Optical polyester film and preparation method thereof

Abstract

The present invention provides an optical polyester film and a preparation method thereof, and relates to the technical field of optical films; the optical polyester film comprises a base film and a primer layer arranged on at least one side of the base film; the primer layer is obtained by coating a primer liquid. The optical polyester film provided by the present invention introduces nano-silicon dioxide modified by dopamine and polyvinyl alcohol on the surface of the polyester film base film, fully utilizes the characteristics of dopamine and polyvinyl alcohol, enhances the chemical reaction between nano-silicon dioxide and waterborne polyurethane, thereby improving the stability of the primer liquid on the basis of obtaining a primer liquid with uniform dispersion and good compatibility; and avoids adding a lubricant internally by coating the primer liquid online, so as to provide the optical polyester film with better optical performance and hydrophobic and stain-resistant performance, thereby improving its opening performance on the basis of ensuring the optical performance of the polyester film, so that the prepared polyester film can take into account both the opening performance and the optical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of optical films, and in particular to an optical polyester film and a preparation method thereof. Background Art

[0002] Biaxially stretched optical polyester film is widely used in the deep processing of various optical functional film materials such as brightening films, diffusion brightening composite films, etc. due to its good dimensional stability, chemical resistance, high transparency and good processability compared with other plastic films. It has huge market potential in the field of display devices.

[0003] In order to ensure that the film does not stick during production, storage and transportation, a certain amount of open masterbatch is added during the production of biaxially stretched optical polyester film at this stage; however, as the amount of open masterbatch added increases, the optical properties of the polyester film will continue to decline, which will inevitably affect the application of polyester film in fields requiring high optical properties.

[0004] In view of this, providing a polyester film that takes both opening performance and optical performance into consideration is a technical problem that urgently needs to be solved. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in order to solve the problem that it is difficult for polyester films in the prior art to strike a balance between opening performance and optical performance, the present invention provides an optical polyester film, which, by coating a primer layer on a base film, can improve the opening performance of the polyester film while ensuring its optical performance, thereby solving the problem that it is difficult for polyester films in the prior art to strike a balance between opening performance and optical performance.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] An optical polyester film comprises a base film and a primer layer disposed on at least one side of the base film;

[0008] The primer layer is obtained by coating a primer liquid;

[0009] The primer solution is prepared as follows:

[0010] S01: mixing water and DMF to obtain a DMF mixed solution;

[0011] S02: placing nano-silicon dioxide in water to prepare a nano-silicon dioxide dispersion; adding dopamine to the nano-silicon dioxide dispersion under high-speed stirring, reacting at 35° C. for 48 hours, then centrifugally washing it, dispersing it in a DMF mixed solution, and performing ultrasonic dispersion treatment to obtain a dopamine-modified nano-silicon dioxide dispersion;

[0012] S03: adding polyvinyl alcohol dropwise to the dopamine-modified nano-silicon dioxide dispersion under high-speed stirring to obtain a modified nano-silicon dioxide dispersion;

[0013] S04: preparing a polyurethane prepolymer using oligomer diol, diisocyanate compound, hydrophilic monomer and hydroxide as raw materials;

[0014] S05: adding the polyurethane prepolymer to the modified nano-silicon dioxide dispersion, stirring at high speed for reaction for 1 hour; adding deionized water dropwise to the system for emulsification to obtain a primer solution.

[0015] Optionally, the mass ratio of the dopamine to the nano-silicon dioxide is in the range of (0.1-5):1; the mass ratio of the polyvinyl alcohol to the nano-silicon dioxide is in the range of (0.3-10):1.

[0016] Optionally, the mass ratio of the polyurethane prepolymer to the nano-silicon dioxide is in the range of 1:(0.03-0.4).

[0017] Optionally, step S04 includes: adding 10-50 parts of oligomer diol and 2-9 parts of catalyst to 10-40 parts of diisocyanate compound in parts by weight, reacting at 50° C. for 1-2 hours, then heating to 60° C., adding 2-9 parts of hydrophilic monomer, and continuing to react for 6-8 hours; adding hydroxide and reacting for 1-2 hours to obtain the polyurethane prepolymer.

