A high-definition optical polyester film and its preparation method

Abstract

A high-definition optical polyester film, the polyester film comprising layer B and layer A on both sides of layer B, layer A containing the following components in parts by weight: 3 to 25 parts by weight of polyester masterbatch E and 75 to 97 parts by weight of polyethylene terephthalate; layer B containing the following components in parts by weight: 10 to 40 parts by weight of modified polyester F and 60 to 90 parts by weight of polyethylene terephthalate. The high-definition optical polyester film prepared by the present invention has the characteristics of clear film surface, clear film body, low haze, good mechanical properties, thermal properties, flatness, and apparent quality, and can be widely used in the fields of high-end protection / release, window films, car wrap films, etc.

Description

Technical Field

[0001] The present invention relates to a high-definition optical polyester film and a preparation method thereof, in particular to an optical polyester film with a clear film surface and a clear film body and a preparation method thereof, belonging to the technical field of optical films. Background Art

[0002] Polyethylene terephthalate (PET), as an important polymer material, is widely used in people's daily lives. As a main use of PET, "polyester" is not unfamiliar to everyone. However, another important use of PET - "BOPET film" is also closely related to people's daily lives. BOPET film is made by melt co-extrusion of polyethylene terephthalate material and then biaxially stretched under certain conditions. Due to its good mechanical properties, thermal properties, electrical insulation properties and optical properties, it is widely used in packaging, industry, electrical, electronics, display, protection, explosion-proof and other fields.

[0003] Electronics, automobiles, buildings, etc. are the main application fields of optical polyester films. For mid- to high-end positioning, there are high requirements for the optical properties of optical polyester films. Downstream, mainly on one or both sides of the optical polyester film, after coating or release layer processing, it is used, such as high-definition mobile phone films, camera lens films, window films, etc. Some even do not require surface processing and are directly cold-pasted, such as the protective film of the self-healing layer of car paint films. For the above uses, the optical polyester film is required to have a clear film surface, a clear film body and a low haze. In view of the requirements for the optical properties of polyester films for different fields and various uses, the existing technical solutions in the polyester film field to solve problems are as follows: 1. Extremely reduce the surface haze, reduce the addition of particles such as silica, and improve the film surface clarity. 2. Add little or even no particles such as silica in the film, and perform double-sided polyester / acrylic ester / polyurethane precoating bottom layer treatment on the surface of the polyester film to ensure smoothness while obtaining good film body clarity.

[0004] Although technicians have conducted a lot of research on improving the optical properties of polyester film, the existing technical solutions to solve the optical properties of polyester film still have many shortcomings: 1. Surface haze is related to the clarity of the film surface, but has nothing to do with the clarity of the film body. In the film industry, many technicians tend to confuse the two concepts, which misleads the formulation design. Simply reducing the haze not only makes it difficult for polyester film to achieve the purpose of "high definition", but also makes the film astringent and difficult to roll up, reduces the yield rate, and causes problems such as scratches. 2. Although pre-coating treatment is performed on the surface of polyester film, it can ensure smoothness when adding less or even no particles such as silica in the film. However, this method will have the following problems: ① If the downstream does not process on the pre-coated bottom layer, it will be wrapped. As we all know, the pre-coated bottom layer contains more active groups, which is easy to absorb water and produce adhesion. ② As time goes by, the fastness of the pre-coated bottom layer will also deteriorate, affecting the smoothness during downstream processing. ③ For industries that do not require film surface treatment, the introduction of the pre-coated bottom layer limits its use. This is mainly because the pre-coated base layer will increase the strength of the bonding surface, and it is easy to damage the surface of the original material when peeling it off. Summary of the invention

[0005] In order to overcome the drawbacks of the prior art, the present invention provides a high-definition optical polyester film and a preparation method thereof. The high-definition optical polyester film has the characteristics of clear film surface, clear film body, low haze, good mechanical properties, thermal properties, flatness, and surface quality, and can be widely used in high-end protection / release, window film, car cover film and other fields.

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

[0007] A high-definition optical polyester film, comprising a layer B and layers A located on both sides of the layer B, wherein the layer A comprises the following components in parts by weight: 3 to 25 parts by weight of a polyester masterbatch E and 75 to 97 parts by weight of polyethylene terephthalate; and the layer B comprises the following components in parts by weight: 10 to 40 parts by weight of a modified polyester F and 60 to 90 parts by weight of polyethylene terephthalate.

[0008] In the high-definition optical polyester film, the polyester masterbatch E comprises 0.3 to 10 parts by weight of silica particles T and 90 to 99.7 parts by weight of modified polyester F.

[0009] In the above-mentioned high-definition optical polyester film, the surface of the silica particles T is double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane. After modification, the number of hydroxyl groups R on the surface of the silica particles T satisfies 0<R≤0.6 / nm 2 The average particle size D of the silicon dioxide particles T satisfies 0.05 μm≤D≤2.5 μm.

[0010] The above-mentioned high-definition optical polyester film, the modified polyester F is modified by 1,3-cyclohexanedicarboxylic acid, isophthalic acid and terephthalic acid, wherein the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid and terephthalic acid is (1-7):(1-3):(7-10).

[0011] The above-mentioned high-definition optical polyester film, the structure of the polyester film is a three-layer structure of A / B / A, the thickness of the polyester film is 19μm - 250μm, and the ratio of the thickness of layer A to the thickness of layer B is 1:30 - 1:10.

[0012] The above-mentioned high-definition optical polyester film, the polyethylene terephthalate is esterified and polycondensed from purified terephthalic acid and ethylene glycol, and its intrinsic viscosity is 0.63 dl / g - 0.68 dl / g.

