Low-blue-phase transparent heat-insulating PET (polyethylene terephthalate) film and preparation method thereof

Abstract

The invention belongs to the technical field of transparent heat insulation materials, and provides a low-blue-phase transparent heat insulation PET film and a preparation method thereof, and the PET film comprises a PET matrix, and cesium tungsten bronze and an organic yellow dye dispersed in the PET matrix. According to the invention, the spectrum complementary effect between the yellow dye and the cesium tungsten bronze blue phase is utilized to realize the low blue phase of the PET film, and even the PET film can be neutral and colorless; meanwhile, in order to further enhance the dispersity of the cesium-tungsten bronze in a PET matrix, a high-speed stirring and micro-injection process is used in the preparation process, so that the agglomeration phenomenon of the cesium-tungsten bronze is avoided, and the high transparency of the PET film is ensured.

Description

Technical Field

[0001] This invention belongs to the field of transparent heat insulation materials technology, specifically relating to a low blue phase transparent heat insulation PET film and its preparation method. Background Technology

[0002] With the continued escalation of the global energy crisis and environmental problems, developing energy-saving materials that combine multi-spectral modulation and zero carbon emission characteristics has become a core focus of global scientific research and industry. Against this backdrop, transparent thermal insulation materials, with their groundbreaking light-heat-electricity synergistic management capabilities, are moving from the laboratory to large-scale applications, becoming disruptive technological solutions in fields such as building curtain walls, new energy vehicles, and flexible electronics. Among these, cesium tungsten bronze (Cs) is particularly promising. x WO3 is a preferred material for making transparent heat-insulating PET films due to its excellent near-infrared absorption properties.

[0003] Cesium tungsten bronze is a non-stoichiometric functional compound with a unique oxygen octahedral structure. It exhibits localized surface plasmon resonance and possesses excellent shielding capabilities across the entire infrared band. However, its blue-phase color rendering characteristic is a significant drawback limiting its applications. For example, in fields such as building curtain walls and new energy vehicles, transparent thermal insulation materials typically need to be used in conjunction with substrates such as glass. The blue appearance of PET films containing cesium tungsten bronze affects their overall aesthetics and visual appeal, thus restricting their use.

[0004] Furthermore, due to the high surface activity of cesium tungsten bronze powder, it is prone to agglomeration during processing, leading to a decrease in the transparency of the film. Currently, the visible light transmittance of films with added cesium tungsten bronze is typically only around 70%. To improve the dispersibility and compatibility of cesium tungsten bronze when used in combination with polymers, patent application CN116515261A discloses a cesium tungsten bronze composite PET material and its preparation method. This method uses PET masterbatch and a CWO dispersion mainly composed of cesium tungsten bronze powder, organic solvent, and dispersant. The mixture is premixed in a high-speed disperser, milled in a grinding disperser, and stirred in a mixer to obtain the cesium tungsten bronze composite PET material. However, the visible light transmittance of this material is also only around 74%. Patent application CN118497673A discloses a cesium tungsten bronze thin film for near-infrared light shielding film and its preparation method. The method involves magnetron sputtering using a cesium tungsten bronze sputtering target, followed by annealing the cesium tungsten bronze thin film at 400°C for 90 minutes in an H2 atmosphere to obtain a cesium tungsten bronze thin film with a visible light transmittance of 81.5%. However, this method is complex to operate and requires sophisticated equipment. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a low-blue-phase transparent heat-insulating PET film and its preparation method. The PET film comprises a PET matrix and cesium tungsten bronze and an organic yellow dye dispersed therein. By utilizing the spectral complementarity between the yellow dye and the blue phase of the cesium tungsten bronze, a low-blue phase is achieved in the PET film, and it can even reach neutral colorlessness at a certain ratio. At the same time, in order to further enhance the dispersibility of cesium tungsten bronze in the PET matrix, a high-speed stirring and micro-injection process is used during the preparation process to avoid the agglomeration of cesium tungsten bronze and dye, thus ensuring the high transparency of the PET film.

