High-definition flexible optical film and method of making the same

Abstract

The application relates to a high-definition flexible optical film and a preparation method thereof. PET master batches, PEN master batches, flexible polyester elastomers and a nano composite dispersion liquid are subjected to melt extrusion, asynchronous bidirectional stretching, in-situ heat relaxation and cooling and winding to obtain the optical film, wherein the nano composite dispersion liquid comprises mCNC, SEBS, SA-BaSO4 and ethylene glycol. The application effectively reduces light scattering and greatly improves high-definition optical performance by using refractive index matched modified nano barium sulfate and highly dispersed modified nano cellulose crystals; the modified nano cellulose crystals improve the high compatibility and thermal stability of the PET base material, so that the PET base material can effectively transfer and disperse stress; SEBS and the composite flexible polyester elastomer synergistically toughen, internal stress is released and a flexible microstructure is constructed by combining the asynchronous stretching and heat relaxation process, so that the film is endowed with super-flexibility; the components have good compatibility, the film size is stable, and there is no rainbow stripe.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical-grade PET film, in particular to a high-definition flexible optical film and a preparation method thereof. BACKGROUND

[0002] With the rapid development of display technology, flexible display devices, such as foldable mobile phones, rollable televisions, and wearable devices, are gradually becoming a new trend in the market. One of the core components of these devices is their screen cover or surface optical film, which is required to not only have high light transmittance, low haze, and other characteristics of traditional optical films, but also have excellent flexibility, folding resistance, and impact resistance. However, the balance between flexibility and strength of super-flexible optical films is difficult to achieve. Reducing the thickness for flexibility will weaken the material strength, and frequent bending can easily cause molecular chain rupture, affecting the light guiding performance. In addition, stretching and shearing stress are generated during frequent folding, thus easily causing scratches or cracks. SUMMARY

[0003] In view of the deficiencies in the prior art, the present application solves the technical contradiction that high definition and super flexibility cannot be reconciled by synergistically modifying the nanoparticles and optimizing the overall formulation and process.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] A high-definition flexible optical film is obtained by melt extrusion, asynchronous bidirectional stretching, in-situ heat relaxation, and cooling and winding of the following raw materials in weight parts:

[0006] PET master batch 100 parts;

[0007] PEN master batch 5-10 parts;

[0008] Flexible polyester elastomer 6-12 parts;

[0009] Nano-composite dispersion liquid 10-16 parts;

[0010] The nano-composite dispersion liquid includes 20-30 wt% modified nanocellulose crystals (mCNC), 15-25 wt% hydrogenated styrene-butadiene block copolymer (SEBS), 10-15 wt% stearic acid surface-coated nano-barium sulfate (SA-BaSO4), and the balance of ethylene glycol. The addition method is to inject the extruder through the side feeding device in the middle section of the extruder.

[0011] Further, the modification method of the modified nanocellulose crystals is as follows: the nanocellulose crystals are dispersed in anhydrous ethanol, γ-methacryloxypropyltrimethoxysilane (KH570) is added, the temperature is raised to 70°C and refluxed overnight. After the reaction is completed, the mixture is centrifuged, washed and dried. The dried solid is redispersed in tetrahydrofuran, 2-vinyl-2-oxazoline, acrylic acid and glycidyl methacrylate are added, the mixture is stirred and mixed evenly, nitrogen gas is purged for 30 min, then benzoyl peroxide is added, and the reaction is carried out under nitrogen protection for 4-6 h. After the reaction is completed, the reaction solution is poured into a large amount of n-hexane, allowed to stand to precipitate, filtered, washed and dried to obtain the final product.

[0012] Further, the mass ratio of γ-methacryloxypropyltrimethoxysilane to nanocellulose crystals is 5~10:1; the molar ratio of 2-vinyl-2-oxazoline, acrylic acid, glycidyl methacrylate, and benzoyl peroxide is 1~3:3~6:2~5:0.01~0.1.

[0013] Furthermore, the hydrogenated styrene-butadiene block copolymer is a linear triblock copolymer with polystyrene as the end block and ethylene-butene copolymer obtained by hydrogenating polybutadiene as the middle elastic block.

[0014] Furthermore, the preparation method of the stearic acid surface coated with nano-barium sulfate is as follows: disperse nano-barium sulfate in deionized water, heat to 60°C, add stearic acid accounting for 3-8% of the mass of nano-barium sulfate, stir at high speed to emulsify for 1-2 hours, centrifuge after the reaction is completed, wash and dry to obtain the product.

