OCA of rubber modified acrylate system and preparation method of OCA

Abstract

The invention belongs to the field of material synthesis, and particularly relates to OCA of a rubber modified acrylate system and a preparation method of the OCA, and the OCA comprises matrix resin, a rubber modifier, a functional filler and an auxiliary agent; the matrix resin is selected from one or a combination of more of 2-ethylhexyl acrylate, methyl methacrylate and isobornyl acrylate; the rubber modifier is selected from one or a combination of more of natural rubber, butadiene styrene rubber, butadiene rubber, isoprene rubber and nitrile rubber; the functional filler is selected from nano silicon dioxide aerogel; the auxiliary agent is selected from one or a combination of more of a photoinitiator, a silane coupling agent, an antioxidant and an anti-ultraviolet aging agent. The problem of how to balance the OCA among low dielectric constant, high light transmittance, strong adhesion and flexibility is solved.

Description

Technical Field

[0001] This invention relates to the field of materials synthesis technology, specifically to a rubber-modified acrylate system OCA and its preparation method. Background Technology

[0002] Currently, commercially available OCAs primarily use acrylates or polyurethane acrylates as the matrix. While these meet basic optical and adhesive requirements, the polar groups in their molecular chains (such as ester groups and hydroxyl groups) are prone to orientation polarization under high-frequency electric fields, resulting in a high dielectric constant (typically 3.5–4.2), which in turn causes signal attenuation and crosstalk. To reduce dielectric properties, existing technologies often employ the addition of inorganic nanofillers (such as titanium dioxide and boron nitride) or the introduction of fluorinated polymers. For example, CN112225816A discloses a fluorinated polyurethane acrylate OCA, whose dielectric constant can be reduced to 3.2, but the hydrophobic properties of the fluorinated component lead to decreased adhesion to the substrate; CN110527125A uses nano-alumina fillers to improve dielectric properties, but the difference in refractive index between the filler and the matrix causes light scattering, reducing the transmittance to below 88%. Furthermore, high filler content can exacerbate material embrittlement, affecting the bending life of flexible devices. Therefore, the industry urgently needs an innovative material solution that can achieve a balance between low dielectric constant, high light transmittance, strong adhesion, and flexibility. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a rubber-modified acrylate system OCA and its preparation method to solve the problem of how to achieve a balance between low dielectric constant, high light transmittance, strong adhesion and flexibility in OCA.

[0004] On one hand, embodiments of the present invention provide an OCA of a rubber-modified acrylate system, wherein the OCA comprises: a matrix resin, a rubber modifier, a functional filler, and an additive; The matrix resin is selected from one or more combinations of isooctyl acrylate, methyl methacrylate, and isobornyl acrylate; The rubber modifier is selected from one or more combinations of natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, and nitrile rubber. The functional filler is selected from nano-silica aerogel; The additives are selected from one or more combinations of photoinitiators, silane coupling agents, antioxidants, and UV aging agents; The matrix resin is added at a rate of 83%-90%; the rubber modifier is added at a rate of 5%-15%; the functional filler is added at a rate of 0.5%-1%; and the additives are added at a rate of 1%-2%.

[0005] Furthermore, the matrix resin is selected from isooctyl acrylate and methyl methacrylate; or the matrix resin is selected from isooctyl acrylate, methyl methacrylate and isobornyl acrylate; The amount of the matrix resin added is 85%-90%.

[0006] Furthermore, the rubber modifier is selected from nitrile rubber, which contains 22% acrylonitrile; The amount of rubber modifier added is 8%-12%.

[0007] Furthermore, the nano-silica aerogel has a particle size of 50–100 nm and a specific surface area >600 m². 2 / g; The amount of nano-silica aerogel added is 0.7%-0.9%.

[0008] Furthermore, the additive is selected from TPO photoinitiator and KH-570 silane coupling agent; the additive content is 1.2%-1.6%.

[0009] Furthermore, the OCA comprises methyl methacrylate, isooctyl acrylate, nitrile rubber, nano-silica aerogel, TPO photoinitiator, and KH-570 silane coupling agent; or The OCA comprises methyl methacrylate, isooctyl acrylate, isobornyl acrylate, nitrile rubber, nano silica aerogel, TPO photoinitiator, and KH-570 silane coupling agent.

[0010] Furthermore, the OCA comprises 100g of methyl methacrylate, 10g of isooctyl acrylate, 10g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent; The OCA comprises 100g of methyl methacrylate, 10g of isooctyl acrylate, 15g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator, and 0.8g of KH-570 silane coupling agent; or The OCA contains 40g of methyl methacrylate, 10g of isooctyl acrylate, 60g of isobornyl acrylate, 10g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator, and 0.8g of KH-570 silane coupling agent.

