A coating for release films, its preparation method and application

Abstract

This invention relates to the field of coating technology, specifically to a release film coating, its preparation method, and its application. This coating aims to solve the problem that existing addition-type silicone release coatings struggle to simultaneously ensure coating continuity, peel strength stability, and low migration at ultra-low dry coating weights. It employs a divinyl component composed of vinyl-terminated polydimethylsiloxane and a vinylmethylsiloxane-dimethylsiloxane copolymer, combined with hydrogen-terminated and methyl hydrogen-terminated disiloxane components, through a specific stepwise and sequential addition process, synergistically optimizing the coating's spreading, crosslinking, and defect repair processes. Simultaneously, the introduced epoxy silane coupling agent enhances interfacial bonding. This approach enables the prepared release film to achieve a peel strength of 50-80 mg / m³. 2 Even with an ultra-low coating amount, it still has moderate release force, excellent stability after thermal aging and peeling, low extraction rate and high residual adhesion.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a release film coating, its preparation method, and its application. Background Technology

[0002] In applications such as optical protection, tapes, and labels, release films serve as a crucial auxiliary material. Their core function is to provide stable and moderate peel force while protecting the pressure-sensitive adhesive layer. With the trend towards thinner and lighter electronic products and increasingly stringent environmental requirements, reducing the dry coating weight of release films has become a clear technological trend. However, when the dry coating weight is reduced to 80 mg / m³... 2 Even 60mg / m 2 At the following ultra-low levels, the continuous film formation, interface uniformity, and long-term stability of the coating system are severely challenged.

[0003] Conventional addition-type silicone release systems typically employ a single type of vinyl polysiloxane reacting with a crosslinking agent containing silane-hydrogen bonds. At extremely low coating weights, the coating thickness decreases drastically. This simple system struggles to form a complete, dense, and uniform crosslinked network on the substrate surface, easily leading to poor local coverage or microscopic defects. This results in increased release force fluctuations and may cause adhesive penetration or contamination due to coating discontinuity.

[0004] To improve performance under low coating weights, existing technologies attempt to introduce polysiloxanes with vinyl-containing side chains to increase the density of reaction sites. However, simply blending different vinyl components has limited synergistic effects and cannot accurately address the dynamic balance between early film spreading and late-stage defect repair during curing. Similarly, regarding crosslinking agents, if silicon-hydrogen bond-containing components with different structures are added through simple mixing, the network construction process is difficult to control in an orderly manner, potentially leading to localized over-density or under-density of the crosslinked network, affecting the mechanical uniformity of the coating.

[0005] The aforementioned problems are interconnected, often presenting a dilemma for release films with ultra-low coating weights: increasing crosslinking density to ensure continuous coverage can lead to increased release force, coating brittleness, and potentially affect post-aging peel stability due to stress concentration; conversely, maintaining moderate release force and flexibility may sacrifice network density, increasing the risk of low-molecular-weight substance migration and contaminating the adhesive, resulting in decreased residual adhesion. Therefore, developing a release coating system that can simultaneously achieve continuous film formation, moderate and stable release force, excellent aging stability, and low migration characteristics under ultra-low coating weights has become a critical technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a release film coating, its preparation method and application, in order to solve the technical problem that existing addition-type silicone release coatings are difficult to simultaneously ensure coating continuity and integrity, moderate and stable peel force, excellent post-heat aging re-peel stability and low migration under ultra-low dry coating weight.

[0007] To achieve the above objectives, the present invention provides a release film coating, which is prepared from the following components in parts by mass: The main spreading phase comprises 3800-4000 parts of anhydrous n-heptane, 900-1050 parts of ethyl acetate, 65-82 parts of vinyl-terminated polydimethylsiloxane, 14-22 parts of vinylmethylsiloxane-dimethylsiloxane copolymer and 2-4 parts of 3-glycidyl etheroxypropyltrimethoxysilane. A repair phase premix comprising 8-14 parts vinylmethylsiloxane-dimethylsiloxane copolymer and 0.8-1.2 parts hydrogen-terminated polydimethylsiloxane; and After the main spreading phase is added to the repair phase premix, 0.8-1.4 parts of methylhydrosiloxane-dimethylsiloxane copolymer and 8-12 parts of platinum catalyst dilution are added.

[0008] Preferably, the platinum catalyst diluent is obtained by mixing a platinum-divinyltetramethyldisiloxane complex xylene solution with anhydrous n-heptane at a mass ratio of 1:99.