[0015] Furthermore, the preparation process of the nanocomposite dispersion is as follows: modified cellulose nanocrystals, SEBS, and barium sulfate nanocoated with stearic acid are sequentially added to ethylene glycol, and high-speed shear emulsification is carried out at 50~60℃ for 0.5~1 hours to form a uniform and stable suspension.

[0016] Furthermore, the flexible polyester elastomer is obtained by melt blending TPEE and maleic anhydride-grafted polyethylene at a mass ratio of 2:1, wherein the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 1% to 2%.

[0017] A second objective of this invention is to provide a method for preparing the high-definition flexible optical film as described above, comprising the following steps:

[0018] S1. After thoroughly drying PET masterbatch, PEN masterbatch and flexible polyester elastomer, mix them evenly and feed them into an extruder. In the middle section of the extruder, add nano-composite dispersion through a side feeding device, mix with PET and extrude through a die to form a cast sheet.

[0019] S2, the cast sheet is first stretched longitudinally, the longitudinal stretching ratio is 2.5~3.0:1, the temperature is 85~95℃; then transversely stretched, the transverse stretching ratio is 3.8~4.5:1, the temperature is 110~120℃;

[0020] S3, the film sheet after transverse stretching is in the film drawing clamp, and is subjected to heat relaxation treatment at 150~160℃ for 3~8 seconds, so that the film sheet is retracted by 3%~5%;

[0021] S4, cooling and winding: the film sheet after relaxation treatment is cooled, edge cut and wound, and the film is obtained.

[0022] Compared with the prior art, the beneficial effects of the present application are:

[0023] 1. By using the refractive index matched modified nano-barium sulfate and highly dispersed modified nanocellulose crystals, the light scattering is effectively reduced, and the high-definition optical performance is greatly improved;

[0024] 2. By modifying the nanocellulose crystals with vinyl siloxane, active sites are introduced on the surface, and then in-situ radical polymerization with 2-vinyl-2-oxazoline, acrylic acid and glycidyl methacrylate can improve the high compatibility and thermal stability with the PET substrate, so that it can effectively transfer and disperse stress; SEBS and composite flexible polyester elastomer synergistically toughen, and the internal stress is released and the flexible microstructure is constructed by combining asynchronous stretching and heat relaxation process, so as to give the film super-soft characteristics;

[0025] 3. The nanocomposite dispersion liquid is injected in-situ through side feeding, which avoids the pre-drying and high-speed shearing damage of nanoparticles, improves the dispersion uniformity and processing efficiency, and has high stability; the components have good compatibility, the film size is stable, and there is no rainbow stripe. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0027] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0028] Raw material source: most of the raw materials used in the present application are conventional chemical reagents, which can be purchased in the market, and part of the raw material sources are as follows.

[0029]

[0030] Embodiment: A high-definition flexible optical film

[0031] S1, 100 parts of PET masterbatch, 5-10 parts of PEN masterbatch and 6-12 parts of flexible polyester elastomer are mixed uniformly after being dried sufficiently and are put into an extruder, 10-16 parts of nano composite dispersion liquid is added through a side feeding device in the middle section of the extruder, and the PET mixture is extruded through a die to form a cast sheet;

[0032] S2, the cast sheet is first stretched longitudinally at a longitudinal stretching ratio of 2.5-3.0:1 and a temperature of 85-95℃, and then is stretched transversely at a transverse stretching ratio of 3.8-4.5:1 and a temperature of 110-120℃;

[0033] S3, the film sheet after bidirectional stretching is subjected to heat relaxation treatment at 150-160℃ for 3-8 seconds in a film drawing clamp, so that the film sheet is retracted by 3%-5%;

[0034] S4, cooling and winding: the film sheet after relaxation treatment is cooled, edge cut and wound, and the high-definition flexible optical film is obtained.

[0035] The nano composite dispersion liquid is obtained by adding 20-30wt% mCNC, 15-25wt% SEBS and 10-15wt% SA-BaSO4 into ethylene glycol in sequence, and high-speed shearing emulsification is carried out at 50-60℃ for 0.5-1 hour to form a uniform and stable suspension.