[0011] On the one hand, embodiments of the present invention provide a method for indicative OCA of a rubber-modified acrylate system as described above. include: S1: Under a nitrogen atmosphere, the matrix resin, rubber modifier and additives are stirred at a constant temperature of 50-60℃ for 6 hours to obtain OCA prepolymer; S2: Disperse the functional filler in anhydrous ethanol and treat it with an ultrasonic instrument for 30 minutes to obtain the functional filler dispersion; S3: Mix the OCA prepolymer and the functional filler dispersion evenly to obtain a mixed slurry of OCA and functional filler; S4: Remove dissolved gases and solvents from the mixed slurry to obtain OCA mixed slurry; S5: The OCA mixture is evenly coated onto the PET release film and then irradiated with an LED light source; S6: At 120℃, the wet film on the PET release film is cured for 2 hours to obtain an OCA film material with a thickness of 50–200μm.

[0012] Furthermore, in step S1, under a nitrogen atmosphere, the matrix resin, rubber modifier, and additives are placed in a three-necked flask equipped with a mechanical stirrer and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer; wherein the matrix resin content is 86%-90%; the rubber modifier content is 8%-12%; and the additive content is 1.2%-1.6%. In step S2, 1 g of nano-silica aerogel is added to 50 mL of ethanol and ultrasonically treated for 30 minutes; wherein the functional filler is selected from nano-silica aerogel, and the nano-silica aerogel has a particle size of 50–100 nm and a specific surface area >600 m². 2 / g, and its addition amount is 0.7%-0.9%; In S4, the mixture is injected into a vacuum degassing tank and degassed at -0.095 MPa for 30 minutes until no more bubbles are precipitated. In S5, the OCA mixture slurry is uniformly coated onto the PET release film using a slot coater, with the wet film thickness controlled at 60–250 μm; the LED light source has a wavelength of 365 nm and an intensity of 8 mW / cm². 2 The irradiation time is 150-300 seconds; preferably, the irradiation time is 180 seconds.

[0013] Furthermore, in S5, an OCA mixed slurry is coated between 50μm and 75μm release films using a coating machine, and the wet film thickness is set to 150μm.

[0014] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. This invention achieves a combination of rigidity and flexibility through the interpenetrating network structure of rubber phase and acrylate. The dielectric constant is stable in the range of 2.6-2.8 under 1MHz conditions, the loss factor is less than 0.005, and the light transmittance exceeds 92% and the haze is less than 0.5%.

[0015] 2. This invention utilizes the porous structure of nano-silica aerogel to adsorb polar small molecules. After silane modification, the surface of the aerogel forms covalent bonds with the matrix, significantly improving interfacial adhesion and resistance to damp heat (no delamination after 168 hours under 85℃ / 85%RH test).

[0016] 3. This invention combines ultrasonic dispersion and vacuum degassing technology to eliminate microscopic defects, enabling the product to maintain stable performance and dielectric constant fluctuation of less than 5% after being bent at -40℃ (radius 3mm, 100,000 cycles) and aged at 120℃ (1000 hours).

[0017] 4. This invention provides a rubber-modified acrylate OCA material with low dielectric constant (<2.8), high light transmittance (>92%), and excellent flexibility and thermal stability. Through molecular structure design, elastic rubber network segments are constructed in the acrylate matrix. By suppressing dipole polarization and space charge accumulation, dielectric loss is reduced. At the same time, nanoporous fillers are used to optimize interfacial compatibility and avoid loss of optical performance.

[0018] 5. The present invention also provides a large-scale preparation process for the material, which ensures the performance consistency of the product in a wide temperature range (-40℃ to 120℃) and high frequency environment (1–10MHz) by precisely controlling the prepolymerization reaction, filler dispersion and curing conditions, thus filling the application gap of the existing technology in the field of high-end electronic packaging.

[0019] 6. This invention introduces a rubber elastomer to construct a composite system with a microscopic phase separation structure. While maintaining high light transmittance and bonding strength, it significantly reduces the dielectric constant. This material can be widely used in 5G antenna modules, flexible OLED displays, high-frequency circuit board bonding, and vehicle radar sensors, meeting the multiple requirements of modern electronic devices for signal integrity, mechanical flexibility, and environmental stability.

[0020] 7. The material of this invention has a narrow dielectric constant fluctuation range in the 1–10MHz frequency band and a dielectric loss that is more than 60% lower than that of traditional OCA, which can significantly improve the efficiency of 5G millimeter wave antennas and reduce electromagnetic interference between adjacent circuits.

