A double-sided release film with a matte effect based on a PET substrate and a preparation method thereof

Abstract

The present invention relates to the technical field of release films, and particularly to a double-sided release film with a matte effect based on a PET substrate and a preparation method thereof. After the PET substrate is pretreated by double-sided corona treatment, pure water cleaning and hot air drying, under nitrogen protection, a copolymer resin and a crosslinking agent are slowly mixed, and then are highly dispersed with a matting agent and a dispersant to obtain a matte release coating. After double-sided coating, gradient curing and constant temperature aging, it is slit and wound to obtain a matte PET double-sided release film. The matte release layer with both a rigid skeleton and hydrophobic microphase separation is formed on the surface of the PET substrate prepared by the present invention, achieving low gloss, stable release force and high residual adhesion rate. At the same time, the coating is endued with high temperature resistance, anti-deformation and anti-humid heat aging properties, significantly reducing the dosage of the matting agent and avoiding agglomeration failure.

Description

Technical Field

[0001] The present invention relates to the technical field of release films, and particularly to a double-sided release film with a matte effect on a PET substrate and a preparation method thereof. Background Art

[0002] Release films are a type of functional films with controllable peeling properties on the surface, widely used in die-cutting processing, electronic device packaging, adhesive protection and other fields. Their core function is to achieve controllable separation from the sticky material through the surface release layer, while protecting the substrate from scratches or contamination during transportation or processing. Traditional release films mostly use PET, PE / PP, etc. as substrates. Among them, the double-sided release film with a PET (polyethylene terephthalate) substrate is a polymer material film coated with silicone oil on the surface, having excellent transparency, mechanical strength, heat resistance, chemical resistance and good processing performance. The matte effect is achieved by special treatment on the surface of the PET substrate, usually including adding special raw materials such as silica into the PET film, and forming a matte layer on the film surface through a specific manufacturing process. The matte layer can significantly reduce the gloss of the film surface, increase the haze, making the film present a soft and non-reflective effect, and has broad application prospects in industries such as electronics, printing, packaging, etc., such as high-grade label production, indoor matte decorative materials, high-grade tobacco and alcohol printing and packaging, etc.

[0003] The invention patent with the patent publication number CN108755255A discloses a transparent PET double-sided antistatic release film and its manufacturing process, including a base paper layer, with laminating layers on both sides, a high-temperature resistant layer on the surface of the laminating layer, a matte layer on one side of the high-temperature resistant layer, a window area formed on the matte layer, and a release agent coating above the matte layer, wherein the matte layer contains silica matting powder. This partial matte high-temperature resistant release paper has strong adhesion, long service life, simple production process and wide application range.

[0004] However, when the matting agent is added in excess, although it can reduce the gloss of the coating to a certain extent and achieve the expected matte effect, it will seriously damage the continuity of the coating, making the surface condition of the coating complex, and then resulting in extremely unstable release force. During actual use, the local release force may suddenly increase or decrease, greatly affecting the quality and performance of the product. Moreover, in a high-temperature environment, the coating is prone to softening and even yellowing, which will not only cause the release force to fail and unable to play its normal role, but also lead to the complete loss of the matte effect, affecting the appearance and quality of the product. In addition, the matting agent itself has the characteristic of easy agglomeration, resulting in the gradual decline of the matte effect of the coating during the long-term storage of the coating, and it is difficult to meet the requirements of continuous and stable quality. Summary of the Invention

[0005] To solve the problems mentioned in the above background technology, the present invention provides a double-sided release film with a matte effect based on a PET substrate and a preparation method thereof.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A preparation method of a double-sided release film with a matte effect based on a PET substrate, comprising the following steps:

[0008] S1. Place the PET substrate into a corona processor, perform double-sided treatment, spray and rinse the surface of the substrate with pure water, and dry it with hot air for 30 - 40 min to obtain a pretreated PET substrate;

[0009] S2. Under nitrogen protection, first add the copolymer resin and the crosslinking agent into the reaction kettle, stir at a low speed for 10 - 20 min, then add the matting agent and the dispersant, stir at a high speed for 30 - 40 min, and filter through a 200-mesh filter screen to obtain a matte release coating;

[0010] S3. Place the pretreated PET substrate and the matte release coating into a coater for double-sided synchronous coating, place it into an oven for curing with three-stage curing, hang and treat it in a constant-temperature aging room for 24 - 48 h, slit and wind it up to obtain a double-sided release film with a matte effect based on a PET substrate.

