Antistatic PET (Polyethylene Terephthalate) base film for preparing polaroid release film and preparation method of antistatic PET base film

Abstract

The invention relates to an antistatic PET (Polyethylene Terephthalate) base film for preparing a polaroid release film and a preparation method thereof, the release film base film is prepared by taking an optical-grade PET slice as a main body, adding modified PET with a specific structure and a modified SiO2 filler, and carrying out co-extrusion casting, a unique three-section stretching process and coating with a coating liquid. According to the invention, material modification and process improvement are carried out, specifically, an optical-grade PET slice is taken as a main body material, modified PET and a modified SiO2 filler with a specific structure are added, a film is prepared through co-extrusion casting and a unique three-section stretching process, and then the surface of the film is coated with a layer of antistatic coating liquid, so that the antistatic film is obtained. The finally prepared base film has low alignment angle, low transverse hot shrinkage rate and high surface adhesion, keeps the characteristics of high light transmittance and low haze of an optical-grade polyester film, endows the film with certain antistatic property, and is particularly suitable for being used as a release film of a high-end polaroid.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical display device protective film, in particular to an antistatic PET base film for preparing a polarizing plate release film and a preparation method thereof. BACKGROUND

[0002] The polarizing plate is a core component necessary for imaging of a liquid crystal display, is composed of multiple layers of composite structure, and has a polyvinyl alcohol (PVA) core layer for polarizing in the middle, and triacetate cellulose (TAC) protective layers on both sides, forming a polarizing plate original plate. According to different use requirements or storage and transportation requirements, a certain thickness of pressure sensitive adhesive (PSA) needs to be coated on one side of the polarizing plate original plate, and a release film for protecting the PSA is compounded; and on the other side, a protective film, a reflective film, or a semi-transmissive reflective film is compounded according to the product type, thereby forming a polarizing plate finished product.

[0003] Each layer of structure of the polarizing plate has a specific function, and the release film as a protective layer of the pressure sensitive adhesive needs to be peeled off during use, but cannot be peeled off together with the pressure sensitive adhesive, so the release film needs to have controllable release force and cleanliness. In the production of the polarizing plate release film, common raw materials include polyester base film, release agent, etc., and the polyester base film is a key raw material of the polarizing plate release film. However, the alignment angle of the polyester film used at present is relatively large, and when the quality of the polarizing plate is monitored, the high alignment angle leads to phase delay and angle deviation of light, which easily affects the final detection result. The existing technologies reduce the alignment angle of the polyester film from the process equipment or from the raw material, such as CN106433502A, CN113752600A, and CN116694038B, etc., but these technical solutions may not fully consider the high thermal dimensional stability (i.e. low shrinkage) and high adhesion of the release agent required by the polyester film as the release film base film when reducing the alignment angle. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application starts from the raw material itself and combines process improvement to prepare a polyester film, which meets the low thermal shrinkage, high release agent adhesion of the release film base film, and also meets the low alignment angle requirement of the polarizing plate, and the film can also be given certain antistatic property by coating liquid.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A preparation method of an antistatic PET base film for preparing a polarizing plate release film, comprising the following steps: S1, weighing a metered amount of optical grade PET chips, modified PET, and modified SiO2 filler, mixing them in a high-speed mixer, and then drying under vacuum drying; S2, the dried mixture is sent into a single screw extruder, the extrusion temperature is set to 255~285℃, and after extrusion through the die, it is rapidly cooled on a cooling roller to form a cast sheet; S3, the cast sheet is preheated to 90℃, and is subjected to a first transverse stretching with a stretching ratio of 1.5~2.5 times and a temperature setting of 95~105℃; then is subjected to a longitudinal stretching with a stretching ratio of 3.2~5 times and a temperature setting of 105~115℃; the film after the longitudinal stretching is subjected to a second transverse stretching with a stretching ratio of 2.5~3.5 times and a temperature setting of 120~135℃; the three-stage stretching temperature is gradually increased, and the total transverse stretching ratio is 3.75~6 times; S4, the stretched film is subjected to a heat setting treatment at 190~220℃ for 5~15s, is slowly cooled to 150℃ and kept for 10~30min, and then is cooled to room temperature, is coated with an antistatic coating liquid on the surface, is dried at 100~120℃, and finally is subjected to a corona treatment; is drawn and wound up; wherein, The modified PET is prepared by introducing 2-(pyridine-3-yl) terephthalic acid instead of part of terephthalic acid in the PET polymerization process, and then blending and melt-extruding with 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite after the polymerization is completed; The modified SiO2 filler is obtained by grafting a terpolymer of lauryl acrylate, glycidyl methacrylate and N-(4-vinylphenyl) acetamide onto the surface of KH570 modified SiO2 through free radical polymerization; The antistatic coating liquid comprises 70~80wt% water-based hydroxyl acrylate-polyurethane dispersion, 5~15wt% ionic liquid type antistatic agent, 1~3wt% curing agent, 0.5~2wt% accelerator, 0.1~0.5wt% wetting and leveling agent, and the balance of deionized water.