[0021] 8. By optimizing the rubber phase distribution, this invention maintains high light transmittance while controlling the elastic modulus at 25°C to 50–120 kPa, making it suitable for curved screen bonding and dynamic bending applications. Attached Figure Description

[0022] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0023] Figure 1 This is a schematic diagram of the physical crosslinking of the rubber and acrylate in this invention. Detailed Implementation

[0024] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0025] With the rapid development of fifth-generation mobile communication technology (5G), the Internet of Things, and flexible electronic devices, the operating frequency of electronic components has increased to the millimeter-wave range (such as 28 GHz and above). Traditional OCA (Optically Clear Adhesive) is prone to problems such as signal transmission delay, impedance mismatch, and energy loss due to its excessively high dielectric constant (usually greater than 3.5).

[0026] As a key encapsulation material for display modules and touchscreens, OCA (Optical Carbon Adhesive) must simultaneously possess excellent optical performance (transmittance >90%, haze <1%), reliable adhesive strength (peel strength >10 N / cm), and good weather resistance. Currently, commercial OCA mainly uses acrylate or polyurethane acrylate as the matrix. Although it meets basic optical and adhesive requirements, the polar groups in its molecular chain (such as ester groups and hydroxyl groups) are prone to orientation polarization under high-frequency electric fields, resulting in a high dielectric constant (generally 3.5–4.2), which in turn causes signal attenuation and crosstalk. Existing technologies introduce fluorinated polymers into OCA, but the hydrophobic properties of the fluorinated components reduce adhesion to the substrate; or add nano-alumina fillers, but the difference in refractive index between the filler and the matrix causes light scattering. In addition, high filler content can exacerbate material embrittlement and affect the bending life of flexible devices. Therefore, the industry urgently needs an innovative material solution that can achieve a balance between low dielectric constant, high transmittance, strong adhesion, and flexibility.

[0027] To address the above problems, the present invention provides a rubber-modified acrylate system OCA, wherein the OCA comprises: a matrix resin, a rubber modifier, a functional filler, and additives; The matrix resin is selected from one or more combinations of isooctyl acrylate, methyl methacrylate, and isobornyl acrylate; The rubber modifier is selected from one or more combinations of natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, and nitrile rubber. The functional filler is selected from nano-silica aerogel; The additives are selected from one or more combinations of photoinitiators, silane coupling agents, antioxidants, and UV aging agents; The matrix resin is added at a rate of 83%-90%; the rubber modifier at a rate of 5%-15%; the functional filler at a rate of 0.5%-1%; and the additives at a rate of 1%-2%. The percentage of each substance added is calculated as: (mass of each substance added (g)) / (total mass of matrix resin, rubber modifier, functional filler, and additives, in g) * 100%.

[0028] In one embodiment, the matrix resin is selected from isooctyl acrylate and methyl methacrylate.

[0029] In one embodiment, the matrix resin is selected from isooctyl acrylate, methyl methacrylate, and isobornyl acrylate.

[0030] In one embodiment, the amount of the matrix resin added is 85%-90%.

[0031] In a preferred embodiment, the amount of matrix resin added is 86%-90%.

[0032] In one embodiment, the rubber modifier is selected from nitrile rubber, which contains 18%-25% acrylonitrile; preferably, the nitrile rubber contains 22% acrylonitrile.

[0033] In one embodiment, the amount of rubber modifier added is 5%-12%.

[0034] In a preferred embodiment, the amount of rubber modifier added is 8%-12%.

[0035] In one embodiment, the functional filler is selected from nano-silica aerogel, wherein the nano-silica aerogel has a particle size of 50–100 nm and a specific surface area >600 m². 2 / g.

[0036] In one embodiment, the amount of the functional filler added is 0.7%-0.9%.

[0037] In one embodiment, the additive is selected from TPO photoinitiator and KH-570 silane coupling agent.

[0038] In one embodiment, the content of the additive is 1.2%-1.6%.

[0039] In one embodiment, the OCA comprises methyl methacrylate, isooctyl acrylate, nitrile rubber, nano-silica aerogel, TPO photoinitiator, and KH-570 silane coupling agent.

[0040] In one embodiment, the OCA comprises methyl methacrylate, isooctyl acrylate, isobornyl acrylate, nitrile rubber, nano-silica aerogel, TPO photoinitiator, and KH-570 silane coupling agent.

[0041] In one embodiment, the OCA comprises 100g of methyl methacrylate, 10g of isooctyl acrylate, 10g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator, and 0.8g of KH-570 silane coupling agent.