[0011] Further, in step S1, the frequency of the corona processor is 20 - 30 kHz, the power is 5 - 10 kW, the processing speed is 20 - 30 m / min, the distance between the electrodes is 1.5 - 2.0 mm, and the temperature of the hot air during hot air drying is 50 - 55 °C.

[0012] Further, in step S2, the speed of low-speed stirring is 500 - 600 rpm, and the speed of high-speed stirring is 2000 - 2500 rpm.

[0013] Further, the matte release coating in step S2 comprises, by weight: 100 - 110 parts of copolymer resin, 3.2 - 4.4 parts of crosslinking agent, 3 - 5 parts of matting agent, and 1.2 - 1.5 parts of dispersant, wherein the crosslinking agent includes one of toluene diisocyanate, bisphenol A epoxy resin, and trimethylolpropane triglycidyl ether, the matting agent is silicon dioxide, and the dispersant includes one of BYK - 163, EFKA - 4010, BYK - 111, and KH - 550.

[0014] Further, the copolymer resin in step S2 is prepared by the following steps:

[0015] Maleic anhydride, 2,4-diphenyl-4-methyl-1-pentene and a part of vinyltriphenylsilane are added to a reaction kettle pre-filled with N-methylpyrrolidone. Under the protection of nitrogen, diisopropylbenzene peroxide is added. The temperature is raised for the first time and stirred for 2 - 3 h. Then the remaining vinyltriphenylsilane is added and the temperature is raised for the second time and stirred for 4 - 5 h. After the reaction is completed, it is kept warm for 1 - 2 h, and then the reaction system is cooled down. 0.01 wt% hydroquinone is added to terminate the reaction. The reaction solution is poured into excessive cold methanol for precipitation, and white flocculates are obtained by filtration, washed 3 - 5 times, and dried at 60 °C to constant weight to obtain the copolymer resin.

[0016] Further, in step S3, the coating speed of the coater is 20 - 40 m / min, the wet film thickness is 5.5 - 8 μm on one side, the wire number of the coating roll is 180 - 200 lines / inch, and the depth of the mesh cavity is 5.5 - 8 μm.

[0017] Further, in step S3, the curing in the oven adopts three-stage curing. The curing temperature in the first zone is 80 - 82 °C, the curing time is 2 - 4 s, the curing temperature in the second zone is 130 - 132 °C, the curing time is 5 - 10 s, the curing temperature in the third zone is 160 - 162 °C, the curing time is 8 - 15 s, the temperature in the constant-temperature aging room is 50 - 60 °C, and the humidity < 40%RH.

[0018] Further, the mass ratio of maleic anhydride, 2,4-diphenyl-4-methyl-1-pentene, vinyltriphenylsilane, N-methylpyrrolidone and diisopropylbenzene peroxide is: (115 - 120):(72 - 75):(44 - 46):300:(0.9 - 1.1). Among them, the amount of vinyltriphenylsilane added for the first time is 30 - 40 wt% of the total mass of vinyltriphenylsilane, and the amount added for the second time is 60 - 70 wt% of the total mass of vinyltriphenylsilane.

[0019] Further, the temperature rise for the first time is 118 - 122 °C, the temperature rise for the second time is 138 - 142 °C, the temperature for heat preservation is 128 - 132 °C, and the temperature for cooling is 58 - 62 °C.

[0020] According to another aspect of the present invention, there is provided a PET base material double-sided release film with a matte effect prepared by the above preparation method.