[0009] Preferably, the repair phase premix is ​​added to the main spreading phase within 3-8 minutes, the methylhydrosiloxane-dimethylsiloxane copolymer is added after the repair phase premix is ​​added and mixed, and the platinum catalyst diluent is added after the methylhydrosiloxane-dimethylsiloxane copolymer is added.

[0010] Preferably, the release membrane coating is obtained by filtration through a 1μm polytetrafluoroethylene filter membrane.

[0011] Preferably, the vinyl-terminated polydimethylsiloxane is of type DMS-V42; the vinylmethylsiloxane-dimethylsiloxane copolymer is of type VDT-123; the hydrogen-terminated polydimethylsiloxane is of type DMS-H05; and the methylhydrosiloxane-dimethylsiloxane copolymer is of type HMS-301.

[0012] Furthermore, the present invention also provides a method for preparing a coating for release films, comprising the following steps: S1. Anhydrous n-heptane, ethyl acetate, vinyl-terminated polydimethylsiloxane, a portion of vinylmethylsiloxane-dimethylsiloxane copolymer and 3-glycidoxypropyltrimethoxysilane are mixed to obtain the main spreading phase; S2. Mix the remaining vinylmethylsiloxane-dimethylsiloxane copolymer with hydrogen-terminated polydimethylsiloxane to obtain a repair phase premix; S3. Add the repair phase premix to the main spreading phase, mix, and then add methylhydrosiloxane-dimethylsiloxane copolymer to obtain the coating solution to be catalyzed. S4. Add platinum catalyst dilution to the coating solution to be catalyzed, filter, and obtain a coating for release film.

[0013] Furthermore, the present invention also provides an application of a release film coating for preparing release films.

[0014] Preferably, the release film includes a polyester base film and a release layer disposed on the surface of the polyester base film, wherein the release layer is formed by curing a release film coating.

[0015] Preferably, the polyester base film is a biaxially oriented polyester film with a thickness of 50 μm.

[0016] Preferably, the polyester-based film is corona-treated, and the surface tension of the corona-treated film is 50-54 mN / m.

[0017] Preferably, the dry coating weight of the release layer is 50-80 mg / m². 2 .

[0018] Preferably, the preparation of the release film includes: coating the release film with a coating material onto the surface of a corona-treated polyester base film; heating and curing the coated wet film at 90-100℃ for 10-15s, then heating and curing at 145-155℃ for 25-30s, followed by cooling, and then curing in an environment of 20-30℃ and 40%-50% relative humidity for 16-24h to obtain the release film.

[0019] The beneficial effects of this invention are: This invention employs a specific vinyl-terminated polydimethylsiloxane and vinylmethylsiloxane-dimethylsiloxane copolymer bivinyl component system, combined with a time-phased addition process, to effectively synergistically enhance the coating's initial spreading and defect repair functions during curing. This design enables the coating to form a continuous and uniform release interface even at ultra-low coating weights, thereby significantly reducing release force fluctuations and achieving moderate initial peel strength.

[0020] By employing a dual-siloxane system composed of hydrogen-terminated polydimethylsiloxane and methylhydrosiloxane-dimethylsiloxane copolymer, and controlling the order of their addition, an ordered division of labor in crosslinking network construction was achieved. The first addition of hydrogen-terminated polydimethylsiloxane facilitates the formation of a flexible main chain connection, while the subsequent addition of methylhydrosiloxane-dimethylsiloxane copolymer effectively constructs uniform crosslinking nodes. This sequential crosslinking strategy results in a silicone rubber network that possesses both good flexibility and structural density, thereby significantly improving the release film's re-peel stability after thermal aging.

[0021] The epoxy silane coupling agent introduced into the system enhances the interfacial adhesion between the silicone coating and the polyester base film. This strong anchoring effect not only improves the adhesion of the coating to the substrate but also effectively binds migratable low-molecular-weight siloxane components, significantly reducing the extract content. This effect directly translates into minimizing subsequent adhesive contamination, allowing the adhesive tape to maintain extremely high residual adhesion and holding power even after being protected by this release film.