[0036] The modification method of the mCNC is as follows: 10g of nanocrystalline cellulose is dispersed in anhydrous ethanol, 50g of γ-methacryloxypropyltrimethoxysilane is added, the temperature is raised to 70℃ for reflux reaction overnight, after the reaction is completed, centrifugal separation, washing and drying are carried out; 10g of the dried solid is dispersed in tetrahydrofuran again, 1.4g of 2-vinyl-2-oxazoline, 3.6g of acrylic acid and 4.3g of glycidyl methacrylate are added, stirring is carried out until they are mixed uniformly, then nitrogen is blown in for 30min, then 0.1g of benzoyl peroxide is added, reaction is carried out for 4-6h under nitrogen protection, after the reaction is completed, the reaction liquid is poured into a large amount of n-hexane, and then is left to precipitate, filtered, washed and dried.

[0037] The hydrogenated styrene-butadiene block copolymer is a linear three-block copolymer with polystyrene as the terminal segment and ethylene-butene copolymer obtained by hydrogenation of polybutadiene as the intermediate elastic block.

[0038] The preparation method of the SA-BaSO4 is as follows: nanometer barium sulfate is dispersed in deionized water, the temperature is raised to 60℃, 8% of the mass of the nanometer barium sulfate of stearic acid is added, high-speed stirring emulsification reaction is carried out for 1-2h, after the reaction is completed, centrifugal separation, washing and drying are carried out, and the SA-BaSO4 is obtained.

[0039] The flexible polyester elastomer is obtained by melt blending TPEE and maleic anhydride grafted polyethylene at a mass ratio of 2:1, and the grafting rate of maleic anhydride in the maleic anhydride grafted polyethylene is 1% to 2%.

[0040] According to the preparation method and raw materials described above, the following specific examples can be obtained by changing the composition of raw materials and the preparation process conditions.

[0041] Example 1: A high-definition flexible optical film

[0042] S1, 100 parts of PET master batch, 5 parts of PEN master batch and 6 parts of flexible polyester elastomer are mixed uniformly after being dried sufficiently, and are put into an extruder, 10 parts of nano composite dispersion liquid is added through a side feeding device in the middle section of the extruder, and the PET mixed material is extruded through a die to form a casting sheet;

[0043] S2, the casting sheet is first stretched longitudinally at a longitudinal stretching ratio of 2.5 and a temperature of 90℃, and then is stretched transversely at a transverse stretching ratio of 3.8:1 and a temperature of 110℃;

[0044] S3, the film sheet after bidirectional stretching is subjected to heat relaxation treatment at 150℃ for 3 to 8 seconds in a film drawing clamp, so that the film sheet is retracted by 3% to 5%;

[0045] S4, cooling and winding: the film sheet after relaxation treatment is cooled, edge cut and wound, and a high-definition flexible optical film is obtained.

[0046] The nano composite dispersion liquid is obtained by adding 25wt% mCNC, 20wt% SEBS and 15wt% SA-BaSO4 into 40wt% ethylene glycol in sequence, and high-speed shearing emulsifying at 60℃ for 0.5 hours to form a uniform and stable suspension.

[0047] Example 2: A high-definition flexible optical film

[0048] S1, 100 parts of PET master batch, 8 parts of PEN master batch and 9 parts of flexible polyester elastomer are mixed uniformly after being dried sufficiently, and are put into an extruder, 13 parts of nano composite dispersion liquid is added through a side feeding device in the middle section of the extruder, and the PET mixed material is extruded through a die to form a casting sheet;

[0049] S2, the casting sheet is first stretched longitudinally at a longitudinal stretching ratio of 3.0 and a temperature of 90℃, and then is stretched transversely at a transverse stretching ratio of 4.2:1 and a temperature of 115℃;

[0050] S3, the film sheet after bidirectional stretching is subjected to heat relaxation treatment at 150℃ for 3 to 8 seconds in a film drawing clamp, so that the film sheet is retracted by 3% to 5%;

[0051] S4, cooling and winding: the film sheet after relaxation treatment is cooled, edge cut and wound, and the high-definition flexible optical film is obtained.

[0052] The nanocomposite dispersion liquid is prepared by adding 30wt% mCNC, 22wt% SEBS and 10wt% SA-BaSO4 into 38wt% ethylene glycol in sequence, and emulsifying at 60℃ for 0.5 hours under high-speed shearing to form a uniform and stable suspension.

