Anti-blue-light and anti-ultraviolet polyester film as well as preparation method and application thereof

Abstract

The invention discloses an anti-blue-light and anti-ultraviolet polyester film as well as a preparation method and application thereof, and mainly relates to the technical field of layered products consisting of polyester. Compared with the prior art, the anti-blue light and anti-ultraviolet polyester film is obtained by melting, casting and stretching three layers of master batch materials A, B and C, the layer A master batch material is polyethylene glycol terephthalate, synergistic resin and an anti-blocking agent, the layer B master batch material is polyethylene glycol terephthalate, an ultraviolet light absorber and a blue light absorber, and the layer C master batch material is polyethylene glycol terephthalate, a synergistic resin and an anti-blocking agent. And the master batch material of the layer C is polyethylene glycol terephthalate, synergistic resin and polyethylene naphthalate. Compared with the prior art, the method has the advantages that the compactness and uniformity of the internal structure of the film are improved, the dispersity and stability of the functional additive are improved, the defects are reduced, the synergistic improvement of blue light resistance and ultraviolet resistance is finally realized, and meanwhile, the mechanical property of the film is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of layered products composed of polyester, and in particular to a blue light-proof and ultraviolet-resistant polyester film, and a preparation method and application thereof. Background Art

[0002] Polyester film is a biaxially stretched polyethylene terephthalate (PET) film material. It exhibits high strength, toughness, dimensionally stable, thin, transparent, chemical, water, and high-temperature resistance, and high insulation properties. It is primarily used in the packaging industry, electrical and electronics, optics and imaging, industrial and composite materials, as well as agriculture, insulating tape, and other fields. Blue light and UV resistant polyester film is a functional film made by adding specific functional additives to ordinary polyester film. Its blue light protection principle is to selectively absorb or refract blue light through absorbents, while its UV protection principle is to absorb or reflect UV rays and convert them into energy, thereby blocking and shielding blue light and UV rays. This reduces blue light damage to the eyes and prevents UV aging of the polyester film.

[0003] In the existing technology, in order to simultaneously improve the blue light protection and UV aging protection capabilities, specific blue light absorbers and UV absorbers can be added to the raw materials to achieve functional enhancements. Additives can also be added during the film preparation process to effectively improve the stability of film formation by improving the compatibility, dispersibility, and uniformity of the film-forming system, thereby indirectly enhancing its blue light and UV protection effects. This can be manifested in promoting the uniform dispersion of functional additives such as blue light absorbers and UV absorbers in the matrix, avoiding protective performance shortcomings caused by additive agglomeration or uneven distribution; improving the density and integrity of the film structure, reducing the generation of defects such as pinholes and bubbles during the film formation process, allowing the functional additives to more fully absorb and block light, and ultimately achieving a synergistic improvement in blue light protection and UV protection.

[0004] CN112959784A discloses a highly transparent, heat-insulating, and UV-blocking polyester film and its preparation method. The film comprises an upper surface layer, an intermediate layer, and a lower surface layer. The upper and lower surface layers are composed of polyester chips, an optical-grade anti-blocking agent, a heat-insulating masterbatch, and a UV absorber; the intermediate layer is composed of polyester chips, a heat-insulating masterbatch, a UV absorber, and a blue light absorber. This invention effectively improves infrared rejection and visible light transmittance, but does not reduce the effects of UV aging on tensile strength.

[0005] CN104015438A discloses an anti-blue light and fingerprint-resistant film and its preparation method. The film comprises a fingerprint-resistant coating, a film substrate layer, a blue light blocking layer, and a release film layer. The fingerprint-resistant coating and blue light blocking layer are applied to both sides of the substrate layer, respectively, and the release film layer is applied to the outer side of the blue light blocking layer. This invention can effectively block 380-480nm blue light, reducing retinal damage, while also providing fingerprint resistance and improving display visibility and operability, but does not simultaneously enhance UV resistance. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to improve the blue light protection and UV resistance of the polyester film.

[0007] To achieve the above objectives, the present invention provides a blue light-proof and UV-resistant polyester film and a preparation method and application thereof.

