An OCA optical adhesive, its preparation method and application

Abstract

This invention relates to an OCA optical adhesive, its preparation method, and its application, belonging to the field of optical adhesive technology. The OCA optical adhesive comprises an intermediate OCA layer and a surface layer; the surface layer comprises an OCA layer one and an OCA layer two, with the intermediate OCA layer disposed between the OCA layer one and the OCA layer two; the raw materials for preparing the intermediate OCA layer include acrylate resin, curing agent A, coupling agent A, UV absorber, and light stabilizer; the raw materials for preparing the surface layer include acrylate prepolymer, curing agent B, coupling agent B, and photoinitiator. The OCA optical adhesive provided by this invention has a three-layer composite structure. By combining a low-modulus, low-curing-rate surface layer with a high-modulus, high-curing-rate intermediate OCA layer, the contradiction between UV resistance stability and reworkability is effectively resolved, making it particularly suitable for long-term reliable bonding of automotive and outdoor displays.

Description

Technical Field

[0001] This invention relates to the field of optical adhesives, and more particularly to an OCA optical adhesive, its preparation method, and its application. Background Technology

[0002] As automotive and outdoor displays become larger and more curved, the performance requirements for optically clear adhesives (OCAs) are becoming increasingly stringent. Ultraviolet (UV) radiation is a key factor causing aging of components such as polarizers and liquid crystal materials in displays, leading to yellowing, brightness reduction, and even functional failure. Therefore, automotive OCAs must possess long-term, stable UV resistance.

[0003] Currently, to impart UV resistance to OCA optical adhesives, UV absorbers are typically added to the adhesive. However, this method has two major technical bottlenecks: First, to maintain the bonding yield and filling properties of the OCA optical adhesive, its modulus and curing rate cannot be too high, which leads to insufficient cohesive strength, making the adhesive layer prone to breakage and residue during rework peeling, resulting in poor rework performance; Second, most small-molecule UV absorbers tend to migrate and precipitate in OCA optical adhesive systems with low crosslinking density, causing a significant decrease in the UV resistance of the OCA optical adhesive after long-term use, thus failing to provide durable protection for the display screen.

[0004] Therefore, developing an OCA optical adhesive that can simultaneously resolve the contradiction between long-term stability of UV resistance and excellent reworkability has become a pressing technical challenge in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an OCA optical adhesive, its preparation method, and its applications. The OCA optical adhesive has a three-layer composite structure, which effectively resolves the conflict between UV resistance stability and reworkability by combining a low-modulus, low-curing-rate surface layer with a high-modulus, high-curing-rate intermediate OCA layer. This makes it particularly suitable for long-term reliable bonding of automotive and outdoor displays.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an OCA optical adhesive, the OCA optical adhesive comprising an intermediate OCA layer and a surface layer;

[0008] The surface layer includes OCA layer one and OCA layer two, and the intermediate OCA layer is disposed between OCA layer one and OCA layer two;

[0009] The raw materials for preparing the intermediate OCA layer include acrylate resin, curing agent A, coupling agent A, ultraviolet absorber and light stabilizer;

[0010] The raw materials for preparing the surface layer include acrylate prepolymer, curing agent B, coupling agent B, and photoinitiator.

[0011] This invention optimizes the design of the raw material components of the intermediate OCA layer and the surface layer, resulting in a high-modulus, high-curing-rate intermediate OCA layer (storage modulus ≥150 kPa at 25℃, curing rate ≥80%) and a low-modulus, low-curing-rate surface layer (storage modulus ≤80 kPa at 25℃, curing rate ≤70%). Furthermore, it cleverly combines the low-modulus, low-curing-rate surface layer (OCA layer one and OCA layer two) with the high-modulus, high-curing-rate intermediate OCA layer to form a three-layer composite structure. This optimizes the design of the OCA optical adhesive structure, concentrating the "UV resistance" and "mechanical support" functions in the intermediate OCA layer, while assigning the "bonding and filling" function to the surface layer. This decouples the UV resistance function and mechanical performance requirements of the OCA optical adhesive, enabling it to simultaneously achieve excellent long-term UV resistance stability and superior reworkability. It effectively resolves the contradiction between UV resistance stability and reworkability in existing OCA optical adhesives, making it particularly suitable for long-term reliable bonding of automotive and outdoor displays.

[0012] The use of a high-modulus, high-curing-rate intermediate OCA layer in the OCA optical adhesive provided by this invention can significantly improve the cohesive strength of OCA. On the one hand, it allows stress to be effectively transferred during rework peeling of the OCA optical adhesive, making it less prone to breakage and residue, and allowing it to be peeled off cleanly and completely from the substrate, greatly reducing the risk of residual adhesive, thereby improving rework performance and reducing rework difficulty and cost. On the other hand, the high cross-linking density network of the intermediate OCA layer can effectively lock UV absorber molecules and prevent migration, so that the OCA optical adhesive can still maintain excellent UV blocking rate after long-term exposure to high temperature and humidity, thermal shock and ultraviolet light, thus giving the OCA optical adhesive extremely stable and long-lasting UV resistance.

[0013] The use of low-modulus, low-curing-rate surface layers (OCA layer one and OCA layer two) in the OCA optical adhesive provided by this invention gives the OCA optical adhesive excellent flowability and gap-filling ability. This effectively adapts to differences in screen ink distribution and curved surface designs, eliminating the risk of display unevenness (mura) or bubbles during bonding, thereby ensuring a clear and uniform final display effect and improving bonding performance. If the curing rate of the surface layer is too high, it will reduce the OCA optical adhesive's filling performance for the display screen ink, preventing it from fully filling the ink gaps. This also increases the risk of display unevenness during module bonding, thus affecting product yield.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0015] As a preferred embodiment of the present invention, the thickness of the intermediate OCA layer is 50-150 μm, for example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm or 150 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0016] Preferably, the thickness of the surface layer is 50-100 μm, for example, it can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm or 100 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0017] Preferably, a release film is provided on the side of the OCA layer one and OCA layer two away from the middle OCA layer.

[0018] Preferably, the release film used in this invention includes a light release film and a heavy release film, so that the structure of the obtained OCA optical adhesive is "light release film - OCA layer one - intermediate OCA layer - OCA layer two - heavy release film" or "heavy release film - OCA layer one - intermediate OCA layer - OCA layer two - light release film".

