A polyethylene naphthalate film with high light transmittance and its preparation method

Abstract

The present invention discloses a polyethylene naphthalate film with high light transmittance and a preparation method thereof. The surface of the PEN film is subjected to plasma treatment; dimethyldiethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane and a solvent are mixed, and hydrolysis and condensation are carried out under the action of a catalyst to obtain a phenylvinyl silicone resin sol; a high-boiling solvent is used to displace ethanol in the phenylvinyl silicone resin sol, and filtration is carried out to obtain a high-transparency silicone resin solution; the high-transparency silicone resin solution is coated on the surface of the plasma-treated PEN film, and baking is carried out. The PEN film has excellent light-transmitting performance, and also has excellent heat resistance and dimensional stability, and can be used as an ITO base film, a support film for a liquid crystal display polarizer, and other fields. The method is simple, easy to operate, and the raw materials used are non-toxic and easily available, and a PEN optical-grade film with high cost performance can be prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of PEN optical films, and particularly to a polyethylene naphthalate film with high light transmittance and a preparation method thereof. Background Art

[0002] Optical transparent films are ubiquitous in life and are widely used in optoelectronic fields such as optical lenses, liquid crystal displays, and solar backsheets. Light transmittance is one of the most basic optical indicators for evaluating the performance of optical transparent films. Among them, PEN films have important application prospects in the optoelectronic industry due to their excellent mechanical properties, dimensional stability, good chemical stability, and weather resistance.

[0003] However, when PEN films are used as optical-grade films, there is a problem of low light transmittance. This is mainly caused by the following factors: on the one hand, the crystallization rate of PEN is relatively fast, and the crystalline region will affect the transmission of light, thus affecting the light transmittance and haze of PEN films; on the other hand, the production of optical films includes many links such as base material synthesis, biaxial stretching, and surface coating of optical coatings. It not only inherits the technical foundation of general films but also includes more high-precision production technologies. At present, only a few countries and regions such as Japan and South Korea have the production capacity. There are many varieties of ordinary PEN films on the market, but in terms of optical performance, the light transmittance that PEN films can reach is about 87%, which is difficult to meet the requirements of high-end optical-grade films. Therefore, researching new technologies and developing PEN optical films with high light transmittance to meet their diversified needs in the optoelectronic industry and broaden the application fields of PEN films have direct and practical social value.

[0004] In response to the problem of low light transmittance of PEN films, various enterprises and university experts have conducted research. Commonly used methods to improve the light transmittance of PEN films include reducing the crystallization rate during PEN production, directly adding materials that can improve light transmittance during PEN preparation for blending, and modifying the surface of PEN films. However, limited by the domestic production technology level, the light transmittance improvement effect achieved by reducing the crystallization rate is limited; directly adding substances will change many aspects such as the mechanical properties and mechanical performance of PEN films in the PEN matrix and make the preparation process more complex. Therefore, surface coating modification of PEN films is currently the simplest and most effective antireflection means. Summary of the Invention

[0005] To solve the problems in the prior art, the purpose of the present invention is to provide a polyethylene naphthalate film with high light transmittance and a preparation method thereof. The PEN composite film prepared by this method has a relatively high light transmittance.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a polyethylene naphthalate film with high light transmittance, comprising the following steps:

[0008] Perform plasma treatment on the surface of the PEN film;

[0009] Mix dimethyldiethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane and a solvent, and hydrolyze and condense under the action of a catalyst to obtain a phenylvinyl silicone resin sol; Replace ethanol in the phenylvinyl silicone resin sol with a high-boiling solvent, and filter to obtain a high-transparency silicone resin solution;

[0010] Coat the high-transparency silicone resin solution on the surface of the plasma-treated PEN film, and bake to obtain a polyethylene naphthalate film with high light transmittance.

[0011] The specific process of performing plasma treatment on the surface of the PEN film is: clean the PEN film, dry it, and then treat it at a plasma treatment temperature of 20 - 40 °C, a chamber pressure of 9.0 Pa, and a discharge power of 100 W for 100 - 150 s.