[0006] The technical solution of this invention is as follows:

[0007] A low blue phase transparent heat-insulating PET film includes a PET matrix and cesium tungsten bronze and an organic yellow dye dispersed in the PET matrix, wherein the mass ratio of the cesium tungsten bronze to the organic yellow dye is 100:(0.1-0.5), and the visible light absorption range of the organic yellow dye is 400-500 nm.

[0008] By adding cesium tungsten bronze and organic yellow dye to the PET matrix material, the cesium tungsten bronze absorbs near-infrared light and reflects blue light, while the organic yellow dye absorbs ultraviolet light and residual blue light and reflects yellow light. When the two work together, the cesium tungsten bronze and organic yellow dye produce a spectral complementary effect, so that the finished PET film not only has a near-infrared shielding effect, but also the blue color deviation caused by cesium tungsten bronze is reduced, and it can even be colorless under certain conditions, resulting in a PET film with multiple effects such as heat insulation, transparency, and low blue color deviation.

[0009] As a further improvement to the above scheme, the mass ratio of the cesium tungsten bronze to the organic yellow dye is 100:0.3.

[0010] As a further improvement to the above scheme, the thickness of the low blue phase transparent heat-insulating PET film is 10-40 μm.

[0011] As a further improvement to the above scheme, the organic yellow dye has a half-width of <30nm and a decomposition temperature of ≥250℃; as a further preferred embodiment, the organic yellow dye is one or more of azo yellow dyes, phthalocyanine yellow dyes, and anthraquinone yellow dyes.

[0012] A method for preparing a low-blue-phase transparent heat-insulating PET film according to any one of the above-mentioned methods includes the following steps:

[0013] S1. Add the organic yellow dye to the cesium tungsten bronze dispersion and stir to form a composite slurry;

[0014] S2. The composite slurry is injected dropwise into PET resin and stirred to obtain a premix;

[0015] S3. Dry the premixed material;

[0016] S4. The dried premixed material is extruded and stretched to obtain the low blue phase transparent heat-insulating PET film.

[0017] The cesium tungsten bronze dispersion used in the preparation process is formed by dispersing cesium tungsten bronze in an organic solvent. The cesium tungsten bronze is preferably nano-sized cesium tungsten bronze powder with a particle size of 20-50 nm. The organic solvent is a conventional solvent, such as ethyl acetate, ethanol, acetone, isopropanol, propylene glycol methyl ether, etc. The dispersant can be polyethylene glycol or silane coupling agent (such as KH-560, KH-570, A-174 or BYK-190, etc.).

[0018] As a further improvement to the above scheme, in the cesium tungsten bronze dispersion, the mass ratio of cesium tungsten bronze, organic solvent and dispersant is cesium tungsten bronze: organic solvent: dispersant = (10-30):(60-80):1.

[0019] As a further improvement to the above scheme, the mass ratio of cesium tungsten bronze to organic yellow dye in step S1 is 100:(0.1~0.5), and more preferably 100:0.3.

[0020] As a further improvement to the above scheme, in step S2, a micro-injection pump is used to inject the composite slurry dropwise into PET resin, and a high-speed mixer is used to stir it to obtain a premix.

[0021] As a further improvement to the above scheme, the dripping rate of the composite slurry in step S2 is 60-200 ml / min.

[0022] As a further improvement to the above scheme, the stirring speed in step S2 is 5000-15000 rpm.

[0023] As a further improvement to the above scheme, the mass ratio of PET resin to composite slurry in step S2 is 100:(12-24), and more preferably 100:20.

[0024] As a further improvement to the above scheme, the drying temperature in step S3 is 65-105℃ and the drying time is 4-6h.

[0025] As a further improvement to the above scheme, the extrusion temperature in step S4 is 200-250℃ and the film stretching speed is 5-10m / min.