[0006] Further, the weight fractions of the optical grade PET chip, the modified PET and the nano filler are 100 parts, 8~15 parts and 3~8 parts.

[0007] Further, the preparation process of the 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite is as follows: Sodium-based montmorillonite and deionized water are added in a beaker, ultrasonic dispersion is performed to make them uniformly dispersed, then the mixture is moved to a water bath and heated to 60-70℃, 1-carboxyethyl-3-methyl imidazole chloride with a mass fraction of 20% of the sodium-based montmorillonite is slowly added while stirring, after the addition is completed, the mixture is kept for 2-3h, is filtered, is washed with water and is dried, and is ground to obtain the product.

[0008] Further, the modified PET is prepared by the following method: The reactor is charged with ethylene glycol and 2-(pyridine-3-yl) terephthalic acid, and tetrabutyl titanate is added as a catalyst, the temperature is raised to 200-230℃ for esterification, 2-4 hours after the reaction, terephthalic acid is added, the temperature is raised to 250℃, 2-4 hours after the reaction, antimony glycol is added as a catalyst, the pressure in the reactor is controlled at 0.3 MPa, the temperature is raised to 270℃, and the reaction is carried out for 2-3 hours; the reaction is naturally cooled and discharged to obtain polyterephthalic acid-co-2-(pyridine-3-yl) terephthalic acid-ethylene glycol ester; then the product is mixed with 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite in a high-speed mixer, and the mixture is melt blended and granulated by a twin-screw extruder to obtain the product.

[0009] Further, the molar ratio of terephthalic acid, 2-(pyridine-3-yl) terephthalic acid and ethylene glycol is 100:10-20:120; the mass ratio of polyterephthalic acid-co-2-(pyridine-3-yl) terephthalic acid-ethylene glycol ester to 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite is 9-9.5:0.5-1.

[0010] Further, the preparation steps of the modified SiO2 filler are as follows: 1) A certain amount of nano-SiO2 particles are first activated by potassium hydroxide, then dispersed in deionized water, and an equal amount of KH570 is added, stirred at 50℃ for 24 hours, filtered, washed, dried, and ground to obtain KH570 modified SiO2 powder; 2) The KH570 modified SiO2 powder is dispersed in THF, and lauryl acrylate, glycidyl methacrylate and N-(4-vinylphenyl) acetamide are added in sequence, and 1% of AIBN based on the total mass of monomers is added as an initiator, and the reaction is carried out at 70℃ under nitrogen protection for 12 hours; after the reaction is completed, centrifugal separation is carried out, and THF is used for washing three times to remove homopolymers, and the modified SiO2 filler is obtained after vacuum drying.

[0011] Further, the molar ratio of lauryl acrylate, glycidyl methacrylate and N-(4-vinylphenyl) acetamide is 50-70:15-25:15-25; and the sum of their masses is 80%-120% of the mass of the KH570 modified SiO2 powder.

[0012] Further, the ionic liquid type antistatic agent in the antistatic coating liquid is 1-ethyl-3-methyl imidazole bis-trifluoromethanesulfonylimide salt; the curing agent is hydrophilic aliphatic polyisocyanate; the accelerator is KH-560; the wetting and leveling agent is polyether modified polysiloxane; and the wet coating amount of the antistatic coating liquid is 5-15 g / m 2 .

[0013] Further, the preparation process of the aqueous hydroxyl acrylate-polyurethane dispersion is as follows: S1, preparing a polyurethane prepolymer In a reaction bottle, 60 parts by weight of polybutylene adipate glycol, 10 parts by weight of dimethylol propionic acid, 30 parts by weight of N-methyl pyrrolidone as a solvent were added, nitrogen was introduced, and the mixture was stirred and mixed uniformly at 80℃. The system was cooled to 60℃, 34 parts by weight of isophorone diisocyanate was added dropwise while stirring, 2 drops of dibutyltin dilaurate was added as a catalyst, the temperature was raised to 85℃, and the reaction was kept for 3-5h. After the reaction was completed, the temperature was lowered to 70℃, 6.5 parts by weight of hydroxyethyl methacrylate was slowly added, and the reaction was kept for 3h. S2, preparing a pre-emulsion The polyurethane prepolymer system of step S1 was cooled to 40℃, 7.5 parts by weight of triethylamine was added for neutralization reaction, then 400 parts by weight of deionized water was slowly added to the system under high-speed stirring, and high-speed shear emulsification was carried out, and the pre-emulsion was obtained. S3, preparing an acrylate monomer mixture 15 parts by weight of methyl methacrylate, 7 parts by weight of glycidyl methacrylate, 14 parts by weight of lauryl acrylate, 2 parts by weight of acrylic acid and 2 parts by weight of N-(4-vinyl)-acetamide were mixed uniformly, and the acrylate monomer mixture was obtained. S4, preparing a dispersion 0.5 parts by weight of potassium persulfate was dissolved in 10 parts by weight of deionized water to form an initiator aqueous solution, then one third of the amount was added to the pre-emulsion, the temperature was raised to 75℃, then the acrylate monomer mixture and the remaining initiator aqueous solution were added within 3h, after the dropwise addition was completed, the reaction was continued for 2h, and the reaction was completed after the reaction was completed. The temperature was lowered to room temperature, and the dispersion was obtained.