[0053] Example 3: a high-definition flexible optical film

[0054] S1, 100 parts of PET masterbatch, 10 parts of PEN masterbatch and 12 parts of flexible polyester elastomer are mixed uniformly after being fully dried, and are put into an extruder. 16 parts of nanocomposite dispersion liquid is added through a side feeding device in the middle section of the extruder. The PET mixed material is extruded through a die to form a cast sheet;

[0055] S2, the cast sheet is first stretched longitudinally at a longitudinal stretching ratio of 3.0:1 and a temperature of 95℃, and then is stretched transversely at a transverse stretching ratio of 4.5:1 and a temperature of 120℃;

[0056] S3, the film sheet after bidirectional stretching is subjected to heat relaxation treatment at 160℃ for 3-8 seconds in a film drawing clamp, so that the film sheet is retracted by 3%-5%;

[0057] S4, cooling and winding: the film sheet after relaxation treatment is cooled, edge cut and wound, and the high-definition flexible optical film is obtained.

[0058] The nanocomposite dispersion liquid is prepared by adding 30wt% mCNC, 22wt% SEBS and 10wt% SA-BaSO4 into 38wt% ethylene glycol in sequence, and emulsifying at 60℃ for 0.5 hours under high-speed shearing to form a uniform and stable suspension.

[0059] Comparative Example 1: comparison of the influence of composite particles and composite dispersion liquid on performance

[0060] S1, 100 parts of PET masterbatch, 10 parts of PEN masterbatch and 12 parts of flexible polyester elastomer are mixed uniformly after being fully dried, and are put into an extruder. 16 parts of nanocomposite dispersion liquid is added through a side feeding device in the middle section of the extruder. The PET mixed material is extruded through a die to form a cast sheet;

[0061] S2, the cast sheet is first stretched longitudinally at a longitudinal stretching ratio of 3.0:1 and a temperature of 95℃, and then is stretched transversely at a transverse stretching ratio of 4.5:1 and a temperature of 120℃;

[0062] S3, the film sheet after bidirectional stretching is subjected to heat relaxation treatment at 160℃ for 3-8 seconds in a film drawing clamp, so that the film sheet is retracted by 3%-5%;

[0063] S4, cooling and winding: the film sheet after relaxation treatment is cooled, edge cut and wound, and the product is obtained.

[0064] The nanocomposite particles are obtained by putting 25wt% mCNC, 20wt% SEBS and 15wt% SA-BaSO4 into an extruder after blending.

[0065] Comparative Example 2: comparison of the influence of modification of nanocellulose crystals on performance

[0066] S1, 100 parts of PET masterbatch, 10 parts of PEN masterbatch and 12 parts of flexible polyester elastomer are fully dried and uniformly mixed, and then put into an extruder. 16 parts of nanocomposite dispersion liquid is added through a side feeding device in the middle of the extruder. The PET mixture is extruded through a die to form a casting sheet.

[0067] S2, the casting sheet is first stretched longitudinally at a longitudinal stretching ratio of 3.0:1 and a temperature of 95℃, and then stretched transversely at a transverse stretching ratio of 4.5:1 and a temperature of 120℃.

[0068] S3, the film sheet after bidirectional stretching is subjected to heat relaxation treatment at 160℃ for 3-8 seconds in a film stretching clamp, so that the film sheet is retracted by 3%-5%;

[0069] S4, cooling and winding: the film sheet after relaxation treatment is cooled, edge cut and wound, and the product is obtained.

[0070] The nanocomposite dispersion liquid is obtained by adding 25wt% nanocellulose crystals, 20wt% SEBS and 15wt% BaSO4 into 40wt% ethylene glycol in sequence, and high-speed shearing emulsifying at 60℃ for 0.5 hours to form a uniform and stable suspension.

[0071] The nanocellulose crystals are modified by the following method:

[0072] 10g of nanocellulose crystals are dispersed in anhydrous ethanol, 50g of γ-methacryloxypropyltrimethoxysilane is added, the temperature is raised to 70℃ for reflux reaction overnight, and after the reaction is completed, centrifugal separation, washing and drying are carried out. 10g of the dried solid is dispersed in tetrahydrofuran again, 3.6g of acrylic acid is added, and after stirring and mixing uniformly, nitrogen is blown for 30min, then 0.1g of benzoyl peroxide is added, and the reaction is carried out under nitrogen protection for 4-6h. After the reaction is completed, the reaction liquid is poured into a large amount of n-hexane, and after standing and precipitating, filtration, washing and drying are carried out.

