Polarizer protective film base film and preparation method thereof

Abstract

The invention relates to the technical field of polyester films, in particular to a polaroid protective film base film and a preparation method thereof, and the polaroid protective film base film is of an ABC three-layer co-extrusion structure; raw materials of the layer A and the layer C comprise the following components in parts by weight: 70-95 parts of bright polyester chips; 5-30 parts of a special master batch; the layer B is prepared from the following raw materials in parts by weight: 90 to 98 parts of bright polyester chips; 2-10 parts of a high-speed material; wherein the special master batch is prepared through an in-situ polymerization reaction; and the surface of the layer A or the layer C is coated with an antistatic pre-coating layer. The special master batch prepared by the in-situ polymerization reaction is introduced as the polyester film master batch, so that particle aggregation can be reduced, and the prepared master batch particles are good in dispersity; the polyester film prepared from the special master batch is small in internal gel point and crystal point size and small in number, has better apparent performance, and meets the optical requirements of a polaroid protective film base film.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyester film, in particular to a polarizer protective film base film and a preparation method thereof. BACKGROUND

[0002] As a core component of display panels, the performance of the polarizer directly determines the key optical properties of the liquid crystal display screen, such as brightness, contrast, viewing angle range and color performance. The polarizer protective film is a PET base film coated with EVA on one side, which mainly protects the surface of the TAC film. With the development of display panels towards large size and thinness, higher requirements are put forward for the performance of the polarizer protective film and the polarizer protective film base film, which also provides new impetus for the market growth of the polarizer protective film.

[0003] The existing polarizer protective film base film has a large number of crystal points, which cannot meet the optical performance requirements of the display panel. SUMMARY

[0004] In order to solve the problem of a large number of crystal points in the polarizer protective film base film in the prior art, the present application provides a polarizer protective film base film. The polarizer protective film base film is prepared by introducing a polyester film master batch synthesized by an in-situ polymerization method into the raw material, so that the size of the gel points and crystal points in the prepared polyester film is small and the number is few, solving the problem of a large number of crystal points in the polarizer protective film base film in the prior art.

[0005] The technical scheme adopted by the present application to solve the technical problems is: A polarizer protective film base film, the polarizer protective film base film is an ABC three-layer co-extrusion structure. The raw material of the A layer and the C layer comprises the following components in parts by weight: Matt polyester chip 70-95 parts; Special master batch 5-30 parts; The raw material of the B layer comprises the following components in parts by weight: Matt polyester chip 90-98 parts; High-speed material 2-10 parts; The special master batch is prepared by in-situ polymerization reaction. The surface of the A layer or the C layer is coated with an antistatic pre-coating layer.

[0006] Optionally, the special masterbatch is prepared by the following method: dispersing silica in an ethanol solution, adding a modifier, refluxing at a temperature of 50-100℃, and then filtering, washing and drying to obtain modified silica; mixing the modified silica, ethylene glycol, a dispersant and a stabilizer at 15-25℃, adjusting the pH to 8-10, and then obtaining a silica dispersion liquid by ultrasonic treatment; adding terephthalic acid and the silica dispersion liquid into an esterification reactor, adding a catalyst, filling the reactor with inert gas, and then obtaining the special masterbatch by esterification, polycondensation, melt extrusion and granulation.

[0007] Optionally, the modifier is at least one selected from phosphate coupling agent, γ-aminopropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane.

[0008] Optionally, the dispersant is at least one selected from polyphosphate, sodium silicate, polyoxyethylene ether phosphate and nonylphenol polyoxyethylene ether.

[0009] Optionally, the stabilizer is at least one selected from polyoxyethylene, hydroxyl cellulose, citric acid, pentaerythritol stearate and polyethylene glycol laurate.

[0010] Optionally, the mass ratio of the silica to the modifier is 100: (1-6).

[0011] Optionally, the mass ratio of the modified silica, the ethylene glycol, the dispersant and the stabilizer is (2.5-13.0): 100: (0.01-1.1): (0.03-0.55); and the mass ratio of the terephthalic acid to the silica dispersion liquid is 1: (1.03-1.40).