[0026] As a further improvement to the above solution, the preparation method of the low blue phase transparent heat-insulating PET film includes the following steps:

[0027] S1. Dissolve the organic yellow dye in a solvent and add it to the cesium tungsten bronze dispersion at a mass ratio of cesium tungsten bronze: organic yellow dye = 100:(0.1~0.5) and stir to form a composite slurry;

[0028] S2. Add PET resin to a high-speed mixer, set the speed to 5000-15000 rpm, and inject the composite slurry into the PET resin dropwise at a speed of 60-200 ml / min using a micro-injection pump according to the mass ratio of PET resin: composite slurry = 100:(12-24) to obtain a premix.

[0029] S3. The premixed material is vacuum dried at 65-105°C for 4-6 hours to remove the solvent;

[0030] S4. The dried premixed material is extruded and stretched at 200-250°C at a stretching speed of 5-10 m / min to obtain the low blue phase transparent heat-insulating PET film.

[0031] As a further improvement to the above scheme, the solvent used to dissolve the organic yellow dye in step S1 is a conventional organic solvent, such as ethyl acetate, ethanol, acetone, isopropanol, propylene glycol methyl ether, etc.; the amount of solvent used should be such that the organic yellow dye is evenly dispersed in the solvent.

[0032] To further improve the dispersion of cesium tungsten bronze and organic yellow dye in PET resin, a high-speed stirring combined with gradient injection mixing process can be adopted in step S2. This process consists of two stages: Stage 1 is the pre-mixing stage, where 40%–80% of the total composite slurry is added dropwise to the PET resin using a micro-injection pump at a first injection rate, and the composite slurry is stirred and mixed with the PET resin using a first rotation speed, allowing the composite slurry to fully penetrate into the inter-chain spaces of the PET molecules and form a uniformly dispersed substrate; Stage 2 is the post-mixing stage, where the remaining 20%–60% of the composite slurry is added dropwise to the PET resin at a second injection rate, and the composite slurry is stirred and mixed at high speed using a second rotation speed. The strong vortex flow field promotes rapid diffusion of the slurry, further refining the dispersed phase and improving mixing efficiency. This staged gradient mixing method ensures uniform dispersion of cesium tungsten bronze powder and dye, and optimizes production efficiency through high-speed stirring in the later stage, making it suitable for large-scale preparation of high-performance PET composite materials.

[0033] As a further improvement to the above scheme, the first injection speed is 60-100 ml / min, the second injection speed is the first injection speed + (20-80) ml / min, the first rotation speed is 5000-10000 rpm, and the second rotation speed is the first rotation speed + (2000-5000) rpm.

[0034] As a further improvement to the above scheme, in step S2, stage one is to add 50% of the total composite slurry dropwise to the PET resin and stir and mix, and stage two is to add the remaining 50% of the composite slurry dropwise to the PET resin and stir and mix.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. Through the synergistic effect of yellow dye and cesium tungsten bronze, precise neutralization and spectral complementarity of PET film color are achieved. Traditional cesium tungsten bronze PET film suffers from color shift due to strong blue light reflection. However, this invention innovatively introduces a highly selective organic yellow dye. The spectral complementarity between the dye and the blue-phase cesium tungsten bronze can produce a low-blue-phase PET film. Under certain conditions, it can even make the PET film exhibit a neutral colorless and transparent effect: cesium tungsten bronze absorbs near-infrared light and reflects blue light, while organic yellow dye absorbs ultraviolet light and residual blue light and reflects yellow light. By rationally adjusting the ratio of cesium tungsten bronze and organic yellow dye in the raw materials, a high degree of "blue light absorption - yellow light compensation" is achieved, adjusting the color coordinates to the neutral range, making the PET film appear colorless and transparent.

[0037] 2. By setting ultra-high-speed stirring conditions, cesium tungsten bronze and organic yellow dye are dispersed at the single-particle level in the PET resin matrix, which effectively breaks the van der Waals forces of nanoparticles and the π-π stacking between dye molecules, avoiding agglomeration that leads to a decrease in the light transmittance of the finished PET film.