[0018] Optionally, the oligomer diol is selected from at least one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone diol, polycarbonate diol, polyoxyethylene-polyoxypropylene-polyoxyethylene glycol, polyethylene adipate diol, polybutylene adipate diol, polyethylene terephthalate diol, polybutylene terephthalate diol, α, ω-dihydroxy polydimethylsiloxane, dihydroxy polydiphenylsiloxane, and dihydroxy polytrifluoropropylmethylsiloxane.

[0019] Optionally, the diisocyanate compound is selected from at least one of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate, diphenylmethane 4,4-diisocyanate, methylcyclohexyl diisocyanate, and 2,2,4-trimethylhexane diisocyanate.

[0020] Optionally, the hydrophilic monomer is selected from at least one of dimethylol propionic acid, dimethylol butyric acid, and sodium 1,2-dihydroxy-3-propanesulfonate.

[0021] Optionally, the catalyst is dibutyltin dilaurate.

[0022] Optionally, the hydroxide is potassium hydroxide.

[0023] Another object of the present invention is to provide a method for preparing the optical polyester film as described above, comprising the following steps:

[0024] S1: feeding the base film raw material into the corresponding extrusion system for melt extrusion, the melt extrusion temperature is 255°C to 290°C, and obtaining a base film melt;

[0025] S2: After the base film melt flows through the die head, it forms an unoriented cast thick sheet on the rotating cooling roller;

[0026] S3: preheating the cooled cast thick sheet and longitudinally stretching it by 2.8 to 3.8 times to obtain a longitudinally stretched film;

[0027] S4: coating the primer liquid on at least one surface of the longitudinally stretched film to obtain a film coated with the primer liquid;

[0028] S5: The film coated with the primer is held by a clip and introduced into a preheating zone for transverse stretching, and after preheating and drying at 90°C-110°C, it is transversely stretched by 2.5 times to 4.5 times at 140°C-160°C to obtain a stretched film;

[0029] S6: heat-setting the stretched film at a temperature of 160° C. to 250° C., and rolling it up after cooling to obtain an optical polyester film.

[0030] The beneficial effects of the present invention are:

[0031] The optical polyester film provided by the present invention introduces nano silicon dioxide modified by dopamine and polyvinyl alcohol on the surface of the polyester film base film, fully utilizes the characteristics of dopamine and polyvinyl alcohol, enhances the chemical reaction between nano silicon dioxide and waterborne polyurethane, thereby improving the stability of the primer liquid on the basis of preparing a primer liquid with uniform dispersion and good compatibility; and avoids internal addition of a lubricant by online coating of the primer liquid, so as to provide the optical polyester film with better optical performance and hydrophobic and stain-resistant performance, thereby improving the opening performance of the polyester film on the basis of ensuring the optical performance of the polyester film, so that the prepared polyester film can take into account the problems of opening performance and optical performance, and at the same time, is endowed with hydrophobic and stain-resistant performance that ordinary films with internal addition of an opening agent do not have. DETAILED DESCRIPTION

[0032] The present invention is now further described in detail. The embodiments described below are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0033] In order to solve the problem that it is difficult for polyester films in the prior art to balance opening performance and optical performance, the present invention provides an optical polyester film, which includes a base film and a primer layer arranged on at least one side of the base film; wherein the base film can be any existing polyester film base film; the primer layer is obtained by coating a primer liquid on the base film; the primer liquid in the present invention is prepared according to the following method:

[0034] S01: mixing water and DMF to obtain a DMF mixed solution;

[0035] S02: placing nano-silicon dioxide in water to prepare a nano-silicon dioxide dispersion; adding dopamine to the nano-silicon dioxide dispersion under high-speed stirring, reacting at 35° C. for 48 hours, then centrifugally washing it, dispersing it in a DMF mixed solution, and performing ultrasonic dispersion treatment to obtain a dopamine-modified nano-silicon dioxide dispersion;