[0012] The phenylvinyl silicone resin sol is specifically prepared through the following process: by mass, mix 5 - 10 parts of dimethyldiethoxysilane, 1 - 5 parts of vinyltrimethoxysilane, 10 - 15 parts of phenyltrimethoxysilane, 1 - 5 parts of diphenyldimethoxysilane, 0.01 - 1 part of a catalyst, 5 - 10 parts of water and 60 - 80 parts of a solvent, adjust the pH value to 4 - 6, and react at 40 - 70 °C for 4 - 6 h to obtain the phenylvinyl silicone resin sol.

[0013] The catalyst is one or both of hydrochloric acid and concentrated sulfuric acid.

[0014] The solvent is one or two of methanol, ethanol, ethyl acetate and acetone.

[0015] Replacing ethanol in the phenylvinyl silicone resin sol with a high-boiling solvent and filtering to obtain a high-transparency silicone resin solution includes the following process: adjust the pH value of the phenylvinyl silicone resin sol to 6 - 8, then add 60 - 80 parts of a high-boiling solvent, and heat up to 70 - 100 °C to distill out ethanol, and filter to obtain a high-transparency silicone resin solution.

[0016] Use one or several of sodium carbonate, sodium bicarbonate, sodium phosphate and disodium hydrogen phosphate to adjust the pH value of the phenylvinyl silicone resin sol to 6 - 8.

[0017] The high-boiling solvent is one or two of toluene and xylene.

[0018] The baking temperature is 100 - 140 °C and the time is 60 - 180 s.

[0019] A polyethylene naphthalate film with high light transmittance prepared according to the preparation method described above, the light transmittance of the film is 94 - 97%, and the haze is 1.9 - 2.3%.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: In the present invention, the surface of the PEN film is treated with oxygen plasma to increase the surface roughness and generate a large number of polar oxygen-containing functional groups, which react with the phenyl vinyl silicone resin sol to further improve the adhesion between the PEN film and the methyl vinyl silicone resin coating. The phenyl vinyl silicone resin is used as an antireflection coating to improve the light transmittance of the PEN film. During the baking process, the PEN film treated with oxygen plasma reacts with the polar groups in the high-transparency silicone resin, which is beneficial to enhancing the adhesion between the base film and the coating, avoiding the uneven refractive index caused by the tiny voids between the antireflection coating and the base film, and finally obtaining a polyethylene naphthalate film with high light transmittance. Since the content of phenyl and siloxane can be easily adjusted during the production process of phenyl vinyl silicone resin, it can meet the refractive index requirements of the PEN film for the antireflection coating, and has a uniform structure, moderate viscosity, and good ultraviolet resistance and high-temperature resistance. It is very suitable for use as an antireflection coating to improve the light transmittance of the PEN film. Therefore, phenyl vinyl silicone resin is used as a raw material in the present invention. The polyethylene naphthalate film with high light transmittance prepared by the present invention includes a phenyl vinyl silicone resin antireflection coating with a controllable refractive index formed after coating with a high-transparency silicone resin solution. Among them, phenyl is a high refractive index group, which can increase the refractive index of silicone, and vinyl can improve the crosslinking density and mechanical strength, and increase the viscosity. However, when using only silane monomers containing phenyl or vinyl, it is difficult to polymerize to form a macromolecular silicone resin due to steric hindrance. Therefore, methyl silane is added at the same time, and the dosage of each silane monomer is adjusted to adjust the molecular weight of the silicone resin, control the crystallization rate, and facilitate the regulation of the refractive index of the coating to meet the refractive index requirements of the antireflection coating required by the PEN film. The PEN film has excellent light transmission performance, and excellent heat resistance and dimensional stability. It can be used as an ITO base film, a support film for liquid crystal display polarizers, etc. The preparation method of the present invention is simple, easy to operate, and the raw materials used are non-toxic and easily available. It can prepare a PEN optical grade film with high cost performance and has good commercial prospects.

[0021] Furthermore, by coating a high-transparency silicone resin coating with a controllable refractive index on the surface of the PEN base film, the light transmittance of the film is increased. For the antireflection coating, by controlling the content of phenyl and vinyl, the refractive index of the coating can be adjusted to match that of the base film, thereby achieving the purpose of antireflection. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments:

[0023] Figure 1 It is the structural formula of a high light-transmitting silicone resin.

[0024] Figure 2 It is the ultraviolet-visible light absorption spectrum of a PEN antireflection film. Specific embodiments

[0025] For ease of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present invention can be understood more thoroughly and comprehensively.