[0022] In summary, the solution of this invention achieves an excellent balance between release performance, aging stability and low migration characteristics under the harsh condition of ultra-low dry coating amount through precise design of the functions of each component and optimized control of the addition sequence, significantly broadening the process window and improving product reliability. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0024] The raw materials used are as follows: vinyl-terminated polydimethylsiloxane, Gelest, model DMS-V42; vinylmethylsiloxane-dimethylsiloxane copolymer, Gelest, model VDT-123; hydrogen-terminated polydimethylsiloxane, Gelest, model DMS-H05; methylhydrosiloxane-dimethylsiloxane copolymer, Gelest, model HMS-301; the platinum catalyst diluent was prepared by mixing 1g of platinum-divinyltetramethyldisiloxane complex xylene solution, Gelest, model SIP6831.2LC, with 99g of anhydrous n-heptane; the substrate is a 50μm thick biaxially oriented polyester film, Toray Lumirror standard grade T60.

[0025] Example 1:

[0026] Step S1: Add 3880g anhydrous n-heptane, 1000g ethyl acetate, 75g vinyl-terminated polydimethylsiloxane, 18g vinylmethylsiloxane-dimethylsiloxane copolymer and 3g 3-glycidoxypropyltrimethoxysilane to a dry container, and stir at 500rpm for 30min at 25℃ to obtain the main spreading phase; Step S2: Take another dry container, add 12g of vinylmethylsiloxane-dimethylsiloxane copolymer and 1g of hydrogen-terminated polydimethylsiloxane, and stir at 300rpm for 10min at 25℃ to obtain the repair phase premix. Step S3: Add the repair phase premix to the main spreading phase within 5 min, stir at 400 rpm for 10 min at 25℃, then add 1 g of methylhydrosiloxane-dimethylsiloxane copolymer, and stir at 400 rpm for 5 min to obtain the catalytic coating solution. Step S4: Add 10g of platinum catalyst dilution to the coating solution to be catalyzed, stir at 300rpm for 2min at 25℃, and then immediately filter through a 1μm polytetrafluoroethylene filter membrane to obtain the coating for release membrane. Step S5: Apply the release film coating to the surface of the polyester base film, which has been corona-treated to 52 mN / m, with the wet coating amount controlled at 2.8 g / m. 2 The coated wet film is first heated and cured at 95℃ for 12s, then heated and cured at 150℃ for 28s, then cooled, and then cured at 25℃ and 45% relative humidity for 24h to obtain a release film.

[0027] Example 2:

[0028] Step S1: Add 3930g anhydrous n-heptane, 950g ethyl acetate, 72g vinyl-terminated polydimethylsiloxane, 20g vinylmethylsiloxane-dimethylsiloxane copolymer and 2g 3-glycidoxypropyltrimethoxysilane to a dry container, and stir at 500rpm for 25min at 25℃ to obtain the main spreading phase; Step S2: Take another dry container, add 14g of vinylmethylsiloxane-dimethylsiloxane copolymer and 1g of hydrogen-terminated polydimethylsiloxane, and stir at 300rpm for 10min at 25℃ to obtain the repair phase premix. Step S3: Add the repair phase premix to the main spreading phase within 5 min, stir at 400 rpm for 10 min at 25℃, then add 1 g of methylhydrosiloxane-dimethylsiloxane copolymer, and stir at 400 rpm for 5 min to obtain the catalytic coating solution. Step S4: Add 10g of platinum catalyst dilution to the coating solution to be catalyzed, stir at 300rpm for 2min at 25℃, and then immediately filter through a 1μm polytetrafluoroethylene filter membrane to obtain the coating for release membrane. Step S5: Apply the release film coating to the surface of the polyester base film, which has been corona-treated to 50 mN / m, with the wet coating amount controlled at 2.6 g / m. 2 The coated wet film is first heated and cured at 90℃ for 15s, then heated and cured at 150℃ for 30s, then cooled, and then aged at 20℃ and 40% relative humidity for 24h to obtain a release film.

[0029] Example 3:

[0030] Step S1: Add 3800g anhydrous n-heptane, 1050g ethyl acetate, 65g vinyl-terminated polydimethylsiloxane, 14g vinylmethylsiloxane-dimethylsiloxane copolymer and 4g 3-glycidoxypropyltrimethoxysilane to a dry container, and stir at 550rpm for 30min at 25℃ to obtain the main spreading phase; Step S2: Take another dry container, add 10g of vinylmethylsiloxane-dimethylsiloxane copolymer and 0.8g of hydrogen-terminated polydimethylsiloxane, and stir at 350rpm for 8min at 25℃ to obtain the repair phase premix; Step S3: Add the repair phase premix to the main spreading phase within 4 min, stir at 450 rpm for 8 min at 25℃, then add 1 g of methylhydrosiloxane-dimethylsiloxane copolymer, and stir at 450 rpm for 4 min to obtain the catalytic coating solution. Step S4: Add 12g of platinum catalyst dilution to the coating solution to be catalyzed, stir at 350rpm for 1min at 25℃, and then immediately filter through a 1μm polytetrafluoroethylene filter membrane to obtain the coating for release membrane. Step S5: Apply the release film coating to the surface of the polyester base film, which has been corona-treated to 54 mN / m, with the wet coating amount controlled at 2.9 g / m. 2 The coated wet film is first heated and cured at 100℃ for 10 seconds, then heated and cured at 145℃ for 30 seconds, then cooled, and then aged at 30℃ and 50% relative humidity for 18 hours to obtain a release film.

