A blue light blocking and UV-resistant polyester film, its preparation method and application

Abstract

This invention discloses a blue light blocking and UV-resistant polyester film, its preparation method, and its applications, primarily relating to the field of layered products composed of polyester. Compared with existing technologies, the blue light blocking and UV-resistant polyester film of this invention is obtained from three layers of masterbatch materials (A, B, and C) through steps such as melting, casting, and stretching. The masterbatch material A consists of polyethylene terephthalate, a synergistic resin, and an opening agent; the masterbatch material B consists of polyethylene terephthalate, a UV absorber, and a blue light absorber; and the masterbatch material C consists of polyethylene terephthalate, a synergistic resin, and polyethylene naphthalate. Compared with existing technologies, this invention improves the density and uniformity of the film's internal structure, enhances the dispersibility and stability of functional additives, reduces defects, and ultimately achieves a synergistic improvement in blue light blocking and UV resistance performance while ensuring the film's mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of layered products composed of polyester, and more particularly to a blue light blocking and UV resistant polyester film, its preparation method and application. Background Technology

[0002] Polyester film is a film material made from polyethylene terephthalate through biaxial stretching. It possesses high strength, high toughness, dimensional stability, thinness, transparency, chemical resistance, water resistance, high temperature resistance, and high insulation properties. It is mainly used in the packaging industry, electronics and electrical fields, optics and imaging fields, industrial and composite materials, agriculture, insulating tapes, and other fields. Anti-blue light and anti-UV polyester film is a functional film made by adding specific functional additives to ordinary polyester film. Its anti-blue light principle is based on the selective absorption or refraction of blue light by absorbers, and its anti-UV principle is based on the absorption or reflection of ultraviolet rays and the conversion of energy, thereby blocking and shielding against blue light and ultraviolet rays; it can reduce the damage of blue light to the eyes and prevent ultraviolet aging of the polyester film.

[0003] In existing technologies, to simultaneously improve blue light and UV aging protection capabilities, specific blue light absorbers and UV absorbers can be added to the raw materials to enhance functionality. Alternatively, additives can be added during the film preparation process to improve the compatibility, dispersibility, and uniformity of the film-forming system, effectively improving film stability and 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 shortcomings in protective performance 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 film formation, allowing functional additives to more fully exert their functions of absorbing and blocking light, ultimately achieving a synergistic improvement in blue light and UV protection effects.

[0004] CN112959784A discloses a high-transmittance, heat-insulating, and UV-blocking polyester film and its preparation method, comprising an upper surface layer, a middle layer, and a lower surface layer. The upper and lower surface layers are composed of polyester chips, an optical-grade opening agent, a heat-insulating masterbatch, and a UV absorber; the middle layer is composed of polyester chips, a heat-insulating masterbatch, a UV absorber, and a blue light absorber. This invention can effectively improve infrared blocking rate and visible light transmittance, but it does not reduce the impact of UV aging on tensile strength.

[0005] CN104015438A discloses a blue light blocking and fingerprint-resistant film and its preparation method, comprising a fingerprint-resistant coating, a film substrate layer, a blue light blocking layer, and a release film layer. The fingerprint-resistant coating and the blue light blocking layer are coated on both sides of the substrate layer, and the release film layer is attached to the outside of the blue light blocking layer. This invention can effectively block 380-480nm blue light, reducing retinal damage, while also possessing fingerprint resistance, improving display visibility and operability, but does not simultaneously improve UV resistance. Summary of the Invention

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

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

[0008] A method for preparing a blue light blocking and UV-resistant polyester film includes the following steps, in parts by weight:

[0009] (1) 45-55 parts of polyethylene terephthalate, 25-35 parts of synergistic resin and 10-15 parts of opening agent are melt-granulated by a twin-screw extruder, cooled to 50-60℃ and granulated to obtain layer A masterbatch for later use;

[0010] (2) Mix 60-80 parts of polyethylene terephthalate, 10-15 parts of ultraviolet absorber and 15-20 parts of blue light absorber at a speed of 2500-3500r / min for 10-30 minutes, melt and granulate through a single screw extruder, cool to 50-60℃ and granulate to obtain B layer masterbatch for later use;

[0011] (3) 35-45 parts of polyethylene terephthalate, 25-35 parts of synergistic resin and 25-35 parts of polyethylene naphthalate are melt-granulated by a twin-screw extruder, cooled to 50-60℃ and granulated to obtain C-layer masterbatch for later use;

[0012] (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100℃ and hold for 0.5-1.5 hours, heat to 120-140℃ and hold for 0.5-1.5 hours, and heat to 150-170℃ and hold for 4-6 hours to allow them to fully crystallize; melt them separately in three extruders, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time; cool it to 50-60℃ and wind it up to obtain the blue light blocking and UV protection polyester film.

