Gradient cross-linked structure-based PET release film with low silicon transfer and high adhesive force
By using a gradient crosslinking structure and a staged UV-cured PET release film design, the contradiction between anti-silicone transfer and adhesion in traditional PET release films is resolved, achieving a balance between high adhesion and low silicon transfer, making it suitable for high-cleanliness applications such as optical adhesives and semiconductor packaging.
Patent Information
- Application Number
- CN202511657134.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-13
- Publication Date
- 2026-01-23
AI Technical Summary
Traditional PET release films have a trade-off between their anti-silicone transfer properties and their adhesion to the substrate, which can lead to residue or peeling in applications requiring high cleanliness, thus affecting product performance.
The PET release film design employs a gradient crosslinking structure, with the crosslinking density increasing in the thickness direction of the silicone release layer. Combined with staged curing under ultraviolet light, it forms a structure with high surface crosslinking degree and low interfacial crosslinking degree, achieved through UV light sources of different wavelengths.
It achieves a balance between high adhesion and low silicone transfer, ensuring that the coating does not peel off and blocking silicone oil migration. It is suitable for a variety of high-end application scenarios and has stable and reliable performance.
Smart Images
Figure CN121379408A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a low-silicon transfer high-adhesion PET release film based on a gradient crosslinking structure and belongs to the technical field of high polymer composites. BACKGROUND
[0002] The PET release film is a key auxiliary material in the production, transportation and storage of adhesive tapes, labels and functional film products. Its core function is to effectively protect the pressure-sensitive adhesive from pollution and damage while cleanly and smoothly peeling off in subsequent processing without leaving residues or contaminating the adhesive surface.
[0003] The organic silicon release layer of the traditional release film is usually a chemical homogeneous structure, and there is an inherent contradiction between the “anti-silicon transfer” performance and the “adhesion to the substrate” and “stable release force” that is difficult to reconcile: if the overall crosslinking density is increased to lock small silicon oil molecules, the coating will become brittle, the adhesion to the PET substrate will be reduced, and cohesive failure or interfacial peeling will occur during peeling, resulting in residue or overall shedding; on the contrary, if the crosslinking density is reduced to ensure adhesion, the siloxane oligomers cannot be effectively bound, which leads to migration to the adhesive surface during the peeling process or in a high-temperature environment, forming a “fog-like” pollution that cannot be seen by the naked eye, which seriously reduces the secondary bonding performance of the adhesive.
[0004] This contradiction is particularly prominent in application scenarios such as optical glue (OCA), semiconductor packaging, medical pressure-sensitive adhesive tape, etc. that have extreme requirements for cleanliness. A small amount of silicon transfer can lead to product functional failure and a sharp drop in yield. Therefore, developing a new release film structure that can fundamentally solve this contradiction has become an urgent need in the industry. SUMMARY
[0005] The purpose of the present application is to provide a low-silicon transfer high-adhesion PET release film based on a gradient crosslinking structure, to provide a PET release film with a novel structure that realizes functional partitioning at the molecular level through gradient crosslinking design, thereby simultaneously improving the anti-transfer property and adhesion.
[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows: the present application comprises a PET substrate layer (2) and a cured organic silicon release layer on the PET substrate layer, the organic silicon release layer has a continuously changing gradient crosslinking density distribution in the thickness direction, and the crosslinking density increases from the bonding interface of the organic silicon release layer and the PET substrate layer to the outer surface of the organic silicon release layer away from the PET substrate layer. Further, the bonding interface of the organic silicon release layer and the PET substrate layer has a low crosslinking degree to ensure that the organic silicon release layer has flexibility and mechanical interlocking ability, and the outer surface of the organic silicon release layer away from the PET substrate layer has a high crosslinking density to form a dense and firm barrier.
[0007] The maximum crosslinking density of the organic silicon release layer is 20% to 50% higher than the minimum crosslinking density. Further, the maximum crosslinking density of the organic silicon release layer is distributed in the outer surface area of the organic silicon release layer, and the minimum crosslinking density of the organic silicon release layer is distributed in the bonding surface area of the organic silicon release layer and the PET substrate layer, that is, the crosslinking density of the outer surface of the organic silicon release layer is 20% to 50% higher than the crosslinking density of the bonding interface of the organic silicon release layer and the PET substrate layer.
