OCA optical pressure-sensitive adhesive based on carboxyl clusters and preparation method of OCA optical pressure-sensitive adhesive

Abstract

The invention discloses an OCA (Optical Clear Adhesive) based on carboxyl clusters and a preparation method of the OCA. The structure of the OCA is (M2-ran-M3)-b-(M2)-b-(M2-ran-M3) or (M2-ran-M3)-b-(M1-ran-M2-ran-M3)-b-(M2-ran-M3), the number-average molecular weight of the OCA optical pressure-sensitive adhesive is 0.1 to 100 thousand g / mol; the mass content of the hard monomer M1 is 0-18%, the mass content of the soft monomer M2 is 40-88%, and the mass content of the functional monomer M3 is 12-40%; the functional monomer is a monomer containing carboxyl and double bonds. The polymer containing carboxyl functional monomers at two ends is prepared by adopting a reversible addition fragmentation chain transfer solution polymerization method, and carboxyl clusters can be formed among carboxyl groups, so that the fracture rebound rate of the polymer is greatly improved, and the polymer has the characteristics of high peel strength and low modulus.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to an OCA optical pressure-sensitive adhesive based on carboxyl clusters and a preparation method thereof. Background Art

[0002] Against the backdrop of today's rapidly advancing technology, the demand for optical devices is growing. Optically Clear Adhesive (OCA), a key material, plays a vital role in the assembly of optical devices such as liquid crystal displays and touch screens. In traditional OCA adhesives, adhesion and optical performance are key performance indicators. However, existing materials have limitations in practical applications. For fold-resistant optical adhesives, the material must exhibit high resilience, enabling them to return to their original state without wrinkling during repeated folding.

[0003] CN115260921A discloses an OCA optical pressure-sensitive adhesive and a preparation method thereof. The method utilizes reversible addition-fragmentation chain transfer emulsion polymerization to control the monomer types and feed sequence to controllably design and prepare block copolymers. The prepared one or more block copolymers are then mixed and the OCA optical pressure-sensitive adhesive is prepared by solution film formation. The OCA optical pressure-sensitive adhesive prepared by the present invention has the advantages of high stretchability, high transparency, and low haze. It can also effectively reduce modulus and increase peel strength without affecting rebound resilience. It has great application prospects in electronic display devices, wearable electronic devices, resistive touch screens, intelligent optical devices, and other fields.

[0004] CN117510751A discloses an OCA optical adhesive and adhesive film based on a high-temperature resistant acrylate polymer. The acrylate polymer comprises the following raw material components by weight: 45-75 parts of a soft monomer; 15-40 parts of a hard elastomer; 1-20 parts of a functional monomer; 1-10 parts of a VMQ silicone resin; 0.1-2.0 parts of an initiator; 100-250 parts of a solvent; 0.01-1.0 parts of a polymerization inhibitor; and 0.01-2.5 parts of a grafting monomer. The OCA optical adhesive synthesized through secondary curing not only has excellent optical and adhesive properties, but is also modified to withstand high temperatures by introducing crosslinking agents such as isocyanate, aluminum acetylacetonate, and a high-temperature resistant silicone resin, resulting in an OCA optical adhesive with excellent high-temperature resistance. The introduction of the VMQ silicone resin significantly improves the high-temperature resistance of the OCA optical adhesive and also enhances its viscosity and cohesive strength.

[0005] To address these issues, carboxyl cluster-based OCA optical adhesive technology has emerged. This technology exploits the interactions between carboxyl groups in functional monomers to form a novel structure—carboxyl clusters. These carboxyl clusters play a key role in the material, enhancing its resilience and flexibility, improving its ability to withstand stress, and optimizing its optical properties, ensuring the clarity and brightness of optical devices.

