A functional film with tackiness that can be increased in response and a method for manufacturing the same
By introducing an epoxy curing agent with o-nitrobenzyl ester groups into the pressure-sensitive adhesive layer and increasing the viscosity by ultraviolet light irradiation, the problems of high initial viscosity and excessive current of the pressure-sensitive tape are solved, and the reworkability and electrical stability are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SUZHOU SHIHUA NEW MATERIAL TECH
- Filing Date
- 2026-03-02
- Publication Date
- 2026-05-29
AI Technical Summary
Existing pressure-sensitive tapes used in electronic products suffer from problems such as high initial tack, difficulty in rework, and excessively high penetration current and adhesive surface current, which affect the stability and safety of the equipment, and accelerate aging, especially in high temperature, high humidity or long-term vibration environments.
Design a functional film with responsively increased viscosity, comprising a film substrate, a pressure-sensitive adhesive layer, and a release film layer. The pressure-sensitive adhesive layer contains an epoxy curing agent with o-nitrobenzyl ester groups. The viscosity is increased by ultraviolet light irradiation, and a cleavage and rearrangement reaction occurs inside the molecule, reducing the adhesive surface current and the penetration current.
The functional thin film exhibits excellent reworkability, with adhesive surface current and penetration current within a suitable range, thereby improving the electrical stability and safety of electronic products and avoiding signal interference and localized overheating issues.
Smart Images
Figure CN122104084A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of functional thin film technology, specifically to a functional thin film with responsively increased viscosity and its preparation method. Background Technology
[0002] Functional thin film materials, represented by pressure-sensitive adhesive tape, play an irreplaceable and crucial role in electronic products. Their precision and functionality directly determine the reliability and safety of the equipment.
[0003] As an "invisible adhesive" for electronic components, high-performance tapes are not only used to fix precision components (such as chips, displays, and batteries) and prevent displacement caused by vibration or temperature changes, but also undertake multiple technical missions such as insulation protection, electromagnetic shielding, and heat dissipation. Conventional pressure-sensitive tapes have high initial tack, and after being applied to electronic components, they have disadvantages such as difficulty in separation and poor rework performance, and cannot be quickly peeled off and repositioned.
[0004] Therefore, there is a need to develop a pressure-sensitive adhesive tape with low initial tack and controllable tack enhancement after bonding. For example, Chinese patent application CN119432262A discloses a dual-curing UV-curing adhesive and its products. Through the compounding of its components, the adhesive can be given relatively low but suitable adhesive strength during the thermosetting stage, meeting the bonding and positioning requirements, and can be peeled off from the substrate, exhibiting excellent reworkability. After positioning, UV irradiation increases the adhesion between the adhesive and the substrate, ensuring the adhesive's bonding effect on the substrate.
[0005] However, aside from reworkability, the electrical stability of pressure-sensitive tapes in electronic products is often overlooked. In electronic products, the penetration current and surface current of the pressure-sensitive tape are core elements ensuring stable equipment operation. If the penetration current is too high, the tape's insulation performance will significantly decrease, leading to abnormal leakage or short circuits between circuits, potentially causing component failure or even burnout. Meanwhile, the surface current can create unexpected conductive paths in high-frequency or precision circuits, interfering with signal transmission accuracy (such as sensor false alarms and communication noise), exacerbating electromagnetic interference, and affecting equipment compatibility. Especially in high-temperature, high-humidity, or long-term vibration environments, the cumulative effect of these two types of currents can also cause localized overheating, accelerating tape aging or material delamination, and reducing product lifespan.
[0006] However, the aforementioned inventions did not investigate the penetration current and adhesive surface current of reworkable tapes.
[0007] To address the above problems, this invention provides a functional thin film with responsively increased viscosity and a method for preparing the same. Summary of the Invention
[0008] The purpose of this invention is to provide a functional film with responsively increased adhesion and a method for preparing the same, which is a reworkable pressure-sensitive tape with suitable adhesive surface current and penetration current, in order to solve the problems mentioned in the background art.
