CN117922138A - Multilayer structure optical polyester film and preparation method thereof - Google Patents

Abstract

The invention discloses a multilayer structure optical polyester film and a preparation method thereof, belonging to the field of optical grade films; the multilayer structure optical polyester film comprises a main layer A of polyester material, high-permeability layers B containing high-transparency organic filling particles are arranged on two sides of the main layer A, and a low-refractive-index layer C is coated on at least one high-permeability layer B by using an on-line coating technology; transparent particles D are arranged on the low refractive index layer C; the high-transparency layer B is prepared by adding high-transparency organic filling particles in the process of synthesizing polyester to prepare polyester master batch, and then mixing the polyester and the polyester master batch and preparing the polyester master batch by a screw extruder; the coating liquid for preparing the low refractive index layer C comprises the following components: 0.1-0.3 part by mass of a cross-linking agent, 8 parts by mass of an adhesive, 0.4-3.8 parts by mass of silica sol, 0.02-0.1 part by mass of a surfactant, 0.5-2 parts by mass of an organic solvent and deionized water; the obtained optical polyester film has high light transmittance and low haze.

Description

A multi-layer optical polyester film and preparation method thereof

Technical Field

The invention belongs to the field of optical-grade films, and in particular relates to a multi-layered optical polyester film and a preparation method thereof.

Background technique

Biaxially oriented polyester film has many excellent properties, including good mechanical properties, electrical insulation properties, optical properties, etc. It plays an important role in the national economy. In recent years, with the development of new display industries, biaxially oriented polyester film has been increasingly used in the optical field, playing an important role in various films of display modules. It is mainly used in diffusion films, brightening films, reflective films, antistatic protective films, protective films in touch screens, and films for flexible displays in high-end liquid crystal display equipment.

Polyester films have higher requirements in optical applications than in packaging or electronic power applications. In addition to mechanical strength and thermal stability, they also require better optical properties. For example, for diffusion films and brightness enhancement films used in liquid crystal display panels, the light transmittance of polyester films used as base films is required to reach more than 90%, and the base films used as liquid crystal display protective films are even required to reach more than 94%. In addition to high light transmittance, low haze is also required. Some optical base films require a haze of less than 1%.

At present, the light transmittance of polyester base films for general use in the new display field is generally ≤85% and the haze is ≥2% at the same thickness as polyester films. Such optical properties are difficult to meet the requirements of optical applications.

In addition to the polyester raw materials themselves, the factors that affect the optical properties of the film are also related to the film making formula and process. In the process of producing biaxially oriented polyester film, in order to prevent the film from contacting with the roller and scratching during the winding process, and to prevent the film from sticking after winding, anti-sticking filler particles are often added to the film to increase the smoothness between the films, so as to prevent the above phenomenon. This method has a certain impact on the optical properties of the film due to the difference in refractive index between the filler and the polyester material, and the product haze is generally high. On the one hand, inorganic particles block part of the light and reduce the light transmittance; on the other hand, these particles will cause part of the light to deviate from the original direction and increase the haze. Although the optical properties can be improved by reducing the amount of inorganic particles added, the effect is not ideal, and it will significantly reduce the anti-sticking properties of the film surface. Although the ABA three-layer structure allows the middle layer to not add inorganic particles, thereby slowing down the decline in optical properties to a certain extent, the effect is often not very obvious.

Summary of the invention

In view of the deficiencies of the prior art, the purpose of the present invention is to provide a multi-layer optical polyester film and a preparation method thereof, which solves the problems in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A multi-layer optical polyester film, comprising a main layer A made of polyester, high-transmittance layers B containing highly transparent organic filling particles are arranged on both sides of the main layer A, at least one high-transmittance layer B is coated with a low-refractive index layer C by online coating technology; transparent particles D with an average particle size of 40-100nm are arranged on the low-refractive index layer C;

The high-transmittance layer B is prepared by adding highly transparent organic filler particles to obtain a polyester masterbatch during the synthesis of polyester, and then mixing the polyester and the polyester masterbatch in a mass ratio of 70-90:10-30, and then passing through a screw extruder;

The low refractive index layer C is formed by applying a coating liquid on the high transmittance layer B in an online coating manner; the coating liquid includes: 0.1-0.3 parts by mass of a cross-linking agent, 8 parts by mass of an adhesive, 0.4-3.8 parts by mass of a silica sol, 0.02-0.1 parts by mass of a surfactant, 0.5-2 parts by mass of an organic solvent, and 85.84-90.98 parts by mass of deionized water.