[0038] 3. A gradient injection strategy is adopted. The initial low speed ensures that the composite slurry can penetrate evenly into the gaps between PET molecular chains. The speed is increased later to meet production capacity requirements. The injection speed and stirring speed are coordinated. Low-speed injection matched with high speed can form a vortex flow field, which promotes the uniformity of radial distribution of nanoparticles / dye molecules. High-speed injection and simultaneous increase of stirring speed can prevent local concentration overload and ensure the optical consistency of PET film.

[0039] 4. The PET film obtained by this invention has a low blue phase characteristic. By controlling the amount of dye added, it can also present a medium gray effect. Moreover, it has high transparency, with a visible light transmittance of over 80%. At the same time, it retains a highly efficient near-infrared shielding effect. Through the "absorption-reflection synergy" strategy, it not only solves the color deviation problem of cesium tungsten bronze film, but also optimizes photothermal management efficiency by adjusting the concentration of dye, cesium tungsten bronze and film thickness, providing a broader prospect for the application of PET film. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below.

[0041] Figure 1UV-PC images of the transparent heat-insulating PET films obtained in Examples 1-2 and Comparative Example 1;

[0042] Figure 2 The CIE 1931 color space diagrams are of the transparent heat-insulating PET films obtained in Examples 1-2 and Comparative Example 1. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these equivalent forms still fall within the scope defined by the claims of this invention.

[0044] Cesium tungsten bronze is made from commercially available nano-sized cesium tungsten bronze powder with a particle size of 30-50 nm.

[0045] Organic yellow dyes AKS and OO / A were purchased from Guangdong Elite Pigment Co., Ltd., and meet the following characteristics: absorption band: 400~500nm, half maximum width at half maximum (WHM) <30nm; thermal stability: decomposition temperature ≥250℃.

[0046] Example 1:

[0047] S1. Cesium tungsten bronze, ethyl acetate, and silane coupling agent KH-570 are uniformly mixed and dispersed according to a mass ratio of cesium tungsten bronze: ethyl acetate: silane coupling agent KH-570 = 20:80:1 to obtain a cesium tungsten bronze dispersion. Organic yellow dye AKS is dissolved in ethyl acetate to obtain a dye solution with a concentration of 5 wt%. The dye solution is added to the cesium tungsten bronze dispersion according to a mass ratio of cesium tungsten bronze: organic yellow dye AKS = 100:0.3, and stirred at 2000 rpm for 30 min to form a composite slurry.

[0048] S2. Add PET resin to a high-speed mixer, set the speed to 12000 rpm, and inject the composite slurry into the PET resin dropwise at a rate of 100 ml / min using a micro-injection pump according to the mass ratio of PET resin: composite slurry = 100:20, and stir to obtain a premix.

[0049] S3. Place the premixed material under vacuum drying at 85℃ for 4 hours to remove the solvent;

[0050] S4. The dried premixed material is extruded and stretched into a film using a twin-screw extruder at 240°C and a film stretching speed of 10m / min to obtain a transparent heat-insulating PET film.

[0051] Example 2:

[0052] The only difference from Example 1 is that the organic yellow dye AKS in step S1 is replaced with the organic yellow dye OO / A.

[0053] Example 3:

[0054] The only difference from Example 1 is that the mass ratio of cesium tungsten bronze to organic yellow dye AKS in step S1 is 100:0.1.

[0055] Example 4:

[0056] The only difference from Example 1 is that the mass ratio of cesium tungsten bronze to organic yellow dye AKS in step S1 is 100:0.5.

[0057] Example 5:

[0058] The only difference from Example 2 is that the mass ratio of cesium tungsten bronze to organic yellow dye OO / A in step S1 is 100:0.1.

[0059] Example 6:

[0060] The only difference from Example 2 is that the mass ratio of cesium tungsten bronze to organic yellow dye OO / A in step S1 is 100:0.5.

