copolymerizing terephthalic acid, ethylene glycol, adipic acid, polyether glycol, and dimethyl terephthalate, and blended with MAH-g-PET and an antistatic agent. Layer C is composed of optical-grade PET, special polyester chips, and TPEE blended together. This invention, through innovative material combination and three-layer structure design, synergistically achieves low heat shrinkage rate, high release agent adhesion, excellent peel strength stability, antistatic properties, and anti-curling properties on a single base film, making it suitable for the manufacture of high-end polarizers.

Description

Technical Field

[0001] This invention relates to the field of polarizer composite film technology, specifically to a high dimensional stability release film base film for polarizers. Background Technology

[0002] Polarizing films are mainly used in various optical instruments such as displays, digital cameras, and projectors. They are multi-layered composite films, including a surface protective film, a polarizing substrate layer, an inner protective film, an optical pressure-sensitive adhesive layer, and a release film layer. Polarizing films are adhered to liquid crystal displays using pressure-sensitive adhesive. Before lamination, the release film protects the integrity and uniformity of the pressure-sensitive adhesive layer, preventing defects such as air bubbles and impurities from forming during lamination. Release films typically use polyethylene terephthalate (PET), requiring high light transmittance, mechanical properties, and surface smoothness. Currently, release film base films have the following problems: 1) High thermal shrinkage rate, easily deformed by heat during coating and subsequent processing, leading to uneven release agent coating and fluctuating peel force; 2) Low surface energy and poor uniformity, affecting the adhesion and spreading of the release agent; 3) Insufficient performance, potentially generating discharge sparks during peeling that could damage precision circuits or attract dust to contaminate the adhesive surface; 4) Excessive rigidity, easily causing warping after slitting and winding. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention achieves high dimensional stability through a structural design of different functional layers, ensuring that the upper and lower surfaces satisfy surface energy stability for easy release agent coating, and providing moderate toughness to prevent warping.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A high-dimensional stability release film base film for polarizers, wherein the base film has an ABC three-layer co-extrusion structure, wherein layers A and C are surface layers and layer B is a core layer;

[0006] Layer A comprises the following components by weight: 100 parts optical grade PET, 5-12 parts functional filler;

[0007] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 1-3 parts antistatic agent;

[0008] Layer C comprises the following components by weight: 50-80 parts optical grade PET, 20-50 parts specialty polyester chips, and 10-20 parts TPEE;

[0009] The functional filler is obtained by intercalating montmorillonite with ATRP initiator, which has cationic surface activity, and then adding styrene, methacrylic acid, glycidyl methacrylate and KH570 modified nano-SiO2 for in-situ graft polymerization.

[0010] The polyester chips are prepared by a series of esterification reactions, transesterification reactions, and polycondensation reactions of terephthalic acid, ethylene glycol, adipic acid, polyether glycol, and dimethyl terephthalate.

[0011] Furthermore, the thickness of layer A is 10~15 μm, the thickness of layer B is 12~18 μm, and the thickness of layer C is 20~25 μm.

[0012] Furthermore, the antistatic agent is a polyether ester amide or an acrylate copolymer containing a quaternary ammonium salt structure.

[0013] Furthermore, the ATRP initiator with cationic surface activity has the following structural formula: .

[0014] Furthermore, the preparation process of the functional filler is as follows:

[0015] 1) Disperse sodium montmorillonite in deionized water to prepare a 3-5 wt% suspension. Stir at high speed at 80°C for 24 h. Then add an equal volume of THF and continue stirring for 2 h. Dissolve the cationic surface-active ATRP initiator in THF and add it dropwise to the above suspension. Continue stirring for 8-12 h. Cool down, centrifuge, wash repeatedly with hot ethanol aqueous solution, vacuum dry, grind and sieve.

[0016] 2) Add N,N,N',N'',N'''-pentamethyldivinyltriamine and cuprous bromide to the reaction flask. Add the sieved powder and KH570 modified nano-SiO2 to the reaction flask, add THF and mix evenly by ultrasonication. Then add styrene, methacrylic acid and glycidyl methacrylate. Purge nitrogen to remove oxygen from the reaction flask. Under nitrogen protection, heat to 70℃ and react for 8-24 h. After the reaction is completed, centrifuge to separate the solid, wash with THF several times, and vacuum dry to obtain the final product.