[0036] S03: adding polyvinyl alcohol dropwise to the dopamine-modified nano-silicon dioxide dispersion under high-speed stirring to obtain a modified nano-silicon dioxide dispersion;

[0037] S04: preparing a polyurethane prepolymer using oligomer diol, diisocyanate compound, hydrophilic monomer and hydroxide as raw materials;

[0038] S05: adding the polyurethane prepolymer to the modified nano-silicon dioxide dispersion, stirring at high speed for reaction for 1 hour; adding deionized water dropwise to the system for emulsification to obtain a primer solution.

[0039] Step S01 specifically includes: mixing water and DMF in a mass ratio of 1:(1-20) to prepare a DMF mixed solution.

[0040] Based on the fact that dopamine contains many amine functional groups and catechol functional groups, dopamine will self-polymerize into a sticky polymer - polydopamine (PDA), which can adhere to nano-silica through oxidation of the catechol group into a quinone form. In the present invention, dopamine is preferably first added to the nano-silica dispersion, and the nano-silica is modified by dopamine, so as to make full use of the characteristics of dopamine and enhance the chemical reaction between nano-silica and polyurethane, thereby improving the uniformity of nano-silica dispersion and the compatibility in the primer.

[0041] Specifically, the present invention preferably adds dopamine to the nano-silica dispersion for modification according to the following method: the nano-silica dispersion is placed in a three-necked flask, dopamine hydrochloride is added according to the formula amount under high-speed stirring, reacts at room temperature for 24 hours, and then centrifuges and washes, and then disperses the nano-silica after centrifugation and washing in a DMF mixture prepared by water and DMF, and performs ultrasonic dispersion treatment to obtain a first modified nano-silica dispersion.

[0042] In order to further improve the stability of the primer, the present invention drips polyvinyl alcohol into the nano-silicon dioxide dispersion after the first modification according to the formula amount under high-speed stirring conditions to obtain a modified nano-silicon dioxide dispersion.

[0043] The invention improves the dispersibility of nano silicon dioxide by modifying the nano silicon dioxide. Specifically, the invention first introduces dopamine and polyvinyl alcohol into the nano silicon dioxide dispersion liquid. On the one hand, the nano silicon dioxide is modified by dopamine to improve the dispersibility of the nano silicon dioxide. On the other hand, the polyvinyl alcohol is used to improve the stability of the modified nano silicon dioxide dispersion liquid, thereby improving the stability of the prepared primer liquid. The nano silicon dioxide dispersion liquid after secondary modification is mixed with a polyurethane prepolymer. On the basis of improving the dispersibility of the nano silicon dioxide, the strong hydrogen bonding effect between dopamine hydrochloride, polyvinyl alcohol and polyurethane is used to further improve the stability of the primer liquid.

[0044] The preparation method of the primer provided by the present invention introduces dopamine and polyvinyl alcohol in situ into waterborne polyurethane to modify nano-silicon dioxide, fully utilizes the characteristics of dopamine, enhances the chemical reaction between nano-silicon dioxide and waterborne polyurethane, thereby improving the stability of the composite emulsion on the basis of preparing a composite emulsion with uniform dispersion and good compatibility, thereby improving the dispersibility of the waterborne polyurethane coating and improving the mechanical properties of the waterborne polyurethane coating.

[0045] The optical polyester film provided by the present invention introduces nano-silicon dioxide modified by dopamine and polyvinyl alcohol on the surface of the polyester film base film, fully utilizes the characteristics of dopamine and polyvinyl alcohol, enhances the chemical reaction between the nano-silicon dioxide and the aqueous polyurethane, thereby improving the stability of the primer liquid on the basis of preparing a primer liquid with uniform dispersion and good compatibility; and avoids internal addition of a lubricant by online coating of the primer liquid, so as to provide the optical polyester film with better optical performance and hydrophobic and anti-fouling performance, thereby improving its opening performance on the basis of ensuring the optical performance of the polyester film, so that the prepared polyester film can take into account the problems of both opening performance and optical performance.

