Pressure-sensitive optical adhesive film and preparation method thereof

Abstract

The invention provides a pressure-sensitive optical adhesive film, which is prepared by coating and photocuring an adhesive, and the adhesive comprises the following raw materials by mass: 40-80 parts of a soft monomer; 5-15 parts by mass of a hard monomer; 10 parts by mass to 40 parts by mass of a crosslinkable monomer; 0.5 to 10 parts by mass of a special monomer; wherein the special monomer is a solvent-free acrylic polymer. The special monomer is added into the adhesive, so that the adhesion and fluidity of an adhesive film are effectively improved, the hardness of an adhesive layer is reduced, the processability of the adhesive film is improved, and the cohesive force of the adhesive film is not lost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, in particular to a pressure-sensitive optical adhesive film and a preparation method thereof. BACKGROUND

[0002] Optical adhesive film is a kind of special adhesive used for bonding transparent optical elements. It requires colorless transparency, light transmittance of more than 90%, good bonding strength, curing at room temperature or medium temperature, and small curing shrinkage. With the development of modern society, smart phones, tablet computers, vehicle control, and wearable devices are being used more and more widely. In these display devices, optical adhesive film is mainly used to bond the touch layer and the display cover plate to improve the display effect and isolate dust and moisture. Usually on the inner side of the display panel, the frame will print an ink layer of 5-30 microns, thereby forming a certain step difference with the non-printed part, and the optical pressure-sensitive adhesive needs to have good step difference filling performance. If the filling performance of the adhesive film is not enough, the adhesive layer near the ink step difference will float up and easily produce bubbles between the panel and the adhesive layer, which is not easy to adhere and deaerate. If the step difference filling performance of the optical adhesive film is good, the optical adhesive film is too soft, which on the one hand causes overflow during die cutting, and on the other hand has poor cohesion and poor reliability.

[0003] The existing technical solution is to add a photoinitiator and a photocuring group during the preparation of the optical adhesive film to solve this problem. The solution idea is that when the display cover plate and the touch layer are bonded, the initial adhesive layer is soft, the step difference filling performance is good, and it is easy to adhere and deaerate. After deaeration, the photoinitiator and the photocuring group in the adhesive film are initiated by UV irradiation to react, and the adhesive layer is secondarily cured to improve the gel fraction and the cohesion of the adhesive layer to ensure good reliability.

[0004] However, the above-mentioned adhesive film is prone to overflow during storage and die cutting due to its good flowability before UV irradiation. In order to realize this two-stage process, the optical adhesive film needs to be shielded from light during production, transportation and storage to prevent the photoinitiator from decomposing, which increases the cost and complicates the process. On the other hand, the UV irradiation process and equipment need to be added during the subsequent bonding with transparent optical elements, which increases the cost and reduces the efficiency. Therefore, there is a need for an optical adhesive film that has good step difference filling performance, good bubble suppression ability and cohesion in various harsh scenarios, and is convenient for customers to use. SUMMARY

[0005] The present application provides a pressure-sensitive optical adhesive film, which effectively improves the adhesion and flowability of the adhesive film, reduces the hardness of the adhesive layer, improves the processing performance of the adhesive film, and does not lose the cohesion of the adhesive film.

[0006] Therefore, the first object of the present application is to provide a pressure-sensitive optical adhesive film.

[0007] The second object of the present application is to provide a preparation method of the pressure-sensitive optical adhesive film.

[0008] To achieve the first object of the present application, the technical solution of the present application provides a pressure-sensitive optical adhesive film prepared by coating and photocuring of an adhesive, wherein the raw materials of the adhesive include, in terms of mass fraction, 40-80 mass fraction of soft monomers, 5-15 mass fraction of hard monomers, 10-40 mass fraction of cross-linkable monomers, and 0.5-10 mass fraction of special monomers, wherein the special monomers are solvent-free acrylic polymers.

[0009] In one technical solution of the present application, the tan delta of the pressure-sensitive optical adhesive film is 0.22-0.55 at 25-120℃ and 1Hz frequency, the weight average molecular weight of the pressure-sensitive optical adhesive film is 30000-700000 g / mol, and the Tg of the pressure-sensitive optical adhesive film is -60--30℃.