[0017] Further, in step 2), the mass ratio of the sieved powder to KH570 modified nano-SiO2 is 1:0.5~1, the molar ratio of styrene, methacrylic acid, and glycidyl methacrylate is 3~5:2~4:2~4, and the mass ratio of the total mass of the monomers to the mass of the sieved powder is 4~6:1.

[0018] Furthermore, the KH570 modified nano-SiO2 is prepared by the following method: a certain amount of nano-silica is soaked in 2 mol / L potassium hydroxide for activation treatment, then dispersed in deionized water and an equal mass of KH570 is added. The mixture is stirred at 50°C for 24 h, filtered, washed, dried and ground to obtain KH570 modified nano-SiO2.

[0019] Furthermore, the specific preparation process of the special polyester chips is as follows:

[0020] 1) In a reaction vessel, terephthalic acid, ethylene glycol, adipic acid, and polyether glycol are added, along with antimony acetate as a catalyst and triphenyl phosphite as a stabilizer. Under nitrogen protection, the temperature is gradually increased to 240-260℃ to carry out the esterification reaction, yielding product 1.

[0021] 2) In a reaction vessel, dimethyl p-naphthalenedicarboxylate, ethylene glycol, zinc acetate, and the stabilizer triphenyl phosphite are added, and the temperature is gradually raised to 170~215℃ to carry out the transesterification reaction to obtain product 2;

[0022] 3) Transfer product 2 to the product 1 system, draw a low vacuum, reduce the pressure to below 100 Pa, raise the temperature to 270-285℃, and carry out the polycondensation reaction for 2-4 hours. After the reaction is completed, release the vacuum, discharge the material, cool it, and granulate it to obtain the product.

[0023] Further, in step 1), the molar ratio of terephthalic acid, ethylene glycol, adipic acid, and polyether glycol is 1:0.9~1.1:0.05~0.15:0.05~0.1; the number average molecular weight of the polyether glycol is 500~1000;

[0024] In step 2), the molar ratio of dimethyl naphthalate to ethylene glycol is 1:2.1~2.2;

[0025] The mass ratio of product 2 to product 1 is 0.1~0.3:1.

[0026] The beneficial effects of this invention are as follows: By introducing self-made functional fillers and special polyester chips, combined with a three-layer structure design, this invention successfully produced a polyester film with high dimensional stability and excellent release agent adhesion, which can be used as a release film base film. Specifically, by introducing functional fillers on its adhesive surface, the fillers use nano-montmorillonite as a carrier material and have PS-PMAA-PGMA and nano-silica grown in its interlayer and on its surface. The abundant active sites form a highly active, high surface energy nanocomposite interface in the PET matrix, making the silicone release agent adhere firmly and the peel force stable. The special polyester chips introduce adipic acid and polyether glycol soft segments to improve the toughness of the material, and at the same time introduce naphthalene ring structures to enhance rigidity and effectively improve heat resistance. They are added to the B-layer core layer, which plays a supporting role in the composite with MAH-g-PET and the bonding role between the A-layer and C-layer. They are added to the C-layer surface structure, which works with TPEE to reduce the surface curl of the film, while balancing the thermal deformation that may be caused by the introduction of flexible segments and maintaining good heat resistance. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Example

[0029] Most of the raw materials used in this application were purchased from the market, and a small portion were produced in-house, as described in detail below. Some of the raw materials may affect the product due to their properties, and their sources are provided below:

[0030]

[0031] In addition, MAH-g-PET can be custom-produced with manufacturers, or obtained through the following methods:

[0032] 100 parts by weight of PET are fed into the main feed port. 2 parts of maleic anhydride, 0.2 parts of DCP initiator and 0.5 parts of styrene are mixed evenly and injected into the extruder through the side feed port. The mixture is melt-extruded at a melting temperature of 260~280℃, stretched, water-cooled, pelletized and dried to obtain MAH-g-PET.