[0006] Carboxyl clusters are generally a negative factor for optical adhesives, leading to reduced peel strength and poorer bonding performance. Therefore, further research and exploration is needed to leverage the advantages of carboxyl clusters to impart high resilience to optical adhesives while ensuring good peel strength and strong adhesion. This holds great promise for the broad application and market potential of OCA optical adhesive technology in the field of optical device assembly, potentially injecting new vitality into optical device performance enhancement and product innovation. Summary of the Invention

[0007] The present invention addresses the problems of poor rebound resilience and peel strength of OCA pressure-sensitive adhesives and provides an OCA optical pressure-sensitive adhesive based on carboxyl clusters. A polymer containing carboxyl functional monomers at both ends is prepared by a reversible addition-fragmentation chain transfer solution polymerization method. Carboxyl clusters can be formed between the carboxyl groups, thereby significantly improving the fracture rebound rate of the polymer and exhibiting the characteristics of high peel strength and low modulus.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] An OCA optical pressure-sensitive adhesive based on carboxyl clusters, wherein the structure of the OCA optical pressure-sensitive adhesive is (M2-ran-M3)-b-(M2)-b-(M2-ran-M3) or (M2-ran-M3)-b-(M1-ran-M2-ran-M3)-b-(M2-ran-M3);

[0010] The OCA optical pressure-sensitive adhesive has a number average molecular weight of 0.1 to 100,000 g / mol, wherein M1 is composed of a hard monomer, M2 is composed of a soft monomer, and M3 is composed of a functional monomer; the mass content of the hard monomer is 0-18%, the mass content of the soft monomer is 40-88%, and the mass content of the functional monomer is 12-40%;

[0011] The functional monomer is a monomer containing a carboxyl group and a double bond.

[0012] In the present invention, a block copolymer containing carboxyl functional monomers at both ends is used as the OCA optical adhesive. Carboxyl clusters can be formed between carboxyl groups, and the carboxyl clusters are used as connections between different molecular chains or to enhance the links between hard segments of different molecular chains, so as to enhance the resilience of the optical adhesive. It solves the adhesion and optical performance problems of traditional OCA optical adhesives and also makes the optical adhesive have resilience. This technology provides a new material design idea and a new way to optimize the performance of optical adhesives. Secondly, the OCA optical adhesive based on carboxyl clusters has high application flexibility and adjustability, and can be customized according to actual needs to meet the requirements of different optical devices. Thirdly, the implementation of this technology is relatively simple and low-cost, and is suitable for large-scale production and industrial applications.

[0013] The functional monomer is one or more of methacrylic acid, acrylic acid, itaconic acid, β-acryloyloxypropionic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, ethylenedimethylamine methacrylate, methacrylic acid amine, N-hydroxymethyl acrylamide, glycidyl methacrylate and maleic anhydride.

[0014] The functional monomer is one or more of methacrylic acid, acrylic acid, itaconic acid, and β-acryloyloxypropionic acid.

[0015] Preferably, the functional monomer is one or more of methacrylic acid and acrylic acid, which are low in cost, easily available, and suitable for large-scale production and industrial preparation.

[0016] The hard monomer includes one or more of styrene, methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile and vinyl acetate, and the formed block has a glass transition temperature ranging from 60 to 150°C.

[0017] The hard monomer is one or more of styrene, methyl acrylate, and methyl methacrylate, which are low in cost, easy to obtain, and suitable for large-scale production and industrial preparation.

[0018] The soft monomer includes one or more of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, octyl acrylate, 2-propylheptyl acrylate, isononyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, butadiene, isoprene, ethylene-butene and methacrylic acid, and the formed block has a glass transition temperature range of -90 to -30°C.

[0019] The soft monomer is one or more of n-butyl acrylate, isooctyl acrylate, and octyl acrylate, and the polymer thereof has a low glass transition temperature and a low modulus; the prepared optical adhesive is soft.

[0020] The present invention also provides a method for preparing an OCA optical pressure-sensitive adhesive based on a carboxyl cluster. When the structure of the OCA optical pressure-sensitive adhesive is (M2-ran-M3)-b-(M2)-b-(M2-ran-M3), the preparation comprises the following steps:

[0021] Step 1: Mix 1 / 30-1 / 5 of the soft monomer, 1 / 5-4 / 5 of the functional monomer, an initiator, and a small molecule reversible addition-fragmentation chain transfer agent in a reaction solvent, heat to 50-80° C., and react in an oxygen-free environment for 2-10 hours;

[0022] Step 2: add 4 / 5-14 / 15 of the soft monomer to the reaction system, react for 2-10 hours in an oxygen-free environment, then add the remaining soft monomer and functional monomer, and continue to react for 2-10 hours.