[0026] The method of improving the light transmittance of the film by surface coating modification essentially utilizes the thin film interference generated by the antireflection coating. Due to the half-wave loss during film reflection, the reflected light at the interface between the PEN film and the coating and the reflected light at the interface between the coating and the air can interfere and cancel each other out, achieving complete transmission and improving the light transmittance. The following formula should be satisfied among the completely antireflective single-layer film, the substrate material, and the air:

[0027]

[0028] Among them, n0 is the refractive index of air, n s is the refractive index of the substrate, and n f is the refractive index of the coating for achieving complete antireflection.

[0029] The above formula reveals the mechanism of the coating for antireflecting the base film. When the refractive index of the base film is a fixed value, the refractive index of the antireflection coating can be calculated to obtain a definite value according to the above formula. Only when the refractive indices of the base film and the coating match each other and the reflected lights cancel each other out can the optimal light transmittance be achieved. The refractive index n of the PEN base film used in the present invention s is approximately 2.235. After calculation, when the refractive index of the antireflection coating is 1.495, its antireflection effect is the best.

[0030] Organic silicone resin has excellent properties. The rotational steric hindrance of the Si-O bond in the molecular chain is small, and the chain segment flexibility is good, which makes the silicone material have a very high light transmittance. It is worth noting that by designing the molecular chain structure of the silicone resin, such as the content of functional groups such as phenyl and vinyl, the refractive index of the antireflection coating can be controlled, which is very suitable for use as an antireflection coating. Therefore, the present invention uses a PEN resin as the base film and a silicone resin with a controllable refractive index as the antireflection coating to prepare a composite film with a high light transmittance.

[0031] A method for preparing a high light-transmitting polyethylene naphthalate (PEN) film of the present invention includes the following steps:

[0032] (1) The surface treatment method of the PEN base film is as follows: Place the cut PEN base film in a vacuum drying oven to dry the moisture on the film surface, and then put it into a plasma generator to functionalize the film surface under a nitrogen atmosphere to obtain a surface-treated PEN film for standby. Perform plasma treatment on the surface of the PEN film to enhance its interfacial adhesion.

[0033] Specifically, ultrasonically clean the PEN film with absolute ethanol and deionized water for 20 min successively, then rinse it with deionized water and dry it under vacuum conditions at 50 °C. Then place it in a surface plasma processor, with the plasma treatment temperature being 20 - 40 °C, the pressure in the chamber being 9.0 Pa, the discharge power being 100 W, and the treatment time being 100 - 150 s.

[0034] (2) The preparation method of the antireflection coating is as follows: Add dimethyldiethoxysilane (DD), vinyltrimethoxysilane (VTMS), phenyltrimethoxysilane (PTMS), diphenyldimethoxysilane (DDS) and a solvent into a three-necked flask and mix them, and hydrolyze and condense them under the action of a catalyst to obtain a phenylvinyl silicone resin sol. Then neutralize the acidity of the system with a weak base, and displace the solvent in the system with a high-boiling solvent to precipitate the sodium salt dissolved in the system, and filter it out to obtain a high-transparency silicone resin solution.

[0035] Specifically, by mass, take 5 - 10 parts of dimethyldiethoxysilane (DD), 1 - 5 parts of vinyltrimethoxysilane (VTMS), 10 - 15 parts of phenyltrimethoxysilane (PTMS), 1 - 5 parts of diphenyldimethoxysilane (DDS), 0.01 - 1 part of hydrochloric acid (mass concentration 37%), 5 - 10 parts of water, and 60 - 80 parts of a solvent into the flask, control the pH value of the reaction system to be 4 - 6, react at 40 - 70 °C for 4 - 6 h, and hydrolyze and condense under the action of a catalyst to obtain a phenylvinyl silicone resin sol; then add 0.1 - 3 parts of a weak base to the phenylvinyl silicone resin sol to adjust the pH value of the system to 6 - 8, then add 60 - 80 parts of a high-boiling solvent to the system, and raise the temperature to 70 - 100 °C to distill out the ethanol in the system, then cool down, and filter out the insoluble particulate matter to obtain an antireflection silicone resin solution, that is, a high-transparency silicone resin solution, for standby. The antireflection silicone resin solution has a specific refractive index.