[0019] It should be noted that the present invention does not have any special limitation on the specific types of light and heavy release films. Commonly used light and heavy release films in the art are applicable. Among them, light release films include, but are not limited to: Suzhou Tailun UM-0501, Suzhou Tailun Electronic Materials Co., Ltd. E-ST7510, E-ST7513ESD or E-ST5008, etc.; heavy release films include, but are not limited to: Suzhou Tailun E-ST10020E2, Suzhou Tailun E-ST7520 or Jiangyin Huamei Optoelectronics Technology Co., Ltd. HMC100T15A, etc.

[0020] Preferably, the raw materials for preparing the intermediate OCA layer comprise the following components in parts by weight:

[0021] 90-100 parts of acrylate resin;

[0022] Hardener A: 0.03-0.15 parts;

[0023] Coupling agent A: 0.1-0.5 parts;

[0024] 0.1-1.0 parts of ultraviolet absorber;

[0025] Light stabilizer 0.05-0.3 parts.

[0026] This invention designs the raw materials for preparing the intermediate OCA layer. By combining components with specific amounts, the resulting intermediate OCA layer can be well controlled to meet the characteristics of high modulus and high curing rate, thereby obtaining an OCA optical adhesive with excellent UV resistance and rework performance.

[0027] The weight percentage of acrylate resin in the raw materials for preparing the intermediate OCA layer provided by this invention can be 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, 98 parts, 99 parts, or 100 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0028] The weight percentage of curing agent A in the raw materials for preparing the intermediate OCA layer provided by this invention can be 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.11 parts, 0.12 parts, 0.13 parts, 0.14 parts, or 0.15 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0029] The weight percentage of coupling agent A in the raw materials for preparing the intermediate OCA layer provided by this invention can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.48 parts, or 0.5 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0030] The weight percentage of the ultraviolet absorber in the raw materials for preparing the intermediate OCA layer provided by this invention can be 0.1 parts, 0.15 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1.0 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0031] The weight percentage of the light stabilizer in the raw materials for preparing the intermediate OCA layer provided by this invention can be 0.05 parts, 0.08 parts, 0.1 parts, 0.12 parts, 0.15 parts, 0.18 parts, 0.2 parts, 0.22 parts, 0.25 parts, 0.28 parts, or 0.3 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0032] Preferably, the acrylate resin is prepared by polymerization of acrylate monomer A under the action of initiator A.

[0033] Preferably, the acrylate monomer A includes acrylate monomers without hydroxyl groups and acrylate monomers containing hydroxyl groups.

[0034] Preferably, the weight percentage of the hydroxyl-free acrylate monomer is 72-80 parts, for example, 72, 73, 74, 75, 76, 77, 78, 79 or 80 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0035] Preferably, the combination of butyl acrylate (BA) and isobornyl acrylate (IBOA) or the combination of isooctyl acrylate (2-EHA) and isobornyl acrylate are used.

[0036] Preferably, the weight percentage of isoborneol acrylate in the hydroxyl-free acrylate monomer is 27-30 parts, for example, 27 parts, 27.5 parts, 28 parts, 28.5 parts, 29 parts, 29.5 parts or 30 parts, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0037] Preferably, the weight parts of the hydroxyl-containing acrylate monomer are 18-20 parts, for example, 18 parts, 18.2 parts, 18.5 parts, 18.8 parts, 19 parts, 19.2 parts, 19.5 parts, 19.8 parts or 20 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0038] Preferably, the hydroxyl-containing acrylate monomer includes any one or a combination of at least two of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate, and more preferably hydroxyethyl acrylate (HEA).

[0039] Preferably, the initiator A includes an azo initiator and / or a peroxide initiator.

[0040] Preferably, the azo initiator includes any one or a combination of at least two of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), or dimethyl azobisisobutyrate.

[0041] Preferably, the peroxide initiator includes any one or a combination of at least two of benzoyl peroxide (BPO), dilauryl peroxide (LPO), or tert-butyl peroxide-2-ethylhexanoate (TBPO).

[0042] Preferably, the mass of the initiator A is 0.03-0.10% of the mass of the acrylate monomer, for example, it can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.10%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0043] Preferably, the polymerization reaction is carried out in a solvent.

[0044] Preferably, the solvent includes ethyl acetate and / or toluene.

[0045] Preferably, the polymerization reaction includes reacting at 60-70°C for 2-4 hours, followed by holding at 70-85°C for 2-4 hours.

[0046] Wherein, 60-70℃ can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃ or 70℃, 70-85℃ can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 82℃ or 85℃, 2-4 h can be 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 or 4 h, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0047] Preferably, the polymerization reaction is carried out in a protective gas atmosphere, which includes any one or a combination of at least two of nitrogen, argon, or helium.

[0048] Preferably, the conversion rate of acrylate monomer A in the acrylate resin is 45-55%, for example, it can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0049] Specifically, the acrylate resin is prepared by the following method, which includes the following steps:

[0050] Under a protective gas atmosphere, acrylate monomers, initiator A, and optional solvent are mixed and reacted at 60-70°C for 2-4 h, and then kept at 70-85°C for 2-4 h to obtain the acrylate resin.

[0051] Preferably, the curing agent comprises an isocyanate curing agent.

[0052] Preferably, the coupling agent A comprises a silane coupling agent.

[0053] Preferably, the coupling agent A comprises 3-glycidyl etheroxypropyltrimethoxysilane (KBM403) and / or γ-aminopropyltriethoxysilane (KH-550).

[0054] Preferably, the ultraviolet absorber includes triazole ultraviolet absorbers and / or triazine ultraviolet absorbers.

[0055] Preferably, the triazole UV absorber includes 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (Tinuvin 329) and / or 2-(2H-benzotriazol-2-yl)-4,6-di(1-methyl-1-phenylethyl)phenol (Tinuvin 234).

[0056] Preferably, the triazine UV absorber includes 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol (Tinuvin 1577 ED).

[0057] Preferably, the light stabilizer includes hindered amine light stabilizers (HALS).

[0058] Preferably, the hindered amine light stabilizer includes bis(1,2,2,6,6-pentamethyl-4-piperidine) sebacate (Tinuvin 292) and / or bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidine) sebacate (Tinuvin 123).

[0059] Preferably, the raw materials for preparing the intermediate OCA layer also include a diluent.

[0060] Preferably, the diluent comprises ethyl acetate (EAC) and / or toluene.

[0061] It should be noted that the specific choice of diluent in this invention is the same as that used in the preparation process of acrylate resin.