[0021] The beneficial effects of the present invention:

[0022] 1. In the technical solution of the present invention, the main chain of the copolymer resin is formed by the alternating copolymerization of maleic anhydride and 2,4-diphenyl-4-methyl-1-pentene to form a rigid skeleton, and at the same time, vinyltriphenylsilane forms a gradient distribution by stepwise feeding. The polar carboxylic acid groups of maleic anhydride and the benzene ring rigid structure of 2,4-diphenyl-4-methyl-1-pentene inhibit the close stacking of molecular chains, while the hydrophobic triphenylsilyl groups of vinyltriphenylsilane induce microphase separation to form a concavo-convex structure on the coating surface, thereby reducing the proportion of specular reflected light, enhancing diffuse reflection, achieving a certain matte effect, and reducing the use of matting agents such as silica. In addition, the copolymer structure provides uniformly dispersed anchoring sites for the matting agent, further synergistically improving the matting efficiency.

[0023] 2. In the technical solution of the present invention, the triphenylsilyl groups of vinyltriphenylsilane are strongly hydrophobic, and their gradient distribution causes these groups to accumulate on the coating surface to form a low surface energy barrier layer, effectively reducing the adhesion to materials such as adhesives. At the same time, the carboxylic acid groups that can be generated by the hydrolysis of maleic anhydride units can react with crosslinking agents to form a three-dimensional crosslinked network. By regulating the crosslinking density, both the mechanical strength of the coating and the adjustability of the release force can be ensured to meet the diverse application requirements.

[0024] 3. In the technical solution of the present invention, the carboxylic acid groups of maleic anhydride form strong interfacial bonding with the ester groups on the surface of the PET substrate through hydrogen bonding and dipole-dipole interactions, improving the adhesion between the coating and the substrate. In addition, the reaction of the crosslinking agent with the carboxylic acid groups of maleic anhydride generates a covalent bond network, endowing the coating with excellent scratch resistance and tear resistance. The benzene ring rigid structure of the 2,4-diphenyl-4-methyl-1-pentene unit further inhibits the movement of chain segments, enhancing the dimensional stability of the coating and avoiding deformation under high-temperature curing or mechanical stress.

[0025] 4. In the technical solution of the present invention, the benzene ring conjugated structure of 2,4-diphenyl-4-methyl-1-pentene and the triphenylsilyl groups of vinyltriphenylsilane significantly increase the glass transition temperature of the copolymer, enabling it to maintain chain segment rigidity during oven curing and avoiding coating leveling defects caused by thermal relaxation. N-methylpyrrolidone, as a good solvent, ensures that the copolymer molecular chains are fully extended to form a uniform film during coating, guaranteeing the denseness and optical uniformity of the coating.

[0026] 5. In the technical solution of the present invention, the dense barrier formed by the hydrophobic groups of vinyltriphenylsilane on the coating surface can block the penetration of water molecules, delay the hydrolysis aging of the PET substrate, and improve the moisture and heat resistance of the release film. Detailed implementation mode

[0027] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0029] Preparation Example 1

[0030] The copolymer resin is prepared by the following steps:

[0031] 11.75 g of maleic anhydride, 7.35 g of 2,4-diphenyl-4-methyl-1-pentene, and 1.58 g of vinyltriphenylsilane are added to a reaction kettle pre-filled with 30 g of N-methylpyrrolidone. Under nitrogen protection, 0.1 g of diisopropylbenzene peroxide is added. The temperature is first raised to 118 °C and stirred for 2 h. Then, the remaining 2.92 g of vinyltriphenylsilane is added, and the temperature is raised to 138 °C for a second time and stirred for 4 h. After the reaction is completed, the reaction system is kept at 128 °C for 1 h, and then the temperature of the reaction system is lowered to 58 °C. 0.01 wt% hydroquinone is added to terminate the reaction. The reaction solution is poured into an excess of cold methanol for precipitation, and a white flocculent substance is obtained by filtration. It is washed 3 times and dried to a constant weight at 60 °C to obtain the copolymer resin.