[0012] Optionally, the antistatic pre-coating is obtained by coating an antistatic coating liquid; the antistatic coating liquid comprises water, water-based polyurethane resin, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), an opening agent, a wetting agent, a curing agent and a pH adjuster.

[0013] Optionally, the pH of the antistatic coating liquid is 8-10. Another objective of this invention is to provide a method for preparing the polarizer protective film base film as described above, characterized by the following process: drying and vacuuming the raw materials of layers A, B, and C, then melting and mixing them and extruding them through a three-layer co-extrusion die to a casting roller at 18-40°C to form a casting sheet; the casting sheet is preheated to 78-90°C by a longitudinal stretching preheating roller, then heated to 95-120°C by an infrared lamp tube, and then stretched 2.8-4.3 times longitudinally, and then rapidly cooled by a cooling roller at 25-35°C to form a unidirectional sheet; the unidirectional sheet is coated with an antistatic coating liquid in an online coating unit to obtain a unidirectional sheet with an antistatic coating, preheated to 105-125°C, stretched 3.5-4.7 times transversely at 125-135°C, and then set at 225-240°C for 5-325 seconds and cooled at 50-180°C, and then traction and winding to obtain the polarizer protective film base film.

[0014] The beneficial effects of this invention are: The polarizer protective film base film provided by this invention introduces a special masterbatch prepared by in-situ polymerization as the masterbatch for polyester film. Because the masterbatch is synthesized by in-situ polymerization, particle agglomeration can be reduced, and the resulting masterbatch has good particle dispersion. The polyester film made with this special masterbatch has small internal gel points and crystal points, and fewer in number, resulting in better appearance properties and meeting the optical requirements of the polarizer protective film base film. Detailed Implementation

[0015] The present invention will now be described in further detail. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0016] To address the problem of a large number of crystal points in the base film of polarizer protective film in the prior art, the present invention provides a base film for polarizer protective film, which has an ABC three-layer co-extruded structure. The raw materials for layers A and C, by weight, include the following components: 70-95 portions of bright polyester chips; Special masterbatch 5-30 parts; The raw materials for layer B, by weight, include the following components: 90-98 portions of bright polyester chips; 2-10 parts of high-speed feed; Among them, the special masterbatch is prepared by in-situ polymerization reaction; The surface of layer A or layer C is coated with an antistatic pre-coating.

[0017] The polarizer protective film base film provided by this invention introduces a special masterbatch prepared by in-situ polymerization as the masterbatch for polyester film. Because the masterbatch is synthesized by in-situ polymerization, particle agglomeration can be reduced, and the resulting masterbatch has good particle dispersion. The polyester film made with this special masterbatch has small internal gel points and crystal points, and fewer in number, resulting in better appearance properties and meeting the optical requirements of the polarizer protective film base film.

[0018] Furthermore, by coating the surface of layer A or layer C with an antistatic pre-coating layer, the surface resistance of the thin film is reduced, which can effectively prevent electrostatic adsorption of impurities and thus avoid contamination of the base film surface of the polarizer protective film.

[0019] The technical solution provided by this invention can significantly reduce the number of crystal points inside the film and improve the surface cleanliness of the film, thereby effectively improving the yield in subsequent processing. It is suitable for the processing of polarizer protective films.

[0020] In this invention, the thickness of layer A in the polarizer protective film base film is preferably 0.2-2.5 μm, the thickness of layer B is preferably 20-50 μm, and the thickness of layer C is preferably 0.2-2.5 μm.