[0008] A method for preparing a blue light-proof and UV-resistant polyester film comprises the following steps, measured in parts by weight: (1) 45-55 parts of polyethylene terephthalate, 25-35 parts of synergistic resin, and 10-15 parts of anti-blocking agent are melted and granulated by a twin-screw extruder, cooled to 50-60°C, and pelletized to obtain A-layer masterbatch for later use; (2) 60-80 parts of polyethylene terephthalate, 10-15 parts of ultraviolet absorber, and 15-20 parts of blue light absorber are shear-mixed at a speed of 2500-3500 r / min for 10-30 minutes, melt-granulated by a single-screw extruder, cooled to 50-60°C, and pelletized to obtain a B-layer masterbatch for later use; (3) 35-45 parts of polyethylene terephthalate, 25-35 parts of synergistic resin, and 25-35 parts of polyethylene naphthalate are melted and pelletized through a twin-screw extruder, cooled to 50-60°C, and pelletized to obtain a C-layer masterbatch for later use; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept at a constant temperature for 0.5-1.5 hours, heated to 120-140°C and kept at a constant temperature for 0.5-1.5 hours, and heated to 150-170°C and kept at a constant temperature for 4-6 hours to allow them to fully crystallize; they are melted separately in three extruders, the three molten streams are mixed through a common die, and a film is obtained by extruding through the die and then stretched; the film is stretched simultaneously in the longitudinal and transverse directions; and the film is cooled to 50-60°C and rolled up to obtain the anti-blue light and anti-ultraviolet polyester film.

[0009] The preparation method of the synergistic resin is as follows, in parts by weight: 1-3 parts of tannic acid are added to 15-25 parts of Tris buffer and stirred for 0.5-1 hour, 8-12 parts of polyethylene terephthalate are added and stirred for 0.5-1 hour; the mixture is filtered and dried at 55-65° C. for 20-25 hours to obtain a synergistic resin.

[0010] Alternatively, 1-3 parts of tannic acid are added to 15-25 parts of Tris buffer and stirred for 0.5-1 hour, 0.5-1.5 parts of inorganic salt and 8-12 parts of polyethylene terephthalate are added and stirred for 0.5-1 hour; filtered, and dried at 55-65° C. for 20-25 hours to obtain the synergistic resin.

[0011] Alternatively, 1-3 parts of tannic acid are added to 15-25 parts of Tris buffer and stirred for 0.5-1 hour, 0.5-1.5 parts of inorganic salt and 8-12 parts of polyethylene terephthalate are added and stirred for 0.5-1 hour; 0.1-0.5 parts of ε-polylysine ester are added and stirred for 10-15 hours to continue surface modification, filtered, and dried at 55-65° C. for 20-25 hours to obtain a synergistic resin.

[0012] The inorganic salt is one of zinc chloride, copper chloride and magnesium chloride.

[0013] The opening agent in step (1) is amorphous silicon dioxide.

[0014] The ultraviolet absorber in step (2) is one of UV-320, UV-326, UV-327, UV-328, and UV-350.

[0015] The blue light absorber in step (2) is LOTSORB ® B-30, LOTSORB ® B-60, LOTSORB ® One of the B-100.

[0016] The particle size of the masterbatch of layer A, layer B and layer C in step (1), step (2) and step (3) is 3-4 mm.

[0017] The melting temperature of the melt granulation in steps (1), (2) and (3) is 260-280°C.

[0018] The melting temperature in step (4) is 270-290°C.

[0019] The stretching ratio of the longitudinal and transverse stretching in step (4) is 3.0-4.0.

[0020] The stretching temperature for the simultaneous longitudinal and transverse stretching in step (4) is 80-120°C.

[0021] The stretching time for the simultaneous longitudinal and transverse stretching in step (4) is 30-60 seconds.

[0022] The blue light-proof and ultraviolet-resistant polyester film can be used to prepare a mobile phone film, a car film, a display screen film, or a decoration.