[0032] Preparation Example 2

[0033] The copolymer resin is prepared by the following steps:

[0034] 11.5 g of maleic anhydride, 7.2 g of 2,4-diphenyl-4-methyl-1-pentene, and 1.32 g of vinyltriphenylsilane are added to a reaction kettle pre-filled with 30 g of N-methylpyrrolidone. Under nitrogen protection, 0.09 g of diisopropylbenzene peroxide is added. The temperature is first raised to 120 °C and stirred for 2.5 h. Then, the remaining 3.08 g of vinyltriphenylsilane is added, and the temperature is raised to 140 °C for a second time and stirred for 4.5 h. After the reaction is completed, the reaction system is kept at 130 °C for 1.5 h, and then the temperature of the reaction system is lowered to 60 °C. 0.01 wt% hydroquinone is added to terminate the reaction. The reaction solution is poured into an excess of cold methanol for precipitation, and a white flocculent substance is obtained by filtration. It is washed 4 times and dried to a constant weight at 60 °C to obtain the copolymer resin.

[0035] Preparation Example 3

[0036] The copolymer resin is prepared by the following steps:

[0037] 12 g of maleic anhydride, 7.5 g of 2,4-diphenyl-4-methyl-1-pentene, and 1.84 g of vinyltriphenylsilane were added to a reaction kettle pre-filled with 30 g of N-methylpyrrolidone. Under nitrogen protection, 0.11 g of diisopropylbenzene peroxide was added. The temperature was first raised to 122 °C and stirred for 3 h. Then, the remaining 2.76 g of vinyltriphenylsilane was added, and the temperature was raised to 142 °C for a second time and stirred for 5 h. After the reaction ended, it was kept warm at 132 °C for 2 h, and then the reaction system was cooled to 62 °C. 0.01 wt% hydroquinone was added to terminate the reaction. The reaction solution was poured into excessive cold methanol for precipitation, and a white floc was obtained by filtration. It was washed 5 times and dried to a constant weight at 60 °C to obtain a copolymer resin.

[0038] Example 1: A preparation method of a double-sided release film for PET substrate with a matte effect, comprising the following steps:

[0039] S1. The PET substrate was placed into a corona treatment machine. The frequency of the corona treatment machine was 20 kHz, the power was 5 kW, the treatment speed was 20 m / min, the distance between the electrodes was 1.5 mm, and each side was treated 2 times. The surface of the substrate was rinsed with pure water and dried with hot air at 50 °C for 30 min to obtain a pretreated PET substrate.

[0040] S2. Under nitrogen protection, first, 100 parts of the copolymer resin prepared in Preparation Example 1 and 3.2 parts of bisphenol A epoxy resin were added to a reaction kettle, and stirred at a low speed of 500 rpm for 10 min. Then, 3 parts of silica and 1.2 parts of BYK-163 were added, and stirred at a high speed of 2000 rpm for 30 min. It was filtered through a 200-mesh filter screen to obtain a matte release coating.

[0041] S3. The pretreated PET substrate and the matte release coating were placed into a coater for double-sided synchronous coating. The coating speed of the coater was 20 m / min, the wet film thickness was 8 μm on each side, the number of screen lines of the coating roller was 180 lines / inch, and the depth of the mesh cavity was 8 μm. After coating, it was placed into an oven for curing. The curing temperature in the first zone was 80 °C, the curing time was 2 s, the curing temperature in the second zone was 130 °C, the curing time was 5 s, the curing temperature in the third zone was 160 °C, and the curing time was 8 s. It was hung and treated in a constant temperature aging room at 50 °C and 30% RH for 24 h, slit, and wound up to obtain a double-sided release film for PET substrate with a matte effect.