[0021] The preferred method for preparing the special masterbatch of this invention is as follows: Silica is dispersed in an ethanol solution, a modifier is added, and the mixture is refluxed at 50-100℃ for 3-5 hours. After filtration, washing, and drying, modified silica is obtained. At 15-25℃, the modified silica, ethylene glycol, dispersant, and stabilizer are mixed, the pH is adjusted to 8-10, and the mixture is ultrasonically treated to obtain a silica dispersion. Preferably, the silica dispersion is obtained by pulsed ultrasonic high-energy treatment, and more preferably, the power of the pulsed ultrasound is 200-600W, and the treatment time is 20-100min. Terephthalic acid and the silica dispersion are added to an esterification reactor, along with a catalyst. The reactor is filled with an inert gas, and after esterification, polycondensation, melt extrusion, and granulation, the special masterbatch is obtained.

[0022] The preferred esterification reaction temperature of this invention is 190-260℃, the reaction time is 3-5 hours, and the reaction pressure is 3.0-4.5 bar; the preferred polycondensation reaction temperature is 220-250℃, the reaction time is 5-10 hours, and the reaction pressure is 10-50 Pa.

[0023] This invention first modifies silica, then mixes the modified silica with ethylene glycol, a dispersant, and a stabilizer, so that the silica is fully and uniformly dispersed in ethylene glycol. Then, terephthalic acid is added to prepare a special masterbatch through in-situ polymerization, which makes the silica uniformly dispersed in the special masterbatch, thereby reducing the gel points inside the film and giving the polarizer protective film a better appearance, thus improving the efficiency and accuracy of polarizer inspection.

[0024] The preferred modifier of this invention is selected from at least one of phosphate ester coupling agents, γ-aminopropyltriethoxysilane, and γ-glycidyl etheroxypropyltrimethoxysilane; the preferred dispersant is selected from at least one of polyphosphate esters, sodium silicate, polyoxyethylene ether phosphate, and nonylphenol polyoxyethylene ether; the preferred stabilizer is selected from at least one of polyoxyethylene, hydroxycellulose, citric acid, pentaerythritol stearate, and polyethylene glycol laurate; and the preferred catalyst is antimony glycolide.

[0025] The present invention preferably has an ethanol solution concentration of 1-3% and a silica to ethanol solution mass ratio of 100:(320-650).

[0026] The preferred particle size of silica in this invention is 30-800 nm; the preferred mass ratio of silica to modifier is 100:(1-6).

[0027] The preferred mass ratio of modified silica, ethylene glycol, dispersant, and stabilizer in this invention is (2.5-13.0):100:(0.01-1.1):(0.03-0.55); the mass ratio of terephthalic acid to silica dispersion is 1:(1.03-1.40); and the preferred amount of catalyst added is 0.1-0.4% of the weight of terephthalic acid.

[0028] The present invention preferably uses bright polyester chips selected from at least one of Yizheng Chemical Fiber FG600 and Yizheng Chemical Fiber FG604; preferably uses high-speed material selected from at least one of Yizheng Chemical Fiber FG6200 and Zhuben Oil S-626.

[0029] The present invention preferably obtains the antistatic pre-coating layer by coating with an antistatic coating liquid. Specifically, the antistatic pre-coating layer is preferably coated onto the film surface by an online coating process. The present invention further preferably includes water, waterborne polyurethane resin, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), opening agent, wetting agent, curing agent and pH adjuster.

[0030] Furthermore, the waterborne polyurethane resin of the present invention is preferably a synthetic product of aromatic polyester polyol and aromatic diisocyanate, and preferably selected from at least one of HYDRAN AP-50RI and HYDRANVR-001 from DIC Corporation of Japan, specifically preferably HYDRAN AP-50RI and HYDRAN from DIC Corporation of Japan. VR-001 is a mixture composed of a mass ratio of 1:2, and more preferably, waterborne polyurethane accounts for 3-10% of the total mass of the coating liquid; preferably, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) accounts for 0.5-5% of the total mass of the coating liquid; preferably, the opening agent is a nano-SiO2 suspension with a particle size of 20-200 nm, and preferably, the opening agent accounts for 0.05-2% of the total mass of the coating liquid; preferably, the wetting agent is selected from at least one of isopropanol and methylene sulfoxide, and preferably, the wetting agent accounts for 4-20% of the total mass of the coating liquid; preferably, the curing agent is selected from at least one of melamine and isocyanate, and preferably, the curing agent accounts for 0.05-0.4% of the total mass of the coating liquid; preferably, the pH adjuster is disodium EDTA, and preferably, the pH of the coating liquid is adjusted to 8-10 by the pH adjuster, specifically, the pH of the antistatic coating liquid is preferably 8-10.