[0062] Preferably, the diluent in the raw materials for preparing the intermediate OCA layer is 10-40 parts by weight, for example, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts or 40 parts, and specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0063] Preferably, the intermediate OCA layer is prepared by the following method, which includes the following steps:

[0064] The acrylate resin, curing agent A, coupling agent A, ultraviolet absorber, light stabilizer and optional diluent are mixed, allowed to stand to degas, coated onto a release film, and dried to obtain the intermediate OCA layer.

[0065] Preferably, the drying temperature is 95-110℃ and the time is 3-7 min.

[0066] Wherein, 95-110℃ can be 95℃, 98℃, 100℃, 102℃, 105℃, 108℃ or 110℃, 3-7 min can be 3 min, 4 min, 5 min, 6 min or 7 min, and the specific point values ​​between the above point values ​​are not exhaustively listed in this invention due to space limitations and for the sake of brevity.

[0067] Preferably, the drying process further includes a ripening step.

[0068] Preferably, the curing temperature is 50-60℃ and the time is 2-3 days.

[0069] Among them, 50-60℃ can be 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃ or 60℃, 2-5 days can be 2 days, 2.5 days or 3 days, and the specific point values ​​between the above point values ​​are not exhaustively listed in this invention due to space limitations and for the sake of brevity.

[0070] As a preferred embodiment of the present invention, the acrylate resin obtained by polymerization in the intermediate OCA layer provided by the present invention has a viscosity of 7000-24000 cP at 25°C and a weight-average molecular weight of 0.95 × 10⁻⁶. 6 -1.4×10 6 g / mol, PDI is 7.5-10.1; Tg of surface layer is -28℃~-26℃, curing rate is 83-93%, and storage modulus at 25℃ is 153-185 kPa.

[0071] Preferably, the raw materials for preparing the surface layer comprise the following components in parts by weight:

[0072] 100 parts of acrylate prepolymer;

[0073] Hardener B: 0.01-0.1 parts;

[0074] Coupling agent B, 0.1-0.5 parts;

[0075] 0.1-0.3 parts of photoinitiator.

[0076] This invention designs the raw materials for the surface layer, and by combining components in specific amounts, it can effectively control the resulting surface layer to meet the characteristics of low storage modulus and low curing rate, thereby obtaining OCA optical adhesive with excellent ink filling and bonding yield. When the content of curing agent B is high, the storage modulus and curing rate of the resulting surface layer both increase, which greatly increases the probability of uneven bonding and reduces the bonding yield.

[0077] The weight percentage of curing agent B in the surface preparation raw material provided by the present invention can be 0.01 parts, 0.02 parts, 0.025 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, or 0.1 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0078] The weight parts of coupling agent B in the surface preparation raw materials provided by the present invention can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, or 0.5 parts, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0079] The photoinitiator in the surface preparation raw materials provided by the present invention can be 0.1 parts, 0.12 parts, 0.15 parts, 0.18 parts, 0.2 parts, 0.22 parts, 0.25 parts, 0.28 parts or 0.3 parts by weight, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0080] Preferably, the acrylate prepolymer is prepared by acrylate monomer B under the action of initiator B and ultraviolet radiation.

[0081] Preferably, the acrylate monomer B includes acrylate monomer 1, acrylate monomer 2 and acrylate monomer 3.

[0082] Preferably, the acrylate monomer 1 includes isooctyl acrylate and / or butyl acrylate.

[0083] Preferably, the acrylate monomer 1 in the acrylate prepolymer is 65-75 parts by weight, for example, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74 or 75 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0084] Preferably, the acrylate monomer 2 includes isoborneol acrylate and / or methyl methacrylate.

[0085] Preferably, the acrylate monomer 2 in the acrylate prepolymer is 5-15 parts by weight, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0086] Preferably, the acrylate monomer 3 includes any one or a combination of at least two of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl methacrylate.

[0087] Preferably, the acrylate monomer 3 in the acrylate prepolymer is 10-30 parts by weight, for example, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts or 30 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0088] Preferably, the preparation of the acrylate prepolymer is carried out under a protective gas atmosphere, wherein the protective gas includes any one or a combination of at least two of nitrogen, argon or helium.

[0089] Preferably, the initiator B comprises photoinitiator 184 and / or initiator TPO.

[0090] Preferably, the initiator B in the acrylate prepolymer is 0.01-0.1 parts by weight, for example, 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts or 0.1 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0091] Preferably, the conversion rate of acrylate monomer B in the acrylate prepolymer is 9-11%, for example, it can be 9%, 9.2%, 9.5%, 9.8%, 10%, 10.2%, 10.5%, 10.8% or 11%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0092] Preferably, the curing agent B comprises an acrylate curing agent.

[0093] Preferably, the acrylate curing agent includes any one or a combination of at least two of 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), neopentyl glycol diacrylate (NPGDA), or ethylene glycol diacrylate (PDDA).

[0094] Preferably, the coupling agent B comprises a silane coupling agent.

[0095] Preferably, the coupling agent B comprises 3-glycidyl etheroxypropyltrimethoxysilane (KBM403) and / or γ-methacryloyloxypropyltrimethoxysilane (KH-570).

[0096] Preferably, the photoinitiator includes any one or a combination of at least two of the following: photoinitiator TPO, photoinitiator 651, or photoinitiator 819.

[0097] Preferably, the surface layer is prepared by the following method, which includes the following steps:

[0098] The acrylate prepolymer, curing agent B, coupling agent B and photoinitiator are mixed, allowed to stand to degas, and then coated onto a release film and cured to obtain the surface layer.

[0099] Preferably, the curing is carried out in a protective gas atmosphere, the protective gas including any one or a combination of at least two of nitrogen, argon or helium.

[0100] Preferably, the curing is performed under a UV curing lamp.

[0101] Preferably, the light intensity of the UV curing lamp is 2.0-5.0 mW, for example, it can be 2 mW, 2.5 mW, 3 mW, 3.5 mW, 4 mW, 4.5 mW or 5 mW, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0102] Preferably, the curing time is 220-380 s, for example, it can be 220 s, 250 s, 280 s, 300 s, 320 s, 350 s or 380 s, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0103] As a preferred embodiment of the present invention, the acrylic prepolymer obtained by polymerization in the surface layer provided by the present invention has a viscosity of 2000-14000 cP at 25°C and a weight-average molecular weight of 1.45 × 10⁻⁶. 6 -2.5×10 6 g / mol, PDI is 1.7-2.1; Tg of surface layer is -52℃ to -40℃, curing rate is 55-70%, and storage modulus at 25℃ is 41-60 kPa.