[0013] A preparation method of a high-definition optical polyester film, the preparation method includes the following steps:

[0014] Step a: Mix the polyester masterbatch E, modified polyester F and polyethylene terephthalate chips in a proportion in advance, send them into the corresponding melt extrusion system, extrude at a temperature of 260°C - 275°C, and enter the die co-extrusion;

[0015] Step b: Obtain the high-definition optical polyester film through casting, longitudinal stretching, transverse stretching, shaping, cooling, traction and winding.

[0016] The preparation method of the above-mentioned high-definition optical polyester film, the longitudinal stretching ratio in the longitudinal stretching process is 2.8 - 3.6.

[0017] The preparation method of the above-mentioned high-definition optical polyester film, the transverse stretching ratio in the transverse stretching process is 3.6 - 5.2.

[0018] The preparation method of the above-mentioned high-definition optical polyester film, the heat setting temperature in the shaping process is 225°C - 240°C.

[0019] The polyester masterbatch E, modified polyester F, and silica particles T in the present invention are named to distinguish the types of materials used in each step, and the surface hydroxyl number R and average particle size D are named to distinguish the surface hydroxyl number and average particle size of the materials used in each step. The letters themselves have no meaning.

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

[0021] 1. Starting from the surface structure of microscopic particles, double modification is performed on the surface, and silica particles with a reasonable number of surface hydroxyl groups are selected, which can play a lubricating role without adversely affecting the optical properties of the film.

[0022] 2. The use of the second and third monomers to modify the polyester polymer optimizes the polymer crystallization kinetics mechanism and improves the film surface clarity and film body clarity.

[0023] 3. It is conducive to promoting the domestic polyester film industry to develop towards a higher end. Detailed implementation manners

[0024] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] A high-definition optical polyester film of the present invention includes layer B and layer A on both sides of layer B. Among them, layer A contains 3 parts by weight to 25 parts by weight of polyester masterbatch E and 75 parts by weight to 97 parts by weight of polyethylene terephthalate. When the addition of polyester masterbatch E is less than 3 parts by weight, the silica particles in the masterbatch are difficult to play a lubricating role, and problems such as scratches on the film surface or inability to wind up the film are likely to occur; when the addition of polyester masterbatch E is greater than 25 parts by weight, the particles on the film surface accumulate excessively, are prone to slipping, and will also affect the optical properties of the film.

[0027] Layer B contains 10 parts by weight to 40 parts by weight of modified polyester F and 60 parts by weight to 90 parts by weight of polyethylene terephthalate. When the addition of modified polyester F is less than 10 parts by weight, it is difficult to exert the modification effect of the modified polyester; when the addition of modified polyester F is greater than 40 parts by weight, the addition amount of the modified polyester is large, which easily leads to insufficient thermal performance of the polyester film and affects the downstream processability.

[0028] The polyester masterbatch E of the present invention contains 0.3 parts by weight to 10 parts by weight of silica particles T and 90 parts by weight to 99.7 parts by weight of modified polyester F. When the addition of silica particles T in polyester masterbatch E is less than 0.3 parts by weight, the content of the active ingredient in the masterbatch is low, resulting in an excessive addition ratio of the masterbatch, reduced production efficiency, and increased cost; when the addition of silica particles T in polyester masterbatch E is greater than 10 parts by weight, the content of silica particles in the masterbatch is high, and when the masterbatch is added to the polyester mixture, it is easy to stratify, resulting in uneven feeding and affecting the performance of the polyester film.

[0029] The optical properties, film surface clarity and film body clarity of polyester film are all related to the haze of polyester film. However, this haze is not just a surface haze, but actually includes surface haze and internal haze. The relationship between them is often confused by technicians, which makes the formula design fail to meet expectations. The clarity of the film surface and the clarity of the film body are the effects of the combined effect of surface haze and internal haze. The present invention selects γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane to double-modify the silica particles, and at the same time limits the number of surface hydroxyl groups R to satisfy 0<R≤0.6 / nm 2 . The presence of epoxy groups increases the stability of silica particles in polyester. The oxygen atoms in the oxygen ring groups can form hydrogen bonds with the terminal carboxyl groups of polyester. The modified silica particles greatly reduce the interfacial gap between particles and polyester, and reduce the scattering of light on the interface between polyester and silica particles. The amino group can form a carbonyl group with the active functional group of 1,3-cyclohexanedicarboxylic acid in the modified polyester to a certain extent. Through chemical bonds, the modified silica particles are placed in the polymer chain, which increases the stability of dispersion. At the same time, they can also be connected with the oxygen-hydrogen bonds in the ester group. The epoxy group and the amino group can also form a triangular stable structure with the polyester polymer through hydrogen bonding, ensuring that the modified silica particles will not migrate on the surface during the later film formation process. If γ-(2,3-epoxypropoxy)propyltrimethoxysilane or 3-aminotriethoxysilane is used to modify silica particles alone or by conventional physical methods, surface migration is likely to occur, affecting the optical properties of the film. Ordinary silica particles have many hydroxyl groups on the surface, are extremely hydrophilic, have high surface free energy, are easily agglomerated, have uneven particle size distribution, and have poor dispersibility in polyester. When used in the production of polyester film, they will directly affect the optical properties of the film and cause serious fogging of the film. The present invention can effectively prevent the adverse effects of particle agglomeration or uneven particle size distribution on optical properties by limiting the number of hydroxyl groups on the surface of silica particles. It can be known from common sense of surface modification that the number of hydroxyl groups on the surface of silica particles R>0 / nm 2 It is suitable when the number of surface hydroxyl groups R>0.6 / nm 2 When the silica particles are mixed, it is easy to have uneven particle size distribution and poor dispersibility in polyester.