[0031] This invention utilizes online coating technology to coat a polyester film surface with an antistatic coating liquid. This coating liquid system is water-based, meeting environmental protection requirements, and the antistatic coating exhibits stable performance unaffected by temperature and humidity. Furthermore, the antistatic coating possesses high surface tension, improving its suitability for downstream processing.

[0032] Another object of the present invention is to provide a method for preparing the polarizer protective film base film as described above. This method includes the following steps: According to the formula, the raw materials for layers A, B, and C are dried, preferably in drying towers at 165-185°C for 2-5 hours respectively. After vacuuming, they are melt-mixed through extruders A, B, and C respectively, and extruded through a three-layer co-extrusion die to a casting roll at 18-40°C to form a cast sheet. The cast sheet is preheated to 78-90°C by a longitudinal stretching preheating roller, and then passed through an infrared lamp. After the tube is heated to 95-120℃, it is stretched 2.8-4.3 times longitudinally. After stretching, it is rapidly cooled by a cooling roller at 25-35℃ to form a unidirectional sheet. The unidirectional sheet is then coated with an antistatic coating liquid in an online coating unit to obtain a unidirectional sheet with an antistatic coating. After preheating at 105-125℃, it is stretched 3.5-4.7 times transversely at 125-135℃, and after setting at 225-240℃ for 5-325 seconds, it is cooled at 50-180℃. After traction and winding, the polarizer protective film base film is obtained.

[0033] The polarizer protective film base film provided by this invention has a simple preparation process, is easy to operate, has low cost, good processability, and strong applicability.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0035] Unless otherwise specified, the bright polyester chips in the embodiments and comparative examples of the present invention are Yizheng Chemical Fiber FG600, the high-speed material is Yizheng Chemical Fiber FG6200, and the waterborne polyurethane resin is a mixture of HYDRAN AP-50RI and HYDRAN VR-001 from DIC Corporation of Japan in a mass ratio of 1:2.

[0036] The polarizer protective film base film in each embodiment and comparative example of the present invention was prepared according to the following method: According to the formula, the raw materials for layers A, B, and C are dried in a drying tower at 175℃ for 3 hours. After vacuuming, they are melt-mixed and extruded through extruders for surface layer 1 (layer A), core layer (layer B), and surface layer 2 (layer C) respectively, and then cast onto a casting roll at 30℃ using a three-layer co-extrusion die to form a cast sheet. The cast sheet is preheated to 85℃ by a longitudinal stretching preheating roll, then instantaneously heated to 100℃ by an infrared lamp, and then subjected to 3.5 times longitudinal stretching. After stretching, it is rapidly cooled by a cooling roll at 30℃ to form a unidirectional sheet. The film is coated with an antistatic coating liquid in an online coating unit to obtain a unidirectional film with an antistatic coating. After preheating at 115°C, it is stretched 4.1 times laterally at 130°C, and then set at 230°C for 115 seconds before cooling at 115°C. After traction and winding, the polarizer protective film base film is obtained. The thickness of layer A is 1.3μm, the thickness of layer B is 35.4μm, and the thickness of layer C is 1.3μm. The surface of layer C is coated with an antistatic pre-coating layer with a thickness of 40nm.

[0037] Example 1 This embodiment provides a polarizer protective film base film, which has an ABC three-layer co-extruded structure; The raw materials for layers A and C, by weight, include the following components: 85 portions of bright polyester chips; 15 portions of special masterbatch; The raw materials for layer B, by weight, include the following components: 95 portions of bright polyester chips; 5 portions of high-speed feed.