[0031] Example 4:

[0032] Step S1: Add 3880g anhydrous n-heptane, 1000g ethyl acetate, 78g vinyl-terminated polydimethylsiloxane, 18g vinylmethylsiloxane-dimethylsiloxane copolymer and 3g 3-glycidoxypropyltrimethoxysilane to a dry container, and stir at 450rpm for 35min at 25℃ to obtain the main spreading phase; Step S2: Take another dry container, add 10g of vinylmethylsiloxane-dimethylsiloxane copolymer and 1.2g of hydrogen-terminated polydimethylsiloxane, and stir at 250rpm for 12min at 25℃ to obtain the repair phase premix; Step S3: Add the repair phase premix to the main spreading phase within 6 min, stir at 350 rpm for 12 min at 25 °C, then add 0.8 g of methylhydrosiloxane-dimethylsiloxane copolymer, and stir at 350 rpm for 6 min to obtain the catalytic coating solution. Step S4: Add 8g of platinum catalyst dilution to the coating solution to be catalyzed, stir at 250rpm for 3min at 25℃, and then immediately filter through a 1μm polytetrafluoroethylene filter membrane to obtain the coating for release membrane. Step S5: Apply the release film coating to the surface of the polyester base film, which has been corona-treated to 52 mN / m, with a wet coating amount controlled at 3.0 g / m. 2 The coated wet film is first heated and cured at 95℃ for 12 seconds, then heated and cured at 155℃ for 25 seconds, then cooled, and then aged at 25℃ and 45% relative humidity for 24 hours to obtain a release film.

[0033] Example 5:

[0034] Step S1: Add 4000g anhydrous n-heptane, 900g ethyl acetate, 82g vinyl-terminated polydimethylsiloxane, 16g vinylmethylsiloxane-dimethylsiloxane copolymer and 3g 3-glycidoxypropyltrimethoxysilane to a dry container, and stir at 600rpm for 20min at 25℃ to obtain the main spreading phase; Step S2: Take another dry container, add 8g of vinylmethylsiloxane-dimethylsiloxane copolymer and 1g of hydrogen-terminated polydimethylsiloxane, and stir at 300rpm for 9min at 25℃ to obtain the repair phase premix. Step S3: Add the repair phase premix to the main spreading phase within 3 min, stir at 420 rpm for 9 min at 25℃, then add 1 g of methylhydrosiloxane-dimethylsiloxane copolymer, and stir at 420 rpm for 4 min to obtain the catalytic coating solution. Step S4: Add 10g of platinum catalyst dilution to the coating solution to be catalyzed, stir at 320rpm for 2min at 25℃, and then immediately filter through a 1μm polytetrafluoroethylene filter membrane to obtain the coating for release membrane. Step S5: Apply the release film coating to the surface of the polyester base film, which has been corona-treated to 51 mN / m, with the wet coating amount controlled at 2.7 g / m. 2The coated wet film was first heated and cured at 92℃ for 14s, then heated and cured at 152℃ for 26s, then cooled, and then aged at 22℃ and 42% relative humidity for 20h to obtain a release film.

[0035] Example 6:

[0036] Step S1: Add 3897.6g of anhydrous n-heptane, 980g of ethyl acetate, 70g of vinyl-terminated polydimethylsiloxane, 22g of vinylmethylsiloxane-dimethylsiloxane copolymer and 4g of 3-glycidoxypropyltrimethoxysilane to a dry container, and stir at 400rpm for 28min at 25℃ to obtain the main spreading phase; Step S2: Take another dry container, add 14g of vinylmethylsiloxane-dimethylsiloxane copolymer and 1g of hydrogen-terminated polydimethylsiloxane, and stir at 320rpm for 11min at 25℃ to obtain the repair phase premix. Step S3: Add the repair phase premix to the main spreading phase within 8 min, stir at 380 rpm for 11 min at 25°C, then add 1.4 g of methylhydrosiloxane-dimethylsiloxane copolymer, and stir at 380 rpm for 5 min to obtain the catalytic coating solution. Step S4: Add 10g of platinum catalyst dilution to the coating solution to be catalyzed, stir at 280rpm for 2min at 25℃, and then immediately filter through a 1μm polytetrafluoroethylene filter membrane to obtain the coating for release membrane. Step S5: Apply the release film coating to the surface of the polyester base film, which has been corona-treated to 53 mN / m, with the wet coating amount controlled at 2.8 g / m. 2 The coated wet film was first heated and cured at 98℃ for 11 seconds, then heated and cured at 148℃ for 29 seconds, then cooled, and then aged at 28℃ and 48% relative humidity for 16 hours to obtain a release film.

[0037] Comparative Example 1: The difference from Example 1 is that: in step S1, the amount of vinyl-terminated polydimethylsiloxane added is changed to 105g, and the vinylmethylsiloxane-dimethylsiloxane copolymer is no longer added; in step S2, the amount of hydrogen-terminated polydimethylsiloxane added is changed to 0.48g; in step S3, the amount of methylhydrosiloxane-dimethylsiloxane copolymer added is changed to 0.48g; the other conditions are the same as in Example 1.

[0038] Comparative Example 2: The difference from Example 1 is that the amount of vinylmethylsiloxane-dimethylsiloxane copolymer added in step S1 is changed to 30g, and vinylmethylsiloxane-dimethylsiloxane copolymer is no longer added in step S2; the other conditions are the same as in Example 1.

[0039] Comparative Example 3: The difference from Example 1 is that vinylmethylsiloxane-dimethylsiloxane copolymer is no longer added in step S1, and the amount of vinylmethylsiloxane-dimethylsiloxane copolymer added in step S2 is changed to 30g; the other conditions are the same as in Example 1.

[0040] Comparative Example 4: The difference from Example 1 is that hydrogen-terminated polydimethylsiloxane is not added in step S2, and the amount of methylhydrosiloxane-dimethylsiloxane copolymer added in step S3 is changed to 1.75g ​​so that the total silane equivalent is basically the same as in Example 1; the other conditions are the same as in Example 1.

[0041] Comparative Example 5: The difference from Example 1 is that the amount of hydrogen-capped polydimethylsiloxane added in step S2 is changed to 2.33g, and the methylhydrosiloxane-dimethylsiloxane copolymer is not added in step S3, so that the total silane equivalent is basically the same as that in Example 1; the other conditions are the same as those in Example 1.

[0042] Comparative Example 6: The difference from Example 1 is that: in step S2, 12g of vinylmethylsiloxane-dimethylsiloxane copolymer and 1g of methylhydrosiloxane-dimethylsiloxane copolymer are added, and in step S3, 1g of hydrogen-terminated polydimethylsiloxane is added later; the other conditions are the same as in Example 1.

[0043] Comparative Example 7: The difference from Example 1 is that the amount of hydrogen-capped polydimethylsiloxane added in step S2 is changed to 0.1g, and the amount of methylhydrosiloxane-dimethylsiloxane copolymer added in step S3 is still 1g; the other conditions are the same as in Example 1.

[0044] Comparative Example 8: The difference from Example 1 is that the amount of hydrogen-capped polydimethylsiloxane added in step S2 is changed to 1.5g, and the amount of methylhydrosiloxane-dimethylsiloxane copolymer added in step S3 is changed to 1.4g; the other conditions are the same as in Example 1.

[0045] Sample preparation process before performance testing: Release film coatings obtained in Examples 1-6 and Comparative Examples 1-8 were used to coat a 50μm thick polyester film on one side using the same laboratory precision coating machine. The coating line speed was controlled at 10m / min, and the wet coating amount was controlled according to the set values ​​of each example or comparative example. After coating, the film was cured sequentially through two hot air drying tunnels. The temperature and dwell time of the first tunnel and the temperature and dwell time of the second tunnel were performed according to the corresponding examples or comparative examples. After curing, the film was cooled, rolled up, and placed under the corresponding curing conditions. The dry coating amount of the samples was controlled at 50-80mg / m³ after weighing and conversion.2 Within the specified range, the test tape used for release performance, residual tack, and heavy peel stability testing is uniformly tesa 7475 PV2. Before testing, all samples were placed in a standard environment at 23℃±2℃ and 50%±5% relative humidity for 24 hours. Release film samples were uniformly cut to 175mm×25mm, contact angle samples to 50mm×50mm, extraction samples to 100mm×100mm, and tackiness samples to 75mm×25mm.

