Bending-resistant low-modulus OCA glue for folding screens and preparation method thereof, and OCA adhesive

Abstract

The present invention provides a bending-resistant low-modulus OCA glue for folding screens, the OCA glue comprising: 15-20 parts of isooctyl acrylate, 9-12 parts of butyl acrylate, 2.5-3.5 parts of hydroxybutyl acrylate, 0.002-0.004 parts of methyl methacrylate, 0.002-0.004 parts of 1-vinyl-2-pyrrolidone, 0.002-0.004 parts of silane coupling agent KH570, 0.0008-0.0012 parts of initiator, and 65-75 parts of solvent. The present invention also relates to a preparation method and an OCA adhesive with the OCA as the main component. The OCA glue formed by the present invention has high viscosity, high gel fraction and high creep recovery while meeting the low modulus at low temperature, and has excellent comprehensive performance, simple preparation process and low cost.

Description

Technical Field

[0001] The present invention relates to the field of adhesives, and in particular to a bending-resistant low-modulus OCA glue for a folding screen and a preparation method thereof, and an OCA adhesive. Background Art

[0002] In recent years, foldable devices have become more and more popular due to their excellent portability, and are increasingly widely used in the fields of foldable screen mobile phones, smart wearables, vehicles, electronic equipment, etc. With the popularization of foldable devices, adhesives suitable for the use characteristics of foldable devices are also in demand in the market. In general, OCA adhesives used in foldable devices need to have durability against environmental changes, and should also have effective bonding performance, excellent high and low temperature modulus stability, and good creep recovery, so as to increase the service life of foldable devices.

[0003] In some cases, the adhesive layer of the bendable device will become hard as the temperature decreases. For example, when the bendable device is folded in a low temperature environment, it is easy to whiten or break at the folding layer. In addition, if the OCA adhesive used cannot maintain good viscosity under a specific environment, it will also cause the risk of bubbles and even falling off between the adhesive film and the back sticker substrate. More importantly, if the foldable device is used at a lower or higher temperature, the OCA adhesive must have good creep recovery. In this regard, the "CN 113025238 A" patent published by Nippon Denko Co., Ltd. (Nitto Denko) provides a thermal shock resistance in a bent state and a bending-resistant adhesive in a low temperature environment. The storage modulus at -20°C is 0.05MPa~0.5MPa, and the gel fraction is more than 50%, but its adhesion during the peel test is low, and there is no mention of the creep recovery performance of its adhesive layer in high and low temperatures.

[0004] So far, the OCA adhesive products used for folding screens on the market cannot meet the requirements of low modulus at low temperatures while also meeting high viscosity and high creep recovery at different temperatures. The comprehensive performance is far from meeting the needs of consumers.

[0005] Therefore, it is very important to provide an OCA adhesive for folding screens with excellent comprehensive performance. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the first object of the present invention is to provide a bending-resistant low-modulus OCA glue for a folding screen, wherein the OCA glue is prepared by polymerization reaction of the following components in parts by weight:

[0007] 15-20 parts of isooctyl acrylate, 9-12 parts of butyl acrylate, 2.5-3.5 parts of hydroxybutyl acrylate, 0.002-0.004 parts of methyl methacrylate, 0.002-0.004 parts of 1-vinyl-2-pyrrolidone, 0.002-0.004 parts of silane coupling agent KH570, 0.0008-0.0012 parts of initiator, and 65-75 parts of solvent.

[0008] Preferably, the solvent is ethyl acetate.

[0009] Preferably, the initiator is azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0010] The second object of the present invention is to provide a bending-resistant low-modulus OCA adhesive for folding screens, comprising 80-90 parts of the bending-resistant low-modulus OCA glue for folding screens as described above; and also comprising 0.02-0.04 parts of a thermosetting agent and 10-20 parts of a solvent.

[0011] Preferably, the thermal curing agent is hexamethylene diisocyanate.

[0012] The third object of the present invention is to provide a method for preparing a bending-resistant low-modulus OCA glue for a folding screen, comprising the following steps:

[0013] Step 1: Weigh the monomers of isooctyl acrylate, butyl acrylate, hydroxybutyl acrylate and part of the solvent, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add part of the initiator, maintain the temperature and stir for 2 hours to react; then heat to 65°C and react for 3-4 hours;

[0014] Step 2: Add initiator and continue the reaction for 1 hour;

[0015] Step 3: Then, the remaining initiator, methyl methacrylate, 1-vinyl-2-pyrrolidone, silane coupling agent and a small amount of solvent are mixed and uniformly added to the reaction system within 10 minutes, and the reaction is continued by stirring for 2-3 hours; after cooling, the remaining solvent is added to dilute to obtain OCA glue.