[0042] Example 2: A preparation method of a double-sided release film for PET substrate with a matte effect, comprising the following steps:

[0043] S1. Place the PET substrate into a corona treater. The frequency of the corona treater is 25 kHz, the power is 8 kW, the treatment speed is 25 m / min, the distance between the electrodes is 1.7 mm, and each side is treated twice. Rinse the surface of the substrate with pure water and dry it with hot air at 52 °C for 35 min to obtain a pretreated PET substrate;

[0044] S2. Under nitrogen protection, first add 105 parts of the copolymer resin prepared in Preparation Example 2 and 4 parts of toluene diisocyanate into a reaction kettle, stir at a low speed of 550 rpm for 15 min, then add 4 parts of silica and 1.3 parts of EFKA-4010, and stir at a high speed of 2200 rpm for 35 min. Filter through a 200-mesh sieve to obtain a matte release coating;

[0045] S3. Place the pretreated PET substrate and the matte release coating into a coater for double-sided synchronous coating. The coating speed of the coater is 30 m / min, the wet film thickness is 7 μm on each side, the number of screen lines of the coating roller is 190 lines / inch, and the depth of the mesh holes is 7 μm. After coating, place it into an oven for curing. The curing temperature in the first zone is 81 °C, the curing time is 3 s, the curing temperature in the second zone is 131 °C, the curing time is 7 s, the curing temperature in the third zone is 161 °C, and the curing time is 10 s. Hang and treat it in a constant temperature aging room at 55 °C and 35% RH for 30 h, slit, and wind up to obtain a double-sided release film of PET substrate with a matte effect.

[0046] Example 3: A method for preparing a double-sided release film of PET substrate with a matte effect, comprising the following steps:

[0047] S1. Place the PET substrate into a corona treater. The frequency of the corona treater is 30 kHz, the power is 10 kW, the treatment speed is 30 m / min, the distance between the electrodes is 2.0 mm, and each side is treated twice. Rinse the surface of the substrate with pure water and dry it with hot air at 55 °C for 40 min to obtain a pretreated PET substrate;

[0048] S2. Under nitrogen protection, first add 110 parts of the copolymer resin prepared in Preparation Example 3 and 4.4 parts of trimethylolpropane triglycidyl ether into a reaction kettle, stir at a low speed of 600 rpm for 20 min, then add 5 parts of silica and 1.5 parts of BYK-111, and stir at a high speed of 2500 rpm for 40 min. Filter through a 200-mesh sieve to obtain a matte release coating;

[0049] S3. Place the pre-treated PET substrate and the matte release coating into a coater for double-sided synchronous coating. The coating speed of the coater is 40 m / min, the wet film thickness is 5.5 μm on each side, the number of lines of the coating roller is 200 lines / inch, the depth of the mesh cavity is 5.5 μm. After coating, place it into an oven for curing. The curing temperature in the first zone is 82 °C, the curing time is 4 s, the curing temperature in the second zone is 132 °C, the curing time is 10 s, the curing temperature in the third zone is 162 °C, the curing time is 15 s. Hang and process in a constant temperature aging room at 60 °C and 38% RH for 48 h, slit, and wind up to obtain a double-sided release film of PET substrate with a matte effect.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 1 is that 2,4-diphenyl-4-methyl-1-pentene is used to replace the copolymer resin prepared in Preparation Example 1, and the remaining steps are the same as those in Example 1.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 2 is that vinyltriphenylsilane is used to replace the copolymer resin prepared in Preparation Example 2, and the remaining steps are the same as those in Example 2.

[0054] Comparative Example 3

[0055] The difference between this comparative example and Example 3 is that maleic anhydride is used to replace the copolymer resin prepared in Preparation Example 3, and the remaining steps are the same as those in Example 3.

[0056] Comparative Example 4

[0057] The difference between this comparative example and Example 1 is that an acrylic resin is used to replace the copolymer resin prepared in Preparation Example 1, and the remaining steps are the same as those in Example 1.