[0046] Water contact angle test: Performed according to GB / T 30693-2014 "Measurement of water contact angle of plastic film". Cut each release film into 50mm×50mm samples. Before testing, blow off surface dust with clean air; do not wipe. Use a contact angle meter to inject a drop of 2.0μL deionized water, and read the static contact angle 5 seconds after the drop falls. Select 5 evenly spaced positions along the width of each sample, and test each position 3 times. Take the average of 15 measurements.

[0047] Extraction rate test: The extraction rate was determined according to the principles of weighing, constant temperature extraction, drying, and result calculation in GB / T 37193-2018 "Method for Determination of Extraction Rate of Polyethylene Terephthalate (PET) Films with Optical Functional Films". Each sample was cut into 100mm × 100mm specimens, and the area and initial mass m1 were accurately recorded. The specimens were immersed in a stoppered glass bottle containing ethyl acetate, with a liquid-to-solid ratio controlled at 20mL / g, and extracted at a constant temperature of 50℃ for 2 hours. After extraction, the specimens were quickly rinsed with fresh ethyl acetate and dried in a vacuum drying oven at 60℃ until constant weight. The dried mass m2 was weighed, and the extraction rate was calculated as (m1-m2) / m1 × 100%. Each sample was tested in triplicate.

[0048] 180° release force and release force fluctuation test: The test was conducted according to GB / T 25256-2010 "Test Method for 180° Peel Force and Residual Adhesion of Release Films for Optical Functional Films". Release film samples were cut to 175mm × 25mm, and test tape of the same size was used. After the test tape was applied to the release surface, it was rolled twice back and forth with a 2kg roller at a speed of 300mm / min, and then placed for 20 hours at 23℃±2℃ and 50%±5% relative humidity. Subsequently, a 180° peel was performed on an electronic tensile testing machine at a peel speed of 300mm / min. The average peel force of the middle 100mm stable peel section was recorded, and the result is expressed as mN / 25mm. Five parallel tests were conducted on each sample, and the coefficient of variation of the five results was calculated as the release force fluctuation index.

[0049] Residual adhesion rate test: The test was conducted according to GB / T 25256-2010 "Test Method for 180° Peel Force and Residual Adhesion Rate of Release Films for Optical Functional Films". After peeling, the test tape peeled from the release film was immediately attached to the surface of a stainless steel test plate treated according to GB / T 2792-2014. A 2kg roller was used to roll the tape back and forth twice at a speed of 300mm / min. After being placed at 23℃±2℃ and 50%±5% relative humidity for 20 minutes, the peel force against the stainless steel test plate was measured at 180° and 300mm / min, and recorded as F1. Another test tape from the same batch, which had not been in contact with the release film, was also measured using the same procedure, and its peel force against the stainless steel test plate was recorded as F0. The residual adhesion rate was calculated as F1 / F0×100%. Each sample was tested in parallel five times.

[0050] Re-peel stability test after thermal aging: Samples were prepared according to the bonding and peeling geometry conditions specified in GB / T 25256-2010 "Test Method for 180° Peel Force and Residual Adhesion of Release Films for Optical Functional Films". After the test tape was bonded to the release surface of each sample, it was rolled twice back and forth at 300 mm / min using a 2 kg roller, and then aged in a 70℃ oven for 24 h. After removal, it was equilibrated for 2 h in an environment of 23℃±2℃ and 50%±5% relative humidity, and the release force after the first aging was measured at 180° and 300 mm / min. Subsequently, the same batch of test tape was re-bonded to the untested area of ​​the same sample, and the above aging and peeling steps were repeated to obtain the release force after the second aging. The re-peel retention rate was calculated as (second aging release force / first aging release force) × 100%.

[0051] Initial tack test: The test was conducted according to GB / T 4852-2002 "Test Method for Initial Tack of Pressure-Sensitive Adhesive Tapes (Rolling Ball Method)". The test tape, after release from the release film, was used as the sample and fixed to the inclined rolling ball plate according to the standard method. Both the steel ball and the sample were placed at 23℃±2℃ and 50%±5% relative humidity for 2 hours before testing. The largest steel ball number that allowed the steel ball to adhere to the sample adhesive surface for a distance not exceeding 25mm was recorded. Each sample was tested three times, and the mode was taken as the result.