[0023] The anti-blue light and anti-ultraviolet polyester film of the present invention is obtained by melting, casting and stretching three layers of masterbatch materials A, B and C, wherein the masterbatch material of the A layer is polyethylene terephthalate, a synergistic resin and an opening agent, the masterbatch material of the B layer is polyethylene terephthalate, an ultraviolet absorber and a blue light absorber, and the masterbatch material of the C layer is polyethylene terephthalate, a synergistic resin and polyethylene naphthalate. The polyethylene terephthalate in the A layer material provides basic mechanical strength and film-forming properties, the opening agent reduces the surface friction coefficient by forming a microscopic rough structure to avoid rolling adhesion, and the addition of the synergistic resin enhances the cohesive strength of the A layer and the interfacial bonding stability with the B layer, while optimizing the structural density and preventing interlayer peeling. The B layer uses polyethylene terephthalate as a film-forming carrier, adds an ultraviolet absorber to absorb ultraviolet light through a conjugated system and convert it into energy, and adds a blue light absorber to selectively capture short-wave blue light, consuming energy through electronic transition to achieve balance. The C layer adopts a blend system of polyethylene terephthalate and polyethylene naphthalate, and then adds a synergistic resin. The naphthalene ring structure of polyethylene naphthalate gives the C layer better heat resistance, improves the dimensional stability of the film in a high temperature environment, and is suitable for scenarios such as electronic packaging; and the synergistic resin strengthens the interface bonding between the C layer and the B layer, combines the "rigid and flexible complementary" characteristics of the polyethylene naphthalate rigid chain and the polyethylene terephthalate flexible chain, and enhances the physical properties of the film such as tensile and impact resistance. Finally, the C layer and the A layer form a symmetrical structure, balance the biaxial tensile stress, and can reduce the risk of warping. At the same time, through the synergistic effect of the synergistic resins on both sides, the interlayer bonding and overall mechanical uniformity are further optimized. The present invention also adds a synergistic resin to improve the density and uniformity of the internal structure of the film, improve the dispersibility and stability of functional additives, reduce defects, and ultimately achieve a synergistic improvement in anti-blue light and anti-ultraviolet performance, while ensuring the mechanical properties of the film.

[0024] Beneficial effects of the present invention: Compared to the prior art, the blue light-blocking and UV-resistant polyester film of the present invention is obtained from three layers of masterbatch materials, A, B, and C, through steps such as melting, sheet casting, and stretching. The masterbatch material for layer A comprises polyethylene terephthalate, a synergistic resin, and an anti-blocking agent; the masterbatch material for layer B comprises polyethylene terephthalate, a UV absorber, and a blue light absorber; and the masterbatch material for layer C comprises polyethylene terephthalate, a synergistic resin, and polyethylene naphthalate. The present invention also incorporates a synergistic resin to improve the density and uniformity of the film's internal structure, enhance the dispersibility and stability of the functional additives, and reduce defects, ultimately achieving a synergistic improvement in blue light and UV resistance while ensuring the film's mechanical properties. DETAILED DESCRIPTION

[0025] The parameters of the specific chemical substances used in the examples are derived from the following sources: Polyethylene terephthalate: The manufacturer is Shenzhen Yuanbang New Materials Co., Ltd., and the brand is Rynite®HR540SUV BK544.

[0026] Amorphous silica: Brand is Grace, model is SYLOBLOC ® 45, 4.4-5.4μm.

[0027] Polyethylene naphthalate: brand is Japanese Teijin, model is Teonex ® .

[0028] Example 1 A method for preparing a blue light-proof and ultraviolet-resistant polyester film comprises the following steps: (1) 50 g of polyethylene terephthalate, 30 g of synergistic resin, and 12 g of amorphous silica were melted and pelletized at 270 °C using a twin-screw extruder, cooled to 55 °C, and pelletized to obtain A-layer masterbatch with a particle size of 3.5 mm for later use; (2) 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, 18g LOTSORB ® B-60 blue light absorber was shear-mixed at a speed of 3000 r / min for 20 minutes, melt-granulated at 270°C using a single-screw extruder, cooled to 55°C and pelletized to obtain B-layer masterbatch with a particle size of 3.5 mm for later use; (3) 40 g of polyethylene terephthalate, 30 g of synergistic resin, and 30 g of polyethylene naphthalate were melted and pelletized at 270 °C through a twin-screw extruder, cooled to 55 °C, and pelletized to obtain a C-layer masterbatch with a particle size of 3.5 mm, which was set aside; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept constant for 1 hour, heated to 130°C and kept constant for 1 hour, and heated to 160°C and kept constant for 5 hours to allow them to fully crystallize; they are melted at 280°C in three extruders, and the three molten streams are mixed through a common die head, and the films are extruded through the die head and then stretched; they are stretched simultaneously in the longitudinal and transverse directions, with a stretching ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; they are cooled to 55°C and rolled up to obtain the blue light-proof and UV-resistant polyester film.