[0046] To ensure the mechanical properties of the primer layer, the mass ratio of water to N,N-dimethylformamide in the preferred step S01DMF mixed solution of the present invention is in the range of 1:(1-20), and the concentration of nano-silicon dioxide in the prepared nano-silicon dioxide dispersion is in the range of 1-20 mg / mL; the mass ratio of dopamine to nano-silicon dioxide is preferably in the range of (0.1-5):1; the mass ratio of polyvinyl alcohol to nano-silicon dioxide is in the range of (0.3-10):1; the mass ratio of polyurethane prepolymer to nano-silicon dioxide is preferably in the range of 1:(0.03-0.4).

[0047] The polyurethane prepolymer preferably prepared by the present invention has an oligomer diol as a soft segment and an isocyanate compound as a hard segment; specifically, step S04 comprises: according to parts by weight, 10-50 parts of oligomer diol and 2-9 parts of catalyst are added dropwise to 10-40 parts of diisocyanate compound, reacting at 50° C. for 1-2 hours, then gradually heating to 60° C., adding 2-9 parts of hydrophilic monomer, continuing to react for 6-8 hours, and determining the isocyanate group (NCO) content of the generated prepolymer by the toluene-di-n-butylamine method. When the NCO content is close to the theoretical value, adding hydroxide to react for 1-2 hours to obtain a polyurethane prepolymer.

[0048] The present invention preferably uses at least one of the oligomer diols selected from polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone diol, polycarbonate diol, polyoxyethylene-polyoxypropylene-polyoxyethylene glycol, polyethylene adipate diol, polybutylene adipate diol, polyethylene terephthalate diol, polybutylene terephthalate diol, α,ω-dihydroxy polydimethylsiloxane, dihydroxy polydiphenylsiloxane, and dihydroxy polytrifluoropropylmethylsiloxane; preferably di The isocyanate compound is selected from at least one of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate, diphenylmethane 4,4-diisocyanate, methylcyclohexyl diisocyanate, and 2,2,4-trimethylhexane diisocyanate; the hydrophilic monomer is preferably selected from at least one of dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, and sodium 1,2-dihydroxy-3-propanesulfonate; the catalyst is preferably dibutyltin dilaurate; and the hydroxide is preferably potassium hydroxide.

[0049] In the primer liquid preferably prepared by the present invention, the mass fraction of nano silicon dioxide is 0.005wt%-40wt%; and the solid content of the primer liquid is 0.2%-45%.

[0050] Another object of the present invention is to provide a method for preparing the optical polyester film as described above, comprising the following steps:

[0051] S1: feeding the base film raw material into the corresponding extrusion system for melt extrusion, the melt extrusion temperature is 255°C to 290°C, and obtaining a base film melt;

[0052] S2: After the base film melt flows through the die, it forms an unoriented cast slab on the rotating cooling roller;

[0053] S3: preheating the cooled cast thick sheet and longitudinally stretching it by 2.8 to 3.8 times to obtain a longitudinally stretched film;

[0054] S4: coating the primer liquid on at least one surface of the longitudinally stretched film to obtain a film coated with the primer liquid;

[0055] S5: The film coated with the primer is held by a clip and introduced into a preheating zone for transverse stretching, and after preheating and drying at 90°C-110°C, it is transversely stretched by 2.5 times to 4.5 times at 140°C-160°C to obtain a stretched film;

[0056] S6: heat-setting the stretched film at a temperature of 160° C. to 250° C., and rolling it up after cooling to obtain an optical polyester film.