[0023] Step 3: After naturally cooling the reaction solution, pour it into a precipitant for precipitation, wash, air-dry, and dry to obtain a prepolymer, dissolve the prepolymer in an inactive diluent, apply it into a film in an argon environment, and dry it to obtain the OCA optical pressure-sensitive adhesive.

[0024] When the structure of the OCA optical pressure-sensitive adhesive is (M2-ran-M3)-b-(M1-ran-M2-ran-M3)-b-(M2-ran-M3), the preparation includes the following steps:

[0025] Step 1: Mix 1 / 30-1 / 5 of the soft monomer, 1 / 5-4 / 5 of the functional monomer, an initiator, and a small molecule reversible addition-fragmentation chain transfer agent in a reaction solvent, heat to 50-80° C., and react in an oxygen-free environment for 2-10 hours;

[0026] Step 2: Add hard monomer, 1 / 5-1 / 2 functional monomer and 4 / 5-14 / 15 soft monomer to the reaction system, react for 2-10 hours in an oxygen-free environment, then add the remaining soft monomer and functional monomer, and continue to react for 2-10 hours;

[0027] Step 3: After naturally cooling the reaction solution, pour it into a precipitant for precipitation, wash, air-dry, and dry to obtain a prepolymer, dissolve the prepolymer in an inactive diluent, apply it into a film in an argon environment, and dry it to obtain the OCA optical pressure-sensitive adhesive.

[0028] The chemical structural formula of the small molecule reversible addition-fragmentation chain transfer reagent is: RX; wherein R is an isopropionic acid group, an acetic acid group, a 2-cyanoacetic acid group or a 2-aminoacetic acid group; the X group is an alkyl dithioester group or an alkyl trithioester group; and its mass is 1 / 50-1 / 200 of the total mass of all comonomers.

[0029] The initiator includes any one of azobisisobutylimidazoline hydrochloride, azobisisobutylamidine hydrochloride, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, sodium hydrogen persulfate / potassium persulfate redox initiator and sodium persulfate / ammonium persulfate redox initiator, and the amount used is 1 / 50-1 of the molar mass of the small molecule reversible addition-fragmentation chain transfer reagent.

[0030] The precipitating agent includes one or more of methanol, ethanol, acetone, butanone, nitromethane, methyl phthalate, hexane, hexyl chloride, ether, aliphatic hydrocarbons, aromatic hydrocarbons, ethyl acetate, dioxane, cyclohexanol, aliphatic alcohols, petroleum ether, cyclohexane, tetrahydrofuran and water.

[0031] The inactive diluent includes one or more of butanone, acetone, ethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyl ethyl ketone, ethyl acetate and methyl propionate.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) In the present invention, soft monomers are used as the main monomers, and functional monomers containing carboxyl groups are designed at both ends of the prepolymer. The prepolymer prepared by reversible addition-fragmentation chain transfer solution polymerization can effectively control the position of the functional monomers, thereby controlling the formation of carboxyl clusters and improving the elasticity of the optical adhesive.

[0034] (2) The carboxyl functional monomers of the present invention can also help improve the peel strength of the optical adhesive, thereby improving the bonding ability of the optical adhesive. Compared with the hard monomer phase formed by microphase separation, this method does not require the addition of any hard monomer. Due to the modulus of the hard monomer itself, the modulus is further reduced to a certain extent.

[0035] In summary, carboxyl cluster-based OCA optical adhesive technology has broad application prospects and market potential in the field of optical device assembly, and is expected to inject new vitality into the performance improvement and product innovation of optical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram showing the principle of the functional monomers in the present invention forming carboxyl clusters to strengthen the connection.

[0037] Figure 2 This is a rebound resilience test chart of the OCA optical pressure-sensitive adhesive prepared in Example 1.

[0038] Figure 3 This is a graph showing the folding resistance performance of the OCA optical adhesive prepared in Example 3. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art will make modifications or equivalent substitutions based on understanding the technical solution of the present invention, without departing from the spirit and scope of the technical solution of the present invention, and all should be encompassed within the protection scope of the present invention.