[0073] Comparative Example 3: comparison of the influence of modification of nanocellulose crystals on performance

[0074] S1, 100 parts of PET masterbatch, 10 parts of PEN masterbatch and 12 parts of flexible polyester elastomer were mixed uniformly after being dried sufficiently, and were put into an extruder, 16 parts of nano-composite dispersion liquid was added through a side feeding device in the middle section of the extruder, and the PET mixture was extruded through a die to form a cast sheet;

[0075] S2, the cast sheet was first stretched longitudinally at a longitudinal stretching ratio of 3.0:1 and a temperature of 95°C, and then was stretched transversely at a transverse stretching ratio of 4.5:1 and a temperature of 120°C;

[0076] S3, the film sheet after bidirectional stretching was subjected to heat relaxation treatment at 160°C for 3-8 seconds in a film drawing clamp, so that the film sheet was retracted by 3%-5%;

[0077] S4, cooling and winding: the film sheet after relaxation treatment was cooled, edge cut and wound, and was obtained.

[0078] The nano-composite dispersion liquid is prepared by adding 25wt% nanocellulose crystals, 20wt% SEBS and 15wt% BaSO4 into 40 parts of ethylene glycol in sequence, and is emulsified at a high speed for 0.5 hours at 60°C to form a uniform and stable suspension.

[0079] Comparative Example 4: comparison of the performance of pure PET combined with composite dispersion liquid

[0080] S1, 100 parts of PET masterbatch were mixed uniformly after being dried sufficiently, and were put into an extruder, 16 parts of nano-composite dispersion liquid was added through a side feeding device in the middle section of the extruder, and the PET mixture was extruded through a die to form a cast sheet;

[0081] S2, the cast sheet was first stretched longitudinally at a longitudinal stretching ratio of 3.0:1 and a temperature of 95°C, and then was stretched transversely at a transverse stretching ratio of 4.5:1 and a temperature of 120°C;

[0082] S3, the film sheet after bidirectional stretching was subjected to heat relaxation treatment at 160°C for 3-8 seconds in a film drawing clamp, so that the film sheet was retracted by 3%-5%;

[0083] S4, cooling and winding: the film sheet after relaxation treatment was cooled, edge cut and wound, and was obtained.

[0084] The nano-composite dispersion liquid is prepared by adding 25wt% nanocellulose crystals, 20wt% SEBS and 15wt% BaSO4 into 40 parts of ethylene glycol in sequence, and is emulsified at a high speed for 0.5 hours at 60°C to form a uniform and stable suspension.

[0085] The light transmittance and haze were tested by a haze meter.

[0086] Minimum bending radius: the minimum radius at which the film does not show visible cracks or whitening by mandrel bending method (according to IPC-TM-650 2.4.3).

[0087] Elastic modulus: the elastic modulus in machine direction (MD) was determined by using a universal material testing machine according to ASTM D882 standard.

[0088] Table 1

[0089]

[0090] In combination with the data in Table 1, observing Comparative Examples 1-3, the nanocomposite dispersion prepared in the present application is fed into the middle section of the extruder through the side feeding device, which can effectively improve the dispersion compatibility of the nanoparticles in the PET substrate, avoiding stress concentration leading to the decrease of flexibility and light transmittance; the free radical grafting polymerization modification of nanocellulose crystals effectively enhances its interface bonding capacity, which is also one of the key features to realize high definition and super flexibility; the introduction of flexible components can further enhance the toughness of the material on the basis of adding the nanocomposite dispersion, and has little effect on the improvement of its optical properties.

[0091] Examples 1-3 are high-definition super-flexible optical films prepared by feeding the nanocomposite dispersion into the middle section of the extruder through the side feeding device, combined with asynchronous stretching and in-situ heat relaxation. Asynchronous stretching induces anisotropic orientation of molecular chains and nanoparticles, which preliminarily optimizes the structure; the subsequent heat relaxation effectively releases internal stress and causes slight shrinkage of the mCNC network, forming a flexible microstructure in the matrix that can effectively dissipate bending energy, thereby giving it extremely high folding resistance.

[0092] Although the embodiments of the present application have been disclosed as above, it is not limited to the application listed in the specification and embodiments, and can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, and therefore the present application is not limited to specific details, without departing from the general concept defined by the claims and equivalent scope.