[0057] The preparation method of the optical polyester film provided by the invention has the advantages of simple preparation process and low preparation cost. Nano silicon dioxide modified by dopamine and polyvinyl alcohol is introduced on the surface of the polyester film base film, the characteristics of dopamine and polyvinyl alcohol are fully utilized, and the chemical reaction between the nano silicon dioxide and the aqueous polyurethane is enhanced, so that the stability of the primer liquid is improved on the basis of obtaining a primer liquid with uniform dispersion and good compatibility. Then, the internal addition of a lubricant is avoided by online coating of the primer liquid, so that better optical performance and hydrophobic and stain-resistant performance can be provided for the optical polyester film, so that the opening performance of the polyester film is improved on the basis of ensuring the optical performance of the polyester film, so that the prepared polyester film can take into account the problems of both the opening performance and the optical performance.

[0058] The present invention avoids the use of internally added opening masterbatch and instead uses an online coating method to coat a layer of primer liquid on the surface of the polyester film base film to prepare a primer layer to ensure the opening property. Compared with the internally added opening masterbatch, the present invention not only reduces the cost, but also has less impact on the optical properties of the film. The film has better optical properties and hydrophobic and stain-resistant properties.

[0059] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0060] Example 1

[0061] This embodiment provides a method for preparing an optical polyester film, the preparation method comprising the following steps:

[0062] Primer preparation:

[0063] S01: mixing water and DMF in a mass ratio of 1:5 to obtain a DMF mixed solution;

[0064] S02: placing nano-silica in water to prepare a nano-silica dispersion with a concentration of 10 mg / mL; adding 0.5 g of dopamine to 100 mL of the nano-silica dispersion under high-speed stirring, reacting at 35° C. for 48 hours, then centrifuging and washing, and then dispersing in a DMF mixed solution, and performing ultrasonic dispersion treatment to obtain a dopamine-modified nano-silica dispersion;

[0065] S03: adding 1 g of polyvinyl alcohol to the dopamine-modified nano-silica dispersion under high-speed stirring to obtain a modified nano-silica dispersion;

[0066] S04: Add 25.1g of isophorone diisocyanate (IPDI) to a 1000mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and add 70.0g of polycarbonate diol (PCD2000) and 0.15g of catalyst dibutyltin dilaurate (DBTDL) dropwise using a dropping funnel while stirring at room temperature. The dropping speed is controlled within 1.5h. After the dropping is completed, react at 50±5°C for 1.5h; then heat to 60°C, add 4.96g of dimethylolpropionic acid (DMPA), react for 5.5h, and determine the degree of reaction by toluene-di-n-butylamine back titration method until the NCO group content reaches the theoretical value; then add 2.10g of potassium hydroxide to the resin and react for 1.5h to prepare a polyurethane prepolymer;

[0067] S05: Add the polyurethane prepolymer to 200 mL of modified nano-silicon dioxide dispersion and react at high speed for 1 hour; add deionized water dropwise to the system for emulsification to obtain a primer solution.

[0068] The preparation method of optical polyester film is as follows:

[0069] S1: feeding optical polyester raw material slices (model FG600, Sinopec Yizheng Chemical Fiber Co., Ltd.) into a corresponding extrusion system for melt extrusion at a temperature of 255° C. to 290° C. to obtain a base film melt;

[0070] S2: After the base film melt flows through the die, it forms an unoriented cast slab on the rotating cooling roller;

[0071] S3: preheating the cooled cast thick sheet and longitudinally stretching it by 2.8 to 3.8 times to obtain a longitudinally stretched film;

[0072] S4: coating a primer liquid on one surface of the longitudinally stretched film to obtain a film coated with the primer liquid;

[0073] S5: The film coated with the primer is held by a clip and introduced into a preheating zone for transverse stretching, and after preheating and drying at 90°C-110°C, it is transversely stretched by 2.5 times to 4.5 times at 140°C-160°C to obtain a stretched film;

[0074] S6: heat-setting the stretched film at a temperature of 160° C. to 250° C., and rolling it up after cooling to obtain an optical polyester film.