[0061] Example 7:

[0062] S1. Cesium tungsten bronze, ethanol, and polyethylene glycol are uniformly mixed and dispersed according to a mass ratio of cesium tungsten bronze: ethanol: polyethylene glycol = 20:80:1 to obtain a cesium tungsten bronze dispersion. Organic yellow dye AKS is dissolved in ethanol to obtain a dye solution with a concentration of 10 wt%. The dye solution is added to the cesium tungsten bronze dispersion according to a mass ratio of cesium tungsten bronze: organic yellow dye AKS = 100:0.3, and stirred at 3000 rpm for 10 min to form a composite slurry.

[0063] S2. Add PET resin to a high-speed mixer, set the speed to 5000 rpm, and inject the composite slurry into the PET resin dropwise at a rate of 200 ml / min using a micro-injection pump according to a mass ratio of PET resin: composite slurry = 100:12 to obtain a premix.

[0064] S3. Place the premixed material under vacuum drying at 65℃ for 6 hours to remove the solvent;

[0065] S4. The dried premixed material is extruded and stretched into a film using a twin-screw extruder at 200°C with a film stretching speed of 5m / min to obtain a transparent heat-insulating PET film.

[0066] Example 8:

[0067] S1. Cesium tungsten bronze, ethyl acetate, and silane coupling agent KH-570 are uniformly mixed and dispersed according to a mass ratio of 20:80:1 to obtain a cesium tungsten bronze dispersion. Organic yellow dye AKS is dissolved in ethyl acetate to obtain a dye solution with a concentration of 5 wt%. The dye solution is added to the cesium tungsten bronze dispersion according to a mass ratio of 100:0.3 to 100 tungsten bronze and stirred at 2000 rpm for 30 min to form a composite slurry.

[0068] S2. Add PET resin to a high-speed mixer and add composite slurry according to the mass ratio of PET resin: composite slurry = 100:20. Mix the slurry. First, set the speed of the high-speed mixer to 8000 rpm. Add the composite slurry dropwise to the PET resin at a rate of 80 ml / min using a micro-injection pump. After about 50% of the total composite slurry has been added, increase the speed of the high-speed mixer to 10000 rpm and the injection rate of the micro-injection pump to 160 ml / min. Continue to add the remaining 50% of the composite slurry. After mixing, a premix is ​​obtained.

[0069] S3. Place the premixed material under vacuum drying at 85℃ for 4 hours to remove the solvent;

[0070] S4. The dried premixed material is extruded and stretched into a film using a twin-screw extruder at 240°C and a film stretching speed of 10m / min to obtain a transparent heat-insulating PET film.

[0071] Comparative Example 1:

[0072] The only difference between Comparative Example 1 and Example 1 is that the organic yellow dye AKS is not added in step S1.

[0073] The specific steps of Comparative Example 1 are as follows:

[0074] S1. Cesium tungsten bronze, ethyl acetate and silane coupling agent KH-570 are uniformly mixed and dispersed according to the mass ratio of cesium tungsten bronze: ethyl acetate: silane coupling agent KH-570 = 20:80:1. The mixture is stirred at 2000 rpm for 30 min to obtain a cesium tungsten bronze dispersion.

[0075] S2. Add PET resin to a high-speed mixer and set the speed to 12000 rpm. According to the mass ratio of PET resin to cesium tungsten bronze = 100:20, inject the cesium tungsten bronze dispersion into the PET resin dropwise at a rate of 100 ml / min using a micro-injection pump and stir to obtain a premix.

[0076] S3. Place the premixed material under vacuum drying at 85℃ for 4 hours to remove the solvent;

[0077] S4. The dried premixed material is extruded and stretched into a film using a twin-screw extruder at 240°C and a film stretching speed of 10m / min to obtain a transparent heat-insulating PET film.

[0078] Comparative Example 2:

[0079] The only difference from Comparative Example 1 is that the speed of the high-speed mixer in step S2 is set to 3000 rpm.