[0104] In a second aspect, the present invention provides a method for preparing OCA optical adhesive as described in the first aspect, the method comprising the following steps:

[0105] The OCA layer 1, the intermediate OCA layer, and the OCA layer 2 are sequentially stacked and bonded together to obtain the OCA optical adhesive.

[0106] The method for preparing OCA optical adhesive provided by this invention is simple, easy to scale up, and highly practical.

[0107] Thirdly, the present invention provides an application of OCA optical adhesive as described in the first aspect in the fabrication of automotive displays or outdoor equipment displays.

[0108] Compared with the prior art, the present invention has at least the following beneficial effects:

[0109] (1) This invention optimizes the design of the raw material components of the intermediate OCA layer and the surface layer to obtain an intermediate OCA layer with high modulus and high curing rate (storage modulus ≥150 kPa and curing rate ≥80%) and a surface layer with low modulus and low curing rate (storage modulus ≤80 kPa and curing rate ≤70%). It also cleverly combines the surface layer with low modulus and low curing rate (OCA layer one and OCA layer two) with the intermediate OCA layer with high modulus and high curing rate to form a three-layer composite structure. This achieves the optimized design of the OCA optical adhesive structure, so that the "anti-UV" and "mechanical support" functions are concentrated in the intermediate OCA layer, and the "bonding and filling" function is given to the surface layer. This is conducive to decoupling the anti-UV function and mechanical performance requirements of the OCA optical adhesive, so that the OCA optical adhesive can simultaneously achieve excellent long-term anti-UV stability and excellent rework performance. It solves the contradiction between anti-UV stability and rework performance in existing OCA optical adhesives, and is particularly suitable for long-term reliable bonding of automotive and outdoor displays.

[0110] (2) The OCA optical adhesive provided by the present invention has excellent die-cutting performance, rework performance, ink filling performance and bonding performance, as well as excellent UV blocking performance and long-term environmental reliability (resistance to damp heat, resistance to thermal shock, high temperature and resistance to UV aging such as Q-sun). At a wavelength of 360 nm: the initial transmittance of the OCA optical adhesive is 0.6-1.3%, the transmittance after 1000 h in a high temperature and high humidity (85℃, 85%RH) environment is 1.2-1.9%, the transmittance after 1000 h in a thermal shock (-40℃~85℃) environment is 1.1-1.9%, the transmittance after 1000 h in a high temperature (95℃) environment is 1.3-2.6%, and the transmittance after 1000 h in a Q-sun environment is 2.7-4.5%. Attached Figure Description

[0111] Figure 1 This is a schematic diagram of the structure of the OCA optical adhesive provided in Example 1; wherein, 1-release film, 2-OCA layer one, 3-intermediate OCA layer, 4-OCA layer two, and 5-release film. Detailed Implementation

[0112] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0113] Unless otherwise specified, the materials and equipment involved in the following detailed embodiments are all conventional materials and equipment in the art and will not affect the technical effects of the present invention.

[0114] Unless otherwise specified, all reagents and raw materials used in the following examples and comparative examples are commercially available products. Some raw material information is shown below:

[0115] Tinuvin 292: Hindered amine light stabilizer, purchased from BASF;

[0116] Release film 1: Light release film E-ST7510 purchased from Suzhou Tailun Electronic Materials Co., Ltd.;

[0117] Release film 2: Heavy release film E-ST10020E2 purchased from Suzhou Tailun Electronic Materials Co., Ltd.

[0118] The English abbreviations of some of the raw materials used in the embodiments and comparative examples of this invention are shown in the table below:

[0119]

[0120] Example 1

[0121] This embodiment provides an OCA optical adhesive and its preparation method. The OCA optical adhesive includes an OCA layer one, an intermediate OCA layer and an OCA layer two that are sequentially stacked and bonded together. A release film is disposed on the side of the OCA layer one and the OCA layer two away from the intermediate OCA layer.

[0122] OCA layer one and OCA layer two are identical and are both prepared using the following method, which includes the following steps:

[0123] In a glass reaction apparatus under a nitrogen atmosphere, 70 parts of 2-EHA, 10 parts of IBOA, 20 parts of HEA and 0.05 parts of photoinitiator 184 were added, and an acrylate prepolymer with a monomer conversion rate of 10% was obtained by ultraviolet light irradiation.

[0124] Mix 100 parts of the above-mentioned acrylate prepolymer, 0.05 parts of curing agent HDDA, 0.2 parts of silane coupling agent KBM403 and 0.15 parts of photoinitiator TPO, stir evenly, let stand to remove bubbles, and then coat it onto the release film with a thickness of 75 μm. Then cure it under a UV curing lamp with a nitrogen atmosphere for 300 s with a light intensity of 3.5 mW to obtain OCA layer one with release film 1 or OCA layer two with release film 2.

[0125] The intermediate OCA layer is prepared using the following method, which includes the following steps:

[0126] In a glass reaction apparatus under a nitrogen atmosphere, 50 parts of 2-EHA, 30 parts of IBOA, 20 parts of HEA, 0.05 parts of initiator AIBN and 100 parts of ethyl acetate were added and mixed. The mixture was reacted at 65°C for 3 h and then kept at 75°C for 3 h to obtain acrylate resin.

[0127] Mix 100 parts of the above-mentioned acrylate resin, 0.05 parts of isocyanate curing agent L-75, 0.1 parts of silane coupling agent KBM403, 0.2 parts of UV absorber Tinuvin 329, 0.1 parts of light stabilizer Tinuvin 292 and 25 parts of diluent EAC, stir evenly, let stand to remove bubbles, and then coat it onto the release film. Place it in an oven at 100℃ and bake for 5 min to obtain a 100 μm thick film. Cure it at 50℃ for 3 days to obtain the intermediate OCA layer.

[0128] The preparation method of the OCA optical adhesive includes the following steps: sequentially stacking and bonding the above-mentioned OCA layer one with release film 1, intermediate OCA layer and OCA layer two with release film 2 to obtain the OCA optical adhesive.

[0129] Example 2

[0130] This embodiment provides an OCA optical adhesive and its preparation method. The OCA optical adhesive includes an OCA layer one, an intermediate OCA layer and an OCA layer two that are sequentially stacked and bonded together. A release film is disposed on the side of the OCA layer one and the OCA layer two away from the intermediate OCA layer.