[0040] The raw materials used in the following specific embodiments are all purchased from the market.

[0041] Example 1

[0042] An OCA optical pressure-sensitive adhesive and a preparation method thereof, wherein the optical adhesive structure is (isooctyl acrylate-ran-acrylic acid)-b-(isooctyl acrylate)-b-(isooctyl acrylate-ran-acrylic acid), wherein the mass fraction of isooctyl acrylate is 100 parts and the mass fraction of acrylic acid is 20-50 parts;

[0043] The prepolymer in this embodiment is prepared by RAFT reversible addition fragmentation chain transfer solution polymerization. The specific synthesis steps of the OCA optical pressure-sensitive adhesive are as follows:

[0044] Step 1: 1 / 30 of isooctyl acrylate, 1 / 2 of acrylic acid, 0.06 parts by mass of azobisisobutylimidazoline hydrochloride, and 0.05 parts by mass of a small molecule reversible addition-fragmentation chain transfer reagent are mixed in 150 parts by mass of dioxane, heated to 50-80° C., and reacted in an oxygen-free environment for 5 hours; the chemical structure of the small molecule reversible addition-fragmentation chain transfer reagent is:

[0045]

[0046] Step 2: Then add 14 / 15 isooctyl acrylate into the reaction system, react for 5 hours in an oxygen-free environment, and finally add the remaining isooctyl acrylate and acrylic acid, and continue to react for 5 hours.

[0047] Step 3, naturally cooling the system to about room temperature, slowly pouring the solution into cyclohexane for precipitation, washing, air-drying, and drying to obtain the polymer;

[0048] Step 4: dissolving the polymer in tetrahydrofuran, coating the film in an argon environment, and drying the film to finally obtain the OCA optical adhesive.

[0049] The mechanical properties of the optical adhesive were tested using a universal materials testing machine (Zwick / Roll Z020). The final prepared optical adhesive was cut into dumbbell-shaped specimens using a standard cutting knife. The test method adopted GB 16421-1996, the tensile rate was 30 mm / min, and the test of each sample was repeated at least three times.

[0050] The stress relaxation recovery performance of the optical adhesive was tested by DMA (TAQ800). The OCA optical pressure-sensitive adhesive film prepared in the fourth step was cut into strips with a width of 5 mm and a length of 25 mm. A constant stress of 30 kPa was applied for 6 seconds. After the stress was removed, the film recovered for 60 seconds and its recovery curve was recorded.

[0051] The dynamic mechanical properties of the optical adhesive were characterized using a rotational rheometer (HAAKE MARS 60). The polymer film was cut into circular strips with a diameter of 2 cm. The test frequency was 0.01 Hz to 1 Hz and the test temperature was 25°C. The loss factor tan δ of the material was recorded during the measurement.

[0052] The peel strength of the optical adhesive was tested using an adhesive shear strength tester (KJ-1066A). The OCA optical pressure-sensitive adhesive film prepared in step 5 was cut into strips with a width of 25 mm and a length of approximately 300 mm. The test method was based on GB / T 2792-2014, and the test was repeated at least three times for each sample.

[0053] The cyclic loading and unloading deformation characteristics of optical adhesives were measured by a universal material testing machine (UTM 2502, Shenzhen Sansi Zongheng). The experimental temperature was 25°C, the tensile rate was 60 mm / min, and the size of the cut specimens was the same as that of the samples for tensile performance testing.

[0054] Table 1 shows the storage modulus, peel strength, and resilience of the optical adhesive. As the mass fraction of acrylic acid increases from 20 to 50, the peel strength of the optical adhesive increases from 11.2N / 25mm to 12.5N / 25mm. Compared with Comparative Example 1, after adding acrylic acid, the strain recovery rate of the optical adhesive is above 95%, indicating that the rebound points formed by the carboxyl clusters can provide a good strain recovery rate for the optical adhesive. The internal structure connection diagram is shown in FIG. Figure 1 The higher the acrylic acid content, the better the resilience of the optical adhesive, but it will lead to a slight increase in Young's modulus and storage modulus.