Claims

1. A high-clarity flexible optical film characterized by, The raw materials are melt-extruded, biaxially stretched, relaxed in situ, and wound after cooling to obtain a film using the following weight parts of raw materials: PET masterbatch 100 parts; PEN masterbatch 5-10 parts; Flexible polyester elastomer 6-12 parts; Nano-composite dispersion liquid 10-16 parts; The nano-composite dispersion liquid comprises 20-30 wt% modified nanocellulose crystals, 15-25 wt% hydrogenated styrene-butadiene block copolymer, 10-15 wt% stearic acid surface-coated nano-barium sulfate, and the balance of ethylene glycol; and the addition method is to inject the nano-composite dispersion liquid into the extruder through a side feeding device in the middle section of the extruder. The modification method of the modified nanocellulose crystals is as follows: the nanocellulose crystals are dispersed in anhydrous ethanol, γ-methacryloxypropyltrimethoxysilane is added, the temperature is raised to 70°C for reflux reaction overnight, centrifugal separation is performed after the reaction is completed, and washing and drying are performed; the dried solid is redispersed in tetrahydrofuran, 2-vinyl-2-oxazoline, acrylic acid, and glycidyl methacrylate are added, stirring is performed until they are uniformly mixed, nitrogen is introduced for blowing for 30 min, then benzoyl peroxide is added, and reaction is performed under nitrogen protection for 4-6 h; after the reaction is completed, the reaction solution is poured into a large amount of n-hexane, precipitation is performed after standing, filtration is performed, and washing and drying are performed to obtain the modified nanocellulose crystals. The hydrogenated styrene-butadiene block copolymer is a linear tri-block copolymer with polystyrene as the terminal segment and ethylene-butene copolymer obtained by hydrogenation of polybutadiene as the intermediate elastic block.

2. The high-clarity flexible optical film of claim 1, wherein, The mass ratio of the γ-methacryloxypropyltrimethoxysilane to the nanocellulose crystals is 5-10:1; and the molar ratio of the 2-vinyl-2-oxazoline, the acrylic acid, the glycidyl methacrylate, and the benzoyl peroxide is 1-3:3-6:2-5:0.01-0.

1.

3. The high-clarity flexible optical film of claim 1, wherein, The preparation method of the stearic acid surface-coated nano-barium sulfate is as follows: the nano-barium sulfate is dispersed in deionized water, the temperature is raised to 60°C, 3-8% of the mass of the nano-barium sulfate of stearic acid is added, high-speed stirring and emulsification reaction are performed for 1-2 h, centrifugal separation is performed after the reaction is completed, and washing and drying are performed to obtain the stearic acid surface-coated nano-barium sulfate.

4. The high-clarity flexible optical film of claim 1, wherein The preparation process of the nano-composite dispersion liquid is as follows: the modified nanocellulose crystals, the SEBS, and the stearic acid surface-coated nano-barium sulfate are sequentially added to ethylene glycol, high-speed shearing and emulsification are performed at 50-60°C for 0.5-1 h to form a uniform and stable suspension.

5. The high-clarity flexible optical film of claim 1, wherein The flexible polyester elastomer is obtained by melt blending TPEE and maleic anhydride grafted polyethylene at a mass ratio of 2:1, and the grafting rate of maleic anhydride in the maleic anhydride grafted polyethylene is 1%-2%.

6. A method of making the high-clarity flexible optical film of any one of claims 1-5, wherein, The method comprises the following steps: S1, the PET masterbatch, the PEN masterbatch, and the flexible polyester elastomer are fully dried and then uniformly mixed, and are then put into an extruder, the nano-composite dispersion liquid is added through a side feeding device in the middle section of the extruder, and the PET mixture is extruded through a die to form a cast sheet; S2, the cast sheet is first stretched in the longitudinal direction at a longitudinal stretching ratio of 2.5-3.0:1 and at a temperature of 85-95°C, and is then stretched in the transverse direction at a transverse stretching ratio of 3.8-4.5:1 and at a temperature of 110-120°C. S3, after the film is stretched in both directions, the film is subjected to heat relaxation treatment at 150-160℃ for 3-8 seconds in the film stretching clamp, so that the film is retracted by 3%-5%; S4, cooling and winding: the film subjected to relaxation treatment is cooled, edge cut and then wound, and the film is obtained.

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