[0010] In one technical solution of the present application, the soft monomers include at least one of 2-ethylhexyl acrylate, isooctyl (meth)acrylate, butyl acrylate, and dodecyl (meth)acrylate; the hard monomers include at least one of vinyl acetate, isobornyl (meth)acrylate, methyl (meth)acrylate, acrylamide, acryloyl morpholine, and N-vinyl pyrrolidone; the cross-linkable monomers include at least one of (meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl acrylate, and glycidyl (meth)acrylate; and the special monomers include at least one of non-functional acrylic polymers, hydroxyl-containing acrylic polymers, carboxyl-containing acrylic polymers, alkoxysilane-containing acrylic polymers, and epoxy-containing acrylic polymers.

[0011] To achieve the second object of the present application, the technical solution of the present application provides a preparation method of the pressure-sensitive optical adhesive film, which includes the following steps: S100, mixing the raw materials of the adhesive, a chain transfer agent, and a photoinitiator uniformly under an inert gas protection atmosphere to obtain a first reactant; S200, photocuring the first reactant to obtain a second reactant; S300, adding a silane coupling agent, an antioxidant, and a photoinitiator to the second reactant, mixing uniformly, and cooling to room temperature to prepare the adhesive; and S400, mixing and defoaming the adhesive and a cross-linking agent, and then coating and photocuring in sequence to prepare the pressure-sensitive optical adhesive film.

[0012] In one technical solution of the present invention, in S100, the mixing time is 40 min to 80 min; in S100, the flow rate of the inert gas is 0.5 L / min to 2 L / min; in S100, the chain transfer agent and photoinitiator are in the mass ratio of (4 to 6): (0.02 to 0.08): (0.08 to 0.12).

[0013] In one embodiment of the present invention, in step S200, the illumination reaction uses an LED lamp with a wavelength of 365nm; in step S200, the illumination intensity is 2mw / cm². 2 ~5mw / cm 2 In S200, the photochemical reaction is carried out under an inert gas protective atmosphere.

[0014] In one embodiment of the present invention, in S300, the silane coupling agent, antioxidant, and photoinitiator are in the following mass ratio: (0.08~0.12):(0.08~0.12):(0.2~0.4).

[0015] In one embodiment of the present invention, in step S400, the coating process employs a double-layer clamp-type coating shaft; in step S400, the light intensity is 1 mw / cm². 2 ~3mw / cm 2 In S400, the photocuring time is 5 min to 15 min.

[0016] In one embodiment of the present invention, the chain transfer agent includes at least one of 2-mercaptoethanol, α-thioglycerol, octylthiol, dodecylthiol, and tert-dodecylthiol; the photoinitiator includes at least one of 1-hydroxycyclohexylphenyl ketone, benzoyl dimethyl ether, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-hydroxy-2-methyl-1-phenylpropanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; the silane coupling agent includes at least one of KH-550, KH560, KH-561, KH-570, KH-580, KH-590, and KH-792; the antioxidant includes at least one of 1010 and 1076; and the crosslinking agent includes at least one of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, polyethylene glycol diacrylate, and dipentaerythritol hexaacrylate.

[0017] The technical solution provided by this invention can achieve at least one of the following effects: (1) Excellent reliability: Pressure-sensitive optical adhesive film has good storage stability and filling properties. It does not overflow during die cutting. Even in harsh environments, it also has good step filling properties, anti-foaming ability, gel fraction and cohesion. (2) The adhesive film does not need to be shaded during the subsequent transportation and storage after being coated and formed, and does not need to increase the UV irradiation process when being used in combination with the transparent optical element, thereby greatly reducing the cost and improving the production efficiency; (3) The preparation method of the pressure-sensitive optical adhesive film has simple process steps and low equipment requirements, and has a broad application prospect. DETAILED DESCRIPTION

[0018] To make the above-mentioned objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below. It should be noted that the embodiments of the present application and the characteristics in the embodiments can be combined with each other without conflict. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0019] The embodiment of the present application provides a pressure-sensitive optical adhesive film, which is prepared by coating and photocuring of an adhesive, and the raw materials of the adhesive include, in terms of mass fraction, 40-80 mass fraction of soft monomers, 5-15 mass fraction of hard monomers, 10-40 mass fraction of cross-linkable monomers, and 0.5-10 mass fraction of special monomers, wherein the special monomers are solvent-free acrylic polymers.