[0080] Comparative Example 3:

[0081] The only difference from Comparative Example 1 is that the speed of the high-speed mixer in step S2 is set to 18,000 rpm.

[0082] Comparative Example 4:

[0083] S1. Cesium tungsten bronze, ethyl acetate and silane coupling agent KH-570 are uniformly mixed and dispersed according to the mass ratio of cesium tungsten bronze: ethyl acetate: silane coupling agent KH-570 = 20:80:1. The mixture is stirred at 2000 rpm for 30 min to obtain a cesium tungsten bronze dispersion.

[0084] S2. Add PET resin to a high-speed mixer, set the speed to 12000 rpm, and pour the cesium tungsten bronze dispersion directly into the PET resin according to the mass ratio of PET resin: cesium tungsten bronze = 100:20 and stir to obtain a premix.

[0085] S3. Place the premixed material under vacuum drying at 85℃ for 4 hours to remove the solvent;

[0086] S4. The dried premixed material is extruded and stretched into a film using a twin-screw extruder at 240°C and a film stretching speed of 10m / min to obtain a transparent heat-insulating PET film.

[0087] Test example:

[0088] The light transmittance and color difference of the transparent heat-insulating PET films obtained in the examples and comparative examples were tested using a spectrophotometer and a color difference meter, respectively.

[0089] The light transmittance of the transparent heat-insulating PET films obtained in Examples 1-8 and Comparative Examples 1-4 is shown in Table 1. The UV-PC images of the transparent heat-insulating PET films obtained in Examples 1-2 and Comparative Example 1 are shown in Table 1. Figure 1 As shown.

[0090] Table 1. Light transmittance of different PET films

[0091]

[0092]

[0093] The results show that the transparent heat-insulating PET film prepared by the method of this invention can achieve an average transmittance of about 70% in the wavelength range of 380-780nm, and an average transmittance of over 80% in the wavelength range of 400-600nm. A comparison of the data from Comparative Examples 2-4 with Comparative Example 1 shows that both excessively high and low mixing speeds of PET resin and cesium tungsten bronze significantly affect the transparency of the finished PET film. When the mixing speed is too low, insufficient shear force easily leads to the formation of cesium tungsten bronze agglomerates, reducing the film's transmittance; while excessively high mixing speeds may cause the PET molecular chains to break, also affecting the transmittance of the PET film and its mechanical properties. Furthermore, the rate at which cesium tungsten bronze is added to the PET resin also affects the transmittance of the finished film. By dispersing cesium tungsten bronze in a solvent and then injecting it dropwise into the PET resin, and precisely controlling the mixing speed, a cesium tungsten bronze-containing PET film with excellent transmittance can be obtained.

[0094] from Figure 1 It can be seen that the addition of organic yellow dye only causes a slight decrease in the transmittance of PET film in the visible light region, while the performance in the near-infrared region is completely preserved. This proves that the process design combining high-speed stirring and micro-injection strategy has achieved precise composite of organic yellow dye, cesium tungsten bronze and PET resin, resulting in PET film with good dispersibility and high transparency.

[0095] The color coordinates and colors of the transparent heat-insulating PET films obtained with different amounts of organic yellow dye are shown in Table 2. The CIE 1931 color space diagrams for Examples 1-2 and Comparative Example 1 are shown below. Figure 2 As shown, Comparative Example 1 (color coordinates 0.31, 0.29) demonstrates the intrinsic blue hue shift of the cesium tungsten bronze PET film without the addition of organic yellow dye. Examples 1 (color coordinates 0.33, 0.35) and 2 (color coordinates 0.32, 0.35) successfully neutralized the blue hue by adding specific amounts of organic yellow dyes AKS and OO / A, respectively, shifting the color coordinates of the PET film towards the neutral white region (500–580 nm). Combining the color coordinate changes of the transparent heat-insulating PET films obtained in Examples 3-6, it can be seen that the amount of organic yellow dye added during PET film preparation has a non-linear regulatory relationship with the color coordinate change. Appropriate addition of organic yellow dye can adjust the blue hue shift of the PET film, while excessive addition will lead to excessive color shift. Reasonable process adjustments are needed to accurately balance its optical performance and color.