[0055] Table 1 Properties of OCA optical pressure-sensitive adhesives prepared with different acrylic acid amounts

[0056]

[0057]

[0058] Comparative Example 1

[0059] The preparation method of Comparative Example 1 is roughly the same as that of Example 1, except that the formula does not contain acrylic acid, and the optical adhesive structure is (isooctyl acrylate)-b-(isooctyl acrylate)-b-(isooctyl acrylate), wherein the mass fraction of isooctyl acrylate is 100, and the other steps are the same.

[0060] Example 2

[0061] An OCA optical pressure-sensitive adhesive and a preparation method thereof, wherein the optical adhesive structure is (isooctyl acrylate-ran-acrylic acid)-b-(isooctyl acrylate)-b-(isooctyl acrylate-ran-acrylic acid), wherein the mass fraction of isooctyl acrylate is 80-120 parts and the mass fraction of acrylic acid is 35 parts;

[0062] The prepolymer in this embodiment is prepared by RAFT reversible addition fragmentation chain transfer solution polymerization. The specific synthesis steps of the OCA optical pressure-sensitive adhesive are as follows:

[0063] Step 1: 1 / 30 of isooctyl acrylate, 1 / 2 of acrylic acid, 0.06 parts by mass of azobisisobutylimidazoline hydrochloride, and 0.05 parts by mass of a small molecule reversible addition-fragmentation chain transfer reagent are mixed in 150 parts by mass of dioxane, heated to 50-80° C., and reacted in an oxygen-free environment for 5 hours; the chemical structure of the small molecule reversible addition-fragmentation chain transfer reagent is:

[0064]

[0065] Step 2: Then add 14 / 15 isooctyl acrylate into the reaction system, react for 5 hours in an oxygen-free environment, and finally add the remaining isooctyl acrylate and acrylic acid, and continue to react for 5 hours.

[0066] Step 3, naturally cooling the system to about room temperature, slowly pouring the solution into cyclohexane for precipitation, washing, air-drying, and drying to obtain the polymer;

[0067] Step 4: dissolving the polymer in tetrahydrofuran, coating the film in an argon environment, and drying the film to finally obtain the OCA optical adhesive.

[0068] The amounts of isooctyl acrylate used were 80 parts, 100 parts, and 120 parts, respectively, to prepare different pressure-sensitive adhesives, and their properties were tested. The mechanical property test of the optical adhesive was similar to that in Example 1.

[0069] Figure 2 This image shows an optical adhesive containing 100 parts by mass of isooctyl acrylate and subjected to 100 cycles of tensile testing, with the tensile strain set to 300%. One hour after the cycle, the adhesive essentially returned to its original state, demonstrating good resilience.

[0070] Table 2: Properties of optical pressure-sensitive adhesives prepared with varying weights of isooctyl acrylate. With increasing isooctyl acrylate content, the Young's modulus and storage modulus of the optical adhesive decrease, while flexibility increases. This is because the polymer formed by isooctyl acrylate has a lower modulus than that formed by acrylic acid. As the chain segments increase, the flexible segments of the optical adhesive increase, while the total amount of carboxyl clusters formed by acrylic acid remains unchanged, resulting in a decrease in modulus. Modulating the modulus can improve the adaptability of the optical adhesive.

[0071] Table 2 Properties of pressure-sensitive adhesives prepared with different weight fractions of isooctyl acrylate

[0072]

[0073] Example 3

[0074] An OCA optical pressure-sensitive adhesive and a preparation method thereof. The optical adhesive has a structure of (isooctyl acrylate-ran-functional monomer)-b-(isooctyl acrylate)-b-(isooctyl acrylate-ran-functional monomer), wherein the mass fraction of isooctyl acrylate is 100 parts and the mass fraction of the functional monomer is 35 parts; and the functional monomers are acrylic acid, hydroxyethyl acrylate, and ethylenedimethylamine methacrylate.