[0131] OCA layer one and OCA layer two are identical and are both prepared using the following method, which includes the following steps:

[0132] In a glass reaction apparatus under a nitrogen atmosphere, 70 parts of 2-EHA, 10 parts of IBOA, 20 parts of HEA and 0.1 parts of photoinitiator 184 were added, and an acrylate prepolymer with a monomer conversion rate of 10% was obtained by ultraviolet light irradiation.

[0133] Mix 100 parts of the above-mentioned acrylate prepolymer, 0.01 parts of curing agent HDDA, 0.45 parts of silane coupling agent KBM403 and 0.1 parts of photoinitiator TPO, stir evenly, let stand to remove bubbles, and then coat it onto the release film with a thickness of 50 μm. Then cure it under a UV curing lamp with a nitrogen atmosphere for 220 s with a light intensity of 5.0 mW to obtain OCA layer one with release film 1 or OCA layer two with release film 2.

[0134] The intermediate OCA layer is prepared using the following method, which includes the following steps:

[0135] In a glass reaction apparatus under a nitrogen atmosphere, 45 parts of 2-EHA, 27 parts of IBOA, 18 parts of HEA, 0.03 parts of initiator AIBN and 90 parts of ethyl acetate were added and mixed. The mixture was reacted at 70°C for 3 hours and then kept at 80°C for 2 hours to obtain acrylate resin.

[0136] Mix 90 parts of the above-mentioned acrylate resin, 0.03 parts of isocyanate curing agent L-75, 0.2 parts of silane coupling agent KBM403, 0.5 parts of UV absorber Tinuvin 329, 0.3 parts of light stabilizer Tinuvin 292 and 10 parts of diluent EAC, stir evenly, let stand to remove bubbles, and then coat it onto the release film. Place it in a 95℃ oven and bake for 7 min to obtain a 150 μm thick film. Cure it at 55℃ for 2.5 days to obtain the intermediate OCA layer.

[0137] The preparation method of the OCA optical adhesive includes the following steps: sequentially stacking and bonding the above-mentioned OCA layer one with release film 1, intermediate OCA layer and OCA layer two with release film 2 to obtain the OCA optical adhesive.

[0138] Example 3

[0139] This embodiment provides an OCA optical adhesive and its preparation method. The OCA optical adhesive includes an OCA layer one, an intermediate OCA layer and an OCA layer two that are sequentially stacked and bonded together. A release film is disposed on the side of the OCA layer one and the OCA layer two away from the intermediate OCA layer.

[0140] OCA layer one and OCA layer two are identical and are both prepared using the following method, which includes the following steps:

[0141] In a glass reaction apparatus under a nitrogen atmosphere, 70 parts of 2-EHA, 10 parts of IBOA, 20 parts of HEA and 0.03 parts of photoinitiator 184 were added, and an acrylate prepolymer with a monomer conversion rate of 10% was obtained by ultraviolet light irradiation.

[0142] Mix 100 parts of the above-mentioned acrylate prepolymer, 0.03 parts of curing agent HDDA, 0.45 parts of silane coupling agent KH-570 and 0.3 parts of photoinitiator TPO, stir evenly, let stand to remove bubbles, and then coat it onto the release film with a thickness of 100 μm. Then cure it under a UV curing lamp with a nitrogen atmosphere for 380 s with a light intensity of 2.0 mW to obtain OCA layer one with release film 1 or OCA layer two with release film 2.

[0143] The intermediate OCA layer is prepared using the following method, which includes the following steps:

[0144] In a glass reaction apparatus under a nitrogen atmosphere, 47.5 parts of 2-EHA, 28.5 parts of IBOA, 19 parts of HEA, 0.10 parts of initiator AIBN and 95 parts of toluene were added and mixed. The mixture was reacted at 60°C for 4 h and then kept at 85°C for 4 h to obtain acrylate resin.

[0145] 95 parts of the above-mentioned acrylate resin, 0.05 parts of isocyanate curing agent L-75, 0.45 parts of silane coupling agent KBM403, 0.8 parts of UV absorber Tinuvin 329, 0.2 parts of light stabilizer Tinuvin 292 and 40 parts of diluent toluene were mixed and stirred evenly. After standing to remove bubbles, the mixture was scraped onto the release film and placed in an oven at 110℃ for 7 min to obtain a 50 μm thick film. The film was then cured at 60℃ for 2 days to obtain the intermediate OCA layer.

[0146] The preparation method of the OCA optical adhesive includes the following steps: sequentially stacking and bonding the above-mentioned OCA layer one with release film 1, intermediate OCA layer and OCA layer two with release film 2 to obtain the OCA optical adhesive.

[0147] Example 4

[0148] This embodiment provides an OCA optical adhesive and its preparation method. The OCA optical adhesive includes an OCA layer one, an intermediate OCA layer and an OCA layer two that are sequentially stacked and bonded together. A release film is disposed on the side of the OCA layer one and the OCA layer two away from the intermediate OCA layer.

[0149] OCA layer one and OCA layer two are identical and are both prepared using the following method, which includes the following steps:

[0150] In a glass reaction apparatus under a nitrogen atmosphere, 70 parts of 2-EHA, 10 parts of IBOA, 20 parts of HEA and 0.08 parts of photoinitiator 184 were added, and an acrylate prepolymer with a monomer conversion rate of 9% was obtained by ultraviolet light irradiation.

[0151] Mix 100 parts of the above-mentioned acrylate prepolymer, 0.1 parts of curing agent HDDA, 0.3 parts of silane coupling agent KBM403 and 0.25 parts of photoinitiator 819, stir evenly, let stand to remove bubbles, and then coat it onto the release film with a thickness of 75 μm. Then cure it under a UV curing lamp with a nitrogen atmosphere for 300 s with a light intensity of 3.5 mW to obtain OCA layer one with release film 1 or OCA layer two with release film 2.

[0152] The intermediate OCA layer is prepared using the following method, which includes the following steps:

[0153] In a glass reaction apparatus under a nitrogen atmosphere, 50 parts of 2-EHA, 30 parts of IBOA, 20 parts of HEA, 0.05 parts of initiator dimethyl azobisisobutyrate and 100 parts of ethyl acetate were added and mixed. The mixture was reacted at 65°C for 3 h and then kept at 75°C for 3 h to obtain acrylate resin.