[0008] The gradient crosslinking density distribution of the organic silicon release layer is formed by different wavelength ultraviolet light curing in stages, first using a first wavelength ultraviolet light to preliminarily cure the organic silicon release layer, and then using a second wavelength ultraviolet light to deeply cure the preliminarily cured organic silicon release layer, the wavelength of the second wavelength ultraviolet light being smaller than the wavelength of the first wavelength ultraviolet light. Further, the main wavelength range of the first wavelength ultraviolet light is 300nm to 365nm, and the main wavelength range of the second wavelength ultraviolet light is 200nm to 280nm.
[0009] The surface of the PET substrate layer is subjected to corona treatment or atmospheric pressure plasma treatment. Further, the thickness of the PET substrate layer is 25μm to 100μm, and the surface energy of the PET substrate layer is not less than 50 dynes / cm.
[0010] The organic silicon release layer uses an addition reaction type platinum gold catalytic silicone oil system, and the thickness of the organic silicon release layer is 0.5μm to 3.0μm. Further, the outer surface area of the organic silicon release layer forms a dense shielding layer after curing, with a higher crosslinking network density than the bonding interface area of the organic silicon release layer and the PET substrate layer.
[0011] The beneficial effects of the present application are: 1. By providing a high crosslinking density on the outer surface of the organic silicon release layer, a dense "shielding layer" is formed, which physically blocks the migration channel of small silicone molecules, and can meet the most demanding optical and semiconductor application requirements; the low crosslinking degree setting of the bonding interface of the organic silicon release layer and the PET substrate layer can maintain the flexibility of the material and the anchoring ability to the PET substrate layer, ensuring the bonding force between the coating and the PET substrate, and eliminating the risk of peeling and overall falling off; through the gradient structure design of a single coating, the two seemingly contradictory properties of "high surface crosslinking degree" and "low interface crosslinking degree" are simultaneously realized in a material system, perfectly solving the core contradiction in traditional technology.
[0012] 2. The organic silicon release layer is preliminarily cured by using ultraviolet light of a first wavelength, and then is deeply cured by using ultraviolet light of a second wavelength, so that the required gradient cross-linking structure of the organic silicon release layer in the thickness direction is formed, the core equipment of the existing coating production line does not need to be changed, only the UV curing system needs to be upgraded and precisely controlled, industrial production can be realized, the process is easy to implement and compatible, and the process is easy to implement and compatible. BRIEF DESCRIPTION OF DRAWINGS
[0013] Figure 1 is a schematic diagram of a layered structure of the present application.
[0014] 1, organic silicon release layer; 2, PET substrate layer. DETAILED DESCRIPTION
[0015] The technical solutions in the embodiments will be described below with reference to the accompanying drawings. Figure 1 The technical solutions in the embodiments will be described below with reference to the accompanying drawings.
[0016] The layered structure of the PET release film as a whole is sequentially from bottom to top: the PET substrate layer 2 and the organic silicon release layer 1, and the organic silicon release layer 1 is cured on the PET substrate layer 2, the organic silicon release layer 1 has a non-uniform and continuously changing gradient cross-linking density distribution in the thickness direction, and the cross-linking density increases from the bonding interface of the organic silicon release layer 1 and the PET substrate layer 2 to the outer surface of the organic silicon release layer 1 away from the PET substrate layer 2. Specifically, the cross-linking density at the bonding interface of the organic silicon release layer 1 and the PET substrate layer 2 is designed to be relatively low, which ensures that the organic silicon release layer 1 has sufficient flexibility and mechanical interlocking ability, and the organic silicon release layer 1 and the surface-activated PET substrate layer 2 can form a firm adhesion, fundamentally preventing the organic silicon release layer 1 from being completely peeled off or producing residue from the PET substrate layer 2 during use. The cross-linking density of the outer surface of the organic silicon release layer 1 away from the PET substrate layer 2 is designed to be significantly increased, forming a dense and firm "cross-linking shielding layer", which can effectively physically bind the migratable small molecules such as low molecular weight siloxane in the silicone oil, preventing them from migrating to the protected adhesive surface, thereby achieving excellent anti-silicone transfer performance. The gradient cross-linking density distribution curve is a continuous function that monotonically increases from the PET substrate layer 2 interface to the upper surface, which is in sharp contrast to the nearly horizontal distribution curve of the