[0036] (3) The coating method of the antireflection coating is as follows: Use a 25-μm-thick wet film applicator to scrape the high-transparency silicone resin solution onto the surface of the surface-treated PEN film at a rate of 500 mm / s, and obtain a high-transparency polyethylene naphthalate film by thermal baking at 100 - 140 °C for 60 - 180 s; The high-transparency polyethylene naphthalate film includes a PEN film and a coating on the PEN film, and the coating is a high-transparency silicone resin, and the structural formula is shown inFigure 1 The coating thickness is 3 - 5 μm, and the thickness of the high light transmittance polyethylene naphthalate film is 50 - 60 μm.

[0037] Methoxysilane, triphenylethoxysilane, cyclotetrasiloxane and cyclohexasiloxane are organosiloxane monomers.

[0038] The catalyst is one of concentrated hydrochloric acid (mass concentration 37%) and concentrated sulfuric acid (mass concentration 98%), or both are used simultaneously.

[0039] The solvent is one or a mixture of two of methanol, ethanol, ethyl acetate and acetone.

[0040] The weak base is one or several of sodium carbonate, sodium bicarbonate, sodium phosphate and disodium hydrogen phosphate.

[0041] The high boiling point solvent is one or both of toluene and xylene used simultaneously.

[0042] In the present invention, coating the high light transmittance silicone resin solution on the upper surface of the polyethylene naphthalate (PEN) film can achieve the purpose of increasing light transmittance.

[0043] Example 1

[0044] This example provides a preparation method of a high light transmittance polyethylene naphthalate (PEN) film, including the following steps:

[0045] (1) Ultrasonically clean the cut PEN film with absolute ethanol and deionized water for 20 min successively, then rinse it with deionized water and dry it under vacuum at 50 °C. Then place it in a surface plasma processor, with the plasma treatment temperature of 20 °C, the pressure in the chamber of 9.0 Pa, the discharge power of 100 W, and the treatment time of 100 s to obtain a surface plasma treated PEN base film.

[0046] (2) Take 7 g of dimethyldiethoxysilane (DD), 3 g of vinyltrimethoxysilane (VTMS), 13 g of phenyltrimethoxysilane (PTMS), 3 g of diphenyldimethoxysilane, 0.05 g of hydrochloric acid, 7 g of water and 70 g of ethanol in a flask, control the pH value of the reaction system to be 5, react at 50 °C for 5 h, then add 2 g of sodium bicarbonate to the system to adjust the pH value of the system to 7, then add 70 g of the high boiling point solvent xylene to the system and raise the temperature to 100 °C to distill out the ethanol in the system, then cool down, filter the insoluble particulate matter therein to obtain an anti-reflection silicone resin solution for standby.

[0047] (3) The antireflective silicone resin solution was scrape-coated on the surface of the surface plasmon-treated PEN-based film using a wet film coater with a thickness of 25 μm, and then baked at 120 °C for 3 min to obtain a high light transmittance polyethylene naphthalate film; the high light transmittance polyethylene naphthalate film includes a PEN film and a coating layer on the PEN film, the coating layer thickness is 3 - 5 μm, and the thickness of the high light transmittance polyethylene naphthalate film is 50 - 60 μm.

[0048] The PEN film products obtained in the above examples were subjected to performance tests. The results are shown in the following table:

[0049] Item Transmittance Haze Unit ％ ％ Example 1 96 2.0

[0050] See Figure 2 , it can be seen that the silicone resin has an antireflective effect on the film, and the synthesized PEN film has the characteristic of high light transmittance.

[0051] Example 2

[0052] This example provides a method for preparing a high light transmittance polyethylene naphthalate (PEN) film, including the following steps:

[0053] (1) The cut PEN film was ultrasonically cleaned with anhydrous ethanol and deionized water for 20 min successively, then rinsed with deionized water and dried under vacuum at 50 °C. Then it was placed in a surface plasmon processor, the plasma treatment temperature was 40 °C, the pressure in the chamber was 9.0 Pa, the discharge power was 100 W, and the treatment time was 120 s to obtain a surface plasmon-treated PEN-based film.

[0054] (2) 7 g of dimethyldiethoxysilane (DD), 3 g of vinyltrimethoxysilane (VTMS), 10 g of phenyltrimethoxysilane (PTMS), 3 g of diphenyldimethoxysilane (DDS), 0.05 g of hydrochloric acid, 7 g of water, and 70 g of ethanol were taken in a flask, the pH value of the reaction system was controlled to be 4, reacted at 50 °C for 5 h, then 2 g of sodium bicarbonate was added to the system to adjust the pH value of the system to 7, and then 70 g of high boiling point solvent xylene was added to the system and heated to 100 °C to distill out the ethanol in the system, and then cooled, and the insoluble particulate matter was filtered to obtain an antireflective silicone resin solution for standby.