[0013] The preparation method of the synergistic resin is as follows, in parts by weight:

[0014] Add 1-3 parts of tannic acid to 15-25 parts of Tris buffer and stir for 0.5-1 hour. Add 8-12 parts of polyethylene terephthalate and continue stirring for 0.5-1 hour. Filter and dry at 55-65℃ for 20-25 hours to obtain the synergistic resin.

[0015] Alternatively, add 1-3 parts tannic acid to 15-25 parts Tris buffer and stir for 0.5-1 hour, then add 0.5-1.5 parts inorganic salt and 8-12 parts polyethylene terephthalate and continue stirring for 0.5-1 hour; filter and dry at 55-65℃ for 20-25 hours to obtain the synergistic resin.

[0016] Alternatively, add 1-3 parts tannic acid to 15-25 parts Tris buffer and stir for 0.5-1 hour. Add 0.5-1.5 parts inorganic salt and 8-12 parts polyethylene terephthalate and continue stirring for 0.5-1 hour. Add 0.1-0.5 parts ε-polylysine ester and stir for 10-15 hours to continue surface modification. Filter and dry at 55-65℃ for 20-25 hours to obtain the synergistic resin.

[0017] The inorganic salt is one of zinc chloride, copper chloride, and magnesium chloride.

[0018] The opening agent in step (1) is amorphous silicon dioxide.

[0019] In step (2), the ultraviolet absorber is one of UV-320, UV-326, UV-327, UV-328, and UV-350.

[0020] In step (2), the blue light absorber is LOTSORB. ® B-30, LOTSORB ® B-60, LOTSORB ® One of the B-100s.

[0021] The particle size of the masterbatch in layer A, layer B, and layer C in steps (1), (2), and (3) is 3-4 mm.

[0022] The melting temperature of the melt granulation in steps (1), (2), and (3) is 260-280℃.

[0023] The melting temperature in step (4) is 270-290℃.

[0024] In step (4), the stretching ratio of the longitudinal and transverse stretching is 3.0-4.0.

[0025] The stretching temperature for both longitudinal and transverse stretching in step (4) is 80-120℃.

[0026] In step (4), the stretching time for both longitudinal and transverse stretching is 30-60 seconds.

[0027] The blue light blocking and UV protection polyester film can be used to prepare mobile phone films, car films, display screen films, and decorative items.

[0028] The blue light blocking and UV protection polyester film of this invention is obtained from three layers of masterbatch materials (A, B, and C) through melting, casting, and stretching. Layer A masterbatch material consists of polyethylene terephthalate (PET), a synergistic resin, and an opening agent; layer B masterbatch material consists of PET, a UV absorber, and a blue light absorber; and layer C masterbatch material consists of PET, a synergistic resin, and polyethylene naphthalate (PAN). PET in layer A provides basic mechanical strength and film-forming properties. The opening agent reduces the surface friction coefficient by forming a micro-rough structure, preventing roll-up adhesion. The addition of the synergistic resin enhances the cohesive strength of layer A and the interfacial bonding stability with layer B, while optimizing structural density and preventing interlayer delamination. Layer B uses PET as the film-forming carrier. The addition of a UV absorber allows for the absorption of UV light through a conjugated system, converting it into energy. The addition of a blue light absorber selectively captures short-wavelength blue light, achieving equilibrium through energy consumption via electron transitions. Layer C employs a blend of polyethylene terephthalate (PET) and polyethylene naphthalate (PET), with the addition of synergistic resins. The naphthalene ring structure of PET imparts better heat resistance to Layer C, enhancing the dimensional stability of the film at high temperatures, making it suitable for applications such as electronic packaging. The synergistic resins strengthen the interfacial bond between Layer C and Layer B, combining the "rigid-flexible complementary" characteristics of the rigid chains of PET and the flexible chains of PET, thereby enhancing the film's tensile and impact resistance. Finally, Layer C and Layer A form a symmetrical structure, balancing biaxial tensile stress and reducing the risk of warpage. Simultaneously, the synergistic effect of the synergistic resins on both sides further optimizes interlayer adhesion and overall mechanical uniformity. This invention also incorporates synergistic resins to improve the density and uniformity of the film's internal structure, enhance the dispersibility and stability of functional additives, reduce defects, and ultimately achieve a synergistic improvement in blue light protection and UV resistance while ensuring the film's mechanical properties.