[0075] Example 2

[0076] The difference between this embodiment and embodiment 1 is that the amount of dopamine added is 0.1 g.

[0077] Example 3

[0078] The difference between this embodiment and embodiment 1 is that the amount of dopamine added is 1 g.

[0079] Example 4

[0080] The difference between this embodiment and embodiment 1 is that the amount of dopamine added is 5 g.

[0081] Example 5

[0082] The difference between this embodiment and embodiment 1 is that the amount of polyvinyl alcohol added is 0.3 g.

[0083] Example 6

[0084] The difference between this embodiment and embodiment 1 is that the amount of polyvinyl alcohol added is 10 g.

[0085] Comparative Example 1

[0086] The difference between this embodiment and embodiment 1 is that the amount of dopamine added is 0.05 g.

[0087] Comparative Example 2

[0088] The difference between this embodiment and embodiment 1 is that the amount of dopamine added is 6 g.

[0089] Comparative Example 3

[0090] This comparative example provides a method for preparing a common internally added optical polyester film, the preparation method comprising the following steps:

[0091] S1: feeding optical polyester raw material slices (model FG600, Sinopec Yizheng Chemical Fiber Co., Ltd.) and open slices (model FG611, Sinopec Yizheng Chemical Fiber Co., Ltd.) into corresponding extrusion systems for melt extrusion, wherein the mass proportion of the open slices is 15%, and the melt extrusion temperature is 255°C to 290°C;

[0092] S2: The base film melt flows through the die and forms an unoriented thick sheet on the rotating cooling roller;

[0093] S3: preheating the cooled cast thick sheet and stretching it longitudinally by 2.8 to 3.8 times;

[0094] S4: The film is clamped and introduced into a preheating zone for transverse stretching. After preheating and drying at 90°C-110°C, the film is transversely stretched by 2.5 times to 4.5 times at 140°C-160°C.

[0095] S5: heat-setting the stretched film at a temperature of 160°C to 250°C, and rolling it up after cooling to obtain a common internally added optical polyester film.

[0096] Comparative Example 4

[0097] The difference between this comparative example and Example 1 is that the amount of polyvinyl alcohol added is 0.1 g.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 1 is that polyethyleneimine is used instead of dopamine during the preparation of the primer solution.

[0100] Comparative Example 6

[0101] The difference between this comparative example and Example 1 is that the preparation method of the primer solution is as follows:

[0102] S01: mixing water and DMF in a mass ratio of 1:5 to obtain a DMF mixed solution;

[0103] S02: dispersing 10 mg of nano-silicon dioxide in the DMF mixed solution to obtain a nano-silicon dioxide dispersion;

[0104] S03: Add 25.1g of isophorone diisocyanate (IPDI) to a 1000mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and add 70.0g of polycarbonate diol (PCD2000) and 0.15g of catalyst dibutyltin dilaurate (DBTDL) dropwise with a dropping funnel while stirring at room temperature. The dropping speed is controlled within 1.5h. After the dropping is completed, react at 50±5℃ for 1.5h; then heat to 60℃, add 4.96g of dimethylolpropionic acid (DMPA), react for 5.5h, and determine the degree of reaction by toluene-di-n-butylamine back titration method until the NCO group content reaches the theoretical value; then add 2.10g of potassium hydroxide to the resin and react for 1.5h to prepare a polyurethane prepolymer;

[0105] S04: Add the polyurethane prepolymer to 200 mL of nano-silicon dioxide dispersion and react with high-speed stirring for 1 hour; add deionized water dropwise to the system for emulsification to obtain a primer solution.