[0030] The average particle size D of the silicon dioxide particles T described in the present invention satisfies 0.05 μm≤D≤2.5 μm. When D<0.05 μm, the particle size is too small, and after being stretched into a film, the particles on the film surface are less protruding, the smoothness is insufficient, and the film surface is easily scratched; when D>2.5 μm, the particle size is too large, especially when used in the production of optical polyester film, the light will be significantly scattered around the particles, resulting in fogging of the film.

[0031] The modified polyester F described in the present invention is modified by 1,3 - cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid. Among them, the molar ratio of 1,3 - cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid is 1 - 7:1 - 3:7 - 10.

[0032] In addition to the influence of externally added particles on the clarity and transparency of the polyester film, the polyester material itself will also affect the optical properties. We know that polyethylene terephthalate belongs to a semi - crystalline polymer, and homogeneous, heterogeneous, or self - nucleation phenomena will occur during the production of polyester films, thus forming crystals. Crystals have birefringence, which will affect the propagation direction of light. Since terephthalic acid has a high degree of regularity and is more likely to crystallize, the present invention uses 1,3 - cyclohexanedicarboxylic acid and isophthalic acid for acid modification, which slows down the crystallization process to a certain extent and improves the clarity and transparency of the film without affecting the original mechanical properties of the polyester film. As a dibasic acid monomer in polyester synthesis, 1,3 - cyclohexanedicarboxylic acid can fully participate in the modified polyester reaction, without incomplete reaction or incomplete extraction, resulting in small molecule residues affecting the optical properties of the film, and can also avoid the generation of molecules such as self - polycondensation to form ether bonds. At the same time, compared with benzene hexacyclic, cyclohexane hexacyclic has more advantages in the three - dimensional structure for light passing through, and 1,3 are e - bond in the same direction, which is more stable than 1,2 or 1,4 isomers. The modified polyester and the double - modified silica particles work synergistically, and neither can be absent, which can make the clarity and transparency of the polyester film reach the best.

[0033] The modified polyester F and the polyester masterbatch E described in the present invention can be prepared by the following method:

[0034] The preparation method of the modified polyester F is as follows:

[0035] 1. Add the required dibasic acid, diol, catalyst, and stabilizer into the polyester reaction kettle in sequence. Among them, the molar ratio of dibasic acid to diol is 1:1.2 - 1:1.43, and carry out pulping for 15 minutes, and introduce nitrogen for protection. Carry out esterification at 234°C - 260°C and 258 KPa for 3h - 4h. Among them, the dibasic acid is 1,3 - cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid, and the molar ratio of 1,3 - cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid is 1 - 7:1 - 3:7 - 10; the diol is ethylene glycol, propylene glycol, butylene glycol, etc. or any combination thereof, preferably ethylene glycol and butylene glycol, and most preferably ethylene glycol; the catalyst is one or any combination of antimony - based, aluminum - based, germanium - based, titanium - based, etc., preferably antimony - based and titanium - based, and most preferably ethylene glycol antimonate; the stabilizer is one or any combination of trimethyl phosphate, triphenyl phosphate, tetrabutyl titanate, tetraethyl titanate, etc., preferably trimethyl phosphate and triphenyl phosphate, and most preferably triphenyl phosphate.

[0036] 2. Determine the esterification end point based on the water output. After the esterification is complete, turn on the vacuum pump and carry out the polycondensation reaction at 268°C to 282°C and 20 Pa to 90 Pa for 2.5 h to 4.5 h. After spinning, cooling, pelletizing, and drying, the modified polyester F described in the present invention is obtained, and the intrinsic viscosity is 0.67 dl / g to 0.72 dl / g.

[0037] The preparation method of the polyester masterbatch E is as follows:

[0038] Select the above-prepared modified polyester F with an intrinsic viscosity of 0.67 dl / g to 0.72 dl / g as the base material, and then 0.3 to 10 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, and the number of surface hydroxyl groups 0 < R ≤ 0.6 per nm 2 , with an average particle size of 0.05 μm ≤ D ≤ 2.5 μm, and 90 to 99.7 parts by weight of modified polyester F are premixed evenly and fed into a twin-screw extruder together. Turn on the vacuum pump and obtain the polyester masterbatch E described in the present invention after spinning, cooling, pelletizing, and drying. The intrinsic viscosity of the polyester masterbatch E is 0.61 dl / g to 0.67 dl / g. For the polyester masterbatch E of the present invention, the twin-screw granulation method is selected instead of the synthesis method. The main reason is that during the esterification and polycondensation processes in the synthesis method, high temperature for a long time may damage the groups on the surface of the silica particles and affect their effect. At the same time, the twin-screw granulation method is more suitable for the preparation of high-concentration masterbatches.

[0039] The thickness of the high-definition optical polyester film described in the present invention is 19 μm to 250 μm.

[0040] The structure of the high-definition optical polyester film described in the present invention is an A / B / A three-layer structure, and the ratio of the thickness of layer A to the thickness of layer B is 1:30 to 1:10.

[0041] The polyethylene terephthalate described in the present invention is formed by esterification and polycondensation of purified terephthalic acid and ethylene glycol, and its intrinsic viscosity is 0.63 dl / g to 0.68 dl / g.