[0033] The preparation process of functional fillers is as follows:

[0034] 1) Disperse 10g of sodium montmorillonite in deionized water to prepare a 5wt% suspension. Stir at high speed at 80℃ for 24h, then add an equal volume of THF and continue stirring for 2h. Add 4.2g of ATRP initiator with cationic surface activity ( (Referring to the synthesis of ATRP initiators with cationic surface activity, Chinese Journal of Synthetic Chemister, Vol 18, 2010, 741-744) was dissolved in THF and then added dropwise to the above suspension. The mixture was stirred for 8-12 h, cooled, centrifuged, washed repeatedly with hot ethanol aqueous solution, vacuum dried, ground and sieved.

[0035] 2) Add 0.64 g N,N,N',N'',N'''-pentamethyldivinyltriamine, 0.53 g cuprous bromide, 5 g sieved powder, 2.5 g KH570 modified nano-SiO2, and 200 ml THF to a reaction flask, and mix thoroughly by ultrasonication. Then add 8.32 g styrene, 5.16 g methacrylic acid, and 8.52 g glycidyl methacrylate (molar ratio 4:3:3). Purge nitrogen gas to remove oxygen from the reaction flask, and react at 70 °C for 16 h under nitrogen protection. After the reaction is complete, centrifuge to separate the solid, wash repeatedly with THF, and vacuum dry to obtain the intercalated modified montmorillonite.

[0036] The preparation method of the special polyester chips is as follows:

[0037] 1) In a reaction vessel, add 2 mol terephthalic acid, 2.2 mol ethylene glycol, 0.2 mol adipic acid, 0.1 mol polyether glycol (molecular weight 1000), 0.6 g antimony acetate catalyst and 0.4 g triphenyl phosphite stabilizer. Under nitrogen protection, gradually raise the temperature to 250℃ to carry out the esterification reaction to obtain product 1;

[0038] 2) In a reaction vessel, add 0.2 mol of dimethyl p-naphthalenecarboxylate, 0.42 mol of ethylene glycol, 0.05 g of zinc acetate, and 0.05 g of the stabilizer triphenyl phosphite, and gradually raise the temperature to 190 °C to carry out the transesterification reaction to obtain product 2;

[0039] 3) Mix product 2 with product 1 (m(product 2):m(product 1) = 0.15:1), draw a low vacuum, reduce the pressure to below 100 Pa, raise the temperature to 280℃, and carry out polycondensation reaction for 3 hours. After the reaction is completed, release the vacuum, discharge the material, cool it, and granulate it to obtain the product.

[0040] The preparation process of this application is as follows:

[0041] S1. Weigh the raw materials according to the formula, dry and mix them separately, wherein...

[0042] Layer A comprises the following components by weight: 100 parts optical grade PET, 5-12 parts functional filler;

[0043] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 1-3 parts antistatic agent;

[0044] Layer C comprises the following components by weight: 50-80 parts optical grade PET, 20-50 parts specialty polyester chips, and 10-20 parts TPEE;

[0045] S2. The three layers of raw materials are extruded separately through a screw extruder, with the temperature of each layer set to 280℃ for layer A, 275℃ for layer B, and 265℃ for layer C. The three layers of melt are then extruded together through a three-layer co-extrusion distributor and a die onto a 50℃ cooling roller to form a cast sheet.

[0046] S3. Preheat the casting to 90℃ and perform longitudinal stretching at 95℃ with a stretching ratio of 3.5. Then preheat to 105℃ and perform transverse stretching at 110℃ with a stretching ratio of 3.7.

[0047] S4. Heat set at 210℃ and wind up to obtain a three-layer co-extruded release film base film.

[0048] Example 1: Layer A comprises the following components by weight: 100 parts optical grade PET, 5 parts functional filler;

[0049] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 1 part antistatic agent;

[0050] Layer C comprises the following components by weight: 70 parts optical grade PET, 30 parts specialty polyester chips, and 10 parts TPEE;

[0051] The thickness of layer A is controlled at 10 μm, the thickness of layer B at 15 μm, and the thickness of layer C at 20 μm.

[0052] Example 2: Layer A comprises the following components by weight: 100 parts optical grade PET, 8 parts functional filler;

[0053] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 2 parts antistatic agent;

[0054] Layer C comprises the following components by weight: 60 parts optical grade PET, 40 parts specialty polyester chips, and 10 parts TPEE;

[0055] The thickness of layer A is controlled at 12 μm, the thickness of layer B at 15 μm, and the thickness of layer C at 22 μm.