[0106] Comparative Example 7

[0107] The difference between this comparative example and Example 1 is that the preparation method of the primer solution is as follows:

[0108] S01: mixing water and DMF in a mass ratio of 1:5 to obtain a DMF mixed solution;

[0109] S02: placing nano-silica in water to prepare a nano-silica dispersion with a concentration of 10 mg / mL; adding 0.5 g of dopamine to 100 mL of the nano-silica dispersion under high-speed stirring, reacting at 35° C. for 48 hours, then centrifuging and washing, and then dispersing in a DMF mixed solution, and performing ultrasonic dispersion treatment to obtain a dopamine-modified nano-silica dispersion;

[0110] S03: adding 1 g of polyvinyl alcohol to the dopamine-modified nano-silica dispersion under high-speed stirring to obtain a modified nano-silica dispersion;

[0111] S04: washing the modified nano-silica dispersion with DMF solvent and deionized water respectively, filtering and then vacuum drying at 105°C for 12 hours to obtain modified nano-silica; adding the modified nano-silica to DMF solvent, ultrasonically dispersing for 10 minutes at a power of 200 W and a frequency of 40 KHz to obtain a modified nano-silica dispersion with a concentration of 10 mg / mL;

[0112] S05: Add 25.1g of isophorone diisocyanate (IPDI) to a 1000mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and add 70.0g of polycarbonate diol (PCD2000), 0.15g of catalyst dibutyltin dilaurate (DBTDL) and modified nano-silica dispersion with a dropping funnel while stirring at room temperature. The dropping speed is controlled within 1.5h. After the addition is completed, react at 50±5℃ for 1.5h; then heat to 60℃, add 4.96g of dihydroxymethylpropionic acid (DMPA), react for 5.5h, and determine the degree of reaction by toluene-di-n-butylamine back titration method until the NCO group content reaches the theoretical value; then add 2.10g of potassium hydroxide to the resin and react for 1.5h; add deionized water to the system for emulsification to obtain a primer.

[0113] The optical polyester films prepared in the above embodiments and comparative examples were tested according to the following method:

[0114] Transmittance and haze test method: Use a haze meter to measure the transmittance and haze of the sample.

[0115] Water contact angle test method: Use a water contact angle tester for measurement.

[0116] The test results are shown in Table 1:

[0117] Table 1

[0118]

[0119] It can be seen from the above data that the optical polyester films prepared in each embodiment of the present invention have excellent opening performance and optical properties at the same time; compared with the ordinary internally added optical polyester film, the online coating of dopamine polyvinyl alcohol modified nano-silica aqueous polyurethane dispersion can effectively improve the transmittance and haze of the polyester film, and has a higher water contact angle (the film has hydrophobic and stain-resistant properties only when the water contact angle is greater than 90°) and better production stability, thereby achieving the purpose of simultaneously increasing transmittance and brightening and hydrophobic opening.

[0120] The difference between Comparative Example 1 and Example 1 is that the amount of dopamine added is reduced. Although the prepared film still has good light transmittance, the haze is slightly worse and the production is unstable.

[0121] The difference between Comparative Example 2 and Example 1 is that the amount of dopamine added is increased, which not only fails to improve the dispersibility and stability of the primer, but also causes serious agglomeration of the primer, making it impossible to apply.

[0122] Comparative Example 3 provides an existing internally added optical polyester film, the water contact angle of which is 70°. Although it can meet general opening requirements, the film does not have hydrophobic and stain-resistant properties, and its optical properties are relatively poor.

[0123] Compared with Example 1, Comparative Example 4 reduces the amount of polyvinyl alcohol added, Comparative Example 5 replaces dopamine in Example 1 with polyethyleneimine, and Comparative Example 6 does not modify the nano-silicon dioxide, all of which result in the inability to coat the primer.

[0124] The difference between Comparative Example 7 and Example 1 is that modified nano-silica is added during the preparation of the polyurethane prepolymer. Although the optical properties and water contact angle of the prepared optical polyester film are improved compared with the internally added optical polyester film provided in Comparative Example 3, they are still far inferior to the performance of the film prepared in Example 1, and the prepared film only has opening performance, and does not have hydrophobic and stain-resistant properties.