traditional release film. The gradient crosslinking structure is realized by a staged precision curing process with different wavelengths of ultraviolet light (UV); first, a longer wavelength (such as 300-365 nm) UV light source is used to preliminarily cure the coating, the wavelength UV light has good penetration, can make the internal of the coating fully crosslinking reaction, form the basic three-dimensional network structure; then a shorter wavelength (such as 200-280 nm) UV light source is used to deeply cure the surface layer of the coating, the short wavelength UV light photon energy is high but the penetration depth is shallow, its energy is mainly absorbed by the surface layer molecules, thereby inducing higher density and degree of crosslinking reaction in the surface layer, finally forming the required gradient crosslinking structure in the thickness direction of the coating, the crosslinking density of the outer surface of the silicone release layer 1 is 20% to 50% higher than the crosslinking density of the interface between the silicone release layer 1 and the PET substrate layer 2; Specific embodiment 1: The PET substrate layer 2 is selected to have a thickness of 50 μm and is made of optical-grade PET, the PET substrate layer 2 is treated by corona treatment and the surface energy of the PET substrate layer 2 is not less than 50 dynes / cm; the silicone release layer 1 adopts an addition reaction type platinum catalytic silicone oil system, the silicone oil can be selected from vinyl silicone oil or hydrogen-containing silicone oil, the coating thickness of the silicone release layer 1 is 2.0 μm, thereby preparing a general high-performance PET release film; The curing process of the general high-performance PET release film is twice curing, the first curing uses a 365 nm medium pressure mercury lamp with an energy of 200 mJ / cm², the second curing uses a 254 nm UV-LED surface light source with an energy of 100 mJ / cm², thereby balancing the adhesion and anti-transfer property of the high-performance PET release film, which is suitable for most high-end applications; Specific embodiment 2: The PET substrate layer 2 is selected to have a thickness of 75 μm and is made of thick PET, the PET substrate layer 2 is treated by atmospheric pressure plasma treatment and the surface energy of the PET substrate layer 2 is not less than 50 dynes / cm; the silicone release layer 1 adopts an addition reaction type platinum catalytic silicone oil system, the silicone oil can be selected from vinyl silicone oil or hydrogen-containing silicone oil, and 1 wt% of an adhesion promoter is added, and the promoter is an epoxy functional silane, the coating thickness of the silicone release layer 1 is 2.5 μm, thereby preparing a super adhesion PET release film; The curing process of the super adhesion PET release film is twice curing, the first curing uses a 355 nm UV lamp with an energy of 250 mJ / cm², which needs to ensure that the bottom layer is fully cured, the second curing uses a 222 nm KrCl* excimer lamp with an energy of 80 mJ / cm², which cures the very shallow surface layer, thereby making the super adhesion PET release film capable of die-cutting for heavy, high-adhesion tapes (such as VHB™), and ensuring no residue; Specific embodiment 3: The PET substrate layer 2 is selected to have a thickness of 38 pm and is made of super-smooth PET. The PET substrate layer 2 is treated by atmospheric pressure plasma, and the surface energy of the PET substrate layer 2 is not less than 56 dynes / cm. The silicone release layer 1 is made of ultra-high cross-linking density platinum silicone oil, and the silicone oil has high vinyl content. The coating thickness of the silicone release layer 1 is 1.5 pm. In this way, the ultra-low silicone transfer type PET release film is prepared. The curing process of the ultra-low silicone transfer type PET release film is twice curing. The first curing is mild deep curing by using a 385 nm LED lamp with an energy of 180 mJ / cm2. The second curing is high-strength surface layer curing by using a 235 nm UV lamp with an energy of 120 mJ / cm2. In this way, the ultra-low silicone transfer type PET release film can pursue the ultimate anti-silicone transfer performance and be used for OLED optical adhesive (OCA) protection. Comparative Example 1 The PET substrate layer 2 is selected to have a thickness of 50 pm and is made of optical-grade PET. The PET substrate layer 2 is treated by corona discharge, and the surface energy of the PET substrate layer 2 is not less than 50 dynes / cm. The silicone release layer 1 is made of an addition reaction type platinum catalytic silicone oil system. The silicone oil can be selected from vinyl silicone oil or hydrogen-containing silicone oil. The coating thickness of the silicone release layer 1 is 2.0 pm. The curing process is one-time curing by using a single 365 nm UV light source with an energy of 350 mJ / cm2, forming a cross-linking density uniform release layer. Comparative Example 2 The PET substrate layer 2 is selected to have a thickness of 50 pm and is made of optical-grade PET. The PET substrate layer 2 is treated by corona discharge, and the surface energy of the PET substrate layer 2 is not less than 50 dynes / cm. The silicone release layer 1 is made of an addition reaction type platinum catalytic silicone oil system. The silicone oil can be selected from vinyl silicone oil or hydrogen-containing silicone oil. The coating thickness of the silicone release layer 1 is 2.0 pm. The curing process is one-time curing by using a single 254 nm UV light source with an energy of 300 mJ / cm2. However, the short wavelength has poor penetration, which will lead to excessive curing of the surface layer and insufficient curing of the bottom layer. The release films prepared in the above examples and comparative examples are compounded with 3M VHB™ 4955 adhesive tape, and the following tests are performed. The results are summarized in the following table. Comparison of data of release films prepared in examples and comparative examples and 3M VHB™ 4955 adhesive tape