Furthermore, the main layer A is: PET, PBT, PEN or copolymer-modified polyesters thereof.

Furthermore, in the polyester masterbatch, the mass percentage of the highly transparent organic filler particles is 0.3%-0.35%.

Furthermore, the highly transparent organic filling particles are one or a combination of polymethyl methacrylate microspheres, polystyrene microspheres, cycloolefin copolymer microspheres, polydimethylsiloxane microspheres, polyoxyethylene propyltrichlorosilane microspheres and polymethyl polydimethylsiloxane microspheres.

Furthermore, in the coating liquid, the crosslinking agent is one or more of melamine, polyisocyanate resin, and oxazolines; the adhesive is a polyurethane resin and/or an acrylic resin; the surfactant is one or more of alkylaryl polyether alcohols, polysiloxanes, organic fluorocarbon compounds, and polyoxyalkyl ether compounds; and the organic solvent is one or more of isopropyl alcohol, N-methylpyrrolidone, butyl cellosolve, and anhydrous ethanol.

Furthermore, the transparent particles D are vapor deposited silica particles.

Furthermore, the thickness of the high-transmittance layer B is 2-4 μm, and the thickness of the low-refractive index layer C is 0.09-0.19 μm; the relationship between the thickness d of the low-refractive index layer C and its refractive index n satisfies:

n×d=

Where λ is the wavelength of visible light and k is a positive integer.

A method for preparing the above-mentioned multi-layer optical polyester film comprises the following steps:

S1, adding 60-70 parts by mass of PMMA particles into 30-40 parts by mass of polydimethylsiloxane and stirring at high speed to obtain a paste; then preparing 100 parts by mass of phthalic acid, 130 parts by mass of ethylene glycol and 0.001-0.02 parts by mass of sodium acetate into a slurry, carrying out an esterification reaction, and adding 0.02-0.05 parts by mass of a composite catalyst of ethanol antimony and p-toluenesulfonic acid to sequentially carry out a pre-polycondensation reaction and a final polycondensation reaction; adding 0.6-0.7 parts of the above paste near the end of the pre-polycondensation reaction; adding 0.001-0.02 parts by mass of trimethyl phosphate in the final polycondensation reaction stage; finally adding a photocurable monomer and a photoinitiator, cooling and slicing to obtain a polyester masterbatch;

S2, adding 0.1-0.3 parts by weight of a crosslinking agent to 0.2-0.9 parts by weight of deionized water and stirring evenly, then adding 8 parts by weight of a binder, 0.4-3.8 parts by weight of silica sol, and 0.02-0.1 parts by weight of a surfactant, stirring evenly, and then adding deionized water to prepare a coating solution;

S3, 10-30 parts by weight of polyester masterbatch and 70-90 parts by weight of high-gloss polyester are mixed and then respectively put into the first twin-screw extruder and the third twin-screw extruder; 100 parts of high-gloss polyester are put into the pre-crystallizer, and pre-crystallized at 140°C-160°C for 5min-15min, and then the polyester enters the drying tower, and is dried at 150°C-180°C for 4-6h, and then enters the second single-screw extruder;

S4, adjusting the temperature of the first and third twin-screw extruders to 270°C-280°C, and the temperature of the second single-screw extruder to 265°C-280°C; after melting, filtering, using the materials extruded by the first and third twin-screw extruders as the high-transmittance layers B on both sides, and the material extruded by the second single-screw extruder as the main layer A, the three-layer die is merged, and the multi-layer co-extrusion process is used to make a three-layer composite melt, which is attached to a cooling roller through an electrostatic adsorption device to form a thick sheet;

S5, preheating the thick sheet at a temperature of 50°C-90°C, entering an infrared heating zone at 300°C-500°C, and longitudinally stretching the thick sheet by 3.0-4.5 times at a line speed of 40-150 m/min to obtain a stretched sheet;

S6, applying the coating liquid prepared in S2 onto the surface of the longitudinally stretched stretching sheet by an online coating machine using an anilox roller coating method;

S7, preheating the coated stretched sheet at 90°C-120°C, stretching it transversely by 3.0-4.5 times at 100°C-160°C, and then shaping it at 160°C-240°C;

S8, the film is cooled at 100°C-150°C and flattened, and then the thickness is measured online, and the automatic die head is fed back for automatic thickness adjustment. After the film is trimmed, it is wound by a winder to obtain a multi-layer optical polyester film.