[0038] Special masterbatch is prepared according to the following method: 100 parts by weight of silica (particle size 400 nm) were dispersed in 500 parts by weight of a 2% ethanol solution. 3 parts by weight of γ-aminopropyltriethoxysilane, a modifier, were added. The mixture was refluxed at 75°C for 4 hours. After filtration, washing, and drying, modified silica was obtained. 3.0 parts of the modified silica were cooled to 20°C, and 100 parts by weight of ethylene glycol, 0.5 parts by weight of sodium silicate, and 0.3 parts by weight of polyethylene oxide, along with disodium EDTA to adjust the pH to 9, were subjected to pulsed ultrasonic high-energy treatment. After treatment, a silica dispersion was obtained; the pulsed ultrasound power was 400W and the treatment time was 60min; 100 parts of terephthalic acid and 120 parts of silica dispersion were added to the esterification reactor, along with 0.2 parts of antimony glycolate catalyst. The reactor was filled with inert nitrogen gas and the esterification reaction was carried out at 220℃ and 3.8bar for 4 hours; then a polycondensation reaction was carried out at 230℃ and 30Pa for 7 hours to obtain a special polyester masterbatch. After melt extrusion and granulation, the special masterbatch was obtained.

[0039] The antistatic coating solution applied to the C layer surface is a mixed system consisting of water, waterborne polyurethane resin, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), nano-SiO2 as an opening agent, isopropanol as a wetting agent, melamine as a curing agent, and disodium EDTA as a pH adjuster. The waterborne polyurethane resin comprises 6% by mass, the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) comprises 3% by mass, the nano-SiO2 as an opening agent has a particle size of 100 nm, the opening agent comprises 1% by mass, the wetting agent comprises 12% by mass, the curing agent comprises 0.2% by mass, and the pH of the antistatic coating solution is adjusted to 9 by the pH adjuster.

[0040] Example 2 The difference between this embodiment and Embodiment 1 is that the raw materials for layers A and C, by weight, include the following components: 70 portions of bright polyester chips; 30 parts of special masterbatch; The raw materials for layer B, by weight, include the following components: 90 portions of bright polyester chips; 10 portions of high-speed feed.

[0041] Example 3 The difference between this embodiment and Embodiment 1 is that the raw materials for layers A and C, by weight, include the following components: 95 portions of bright polyester chips; 5 parts of special masterbatch; The raw materials for layer B, by weight, include the following components: 98 portions of bright polyester chips; Two portions of high-speed feed.

[0042] Example 4 The difference between this embodiment and Embodiment 1 is that the special masterbatch is prepared according to the following method: By weight, 100 parts of silica (particle size 400 nm) were dispersed in 580 parts of a 2% ethanol solution, and 6 parts of a phosphate coupling agent modifier were added. The mixture was refluxed at 100°C for 3 hours, and after filtration, washing, and drying, modified silica was obtained. 3.3 parts of the modified silica were cooled to 25°C, and 100 parts of ethylene glycol, 1.1 parts of polyphosphate dispersant, and 0.55 parts of hydroxyl cellulose stabilizer were added. Disodium EDTA was added to adjust the pH to 8, and the mixture was subjected to pulsed ultrasonic high-energy treatment. After treatment, a silica dispersion was obtained; the power of the pulsed ultrasound was 600W, and the treatment time was 20min; 100 parts of terephthalic acid and 140 parts of silica dispersion were added to the esterification reactor, along with 0.4 parts of antimony glycolate catalyst. The reactor was filled with inert nitrogen gas, and the esterification reaction was carried out at 260℃ and 3.0bar for 3 hours; then, a polycondensation reaction was carried out at 250℃ and 10Pa for 5 hours to obtain a special polyester masterbatch. After melt extrusion and granulation, the special masterbatch was obtained.