[0042] The specific preparation method of the high-definition optical polyester film of the present invention is as follows:

[0043] Step 1: Mix the proportioned polyester masterbatch E, modified polyester F, and polyethylene terephthalate chips in advance, feed them into the corresponding melt extrusion system, and extrude at a temperature of 260°C to 275°C, and enter the A / B / A three-layer die co-extrusion;

[0044] Step 2: Obtain the high-definition optical polyester film through casting, longitudinal stretching, transverse stretching, shaping, cooling, traction, and winding.

[0045] ①Perform longitudinal stretching on the cast film, with the longitudinal stretching ratio being 2.8 - 3.8.

[0046] ②Perform transverse stretching on the longitudinally stretched film, with the transverse stretching ratio being 3.6 - 5.2.

[0047] ③Perform heat setting on the stretched film, with the heat setting temperature being 225°C - 240°C.

[0048] ④Then carry out cooling, traction, and winding.

[0049] It should be noted that, on the premise of not affecting the technical effects of the present invention, corona pretreatment can be carried out on one or both sides of the polyester film of the present invention, or primer pretreatment with a thickness of 0.01μm - 0.20μm, and then supplied to the downstream for further processing on its surface.

[0050] The following further illustrates the present invention with reference to embodiments, but the implementation and protection scope of the present invention are not limited to these embodiments.

[0051] Example 1

[0052] Preparation of modified polyester F:

[0053] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.2, the addition amount of antimony glycolate is 150 ppm, the addition amount of triphenyl phosphate is 30 ppm, and the molar ratio of 1,3 - cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 1:1:7. After the above is mixed evenly, it is added to the polyester synthesis reaction kettle, slurried for 15 minutes, and protected by introducing nitrogen. Esterification is carried out at 234°C - 260°C and 258 KPa for 3 h. The esterification end point is determined according to the water output. After complete esterification, vacuum is pumped, and polycondensation reaction is carried out at 258°C - 282°C and 20 Pa for 4.5 h. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.72 dl / g is obtained.

[0054] Preparation of polyester masterbatch E:

[0055] 10 parts by weight of silica particles T with a surface double - modified by γ - (2,3 - epoxypropoxy) propyltrimethoxysilane and 3 - aminotriethoxysilane, with a surface hydroxyl number R = 0.05 pieces / nm 2 , and an average particle size D = 0.05μm, and 90 parts by weight of the above - prepared modified polyester F with an intrinsic viscosity of 0.72 dl / g are pre - mixed evenly, and then sent into a twin - screw extruder together. Vacuum is pumped, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.61 dl / g is obtained.

[0056] 3 parts by weight of polyester masterbatch E with an intrinsic viscosity of 0.61 dl / g and 97 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.64 dl / g (layer A), 10 parts by weight of modified polyester F with an intrinsic viscosity of 0.72 dl / g and 90 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.64 dl / g (layer B) are respectively pre-mixed and processed in advance, and then fed into the corresponding melt extrusion system. At a temperature of 260 °C, they enter a three-layer die co-extrusion, and are cast onto a casting roll to form an A / B / A structure extruded cast sheet. The cast sheet is longitudinally stretched, the longitudinal stretching temperature is 52 °C to 83 °C, and the longitudinal stretching ratio is 3.6. The longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98 °C to 130 °C, and the transverse stretching ratio is 4.3. The stretched film is shaped at a shaping temperature of 225 °C. Then the film is cooled, drawn, and wound to obtain a 19-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:30.

[0057] Example 2

[0058] Preparation of modified polyester F:

[0059] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.23, the addition amount of antimony glycolate is 180 ppm, the addition amount of triphenyl phosphate is 35 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 3:2:7. After the above is mixed evenly, it is added to a polyester synthesis reaction kettle, slurried for 15 minutes, and protected by introducing nitrogen. Esterification is carried out for 3 h under the conditions of 234 °C to 260 °C and 258 KPa. The esterification end point is determined according to the water output. After complete esterification, vacuum is pumped, and polycondensation reaction is carried out for 4 h under the conditions of 258 °C to 282 °C and 30 Pa. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.70 dl / g is obtained.

[0060] Preparation of polyester masterbatch E:

[0061] 8 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, with a surface hydroxyl number R = 0.1 per nm 2 , and an average particle size D = 0.1 μm and 92 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.70 dl / g are pre-mixed evenly, and then fed into a twin-screw extruder together. Vacuum is pumped, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.63 dl / g is obtained.

[0062] 4 parts by weight of polyester masterbatch E with an intrinsic viscosity of 0.61 dl / g and 96 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.63 dl / g (layer A), 15 parts by weight of modified polyester F with an intrinsic viscosity of 0.70 dl / g and 85 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.63 dl / g (layer B) are respectively pre-mixed and processed, then fed into the corresponding melt extrusion system. At a temperature of 262 °C, they enter a three-layer die for co-extrusion and are cast onto a casting roll to form an A / B / A structure extruded cast sheet; the cast sheet is longitudinally stretched, the longitudinal stretching temperature is 52 °C to 83 °C, and the longitudinal stretching ratio is 2.9; the longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98 °C to 130 °C, and the transverse stretching ratio is 5.2; the stretched film is shaped, the shaping temperature is 230 °C; then the film is cooled, drawn, and wound up to obtain a high-definition optical polyester film with a thickness of 23 μm, where the thickness ratio of layer A to layer B is 1:25.