[0020] Specifically, the special monomers are solvent-free acrylic polymers with plasticizing effect.

[0021] The special monomers are macromolecular polymers with a molecular weight of 1000-12000.

[0022] The present application designs a high-performance pressure-sensitive optical adhesive film through monomer ratio optimization and the introduction of special monomers, and the core advantages are reflected in the balance of mechanical properties, interface adaptability and process compatibility. The soft monomers provide the initial adhesion and flexibility of the adhesive film, and the content of 40-80 mass fraction ensures that the adhesive layer is not easy to crack at low temperature; the hard monomers improve the cohesive strength and creep resistance to prevent the adhesive film from slipping under long-term stress, and the content of 5-15 mass fraction avoids excessive sacrifice of flexibility to balance the "adhesion-strength"; the cross-linkable monomers form a three-dimensional cross-linked network with the remaining components through UV curing, and the content of 10-40 mass fraction enhances the heat flow hanging resistance and shear resistance; the special monomers realize the multiple synergistic effects of plasticizing-crosslinking-interface enhancement, and solve the migration problem of small molecule plasticizers through reactive functional groups, and when the content is 0.5-10 mass fraction, the performance improvement and negative effect reach the optimal balance.

[0023] In some embodiments of the present application, the tan delta of the pressure-sensitive optical adhesive film is 0.22-0.55 at 25-120°C at a frequency of 1 Hz; the weight average molecular weight of the pressure-sensitive optical adhesive film is 30,000-700,000 g / mol; and the Tg of the pressure-sensitive optical adhesive film is -60- -30°C.

[0024] Specifically, the tan delta is 0.45-0.55 at 50°C.

[0025] Specifically, the tan delta is below 0.4 at 100°C.

[0026] The pressure-sensitive optical adhesive film of the present application can achieve precise control of the loss factor tan delta in the range of 0.22-0.55 at 25-120°C. When the tan delta is in the above range, the optical adhesive film not only does not overflow during storage and die cutting, but also is easy to adhere and defoam during use, and can inhibit the generation of bubbles, peeling and floating in long-term high-temperature and high-humidity conditions, meeting the viscoelasticity requirements in high-temperature scenarios; the weight average molecular weight is regulated to be 30,000-700,000 g / mol, balancing the processability and mechanical properties; the lower limit of Tg of -60°C ensures that the film remains flexible in extremely low-temperature environments, avoiding brittle fracture; and the upper limit of -30°C ensures sufficient modulus when used at room temperature.

[0027] In some embodiments of the present application, the soft monomer includes at least one of 2-ethylhexyl acrylate, isooctyl (meth)acrylate, butyl acrylate, and dodecyl (meth)acrylate; the hard monomer includes at least one of vinyl acetate, isobornyl (meth)acrylate, methyl (meth)acrylate, acrylamide, acryloyl morpholine, and N-vinyl pyrrolidone; the cross-linkable monomer includes at least one of (meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl acrylate, and glycidyl (meth)acrylate; and the special monomer includes at least one of a non-functional acrylic polymer, a hydroxyl-containing acrylic polymer, a carboxyl-containing acrylic polymer, an alkoxy silicon-containing acrylic polymer, and an epoxy-containing acrylic polymer.

[0028] The homopolymer of the soft monomer of the present application has a low Tg and a large molecular structure space, so that the adhesive film has good initial adhesion and flexibility, and all are saturated hydrocarbon side chains to avoid yellowing after UV curing; the hard monomer provides a rigid skeleton and a polar functional group to enhance the cohesive strength of the adhesive film; the cross-linkable monomer is a double reactive site compound, the α, β-unsaturated carbonyl group is copolymerized with the soft / hard monomer to participate in the formation of the main chain, and the remaining functional groups impart post-crosslinking ability to form a three-dimensional network through condensation, ring-opening and other reactions to enhance the interfacial bonding force of the adhesive film; the special monomer has plasticizing effect and anti-migration property, avoiding the volatilization and bleeding problems of small molecule plasticizers. The formula design of the pressure-sensitive optical adhesive film of the present application realizes multi-dimensional optimization of adhesion, durability and processability through precise combination of monomer types and synergistic effect of functional groups.