[0052] Holding power test: The test was conducted according to GB / T 4851-2014, "Test Method for Holding Power of Adhesive Tapes". The test tape, after release from the release film, was cut into 25mm × 75mm pieces and attached to a stainless steel test plate treated according to GB / T 4851-2014, with a bonding area of ​​25mm × 25mm. A 2kg roller was used to roll the tape back and forth twice at a speed of 300mm / min. The tape was then allowed to stand for 20 minutes at 23℃±2℃ and 50%±5% relative humidity. A 1kg weight was then suspended from the free end, and the time required for the tape to completely slide off or detach from the test plate was recorded. Results were expressed in minutes; values ​​exceeding 10,000 minutes were recorded as 10,000 minutes. Each sample was tested in triplicate, and the average value was taken.

[0053] Data Analysis: As can be seen from the data in Table 1, the release film prepared by this invention maintains a high water contact angle, low extraction rate, small release force fluctuation, and high residual adhesion and re-peel retention rate even under ultra-low dry coating conditions. This may be because vinyl-terminated polydimethylsiloxane provides good surface migration ability and low surface energy, while the vinylmethylsiloxane-dimethylsiloxane copolymer increases side chain reaction sites, making it easier for the network to form a continuous coverage under ultra-low coating. Hydrogen-terminated polydimethylsiloxane first participates in chain growth and compliant connection, while the methylhydrosiloxane-dimethylsiloxane copolymer subsequently adds crosslinking nodes, both contributing to a crosslinked network that is both dense and uniform. Simultaneously, 3-glycidyl etheroxypropyltrimethoxysilane enhances the bonding between the coating and the polyester film interface and inhibits the migration of extractable low-molecular-weight molecules, thus achieving a good balance between release, subsequent adhesive retention, and aging stability.

[0054] As can be seen from the data in Example 1 and Comparative Example 1 in Table 1, when only vinyl-terminated polydimethylsiloxane is retained in the system without introducing vinylmethylsiloxane-dimethylsiloxane copolymer, the release force fluctuation increases, and the stability after aging and subsequent adhesion retention both decrease. The main reason is that the vinyl-terminated groups are mainly distributed at the ends of the molecular chains. Under ultra-low dry coating weight, the effective reaction points are sparsely distributed, making it difficult to simultaneously achieve both spreading coverage and local repair, easily leading to localized loss of coverage or uneven mesh, resulting in insufficient continuity of the surface release layer.

[0055] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 2 and 3, although the total amount of vinylmethylsiloxane-dimethylsiloxane copolymer added is the same, the overall performance is not as good as that of the examples. The pre-added system is beneficial for initial spreading, but lacks subsequent compensation for weak areas; the post-added system has a certain repair effect, but lacks side chain reaction sites in the main spreading stage, resulting in insufficient coverage. This indicates that the pre-added and post-added parts of the copolymer undertake two different functions: film spreading and defect repair. The continuous coverage effect produced by their synergy is not a simple additive one, thus achieving a better balance between release force, fluctuation, residual adhesion, and aging retention.

[0056] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 4 and 5, even when adjusting the total silane equivalent to approximate the amounts of methylhydrosiloxane-dimethylsiloxane alone or using only hydrogen-terminated polydimethylsiloxane, it is difficult to achieve the same balanced performance as in the examples. The former is more likely to form a network with excessively dense local crosslinking points, making the coating harder and stress-concentrated, resulting in increased release force and decreased stability after repeated aging; the latter is more inclined towards chain growth and compliant connections, with insufficient network nodes, making low molecular weight molecules more prone to migration, thus increasing the extraction rate and decreasing the residual adhesion and holding power. This indicates that the two types of silane components have distinct roles in network construction, and only when they exist simultaneously and are used in a predetermined order can the integrity of crosslinking, low interfacial migration, and subsequent adhesive retention be balanced.

[0057] As can be seen from the data in Example 1 and Comparative Example 6 in Table 1, with the total amount of components remaining basically unchanged, simply changing the order of addition of hydrogen-terminated polydimethylsiloxane and methylhydrosiloxane-dimethylsiloxane copolymer leads to fluctuations in release force and deterioration in performance after aging. This may be because hydrogen-terminated polydimethylsiloxane is more suitable as an early chain growth and compliance bridging component; if added later, the early network lacks compliant connections. Conversely, if the methylhydrosiloxane-dimethylsiloxane copolymer is added earlier, local crosslinking is too rapid, making it easier to solidify into a non-uniform structure.