[0014] Further, in step S2, the temperature of each section of the extruder is set as follows: zone 1: 255-270℃, zone 2: 275-280℃, zone 3: 280-285℃, zone 4: 280-285℃, and die: 275-280℃.

[0015] The application further provides an antistatic PET base film for preparing a polarizing plate release film prepared by the preparation method.

[0016] The application realizes the highly uniform orientation of the molecular chain in the plane by introducing the rigid comonomer containing a pyridine ring and the modified PET with intercalated montmorillonite, and the synergistic effect of the three-stage stretching process, effectively reduces the optical anisotropy, and meets the needs of precise optical detection of the polarizing plate.

[0017] The montmorillonite and modified SiO2filler added in the modified PET provide rigidity and improve the heat resistance of the film, ensuring the dimensional stability during the processing and use of the polarizing plate.

[0018] The ternary copolymer grafted on the surface of the modified SiO2 filler improves the dispersibility of the filler in the PET matrix, greatly enhances the interface bonding force between the filler and the matrix, and ensures the high light transmittance and low haze of the PET film; on the other hand, the abundant active sites can form stronger chemical bonds or hydrogen bonds, thereby enhancing the activity of the antistatic agent coating and the adhesion of the antistatic agent coating.

[0019] The antistatic coating liquid formula is composed of a water-based hydroxyl acrylate-polyurethane dispersion, an antistatic agent and other additives, and the antistatic coating is thin, which has little effect on the optical properties of the base film; the formula adds an ionic liquid type antistatic agent, which can give the film certain antistatic properties; at the same time, the water-based hydroxyl acrylate-polyurethane dispersion is prepared by free radical polymerization of an unsaturated double bond-terminated polyurethane prepolymer and an acrylate monomer under an initiator, and the water-based resin used contains epoxy groups and long-chain alkyl groups that match the modified filler on the surface of the base film, so that high-strength crosslinking inside the coating and chemical bonding between the coating and the base film interface can be achieved during the curing process, solving the problems of poor adhesion, easy migration and poor durability of conventional coating liquids on inert PET surfaces, making the antistatic properties persistent and stable, and not affecting the optical properties of the base film; the active sites such as epoxy groups in the coating that match the modified filler can also form stronger chemical bonds or hydrogen bonds with the release agent, thereby enhancing the adhesion, and further ensuring the adhesion of the coating to the PET base film and the subsequent coating to the release agent.

[0020] Compared with the prior art, the present application has the following advantages: through material modification and process improvement, the present application specifically uses optical grade PET chips as the main material, adds modified PET and modified SiO2 filler with specific structures, and prepares a film through co-extrusion and a unique three-stage stretching process. The modified PET improves the rigidity and heat resistance of the molecular chain and provides heterogeneous nucleation points by introducing 2-(pyridine-3-yl) terephthalic acid comonomer and ionic liquid intercalated montmorillonite; the modified SiO2 filler realizes good compatibility with the matrix and internal lubrication by grafting a ternary copolymer on the surface; the three-stage stretching sequence of "lateral-longitudinal-lateral" and the step-by-step increasing temperature control synergistically control the orientation and crystallization of the molecular chain; and then a layer of antistatic coating liquid is coated on the surface of the film, and finally a base film with low orientation angle, low transverse thermal shrinkage rate and high surface adhesion is obtained, while maintaining the high light transmittance and low haze of the optical grade polyester film, and giving the film certain antistatic properties, which is particularly suitable for the manufacture of release films for high-end polarizing sheets. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be clearly and completely described below in connection with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0022] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0023] Most of the raw materials used in the present application are bulk products, which can be purchased in the market. The sources and models of some products are as follows:

[0024] Embodiment: An antistatic PET base film for preparing polarizing plate release film S1, weigh the measured optical grade PET chips, modified PET and modified SiO2filler, and mix them in a high-speed mixer, and then dry them under vacuum drying; S2, send the dried mixture into a single screw extruder, and set the extrusion temperature to 255-285℃ (the temperature of each section of the extruder is set to one zone: 255-270℃, two zones: 275-280℃, three zones: 280-285℃, four zones: 280-285℃, and the die: 275-280℃), and then quickly cool it on a cooling roller after extruding through the die to form a cast sheet; S3, preheat the cast sheet to 90℃, and perform a first transverse stretching with a stretching ratio of 1.8 times and a temperature of 105℃; then perform a longitudinal stretching with a stretching ratio of 4.6 times and a longitudinal stretching temperature of 115℃; and perform a second transverse stretching on the film after longitudinal stretching with a stretching ratio of 2.5 times and a temperature of 125℃; the three-stage stretching temperature increases gradually, and the total transverse stretching ratio (the product of the two stretching ratios) is 4.5 times; S4, heat set the stretched film at 190℃ for 15s, slowly cool it to 150℃ and keep it for 30min, and then cool it to room temperature, coat an antistatic coating liquid on the surface of the film, dry it at 100-120℃, and finally perform a corona treatment; and then pull and wind it.

[0025] The preparation methods of some raw materials used in the above experiments are as follows: 1. The modified PET is prepared by the following method: 1) In a beaker, add sodium-based montmorillonite and deionized water, ultrasonic dispersion to make it uniform, then move to the water bath condition, heating to 60-70℃, slowly add 20% of the mass of sodium-based montmorillonite 1-carboxyethyl-3-methyl imidazole chloride, after the completion of the drop, 2-3h, filter, water washing and drying, grinding to get 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite; 2) Add ethylene glycol and 2- (pyridine-3-yl) terephthalic acid to the reactor, add tetrabutyl titanate as catalyst, raise the temperature to 200~230℃ for esterification, after 2~3h, add terephthalic acid, raise the temperature to 250℃, after 2~4h, add ethylene glycol antimony as catalyst, control the pressure in the reactor at 0.3 MPa, raise the temperature to 270 ℃ for 2~3h; after the reaction is completed, the material is naturally cooled and discharged to obtain polyterephthalic acid-2- (pyridine-3-yl) terephthalic acid-ethylene glycol ester; then mix it with 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite in a high-speed mixer, melt blend and granulate through a twin-screw extruder to obtain the product.

[0026] In the preparation process of the modified PET, the molar ratio of terephthalic acid, 2- (pyridine-3-yl) terephthalic acid and ethylene glycol is 100:20:120; the mass ratio of polyterephthalic acid-2- (pyridine-3-yl) terephthalic acid-ethylene glycol ester to 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite is 9:1.

[0027] 2, the preparation steps of the modified SiO2 filler are as follows: 1) A certain amount of nano-SiO2 particles are first activated with potassium hydroxide, then dispersed in deionized water and added with an equal amount of KH570, stirred at 50℃ for 24h, filtered, washed, dried and ground to obtain KH570 modified SiO2 powder; 2) The KH570 modified SiO2 powder is dispersed in THF, and lauryl acrylate, glycidyl methacrylate and N- (4-vinylphenyl) acetamide are added in sequence, and 1% of the total mass of monomers AIBN is added as initiator, and the reaction is carried out at 70℃ under nitrogen protection for 12h; after the reaction is completed, centrifugal separation is carried out, and THF is used for washing three times to remove homopolymer, and vacuum drying is carried out to obtain the modified SiO2 filler.

[0028] In the preparation process of the modified SiO2 filler, the molar ratio of lauryl acrylate, glycidyl methacrylate and N- (4-vinylphenyl) acetamide is 60:20:20; the sum of their masses is 100% of the KH570 modified SiO2 powder.

[0029] 3, the preparation process of the antistatic coating liquid is as follows: An aqueous hydroxyl acrylate-polyurethane dispersion is prepared by the following steps: S1, preparing a polyurethane prepolymer In a reaction bottle, 60 parts by weight of polybutylene adipate glycol, 10 parts by weight of dimethylol propionic acid, 30 parts by weight of N-methyl pyrrolidone as a solvent, nitrogen is introduced, the temperature is raised to 80℃, and the mixture is stirred until uniform, the system is cooled to 60℃, 34 parts by weight of isophorone diisocyanate is added dropwise while stirring, 2 drops of dibutyltin dilaurate is added as a catalyst, the temperature is raised to 85℃, and the reaction is kept for 3-5 hours; after the reaction is completed, the temperature is lowered to 70℃, 6.5 parts by weight of hydroxyethyl methacrylate is slowly added, and the reaction is kept for 3 hours; S2, preparing a pre-emulsion The polyurethane prepolymer system of step S1 is cooled to 40℃, 7.5 parts by weight of triethylamine is added for neutralization reaction, then 400 parts by weight of deionized water is slowly added to the system under high-speed stirring, and high-speed shearing emulsification is carried out, and the pre-emulsion is obtained; S3, preparing an acrylate monomer mixture 15 parts by weight of methyl methacrylate, 7 parts by weight of glycidyl methacrylate, 14 parts by weight of lauryl acrylate, 2 parts by weight of acrylic acid, and 2 parts by weight of N-(4-vinyl)-acetamide are mixed uniformly, and the acrylate monomer mixture is obtained; S4, preparing a dispersion 0.5 parts by weight of potassium persulfate is dissolved in 10 parts by weight of deionized water to form an initiator aqueous solution, then one-third of the amount is added to the pre-emulsion, the temperature is raised to 75℃, then the acrylate monomer mixture and the remaining initiator aqueous solution are added within 3 hours, after the dropwise addition is completed, the reaction is continued for 2 hours; after the reaction is completed, the temperature is lowered to room temperature, and the dispersion is obtained.