[0063] Example 3

[0064] Preparation of modified polyester F:

[0065] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.3, the addition amount of antimony glycolate is 190 ppm, the addition amount of triphenyl phosphate is 40 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 3:3:8. After mixing the above evenly, it is added to a polyester synthesis reaction kettle, slurried for 15 minutes, and purged with nitrogen for protection. Esterification is carried out at 234 °C to 260 °C and 258 KPa for 3.5 h. The end point of esterification is determined according to the water output. After complete esterification, vacuum is applied, and polycondensation reaction is carried out at 258 °C to 282 °C and 50 Pa for 3 h. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.69 dl / g is obtained.

[0066] Preparation of polyester masterbatch E:

[0067] 7.5 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, with a surface hydroxyl number R = 0.15 per nm 2 , and an average particle size D = 0.2 μm and 92.5 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.69 dl / g are pre-mixed evenly and fed into a twin-screw extruder together. Vacuum is applied, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.63 dl / g is obtained.

[0068] 5 parts by weight of polyester masterbatch E with an intrinsic viscosity of 0.63 dl / g and 95 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer A), 18 parts by weight of modified polyester F with an intrinsic viscosity of 0.69 dl / g and 82 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer B) are respectively premixed and processed in advance, and then fed into the corresponding melt extrusion system. At a temperature of 265 °C, they enter a three-layer die for co-extrusion and are cast onto a casting roll to form an A / B / A structure extruded cast sheet; the cast sheet is longitudinally stretched, the longitudinal stretching temperature is 52 °C to 83 °C, and the longitudinal stretching ratio is 3.4; the longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98 °C to 130 °C, and the transverse stretching ratio is 4.9; the stretched film is shaped, the shaping temperature is 235 °C; then the film is cooled, drawn, and wound to obtain a high-definition optical polyester film with a thickness of 38 μm, where the thickness ratio of layer A to layer B is 1:25.

[0069] Example 4

[0070] Preparation of modified polyester F:

[0071] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.3, the addition amount of antimony glycolate is 200 ppm, the addition amount of triphenyl phosphate is 50 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 4:3:9. After the above is mixed evenly, it is added to a polyester synthesis reaction kettle, slurried for 15 minutes, and nitrogen is introduced for protection. Esterification is carried out at 234 °C to 260 °C and 258 KPa for 3.5 h. The end point of esterification is determined according to the water output. After complete esterification, vacuum is started, and polycondensation reaction is carried out at 258 °C to 282 °C and 35 Pa for 3.5 h. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.68 dl / g is obtained.

[0072] Preparation of polyester masterbatch E:

[0073] 3 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, with a surface hydroxyl number R = 0.2 per nm 2 , with an average particle size D = 0.5 μm and 97 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.68 dl / g are premixed evenly in advance, and then fed into a twin-screw extruder together. Vacuum is started, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.64 dl / g is obtained.

[0074] 6.5 parts by weight of polyester masterbatch E with an intrinsic viscosity of 0.64 dl / g and 93.5 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.65 dl / g (layer A), 19 parts by weight of modified polyester F with an intrinsic viscosity of 0.68 dl / g and 81 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.65 dl / g (layer B) are respectively pre-mixed and processed in advance, and then fed into the corresponding melt extrusion system. At a temperature of 265 °C, they enter a three-layer die for co-extrusion and are cast onto a casting roll to form an A / B / A structure extruded cast sheet. The cast sheet is longitudinally stretched at a longitudinal stretching temperature of 52 °C to 83 °C and a longitudinal stretching ratio of 3.4. The longitudinally stretched sheet is then transversely stretched at a transverse stretching temperature of 98 °C to 130 °C and a transverse stretching ratio of 4.8. The stretched film is then shaped at a shaping temperature of 235 °C. Then the film is cooled, drawn, and wound up to obtain a 50-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:23.

[0075] Example 5

[0076] Preparation of modified polyester F:

[0077] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.35, the addition amount of antimony glycolate is 200 ppm, the addition amount of triphenyl phosphate is 65 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 2:2:9. After the above is mixed evenly, it is added to a polyester synthesis reaction kettle, slurried for 15 minutes, and protected by introducing nitrogen. Esterification is carried out for 3 h under the conditions of 234 °C to 260 °C and 258 KPa. The end point of esterification is determined according to the amount of water discharged. After complete esterification, vacuum is applied, and polycondensation reaction is carried out for 3 h under the conditions of 258 °C to 282 °C and 55 Pa. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.67 dl / g is obtained.

[0078] Preparation of polyester masterbatch E:

[0079] 2 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, with a surface hydroxyl number R = 0.25 per nm 2 , and an average particle size D = 0.9 μm and 98 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.67 dl / g are pre-mixed evenly and fed into a twin-screw extruder together. Vacuum is applied, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.63 dl / g is obtained.

[0080] 7 parts by weight of polyester masterbatch E with an intrinsic viscosity of 0.63 dl / g and 93 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.65 dl / g (layer A), 22 parts by weight of modified polyester F with an intrinsic viscosity of 0.67 dl / g and 78 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.65 dl / g (layer B) are respectively pre-mixed and processed, then fed into the corresponding melt extrusion system. At a temperature of 268 °C, they enter a three-layer die for co-extrusion and are cast onto a casting roll to form an A / B / A structure extruded cast sheet. The cast sheet is longitudinally stretched at a longitudinal stretching temperature of 52 °C to 83 °C and a longitudinal stretching ratio of 3.3. The longitudinally stretched sheet is then transversely stretched at a transverse stretching temperature of 98 °C to 130 °C and a transverse stretching ratio of 4.4. The stretched film is then shaped at a shaping temperature of 235 °C. Then the film is cooled, drawn, and wound up to obtain a 75-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:18.