[0055] (3) The silicone resin coating was scrape-coated on the surface of the surface plasmon-treated PEN-based film using a wet film coater with a thickness of 25 μm, and then baked at 120 °C for 3 min to obtain a high light transmittance polyethylene naphthalate film; the high light transmittance polyethylene naphthalate film includes a PEN film and a coating layer on the PEN film, the coating layer thickness is 3 - 5 μm, and the thickness of the high light transmittance polyethylene naphthalate film is 50 - 60 μm.

[0056] The PEN thin film products obtained from the above embodiments were subjected to performance tests. The results are shown in the following table:

[0057] Item Transmittance Haze Unit ％ ％ Example 2 95 2.0

[0058] Example 3

[0059] This embodiment provides a method for preparing a polyethylene naphthalate (PEN) thin film with high light transmittance, comprising the following steps:

[0060] (1) The cut PEN thin film was ultrasonically cleaned with absolute ethanol and deionized water successively for 20 min, then rinsed with deionized water and dried under vacuum at 50 °C. Then it was placed in a surface plasma processor, with the plasma treatment temperature of 30 °C, the pressure in the chamber of 9.0 Pa, the discharge power of 100 W, and the treatment time of 130 s, to obtain a surface plasma-treated PEN base film.

[0061] (2) 7 g of dimethyldiethoxysilane (DD), 3 g of vinyltrimethoxysilane (VTMS), 13 g of phenyltrimethoxysilane (PTMS), 1 g of diphenyldimethoxysilane, 0.05 g of hydrochloric acid, 7 g of water, and 70 g of ethanol were taken in a flask, the pH value of the reaction system was controlled to be 6, and after reacting at 50 °C for 5 h, 2 g of sodium bicarbonate was added to the system to adjust the pH value of the system to 7. Then 70 g of high-boiling solvent xylene was added to the system, and the temperature was raised to 100 °C to distill out the ethanol in the system. After cooling, the insoluble particulate matter was filtered to obtain a light-transmitting silicone resin solution for standby.

[0062] (3) The silicone resin coating was scraped onto the surface of the surface plasma-treated PEN base film with a 25-μm-thick wet film applicator, and baked at 120 °C for 3 min to obtain a polyethylene naphthalate thin film with high light transmittance; the polyethylene naphthalate thin film with high light transmittance includes a PEN thin film and a coating on the PEN thin film, the thickness of the coating is 3 - 5 μm, and the thickness of the polyethylene naphthalate thin film with high light transmittance is 50 - 60 μm.

[0063] The PEN thin film products obtained from the above embodiments were subjected to performance tests. The results are shown in the following table:

[0064] Item Transmittance Haze Unit ％ ％ Example 3 96 2.3

[0065] Example 4

[0066] This embodiment provides a method for preparing a polyethylene naphthalate (PEN) thin film with high light transmittance, comprising the following steps:

[0067] (1) The cut PEN film was ultrasonically cleaned with absolute ethanol and deionized water for 20 min successively, then rinsed with deionized water and dried under vacuum at 50 °C. Then it was placed in a surface plasma processor. The plasma treatment temperature was 25 °C, the pressure in the chamber was 9.0 Pa, the discharge power was 100 W, and the treatment time was 140 s to obtain a surface plasma-treated PEN base film.

[0068] (2) 7 g of dimethyldiethoxysilane (DD), 3 g of vinyltrimethoxysilane (VTMS), 10 g of phenyltrimethoxysilane (PTMS), 1 g of diphenyldimethoxysilane (DDS), 0.05 g of hydrochloric acid, 7 g of water, and 70 g of ethanol were placed in a flask. The pH value of the reaction system was controlled to be 6, and the reaction was carried out at 50 °C for 5 h. Then 2 g of sodium bicarbonate was added to the system to adjust the pH value of the system to 8. Then 70 g of high-boiling solvent xylene was added to the system, and the temperature was raised to 100 °C to distill out the ethanol in the system. After that, the temperature was lowered, and the insoluble particulate matter was filtered to obtain a light-transmitting silicon resin solution for standby.