[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a functional film with responsive adhesion, the structure of which includes a film substrate, a pressure-sensitive adhesive layer coated on the film substrate, and a release film layer temporarily attached to the pressure-sensitive adhesive layer; The tack-enhancing functional film exhibits increased tackiness after exposure to ultraviolet light; The ratio of the peel force F2 after UV irradiation to the peel force F1 before UV irradiation for the tack-enhancing functional film is F2 / F1 > 5; The adhesive current of the tackifying functional film is 10~1000pA, and the penetration current is 50~5000pA; The pressure-sensitive adhesive layer contains a curing agent, and each molecule of the curing agent contains at least two crosslinkable groups.
[0010] The crosslinkable group of the curing agent is an epoxy group, and the curing agent contains o-nitrobenzyl ester group.
[0011] Ideally, F1 < 0.4 N / 25 mm; F2 > 2 N / 25 mm.
[0012] Ideally, the total energy of ultraviolet light received by the tackifying functional film to achieve tackification is 500~5000mJ.
[0013] Ideally, the curing agent is an epoxy curing agent containing o-nitrobenzyl ester groups, and each molecule of the curing agent contains at least 2 epoxy groups.
[0014] Ideally, the adhesive surface current is 10-200 pA and the penetration current is 50-500 pA.
[0015] Ideally, the adhesive surface current is 10-100pA and the penetration current is 50-200pA.
[0016] Ideally, the rated voltage for testing both the adhesive surface current and the leakage current is 1000V.
[0017] This invention also provides a method for preparing a functional thin film with responsively increased viscosity, for preparing any of the above-mentioned functional thin films with responsively increased viscosity, comprising the following steps: S1, Thin film substrate selection: The thin film substrate is selected from polyester, polyolefin, polyamide, or polyimide films, with a thickness of 38~200um; the light transmittance of the thin film substrate itself is above 80%; the haze of the thin film substrate itself is less than 5%; S2, Synthesis of acrylic polymer copolymer: A certain amount of isooctyl acrylate, butyl acrylate, isobornyl methacrylate, acrylic acid and benzoyl peroxide were added to a certain amount of ethyl acetate, nitrogen gas was introduced, and the reaction was carried out at 65°C for 6.5 hours to obtain an acrylic polymer copolymer with a weight average molecular weight of 900,000. S3, Functional film preparation: Acrylic polymer copolymer is mixed with curing agent in a specified ratio to obtain pressure-sensitive adhesive, pressure-sensitive adhesive is coated on film substrate, and after curing, release film layer is laminated to obtain tack-enhancing functional film finished product.
[0018] Ideally, the thickness of the thin film substrate is 50~150um; the light transmittance of the thin film substrate itself is above 85%; and the haze of the thin film substrate itself is less than 4%.
[0019] Ideally, the thickness of the thin film substrate is 70~100um; the light transmittance of the thin film substrate itself is above 88%; and the haze of the thin film substrate itself is less than 2%.
[0020] Compared with the prior art, the beneficial effects achieved by the present invention are: The functional film prepared by this invention consists of a film substrate and a pressure-sensitive adhesive layer. Due to the low adhesion of the pressure-sensitive adhesive layer, the material can be easily repositioned or peeled off from the surface of the object after being bonded to it, thus exhibiting excellent reworkability. After the bonding and alignment are completed, irradiation with ultraviolet light of a certain intensity increases the adhesion of the pressure-sensitive adhesive layer, permanently bonding it to the object and providing highly reliable bonding performance.
[0021] The curing agent used in the pressure-sensitive adhesive layer of this invention contains o-nitrobenzyl ester groups. Under ultraviolet light irradiation, these groups can absorb ultraviolet light energy and undergo a cleavage and rearrangement reaction inside the molecule, resulting in molecular breakage and the generation of nitro and carboxyl groups, which increases the adhesive surface impedance. Under the same rated voltage, this reduces the adhesive surface current and penetration current of the functional film itself, avoiding current accumulation in the adhesive layer that interferes with signal transmission accuracy and causes local overheating, thus improving the application safety of the material. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the structure of the functional thin film prepared in the embodiment.
[0023] Among them, 1. thin film substrate; 2. pressure-sensitive adhesive layer; 3. release film layer. Detailed Implementation
[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] This invention provides several embodiments and comparative examples to verify the performance and effects of the prepared functional thin films, specifically through the following steps: S1, Film substrate selection: Polyester, polyolefin, polyamide, and polyimide films can be selected. Considering that the functional film needs to achieve adhesion enhancement and structural bonding under ultraviolet light irradiation, polyester films with excellent mechanical strength and transparency are preferred, and polyethylene terephthalate films are further preferred as the film substrate.