[0154] Mix 100 parts of the above-mentioned acrylate resin, 0.15 parts of isocyanate curing agent L-75, 0.3 parts of silane coupling agent KH-550, 1 part of UV absorber Tinuvin 1577 ED, 0.1 parts of light stabilizer Tinuvin 123 and 25 parts of diluent EAC, stir evenly, let stand to remove bubbles, and then coat it onto the release film. Place it in an oven at 100℃ and bake for 5 min to obtain a 100 μm thick film. Cure it at 50℃ for 3 days to obtain the intermediate OCA layer.

[0155] The preparation method of the OCA optical adhesive includes the following steps: sequentially stacking and bonding the above-mentioned OCA layer one with release film 1, intermediate OCA layer and OCA layer two with release film 2 to obtain the OCA optical adhesive.

[0156] Example 5

[0157] This embodiment provides an OCA optical adhesive and its preparation method. The only difference between this embodiment and Example 1 is that 0.05 parts of curing agent HDDA in the preparation of OCA layer one and OCA layer two in Example 1 are replaced with 0.03 parts of curing agent trimethylolpropane triacrylate (TMPTA). All other components, contents and preparation methods are the same as in Example 1.

[0158] Example 6

[0159] This embodiment provides an OCA optical adhesive and its preparation method. The only difference between this embodiment and Example 1 is that the raw material 2-EHA used in the preparation of OCA layer one and OCA layer two in Example 1 is replaced with an equal mass of BA. All other components, contents and preparation methods are the same as in Example 1.

[0160] Example 7

[0161] This embodiment provides an OCA optical adhesive and its preparation method. The only difference between this embodiment and Example 1 is that the raw material 2-EHA for preparing the intermediate OCA layer in Example 1 is replaced with an equal mass of BA. All other components, contents, and preparation methods are the same as in Example 1.

[0162] Example 8

[0163] This embodiment provides an OCA optical adhesive and its preparation method. The only difference between this embodiment and Example 1 is that the 10 parts IBOA raw materials for preparing OCA layer one and OCA layer two in Example 1 are replaced with 8 parts IBOA and 2 parts MMA. The other components, contents and preparation methods are the same as in Example 1.

[0164] Example 9

[0165] This embodiment provides an OCA optical adhesive and its preparation method. The only difference between this embodiment and Example 1 is that the weight of the ultraviolet absorber Tinuvin 329, the raw material for preparing the intermediate OCA layer in Example 1, is adjusted from 0.2 parts to 0.5 parts. All other components, contents, and preparation methods are the same as in Example 1.

[0166] Example 10

[0167] This embodiment provides an OCA optical adhesive and its preparation method. The only difference between this embodiment and Example 1 is that the weight of the isocyanate curing agent L-75, the raw material for preparing the intermediate OCA layer in Example 1, is replaced from 0.05 parts to 0.07 parts. All other components, contents, and preparation methods are the same as in Example 1.

[0168] Comparative Example 1

[0169] This comparative example provides an OCA optical adhesive and its preparation method. The only difference between this example and Example 1 is that the weight of the curing agent HDDA used in the preparation of OCA layer one and OCA layer two in Example 1 is adjusted from 0.05 parts to 0.11 parts by weight. All other components, contents and preparation methods are the same as in Example 1.

[0170] Comparative Example 2

[0171] This comparative example provides an OCA optical adhesive and its preparation method. The OCA optical adhesive is a single-layer structure of an OCA layer, and release film 1 and release film 2 are respectively disposed on both sides of the OCA layer.

[0172] The preparation method of the OCA optical adhesive includes the following steps:

[0173] In a glass reaction apparatus under a nitrogen atmosphere, 70 parts of 2-EHA, 10 parts of IBOA, 20 parts of HEA and 0.05 parts of photoinitiator 184 were added, and an acrylate prepolymer with a monomer conversion rate of 10% was obtained by ultraviolet light irradiation.

[0174] 100 parts of the above-mentioned acrylate prepolymer, 0.05 parts of curing agent HDDA, 0.2 parts of silane coupling agent KBM403, 0.15 parts of photoinitiator TPO, 0.2 parts of ultraviolet absorber UV390 and 0.1 parts of light stabilizer Tinuvin 292 were mixed, stirred evenly, and allowed to stand to remove bubbles. The mixture was then coated onto a release film with a thickness of 250 μm and cured for 300 s under a UV curing lamp in a nitrogen atmosphere with a light intensity of 3.5 mW to obtain the OCA optical adhesive.

[0175] Comparative Example 3

[0176] This comparison provides an OCA optical adhesive and its preparation method. The OCA optical adhesive is a single-layer structure of an OCA layer, and release films 1 and 2 are respectively disposed on both sides of the OCA layer.

[0177] The preparation method of the OCA optical adhesive includes the following steps:

[0178] In a glass reaction apparatus under a nitrogen atmosphere, 50 parts of 2-EHA, 30 parts of IBOA, 20 parts of HEA, 0.05 parts of initiator AIBN and 100 parts of ethyl acetate were added and mixed. The mixture was reacted at 65°C for 3 h and then kept at 75°C for 3 h to obtain an acrylate prepolymer with an acrylate monomer conversion rate of 50%.

[0179] 100 parts of the above-mentioned acrylate prepolymer, 0.05 parts of isocyanate curing agent L-75, 0.1 parts of silane coupling agent KBM403, 0.2 parts of UV absorber Tinuvin 329, 0.1 parts of light stabilizer Tinuvin 292 and 25 parts of diluent EAC were mixed and stirred evenly. After standing to remove bubbles, the mixture was scraped onto a release film and placed in an oven at 100°C for 7 min to obtain a 250 μm thick film. The film was then cured at 50°C for 3 days to obtain the OCA optical adhesive.

[0180] The performance parameters of the acrylate resin / acrylate prepolymer obtained by polymerization during the preparation process of the OCA optical adhesives provided in Examples 1-10 and Comparative Examples 1-3, as well as the surface layer (OCA layer one and OCA layer two) / intermediate OCA layer after coating, are shown in Table 1.