[0069] (3) The silicon resin coating was scraped onto the surface of the surface plasma-treated PEN base film with a 25-μm-thick wet film applicator and baked at 120 °C for 3 min to obtain a high light-transmittance polyethylene naphthalate film; the high light-transmittance polyethylene naphthalate film includes a PEN film and a coating on the PEN film. The thickness of the coating is 3 - 5 μm, and the thickness of the high light-transmittance polyethylene naphthalate film is 50 - 60 μm.

[0070] The PEN film products obtained in the above examples were subjected to performance tests. The results are shown in the following table:

[0071] Item Transmittance Haze Unit ％ ％ Example 4 94 2.1

[0072] Example 5

[0073] This example provides a method for preparing a high light-transmittance polyethylene naphthalate (PEN) film, including the following steps:

[0074] (1) The cut PEN film was ultrasonically cleaned with absolute ethanol and deionized water for 20 min successively, then rinsed with deionized water and dried under vacuum at 50 °C. Then it was placed in a surface plasma processor. The plasma treatment temperature was 35 °C, the pressure in the chamber was 9.0 Pa, the discharge power was 100 W, and the treatment time was 125 s to obtain a surface plasma-treated PEN base film.

[0075] (2) Take 7 g of dimethyldiethoxysilane (DD), 3 g of vinyltrimethoxysilane (VTMS), 13 g of phenyltrimethoxysilane (PTMS), 5 g of diphenyldimethoxysilane (DDS), 0.05 g of hydrochloric acid, 7 g of water, and 70 g of ethanol in a flask. Control the pH value of the reaction system to be 5. After reacting at 50 °C for 5 h, add 2 g of sodium bicarbonate to the system to adjust the pH value of the system to 7. Then add 70 g of high-boiling solvent xylene to the system and raise the temperature to 100 °C to distill out the ethanol in the system. After cooling, filter the insoluble particulate matter to obtain a light-transmitting silicone resin solution for standby.

[0076] (3) Use a 25-μm-thick wet film applicator to scrape the silicone resin coating onto the surface of a surface plasmon-treated PEN-based film. Bake it at 120 °C for 3 min to obtain a high light transmittance polyethylene naphthalate film; the high light transmittance polyethylene naphthalate film includes a PEN film and a coating on the PEN film. The thickness of the coating is 3 - 5 μm, and the thickness of the high light transmittance polyethylene naphthalate film is 50 - 60 μm.

[0077] Perform performance tests on the PEN film products obtained in the above examples. The results are shown in the following table:

[0078] Item Transmittance Haze Unit ％ ％ Example 5 97 1.9

[0079] The light transmittance of the products prepared in Examples 1 - 5 is 94 - 97%, and the haze is 1.9 - 2.3%.

[0080] Example 6

[0081] (1) Ultrasonically clean the cut PEN film with anhydrous ethanol and deionized water for 20 min successively, then rinse it with deionized water and dry it under vacuum at 50 °C. Then place it in a surface plasmon processor. The plasma treatment temperature is 30 °C, the pressure in the chamber is 9.0 Pa, the discharge power is 100 W, and the treatment time is 100 s to obtain a surface plasmon-treated PEN-based film.

[0082] (2) Take 5 g of dimethyldiethoxysilane (DD), 1 g of vinyltrimethoxysilane (VTMS), 11 g of phenyltrimethoxysilane (PTMS), 5 g of diphenyldimethoxysilane, 0.01 g of hydrochloric acid, 5 g of water, and 60 g of ethyl acetate in a flask. Control the pH value of the reaction system to be 4. After reacting at 40 °C for 6 h, add a mixture of sodium phosphate and disodium hydrogen phosphate with a mass ratio of 1:1 to the system to adjust the pH value of the system to 8. Then add 60 g of high-boiling solvent toluene to the system and raise the temperature to 70 °C to distill out the ethanol in the system. After cooling, filter the insoluble particulate matter to obtain a light-transmitting silicone resin solution for standby.

[0083] (3) Coat the anti-reflection silicone resin solution on the surface of the surface plasma-treated PEN-based film with a wet film coater with a thickness of 25 μm, and bake it at 100 °C for 3 min to obtain a high light transmittance polyethylene naphthalate film.