[0043] Example 5 The difference between this embodiment and Embodiment 1 is that the special masterbatch is prepared according to the following method: By weight, 100 parts of silica (particle size 400 nm) were dispersed in 400 parts of a 2% ethanol solution, and 1 part of γ-glycidyl etheroxypropyltrimethoxysilane, a modifier, was added. The mixture was refluxed at 50°C for 5 hours. After filtration, washing, and drying, modified silica was obtained. 10.5 parts of the modified silica were cooled to 15°C, and 100 parts of ethylene glycol, 0.1 parts of polyoxyethylene ether phosphate, a dispersant, and 0.03 parts of citric acid, a stabilizer, were added. Disodium EDTA was added to adjust the pH to 10. The mixture was then subjected to pulse... A silica dispersion was obtained after ultrasonic high-energy treatment; the power of the pulsed ultrasound was 200W and the treatment time was 100min. 100 parts of terephthalic acid and 103 parts of silica dispersion were added to an esterification reactor, along with 0.1 parts of antimony glycolate catalyst. The reactor was filled with inert nitrogen gas and the esterification reaction was carried out at 190℃ and 4.5bar for 5 hours. Then, a polycondensation reaction was carried out at 220℃ and 50Pa for 10 hours to obtain a special polyester masterbatch. After melt extrusion and granulation, the special masterbatch was obtained.

[0044] Example 6 The difference between this embodiment and Embodiment 1 is that the antistatic coating liquid coated on the surface of layer C is a mixed system composed of water, waterborne polyurethane resin, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), nano-SiO2 as an opening agent, methylene sulfoxide as a wetting agent, isocyanate as a curing agent, and disodium EDTA as a pH adjuster. The waterborne polyurethane resin in the antistatic coating liquid has a mass fraction of 10%, the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) has a mass fraction of 5%, the nano-SiO2 as an opening agent has a particle size of 100 nm, the opening agent has a mass fraction of 2%, the wetting agent has a mass fraction of 20%, the curing agent has a mass fraction of 0.4%, and the pH of the antistatic coating liquid is adjusted to 10 using a pH adjuster.

[0045] Example 7 The difference between this embodiment and Embodiment 1 is that the antistatic coating liquid coated on the surface of layer C is a mixed system composed of water, waterborne polyurethane resin, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), nano-SiO2 as an opening agent, methylene sulfoxide as a wetting agent, isocyanate as a curing agent, and disodium EDTA as a pH adjuster. The waterborne polyurethane resin in the antistatic coating liquid has a mass fraction of 3%, the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) has a mass fraction of 0.5%, the nano-SiO2 as an opening agent has a particle size of 100 nm, the opening agent has a mass fraction of 0.05%, the wetting agent has a mass fraction of 4%, the curing agent has a mass fraction of 0.05%, and the pH of the antistatic coating liquid is adjusted to 8 using a pH adjuster.

[0046] All comparative examples in this invention are compared with Example 1.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that the special masterbatch was prepared according to the following method: 100 parts by weight of silica (particle size 400 nm) were dispersed in 500 parts by weight of a 2% ethanol solution, and 3 parts by weight of γ-aminopropyltriethoxysilane modifier were added. The mixture was refluxed at 75°C for 4 hours. After filtration, washing, and drying, modified silica was obtained. 100 parts by weight of terephthalic acid and 100 parts by weight of ethylene glycol were added to an esterification reactor, along with 0.2 parts by weight of antimony glycolate catalyst. The reactor was filled with inert nitrogen gas and incubated at 220°C for 3 hours. Esterification was carried out at 8 bar for 4 hours; followed by polycondensation at 230℃ and 30 Pa for 7 hours to obtain polyester masterbatch; at 20℃, the polyester masterbatch was mixed with modified silica, 0.5 parts of dispersant sodium silicate and 0.3 parts of stabilizer polyethylene oxide, and EDTA disodium was added to adjust the pH to 9. The mixture was then subjected to pulsed ultrasonic high-energy treatment with a power of 400 W for 60 min. After melt extrusion and granulation, a special masterbatch was obtained.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is that the special masterbatch was prepared according to the following method: By weight, 100 parts ethylene glycol, 0.5 parts sodium silicate dispersant, and 0.3 parts polyethylene oxide stabilizer were added to 20 parts silica. Disodium EDTA was added to adjust the pH to 9. The silica dispersion was obtained by pulsed ultrasonic high-energy treatment; the power of the pulsed ultrasound was 400W, and the treatment time was 60min. 100 parts terephthalic acid and 120 parts silica dispersion were added to an esterification reactor, along with 0.2 parts antimony glycolate catalyst. The reactor was filled with inert nitrogen gas, and the esterification reaction was carried out at 220℃ and 3.8 bar for 4 hours. Then, a polycondensation reaction was carried out at 230℃ and 30 Pa for 7 hours to obtain a special polyester masterbatch. After melt extrusion and granulation, the special masterbatch was obtained.