[0058] Place the release film samples prepared in Examples 1 - 3 and Comparative Examples 1 - 4 into a constant temperature and humidity chamber at 23 °C and 50% RH for 24 h. Cut the 3M 9080 tape into 25 mm wide × 200 mm long, attach it to the surface of the release film to ensure no bubbles, roll it back and forth 3 times with a 2 kg pressure roller at a speed of 10 mm / s, and let it stand for 20 min after attachment. Fix the sample on the test machine fixture, with a peeling angle of 180°, a peeling speed of 300 mm / min, record the release force (F0, N / 25 mm) during the peeling process, measure 5 points for each sample, and take the average value. Reattach the peeled tape to the stainless steel plate and test its adhesion (F1) under the same conditions, and calculate the residual adhesion rate. Residual adhesion rate = (F1 / F0) × 100%. The results are shown in Table 1:

[0059]

[0060] Referring to ASTM D523-2014 "Standard Test Method for Specular Gloss", the surface gloss of the release film samples prepared in Examples 1-3 and Comparative Examples 1-4 was tested. Using a glossmeter with an incident angle of 60°, 10 points were randomly selected on the surface of the release film to measure the gloss (GU value). Excluding the highest and lowest values, the average of the remaining 8 points was taken as the final result. The results are shown in Table 2:

[0061]

[0062] As can be seen from Table 1, the release forces of Examples 1-3 were 0.14±0.03 N / 25 mm, 0.16±0.02 N / 25 mm, and 0.12±0.04 N / 25 mm, respectively, and the residual adhesion rates were 93.5±1.2%, 92.1±1.5%, and 94.7±0.9%, respectively. The release forces of Comparative Examples 1-4 were significantly higher than those of the examples, and the residual adhesion rates were significantly lower than those of the examples. This shows that the release film prepared with the copolymer resin obtained in the Preparation Example has a lower release force and a higher residual adhesion rate, and can better balance the release performance and the re-adhesion performance of the tape.

[0063] In Comparative Example 1, 2,4-diphenyl-4-methyl-1-pentene was used to replace the copolymer resin. In Comparative Example 2, vinyltriphenylsilane was used to replace it. In Comparative Example 3, maleic anhydride was used to replace it. In Comparative Example 4, an acrylic resin was used to replace it. From the data of the release force and the residual adhesion rate, it can be seen that after different monomers or resins replace the copolymer resin, the performance of the release film has decreased to varying degrees. This shows that the copolymer resin obtained in the Preparation Example may have unique advantages in preparing a release film with a suitable release force and a high residual adhesion rate, and cannot be replaced by a single monomer or other resins.

[0064] As can be seen from Table 2, the surface gloss of Examples 1-3 all showed a relatively low gloss, presenting a matte effect, while the surface gloss of Comparative Examples 1-4 was significantly higher than that of the examples. This shows that the copolymer resin obtained in the Preparation Example has a significant effect in preparing a matte release film, can effectively reduce the surface gloss of the release film, and meet the requirements of the matte effect.

[0065] After using different substances to replace the copolymer resin in different comparative examples, the surface gloss has increased significantly. This further proves that the copolymer resin obtained in the Preparation Example plays a key role in achieving the matte effect of the release film, and other monomers or resins cannot endow the release film with ideal matte characteristics.

[0066] In summary, the copolymer resin prepared in the Preparation Example has obvious advantages in preparing a double-sided release film of a PET substrate with a matte effect. Through a specific copolymer resin formulation and preparation process, a release film with moderate release force, high residual adhesion rate and low surface gloss can be prepared, meeting the requirements for the performance of the release film in specific application scenarios.

[0067] In the description of the specification, the descriptions referring to terms such as "Preparation Example", "Example", "each Example", etc. mean that the specific features, structures, materials or characteristics described in connection with that Example or Preparation Example are included in at least one Example or Preparation Example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same Example or Preparation Example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more Examples or Preparation Examples.