[0029] The beneficial effects of this invention are:

[0030] Compared with existing technologies, the blue light blocking and UV protection polyester film of the present invention is obtained by melting, casting, and stretching three layers of masterbatch materials (A, B, and C). The masterbatch material A consists of polyethylene terephthalate, synergistic resin, and an opening agent; the masterbatch material B consists of polyethylene terephthalate, a UV absorber, and a blue light absorber; and the masterbatch material C consists of polyethylene terephthalate, synergistic resin, and polyethylene naphthalate. The present invention also incorporates synergistic resin to improve the density and uniformity of the film's internal structure, enhance the dispersibility and stability of functional additives, and reduce defects, ultimately achieving a synergistic improvement in blue light blocking and UV protection performance while ensuring the film's mechanical properties. Detailed Implementation

[0031] The parameters of the specific chemical substances used in the examples are from the following sources:

[0032] Polyethylene terephthalate: Manufacturer: Shenzhen Yuanbang New Materials Co., Ltd., Brand: Rynite®HR540SUV BK544.

[0033] Amorphous silica: Brand: Grace, Model: SYLOBLOC ® 45, 4.4-5.4μm.

[0034] Polyethylene naphthalate: Brand: Teijin (Japan), Model: Teonex ® .

[0035] Example 1

[0036] A method for preparing a blue light blocking and UV-resistant polyester film includes the following steps:

[0037] (1) 50g of polyethylene terephthalate, 30g of synergistic resin and 12g of amorphous silica were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain layer A masterbatch with a particle size of 3.5mm, for later use;

[0038] (2) Add 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, and 18g LOTSORB. ® The B-60 blue light absorber was sheared and mixed at 3000 r / min for 20 minutes, then melt-granulated at 270℃ using a single screw extruder, cooled to 55℃ and granulated to obtain B-layer masterbatch with a particle size of 3.5 mm, for later use.

[0039] (3) 40g of polyethylene terephthalate, 30g of synergistic resin and 30g of polyethylene naphthalate were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain C-layer masterbatch with a particle size of 3.5mm, for later use;

[0040] (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100°C and hold for 1 hour, then heat to 130°C and hold for 1 hour, then heat to 160°C and hold for 5 hours to allow them to fully crystallize; melt them separately in three extruders at 280°C, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time, with a stretch ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; cool it to 55°C and then wind it up to obtain the blue light blocking and UV protection polyester film.

[0041] The preparation method of the synergistic resin is as follows:

[0042] Add 2g of tannic acid to 20g of 1wt% Tris buffer and stir for 0.5 hours. Add 10g of polyethylene terephthalate and continue stirring for 1 hour. Filter and dry at 60℃ for 24 hours to obtain the synergistic resin.

[0043] Example 2

[0044] A method for preparing a blue light blocking and UV-resistant polyester film includes the following steps:

[0045] (1) 50g of polyethylene terephthalate, 30g of synergistic resin and 12g of amorphous silica were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain layer A masterbatch with a particle size of 3.5mm, for later use;

[0046] (2) Add 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, and 18g LOTSORB. ® The B-60 blue light absorber was sheared and mixed at 3000 r / min for 20 minutes, then melt-granulated at 270℃ using a single screw extruder, cooled to 55℃ and granulated to obtain B-layer masterbatch with a particle size of 3.5 mm, for later use.