[0029] In some embodiments of the present application, the preparation method of the pressure-sensitive optical adhesive film comprises the following steps: S100, mixing raw materials of an adhesive, a chain transfer agent and a photoinitiator uniformly under an inert gas protection atmosphere to obtain a first reactant; S200, performing photoreaction on the first reactant to obtain a second reactant; S300, adding a silane coupling agent, an antioxidant and a photoinitiator to the second reactant, mixing uniformly and cooling to room temperature to obtain the adhesive; S400, mixing the adhesive and a crosslinking agent uniformly and defoaming, and then coating and photocuring in sequence to obtain the pressure-sensitive optical adhesive film.

[0030] The preparation method of the pressure-sensitive optical adhesive film adopts a segmented photocuring process, which can precisely control the polymerization reaction process, avoid the occurrence of side reactions, is suitable for active monomer reaction systems sensitive to oxygen, retains the activity of additives, and improves the reaction efficiency.

[0031] In some embodiments of the present application, in S100, the mixing time is 40 min to 80 min; in S100, the flow rate of the inert gas is 0.5 L / min to 2 L / min; in S100, the chain transfer agent and the photoinitiator are in a mass ratio of (4-6):(0.02-0.08):(0.08-0.12).

[0032] Specifically, the inert gas is nitrogen.

[0033] Controlling the mixing time ensures uniform dispersion of each monomer and avoids differences in local polymerization rates that cause uneven gel points; inert gas protection prevents the oxygen inhibition effect in free radical polymerization; the raw material ratio of the prepolymerization reaction is optimized to balance the molecular weight control and curing efficiency.

[0034] In some embodiments of the present application, specifically, in S200, the photoreaction uses a 365 nm wavelength LED lamp; in S200, the light intensity is 2 mw / cm 2 ~5 mw / cm 2In S200, the photoreaction is carried out under an inert gas protection atmosphere.

[0035] The wavelength, intensity and protection atmosphere are regulated, the initiator spectrum is matched, the side reaction is reduced, the reaction speed and molecular weight distribution are balanced, and the surface oxygen inhibition phenomenon is reduced.

[0036] In some embodiments of the present application, specifically, in S300, the mass ratio of the silane coupling agent, the antioxidant and the photoinitiator is (0.08-0.12):(0.08-0.12):(0.2-0.4).

[0037] This step further guarantees the adhesion of the substrate and the moisture resistance, resists heat and UV aging, ensures deep curing and low residue by regulating the ratio of the silane coupling agent, the antioxidant and the photoinitiator.

[0038] In some embodiments of the present application, specifically, in S400, a double-layer pinch roll type coating shaft is used for coating; in S400, the light intensity is 1 mw / cm 2 ~3 mw / cm 2 ; in S400, the light curing time is 5 min-15 min.

[0039] The coating speed and the surface density deviation control effect of the double-cavity die synchronous extrusion technology are good, and the defect rate is low; the light intensity balances the curing depth and the material stability, and improves the conversion rate; the curing time of 5 min-15 min ensures the completeness of the reaction and takes into account the production efficiency.

[0040] In some embodiments of the present application, specifically, the chain transfer agent includes at least one of 2-mercaptoethanol, alpha-thioglycerol, octyl mercaptan, dodecyl mercaptan and tertiary dodecyl mercaptan; the photoinitiator includes at least one of 1-hydroxycyclohexyl phenyl ketone, benzoin dimethyl ether, 2,4,6-trimethylbenzoyl phenyl phosphonic acid ethyl ester, 2-hydroxy-2-methyl-1-phenylpropanone and 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide; the silane coupling agent includes at least one of KH-550, KH560, KH-561, KH-570, KH-580, KH-590 and KH-792; the antioxidant includes at least one of 1010 and 1076; and the crosslinking agent includes at least one of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, polyethylene glycol diacrylate and dipentaerythritol hexaacrylate.

[0041] The introduction of the present application optimizes the auxiliary agent, the selection of the chain transfer agent is a steric hindrance compound, the inhibition of the branching side reaction; the synergism of the photoinitiator and the silane coupling agent improves the cohesion and the interfacial bonding force; the antioxidant inhibits thermal and oxidative degradation; the crosslinking agent can be selected as a photocurable or heat-curable type, and the adhesive layer after crosslinking can easily obtain good re-peeling performance.