[0081] Example 6

[0082] Preparation of modified polyester F:

[0083] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.39, the addition amount of antimony glycolate is 180 ppm, the addition amount of triphenyl phosphate is 70 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 5:3:10. After mixing the above evenly, it is added to a polyester synthesis reaction kettle, pulped for 15 minutes, and protected by introducing nitrogen. Esterification is carried out at 234 °C to 260 °C and 258 KPa for 3.5 h. The end point of esterification is determined according to the amount of water discharged. After complete esterification, vacuum is started, and polycondensation reaction is carried out at 258 °C to 282 °C and 70 Pa for 3 h. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.71 dl / g is obtained.

[0084] Preparation of polyester masterbatch E:

[0085] 1.5 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, with a surface hydroxyl number R = 0.35 per nm 2 , and an average particle size D = 0.9 μm and 98.5 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.71 dl / g are pre-mixed evenly, then fed into a twin-screw extruder together. Vacuum is started, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.66 dl / g is obtained.

[0086] 10 parts by weight of polyester masterbatch E with an intrinsic viscosity of 0.66 dl / g and 90 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer A), 25 parts by weight of modified polyester F with an intrinsic viscosity of 0.71 dl / g and 75 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer B) are respectively pre-mixed and processed in advance, and then fed into the corresponding melt extrusion system. At a temperature of 265 °C, they enter a three-layer die co-extrusion, and are cast onto a casting roll to form an A / B / A structure extruded cast sheet. The cast sheet is longitudinally stretched, the longitudinal stretching temperature is 52 °C to 83 °C, and the longitudinal stretching ratio is 3.3. The longitudinally stretched sheet is then transversely stretched, the transverse stretching temperature is 98 °C to 130 °C, and the transverse stretching ratio is 4.1. The stretched film is then shaped at a shaping temperature of 240 °C. Then the film is cooled, drawn, and wound to obtain a 100-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:15.

[0087] Example 7

[0088] Preparation of modified polyester F:

[0089] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.43, the addition amount of antimony glycolate is 200 ppm, the addition amount of triphenyl phosphate is 80 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 7:2:8. After the above is mixed evenly, it is added to a polyester synthesis reaction kettle, slurried for 15 minutes, and protected by introducing nitrogen. Esterification is carried out at 234 °C to 260 °C and 258 KPa for 4 h. The end point of esterification is determined according to the water output. After complete esterification, vacuum is applied, and polycondensation reaction is carried out at 258 °C to 282 °C and 30 Pa for 4 h. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.69 dl / g is obtained.

[0090] Preparation of polyester masterbatch E:

[0091] 1 part by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, a surface hydroxyl number R = 0.4 per nm 2 , with an average particle size D = 1.0 μm and 99 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.69 dl / g are pre-mixed evenly, and then fed into a twin-screw extruder together. Vacuum is applied, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.65 dl / g is obtained.

[0092] Mix 15 parts by weight of polyester masterbatch E with an intrinsic viscosity of 0.65 dl / g and 85 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.68 dl / g (layer A), and 30 parts by weight of modified polyester F with an intrinsic viscosity of 0.69 dl / g and 70 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.68 dl / g (layer B). After pre-mixing and other treatments respectively, feed them into the corresponding melt extrusion system. At a temperature of 270 °C, enter a three-layer die for co-extrusion, and cast onto a casting roll to form an A / B / A structure extruded casting; longitudinally stretch the casting, with the longitudinal stretching temperature being 52 °C to 83 °C and the longitudinal stretching ratio being 3.2; transversely stretch the longitudinally stretched sheet, with the transverse stretching temperature being 98 °C to 130 °C and the transverse stretching ratio being 4.0; shape the stretched film, with the shaping temperature being 240 °C; then cool, draw, and wind up the film to obtain a high-definition optical polyester film with a thickness of 125 μm, where the thickness ratio of layer A to layer B is 1:15.

[0093] Example 8

[0094] Preparation of modified polyester F:

[0095] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.4, the addition amount of antimony glycolate is 300 ppm, the addition amount of triphenyl phosphate is 100 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 6:2:7. After mixing the above evenly, add them to a polyester synthesis reaction kettle, carry out pulping for 15 minutes, and introduce nitrogen protection. Carry out esterification at 234 °C to 260 °C and 258 KPa for 3.5 h. Determine the end point of esterification according to the water output. After complete esterification, start vacuum pumping, and carry out polycondensation reaction at 258 °C to 282 °C and 80 Pa for 4.5 h. After spinning, cooling, pelletizing, and drying, obtain modified polyester F with an intrinsic viscosity of 0.72 dl / g.

[0096] Preparation of polyester masterbatch E:

[0097] Mix 0.4 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, with a surface hydroxyl number R = 0.5 per nm 2 , and an average particle size D = 1.5 μm and 99.6 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.72 dl / g in advance and mix evenly. Then feed them into a twin-screw extruder, start vacuum pumping, and after spinning, cooling, pelletizing, and drying, obtain polyester masterbatch E with an intrinsic viscosity of 0.67 dl / g.

[0098] 20 parts by weight of a polyester masterbatch E with an intrinsic viscosity of 0.67 dl / g and 80 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.68 dl / g (layer A), 35 parts by weight of a modified polyester F with an intrinsic viscosity of 0.72 dl / g and 65 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.68 dl / g (layer B) are respectively pre-mixed and processed in advance, and fed into the corresponding melt extrusion system. At a temperature of 275 °C, they enter a three-layer die co-extrusion, are cast onto a casting roll, and an A / B / A structure extruded cast sheet is formed; the cast sheet is longitudinally stretched, the longitudinal stretching temperature is 52 °C to 83 °C, and the longitudinal stretching ratio is 2.9; the longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98 °C to 130 °C, and the transverse stretching ratio is 3.8; the stretched film is shaped, the shaping temperature is 240 °C; then the film is cooled, drawn, and wound to obtain a high-definition optical polyester film with a thickness of 188 μm, where the thickness ratio of layer A to layer B is 1:13.