[0047] (3) 40g of polyethylene terephthalate, 30g of synergistic resin and 30g of polyethylene naphthalate were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain C-layer masterbatch with a particle size of 3.5mm, for later use;

[0048] (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100°C and hold for 1 hour, then heat to 130°C and hold for 1 hour, then heat to 160°C and hold for 5 hours to allow them to fully crystallize; melt them separately in three extruders at 280°C, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time, with a stretch ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; cool it to 55°C and then wind it up to obtain the blue light blocking and UV protection polyester film.

[0049] The preparation method of the synergistic resin is as follows:

[0050] Add 2g of tannic acid to 20g of 1wt% Tris buffer and stir for 0.5 hours. Add 1g of zinc chloride and 10g of polyethylene terephthalate and continue stirring for 1 hour. Dry at 60℃ for 24 hours to obtain the synergistic resin.

[0051] Example 3

[0052] A method for preparing a blue light blocking and UV-resistant polyester film includes the following steps:

[0053] (1) 50g of polyethylene terephthalate, 30g of synergistic resin and 12g of amorphous silica were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain layer A masterbatch with a particle size of 3.5mm, for later use;

[0054] (2) Add 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, and 18g LOTSORB. ® The B-60 blue light absorber was sheared and mixed at 3000 r / min for 20 minutes, then melt-granulated at 270℃ using a single screw extruder, cooled to 55℃ and granulated to obtain B-layer masterbatch with a particle size of 3.5 mm, for later use.

[0055] (3) 40g of polyethylene terephthalate, 30g of synergistic resin and 30g of polyethylene naphthalate were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain C-layer masterbatch with a particle size of 3.5mm, for later use;

[0056] (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100°C and hold for 1 hour, then heat to 130°C and hold for 1 hour, then heat to 160°C and hold for 5 hours to allow them to fully crystallize; melt them separately in three extruders at 280°C, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time, with a stretch ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; cool it to 55°C and then wind it up to obtain the blue light blocking and UV protection polyester film.

[0057] The preparation method of the synergistic resin is as follows:

[0058] Add 2g of tannic acid to 20g of 1wt% Tris buffer and stir for 0.5 hours. Add 1g of copper chloride and 10g of polyethylene terephthalate and continue stirring for 1 hour. Filter and dry at 60℃ for 24 hours to obtain the synergistic resin.

[0059] Example 4

[0060] A method for preparing a blue light blocking and UV-resistant polyester film includes the following steps:

[0061] (1) 50g of polyethylene terephthalate, 30g of synergistic resin and 12g of amorphous silica were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain layer A masterbatch with a particle size of 3.5mm, for later use;

[0062] (2) Add 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, and 18g LOTSORB. ® The B-60 blue light absorber was sheared and mixed at 3000 r / min for 20 minutes, then melt-granulated at 270℃ using a single screw extruder, cooled to 55℃ and granulated to obtain B-layer masterbatch with a particle size of 3.5 mm, for later use.

[0063] (3) 40g of polyethylene terephthalate, 30g of synergistic resin and 30g of polyethylene naphthalate were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain C-layer masterbatch with a particle size of 3.5mm, for later use;

[0064] (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100°C and hold for 1 hour, then heat to 130°C and hold for 1 hour, then heat to 160°C and hold for 5 hours to allow them to fully crystallize; melt them separately in three extruders at 280°C, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time, with a stretch ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; cool it to 55°C and then wind it up to obtain the blue light blocking and UV protection polyester film.

[0065] The preparation method of the synergistic resin is as follows:

[0066] Add 2g of tannic acid to 20g of 1wt% Tris buffer and stir for 0.5 hours. Add 1g of magnesium chloride and 10g of polyethylene terephthalate and continue stirring for 1 hour. Filter and dry at 60℃ for 24 hours to obtain the synergistic resin.

[0067] Example 5

[0068] A method for preparing a blue light blocking and UV-resistant polyester film includes the following steps:

[0069] (1) 50g of polyethylene terephthalate, 30g of synergistic resin and 12g of amorphous silica were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain layer A masterbatch with a particle size of 3.5mm, for later use;

[0070] (2) Add 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, and 18g LOTSORB. ® The B-60 blue light absorber was sheared and mixed at 3000 r / min for 20 minutes, then melt-granulated at 270℃ using a single screw extruder, cooled to 55℃ and granulated to obtain B-layer masterbatch with a particle size of 3.5 mm, for later use.