Beneficial effects of the present invention:

1. The polyester film prepared by the present invention has higher light transmittance and lower haze than the film in the prior art, and provides a polyester film for use in the optical field and a preparation method thereof.

2. The base film of the optical polyester film provided by the present invention is multi-layer co-extruded and formed in one step, and a functional layer is coated by an online coating process. The preparation process of the optical anti-reflection film provided by the present invention is simple, and the online coating process greatly improves the production efficiency, reduces energy consumption, and has excellent anti-reflection effect, and is suitable for large-scale production.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

FIG. 1 is a schematic diagram of the structure of a multi-layer optical polyester film according to the present invention.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

As shown in FIG1 , a multi-layer structure optical polyester film includes a polyester base film, the polyester base film includes a main layer A, high-transmittance layers B containing highly transparent organic filling particles are arranged on both sides of the main layer A, at least one high-transmittance layer B is coated with a layer of low-refractive index layer C by online coating technology; the low-refractive index layer C is provided with organic/inorganic transparent particles D with an average particle size of 40-100 nm;

The thickness of the high-transmittance layer B is 2-4 μm, and the thickness of the low-refractive index layer C is 0.09-0.19 μm; (the relationship between the thickness d of the low-refractive index layer C and its refractive index n satisfies: n×d= Wherein, λ is the wavelength of visible light, usually 380-780nm, and k is a positive integer. Considering the cost and the adverse effect on haze, k is taken as 1 here).

The main layer A is polyester, specifically polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) or copolymer-modified polyesters thereof.

The high-transmittance layer B is prepared by using highly transparent organic filler particles and polyester to prepare a polyester masterbatch, and then mixing the polyester and the polyester masterbatch in a mass ratio of 70-90:10-30, and then passing through a screw extruder to prepare the high-transmittance layer B;

Among them, in the polyester masterbatch, the mass percentage of highly transparent organic filler particles is 0.3%-0.35%; the highly transparent organic filler particles can be selected from one or a combination of polymethyl methacrylate (PMMA) microspheres, polystyrene microspheres, cycloolefin copolymer microspheres, polydimethylsiloxane microspheres, polyoxyethylene propyltrichlorosilane microspheres, and polymethyl polydimethylsiloxane microspheres.

The low refractive index layer C is formed by applying a coating liquid on the high transmittance layer B in an online coating manner; the coating liquid is composed of: 0.1-0.3 parts by mass of a cross-linking agent (one or more of melamine, polyisocyanate resin, and oxazoline), 8 parts by mass of an adhesive (including a polyurethane resin and/or an acrylic resin), 0.4-3.8 parts by mass of a silica sol, 0.02-0.1 parts by mass of a surfactant (one or more of an alkylaryl polyether alcohol, a polysiloxane, an organic fluorocarbon compound, and a polyoxyalkyl ether compound), 0.5-2 parts by mass of an organic solvent (one or more of isopropyl alcohol, N-methylpyrrolidone, butyl cellosolve, and anhydrous ethanol), and 85.84-90.98 parts by mass of deionized water.

In addition, the transparent particles D are preferably vapor-deposited silica particles, and may also be polydimethylsiloxane, polyoxyethylene propyl trichlorosilane, polymethyl polydimethylsiloxane, and polyoxyethylene propyl trichlorosilane.

The preparation process of the multilayer optical polyester film of the present application is described in detail below through the following examples; wherein the parts in the examples are all parts by mass.