[0084] Example 7

[0085] (1) Ultrasonically clean the cut PEN film with anhydrous ethanol and deionized water for 20 min successively, then rinse it with deionized water and dry it under vacuum at 50 °C. Then place it in a surface plasma processor, with the plasma treatment temperature being 40 °C, the chamber pressure being 9.0 Pa, the discharge power being 100 W, and the treatment time being 120 s to obtain a surface plasma-treated PEN-based film.

[0086] (2) Take 8 g of dimethyldiethoxysilane (DD), 2 g of vinyltrimethoxysilane (VTMS), 12 g of phenyltrimethoxysilane (PTMS), 4 g of diphenyldimethoxysilane, 0.07 g of concentrated sulfuric acid, 8 g of water, and 75 g of methanol in a flask, control the pH value of the reaction system to be 5, react at 70 °C for 4 h, then add sodium phosphate to the system to adjust the pH value of the system to 8, then add 80 g of a high-boiling solvent (a mixture of toluene and xylene with a mass ratio of 1:1) to the system, and raise the temperature to 80 °C to distill out the ethanol in the system, then cool down, filter the insoluble particulate matter therein to obtain an anti-reflection silicone resin solution for standby.

[0087] (3) Coat the anti-reflection silicone resin solution on the surface of the surface plasma-treated PEN-based film with a wet film coater with a thickness of 25 μm, and bake it at 140 °C for 1 min to obtain a high light transmittance polyethylene naphthalate film.

[0088] Example 8

[0089] (1) Ultrasonically clean the cut PEN film with anhydrous ethanol and deionized water for 20 min successively, then rinse it with deionized water and dry it under vacuum at 50 °C. Then place it in a surface plasma processor, with the plasma treatment temperature being 20 °C, the chamber pressure being 9.0 Pa, the discharge power being 100 W, and the treatment time being 150 s to obtain a surface plasma-treated PEN-based film.

[0090] (2) Take 10 g of dimethyldiethoxysilane (DD), 5 g of vinyltrimethoxysilane (VTMS), 15 g of phenyltrimethoxysilane (PTMS), 2 g of diphenyldimethoxysilane, 1 g of hydrochloric acid, 10 g of water, and 80 g of a solvent (a mixture of acetone and ethanol with a mass ratio of 1:1) in a flask. Control the pH value of the reaction system to be 6. After reacting at 60 °C for 5 h, add sodium carbonate to the system to adjust the pH value to 7. Then add 75 g of high-boiling solvent xylene to the system and heat up to 90 °C to distill out the ethanol in the system. After that, cool down and filter the insoluble particulate matter to obtain an antireflective silicone resin solution for standby.

[0091] (3) Use a wet film applicator with a thickness of 25 μm to scrape the antireflective silicone resin solution onto the surface of a surface plasmon-treated PEN-based film, and bake it at 130 °C for 100 s to obtain a high light transmittance polyethylene naphthalate film.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing a high light transmittance polyethylene naphthalate (PEN) film, including the following steps:

[0094] (1) Ultrasonically clean the cut PEN film with anhydrous ethanol and deionized water for 20 min successively, then rinse it with deionized water and dry it under vacuum at 50 °C. Then place it in a surface plasmon processor. The plasma treatment temperature is 20 - 40 °C, the pressure in the chamber is 9.0 Pa, the discharge power is 100 W, and the treatment time is 100 - 150 s to obtain a surface plasmon-treated PEN-based film.

[0095] Perform performance tests on the PEN film products obtained in the above comparative example. The results are shown in the following table:

[0096] Item Transmittance Haze Unit ％ ％ Comparative Example 1 90 3.4

[0097] Comparative Example 2

[0098] This comparative example provides a method for preparing a high light transmittance polyethylene naphthalate (PEN) film, including the following steps:

[0099] (1) Ultrasonically clean the cut PEN film with anhydrous ethanol and deionized water for 20 min successively, then rinse it with deionized water and dry it under vacuum at 50 °C. Then place it in a surface plasmon processor. The plasma treatment temperature is 20 - 40 °C, the pressure in the chamber is 9.0 Pa, the discharge power is 100 W, and the treatment time is 100 - 150 s to obtain a surface plasmon-treated PEN-based film.