[0029] The preparation method of the synergistic resin is as follows: 2 g of tannic acid was added to 20 g of 1 wt% Tris buffer and stirred for 0.5 hour. 10 g of polyethylene terephthalate was added and stirred for 1 hour. The mixture was filtered and dried at 60° C. for 24 hours to obtain a synergistic resin.

[0030] Example 2 A method for preparing a blue light-proof and ultraviolet-resistant polyester film comprises the following steps: (1) 50 g of polyethylene terephthalate, 30 g of synergistic resin, and 12 g of amorphous silica were melted and pelletized at 270 °C using a twin-screw extruder, cooled to 55 °C, and pelletized to obtain A-layer masterbatch with a particle size of 3.5 mm for later use; (2) 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, 18g LOTSORB ® B-60 blue light absorber was shear-mixed at a speed of 3000 r / min for 20 minutes, melt-granulated at 270°C using a single-screw extruder, cooled to 55°C and pelletized to obtain B-layer masterbatch with a particle size of 3.5 mm for later use; (3) 40 g of polyethylene terephthalate, 30 g of synergistic resin, and 30 g of polyethylene naphthalate were melted and pelletized at 270 °C through a twin-screw extruder, cooled to 55 °C, and pelletized to obtain a C-layer masterbatch with a particle size of 3.5 mm, which was set aside; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept constant for 1 hour, heated to 130°C and kept constant for 1 hour, and heated to 160°C and kept constant for 5 hours to allow them to fully crystallize; they are melted at 280°C in three extruders, and the three molten streams are mixed through a common die head, and the films are extruded through the die head and then stretched; they are stretched simultaneously in the longitudinal and transverse directions, with a stretching ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; they are cooled to 55°C and rolled up to obtain the blue light-proof and UV-resistant polyester film.

[0031] The preparation method of the synergistic resin is as follows: 2 g of tannic acid was added to 20 g of 1 wt% Tris buffer and stirred for 0.5 hour. 1 g of zinc chloride and 10 g of polyethylene terephthalate were added and stirred for 1 hour. The mixture was dried at 60° C. for 24 hours to obtain a synergistic resin.

[0032] Example 3 A method for preparing a blue light-proof and ultraviolet-resistant polyester film comprises the following steps: (1) 50 g of polyethylene terephthalate, 30 g of synergistic resin, and 12 g of amorphous silica were melted and pelletized at 270 °C using a twin-screw extruder, cooled to 55 °C, and pelletized to obtain A-layer masterbatch with a particle size of 3.5 mm for later use; (2) 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, 18g LOTSORB ® B-60 blue light absorber was shear-mixed at a speed of 3000 r / min for 20 minutes, melt-granulated at 270°C using a single-screw extruder, cooled to 55°C and pelletized to obtain B-layer masterbatch with a particle size of 3.5 mm for later use; (3) 40 g of polyethylene terephthalate, 30 g of synergistic resin, and 30 g of polyethylene naphthalate were melted and pelletized at 270 °C through a twin-screw extruder, cooled to 55 °C, and pelletized to obtain a C-layer masterbatch with a particle size of 3.5 mm, which was set aside; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept constant for 1 hour, heated to 130°C and kept constant for 1 hour, and heated to 160°C and kept constant for 5 hours to allow them to fully crystallize; they are melted at 280°C in three extruders, and the three molten streams are mixed through a common die head, and the films are extruded through the die head and then stretched; they are stretched simultaneously in the longitudinal and transverse directions, with a stretching ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; they are cooled to 55°C and rolled up to obtain the blue light-proof and UV-resistant polyester film.

[0033] The preparation method of the synergistic resin is as follows: 2 g of tannic acid was added to 20 g of 1 wt% Tris buffer and stirred for 0.5 hour. 1 g of copper chloride and 10 g of polyethylene terephthalate were added and stirred for another hour. The mixture was filtered and dried at 60° C. for 24 hours to obtain a synergistic resin.