Example 1

A method for preparing a multi-layer optical polyester film comprises the following steps:

S1, preparing polyester masterbatch;

1) Add 60 parts of PMMA particles into 40 parts of polydimethylsiloxane and stir at high speed to obtain a paste;

2) 100 parts of phthalic acid, 130 parts of ethylene glycol and 0.001 parts of sodium acetate are prepared into a slurry, which is then transferred to an esterification reactor for esterification reaction, and then 0.02 parts of a composite catalyst of ethanol antimony and p-toluenesulfonic acid are added to sequentially carry out a pre-polycondensation reaction and a final polycondensation reaction; 0.6 parts of the above paste is added near the end of the pre-polycondensation reaction; and 0.001 parts of trimethyl phosphate are added in the final polycondensation reaction stage;

3) During the cooling process after the final polycondensation, when the temperature drops below the melting point of the photocurable monomer and the photoinitiator, the photocurable monomer and the photoinitiator are added, and finally the final polymer is unloaded into the cooling pool and sliced to obtain the polyester masterbatch.

S2, preparing a coating solution;

0.1 parts of melamine were added to 0.5 parts of deionized water and stirred evenly, and then 8 parts of acrylic resin, 0.4 parts of silica sol, 0.02 parts of alkylaryl polyether alcohol and 0.5 parts of isopropanol were added, stirred evenly and then the remaining amount of deionized water was added to prepare a coating solution.

S3, 30 parts of polyester masterbatch and 70 parts of bright PET are mixed and then respectively put into the first twin-screw extruder and the third twin-screw extruder; 100 parts of bright PET are put into the pre-crystallizer, pre-crystallized at 140°C for 5 minutes, and then the PET enters the drying tower, is dried at 150°C for 4 hours, and then enters the second single-screw extruder;

S4, adjusting the temperature of the first and third twin-screw extruders to 270°C, and the temperature of the second single-screw extruder to 265°C; after melting, filtering, using the materials extruded by the first and third twin-screw extruders as the high-transmittance layers B on both sides, and the material extruded by the second single-screw extruder as the main layer A, after the three-layer die is merged, a three-layer composite melt is made by a multi-layer co-extrusion process, and the melt is attached to a cooling roller through an electrostatic adsorption device to form a thick sheet, and the thickness of the thick sheet can be automatically/manually adjusted by the extrusion amount of the extruder and the die opening;

S5, preheating the thick sheet at 50°C, placing it in an infrared heating zone at 300°C, and longitudinally stretching it at a line speed of 40 m/min with a longitudinal stretching ratio of 3.0 to obtain a stretched sheet;

S6, applying the coating liquid prepared in S2 onto the surface of the longitudinally stretched stretching sheet by an online coating machine using an anilox roller coating method;

S7, preheating the coated stretched sheet at 90°C, stretching it transversely at 100°C, with a transverse stretching ratio of 3.0; and then shaping it at 160°C;

S8, the film is cooled to 100°C and flattened, and then the thickness is measured online, and the film is fed back to the automatic die head for automatic thickness adjustment; after the film is trimmed, it is wound by a winder to obtain a multi-layer optical polyester film.

Example 2

A method for preparing a multi-layer optical polyester film comprises the following steps:

S1, preparing polyester masterbatch;

1) Add 70 parts of PMMA particles into 30 parts of polydimethylsiloxane and stir at high speed to obtain a paste;

2) 100 parts of phthalic acid, 130 parts of ethylene glycol and 0.002 parts of sodium acetate are prepared into a slurry, which is then transferred to an esterification reactor for esterification reaction, and then 0.05 parts of a composite catalyst of ethanol antimony and p-toluenesulfonic acid are added to sequentially carry out a pre-polycondensation reaction and a final polycondensation reaction; 0.7 parts of the above paste is added near the end of the pre-polycondensation reaction; and 0.002 parts of trimethyl phosphate is added at the final polycondensation reaction stage;

3) During the cooling process after the final polycondensation, when the temperature drops below the melting point of the photocurable monomer and the photoinitiator, the photocurable monomer and the photoinitiator are added, and finally the final polymer is unloaded into the cooling pool and sliced to obtain the polyester masterbatch.

S2, preparing a coating solution;

0.2 parts of polyisocyanate resin were added to 0.7 parts of deionized water and stirred evenly, and then 8 parts of polyurethane resin, 0.4 parts of silica sol, 0.05 parts of polysiloxane and 1 part of N-methylpyrrolidone were added, stirred evenly, and the remaining amount of deionized water was added to prepare a coating liquid.