[0071] (3) 40g of polyethylene terephthalate, 30g of synergistic resin and 30g of polyethylene naphthalate were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain C-layer masterbatch with a particle size of 3.5mm, for later use;

[0072] (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100°C and hold for 1 hour, then heat to 130°C and hold for 1 hour, then heat to 160°C and hold for 5 hours to allow them to fully crystallize; melt them separately in three extruders at 280°C, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time, with a stretch ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; cool it to 55°C and then wind it up to obtain the blue light blocking and UV protection polyester film.

[0073] The preparation method of the synergistic resin is as follows:

[0074] Add 2g of tannic acid to 20g of 1wt% Tris buffer and stir for 0.5 hours. Add 1g of magnesium chloride and 10g of polyethylene terephthalate and continue stirring for 1 hour. Add 0.2g of ε-polylysine ester and stir for 12 hours to continue surface modification. Filter and dry at 60℃ for 24 hours to obtain the synergistic resin.

[0075] Comparative Example 1

[0076] A method for preparing a blue light blocking and UV-resistant polyester film includes the following steps:

[0077] (1) 50g of polyethylene terephthalate and 12g of amorphous silica were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain layer A masterbatch with a particle size of 3.5mm, for later use;

[0078] (2) Add 70g polyethylene terephthalate, 12g UV-326 ultraviolet absorber, and 18g LOTSORB. ® The B-60 blue light absorber was sheared and mixed at 3000 r / min for 20 minutes, then melt-granulated at 270℃ using a single screw extruder, cooled to 55℃ and granulated to obtain B-layer masterbatch with a particle size of 3.5 mm, for later use.

[0079] (3) 40g of polyethylene terephthalate and 30g of polyethylene naphthalate were melt-granulated at 270°C using a twin-screw extruder, cooled to 55°C and granulated to obtain C-layer masterbatch with a particle size of 3.5mm, for later use;

[0080] (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100°C and hold for 1 hour, then heat to 130°C and hold for 1 hour, then heat to 160°C and hold for 5 hours to allow them to fully crystallize; melt them separately in three extruders at 280°C, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time, with a stretch ratio of 3.5, a stretching temperature of 95°C, and a stretching time of 45 seconds; cool it to 55°C and then wind it up to obtain the blue light blocking and UV protection polyester film.

[0081] Test Example 1

[0082] Tensile properties test before and after UV aging:

[0083] According to the national standard GB / T 16422.3-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps", the blue light blocking and UV-resistant polyester films prepared by the methods in Examples 1-5 were subjected to artificial accelerated aging. The irradiation method was Method A, and the UV lamp model was UVA-340(1A), with an irradiance of 0.76 W / (m²) at 340 nm. 2 The irradiance was narrow-band (·nm), and temperature control was performed using a black-label thermometer. The exposure cycle was cycle number 1, lasting 100 hours. The tensile properties of the polyester films from Examples 1-5 were tested before and after aging according to the national standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The average value of the test data was taken. The tensile properties are summarized in Table 1.

[0084] Table 1

[0085] 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

[0086] The main difference between Examples 1-5 in Test Example 1 lies in the synergistic resin. The synergistic resin in Example 1 is prepared by modifying polyethylene terephthalate with tannic acid. Tannic acid has a polyphenol structure and can interact with the polyethylene terephthalate molecular chain through hydrogen bonds and van der Waals forces, which improves 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 crosslink by coordinating or complexing with the polar groups of the polymer molecular chain, thereby enhancing the interaction between molecular chains and the structural stability, resulting in the synergistic resin, which is added to the preparation of the A and C layer masterbatches. Among them, the ionic radius of magnesium ions is smaller than that of copper and zinc ions. The smaller ionic radius will result in a higher charge density of metal ions, which will generate a stronger electrostatic attraction to the oxygen atoms of the phenolic hydroxyl groups in tannic acid, increasing the interaction between molecular chains to improve the stability of the multilayer bonding. Therefore, the effect is better than that of copper chloride and zinc chloride. Example 5 adds ε-polylysine ester to Example 4. Its molecular chain forms a synergistic effect with the polyester molecular chain, which further improves the mechanical properties and UV aging resistance of the film, and ultimately reduces the impact of UV aging on the tensile properties of the polyester film.