[0181] Table 1

[0182]

[0183] The performance of the OCA optical adhesives provided in Examples 1-10 and Comparative Examples 1-3 was tested using the following methods / standards:

[0184] (1) Die-cutting performance: The main evaluation factors are the dimensional stability and edge quality after die-cutting. Before die-cutting, OCA optical adhesive is left to stand in a constant temperature and humidity environment (25℃, 50%RH) for 24 h, and then die-cut using a rotary die-cutting machine. After die-cutting, the cut edge is observed visually under yellow light to see if there is any glue seepage. If there is no visible glue overflow, the difference between the die-cut sample and the expected size is measured. If the size difference is ≤0.05 mm, the cut is observed under a microscope. If it is flat, without burrs, and without glue layer tearing, it is considered excellent; if there are slight burrs (roughness 3-10 μm), occasional trace glue threads (length <0.5 mm), and a size deviation of ±0.05-0.1 mm, it is considered good; if there are obvious serrated edges (roughness >10 μm) or glue layer breakage, and a size deviation >0.2 mm, it is considered poor.

[0185] (2) Rework performance: Heat the OCA area evenly for 2 minutes on a heating table to reduce adhesion. Use a thin scraper (thickness ≤0.1mm) to gradually lift it from the edge at an angle ≤30°. Combine with slow stretching (manual peeling speed ≤10 cm / min). Use a non-woven cloth dipped in ethyl acetate to gently wipe away residual adhesive. Do not use strong solvents such as acetone. Ionize the dust to ensure that the surface can recover to ≥40mN / m.

[0186] Excellent: When peeling at 180°, the peeling force is uniform, without sudden increases or decreases, the adhesive layer is 100% completely peeled off, and there is no residue on the substrate surface. Good: When peeling at 180°, the peeling force fluctuates slightly, with local force fluctuations ≤20%, and the adhesive peeling area ≥95%. Poor: When peeling, the adhesive layer breaks or the substrate is damaged, the residual adhesive area is >10%, or the substrate damage affects secondary bonding.

[0187] (3) Ink filling: The die-cut OCA optical adhesive is bonded to the glass / FOG. The OCA optical adhesive can completely fill the micropores and edge steps of the ink layer, without optical refraction or weak interface adhesion caused by incomplete filling, and the overall thickness of OCA is uniform after filling. The ink layer is 100% filled without gaps (no bubbles / layers under SEM), which is recorded as excellent; local micro-gaps (area ratio ≤4%) are recorded as good; obvious unfilled areas (area ≥5%) are recorded as poor.

[0188] (4) Bonding yield: The die-cut OCA optical adhesive is bonded to the glass / FOG, and defects such as bubbles and foreign objects are evaluated. The probability of bonding without abnormalities is the bonding yield. If there are ≤1 bubble (diameter ≤0.1 mm) and ≤1 foreign object (particle size ≤50 μm), the yield is ≥99.5% and is recorded as excellent; if there are ≤3 bubbles (diameter ≤0.2 mm) and ≤3 foreign objects (particle size ≤100 μm), the yield is 98-99.4% and is recorded as good; if the number of bubbles and foreign objects exceeds the above standards, the yield is <98% and is recorded as poor.

[0189] (5) Initial transmittance: Refer to the test standard ASTM D1003 and use a spectrophotometer to test the transmittance of OCA optical adhesive at 360nm.

[0190] (6) High temperature and high humidity resistance: After the OCA optical adhesive was placed at 85℃ and 85%RH for 1000 h, its transmittance at 360 nm was tested;

[0191] (7) Thermal shock performance: The instrument was set to -40℃~85℃, with the temperature changing every 30 min. The transmittance of OCA optical adhesive at 360 nm was tested after 1000 h.

[0192] (8) High temperature resistance: After the OCA optical adhesive was placed in an environment of 95℃ for 1000 h, its transmittance at 360 nm was tested;

[0193] (9) Testing Q-sun performance: The OCA optical adhesive was subjected to a Q-SUN aging test, with an irradiance of 0.93 W / m. 2 @340nm, blackboard temperature 63℃, chamber temperature 45℃, humidity 20%, aging time is 1000 h.

[0194] The test results are shown in Table 2.

[0195] Table 2

[0196]

[0197] According to the test results in Table 2:

[0198] (1) As can be seen from Examples 1 to 10, the present invention uses a surface layer with low modulus and low curing rate (storage modulus ≤80 kPa and curing rate ≤70%) and an intermediate OCA layer with high modulus and high curing rate (storage modulus ≥150 kPa and curing rate ≥80%) to make the OCA optical adhesive a three-layer composite structure. This ensures that the OCA optical adhesive has excellent UV blocking performance and UV aging resistance (initial transmittance is 0.6-1.3%, transmittance after 1000 h in high temperature and high humidity environment is 1.2-1.9%, transmittance after 1000 h in thermal shock environment is 1.1-1.9%, transmittance after 1000 h in high temperature environment is 1.3-2.6%, and transmittance after 1000 h in Q-sun environment is 2.7-4.5%).

[0199] (2) By comparing Example 1 and Comparative Example 1, it can be seen that when the curing rate and storage modulus of the surface layer are too high, the ink filling effect and bonding yield of the obtained OCA optical adhesive are worse. This shows that the present invention can control the curing rate and storage modulus of the obtained surface layer by adjusting the raw materials for surface preparation, thereby obtaining OCA optical adhesive with better ink filling effect and bonding yield.

[0200] (3) By comparing Examples 1-10 with Comparative Examples 2-3, it can be seen that Comparative Examples 2 and 3 are both single-layer OCA optical adhesives. The measured high temperature and high humidity resistance, thermal shock resistance, high temperature resistance and Q-sun resistance of both are significantly worse. Comparative Example 2 provides OCA optical adhesives with low curing rate and low storage modulus, and its die-cutting performance and rework performance are worse. Comparative Example 3 provides OCA optical adhesives with high curing rate and high storage modulus, and its ink filling effect and bonding yield are worse. This shows that the OCA optical adhesive formed by the combination of a low modulus, low curing rate surface layer and a high modulus, high curing rate intermediate OCA layer of the present invention has good die-cutting performance, rework performance, ink filling performance and bonding performance, as well as better UV blocking performance and long-term environmental reliability.

[0201] In summary, this invention, through its innovative three-layer structure design—a surface layer (low modulus / low curing rate), an intermediate layer (high modulus / high curing rate), and a final surface layer (low modulus / low curing rate)—successfully resolves the long-standing contradiction between "UV resistance stability," "rework performance," and "bonding yield" in the high-performance automotive OCA field. The resulting OCA optical adhesive maintains excellent processability and bonding performance while achieving long-term environmental reliability unattainable by single-layer structures, particularly in terms of UV aging resistance, fully meeting the stringent lifespan and reliability requirements of automotive displays.