S3, 25 parts of polyester masterbatch and 75 parts of bright PET are mixed and then respectively put into the first twin-screw extruder and the third twin-screw extruder; 100 parts of bright PET are put into the pre-crystallizer, pre-crystallized at 150°C for 10 minutes, and then the PET enters the drying tower, is dried at 170°C for 5 hours, and then enters the second single-screw extruder;

S4, adjusting the temperature of the first and third twin-screw extruders to 275°C, and the temperature of the second single-screw extruder to 275°C; after melting, filtering, using the materials extruded by the first and third twin-screw extruders as the high-transmittance layers B on both sides, and the material extruded by the second single-screw extruder as the main layer A, after the three-layer die is merged, a three-layer composite melt is made by a multi-layer co-extrusion process, and the melt is attached to a cooling roller through an electrostatic adsorption device to form a thick sheet, and the thickness of the thick sheet can be automatically/manually adjusted by the extrusion amount of the extruder and the die opening;

S5, preheating the thick sheet at 70°C, placing it in an infrared heating zone at 400°C, and longitudinally stretching it at a line speed of 80 m/min with a longitudinal stretching ratio of 4.0 to obtain a stretched sheet;

S6, applying the coating liquid prepared in S2 onto the surface of the longitudinally stretched stretching sheet by an online coating machine using an anilox roller coating method;

S7, preheating the coated stretched sheet at 100°C, stretching it transversely at 130°C, with a transverse stretching ratio of 4.0; and then shaping it at 200°C;

S8, the film is cooled at 80°C and flattened, and then the thickness is measured online, and the film is fed back to the automatic die head for automatic thickness adjustment; after the film is trimmed, it is wound by a winder to obtain a multi-layer optical polyester film.

Example 3

A method for preparing a multi-layer optical polyester film comprises the following steps:

S1, preparing polyester masterbatch;

1) Add 60 parts of PMMA particles into 40 parts of polydimethylsiloxane and stir at high speed to obtain a paste;

2) 100 parts of phthalic acid, 130 parts of ethylene glycol and 0.001 parts of sodium acetate are prepared into a slurry, which is then transferred to an esterification reactor for esterification reaction, and then 0.02 parts of a composite catalyst of ethanol antimony and p-toluenesulfonic acid are added to sequentially carry out a pre-polycondensation reaction and a final polycondensation reaction; 0.6 parts of the above paste is added near the end of the pre-polycondensation reaction; and 0.001 parts of trimethyl phosphate are added in the final polycondensation reaction stage;

3) During the cooling process after the final polycondensation, when the temperature drops below the melting point of the photocurable monomer and the photoinitiator, the photocurable monomer and the photoinitiator are added, and finally the final polymer is unloaded into the cooling pool and sliced to obtain the polyester masterbatch.

S2, preparing a coating solution;

0.3 parts of melamine were added to 0.8 parts of deionized water and stirred evenly, and then 8 parts of polyurethane resin, 0.4 parts of silica sol, 0.08 parts of organic fluorocarbon compound and 1.5 parts of butyl cellosolve were added, stirred evenly and then the remaining amount of deionized water was added to prepare a coating liquid.

S3, 20 parts of polyester masterbatch and 80 parts of bright PET are mixed and then respectively put into the first twin-screw extruder and the third twin-screw extruder; 100 parts of bright PET are put into the pre-crystallizer, pre-crystallized at 1640°C for 15 minutes, and then the PET enters the drying tower, is dried at 180°C for 4 hours, and then enters the second single-screw extruder;

S4, adjusting the temperature of the first and third twin-screw extruders to 280°C, and the temperature of the second single-screw extruder to 280°C; after melting, filtering, using the materials extruded by the first and third twin-screw extruders as the high-transmittance layers B on both sides, and the material extruded by the second single-screw extruder as the main layer A, after the three-layer die is merged, a three-layer composite melt is made by a multi-layer co-extrusion process, and the melt is attached to a cooling roller through an electrostatic adsorption device to form a thick sheet, and the thickness of the thick sheet can be automatically/manually adjusted by the extrusion amount of the extruder and the die opening;