[0042] Example 1 The preparation method of the pressure-sensitive optical adhesive film comprises the following steps: S100, under the protection of nitrogen atmosphere, 60 parts of 2-ethylhexyl acrylate, 10 parts of cyclohexyl acrylate, 15 parts of hydroxybutyl acrylate, 10 parts of hydroxyethyl acrylate, 5 parts of epoxy acrylate polymer, 0.05 parts of dodecyl mercaptan and 0.1 parts of 1-hydroxycyclohexyl phenyl ketone are added, the nitrogen flow is 1L / min, and stirring is performed for 60min to obtain a first reactant; S200, under the protection of nitrogen atmosphere, the first reactant is irradiated by using a 365nm wavelength LED lamp, the light intensity is 2mw / cm 2 , the light is turned off when the reaction conversion rate reaches 15%, and a second reactant is obtained; S300, 0.1 parts of KH560, 0.1 parts of 1-hydroxycyclohexyl phenyl ketone and 0.3 parts of 1010 are added into the second reactant, and the mixture is uniformly mixed and cooled to room temperature to prepare an adhesive; S400, after the adhesive and 1 part of trimethylolpropane triacrylate are uniformly mixed and degassed, a double-layer pinch roller coating shaft is used to coat them in the middle of two layers of 75μm-thick polyester films, and the coated adhesive is cured under the irradiation of a mercury lamp with a light intensity of 2mw / cm 2 for 10min to obtain a pressure-sensitive optical adhesive film with a thickness of 150μm.

[0043] Example 2 The preparation method of this example is the same as that of Example 1, except that the raw materials and the mass ratio of the adhesive are as follows: the ratio of butyl acrylate, cyclohexyl acrylate, hydroxybutyl acrylate, hydroxyethyl acrylate and epoxy acrylate polymer = 60:10:15:10:5.

[0044] Example 3 The preparation method of this example is the same as that of Example 1, except that the raw materials and the mass ratio of the adhesive are as follows: the ratio of 2-ethylhexyl acrylate, cyclohexyl acrylate, hydroxybutyl acrylate, hydroxyethyl acrylate and epoxy acrylate polymer = 60:8:15:10:2.

[0045] Example 4 The preparation method of this example is according to Example 1, except that the raw materials and mass ratio of the adhesive are as follows: the ratio of butyl acrylate, isobornyl acrylate, hydroxyethyl acrylate, and epoxy acrylate polymer = 80:5:10:5.

[0046] [Example 5] The preparation method of this example is according to Example 1, except that the raw materials and mass ratio of the adhesive are as follows: the ratio of 2-ethylhexyl acrylate, isobornyl acrylate, hydroxybutyl acrylate, and epoxy acrylate polymer = 40:15:35:10.

[0047] [Example 6] The preparation method of this example is according to Example 1, except that the raw materials and mass ratio of the adhesive are as follows: the ratio of butyl acrylate, cyclohexyl acrylate, hydroxybutyl acrylate, hydroxyethyl acrylate, and epoxy acrylate polymer = 65:10:10:10:5.

[0048] [Example 7] The preparation method of this example is according to Example 1, except that the raw materials and mass ratio of the adhesive are as follows: the ratio of isooctyl (meth)acrylate, acryloyl morpholine, (meth)acrylic acid, glycidyl (meth)acrylate, and non-functional acrylic polymer = 60:10:15:10:5.

[0049] [Example 8] The preparation method of this example is according to Example 1, except that the raw materials and mass ratio of the adhesive are as follows: the ratio of dodecyl (meth)acrylate, cyclohexyl acrylate, hydroxypropyl (meth)acrylate, and alkoxysilane-containing acrylic polymer = 60:10:30:5.

[0050] [Example 9] The preparation method of this example is according to Example 1, except that the raw materials and mass ratio of the adhesive are as follows: the ratio of butyl acrylate, cyclohexyl acrylate, hydroxybutyl acrylate, hydroxyethyl acrylate, and carboxyl-containing acrylic polymer = 60:10:15:10:12.

[0051] [Example 10] The preparation method of this example is according to Example 1, except that the raw materials and mass ratio of the adhesive are as follows: the ratio of butyl acrylate, cyclohexyl acrylate, hydroxybutyl acrylate, hydroxyethyl acrylate, and carboxyl-containing acrylic polymer = 60:10:15:10:0.3.