[0034] Example 4 A method for preparing a blue light-proof and ultraviolet-resistant polyester film comprises the following steps: (1) 50 g of polyethylene terephthalate, 30 g of synergistic resin, and 12 g of amorphous silica were melted and pelletized at 270 °C using a twin-screw extruder, cooled to 55 °C, and pelletized to obtain A-layer masterbatch with a particle size of 3.5 mm for later use; (2) 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, 18g LOTSORB ® B-60 blue light absorber was shear-mixed at a speed of 3000 r / min for 20 minutes, melt-granulated at 270°C using a single-screw extruder, cooled to 55°C and pelletized to obtain B-layer masterbatch with a particle size of 3.5 mm for later use; (3) 40 g of polyethylene terephthalate, 30 g of synergistic resin, and 30 g of polyethylene naphthalate were melted and pelletized at 270 °C through a twin-screw extruder, cooled to 55 °C, and pelletized to obtain a C-layer masterbatch with a particle size of 3.5 mm, which was set aside; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept constant for 1 hour, heated to 130°C and kept constant for 1 hour, and heated to 160°C and kept constant for 5 hours to allow them to fully crystallize; they are melted at 280°C in three extruders, and the three molten streams are mixed through a common die head, and the films are extruded through the die head and then stretched; they are stretched simultaneously in the longitudinal and transverse directions, with a stretching ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; they are cooled to 55°C and rolled up to obtain the blue light-proof and UV-resistant polyester film.

[0035] The preparation method of the synergistic resin is as follows: 2 g of tannic acid was added to 20 g of 1 wt% Tris buffer and stirred for 0.5 hour. 1 g of magnesium chloride and 10 g of polyethylene terephthalate were added and stirred for another hour. The mixture was filtered and dried at 60° C. for 24 hours to obtain a synergistic resin.

[0036] Example 5 A method for preparing a blue light-proof and ultraviolet-resistant polyester film comprises the following steps: (1) 50 g of polyethylene terephthalate, 30 g of synergistic resin, and 12 g of amorphous silica were melted and pelletized at 270 °C using a twin-screw extruder, cooled to 55 °C, and pelletized to obtain A-layer masterbatch with a particle size of 3.5 mm for later use; (2) 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, 18g LOTSORB ® B-60 blue light absorber was shear-mixed at a speed of 3000 r / min for 20 minutes, melt-granulated at 270°C using a single-screw extruder, cooled to 55°C and pelletized to obtain B-layer masterbatch with a particle size of 3.5 mm for later use; (3) 40 g of polyethylene terephthalate, 30 g of synergistic resin, and 30 g of polyethylene naphthalate were melted and pelletized at 270 °C through a twin-screw extruder, cooled to 55 °C, and pelletized to obtain a C-layer masterbatch with a particle size of 3.5 mm, which was set aside; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept constant for 1 hour, heated to 130°C and kept constant for 1 hour, and heated to 160°C and kept constant for 5 hours to allow them to fully crystallize; they are melted at 280°C in three extruders, and the three molten streams are mixed through a common die head, and the films are extruded through the die head and then stretched; they are stretched simultaneously in the longitudinal and transverse directions, with a stretching ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; they are cooled to 55°C and rolled up to obtain the blue light-proof and UV-resistant polyester film.

[0037] The preparation method of the synergistic resin is as follows: 2 g of tannic acid was added to 20 g of 1 wt% Tris buffer and stirred for 0.5 hours. 1 g of magnesium chloride and 10 g of polyethylene terephthalate were added and stirred for another hour. 0.2 g of ε-polylysine ester was added and stirred for 12 hours to continue surface modification. The mixture was filtered and dried at 60°C for 24 hours to obtain a synergistic resin.

[0038] Comparative Example 1 A method for preparing a blue light-proof and ultraviolet-resistant polyester film comprises the following steps: (1) 50 g of polyethylene terephthalate and 12 g of amorphous silica were melted and pelletized at 270 °C using a twin-screw extruder, cooled to 55 °C, and pelletized to obtain A-layer masterbatch with a particle size of 3.5 mm for later use; (2) 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, 18g LOTSORB ® B-60 blue light absorber was shear-mixed at a speed of 3000 r / min for 20 minutes, melt-granulated at 270°C using a single-screw extruder, cooled to 55°C and pelletized to obtain B-layer masterbatch with a particle size of 3.5 mm for later use; (3) 40 g of polyethylene terephthalate and 30 g of polyethylene naphthalate were melted and pelletized at 270 °C through a twin-screw extruder, cooled to 55 °C, and pelletized to obtain a C-layer masterbatch with a particle size of 3.5 mm for later use; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept constant for 1 hour, heated to 130°C and kept constant for 1 hour, and heated to 160°C and kept constant for 5 hours to allow them to fully crystallize; they are melted at 280°C in three extruders, and the three molten streams are mixed through a common die head, and the films are extruded through the die head and then stretched; they are stretched simultaneously in the longitudinal and transverse directions, with a stretching ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; they are cooled to 55°C and rolled up to obtain the blue light-proof and UV-resistant polyester film.