[0026] To improve the rigidity and cushioning mechanical properties of the functional film, the thickness of the film substrate is preferably 38 μm or more, more preferably 50 μm or more, and even more preferably 70 μm or more. From the perspective of operability, the thickness of the film substrate is preferably 200 μm or less, more preferably 150 μm or more, and even more preferably 100 μm or less.
[0027] To improve the transmittance of the illumination light source, the thin film substrate is preferably a thin film that meets optical grade standards, and the transmittance of the thin film itself is preferably 80% or more, further preferably 85% or more, and more preferably 88% or more; the haze of the thin film itself is preferably less than 5%, further preferably less than 4%, and more preferably less than 2%.
[0028] S2, Preparation of pressure-sensitive adhesive layer. The main components of the pressure-sensitive adhesive layer include acrylic polymer copolymers and epoxy curing agents.
[0029] The preparation route of the acrylic polymer copolymer is as follows: 68 parts of isooctyl acrylate, 19 parts of butyl acrylate, 7 parts of isobornyl methacrylate, 6 parts of acrylic acid and 0.2g of benzoyl peroxide are added to 300 parts of ethyl acetate, nitrogen gas is introduced, and the reaction is carried out at 65°C for 6.5 hours to obtain an acrylic polymer copolymer with a weight average molecular weight of 900,000.
[0030] The epoxy curing agents used in the embodiments of this invention include two types: difunctional group C and tetrafunctional group D. Both types of curing agents contain o-nitrobenzyl ester groups in their chemical structures. The o-nitrobenzyl ester group is UV responsive. Under UV irradiation of a certain intensity, this group can absorb UV light energy and undergo a cleavage and rearrangement reaction within the molecule, leading to molecular breakage and the generation of polar groups such as nitro and carboxyl groups.
[0031] Synthesis of epoxy curing agent C: 5 g of 2-nitroterephthalic acid was added to 100 mL of borane-tetrahydrofuran complex solution and stirred at room temperature for 4 hours, then refluxed and stirred at 50 °C for 15 hours; 2.2 g of 3-butenoic acid was added and stirred at room temperature for 5 hours; finally, 3.6 g of 3-chloroperoxybenzoic acid was added and stirred at room temperature for 24 hours; the product was obtained after separation and purification.
[0032] Synthesis of epoxy curing agent D: 8 g of 3-nitrobenzene-1,2,4,5-tetracarboxylic acid was added to 100 mL of borane-tetrahydrofuran complex solution and stirred at room temperature for 3.6 hours, then refluxed and stirred at 50 °C for 15 hours; 6.4 g of 3-butenoic acid was added and stirred at room temperature for 5 hours; finally, 8.4 g of 3-chloroperoxybenzoic acid was added and stirred at room temperature for 24 hours; the product was obtained after separation and purification.
[0033] The epoxy curing agents used in the comparative examples include two types: difunctional E (brand name: YX-8000, Mitsubishi Chemical) and tetrafunctional F (brand name: TETRAD-X, Mitsubishi Chemical). Neither type of curing agent contains o-nitrobenzyl ester groups in its chemical structure.
[0034] Regarding the content of acrylic polymer copolymers and epoxy curing agents, considering that the adhesion of the pressure-sensitive adhesive layer is low before ultraviolet light irradiation, it is preferable that each 100 parts of acrylic polymer contains more than 0.2 parts of epoxy curing agent, and more preferably, each 100 parts of acrylic polymer contains more than 0.5 parts of epoxy curing agent; considering that as the curing agent content increases, the crosslinking density of the pressure-sensitive adhesive layer increases, the cohesive energy is enhanced, and it is easy to lose adhesion, it is preferable that each 100 parts of acrylic polymer contains less than 5 parts of epoxy curing agent, and more preferably, each 100 parts of acrylic polymer contains less than 3 parts of epoxy curing agent.
[0035] S3, Functional film preparation: Acrylic polymer copolymer and epoxy curing agent are mixed in a specified amount and coated onto the surface of film substrate. After curing, a release film layer is laminated to obtain the finished tack-enhancing functional film.