[0042] In one embodiment, the OCA comprises 100g of methyl methacrylate, 10g of isooctyl acrylate, 15g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator, and 0.8g of KH-570 silane coupling agent.

[0043] In one embodiment, the OCA comprises 40g of methyl methacrylate, 10g of isooctyl acrylate, 60g of isobornyl acrylate, 10g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator, and 0.8g of KH-570 silane coupling agent.

[0044] This invention also provides a method for preparing an OCA of a rubber-modified acrylate system, comprising: S1: Under a nitrogen atmosphere, the matrix resin, rubber modifier and additives are stirred at a constant temperature of 50-60℃ for 6 hours to obtain OCA prepolymer; S2: Disperse the functional filler in anhydrous ethanol and treat it with an ultrasonic instrument for 30 minutes to obtain the functional filler dispersion; S3: Mix the OCA prepolymer and the functional filler dispersion evenly to obtain a mixed slurry of OCA and functional filler; S4: Remove dissolved gases and solvents from the mixed slurry to obtain OCA mixed slurry; S5: The OCA mixture is evenly coated onto the PET release film and then irradiated with an LED light source; S6: At 120℃, the wet film on the PET release film is cured for 2 hours to obtain an OCA film material with a thickness of 50–200μm.

[0045] In S1, the amount of matrix resin added is 83%-90%; the amount of rubber modifier added is 5%-15%; and the amount of additives added is 1%-2%.

[0046] Preferably, the amount of the matrix resin added is 86%-90%; the amount of the rubber modifier added is 8%-12%; and the amount of the additives added is 1.2%-1.6%.

[0047] In one embodiment, the matrix resin is selected from isooctyl acrylate and methyl methacrylate.

[0048] In one embodiment, the matrix resin is selected from isooctyl acrylate, methyl methacrylate, and isobornyl acrylate.

[0049] In one embodiment, the rubber modifier is selected from nitrile rubber, which contains 22% acrylonitrile.

[0050] In one embodiment, the additive is selected from TPO photoinitiator and KH-570 silane coupling agent.

[0051] In one embodiment, the matrix resin is selected from 10g of isooctyl acrylate and 100g of methyl methacrylate.

[0052] In one embodiment, the matrix resin is selected from 10g of isooctyl acrylate, 40g of methyl methacrylate, and 60g of isobornyl acrylate.

[0053] In one embodiment, the rubber modifier is selected from 10g of nitrile rubber.

[0054] In one embodiment, the rubber modifier is selected from 15g of nitrile rubber.

[0055] In one embodiment, the additive is selected from 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent.

[0056] In one embodiment, the matrix resin, rubber modifier, and additives are stirred at a constant temperature of 55°C for 6 hours under a nitrogen atmosphere.

[0057] In one embodiment, under a nitrogen atmosphere, the matrix resin, rubber modifier, and additives are placed in a three-necked flask with mechanical stirring and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer.

[0058] Specifically, in S2, the ultrasonic instrument has a power of 500W and a frequency of 20kHz.

[0059] In one embodiment, the functional filler is selected from nano-silica aerogel, wherein the nano-silica aerogel has a particle size of 50–100 nm and a specific surface area >600 m². 2 / g.

[0060] In one embodiment, the amount of the functional filler added is 0.7%-0.9%.

[0061] In one embodiment, 1g of nano-silica aerogel is added to 50mL of ethanol at room temperature and ultrasonically treated for 30 minutes.

[0062] Specifically, in S3, the functional filler dispersion is mixed with the OCA prepolymer using a high-speed shear emulsifier to ensure uniform distribution of the functional filler.

[0063] The high-speed shear emulsifier operates at a speed of 3000 rpm.

[0064] In one embodiment, the OCA prepolymer obtained in step S1 and the functional filler dispersion obtained in step S2 are transferred together to a high-speed disperser and stirred at 2500 rpm for 15 minutes to form a homogeneous mixture.

[0065] Specifically, in S4, dissolved gases and solvents in the mixed slurry are removed by a vacuum degassing device.

[0066] The solvent is anhydrous ethanol.

[0067] In one embodiment, the mixture is injected into a vacuum degassing tank and degassed at -0.095 MPa for 30 minutes until no more bubbles are precipitated.

[0068] Specifically, in S5, the OCA mixed slurry is uniformly coated onto the PET release film using a slot coater, with the wet film thickness controlled at 60–250 μm; The LED light source has a wavelength of 365nm and an intensity of 8mW / cm². 2 The irradiation time is 150-300 seconds; preferably, the irradiation time is 180 seconds; the LED light source irradiation is used to initiate the rapid cross-linking of the OCA mixed slurry (wet film area) to form a preliminary cross-linking network. In one embodiment, an OCA mixture slurry is coated between 50 μm and 75 μm release films using a coating machine, with the wet film thickness set to 150 μm.