[0030] 75 g of the aqueous hydroxyl acrylate-polyurethane dispersion, 10 g of 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonimide salt, 2 g of hydrophilic aliphatic polyisocyanate, 1 g of KH560, 0.3 g of polyether modified polysiloxane, and 11.7 g of deionized water are weighed.

[0031] The above raw materials and the above preparation process are used to obtain the following specific examples: In example 1, 100 parts by weight of optical grade PET chips, 8 parts by weight of modified PET, and 3 parts by weight of modified SiO2 filler are mixed in a high-speed mixer, and then dried under vacuum drying; S2, the dry mixture is sent into a single screw extruder, the extrusion temperature is set to 255-285℃ (the temperature of each section of the extruder is set to a zone: 255-270℃, a second zone: 275-280℃, a third zone: 280-285℃, a fourth zone: 280-285℃, a die: 275-280℃), and after extrusion through the die, it is rapidly cooled on a cooling roller to form a cast sheet; S3, the cast sheet is preheated to 90℃, and is subjected to a first transverse stretching with a stretching ratio of 1.8 times and a temperature of 105℃; then is subjected to a longitudinal stretching with a stretching ratio of 4.6 times and a longitudinal stretching temperature set to 115℃; the film after the longitudinal stretching is subjected to a second transverse stretching with a stretching ratio of 2.5 times and a temperature set to 125℃; the three-stage stretching temperature is gradually increased, and the total transverse stretching ratio (the product of the two stretching ratios) is 4.5 times; S4, the stretched film is subjected to a heat setting treatment at 190℃ for 15s, is slowly cooled to 150℃ and kept for 30min, and then is cooled to room temperature, a layer of antistatic coating liquid is coated on the surface of the film, the wet coating amount is 5g / m 2 ; is dried at 100-120℃, and finally is subjected to a corona treatment; is drawn and wound.

[0032] S1, 100 parts by weight of optical grade PET chips, 8 parts by weight of modified PET, and 3 parts by weight of modified SiO2filler are weighed and mixed in a high-speed mixer, and then are dried under vacuum drying; S2, the dry mixture is sent into a single screw extruder, the extrusion temperature is set to 255-285℃ (the temperature of each section of the extruder is set to a zone: 255-270℃, a second zone: 275-280℃, a third zone: 280-285℃, a fourth zone: 280-285℃, a die: 275-280℃), and after extrusion through the die, it is rapidly cooled on a cooling roller to form a cast sheet; S3, the cast sheet is preheated to 90℃, and is subjected to a first transverse stretching with a stretching ratio of 1.8 times and a temperature of 105℃; then is subjected to a longitudinal stretching with a stretching ratio of 4.6 times and a longitudinal stretching temperature set to 115℃; the film after the longitudinal stretching is subjected to a second transverse stretching with a stretching ratio of 2.5 times and a temperature set to 125℃; the three-stage stretching temperature is gradually increased, and the total transverse stretching ratio (the product of the two stretching ratios) is 4.5 times; S4, the stretched film is subjected to a heat setting treatment at 190℃ for 15s, is slowly cooled to 150℃ and kept for 30min, and then is cooled to room temperature, a layer of antistatic coating liquid is coated on the surface of the film, the wet coating amount is 10g / m 2 ; is dried at 100-120℃, and finally is subjected to a corona treatment; is drawn and wound.

[0033] Example 3 S1, take 100 parts by weight of optical grade PET chips, 8 parts by weight of modified PET, 3 parts by weight of modified SiO2filler into a high-speed mixer, then dry under vacuum drying; S2, the dried mixture is sent into a single screw extruder, the extrusion temperature is set to 255~285℃ (the temperature of each section of the extruder is set to one zone: 255~270℃, two zones: 275~280℃, three zones: 280~285℃, four zones: 280~285℃, die: 275~280℃), after extruding through the die, it is rapidly cooled on the cooling roller to form a cast sheet; S3, the cast sheet is preheated to 90℃, and is stretched once in the transverse direction at a stretch ratio of 1.8 times and a temperature of 105℃; then it is stretched in the longitudinal direction at a stretch ratio of 4.6 times, and the longitudinal stretching temperature is set to 115℃; the film after longitudinal stretching is stretched twice in the transverse direction at a stretch ratio of 2.5 times and a temperature of 125℃; the three-stage stretching temperature increases gradually, and the total transverse stretching ratio (the product of the two stretching ratios) is 4.5 times; S4, the stretched film is heat set at 190℃ for 15s, slowly cooled to 150℃ for 30min, and then cooled to room temperature, a layer of antistatic coating liquid is coated on the surface of the film, the wet coating amount is 15g / m 2 ; dried at 100~120℃, and finally subjected to corona treatment; traction winding.