[0052] [Comparative Example 1] The preparation method of this example is according to Example 1, except that the ratio of epoxy acrylate polymer is 0.

[0053] [Comparative Example 2] The comparative example was prepared according to the method of Example 1, except that the epoxy acrylate polymer was replaced by dibutyl itaconate.

[0054] Performance test 1. Peel strength test: The peel strength was measured according to GB / T 2792-1998 (Test method for 180° peel strength of pressure-sensitive adhesive tape). SUS304 stainless steel plates with a special surface treatment were used as the adherend.

[0055] 2. Adhesion retention test: The adhesion retention of the adhesive tape was measured according to GB / T 4851-2014. The failure time of the adhesive tape under load was measured.

[0056] 3. Hardness test: The adhesive film obtained in the examples and comparative examples was peeled off from the release film and stacked to a thickness of 1950 μm. The stacked sample was peeled off from the release film on one side and attached to a glass plate. The other release film was peeled off and the sample was measured using a Bareiss Digitest II-VLRH hardness meter. The test results were recorded.

[0057] 4. Step filling property A glass plate with a step (height of step: 15 μ, 30 μ) formed by printing ink was prepared. The adhesive film obtained in the examples and comparative examples was peeled off from the release film and attached to a polyethylene terephthalate film (PET, thickness: 100 μm) that had been previously subjected to corona treatment. Then, the release film was peeled off and the adhesive film was attached to the glass plate with a step. This was used as the evaluation sample.

[0058] The obtained sample was subjected to high-pressure degassing treatment at 50°C and 0.5 MPa for 30 min, and then left to stand at normal pressure, 23°C and 50% RH for 24 hours. Then, the sample was left to stand at high temperature and high humidity conditions of 85°C and 85% RH for 7 days, and then the step filling property was evaluated. The step filling property was evaluated as the step filling rate (%) represented by the following formula. Step filling rate (%) = (height of ink step without bubbles, floating, peeling, etc. at the step after the aging test / thickness of the adhesive film) x 100%.

[0059] 5. High temperature and high humidity bubble suppression property Take a glass cover plate with a step pattern (step height: 15 μm) formed by printing ink. Peel off the light release film from the adhesive film obtained in the examples and comparative examples, and attach the exposed adhesive film to the glass cover plate with the step pattern. Next, peel off the heavy release film, adhere the above adhesive film to a glass plate without ink step patterns, and vacuum laminate it using a laminating machine (vacuum degree -100 kPa, pressure 0.5 MPa, 15 s). This is used as an evaluation sample.

[0060] The obtained samples were subjected to high-pressure degassing at 50℃ and 0.5MPa for 30 minutes, followed by 24 hours at normal pressure, 25℃, and 50%RH. Then, they were stored at 85℃ and 85%RH for 500 hours. Afterward, the samples were removed and cooled to room temperature at 25℃ and 50%RH for 2 hours. The adhesion to the sample was then observed, and the bubbling condition was recorded: no bubbles (○), a few bubbles (△), and a large amount of bubbling (×).

[0061] 6. Determination of tanδ A circular adhesive sheet with a thickness of 1 mm and a diameter of 8 mm was prepared and placed in the testing equipment: DMA-TA Instruments-water LLC, with an axial force of 0.5 N, a frequency of 1 Hz, a strain of 0.1%, a temperature range of 20℃~120℃, and a heating rate of 5℃ / min for measurement.

[0062] Table 1

[0063] Based on the performance test results in Table 1, the data from the examples and comparative examples show that the pressure-sensitive optical adhesive film prepared by this invention, through optimization of the type and ratio of adhesive monomers, significantly improves the peel strength, cohesive strength, and anti-bubble properties, while also exhibiting controllable loss factors and excellent high-temperature and high-humidity resistance. Comparative Example 1, lacking specific monomers and block copolymers and structures that can plastically modify the adhesive, suffers from decreased crystallinity, reduced peel strength, and poor cohesive strength and anti-bubble properties. Comparative Example 2, with the addition of plasticizing compounds, improves peel strength and step filling properties, but its cohesive strength and anti-bubble properties remain unsatisfactory.

[0064] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0065] The writing manner of "S10", "S20", "S30" and "S40" and the like in the present specification is for facilitating the description of the embodiments of the present application, and the present application can also be implemented in other manners different from those described herein, and therefore the protection scope of the present application is not limited by the sequence of the above writing manner of the specific embodiments.