[0202] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An OCA optical adhesive, characterized in that, The OCA optical adhesive includes an intermediate OCA layer and a surface layer; The surface layer includes OCA layer one and OCA layer two, and the intermediate OCA layer is disposed between OCA layer one and OCA layer two; The intermediate OCA layer has a storage modulus ≥150 kPa at 25°C and a curing rate ≥80%. The surface layer has a storage modulus ≤80 kPa and a curing rate ≤70% at 25°C. The raw materials for preparing the intermediate OCA layer include acrylate resin, curing agent A, coupling agent A, ultraviolet absorber and light stabilizer; The raw materials for preparing the surface layer include acrylate prepolymer, curing agent B, coupling agent B, and photoinitiator.

2. The OCA optical adhesive according to claim 1, characterized in that, The thickness of the intermediate OCA layer is 50-150 μm; The thickness of the surface layer is 50-100 μm; A release film is also provided on the side of OCA layer one and OCA layer two away from the middle OCA layer.

3. The OCA optical adhesive according to claim 1, characterized in that, The raw materials for preparing the intermediate OCA layer include the following components in parts by weight: 90-100 parts of acrylate resin; Hardener A: 0.03-0.15 parts; Coupling agent A: 0.1-0.5 parts; 0.1-1.0 parts of ultraviolet absorber; Light stabilizer 0.05-0.3 parts.

4. The OCA optical adhesive according to any one of claims 1-3, characterized in that, The acrylate resin is prepared by polymerization of acrylate monomer A under the action of initiator A; The acrylate monomer A includes acrylate monomers without hydroxyl groups and acrylate monomers containing hydroxyl groups; The hydroxyl-free acrylate monomer is present in parts by weight of 72-80 parts; The hydroxyl-free acrylate monomers include a combination of butyl acrylate and isoborneol acrylate or a combination of isooctyl acrylate and isoborneol acrylate. The weight percentage of isoborneol acrylate in the hydroxyl-free acrylate monomer is 27-30 parts. The hydroxyl-containing acrylate monomer is present in parts by weight of 18-20 parts; The hydroxyl-containing acrylate monomer includes any one or a combination of at least two of hydroxyethyl acrylate, hydroxypropyl acrylate, or hydroxybutyl acrylate. The initiator A includes azo initiators and / or peroxide initiators; The mass of initiator A is 0.03-0.10% of the mass of the acrylate monomer; The polymerization reaction is carried out in a solvent; The solvent includes ethyl acetate and / or toluene; The polymerization reaction includes reacting at 60-70°C for 2-4 hours, followed by holding at 70-85°C for 2-4 hours. The polymerization reaction is carried out in a protective gas atmosphere, which includes any one or a combination of at least two of nitrogen, argon or helium; The curing agent A includes an isocyanate curing agent; The coupling agent A includes a silane coupling agent; The ultraviolet absorber includes triazole ultraviolet absorbers and / or triazine ultraviolet absorbers; The light stabilizer includes hindered amine light stabilizers; The raw materials for preparing the intermediate OCA layer also include a diluent; The diluent in the raw materials for preparing the intermediate OCA layer is 10-40 parts by weight.

5. The OCA optical adhesive according to claim 1, characterized in that, The intermediate OCA layer is prepared using the following method, which includes the following steps: The acrylate resin, curing agent A, coupling agent A, ultraviolet absorber, light stabilizer and optional diluent are mixed, allowed to stand to degas, coated onto the release film, and dried to obtain the intermediate OCA layer. The drying temperature is 95-110℃, and the time is 3-7 min; The drying process also includes a ripening step; The ripening temperature is 50-60℃, and the time is 2-3 days.

6. The OCA optical adhesive according to claim 1, characterized in that, The raw materials for preparing the surface layer include the following components in parts by weight: 100 parts of acrylate prepolymer; Hardener B: 0.01-0.1 parts; Coupling agent B, 0.1-0.5 parts; 0.1-0.3 parts of photoinitiator.

7. The OCA optical adhesive according to claim 1 or 6, characterized in that, The acrylate prepolymer is prepared by acrylate monomer B under the action of initiator B and ultraviolet radiation. The acrylate monomer B includes acrylate monomer 1, acrylate monomer 2 and acrylate monomer 3; The acrylate monomer 1 includes isooctyl acrylate and / or butyl acrylate; The acrylate prepolymer contains 65-75 parts by weight of acrylate monomer 1. The acrylate monomer 2 includes isobornyl acrylate and / or methyl methacrylate; The acrylate prepolymer contains 5-15 parts by weight of acrylate monomer 2; The acrylate monomer 3 includes any one or a combination of at least two of hydroxyethyl acrylate, hydroxypropyl acrylate, or hydroxybutyl acrylate. The acrylate prepolymer contains 10-30 parts by weight of acrylate monomer 3; The preparation of the acrylate prepolymer is carried out under a protective gas atmosphere, wherein the protective gas includes any one or a combination of at least two of nitrogen, argon or helium; The initiator B includes photoinitiator 184 and / or photoinitiator TPO; The initiator B in the acrylate prepolymer is 0.01-0.1 parts by weight; The curing agent B includes acrylate curing agents; The coupling agent B includes a silane coupling agent; The photoinitiator includes any one or a combination of at least two of the following: photoinitiator TPO, photoinitiator 651, or photoinitiator 819.

8. The OCA optical adhesive according to claim 1, characterized in that, The surface layer is prepared using the following method, which includes the following steps: The acrylate prepolymer, curing agent B, coupling agent B and photoinitiator are mixed, allowed to stand to degas, coated onto a release film and cured to obtain the surface layer. The curing is carried out in a protective gas atmosphere, wherein the protective gas includes any one or a combination of at least two of nitrogen, argon or helium; The curing process is carried out under a UV curing lamp; The light intensity of the UV curing lamp is 2.0-5.0 mW; The curing time is 220-380 s.

9. A method for preparing OCA optical adhesive as described in any one of claims 1-8, characterized in that, The preparation method includes the following steps: The OCA layer 1, the intermediate OCA layer, and the OCA layer 2 are sequentially stacked and bonded together to obtain the OCA optical adhesive.

10. The application of the OCA optical adhesive as described in any one of claims 1-8 in the fabrication of automotive displays or outdoor equipment displays.

Images