[0034] Example 4 S1, take 100 parts by weight of optical grade PET chips, 12 parts by weight of modified PET, 5 parts by weight of modified SiO2filler into a high-speed mixer, then dry under vacuum drying; S2, the dried mixture is sent into a single screw extruder, the extrusion temperature is set to 255~285℃ (the temperature of each section of the extruder is set to one zone: 255~270℃, two zones: 275~280℃, three zones: 280~285℃, four zones: 280~285℃, die: 275~280℃), after extruding through the die, it is rapidly cooled on the cooling roller to form a cast sheet; S3, the cast sheet is preheated to 90℃, and is stretched once in the transverse direction at a stretch ratio of 1.8 times and a temperature of 105℃; then it is stretched in the longitudinal direction at a stretch ratio of 4.6 times, and the longitudinal stretching temperature is set to 115℃; the film after longitudinal stretching is stretched twice in the transverse direction at a stretch ratio of 2.5 times and a temperature of 125℃; the three-stage stretching temperature increases gradually, and the total transverse stretching ratio (the product of the two stretching ratios) is 4.5 times; S4, the stretched film is heat set at 190℃ for 15s, slowly cooled to 150℃ for 30min, and then cooled to room temperature, a layer of antistatic coating liquid is coated on the surface of the film, the wet coating amount is 10 g / m2 ; drying at 100-120°C, and finally corona treatment; traction and winding.

[0035] Example 5 S1, 100 parts by weight of optical grade PET chips, 15 parts by weight of modified PET, and 8 parts by weight of modified SiO2filler were placed in a high-speed mixer and mixed, and then dried under vacuum drying; S2, the dried mixture was sent into a single-screw extruder, the extrusion temperature was set to 255-285°C (the temperature of each section of the extruder was set to a first zone: 255-270°C, a second zone: 275-280°C, a third zone: 280-285°C, a fourth zone: 280-285°C, and a die: 275-280°C), and after extrusion through the die, the film was rapidly cooled on a cooling roller to form a cast sheet; S3, the cast sheet was preheated to 90°C, and then stretched in the transverse direction at a stretch ratio of 1.8 times at a temperature of 105°C, and then stretched in the longitudinal direction at a stretch ratio of 4.6 times at a longitudinal stretching temperature of 115°C; the film after longitudinal stretching was stretched in the transverse direction again at a stretch ratio of 2.5 times at a temperature of 125°C; the three-stage stretching temperature was increased step by step, and the total transverse stretching ratio (the product of the two stretching ratios) was 4.5 times; S4, the stretched film was heat set at 190°C for 15s, slowly cooled to 150°C for 30min, and then cooled to room temperature, and a layer of antistatic coating liquid was coated on the surface of the film, with a wet coating amount of 10 g / m 2 ; drying at 100-120°C, and finally corona treatment; traction and winding.

[0036] Comparative Example 1 Compared with Example 4, no modified PET was added, and the amount was replaced by an equal amount of ordinary optical grade PET chips.

[0037] Comparative Example 2 Compared with Example 4, ungrafted KH570-SiO2powder was used instead of modified SiO2filler.

[0038] Comparative Example 3 Compared with Example 4, no antistatic coating liquid was coated.

[0039] Comparative Example 4 Compared with Example 4, the antistatic coating liquid was a commercially available antistatic liquid (PEDOT / PSS dispersion slurry, Clevios™ series of Heraeus).

[0040] In the above preparation process, the thickness of the film was controlled to be 40±2 μm; the prepared film was tested for the following properties, and the results are recorded in Table 1.

[0041] Orientation angle: The orientation angle of the film was measured every 50mm by an automatic ellipsometer, and the maximum value was recorded.

[0042] Thermal shrinkage: The film was placed in a 150°C air oven for 30 minutes, and the change in the transverse direction (TD) dimension was measured.

[0043] Transmittance and haze: According to GB / T 2410-2008, a hazemeter was used to measure the transmittance and haze.

[0044] Adhesion: The adhesion of the cured film to the base film was tested by the cross-hatch method, with 0B being the worst and 5B being the best.

[0045] Residual adhesion: The silicone release agent was coated, and the residual adhesion was tested according to GB / T 25256-2010.

[0046] Surface resistance: GB / T 1410-2006, test voltage 500V, charging time 60s, environmental conditions 23°C / 50% RH.