[0099] Example 9

[0100] Preparation of modified polyester F:

[0101] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.35, the addition amount of antimony glycolate is 200 ppm, the addition amount of triphenyl phosphate is 60 ppm, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid, and terephthalic acid in the dibasic acid is 5:2:8. After the above is mixed evenly, it is added to a polyester synthesis reaction kettle, pulped for 15 minutes, and nitrogen is introduced for protection. Esterification is carried out at 234 °C to 260 °C and 258 KPa for 3.5 h. The end point of esterification is determined according to the water output. After complete esterification, vacuum is started, and polycondensation reaction is carried out at 258 °C to 282 °C and 90 Pa for 4 h. After spinning, cooling, pelletizing, and drying, modified polyester F with an intrinsic viscosity of 0.69 dl / g is obtained.

[0102] Preparation of polyester masterbatch E:

[0103] 0.3 parts by weight of silica particles T with a surface double-modified by γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane, with a surface hydroxyl number R = 0.6 per nm 2 , with an average particle size D = 2.5 μm and 99.7 parts by weight of the above-prepared modified polyester F with an intrinsic viscosity of 0.69 dl / g are pre-mixed evenly and fed into a twin-screw extruder together. Vacuum is started, and after spinning, cooling, pelletizing, and drying, polyester masterbatch E with an intrinsic viscosity of 0.66 dl / g is obtained.

[0104] 25 parts by weight of a polyester masterbatch E with an intrinsic viscosity of 0.66 dl / g and 75 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer A), 40 parts by weight of a modified polyester F with an intrinsic viscosity of 0.69 dl / g and 60 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer B) are respectively pre-mixed and processed, then fed into the corresponding melt extrusion system. At a temperature of 265°C, they enter a three-layer die co-extrusion, are cast onto a casting roll, and an A / B / A structure extruded cast sheet is formed. The cast sheet is longitudinally stretched, the longitudinal stretching temperature is 52°C to 83°C, and the longitudinal stretching ratio is 2.8. The longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98°C to 130°C, and the transverse stretching ratio is 3.6. The stretched film is shaped, and the shaping temperature is 240°C. Then the film is cooled, drawn, and wound up to obtain a 250-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:10.

[0105] Comparative Example 1

[0106] 4 parts by weight of a common polyester masterbatch with an intrinsic viscosity of 0.61 dl / g, a silica particle concentration of 8%, and a particle size of 0.1 μm (the silica particles on the surface of the masterbatch are untreated or only generally treated and do not contain modified polyester) and 96 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.63 dl / g (layer A), 100 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.63 dl / g (layer B) are respectively pre-mixed and processed, then fed into the corresponding melt extrusion system. At a temperature of 262°C, they enter a three-layer die co-extrusion, are cast onto a casting roll, and an A / B / A structure extruded cast sheet is formed. The cast sheet is longitudinally stretched, the longitudinal stretching temperature is 52°C to 83°C, and the longitudinal stretching ratio is 2.9. The longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98°C to 130°C, and the transverse stretching ratio is 5.2. The stretched film is shaped, and the shaping temperature is 230°C. Then the film is cooled, drawn, and wound up to obtain a 23-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:25.

[0107] Comparative Example 2

[0108] 6.5 parts by weight of a common polyester masterbatch with an intrinsic viscosity of 0.64 dl / g, a silica particle concentration of 3%, and a particle size of 0.5 μm (the silica particles on the surface of the masterbatch are untreated or only generally treated, and it does not contain modified polyester), 93.5 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.65 dl / g (layer A), and 100 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.65 dl / g (layer B) are respectively pre-mixed and processed, then fed into the corresponding melt extrusion system. At a temperature of 265°C, they enter a three-layer die co-extrusion, are cast onto a casting roll, and an A / B / A structure extruded sheet is formed; the sheet is longitudinally stretched, the longitudinal stretching temperature is 52°C to 83°C, and the longitudinal stretching ratio is 3.4; the longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98°C to 130°C, and the transverse stretching ratio is 4.8; the stretched film is shaped, the shaping temperature is 235°C; then the film is cooled, drawn, and wound to obtain a 50-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:23.

[0109] Comparative Example 3

[0110] 20 parts by weight of a common polyester masterbatch with an intrinsic viscosity of 0.67 dl / g, a silica particle concentration of 0.4%, and a particle size of 1.5 μm (the silica particles on the surface of the masterbatch are untreated or only generally treated, and it does not contain modified polyester), 80 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.68 dl / g (layer A), and 100 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.68 dl / g (layer B) are respectively pre-mixed and processed, then fed into the corresponding melt extrusion system. At a temperature of 275°C, they enter a three-layer die co-extrusion, are cast onto a casting roll, and an A / B / A structure extruded sheet is formed; the sheet is longitudinally stretched, the longitudinal stretching temperature is 52°C to 83°C, and the longitudinal stretching ratio is 2.9; the longitudinally stretched sheet is transversely stretched, the transverse stretching temperature is 98°C to 130°C, and the transverse stretching ratio is 3.8; the stretched film is shaped, the shaping temperature is 240°C; then the film is cooled, drawn, and wound to obtain a 188-μm-thick high-definition optical polyester film, where the thickness ratio of layer A to layer B is 1:13.