[0049] Comparative Example 3 The difference between this comparative example and Example 1 is that the antistatic coating solution coated on the surface of layer C is a mixed system composed of water, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), nano-SiO2 as an opening agent, isopropanol as a wetting agent, melamine as a curing agent, and disodium EDTA as a pH adjuster. The mass fraction of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) in the antistatic coating solution is 3%, the particle size of nano-SiO2 as an opening agent is 100 nm, the mass fraction of the opening agent in the antistatic coating solution is 1%, the mass fraction of the wetting agent is 12%, the mass fraction of the curing agent is 0.2%, and the pH of the antistatic coating solution is adjusted to 9 by the pH adjuster.

[0050] Comparative Example 4 The difference between this comparative example and Example 1 is that the antistatic coating solution applied to the surface of layer C is a mixed system consisting of water, waterborne polyurethane resin, nano-SiO2 as an opening agent, isopropanol as a wetting agent, melamine as a curing agent, and disodium EDTA as a pH adjuster; wherein the mass fraction of waterborne polyurethane resin in the antistatic coating solution is 6%. The particle size of the opening agent nano-SiO2 is 100nm. The mass fraction of the opening agent in the antistatic coating solution is 1%, the mass fraction of the wetting agent is 12%, the mass fraction of the curing agent is 0.2%, and the pH of the antistatic coating solution is adjusted to 9 by a pH adjuster.

[0051] The performance of the polarizer protective film base films prepared in the above embodiments and comparative examples was tested using the following methods: Gel dots inside the base film of polarizer protective film: Take a sample from the master roll, 50cm wide, and suspend it on the inspection lamp stand. Turn off all lights and observe the film surface (reflected light and transmitted light) with a strong flashlight in a dark room. Circle the defect points with a marker and measure the size of the defect points under a microscope. Count the number of defect points with diameters of 0.05-0.1mm (excluding), 0.1-0.15mm (excluding), 0.15-0.2mm (excluding), and larger than 0.2mm, and record the results. Surface roughness of polarizer protective film base film: Tested using a Kosaka Research Institute SE800 surface roughness tester according to the method specified in GB / T 1031-2009; Surface resistance of polarizer protective film base film: Tested using a Keithley 6517B surface resistance meter according to the method specified in GB / T31838.3-2019.

[0052] The test results are shown in Table 1: Table 1 The difference between Comparative Example 1 and Example 1 is that polyester was first prepared using terephthalic acid and ethylene glycol, and then the polyester was mixed with modified silica. Because the silica masterbatch was synthesized by blending, agglomeration of silica occurred during the blending process, resulting in an increase in the number and size of gel points and crystal points inside the film, which also affected the surface roughness.

[0053] The difference between Comparative Example 2 and Example 1 is that the silica was not modified. Because the surface polarity of silica is very high, hydrogen bonding causes high aggregation between silica particles, which cannot be better dispersed in the solution during the synthesis process. This results in a large number of gel points on the film surface, with extremely large sizes, and a sharp increase in surface roughness Rmax.