[0066] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be defined by the scope of the claims.

Claims

1. A pressure-sensitive optical adhesive film, prepared by coating and photocuring an adhesive, characterized in that, The raw materials of the adhesive include, by weight parts: Soft monomer, 40 to 80 parts by weight; Hard monomer, 5 to 15 parts by weight; Crosslinkable monomer, 10 parts by weight to 40 parts by weight; Special monomers, 0.5 parts by weight to 10 parts by weight; The special monomer is a solvent-free acrylic polymer.

2. The pressure-sensitive optical adhesive film according to claim 1, characterized in that, At a temperature of 25°C to 120°C and a frequency of 1Hz, the tanδ of the pressure-sensitive optical film is 0.22~0.

55. The weight-average molecular weight of the pressure-sensitive optical adhesive film is 30,000 g / mol to 700,000 g / mol; The pressure-sensitive optical adhesive film has a Tg of -60℃ to -30℃.

3. The pressure-sensitive optical adhesive film according to claim 1, characterized in that, The soft monomer includes at least one of the following: 2-ethylhexyl acrylate, isooctyl acrylate, butyl acrylate, and dodecyl acrylate. The hard monomers include at least one of the following: vinyl acetate, isobornyl methacrylate, methyl methacrylate, acrylamide, acrylmorpholine, N-vinylpyrrolidone, and cyclohexyl acrylate; The crosslinkable monomer includes at least one of (meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl acrylate, and glycidyl (meth)acrylate. The special monomers include at least one of the following: non-functional acrylic polymers, hydroxyl-containing acrylic polymers, carboxyl-containing acrylic polymers, alkoxysilyl-containing acrylic polymers, and epoxy-containing acrylic polymers.

4. A method for preparing a pressure-sensitive optical adhesive film as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: S100. Under an inert gas protective atmosphere, the raw materials, chain transfer agent, and photoinitiator of the adhesive are mixed evenly to obtain the first reactant. S200. The first reactant is subjected to light irradiation to obtain the second reactant; S300: Add silane coupling agent, antioxidant and photoinitiator to the second reactant, mix evenly, cool to room temperature, and obtain the adhesive. S400: The adhesive and crosslinking agent are sequentially coated and photocured to obtain the pressure-sensitive optical film.

5. The method for preparing the pressure-sensitive optical adhesive film according to claim 4, characterized in that, In S100, the mixing time is 40 min to 80 min; In S100, the flow rate of inert gas is 0.5 L / min to 2 L / min; In S100, the chain transfer agent and photoinitiator are in a mass ratio of (4~6):(0.02~0.08):(0.08~0.12).

6. The method for preparing the pressure-sensitive optical adhesive film according to claim 4, characterized in that, In the S200, the light response uses LEDs with a wavelength of 365nm; In S200, the illuminance is 2 mw / cm². 2 ~5mw / cm 2 ; In S200, the photochemical reaction is carried out under an inert gas protective atmosphere.

7. The method for preparing the pressure-sensitive optical adhesive film according to claim 4, characterized in that, In S300, the silane coupling agent, antioxidant, and photoinitiator are in the following mass ratio: (0.08~0.12):(0.08~0.12):(0.2~0.4).

8. The method for preparing the pressure-sensitive optical adhesive film according to claim 4, characterized in that, In the S400, coating is performed using a double-layer clamp-type coating shaft; In S400, the illuminance is 1 mw / cm². 2 ~3mw / cm 2 ; In S400, the light curing time is 5 min to 15 min.

9. The method for preparing the pressure-sensitive optical adhesive film according to claim 4, characterized in that, The chain transfer agent includes at least one of 2-mercaptoethanol, α-thioglycerol, octylthiol, dodecylthiol, and tert-dodecylthiol; The photoinitiator includes at least one of the following: 1-hydroxycyclohexylphenyl ketone, benzoyl dimethyl ether, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-hydroxy-2-methyl-1-phenylpropanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. The silane coupling agent includes at least one of KH-550, KH560, KH-561, KH-570, KH-580, KH-590, and KH-792; The antioxidant includes at least one of 1010 and 1076; The crosslinking agent includes at least one of the following: 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, polyethylene glycol diacrylate, and dipentaerythritol hexaacrylate.

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