[0039] Test Example 1 Tensile properties test before and after UV aging: According to the national standard GB / T 16422.3-2022 "Plastic laboratory light source exposure test method Part 3: Fluorescent ultraviolet lamp", the blue light protection and ultraviolet resistance polyester film obtained by the preparation method of Examples 1-5 was subjected to artificial accelerated aging. The irradiation method adopted method A, the ultraviolet lamp model was UVA-340 (1A), and the irradiance at 340nm was 0.76W / (m 2 nm), with a narrowband irradiance. A black-mark thermometer was used for temperature control. The exposure cycle used was cycle number 1, with a duration of 100 hours. The polyester films of Examples 1-5 were subjected to tensile properties testing before and after aging in accordance with the national standard GB / T 1040.3-2006, "Determination of Tensile Properties of Plastics - Part 3: Film and Sheeting - Test Conditions." The test data were averaged; the tensile properties are summarized in Table 1.

[0040] Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength before aging / MPa 213 220 223 226 231 Tensile strength after aging / MPa 188 191 197 206 228 The main difference between Examples 1-5 in Test Example 1 lies in the synergistic resin. The synergistic resin in Example 1 is made from tannic acid-modified polyethylene terephthalate. Tannic acid has a polyphenol structure and can interact with the polyethylene terephthalate molecular chain through hydrogen bonds and van der Waals forces, thereby improving the intermolecular bonding force and the stability of the multilayer structure to a certain extent. In Examples 2-4, magnesium chloride, copper chloride, and zinc chloride inorganic salts are added to the tannic acid step, respectively. Magnesium, copper, and zinc ions can be cross-linked by coordination or complexation with the polar groups of the polymer molecular chains, thereby enhancing the interaction between the molecular chains and the structural stability. A synergistic resin is obtained and added to the preparation of the A and C layer masterbatches. The ionic radius of magnesium ions is smaller than that of copper ions and zinc ions. A smaller ionic radius will increase the charge density of the metal ions, produce a stronger electrostatic attraction on the oxygen atoms of the phenolic hydroxyl groups in the tannic acid, increase the interaction between the molecular chains to improve the stability of the multilayer bonding, and therefore the effect is better than copper chloride and zinc chloride. In Example 5, ε-polylysine ester is added to Example 4, and its molecular chain forms a synergistic effect with the polyester molecular chain, further improving the mechanical properties and anti-ultraviolet aging properties of the film, which is ultimately reflected in reducing the impact of ultraviolet aging on the tensile properties of the polyester film.

[0041] Test Example 2 Average transmittance test of shortwave blue light: The anti-blue light and anti-ultraviolet polyester films obtained by the preparation methods of Examples 1-5 and Comparative Example 1 were cut into 100 mm × 100 mm samples, and 5 samples were prepared for each example; the blue light shielding rate of the samples in the 400-460 nm short-wave blue light band was tested using an anti-blue light tester, and the test data were averaged and summarized as shown in Table 2.

[0042] Table 2 Example Blue light shielding rate Example 1 47.5% Example 2 48.4% Example 3 49.7% Example 4 51.5% Example 5 53.8% Comparative Example 1 42.5% The synergistic resin of Example 1 is made only of tannic acid-modified polyethylene terephthalate. Examples 2-4 respectively add zinc chloride, copper chloride, and magnesium chloride inorganic salts on the basis of Example 1, mainly through the interaction between ions and polymer molecular chains to form physical cross-linking points, thereby enhancing the density of the film and making the layers more tightly bonded, which helps to disperse the blue light absorber more evenly in the film, thereby improving the blue light shielding rate; Example 5 adds ε-polylysine ester on the basis of Example 4. In addition to improving the density, it also optimizes the compatibility and stability of the synergistic resin with other materials, enhances the multiple reflections and absorption of blue light, reduces its migration loss, and thus improves the blue light shielding rate; Comparative Example 1 does not use a synergistic resin, the bonding between the film layers is relatively loose, and the dispersion and fixation effects of the blue light absorber are poor, so the blue light shielding rate is significantly lower than that of each example.