[0100] (2) Take 7 g of dimethyldiethoxysilane (DD), 3 g of vinyltrimethoxysilane (VTMS), 13 g of phenyltrimethoxysilane (PTMS), 3 g of diphenyldimethoxysilane, 0.05 g of hydrochloric acid, 7 g of water, and 70 g of ethanol in a flask. Control the pH value of the reaction system to be 5 and react at 50 °C for 5 h to obtain a resin solution for standby.

[0101] (3) Use a 25-μm-thick wet film coater to scrape the silicone resin coating onto the surface of the PEN-based film treated by surface plasma. Bake it at 120 °C for 3 min to obtain a high-transparency PEN film with a coating thickness of 3-5 μm. The final composite film thickness is 50-60 μm.

[0102] Perform performance tests on the PEN film products obtained in the above comparative examples. The results are shown in the following table:

[0103] Item Transmittance Haze Unit ％ ％ Comparative Example 2 89 2.9

[0104] According to the above Examples 1-5 and Comparative Examples 1-2, it can be seen that the phenylvinyl silicone resin has an obvious light-transmitting enhancing effect on the PEN-based film. The obtained products have good light transmittance and low haze. The preparation method is simple, easy to operate, and convenient for industrial mass production of optical transparent films with high light transmittance.

[0105] The above is only an illustration of the best embodiments of the present invention, but it should not be construed as a limitation of the claims. The present invention is not limited to the above embodiments, and its specific structure allows changes. Any changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0106] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

Claims

1. A method for preparing a polyethylene naphthalate film with high light transmittance, characterized in that, It includes the following steps: Perform plasma treatment on the surface of the PEN film; Mix dimethyldiethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane and a solvent, and carry out hydrolysis and condensation under the action of a catalyst to obtain a phenylvinyl silicone resin sol; Replace ethanol in the phenylvinyl silicone resin sol with a high-boiling solvent, and filter to obtain a high-transparency silicone resin solution; Coat the high-transparency silicone resin solution on the surface of the plasma-treated PEN film, and bake to obtain a polyethylene naphthalate film with a high light transmittance; The phenylvinyl silicone resin sol is specifically prepared through the following process: By mass, mix 5-10 parts of dimethyldiethoxysilane, 1-5 parts of vinyltrimethoxysilane, 10-15 parts of phenyltrimethoxysilane, 1-5 parts of diphenyldimethoxysilane, 0.01-1 part of a catalyst, 5-10 parts of water and 60-80 parts of a solvent, adjust the pH value to 4-6, and react at 40-70 °C for 4-6 h to obtain a phenylvinyl silicone resin sol; Replacing ethanol in the phenylvinyl silicone resin sol with a high-boiling solvent and filtering to obtain a high-transparency silicone resin solution includes the following process: Adjust the pH value of the phenylvinyl silicone resin sol to 6-8, then add 60-80 parts of a high-boiling solvent, and heat up to 70-100 °C to distill out ethanol, and filter to obtain a high-transparency silicone resin solution.

2. The preparation method of the polyethylene naphthalate film with high light transmittance according to claim 1, characterized in that, The specific process for performing plasma treatment on the surface of the PEN film is: Clean the PEN film, dry it, and then treat it at a plasma treatment temperature of 20-40 °C, a chamber pressure of 9.0 Pa, and a discharge power of 100 W for 100-150 s.

3. The preparation method of the polyethylene naphthalate film with high light transmittance according to claim 1, characterized in that, The catalyst is one or both of hydrochloric acid and concentrated sulfuric acid.

4. The preparation method of the polyethylene naphthalate film with high light transmittance according to claim 1, characterized in that, The solvent is one or two of methanol, ethanol, ethyl acetate and acetone.

5. The preparation method of the polyethylene naphthalate film with high light transmittance according to claim 1, characterized in that, Use one or several of sodium carbonate, sodium bicarbonate, sodium phosphate and disodium hydrogen phosphate to adjust the pH value of the phenylvinyl silicone resin sol to 6-8.

6. The preparation method of the polyethylene naphthalate film with high light transmittance according to claim 1, characterized in that, The high-boiling solvent is one or two of toluene and xylene.

7. The preparation method of the polyethylene naphthalate film with high light transmittance according to claim 1, characterized in that, The baking temperature is 100-140 °C and the time is 60-180 s.

8. A polyethylene naphthalate film with high light transmittance prepared by the preparation method according to any one of claims 1-7, characterized in that, The light transmittance of the film is 94-97% and the haze is 1.9-2.3%.

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