[0056] Example 3: Layer A comprises the following components by weight: 100 parts optical grade PET, 12 parts functional filler;

[0057] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 3 parts antistatic agent;

[0058] Layer C comprises the following components by weight: 50 parts optical grade PET, 50 parts specialty polyester chips, and 15 parts TPEE;

[0059] The thickness of layer A is controlled at 15 μm, the thickness of layer B at 15 μm, and the thickness of layer C at 25 μm.

[0060] Comparative Example 1: Layer A comprises the following components by weight: 100 parts optical grade PET;

[0061] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 3 parts antistatic agent;

[0062] Layer C comprises the following components by weight: 50 parts optical grade PET, 50 parts specialty polyester chips, and 15 parts TPEE;

[0063] The thickness of layer A is controlled at 15 μm, the thickness of layer B at 15 μm, and the thickness of layer C at 25 μm.

[0064] Comparative Example 2: Layer A comprises the following components by weight: 100 parts optical grade PET, 12 parts functional filler;

[0065] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 1-3 parts antistatic agent;

[0066] Layer C comprises the following components by weight: 100 parts optical grade PET;

[0067] The thickness of layer A is controlled at 15 μm, the thickness of layer B at 15 μm, and the thickness of layer C at 25 μm.

[0068] Comparative Example 3: Layer A comprises the following components by weight: 100 parts optical grade PET, 6 parts CTAB intercalated montmorillonite (intercalation process consistent with that of functional fillers for sodium-based montmorillonite), and 6 parts nano-SiO2;

[0069] Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 1 part antistatic agent;

[0070] Layer C comprises the following components by weight: 100 parts optical grade PET, 15 parts TPEE;

[0071] The thickness of layer A is controlled at 15 μm, the thickness of layer B at 15 μm, and the thickness of layer C at 25 μm.

[0072] The above-described embodiments and comparative samples were tested as follows, and the results are recorded in Table 1.

[0073] Heat shrinkage rate: After being placed in an oven at 150℃ for 30 minutes, the dimensional change rate in the MD / TD direction was measured.

[0074] Surface roughness (Ra): The surface of layer A was measured using atomic force microscopy (AFM).

[0075] Release agent adhesion (cross-cut test): After coating the surface of sample A with standard silicone release agent and curing, a cross-cut test is performed to evaluate the percentage of release coating peeling area (0 is the best, 5 is the worst).

[0076] Peel strength stability: After applying the release agent, the peel strength against a standard pressure-sensitive tape (FINAT FTM 10) was measured, and the standard deviation (SD) of the peel strength for 10 consecutive peels was calculated. The smaller the SD, the more stable the peel strength.

[0077] Curl: After equilibrating a 100 mm × 100 mm sample at 23℃ / 50%RH for 24 h, place it freely on a flat plate and measure the average value of the height of the four corners curling up.

[0078] Orientation angle deviation: Using a 20cm×700cm polyester film, ten points were randomly selected at the ends of the film (within 30cm of both ends) and the middle of the film (within ±35cm of the middle position) to test its orientation angle. The average value was calculated to obtain the difference between the average orientation angles at the ends and the middle position of the polyester film.

[0079] Table 1

[0080]

[0081] Comparing Comparative Examples 1 and 3, it can be found that the introduction of functional fillers plays a crucial role in the adhesion of the release agent. Comparative Example 3 exhibits the worst release agent adhesion. This is because directly adding intercalated modified montmorillonite and nano-silica to PET can easily lead to agglomeration due to poor compatibility, resulting in discontinuous coatings during release agent application and thus poor adhesion. Analysis of Comparative Examples 2 and 3 reveals that the absence of special polyester chips and TPEE significantly increases curl and reduces heat resistance. While adding only TPEE improves curl, it further reduces heat resistance.