[0075] The prepolymer in this embodiment is prepared by RAFT reversible addition fragmentation chain transfer solution polymerization. The specific synthesis steps of the OCA optical pressure-sensitive adhesive are as follows:

[0076] Step 1: 1 / 30 of isooctyl acrylate, 1 / 2 of the functional monomer, 0.06 parts by mass of azobisisobutylimidazoline hydrochloride, and 0.05 parts by mass of a small molecule reversible addition-fragmentation chain transfer agent are mixed in 150 parts by mass of dioxane, heated to 50-80° C., and reacted in an oxygen-free environment for 5 hours; the chemical structure of the small molecule reversible addition-fragmentation chain transfer agent is:

[0077]

[0078] Step 2: Then add 14 / 15 isooctyl acrylate into the reaction system, react for 5 hours in an anaerobic environment, and finally add the remaining isooctyl acrylate and functional monomers, and continue to react for 5 hours.

[0079] Step 3, naturally cooling the system to about room temperature, slowly pouring the solution into cyclohexane for precipitation, washing, air-drying, and drying to obtain the polymer;

[0080] Step 4: dissolving the polymer in tetrahydrofuran, coating the film in an argon environment, and drying the film to finally obtain the OCA optical adhesive.

[0081] Figure 3This is a picture of the optical pressure-sensitive adhesive whose functional monomer is ethylenedimethylamine methacrylate after the folding test. After 200,000 folding tests, the state of the optical adhesive has basically no obvious change.

[0082] Table 3 shows the properties of optical pressure-sensitive adhesives containing different types of functional monomers. In addition to acrylic acid, the functional monomers used in this example also include hydroxyethyl acrylate and ethylenedimethylamine methacrylate. The mechanical properties of the polymers tested were similar to those in Example 1. The peel strength of ethylenedimethylamine methacrylate was significantly higher than that of the other two. This is because it contains more polar groups and is located in the middle segment, resulting in fewer hydrogen bonds between the polar groups, allowing it to fully interact with the surface of the adhesive.

[0083] Table 3 shows the properties of optical pressure-sensitive adhesives with different types of functional monomers added

[0084]

[0085] Example 4

[0086] An OCA optical pressure-sensitive adhesive and a preparation method thereof, wherein the optical adhesive structure is (isooctyl acrylate-ran-acrylic acid)-b-(isooctyl acrylate-ran-acrylic acid-ran-styrene)-b-(isooctyl acrylate-ran-acrylic acid), wherein the mass fraction of isooctyl acrylate is 100 parts and the mass fraction of acrylic acid is 36 parts;

[0087] The prepolymer in this embodiment is prepared by RAFT reversible addition fragmentation chain transfer solution polymerization. The specific synthesis steps of the OCA optical pressure-sensitive adhesive are as follows:

[0088] Step 1: 1 / 30 of isooctyl acrylate, 1 / 3 of acrylic acid, 0.06 parts by mass of azobisisobutylimidazoline hydrochloride, and 0.05 parts by mass of a small molecule reversible addition-fragmentation chain transfer reagent are mixed in 150 parts by mass of dioxane, heated to 50-80° C., and reacted in an oxygen-free environment for 5 hours; the chemical structure of the small molecule reversible addition-fragmentation chain transfer reagent is:

[0089]

[0090] Step 2: Then add 14 / 15 isooctyl acrylate into the reaction system, react for 5 hours in an anaerobic environment, and finally add the remaining isooctyl acrylate and functional monomers, and continue to react for 5 hours.

[0091] Step 3, naturally cooling the system to about room temperature, slowly pouring the solution into cyclohexane for precipitation, washing, air-drying, and drying to obtain the polymer;

[0092] Step 4: dissolving the polymer in tetrahydrofuran, coating the film in an argon environment, and drying the film to finally obtain the OCA optical adhesive.

[0093] Table 4 shows the performance of optical pressure-sensitive adhesives containing different types of functional monomers. The difference lies in the middle section: Example 4's middle section is composed of a soft monomer, a functional monomer, and a hard monomer, while Comparative Example 2's middle section is composed of a soft monomer and a functional monomer, and Comparative Example 3's middle section is composed of a soft monomer and a hard monomer. Comparative Examples 2 and 3 show a significant improvement in holding power compared to Example 1, but a significant decrease compared to Example 4, demonstrating that acrylic acid or styrene can provide better holding power for optical adhesives.