[0125] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. An optical polyester film, characterized in that: It includes a base film, and a primer layer disposed on at least one side of the base film; The primer layer is obtained by coating a primer liquid; The primer solution is prepared as follows: S01: mixing water and DMF to obtain a DMF mixed solution; S02: placing nano-silicon dioxide in water to prepare a nano-silicon dioxide dispersion; adding dopamine to the nano-silicon dioxide dispersion under high-speed stirring, reacting at 35° C. for 48 hours, then centrifugally washing it, dispersing it in a DMF mixed solution, and performing ultrasonic dispersion treatment to obtain a dopamine-modified nano-silicon dioxide dispersion; S03: adding polyvinyl alcohol dropwise to the dopamine-modified nano-silicon dioxide dispersion under high-speed stirring to obtain a modified nano-silicon dioxide dispersion; S04: preparing a polyurethane prepolymer using oligomer diol, diisocyanate compound, hydrophilic monomer and hydroxide as raw materials; S05: adding the polyurethane prepolymer to the modified nano-silicon dioxide dispersion and reacting it for 1 hour with high-speed stirring; adding deionized water dropwise to the system for emulsification to obtain a primer; The mass ratio of the dopamine to the nano-silicon dioxide is in the range of (0.1-5):1; the mass ratio of the polyvinyl alcohol to the nano-silicon dioxide is in the range of (0.3-10):1; The mass ratio of the polyurethane prepolymer to the nano-silicon dioxide is in the range of 1:(0.03-0.4).

2. The optical polyester film according to claim 1, characterized in that Step S04 comprises: adding 10-50 parts of oligomer diol and 2-9 parts of catalyst to 10-40 parts of diisocyanate compound by weight, reacting at 50° C. for 1-2 hours, then heating to 60° C., adding 2-9 parts of hydrophilic monomer, and continuing to react for 6-8 hours; adding hydroxide and reacting for 1-2 hours to obtain the polyurethane prepolymer.

3. The optical polyester film according to claim 2, characterized in that The oligomer diol is selected from at least one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone diol, polycarbonate diol, polyoxyethylene-polyoxypropylene-polyoxyethylene glycol, polyethylene adipate diol, polybutylene adipate diol, polyethylene terephthalate diol, polybutylene terephthalate diol, α,ω-dihydroxy polydimethylsiloxane, dihydroxy polydiphenylsiloxane, and dihydroxy polytrifluoropropylmethylsiloxane.

4. The optical polyester film according to claim 2, characterized in that: The diisocyanate compound is at least one selected from 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate, diphenylmethane 4,4-diisocyanate, methylcyclohexyl diisocyanate, and 2,2,4-trimethylhexane diisocyanate.

5. The optical polyester film according to claim 2, characterized in that: The hydrophilic monomer is selected from at least one of dimethylol propionic acid, dimethylol butyric acid, and sodium 1,2-dihydroxy-3-propanesulfonate.

6. The optical polyester film according to claim 2, characterized in that: The catalyst is dibutyltin dilaurate.

7. The optical polyester film according to claim 2, characterized in that: The hydroxide is potassium hydroxide.

8. A method for preparing an optical polyester film according to any one of claims 1 to 7, characterized in that: The steps include: S1: feeding the base film raw material into the corresponding extrusion system for melt extrusion, the melt extrusion temperature is 255°C~290°C, and obtaining the base film melt; S2: After the base film melt flows through the die head, it forms an unoriented cast thick sheet on the rotating cooling roller; S3: preheating the cooled cast thick sheet and longitudinally stretching it by 2.8 to 3.8 times to obtain a longitudinally stretched film; S4: coating the primer liquid on at least one surface of the longitudinally stretched film to obtain a film coated with the primer liquid; S5: The film coated with the primer is held by a clip and introduced into a preheating zone for transverse stretching, and after preheating and drying at 90°C-110°C, it is transversely stretched by 2.5 times to 4.5 times at 140°C-160°C to obtain a stretched film; S6: heat-setting the stretched film at a temperature of 160°C to 250°C, and rolling it up after cooling to obtain an optical polyester film.

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