[0017] The silicone transfer inhibition rates of all examples are significantly higher than that of Comparative Example 1 (traditional release film homogeneous structure), which proves the fundamental advantage of the gradient cross-linking structure in inhibiting silicone transfer. Example 3 achieves an ultimate performance of 99.5% through formulation and process optimization. All examples show 100% cohesive failure, proving excellent adhesion, while Comparative Example 2 (single short wavelength curing) has a serious adhesion failure due to insufficient curing of the bottom layer, and the coating falls off as a whole when peeled, completely unable to use; Examples 1, 2, and 3 have very small changes in release force after high-temperature aging, and stable performance, while Comparative Examples 1 and 2 have a large drift, because homogeneous structure or poor structure is more unstable under thermal stress; Gradient curing process (combination of long and short waves) shows good process adaptability and stability, while single wavelength curing (whether long or short wave) cannot achieve balanced optimization of performance; The above experimental results fully show that through gradient crosslinking structure design, the perfect unity of high adhesion and low silicon transfer is successfully achieved, and the performance is stable and reliable, significantly better than the traditional uniform structure product of release film, and the differentiated performance of different examples also proves that the technical scheme has good adjustability and wide applicability, and can meet the harsh needs of different application scenarios from general high-end to optical grade.
[0018] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent replacement and improvement of the above examples within the scope of the technical solution of the present application, according to the technical essence of the present application, within the spirit and principles of the present application, are all within the protection scope of the present application.
Claims
1. A low silicon transfer high adhesion PET release film based on gradient crosslinked structure, characterized in that, The PET base material layer (2) and the silicone release layer (1) solidified on the PET base material layer (2) are included, the silicone release layer (1) has a continuously changing gradient crosslinking density distribution in the thickness direction, and the crosslinking density increases from the bonding interface of the silicone release layer (1) and the PET base material layer (2) to the outer surface of the silicone release layer (1) away from the PET base material layer (2).
2. The low-silicon transfer high-adhesion PET release film based on gradient crosslinking structure according to claim 1, characterized in that, The maximum crosslinking density of the silicone release layer (1) is 20% to 50% higher than the minimum crosslinking density.
3. The low-silicon transfer high-adhesion PET release film based on gradient crosslinking structure according to claim 1, characterized in that, The gradient crosslinking density distribution of the silicone release layer (1) is formed by staged curing with different wavelengths of ultraviolet light, the silicone release layer (1) is preliminarily cured with ultraviolet light of a first wavelength, and the preliminarily cured silicone release layer (1) is deeply cured with ultraviolet light of a second wavelength, the wavelength of the ultraviolet light of the second wavelength is smaller than the wavelength of the ultraviolet light of the first wavelength.
4. The low-silicon transfer high-adhesion PET release film based on gradient crosslinking structure according to claim 3, characterized in that, The main wavelength range of the ultraviolet light of the first wavelength is 300 nm to 365 nm, and the main wavelength range of the ultraviolet light of the second wavelength is 200 nm to 280 nm.
5. The low silicon transfer high adhesion PET release film based on gradient crosslinking structure according to claim 1, characterized in that, The thickness of the PET base material layer (2) is 25 μm to 100 μm, the surface of the PET base material layer (2) is subjected to corona treatment or atmospheric pressure plasma treatment, and the surface energy of the PET base material layer (2) is not less than 50 dynes / cm.
6. The low silicon transfer high adhesion PET release film based on gradient crosslinking structure according to claim 1, characterized in that, The silicone release layer (1) uses an addition reaction type platinum gold catalytic silicone oil system, and the thickness of the silicone release layer (1) is 0.5 μm to 3.0 μm.