S5, preheating the thick sheet at 90°C, placing it in an infrared heating zone at 500°C, and longitudinally stretching it at a line speed of 150 m/min with a longitudinal stretching ratio of 4.5 to obtain a stretched sheet;

S6, applying the coating liquid prepared in S2 onto the surface of the longitudinally stretched stretching sheet by an online coating machine using an anilox roller coating method;

S7, preheating the coated stretched sheet at 120°C, stretching it transversely at 160°C, with a transverse stretching ratio of 4.5; and then shaping it at 240°C;

S8, the film is cooled at 50°C and flattened, and then the thickness is measured online, and the film is fed back to the automatic die head for automatic thickness adjustment; after the film is trimmed, it is wound by a winder to obtain a multi-layer optical polyester film.

Example 4

The difference between Example 4 and Example 1 is only that:

The process of preparing the coating solution in S2 is as follows:

Add 0.15 parts of melamine and 0.15 parts of oxazolines to 0.5 parts of deionized water and stir evenly, then add 2.5 parts of polyurethane resin, 5.5 parts of acrylic resin, 0.4 parts of silica sol, 0.05 parts of polyoxyalkyl ether compound and 2 parts of anhydrous ethanol, stir evenly and add the remaining amount of deionized water to prepare a coating solution.

Take 15 parts of polyester masterbatch and 85 parts of bright PET in S3.

Example 5

The difference between Example 5 and Example 1 is only that:

The process of preparing the coating solution in S2 is as follows:

0.1 parts of polyisocyanate resin are added to 0.2 parts of deionized water and stirred evenly, and then 4 parts of polyurethane resin, 4 parts of acrylic resin, 3.5 parts of silica sol, 0.05 parts of alkylaryl polyether alcohol, 0.02 parts of polysiloxane, 0.02 parts of organic fluorocarbon compounds, 0.01 parts of polyoxyalkyl ether compounds, 0.5 parts of isopropanol, 0.5 parts of N-methylpyrrolidone and 0.5 parts of butyl cellosolve are added, stirred evenly, and the remaining amount of deionized water is added to prepare a coating solution.

Take 10 parts of polyester masterbatch and 90 parts of bright PET in S3.

Example 6

The difference between Example 6 and Example 1 is only that:

The process of preparing the coating solution in S2 is as follows:

Add 0.2 parts of melamine to 0.5 parts of deionized water and stir evenly, then add 5 parts of polyurethane resin, 3 parts of acrylic resin, 3.5 parts of silica sol, 0.04 parts of polysiloxane, 0.04 parts of organic fluorocarbon compounds, 1 part of N-methylpyrrolidone and 1 part of anhydrous ethanol, stir evenly and add the remaining amount of deionized water to prepare a coating liquid.

Take 10 parts of polyester masterbatch and 90 parts of bright PET in S3.

Example 7

The difference between Example 7 and Example 1 is only that:

The process of preparing the coating solution in S2 is as follows:

0.1 parts of melamine, 0.1 parts of polyisocyanate resin, and 0.1 parts of oxazolines are added to 0.8 parts of deionized water and stirred evenly. Then, 6 parts of polyurethane resin, 2 parts of acrylic resin, 3.8 parts of silica sol, 0.03 parts of alkylaryl polyether alcohol, 0.03 parts of polyoxyalkyl ether compound, 1 part of isopropyl alcohol, and 1 part of butyl cellosolve are added. After stirring evenly, the remaining amount of deionized water is added to prepare a coating solution.

Take 10 parts of polyester masterbatch and 90 parts of bright PET in S3.

Example 8

The difference between Example 8 and Example 1 is only that:

The process of preparing the coating solution in S2 is as follows:

0.3 parts of polyisocyanate resin were added to 0.9 parts of deionized water and stirred evenly, and then 8 parts of acrylic resin, 3.8 parts of silica sol, 0.1 parts of polyoxyalkyl ether compound, 0.5 parts of isopropanol, 0.5 parts of N-methylpyrrolidone, 0.5 parts of butyl cellosolve and 0.2 parts of anhydrous ethanol were added, stirred evenly and then the remaining amount of deionized water was added to prepare a coating solution.