[0096] Table 2 Color coordinates and colors of different PET films

[0097]

[0098] In summary, this invention achieves spectral complementarity between organic yellow dye and cesium tungsten bronze by rationally controlling the addition amounts of the two, resulting in a cesium tungsten bronze-containing PET film exhibiting a low blue phase characteristic. Precise control of the ratio also allows the PET film to exhibit a neutral gray color. The use of high-speed stirring and micro-injection processes during PET film preparation further disperses the cesium tungsten bronze and dye, significantly improving film transparency. This invention's low-blue-phase transparent heat-insulating PET film not only has a simple preparation method and low equipment requirements, but also achieves an average light transmittance of over 80% in the 400-600nm wavelength range and a blocking rate exceeding 80% in some near-infrared bands. Furthermore, it possesses a low blue phase characteristic, achieving simultaneous optimization of heat insulation performance, transparency, and color rendering performance. It has broad application prospects in fields such as energy-saving building glass, new energy vehicle windows, and optical display devices.

[0099] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention.

[0100] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0101] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to provide exhaustive examples of all embodiments. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A low-blue-phase transparent heat-insulating PET film, characterized in that, It includes a PET matrix and cesium tungsten bronze and an organic yellow dye dispersed therein, wherein the mass ratio of cesium tungsten bronze to organic yellow dye is 100:(0.1-0.5), and the visible light absorption range of the organic yellow dye is 400-500 nm.

2. The low blue phase transparent heat-insulating PET film as described in claim 1, characterized in that, The mass ratio of the cesium tungsten bronze to the organic yellow dye is 100:0.

3.

3. The low blue phase transparent heat-insulating PET film as described in claim 1, characterized in that, The organic yellow dye has a half-peak width of <30nm and a decomposition temperature of ≥250℃.

4. A method for preparing a low-blue-phase transparent heat-insulating PET film as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Add the organic yellow dye to the cesium tungsten bronze dispersion and stir to form a composite slurry; S2. The composite slurry is injected dropwise into PET resin and stirred to obtain a premix; S3. Dry the premixed material; S4. The dried premixed material is extruded and stretched to obtain the low blue phase transparent heat-insulating PET film.

5. The method for preparing the low blue phase transparent heat-insulating PET film as described in claim 4, characterized in that, In step S2, the stirring speed is set to 5000-15000 rpm.

6. The method for preparing the low blue phase transparent heat-insulating PET film as described in claim 4, characterized in that, In step S2, the dripping rate of the composite slurry is 60–200 ml / min.

7. The method for preparing the low blue phase transparent heat-insulating PET film as described in claim 4, characterized in that, In step S2, the mass ratio of PET resin to composite slurry is 100:(12-24).

8. The method for preparing the low blue phase transparent heat-insulating PET film as described in claim 4, characterized in that, In step S3, the drying temperature is 65–105℃ and the drying time is 4–6 h; in step S4, the extrusion temperature is 200–250℃ and the film stretching speed is 5–10 m / min.

9. The method for preparing the low blue phase transparent heat-insulating PET film as described in claim 4, characterized in that, Step S2 is divided into two stages: Stage 1 is that 40% to 80% of the total composite slurry is injected dropwise into the PET resin at a first injection speed and stirred at a first rotation speed; Stage 2 is that 20% to 60% of the total composite slurry is injected dropwise into the PET resin at a second injection speed and stirred at a second rotation speed. The second injection speed = the first injection speed + (20 to 80) ml / min, and the second rotation speed = the first rotation speed + (2000 to 5000) rpm.

10. The method for preparing the low blue phase transparent heat-insulating PET film as described in claim 9, characterized in that, The first injection speed is 60-100 ml / min, and the first rotation speed is 5000-10000 rpm.

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