[0054] The difference between Comparative Example 3 and Example 1 is that no water-based polyurethane was added to the antistatic coating liquid. Because poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) will shrink significantly when water evaporates, and its own flexibility is insufficient, it cannot release stress through deformation and cause the coating to crack, resulting in the breakage of the conductive path of the coating and the failure of antistatic performance.

[0055] The difference between Comparative Example 4 and Example 1 is that poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) was not added to the antistatic coating solution. Because the coating solution lacks an effective conductive polymer, the film surface does not have antistatic properties.

[0056] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A polarizer protective film base film, characterized in that, The polarizer protective film base film has an ABC three-layer co-extruded structure; The raw materials for layers A and C, by weight, include the following components: 70-95 portions of bright polyester chips; Special masterbatch 5-30 parts; The raw materials for layer B, by weight, include the following components: 90-98 portions of bright polyester chips; 2-10 parts of high-speed feed; The special masterbatch is prepared by in-situ polymerization. The surface of layer A or layer C is coated with an antistatic pre-coating.

2. The polarizer protective film base film as described in claim 1, characterized in that, The special masterbatch is prepared as follows: Silica is dispersed in an ethanol solution, a modifier is added, and the mixture is refluxed at 50-100℃. After filtration, washing, and drying, modified silica is obtained. The modified silica, ethylene glycol, dispersant, and stabilizer are mixed at 15-25℃, the pH is adjusted to 8-10, and the mixture is ultrasonically treated to obtain a silica dispersion. Terephthalic acid and the silica dispersion are added to an esterification reactor, along with a catalyst. The reactor is filled with inert gas, and after esterification, polycondensation, melt extrusion, and granulation, the special masterbatch is obtained.

3. The polarizer protective film base film as described in claim 2, characterized in that, The modifier is selected from at least one of phosphate ester coupling agents, γ-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

4. The polarizer protective film base film as described in claim 2, characterized in that, The dispersant is selected from at least one of polyphosphate, sodium silicate, polyoxyethylene ether phosphate, and nonylphenol polyoxyethylene ether.

5. The polarizer protective film base film as described in claim 2, characterized in that, The stabilizer is selected from at least one of polyoxyethylene, hydroxycellulose, citric acid, pentaerythritol stearate, and polyethylene glycol laurate.

6. The polarizer protective film base film as described in any one of claims 2-5, characterized in that, The mass ratio of silicon dioxide to the modifier is 100:(1-6).

7. The polarizer protective film base film as described in claim 6, characterized in that, The mass ratio of the modified silica, the ethylene glycol, the dispersant, and the stabilizer is (2.5-13.0):100:(0.01-1.1):(0.03-0.55); the mass ratio of the terephthalic acid to the silica dispersion is 1:(1.03-1.40).

8. The polarizer protective film base film as described in any one of claims 2-5, characterized in that, The antistatic pre-coating layer is obtained by coating with an antistatic coating liquid; the antistatic coating liquid includes water, waterborne polyurethane resin, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), opening agent, wetting agent, curing agent and pH adjuster.

9. The polarizer protective film base film as described in claim 8, characterized in that, The pH of the antistatic coating solution is 8-10.

10. A method for preparing a polarizer protective film base film as described in any one of claims 1-9, characterized in that, The process includes the following steps: The raw materials for layers A, B, and C are dried, vacuumed, melt-mixed, and extruded through a three-layer co-extrusion die to a casting roller at 18-40°C to form a casting sheet; the casting sheet is preheated to 78-90°C by a longitudinal stretching preheating roller, then heated to 95-120°C by an infrared lamp, and then stretched 2.8-4.3 times longitudinally. After stretching, it is rapidly cooled by a cooling roller at 25-35°C to form a unidirectional sheet; the unidirectional sheet is coated with an antistatic coating liquid in an online coating unit to obtain a unidirectional sheet with an antistatic coating, preheated to 105-125°C, stretched 3.5-4.7 times transversely at 125-135°C, and then set at 225-240°C for 5-325 seconds before cooling at 50-180°C. After traction and winding, a polarizer protective film base film is obtained.

Images