[0036] Adhesive surface current refers to the current flowing along the adhesive surface from one conductor to another adjacent conductor. Excessive adhesive surface current on the tape surface is equivalent to forming an unintended resistive path, which can lead to signal or power short circuits, causing equipment malfunctions, damage to components, or even safety accidents. Therefore, in the embodiments of this invention, the functional film prepared at a rated voltage of 1000V preferably has an adhesive surface current of 10-1000pA, more preferably 10-500pA, more preferably 10-200pA, and particularly preferably 10-100pA.
[0037] Penetration current refers to the current that directly penetrates the insulating material of the tape itself (from one conductor to another). Excessive penetration current can lead to serious short-circuit faults, causing electric shock hazards or equipment damage. Therefore, in the embodiments of this invention, the functional film, at a rated voltage of 1000V, preferably has a penetration current of 50-5000pA, more preferably 50-2000pA, more preferably 50-500pA, and particularly preferably 50-200pA.
[0038] Preparation conditions of the examples and comparative examples
[0039] In Examples 1-4 of the present invention, a curing agent C containing two epoxy functional groups was mixed with an acrylic polymer A and coated onto the surface of a thin film substrate. The substrate was then irradiated with ultraviolet light of different energies. The differences between the various examples are shown in Table 1.
[0040] In Examples 5-8 of the present invention, a curing agent D containing four epoxy functional groups was mixed with an acrylic polymer A and coated onto the surface of a thin film substrate. The substrate was then irradiated with ultraviolet light of different energies. The differences between the various examples are shown in Table 1.
[0041] In Comparative Examples 1-4 of the present invention, a curing agent E containing two epoxy functional groups was mixed with an acrylic polymer A and coated onto the surface of a thin film substrate. The substrate was then irradiated with ultraviolet light of different energies. The differences between the various embodiments are shown in Table 1.
[0042] In Comparative Examples 5-8 of the present invention, a curing agent F containing four epoxy functional groups was mixed with an acrylic polymer A and coated onto the surface of a thin film substrate. The substrate was then irradiated with ultraviolet light of different energies. The differences between the various embodiments are shown in Table 1.
[0043] The ultraviolet light energies used in each embodiment and comparative example are shown in Table 1.
[0044] Test methods
[0045] The surface current and leakage current were tested using a Kikusui TOS9301 withstand voltage tester from Japan, with the rated voltage set to 1000V.
[0046] The peel strength test method is as follows: the adhesive side of the sample is attached to a stainless steel mirror plate (150mm long × 50mm wide × 2mm thick with a surface roughness of 10nm ± 10nm) that meets the material requirements of GB / T2792 peel test steel plate. Ensure the plate is flat and free of bubbles, impurities, wrinkles, etc. A 2kg roller is used to roll the sample back and forth once on the stainless steel mirror plate at a speed of 300mm / min. After standing for 20 minutes in the test environment (23℃~50%RH), a 180° peel strength test is performed using a tensile testing machine in the same test environment (23℃~50%RH) at a peel speed of 300mm / min. Three samples are tested, and the arithmetic mean of the three test results is taken as the peel strength result.
[0047] The specific test results are shown in Table 1.
[0048] Table 1. Composition and performance parameters of each embodiment and comparative example.
[0049] As shown in Table 1, comparing Examples 1-4 and Examples 5-8, it can be found that in the same formulation, the higher the UV light energy, the greater the peel force ratio F2 / F1, and the smaller the adhesive surface current and penetration current. This is because, under the same degree of crosslinking, the cleavage of the o-nitrobenzyl ester group in the curing agent intensifies with the increase of UV light energy, leading to a rapid decrease in the degree of crosslinking of the system, while the resistance value increases more.
[0050] A comparison between Examples 1 and 5, Examples 2 and 6, Examples 3 and 7, and Examples 4 and 8 reveals that, under the same curing agent dosage and UV light energy, the more functional groups the curing agent has, the greater the peel force ratio F2 / F1, and the smaller the adhesive surface current and penetration current. This is because, under the same curing agent dosage, the more functional groups there are, the higher the degree of cross-linking of the pressure-sensitive adhesive layer, and the more obvious the tack-enhancing performance of the adhesive surface after UV irradiation, while the resistance value increases more.