[0094] Table 4 shows the properties of optical pressure-sensitive adhesives with different types of functional monomers added

[0095]

[0096] Comparative Example 2

[0097] Comparative Example 2 is prepared in substantially the same manner as Example 4, using the same materials in parts by weight, and the preparation steps are as follows:

[0098] Step 1: 1 / 30 of isooctyl acrylate, 1 / 3 of acrylic acid, 0.06 parts by mass of azobisisobutylimidazoline hydrochloride, and 0.05 parts by mass of a small molecule reversible addition-fragmentation chain transfer reagent are mixed in 150 parts by mass of dioxane, heated to 50-80° C., and reacted in an oxygen-free environment for 5 hours; the chemical structure of the small molecule reversible addition-fragmentation chain transfer reagent is:

[0099]

[0100] In step 2, 14 / 15 of isooctyl acrylate and 1 / 3 of acrylic acid are added to the reaction system, and the mixture is reacted for 5 hours in an oxygen-free environment. Finally, the remaining isooctyl acrylate and acrylic acid are added, and the reaction is continued for 5 hours.

[0101] Step 3, naturally cooling the system to about room temperature, slowly pouring the solution into cyclohexane for precipitation, washing, air-drying, and drying to obtain the polymer;

[0102] Step 4: dissolving the polymer in tetrahydrofuran, coating the film in an argon environment, and drying the film to finally obtain the OCA optical adhesive.

[0103] Comparative Example 3

[0104] The preparation method of Comparative Example 3 is substantially the same as that of Example 4, and the mass parts of the materials used are the same. The preparation steps are as follows:

[0105] Step 1: 1 / 30 of isooctyl acrylate, 1 / 2 of acrylic acid, 0.06 parts by mass of azobisisobutylimidazoline hydrochloride, and 0.05 parts by mass of a small molecule reversible addition-fragmentation chain transfer reagent are mixed in 150 parts by mass of dioxane, heated to 50-80° C., and reacted in an oxygen-free environment for 5 hours; the chemical structure of the small molecule reversible addition-fragmentation chain transfer reagent is:

[0106] Step 2: Then add 14 / 15 isooctyl acrylate and all the styrene into the reaction system, react for 5 hours in an oxygen-free environment, and finally add the remaining isooctyl acrylate and acrylic acid, and continue to react for 5 hours.

[0107] Step 3, naturally cooling the system to about room temperature, slowly pouring the solution into cyclohexane for precipitation, washing, air-drying, and drying to obtain the polymer;

[0108] Step 4: dissolving the polymer in tetrahydrofuran, coating the film in an argon environment, and drying the film to finally obtain the OCA optical adhesive.

Claims

1. An OCA optical pressure-sensitive adhesive based on carboxyl clusters, characterized in that: The OCA optical pressure-sensitive adhesive structure is (M2-ran-M3)-b-(M2)-b-(M2-ran-M3) or (M2-ran-M3)-b-(M1-ran-M2-ran-M3)-b-(M2-ran-M3); The OCA optical pressure-sensitive adhesive has a number average molecular weight of 0.1 to 100,000 g / mol, wherein M1 is composed of a hard monomer, M2 is composed of a soft monomer, and M3 is composed of a functional monomer; the mass content of the hard monomer is 0-18%, the mass content of the soft monomer is 40-88%, and the mass content of the functional monomer is 12-40%; The functional monomer is a monomer containing a carboxyl group and a double bond.

2. The OCA optical pressure-sensitive adhesive based on carboxyl clusters according to claim 1, characterized in that: The functional monomer is one or more of methacrylic acid, acrylic acid, itaconic acid, β-acryloyloxypropionic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, ethylenedimethylamine methacrylate, methacrylic acid amine, N-hydroxymethyl acrylamide, glycidyl methacrylate and maleic anhydride.

3. The OCA optical pressure-sensitive adhesive based on carboxyl clusters according to claim 1, characterized in that: The hard monomer includes one or more of styrene, methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile and vinyl acetate, and the formed block has a glass transition temperature ranging from 60 to 150°C.

4. The OCA optical pressure-sensitive adhesive based on carboxyl clusters according to claim 1, characterized in that: The soft monomer includes one or more of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, octyl acrylate, 2-propylheptyl acrylate, isononyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, butadiene, isoprene, ethylene-butene and methacrylic acid, and the formed block has a glass transition temperature range of -90 to -30°C.