[0047] Table 1

[0048] Comparative Examples 1-3, the antistatic agent coating amount increased, the conductivity was enhanced, and the optical performance had a slight decline, but because the coating was well combined with the base film, the adhesion remained at a high level (4B-5B). Comparative Example 2 and Examples 4 and 5, the fixed coating amount was 10g / m 2, increasing the amount of modified PET and modified SiO2 filler, although the light transmittance will slightly decrease due to the scattering of fillers, the dimensional stability of the film (thermal shrinkage rate is reduced to 0.9%) is significantly improved and the alignment angle is further reduced, which reflects the decisive role of matrix modification on the core optical and thermal properties. In Comparative Examples 1 and 2, the modified PET and modified SiO2 filler in the system affect the alignment angle and surface adhesion of the film material, respectively. The adhesion of Comparative Example 2 decreases significantly because the interface effect of the modified SiO2 filler and the rich active sites are lacking, which leads to slight aggregation of the filler in the base film, resulting in uneven coating of the antistatic coating liquid and a decrease in adhesion. This further leads to a decrease in the stability of the release agent on its surface and a significant decrease in residual adhesion. Comparative Example 4 is coated with a common antistatic coating liquid, which has a significant antistatic effect, but has weak adhesion to PET. Since the antistatic coating layer serves as an intermediate coating layer between the base film and the release agent, it needs to have good adhesion to both the base film and the release agent. The water-based hydroxyl acrylate-polyurethane dispersion plays a significant role as a bridging agent between the two. The use of commercially available antistatic liquid cannot establish this chemical bridge, resulting in weak interfacial adhesion, which further leads to unstable release agent coating and a decrease in residual adhesion. Comparative Example 3 is not coated with an antistatic coating liquid, but the surface of its base film contains modified SiO2 filler, which provides a rich source of active sites, so it can still maintain high adhesion to the release agent (5B). However, its antistatic performance is significantly reduced due to the lack of an antistatic coating layer.

[0049] Although the embodiments of the present application have been disclosed as above, they are not limited to the applications listed in the specification and embodiments, and can be fully applied to various fields suitable for the present application. Additional modifications can be easily made by those skilled in the art, and therefore the present application is not limited to specific details, but is within the general concept defined by the claims and their equivalents.

Claims

1. A method for producing an antistatic PET base film for a polarizing sheet release film, characterized by, It comprises the following steps: S1, weigh the measured optical grade PET chips, modified PET, and modified SiO2 filler, and mix them in a high-speed mixer, and then dry them under vacuum drying; S2, send the dried mixture into a single screw extruder, set the extrusion temperature to 255-285℃, extrude through the die, and then quickly cool on the cooling roller to form a cast sheet; S3, preheat the cast sheet to 90℃, perform a first transverse stretching with a stretching ratio of 1.5-2.5 times and a temperature setting of 95-105℃, then perform a longitudinal stretching with a stretching ratio of 3.2-5 times and a temperature setting of 105-115℃, and then perform a second transverse stretching on the longitudinally stretched film with a stretching ratio of 2.5-3.5 times and a temperature setting of 120-135℃; the three-stage stretching temperature gradually increases, and the total transverse stretching ratio is 3.75-6 times; S4, heat set the stretched film at 190-220℃ for 5-15s, slowly cool to 150℃ and keep for 10-30min, then cool to room temperature, coat an antistatic coating liquid on the surface of the film, dry at 100-120℃, and finally perform a corona treatment; pull and wind up; wherein, The modified PET is prepared by introducing 2-(pyridine-3-yl) terephthalic acid instead of part of terephthalic acid in the PET polymerization process, and then blending with 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite and melt extruding after polymerization is completed; The modified SiO2 filler is a ternary copolymer of lauryl acrylate, glycidyl methacrylate, and N-(4-vinylphenyl) acetamide grafted on the surface of KH570 modified SiO2 through free radical polymerization; The antistatic coating liquid comprises 70-80wt% water-based hydroxyl acrylate-polyurethane dispersion, 5-15wt% ionic liquid type antistatic agent, 1-3wt% curing agent, 0.5-2wt% accelerator, 0.1-0.5wt% wetting and leveling agent, and the balance of deionized water.

2. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 1, characterized by, The weight fractions of the optical grade PET chips, modified PET, and nano filler are 100 parts, 8-15 parts, and 3-8 parts.

3. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 1, characterized by, The preparation process of the 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite is as follows: In a beaker, add sodium-based montmorillonite and deionized water, ultrasonic to disperse uniformly, then move to water bath condition, heat to 60-70℃, slowly add 1-carboxyethyl-3-methyl imidazole chloride with a mass fraction of 20% of sodium-based montmorillonite while stirring, after adding, keep for 2-3h, filter, wash with water, and dry, then crush to obtain.

4. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 1, characterized by, The modified PET is prepared by the following method: The reactor is added with ethylene glycol and 2-(pyridine-3-yl) terephthalic acid, and tetrabutyl titanate is added as a catalyst, the temperature is raised to 200-230 DEG C for esterification, 2-4 hours later, terephthalic acid is added, the temperature is raised to 250 DEG C, 2-4 hours later, antimony ethylene glycol is added as a catalyst, the pressure in the reactor is controlled at 0.3 MPa, the temperature is raised to 270 DEG C, and the reaction is carried out for 2-3 hours; the reaction is finished, the product is discharged after natural cooling, and polyterephthalic acid-co-2-(pyridine-3-yl) terephthalic acid-ethylene glycol ester is obtained; then the product is mixed with 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite in a high-speed mixer, and the mixture is melt blended and granulated through a double-screw extruder, and the modified polyterephthalic acid-co-2-(pyridine-3-yl) terephthalic acid-ethylene glycol ester is obtained.

5. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 4, characterized by, The molar ratio of the terephthalic acid, 2-(pyridine-3-yl) terephthalic acid and ethylene glycol is 100:10-20:120; and the mass ratio of the polyterephthalic acid-co-2-(pyridine-3-yl) terephthalic acid-ethylene glycol ester and 1-carboxyethyl-3-methyl imidazole chloride intercalated montmorillonite is 9-9.5:0.5-1.

6. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 1, characterized in that, The preparation steps of the modified SiO2 filler are as follows: 1) a certain amount of nano-SiO2 particles are first activated by potassium hydroxide, then dispersed in deionized water, and an equal amount of KH570 is added, stirred at 50 DEG C for 24 hours, filtered, washed, dried and ground to obtain KH570 modified SiO2 powder; 2) the KH570 modified SiO2 powder is dispersed in THF, and lauryl acrylate, glycidyl methacrylate and N-(4-vinylphenyl) acetamide are added in sequence, and 1% of AIBN based on the total mass of monomers is added as an initiator, and the reaction is carried out at 70 DEG C under nitrogen protection for 12 hours; after the reaction is completed, centrifugal separation is carried out, and the product is washed with THF three times to remove homopolymers, and the modified SiO2 filler is obtained after vacuum drying.

7. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 6, characterized in that, The molar ratio of the lauryl acrylate, glycidyl methacrylate and N-(4-vinylphenyl) acetamide is 50-70:15-25:15-25; and the sum of the masses thereof is 80%-120% of the mass of the KH570 modified SiO2 powder.

8. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 1, characterized by, The ionic liquid type antistatic agent in the antistatic coating solution is 1-ethyl-3-methyl imidazole bis-trifluoromethyl sulfonimide salt; the curing agent is hydrophilic aliphatic polyisocyanate; the accelerator is KH-560; the wetting and leveling agent is polyether modified polysiloxane; the wet coating amount of the antistatic coating solution is 5~15g / m 2 .

9. The method for producing an antistatic PET base film for a polarizing sheet release film according to claim 1, characterized in that, The preparation process of the aqueous hydroxyl acrylate-polyurethane dispersion is as follows: S1, preparation of polyurethane prepolymer In a reaction bottle, 60 parts by weight of polybutylene adipate glycol, 10 parts by weight of dimethylolpropionic acid, 30 parts by weight of N-methylpyrrolidone as a solvent, nitrogen is introduced, the temperature is raised to 80 DEG C, the system is cooled to 60 DEG C, 34 parts by weight of isophorone diisocyanate is added dropwise, and 2 drops of dibutyltin dilaurate is added as a catalyst, the temperature is raised to 85 DEG C, and the reaction is carried out for 3-5 hours; after the reaction is completed, the temperature is lowered to 70 DEG C, 6.5 parts by weight of hydroxyethyl methacrylate is slowly added, and the reaction is carried out for 3 hours; S2, preparation of pre-emulsion The polyurethane prepolymer system of step S1 is cooled to 40 DEG C, 7.5 parts by weight of triethylamine is added for neutralization, and then 400 parts by weight of deionized water is slowly added to the system under high-speed stirring for high-speed shearing emulsification, and the pre-emulsion is obtained; S3, preparation of acrylate monomer mixture 15 parts by weight of methyl methacrylate, 7 parts by weight of glycidyl methacrylate, 14 parts by weight of lauryl acrylate, 2 parts by weight of acrylic acid and 2 parts by weight of N-(4-vinyl)-acetamide are mixed homogeneously, and thus obtained; S4, preparing a dispersion Dissolve 0.5 parts by weight of potassium persulfate in 10 parts by weight of deionized water to form an initiator aqueous solution, then take one-third of the amount and add it to the pre-emulsion, the temperature rises to 75℃, then in 3 hours, add the acrylate monomer mixture and the remaining initiator aqueous solution, after the dropwise addition is completed, continue to react for 2h; after the reaction is completed, it is cooled to room temperature.

10. The antistatic PET base film for preparing a polarizing plate release film prepared by the preparation method according to any one of claims 1 to 9.

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