[0043] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a blue light-proof and UV-resistant polyester film, characterized in that: The method comprises the following steps, in parts by weight: (1) 45-55 parts of polyethylene terephthalate, 25-35 parts of synergistic resin, and 10-15 parts of anti-blocking agent are melted and granulated by a twin-screw extruder, cooled to 50-60°C, and pelletized to obtain A-layer masterbatch for later use; (2) 60-80 parts of polyethylene terephthalate, 10-15 parts of ultraviolet absorber, and 15-20 parts of blue light absorber are shear-mixed at a speed of 2500-3500 r / min for 10-30 minutes, melt-granulated by a single-screw extruder, cooled to 50-60°C, and pelletized to obtain a B-layer masterbatch for later use; (3) 35-45 parts of polyethylene terephthalate, 25-35 parts of synergistic resin, and 25-35 parts of polyethylene naphthalate are melted and pelletized through a twin-screw extruder, cooled to 50-60°C, and pelletized to obtain a C-layer masterbatch for later use; (4) The A-layer masterbatch, the B-layer masterbatch, and the C-layer masterbatch are heated to 100°C and kept at a constant temperature for 0.5-1.5 hours, heated to 120-140°C and kept at a constant temperature for 0.5-1.5 hours, and heated to 150-170°C and kept at a constant temperature for 4-6 hours to fully crystallize; they are melted in three extruders respectively, and the three molten streams are mixed through a common die head, and a film is extruded through the die head to obtain a film and then stretched; the film is stretched simultaneously in the longitudinal and transverse directions; the film is cooled to 50-60°C and rolled up to obtain the anti-blue light and anti-ultraviolet polyester film; The synergistic resin is prepared from polyethylene terephthalate and one or more of tannic acid, inorganic salt and epsilon-polylysine ester.

2. The method for preparing the blue light-proof and UV-resistant polyester film according to claim 1, wherein: The inorganic salt is one of zinc chloride, copper chloride and magnesium chloride.

3. The method for preparing the blue light-proof and UV-resistant polyester film according to claim 1, wherein: The preparation method of the synergistic resin is as follows, in parts by weight: Add 1-3 parts of tannic acid to 15-25 parts of Tris buffer and stir for 0.5-1 hour, then add 8-12 parts of polyethylene terephthalate and continue stirring for 0.5-1 hour; Filter and dry at 55-65°C for 20-25 hours to obtain a synergistic resin.

4. The method for preparing the blue light-proof and UV-resistant polyester film according to claim 1, wherein: The preparation method of the synergistic resin is as follows, in parts by weight: Add 1-3 parts of tannic acid to 15-25 parts of Tris buffer and stir for 0.5-1 hour, add 0.5-1.5 parts of inorganic salt and 8-12 parts of polyethylene terephthalate and continue stirring for 0.5-1 hour; filter and dry at 55-65° C. for 20-25 hours to obtain a synergistic resin.

5. The method for preparing the blue light-proof and UV-resistant polyester film according to claim 1, wherein: The preparation method of the synergistic resin is as follows, in parts by weight: 1-3 parts of tannic acid are added to 15-25 parts of Tris buffer and stirred for 0.5-1 hour, 0.5-1.5 parts of inorganic salt and 8-12 parts of polyethylene terephthalate are added and stirred for 0.5-1 hour; 0.1-0.5 parts of ε-polylysine ester are added and stirred for 10-15 hours to continue surface modification, filtered, and dried at 55-65° C. for 20-25 hours to obtain a synergistic resin.

6. The method for preparing the blue light-proof and UV-resistant polyester film according to claim 1, wherein: The ultraviolet absorber in step (2) is one of UV-320, UV-326, UV-327, UV-328, and UV-350.

7. The method for preparing the blue light-proof and UV-resistant polyester film according to claim 1, wherein: The blue light absorber in step (2) is LOTSORB ® B-30, LOTSORB ® B-60, LOTSORB ® One of the B-100.

8. The method for preparing the blue light-proof and UV-resistant polyester film according to claim 1, wherein: The stretching ratio of the longitudinal and transverse stretching in step (4) is 3.0-4.

0.

9. A blue light and UV resistant polyester film, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the blue light-proof and UV-resistant polyester film according to claim 9, characterized in that: The invention can be used to prepare mobile phone films, car films, display screen films and decorations.