[0058] As can be seen from the data in Example 1 and Comparative Example 7 in Table 1, when the silane component is insufficient, the extraction rate of the coating increases significantly, while the residual adhesion, initial ball tack, and holding time all decrease significantly, and the re-peel retention is poor. The main reason for this is that the amount of silane that can participate in the addition reaction is insufficient, making it difficult to effectively fix some vinyl components. After curing, the network is loose and contains many migratable components, which are more likely to transfer to the surface of the test tape and weaken the subsequent adhesion of the adhesive layer.

[0059] As can be seen from the data in Example 1 and Comparative Example 8 in Table 1, when the silane component is excessive, both the initial release force and the release force after aging are relatively high, and the subsequent adhesion retention is also adversely affected. Analysis suggests that excessive methylhydrosiloxane-dimethylsiloxane copolymer and hydrogen-terminated polydimethylsiloxane cause the network crosslinking to be too rapid and too dense, limiting the proper orientation of the surface organosilicon segments and resulting in a harder release interface. Simultaneously, the residual active silane-related structures may also enhance the interaction with the acrylic adhesive layer, causing increased peeling after aging.

[0060] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A coating for release films, characterized in that, It is prepared from the following components in parts by mass: The main spreading phase comprises 3800-4000 parts of anhydrous n-heptane, 900-1050 parts of ethyl acetate, 65-82 parts of vinyl-terminated polydimethylsiloxane, 14-22 parts of vinylmethylsiloxane-dimethylsiloxane copolymer and 2-4 parts of 3-glycidyl etheroxypropyltrimethoxysilane. The repair phase premix comprises 8-14 parts of vinylmethylsiloxane-dimethylsiloxane copolymer and 0.8-1.2 parts of hydrogen-terminated polydimethylsiloxane; as well as After the main spreading phase is added to the repair phase premix, 0.8-1.4 parts of methylhydrosiloxane-dimethylsiloxane copolymer and 8-12 parts of platinum catalyst dilution are added.

2. The coating for release films according to claim 1, characterized in that, The platinum catalyst diluent was obtained by mixing a platinum-divinyltetramethyldisiloxane complex xylene solution with anhydrous n-heptane at a mass ratio of 1:

99.

3. The coating for release films according to claim 1, characterized in that, The repair phase premix is ​​added to the main spreading phase within 3-8 minutes. The methylhydrosiloxane-dimethylsiloxane copolymer is added after the repair phase premix is ​​added and mixed. The platinum catalyst diluent is added after the methylhydrosiloxane-dimethylsiloxane copolymer is added.

4. The coating for release films according to claim 1, characterized in that, The release membrane coating is obtained by filtration through a 1μm polytetrafluoroethylene filter membrane.

5. The coating for release films according to claim 1, characterized in that, The vinyl-terminated polydimethylsiloxane is designated as DMS-V42; the vinylmethylsiloxane-dimethylsiloxane copolymer is designated as VDT-123; the hydrogen-terminated polydimethylsiloxane is designated as DMS-H05; and the methylhydrosiloxane-dimethylsiloxane copolymer is designated as HMS-301.

6. A method for preparing a release film coating according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Anhydrous n-heptane, ethyl acetate, vinyl-terminated polydimethylsiloxane, a portion of vinylmethylsiloxane-dimethylsiloxane copolymer and 3-glycidoxypropyltrimethoxysilane are mixed to obtain the main spreading phase; S2. Mix the remaining vinylmethylsiloxane-dimethylsiloxane copolymer with hydrogen-terminated polydimethylsiloxane to obtain a repair phase premix; S3. Add the repair phase premix to the main spreading phase, mix, and then add methylhydrosiloxane-dimethylsiloxane copolymer to obtain the coating solution to be catalyzed. S4. Add platinum catalyst dilution to the coating solution to be catalyzed, filter, and obtain a coating for release film.

7. The application of a coating for release films according to any one of claims 1-5, characterized in that, Used to prepare release films.

8. The application of the release film coating according to claim 7, characterized in that, The release film includes a polyester base film and a release layer disposed on the surface of the polyester base film, wherein the release layer is formed by curing a release film coating.

9. The application of the release film coating according to claim 7, characterized in that, The polyester-based film is subjected to corona treatment, and the surface tension of the corona treatment is 50-54 mN / m.

10. The application of the release film coating according to claim 7, characterized in that, The dry coating amount of the release layer is 50-80 mg / m 2 .

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