[0111] Comparative Example 4

[0112] Mix 25 parts by weight of a common polyester masterbatch with an intrinsic viscosity of 0.66 dl / g, a silica particle concentration of 0.3%, and a particle size of 2.5 μm (the silica particles on the surface of the masterbatch are untreated or only generally treated and do not contain modified polyester) and 75 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer A), 100 parts by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.67 dl / g (layer B), respectively, and perform pre-mixing and other treatments in advance, then feed them into the corresponding melt extrusion system. At a temperature of 265 °C, enter a three-layer die co-extrusion, and cast it onto a casting roll to form an A / B / A structure extruded cast sheet; longitudinally stretch the cast sheet, the longitudinal stretching temperature is 52 °C to 83 °C, and the longitudinal stretching ratio is 2.8; transversely stretch the longitudinally stretched sheet, the transverse stretching temperature is 98 °C to 130 °C, and the transverse stretching ratio is 3.6; shape the stretched film, the shaping temperature is 240 °C; then cool, draw, and wind up the film to obtain a high-definition optical polyester film with a thickness of 250 μm, where the thickness ratio of layer A to layer B is 1:10.

[0113] The specific implementation effects are shown in Table 1 below.

[0114] Test result table

[0115]

[0116] Thickness test method: GB / T 33399-2016.

[0117] Optical property test method: ASTM D1003 (instrument model: BYK-4725) (T: transmittance, H: haze, C: clarity).

[0118] Film clarity: Randomly take 3 A4 film samples. The observer's line of sight, the film, and the three-wavelength lamp (illuminance 400 lux) are successively on the same straight line (keep the line of sight perpendicular to the film plane and the three-wavelength light perpendicular to the film plane). Then the film starts to move from a position 3 cm away from the observer's eyes towards the three-wavelength lamp until it is 20 cm away from the observer's eyes. During the entire movement process, if there is no fogging phenomenon in the film of all 3 A4 film samples on the observer's line of sight path, it is recorded as "clear"; if there is a fogging phenomenon in the film of ≥1 A4 film sample, it is recorded as "foggy".

[0119] By separately comparing Example 2 with Comparative Example 1, Example 4 with Comparative Example 2, and Example 9 with Comparative Example 4, it can be seen that: under the same conditions of polyester film thickness, film-making process, addition amount of silica particles, light transmittance, etc., the film surface clarity, film body clarity, and haze of a high-definition optical polyester film of the present invention are significantly better than those of ordinary polyester films; by comparing Example 8 with Comparative Example 3, it can be seen that: under the same conditions of polyester film thickness, film-making process, addition amount of silica particles, light transmittance, etc., although the haze in the comparative example is equivalent to or even slightly less than the haze in the example, the film surface clarity and film body clarity of a high-definition optical polyester film of the present invention are still significantly better than those of ordinary polyester films.

[0120] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-definition optical polyester film, characterized in that: the polyester film comprises layer B and layer A on both sides of layer B, and layer A contains the following components in parts by weight: 3 to 25 parts by weight of polyester masterbatch E and 75 to 97 parts by weight of polyethylene terephthalate; layer B contains the following components in parts by weight: 10 to 40 parts by weight of modified polyester F and 60 to 90 parts by weight of polyethylene terephthalate; the polyester masterbatch E contains 0.3 to 10 parts by weight of silica particles T and 90 to 99.7 parts by weight of modified polyester F; The silica particle T is double-modified on the surface with γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-aminotriethoxysilane. After modification, the number of hydroxyl groups R on the surface of the silica particle T satisfies 0 < R ≤ 0.6 per nm 2 , and the average particle size D of the silica particle T satisfies 0.05 μm ≤ D ≤ 2.5 μm; the modified polyester F is modified by 1,3-cyclohexanedicarboxylic acid, isophthalic acid and terephthalic acid, and the molar ratio of 1,3-cyclohexanedicarboxylic acid, isophthalic acid and terephthalic acid is (1 to 7):(1 to 3):(7 to 10).

2. The high-definition optical polyester film according to claim 1, characterized in that: the structure of the polyester film is an A / B / A three-layer structure, and the thickness of the polyester film is 19 μm to 250 μm, wherein the ratio of the thickness of layer A to the thickness of layer B is 1:30 to 1:

10.

3. The high-definition optical polyester film according to claim 1, characterized in that: the polyethylene terephthalate is esterified and polycondensed from purified terephthalic acid and ethylene glycol, and its intrinsic viscosity is 0.63 dl / g to 0.68 dl / g.

4. A method for preparing a high-definition optical polyester film according to any one of claims 1-3, characterized in that: the preparation method comprises the following steps: Step a: Mix the sliced polyester masterbatch E, modified polyester F and polyethylene terephthalate in the required proportions in advance, feed them into the corresponding melt extrusion system, extrude at a temperature of 260 °C to 275 °C, and enter the die co-extrusion; Step b: Obtain the high-definition optical polyester film through casting, longitudinal stretching, transverse stretching, shaping, cooling, traction and winding.

5. The method for preparing a high-definition optical polyester film according to claim 4, characterized in that: the longitudinal stretching ratio in the longitudinal stretching process is 2.8 to 3.

6.

6. The method for preparing a high-definition optical polyester film according to claim 5, characterized in that: the transverse stretching ratio in the transverse stretching process is 3.6 to 5.

2.

7. The method for preparing a high-definition optical polyester film according to claim 6, characterized in that: the heat setting temperature in the shaping process is 225 °C to 240 °C.

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