[0016] Preferably, in the second step, the temperature is raised to 70-72° C. and the reaction is continued for 1 hour.

[0017] Preferably, the portion of solvent in the first step is 45-55 parts.

[0018] Compared with the prior art, the beneficial effect of the present invention is that the present invention relates to a low-modulus OCA glue for bending resistance of folding screens, the OCA glue comprising: 15-20 parts of isooctyl acrylate, 9-12 parts of butyl acrylate, 2.5-3.5 parts of hydroxybutyl acrylate, 0.002-0.004 parts of methyl methacrylate, 0.002-0.004 parts of 1-vinyl-2-pyrrolidone, 0.002-0.004 parts of silane coupling agent KH570, 0.0008-0.0012 parts of initiator, and 65-75 parts of solvent. The present invention also relates to a preparation method and an OCA adhesive with the OCA as the main component. The OCA glue formed by the present invention satisfies the low modulus at low temperature and has high viscosity, high gel fraction and high creep recovery. It has excellent comprehensive performance, simple preparation process and low cost.

[0019] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below. The specific implementation of the present invention is given in detail by the following embodiments. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0021] In order to solve the above problems, the present invention relates to a bending-resistant low-modulus OCA glue for a folding screen, wherein the OCA glue is prepared by polymerization reaction of the following components in parts by weight:

[0022] 15-20 parts of isooctyl acrylate (2-EHA), 9-12 parts of butyl acrylate (BA), 2.5-3.5 parts of hydroxybutyl acrylate (4-HBA), 0.002-0.004 parts of methyl methacrylate, 0.002-0.004 parts of 1-vinyl-2-pyrrolidone, 0.002-0.004 parts of silane coupling agent KH570, 0.0008-0.0012 parts of initiator, and 65-75 parts of solvent. The copolymer of NVP and acrylate has strong bonding ability. The copolymerization of silane coupling agent KH570 and acrylate copolymer not only improves the crosslinking degree and cohesion, prolongs its service life, but also improves the adhesion and viscosity of the film made of this as the main component; therefore, the formed OCA glue meets the low modulus at low temperature and has high viscosity, high gel fraction and high creep recovery, and has excellent comprehensive performance, simple preparation process and low cost.

[0023] The present invention drips part of the monomer and the silane coupling agent into the reaction system in the high temperature section, thereby satisfying the low-temperature and low-modulus characteristics of the glue and improving the viscosity of the glue. This purpose can also be achieved by adding a tackifying resin, but it is likely to cause the system to be non-uniform, poor compatibility, fogging and opacity, and high cost.

[0024] Considering the compatibility problem in the reaction process, the polarity of the solvent and the cost problem, in some embodiments, the solvent is ethyl acetate.

[0025] In some embodiments, the initiator is azobisisobutyronitrile AIBN and / or azobisisoheptanenitrile ABVN; the initiation temperatures of these two initiators are slightly lower than those of peroxide initiators, and are suitable for this synthesis reaction temperature. The lower initiation temperature can make the reaction easier to control and the process conditions are simpler.

[0026] The present invention also relates to a bending-resistant low-modulus OCA adhesive for folding screens, comprising 80-90 parts of the above-mentioned bending-resistant low-modulus OCA glue for folding screens; and further comprising 0.02-0.04 parts of a thermal curing agent and 10-20 parts of a solvent. The adhesive thus formed has the following properties:

[0027] After the adhesive is cross-linked and cured to form a film, the Tg value is between -30 and -45°C, and the storage modulus at -20°C is between 0.1 and 0.2 MPa.

[0028] The adhesive has good creep performance. Under the condition of applying 20KPa, the creep recovery rate at -20°C under the 20KPa stress condition exceeds 85%, and the maximum strain is greater than 100%.

[0029] After the adhesive is cross-linked and cured to form a film, the gel fraction is above 70%.

[0030] After the adhesive is cross-linked and cured to form a film, the peeling force test result on the stainless steel plate is not less than 8N / 25mm in a conventional 30-minute test, and the test result is not less than 10N / 25mm in a 24-hour test.

[0031] In some embodiments, the thermal curing agent is hexamethylene diisocyanate, which can undergo a rapid cross-linking and curing reaction with the OCA glue to increase its cross-linking degree and enhance its cohesive force.