[0069] The coating process is a "sandwich coating" process, which uses a thin release film as a "carrying base film", and covers the base film with another release film as a "protective surface film". A paste is applied between the two films, resulting in a three-layer composite structure of "release film A / paste coating / release film B". Specifically, in S6, the wet film is cured in a hot air circulating oven to obtain an OCA film material with a smooth and defect-free surface.

[0070] Compared with the prior art, the present invention achieves a combination of rigidity and flexibility through the interpenetrating network structure of rubber phase and acrylate. The dielectric constant is stable in the range of 2.6-2.8 under 1MHz conditions, the loss factor is less than 0.005, and the light transmittance exceeds 92% and the haze is less than 0.5%.

[0071] This invention utilizes the porous structure of nano-silica aerogel to adsorb polar small molecules. After silane modification, the surface of the aerogel forms covalent bonds with the matrix, significantly improving interfacial adhesion and resistance to damp heat (no delamination after 168 hours under 85℃ / 85%RH test).

[0072] This invention combines ultrasonic dispersion and vacuum degassing technology to eliminate microscopic defects, enabling the product to maintain stable performance and dielectric constant fluctuation of less than 5% after being bent at -40℃ (3mm radius, 100,000 cycles) and aged at 120℃ (1000 hours).

[0073] This invention provides a rubber-modified acrylate OCA material with low dielectric constant (<2.8), high light transmittance (>92%), and excellent flexibility and thermal stability. Through molecular structure design, an elastic rubber network segment is constructed in the acrylate matrix. By suppressing dipole polarization and space charge accumulation, dielectric loss is reduced. At the same time, nanoporous fillers are used to optimize interfacial compatibility and avoid loss of optical performance.

[0074] This invention also provides a large-scale preparation process for the material, which ensures consistent performance of the product over a wide temperature range (-40℃ to 120℃) and high-frequency environment (1–10MHz) by precisely controlling the prepolymerization reaction, filler dispersion and curing conditions, thus filling the application gap of existing technology in the field of high-end electronic packaging.

[0075] This invention introduces a rubber elastomer to construct a composite system with a microscopic phase separation structure. While maintaining high light transmittance and bonding strength, it significantly reduces the dielectric constant. This material can be widely used in 5G antenna modules, flexible OLED displays, high-frequency circuit board bonding, and automotive radar sensors, meeting the multiple requirements of modern electronic devices for signal integrity, mechanical flexibility, and environmental stability.

[0076] The material of this invention has a narrow dielectric constant fluctuation range in the 1–10MHz frequency band and a dielectric loss that is more than 60% lower than that of traditional OCA, which can significantly improve the efficiency of 5G millimeter wave antennas and reduce electromagnetic interference between adjacent circuits.

[0077] This invention optimizes the rubber phase distribution, maintaining high light transmittance while controlling the elastic modulus at 25°C to 50–120 kPa, making it suitable for curved screen bonding and dynamic bending applications.

[0078] This invention, through accelerated aging tests (85℃ / 85%RH, 1000 hours) and thermal cycling tests (-40℃ to 85℃, 500 cycles), shows that the material's adhesive strength retention rate is >90% and the dielectric property change rate is <3%, meeting the automotive electronics Grade 1 standard.

[0079] This invention features a solvent-free production process with volatile organic compound (VOC) emissions below 10 ppm, complying with EU REACH regulations and halogen-free requirements for the electronics industry.

[0080] Example 1 A method for preparing a rubber-modified acrylate system OCA, comprising: S1: Under a nitrogen atmosphere, 10g of isooctyl acrylate, 100g of methyl methacrylate, 10g of acrylonitrile rubber (acrylonitrile content 22%), 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent were placed in a three-necked flask with a mechanical stirrer and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer. Among them, the rigid segments of isooctyl acrylate (2EHA) and methyl methacrylate (MMA) provide the material skeleton strength and optical transparency; the rubber phase of the nitrile rubber (NBR) forms elastic microdomains through physical cross-linking, which not only absorbs mechanical stress and improves impact resistance, but its non-polar molecular chains can also reduce the density of polarized groups, thereby reducing the dielectric constant. Moreover, its cyano group has good compatibility with the acrylate matrix, thereby avoiding the increase of OCA haze caused by phase separation; the KH-570 silane coupling agent is used to enhance the bonding of the filler-matrix interface.