Take 10 parts of polyester masterbatch and 90 parts of bright PET in S3.

Comparative Example 1

The only difference between this comparative example and Example 1 is that the online coating of S6 is not performed, and the highly transparent film is directly produced by a biaxial stretching process.

Comparative Example 2

The only difference between this comparative example and Example 2 is that the online coating of S6 is not performed, and the highly transparent film is directly produced by a biaxial stretching process.

The coating liquid ratios (mass percentages) corresponding to Examples 1-8 are shown in Table 1, the base film ratios (mass percentages) are shown in Table 2, and the thicknesses (μm) of the generated A, B, and C layers are shown in Table 3;

Table 1 Coating liquid ratio table (mass percentage)

Table 2 Base film ratio table (mass percentage)

Table 3 Thickness of each layer (μm)

The optical properties of the polyester films prepared in Examples 1-8 and Comparative Examples 1-2 are evaluated by measuring light transmittance and haze. The higher the light transmittance and the lower the haze, the higher the optical properties. The test was carried out according to the method specified in GB/T 2410-2008, and the instrument was a 4725 haze meter from German BYK. The test results are shown in Table 4.

Table 4 Related performance test results

The above results show that the light transmittance of the polyester films prepared in Examples 1-8 is greater than 90%, and the haze is less than 2.0%, which is significantly better than the prior art (light transmittance ≤ about 85%, haze ≥ about 2%).

Combining the test data of Example 1 and Comparative Example 1, and the test data of Example 2 and Comparative Example 2, it can be seen that the present invention can effectively improve the optical properties of the film, significantly improve the light transmittance of the film, and the haze of the film is significantly reduced, especially after a low refractive index layer is coated online. The effect is most obvious when the two technologies of adding the prepared optical grade masterbatch and coating the low refractive index layer online are used simultaneously.

In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims (11)

1. The multilayer structure optical polyester film is characterized by comprising a main layer A made of polyester, wherein high-permeability layers B containing high-transparency organic filling particles are arranged on two sides of the main layer A, and at least one high-permeability layer B is coated with a low-refractive-index layer C by using an online coating technology; transparent particles D with the average particle diameter of 40-100nm are arranged on the low refractive index layer C;

The Gao Touceng B is that high transparent organic filling particles are added in the process of synthesizing polyester to obtain polyester master batch, and then the polyester and the polyester master batch are mixed according to the proportion of 70-90: mixing the materials according to the mass ratio of 10-30, and preparing the materials by a screw extruder;

The low refractive index layer C is formed by coating the coating liquid on the high-permeability layer B in an on-line coating mode; the coating liquid comprises the following components: 0.1-0.3 part by mass of cross-linking agent, 8 parts by mass of adhesive, 0.4-3.8 parts by mass of silica sol, 0.02-0.1 part by mass of surfactant, 0.5-2 parts by mass of organic solvent and 85.84-90.98 parts by mass of deionized water.

2. The multilayer optical polyester film according to claim 1, wherein the main layer a is: PET, PBT, PEN or a copolymerized modified polyester thereof.

3. The multilayer optical polyester film according to claim 1, wherein the mass percentage of the high transparent organic filler particles in the polyester master batch is 0.3% -0.35%.

4. A multilayer optical polyester film according to claim 1 or 3, wherein the highly transparent organic filler particles are: polymethyl methacrylate microsphere, polystyrene microsphere, cycloolefin copolymer microsphere, polydimethylsiloxane microsphere, polyoxyethylene propyl trichlorosilane microsphere, and one or more of polymethyl polydimethylsiloxane microsphere.

5. The multilayer optical polyester film according to claim 1, wherein the crosslinking agent in the coating liquid is one or more of melamine, polyisocyanate, and oxazolines; the adhesive is polyurethane resin and/or acrylic resin; the surfactant is one or more of alkylaryl polyether alcohol, polysiloxane, organic fluorocarbon and polyepoxy alkyl ether compound; the organic solvent is one or more of isopropanol, N-methyl pyrrolidone, butyl cellosolve and absolute ethyl alcohol.

6. The multilayer optical polyester film according to claim 1, wherein the transparent particles D are fumed silica particles.