[0032] The present invention also relates to a method for preparing a bending-resistant low-modulus OCA glue for a folding screen, comprising the following steps:

[0033] Step 1: Weigh the monomers of isooctyl acrylate, butyl acrylate, hydroxybutyl acrylate and part of the solvent, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add part of the initiator, maintain the temperature and stir for 2 hours to react; then heat to 65°C and react for 3-4 hours; it should be understood that the part of the solvent in the first step is in the range of 45-55 parts.

[0034] Step 2: Add initiator and continue the reaction for 1 hour;

[0035] Step 3: Then, the remaining initiator, methyl methacrylate, 1-vinyl-2-pyrrolidone, silane coupling agent and a small amount of solvent are mixed and uniformly added to the reaction system within 10 minutes, and the reaction is continued by stirring for 2-3 hours; after cooling, the remaining solvent is added to dilute to obtain OCA glue.

[0036] Specifically, the amount of initiator added in the first step of the reaction is in the range of 0.0002 to 0.0003; the amount of initiator added in the second step of the reaction is in the range of 0.0005 to 0.0006; and the amount of initiator added in the third step is in the range of 0.00001 to 0.00002. It should be understood that the stepwise addition of the initiator can regulate the molecular weight and molecular weight distribution of the polymer compared to the one-time addition of the initiator, so as to meet the required modulus and higher viscosity requirements.

[0037] The present invention adopts the method of dripping NVP and KH570, which are monomers with good compatibility with the system, into the reaction system in the high temperature section. In this system, the two monomers have high reactivity, can quickly undergo polymerization reaction, and can provide good viscosity, which plays a key role in the low modulus after the film is formed in the later stage. In addition, the present invention abandons the scheme of adding tackifying resin, greatly reduces the risk of incompatibility of the glue system, and reduces the probability of fogging and yellowing.

[0038] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue is added with a heat curing agent and an appropriate proportion of a solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture is placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture is attached to release films with different release forces, and the adhesive product is obtained after ripening at 60°C for 36 hours.

[0039] In some embodiments, the temperature in the second step is raised to 70-72°C and the reaction is continued for 1 hour. This is because the addition of methyl methacrylate, 1-vinyl-2-pyrrolidone (NVP), and silane coupling agent (KH570) in the temperature range of 70-72°C not only meets the low-temperature and low-modulus characteristics of the glue, but also improves the viscosity of the glue.

[0040] Embodiment 1

[0041] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0042] Under the conditions of 23-25°C and humidity of 50±3%, add 0.02% isocyanate curing agent by mass of the glue and an appropriate proportion of solvent to the prepared OCA glue, mix and stir evenly, dilute to a suitable coating viscosity, and coat on the first layer of release film to a thickness of 50 μm, put into an oven at room temperature of 25°C to 120°C and stabilize for about 2 minutes, and after drying, stick it on release films with different release forces, and mature at 60°C for 36 hours to obtain an adhesive product.

[0043] Embodiment 2

[0044] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0045] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0046] Embodiment 3

[0047] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.4‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0048] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0049] Embodiment 4

[0050] Accurately weigh 18 parts of isooctyl acrylate, 10 parts of butyl acrylate, 3.2 parts of hydroxybutyl acrylate, and 50 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0051] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0052] Embodiment 5

[0053] Accurately weigh 15 parts of isooctyl acrylate, 9 parts of butyl acrylate, 2.5 parts of hydroxybutyl acrylate, and 43 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0054] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0055] Embodiment 6

[0056] Accurately weigh 20 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3.5 parts of hydroxybutyl acrylate, and 56 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.5‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.7‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0057] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0058] Comparative Example 1

[0059] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours; then raise the temperature to 65°C and react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 3 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0060] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0061] Comparative Example 2

[0062] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C and react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, and a small amount of solvent, and uniformly add them dropwise to the reaction system within 10 minutes, and continue to stir and react for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0063] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0064] Comparative Example 3

[0065] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0066] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0067] Comparative Example 4

[0068] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0069] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0070] Comparative Example 5

[0071] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH560, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0072] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.03% isocyanate curing agent by mass and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm. The mixture was placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes. After drying, the mixture was attached to release films with different release forces, and the adhesive product was obtained after ripening at 60°C for 36 hours.

[0073] Comparative Example 6

[0074] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of solvent butanone, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of butanone, then uniformly add them dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0075] Under the conditions of 23-25°C and humidity of 50±3%, add 0.02% isocyanate curing agent by mass of the glue and an appropriate proportion of solvent to the prepared OCA glue, mix and stir evenly, dilute to a suitable coating viscosity, and coat on the first layer of release film to a thickness of 50 μm, put into an oven at room temperature of 25°C to 120°C and stabilize for about 2 minutes, and after drying, stick it on release films with different release forces, and mature at 60°C for 36 hours to obtain an adhesive product.