[0051] Comparing Examples 1-8 with Comparative Examples 1-8, it can be found that under the same conditions of curing agent dosage, number of epoxy functional groups, and UV irradiation intensity, Examples 1-8, which contain o-nitrobenzyl ester groups in the curing agent, have a greater peel force ratio F2 / F1 after UV irradiation than Examples 1-8. The adhesive surface current and penetration current of Examples 1-8 are much smaller than those of Examples 1-8. This is because the introduction of o-nitrobenzyl ester groups can make the pressure-sensitive adhesive layer have the characteristic of UV light tackification. At the same time, the characteristic of this group to break under UV light can also increase the adhesive surface resistance after UV irradiation.
[0052] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A functional thin film with responsively increasing viscosity, characterized in that, The structure includes a thin film substrate, a pressure-sensitive adhesive layer coated on the thin film substrate, and a release film layer temporarily bonded to the pressure-sensitive adhesive layer; The adhesive-enhancing functional film exhibits increased adhesion after exposure to ultraviolet light; The ratio of the peeling force F2 after UV irradiation to the peeling force F1 before UV irradiation of the adhesive functional film is F2 / F1>5; The adhesive surface current of the adhesive-enhancing functional film is 10~1000pA, and the penetration current is 50~5000pA. The pressure-sensitive adhesive layer contains a curing agent, and each molecule of the curing agent contains at least two crosslinkable groups.
2. The functional thin film with responsively increasing viscosity according to claim 1, characterized in that: The pressure-sensitive adhesive layer comprises an acrylic polymer copolymer, wherein each 100 parts of the acrylic polymer copolymer contains 0.2 to 5 parts of curing agent.
3. A functional thin film with responsively increasing viscosity according to claim 1 or 2, characterized in that: F1 < 0.4 N / 25 mm; F2 > 2 N / 25 mm.
4. The functional thin film with responsively increasing viscosity according to claim 3, characterized in that: The total energy of ultraviolet light received by the adhesive-enhancing functional film to achieve adhesive enhancement is 500~5000mJ.
5. The functional thin film with responsively increasing viscosity according to claim 2, characterized in that: The crosslinkable group of the curing agent is an epoxy group, and the curing agent contains an o-nitrobenzyl ester group.
6. The functional thin film with responsively increasing viscosity according to claim 1, characterized in that: The adhesive surface current is 10-200pA; the penetration current is 50-500pA.
7. A functional thin film with responsively increasing viscosity according to claim 6, characterized in that: The adhesive surface current is 10-100pA; the penetration current is 50-200pA.
8. A functional thin film with responsively increasing viscosity according to claim 7, characterized in that: The rated voltage for testing the adhesive surface current and the penetration current is 1000V.
9. A method for preparing a functional thin film with responsively increasing viscosity, used to prepare any one of the functional thin films with responsively increasing viscosity as described in claims 1, 2, or 4-8, characterized in that, Includes the following steps: S1, Thin film substrate selection: The thin film substrate is selected from polyester, polyolefin, polyamide, or polyimide films, with a thickness of 38~200um; the light transmittance of the thin film substrate itself is above 80%; the haze of the thin film substrate itself is less than 5%; S2, Synthesis of acrylic polymer copolymer: A certain amount of isooctyl acrylate, butyl acrylate, isobornyl methacrylate, acrylic acid and benzoyl peroxide were added to a certain amount of ethyl acetate, nitrogen gas was introduced, and the reaction was carried out at 65°C for 6.5 hours to obtain an acrylic polymer copolymer with a weight average molecular weight of 900,000. S3, Functional film preparation: an acrylic polymer copolymer is mixed with a curing agent in a specified ratio to obtain a pressure-sensitive adhesive. The pressure-sensitive adhesive is coated on the film substrate, and after curing, a release film layer is laminated to obtain the adhesive-enhanced functional film product.
10. The method for preparing a functional thin film with responsively increased viscosity according to claim 9, characterized in that: The thickness of the thin film substrate is 50~150um; the light transmittance of the thin film substrate itself is above 85%; and the haze of the thin film substrate itself is less than 4%.
11. The method for preparing a functional thin film with responsively increased viscosity according to claim 10, characterized in that: The thickness of the thin film substrate is 70~100um; the light transmittance of the thin film substrate itself is above 88%; and the haze of the thin film substrate itself is less than 2%.