[0081] S2: Add 1g of nano-silica aerogel to 50mL of ethanol and treat it with an ultrasonic instrument (power 500W, frequency 20kHz) for 30 minutes to obtain a functional filler dispersion; The nano-silica aerogel has a particle size of 50–100 nm and a specific surface area >600 m². 2 / g.

[0082] The three-dimensional nanoporous structure of the nano-silica aerogel can capture free polar molecules and reduce the interfacial polarization effect. At the same time, since the refractive index of the aerogel is close to that of the matrix (about 1.45), it will not significantly affect the light transmittance.

[0083] S3: Transfer the OCA prepolymer obtained in step S1 and the functional filler dispersion obtained in S2 to a high-speed disperser and stir at 2500 rpm for 15 minutes to form a homogeneous mixture; S4: Inject the mixture into a vacuum degassing tank and degas at -0.095MPa for 30 minutes until no bubbles are precipitated; to remove dissolved gases and anhydrous ethanol from the mixed slurry and obtain OCA mixed slurry; S5: The OCA mixture is evenly coated onto the PET release film using a slot coater, and then irradiated with an LED light source. The LED light source irradiation is used to initiate rapid cross-linking of the OCA mixture (wet film area) to form a preliminary cross-linking network. The wet film thickness is controlled at 150 μm; The LED light source has a wavelength of 365nm and an intensity of 8mW / cm². 2 The irradiation time is 180 seconds; In this process, an OCA mixed slurry is coated between 50μm and 75μm release films using a coating machine, with the wet film thickness set at 150μm. This coating process is a "sandwich coating" process, in which a thin release film is used as a "carrying base film", and a release film is placed on top of the base film as a "protective surface film". Slurry is applied between the two films, resulting in a three-layer composite structure of "release film A / slurry coating / release film B".

[0084] S6: At 120℃, the wet film on the PET release film is cured for 2 hours in a hot air circulating oven to obtain an OCA film material with a thickness of 50–200μm and a smooth, defect-free surface.

[0085] Performance test results: transmittance (ASTM D1003) 92.3%, haze 0.3%, dielectric constant (1MHz, IPC TM-650) 2.85, dielectric loss 0.004, peel strength (GB / T 2792) 12N / cm, water absorption (immersion at 23℃ for 24h) 0.8%.

[0086] Example 2: The difference from Example 1 is as follows: In S1, under a nitrogen atmosphere, 10g of isooctyl acrylate, 40g of methyl methacrylate, 60g of isobornyl acrylate, 10g of nitrile rubber (acrylonitrile content 22%), 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent were placed in a three-necked flask equipped with a mechanical stirrer and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer. Among them, the rigid segments of isooctyl acrylate (2EHA), methyl methacrylate (MMA), and isobornyl acrylate (IBOA) provide the material's skeletal strength and optical transparency.

[0087] Performance test results: transmittance (ASTM D1003) 92.6%, haze 0.4%, dielectric constant (1MHz, IPC TM-650) 2.88, dielectric loss 0.006, peel strength (GB / T 2792) 18 N / cm, water absorption (immersion at 23℃ for 24h) 0.9%.

[0088] Example 3: The difference from Example 1 is as follows: In S1, under a nitrogen atmosphere, 10g of isooctyl acrylate, 100g of methyl methacrylate, 15g of nitrile rubber (acrylonitrile content 22%), 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent were placed in a three-necked flask equipped with a mechanical stirrer and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer.

[0089] Performance test results: light transmittance 91.7%, dielectric constant 2.78, dielectric loss 0.003, peel strength 10 N / cm, and elongation at break (GB / T 1040) increased to 180%. This formulation is more suitable for flexible screen modules that require frequent bending, such as the hinge area encapsulation of foldable mobile phones.

[0090] Comparative Example 1: The difference from Example 1 is as follows: In S1, under a nitrogen atmosphere, 10g of isooctyl acrylate, 100g of methyl methacrylate, 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent were placed in a three-necked flask equipped with a mechanical stirrer and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer.

[0091] Performance test results: transmittance (ASTM D1003) 92.6%, haze 0.3%, dielectric constant (1MHz, IPC TM-650) 4.12, dielectric loss 0.016, peel strength 22N / cm, but microcracks appeared after bending test (radius 5mm, 1000 times), indicating poor performance stability.

[0092] Comparative Example 2: The difference from Example 1 is as follows: In S1, under a nitrogen atmosphere, 10g of isooctyl acrylate, 60g of methyl methacrylate, 40g of isobornyl acrylate, 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent were placed in a three-necked flask equipped with a mechanical stirrer and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer.