[0082] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A high dimensional stability release film base film for a polarizing sheet, characterized by, The base film has an ABC three-layer co-extrusion structure, wherein layers A and C are surface layers and layer B is the core layer; Layer A comprises the following components by weight: 100 parts optical grade PET, 5-12 parts functional filler; Layer B comprises the following components by weight: 50 parts special polyester chips, 50 parts MAH-g-PET, and 1-3 parts antistatic agent; Layer C comprises the following components by weight: 50-80 parts optical grade PET, 20-50 parts specialty polyester chips, and 10-20 parts TPEE; The functional filler is obtained by intercalating montmorillonite with ATRP initiator, which has cationic surface activity, and then adding styrene, methacrylic acid, glycidyl methacrylate and KH570 modified nano-SiO2 for in-situ graft polymerization. The preparation process of the functional filler is as follows: 1) Disperse sodium montmorillonite in deionized water to prepare a 3-5 wt% suspension. Stir at high speed at 80°C for 24 h. Then add an equal volume of THF and continue stirring for 2 h. Dissolve the cationic surface-active ATRP initiator in THF and add it dropwise to the above suspension. Continue stirring for 8-12 h. Cool down, centrifuge, wash repeatedly with hot ethanol aqueous solution, vacuum dry, grind and sieve. 2) Add N,N,N',N'',N'''-pentamethyldivinyltriamine and cuprous bromide to the reaction flask. Add the sieved powder and KH570 modified nano-SiO2 to the reaction flask, add THF and mix evenly by ultrasonication. Then add styrene, methacrylic acid, and glycidyl methacrylate. Purge nitrogen gas to remove oxygen from the reaction flask. Under nitrogen protection, heat to 70℃ and react for 8-24 h. After the reaction is complete, centrifuge to separate the solid, wash with THF several times, and vacuum dry to obtain the product. The polyester chips are prepared by a series of esterification reactions, transesterification reactions, and polycondensation reactions of terephthalic acid, ethylene glycol, adipic acid, polyether glycol, and dimethyl terephthalate. The specific preparation process of the special polyester chips is as follows: 1) In a reaction vessel, terephthalic acid, ethylene glycol, adipic acid, and polyether glycol are added, along with antimony acetate as a catalyst and triphenyl phosphite as a stabilizer. Under nitrogen protection, the temperature is gradually increased to 240-260℃ to carry out the esterification reaction, yielding product 1. 2) In a reaction vessel, dimethyl p-naphthalenedicarboxylate, ethylene glycol, zinc acetate, and the stabilizer triphenyl phosphite are added, and the temperature is gradually raised to 170~215℃ to carry out the transesterification reaction to obtain product 2; 3) Transfer product 2 to the product 1 system, draw a low vacuum, reduce the pressure to below 100 Pa, raise the temperature to 270-285℃, and carry out the polycondensation reaction for 2-4 hours. After the reaction is completed, release the vacuum, discharge the material, cool it, and granulate it to obtain the product.

2. The high dimensional stability release film base film for a polarizing plate according to claim 1, characterized by, The thickness of layer A is 10~15μm, the thickness of layer B is 12~18μm, and the thickness of layer C is 20~25μm.

3. The high dimensional stability release film base film for a polarizing plate according to claim 1, characterized by, The antistatic agent is a polyether ester amide or an acrylate copolymer containing a quaternary ammonium salt structure.

4. The high dimensional stability release film base film for a polarizing plate according to claim 1, characterized by, The ATRP initiator having cationic surface activity has a structural formula of .

5. The high dimensional stability release film base film for a polarizing plate according to claim 1, characterized by, In step 2), the mass ratio of the sieved powder to KH570 modified nano-SiO2 is 1:0.5~1, the molar ratio of styrene, methacrylic acid, and glycidyl methacrylate is 3~5:2~4:2~4, and the mass ratio of the total mass of the monomers to the mass of the sieved powder is 4~6:

1.

6. The high dimensional stability release film base film for a polarizing plate according to claim 1, characterized by, The KH570 modified nano-SiO2 was prepared by the following method: a certain amount of nano-silica was soaked in 2 mol / L potassium hydroxide for activation treatment, then dispersed in deionized water and an equal mass of KH570 was added. The mixture was stirred at 50°C for 24 h, filtered, washed, dried and ground to obtain KH570 modified nano-SiO2.

7. The high dimensional stability release film base film for a polarizing plate according to claim 1, characterized by, In step 1), the molar ratio of terephthalic acid, ethylene glycol, adipic acid, and polyether glycol is 1:0.9~1.1:0.05~0.15:0.05~0.1; the number average molecular weight of the polyether glycol is 500~1000. In step 2), the molar ratio of dimethyl naphthalate to ethylene glycol is 1:2.1~2.2; The mass ratio of product 2 to product 1 is 0.1~0.3:1.

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