7. The multilayer optical polyester film according to claim 1, wherein the high-transmittance layer B has a thickness of 2 to 4 μm and the low-refractive-index layer C has a thickness of 0.09 to 0.19 μm; the relationship between the thickness d of the low refractive index layer C and its refractive index n should be such that:

n×d=

where λ is the wavelength of visible light, and k is a positive integer.

8. A method for producing the optical polyester film of multilayer structure according to any one of claims 1 to 7, comprising the steps of:

S1, adding 60-70 parts by mass of PMMA particles into 30-40 parts by mass of polydimethylsiloxane, and stirring at a high speed to obtain paste; preparing 100 parts by mass of phthalic acid, 130 parts by mass of ethylene glycol and 0.001-0.02 part by mass of sodium acetate into slurry, performing esterification reaction, and adding 0.02-0.05 part by mass of antimony ethoxide and p-toluenesulfonic acid composite catalyst to sequentially perform pre-polycondensation reaction and final polycondensation reaction; adding 0.6-0.7 part of the paste material near the end of the pre-polycondensation reaction; adding 0.001-0.02 parts by mass of trimethyl phosphate in the final polycondensation stage; finally adding a photo-curing monomer and a photo-initiator, and cooling and slicing to obtain a polyester master batch;

S2, adding 0.1-0.3 part by mass of a cross-linking agent into 0.2-0.9 part by mass of deionized water, uniformly stirring, adding 8 parts by mass of an adhesive, 0.4-3.8 parts by mass of silica sol and 0.02-0.1 part by mass of a surfactant, uniformly stirring, and then adding deionized water to prepare a coating solution;

S3, mixing 10-30 parts by mass of polyester master batch with 70-90 parts by mass of large gloss polyester, and then respectively putting the mixture into a first double-screw extruder and a third double-screw extruder; 100 parts of large bright polyester is put into a pre-crystallizer, pre-crystallized for 5min-15min at 140-160 ℃, then the polyester enters a drying tower, dried for 4-6h at 150-180 ℃, and then enters a second single screw extruder;

S4, adjusting the temperature of the first twin-screw extruder and the third twin-screw extruder to 270-280 ℃, and adjusting the temperature of the second single-screw extruder to 265-280 ℃; after melting, filtering, taking the materials extruded by the first and third double-screw extruders as high-permeability layers B on two sides, taking the material extruded by the second single-screw extruder as a main layer A, converging by a three-layer die head, preparing a three-layer composite melt by a multi-layer coextrusion process, and attaching to a cooling roller by an electrostatic adsorption device to prepare a thick sheet;

s5, preheating the thick sheet at 50-90 ℃, entering an infrared heating area at 300-500 ℃, and longitudinally stretching at a linear speed of 40-150m/min for 3.0-4.5 times to obtain a stretched sheet;

s6, coating the coating liquid prepared in the step S2 on the surface of the longitudinally stretched stretching sheet by an online coater in an anilox roller coating mode;

S7, preheating the coated stretch sheet at the temperature of 90-120 ℃, transversely stretching the stretch sheet at the temperature of 100-160 ℃ for 3.0-4.5 times, and shaping the stretch sheet at the temperature of 160-240 ℃;

S8, cooling the film at the temperature of 100-150 ℃ and flattening, performing on-line thickness measurement, feeding back to an automatic die head for automatic thickness adjustment, trimming the film, and then rolling by a rolling machine to obtain the multilayer structure optical polyester film.

9. The method for preparing the multilayer structure optical polyester film according to claim 8, wherein the crosslinking agent in the coating liquid is one or more of melamine, polyisocyanate resin and oxazolines; the adhesive is polyurethane resin and/or acrylic resin; the surfactant is one or more of alkylaryl polyether alcohol, polysiloxane, organic fluorocarbon and polyepoxy alkyl ether compound; the organic solvent is one or more of isopropanol, N-methyl pyrrolidone, butyl cellosolve and absolute ethyl alcohol.

10. A novel optical antireflection film for display, characterized by comprising the multilayer structure optical polyester film as claimed in any one of claims 1 to 7.

11. Use of a multilayer optical polyester film according to any one of claims 1 to 7 for the preparation of novel optical antireflection films for display applications.