[0093] Performance test results: transmittance (ASTM D1003) 92.4%, haze 0.2%, dielectric constant (1MHz, IPC TM-650) 3.88, dielectric loss 0.012, peel strength 25N / cm, but microcracks appeared after bending test (radius 5mm, 1000 times).

[0094] The conventional testing methods for the performance involved in the embodiments and comparative examples are as follows: 1. Transmittance and haze test: Cut OCA into 50mm*50mm strips, remove the light release film, attach it to optical quartz glass, remove the heavy release film, and test a series of optical properties using a spectrophotometer in a constant temperature and humidity room.

[0095] 2. Dielectric constant and dielectric loss: OCA is laminated and stacked onto a sample with a thickness of more than 500μm (actual thickness T). Then, the release film is peeled off and it is laminated onto a metal electrode (area S). Another metal electrode is laminated on top of it. The laminated metal electrodes are clamped together with clips. The test frequency is adjusted and the intrinsic capacitance (Cp) value is recorded. The dielectric constant is calculated as Cp×T / (8.854×S), where 8.854 is a constant.

[0096] 3. Peel strength: Peel off one side of the OCA adhesive film release film and attach it to a 0.05mm transparent PET film. Cut the sample into 25.4mm wide and 300mm long pieces. Peel off the other side of the polyester film (release film) and roll it onto a SUS 304 steel plate at a speed of 600mm / min using a 2KG roller. Let it stand for 20 minutes and use a tensile testing machine to test its 180° peel adhesion. The specific test method refers to the ASTM D3330 international standard.

[0097] 4. Water Absorption Rate: Take a 50mm × 50mm OCA sample, remove the release film, and dry it in an oven at 23℃±2℃ and 50%±5%RH until constant weight. Record the initial weight as m0. Immerse the sample in deionized water at 23℃ for 24 hours; record the weight at this point as m1. Water absorption rate = (m1 - m0) / m0 × 100% 5. Elongation at break: Cut OCA optical adhesive to a width of 6.5cm, remove the release film, and stack the samples to a thickness of 0.7mm. Then cut the sample to a width of 25mm. Remove the release film from one end of the sample and cut an effective length of 25mm using invisible tape. Remove the release film from the other end and attach the invisible tape in the form of a handle. Fix the handle to the fixture and test it using a tensile testing machine. When the OCA breaks, the distance between the fixtures is L. Elongation at break = (L-25) / 25×100% 6. Bending Test: OCA was attached between 50µm CPI sheets to form a three-layer structure, which was then cut into 5cm long × 1cm wide pieces. Alternatively, a five-layer structure consisting of CPI / OCA / CPI / OCA / CPI was prepared using a similar method with OCA and 50µm CPI. Samples were mounted in a dynamic folding apparatus with two folding stages, which rotated from 180 degrees (sample not bent) to 0 degrees (sample folded), and 200,000 cycles were performed at a test rate of approximately 40 cycles / minute. The bending radius of 5mm was determined by the gap between the two rigid plates in the closed state (0 degrees). No mandrel-guided curvature was used (i.e., free bending was employed), and folding was performed at room temperature.

[0098] In summary, the OCA obtained using the preparation method of the present invention has the following advantages: 1. High-frequency signal compatibility: The OCA material of this invention has a narrow dielectric constant fluctuation range in the 1–10MHz frequency band, and the dielectric loss is reduced by more than 60% compared with traditional OCA, which can significantly improve the efficiency of 5G millimeter wave antennas and reduce electromagnetic interference between adjacent circuits.

[0099] 2. Balance of optical and mechanical properties: By optimizing the rubber phase distribution, while maintaining high light transmittance, the elastic modulus at 25℃ is controlled at 50–120 kPa, making it suitable for curved screen bonding and dynamic bending applications.

[0100] 3. Wide environmental adaptability: Through accelerated aging tests (85℃ / 85%RH, 1000 hours) and thermal cycling tests (-40℃ to 85℃, 500 cycles), the material's adhesive strength retention rate is >90%, and the dielectric property change rate is <3%, meeting the automotive electronics Grade 1 standard.

[0101] 4. Green manufacturing compatibility: The entire process is solvent-free, with volatile organic compound (VOC) emissions below 10 ppm, complying with EU REACH regulations and halogen-free requirements for the electronics industry.