[0076] Comparative Example 7

[0077] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of BPO, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of BPO, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator BPO, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add them dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0078] Under the conditions of 23-25°C and humidity of 50±3%, add 0.02% isocyanate curing agent by mass of the glue and an appropriate proportion of solvent to the prepared OCA glue, mix and stir evenly, dilute to a suitable coating viscosity, and coat on the first layer of release film to a thickness of 50 μm, put into an oven at room temperature of 25°C to 120°C and stabilize for about 2 minutes, and after drying, stick it on release films with different release forces, and mature at 60°C for 36 hours to obtain an adhesive product.

[0079] Comparative Example 8

[0080] Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of AIBN, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of AIBN, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of NVP (1-vinyl-2-pyrrolidone), 3‰ parts of KH570, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

[0081] Under the conditions of 23-25°C and humidity of 50±3%, the prepared OCA glue was added with 0.02% diphenylmethane diisocyanate curing agent and an appropriate proportion of solvent, mixed and stirred evenly, diluted to a suitable coating viscosity, and coated on the first layer of release film to a thickness of 50 μm, placed in an oven at room temperature of 25°C to 120°C and stabilized for about 2 minutes, and after drying, attached to release films with different release forces, and aged at 60°C for 36 hours to obtain an adhesive product.

[0082] Peel force test: The peel force is carried out according to the 180° peel strength test method for pressure-sensitive adhesive tapes and in accordance with GB / T2792-1998.

[0083] Gel rate test: Place a 1 gram film on a nickel mesh and soak it in a mixed solvent of toluene and ethyl acetate (1:1). After standing for 72 hours, take out the sample, dry it at 150°C for 2 hours, and then weigh it. The ratio of the residual weight of the film to the original weight is the gel rate.

[0084] Cohesion test: Make the sample into a size of 25mm*150mm (the back of the double-sided tape needs to be pasted with 25um PET as the backing), and the test board is SUS304 mirror plate. After lamination, use a 2kg roller to roll back and forth 3 times. After 20 minutes, hang a weight of 1kg. The displacement after room temperature / 24h is ≤1.0mm, and the displacement after 70℃ / 24h is ≤2.0mm, which is qualified.

[0085] Creep recovery test: TA rheometer applies 20kpa shear stress, recovery time is 600s, creep recovery rate at room temperature exceeds 90%, maximum strain exceeds 300%, creep recovery rate at -20℃ exceeds 85%, maximum strain exceeds 90%, which is qualified.

[0086] Static bending test: stick 50μm thick film on both sides with 50μm PET, and then cut it into 160mm long * 40mm wide strips, and then fix a 1N weight (100g) at the tail of the sample with high-temperature insulating tape, hang it on a fixture with a radius of R = 1.5mm, put it into a 65℃ / 95 humidity storage test box for 24h, take it out after cooling to measure the width of the tail crease. According to the current situation in the industry, a measured width of 35mm means it has good bending resistance.

[0087] Table 1 Monomer usage in different embodiments

[0088]

[0089]

[0090] Table 2 Performance test table of different embodiments

[0091] <![CDATA[-20℃ energy storage / M p a]]> <![CDATA[60℃ Energy Storage / M p a]]> TG 24h peel strength Gel rate Creep Recovery Cohesion Static bending Example 1 0.105 0.023 -39.8 11.8N 71.8％ PASS PASS PASS Example 2 0.124 0.031 -36.4 10.6N 72.6％ PASS PASS PASS Example 3 0.120 0.030 -38.2 11.3N 74.3％ PASS PASS PASS Example 4 0.146 0.037 -36.8 10.9N 72.9％ PASS PASS PASS Example 5 0.119 0.026 -35.6 11.4N 74.1％ PASS PASS PASS Example 6 0.158 0.038 -38.4 11N 73.6％ PASS PASS PASS Comparative Example 1 0.196 0.047 -39.9 8.4N 76.1％ FAIL PASS PASS Comparative Example 2 0.178 0.043 -38.5 8.7N 75.4％ FAIL PASS PASS Comparative Example 3 0.148 0.039 -36.7 9.1N 74.3％ PASS PASS PASS Comparative Example 4 0.144 0.037 -38.1 <![CDATA[9.2 n ]]> 74.5％ PASS PASS PASS Comparative Example 5 0.127 0.032 -37.2 9.1N 71.2％ PASS PASS PASS Comparative Example 6 0.095 0.018 -38.5 11.9N 63.4％ NG NG NG Comparative Example 7 0.098 0.020 -39.1 12.5N 62.1％ NG NG NG Comparative Example 8 0.140 (high) 0.051 (high) -38.9 11.4N 71.5％ PASS PASS PASS

[0092] It can be seen from the experimental data that the various test performances of Examples 1-6 are relatively excellent.