[0087] Test Example 2

[0088] Average transmittance test of short-wavelength blue light:

[0089] The blue light blocking and UV protection polyester films prepared by the methods in Examples 1-5 and Comparative Example 1 were cut into 100mm×100mm samples, with 5 samples prepared for each example. The blue light shielding rate of the samples in the 400-460nm short-wavelength blue light band was tested using a blue light shielding tester. The average value of the test data was taken and summarized as shown in Table 2.

[0090] Table 2

[0091] 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%

[0092] The synergistic resin in Example 1 was prepared solely from tannic acid-modified polyethylene terephthalate. Examples 2-4, based on Example 1, added zinc chloride, copper chloride, and magnesium chloride inorganic salts, respectively. These substances primarily enhance the film's density by forming physical crosslinking points through the interaction of ions with polymer molecular chains. This also strengthens the bond between layers, facilitating more uniform dispersion of the blue light absorber within the film and thus improving the blue light shielding efficiency. Example 5, based on Example 4, added ε-polylysine ester. Besides improving density, this also optimized the compatibility and stability of the synergistic resin with other materials, enhancing multiple reflections and absorption of blue light and reducing its migration loss, thereby improving the blue light shielding efficiency. Comparative Example 1, without using synergistic resin, had relatively loose interlayer bonding, resulting in poor dispersion and fixation of the blue light absorber. Consequently, its blue light shielding efficiency was significantly lower than that of the other examples.

[0093] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a blue light blocking and UV-resistant polyester film, characterized in that, Includes 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 opening agent are melt-granulated by a twin-screw extruder, cooled to 50-60℃ and granulated to obtain layer A masterbatch for later use; (2) Mix 60-80 parts of polyethylene terephthalate, 10-15 parts of ultraviolet absorber and 15-20 parts of blue light absorber at a speed of 2500-3500r / min for 10-30 minutes, melt and granulate through a single screw extruder, cool to 50-60℃ and granulate to obtain 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 melt-granulated by a twin-screw extruder, cooled to 50-60℃ and granulated to obtain C-layer masterbatch for later use; (4) Heat the A-layer masterbatch, B-layer masterbatch, and C-layer masterbatch to 100℃ and hold for 0.5-1.5 hours, heat to 120-140℃ and hold for 0.5-1.5 hours, and heat to 150-170℃ and hold for 4-6 hours to allow them to fully crystallize; melt them separately in three extruders, mix the three melt streams through a common die, extrude the film through the die, and then stretch it; stretch it longitudinally and transversely at the same time; cool it to 50-60℃ and wind it up to obtain the blue light blocking and UV protection polyester film; 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. Add 0.1-0.5 parts of ε-polylysine ester and stir for 10-15 hours to continue surface modification. Filter and dry at 55-65℃ for 20-25 hours to obtain the synergistic resin. The inorganic salt is one of zinc chloride, copper chloride, and magnesium chloride.

2. The method for preparing the blue light blocking and UV-resistant polyester film as described in claim 1, characterized in that, In step (2), the ultraviolet absorber is one of UV-320, UV-326, UV-327, UV-328, and UV-350.

3. The method for preparing the blue light blocking and UV-resistant polyester film as described in claim 1, characterized in that, In step (2), the blue light absorber is LOTSORB. ® B-30, LOTSORB ® B-60, LOTSORB ® One of the B-100s.

4. The method for preparing the blue light blocking and UV-resistant polyester film as described in claim 1, characterized in that, In step (4), the stretching ratio of the longitudinal and transverse stretching is 3.0-4.

0.

5. A blue light blocking and UV-resistant polyester film, characterized in that, It is prepared by the preparation method described in any one of claims 1-4.

6. An application of the blue light blocking and UV protection polyester film as described in claim 5, characterized in that, It can be used in the preparation of mobile phone screen protectors, car screen protectors, display screen protectors, and decorative items.