[0102] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An OCA based on a rubber-modified acrylate system, characterized in that, The OCA includes: a matrix resin, a rubber modifier, a functional filler, and additives; The matrix resin is selected from one or more combinations of isooctyl acrylate, methyl methacrylate, and isobornyl acrylate; The rubber modifier is selected from one or more combinations of natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, and nitrile rubber. The functional filler is selected from nano-silica aerogel; The additives are selected from one or more combinations of photoinitiators, silane coupling agents, antioxidants, and UV aging agents; The matrix resin is added at a rate of 83%-90%; the rubber modifier is added at a rate of 5%-15%; the functional filler is added at a rate of 0.5%-1%; and the additives are added at a rate of 1%-2%.

2. The OCA according to claim 1, characterized in that: The matrix resin is selected from isooctyl acrylate and methyl methacrylate; or the matrix resin is selected from isooctyl acrylate, methyl methacrylate and isobornyl acrylate; The amount of the matrix resin added is 85%-90%.

3. The OCA according to claim 1 or 2, characterized in that: The rubber modifier is selected from nitrile rubber, which contains 22% acrylonitrile; The amount of rubber modifier added is 8%-12%.

4. The OCA according to any one of claims 1-3, characterized in that: The nano-silica aerogel has a particle size of 50–100 nm and a specific surface area >600 m². 2 / g; The amount of nano-silica aerogel added is 0.7%-0.9%.

5. The OCA according to any one of claims 1-4, characterized in that: The additives are selected from TPO photoinitiator and KH-570 silane coupling agent; the additive content is 1.2%-1.6%.

6. The OCA according to any one of claims 1-5, characterized in that: The OCA comprises methyl methacrylate, isooctyl acrylate, nitrile rubber, nano-silica aerogel, TPO photoinitiator, and KH-570 silane coupling agent; or The OCA comprises methyl methacrylate, isooctyl acrylate, isobornyl acrylate, nitrile rubber, nano silica aerogel, TPO photoinitiator, and KH-570 silane coupling agent.

7. The OCA according to any one of claims 1-6, characterized in that: The OCA comprises 100g of methyl methacrylate, 10g of isooctyl acrylate, 10g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator and 0.8g of KH-570 silane coupling agent; The OCA comprises 100g of methyl methacrylate, 10g of isooctyl acrylate, 15g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator, and 0.8g of KH-570 silane coupling agent; or The OCA contains 40g of methyl methacrylate, 10g of isooctyl acrylate, 60g of isobornyl acrylate, 10g of nitrile rubber, 1g of nano-silica aerogel, 1g of TPO photoinitiator, and 0.8g of KH-570 silane coupling agent.

8. A method for preparing an OCA of a rubber-modified acrylate system according to any one of claims 1-7, characterized in that, include: S1: Under a nitrogen atmosphere, the matrix resin, rubber modifier and additives are stirred at a constant temperature of 50-60℃ for 6 hours to obtain OCA prepolymer; S2: Disperse the functional filler in anhydrous ethanol and treat it with an ultrasonic instrument for 30 minutes to obtain the functional filler dispersion; S3: Mix the OCA prepolymer and the functional filler dispersion evenly to obtain a mixed slurry of OCA and functional filler; S4: Remove dissolved gases and solvents from the mixed slurry to obtain OCA mixed slurry; S5: The OCA mixture is evenly coated onto the PET release film and then irradiated with an LED light source; S6: At 120℃, the wet film on the PET release film is cured for 2 hours to obtain an OCA film material with a thickness of 50–200μm.

9. The method according to claim 8, characterized in that: In step S1, under a nitrogen atmosphere, the matrix resin, rubber modifier, and additives are placed in a three-necked flask equipped with a mechanical stirrer and stirred in a water bath at 55°C for 6 hours to obtain a transparent and viscous OCA prepolymer; wherein the matrix resin content is 86%-90%; the rubber modifier content is 8%-12%; and the additive content is 1.2%-1.6%. In step S2, 1 g of nano-silica aerogel is added to 50 mL of ethanol and ultrasonically treated for 30 minutes; wherein the functional filler is selected from nano-silica aerogel, and the nano-silica aerogel has a particle size of 50–100 nm and a specific surface area >600 m². 2 / g, and its addition amount is 0.7%-0.9%; In S4, the mixture is injected into a vacuum degassing tank and degassed at -0.095 MPa for 30 minutes until no more bubbles are precipitated. In S5, the OCA mixture slurry is uniformly coated onto the PET release film using a slot coater, with the wet film thickness controlled at 60–250 μm; the LED light source has a wavelength of 365 nm and an intensity of 8 mW / cm². 2 The irradiation time is 150-300 seconds; preferably, the irradiation time is 180 seconds.

10. The method according to claim 8 or 9, characterized in that: In S5, an OCA mixed slurry is coated between 50μm and 75μm release films using a coating machine, and the wet film thickness is set to 150μm.

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