[0068] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A preparation method of a double-sided release film with a matte effect based on a PET substrate, characterized in that, It includes the following steps: S1. Place the PET substrate into a corona processor for double-sided treatment. Rinse the surface of the substrate with pure water and dry it with hot air for 30 - 40 min to obtain a pretreated PET substrate; S2. Under nitrogen protection, first add the copolymer resin and the crosslinking agent into a reaction kettle, stir at a low speed for 10 - 20 min, then add the matting agent and the dispersant, stir at a high speed for 30 - 40 min, and filter through a 200 - mesh sieve to obtain a matte release coating; S3. Place the pretreated PET substrate and the matte release coating into a coater for double-sided synchronous coating, place it in an oven for curing with three-stage curing, hang it in a constant-temperature aging room for 24 - 48 h, slit it, and wind it up to obtain a double-sided matte PET substrate release film; Among them, the copolymer resin in step S2 is prepared by the following steps: Add maleic anhydride, 2,4 - diphenyl - 4 - methyl - 1 - pentene, and a part of vinyltriphenylsilane into a reaction kettle pre-filled with N - methylpyrrolidone. Under nitrogen protection, add diisopropylbenzene peroxide, raise the temperature for the first time and stir for 2 - 3 h, then add the remaining vinyltriphenylsilane, raise the temperature for the second time and stir for 4 - 5 h. After the reaction is completed, keep it warm for 1 - 2 h, then cool down the reaction system to terminate the reaction. Pour the reaction solution into cold methanol for precipitation, filter, wash, and dry to obtain the copolymer resin; The mass ratio of maleic anhydride, 2,4 - diphenyl - 4 - methyl - 1 - pentene, vinyltriphenylsilane, N - methylpyrrolidone, and diisopropylbenzene peroxide is: (115 - 120) : (72 - 75) : (44 - 46) : 300 : (0.9 - 1.1). Among them, the amount of vinyltriphenylsilane added for the first time is 30 - 40 wt% of the total mass of vinyltriphenylsilane, and the amount added for the second time is 60 - 70 wt% of the total mass of vinyltriphenylsilane; The temperature for the first temperature rise is 118 - 122 °C, the temperature for the second temperature rise is 138 - 142 °C, the temperature for heat preservation is 128 - 132 °C, and the temperature for cooling is 58 - 62 °C.

2. The preparation method of a double-sided release film of a PET substrate with a matte effect according to claim 1, characterized in that, In step S1, the frequency of the corona processor is 20 - 30 kHz, the power is 5 - 10 kW, the processing speed is 20 - 30 m / min, the distance between the electrodes is 1.5 - 2.0 mm, and the temperature of the hot air in the hot air drying is 50 - 55 °C.

3. The preparation method of a double-sided release film of a PET substrate with a matte effect according to claim 1, characterized in that, In step S2, the speed of the low-speed stirring is 500 - 600 rpm, and the speed of the high-speed stirring is 2000 - 2500 rpm.

4. The preparation method of a double-sided release film of a PET substrate with a matte effect according to claim 1, characterized in that, In step S2, the matte release coating includes, by weight: 100 - 110 parts of copolymer resin, 3.2 - 4.4 parts of crosslinking agent, 3 - 5 parts of matting agent, and 1.2 - 1.5 parts of dispersant. Among them, the crosslinking agent includes one of toluene diisocyanate, bisphenol A epoxy resin, and trimethylolpropane triglycidyl ether, the matting agent is silica, and the dispersant includes one of BYK - 163, EFKA - 4010, BYK - 111, and KH - 550.

5. The preparation method of a double-sided release film made of PET substrate with a matte effect according to claim 1, characterized in that, In step S3, the coating speed of the coater is 20 - 40 m / min, the wet film thickness is 5.5 - 8 μm on one side, the number of screen lines of the coating roll is 180 - 200 lines / inch, and the depth of the mesh cavity is 5.5 - 8 μm.

6. The preparation method of a double-sided release film of a PET substrate with a matte effect according to claim 1, wherein, In step S3, three-stage curing is used for curing in the oven. The curing temperature in the first zone is 80 - 82 °C, and the curing time is 2 - 4 s. The curing temperature in the second zone is 130 - 132 °C, and the curing time is 5 - 10 s. The curing temperature in the third zone is 160 - 162 °C, and the curing time is 8 - 15 s. The temperature of the constant-temperature aging chamber is 50 - 60 °C, and the humidity < 40%RH.

7. A matte-effect PET substrate double-sided release film prepared by the preparation method according to any one of claims 1 - 6.

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