5. The method for preparing the OCA optical pressure-sensitive adhesive based on carboxyl clusters according to any one of claims 1 to 4, characterized in that: When the structure of the OCA optical pressure-sensitive adhesive is (M2-ran-M3)-b-(M2)-b-(M2-ran-M3), the preparation includes the following steps: Step 1: Mix 1 / 30-1 / 5 of the soft monomer, 1 / 5-4 / 5 of the functional monomer, an initiator, and a small molecule reversible addition-fragmentation chain transfer agent in a reaction solvent, heat to 50-80° C., and react in an oxygen-free environment for 2-10 hours; Step 2: Add 4 / 5-14 / 15 of the soft monomer to the reaction system, react for 2-10 hours in an oxygen-free environment, then add the remaining soft monomer and functional monomer, and continue to react for 2-10 hours; Step 3: After naturally cooling the reaction solution, pour it into a precipitant for precipitation, wash, air-dry, and dry to obtain a prepolymer, dissolve the prepolymer in an inactive diluent, apply it into a film in an argon environment, and dry it to obtain the OCA optical pressure-sensitive adhesive.

6. The method for preparing the OCA optical pressure-sensitive adhesive based on carboxyl clusters according to any one of claims 1 to 4, characterized in that: When the structure of the OCA optical pressure-sensitive adhesive is (M2-ran-M3)-b-(M1-ran-M2-ran-M3)-b-(M2-ran-M3), the preparation includes the following steps: Step 1: Mix 1 / 30-1 / 5 of the soft monomer, 1 / 5-4 / 5 of the functional monomer, an initiator, and a small molecule reversible addition-fragmentation chain transfer agent in a reaction solvent, heat to 50-80° C., and react in an oxygen-free environment for 2-10 hours; Step 2: Add hard monomer, 1 / 5-1 / 2 functional monomer and 4 / 5-14 / 15 soft monomer to the reaction system, react for 2-10 hours in an oxygen-free environment, then add the remaining soft monomer and functional monomer, and continue to react for 2-10 hours; Step 3: After naturally cooling the reaction solution, pour it into a precipitant for precipitation, wash, air-dry, and dry to obtain a prepolymer, dissolve the prepolymer in an inactive diluent, apply it into a film in an argon environment, and dry it to obtain the OCA optical pressure-sensitive adhesive.

7. The method for preparing the OCA optical pressure-sensitive adhesive based on carboxyl clusters according to claim 5 or 6, characterized in that: The chemical structural formula of the small molecule reversible addition-fragmentation chain transfer reagent is: RX; wherein R is an isopropionic acid group, an acetic acid group, a 2-cyanoacetic acid group or a 2-aminoacetic acid group; the X group is an alkyl dithioester group or an alkyl trithioester group; and its mass is 1 / 50-1 / 200 of the total mass of all comonomers.

8. The method for preparing the OCA optical pressure-sensitive adhesive based on carboxyl clusters according to claim 5 or 6, characterized in that: The initiator includes any one of azobisisobutylimidazoline hydrochloride, azobisisobutylamidine hydrochloride, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, sodium hydrogen persulfate / potassium persulfate redox initiator and sodium persulfate / ammonium persulfate redox initiator, and the amount used is 1 / 50-1 of the molar mass of the small molecule reversible addition-fragmentation chain transfer reagent.

9. The method for preparing the OCA optical pressure-sensitive adhesive based on carboxyl clusters according to claim 5 or 6, characterized in that: The precipitating agent includes one or more of methanol, ethanol, acetone, butanone, nitromethane, methyl phthalate, hexane, hexyl chloride, ether, aliphatic hydrocarbons, aromatic hydrocarbons, ethyl acetate, dioxane, cyclohexanol, aliphatic alcohols, petroleum ether, cyclohexane, tetrahydrofuran and water.

10. The method for preparing the OCA optical pressure-sensitive adhesive based on carboxyl clusters according to claim 5 or 6, characterized in that: The inactive diluent includes one or more of butanone, acetone, ethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyl ethyl ketone, ethyl acetate and methyl propionate.

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