[0093] Among them, the comparative example 1 did not add the monomer in the high temperature section, could not meet the low modulus and high viscosity performance, and the creep performance test did not meet the standard;

[0094] Comparative Example 2 lacks silane coupling agent KH570 and epoxy monomer NVP, and cannot simultaneously meet low modulus and high viscosity, and the creep performance test is also not up to standard;

[0095] Comparative Example 3 did not add silane coupling agent KH570, and the viscosity was poor;

[0096] Comparative Example 4 did not add epoxy monomer NVP, and the effect was the same as that of Example 3;

[0097] In comparative example 5, the silane coupling agent was replaced with KH560, and the peeling force and gel rate tests were not ideal.

[0098] In Comparative Example 6, ethyl acetate was replaced with butanone. Due to the large difference in solvent polarity, the molecular weight was lower, and the creep and gel fraction were poor.

[0099] In Comparative Example 7, the initiator is replaced with BPO. Since the initiation temperature of BPO is relatively high, the initiation reaction is extremely slow, the molecular weight is low, and the creep performance and cohesion are poor.

[0100] In Comparative Example 8, the thermal curing agent was replaced with diphenylmethane diisocyanate, and it was found that its low-temperature modulus was significantly higher than that when hexamethylene diisocyanate was used, which is contrary to the purpose of the present invention.

[0101] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown here.

Claims

1. A bending-resistant low-modulus OCA adhesive for folding screens, characterized in that: It includes 80-90 parts of bending-resistant low-modulus OCA glue for folding screens; it also includes 0.02-0.04 parts of a thermal curing agent and 10-20 parts of a solvent; the thermal curing agent is hexamethylene diisocyanate; The OCA glue is prepared by polymerization of the following components in parts by weight: Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of azobisisobutyronitrile, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of azobisisobutyronitrile, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of 1-vinyl-2-pyrrolidone, 3‰ parts of KH-570 silane coupling agent, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

2. A bending-resistant low-modulus OCA adhesive for folding screens, characterized in that: It includes 80-90 parts of bending-resistant low-modulus OCA glue for folding screens; it also includes 0.02-0.04 parts of a thermal curing agent and 10-20 parts of a solvent; the thermal curing agent is hexamethylene diisocyanate; The OCA glue is prepared by polymerization of the following components in parts by weight: Accurately weigh 15 parts of isooctyl acrylate, 12 parts of butyl acrylate, 3 parts of hydroxybutyl acrylate, and 48 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.4‰ parts of azobisisobutyronitrile, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of azobisisobutyronitrile, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of 1-vinyl-2-pyrrolidone, 3‰ parts of KH-570 silane coupling agent, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

3. A bending-resistant low-modulus OCA adhesive for folding screens, characterized in that: It includes 80-90 parts of bending-resistant low-modulus OCA glue for folding screens; it also includes 0.02-0.04 parts of a thermal curing agent and 10-20 parts of a solvent; the thermal curing agent is hexamethylene diisocyanate; The OCA glue is prepared by polymerization of the following components in parts by weight: Accurately weigh 15 parts of isooctyl acrylate, 9 parts of butyl acrylate, 2.5 parts of hydroxybutyl acrylate, and 43 parts of ethyl acetate, place them in a four-necked flask equipped with a stirrer, a condenser and a nitrogen tube, introduce nitrogen, stir at 60-62°C for at least 30 minutes, then add 0.25‰ parts of azobisisobutyronitrile, maintain the temperature and stir for 2 hours to react; then heat to 65°C to react for 3 hours; add 0.6‰ parts of azobisisobutyronitrile, raise the temperature to 70-72°C and continue to react for 1 hour; mix 0.01‰ parts of initiator, 3‰ parts of methyl methacrylate, 3‰ parts of 1-vinyl-2-pyrrolidone, 3‰ parts of KH-570 silane coupling agent, and a small amount of solvent, then uniformly add dropwise to the reaction system within 10 minutes, continue stirring and reacting for 2 hours; after cooling, add the remaining solvent to dilute to obtain OCA glue with a solid content of 25-30%.

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